Quantification of EUV resist outgassing

Outgassing from EUV photoresists under EUV irradiation must be minimal in order to prevent contamination of EUV optics. A better understanding of both the level of outgassing of current EUV resists, and the effect of outgassing on EUV optics is needed to set outgassing targets and to assess the risk of resist outgassing in EUV tools. In this paper, we document a technique for quantifying the EUV resist outgassing using both internal and external standards to baseline the GC/MS. In a comparison of internal and external standard, the two techniques give consistent baseline results. Quantification of the outgassing of a number of experimental EUV photoresists shows outgassing levels of 1E+10 - 1E+15 molecules/cm² at the relevant lithographic dose. Protecting groups and PAG fragments are identified as the main outgassing components. The use of high activation energy resists, and non-ionic PAGs are identified as possible methods to reduce the outgassing levels of EUV photoresists.