Porous silicon composite structure as large filtration array

Abstract

A novel asymmetric filter membrane, and process for making is disclosed in several exemplary versions. The membrane structure is physically robust and suitable for use in a wide variety of applications. The support membrane is may be comprised of material such as a porous silicon or a silicon oxide, and the separation membrane may be comprised of material such as a polymer, zeolite film, or silicon oxide. The process relies on steps adapted from the microelectronics industry.

1 . A process for fabricating a composite microfilter structure comprising: 
 etching a pattern of micropores through a standard-size semiconductor wafer to form a support membrane; and    providing at least one separation membrane atop the support membrane.    
   
   
       2 . The process recited in  claim 1 , wherein the step of providing a separation membrane comprises providing an organic separation membrane.  
   
   
       3 . The process recited in  claim 3 , wherein the organic separation membrane provided comprises a thermoplastic polymer.  
   
   
       4 . The process recited in  claim 2 , wherein the organic separation membrane provided comprises a polymer that will cleanly and efficiently transmit a permeate to a support layer.  
   
   
       5 . The process recited in  claim 3 , wherein the thermoplastic polymer is selected from the group consisting of polyimide, SiLK, polysulfone, and polyethersulfone.  
   
   
       6 . The process recited in  claim 1 , wherein the step of providing a separation membrane comprises providing an inorganic separation membrane.  
   
   
       7 . The process recited in  claim 6 , wherein the step of providing an inorganic separation membrane comprises providing an inorganic membrane that will cleanly and efficiently transmit a permeate to a support layer.  
   
   
       8 . The process recited in  claim 6 , wherein the inorganic separation membrane is selected from the group consisting of silicon, silicon dioxide, zeolite and any combination thereof.  
   
   
       9 . The process recited in  claim 6 , wherein the step of etching a pattern of micropores in a semiconductor wafer comprises dry etching a silicon-containing wafer by fluorine radicals in a plasma using TMDE.  
   
   
       10 . The process recited in  claim 6 , wherein the step of providing an inorganic separation membrane comprises depositing an inorganic material by a method selected from the group consisting of CVD and plasma-enhanced CVD.  
   
   
       11 . A process for fabricating a silicon oxide membrane for a composite asymmetric microfilter structure, comprising: 
 depositing a silicon oxide atop a support membrane by a method selected from the group consisting of CVD and plasma-enhanced CVD with a TEOS source;    depositing and curing a photoresist layer atop the silicon oxide;    providing the photoresist layer with a pattern for a plurality of micropores;    exposing and developing the pattern in the photoresist layer;    transferring the pattern into the silicon oxide using a dry etch method; and    removing the remaining photoresist.