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7 June 1996 Implementation of attenuated PSMs in DRAM production
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We studied the use of attenuated phase shift mask (PSM) in DRAM production. There exists several problems with the use of an attenuated PSM compared to a conventional Cr mask. These include a need to form an opaque region, facilitate reticle alignment with a stepper, and optimize mask bias to prevent side peak printing. First, we investigated the characteristics of checkerboard patterns in achieving an opaque region. We confirmed the feasibility of making a mask to maintain opaqueness. Next we developed a mask fabrication process so to enable reticle alignment in some kinds of steppers by using an additional Cr layer under the attenuated layer. Finally, we tried to implement attenuated PSM in a previous generation stepper. We found that we must pay attention to lens aberration when optimizing mask bias.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Tatsuo Chijimatsu, Toru Higashi, Yasuko Tabata, Naoyuki Ishiwata, Satoru Asai, and Isamu Hanyu "Implementation of attenuated PSMs in DRAM production", Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996);


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