Underlayer designs to enhance the performance of EUV resists

Extreme ultraviolet (EUV) lithography has gained momentum as the method of choice for <32-nm half-pitch device fabrication. In this paper, we describe our initial attempts to increase an EUV resist's sensitivity without compromising resolution and line roughness via introduction of a thermally crosslinkable underlayer. The main purpose is to test the possibility of using a combination of photoacid generators (PAGs) and EUV sensitizers (phenol type) in the underlayer designs to enhance the overall performance of EUV resists. We have demonstrated the possible benefits of adding an EUV underlayer into the regular EUV litho stack and investigated the effect of PAG types and loadings on the photospeed and litho performance of three different EUV resists.