Decomposition behavior of acetal-protected dissolution inhibitors with and without PEB in chemically amplified three-component novolac resists

Chemically amplified three-component novolac resists consist of novolac resin, photoacid generator, and dissolution inhibitor that is deprotected by acid. In this study, we synthesized dissolution inhibitors protected by acetals with different decomposability and investigated the relationship between the decomposability of the acetals and the resist sensitivity. At low post-exposure bake (PEB) temperatures, the higher the decomposability of the acetals, the higher the resist sensitivity. However, at high PEB temperatures, the resist sensitivity order was not the same as at lower PEB temperatures. At high temperature PEB, the decomposition of acetal is accelerated by the volatilization of the decomposition products, so the lower the boiling point of the decomposition products, the higher the sensitivity of the resist. The change in decomposition property with temperature was also supported by FT-IR. This suggests that the sensitivity of resists using acetal depends not only on the decomposition characteristics of acetal but also on the volatility of the deprotection product at PEB.