Acid-labile, chain-scission polymer systems used as positive-tone photoresists developable in supercritical CO2

摘要

A new type of acid-catalyzed, chain-scission polymeric system is reported based on main-chain acetal linkages and designed for solubility selectivity in supercritical (SO CO2. These low-molecular-weight polymer segments, formed by the stepwise polymerization of divinyl ethers and dihydroxy-based monomers, are linked together to render these individually soluble components insoluble in scCO(2). Upon exposure to an acid, the linkages are cleaved and result in a system soluble in both aqueous base and scCO(2), two widely disparate solvents. This fact is utilized to make a positive-tone photoresist system developable in scCO(2) as well as aqueous developer. This represents to the best of our knowledge the first known report of an intrinsically positive-tone photoresist developable in pure scCO(2). Excellent solubility contrasts are shown and feature sizes below 200 nm can be obtained with this system.