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Ultra Fine Silicon Filter Element

IP.com Disclosure Number: IPCOM000043342D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Iyer, SS: AUTHOR [+2]

Abstract

Increasing demands are being made on the maximum size of particulates that may be tolerated in fluids. In order to filter out particulates of the order of a micron or so, technology exists to make filters with filtering channels of the order of a micrometer or material used in such applications is usually some polymer that has been suitably treated and the filtering pores etched. The use of polymers in these applications may preclude their use in many organic solvents and the size of the pores today need to be made much smaller, of technology. p-conductivity type silicon, when anodized in a hydrofluoric acid (HF) solution acquires a surface layer composed of microscopic pores. These pores form a network of channels that span the upper layer in all directions.

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Ultra Fine Silicon Filter Element

Increasing demands are being made on the maximum size of particulates that may be tolerated in fluids. In order to filter out particulates of the order of a micron or so, technology exists to make filters with filtering channels of the order of a micrometer or material used in such applications is usually some polymer that has been suitably treated and the filtering pores etched. The use of polymers in these applications may preclude their use in many organic solvents and the size of the pores today need to be made much smaller, of technology. p-conductivity type silicon, when anodized in a hydrofluoric acid (HF) solution acquires a surface layer composed of microscopic pores. These pores form a network of channels that span the upper layer in all directions. The dimensions of these pores can be controlled to as low as a few tens of angstroms. This porous silicon can serve as a filtering element of an extremely fine filtering system as follows. p-type silicon is deposited on an oxidized silicon wafer. The thickness of the film may be several microns. The wafer is then anodized as described above. The deposited silicon is thus converted to the porous variety with pore size adjusted to the required dimensions. With the front side protected, apertures are defined photolithographically on the back. The silicon is then etched from the back to the oxide stop. The front side protection is then removed, and the oxide dipped away.

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