An investigation of the lithographic properties of the poly (p-methylstyrene-co-chloromethylstyrene) resist system

Abstract

The lithographic performance of the resist system poly(p‐methylstyrene‐co‐chloromethylstyrene) PMS–CMS has been assessed. Copolymerization of the monomers, PMS and CMS, produced resists with CMS increasing from 0% to 52%, molecular weights between 122 000 and 167 000, and dispersivities between 1.7 and 2.3. The sensitivity (D0.5 n ) and contrast of pure PMS for 20 kV electrons was 38 μC cm− 2 and 2.8, respectively. Addition of 4.2% CMS increased the sensitivity to 2.1 μC cm− 2 but only reduced the contrast to 2.3, a value sufficient for submicron resolution. Further increases in CMS content, to 52%, produced smooth variations in sensitivity and contrast to 1.2 μC cm− 2 and 1.5, respectively. Exposure of 4.5% CMS resist with deep UV light (22 mJ cm− 2) produced 1 μm lines and spaces with vertical profiles. The etch rate of this resist, during poly‐Si definition in a chlorine plasma, was almost half that of the photoresist HPR206.