The material design to reduce outgassing in acetal based chemically amplified resist for EUV lithography

摘要

In case of EUV lithography, resist material needs to be developed to improve high sensitivity and to minimize outgassing. The outgassing segments from resist were mainly from PAG decomposition. The new type PAG was synthesized by modifying cation group of the sulfonium salt. The sensitivity of the PAG could be enhanced by loading electron withdrawing group on the PAG, which has low volatility during EUV exposure. Then the newly developed PAGs were capable to reduce outgassing during EUV exposure maintaining high acid generating efficiency against EB and EUV exposure. The other approaches to improve the resist sensitivity and minimizing outgassing property were to design PHS based polymer platform with bulky acetal group. The various kind of acetal groups were simulated to determine the Van der Waals volume. The bulkiness of the protection group is effective to both a) increasing inhibition rate of the resist matrix and b) boiling points of deprotected group. The optimum protection ratio has been studied to obtain proper dissolution rate changes before and after exposure. The resist sensitivity is depend on the protection ratio of the bulky acetal group. By modifying PAG and optimizing bulky acetal group in the polymer, it is possible to minimize the amount of the outgassing segments during EUV exposure maintaining high resist sensitivity. The EUV exposure was demonstrated. It was observed that the resist had a high resolution capability in EUV exposure.