Semiconductor device and method of manufacturing the same
A method of manufacturing a semiconductor device includes irradiation of laser on a semiconductor substrate and cutting of the semiconductor substrate. The laser is irradiated on the semiconductor substrate while moving a focal point of the laser inside the semiconductor substrate. The semiconductor includes a specific crystal plane that is easier to be cleaved, and that is tilted to the surface of the semiconductor substrate. The irradiation of the laser includes repetition of a specific modified layer formation process in which one of the specific modified layers along the specific crystal plane is formed by moving the focal point along the specific crystal plane. In the irradiation of the laser, the specific modified layers are arranged in a direction parallel to the surface of the semiconductor substrate. In the cutting of the semiconductor substrate, the semiconductor substrate is cut along the specific modified layers.
1 . A semiconductor substrate for a semiconductor device, the semiconductor substrate comprising:
a front surface and a rear surface located on a side opposite from the front surface,
wherein the semiconductor substrate includes a specific crystal plane forming an acute angle with respect to the front surface and defining a direction along which the semiconductor substrate is more easily cleaved than along a direction parallel to the front surface under a constant energy of a cleaving tool,
wherein the rear surface has surface roughness with a plurality of protrusions,
wherein each of the plurality of protrusions has a tilted surface extending along the specific crystal plane, and
wherein the front surface of the semiconductor substrate is a c-plane.
2 . The semiconductor substrate according to claim 1 ,
wherein the semiconductor substrate is made of gallium nitride,
wherein the front surface of the semiconductor substrate is the c-plane of the gallium nitride, and
wherein the specific crystal plane is a (11-28) plane of the gallium nitride.
3 . The semiconductor substrate according to claim 1 ,
wherein the semiconductor substrate is made of gallium nitride,
wherein the front surface of the semiconductor substrate is the c-plane of the gallium nitride, and
wherein the specific crystal plane is tilted to the c-plane at an angle of 21.8 degrees in a cross section along an m-plane of the gallium nitride.
4 . The semiconductor substrate according to claim 1 , wherein
a tip of each of the plurality of protrusions points away from the rear surface of the semiconductor substrate.
5 . The semiconductor substrate according to claim 1 , wherein the semiconductor substrate is made of a material having a hexagonal crystal structure.
6 . The semiconductor substrate according to claim 1 , wherein the semiconductor substrate is made of a single crystal material having a hexagonal crystal structure.
7 . The semiconductor substrate according to claim 1 , wherein the semiconductor substrate is made of gallium nitride.
8 . The semiconductor substrate according to claim 1 , wherein the semiconductor substrate has optical transparency.
9 . The semiconductor substrate according to claim 5 , wherein the semiconductor substrate has optical transparency.
10 . A semiconductor substrate for a semiconductor device, the semiconductor substrate comprising:
a front surface; and
a rear surface located on a side opposite from the front surface, wherein
the semiconductor substrate is made of single-crystal gallium nitride,
the front surface is a c-plane of the single-crystal gallium nitride,
the rear surface has surface roughness with a plurality of protrusions, and
each of the plurality of protrusions has a tilted surface being a (11-28) plane of the single-crystal gallium nitride.