John R Macaulay

US Patent:

51396246, Aug 18, 1992

Filed:

Dec 6, 1990

Appl. No.:

7/624422

Inventors:

Peter C. Searson - Baltimore MD
John M. Macaulay - Summit NJ

Assignee:

SRI International - Menlo Park CA

International Classification:

C25F 312
C25F 330

US Classification:

2041293

Abstract:

A method for making a self-supporting porous semiconductor membrane characterized by the electrolytic etching of a surface of a semiconductor wafer until at least one pore propagates fully through the wafer. The wafer forms the anode of the cell and a relatively inert material, such as platinum, forms the cathode of the cell. The electrolyte is a mixture of HF, H. sub. 2 O and possibly a wetting agent. One side of the semiconductor wafer is shielded from the electrolyte and pores are allowed to propagate through the body of the wafer towards the shielded side. In one embodiment of the invention the pores are allowed to propagate fully through the body of the wafer and in another embodiment the pores are partially propagated through the wafer and then material is removed from the shielded side of the wafer to expose the pores. Also disclosed are asymmetrical filters and molecular sieves, an electronic component utilizing a porous semiconductor membrane and a micromechanical device using a porous semiconductor membrane.