III-V group nitride system semiconductor self-standing substrate, method of making the same and III-V group nitride system semiconductor wafer

• US 20060033119A1
• Filed: 02/09/2005
• Published: 02/16/2006
• Est. Priority Date: 08/10/2004
• Status: Active Grant

• Current Assignee: Sumitomo Chemical Company Limited
• Original Assignee: Hitachi Cable Limited (Proterial Ltd.)
• Inventors: Shibata, Masatomo
• Granted Patent: US 7,230,282 B2
• Time in Patent Office: Days
• US Class Current: 257/103
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02491 Conductive materials
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/02647 Lateral overgrowth

Abstract

A III-V group nitride system semiconductor self-standing substrate has: a first III-V group nitride system semiconductor crystal layer that has a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly; and a second III-V group nitride system semiconductor crystal layer that is formed up to 10 μm from the surface of the substrate on the first III-V group nitride system semiconductor crystal layer and that has a dislocation density distribution that is substantially uniform.

Claims

1. A III-V group nitride system semiconductor self-standing substrate, comprising:

III-V group nitride system semiconductor crystal,

wherein the substrate has a dislocation density distribution that is substantially uniform at least at a surface of the substrate.

2. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has a dislocation density distribution that is substantially uniform at an arbitrary cross section that is in parallel to the surface of the substrate and is located up to 10 μ

m from the surface of the substrate.

3. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has an average dislocation density of 5×

10⁷ cm<sup>−

2</sup> or less at an arbitrary cross section that is in parallel to the surface of the substrate and is located up to 10 μ

m from the surface of the substrate, and

the number of dislocation lines intersecting a unit area of 400 μ

m at an arbitrary position on the cross section is less than 400.

6. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has an average dislocation density of 5×

10⁷ cm<sup>−

2</sup> or less at a surface of the substrate.

7. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has an average dislocation density at a surface of the substrate that is lower than an average dislocation density at a back surface of the substrate.

8. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has a dispersion range of dislocation density at a surface of the substrate that is the same as or smaller than a dispersion range of dislocation density at a back surface of the substrate.

10. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has the surface polished.

11. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has a back surface polished.

12. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has (0001) III-group face at the surface.

13. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the substrate has a thickness of 200 μ

m or more and 1 mm or less.

14. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the III-V group nitride system semiconductor crystal has a composition represented by In_xGa_yAl_1-x-yN (0≦

x≦

1, 0≦

y≦

1, 0≦

x+y≦

1).

15. The III-V group nitride system semiconductor self-standing substrate according to claim 1, wherein:

the III-V group nitride system semiconductor crystal is doped with an impurity.

4. A III-V group nitride system semiconductor self-standing substrate, comprising:

III-V group nitride system semiconductor crystal, wherein the substrate comprises;

a first III-V group nitride system semiconductor crystal layer that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly; and

a second III-V group nitride system semiconductor crystal layer that is formed up to 10 μ

m from the surface of the substrate on the first III-V group nitride system semiconductor crystal layer and that has a dislocation density distribution that is substantially uniform.

5. The III-V group nitride system semiconductor self-standing substrate according to claim 4, wherein:

the dislocation density distribution varies continuously between the first III-V group nitride system semiconductor crystal layer and the second III-V group nitride system semiconductor crystal layer.

9. The III-V group nitride system semiconductor self-standing substrate according to claim 4, wherein:

the first III-V group nitride system semiconductor crystal layer comprises a plurality of the regions with dislocation lines gathered densely, and

the regions are separated with an interval of 10 μ

m or more from each other.

16. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly; and

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution.

23. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, further comprising the step of:

mirror-polishing a surface of the substrate so as not to have a thickness of the substrate 200 μ

m or less.

24. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, further comprising the step of:

removing all the first III-V group nitride system semiconductor crystal layer.

25. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

the second III-V group nitride system semiconductor crystal layer is grown thick; and

the method further comprising the step of;

cutting the second III-V group nitride system semiconductor crystal layer in a direction perpendicular to the growth direction of the crystal to obtain the substrate.

27. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 25, further comprising the step of:

polishing upper and lower surfaces of the substrate obtained by the cutting step.

28. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

part of the crystal growth is conducted by using the HVPE method.

29. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

the flattening step is conducted such that a concentration of hydrogen in growth atmosphere gas is increased in process of the crystal growth such that the concaves on the crystal growth interface are filled to flatten the crystal growth interface.

30. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

the flattening step is conducted such that a partial pressure of III-group source gas is increased in process of the crystal growth such that the concaves on the crystal growth interface are filled to flatten the crystal growth interface.

31. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

the step of growing the crystal while generating the plurality of concaves is conducted such that the concave is V-shaped or inverted trapezoidal in cross section parallel to a growth direction of the crystal while being surrounded by low index crystal facets.

32. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 16, wherein:

the step of growing the crystal while generating the plurality of concaves is conducted such that the concave is cone-shaped in cross section parallel to a growth direction of the crystal while being surrounded by facets.

17. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly;

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution; and

polishing a surface of the substrate such that the second III-V group nitride system semiconductor crystal layer has a thickness of 10 μ

m or more after the polishing.

18. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal on a hetero-substrate while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly;

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution; and

separating the III-V group nitride system semiconductor crystal grown on the hetero-substrate from the hetero-substrate.

26. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 18, further comprising the step of:

cutting the second III-V group nitride system semiconductor crystal layer in a direction perpendicular to the growth direction of the crystal to obtain the substrate.

19. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal on a hetero-substrate while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly;

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution;

separating the III-V group nitride system semiconductor crystal grown on the hetero-substrate from the hetero-substrate; and

subsequently polishing a surface of the substrate such that the second III-V group nitride system semiconductor crystal layer has a thickness of 10 μ

m or more after the polishing.

20. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly;

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution; and

removing part of the first III-V group nitride system semiconductor crystal layer.

21. A method of making a III-V group nitride system semiconductor self-standing substrate, comprising the steps of:

growing a III-V group nitride system semiconductor crystal on a hetero-substrate while generating a plurality of concaves on a crystal growth interface;

flattening the crystal growth interface by growing the III-V group nitride system semiconductor crystal to fill the plurality of concaves, whereby dislocation lines generated in the crystal are gathered while reducing a dislocation density of the entire III-V group nitride system semiconductor crystal, and a first III-V group nitride system semiconductor crystal layer is formed that comprises a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly;

subsequently growing the crystal while keeping the crystal growth interface flattened, whereby a transitional layer is formed that the dislocation lines once gathered are uniformly dispersed again in the crystal, and a second III-V group nitride system semiconductor crystal layer is formed with a thickness of 10 μ

m or more on the transitional layer, the second III-V group nitride system semiconductor crystal layer having a low dislocation density and a substantially uniform dislocation density distribution;

separating the III-V group nitride system semiconductor crystal grown on the hetero-substrate from the hetero-substrate; and

subsequently removing part of the first III-V group nitride system semiconductor crystal layer.

22. The method of making a III-V group nitride system semiconductor self-standing substrate according to claim 21, wherein:

the removing step is conducted by polishing a back surface of the substrate so as not to have a thickness of the substrate 200 μ

m or less.

33. A III-V group nitride system semiconductor wafer, comprising:

a self-standing substrate that is of III-V group nitride system semiconductor crystal, the substrate having a dislocation density distribution that is substantially uniform at a surface layer up to 10 μ

m from a surface of the substrate; and

a III-V group nitride system semiconductor layer that is homo-epitaxially grown on the self-standing substrate.