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.