POROUS SILICON ELECTRO-ETCHING SYSTEM AND METHOD
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.
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.