Porous silicon electro-etching system and method

Abstract

It is an object of this disclosure to provide high productivity, low cost-of-ownership manufacturing equipment for the high volume production of photovoltaic (PV) solar cell device architecture. It is a further object of this disclosure to reduce material processing steps and material cost compared to existing technologies by using gas-phase source silicon. The present disclosure teaches the fabrication of a sacrificial substrate base layer that is compatible with a gas-phase substrate growth process. Porous silicon is used as the sacrificial layer in the present disclosure. Further, the present disclosure provides equipment to produce a sacrificial porous silicon PV cell-substrate base layer.

What is claimed is: 
     
         1 . An apparatus for producing porous silicon on a front side of a silicon wafer comprising:
 a housing;   at least one vertically oriented electrolytic cell comprising:
 an anode; 
 a cathode; and 
 an electrolyte; 
   a sealing mechanism within said electrolytic cell, said sealing mechanism comprising a surface for contacting a back side of the silicon wafer, said sealing mechanism not in contact with the front side of the silicon wafer; and   a rinsing mechanism for removing said electrolyte from the silicon wafer.   
     
     
         2 . The apparatus of  claim 1 , wherein said rinsing mechanism comprises a spray of deionized water. 
     
     
         3 . The apparatus of  claim 1 , wherein said rinsing mechanism comprises a tank of deionized water. 
     
     
         4 . The apparatus of  claim 1 , wherein said sealing mechanism comprises a first pallet, said first pallet comprising:
 an electrically insulating material;   an opening for holding the silicon wafer; and   an edge capable of being attached to a second pallet.   
     
     
         5 . The apparatus of  claim 4 , further comprising
 a motor for moving said first pallet through said at least one electrolytic cell.   
     
     
         6 . The apparatus of  claim 1 , wherein said sealing mechanism comprises a circumferential seal within said electrolytic cell. 
     
     
         7 . The apparatus of  claim 6 , further comprising a mechanism capable of placing the silicon wafer inside said electrolytic cell and removing the silicon wafer from said electrolytic cell. 
     
     
         8 . The apparatus of  claim 1 , wherein said at least one electrolytic cell comprises a plurality of electrolytic cells. 
     
     
         9 . The apparatus of  claim 1 , wherein said electrolyte of said at least one electrolytic cell comprises HF/IPA. 
     
     
         10 . The apparatus of  claim 1 , wherein said at least one electrolytic cell further comprises an electrolyte jet for removing a gas from said anode. 
     
     
         11 . The apparatus of  claim 1 , wherein said at least one electrolytic cell further comprises an electrolyte jet for removing a gas from said cathode. 
     
     
         12 . A method for producing porous silicon on a silicon wafer, said method comprising the steps of:
 placing the silicon wafer within a non-confined electrolytic cell;   supporting the silicon wafer on a surface within said non-confined electrolytic cell, said electrolytic cell comprising:
 an electrolyte, 
 an anode, and 
 a cathode; 
   passing an electrical current through the wafer, said electrical current producing a layer of porous silicon on a top surface of the wafer;   removing the wafer from said non-confined electrolytic cell; and   rinsing said electrolyte from the silicon wafer.   
     
     
         13 . The method of  claim 12 , further comprising
 transporting the wafer on a pallet.   
     
     
         14 . The method of  claim 12 , wherein said rinsing step comprises passing the silicon wafer through a rinse tank comprising deionized water. 
     
     
         15 . The method of  claim 12 , wherein said rinsing step comprises spraying the silicon wafer with deionized water. 
     
     
         16 . The method of  claim 13 , further comprising:
 transporting said pallet supporting the wafer through a plurality of non-confined electrolytic cells.   
     
     
         17 . The method of  claim 12 , wherein said electrolyte comprises HF/IPA. 
     
     
         18 . The method of  claim 12 , further comprising removing a gas from said anode with a jet of said electrolyte. 
     
     
         19 . The method of  claim 12 , further comprising removing a gas from said cathode with a jet of said electrolyte. 
     
     
         20 . The method of  claim 12 , wherein said non-confined electrolytic cell is oriented vertically.