High Resolution, Novolak Based Negative Tone Electron Beam Resist

Abstract

A novel, aqueous alkaline developable, sensitive electron beam resist is described. This resist is a three component system consisting of a novolak resin, aminoplast, and a radiation sensitive acid generator (RSAG). The resist has demonstrated high resolution (0.3 μm grating in 0.5 μm thick resist) with under 5uC/cm² exposure dose. Furthermore, the resulting resist images exhibit dry etch stability comparable to optical positive novolak resists. This paper describes the chemistry of this novel resist system. The mechanism of the crosslinking reaction is discussed using data from GPC, FT IR and GCMS as analytical probes. The variation of sensitivity and contrast with resist composition has been analyzed as well. The paper addresses the nature of the post exposure "dark reaction" in this resist and compares it to other electron beam resists (eg. COP) known to exhibit a strong time dependence on processing. Electrical linewidth studies and scanning electron microscopy data are employed in these studies.