Silsesquioxane compound mixture, method of making, resist composition, and patterning process

Abstract

A silsesquioxane compound mixture having a high proportion of silsesquioxane compounds bearing bulky substituent groups on side chain and having a degree of condensation of substantially 100% is prepared by a first stage wherein a silane feed comprising a trifunctional silane bearing a bulky substituent group on side chain represented by formula (1): wherein Y is an aliphatic or aromatic organic group optionally having a functional group, X 1 , X 2 and X 3 are H, halogen, alkoxy or aryloxy is hydrolyzed in the presence of an acid or base catalyst, and a second stage wherein dehydrating condensation is carried out in the presence of a strong base catalyst while removing the water resulting from condensation out of the reaction system.

1 . A silsesquioxane compound mixture comprising silsesquioxane compounds having a degree of condensation of substantially 100%, said mixture being prepared by performing: 
 a first stage wherein a silane feed is hydrolyzed in the presence of an acid or base catalyst, said silane feed comprising a trifunctional silane represented by the general formula (1):                          wherein Y is an organic group of 3 to 20 carbon atoms, optionally having a functional group, containing an aliphatic branched, cyclic or polycyclic structure in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an organic group of 6 to 18 carbon atoms, optionally having a functional group, containing an aromatic structure having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site; X 1 , X 2  and X 3  are each independently a hydrogen atom, halogen atom, straight, branched or cyclic alkoxy group of 1 to 6 carbon atoms, or aryloxy group of 6 to 10 carbon atoms, and    a second stage wherein dehydrating condensation reaction is carried out in the presence of at least 0.5 mol % based on the silane feed of a strong base catalyst while removing water out of the reaction system.    
   
   
       2 . The silsesquioxane compound mixture of  claim 1  wherein an organic solvent is used in the second stage of dehydrating condensation in the presence of a strong base catalyst.  
   
   
       3 . A silsesquioxane compound mixture comprising silsesquioxane compounds having a degree of condensation of substantially 100%, said mixture being prepared by performing: 
 a first stage wherein a silane feed is hydrolyzed in the presence of an acid or base catalyst, said silane feed comprising a trifunctional silane represented by the general formula (1):                          wherein Y is an organic group of 3 to 20 carbon atoms, optionally having a functional group, containing an aliphatic branched, cyclic or polycyclic structure in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an organic group of 6 to 18 carbon atoms, optionally having a functional group, containing an aromatic structure having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site; X 1 , X 2  and X 3  are each independently a hydrogen atom, halogen atom, straight, branched or cyclic alkoxy group of 1 to 6 carbon atoms, or aryloxy group of 6 to 10 carbon atoms, and    a second stage wherein dehydrating condensation reaction is carried out in the presence of at least 0.5 mol % based on the silane feed of a strong base catalyst using an organic solvent in an amount of at least two times the weight of hydrolyzates resulting from hydrolysis while allowing the water resulting from condensation to transfer to the organic solvent.    
   
   
       4 . The silsesquioxane compound mixture of  claim 2  wherein the organic solvent used in the second stage of dehydrating condensation in the presence of a strong base catalyst is one which is separable from water.  
   
   
       5 . The silsesquioxane compound mixture of  claim 1 , which is obtained by further performing the step of removing by fractionation a low condensed component from the reaction mixture obtained in the second stage of dehydrating condensation.  
   
   
       6 . The silsesquioxane compound mixture of  claim 1 , wherein the silane feed comprises as the trifunctional silane at least one member selected from (A) monomer units having the general formula (2) and (B) monomer units having the general formula (3):  
       R 1 —SiX 1   3   (2)  R 2 —SiX 2   3   (3)  
     wherein R 1  is an organic group containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms, optionally containing a halogen (inclusive of fluorine), oxygen or sulfur atom, in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an organic group of 6 to 18 carbon atoms, optionally having a functional group, containing an aromatic structure having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site, the organic groups being capable of imparting adhesive nature to the molecule, 
 R 2  is an organic group containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, said organic group having as a functional group a group which when deblocked, can impart alkali solubility to a molecule protected with an acid labile protective group, and optionally further containing a halogen, oxygen or sulfur atom, or an organic group of 6 to 18 carbon atoms, optionally having a functional group, containing an aromatic structure having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site,  
 X 1  and X 2  are each independently hydrogen, halogen or straight, branched or cyclic alkoxy group of 1 to 6 carbon atoms.  
 
   
   
       7 . The silsesquioxane compound mixture of  claim 6  wherein the functional group structure capable of imparting adhesive nature to the molecule in the monomer units (A) is selected from a structure having a hydroxyl group in which at least three fluorine atoms in total are bonded to one or more carbon atoms bonded to the carbon atom having the hydroxyl group bonded, a carboxylic acid structure, a phenolic hydroxyl structure, and a lactone ring structure.  
   
   
       8 . The silsesquioxane compound mixture of  claim 6  wherein the silane feed comprises as the trifunctional silane at least one member selected from the monomer units (A) having the general formula (2) and at least one member selected from the monomer units (B) having the general formula (3).  
   
   
       9 . A silsesquioxane compound mixture comprising at least 40 mol % based on silicon of silsesquioxane octet having a degree of condensation of substantially 100%, in which side chains comprise at least 75 mol % of side chains selected from: 
 organic groups containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms, optionally containing a halogen (inclusive of fluorine), oxygen or sulfur atom, in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an aromatic structure of 6 to 18 carbon atoms, optionally having a functional group, having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site, said organic groups being capable of imparting adhesive nature to the molecule, and    organic groups containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms, optionally containing a halogen (inclusive of fluorine), oxygen or sulfur atom, in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an aromatic structure of 6 to 18 carbon atoms, optionally having a functional group, having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site, said organic groups having as a functional group a group which when deblocked, can impart alkali solubility to a molecule protected with an acid labile protective group.    
   
   
       10 . The silsesquioxane compound mixture of  claim 9  wherein the functional group structure capable of imparting adhesive nature to the molecule is selected from a structure having a hydroxyl group in which at least three fluorine atoms in total are bonded to one or more carbon atoms bonded to the carbon atom having the hydroxyl group bonded, a carboxylic acid structure, a phenolic hydroxyl structure, and a lactone ring structure.  
   
   
       11 . The silsesquioxane compound mixture of  claim 9  wherein the silsesquioxane octet of cage structure having a degree of condensation of substantially 100% is present in an amount of at least 50 mol % based on silicon.  
   
   
       12 . The silsesquioxane compound mixture of  claim 9  wherein all said side chains are selected from: 
 organic groups containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms, optionally containing a halogen (inclusive of fluorine), oxygen or sulfur atom, in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an aromatic structure of 6 to 18 carbon atoms, optionally having a functional group, having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site, said organic groups being capable of imparting adhesive nature to the molecule, and    organic groups containing an aliphatic branched, cyclic or polycyclic structure of 3 to 20 carbon atoms, optionally containing a halogen (inclusive of fluorine), oxygen or sulfur atom, in which the atom at the silicon-bonding site is a carbon having at least two bonds with atoms other than hydrogen and halogen atoms in addition to said silicon, or an aromatic structure of 6 to 18 carbon atoms, optionally having a functional group, having a substituent group other than hydrogen and halogen atoms at a site neighboring the silicon-bonding site.    
   
   
       13 . A positive resist composition comprising the silsesquioxane compound mixture of  claim 1 .  
   
   
       14 . The positive resist composition of  claim 12 , which is a chemically amplified positive resist composition further comprising an organic solvent and an acid generator.  
   
   
       15 . The positive resist composition of  claim 12 , further comprising a dissolution inhibitor.  
   
   
       16 . The positive resist composition of  claim 12 , further comprising a basic compound and/or a surfactant.  
   
   
       17 . A patterning process comprising the steps of: 
 (1) applying the positive resist composition of  claim 12  onto a substrate;    (2) heat treating the applied resist, then exposing the heat-treated resist through a photomask to high-energy radiation having a wavelength of at most 300 nm or an electron beam; and    (3) optionally heat treating the exposed resist, then developing the resist with a liquid developer.    
   
   
       18 . The patterning process of  claim 17 , further comprising the step of processing the substrate by plasma etching after the developing step.