Low temperature formation of backside ohmic contacts for vertical devices
AssigneeCree, Inc.
InventorsDavid B. Slater JR., Alexander Suvorov
Life of this patent
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Abstract
A semiconductor device is disclosed that includes a semiconductor substrate having a first surface and a second surface and a first conductivity type and at least one epitaxial layer on the first surface of the semiconductor substrate. The epitaxial layer is formed of a material with a dissociation temperature below that of the semiconductor substrate. A zone of increased carrier concentration is in the semiconductor substrate and extends from the second surface of the semiconductor material toward the first surface. A layer of metal is deposited on the second surface of the semiconductor substrate and forms an ohmic contact at the interface of the metal and the zone of increased carrier concentration.
Claims20
A method for forming an ohmic contact to silicon carbide (12) for a semiconductor device, the method comprising:
- implanting at room temperature a selected dopant material into a surface of a silicon carbide substrate (12) thereby forming a layer (16) on the silicon carbide substrate having an increased concentration of dopant material;
- annealing the implanted silicon carbide substrate a first time;
- growing at least one epitaxial layer of a compound other than SiC that dissociates below the dissociation temperature at SiC (14) on the silicon carbide substrate opposite the implanted surface;
- depositing a layer of metal (18) on the implanted surface of the silicon carbide substrate (12);
- and thereafter
- annealing the metal (18) and the implanted silicon carbide substrate (12, 16) a second time at a temperature below that at which significant degradation of the compound forming the epitaxial layer (14) would occur, but high enough to form an ohmic contact between the implanted silicon carbide (12, 16) and the deposited metal.
A semiconductor device (10) comprising:
- a semiconductor substrate (12) having a first surface and a second surface and a first conductivity type;
- at least one epitaxial layer (14) on said first surface of said semiconductor substrate (12), said epitaxial layer formed of a material with a dissociation temperature below that of the semiconductor substrate;
- a zone (16) of increased carrier concentration in said semiconductor substrate (12) and extending from said second surface of said semiconductor material toward said first surface;
- and
- a layer of metal (18) deposited on said second surface of said semiconductor substrates (12) that forms an ohmic contact at the interface (20) of said metal and said zone (16) of increased earner concentration.
A semiconductor device (10) comprising:
- a silicon carbide substrate (12) laving a first surface and a second surface and an initial concentration of dopant imparting an initial conductivity type;
- at least one epitaxial layer (14) on said first surface of silicon carbide substrate (12);
- a zone of increased carrier concentration (16) in said silicon carbide sub substructure (12) and extending from said second surface of said silicon carbide substrate (12) toward said first surface, said zone of dopant material (16) being characterized by a concentration of dopant that progressively decreases from said second surface toward said first surface;
- and
- a nickel ohmic contact (18) on said second surface of said silicon carbide substrate (12).
Dependencies are inferred from the claim text.