Patent ID: 7507668

Claim:
A method of treating a surface of a Ga x In 1−x As y P 1−y crystal (0≦x≦1, 0≦y≦1) using a polishing slurry, said surface treating method comprising the steps of: preparing said polishing slurry containing abrasive grains formed of SiO 2 , said abrasive grain being a secondary particle in which a primary particle is associated, and a ratio d 2 /d 1 of an average particle diameter d 2 of said secondary particle relative to an average particle diameter d 1 of said primary particle being not less than 1.6 and not more than 10; and chemically mechanically polishing the surface of said Ga x In 1−x As y P 1−y crystal using said polishing slurry, wherein a value X of a pH and a value Y (mV) of an oxidation-reduction potential of said polishing slurry satisfy both relationships of the following equations (1) and (2): Y≧− 50 X+ 1000 (1) Y≦− 50 X+ 1900 (2).