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.

Physical and lithographic properties of structurally diverse acetal-derivatized hydroxy styrene polymers are reported. The dissolution and thermal properties of the acetalblocked polymers vary with the size of the pendent acetal moiety. The lithographic performance of the resists containing "bulky" acetal-derivatized polymers was found to be superior to those containing non-bulky acetal functionalized polymers. In the cases where the acidolysis products of the bulky acetal-based polymers are non-volatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved. Bulky acetal-derivatized polymers also show excellent thermal and shelf life stability.

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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Lithographic properties of a variety of acetal-derivatized hydroxy styrene based polymers are reported. The structural modifications in the polymers involve varying the size ofthe pendent acetal moiety. The lithographic performances of the resists containing structurally modified acetals were found to be superior to the conventional acetals. In the cases where the acidolysis products ofthe modified acetals are nonvolatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved.