Indium phosphide substrate, semiconductor epitaxial wafer, and method for producing indium phosphide substrate
Provided is an indium phosphide substrate, a semiconductor epitaxial wafer, and a method for producing an indium phosphide substrate, which can satisfactorily suppress warpage of the back surface of the substrate. The indium phosphide substrate includes a main surface for forming an epitaxial crystal layer and a back surface opposite to the main surface, wherein the back surface has a SORI value of 2.5 μm or less, as measured with the back surface of the indium phosphide substrate facing upward.
1. An indium phosphide substrate comprising a main surface for forming an epitaxial crystal layer and a back surface opposite to the main surface,
wherein the back surface has a SORI value of 2.5 μm or less, as measured with the back surface of the indium phosphide substrate facing upward.
2. The indium phosphide substrate according to claim 1 , wherein the back surface has a SORI value of 1.6 to 2.5 μm, as measured with the back surface of the indium phosphide substrate facing upward.
3. The indium phosphide substrate according to claim 2 , wherein the back surface has a SORI value of 1.6 to 2.5 μm, as measured with the back surface of the indium phosphide substrate facing upward, and the substrate has a diameter of 100 mm or less.
4. The indium phosphide substrate according to claim 2 , wherein the back surface has a SORI value of 1.6 to 1.8 μm, as measured with the back surface of the indium phosphide substrate facing upward, and the substrate has a diameter of 76.2 mm or less.
5. The indium phosphide substrate according to claim 1 , wherein the back surface has a SORI value of 1.7 μm or less, as measured with the back surface of the indium phosphide substrate facing upward, and the substrate has a diameter of 50.8 mm or less.
6. A semiconductor epitaxial wafer comprising an epitaxial crystal layer on the main surface of the indium phosphide substrate according to claim 1 .
7. A method for producing the indium phosphide substrate according to claim 1 , comprising the steps of:
cutting a wafer from an indium phosphide ingot with a wire saw;
etching the cut wafer;
chamfering an outer peripheral portion of the wafer after the etching;
polishing at least one surface of the chamfered wafer; and
etching the polished wafer,
wherein the step of cutting the wafer from the indium phosphide ingot with the wire saw comprises a step of constantly delivering a new wire while reciprocating the wire in a horizontal direction, and moving a stage on which the indium phosphide ingot is placed in a vertical direction toward the wire, wherein a new wire delivering rate of the wire is from 10 to 60 m/min, a reciprocating rate of the wire is from 300 to 350 m/min, a vertical moving rate of the stage on which the indium phosphide ingot is placed is from 200 to 400 μm/min, and abrasive grains of the wire saw have a viscosity of from 300 to 400 mPa·s,
wherein the step of etching the cut wafer comprises etching the cut wafer by a total of 5 to 15 μm from both sides, and
wherein the step of etching the polished wafer comprises etching the polished wafer by a total of 8 to 15 μm from both sides.