Process for producing nanoporous dielectric films at high pH

Abstract

The present invention relates to nanoporous dielectric films and to a process for their manufacture. Such films are useful in the production of integrated circuits. A precursor of an alkoxysilane, and low and high volatility solvents are mixed at a pH of about 2-5, raised to a pH of about 8 or above with a low volatility base and deposited on a semiconductor substrate. After exposure to atmospheric moisture, a nanoporous dielectric film is produced on the substrate.

What is claimed is:  
     
         1 . A process for forming a nanoporous dielectric coating on a substrate which comprises the steps of: 
 (a) blending at least one alkoxysilane with a relatively high volatility solvent composition, a relatively low volatility solvent composition, and optional water to thus form a mixture having a pH of about 2 to about 5, and causing a partial hydrolysis and partial condensation of the alkoxysilane;    (b) adding a sufficient amount of a base to the result of step (a) to raise the pH of the mixture to about 8 or above;    (c) depositing the raised pH mixture resulting from step (b) onto a substrate while evaporating at least a portion of the relatively high volatility solvent composition;    (d) exposing the result from step (c) to a water vapor; and    (e) evaporating the relatively low volatility solvent composition.    
     
     
         2 . The process of  claim 1  wherein step (a) comprises blending water in the mixture.  
     
     
         3 . The process of  claim 1  wherein step (a) further comprises blending a catalytic amount of an acid in the mixture.  
     
     
         4 . The process of  claim 1  wherein the alkoxysilane comprises tetraethoxysilane.  
     
     
         5 . The process of  claim 1  wherein the alkoxysilane comprises tetramethoxysilane.  
     
     
         6 . The process of  claim 1  wherein the relatively high volatility solvent composition has a boiling point of about 120° C. or less.  
     
     
         7 . The process of  claim 1  wherein the relatively low volatility solvent composition has a boiling point of about 175° C. or more.  
     
     
         8 . The process of  claim 1  wherein the relatively high volatility solvent composition comprises one or more components selected form the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol and mixtures thereof.  
     
     
         9 . The process of  claim 1  wherein the relatively low volatility solvent composition comprises an alcohol or a polyol.  
     
     
         10 . The process of  claim 1  wherein the base comprises at least one amine.  
     
     
         11 . The process of  claim 1  wherein the base is selected from the group consisting of primary, secondary and tertiary alkyl amines, aryl amines, alcohol amines and mixtures thereof which have a boiling point of about 100° C. or above.  
     
     
         12 . The process of  claim 1  wherein the base is selected from the group consisting of monoethanolamine, diethanol amine, triethanol amine, monoisopropanol amine, tetraethylenepentamine, 2-(2-aminoethoxy)ethanol; 2-(2-aminoethylamino)ethanol and mixtures thereof.  
     
     
         13 . The process of  claim 1  wherein step (a) is conducted with water at a mole ratio of water to silane is from about 0 to about 2.  
     
     
         14 . The process of  claim 1  wherein the base has a pK b  of from about less than 0 to about 9.  
     
     
         15 . The process of  claim 1  wherein the alkoxysilane has the formula:  
       
         
           
           
               
               
           
         
       
       wherein at least 2 of the R groups are independently C 1  to C 4  alkoxy groups and the balance, if any, are independently selected from the group consisting of hydrogen, alkyl, phenyl, halogen, substituted phenyl.  
     
     
         16 . The process of  claim 15  wherein each R is methoxy, ethoxy or propoxy.  
     
     
         17 . The process of  claim 1  wherein the resulting nanoporous coating has a dielectric constant of from about 1.1 to about 3.5.  
     
     
         18 . The process of  claim 1  wherein the resulting nanoporous coating has a pore size of from about 1 nm to about 100 nm.  
     
     
         19 . The process of  claim 1  wherein substrate comprises a raised pattern of lines on its surface which comprises a metal, an oxide, a nitride and/or an oxynitride material.  
     
     
         20 . The process of  claim 1  wherein the substrate comprises a semiconductor material.  
     
     
         21 . The process of  claim 1  wherein the substrate comprises silicon or gallium arsenide.  
     
     
         22 . The nanoporous dielectric coated substrate produced by the process of  claim 1 .  
     
     
         23 . A semiconductor device produced by the process which comprises the steps of: 
 (a) blending at least one alkoxysilane with a relatively high volatility solvent composition, a relatively low volatility solvent composition, and optional water to thus form a mixture having a pH of about 2 to about 5, and causing a partial hydrolysis and partial condensation of the alkoxysilane;    (b) adding a sufficient amount of a base to the result of step (a) to raise the pH of the mixture to about 8 or above;    (c) depositing the raised pH mixture resulting from step (b) onto a substrate while evaporating at least a portion of the relatively high volatility solvent composition;    (d) exposing the result from step (c) to a water vapor; and    (e) evaporating the relatively low volatility solvent composition.    
     
     
         24 . The semiconductor device produced by the process of  claim 23  wherein the substrate comprises silicon or gallium arsenide.