Semiconductor substrate made of group III nitride, and process for manufacture thereof
View Patent ↗To provide a semiconductor substrate of a group III nitride with low defect density and little warp, this invention provides a process comprising such steps of: forming a GaN layer 2 on a sapphire substrate 1 of the C face ((0001) face); forming a titanium film 3 thereon; heat-treating the substrate in an atmosphere containing hydrogen gas or a gas of a compound containing hydrogen to form voids in the GaN layer 2; and thereafter forming a GaN layer 4 on the GaN layer 2′.
1. A process for manufacturing a semiconductor substrate made of a group III nitride comprising the steps of:
forming a metal film on a basal substrate having a first semiconductor layer of a group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a group III nitride,
heat-treating said basal substrate in an atmosphere containing hydrogen gas or hydrogen-containing compound gas to form voids in said first semiconductor layer of the group III nitride, and
forming a second semiconductor layer of a group III nitride on said metal film.
2. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that fine holes are formed in the metal film or the metal nitride film as a result of the heat treatment.
3. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said metal film contains scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, manganese, copper, platinum or gold.
4. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said metal film contains titanium, nickel, tantalum or tungsten.
5. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized by further comprising a step of etching off said metal film or the nitride film of said metal to peel off said basal substrate, after forming the second semiconductor layer of the group III nitride.
6. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized by further comprising a step of removing said basal substrate, after forming the second semiconductor layer of the group III nitride.
7. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized by further comprising a step of removing said basal substrate, after forming the second semiconductor layer of the group III nitride.
8. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized by further comprising a step of applying stress to said first semiconductor layer of the group III nitride having voids to peel off said basal substrate mechanically, after forming the second semiconductor layer of the group III nitride.
9. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized by further comprising a step of applying stress to said first semiconductor layer of the group III nitride having voids to peel off said basal substrate mechanically, after forming the second semiconductor layer of the group III nitride.
10. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said step of forming the second semiconductor layer of the group III nitride is a step of forming a mask having an opening on the surface of a substrate, and then epitaxially growing the semiconductor layer of the group III nitride on said opening and said mask.
11. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that the thickness of said second semiconductor layer of the group III nitride is at least 1 μm and optionally reaches up to 300 μm.
12. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said first and second semiconductor layers of the group III nitride are independently made of GaN, AlGaN, InGaN or InAlGaN.
13. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that the thickness of said first semiconductor layer of the group III nitride is no less than 10 nm but no more than 5 μm.
14. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 13 , characterized in that the face for crystal growth is selected from (0001) face or (1-100) face of said sapphire substrate.
15. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said base material is a sapphire substrate.
16. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said heat treatment for forming voids in said first semiconductor layer of the group III nitride is carried out at a temperature of no lower than 700° C. but no higher than 1400° C.
17. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said step of forming the second semiconductor layer of the group III nitride is carried out sequentially after the heat treatment for forming voids in said first semiconductor layer of the group III nitride, without removing the basal substrate out of the apparatus for performing said heat treatment.
18. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 2 , characterized in that said step of forming the second semiconductor layer of the group III nitride is carried out using a gas mixture of hydrogen gas and an inert gas as carrier gas for crystal growth.
19. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 18 , characterized in that the content of hydrogen gas in the gas mixture is no less than 5% but no more than 70% by volume.
20. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said metal film contains scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, manganese, copper, platinum or gold.
21. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said metal film contains titanium, nickel, tantalum or tungsten.
22. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized by further comprising a step of etching off said metal film or the nitride film of said metal to peel off said basal substrate, after forming the second semiconductor layer of the group III nitride.
23. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said step of forming the second semiconductor layer of the group III nitride is a step of forming a mask having an opening on the surface of a substrate, and then epitaxially growing the semiconductor layer of the group III nitride on said opening and said mask.
24. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that the thickness of said second semiconductor layer of the group III nitride is at least 1 μm and optionally reaches up to 300 μm.
25. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said first and second semiconductor layers of the group III nitride are independently made of GaN, AlGaN, InGaN or InAlGaN.
26. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that the thickness of said first semiconductor layer of the group III nitride is no less than 10 nm but no more than 5 μm.
27. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said base material is a sapphire substrate.
28. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 27 , characterized in that the face for crystal growth is selected from (0001) face or (1-100) face of said sapphire substrate.
29. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , characterized in that said heat treatment for forming voids in said first semiconductor layer of the group III nitride is carried out at a temperature of no lower than 700° C. but no higher than 1400°C.
30. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , wherein said step of forming the second semiconductor layer of the group III nitride is carried out sequentially after the heat treatment for forming voids in said first semiconductor layer of the group III nitride, without removing the basal substrate out of the apparatus for performing said heat treatment.
31. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 1 , wherein said step of forming the second semiconductor layer of the group III nitride is carried out using a gas mixture of hydrogen gas and an inert gas as carrier gas for crystal growth.
32. A process for manufacturing a semiconductor substrate made of a group III nitride claimed in claim 31 , characterized in that the content of hydrogen gas in the gas mixture is no less than 5% but no more than 70% by volume.
33. A process for manufacturing a semiconductor substrate made of a group III nitride comprising the steps of:
forming a metal film on a basal substrate having a first semiconductor layer of a group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a group III nitride,
heat-treating said basal substrate in an atmosphere containing nitrogen gas, oxygen gas or a mixture of nitrogen gas and oxygen gas to form voids in said first semiconductor layer of the group III nitride, and
forming a second semiconductor layer of a group III nitride on said metal film.
34. A process for manufacturing a semiconductor substrate made of a group III nitride comprising the steps of:
forming a metal film on a basal substrate having a first semiconductor layer of a group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a group III nitride,
heat-treating said basal substrate in an atmosphere containing nitrogen gas or nitrogen-containing compound gas to convert the surface of said metal film into the nitride thereof,
heat-treating said basal substrate in an atmosphere containing hydrogen gas or hydrogen-containing compound gas to form voids in said first semiconductor layer of the group III nitride, and
forming a second semiconductor layer of a group III nitride on said metal film.
35. A process for manufacturing a semiconductor substrate made of a group III nitride comprising the steps of:
forming a metal film on a basal substrate having a first semiconductor layer of a group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a group III nitride,
heat-treating said basal substrate in an atmosphere containing nitrogen gas or nitrogen-containing compound gas and also hydrogen gas or hydrogen-containing compound gas to form voids in said first semiconductor layer of a group III nitride and also to convert the surface of said metal film into the nitride thereof simultaneously, and
forming a second semiconductor layer of a group III nitride on said metal film.
36. A process for manufacturing a semiconductor substrate made of a group III nitride comprising the steps of:
heat-treating a basal substrate having a first semiconductor layer of a group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a group III nitride to form voids in said first semiconductor layer of the group III nitride, and
forming a second semiconductor layer of a group III nitride on said first semiconductor layer of the group III nitride,
wherein said step of heat-treatment is carried out under the controlled condition of temperature and atmosphere where the crystal structure of the group III nitride used for the first semiconductor is decomposed, and at least nitrogen derived from the group III nitride vaporize, resulting in the percentage of the voids formed in the first semiconductor layer being no less than 20% but no more than 90% by volume.
37. A process for manufacturing a semiconductor substrate made of a Group III nitride comprising the steps of:
forming a metal film on a basal substrate having a first semiconductor layer of a Group III nitride formed on a base material or a basal substrate comprising a first semiconductor layer of a Group III nitride;
heat-treating said basal substrate covered with the metal film to form voids in said first semiconductor layer of the Group III nitride; and
forming a second semiconductor layer of a Group III nitride on said first semiconductor layer of the Group III nitride containing the voids formed in advance.