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30 January 1989 Excimer Laser Exposure Characteristics Of Inorganic Resists Based On Peroxo-Polytungstic Acids
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Peroxo-polytungstic acid (HPA) is investigated as a spin-coatable inorganic resist material for excimer laser lithography. HPA is synthesized by dissolving metallic tungsten into an H2O2 solution. It is possible to form an amorphous and microstructure-free film by spin-coating a water-based solution. The sensitivity characteristics of the film were determined for KrF (248 nm) and XeC1 (308 nm) excimer lasers. Absorption coefficients at 248 nm and 308 nm are 7μm-1 and 2μm-1, respectively. Solubility of the film is reduced by laser beam irradiation. Sensitivity for KrF is nine times higher than for XeC1 owing to the difference in laser beam absorbance. Moreover, sensitivity is enhanced by niobium doping to HPA. The best sensitivity is 100 mJ/cm2 at 248 nm, which is almost the same value as that for a typical novolak-based organic resist. The effects of reciprocity failure are small in laser pulse energy less than 16 mJ/cm2-pulse. Reduction projection of KrF excimer laser was performed using a stepper with a lens NA of 0.35. A good profile sub-half micron pattern with an aspect ratio of 3 was successfully fabricated through the two-layer resist process.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Akira Ishikawa, Hiroshi Okamoto, Katsuki Miyauchi, and Tetsuichi Kudo "Excimer Laser Exposure Characteristics Of Inorganic Resists Based On Peroxo-Polytungstic Acids", Proc. SPIE 1086, Advances in Resist Technology and Processing VI, (30 January 1989);

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