Energy Quenching Effects on Dry-Etching Durability of Copolymers and Polymer Blends of Vinylnaphthalene or α-Methyl Styrene with Methyl Methacrylate

Durabilities for O2 reactive ion etching (O2RIE) were studied as a function of number-average molecular weight (Mn) of poly(methyl methacrylate) [PMMA], poly(α-methyl styrene) [PMSt] and poly(2-vinylnaphthalene) [PVN]. Etching rates were independent of the Mn and in the descending order of PMMA, PMSt and PVN. Dry-etching durability which was defined as the reciprocal of etching rate relative to PMMA, of PVN was higher than that of PMSt. 2-Vinylnaphthalene (VN) moiety was found to be more effective for enhancing dry-etching durability than α-methyl styrene (MSt). Dry etching durabilities of copolymers (PMMA-co-MSt, PMMA-co-VN) were equal to those of polymer blends (PMMA/PMSt, PMMA/PVN) of the same composition and larger than the values calculated from the constituent homopolymers assuming the wt% or vol% additivity as the estimated bombardment probability by ion and neutral active species.