US6747291B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ohmic contacts on p-type silicon carbide using carbon films
Assignee: United States Department of the Air Force
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Filing: 2003-01-10
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Granted: 2004-06-08
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Expires: 2023-01-10
Abstract
Abstract Ohmic contact formation on p-type Silicon Carbide is disclosed. The formed contact includes an initial amorphous Carbon film layer converted to graphitic sp<2 >Carbon during an elevated temperature annealing sequence. Decreased annealing sequence temperature, reduced Silicon Carbide doping concentration and reduced specific resistivity in the formed ohmic contact are achieved with respect to a conventional p-type Silicon Carbide ohmic contact. Addition of a Boron carbide layer covering the p-type Silicon Carbide along with the sp<2 >Carbon is also disclosed. Ohmic contact improvement with increased annealing temperature up to an optimum temperature near 1000° C. is included. Addition of several metals including Aluminum, the optimum metal identified, over the Carbon layer is also included; many other of the identified metals provide Schottky rather than the desired ohmic contacts, however.
Inventors
- 👤 Weijie Lu
- 👤 William C. Mitchel
- 👤 Warren E. Collins
- 👤 Gerald Landis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:55
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/60; H10D64/62; H10D64/01; H10D64/011; H10D64/0111; H10D64/0115; H10D62/00; H10D62/80; H10D62/83; H10D62/832; H10D62/8325; Y; Y10; Y10S; Y10S438/00; Y10S438/931
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
186 words
The method of fabricating a graphitic sp 2 Carbon-enabled ohmic contact for a p-type Silicon Carbide semiconductor device, said method comprising the steps of: providing a cleaned surfaced wafer sample of p-type Silicon Carbide having a selected doping concentration of up to 1×10 19 atoms/cm 3 and selected initial resistivity characteristics; covering said sample cleaned surface with a layer of amorphous sp 2 and sp 3 Carbon mixture; supplying a layer of Carbon conversion-accelerating catalytic elemental material over said sample layer of amorphous sp 2 and sp 3 Carbon mixture; converting a substantial portion of said catalytic elemental material layer-covered amorphous sp 2 and sp 3 Carbon mixture on said sample to elemental material-catalyzed graphitic sp 2 Carbon; said converting step including a heat treating annealing of said sample at a temperature less than 1000° C. but sufficiently high to achieve ohmic contact electrical characteristics between said converted, element material catalyzed graphitic sp 2 Carbon and said sample of p-type Silicon Carbide; and disposing an external circuit electrically conductive element in contact with a selected portion of said converted, element material catalyzed graphitic sp 2 Carbon.
Claim 2
Independent Claim
186 words
The method of fabricating a graphitic sp 2 Carbon-enabled ohmic contact for a p-type Silicon Carbide semiconductor device, said method comprising the steps of: providing a cleaned surfaced wafer sample of p-type Silicon Carbide having a selected doping concentration of up to 1×10 19 atoms/cm 3 and selected initial resistivity characteristics; covering said sample cleaned surface with a layer of amorphous sp 2 and sp 3 Carbon mixture; supplying a layer of Carbon conversion-accelerating catalytic elemental material over said sample layer of amorphous sp 2 and sp 3 Carbon mixture; converting a substantial portion of said catalytic elemental material layer-covered amorphous sp 2 and sp 3 Carbon mixture on said sample to elemental material-catalyzed graphitic sp 2 Carbon; said converting step including a heat treating annealing of said sample at a temperature less than 1000° C. but sufficiently high to achieve ohmic contact electrical characteristics between said converted, element material catalyzed graphitic sp 2 Carbon and said sample of p-type Silicon Carbide; and disposing an external circuit electrically conductive element in contact with a selected portion of said converted, element material catalyzed graphitic sp 2 Carbon.
Claim 3
Dependent Claim
52 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for an p-type Silicon Carbide semiconductor device of claim 1 wherein said carbon layer in said step of covering said sample cleaned surface with a layer of amorphous sp 2 and sp 3 Carbon mixture comprises a thickness of five nanometers.
Claim 4
Dependent Claim
63 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for an p-type Silicon Carbide semiconductor device of claim 1 wherein said step of supplying a Carbon conversion-accelerating catalytic element material layer over said sample layer of amorphous sp 2 and sp 3 Carbon mixture comprises covering said layer of amorphous sp 2 and sp 3 Carbon mixture with a metallic layer.
Claim 5
Dependent Claim
59 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for an p-type Silicon Carbide semiconductor device of claim 3 wherein said step of covering said layer of amorphous sp 2 and sp 3 Carbon mixture with a metallic layer comprises covering said layer of amorphous sp 2 and sp 3 Carbon mixture with a layer of Aluminum.
Claim 6
Dependent Claim
46 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for an p-type Silicon Carbide semiconductor device of claim 1 further including the step of testing said Carbon-enabled contact for ohmic contact characteristics and specific resistivity of 10 −5 ohm-centimerter 2 and lower resistivity values.
Claim 7
Dependent Claim
52 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for an p-type Silicon Carbide semiconductor device of claim 1 wherein said clean surfaced wafer sample of p-type Silicon Carbide having selected doping concentration less than 1×10 19 atoms/cm 3 comprises a Silicon faced eight degrees off axis Silicon Carbide sample.
Claim 8
Dependent Claim
35 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for a p-type Silicon Carbide semiconductor device of claim 1 wherein said steps of covering and supplying each include a direct current sputtering sequence.
Claim 9
Dependent Claim
37 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for a p-type Silicon Carbide semiconductor device of claim 1 wherein said converting step is performed in one of a vacuum and an argon sample-surrounding atmosphere.
Claim 10
Dependent Claim
84 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for a p-type Silicon Carbide semiconductor device of claim 1 wherein: said step of supplying a pair of Carbon conversion-accelerating catalytic elemental material layers over said sample layer of amorphous sp 2 and Sp 3 Carbon mixture comprises covering said layer of amorphous sp 2 and sp 3 Carbon mixture with a layer of Boron; and said step of converting said layer of Carbon includes reacting said Boron into a Boron Carbide compound.
Claim 11
Dependent Claim
42 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for a p-type Silicon Carbide semiconductor device of claim 1 wherein said converting step includes a heat treating annealing of said sample at a temperature between 700° C. and 1000° C.
Claim 12
Dependent Claim
45 words
The method of fabricating a graphitic sp 2 Carbon-inclusive ohmic contact for a p-type Silicon Carbide semiconductor device of claim 1 wherein said converting step includes a heat-treating annealing of said sample at a temperature providing minimum electrical specific resistivity in an achieved ohmic contact.
Claim 13
Dependent Claim
131 words
The p-type Silicon Carbide nano-sized graphitic flake ohmic contact apparatus comprising the combination of: a wafer sample of p-type Silicon Carbide of Aluminum impurity doping concentration between 1×10 17 and 1×10 19 atoms per cubic centimeter; a layer of different element-catalyzed sp 2 Carbon and graphitic sp 2 Carbon overlaying said wafer sample of p-type Silicon Carbide in selected contact areas thereof; said layer of different element-catalyzed graphitic sp 2 Carbon in said selected contact areas including a post annealing remainder sub-layer of inter-diffused Sp2 Carbon and said different element molecules; and an external signal-communicating electrical conductor connected with one of said layer of different element-catalyzed graphitic sp 2 Carbon and said post annealing remainder sub-layer of inter-diffused Carbon and different element molecules on said wafer sample of p-type Silicon Carbide.
Claim 14
Dependent Claim
131 words
The p-type Silicon Carbide nano-sized graphitic flake ohmic contact apparatus comprising the combination of: a wafer sample of p-type Silicon Carbide of Aluminum impurity doping concentration between 1×10 17 and 1×10 19 atoms per cubic centimeter; a layer of different element-catalyzed sp 2 Carbon and graphitic sp 2 Carbon overlaying said wafer sample of p-type Silicon Carbide in selected contact areas thereof; said layer of different element-catalyzed graphitic sp 2 Carbon in said selected contact areas including a post annealing remainder sub-layer of inter-diffused Sp2 Carbon and said different element molecules; and an external signal-communicating electrical conductor connected with one of said layer of different element-catalyzed graphitic sp 2 Carbon and said post annealing remainder sub-layer of inter-diffused Carbon and different element molecules on said wafer sample of p-type Silicon Carbide.
Claim 15
Dependent Claim
42 words
The p-type Silicon Carbide graphitic sp 2 Carbon ohmic contact apparatus of claim 12 wherein said different element in said layer of different element-catalyzed graphitic sp 2 Carbon overlaying said wafer sample of p-type Silicon Carbide is comprised of the element Aluminum.
Claim 16
Dependent Claim
42 words
The p-type Silicon Carbide graphitic sp 2 Carbon ohmic contact apparatus of claim 12 wherein said different element in said layer of different element-catalyzed graphitic sp 2 Carbon overlaying said wafer sample of p-type Silicon Carbide is comprised of the element Boron.
Claim 17
Dependent Claim
35 words
The p-type Silicon Carbide graphitic Sp 2 Carbon ohmic contact apparatus of claim 12 wherein said layer of different element-catalyzed graphitic sp 2 Carbon has an initial pre annealing thickness between 5 and 50 nanometers.
Claim 18
Dependent Claim
37 words
The p-type Silicon Carbide ohmic contact comprising the combination of: a layer of annealed Silicon Carbide semiconductor material; and a layer of annealed Boron Carbide overlaying said layer of annealed Silicon Carbide material in ohmic contact therewith.
Claim 19
Dependent Claim
37 words
The p-type Silicon Carbide ohmic contact comprising the combination of: a layer of annealed Silicon Carbide semiconductor material; and a layer of annealed Boron Carbide overlaying said layer of annealed Silicon Carbide material in ohmic contact therewith.
Claim 20
Dependent Claim
19 words
The p-type Silicon Carbide ohmic contact of claim 16 further including one of the metals of Aluminum and Nickel.
Claim 21
Dependent Claim
29 words
The p-type Silicon Carbide ohmic contact of claim 16 wherein said ohmic contact is comprised of the materials Aluminum, Carbon, Boron Carbide and Silicon Carbide each in annealed form.
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