SiC single crystal, production method therefor, SiC wafer and semiconductor device

1. A method for producing an SiC single crystal, having the following constitution:

(a) the method for producing an SiC single crystal repeats an a-plane growth step n (n≧2) times;

(b) a first a-plane growth step is a step for carrying out the a-plane growth of an SiC single crystal on a first growth plane by using a first seed crystal having the first growth plane with an offset angle from the {0001} plane of 80° to 100°;

(c) a k-th a-plane growth step (2≦k≦n) is a step for cutting out a k-th seed crystal having a k-th growth plane with a growth direction 45° to 135° different from the growth direction of a (k−1)-th a-plane growth step and an offset angle from the {0001} plane of 80° to 100° from a (k−1)-th grown crystal obtained in the (k−1)-th a-plane growth step, and carrying out the a-plane growth of an SiC single crystal on the k-th growth plane; and

(d) the k-th a-plane growth step (1≦k≦n) is a step for carrying out the a-plane growth of an SiC single crystal on the k-th growth plane so that an area ratio S facet of a Si-plane side facet region represented by the equation (A) is maintained at 20% or less:

S facet (%)= S 1 ×100 /S 2   (A)

where S 1 is the sum of the total area of areas obtained by projecting polar plane steps of Si-plane side on the k-th growth plane and the total area of areas obtained by projecting {1-100} plane facets sandwiched between the polar plane steps of Si-plane side on the k-th growth plane, and S 2 is the total area of the k-th growth plane.

2. The method for producing an SiC single crystal according to claim 1 ,

wherein the first a-plane growth step is a step for growing the SiC single crystal on the {11-20} plane by using the first seed crystal having the first growth plane with an offset angle θ 1 from the {11-20} plane of −15° to 15°, and

the k-th a-plane growth step (2≦k≦n) is a step for cutting out the k-th seed crystal having the k-th growth plane with a growth direction about 60° or about 120° different from the growth direction of the (k−1)-th a-plane growth step and an offset angle θ k from the {11-20} plane of −15° to 15° from the (k−1)-th grown crystal obtained in the (k−1)-th a-plane growth step, and carrying out the {11-20} plane growth of the SiC single crystal by using the k-th seed crystal.

3. The method for producing an SiC single crystal according to claim 2 , wherein the k-th a-plane growth step (1≦k≦n−1) is a step for carrying out the {11-20} plane growth of SiC on the k-th growth plane so that the relationship of the following expression (1) is established.

H k >L k sin(60°+|θ k |+|θ k+1 |)  (1)

where H k is a growth height in the k-th a-plane growth step, L k is a length in the {0001} plane direction of the k-th growth plane of the k-th seed crystal, and θ k and θ k+1 have opposite signs and their rotation directions are directions for increasing a length L k+1 in the {0001} plane direction of the (k+1)-th growth plane of a (k+1)-th seed crystal.

4. The method for producing an SiC single crystal according to claim 2 , wherein the k-th a-plane growth step (2≦k≦n) is a step for cutting out the k-th seed crystal having the relationship of the following expression (2) from the (k−1)-th grown crystal, and carrying out the {11-20} plane growth of the SiC single crystal on the k-th growth plane:

L k ≈H k−1 /cos(30°−|θ k−1 |−|θ k |)  (2)

where H k−1 is a growth height in the (k−1)-th growth step, L k is a length in the {0001} plane direction of the k-th growth plane of the k-th seed crystal, and θ k+1 and θ k have opposite signs and their rotation directions are directions for increasing L k .

5. The method for producing an SiC single crystal according to claim 2 , wherein the k-th a-plane growth step (1≦k≦n−1) is a step for carrying out the {11-20} plane growth of the SiC single crystal on the k-th growth plane such that the following expression (3) is satisfied:

H k ≧L k tan(60°+|θ k |+|θ k+1 |)  (3)

where H k is a growth height in the k-th a-plane growth step, L k is a length in the {0001} plane direction of the k-th growth plane of the k-th seed crystal, and θ k and θ k+1 have opposite signs and their rotation directions are directions for increasing the length L k+1 in the {0001} plane direction of the (k+1)-th growth plane of the (k+1)-th seed crystal.

6. The method for producing an SiC single crystal according to claim 2 , wherein the k-th a-plane growth step (2≦k≦n) is a step for cutting out the k-th seed crystal from the (k−1)-th grown crystal so that the following expression (4) is satisfied, and carrying out the {11-20} plane growth of the SiC single crystal on the k-th growth plane:

L k−1 ≈L k−1 /sin(30°−|θ k−1 |−|θ k |)  (4)

where L k−1 is a length in the {0001} plane direction of the (k−1)-th growth plane of the (k−1)-th seed crystal, L k is a length in the {0001} plane direction of the k-th growth plane of the k-th seed crystal, and θ k−1 and θ k have opposite signs and their rotation directions are directions for increasing L k .

7. The method for producing an SiC single crystal according to claim 2 , wherein the k-th a-plane growth step (2≦k≦n) is a step for cutting the (k−1)-th grown crystal obtained in the (k−1)-th a-plane growth step along the k-th growth plane having a growth direction about 60° or about 120° different from the growth direction of the (k−1)-th a-plane growth step and an offset angle θ k from the {11-20} plane of −15° to 15° so that most of the (k−1)-th grown crystal remains, and carrying out the {11-20} plane growth of the SiC single crystal by using the (k−1)-th grown crystal from which the k-th growth plane is exposed as the k-th seed crystal.

8. The method for producing an SiC single crystal according to claim 2 , wherein |θ k−1 |=|θ k |(2≦k≦n).

9. The method for producing an SiC single crystal according to claim 1 ,

wherein the first a-plane growth step is a step for carrying out the {1-100} plane growth or {11-20} plane growth of the SiC single crystal by using the first seed crystal having the first growth plane with an offset angle θ 1 from the {1-100} plane or {11-20} plane of −15° to 15°, and

the k-th a-plane growth step (2≦k≦n) is a step for cutting out the k-th seed crystal having the k-th growth plane with a growth direction about 90° different from the growth direction of the (k−1)-th a-plane growth step and an offset angle θ k from the {11-20} plane or {1-100} plane of −15° to 15° from the (k−1)-th grown crystal obtained in the (k−1)-th a-plane growth step, and carrying out {11-20} plane growth or {1-100} plane growth of the SiC single crystal by using the k-th seed crystal.

10. The method for producing an SiC single crystal according to claim 1 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of the SiC single crystal so that the topmost portion of the {1-100} plane facet is situated on the Si-plane near side with respect to the center in the c-axis direction of the k-th growth plane.

11. The method for producing an SiC single crystal according to claim 10 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of the SiC single crystal so that the temperature on the Si-plane near side with respect to the center in the c-axis direction of the k-th growth plane becomes lower than that at the center in the c-axis direction.

12. The method for producing an SiC single crystal according to claim 10 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of the SiC single crystal so that the concentration of SiC gas on the Si-plane near side with respect to the center in the c-axis direction of the k-th growth plane becomes higher than that at the center in the c-axis direction.

13. The method for producing an SiC single crystal according to claim 10 , wherein when the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {11-20} plane growth of the SiC single crystal, the k-th a-plane growth step is a step for carrying out the {11-20} plane growth of SiC by using the k-th seed crystal having a larger length on the Si-plane near side with respect to the center in the c-axis direction than that on the C-plane near side.

14. The method for producing an SiC single crystal according to claim 1 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of SiC by using the k-th seed crystal obtained by joining together at least two seed crystal segments in such a manner that their Si-planes are opposed to each other.

15. The method for producing an SiC single crystal according to claim 1 , wherein when the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth of the SiC single crystal, the k-th a-plane growth step is a step for carrying out the {1-100} plane growth of the SiC single crystal so that the area of a region having a height difference of 1 mm or less within the facet region accounts for 90% or more of the total area of the facet region.

16. The method for producing an SiC single crystal according to claim 1 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of SiC by using the k-th seed crystal obtained by placing a dummy seed crystal next to the main seed crystal.

17. The method for producing an SiC single crystal according to claim 1 , wherein when the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth of the SiC single crystal, the k-th a-plane growth step is a step for carrying out the {1-100} plane growth of the SiC single crystal so that the surface of the k-th grown crystal becomes convex in the {0001} plane direction, that is, r<L is satisfied when “L” represents the length in the {0001} plane direction of the k-th grown crystal and “r” represents the curvature in the {0001} plane direction of the surface of the k-th grown crystal.

18. The method for producing an SiC single crystal according to claim 17 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth of the SiC single crystal so that the topmost portion of the {1-100} plane facet is situated on the end side with respect to the center in the c-plane direction of the k-th growth plane.

19. The method for producing an SiC single crystal according to claim 1 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the {1-100} plane growth or {11-20} plane growth of SiC in an atmosphere in which the nitrogen gas partial pressure is 5% or less.

20. The method for producing an SiC single crystal according to claim 1 , wherein the k-th a-plane growth step (1≦k≦n) is a step for carrying out the a-plane growth of the SiC single crystal on the k-th growth plane by using the k-th seed crystal having the k-th growth plane with an offset angle from the {0001} plane of more than 85° to less than 95°.

21. The method for producing an SiC single crystal according to claim 1 , further comprising the following constitution:

(e) the method for producing an SiC single crystal comprises a c-plane growth step for cutting out a (n+1)-th seed crystal having a (n+1)-th growth plane with an absolute value of offset angle from the {0001} plane of 30° or less from the n-th grown crystal, and carrying out the c-plane growth of the SiC single crystal on the (n+1)-th growth plane.

22. An SiC single crystal which is obtained by the method of claim 1 and does not contain differently oriented crystalline masses or heterogeneous polytype crystalline masses in a region excluding 20% of the region from the periphery.

23. The SiC single crystal according to claim 22 which does not contain the differently oriented crystalline masses or the heterogeneous polytype crystalline masses in a region excluding 10% of the region from the periphery.

24. The SiC single crystal according to claim 22 , wherein a diameter of the {0001} plane is 100 mm or more.

25. The SiC single crystal according to claim 22 , wherein a diameter of the {0001} plane is 150 mm or more.

26. The SiC single crystal according to claim 22 , wherein a volume ratio of a {1-100} plane facet mark is 40% or less.

27. The SiC single crystal according to claim 22 , wherein a volume ratio of the {1-100} plane facet mark is 20% or less.

28. The SiC single crystal according to claim 22 , wherein a volume ratio of the {1-100} plane facet mark including polar plane steps of Si-plane side is 20% or less.

29. The SiC single crystal according to claim 22 , wherein a volume ratio of the {1-100} plane facet mark including polar plane steps of Si-plane side is 10% or less.

30. An SiC wafer which is cut out from the SiC single crystal of claim 22 and whose widest plane has an absolute value of offset angle from the {0001} plane of 30° or less.

31. An SiC single crystal obtained by carrying out c-plane growth using the SiC wafer of claim 30 .

32. An SiC wafer cut out from the SiC single crystal of claim 31 .

33. A semiconductor device produced by using the SiC single crystal of claim 22 .

34. The semiconductor device according to claim 33 which is a diode, transistor or LED.