Method of forming gallium nitride crystal

• US 5,928,421 A
• Filed: 08/26/1997
• Issued: 07/27/1999
• Est. Priority Date: 08/27/1996
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electronics Corp (Panasonic Holdings Corporation)
• Inventors: Yuri, Masaaki, Ueda, Tetsuzo, Baba, Takaaki
• Primary Examiner(s): HITESHEW, FELISA CARLA
• Application Number:
  US08/917,616
• Time in Patent Office: 700 Days
• Field of Search: 117/84, 117/90, 117/94, 117/97, 117/104, 438/479, 438/507
• US Class Current: 117/97
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02447 Silicon carbide
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02658 Pretreatments cleaning in general H01L21/02041

Abstract

To reduce a dislocation density within a gallium nitride crystal and make cleaving possible, after forming a thin film of silicon carbide and a first gallium nitride crystal on a silicon substrate, only the silicon substrate is removed in an acid solution such as hydrofluoric acid and nitric acid as they are mixed. Following this, a second gallium nitride crystal is formed on the remaining thin film of silicon carbide and the first gallium nitride crystal.

Claims

1. A method of forming a gallium nitride crystal, comprising forming a semiconductor thin film and a first gallium nitride crystal on a semiconductor substrate in that order, both said semiconductor thin film and said first gallium nitride crystal having a different lattice constant from a lattice constant of said semiconductor substrate, removing said semiconductor substrate, and thereafter forming a second gallium nitride crystal on said first gallium nitride crystal.

2. A method in accordance with claim 1, wherein a difference between said lattice constant of said first gallium nitride crystal and said lattice constant of said semiconductor thin film is less than a difference between said lattice constant of said semiconductor substrate and said lattice constant of said semiconductor thin film.

3. A method in accordance with claim 1, wherein said semiconductor substrate is removed by immersing said semiconductor substrate, said semiconductor thin film and said first gallium nitride crystal in an acid solution which removes only said semiconductor substrate.

4. A method in accordance with claim 1, wherein said semiconductor thin film is formed to a thickness of about 500 Å

and said second gallium nitride crystal is formed to a thickness of about 30 μ

m on said first gallium nitride crystal.

5. A method of forming a gallium nitride crystal, comprising forming a semiconductor thin film on a semiconductor substrate, said semiconductor thin film having a different lattice constant from a lattice constant of said semiconductor substrate, removing said semiconductor substrate and thereafter forming a gallium nitride crystal on said semiconductor thin film.

6. A method in accordance with claim 5, wherein a difference between said lattice constant of said semiconductor thin film and said lattice constant of said gallium nitride crystal is less than a difference between said lattice constant of said semiconductor substrate and said lattice constant of said gallium nitride crystal.

7. A method in accordance with claim 5, wherein said semiconductor substrate is removed by immersing said semiconductor substrate and said semiconductor thin film in an acid solution which removes only said semiconductor substrate.

8. A method in accordance with claim 5, wherein said semiconductor thin film is formed to a thickness of about 5,000 Å

and said gallium nitride crystal is formed to a thickness of about 30 μ

m on said semiconductor thin film.

9. A method of forming a gallium nitride crystal, comprising forming a semiconductor thin film and a gallium nitride crystal on a semiconductor substrate in that order, both said semiconductor thin film and said gallium nitride crystal having a different lattice constant from a lattice constant of said semiconductor substrate, and thereafter removing said semiconductor substrate.

10. A method in accordance with claim 9, wherein said semiconductor thin film is formed to a thickness of about 500 Å

and said gallium nitride crystal is formed to a thickness of about 30 μ

m on said semiconductor thin film.

11. A method in accordance with claim 9, wherein said semiconductor substrate is removed by immersing said semiconductor substrate, said semiconductor thin film and said gallium nitride crystal in an acid solution which removes only said semiconductor substrate.

12. A method of forming a gallium nitride crystal, comprising forming a thin film of silicon carbide and a first gallium nitride crystal on a silicon substrate in that order, both said thin film and said first gallium nitride crystal having a different lattice constant from a lattice constant of said silicon substrate, removing said silicon substrate, and thereafter forming a second gallium nitride crystal on said first gallium nitride crystal.

13. A method of forming a gallium nitride crystal in accordance with claim 12, wherein said thin film of silicon carbide is formed by heating said silicon substrate in a hydrocarbon atmosphere.

14. A method in accordance with claim 13, wherein after said heating step, said silicon substrate and said silicon carbide thin film are cooled to room temperature in an atmosphere of hydrogen.

15. A method in accordance with claim 12, wherein a difference between said lattice constant of said first gallium nitride crystal and said lattice constant of said silicon carbide thin film is less than a difference between said lattice constant of said silicon substrate and said lattice constant of said first gallium nitride crystal.

16. A method in accordance with claim 12, wherein said silicon substrate is removed by immersing said silicon substrate, said silicon carbide thin film and said first gallium nitride crystal in an acid solution which is obtain by mixing hydrofluoric acid and nitric acid, thereby removing only said silicon substrate.

17. A method in accordance with claim 12, wherein said silicon carbide thin film is formed to a thickness of about 500 Å

and said second gallium nitride crystal is formed to a thickness of about 30 μ

m on said first gallium nitride crystal.

18. A method of forming a gallium nitride crystal, comprising forming a thin film of silicon carbide on a silicon substrate, removing said silicon substrate and thereafter forming a gallium nitride crystal on said thin film of silicon carbide.

19. A method of forming a gallium nitride crystal in accordance with claim 18, wherein said thin film of silicon carbide is formed by heating said silicon substrate in a hydrocarbon atmosphere.

20. A method in accordance with claim 19, wherein after said heating step, said silicon substrate and said silicon carbide thin film are cooled to room temperature in an atmosphere of hydrogen.

21. A method in accordance with claim 18, wherein a difference between said lattice constant of said silicon carbide thin film and said gallium nitride crystal is less than a difference between said lattice constant of said silicon substrate and said gallium nitride crystal.

22. A method in accordance with claim 18, wherein said silicon substrate is removed by immersing said silicon substrate and said silicon carbide thin film in an acid solution which is obtain by mixing hydrofluoric acid and nitric acid, thereby removing only the silicon substrate.

23. A method in accordance with claim 18, wherein said thin film is formed to a thickness of about 5000 Å

and said gallium nitride crystal is formed to a thickness of about 30 μ

m on said semiconductor thin film.

24. A method of forming a gallium nitride crystal, comprising forming a thin film of silicon carbide and a gallium nitride crystal on a silicon substrate in that order, and removing said silicon substrate.

25. A method of forming a gallium nitride crystal in accordance with claim 24, wherein said thin film of silicon carbide is formed by heating said silicon substrate in a hydrocarbon atmosphere.

26. A method in accordance with claim 25, wherein after said heating step, said silicon substrate and said silicon carbide thin film are cooled to room temperature in an atmosphere of hydrogen.

27. A method in accordance with claim 24, wherein said silicon carbide thin film is formed to a thickness of about 500 Å

and said gallium nitride crystal is formed to a thickness of about 30 μ

m on said semiconductor thin film.

28. A method in accordance with claim 24, wherein said silicon substrate is removed by immersing said silicon substrate, said silicon carbide thin film and said gallium nitride crystal in an acid solution which is obtain by mixing hydrofluoric acid and nitric acid, thereby removing only said silicon substrate.