Âûäåëèòü ñëîâà: 

Ïàòåíò ÑØÀ ¹

6306740

Àâòîð(û)

Hattori

Äàòà âûäà÷è

23 îêòÿáðÿ 2001 ã.

Manufacture of field emission element



ÐÅÔÅÐÀÒ

In a field emission element manufacture method, a gate electrode having a gate hole and a getter film having a through hole communicating with the gate hole are formed on the surface of a substrate. A sacrificial film is formed over the substrate to form a mold which is used when an emitter electrode is formed, the sacrificial film covering the side walls of the gate hole and through hole and the partial surface of the substrate exposed via the holes. An emitter electrode is formed covering the surface of the mold, and thereafter the gate hole and emitter electrode are exposed to obtain a field emission element. The vacuum degree in a flat panel display can be raised and molecules are prevented from attaching to the surface of the emitter electrode.

Àâòîðû:

Atsuo Hattori (Hamamatsu, JP)

Çàÿâèòåëü:

Yamaha Corporation (JP)

ID ñåìåéñòâà ïàòåíòîâ

16836288

Íîìåð çàÿâêè:

 09/371,177

Äàòà ðåãèñòðàöèè:

10 àâãóñòà 1999 ã.

Ïðèîðèòåò çàðóáåæíîé çàÿâêè

Aug 10, 1998 [JP]10-225878

Êëàññ ïàòåíòíîé êëàññèôèêàöèè ÑØÀ:

438/584; 445/24

Êëàññ ñîâìåñòíîé ïàòåíòíîé êëàññèôèêàöèè:

H01J 9/025 (20130101); H01J 29/94 (20130101); H01J 9/385 (20130101)

Êëàññ ìåæäóíàðîäíîé ïàòåíòíîé êëàññèôèêàöèè (ÌÏÊ):

H01J 29/94 (20060101); H01J 29/00 (20060101); H01J 9/02 (20060101); H01J 9/385 (20060101); H01J 9/38 (20060101); H01L 021/20 ()

Îáëàñòü ïîèñêà:

;445/24,50 ;437/225,228 ;438/584,20

Èñïîëüçîâàííûå èñòî÷íèêè

[Referenced By]

Ïàòåíòíûå äîêóìåíòû ÑØÀ

5599749February 1997Hattori
5629579May 1997Zimmerrnan

Çàðóáåæíûå ïàòåíòíûå äîêóìåíòû

8-22785Jan 1996JP

Äðóãèå èñòî÷íèêè


Low-Voltage Refective View Type FED Panel With Ni-Based Emitter, T. Nakatani et al., (Fujitsu Laboratories Ltd., Hyogo, Japan, FED 1-3), IDW, 1996, pp. 127-130..

Ãëàâíûé ýêñïåðò: Nelms; David
Assistant Examiner: Vu; David
Óïîëíîìî÷åííûé, äîâåðåííûé èëè ôèðìà: Ostrolenk, Faber, Gerb & Soffen, LLP

Òåêñò ðåøåíèÿ-ïðåöåäåíòà



This application is based on Japanese patent application No. Hei 10-225878 filed on Aug. 10, 1998, the entire contents of which are incorporated herein by reference.

ÔÎÐÌÓËÀ ÈÇÎÁÐÅÒÅÍÈß



What is claimed is:

1. A method of manufacturing a field emission element comprising the steps of:

(a) forming a lamination on a substrate, the lamination including a gate electrode having a gate hole and a getter film having a hole communicating with the gate hole;

(b) depositing a sacrificial film to form a mold which is used when an emitter electrode is formed, the sacrificial film covering from a surface area of the substrate exposed via the gate hole and the hole to an upper surface area of the lamination;

(c) forming the emitter electrode covering a surface of the mold; and

(d) thereafter removing part of the sacrificial film to expose the gate hole and the emitter electrode to thereby obtain the field emission element.

2. A method according to claim 1, wherein said step (a) includes a subsidiary step of forming the getter film made of Ti, Ta, Zr, Al or Mg.

3. A method according to claim 1, wherein said step (a) includes a subsidiary step of forming on the substrate a gate electrode film and a getter material layer in this order.

4. A method according to claim 3, wherein said step (a) includes: a subsidiary step of forming on the substrate a gate electrode film and a getter material layer in this order; a subsidiary step of forming an antireflection film on the getter material layer; a subsidiary step of forming a resist pattern on the antireflection film, while preventing reflection of exposure light by the antireflection film; and a subsidiary step of patterning the getter material layer into the getter film through etching using the resist pattern as a mask.

5. A method according to claim 3, wherein the substrate is a substrate having an anode electrode film, and said step (a) includes a subsidiary step of forming the gate electrode film on the anode electrode film, with an insulating film being interposed therebetween.

6. A method according to claim 1, wherein said step (a) includes a subsidiary step of forming on the substrate a getter material layer and a gate electrode film in this order.

7. A method according to claim 6, wherein said step (a) includes: a subsidiary step of forming on the substrate a getter material layer and a gate electrode film in this order; a subsidiary step of forming an antireflection film on the gate electrode film; a subsidiary step of forming a resist pattern on the antireflection film, while preventing reflection of exposure light by the antireflection film; and a subsidiary step of patterning the gate electrode film into the gate electrode through etching using the resist pattern as a mask.

8. A method according to claim 6, wherein the substrate is a substrate having an anode electrode film, and said step (a) includes a subsidiary step of forming the getter material layer on the anode electrode film, with an insulating film being interposed therebetween.

9. A method according to claim 1, wherein said step (a) includes a subsidiary step of forming the gate electrode having the gate hole and a subsidiary step of forming the getter film on a side wall of the gate hole.

10. A method according to claim 1, wherein said step (b) includes a subsidiary step of forming a side spacer along a side wall of the gate hole.

11. A method according to claim 10, wherein said step (b) includes a subsidiary step of forming a side spacer made of the getter film along the side wall of the gate hole.

12. A method according to claim 1, further comprising a step of (e) reinforcing the emitter electrode before or after said step (d).

13. A method according to claim 12, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of filling the recess with a planarizing film.

14. A method according to claim 12, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of flowing adhesive into the recess.

15. A method according to claim 12, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of forming a blanket film on the recess and a subsidiary step of forming a planarized surface on the blanket film by using a planarizing film.

16. A method according to claim 12, wherein said step (e) includes a subsidiary step of bonding a support substrate to a back surface of the emitter electrode.

17. A method according to claim 12, further comprising a step of (f) forming an emitter wiring line on a back surface of the reinforced emitter electrode, interposing a resistor layer.

18. A method of manufacturing a field emission element comprising the steps of:

(a) forming a gate electrode serving as a getter film having a gate hole on a substrate;

(b) depositing a sacrificial film to form a mold which is used when an emitter electrode is formed, the sacrificial film covering from a surface area of the substrate exposed via the gate hole to an upper surface area of the gate electrode;

(c) forming an emitter electrode covering a surface of the mold; and

(d) thereafter removing part of the sacrificial film to expose the gate hole and the emitter electrode to thereby obtain the field emission element.

19. A method according to claim 18 wherein said step (a) includes a subsidiary step of forming a gate electrode film serving as a getter material layer.

20. A method according to claim 18, wherein said step (a) includes a subsidiary step of forming the gate electrode film made of Ti, Ta, Zr, Al or Mg, serving as a getter material layer.

21. A method according to claim 18, wherein said step (a) includes: a subsidiary step of forming a gate electrode film serving as a getter material layer; a subsidiary step of forming an antireflection film on the gate electrode film; a subsidiary step of forming a resist pattern on the antireflection film, while preventing reflection of exposure light by the antireflection film; and a subsidiary step of patterning the gate electrode film into the gate electrode through etching using the resist pattern as a mask.

22. A method according to claim 18, wherein the substrate is a substrate having an anode electrode film, and said step (a) includes a subsidiary step of forming a gate electrode film serving as a getter material layer on the anode electrode film, with an insulating film being interposed therebetween.

23. A method according to claim 18, wherein said step (b) includes a subsidiary step of forming a side spacer along a side wall of the gate hole.

24. A method according to claim 18, further comprising a step of (e) reinforcing the emitter electrode before or after said step (d).

25. A method according to claim 24, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of filling the recess with a planarizing film.

26. A method according to claim 24, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of flowing adhesive into the recess.

27. A method according to claim 24, wherein said step (c) is a step of forming the emitter electrode having a recess on a back surface thereof, the emitter electrode covering the surface of the mold, and said step (e) includes a subsidiary step of forming a blanket film on the recess and a subsidiary step of forming a planarized surface on the blanket film by using a planarizing film.

28. A method according to claim 24, wherein said step (e) includes a subsidiary step of bonding a support substrate to a back surface of the emitter electrode.

29. A method according to claim 24, further comprising a step of (f) forming an emitter wiring line on a back surface of the reinforced emitter electrode, interposing a resistor layer.

30. A method of manufacturing a field emission element comprising the steps of:

(a) forming a conductive gate electrode film on a surface of a substrate;

(b) forming a getter material layer on the gate electrode film;

(c) forming a resist pattern on the getter material layer through photolithography;

(d) by using the resist pattern as an etching mask, etching the getter material layer to form a hole therethrough reaching the gate electrode film, to thus form a getter film;

(e) by using either the resist pattern or the getter film as an etching mask, etching the gate electrode film to form a gate hole therethrough reaching the substrate, to thus form a gate electrode having the gate hole;

(f) removing the resist pattern before or after said step (e);

(g) forming a first sacrificial film over the substrate, the first sacrificial film covering the gate electrode and the getter film;

(h) etching back the first sacrificial film to leave a side spacer on a side wall of the gate hole of the gate electrode and/or on a side wall of the hole of the getter film;

(i) forming a second sacrificial film over the substrate, the second sacrificial film covering the getter film, the gate electrode and the side spacer;

(j) forming a conductive emitter electrode on the second sacrificial film; and

(k) removing at least part of the second sacrificial film to expose the emitter electrode.

31. A method according to claim 30, wherein the substrate is a substrate having an anode electrode film, and said step (a) is a step of forming the gate electrode film on the anode electrode film, with an insulating film being interposed therebetween.

32. A method according to claim 30, wherein said step (b) is a step of forming the getter material layer of Ti, Ta, Zr, Al or Mg.

33. A method of manufacturing a field emission element comprising the of:

(a) forming a getter material layer on a surface of a substrate;

(b) forming a conductive gate electrode film on the getter material layer;

(c) forming a resist pattern on the gate electrode film through photolithography;

(d) by using the resist pattern as an etching mask, etching the gate electrode film to form a gate hole therethrough reaching the getter material layer, to thus form a gate electrode having the gate hole;

(e) by using either the resist pattern or the gate electrode as an etching mask, etching the getter material layer to form a hole therethrough reaching the substrate, to thus form a getter film;

(f) removing the resist pattern before or after said step (e);

(g) forming a first sacrificial film over the substrate, the first sacrificial film covering the gate electrode and the getter film;

(h) etching back the first sacrificial film to leave a side spacer on a side wall of the hole of the getter film and on a side wall of the gate hole of the gate electrode, or on a side wall of the hole of the getter film;

(i) forming a second sacrificial film over the substrate, the second sacrificial film covering the gate electrode, the getter film and the side spacer;

(j) forming a conductive emitter electrode on the second sacrificial film; and

(k) removing at least part of the second sacrificial film to expose the emitter electrode.

34. A method according to claim 33, wherein the substrate is a substrate having an anode electrode film, and said step (a) is a step of forming the gate electrode film on the anode electrode film, with an insulating film being interposed therebetween.

35. A method according to claim 33, wherein said step (b) is a step of forming the getter material layer made of Ti, Ta, Zr, Al or Mg.

36. A method of manufacturing a field emission element comprising the steps of:

(a) forming a conductive gate electrode film on a surface of a substrate, the gate electrode film being made of getter material;

(b) forming a resist pattern on the gate electrode film through photol ithography;

(c) by using the resist pattern as an etching mask, etching the gate electrode film to form a gate hole therethrough reaching the substrate, to thus form a gate electrode serving as a getter film having the gate hole;

(d) removing the resist pattern;

(e) forming a first sacrificial film over the substrate, the first sacrificial film covering the gate electrode;

(f) etching back the first sacrificial film to leave a side spacer on a side wall of the gate hole of the gate electrode;

(g) forming a second sacrificial film over the substrate, the second sacrificial film covering the side spacer;

(h) forming a conductive emitter electrode on the second sacrificial film; and

(j) removing at least part of the second sacrificial film to expose the emitter electrode.

37. A method according to claim 36, wherein the substrate is a substrate having an anode electrode film, and said step (a) is a step of forming the conductive gate electrode film made of the getter material on the anode electrode film, with an insulating film being interposed therebetween.

38. A method according to claim 36, wherein said step (a) is a step of forming the conductive gate electrode film made of the getter material of Ti, Ta, Zr, Al or Mg.

39. A method of manufacturing a field emission element comprising the steps of:

(a) forming a gate electrode film on a surface of a substrate;

(b) forming a resist pattern on the gate electrode film through photolithography;

(c) by using the resist pattern as an etching mask, etching the gate electrode film to form a gate hole therethrough reaching the substrate, to thus form a gate electrode having the gate hole;

(d) removing the resist pattern;

(e) forming a getter material layer over the substrate, the getter material layer covering the gate electrode;

(f) etching back the getter material layer to form a getter film on a side wall of the gate electrode, the getter film also functioning as a side spacer;

(f) forming a first sacrificial film over the substrate, the first sacrificial film covering the gate electrode and the getter film;

(h) forming an emitter electrode on the first sacrificial film; and

(i) removing at least part of the first sacrificial film to expose the emitter electrode.

40. A method according to claim 39, wherein the substrate is a substrate having an anode electrode film, and said step (a) is a step of forming the gate electrode film on the anode electrode film, with an insulating film being interposed therebetween.

41. A method according to claim 39, wherein said step (e) is a step of forming the getter material layer made of Ti, Ta, Zr, Al or Mg.

42. A method of manufacturing a field emission element comprising the steps of:

(a) forming a gate electrode film on a surface of a substrate;

(b) forming a resist pattern on the gate electrode film through photolithography;

(c) by using the resist pattern as an etching mask, etching the gate electrode film to form a gate hole therethrough reaching the substrate, to thus form a gate electrode having the gate hole;

(d) removing the resist pattern;

(e) forming a getter material layer over the substrate, the getter material layer covering the gate electrode including a side wall and a bottom surface of the gate hole;

(f) forming a first sacrificial film over the substrate, the first sacrificial film covering the getter material layer and not filling the gate hole;

(g) etching back the first sacrificial film to form a side spacer on a side wall of the getter material layer and on the side wall of the gate electrode and expose the getter material layer at the bottom surface of the gate hole;

(h) by using the side spacer as an etching mask, etching the getter material layer to remove at least the getter material layer at the bottom surface of the gate hole, to thus form a getter film having a hole reaching the substrate;

(i) forming a second sacrificial film over the substrate, the second sacrificial film covering the side spacer, the getter film and the gate electrode;

(j) forming an emitter electrode on the second sacrificial film; and

(k) removing at least part of the second sacrificial film to expose the emitter electrode.

43. A method according to claim 42, wherein the substrate is a substrate having an anode electrode film, and said step (a) is a step of forming the gate electrode film on the anode electrode film, with an insulating film being interposed therebetween.

44. A method according to claim 42, wherein said step (e) is a step of forming the getter material layer made of Ti, Ta, Zr, Al or Mg.


ÎÏÈÑÀÍÈÅ




ÏÐÅÄÏÎÑÛËÊÈ ÑÎÇÄÀÍÈß ÈÇÎÁÐÅÒÅÍÈß



a) Field of the Invention

The present invention relates to a filed emission element and more particularly to a field emission element having a field emission cathode whose tip emits electrons and its manufacture method.

b) Description of the Related Art

A field emission element emits electrons from a sharp tip of an emitter (field emission cathode) by utilizing electric field concentration. For example, a flat panel display can be structured by using a field emitter array (FEA) having a number of emitters disposed on a substrate. Each emitter controls the luminance of a corresponding pixel of the display.

FIGS. 15A to 15F schematically illustrate a conventional method of manufacturing a field emission element.

As shown in FIG. 15A, a conductive gate electrode 62 is formed on a substrate 61. For example, the conductive gate electrode 62 is made of polysilicon doped with impurities. On the conductive gate electrode 62, a resist film 63 having a predetermined pattern is formed through photolithography.

Next, by using the resist pattern 63 as a mask, the gate electrode 62 is anisotropically etched to leave as shown in FIG. 15B a gate electrode 62a having a gate hole 67 having a circular flat shape (as viewed from the top). This etching thins the resist pattern 63 and a thin resist pattern 63a is left.

As shown in FIG. 15C, after the resist pattern 63a is removed, a sacrificial film 64 is isotropically deposited on the gate electrode 62a and on the exposed substrate 61.

Next, as shown in FIG. 15D, the sacrificial film 64 is anisotropically etched to leave a sacrificial film (side spacer) 64a on the side wall of the gate hole 67 of the gate electrode 62a.

Next, as shown in FIG. 15E, an insulating film 65 is formed on the whole upper surface of the substrate and a conductive emitter electrode 66 is formed on the insulating film 65.

Next, as shown in FIG. 15F, the whole of the substrate 61 and side spacer 64a and part of the insulating film 65 are etched to leave a peripheral portion of the insulating film 65a between the gate electrode 62a and emitter electrode 66.

As a positive potential is applied to the gate electrode to concentrate an electric field upon the tip of the emitter electrode (cathode) 66, electrons can be emitted from the emitter electrode 66 toward an anode electrode (not shown).

FIG. 16 is a cross sectional view of a flat panel display using such field emission elements.

Each field emission element is manufactured by the above-described method, and has an emitter electrode 44 and a gate electrode 45. Formed on a support substrate 41 made of insulating material are a wiring layer 42 made of Al, Cu, or the like and a resistor layer 43 made of polysilicon or the like. On the resistor layer 43, a number of emitter electrodes 44 having a sharp tip are disposed to form a field emitter array (FEA). Each gate electrode 45 has a small opening (gate hole) near at the tip of each emitter electrode 44 and a voltage can be applied independently to each gate electrode although not specifically shown in FIG. 16. A plurality of emitter electrodes 44 can also be independently applied with a voltage.

Facing an electron source including the emitter electrode 44 and gate electrode 45, an opposing substrate is disposed including a transparent substrate 46 made of glass, quartz, or the like. The opposing substrate has a transparent electrode (anode electrode) 47 made of ITO or the like disposed under the transparent electrode 46 and a fluorescent member 48 disposed under the transparent electrode 47.

The electron source and opposing substrate are joined together via a spacer 50 made of a glass substrate and coated with adhesive, with the distance between the transparent electrode 47 and emitter electrode 44 being maintained about 0.1 to 5 mm. The adhesive may be low melting point glass.

Instead of the spacer 50 of a glass substrate, a spacer 50 made of adhesive such as epoxy resin with glass beads being dispersed therein may be used.

An air exhaust pipe 49 is coupled in advance to the opposing substrate. By using this air exhaust pipe 49, the inside of the flat display panel is evacuated to about 1.times.10.sup.-5 Torr to 1.times.10.sup.-9 Torr (about 1.times.10.sup.-5.times.133.3 Pa to 1.times.10.sup.-9.times.133.3 Pa), and then the air exhaust pipe 49 is sealed by using a burner or the like. Thereafter, the anode electrode (transparent electrode) 47, emitter electrode 44, gate electrode 45 are wired to complete the flat panel display.

The anode electrode (transparent electrode) 47 is always maintained at a positive potential. Pixels are selected two-dimensionally by emitter wiring lines and gate wiring lines. Field emission elements are selected disposed at each cross point of voltage applied emitter and gate wiring lines.

The emitter electrode is applied with a negative potential and the gate electrode is applied with a positive potential. Electrons are emitted from the emitter electrode toward the anode electrode. When electrons are bombarded with the fluorescent member 48, fluorescence is radiated from the bombarded area (pixel).

In order to maintain the inside of the flat panel display at a high vacuum degree, a getter member 51 is provided at the corner in the flat panel display. For example, the getter member 51 is made of Ti, Ta, Zr, Al, Mg, or the like. After the air exhaust pipe 49 is sealed, the getter member 51 is activated by heating it with a lamp or laser beam to adsorb ambient molecules therein. The initial vacuum degree in the flat panel display can therefore be improved.

Other molecules such as He passing through the transparent substrate 46 and support substrate 41 and entering the inside of the flat panel display or other molecules such as H.sub.2 O, O.sub.2, and N.sub.2 emitted in the flat panel display are also adsorbed by the getter member 51. As a result, the vacuum degree in the flat panel display is prevented from being lowered and the flat panel display is prolonged its lifetime.

The getter member 51 is disposed at the corner in the flat panel display so as not to obstruct electrons to be emitted from the emitter electrode 44 toward the transparent electrode 47. The getter member 51 is therefore placed at the position remote from the emitter electrodes 44. As the getter member 51 is placed remotely from the emitter electrodes 44, the function of the getter member 51 cannot be sufficiently demonstrated and the following disadvantages may occur.

(1) Molecules described above are attached to the surface of the emitter electrode 44 in a high electric field, before they are adsorbed by the getter member 51. Radiation current (electron flow) from the emitter electrode 44 therefore reduces.

(2) As molecules attach to or emit from the surface of the emitter electrode 44, a magnitude of the radiation current from the emitter electrode 44 fluctuates and becomes unstable.

(3) As the emitter electrode 44 is bombarded with ions, the emitter electrode 44 is sputtered and the tip of the emitter electrode 44 deforms. As the tip of the emitter electrode 44 is rounded, an electric field is hard to be concentrated and the performance of the field emission element is degraded.

(4) In order to maintain a high vacuum degree during the long span of one to ten years, a getter member 51 having a large area is required. As the large area getter member 51 is used, the flat panel display becomes large and the fluorescence radiation area (display area) becomes relatively small.


ÑÓÙÍÎÑÒÜ ÈÇÎÁÐÅÒÅÍÈß



It is an object of the present invention to provide a field emission element and a manufacture method thereof capable of improving the vacuum degree in the flat panel display and preventing molecules from being attached to the emitter surface.

According to one aspect of the present invention, there is provided a method of manufacturing a field emission element including a process of forming a lamination of a gate electrode and a getter film on a substrate.

In the field emission element, the gate electrode and getter film are laminated. The getter film in a flat panel display using such field emission elements is activated so that the vacuum degree near at the gate electrode can be raised. Since the gate electrode is generally positioned near at the tip of the emitter electrode, the vacuum degree near at the emitter electrode tip can also be raised.


ÊÐÀÒÊÎÅ ÎÏÈÑÀÍÈÅ ÐÈÑÓÍÊÎÂ



FIGS. 1A to 1O are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to a first embodiment of the invention.

FIGS. 2A to 2F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to a modification of the first embodiment of the invention.

FIGS. 3A to 3D are schematic cross sectional views illustrating the methods of reinforcing an emitter electrode by using a support substrate.

FIGS. 4A to 4F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

FIGS. 5A to 5F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

FIGS. 6A to 6F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

FIGS. 7A to 7F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

FIGS. 8A to 8L are schematic cross sectional views illustrating the manufacture steps of a field emission element (three-electrode element) according to a second embodiment of the invention.

FIG. 9 is a schematic perspective view of the field emission element shown in FIG. 8L.

FIGS. 10A to 10D are schematic cross sectional views illustrating the manufacture steps of a field emission element (three-electrode element) according to modification of the second embodiment of the invention.

FIGS. 11A to 11I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to a third embodiment of the invention.

FIGS. 12A to 12I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to a modification of the third embodiment of the invention.

FIGS. 13A to 13I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to another modification of the third embodiment of the invention.

FIGS. 14A to 14I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to another modification of the third embodiment of the invention.

FIGS. 15A to 15F are schematic cross sectional views illustrating the conventional manufacture steps of a field emission element.

FIG. 16 is a schematic cross sectional view of a flat panel display using field emission elements.


ÏÎÄÐÎÁÍÎÅ ÎÏÈÑÀÍÈÅ ÏÐÅÄÏÎ×ÒÈÒÅËÜÍÛÕ ÂÀÐÈÀÍÒΠÎÑÓÙÅÑÒÂËÅÍÈß



FIGS. 1A to 1O are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to the first embodiment of the invention. A two-electrode element has an emitter electrode and a gate electrode.

As shown in FIG. 1A, a substrate 20 is made of a starting substrate 20a and a first lamination film 20b formed thereon. By thermally oxidizing the starting substrate 20a made of Si, the first lamination film 20b made of SiO.sub.2 can be formed 0.05 .mu.m thick.

For the thermal oxidation, for example, wet (water vapor) oxidation is performed in a vertical diffusion furnace at a hydrogen flow rate of 19 slm, an oxygen flow rate of 19 slm, and a temperature of 1000.degree. C.

Next, a getter material layer 20c of Ti is deposited on the first lamination film 20b to a thickness of 0.05 .mu.m by sputtering. This sputtering is performed in a DC sputtering system using Ti as a target while Ar gas is introduced.

Next, as shown in FIG. 1B, a first sacrificial film (antireflection film) 22 of SiN.sub.x is deposited on the getter material layer 20c to a thickness of 0.12 .mu.m by reactive sputtering. The antireflection film 22 has an antireflection function for i-line ray at the surface of the getter material layer 20c. Sputtering for the antireflection film (SiN.sub.x film) 22 is performed in an RF sputtering system by using Si as a target while N.sub.2 +Ar gas is introduced. SiN.sub.x may be used as the target while Ar gas is introduced. The SiN.sub.x film may be formed by plasma CVD.

Next, as shown in FIG. 1C, a resist film 22c having a predetermined pattern is formed on the antireflection film 22 by photolithography, the resist film 22c having a hole 23. More specifically, a resist film is first coated on the whole surface of the antireflection film 22 and then the resist film 22c having a predetermined pattern is formed through selective exposure and development.

The antireflection film 22 can lower the intensity of reflection light during exposure because of light absorption of this film 22 itself and/or interference between reflected light from the surface of this film 22 and reflected light from the underlying layer. Since reflection light hardly exposes an undesired area, the resist film 22c having a predetermined pattern can be formed at a high resolution.

The hole 23 has a generally vertical side wall (inner wall) and has a circular plan shape (as viewed from the top) having a diameter of 0.5 .mu.m.

Next, as shown in FIG. 1D, by using the resist film 22c as a mask, the antireflection film 22 is anisotropically etched to leave an antireflection film 22a having a predetermined pattern with a hole 23a. This hole 23a has a generally vertical side wall (inner wall) and has a circular plan shape (as viewed from the top) having a diameter of 0.5 .mu.m. The antireflection film 22a has two parts (laterally separated regions) as viewed in section of FIG. 1D. Since the resist film 22c was formed at a high resolution, the antireflection film 22a having a predetermined pattern can be formed also at a high resolution.

For example, etching the antireflection film 22a is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a magnetic field of 5 G (Gauss), a reaction chamber pressure of 60 mTorr (about 60.times.10.sup.-3.times.133.3 Pa), a cooling He pressure of 8 Torr (about 8.times.133.3 Pa) and an RF power of 500 W.

Next, as shown in FIG. 1E, the resist pattern 22c is removed to expose the upper surface of the antireflection film 22a.

Next, as shown in FIG. 1F, by using the antireflection film 22a as a mask, the getter material layer 20c is etched to form a getter film 20d having a predetermined pattern with a hole 23b. As will be later described, the hole 23b corresponds to a gate hole. By forming this hole 23b, a gate electrode made of the getter film 20d can be formed. Since the resist film 22c and antireflection film 22a were formed at a high resolution, the getter film 20d can be formed also at a high resolution.

For example, etching the getter material layer 20c is performed in a magnetron RIE system having a susceptor with a gas cooling mechanism, under the conditions of a Cl.sub.2 gas flow rate of 40 sccm, a pressure of 100 mTorr (about 100.times.10.sup.-3.times.133.3 Pa), an Rf power of 250 W, a magnetic field of 50 G (Gauss), and a cooling He pressure of 4 Torr (about 4.times.133.3 Pa).

It is not limited only to that the getter material layer 20c is etched by using only the antireflection film 22a as a mask. The getter material layer 20c may be etched by using the antireflection film 22a and resist film 22c formed on the antireflection film 22a, without removing the resist film 22c. In this case, the resist film 22c is removed thereafter.

Next, as shown in FIG. 1G, a second sacrificial film (insulating film) 24 of SiO.sub.2 is deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. For example, the atmospheric pressure CVD is performed by using O.sub.3 and TEOS (tetraetoxysilane, (C.sub.2 H.sub.5 O).sub.4 Si) as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 1H, the second sacrificial film 24 is anisotropically dry-etched (etched back) to leave a second sacrificial film 24a as a side spacer only on the side walls of the antireflection film 22a and getter film 20d. The "side wall" means a side wall of a hole formed by photolithography and etching, this definition being applied also in the following description. This etching exposes the upper area of the side wall of the antireflection film 22a. The upper surface of the starting substrate 20a is exposed and an etching process stops at the upper surface of the starting substrate 20a.

For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow rate of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G (Gauss), and an RF power of 700 W.

Next, as shown in FIG. 1I, a third sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The third sacrificial film 26 is deposited on the surfaces of the antireflection film 22a, side spacer 24a, first lamination film 20b and starting substrate 20a, inheriting (conformal to) the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. The first stage (upper) curve is dependent on the corner shape of the antireflection film 22a and the second stage (lower) curve is dependent on the surface shape of the side spacer 24a.

A cusp on the surface of the third sacrificial film 26 has an acute angle like a contact point between two circles or ellipses. This cusp is used as a mold for forming a two-stage shaped emitter electrode.

The "two-stage shaped emitter electrode" in this specification means an emitter electrode having a first circumferential surface continuous with the tip and a second circumferential surface continuous with the first circumferential surface, and a contour line of the first circumferential surface and the second circumferential surface, as viewed in vertical cross section of the emitter electrode, have different gradients at the boundary between the contour lines.

Next, as shown in FIG. 1J, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the third sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering. This reactive sputtering is performed in a DC sputtering system by using Ti as a target while gas of N.sub.2 +Ar is introduced.

With this embodiment, a two-stage shaped emitter electrode 27 can be formed. It is easy to make the tip of the two-stage shaped emitter electrode have a smaller radius of curvature than that of the one-stage shaped emitter electrode shown in FIG. 15F. As the radius of curvature of the emitter electrode tip is made small, an electric field can be easily concentrated upon the emitter electrode tip and the performance of the field emission element can be improved.

Next, as shown in FIG. 1K, a blanket film (second emitter electrode) 27c of W (tungsten) is deposited on the emitter electrode (first emitter electrode) 27 to a thickness of 0.2 .mu.m by CVD. For example, this CVD is performed by using WF.sub.6 +H.sub.2 +N.sub.2 +Ar gas as work gas at a pressure of 80 Torr (about 80.times.133.3 Pa) and a temperature of 450.degree. C.

Next, as shown in FIG. 1L, the blanket film 27c of W (tungsten) is etched back 0.2 .mu.m thick by using an RIE etcher to leave a blanket film 27d only in a surface recess of the emitter electrode 27 to planarize the surface of the emitter electrode 27. For example, this RIE (reactive ion etching) is performed in a magnetron RIE system by using SF.sub.6 +Ar+He as etching gas at a reaction chamber pressure of 280 mTorr (about 280.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 1M, a resistor layer 30 of Si is deposited about 0.2 .mu.m thick by sputtering, covering the emitter electrode 27 and blanket film 27d. By serially connecting the resistor layer 30 to the emitter electrode 27, the emission current of the emitter electrode (field emission cathode) 27 can be stabilized sufficiently.

For example, sputtering for the resistor layer (Si) 30 is performed in a DC sputtering system by using Si as a target while Ar gas is introduced. Instead of Si, high resistance material such as SiN.sub.x, SiO.sub.x and SiO.sub.x N.sub.y may be used as the material of the resistor layer 30. In this case, instead of Ar gas, sputtering is performed by using N.sub.2 +Ar gas, O.sub.2 +Ar gas or N.sub.2 +O.sub.2 +Ar gas.

Next, as shown in FIG. 1N, an emitter wiring layer 31 of Al is deposited on the resistor layer 30 to a thickness of 0.3 .mu.m by sputtering. This sputtering is performed in a DC sputtering system by using Al as a target while Ar gas is introduced.

Lastly, as shown in FIG. 1O, the whole of the starting substrate 20a, first lamination film 20b and side spacer 24a and part of the third sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral third sacrificial film 26a and expose the tip of the emitter electrode 27. The getter film 20d surrounds the tip of the emitter electrode 27.

For etching Si of the starting substrate 20a and the like, HF+HNO.sub.3 +CH.sub.3 COOH is used, and for etching SiO.sub.2 of the third sacrificial film 26 and the like, HF+NH.sub.4 F is used.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. Since the getter film (Ti film) 20d is a conductive film, it can function as the gate electrode. This field emission element has the emitter electrode 27 and gate electrode 20d.

The emitter electrode 27 is applied with a negative potential and an unrepresented anode electrode is applied with a positive potential. As a positive potential is applied to the gate electrode 20d, electrons can be emitted from the emitter electrode 27 toward the anode electrode.

After field emission elements are manufactured, a flat panel display such as shown in FIG. 16 is manufactured by the method similar to that described earlier. However, the getter member 51 shown in FIG. 16 is not necessary. After or before the inside of the flat display panel is evacuated and the air exhaust pipe is sealed, the getter film 20d (refer to FIG. 1O) of field emission elements is activated by heating them with a lamp or laser beam or by other light application, so that ambient molecules can be adsorbed. In this manner, the vacuum degree in the flat panel display can be improved.

Other molecules such as He passing through the transparent substrate and support substrate and entering the inside of the flat display panel or other molecules such as H.sub.2 O, O.sub.2, and N.sub.2 emitted in the flat panel display are also adsorbed by the getter film 20d. As a result, the vacuum degree in the flat panel display is prevented from being lowered and the flat panel display is prolonged its lifetime.

The getter member 51 shown in FIG. 16 is disposed at the corner in the flat panel display, remotely from the emitter electrodes, so that the function of the getter member cannot be sufficiently demonstrated.

According to the embodiment, the getter film 20d surrounds near the tip of the emitter electrode so that the following advantages can be obtained.

(1) The getter film 20d adsorbs molecules near the emitter electrode 27 and prevents molecules from attaching the surface of the emitter electrode 27. Since the vacuum degree near at the emitter electrode 27 is improved, radiation current (electron flow) from the emitter electrode 27 can be prevented from being reduced.

(2) Since the vacuum degree near the emitter electrode 27 can be improved, a magnitude of the radiation current of the emitter electrode 27 can be prevented from fluctuating.

(3) Since the vacuum degree near the emitter electrode 27 can be improved, it is possible to prevent the emitter electrode 27 from being deformed through sputtering with ions.

(4) Since the getter film 20d is formed in the field emission element, the size of the flat panel display can be made smaller than when the getter member is provided remotely from field emission elements.

(5) The uniformity and reproductivity of characteristics of field emission elements in each flat display panel and between flat display panels can be improved. Flicker to be caused by luminance differences of a flat display panel can be reduced.

FIGS. 2A to 2F are schematic cross sectional views illustrating other manufacture steps of the field emission element (two-electrode element) according to the first embodiment of the invention.

As shown in FIG. 2A, similar to the first embodiment, by photolithography and etching, a first lamination film 20b of SiO.sub.2 is formed on a starting substrate 20a of Si, and a first gate electrode 25a, a second gate electrode 25b and a getter film 22a respectively having a predetermined pattern are sequentially formed on the first lamination film 20b.

More specifically, on the surface of the starting substrate 20a of Si, the first lamination film 20b is formed through thermal oxidation. On the first lamination film 20b, a first gate electrode film is deposited by CVD to a thickness of 0.15 .mu.m, the first gate electrode film being made of polysilicon doped with P (phosphorous) or B (boron). On the first gate electrode film, a second gate electrode film of WSi.sub.x is deposited by CVD to a thickness of 0.15 .mu.m. On the second gate electrode film, a first sacrificial film (getter material layer) of Ti is deposited by sputtering to a thickness of 0.04 .mu.m. Thereafter, by photolithography and etching, the first and second gate electrode films and getter material layer are patterned. This patterning process forms a hole 23 through the getter material layer and first and second gate electrode films, the hole 23 reaching the surface of the first lamination film 20d. A hole formed through the first and second gate electrode films corresponds to the gate hole. Namely, this patterning process forms a two-layer structure gate electrode constituted of the first gate electrode 25a made of the first gate electrode film with a gate hole and the second gate electrode 25b made of the second gate electrode film with a gate hole. This patterning process also forms the getter film 22a shown in FIG. 2A.

Sputtering for the getter material layer (Ti layer) is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. Instead of Ti, the getter film 22a may be made of Ta or Zr (zirconium).

In the first embodiment (refer to FIG. 1O), the getter film is formed as the gate electrode. In this modification of the first embodiment, the getter film 22a is formed over the gate electrodes 25a and 25b.

Next, as shown in FIG. 2B, a second sacrificial film (insulating film) 24 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD.

Next, as shown in FIG. 2C, the second sacrificial film 24 is anisotropically dry-etched to leave a second sacrificial film 24a as a side spacer only on the side wall of the first gate electrode 25a. This etching process exposes the side walls of the getter film 22a and second gate electrode 25b and a partial surface area of the first lamination film (etching stopper film) 20. For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 2D, a third sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The third sacrificial film 26 is deposited on the surfaces of the starting substrate 20a, first lamination film 20c, side spacer 24a, second gate electrode 25b and getter film 22a, being conformal to the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. This surface of the third sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 2E, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the third sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering. This reactive sputtering is performed in a DC sputtering system by using Ti as a target while gas of N.sub.2 +Ar is introduced.

Next, as shown in FIG. 2F, the whole of the starting substrate 20a, first lamination film 20c and side spacer 24a and part of the third sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral third sacrificial film 26a and expose the tip of the emitter electrode 27.

For etching Si of the starting substrate 20a and the like, HF+HNO.sub.3 +CH.sub.3 COOH is used, and for etching SiO.sub.2 of the third sacrificial film 26 and the like, HF+NH.sub.4 F is used.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. Since the getter film (Ti film) 22a is a conductive film, it can function as the gate electrode together with the first and second gate electrodes 25a and 25b. This field emission element has the emitter electrode 27 and gate electrodes 25a, 25b and 22a. The getter film 22a is formed over the gate electrodes 25a and 25b and surrounds near the tip of the emitter electrode 27.

Similar to the first embodiment, after field emission elements are manufactured, a flat panel display such as shown in FIG. 16 is manufactured. After or before the air exhaust pipe of the flat panel display is sealed, the getter film 22a of field emission elements is activated by heating them with a lamp or laser beam or by other light application, so that ambient molecules can be adsorbed.

For example, light may be applied to the gate electrodes 25a and 25b to heat them and heat the getter film 22a through heat conduction. If the getter film 22a made of a Ti film or the like is heated to 400.degree. C. or higher, it can be activated. Light is preferably applied to the substrate along a direction perpendicular to the substrate surface. However, it may be applied obliquely. The getter film 22a may be activated by baking the substrate in a furnace.

FIGS. 3A to 3D are schematic cross sectional views illustrating four methods of reinforcing the emitter electrode 27 by a support substrate 28. Since the emitter electrode 27 has a small thickness of about 0.2 .mu.m it may preferably be reinforced with the support substrate 28.

FIG. 3A illustrates the first method. A recess of the emitter electrode 27 of the field emission element manufactured to the state shown in FIG. 2E is filled with a planarizing film 29a, e.g., an SOG (spin on glass) film. Thereafter, the planarizing film 29a is etched back through CMP (chemical-mechanical polishing) or RIE to planarize the surface of the emitter electrode 27. Instead of an SOG film, the planarizing film 29a may be formed by reflowing PSG (phosphosilicate glass) or BPSG (borophosphosilicate glass).

Next, a support substrate 28 is bonded to the emitter electrode by electrostatic bonding or with adhesive. The support substrate 28 is made of, for example, glass, quartz, or Al.sub.x O.sub.y (alumina or sapphire). Thereafter, similar to the process shown in FIG. 2F, the substrate 20a and the like are removed to expose the tip of the emitter electrode 27 as shown in FIG. 3A.

FIG. 3B illustrates the second method. In the state of the field emission element shown in FIG. 2E, adhesive 29b made of, e.g., low melting point glass or epoxy resin is flowed on the emitter electrode 27 to bond the emitter electrode 27 and a support substrate 28. The adhesive 29b also provides a function of planarizing the surface of the emitter electrode 27. Thereafter, similar to the process shown in FIG. 2F, the substrate 20a and the like are removed to expose the tip of the emitter electrode 27 as shown in FIG. 3B.

FIG. 3C illustrates the third method. After the field emission element shown in FIG. 2E is manufactured, a recess of the emitter electrode 27 is filled with a planarizing film 29a made of, for example, SOG. Thereafter, the planarizing film 29a is etched back to planarize the surface of the emitter electrode 27. Next, an adhesive layer 29b made of, for example, Al, is formed on the emitter electrode 27, and a support substrate 28 is bonded. Thereafter, similar to the process shown in FIG. 2F, the substrate 20a and the like are removed to expose the tip of the emitter electrode 27 as shown in FIG. 3C.

FIG. 3D illustrates the fourth method. Similar to the processes shown in FIGS. 1K and 1L, after the blanket film (second emitter electrode) 27c of W is formed on the emitter electrode (first emitter electrode) 27 to a thickness of 0.2 .mu.m by CVD, the blanket film 27c is etched back 0.2 .mu.m thick by using an RIE etcher to leave the blanket film 27d. Similar to the process shown in FIG. 3C, a recess of the blanket film 27d is filled with a planarizing film 29a such as SOG and thereafter the planarizing film 29a is etched back to planarize the surface of the blanket film 27d. Next, the emitter electrode 27, blanket film 27d and planarizing film 29a are bonded to a support substrate 28 with adhesive 29b. Thereafter, similar to the process shown in FIG. 2F, the substrate 20a and the like are removed while the getter film 22 is wet-etched, to leave a peripheral getter film 22b and expose the tip of the emitter electrode 27 as shown in FIG. 3D.

Etching the getter film 22a of Ti is performed by using a mixture solution of sulfuric acid and hydrogen peroxide, while the mixture solution is heated to about 120.degree. C. In place of the mixture solution of sulfuric acid and hydrogen peroxide, the etching may be performed by using hydrochloric acid, phosphoric acid or hydrofluoric acid.

FIGS. 4A to 4F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to a modification of the first embodiment of the invention.

As shown in FIG. 4A, similar to the first embodiment, by photolithography and etching, a gate electrode 25a and a first sacrificial film (getter film) 22a having a predetermined pattern are formed on a starting substrate 20e. The gate electrode 25a has a gate hole 23.

More specifically, on the surface of the starting substrate 20e of Si, a gate electrode film of WSi.sub.x is deposited to a thickness of 0.3 .mu.m by sputtering, and on the gate electrode film a getter material layer of Ti is deposited to a thickness of 0.05 .mu.m by sputtering. Thereafter, by photolithography and etching, the gate electrode film and getter material layer are patterned. This patterning process forms the getter film 22a and gate electrode 25a shown in FIG. 4A. The getter film (Ti film) 22a is formed on the gate electrode (WSi.sub.x film) 25a.

For example, this etching process is performed in a magnetron RIE system by using Cl.sub.2 as etching gas under the conditions of a reaction chamber pressure of 100 mTorr (about 100.times.10.sup.-3.times.133.3 Pa), a Cl.sub.2 gas flow of 40 sccm, a substrate cooling He pressure of 4 Torr (about 4.times.133.3 Pa), a magnetic field of 50 G, and an RF power of 250 W.

Sputtering for the gate electrode film (WSi.sub.x film) is performed in a DC sputtering system by using WSi.sub.x as a target while Ar gas is introduced. Sputtering for the getter material layer (Ti film) is performed in a DC sputtering system using Ti as a target while Ar gas is introduced.

Next, as shown in FIG. 4B, a second sacrificial film (insulating film) 24 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD.

Next, as shown in FIG. 4C, the second sacrificial film 24 is anisotropically dry-etched to leave a second sacrificial film 24a as a side spacer only on the side wall of the gate electrode 25a and/or the side wall of the getter film 22a. This etching process exposes the side wall of the getter film 22a and a partial surface of the starting substrate 20e.

For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 4D, a third sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The third sacrificial film 26 is deposited on the surfaces of the starting substrate 20e, side spacer 24a and getter film 22a, being conformal to the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. This surface of the third sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 4E, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the third sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering.

Lastly, as shown in FIG. 4F, the whole of the starting substrate 20e and side spacer 24a and part of the third sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral third sacrificial film 26a and expose the tip of the emitter electrode 27.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. Since the getter film (Ti film) 22a is a conductive film formed on the gate electrode (WSi.sub.x film) 25a, it can function as the gate electrode together with the gate electrode 25a. This field emission element has the emitter electrode 27 and gate electrodes 25a and 22a. After or before field emission elements are hermetically accommodated in the flat panel display, the getter film 22a of field emission elements is activated by heating them or by light application.

FIGS. 5A to 5F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

As shown in FIG. 5A, similar to the first embodiment, by photolithography and etching, a gate electrode 25a, a first sacrificial film (getter film) 22a and a second sacrificial film (insulating film) 22c respectively having a predetermined pattern are formed on a starting substrate 20e of Si.

More specifically, on the surface of the starting substrate 20e of Si, a gate electrode film of WSi.sub.x is deposited to a thickness of 0.3 .mu.m by sputtering, and on the gate electrode film a getter material layer of Ti is deposited to a thickness of 0.04 .mu.m by sputtering, and on the getter material layer a second sacrificial film of SiN.sub.x is deposited to a thickness of 0.3 .mu.m by reactive sputtering. Thereafter, by photolithography and etching, the gate electrode film, getter material layer and second sacrificial film are patterned. This patterning process forms a hole 23 through the second sacrificial film to . the surface of the starting substrate 20e. A hole formed through the gate electrode film corresponds to the gate hole. This patterning process therefore forms the gate electrode 25a having the gate hole, and also forms the getter film 22a and second sacrificial film 22c shown in FIG. 5A. The getter film 22a is formed between the gate electrode 25a and second sacrificial film 22c.

If the thickness of SiN.sub.x is set to 0.3 .mu.m, the antireflection effect can be obtained. A resolution of photolithography and an etching precision are therefore improved.

Sputtering for the getter material layer (Ti film) is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. Reactive sputtering for the second sacrificial film (SiN.sub.x film) is performed in a DC sputtering system by using Si as a target while N.sub.2 +Ar gas is introduced. The second sacrificial film (SiN.sub.x film) may be deposited by plasma CVD or low pressure CVD.

Next, as shown in FIG. 5B, a third sacrificial film (insulating film) 24 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD.

Next, as shown in FIG. 5C, the third sacrificial film 24 is anisotropically dry-etched to leave a third sacrificial film 24a as a side spacer only on the side wall of the gate electrode 25a and/or the side wall of the getter film 22a. This etching process exposes the side wall of the getter film 22a and the side wall of the getter film 22a and a partial surface of the starting substrate 20e.

For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 5D, a fourth sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The fourth sacrificial film 26 is deposited on the surfaces of the starting substrate 20e, side spacer 24a, getter film 22a, and second sacrificial film 22c, being conformal to the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. This surface of the fourth sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 5E, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the fourth sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering.

Lastly, as shown in FIG. 5F, the whole of the starting substrate 20e and side spacer 24a and part of the fourth sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral fourth sacrificial film 26a and expose the tip of the emitter electrode 27.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. Since the getter film (Ti film) 22a is a conductive film formed on the gate electrode 25a, it can function as the gate electrode together with the gate electrode 25a. This field emission element has the emitter electrode 27 and gate electrodes 25a and 22a. After or before field emission elements are hermetically accommodated in the flat panel display, the getter film 22a of field emission elements is activated by heating them or by light application.

FIGS. 6A to 6F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

As shown in FIG. 6A, similar to the first embodiment, by photolithography and etching, a gate electrode 25a and a first sacrificial film (getter film) 22a respectively having a predetermined pattern are formed on a starting substrate 20e of Si.

More specifically, on the surface of the starting substrate 20e of Si, a gate electrode film is deposited by CVD to a thickness of 0.15 .mu.m, the gate electrode film being made of polysilicon doped with P (phosphorous) or B (boron). On the gate electrode film, a getter material layer of Ti is deposited by sputtering to a thickness of 0.04 .mu.m. Thereafter, by photolithography and etching, the gate electrode film and getter material layer are patterned. This patterning process forms a hole 23 through the getter material layer, the hole 23 reaching the surface of the starting substrate 20e. A hole formed through the gate electrode film corresponds to the gate hole. Namely, this patterning process forms the gate electrode 25a having the gate hole and the getter film 22a shown in FIG. 6A.

Next, as shown in FIG. 6B, a second sacrificial film (insulating film) 24 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD.

Next, as shown in FIG. 6C, the second sacrificial film 24 is anisotropically dry-etched to leave a second sacrificial film 24a as a side spacer only on the side wall of the gate electrode 25a. This etching process exposes the side walls of the getter film 22a and gate electrode 25a, and stops when the substrate 20f is trenched 0.1 .mu.m deep. This etching process forms the substrate 20f having a recess. For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 6D, a third sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The third sacrificial film 26 is deposited on the surfaces of the substrate 20f, side spacer 24a, gate electrode 25a, and getter film 22a, being conformal to the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. This surface of the third sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 6E, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the third sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering.

Lastly, as shown in FIG. 6F, the whole of the starting substrate 20f and side spacer 24a and part of the third sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral third sacrificial film 26a and expose the tip of the emitter electrode 27.

This two-electrode element has the emitter electrode 27 positioned lower (as viewed in FIG. 6F) relative to the gate electrode 25a than the two-electrode element shown in FIG. 4F, because the recess is formed in the substrate 20f at the etching process shown in FIG. 6C.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. Since the getter film (Ti film) 22a is a conductive film, it can function as the gate electrode. This field emission element has the emitter electrode 27 and gate electrodes 25a and 22a and can be used with a flat display panel. After or before field emission elements are hermetically accommodated in the flat panel display, the getter film 22a of field emission elements is activated by heating them or by light application.

FIGS. 7A to 7F are schematic cross sectional views illustrating the manufacture steps of a field emission element (two-electrode element) according to another modification of the first embodiment of the invention.

As shown in FIG. 7A, similar to the first embodiment, by photolithography and etching, a gate electrode/getter film 25a having a predetermined pattern is formed on a starting substrate 20e of Si.

More specifically, on the surface of the starting substrate 20e of Si, a gate electrode film/getter material layer is deposited by sputtering to a thickness of 0.3 .mu.m. Thereafter, by photolithography and etching, the gate electrode film/getter material layer is patterned. This patterning process forms a hole 23 through the gate electrode film/getter material layer, the hole 23 reaching the surface of the starting substrate 20e. The hole formed through the gate electrode film/getter material layer corresponds to the gate hole. Namely, this patterning process forms the gate electrode/getter film 25a having the gate hole shown in FIG. 7A.

Next, as shown in FIG. 7B, a second sacrificial film (insulating film) 24 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD.

Next, as shown in FIG. 7C, the second sacrificial film 24 is anisotropically dry-etched to leave a second sacrificial film 24a as a side spacer only on the side wall of the gate electrode/getter film 25a. This etching process exposes the upper area of the side wall of the gate electrode/getter film 25a, and stops when the substrate 20f is trenched 0.1 .mu.m deep. This etching process forms the substrate 20f having a recess. For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 7D, a third sacrificial film (insulating film) 26 of SiO.sub.2 is isotrbpically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The third sacrificial film 26 is deposited on the surfaces of the substrate 20f, side spacer 24a, gate electrode/getter film 25a, being conformal to the surface topology. The surface topology of the third sacrificial film 26 has curves of two stages. This surface of the third sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 7E, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the third sacrificial film 26 to a thickness of about 0.05 .mu.m by reactive sputtering.

Lastly, as shown in FIG. 7F, the whole of the starting substrate 20f and side spacer 24a and part of the third sacrificial film 26 are etched and removed from the bottom side, to leave a peripheral third sacrificial film 26a and expose the tip of the emitter electrode 27.

With the above processes, a field emission element (two-electrode element) having the two-stage shaped emitter electrode 27 is completed. The gate electrode/getter film (Ti film) 25a functions as the gate electrode and getter film. This field emission element has the emitter electrode 27 and gate electrode 25a and can be used with a flat display panel. After or before field emission elements are hermetically accommodated in the flat panel display, the getter film 25a of field emission elements is activated by heating them or by light application.

The manufacture steps of a field emission element (two-electrode element) having an emitter electrode and a gate electrode have been described above. In the following, the manufacture steps of a three-electrode element as an example of another field emission element will be described.

FIGS. 8A to 8L are schematic cross sectional views illustrating the manufacture steps of a field emission element (three-electrode element) according to the second embodiment of the invention. A three-electrode element has an emitter electrode, a gate electrode and an anode electrode.

As shown in FIG. 8A, a substrate 20 is made of a starting substrate 20a and an anode electrode film 20b formed thereon. On the surface of the starting substrate 20a made of SiO.sub.2 or the like, the anode electrode film 20b of WSi.sub.x is deposited to a thickness of 0.05 .mu.m by sputtering. Sputtering for the anode electrode film (WSi.sub.x film) 20b is performed in a DC sputtering system by using WSi.sub.x as a target while Ar gas is introduced.

Next, a first sacrificial film (insulating film) 21 of SiO.sub.2 is deposited on the anode electrode film 20b by CVD, and on the first sacrificial film a gate electrode film of WSi.sub.x is deposited to a thickness of 0.3 .mu.m by sputtering similar to the above.

Next, as shown in FIG. 8B, a second sacrificial film (getter material layer) 22b of Ti is deposited on the gate electrode film 25 to a thickness of 0.04 .mu.m by sputtering. Sputtering for the getter material layer (Ti film) 22b is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. In place of Ti, the getter material layer 22b may be formed by using Ta or Zr (zirconium).

Next as shown in FIG. 8C, a resist film 22c having a predetermined pattern with a hole 23 is formed on the getter material layer through photolithography.

Next, as shown in FIG. 8D, by using the resist film 22c as a mask, the getter material layer 22b is anisotropically etched to leave a getter film 22a having a predetermined pattern with a hole 23a. This hole 23a has a generally vertical side wall and has a circular plan shape (as viewed from the top) having a diameter of 0.5 .mu.m.

Next, as shown in FIG. 8E, the resist pattern 22c is removed to expose the upper surface of the getter film 22a.

Next, as shown in FIG. 8F, by using the getter film 22a as a mask, the gate electrode film 25 is anisotropically etched to form a gate electrode 25a having a predetermined pattern with a hole (gate hole) 23b.

When the gate electrode film 25 is etched, the resist film 22c and getter film 22a may be used as the mask, by leaving the resist film 23c on the getter film 22a. In this case, the resist film 22c is removed thereafter.

Next, as shown in FIG. 8G, a third sacrificial film (insulating film) 24 of SiO.sub.2 is deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. For example, the atmospheric pressure CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 8H, the third sacrificial film 24 is anisotropically dry-etched (etched back) to leave a third sacrificial film 24a as a side spacer only on the side wall of the gate electrode 25a and/or the side wall of the getter film 22a. This etching exposes the upper area of the side wall of the getter film 22a and a partial surface area of the first sacrificial film 21.

For example, this etching is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

Next, as shown in FIG. 8I, a fourth sacrificial film (insulating film) 26 of SiO.sub.2 is isotropically deposited over the whole upper surface of the substrate to a thickness of 0.15 .mu.m by atmospheric pressure CVD. The fourth sacrificial film 26 is deposited on the surfaces of the first sacrificial film 21, side spacer 24a and getter film 22a, being conformal to the surface topology. The surface topology of the fourth sacrificial film 26 has curves of two stages. This surface of the fourth sacrificial film 26 is used as a mold for forming a two-stage shaped emitter electrode.

Next, as shown in FIG. 8J, an emitter electrode 27 of, for example, TiN.sub.x, is deposited on the fourth sacrificial film 26 to a thickness of about 0.05.mu.m by reactive sputtering. This reactive sputtering is performed in a DC sputtering system by using Ti as a target while gas of N.sub.2 +Ar is introduced.

Next, a resist film (not shown) having a predetermined pattern is formed on the emitter electrode 27 by photolithography. As shown in FIG. 8K, by using this resist film as an etching mask, slit openings 32 are formed by RIE through the emitter electrode 27a on both sides thereof in areas where the emitter electrode 27a is not used as the cathode. An emitter electrode 27b shown in FIG. 8K is an emitter electrode formed outside of the slit openings 32. For example, RIE is performed in a magnetron RIE system by using Cl.sub.2 as etching gas at a reaction chamber pressure of 125 mTorr (about 125.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 8L, part of the fourth sacrificial film 26, the whole of the side spacer 24a, and part of the first sacrificial film 21 are isotropically wet etched and removed through the slit openings 32 to leave a peripheral fourth sacrificial film 26a and first sacrificial film 21a.

This etching exposes the emitter electrode 27a, gate electrode 25a and anode electrode film 20b. Since the getter film 22a electrically connects the gate electrode 25a, a resistance of the gate wiring line can be lowered.

FIG. 9 is a schematic perspective view partially in section of the three-electrode element shown in FIG. 8L. The emitter electrode 27a is continuous with the emitter electrode 27b and supported by the latter. The gate electrode 25a and getter film 22a have circular holes (gate holes) near at the tip of the emitter electrode 27a. The getter film 22a surrounds the tip of the emitter electrode 27a. The tip of the emitter electrode 27a has a needle-like sharp edge near the gate hole of the gate electrode 25a.

The three-electrode element has the emitter electrode 27a as a cathode and an anode electrode film 20b as an anode. As a positive potential is applied to the gate electrode 25a, electrons can be emitted from the emitter electrode 27a toward the anode electrode film 20b.

Also in the case of the three-electrode element, by forming the getter film 22a near the tip of the emitter electrode 27a, the vacuum degree in the space near the emitter electrode 27a can be raised.

FIG. 10A is a schematic cross sectional view showing another example of the three-electrode element. This three-electrode element is fundamentally the same as the three-electrode element (shown in FIG. 8L), excepting that the gate electrode 25a is made of a WSi.sub.x film having a thickness of 0.3 .mu.m and the getter film 22a is made of a Ti film having a thickness of 0.2 .mu.m. The other structures are the same.

FIG. 10B is a schematic cross sectional view showing another example of the three-electrode element. This three-electrode element is fundamentally the same as the three-electrode element (shown in FIG. 8L), excepting that the gate electrode 25a is made of a WSi.sub.x film having a thickness of 0.3 .mu.m and the getter film 22a is made of a Ta film having a thickness of 0.15 .mu.m. Another different point is that in the etching process shown in FIG. 8H, an over-etch is performed to form a recess having a depth of 0.1 .mu.m in the first sacrificial film 21. The emitter electrode 27a can therefore be lowered relative to the gate electrode 25a as viewed in FIG. 8H. The other structures are the same. For example, this over-etch is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

FIG. 10C is a schematic cross sectional view showing another example of the three-electrode element. This three-electrode element is fundamentally the same as the three-electrode element (shown in FIG. 8L), excepting that the getter film 22a is made of a Ti film and that in the etching process shown in FIG. 8H, an over-etch is performed to form a recess having a depth of 0.1 .mu.m in the first sacrificial film 21. The other structures are the same. For example, this over-etch is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

FIG. 10D is a schematic cross sectional view showing another example of the three-electrode element. This three-electrode element is fundamentally the same as the three-electrode element (shown in FIG. 8L), excepting that the two layers of the gate electrode and getter film are made of one layer of a gate electrode/getter film 25a of Ti or the like and that in the etching process shown in FIG. 8H, an over-etch is performed to form a recess having a depth of 0.1 .mu.m in the first sacrificial film 21. The other structures are the same. For example, this over-etch is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas under the conditions of a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa), a CHF.sub.3 /CO.sub.2 /Ar flow ratio of 60/10/30 (sccm), a substrate cooling He pressure of 8 Torr (about 8.times.133.3 Pa), a magnetic field of 30 G, and an RF power of 700 W.

In the first and second embodiments, the getter film in a field emission element is formed under or on the gate electrode or by making the gate electrode of getter material. Since the getter film is formed surrounding the tip of the emitter electrode, molecules near the emitter electrode can be adsorbed and the vacuum degree can be raised.

By raising the vacuum degree near the emitter electrode, radiation current from the emitter electrode can be prevented from being lowered, a magnitude of the radiation current can be prevented from fluctuating, and the emitter electrode can be prevented from being deformed through sputtering.

Furthermore, the uniformity and reproductivity of characteristics of field emission elements in each flat display panel and between flat display panels can be improved and flicker to be caused by luminance differences of a flat display panel can be reduced.

Still further, since the getter film is provided in a field emission element, the size of a flat panel display can be made smaller than when the getter material is provided outside of field emission elements. It is not limited only to that the getter film is formed directly on the gate electrode, but an insulating film or other film may be formed between the gate electrode and getter film.

A side spacer made of Ti, Ta or Zr can be used as a getter film.

For the elements shown in FIGS. 2F, 4F, and 6F, the gate electrode may be heated by light application to heat and activate the getter film through heat conduction. For the elements shown in FIGS. 8L and 10D, the emitter electrode may be heated by light application to heat and activate the getter film through heat conduction.

The material of the gate electrode and emitter electrode may be semiconductor such as polysilicon and amorphous silicon, silicide such as SWi.sub.x, TiSi.sub.x and MoSi.sub.x, metal such as Al, Cu, W, Mo and Ni, and conductive nitride such as TiN.sub.x.

FIGS. 11A to 11I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to the third embodiment of the invention.

As shown in FIG. 11A on a substrate 20 of Si or the like, a gate electrode film 25 of 0.2 .mu.m in thickness is formed by CVD or the like. The gate electrode film 25 is, for example, a polysilicon film doped with phosphorous or boron. For example, a polysilicon film is formed by CVD by flowing SiH.sub.4 gas diluted with He at a flow rate of 0.6 slm under the conditions of a chamber temperature of 625.degree. C. and a pressure of about 225 mTorr (30 Pa). Next, in order to lower the resistance of the gate electrode film 25, phosphorous is diffused into the polysilicon film in a vertical diffusion furnace under the conditions of POCl.sub.3 at 50 mg/min, N.sub.2 at 20 slm, O.sub.2 at 0.1 slm, and a temperature of 850.degree. C.

It is preferable to form a silicon oxide film or silicon nitride film between the Si substrate 20 and gate electrode film 25 as an etching stopper when the Si substrate 20 is etched.

Next, as shown in FIG. 11B, by using a resist pattern (not shown) as a mask, the gate electrode film 25 is etched to form a gate electrode 25a with a hole (gate hole) 23. The hole (gate hole) is cylindrical and has a diameter of about 0.5 .mu.m and a depth of about 0.2 .mu.m. Thereafter, the resist pattern is removed.

Next, as shown in FIG. 11C, a getter material layer 22a of Ti is isotropically formed over the whole upper surface of the substrate by sputtering. The getter material layer 22a has a thickness of about 0.15 .mu.m. Sputtering is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. In order to improve the step coverage of the getter material layer 22a, it is preferable to form the getter material layer 22a by long throw sputtering, ionic beam sputtering, CVD, or plating. The getter material layer 22a also functions as a second gate electrode film.

Next, the getter material layer 22a is anisotropically etched (etched back). As shown in FIG. 11D, this etch-back process forms a getter film 22b only on the side wall of the gate electrode 25a. The getter film 22b also functions as a side spacer. The etch-back process is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using Cl.sub.2 as etching gas at a reaction chamber pressure of 125 mTorr (about 125.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 1E, a first sacrificial film (insulating film) 21 of a silicon oxide film is deposited over the whole upper surface of the substrate by atmospheric pressure CVD. The first sacrificial film 21 has a thickness of about 0.1 .mu.m. For example, the atmospheric pressure CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 11F, a first emitter electrode 27 of TiN.sub.x is deposited on the first sacrificial film 21 by reactive sputtering. The first emitter electrode 27 has a thickness of about 0.05 .mu.m. The reactive sputtering is performed in a DC sputtering system by using Ti as a target while N.sub.2 +Ar gas is introduced.

Next, as shown in FIG. 11G, a blanket film 27c of W (tungsten) is isotropically deposited on the first emitter electrode 27 by CVD. The blanket film 27c has a thickness of about 0.2 .mu.m and functions also as a second emitter electrode. For example, CVD is performed under the conditions of source gas of WF.sub.6 +H.sub.2 +N.sub.2 +Ar, a pressure of 80 Torr (about 80.times.133.3 Pa) and a temperature of 450.degree. C.

Next, as shown in FIG. 11H, the second emitter electrode 27c is anisotropically etched (etched back) about 0.2 .mu.m thick to leave a second emitter electrode 27d only in a recess of the first emitter electrode 27. A flat surface of the first emitter electrode 27 is exposed. This etch-back is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using SF.sub.6 +Ar+He as etching gas at a reaction chamber pressure of 280 mTorr (about 280.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 11I, the whole of the substrate 20 and part of the first sacrificial film 21 are etched and removed to leave a peripheral first sacrificial film 21b and expose the tip of the first emitter electrode 27. The substrate 20 made of Si is etched by using HF+HNO.sub.3 +CH.sub.3 COOH. The first sacrificial film 21 of a silicon oxide film is etched by HF+NH.sub.4 F.

With the above processes, a field emission element of a two-electrode structure having the emitter electrodes 27 and 27d and gate electrode 25a is completed. Since the getter film 22b of Ti is a conductive film, it functions as a gate electrode together with the gate electrode 25a. This field emission element has the emitter electrodes 27 and 27d and gate electrodes 25a and 22b. The getter film 22b is formed on the side wall of the gate electrode 25a and surrounds the tip of the first emitter electrode 27.

By heating the getter film 22 by light application or the like, the getter film 22b can be activated. The getter film 22b adsorbs ambient molecules so that the vacuum degree in the flat panel display can be improved.

FIGS. 12A to 12I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to a modification of the third embodiment of the invention.

As shown in FIG. 12A, on a substrate 20 of Si or the like, a getter material layer 20c is formed by sputtering. The getter material layer 20c has a thickness of 0.1 .mu.m, and functions also as a first gate electrode film. The sputtering is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. It is preferable to form a silicon oxide film or silicon nitride film between the substrate 20 and getter material layer 20c as an etching stopper layer.

Next, on the getter material layer 20c, a polysilicon layer doped with phosphorous or boron is formed about 0.2 .mu.m thick by sputtering. This polysilicon film corresponds to a gate electrode film. For example, the sputtering is performed in a DC sputtering system by using silicon doped with phosphorous or boron as a target while Ar gas is introduced.

Next, by using a resist pattern (not shown) as a mask, the polysilicon film doped with phosphorous or boron is etched to form a gate electrode 25a with a hole (gate hole) 23. The hole (gate hole) 23 is cylindrical and has a diameter of about 0.5 .mu.m and a depth of about 0.2 .mu.m. Thereafter, the resist pattern is removed.

Next, as shown in FIG. 12B, a first sacrificial film (insulating film) 21 of a silicon oxide film is deposited on the gate electrode 25a and getter film 20c to a thickness of 0.15 .mu.m by CVD. For example, this CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 12C, the first sacrificial film 21 is anisotropically etched (etched back) to leave a first sacrificial film 21 a only on the side wall of the gate electrode 25a as a side spacer. For example, this etch-back is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas at a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 12D, by using the gate electrode 25a and side spacer 21 a as a mask, the getter material layer 20c is etched to form a getter film 20d under the gate electrode 25a and side spacer 21a. This etching is performed in a magnetron RIE system by using Cl.sub.2 as etching gas at a reaction chamber pressure of 125 mTorr (about 125.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 12E, a second sacrificial film (insulating film) 24 is isotropically formed over the substrate to a thickness of about 0.1 .mu.m by atmospheric pressure CVD. This atmospheric pressure CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 12F, a first emitter electrode 27 of TiN.sub.x is deposited on the second sacrificial film 24 about 0.05 .mu.m thick by reactive sputtering. For example, this reactive sputtering is performed in a DC sputtering system by using Ti as a target while N.sub.2 +Ar gas is introduced.

Next, as shown in FIG. 12G, a blanket film 27c of W (tungsten) is isotropically deposited on the first emitter electrode 27 about 0.2 .mu.m thick by CVD. For example, CVD is performed under the conditions of source gas of WF.sub.6 +H.sub.2 +N.sub.2 +Ar, a pressure of 80 Torr (about 80.times.133.3 Pa) and a temperature of 450.degree. C. The blanket film 27c functions as a second emitter electrode.

Next, as shown in FIG. 12H, the second emitter electrode 27c is anisotropically etched (etched back) about 0.2 .mu.m thick to leave a second emitter electrode 27d only in a recess of the first emitter electrode 27. A flat surface of the first emitter electrode 27 is exposed. This etch-back is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using SF.sub.6 +Ar+He as etching gas at a reaction chamber pressure of 280 mTorr (about 280.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 12I, the whole of the substrate 20 and part of the second sacrificial film 24 are etched and removed to leave a peripheral second sacrificial film 24b and expose the tip of the first emitter electrode 27. The substrate 20 made of Si is etched by using HF+HNO.sub.3 +CH.sub.3 COOH. The second sacrificial film 24 of a silicon oxide film is etched by HF+NH.sub.4 F.

With the above processes, a field emission element of a two-electrode structure having the emitter electrodes 27 and 27d and gate electrode 25a is completed. Since the getter film 20d of Ti is a conductive film, it functions as a gate electrode together with the gate electrode 25a. This field emission element has the emitter electrodes 27 and 27d and gate electrodes 25a and 20d.

The getter film 20d is formed under the gate electrode 25a and surrounds the tip of the first emitter electrode 27. By heating the getter film 20d, the getter film 20d can be activated to improve the vacuum degree in the flat panel display.

FIGS. 13A to 13I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to another modification of the third embodiment of the invention.

First, the processes shown in FIGS. 11A to 11C are executed. Instead of the getter material layer 22a shown in FIG. 11C, a first sacrificial film of a silicon oxide film is used. Thereafter, the process similar to that shown in FIG. 11D is executed. The side spacer 22b and substrate 20 are etched about 0.1 .mu.m thick as shown in FIG. 13A to form a side spacer (silicon oxide film) 21b on the side wall of the gate electrode 25a. The substrate 20f has a recess.

Next, as shown in FIG. 13B, a getter material layer 22a of Ti is formed about 0.10 .mu.m thick over the substrate by sputtering. This sputtering is performed in a DC sputtering system while Ar gas is introduced. Since the recess of the substrate has a small diameter relative to the depth, the getter material layer 22a formed on the substrate 20f is thinner than that formed on the gate electrode 25a. The getter material layer 22a functions also as a gate electrode film.

Next, the getter material layer 22a is anisotropically etched (etched back) to remove the getter material layer 22a on the bottom of the recess. As shown in FIG. 13C, this etch-back forms a getter film 22b on the side wall of the recess, on the side spacer 21b and on the gate electrode 25a. This etch-back is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using Cl.sub.2 as etching gas at a reaction chamber pressure of 125 mTorr (about 125.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 13D, a second sacrificial film (insulating film) 24 of a silicon oxide film or the like is isotropically deposited on the substrate to a thickness of about 0.1 .mu.m by atmospheric pressure CVD. For example, this atmospheric pressure CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 13E, a first emitter electrode 27 of TiN.sub.x is deposited on the second sacrificial film 24 about 0.05 .mu.m thick by reactive sputtering. This reactive sputtering is performed in a DC sputtering system by using Ti as a target while N.sub.2 +Ar gas is introduced.

Next, as shown in FIG. 13F, a blanket film 27c of W (tungsten) is isotropically deposited on the first emitter electrode 27 about 0.2 .mu.m thick by CVD. For example, CVD is performed under the conditions of source gas of WF.sub.6 +H.sub.2 +N.sub.2 +Ar, a pressure of 80 Torr (about 80.times.133.3 Pa) and a temperature of 450.degree. C. The blanket film 27c functions as a second emitter electrode.

Next, as shown in FIG. 13G, the second emitter electrode 27c is anisotropically etched (etched back) about 0.2 .mu.m thick to leave a second emitter electrode 27d only in a recess of the first emitter electrode 27. A flat surface of the first emitter electrode 27 is exposed. This etch-back is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using SF.sub.6 +Ar+He as etching gas at a reaction chamber pressure of 280 mTorr (about 280.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 13H, the whole of the substrate 20 and part of the second sacrificial film 24 are etched and removed to leave a peripheral second sacrificial film 24b and expose the tip of the first emitter electrode 27. The side spacer (silicon oxide film) 21b is etched when the second sacrificial film (silicon oxide film) 24 is etched. The substrate 20 made of Si is etched by using HF+HNO.sub.3 +CH.sub.3 COOH. The second sacrificial film 24 of a silicon oxide film is etched by HF+NH.sub.4 F.

With the above processes, a field emission element of a two-electrode structure having the emitter electrodes 27 and 27d and gate electrode 25a is completed. Since the emitter electrodes 27a and 27d has a two-stage shaped structure, the tip thereof can be easily made sharp. Since the getter film (Ti film) 22b is a conductive film, it functions as a gate electrode together with the gate electrode 25a. This field emission element has the emitter electrodes 27 and 27d and gate electrodes 25a and 22b.

The getter film 22b is formed on the gate electrode 25a and in the gate hole and surrounds the tip of the first emitter electrode 27. By activating the getter film 22b, the vacuum degree in the flat panel display can be improved.

Although a silicon oxide film is used as the side spacer 21b, a silicon nitride film may also be used. In this case, the side spacer 21b is left even after the etching process, as shown in FIG. 13I. The mechanical strength of the gate electrode 22b is therefore reinforced.

FIGS. 14A to 14I are schematic cross sectional views illustrating the manufacture steps of a field emission element according to another modification of the third embodiment of the invention.

As shown in FIG. 14A, on a substrate 20 of Si or the like, a polysilicon film doped with phosphorous or boron is formed to a thickness of about 0.2 .mu.m by sputtering. The sputtering conditions are the same as those described with FIG. 12A. By using a resist pattern (not shown) as a mask, the polysilicon film is etched to form a gate electrode 25a, shown in FIG. 14A, having a hole (gate hole) 23 on the substrate 20. The hole (gate hole) 23 has a diameter of about 0.5 .mu.m and a depth of about 0.2 .mu.m.

Next, as shown in FIG. 14A, a getter material layer 22a of Ti is formed on the substrate 20 and gate electrode 25a about 0.1 .mu.m thick by sputtering. For example, the sputtering is performed in a DC sputtering system by using Ti as a target while Ar gas is introduced. The getter material layer 22a functions also as a gate electrode film.

Next, as shown in FIG. 14B, a first sacrificial film (insulating film) 21 of a silicon oxide film is isotropically deposited on the getter material layer 22a to a thickness of about 0.15 .mu.m by CVD. For example, this CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 14C, the first sacrificial film 21 is anisotropically etched (etched back) to leave a first sacrificial film 21 a only on the side wall of the hole (gate hole) 23, with the getter material layer 22a being interposed therebetween, as a side spacer. For example, this etch-back is performed in a magnetron RIE system by using CHF.sub.3 +CO.sub.2 +Ar as etching gas at a reaction chamber pressure of 50 mTorr (about 50.times.10.sup.-3.times.133.3 Pa).

Next, by using the side spacer 21a as a mask, the getter material layer 22a is etched to remove the getter material layer 22a on the bottom surface of the hole (gate hole) 23 and upper surface of the gate electrode 25a. As shown in FIG. 14D, this etching forms a getter film 22b on the side wall of the gate electrode 25a and leaves the first sacrificial film 21b on the getter film 22b. This etching is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using Cl.sub.2 as etching gas at a reaction chamber pressure of 125 mTorr (about 125.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 14E, a second sacrificial film (insulating film) 24 of a silicon oxide film is formed over the substrate to a thickness of about 0.1 .mu.m by atmospheric pressure CVD. For example, this atmospheric pressure CVD is performed by using O.sub.3 and TEOS as source gas at a substrate temperature of 400.degree. C.

Next, as shown in FIG. 14F, a first emitter electrode 27 of TiN.sub.x is deposited on the second sacrificial film 24 about 0.05 .mu.m thick by reactive sputtering. For example, this reactive sputtering is performed in a DC sputtering system by using Ti as a target while N.sub.2 +Ar gas is introduced.

Next, as shown in FIG. 14G, a blanket film 27c of W (tungsten) is isotropically deposited on the first emitter electrode 27 about 0.2 .mu.m thick by CVD. For example, CVD is performed under the conditions of source gas of WF.sub.6 +H.sub.2 +N.sub.2 +Ar, a pressure of 80 Torr (about 80.times.133.3 Pa) and a temperature of 450.degree. C. The blanket film 27c functions as a second emitter electrode.

Next, as shown in FIG. 14H, the second emitter electrode 27c is anisotropically etched (etched back) about 0.2 .mu.m thick to leave a second emitter electrode 27d only in a recess of the first emitter electrode 27. A flat surface of the first emitter electrode 27 is exposed. This etch-back is performed by anisotropic dry-etching. For example, it is performed in a magnetron RIE system by using SF.sub.6 +Ar+He as etching gas at a reaction chamber pressure of 280 mTorr (about 280.times.10.sup.-3.times.133.3 Pa).

Next, as shown in FIG. 14I, the whole of the substrate 20 and first sacrificial film 21b and part of the second sacrificial film 24 are etched and removed to leave a peripheral second sacrificial film 24b and expose the tip of the first emitter electrode 27. The substrate 20 made of Si is etched by using HF+HNO.sub.3 +CH.sub.3 COOH. The first and second sacrificial films 21b and 24 of a silicon oxide film is etched by HF+NH.sub.4 F.

With the above processes, a field emission element of a two-electrode structure having the emitter electrodes 27 and 27d and gate electrode 25a is completed. Since the getter film 22b of Ti is a conductive film, it functions as a gate electrode together with the gate electrode 25a. This field emission element has the emitter electrodes 27 and 27d and gate electrodes 25a and 22b.

The getter film 22b is formed on the side wall of the gate hole of the gate electrode 25a, extending inward at the lower portion of the side wall (at the lower portion (lower end) as viewed in FIG. 14I), and surrounds the tip of the first emitter electrode 27. This tip of the emitter electrode 27 extends downward in the gate hole. By activating the getter film 22b, the vacuum degree in the flat panel display can be improved.

In the field emission element shown in FIG. 11I, the space between the emitter electrode 27 and getter film 22b is generally constant. Therefore, a conductive particle (fine grain) may be trapped between the emitter electrode 27 and getter film 22b to electrically short the emitter and gate. In the field emission element shown in FIG. 14I, the space between the emitter electrode 27 and getter film 22b is not constant. Therefore, a conductive particle is hard to be trapped between the emitter electrode 27 and getter film 22b so that an electric short between the emitter and gate can be prevented.

The present invention has been described in connection with the preferred embodiments. The invention is not limited only to the above embodiments. It is apparent that various modifications, improvements, combinations, and the like can be made by those skilled in the art.

As described so far, according to the present invention, it is possible to manufacture a field emission element having a lamination of a gate electrode and a getter film. When a flat panel display is assembled by using such field emission elements, the vacuum degree in the space near the gate electrode can be raised by activating the getter film. The gate electrode is generally formed near the tip of the emitter electrode so that the vacuum degree near the emitter electrode tip can be also raised.

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