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In surface imaging, dry developed resist systems, based on gas phase silylation, resist profiles are mainly determined by the silicon distribution between the exposed and the unexposed areas in the upper part of the resist, and by the dry etching process that transfers this silicon image into the rest of the resist layer1 . Contrast enhancement, resulting in steeper roflles and less residues, is obtained by a two-step dry development process23. In a short first step, a small amount of a fluorinated gas is added to remove the upper thin layer of resist. This results In an elimination of residual silicon in the non-exposed areas and also in steeper silicon-profiles in the exposed regions, and thus in steeper resist profiles after dry development. Similar process improvements can be obtained using a two-step dry development process using pure oxygen. The selectivity is then controlled by increasing or decreasing physical sputtering.Instead of using fluorine containing gases for non-selectivity, the silicon, incorporated Into the non-exposed areas, is sputtered away physically In a first step by using elevated power and decreased flow rate conditions. With this in mind and with the help of a statistically designed experiment, The optimum process conditions for this pure oxygen, two-step development process were determined. The results are compared to those obtained using a single step development and to the two-step C2F6 process.

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