Analysis of dissolution kinetics of narrow polydispersity poly(4-hydroxystyrene) in alkaline aqueous solution using machine learning

Understanding the dissolution kinetics of resist materials is essential for their efficient development. In this study, we investigated the dissolution kinetics of poly(4-hydroxystyrene) (PHS) with a weight-average molecular weight (M (w)) of 8000-30 000 and a polydispersity index (M (w) /M (n)) of 1.07-1.20. The dissolution kinetics of PHS films was observed in tetramethylammonium hydroxide (TMAH) aqueous developers by a quartz crystal microbalance (QCM) method. The TMAH concentration was changed from 0 to 2.38 wt%. The formation of a thick transient swelling layer at these M (w) /M (n) values was suppressed compared with that at M (w) /M (n) > 2. QCM data were analyzed using the polynomial regression to clarify the effects of M (w) and M (w) /M (n) on the dissolution kinetics in a narrow polydispersity region. Both dissolving and swelling kinetics largely depended on M (w)/M (n). M (w) had little effect in 2.38 wt% TMAH developer; however, it had a large effect on the swelling when 2.38 wt% TMAH developer was diluted.