Polymers based on tertiary-butyl acrylate were synthesized with different compositions and glass transition temperature (Tg) values. These polymers are formulated identically and exposed under identical optical conditions. Lithographically, these polymers responded differently to different post exposure bake temperature (TPEB) conditions. In general, resist contrast, photosensitivity and PED-sensitivity improved at TPEB above polymer-Tg. The resist resolving power improved as TPEB approaches polymer-Tg. However, loss of resolution is observed at TPEB above polymer-Tg. Also, high Tg polymers show greater PEB sensitivity than the corresponding low Tgpolymers.

The outgassing issues that have long plagued conventional acetal resist designs are shown to be significantly mitigated depending on the structure of the acetalblocked polymer. Resists formulated with acetal-blocked polymers based on low molecular weight vinyl ethers such as ethyl vinyl ether and t-butyl vinyl ether deblock during exposure resulting in considerable outgassing inside the stepper and attendant film shrinkage. By modifying the acetal structure, deblocking can be completely prevented during exposure, in which case the resist requires postexposure baking to initiate the deblocking reaction as with conventional high activation energy systems. Such systems also show superior plasma etch resistance compared to conventional lower molecular weight acetals.

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