Method for making a spacer in a photovoltaic substrate

Abstract

A micron gap thermo-photo-voltaic device including a photovoltaic substrate, a heat source substrate, and a plurality of spacers separating the photovoltaic substrate from the heat source substrate by a submicron gap. Each spacer includes an elongated thin-walled structure disposed in a well formed in the heat source substrate and having a top surface less than a micron above the heat source substrate. Also disclosed are methods of making the spacers.

What is claimed is: 
     
         1 - 9 . (canceled) 
     
     
         10 . A method of making a spacer separating a photovoltaic substrate from a heat source by a submicron gap, the method comprising:
 forming a well in the heat source substrate;   growing or depositing a thermally resistant material on the surface of the well; and   enlarging the well to form an elongated thin-walled structure disposed in the well having a top surface less than a micron above the heat source substrate.   
     
     
         11 . The method of  claim 10  in which the well is formed by photolithography processes and plasma etching. 
     
     
         12 . The method of  claim 10  in which the well is greater than 15 microns deep and 15 microns wide. 
     
     
         13 . The method of  claim 10  in which the thermally resistant material is silicon dioxide grown on the surface of the well. 
     
     
         14 . The method of  claim 13  in which the silicon dioxide is grown to a thickness of greater than 0.5 microns. 
     
     
         15 . The method of  claim 10  in which enlarging the well includes etching. 
     
     
         16 . The method of  claim 15  in which etching includes an anisotropic etch. 
     
     
         17 . The method of  claim 10  in which a recess is formed in the heat source substrate and the well is formed in the recess. 
     
     
         18 . The method of  claim 17  in which the recess is formed by etching. 
     
     
         19 . The method of  claim 17  in which the thermally resistant material is grown or deposited to a thickness greater than the depth of the recess. 
     
     
         20 . The method of  claim 17  in which the thermally resistant material is patterned in the vicinity of the well to form a flange in the recess. 
     
     
         21 . The method of  claim 10  in which the thermally resistant material is a dielectric deposited on the surfaces of the well. 
     
     
         22 . The method of  claim 21  in which the dielectric is zirconia. 
     
     
         23 . The method of  claim 21  further including the step of etching the surface of the heat source substrate so that the thermally resistant material extends above the surface of the heat source substrate. 
     
     
         24 - 29 . (canceled) 
     
     
         30 . A method of making a spacer separating a first substrate from a second substrate, the method comprising:
 forming a well in one said substrate;   growing or depositing a thermally resistant material on the surface of the well; and   enlarging the well to form an elongated thin-walled structure disposed in the well having a top surface above said substrate.   
     
     
         31 . The method of  claim 30  in which the first substrate is a photovoltaic substrate. 
     
     
         32 . The method of  claim 30  in which the second substrate is a heat source substrate. 
     
     
         33 . The method of  claim 32  in which the well is formed in the heat source substrate. 
     
     
         34 . The method of  claim 17  in which the recess is formed by growth and dissolution of thermally grown oxide. 
     
     
         35 . A method of making a spacer separating a photovoltaic substrate from atop surface of a heat source by a submicron gap, the method comprising:
 forming a well in the heat source substrate that extends from the top surface of the heat source substrate and extends into the body of the heat source substrate;   growing or depositing a thermally resistant material on the surface of the well; and   enlarging the well to form an elongated thin-walled structure disposed in the well having atop surface less than a micron above the top surface of the heat source substrate.   
     
     
         36 . The method of  claim 34  wherein the heat source substrate is made of silicon, the spacer is made of silicon dioxide; and the well is greater than 15 microns deep and 15 microns wide.