Molecular parameters and lithographic performance of poly(chloromethylstyrene)—a high-performance negative electron resist

Abstract

Poly(chloromethylstyrene) (PCMS) is shown to have a desirable combination of properties, including high sensitivity, high dry-etch resistance, and high resolution. As a consequence, it is a very attractive candidate for high performance (throughput, resolution, process compatibility) electron beam lithography. PCMS lithographic performance is higher than that of any other previously reported, high-sensitivity negative electron resist. Performance results are compared specifically with COP, PGMA, and CMPS, and are correlated with molecular and chemical properties. PCMS synthesis and evaluation results are reported for polymers with molecular weights (?w) between 20 000 and 450 000 and polydispersivities between 1.3 and 2.3. A typical high molecular weight (?w = 381 000) material with polydispersivity of about 1.6 has sensitivity (Dg0.5)<0.5 μC/cm2, contrast ≳1.5, and resolution <1.0 μm (equal lines and spaces). Respective values for a typical low molecular weight (?w = 22 000) material with polydispersivity of about 1.3 are sensitivity <7 μC/cm2, contrast ≳2.0, and resolution <0.5 μm.