Mobility of photogenerated acid in resists and molecular resists

Abstract

Basic monomers such as bicyclo[2,2,1]hept-5-en-2-yl piperidyl ketone (BPK), azaperhydroepinyl bicyclo[2,2,1]hept-5-en-2-yl ketone (AEBK), azaperhydro ocinyl bicyclo[2,2,1]hept-5-en-2-yl ketone (AOBK), bicyclo[2,2,1]hept-5-en-2-yl-N,N-dicyclohexylmethan amide (BDHMA), bicyclo[2,2,1]hept-5-en-2-yl-N,N-bis(1,1-dimethylethyl)methan amide (BDMEMA), bicyclo[2,2,1] hept-5-en-2-yl 4-ethyl piperazinyl ketone (BEPK), 1-methyl-4-piperidyl bicyclo[2,2,1]hept-5-ene-2 carboxylate (MPBC), and 2-piperidylethyl bicyclo [2,2,1]hept-5-ene carboxylate (PEBC) were synthesized and polymerized with t-butoxy carbonyl norbornene (TBN) and maleic anhydride (MA) with various monomer feed ratios. These polymers are evaluated as a basic matrix for post-exposure delay (PED) stability in ArF lithography. The evaporation of photogenerated acid in a basic polymer film was measured by a spectral change of tetrabromophenol blue sodium (TBPB-Na) salt and diffusion of photogenerated acid in these films was investigated using transport equation of internal diffusion and surface evaporation. As the basic moiety increases in resist composition, the evaporation and diffusion of photogenerated acid are alleviated since only acid surviving deactivation by the basic units diffuses to the surface and evaporates from the surface of resist film. Diffusion of photogenerated acid in basic polymer films and acid trapping capability of the basic units were investigated using copolymer of t-butyl methacrylate (TBMA) and 3-(t-butoxycarbonyl)-1-vinylcaprolactam (BCVC) in KrF lithography. Evaporation of acid and base was studied by a spectral change of TBPB-Na salt. Evaporation of a low molecular weight basic additive is also examined. Whereas the low molecular weight basic additive is evaporated during baking, the basic monomer units in the copolymer are not evaporated at all. Thus, the copolymer with the basic monomer can control the acid diffusion and evaporation effectively. Cis-2,6-di-t-butylpiperi...