EVALUATION METHOD AND MANUFACTURING METHOD OF SiC EPITAXIAL WAFER

Abstract

A SiC epitaxial wafer including a high-concentration epitaxial layer having an impurity concentration of 1×10 18 cm −3 or more, and the number or positions of basal plane dislocations included in the high-concentration epitaxial layer have been identified

1 . A SiC epitaxial wafer, comprising
 a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more, and   the number of basal plane dislocations included in the high-concentration epitaxial layer have been identified.   
     
     
         2 . The SiC epitaxial wafer according to  claim 1 , further comprising a drift layer which has a lower impurity concentration than that of the high-concentration epitaxial layer. 
     
     
         3 . A SiC epitaxial wafer, comprising
 a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more, and   positions of basal plane dislocations included in the high-concentration epitaxial layer have been identified.   
     
     
         4 . The SiC epitaxial wafer according to  claim 3 , further comprising a drift layer which has a lower impurity concentration than that of the high-concentration epitaxial layer. 
     
     
         5 . The SiC epitaxial wafer according to  claim 1 , wherein positions of basal plane dislocations included in the high-concentration epitaxial layer have been identified. 
     
     
         6 . The SiC epitaxial wafer according to  claim 1 , wherein the SiC epitaxial wafer has a diameter of a 6-inch or more. 
     
     
         7 . The SiC epitaxial wafer according to  claim 1 , wherein the high-concentration epitaxial layer has an impurity concentration of 1×10 18  cm −3  or more and 2×10 19  cm −3  or less. 
     
     
         8 . The SiC epitaxial wafer according to  claim 1 , wherein the high-concentration epitaxial layer has an impurity concentration of 1×10 18  cm −3  or more and 1×10 19  cm −3  or less. 
     
     
         9 . The SiC epitaxial wafer according to  claim 1 , wherein the SiC epitaxial wafer is manufactured by a method comprising:
 stacking a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more on one surface of a SiC substrate;   irradiating a surface of the high-concentration epitaxial layer having the impurity concentration of 1×10 18  cm −3  or more with excitation light,   observing via a band-pass filter having a wavelength band of 430 nm or less the surface irradiated with the excitation light, wherein the observing step is referred to as a first observation step,   observing via a band-pass filter having a wavelength band of more than 430 nm the surface irradiated with the excitation light, wherein the observing step is referred to as a second observation step; and   comparing an observation result of the first observation step with an evaluation result of the second observation step to perform a determination, and   stacking a drift layer on the high-concentration epitaxial layer.   
     
     
         10 . The SiC epitaxial wafer according to  claim 1 , wherein the SiC epitaxial wafer is manufactured by a method comprising:
 stacking a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more on one surface of a SiC substrate;   irradiating a surface of the high-concentration epitaxial layer having the impurity concentration of 1×10 18  cm −3  or more with excitation light,   observing via a band-pass filter having a wavelength band of 430 nm or less the surface irradiated with the excitation light, wherein the observing step is referred to as a first observation,   performing surface observation on a surface which is the same as the surface irradiated with the excitation light and before being irradiated with the excitation light, wherein the step is referred to as a third observation; and   comparing an observation result of the first observation step with an evaluation result of the third observation step to perform a determination; and   stacking a drift layer on the high-concentration epitaxial layer.   
     
     
         11 . The SiC epitaxial wafer according to  claim 1 , wherein the number of the basal plane dislocations included in the high-concentration epitaxial layer have been identified by an evaluation method comprising
 a first observation step of
 preparing a SiC epitaxial wafer having a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more, 
 irradiating a surface of the high-concentration epitaxial layer having the impurity concentration of 1×10 18  cm −3  or more with excitation light, and 
 observing via a band-pass filter having a wavelength band of 430 nm or less the surface irradiated with the excitation light, 
   a second observation step of observing via a band-pass filter having a wavelength band of more than 430 nm the surface irradiated with the excitation light; and   a determination step of comparing an observation result of the first observation step with an evaluation result of the second observation step to identify the number of the basal plane dislocations included in the high-concentration epitaxial layer.   
     
     
         12 . The SiC epitaxial wafer according to  claim 1 , wherein the number of the basal plane dislocations included in the high-concentration epitaxial layer have been identified by an evaluation method comprising
 a first observation step of
 preparing a SiC epitaxial wafer having a high-concentration epitaxial layer having an impurity concentration of 1×10 18  cm −3  or more, 
 irradiating a surface of the high-concentration epitaxial layer having the impurity concentration of 1×10 18  cm −3  or more with excitation light, and 
 observing via a band-pass filter having a wavelength band of 430 nm or less the surface irradiated with the excitation light, 
   a third observation step of performing surface observation on a surface which is the same as the surface irradiated with the excitation light and before being irradiated with the excitation light; and   a determination step of comparing an observation result of the first observation step with an evaluation result of the third observation step to identify the number of the basal plane dislocations included in the high-concentration epitaxial layer.   
     
     
         13 . The SiC epitaxial wafer according to  claim 2 , wherein the drift layer has an impurity concentration which is less than 1×10 17  cm 3 . 
     
     
         14 . The SiC epitaxial wafer according to  claim 1 , wherein the basal plane dislocations are dislocations which look dark compared to the other regions, when a surface irradiated with excitation light is observed via a band-pass filter having a wavelength band of 430 nm or less. 
     
     
         15 . The SiC epitaxial wafer according to  claim 2 , wherein the drift layer is stacked on the high-concentration epitaxial layer. 
     
     
         16 . The SiC epitaxial wafer according to  claim 2 , wherein the high-concentration epitaxial layer is located between the drift layer and a SiC substrate which is included in the SiC epitaxial wafer. 
     
     
         17 . The SiC epitaxial wafer according to  claim 4 , wherein the drift layer is stacked on the high-concentration epitaxial layer.