Nonstatistical degradation and development characteristics of poly(methyrmethacrylate) based resists during electron beam exposure

We present an investigation to study the degradation of poly(methylmethacry late) (PMMA) based resists during electron beam exposure and their developm ent characteristics. After exposure to the electron beam we detect for ARP 610 resist (PMMA 74%, PMAA 26%) and for a homopolymeric PMMA resist, a simi lar bimodal respectively multimodal molecular weight distribution curve cha racterized by a shift of the maximum from 10(5) to 10(3) g/mol and an incre ase of low molecular weight fractions (approximate to 10(3) g/mol) with inc reasing exposure dose. The model of Greeneich can only be applied to lower deposited energy densities (ARP 610<4 eV/nm(3), homopolymeric PMMA <8 eV/nm (3)). The difference found between experimental data and modeling values at higher deposited energy densities for both resists, results from a formati on of stable low molecular weight fractions. Comparing the measured dissolu tion rate with the calculated one, the determined difference proves the non applicability of the empirical formula for the dissolution rate given by Gr eeneich. The low molecular weight fractions influence the dissolution rate significantly more than given by their portion in the molecular weight dist ribution. (C) 1998 American Vacuum Society. [S0734-211X(98)11606-2].