Method for Growth of Gan Single Crystal, Method for Preparation of Gan Substrate, Process for Producing Gan-Based Element, and Gan-Based Element

Abstract

A GaN-based thin film (thick film) is grown using a metal buffer layer grown on a substrate. (a) A metal buffer layer ( 210 ) made of, for example, Cr or Cu is vapor-deposited on a sapphire substrate ( 120 ). (b) A substrate obtained by vapor-depositing the metal buffer layer ( 210 ) on the sapphire substrate ( 120 ) is nitrided in an ammonia gas ambient, thereby forming a metal nitride layer ( 212 ). (c) A GaN buffer layer ( 222 ) is grown on the nitrided metal buffer layers ( 210, 212 ). (d) Finally, a GaN single-crystal layer ( 220 ) is grown. This GaN single-crystal layer ( 220 ) can be grown to have various thicknesses depending on the objects. A freestanding substrate can be fabricated by selective chemical etching of the substrate fabricated by the above steps. It is also possible to use the substrate fabricated by the above steps as a GaN template substrate for fabricating a GaN-based light emitting diode or laser diode.

1 : A GaN single crystal growth method comprising:
 a Cu layer growth process of growing a Cu layer on an underlying substrate;   a nitridation process of forming a Cu nitride layer by nitriding at least a surface of the Cu layer;   a GaN buffer layer growth process of growing a GaN buffer layer on the Cu nitride layer; and   a GaN layer growth process of growing a single-crystal GaN layer on the GaN buffer layer.   
     
     
         2 : A GaN single crystal growth method comprising:
 a chromium layer growth process of growing a chromium layer on an underlying substrate;   a nitridation process of forming a chromium nitride layer by nitriding at least a surface of the chromium layer;   a GaN buffer layer growth process of growing a GaN buffer layer on the chromium nitride layer; and   a GaN layer growth process of growing a single-crystal GaN layer on the GaN buffer layer,   wherein the chromium nitride layer has (111) orientation.   
     
     
         3 : A GaN single crystal growth method comprising:
 a nitridation process of forming a Cu nitride layer by nitriding a surface of a Cu underlying substrate;   a GaN buffer layer growth process of growing a GaN buffer layer on the Cu nitride layer; and   a GaN layer growth process of growing a single-crystal GaN layer on the GaN buffer layer.   
     
     
         4 : A GaN single crystal growth method comprising:
 a nitridation process of forming a chromium nitride layer by nitriding a surface of a chromium underlying substrate;   a GaN buffer layer growth process of growing a GaN buffer layer on the chromium nitride layer; and   a GaN layer growth process of growing a single-crystal GaN layer on the GaN buffer layer,   wherein the chromium nitride layer has (111) orientation.   
     
     
         5 : A GaN single crystal growth method according to  claim 1 , wherein
 nitridation is performed by a gas containing ammonia in the nitridation process.   
     
     
         6 : A GaN single crystal growth method according to  claim 1 , wherein
 nitridation is performed at a temperature of 500° C. to 1,000° C. in the nitridation process.   
     
     
         7 : A GaN single crystal growth method according to  claim 1 , wherein
 the GaN buffer layer is grown at a temperature of 800° C. to 1,100° C. in the GaN buffer layer growth process.   
     
     
         8 : A GaN single crystal growth method according to  claim 1 , wherein
 the GaN buffer layer is grown to have a thickness of 50 nm to 30 μm in the GaN buffer layer growth process.   
     
     
         9 : A GaN single crystal growth method according to  claim 1 , wherein
 the underlying substrate has a metal layer on a surface.   
     
     
         10 : A GaN single crystal growth method according to  claim 1 , the method further comprising
 a separation process of separating the single-crystal GaN layer from the underlying substrate by selective chemical etching.   
     
     
         11 : A GaN-based element fabrication method comprising:
 a growing step of sequentially growing a metal buffer layer, a metal nitride layer and a single-crystal GaN layer on an underlying substrate;   an element structure fabrication step of fabricating a GaN-based element structure on the GaN single-crystal layer; and   a chip separation step of separating a stacking structure including the underlying substrate, the metal buffer layer, the metal nitride layer, the single-crystal GaN layer, and the GaN-based element structure, into a plurality of chips   wherein the metal buffer layer and the metal nitride layer respectively include a CU layer and a Cu nitride layer, alternatively the metal buffer layer and the metal nitride layer respectively include a chromium layer and a chromium nitride layer; and   the chip separation step includes:
 a bonding step of bonding a conductive support substrate to the GaN-based element structure through a conductive junction; 
 a primary subscribing step of scribing the stacking structure supported by the conductive support substrate, such that the stacking structure is divided into a plurality of stacking bodies; 
 an etching step of etching the metal buffer layer and the metal nitride layer by selective chemical etching to remove the underlying substrate from each of the stacking bodies; 
 a secondary scribing step of scribing the conductive support substrate at spaces between the stacking bodies, such that the stacking bodies are separated into the plurality of chips. 
   
     
     
         12 : The method according to  claim 11 ,
 wherein, in the etching step,   a chemical solution is supplied to the metal buffer layer and the metal nitride layer through the spaces between the stacking bodies formed in the primary scribing step.   
     
     
         13 : A GaN-based element fabrication method comprising:
 a growing step of sequentially growing a metal buffer layer, a metal nitride layer and a single-crystal GaN layer on an underlying substrate;   an element structure fabrication step of fabricating a GaN-based element structure on the GaN single-crystal layer; and   a chip separation step of separating a stacking structure including the metal buffer layer, the metal nitride layer, the single-crystal GaN layer, and the GaN-based element structure, into a plurality of chips;   wherein the metal buffer layer and the metal nitride layer respectively include a Cu layer and a Cu nitride layer, alternatively the metal buffer layer and the metal nitride layer respectively include a chromium layer and a chromium nitride layer,   the chip separation step includes:
 a primary subscribing step of scribing the stacking structure supported by the underlying substrate, such that the stacking structure is divided into a plurality of stacking bodies; 
 a bonding step of bonding a conductive support substrate to the GaN-based element structure through a conductive junction layer; 
 an etching step of etching the metal buffer layer and the metal nitride layer by selective chemical etching to remove the underlying substrate from each of the stacking bodies; and 
 a secondary scribing step of scribing the conductive support substrate at spaces between the stacking bodies, such that the stacking bodies are separated into the plurality of chips. 
   
     
     
         14 : The method according to  claim 13 , wherein
 in the etching step, a chemical solution is supplied to the metal buffer layer and the metal nitride layer through the spaces between the stacking bodies formed in the primary scribing step.   
     
     
         15 . (canceled) 
     
     
         16 : A GaN single crystal growth method according to  claim 2 , wherein
 nitridation is performed by a gas containing ammonia in the nitridation process.   
     
     
         17 : A GaN single crystal growth method according to any one of  claim 2 , wherein
 nitridation is performed at a temperature of 500° C. to 1,000° C. in the nitridation process.   
     
     
         18 : A GaN single crystal growth method according to  claim 2 , wherein
 the GaN buffer layer is grown at a temperature of 800° C. to 1,100° C. in the GaN buffer layer growth process.   
     
     
         19 : A GaN single crystal growth method according to  claim 2 , wherein
 the GaN buffer layer is grown to have a thickness of 50 nm to 30 μm in the GaN buffer layer growth process.   
     
     
         20 : A GaN single crystal growth method according to  claim 2 , wherein
 the underlying substrate has a metal layer on a surface.   
     
     
         21 : A GaN single crystal growth method according to  claim 2 , the method further comprising
 a separation process of separating the single-crystal GaN layer from the underlying substrate by selective chemical etching.   
     
     
         22 : A GaN single crystal growth method according to  claim 3 , wherein
 nitridation is performed by a gas containing ammonia in the nitridation process.   
     
     
         23 : A GaN single crystal growth method according to  claim 3 , wherein
 nitridation is performed at a temperature of 500° C. to 1,000° C. in the nitridation process.   
     
     
         24 : A GaN single crystal growth method according to  claim 3 , wherein
 the GaN buffer layer is grown at a temperature of 800° C. to 1,100° C. in the GaN buffer layer growth process.   
     
     
         25 : A GaN single crystal growth method according to  claim 3 , wherein
 the GaN buffer layer is grown to have a thickness of 50 nm to 30 μm in the GaN buffer layer growth process.   
     
     
         26 : A GaN single crystal growth method according to  claim 3 , wherein
 the underlying substrate has a metal layer on a surface.   
     
     
         27 : A GaN single crystal growth method according to  claim 3 , the method further comprising
 a separation process of separating the single-crystal GaN layer from the underlying substrate by selective chemical etching.   
     
     
         28 : A GaN single crystal growth method according to  claim 4 , wherein
 nitridation is performed by a gas containing ammonia in the nitridation process.   
     
     
         29 : A GaN single crystal growth method according to  claim 4 , wherein
 nitridation is performed at a temperature of 500° C. to 1,000° C. in the nitridation process.   
     
     
         30 : A GaN single crystal growth method according to  claim 4 , wherein
 the GaN buffer layer is grown at a temperature of 800° C. to 1,100° C. in the GaN buffer layer growth process.   
     
     
         31 : A GaN single crystal growth method according to  claim 4 , wherein
 the GaN buffer layer is grown to have a thickness of 50 nm to 30 μm in the GaN buffer layer growth process.   
     
     
         32 : A GaN single crystal growth method according to  claim 4 , wherein
 the underlying substrate has a metal layer on a surface.   
     
     
         33 : A GaN single crystal growth method according to  claim 4 , the method further comprising
 a separation process of separating the single-crystal GaN layer from the underlying substrate by selective chemical etching.