Photoresist composition for deep ultraviolet lithography comprising a mixture of photoactive compounds

Abstract

The present invention relates to a novel photoresist that can be developed with an aqueous alkaline solution, and is capable of being imaged at exposure wavelengths in the deep ultraviolet. The invention also relates to a process for imaging the novel photoresist. The novel photoresist comprises a) a polymer containing an acid labile group, and b) a novel mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure 1 and 2, and a higher absorbing compound selected from structure 4 and 5, where, R 1 and R 2 are independently (C 1 -C 6 )alkyl, cycloalkyl, cyclohexanone, R 5 -R 9 are independently hydrogen, hydroxyl, (C 1 -C 6 )alkyl, C 1 -C 6 )aliphatic hydrocarbon containing one or more O atoms, m=1-5, X − is an anion, and Ar is selected from naphthyl, anthracyl, and structure 3, where, R 3 is hydrogen or (C 1 -C 6 )alkyl, R 4 is independently hydrogen, (C 1 -C 6 )alkyl, (C 1 -C 6 )aliphatic hydrocarbon containing one or more O atoms, Y is a single bond or (C 1 -C 6 )alkyl, and n=1-4.

1 . A photoresist composition useful for imaging in deep uv comprising; 
 a) a polymer containing an acid labile group; and,    b) a mixture of photoactive compounds, where the mixture comprises a lower absorbing compound selected from structure 1 and 2, and a higher absorbing compound selected from structure 4 and 5,                          where, R 1  and R 2  are independently (C 1 -C 6 )alkyl, cycloalkyl, cyclohexanone, R 5 -R 9  are independently hydrogen, hydroxyl, (C 1 -C 6 )alkyl, C 1 -C 6 )aliphatic hydrocarbon containing one or more O atoms, m=1-5, X −  is an anion, and Ar is selected from naphthyl, anthracyl, and structure 3,                          where, R 3  is hydrogen or (C 1 -C 6 )alkyl, R 4  is independently hydrogen, (C 1 -C 6 )alkyl, (C 1 -C 6 )aliphatic hydrocarbon containing one or more O atoms, Y is a single bond or (C 1 -C 6 )alkyl, and n=1-4.    
     
     
         2 . The composition according to  claim 1 , where the compound of structure 1 is selected from a 4-methoxyphenyl-dimethylsulfonium salt, 3,5-dimethyl-4-methoxyphenyl-dimethyl sulfonium salt, 4-hydroxyphenyl-dimethyl sulfonium salt, and 3,5-dimethyl-4-hydroxyphenyl-dimethyl sulfonium salt.  
     
     
         3 . The composition according to  claim 1 , where the compound of structure 2 is selected from 4-methoxyphenyl-methyliodonium salt, 3,5-dimethyl-4-hydroxyphenyl-methyliodonium salt, 4-hydroxyphenyl-methyl iodonium salt and 3,5-dimethyl-4-methoxyphenyl-methyliodonium salt.  
     
     
         4 . The composition according to  claim 1 , where the compound of structure 4 is selected from a triphenyl sulfonium salt and its derivatives.  
     
     
         5 . The composition according to  claim 1 , where the compound of structure 5 is selected from a diphenyl iodonium salt and its derivatives.  
     
     
         6 . The composition according to  claim 1 , where the polymer is nonaromatic.  
     
     
         7 . The composition according to  claim 1 , where the molar ratio of the higher absorbing compound to the lower absorbing compound is 2:1.  
     
     
         8 . The composition according to  claim 1 , where the molar ratio of higher absorbing compound to the lower absorbing compound is 1:2.  
     
     
         9 . A process for imaging a photoresist comprising the steps of: 
 a) forming on a substrate a photoresist coating from the photoresist composition of  claim 1;     b) image-wise exposing the photoresist coating;    c) optionally, postexposure baking the photoresist coating; and    d) developing the photoresist coating with an aqueous alkaline solution.    
     
     
         10 . The process of  claim 9 , where the image-wise exposure wavelength is below 200 nm.  
     
     
         11 . The process according to  claim 9 , where the aqueous alkaline solution comprises tetramethylammonium hydroxide.  
     
     
         12 . The process according to  claim 9 , where the aqueous alkaline solution further comprises a surfactant.  
     
     
         13 . The process according to  claim 9 , where the substrate is selected from a microelectronic device and a liquid crystal display substrate.