The effect of atomic layer etching (ALE) processes on polyhydroxystyrene-based EUV chemical amplification resist

An analysis of plasma-resist film interactions was conducted to evaluate the impact of atomic layer etching (ALE) adsorption and desorption process steps on a model polyhydroxystyrene-based chemically amplified resist film. The results indicate that resist film thickness loss occurs mainly during the adsorption step and is attributed to the depletion of oxygen-bonded species across the bulk of the resist film. Below the resist film surface, chemical components of the resist material were found to react predominantly during the adsorption step, with clear evidence of polymer deprotection reactions. During the desorption step, the fluorine components of a fluorocarbon layer formed during ALE adsorption were observed to be largely removed from the resist film surface, resulting in a carbon-rich layer. Because film thickness loss during desorption is minimal, the results suggest that the carbon-rich layer minimizes the impact of ion bombardment on resist film thickness.