Method of achieving higher inversion layer mobility in novel silicon carbide semiconductor devices

Abstract

The invention provides a method for the production of high quality thermally grown oxide on top of silicon carbide. The high quality oxide is obtained by selectively removing the carbon from the silicon carbide in the areas where oxide formation is desired or required. The method includes the steps of: (a) amorphizing the silicon carbide in at least one region of a monocrystalline silicon carbide substrate by ion implantation; (b) removing at least an effective amount of the carbon resulting from amorphizing the silicon carbide with an etchant effective to selectively remove carbon from the amorphized silicon carbide to produce an amorphous silicon-rich region; and (c) forming an oxide on the etched surface to provide a device which has an oxide region on (1) either an amorphous silicon-rich region which is (i) predominantly or entirely amorphous silicon or (ii) a mixture of predominantly amorphous silicon in combination with minor amounts of amorphous silicon carbide and/or silicon dioxide or (2) a monocrystalline silicon region; wherein (1) or (2) is present on a region of a silicon carbide substrate, or (3) a region of a silicon carbide substrate.

I claim:  
     
         1 . A method for the production of high quality thermally grown oxide on silicon carbide, which reduces the interface states density and improves the inversion layer mobility by removing carbon from silicon carbide, said method comprising the steps: 
 (a) amorphizing silicon carbide in at least one region of a monocrystalline silicon carbide substrate to convert the silicon carbide in said region to amorphous silicon carbide on a monocrystalline silicon carbide substrate;    (b) removing at least an effective amount of the carbon from the resulting amorphous silicon carbide region with an etchant effective to selectively remove said effective amount of carbon from said amorphous silicon carbide region to produce an amorphous silicon-rich region on a monocrystalline silicon carbide substrate; and    (c) forming an oxide on said amorphous silicon-rich region on said monocrystalline silicon carbide substrate by (i)subjecting the etched region to thermal oxidation under conditions effective to preserve the amorphous silicon layer producing an oxide on an amorphous silicon-rich region on a monocrystalline silicon carbide substrate; or (ii)subjecting the etched region to thermal oxidation under conditions that substantially remove the amorphous silicon layer to produce an oxide on a monocrystalline silicon carbide substrate; or (iii)subjecting the etched region to thermal oxidation under conditions effective to preserve the amorphous silicon region and thereafter subjecting the said region to at least one high temperature thermal annealing step to produce an oxide on a crystalline silicon region on a monocrystalline silicon carbide substrate; or (iv) first growing LTO on the etched region and then subjecting the LTO-bearing etched region to thermal oxidation and high temperature anneal to produce an LTO region on a monocrystalline silicon carbide substrate.    
     
     
         2 . A method for the production of silicon carbide devices which comprise an oxide region on an amorphous silicon-rich region on a region of a silicon carbide substrate which comprises the steps of: 
 (a) amorphizing silicon carbide in at least one region of a monocrystalline silicon carbide substrate;    (b) removing at least an effective amount of carbon from said amorphized silicon carbide with an etchant that etches carbon at a faster rate than it etches silicon and/or silicon carbide to selectively remove said effective amount of carbon from SiC to produce an amorphous silicon-rich region; and    (c) forming an oxide on said amorphous silicon-rich region.    
     
     
         3 . A method as claimed in  claim 2 , wherein the etchant is hot HNO 3 .  
     
     
         4 . A method as claimed in  claim 2 , wherein said amorphous silicon-rich region is at least predominantly amorphous silicon.  
     
     
         5 . A method as claimed in  claim 2 , wherein said amorphous silicon-rich region is a mixture of predominantly amorphous silicon in combination with minor amounts of amorphous silicon carbide and/or silicon dioxide.  
     
     
         6 . A method as claimed in  claim 2 , wherein said oxide is formed by subjecting the amorphous silicon-rich region to thermal oxidation.  
     
     
         7 . A method as claimed in  claim 2 , wherein said oxide is formed by deposition of an oxide on said amorphous silicon-rich region and subjecting the oxide on said amorphous silicon-rich region to thermal oxidation.  
     
     
         8 . A method for the production of silicon carbide devices which comprise an oxide region on a monocrystalline silicon region on a region of a silicon carbide substrate which comprises the steps of: 
 (a) amorphizing silicon carbide in at least one region of a monocrystalline silicon carbide substrate;    (b) removing at least an effective amount of carbon from said amorphized silicon carbide with an etchant that etches carbon at a faster rate than it etches silicon and/or silicon carbide to selectively remove said effective amount of carbon from SiC to produce an amorphous silicon-rich region;    (c) forming an oxide on said amorphous silicon-rich region; and    (d) subjecting the oxide on said amorphous silicon-rich region to high temperature thermal anneal to produce an oxide region on a monocrystalline silicon region on a region of a silicon carbide substrate.    
     
     
         9 . A method as claimed in  claim 8 , wherein the etchant is hot HNO 3 .  
     
     
         10 . A method as claimed in  claim 8 , wherein said amorphous silicon-rich region is at least predominantly amorphous silicon.  
     
     
         11 . A method as claimed in  claim 8 , wherein said amorphous silicon-rich region is a mixture of predominantly amorphous silicon in combination with minor amounts of amorphous silicon carbide and/or silicon dioxide.  
     
     
         12 . A method as claimed in  claim 8 , wherein said oxide is formed by subjecting the amorphous silicon-rich region to thermal oxidation.  
     
     
         13 . A method as claimed in  claim 8 , wherein said oxide is formned by deposition of an oxide on said amorphous silicon-rich region and subjecting the oxide on said amorphous silicon-rich region to thermal oxidation.  
     
     
         14 . A method for the production of silicon carbide devices which comprise an oxide region on a region of a silicon carbide substrate which comprises the steps of: 
 (a) amorphizing silicon carbide in at least one region of a monocrystalline silicon carbide substrate;    (b) removing at least an effective amount of carbon from said amnorphized silicon carbide with an etchant that etches carbon at a faster rate than it etches silicon and/or silicon carbide to selectively remove said effective amount of carbon from SiC to produce an amorphous silicon-rich region; and    (c) subjecting the etched surface to thermal oxidation under conditions effective to oxidize the amorphous silicon layer.    
     
     
         15 . A method as claimed in  claim 14 , wherein the etchant is hot HNO 3 .  
     
     
         16 . A method as claimed in  claim 14 , wherein an oxide is formed on said amorphous silicon-rich region prior to said thermal oxidation.  
     
     
         17 . A method as claimed in  claim 14 , wherein said amorphous silicon-rich region is at least predominantly amorphous silicon.  
     
     
         18 . A method as claimed in  claim 14 , wherein said amorphous silicon-rich region is a mixture of predominantly amorphous silicon in combination with minor amounts of amorphous silicon carbide and/or silicon dioxide.  
     
     
         19 . A method for the production of silicon carbide devices which comprise an oxide region on an amorphous silicon region on a surface region of a silicon carbide substrate which comprises the steps of: 
 (a) providing a monocrystalline silicon carbide substrate;    (b) subjecting at least a portion of a surface of the substrate to ion implantation to convert at least a portion of the substrate surface to amorphous silicon carbide producing a region of amorphous silicon carbide on a monocrystalline silicon carbide substrate;    (c) subjecting at least a portion of the amorphous silicon carbide region to an etchant material which selectively removes carbon to produce a region of amorphous silicon on a monocrystalline silicon carbide substrate; and    (d) subjecting the monocrystalline silicon carbide substrate with at least a region of amorphous silicon to thermal oxidation.    
     
     
         20 . A method for the production of silicon carbide devices which comprise an oxide region on a monocrystalline silicon layer on a surface region of a silicon carbide substrate which comprises the steps of: 
 (a) providing a monocrystalline silicon carbide substrate;    (b) subjecting at least a portion of a surface of the substrate to ion implantation to convert at least a portion of the substrate surface to amorphous silicon carbide producing a region of amorphous silicon carbide on a monocrystalline silicon carbide substrate;    (c) subjecting at least a portion of the amorphous silicon carbide region to an etchant material which selectively removes carbon to produce a region of amorphous silicon on a monocrystalline silicon carbide substrate;    (d) subjecting the monocrystalline silicon carbide substrate with at least a region of amorphous silicon to thermal oxidation; and    (e) subjecting the oxidized surface to high temperature thermal anneal to produce an oxide on a monocrystalline silicon layer on a surface region of a monocrystalline silicon carbide substrate.    
     
     
         21 . A method for the production of silicon carbide devices which comprise an oxide region on a surface region of a monocrystalline silicon carbide substrate which comprises the steps of: 
 (a) providing a monocrystalline silicon carbide substrate;    (b) subjecting at least a portion of a surface of the substrate to ion implantation to convert at least a portion of the substrate surface to amorphous silicon carbide producing a region of amorphous silicon carbide on a monocrystalline silicon carbide substrate;    (c) subjecting at least a portion of the amorphous silicon carbide region to an etchant material which selectively removes carbon to produce a region of amorphous silicon on a monocrystalline silicon carbide substrate; and    (d) subjecting the etched surface to thermal oxidation under conditions effective to oxidize the amorphous silicon layer to produce an oxide on a surface region of a monocrystalline silicon carbide substrate.    
     
     
         22 . A silicon carbide device which comprises at least one oxide region on at least one amorphous silicon-rich region on a region of a silicon carbide substrate.  
     
     
         23 . A silicon carbide device as claimed in  claim 22 , wherein said at least one amorphous silicon-rich region is formed in selected regions of said silicon carbide substrate.  
     
     
         24 . A silicon carbide device as claimed in  claim 22 , wherein said amorphous silicon-rich region is at least predominantly amorphous silicon.  
     
     
         25 . A silicon carbide device as claimed in  claim 22 , wherein said amorphous silicon-rich region is a mixture of predominantly amorphous silicon in combination with minor amounts of amorphous silicon carbide and/or silicon dioxide.  
     
     
         26 . A silicon carbide device as claimed in  claim 22 , wherein said amorphous silicon-rich region is formed from an amorphized region of said silicon carbide substrate which has been subjected to the action of an etchant which selectively removes an effective amount of carbon from said amorphized silicon carbide region.  
     
     
         27 . A silicon carbide device which comprises at least one oxide region on at least one monocrystalline silicon region on a region of a silicon carbide substrate.  
     
     
         28 . A silicon carbide device as claimed in  claim 27 , wherein said at least one monocrystalline silicon region is formed from an amorphized region of said silicon carbide substrate which has been subjected to the action of an etchant which selectively removes an effective amount of carbon from said amorphized silicon carbide region.  
     
     
         29 . A silicon carbide device which comprises at least one oxide region on a region of a silicon carbide substrate.  
     
     
         30 . A silicon carbide device as claimed in  claim 29 , wherein said at least one oxide region is formed from an amorphized region of said silicon carbide substrate which has been subjected to the action of an etchant which selectively removes an effective amount of carbon from said amorphized silicon carbide region and the formation of an oxide on said etched region.  
     
     
         31 . A semiconductor device which comprises a silicon carbide substrate of first conductivity type, a base region of second conductivity type formed in a first region of said silicon carbide substrate, a source region of first conductivity type formed in said first region of said silicon carbide substrate adjacent said base region, an inversion channel adjacent said base and source regions, a gate region separated from the inversion channel by an intervening oxide region and overlying said inversion channel, said inversion channel being formed on a monocrystalline silicon region on said silicon carbide substrate.  
     
     
         32 . A semiconductor device as claimed in  claim 31 , wherein said inversion channel is formed from an amorphized region of said silicon carbide substrate which has been subjected to the action of an etchant which selectively removes an effective amount of carbon from said amnorphized silicon carbide region and the formation of an oxide on said etched region.  
     
     
         33 . A semiconductor device which comprises a monocrystalline silicon carbide substrate of a first conductivity type, a face of said substrate having formed therein a base region of second conductivity type, a source region of first conductivity type adjacent said base region; a channel region adjacent said source region; an insulating region overlying the face of said substrate; and a polysilicon gate region overlying said channel region and separated from the channel region by said insulating region, 
 wherein said inversion channel is formed from an amorphized region of said silicon carbide substrate which has been subjected to the action of an etchant which selectively removes an effective amount of carbon from said amorphized silicon carbide region and the formation of an oxide on said etched amorphized silicon carbide region under conditions effective to convert a substantial proportion of said amorphized silicon carbide region to a silicon region.    
     
     
         34 . A semiconductor device having a high quality thermally grown oxide on top of silicon carbide, said high quality oxide being obtained by selectively amorphizing the silicon carbide and removing carbon from the amorphized silicon carbide in the areas where oxide is to be formed, and subjecting said areas to thermal oxidation.