Chemically amplified resists based on polymer side‐chain rearrangement or electrophilic crosslinking

A variety of resist systems have been studied that owe their sensitivity to the occurrence of catalyzed electrophilic rearrangements or substitution processes. In most designs, polyfunctional or polymer‐bound benzylic ethers, esters, or alcohols are used in the key step of the reaction, which is initiated by protonation of the latent electrophilic moiety, resulting in formation of a carbocationic center. Thermal activation of the electrophilic process leads to the formation of new C–C bonds with liberation of a proton; therefore the overall process is catalytic and amounts to chemical amplification. A variety of polymers and active small molecules that provide access to both negative and positive tone images have been tested, and sensitivities as high as 0.1 mJ/cm² have been measured. In addition, several image reversal schemes involving either selective silylation of non‐exposed areas or the in situ photogeneration of base have been tested and are presented.