Mechanistic study of a novel chemically amplified resist

Over the past years, this laboratory has designed a number of novel chemically amplified photoresists. Many contained molecules with latent electrophilic groups capable of crosslinking aromatic polymers. These groups are activated to carbocationic intermediates by addition of proton generated through irradiation of onium salts. A typical formulation contains poly(4-hydroxystyrene), a small molecule crosslinker and an onium salt. It is apparent that the rate determining step of the crosslinking reaction is the substitution of the benzylic alcohol hydroxyl group by poly(4-hydroxystyrene). In his paper a crosslinker was selected for subsequent study. The phenolic OH group is expected to give increased delocalization of the positive charge by its positive mesomeric effect. In addition, the resist will be fully aqueous base developable due to the solubility of phenols in base.