Plasma polymerized methylsilane. III. Process optimization for 193 nm lithography applications

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New photoresists and processes are required for sub 0.15 μm design rules, and currently an important effect is on-going for single layer resist optimization at 193 nm. Top surface imaging can be an interesting alternative approach. An all dry chemical vapor deposition (CVD) process based on plasma polymerized methylsilane (PPMS) or plasma polymerized dimethylsilane (PP2MS) provides a thin conformal and photosensitive layer at 193 nm. A thin amorphous film of Si–Si bonded material is deposited using plasma enhanced chemical vapor deposition (PECVD) with methylsilane or dimethylsilane as the gas precursor. Upon 193 nm exposure under air, photoinduced oxidation of the CVD resist occurs, generating a latent image. The image is then developed in a chlorine-based plasma (which removes the unexposed areas), providing a negative tone process. This mask can be used to pattern a thick organic underlayer to provide a general bilevel process. Lithographic results on both a 193 microstepper as well as a full field production stepper are presented: resolution down to 0.10 μm equal L/S was obtained. A preliminary comparison between PPMS and PP2MS materials is presented, including Fourier-transform infrared results, stability of the films in air and lithographic performance including line edge roughness.