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Proceedings Paper

Mask CD measurements with an atomic force microscope
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Paper Abstract

The mask pattern edge profile's impact on critical dimension (CD) metrology and printing performance was investigated. Three 193nm attenuating PSMs with intentionally changed pattern edge profiles were made. The three masks had patterns with different CD data width, so that we could chose isolated lines and holes from each mask that gave almost the same CD when measured by a mask CD-SEM. We chose patterns that were measured approximately 400nm and 800nm for isolated lines, and approximately 500nm for isolated holes, and simulated their wafer CD by an AIMS tool and found not only that the AIMS results were different from the mask CD-SEM, but also that the difference was not constant for the three masks. Though in this work, the pattern edge profiles were intentionally changed and were far beyond the actual deviation range in current photomask manufacturing, this meant that the mask CD-SEM might face a difficulty in accurate wafer CD prediction if we should take the pattern edge profile into account. In this work we employed an atomic force microscope (AFM) based mask CD metrology tool, and by comparing the output profile with cross sectional SEM observation, we confirmed that the tool can observe the pattern edge profile nondestructively. If, at a certain slice, this tool can output the same CD as the AIMS for the three masks, we thought that this tool might be a promising candidate in wafer CD prediction. We found that the optimal slice level for the CD-AFM depended on the pattern category. For 400nm isolated lines, a 40% slice was optimal, while an 80% slice was optimal for 800nm isolated lines. For 500nm isolated holes, the range of 30 to 40% show good match between mask metrology and AIMS. Though the cause of this difference among pattern categories should be investigated further, from the fact that a certain slice can match the mask CD and AIMS, we concluded that the CD-SEM was a promising tool for wafer CD prediction.

Paper Details

Date Published: 20 August 2004
PDF: 11 pages
Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); doi: 10.1117/12.557765
Show Author Affiliations
Yuuichi Yoshida, Dai Nippon Printing Co., Ltd. (Japan)
Shiho Sasaki, Dai Nippon Printing Co., Ltd. (Japan)
Tsukasa Abe, Dai Nippon Printing Co., Ltd. (Japan)
Hiroshi Mohri, Dai Nippon Printing Co., Ltd. (Japan)
Naoya Hayashi, Dai Nippon Printing Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 5446:
Photomask and Next-Generation Lithography Mask Technology XI
Hiroyoshi Tanabe, Editor(s)

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