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4 May 2005 Influence of the watermark in immersion lithography process
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In the liquid immersion lithography, uses of the cover material (C/M) films were discussed to reduce elution of resist components to fluid. With fluctuation of exposure tool or resist process, it is possible to remain of waterdrop on the wafer and watermark (W/M) will be made. The investigation of influence of the W/M on resist patterns, formation process of W/M, and reduction of pattern defect due to W/M will be discussed. Resist patterns within and around the intentionally made W/M were observed in three cases, which were without C/M, TOK TSP-3A and alkali-soluble C/M. In all C/M cases, pattern defect were T-topped shapes. Reduction of pattern defects due to waterdrop was examined. It was found that remained waterdrop made defect. It should be required to remove waterdrop before drying, and/or to remove the defect due to waterdrop. But new dry technique and/or unit will be need for making no W/M. It was examined that the observation of waterdrop through the drying step and simulative reproduction of experiment in order to understand the formation mechanism of W/M. If maximum drying time of waterdrop using immersion exposure tool is estimated 90 seconds, the watermark of which volume and diameter are less than 0.02 uL and 350um will be dried and will make pattern defect. The threshold will be large with wafer speed become faster. From result and speculations in this work, it is considered that it will be difficult to development C/M as single film, which makes no pattern defects due to remained waterdrop.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daisuke Kawamura, Tomoyuki Takeishi, Koutarou Sho, Kentarou Matsunaga, Naofumi Shibata, Kaoru Ozawa, Satoru Shimura, Hideharu Kyoda, Tetsu Kawasaki, Seiki Ishida, Takayuki Toshima, Yasunobu Oonishi, and Shinichi Ito "Influence of the watermark in immersion lithography process", Proc. SPIE 5753, Advances in Resist Technology and Processing XXII, (4 May 2005);

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