Dependence of acid generation efficiency on acid molecular structure and concentration of acid generator in chemically amplified EUV resist

The trade-off between resolution, sensitivity, and line edge roughness (LER) is the most serious problem for the development of sub-30 nm resists based on chemical amplification. Because of this trade-off, the increase in acid generation efficiency is essentially required for high resolution patterning with high sensitivity and low LER. Under such circumstances, the absorption coefficient and the acid generation efficiency are elemental key factors for the design of chemically amplified extreme ultraviolet (EUV) resist because the acid distribution in resist films is primarily determined by these two factors. In this study, we investigated the dependence of acid generation efficiency on the molecular structure and concentration of acid generators in chemically amplified EUV resists. The acid generation efficiency (the number of acid molecules generated by a single EUV photon) was obtained within the acid generator concentration range of 2-30 wt % for several kinds of ionic and nonionic acid generators.