Group iii nitride crystal and method for surface treatment thereof, group iii nitride stack and manufacturing method thereof, and group iii nitride semiconductor device and manufacturing method thereof

Abstract

A method for surface treatment of a group III nitride crystal includes the steps of lapping a surface of a group III nitride crystal using a hard abrasive grain with a Mohs hardness higher than 7, and abrasive-grain-free polishing the lapped surface of the group III nitride crystal using a polishing solution without containing abrasive grain, and the polishing solution without containing abrasive grain has a pH of not less than 1 and not more than 6, or not less than 8.5 and not more than 14. Accordingly, the method for surface treatment of a group III nitride crystal can be provided according to which hard abrasive grains remaining at the lapped crystal can be removed to reduce impurities at the crystal surface.

1 - 13 . (canceled) 
     
     
         14 . A method for surface treatment of a group III nitride crystal, comprising the steps of:
 growing a group III nitride crystal by a gas phase method or a liquid phase method;   soft-abrasive-grain polishing for polishing said group III nitride crystal using a polishing solution containing a soft abrasive grain with a Mohs hardness of not more than 7; and   abrasive-grain-free polishing for polishing said group III nitride crystal using a polishing solution without containing abrasive grain.   
     
     
         15 . The method for surface treatment of a group III nitride crystal according to  claim 14 , wherein
 said gas phase method is a hydride vapor phase epitaxy method or a sublimation method.   
     
     
         16 . The method for surface treatment of a group III nitride crystal according to  claim 14 , wherein
 said soft abrasive grain contains one of ZrO 2 , SiO 2 , CeO 2 , MnO 2 , Fe 2 O 3 , Fe 3 O 4 , NiO, ZnO, CoO, CO 3 O 4 , GeO 2 , Ga 2 O 3  and In 2 O 3 .   
     
     
         17 . The method for surface treatment of a group III nitride crystal according to  claim 14 , wherein
 said polishing solution without containing abrasive grain has a pH of not less than 1 and not more than 6, or not less than 8.5 and not more than 14.   
     
     
         18 . The method for surface treatment of a group III nitride crystal according to  claim 14 , wherein
 said polishing solution without containing abrasive grain has a pH of not less than 2 and not more than 4, or not less than 10 and not more than 12.   
     
     
         19 . The method for surface treatment of a group III nitride crystal according to  claim 14 , further comprising the step of water cleaning, after said step of abrasive-grain-free polishing. 
     
     
         20 . The method for surface treatment of a group III nitride crystal according to  claim 14 , further comprising the step of lapping said group III nitride crystal using a hard abrasive grain with a Mohs hardness higher than 7, or the step of grinding said group III nitride crystal, after said step of growing said group III nitride crystal and before said step of soft-abrasive-grain polishing. 
     
     
         21 . The method for surface treatment of a group III nitride crystal according to  claim 20 , wherein
 in said step of lapping said group III nitride crystal using said hard abrasive grain, said hard abrasive grain contains one of diamond, SiC, BN, Si 3 N 4 , Al 2 O 3 , Cr 2 O 3  and ZrO 2 .   
     
     
         22 . The method for surface treatment of a group III nitride crystal according to  claim 20 , wherein
 in said step of lapping said group III nitride crystal using said hard abrasive grain, a multi-step lapping from the step using said hard abrasive grain of larger size to the step using said hard abrasive grain of smaller size is performed.   
     
     
         23 . The method for surface treatment of a group III nitride crystal according to  claim 14 , wherein
 said group III nitride crystal in a GaN crystal.   
     
     
         24 . A method for manufacturing a group III nitride semiconductor device using the group III nitride crystal as recited in  claim 14 , comprising the steps of:
 preparing said group III nitride crystal; and   epitaxially growing at least one group III nitride layer on said group III nitride crystal.