Method for manufacturing group-III nitride substrate and group-III nitride substrate
There is provided a method for manufacturing a group-III nitride substrate, including: (a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal; (b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate; and (c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole.
1. A method for manufacturing a group-III nitride substrate, comprising:
(a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal;
(b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate; and
(c) epitaxially growing the same group-III nitride crystal as the group III-nitride crystal constituting the substrate in the through-hole, and embedding at least a front surface side opening of the through-hole with the group III-nitride crystal without gaps.
2. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), irradiation of laser beam is performed aiming at a domain which is a part of the high oxygen concentration domain, and which includes a center of the high oxygen concentration domain.
3. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), irradiation of laser beam is performed aiming at a domain which is a part of the high oxygen concentration domain, and which includes an intersection of diagonal lines of a polygonal shape which is either a hexagonal shape or a dodecagonal shape in planar view.
4. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), either a dislocation dense domain or a polarity inversion domain in the oxygen high-concentration domain is removed from the substrate.
5. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), a domain which is a part of the high oxygen concentration domain and which includes a dislocation dense domain or a polarity inversion domain, is removed from the substrate, and the other domain thereof is left on the substrate without being removed.
6. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein
in the (a), a substrate in a as-grown state is prepared as the substrate, which is obtained by growing the group-III nitride crystal represented by a composition formula Al x In y Ga l-x-y N (0≤x+y≤1, 0≤x≤1, 0≤y≤1) so that its surface becomes (0001) plane, and
in the (b), at least a part of the high oxygen concentration domain existing on a bottom surface side of a pit which observed on a front surface of the substrate, is removed from the substrate by irradiating the substrate with laser beam aiming at the pit to form the through-hole.
7. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein
in the (a), as the substrate, a substrate is prepared so that a pit appears on a front surface of the substrate by polishing (0001) plane which is the front surface of the substrate made of the group-III nitride crystal represented by a composition formula Al x In y Ga l-x-y N (0≤x+y≤1, 0≤x≤1, 0≤y≤1), and thereafter etching the polished surface, and
in the (b), at least a part of the high oxygen concentration domain existing on a bottom surface side of a pit which is observed on the front surface of the substrate, is removed from the substrate due to formation of the through-hole by irradiating the substrate with laser beam aiming at the pit.
8. The method for manufacturing a group-III nitride substrate according to claim 6 , wherein in the (b), a domain which is a part of the high oxygen concentration domain and which includes at least a polarity inversion domain is removed from the substrate.
9. The method for manufacturing a group-III nitride substrate according to claim 6 , wherein in the (b), a domain which is a part of the high oxygen concentration domain and which includes at least a polarity inversion domain is removed from the substrate, and the other domain thereof is left on the substrate without being removed.
10. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), a light-emitting state of the crystal is observed when irradiating the substrate with ultraviolet ray or electron ray, a domain with a different contrast from the matrix is identified, and the identified domain is irradiated with laser beam.
11. The method for manufacturing a group-III nitride substrate according to claim 10 , wherein in the (b), an image of the substrate is photographed using a camera, a domain with a different contrast from the matrix is identified by image recognition, and the identified domain is irradiated with laser beam.
12. The method for manufacturing a group-III nitride substrate according to claim 6 , wherein in the (b), an image of the front surface of the substrate is photographed using a camera, the pit is identified by image recognition, and the identified pit is irradiated with laser beam.
13. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), intermittently irradiation of laser beam is performed multiple number of times while shifting an irradiating position.
14. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), continuous irradiation of laser beam is performed while shifting an irradiating position.
15. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein in the (b), a laser beam irradiating condition is controlled so that a minimum width of the through-hole as viewed from a front surface side of the substrate is set to 300 μm or less.
16. The method for manufacturing a group-III nitride substrate according to claim 1 , wherein the (c) is performed in a state of holding the substrate on a supporting plate using a vapor phase growth method so as not to seal an opening which is one of two openings of the through-hole, and which is located on a back surface side opposed to the supporting plate.
17. The method for manufacturing a group-III nitiride substrate according to claim 1 , further comprising:
(d) growing a crystal film made of the group-III nitride crystal on the group-III nitride substrate obtained by performing the (c),
wherein in the (c) and (d), crystal growth is respectively performed by a vapor phase growth method, and
processing conditions are differentiated between the (c) and the (d) so that:
a crystal growth toward a creeping direction of the substrate in the (c) becomes more active than a crystal growth toward a creeping direction of the substrate in the (d); and
a crystal growth toward a main surface direction of the substrate in the (d) becomes more active than a crystal growth toward a main surface direction of the substrate in the (c).
18. A method for manufacturing a group-III nitride substrate, comprising:
(a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal;
(b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate;
(c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole; and
(d) growing a crystal film made of the group-III nitride crystal on a group-III nitride substrate obtained by performing (c),
wherein in (c) and (d), crystal growth is respectively performed by a vapor phase growth method.
19. A method for manufacturing a group-III nitride substrate, comprising:
(a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal;
(b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate;
(c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole; and
(d) growing a crystal film made of the group-III nitride crystal on a group-III nitride substrate obtained by performing the (c),
wherein in (c) and (d), crystal growth is respectively performed by a vapor phase growth method, and
processing conditions are differentiated between (c) and (d) so that:
a crystal growth toward a creeping direction of the substrate in (c) becomes more active than a crystal growth toward a creeping direction of the substrate in (d); and
a crystal growth toward a main surface direction of the substrate in (d) becomes more active than a crystal growth toward a main surface direction of the substrate in (c).