Silicon carbide power devices including P-type epitaxial layers and direct ohmic contacts
View Patent ↗A silicon carbide power device is fabricated by forming a p-type silicon carbide epitaxial layer on an n-type silicon carbide substrate, and forming a silicon carbide power device structure on the p-type silicon carbide epitaxial layer. The n-type silicon carbide substrate is at least partially removed, so as to expose the p-type silicon carbide epitaxial layer. An ohmic contact is formed on at least some of the p-type silicon carbide epitaxial layer that is exposed. By at least partially removing the n-type silicon carbide substrate and forming an ohmic contact on the p-type silicon carbide epitaxial layer, the disadvantages of using a p-type substrate may be reduced or eliminated. Related structures are also described.
1. A silicon carbide power device comprising:
a p-type silicon carbide epitaxial layer including first and second opposing faces;
a silicon carbide power device structure on the second face of the p-type silicon carbide epitaxial layer; and
an ohmic contact directly on at least a portion of the first face of the p-type silicon carbide epitaxial layer.
2. A device according to claim 1 , further comprising:
an n-type silicon carbide substrate on the first face, including at least one via that extends therethrough so as to expose at least the portion of the first face of the p-type silicon carbide epitaxial layer;
wherein the ohmic contact extends in the at least one via and directly on at least the portion of the first face of the p-type silicon carbide epitaxial layer that is exposed.
3. A device according to claim 1 , wherein the ohmic contact comprises a metal contact.
4. A device according to claim 3 , wherein the metal contact includes laser annealed portions therein.
5. A device according to claim 4 , wherein the metal contact that includes laser annealed portions therein comprises a first layer comprising aluminum directly on the first face of the p-type silicon carbide epitaxial layer, a second layer comprising titanium on the first layer and a third layer comprising nickel on the second layer.
6. A device according to claim 4 , wherein the metal contact that includes laser annealed portions therein comprises a layer comprising aluminum directly on the first face of the p-type silicon carbide epitaxial layer.
7. A device according to claim 1 , wherein the silicon carbide power device structure comprises an n-channel silicon carbide DMOSFET structure directly on the second face of the p-type silicon carbide epitaxial layer, such that the n-channel silicon carbide DMOSFET structure and the p-type silicon carbide epitaxial layer provide an n-channel silicon carbide IGBT structure.
8. A device according to claim 7 , wherein the silicon carbide power device structure comprises a p-type silicon carbide power device structure on the p-type silicon carbide epitaxial layer.
9. A device according to claim 7 , further comprising:
an n-type silicon carbide substrate on the first face, including at least one via that extends therethrough so as to expose at least the portion of the first face of the p-type silicon carbide epitaxial layer;
wherein the ohmic contact extends in the at least one via and directly on at least the portion of the first face of the p-type silicon carbide epitaxial layer that is exposed.
10. A device according to claim 7 , wherein the ohmic contact comprises a metal contact.
11. A device according to claim 10 , wherein the metal contact includes laser annealed portions therein.
12. A device according to claim 11 , wherein the metal contact that includes laser annealed portions therein comprises a first layer comprising aluminum directly on the first face of the p-type silicon carbide epitaxial layer, a second layer comprising titanium on the first layer and a third layer comprising nickel on the second layer.
13. A device according to claim 11 , wherein the metal contact that includes laser annealed portions therein comprises a layer comprising aluminum directly on the first face of the p-type silicon carbide epitaxial layer.
14. A device according to claim 1 , wherein the silicon carbide power device structure comprises an n-type silicon carbide epitaxial layer directly on the second face of the p-type silicon carbide epitaxial layer so as to form a p-n junction therebetween.