Method for controlled growth of silicon carbide and structures produced by same
View Patent ↗A method for controlled growth of silicon carbide and structures produced by the method are disclosed. A crystal of silicon carbide (SiC) can be grown by placing a sacrificial substrate in a growth zone with a source material. The source material may include a low-solubility impurity. SiC is then grown on the sacrificial substrate to condition the source material. The sacrificial substrate is then replaced with the final substrate, and SiC is grown on the final substrate. A single crystal of silicon carbide is produced, wherein the crystal of silicon carbide has substantially few micropipe defects. Such a crystal may also include a substantially uniform concentration of the low-solubility impurity, and may be used to make wafers and/or SiC die.
1. A method of growing a crystal of silicon carbide, the method comprising:
placing a sacrificial substrate in a growth zone with a source material including a low-solubility impurity;
growing a sacrificial layer of silicon carbide on the sacrificial substrate using physical vapor transport of the source material including the low-solubility impurity to at least past a point where precipitation of the low-solubility impurity in the sacrificial layer of silicon carbide substantially ends;
supplanting the sacrificial substrate with the sacrificial layer of silicon carbide thereon, the sacrificial substrate being supplanted with a final substrate; and
growing the crystal of silicon carbide on the final substrate using at least the source material.
2. The method of claim 1 wherein the crystal of silicon carbide includes a substantially uniform concentration of the low-solubility impurity.
3. The method of claim 2 wherein the low-solubility impurity comprises vanadium.
4. The method of claim 3 wherein the substantially uniform concentration of vanadium is greater than 1×10 15 cm −3 .
5. The method of claim 2 wherein a second impurity is introduced into the growth zone and the crystal of silicon carbide includes a substantially uniform concentration of the second impurity.
6. The method of claim 2 wherein the crystal of silicon carbide is selected from the polytypes of 6H, 4H, 15R and 3C.
7. The method of claim 2 wherein the low-solubility impurity is selected from periodic groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, VIIIB and IIIA.
8. The method of claim 2 wherein the low-solubility impurity is one of vanadium and chromium.
9. The method of claim 5 wherein the low-solubility impurity comprises vanadium.
10. The method of claim 9 wherein the second impurity comprises nitrogen.
11. The method of claim 9 further comprising cutting the crystal of silicon carbide to produce a wafer of vanadium doped silicon carbide for use in making semiconductor devices.
12. The method of claim 10 wherein the vanadium has a concentration of at least 5×10 16 cm −3 and a vanadium to nitrogen ratio having a value from about 1 to a value of about 3 is maintained over at least a portion of a length of the crystal of silicon carbide.
13. The method of claim 11 further comprising cutting the wafer to produce at least one semiconductor device.
14. The method of claim 13 wherein the at least one semiconductor device comprises a photoconductive switch.