Method of Manufacturing GaN-Based Film and Composite Substrate Used Therefor

Abstract

The present method of manufacturing a GaN-based film includes the steps of preparing a composite substrate ( 10 ) including a support substrate ( 11 ) dissoluble in hydrofluoric acid and a single crystal film ( 13 ) arranged on a side of a main surface ( 11 m ) of the support substrate ( 11 ), a coefficient of thermal expansion in the main surface ( 11 m ) of the support substrate ( 11 ) being more than 0.8 time and less than 1.2 times as high as a coefficient of thermal expansion of GaN crystal, forming a GaN-based film ( 20 ) on a main surface ( 13 m ) of the single crystal film ( 13 ) arranged on the side of the main surface ( 11 m ) of the support substrate ( 11 ), and removing the support substrate ( 11 ) by dissolving the support substrate ( 11 ) in hydrofluoric acid. Thus, the method of manufacturing a GaN-based film capable of efficiently obtaining a GaN-based film having a large main surface area, less warpage, and good crystallinity, as well as a composite substrate used therefor are provided.

1 - 6 . (canceled) 
     
     
         7 . A method of manufacturing a GaN-based film, comprising the steps of:
 preparing a composite substrate including a support substrate dissoluble in hydrofluoric acid and a single crystal film arranged on a side of a main surface of said support substrate, a coefficient of thermal expansion in the main surface of said support substrate being more than 0.8 time and less than 1.2 times as high as a coefficient of thermal expansion of GaN crystal;   forming a GaN-based film on a main surface of said single crystal film arranged on the side of the main surface of said support substrate; and   removing said support substrate by dissolving the support substrate in hydrofluoric acid.   
     
     
         8 . The method of manufacturing a GaN-based film according to  claim 7 , wherein
 said support substrate contains at least any of zirconia and silica and a ZrO 2 —SiO 2  composite oxide formed of zirconia and silica.   
     
     
         9 . The method of manufacturing a GaN-based film according to  claim 7 , wherein
 said support substrate contains yttria stabilized zirconia and an Al 2 O 3 —SiO 2  composite oxide formed of alumina and silica.   
     
     
         10 . The method of manufacturing a GaN-based film according to  claim 9 , wherein
 a content of said yttria stabilized zirconia to total of said Al 2 O 3 —SiO 2  composite oxide and said yttria stabilized zirconia is not lower than 20 mass % and not higher than 40 mass %.   
     
     
         11 . The method of manufacturing a GaN-based film according to  claim 10 , wherein
 a content of yttria to said yttria stabilized zirconia is not lower than 5 mol %.   
     
     
         12 . The method of manufacturing a GaN-based film according to  claim 7 , wherein
 an area of the main surface of said single crystal film of said composite substrate is not smaller than 15 cm 2 .   
     
     
         13 . The method of manufacturing a GaN-based film according to  claim 7 , wherein
 said step of forming a GaN-based film includes sub steps of forming a GaN-based buffer layer on the main surface of said single crystal film and forming a GaN-based single crystal layer on a main surface of said GaN-based buffer layer.