High-throughput batch porous silicon manufacturing equipment design and processing methods
This disclosure enables high-productivity fabrication of porous semiconductor layers (made of single layer or multi-layer porous semiconductors such as porous silicon, comprising single porosity or multi-porosity layers). Some applications include fabrication of MEMS separation and sacrificial layers for die detachment and MEMS device fabrication, membrane formation and shallow trench isolation (STI) porous silicon (using porous silicon formation with an optimal porosity and its subsequent oxidation). Further, this disclosure is applicable to the general fields of photovoltaics, MEMS, including sensors and actuators, stand-alone, or integrated with integrated semiconductor microelectronics, semiconductor microelectronics chips and optoelectronics.
1. A bath-in-bath batch processing apparatus for producing porous semiconductor on a plurality of semiconductor wafers, comprising:
an outer housing;
an inner housing removable from said outer housing, said inner housing operable to open and close, and forming a seal when closed;
an anode disposed at a first end of said inner housing;
a cathode disposed at an opposite end of said inner housing, said anode and said cathode coupled to electrical circuitry capable of providing an electrical power comprising electrical voltage and current;
a plurality of peripheral wafer clamps disposed to hold a plurality of semiconductor wafers where each clamp is able to hold a semiconductor wafer around its periphery using an angled shape cross section, wherein each periphery wafer clamp allows substantially all of a front and a back surface of each said plurality of semiconductor wafers exposure to an electrolyte;
a plurality of vent ports in said inner housing for allowing evolved hydrogen gas to escape.
2. The apparatus of claim 1 , further comprising a conductive anode membrane separating said anode from said plurality of semiconductor wafers.
3. The apparatus of claim 1 , further comprising a conductive cathode membrane separating said cathode from said plurality of semiconductor wafers.
4. The apparatus of claim 1 , wherein the electrical circuitry is operable to produce a graded porosity layer of porous semiconductor comprising at least two different porosities on said plurality of semiconductor wafers.
5. The apparatus of claim 4 , wherein said graded porosity layer comprises a higher porosity in depth compared to a lower porosity on the surface.
6. The apparatus of claim 1 , wherein the electrical circuitry is operable to produce a multilayer of porous semiconductor on said plurality of semiconductor wafers, said multilayer comprising discrete layers of porous semiconductor having at least two different porosities.
7. The apparatus of claim 6 , wherein said multilayer comprises a buried porous semiconductor layer with a higher porosity value and a surface porous semiconductor layer with a lower porosity value.
8. The apparatus of claim 1 , wherein the electrical circuitry is operable to produce a porous semiconductor layer on both sides of each of said plurality of semiconductor wafers by switching a voltage polarity and current direction during a porous semiconductor formation process.
9. The apparatus of claim 1 , wherein said plurality of semiconductor wafers are crystalline silicon wafers and said porous semiconductor is porous silicon.
10. The apparatus of claim 1 , further comprising a loading and unloading mechanism for transferring said inner housing into and out of said outer housing.
11. The apparatus of claim 1 , further comprising a loading and unloading mechanism for transferring batches of said semiconductor wafers into and out of said inner housing.
12. The apparatus of claim 1 , wherein said plurality of semiconductor wafers are circular shaped.
13. The apparatus of claim 1 , wherein said plurality of semiconductor wafers are square shaped.
14. The apparatus of claim 1 , wherein said plurality of semiconductor wafers are crystalline silicon wafers.
15. The apparatus of claim 1 , wherein said inner housing may open in multiple sections.