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 wafer handling pallet comprising:
an opening for holding the peripheral edge of the silicon wafer;
a wafer backside sealing mechanism comprising a seal contacting only the backside of the wafer;
a housing comprising at least one vertically oriented non-confined electrolytic cell;
said vertically oriented electrolytic cell comprising:
an anode positioned at the bottom of said electrolytic cell;
a cathode positioned at the top of said electrolytic cell; and
an electrolyte; and
the housing and the wafer handling pallet configured so that a column of said electrolyte above the silicon wafer is applying pressure to the front side of the silicon wafer greater than the pressure applied to the backside of the silicon wafer, the differential pressure sealing the backside surface of the silicon wafer to said sealing mechanism.
2. The apparatus of claim 1 , further comprising a rinsing mechanism using a spray of deionized water.
3. The apparatus of claim 1 further comprising a rinsing mechanism using a tank of deionized water.
4. The apparatus of claim 1 , further comprising a motor for moving said wafer handling pallet through said at least one electrolytic cell.
5. The apparatus of claim 1 , wherein said sealing mechanism comprises a circumferential seal within said electrolytic cell.
6. The apparatus of claim 5 , further comprising a mechanism capable of placing the silicon wafer inside said electrolytic cell and removing the silicon wafer from said electrolytic cell.
7. The apparatus of claim 1 , wherein said at least one electrolytic cell comprises a plurality of electrolytic cells.
8. The apparatus of claim 1 , wherein said electrolyte of said at least one electrolytic cell comprises HF/IPA.
9. The apparatus of claim 1 , wherein said at least one electrolytic cell further comprises an electrolyte jet for removing a gas from said anode.
10. The apparatus of claim 1 , wherein said at least one electrolytic cell further comprises an electrolyte jet for removing a gas from said cathode.
11. The apparatus of claim 1 , wherein said silicon wafer is a p-type silicon wafer.
12. The apparatus of claim 1 , wherein said wafer handling pallet is made of a non-conductive material.
13. The apparatus of claim 12 , wherein said non-conductive material is high-density polyethylene.
14. The apparatus of claim 1 , further comprising a plurality of wafer handling pallets.
15. The apparatus of claim 14 , wherein said plurality of wafer handling pallets are connected in-line.
16. The apparatus of claim 14 , further comprising a motor for moving said plurality of wafer handling pallets through said at least one electrolytic cell.
17. The apparatus of claim 7 , further comprising a plurality of wafer handling pallets.
18. The apparatus of claim 17 , wherein said plurality of wafer handling pallets are connected in-line.
19. The apparatus of claim 17 , further comprising a motor for moving said plurality of wafer handling pallets through said plurality of electrolytic cells.
20. The apparatus of claim 7 , wherein said electrolyte of said plurality of electrolytic cells comprises HF/IPA.