Patterning of GaN crystal films with ion beams and subsequent wet etching

Abstract

The invention provides a method for etching gallium nitride (GaN) comprising the steps of: providing a GaN film; imagewise amorphizing a portion of the GaN film by ion implantation to form an amorphized portion; and wet etching of the GaN film having an amorphized portion to remove the amorphized portion. When the imagewise amorphizing process can be done without a mask, such as with a focused implantation ion beam, the process itself becomes maskless.

What is claimed is:  
     
         1 . A method for etching gallium nitride (GaN) comprising: 
 providing a GaN film;    imagewise amorphizing a portion of said GaN film by ion implantation to form an amorphized portion; and    wet etching of said GaN film having an amorphized portion to remove said amorphized portion.    
     
     
         2 . The method of  claim 1 , wherein said GaN film is a wurzite GaN single crystal film grown either by chemical vapor deposition (CVD) or molecular beam epitaxy (MBE) on a c-plane oriented sapphire substrate.  
     
     
         3 . The method of  claim 1 , wherein said GaN film is between 1 and 15 micrometers thick.  
     
     
         4 . The method of  claim 1 , wherein said GaN film is semi-insulating.  
     
     
         5 . The method of  claim 1  wherein said imagewise amorphizing comprises implanting said GaN film with either B +  or Ar +  ions.  
     
     
         6 . The method of  claim 1  wherein said imagewise amorphizing comprises the use of a focused ion beam to form an image, such that an imagewise mask is not required.  
     
     
         7 . The method of  claim 1  wherein, in said imagewise amorphizing, said ion implantation is carried out at an ion energy between about 30 and 180 keV.  
     
     
         8 . The method of  claim 1  wherein, in said imagewise amorphizing, said ion implantation is carried out with an ion dose from about 1×10 14  to 5×10 16  ions/cm 2 .  
     
     
         9 . The method of  claim 1  wherein, after said imagewise amorphizing, said amorphized portion is thermally annealed.  
     
     
         10 . The method of  claim 9  wherein said amorphized portion is covered by an encapsulant layer before being thermally annealed.  
     
     
         11 . The method of  claim 10  wherein said encapsulant layer is an AlN film.  
     
     
         12 . The method of  claim 1  wherein said wet etching comprises the use of the photoresist developer that comprises an aqueous solution of KOH or NaOH.  
     
     
         13 . The method of  claim 12  wherein said photoresist developer is Az-400K.  
     
     
         14 . The method of  claim 1  wherein said wet etching is carried out at a temperature between about room temperature and 80° C.  
     
     
         15 . The method of  claim 1  wherein, in said wet etching, an etching rate of from about 5 to about 700 Angstroms/min is achieved.  
     
     
         16 . The method of  claim 1  wherein, in said wet etching, an etching rate of from about 500 to about 700 Angstroms/min is achieved.  
     
     
         17 . The method of  claim 1  wherein, in said wet etching, the etching depth substantially corresponds to the amorphized portion of said GaN film.  
     
     
         18 . A device fabricated in accordance with the method of  claim 1.