Many approaches to surface imaging rely upon selective incorporation of silicon into an already imaged resist layer. SAHR$+TM$/ (silylated acid hardened resist) obtains its selectivity by a lower rate of silicon incorporation into exposed and crosslinked areas, providing a positive tone image after RIE development. Two difficulties with the practical implementation of this approach have been the overflow of silylated material onto crosslinked areas, and reduced silicon incorporation in small openings. We have found that surface treatment with a bifunctional silylation agent (the `two gas process') can prevent overflow, and that removing part of the resist layer with dilute tetramethyl ammonium hydroxide (TMAH) (the `presilylation develop process') minimizes overflow and improves silicon incorporation in small features. With a predevelop step, feature size linearity is obtained below k1 $EQ 0.7, with uniformity and repeatability consistent with VLSI manufacturing practices.
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