WAFER, EPITAXIAL WAFER, METHOD FOR MANUFACTURING A WAFER AND METHOD FOR MANUFACTURING AN EPITAXIAL WAFER
An epitaxial wafer including a wafer having one surface and an other surface, and an epitaxial layer formed on the one surface of the wafer, wherein a roughness skewness (Rsk) of the one surface is −3 nm to 3 nm, and a roughness average (Ra) of an edge area of the one surface is different from that of a central area of the one surface by −2 nm to 2 nm when the edge area of the one surface is defined as an area between 13.3% and 32.1% of the radius of the wafer in a direction from the edge of the one surface toward the center thereof and the central area of the one surface is defined as an area at 9.4% of the radius of the wafer from the center of the one surface.
1 . An epitaxial wafer comprising:
a wafer comprising one surface and an other surface; and
an epitaxial layer formed on the one surface of the wafer,
wherein a roughness skewness (Rsk) of the one surface is −3 nm to 3 nm, and a roughness average (Ra) of an edge area of the one surface is different from that of a central area of the one surface by −2 nm to 2 nm when the edge area of the one surface is defined as an area between 13.3% and 32.1% of the radius of the wafer in a direction from the edge of the one surface toward the center thereof and the central area of the one surface is defined as an area at 9.4% of the radius of the wafer from the center of the one surface.
2 . The epitaxial wafer according to claim 1 , wherein the epitaxial wafer has a Tu of 5% or less, the Tu being defined by Equation 1:
T
u
=
(
T
max
-
T
min
)
T
a
v
g
×
1
0
0
(
1
)
where Tu, Tmax, Tmin, and Tavg are the thickness non-uniformity, maximum thickness, minimum thickness, and average thickness of the epitaxial layer, respectively.
3 . The epitaxial wafer according to claim 1 , wherein the one surface is a Si plane where a silicon atomic layer is formed.
4 . The epitaxial wafer according to claim 1 , wherein the Ra of the central area of the one surface is 4 nm or less.
5 . The epitaxial wafer according to claim 1 , wherein the Ra of the edge area of the one surface is 5 nm or less.
6 . The epitaxial wafer according to claim 1 , wherein the Rsk of the one surface is −2 nm to 2 nm.
7 . The epitaxial wafer according to claim 1 , wherein the wafer is a 4H silicon carbide wafer of 4 inches or more.
8 . A wafer comprising:
one surface and an other surface,
wherein a roughness skewness (Rsk) of the one surface is −3 nm to 3 nm and a roughness average (Ra) of an edge area of the one surface is different from that of a central area of the one surface by −2 nm to 2 nm when the edge area of the one surface is defined as an area between 13.3% and 32.1% of the radius of the wafer in a direction from the edge of the one surface toward the center thereof and the central area of the one surface is defined as an area at 9.4% of the radius of the wafer from the center of the one surface.
9 . The wafer according to claim 8 , wherein the one surface is a Si plane where a silicon atomic layer is formed.
10 . The wafer according to claim 8 , wherein the Ra of the central area of the one surface is 4 nm or less and the Ra of the edge area of the one surface is 5 nm or less.
11 . The wafer according to claim 8 , wherein the Rsk of the one surface is −2 nm to 2 nm.
12 . A method for manufacturing an epitaxial wafer, comprising:
arranging a raw material and a silicon carbide seed crystal to face each other in a reactor having an internal space;
controlling the internal space to a predetermined temperature, pressure, and atmosphere to sublimate the raw material and grow a silicon carbide ingot from the seed crystal, wherein a heat insulating material surrounds the outer surface of the reactor, a heater controls the temperature of the reactor or the internal space, and the density of the heat insulating material is 0.13 g/cc to 0.28 g/cc;
cooling the reactor and recovering the silicon carbide ingot;
cutting the recovered silicon carbide ingot into a wafer;
planarizing the wafer and polishing the surface of the planarized wafer comprising bringing a plurality of grinding wheels having different surface particle sizes into contact with the wafer, resulting in the roughness skewness (Rsk) of one surface of the wafer being −3 nm to 3 nm, and the roughness average (Ra) of an edge area of the one surface being different from that of a central area of the one surface by −2 nm to 2 nm when the edge area of the one surface is defined as an area between 13.3% and 32.1% of the radius of the wafer in a direction from the edge of the one surface toward the center thereof and the central area of the one surface is defined as an area at 9.4% of the radius of the wafer from the center of the one surface; and
injecting raw material gases for epitaxial growth into a growth container in which the wafer is arranged, and growing an epitaxial layer on the one surface of the wafer by chemical vapor deposition.
13 . The method according to claim 12 , wherein the epitaxial wafer has a Tu of 5% or less, the Tu being defined by Equation 1:
T
u
=
(
T
max
-
T
min
)
T
a
v
g
×
1
0
0
(
1
)
where Tu, Tmax, Tmin, and Tavg are the thickness non-uniformity, maximum thickness, minimum thickness, and average thickness of the epitaxial layer, respectively.