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27 May 1996 CD uniformity of photomasks written with high-voltage variable-shaped e beam
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The critical dimension uniformity required in the fabrication of photomasks for 1 gigabit DRAMs will be more stringent that 20 nm in terms of 3 sigma. High-voltage variable-shaped e-beam (VSB) writing is advantageous because of its high resolution, linewidth stability, and throughput performance. However, stitching errors in VSB writing have been a critical problem in the fabrication of advanced photomasks. In this paper, an improved method to calibrate the size of a VSB shot and reduce shot stitching errors is proposed. The accuracy of the calibration method depends on that of the linewidth measurement system, and shot-size calibration with an accuracy of +/- 10 nm can be achieved using existing measurement systems. The positioning accuracy of VSB shots was enhanced by a multiple pass exposure scheme. With these procedures applied to a 50 kV VSB system, the linewidth variation of a photomask in a local area such as a square region of 200 micrometers X 200 micrometers was reduced to less than 20 nm.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Noriaki Nakayamada, Shigehiro Hara, Toshiyuki Magoshi, Hideaki Sakurai, Takayuki Abe, and Iwao Higashikawa "CD uniformity of photomasks written with high-voltage variable-shaped e beam", Proc. SPIE 2723, Electron-Beam, X-Ray, EUV, and Ion-Beam Submicrometer Lithographies for Manufacturing VI, (27 May 1996);


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