Method of forming porous silicon

DETAILED DESCRIPTION It is an object of the present invention to provide a process for manufacturing porous silicon having a high degree of uniformity.
Another object of the invention is to fabricate uniformly porous silicon using technology which is compatible with existing silicon techniques in order to form porous silicon having radiative properties.
These objectives, and other objectives, are achieved by the method of the invention for preparing silicon microstructures, in particular, porous silicon microstructures which exhibit bright luminescence and which are suitable for use in optoelectronic devices.
In accordance with the invention, a single crystal silicon substrate is first patterned to form numerous columns of single crystal silicon on the substrate.
The patterned substrate is then electrochemically etched to form pores in the silicon columns and convert the same into uniformly porous silicon.
The etching decreases the width of each column while simultaneously increasing the height of each column and also the distance between each adjoining column.
Preferably, the substrate is patterned using an electron beam technique such that each column has a width of approximately 1000 .
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and a height greater than 10,000 .
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The etching step preferably decreases the width of each column to about 20-30 .
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and preferably includes the step of anodizing the patterned substrate in an electrolyte such as a hydrofluoric acid solution, for 10 minutes at 25.
degree.
C.
, the solution containing 50% by volume of hydrofluoric acid in ethanol or equivalent alcohol at 10-20 mA per square centimeter.
Other features and advantageous of the present invention will become apparent from the following description of the invention which refers to the accompanying drawing.