Abstract
Line edge roughness (LER) is the critical issue in the development of chemically amplified resists used for extreme ultraviolet (EUV) lithography. The main cause of LER in state-of-the-art resists used at 22 nm node is the chemical inhomogeneity intrinsic to chemical reactions. This LER is expressed using the chemical gradient of chemical compounds which determine the solubility of resists. However, the inhomogeneity in the initial acid distribution possibly caused by the inhomogeneous distribution of acid generators becomes a concern with the reduction of feature sizes. In this study, the effect of acid distribution on LER was theoretically investigated on the basis of the reaction mechanisms of chemically amplified EUV resists. The fluctuation of line edge originating from the initial acid distribution was compared with LER originating from the chemical gradient. The microfluctuation in the initial acid distribution was sufficiently smoothed out through catalytic chain reaction. This indicates that the smoothing effect of acid diffusion is essential to the ultrafine patterning with high sensitivity.
