Method of surface treatment of group iii nitride crystal film, group iii nitride crystal substrate, group iii nitride crystal substrate with epitaxial layer, and semiconductor device

Abstract

A method of surface treatment of a Group III nitride crystal film includes polishing a surface of the Group III nitride crystal film, wherein a pH value x and an oxidation-reduction potential value y (mV) of a polishing liquid used for the polishing satisfy both relationships of y≧−50x+1,000 and y≦−50x+1,900.

1 . A method of surface treatment of a Group III nitride crystal film comprising:
 polishing a surface of the Group III nitride crystal film,   wherein a pH value x and an oxidation-reduction potential value y (mV) of a polishing liquid used for the polishing satisfy both relationships represented by Ex. (1) and Ex. (2):
     y≧− 50 x+ 1,000  (1) 
     y≧− 50 x+ 1,900  (2). 
   
   
   
       2 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the pH of the polishing liquid is up to 6 or at least 6. 
   
   
       3 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the polishing liquid comprises abrasive grains and the abrasive grains are high-hardness abrasive grains having a hardness higher than that of the Group III nitride crystal film, low-hardness abrasive grains having a hardness lower than or equal to that of the Group III nitride crystal film, or mixed abrasive grains containing the high-hardness abrasive grains and the low-hardness abrasive grains. 
   
   
       4 . The method of surface treatment of a Group III nitride crystal film according to  claim 3 , wherein the grain size of the high-hardness abrasive grain is 1 μm or less. 
   
   
       5 . The method of surface treatment of a Group III nitride crystal film according to  claim 3 , wherein the high-hardness abrasive grains comprise at least one material selected from the group consisting of diamond, SiC, Si 3 N 4 , BN, Al 2 O 3 , and ZrO 2 . 
   
   
       6 . The method of surface treatment of a Group III nitride crystal film according to  claim 3 , wherein the low-hardness abrasive grains comprise at least one material selected from the group consisting of SiO 2 , CeO 2 , TiO 2 , MgO, MnO 2 , Fe 2 O 3 , Fe 3 O 4 , NiO, ZnO, CoO, CO 3 O 4 , SnO 2 , CuO, Cu 2 O, GeO 2 , CaO, Ga 2 O 3 , and In 2 O 3 . 
   
   
       7 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein a surface of the Group III nitride crystal film is mechanically ground or mechanically lapped and the mechanically ground or mechanically lapped surface of the Group III nitride crystal film is then polished. 
   
   
       8 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the thickness of an affected layer after the polishing of the Group III nitride crystal film is 50 nm or less. 
   
   
       9 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the surface roughness Ry after the polishing of 20 the Group III nitride crystal film is 5 nm or less. 
   
   
       10 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the surface roughness Ra after the polishing of the Group III nitride crystal film is 0.5 nm or less. 
   
   
       11 . The method of surface treatment of a Group III nitride crystal film according to  claim 1 , wherein the Group III nitride crystal film after the polishing is subjected to thermal annealing 
   
   
       12 - 19 . (canceled)