US6852615B2
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ohmic contacts for high electron mobility transistors and a method of making the same
Assignee: HRL Laboratories LLC
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Filing: 2003-06-09
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Granted: 2005-02-08
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Expires: 2023-06-09
Abstract
Abstract A process and related product in which ohmic contacts are formed in High Electron Mobility Transistors (HEMTs) employing compound substrates such as gallium nitride. An improved device and an improvement to a process for fabrication of ohmic contacts to GaN/AlGaN HEMTs using a novel two step resist process to fabricate the ohmic contacts are described. This novel two-step process consists of depositing a plurality of layers having compounds of Group III V elements on a substrate; patterning and depositing a first photoresist on one of the layers; etching recessed areas into this layer; depositing ohmic metals on the recessed areas; removing the first photoresist; patterning and depositing a second photoresist, smaller in profile than the first photoresist, on the layer; depositing more ohmic metal on the layer allowing for complete coverage of the recessed areas; removing the second photoresist, and annealing the semiconductor structure.
Inventors
- 👤 Miroslav Micovic
- 👤 Tahir Hussain
- 👤 Paul Hashimoto
- 👤 Janna Ruth Duvall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:31
CPC Classifications
H; H10; H10D; H10D62/00; H10D62/80; H10D62/85; H10D64/00; H10D64/01; H10D64/011; H10D64/0116; H10D64/20; H10D64/23; H10D64/251; H10D64/60; H10D64/62; H10D62/8503; H10D62/852; Y; Y10; Y10S; Y10S438/00; Y10S438/975; Y10S438/978
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
153 words
A process for fabricating a Group III V semiconductor structure comprising the steps of: depositing Group III V elements in three layers, with a first layer, a second layer, and a third layer, wherein said first layer is deposited on a substrate, said second layer is deposited on said first layer, said third layer is deposited on said second layer; patterning and depositing a first photoresist on said third layer; providing an unprotected portion of said third layer, wherein said unprotected portion of said third layer is not in contact with said first photoresist; reducing a thickness of said unprotected portion of said third layer to form a recessed area; removing said first photoresist; patterning and depositing a second photoresist on said third layer; depositing ohmic metal on at least a portion of said third layer, wherein said ohmic metal covers said recessed area; removing said second photoresist; and annealing said semiconductor structure.
Claim 2
Dependent Claim
153 words
A process for fabricating a Group III V semiconductor structure comprising the steps of: depositing Group III V elements in three layers, with a first layer, a second layer, and a third layer, wherein said first layer is deposited on a substrate, said second layer is deposited on said first layer, said third layer is deposited on said second layer; patterning and depositing a first photoresist on said third layer; providing an unprotected portion of said third layer, wherein said unprotected portion of said third layer is not in contact with said first photoresist; reducing a thickness of said unprotected portion of said third layer to form a recessed area; removing said first photoresist; patterning and depositing a second photoresist on said third layer; depositing ohmic metal on at least a portion of said third layer, wherein said ohmic metal covers said recessed area; removing said second photoresist; and annealing said semiconductor structure.
Claim 3
Dependent Claim
32 words
The process of claim 1 , wherein in said step of depositing said ohmic metal on at least a portion of said third layer, said ohmic metal completely covers said recessed area.
Claim 4
Dependent Claim
14 words
The process of claim 1 , wherein said first photoresist lacks a photoresist ledge.
Claim 5
Dependent Claim
14 words
The process of claim 1 , wherein said second photoresist has a photoresist ledge.
Claim 6
Dependent Claim
21 words
The process of claim 1 further comprising the step of forming gross alignment markers for stepper lithography on said third layer.
Claim 7
Dependent Claim
21 words
The process of claim 1 further comprising the step of forming fine alignment markers for stepper lithography on said third layer.
Claim 8
Dependent Claim
14 words
The process of claim 5 wherein said gross alignment markers comprise Ti and Au.
Claim 9
Dependent Claim
17 words
The process of claim 6 wherein said fine alignment markers comprise Ti and W, or comprise Pt.
Claim 10
Dependent Claim
14 words
The process of claim 1 , wherein said substrate comprises sapphire or semi-insulating SiC.
Claim 11
Dependent Claim
14 words
The process of claim 1 , wherein said first layer comprises a nucleation layer.
Claim 12
Dependent Claim
29 words
The process of claim 10 , wherein said nucleation layer comprises a compound of the formula Al y Ga (1-y) N, wherein y is a value greater than zero.
Claim 13
Dependent Claim
12 words
The process of claim 10 , wherein said second layer comprises GaN.
Claim 14
Dependent Claim
15 words
The process of claim 12 , wherein said third layer comprises a Schottky barrier layer.
Claim 15
Dependent Claim
26 words
The process of claim 13 , wherein said Schottky barrier layer comprises Al x Ga (1-x) N wherein x is a value between 0.1 and 0.4.
Claim 16
Dependent Claim
20 words
The process of claim 11 , wherein said nucleation layer is between about 10 nm and about 20 nm thick.
Claim 17
Dependent Claim
20 words
The process of claim 12 , wherein said second layer is between about 250 nm and about 4000 nm thick.
Claim 18
Dependent Claim
20 words
The process of claim 13 , wherein said third layer is between about 1 nm and about 40 nm thick.
Claim 19
Dependent Claim
70 words
The process of claim 1 , wherein said first photoresist defines a first distance between a source contact pad and a drain contact pad, said second photoresist defines a second distance between said source contact pad and said drain contact pad, said second distance between said source contact pad and said drain contact pad is less than said first distance between said source contact pad and said drain contact pad.
Claim 20
Dependent Claim
18 words
The process of claim 13 further comprising the step of reducing a thickness of said Schottky barrier layer.
Claim 21
Dependent Claim
26 words
The process of claim 1 further comprising the step of removing said first photoresist using a stripper, wherein said stripper is corrosive to said ohmic metal.
Claim 22
Dependent Claim
28 words
The process of claim 1 further comprising the step of removing said second photoresist using an other stripper, wherein said other stripper is inert to said ohmic metal.
Claim 23
Dependent Claim
38 words
The process of claim 1 further comprising the step of depositing said ohmic metal on a Schottky barrier layer, wherein said ohmic metal comprises at least one element from the group consisting of Ti, Al, Ni, and Au.
Claim 24
Dependent Claim
22 words
The process of claim 1 further comprising the step of forming a photoresist ledge on said first photoresist and said second photoresist.
Claim 25
Dependent Claim
27 words
The process of claim 1 wherein in said step of annealing said semiconductor structure, said semiconductor structure is heated for 30 seconds at 875° C. in nitrogen.
Claim 26
Dependent Claim
37 words
The process of claim 1 , wherein the step of annealing includes converting at least a portion of said third layer or said second and said third layer under said ohmic metal to a heavy n-type material.
Claim 27
Dependent Claim
92 words
A semiconductor structure comprising: a substrate; a first layer, a second layer, and a third layer each having compounds of Group III V elements, wherein said first layer is in contact with said second layer, said second layer is in contact with said first layer and said third layer, and said third layer is in contact with said second layer; a recessed area of said third layer; a non-recessed area or said third layer; and ohmic metal, wherein said recessed area of said third layer is completely covered by said ohmic metal.
Claim 28
Dependent Claim
92 words
A semiconductor structure comprising: a substrate; a first layer, a second layer, and a third layer each having compounds of Group III V elements, wherein said first layer is in contact with said second layer, said second layer is in contact with said first layer and said third layer, and said third layer is in contact with said second layer; a recessed area of said third layer; a non-recessed area or said third layer; and ohmic metal, wherein said recessed area of said third layer is completely covered by said ohmic metal.
Claim 29
Dependent Claim
39 words
The structure of claim 26 , further comprising a source contact pad and a drain contact pad, wherein said non-recessed area of said third layer defines a first distance between said source contact pad and said drain contact pad.
Claim 30
Dependent Claim
21 words
The structure of claim 26 , wherein said non-recessed area has a thickness and said recessed area has an other thickness.
Claim 31
Dependent Claim
23 words
The structure of claim 28 , wherein said thickness of said recessed area is smaller than said other thickness of said non-recessed area.
Claim 32
Dependent Claim
22 words
The structure of claim 26 , wherein said non-recessed area of said third layer is not completely covered by said ohmic metal.
Claim 33
Dependent Claim
31 words
The structure of claim 26 , wherein at least a portion of said third layer or said second and said third layers under said ohmic metal comprises a heavy n-type material.
References Cited (Backward Citations)
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| 7.5 Years (Year 8) | 2012-02-08 | 2012-08-09 | 2013-02-08 | $3760.00 | Window Closed / Lapsed |
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