Patent US5789272A successfully refreshed from Google Patents.
US5789272A
Expired / Lapsed
US
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Low voltage field emission device
Assignee: Industrial Technology Research Institute
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Filing: 1996-09-27
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Granted: 1998-08-04
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Expires: 2016-09-27
Abstract
Abstract With a view to reducing the gate voltage in Field Emission Devices, three different methods for reducing the diameter of the gate opening in such devices are described. In the first method, metal is deposited on the gate electrode (which is made of polysilicon or amorphous silicon) at an oblique angle of incidence so that the vertical wall of the opening is coated, but not its lower surface. In the second method, all exposed surfaces are coated with metal. For both methods, metal is then removed from all non-polysilicon surfaces through a silicidation step followed by selective etching. In the third method, the gate electrode is selectively coated with a layer of tungsten. In all cases, a uniform reduction of the gate opening is achieved.
Inventors
- 👤 Wen-Chun Wang
- 👤 Chi-Hua Wang
- 👤 Jiun-Tsuen Lai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:31
CPC Classifications
H; H01; H01J; H01J3/00; H01J3/02; H01J3/021; H01J3/022; H01J9/00; H01J9/02; H01J9/022; H01J9/025
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
210 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon or amorphous silicon, on the gate layer; depositing a passivation layer on the dielectric layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; further reducing the size of the gate opening by causing evaporated metal to arrive at said lip at an oblique angle of incidence, whereby said lip gets coated on its vertical surface and on its upper horizontal surface to a thickness between about 500 and 3,000 Angstroms; annealing the structure, thereby causing the evaporated metal to react with the gate layer to form a silicide; and by etching, selectively removing the parts of the evaporated metal that have not formed a silicide.
Claim 2
Independent Claim
210 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon or amorphous silicon, on the gate layer; depositing a passivation layer on the dielectric layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; further reducing the size of the gate opening by causing evaporated metal to arrive at said lip at an oblique angle of incidence, whereby said lip gets coated on its vertical surface and on its upper horizontal surface to a thickness between about 500 and 3,000 Angstroms; annealing the structure, thereby causing the evaporated metal to react with the gate layer to form a silicide; and by etching, selectively removing the parts of the evaporated metal that have not formed a silicide.
Claim 3
Dependent Claim
27 words
The method of claim 1 wherein causing evaporated metal to arrive at an oblique angle of incidence further comprises using a ring source for said evaporated metal.
Claim 4
Dependent Claim
31 words
The method of claim 1 wherein causing evaporated metal to arrive at an oblique angle of incidence further comprises using a source for said evaporated metal that revolves around the substrate.
Claim 5
Dependent Claim
36 words
The method of claim 1 wherein causing evaporated metal to arrive at an oblique angle of incidence further comprises using a source, for said evaporated metal, that is located to one side and rotating the substrate.
Claim 6
Dependent Claim
39 words
The method of claim 1 wherein causing evaporated metal to arrive at an oblique angle of incidence further comprises using a source for said evaporated metal that revolves around the substrate while the substrate rotates in the opposite direction.
Claim 7
Dependent Claim
19 words
The method of claim 1 wherein said evaporated metal comprises titanium or cobalt or palladium or platinum or nickel.
Claim 8
Dependent Claim
38 words
The method of claim 1 wherein the step of annealing further comprises heating for between about 0.1 and 60 minutes at a temperature between about 400° and 650° C. in an atmosphere of nitrogen or in a vacuum.
Claim 9
Dependent Claim
53 words
The method of claim 1 wherein the step of selectively removing the parts of the evaporated metal that have not formed a silicide comprises, for titanium, etching in NH 4 OH/H 2 O 2 /H 2 O for between about 5 and 30 minutes at a temperature between about 25° and 85° C.
Claim 10
Dependent Claim
27 words
The method of claim 1 wherein the diameter of the gate opening, prior to the deposition of the metal layer, is between about 0.5 and 1 microns.
Claim 11
Dependent Claim
27 words
The method of claim 1 wherein the diameter of the gate opening, after to the deposition of the metal layer, is between about 0.2 and 0.7 microns.
Claim 12
Independent Claim
193 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer, comprising polysilicon or amorphous silicon, on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon, on the dielectric layer; depositing a passivation layer on the gate layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; further reducing the size of the gate opening by depositing a metal layer on all exposed surfaces to a thickness between about 500 and 3,000 Angstroms; annealing the structure, thereby causing the deposited metal to react with the gate and cathode layers to form a silicide; and by etching, selectively removing the parts of the deposited metal that have not formed a silicide.
Claim 13
Independent Claim
193 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer, comprising polysilicon or amorphous silicon, on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon, on the dielectric layer; depositing a passivation layer on the gate layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; further reducing the size of the gate opening by depositing a metal layer on all exposed surfaces to a thickness between about 500 and 3,000 Angstroms; annealing the structure, thereby causing the deposited metal to react with the gate and cathode layers to form a silicide; and by etching, selectively removing the parts of the deposited metal that have not formed a silicide.
Claim 14
Dependent Claim
17 words
The method of claim 11 wherein the metal is deposited by sputtering or by chemical vapor deposition.
Claim 15
Dependent Claim
19 words
The method of claim 11 wherein the deposited metal comprises titanium or cobalt or palladium or platinum or nickel.
Claim 16
Dependent Claim
38 words
The method of claim 11 wherein the step of annealing further comprises heating for between about 0.1 and 60 minutes at a temperature between about 400° and 650° C. in an atmosphere of nitrogen or in a vacuum.
Claim 17
Dependent Claim
53 words
The method of claim 11 wherein the step of selectively removing the parts of the deposited metal that have not formed a silicide comprises, for titanium, etching in NH 4 OH/H 2 O 2 /H 2 O for between about 5 and 30 minutes at a temperature between about 25° and 85° C.
Claim 18
Dependent Claim
27 words
The method of claim 11 wherein the diameter of the gate opening, prior to the deposition of the metal layer, is between about 0.5 and 1 microns.
Claim 19
Dependent Claim
27 words
The method of claim 11 wherein the diameter of the gate opening, after to the deposition of the metal layer, is between about 0.2 and 0.7 microns.
Claim 20
Independent Claim
159 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer, comprising polysilicon or amorphous silicon, on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon, on the dielectric layer; depositing a passivation layer on the gate layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; and further reducing the size of the gate opening by selectively depositing a metal layer on all exposed polysilicon surfaces to a thickness between about 500 and 2,000 Angstroms.
Claim 21
Independent Claim
159 words
A method for reducing the size of the gate opening in a field emission structure comprising: providing an insulating substrate; depositing a cathode layer, comprising polysilicon or amorphous silicon, on said substrate; depositing a dielectric layer on the cathode layer; depositing a gate layer, comprising polysilicon, on the dielectric layer; depositing a passivation layer on the gate layer; etching a first opening in the passivation layer, extending as far as the gate layer; etching a second opening in the gate and dielectric layers, smaller than said first opening and extending as far as the cathode layer, in a manner whereby undercutting of the gate layer occurs, thereby forming a gate opening with a lip, having upper and lower horizontal surfaces and a vertical surface, that extends beyond the dielectric layer; and further reducing the size of the gate opening by selectively depositing a metal layer on all exposed polysilicon surfaces to a thickness between about 500 and 2,000 Angstroms.
Claim 22
Dependent Claim
22 words
The method of claim 18 wherein the metal that is selectively deposited is tungsten and the deposition method is chemical vapor deposition.
Claim 23
Dependent Claim
17 words
The method of claim 19 wherein the deposition method further comprises the silane reduction of tungsten hexafluoride.
Claim 24
Dependent Claim
27 words
The method of claim 18 wherein the diameter of the gate opening, prior to the deposition of the metal layer, is between about 0.5 and 1 microns.
Claim 25
Dependent Claim
27 words
The method of claim 18 wherein the diameter of the gate opening, after to the deposition of the metal layer, is between about 0.1 and 0.6 microns.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2001-08-03 | 2002-02-02 | 2002-08-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-08-03 | 2006-02-02 | 2006-08-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-08-03 | 2010-02-02 | 2010-08-04 | $7700.00 | Window Closed / Lapsed |