Method of producing group iii nitride semiconductor growth substrate

Abstract

An object of the present invention is to provide a method for producing a Group III nitride semiconductor epitaxial substrate, a Group III nitride semiconductor element, and a Group III nitride semiconductor free-standing substrate, which have good crystallinity, with not only AlGaN, GaN, and GaInN the growth temperature of which is 1050° C. or less, but also with Al x Ga 1-x N having a high Al composition, the growth temperature of which is high; a Group III nitride semiconductor growth substrate used for producing these, and a method for efficiently producing those. The present invention provides a Group III nitride semiconductor growth substrate comprising a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al, and a scandium nitride film formed on the surface portion are provided.

1 . A method of producing a Group III nitride semiconductor growth substrate, comprising:
 a step of forming a metal layer made of a Sc material on a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al, and   a step of performing a nitriding process by heating the metal layer in an ambient gas containing an ammonia gas, thereby forming a scandium nitride film.   
     
     
         2 . The method of producing a Group III nitride semiconductor growth substrate, according to  claim 1 , wherein the ambient gas containing the ammonia gas is a mixed gas further containing one or more selected from an inert gas and a hydrogen gas. 
     
     
         3 . The method of producing a Group III nitride semiconductor growth substrate, according to  claim 1 , wherein a highest temperature for heating the metal layer is in the range of 850° C. to 1300° C., and heating time at 850° C. or higher is 1 min to 120 min. 
     
     
         4 . The method of producing a Group III nitride semiconductor growth substrate, according to  claim 1 , further comprising a step of forming an initial growth layer composed of at least one layer of a buffer layer made of Al x Ga 1-x N (0≦x≦1) on the scandium nitride film after the step of the nitriding process. 
     
     
         5 . A method of producing a Group III nitride semiconductor element, comprising:
 a step of forming a metal layer made of a Sc material on a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al;   a step of performing a nitriding process by heating the metal layer in an ambient gas containing an ammonia gas to form a scandium nitride film, thereby producing a Group III nitride semiconductor growth substrate;   a step of epitaxially growing at least one layer of a Group III nitride semiconductor layer over the Group III nitride semiconductor growth substrate, thereby producing a Group III nitride semiconductor epitaxial substrate;   a step of isolating the Group III nitride semiconductor layer into a plurality of elements;   a step of forming a support substrate on the Group III nitride semiconductor layer side; and   a step of separating the Group III nitride semiconductor layer from the crystal growth substrate by chemical lift-off by selectively etching the scandium nitride film, thereby obtaining a Group III nitride semiconductor element.   
     
     
         6 . The method of producing a Group III nitride semiconductor element, according to  claim 5 , wherein the Group III nitride semiconductor layer is grown at a highest temperature in the range of 900° C. to 1300° C. in the step of producing the Group III nitride semiconductor epitaxial substrate. 
     
     
         7 . The method of producing a Group III nitride semiconductor element, according to  claim 5 , further comprising a step of forming an initial growth layer composed of at least one layer of a buffer layer made of Al x Ga 1-x N (0≦x≦1) on the scandium nitride film after performing the nitriding process. 
     
     
         8 . The method of producing a Group III nitride semiconductor element, according to  claim 7 ,
 wherein the initial growth layer is composed of a first buffer layer and a second buffer layer grown on the first buffer layer,   a growth temperature of the first buffer layer is in the range of 900° C. to 1260° C.,   a growth temperature of the second buffer layer is in the range of 1030° C. to 1300° C., and   the growth temperature of the first buffer layer is equal to or lower than the growth temperature of the second buffer layer.   
     
     
         9 . A method of producing a Group III nitride semiconductor free-standing substrate, comprising:
 a step of forming a metal layer made of a Sc material on a crystal growth substrate including a surface portion composed of a Group III nitride semiconductor which contains at least Al;   a step of performing a nitriding process by heating the metal layer in an ambient gas containing an ammonia gas to form a scandium nitride film, thereby producing a Group III nitride semiconductor growth substrate;   a step of epitaxially growing at least one layer of a Group III nitride semiconductor layer over the Group III nitride semiconductor growth substrate; and   a step of separating the Group HI nitride semiconductor layer from the crystal growth substrate by chemical lift-off by selectively etching the scandium nitride film, thereby obtaining a Group III nitride semiconductor free-standing substrate.   
     
     
         10 . The method of producing a Group III nitride semiconductor free-standing substrate, according to  claim 9 , wherein the Group III nitride semiconductor layer is grown at a highest temperature in the range of 900° C. to 1300° C. in the step for producing the Group III nitride semiconductor epitaxial substrate.