Dielectric material and process of insulating a semiconductor device using same

Abstract

A dielectric material formed by contacting a low dielectric constant polymer with liquid or supercritical carbon dioxide, under thermodynamic conditions which maintain the carbon dioxide in the liquid or supercritical state, wherein a porous product is formed. Thereupon, thermodynamic conditions are changed to ambient wherein carbon dioxide escapes from the pores and is replaced with air.

What is claimed is:  
     
         1 . A dielectric material comprising the product formed by the steps of: 
 disposing a polymeric material upon a substrate;    contacting said polymeric material with liquid or supercritical carbon dioxide under thermodynamic conditions consistent with the retention of carbon dioxide in said liquid or supercritical state; and    adjusting said thermodynamic conditions to ambient temperature and pressure.    
     
     
         2 . A dielectric material in accordance with  claim 1  wherein said polymeric material is selected from the group consisting of polyimides, fluorinated polyimides, polyorganohydridosilane, polysiloxanes, polyphenylenes, copolymers of divinylsiloxane and bisbenzocyclobutene, polybenzil, polyarylethers and polytetrafluoroethylene.  
     
     
         3 . A dielectric material in accordance with  claim 2  wherein said polymeric material is a polyphenylene.  
     
     
         4 . A dielectric material in accordance with  claim 1  wherein said polymeric material is contacted with liquid or supercritical carbon dioxide in the presence of a porogen.  
     
     
         5 . A dielectric material in accordance with  claim 4  wherein said porogen is present by disposing said porogen on said polymeric material, by combining said porogen with said polymeric material or by combining said porogen with said liquid or supercritical carbon dioxide.  
     
     
         6 . A dielectric material in accordance with  claim 5  wherein said porogen is present by dispersing water over a polyphenylene film, wherein said water constitutes between about 0.01% and about 1% by weight, based on the weight of said polyphenylene.  
     
     
         7 . A dielectric material in accordance with  claim 5  wherein said porogen is present by dissolving a porogen in a concentration of up to about 10% by weight, based on the total weight of said liquid or supercritical carbon dioxide, wherein said porogen selected from the group consisting of acetone, toluene, methanol, ethanol and propanol in said liquid or supercritical carbon dioxide.  
     
     
         8 . A dielectric material in accordance with  claim 5  wherein said porogen is present by combining up to about 1% by weight of a porogen, based on the weight of said polymeric material, with said polymeric material, said porogen selected from the group consisting of acetone, toluene, methanol, ethanol and propanol.  
     
     
         9 . A dielectric material in accordance with  claim 8  wherein said porogen is water, present in a concentration of up to about 0.25% by weight, and said polymeric material is a polyphenylene.  
     
     
         10 . A dielectric material in accordance with  claim 1  wherein said substrate is a silicon wafer.  
     
     
         11 . A dielectric material comprising a product formed by the steps of: 
 (a) casting a polyphenylene upon a silicon wafer;    (b) disposing water on a surface of said cast polyphenylene, said water present in a concentration of between about 0.01% and about 1%, said percentages being by weight, based on the total weight of said cast polyphenylene;    (c) contacting said polyphenylene with liquid or supercritical carbon dioxide under a pressure in the range of between about 1,000 psi and about 8,000 psi and a temperature in the range of between about 32° C. and about 100° C.; and    (d) changing said thermodynamic conditions to ambient temperature and pressure.    
     
     
         12 . A process of insulating an electrical assembly which includes semiconductor devices comprising the steps of: 
 (a) disposing a polymeric material upon a surface of a semiconductor device;    (b) contacting said polymeric material with liquid or supercritical carbon dioxide under thermodynamic conditions consistent with the maintenance of carbon dioxide in said liquid or supercritical state; and    (c) adjusting said thermodynamic conditions under which said semiconductor device is maintained to those of ambient temperature and pressure.    
     
     
         13 . A process in accordance with  claim 12  wherein said polymeric material is selected from the group consisting of polyimides, fluorinated polyimides, polyorganohydrosilane, polysiloxanes, polyphenylenes, copolymers of divinylsiloxane and bisbenzocyclobutene, polybenzyl, polyarylethers and polytetrafluoroethylene.  
     
     
         14 . A process in accordance with  claim 13  wherein said polymeric material is a polyphenylene.  
     
     
         15 . A process in accordance with  claim 12  including the step of contacting said polymeric material with a porogen prior to contacting said polymeric material with liquid or supercritical carbon dioxide.  
     
     
         16 . A process in accordance with  claim 15  wherein said porogen contacting step comprises disposing said porogen in a concentration of between about 0.01% and about 1% on a polyphenylene film, said percentages being by weight based on the weight of said polyphenylene.  
     
     
         17 . A process in accordance with  claim 15  wherein said porogen contacting step comprises dissolving up to about 10% of said porogen, said porogen selected from the group consisting of acetone, toluene, methanol, ethanol and propanol, in said liquid or supercritical carbon dioxide, said percentage being by weight, based on the total weight of said solution.  
     
     
         18 . A process in accordance with  claim 15  wherein said porogen contacting step comprises combining up to about 1% of said porogen, said porogen selected from the group consisting of acetone, toluene, methanol, ethanol and propanol, in said polymeric material, said percentage being by weight, based on the weight of said polymeric material.  
     
     
         19 . A process in accordance with  claim 15  wherein said porogen contacting step comprises combining up to about 0.25% of water in a polyphenylene, said percentage based on the weight of said polyphenylene.  
     
     
         20 . A process in accordance with  claim 12  wherein said step (b) occurs at a temperature in the range of between about 32° C. and about 100° C. and at a pressure in the range of between about 1,000 psi and about 8,000 psi.