1. A method for manufacturing a silicon single crystal comprising:
producing a silicon melt in a chamber by melting a silicon raw material loaded into a silica glass crucible under a reduced pressure and high temperature;
removing gas bubbles from within the silicon melt by rapidly changing at least the pressure or temperature within the chamber; and
pulling up the silicon single crystal from the silicon melt after the gas bubbles are removed.
2. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
a pressure change ratio within the chamber when removing the gas bubbles within the silicon melt is larger than a pressure change ratio when reducing pressure within the chamber in order to melt the silicon raw material, and
a temperature change ratio within the chamber when removing the gas bubbles within the silicon melt is larger than a temperature change ratio when increasing temperature within the chamber in order to melt the silicon raw material.
3. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
the pressure change ratio within the chamber when removing the gas bubbles within the silicon melt is 5 times or more and 1000 times or less than the pressure change ratio when reducing the pressure inside the chamber in order to melt the silicon raw material.
4. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
a pressure decrease rate inside the chamber when removing the gas bubbles from the silicon melt is 1.5 hPasec or more and 20 hPasec or less.
5. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
the temperature change ratio within the chamber when removing the gas bubbles within the silicon melt is 5 times or more and 100 times or less than the temperature change ratio when increasing the temperature inside the chamber in order to melt the silicon raw material.
6. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
a temperature increase rate inside the chamber when removing the gas bubbles from the silicon melt is 0.5\xb0 C.sec or more and 5\xb0 C.sec or less.
7. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
pulling up the silicon single crystal is started after removing the gas bubbles with the silicon melt by rapidly changing at least the pressure or temperature within the chamber is repeated a plurality of times.
8. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
after producing the silicon melt and before removing the gas bubbles with the silicon melt by rapidly changing at least the pressure or temperature within the chamber, the silicon melt is left for awhile as the temperature and pressure within the chamber 11 are maintained at a constant rate and the gas within the silicon melt is discharged.
9. The method for manufacturing a silicon single crystal as claimed in claim 1, wherein
after the gas bubbles are removed, the temperature is adjusted until the temperature of the silicon melt is stable before pulling up the silicon single crystal from the silicon melt.
10. The method for manufacturing a silicon single crystal as claimed in claim 2, wherein
pulling up the silicon single crystal is started after removing the gas bubbles with the silicon melt by rapidly changing at least the pressure or temperature within the chamber is repeated a plurality of times.
11. The method for manufacturing a silicon single crystal as claimed in claim 2, wherein
after producing the silicon melt and before removing the gas bubbles with the silicon melt by rapidly changing at least the pressure or temperature within the chamber, the silicon melt is left for awhile as the temperature and pressure within the chamber 11 are maintained at a constant rate and the gas within the silicon melt is discharged.
12. The method for manufacturing a silicon single crystal as claimed in claim 2, wherein
after the gas bubbles are removed, the temperature is adjusted until the temperature of the silicon melt is stable before pulling up the silicon single crystal from the silicon melt.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
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.