193 nm lithography using a negative acting P(SI-CMS) resist
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Copolymers of trimethysilylmethyl methacrylate and chloromethylstyrene [P(SI-CMS)] have been formulated as negative resists for exposure at 193 nm. To achieve maximum sensitivity, absorption has been targeted so that the amount of radiation exposing the base of a given film thickness is I0e^−1, leading to an optimum optical absorbance of log10e, or 0.434. Through control of the mole ratio of the monomers in the P(SI-CMS) copolymer, optimum response has been tailored for coating thicknesses from 2000 Å to 5500 Å. Optimal formulations yield working sensitivities of from 4 to 20 mJ/cm^2 for materials having a Mw of 4 × 10^4 g/mole, with resolution demonstrated below 0.4 μm. Resists exhibit etching resistance in O2 RIE and are suitable for application in both single layer and bi-layer processes (Refer to PDF file for exact formulas).