SYNTHESIS OF HIGH-PERFORMANCE PHOTORESISTS CONTAINING NUCLEIC-ACID BASES

Pyrimidine derivatives were found to be applicable to photoresists for microelectronics. This paper deals with synthesis and photochemistry of pyrimidine derivatives, and application to photoresists. Intermolecular photodimerization of pyrimidine bases in the side chains of various polymeric and dimeric compounds upon irradiation of UV light (270 nm) led to photocrosslinking of the polymer chains or photopolymerization of the dimeric compounds. These materials can be used as deep-UV negative type photoresists. On the other hand, the polymers containing thymine photodimers in the main chain underwent dissociation of the thymine photodimers upon irradiation to UV light (250 nm), leading to breakage of the polymer chains. These polymers could be used as positive type photoresists and high resolution (0.3 mum) was demonstrated. Tautomerism of pyrimidine was also applied to a chemical amplification photoresist system. Polymers containing 2,4-dialkoxypyrimidine derivatives that is an enol form of uracil were high sensitive deep-UV, and EB chemical amplification resists.