Positive resist composition

Abstract

A positive resist composition, having a superior resolution as well as good resist performances such as sensitivity, depth of focus and profile, is described and includes a novolac resin, a radiation-sensitive quinonediazide compound and a thioxanthone compound represented by the following formula (I): wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 independently represent hydrogen, halogen, alkyl, alkoxy, aryl, carboxyl or alkoxycarbonyl.

What is claimed is:  
     
         1 . A method for producing a semiconductor comprising the steps of: 
 dissolving a positive resist composition represented by Formula (I): 
                 
    in a suitable solvent; and    applying said positive resist composition to a silicone wafer to thereby form a resist film.    
     
     
         2 . The method of    claim 1   , further comprising irradiating said resist film in a pattern.  
     
     
         3 . The method of    claim 1   , wherein the positive resist composition comprises a novolac resin comprising 25% or less of components based on the total amount of novolac resin excluding unreacted phenol compound having a molecular weight of 1,000 or less.  
     
     
         4 . The method of    claim 1   , wherein the positive resist composition comprises a low molecular weight alkali-soluble phenol compound in an amount within a range of 3 to 40% by weight based on the total amount of novolac resin and the low molecular weight alkali-soluble phenol compound.  
     
     
         5 . The method of    claim 1   , wherein the thioxanthone compound of Formula (I) is selected from thioxanthone, 1-chlorothioxanthone, 2-chlorothioxanthone, 3-chlorothioxanthone, 4-chlorothioxanthone, 1-methylthioxanthone, 2-methylthioxanthone, 3-methylthioxanthone, 4-methylthioxanthone, 1-ethylthioxanthone, 2-ethylthioxanthone, 3-ethylthioxanthone, 4-ethylthioxanthone, 1-isopropylthioxanthone, 2-isopropylthioxanthone, 3-isopropylthioxanthone, 4-isopropylthioxanthone, methyl thioxanthone-1-carboxylate or methyl 7-methylthioxanthone-3-carboxylate.  
     
     
         6 . The method of    claim 1   , wherein the amount of thioxanthone compound is about from 0.01 to 5 parts by weight based on 100 parts by total weight of the novolac resin and a low molecular weight alkali-soluble phenol compound.  
     
     
         7 . The method of    claim 3   , wherein the amount of thioxanthone compound is about from 0.01 to 5 parts by weight based on 100 parts by total weight of the novolac resin and a low molecular weight alkali-soluble phenol compound.