193 nm single layer resist strategies, concepts, and recent results

Matrix resins used in conventional resists are not suitable for use at 193 nm due to their opacity. Hence new materials that are functionally similar to but structurally different from novolac and poly(hydroxy styrene) are re quired for 193 nm lithography. We report on the use of alternating copolyme rs of cycloolefins with maleic anhydride as effective 193 nm matrix resins, with or without dissolution inhibitors based on polyfunctional cholates, f or 193 nm lithography. Due to their structural diversity, the required high transparency and etch stability, compatibility with industry standard 0.26 2 N tetramethyl ammonium hydroxide (TMAH) can be built into the polymer by conventional free redical polymerization techniques. A correlation between the molecular properties ? of the resist components (matrix resin, dissolut ion inhibitor, photoacid generator, and base additive) and resist Lithograp hic performance parameters is illustrated. The formulations containing diss olution inhibitors currently show 0.13 mu m line/space (WS) pair and 0.11 m u m isolated line resolution at 20-30 mJ/cm(2) photospeeds with good proces s latitude, etch resistance; and environmental stability. These materials a re completely compatible with 0.262 N TMAH development, show poly and oxide etch rates comparable to that of deep-ultraviolet resists used in manufact uring today, and exhibit postexposure delay stabilities of greater than 2 h for 0.16 mu m features at 13 ppb concentrations of ammonia or N-methyl pyr rolidone. The importance of reflectivity control at the 193 nm imaging wave length and how it can be handled by a multilayer dielectric antireflective coating (ARC) has been elucidated. An optimized resist and ARC system shows 0.14 mu m Ifs pair resolution over 100 nm poly topography and exhibits a r esolution of 60 nm isolated Lines and 80 nm with >0.8 mu m depth of focus u sing a Levenson phase shift mask. The design and utility of photoacid gener ators that serve both the photoacid generation and amine additive functions in low activation energy resist systems and the base additive function in high activation energy system are also described. The use of these photodec omposable bases (PDBs) has been shown to dramatically alleviate the outgass ing during exposure in low activation energy chemically amplified (CA) resi sts. In high activation energy CA resists, use of a PDB that is basic but g enerates an acid upon exposure to light or radiation provides some relief i n designing 193 nm resists that are fast, yet stable, to environmental and substrate contamination effects. (C) 1998 American Vacuum Society. [S0734-2 11X(98)18006-X].