<title>Design, synthesis and characterization of poly(trimethylsilylmethyl methacrylate-co-chloromethyl styrene) for 193-nm exposure</title>

Abstract

Requirements of materials for lithography at 193 nm limit single layer resist candidates to those with high optical transmission. A random copolymer of trimethylsilymethyl methacrylate (SI) and chloromethyl styrene (CMS), [P(SI-CMS)], has been shown to be highly sensitive negative 193 nm resist in both bi-layer and single layer modes. Such resists show maximum sensitivity with an optical absorbance of the coating of log10e, or 0.434. Through control of the mole ratio of the monomers in the P(SI-CMS) copolymer, absorbance values have been optimized for film thicknesses of 0.2 - 0.3 micrometers for 90:10 SI:CMS, 0.35 - 0.45 micrometers for 95:5 SI:CMS and 0.55 - 0.65 micrometers for 98:2 SI:CMS. Optical absorbance of the CMS is at a maximum in the 190 to 205 nm range, allowing the copolymer to be tailored for a large degree of crosslinking at a relatively low CMS concentration. Spray development of these materials is performed with ethanol, followed by a two step methanol/isopropanol-water rinse. Sensitivities are on the order of 4 to 20 mj/cm2 at Mw near 40,000 g/mol. Furthermore, these ratios have been found to produce optimum O2 etch resistance.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.