We report here, new non-acetal containing low bake (PEB < 100° C ) resists that are suitable for immersion
lithography. These resists are based on novel low activation energy (low-Ea) tertiary ester protecting
groups. One major obstacle to imaging in the sub-50 nm regime using chemically amplified resists is the
diminished image integrity in the pattern ("image blur") due to photo-generated acid diffusion into
unexposed regions. Low processing temperatures are predicted to decrease the degree of photoacid
diffusion and, in turn, decrease the image blur. Even though many low bake resist compositions have
previously been reported, they are all based on acetal/ketal protecting groups. Unfortunately, these
materials require a stoichiometric amount of water for the photoacid-catalyzed deprotection reaction to
proceed. It is usually assumed that the water for the reaction comes from the environment in the bake
station. However, fluctuations in humidity could affect the performance of the resist. Furthermore,
acetal/ketal-based resists generally lack storage stability. For these reasons, acetal/ketal-based resists did
not receive widespread acceptance in the lithography community. With the introduction of water based
immersion lithography, acetal/ketal-based resists are expected to have further performance difficulties.
Therefore, we targeted the development of new "low blur" resists for 193nm lithography that do not
contain acetal/ketal protecting groups.