Method of varying etch selectivities of a film

Abstract

A method of patterning a crystalline film. A crystalline film having a degenerate lattice comprising first atoms in a first region and a second region is provided. Dopants are substituted for said first atoms in said first region to form a non-degenerate crystalline film in said first region. The first region and the second region are exposed to a wet etchant wherein the wet etchant etches the degenerate lattice in said second region without etching the non-degenerate lattice in the first region.

1 . A method of patterning a crystalline film comprising: 
 forming a crystalline film having a degenerate lattice comprising first atoms in a first region and a second region;    placing dopants into interstitial cites in said crystalline film in said first region wherein said dopants are electrically neutral with respect to said crystalline film;    activating said dopants so that said dopants substitute with said first atoms in said lattice to form a non-degenerate lattice in said first region, said second region remaining a degenerate lattice; and    exposing said first region and said second region to a wet etchant wherein said wet etchant etches said degenerate lattice in said second region without etching said non-degenerate lattice in said first region.    
   
   
       2 . The method of  claim 1  wherein said crystalline film is a semiconductor film.  
   
   
       3 . The method of  claim 2  wherein said semiconductor film is a silicon film.  
   
   
       4 . The method of  claim 3  wherein said silicon film is a polycrystalline film.  
   
   
       5 . The method of  claim 1  wherein said crystalline film is selected from the group consisting of gallium arsenide and InSb.  
   
   
       6 . The method of  claim 1  wherein said etchant utilizing an associative reaction to etch said degenerate lattice.  
   
   
       7 . The method of  claim 3  wherein said etchant is a non-oxidizing basic solution.  
   
   
       8 . The method of  claim 7  wherein said etchant comprises a hydroxide with a pH between 9 and 11.  
   
   
       9 . The method of  claim 5  wherein said etchant comprises an oxidant in the presence of an acid.  
   
   
       10 . The method of  claim 9  wherein said etchant comprises an oxidant selected from the group consisting of nitric acid and hydrogen peroxide and wherein said etchant has a pH between 2 and 4.  
   
   
       11 . The method of  claim 1  wherein said non-degenerate lattice in said first region has a first lattice energy and said degenerate lattice in said second region has a second lattice energy wherein said second lattice energy is thermodynamically higher (relatively less stable) than said first lattice energy.  
   
   
       12 . The method of  claim 1  wherein said non-degenerate lattice has a first activation energy barrier to said etchant and said degenerate lattice has a second activation energy barrier to said etchant wherein said second activation energy barrier is less than said first activation barrier.  
   
   
       13 . The method of  claim 12  wherein said etchant has a chemical energy greater than said second activation energy barrier and less than said first activation energy barrier.  
   
   
       14 . A method of patterning a crystalline film comprising: 
 forming a mask having an opening on a crystalline film having a lattice comprising first atoms, said opening formed over a first region and said mask covering a second region;    implanting dopants atoms through said opening and into said first region of said crystalline film beneath said opening wherein said dopant atoms are physically larger than said first atoms;    removing said mask;    heating said crystalline film so that said dopants substitute with said first atoms in said lattice in said crystalline film in said first region; and    exposing said first region and said second region to an etchant wherein said etchant etches said second region without etching said first region.    
   
   
       15 . The method of  claim 14  wherein the lattice comprising dopants in said first region is a non-degenerate lattice.  
   
   
       16 . The method of  claim 15  wherein said lattice in said second region is a degenerate lattice.  
   
   
       17 . A method of patterning a crystalline film comprising: 
 providing a crystalline film having a degenerate lattice comprising first atoms in a first region and a second region;    substituting dopant atoms with said first atoms in said degenerate lattice in said first region to form a non-degenerate lattice in said first region wherein said dopants are electrically neutral with respect to said crystalline film; and    exposing said first region having said non-degenerate lattice and said second region having said degenerate lattice to an etchant wherein said etchant etches said second region and not said first region.    
   
   
       18 . The method of  claim 17  wherein said crystalline film is silicon.  
   
   
       19 . The method of  claim 17  wherein said dopant atoms are boron.