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Proceedings Paper

New overlay pattern design for real-time focus and tilt monitor
Author(s): Chin-Yu Ku; Tan Fu Lei; Jia-Min Shieh; Tsann-Bim Chiou; Hwang-Kuen Lin
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Paper Abstract

The reduced depth of focus (DOF) caused by higher numerical aperture (NA) is making the accuracy of best focus measurement increasingly important. A new overlay pattern is developed herein to precisely measure the best focus of lithographic tools. Specially designed 'bar-in-bar' (BIB) was employed to obtain the best focus by using the opposite shifting direction of inner and outer bars when defocused. The inner and outer bars are composed of various pattern sizes. When defocused, the shrinkage of the smaller patterns is more significant than that of the larger patterns, thus causing the center of gravity to shift. The distribution and pattern sizes are optimized to obtain high reproducibility and sensitive position shifting for various defocus conditions. Employing the special BIB pattern, the best focus, tilting and field curvature can be easily measured via the conventional overlay measurement tool. By adding the special BIB to the scribe lanes of the production wafers, the best focus and tilting of the stepper can be obtained when measuring a layer-to- layer overlay shift, and can then be fed back to the stepper as a reference for following processing wafers.

Paper Details

Date Published: 23 August 2000
PDF: 8 pages
Proc. SPIE 4182, Process Control and Diagnostics, (23 August 2000); doi: 10.1117/12.410087
Show Author Affiliations
Chin-Yu Ku, National Chiao Tung Univ. (Taiwan)
Tan Fu Lei, National Chiao Tung Univ. (Taiwan)
Jia-Min Shieh, National Nano Device Labs./National Chiao Tung Univ. (Taiwan)
Tsann-Bim Chiou, National Nano Device Labs./National Chiao Tung Univ. (Taiwan)
Hwang-Kuen Lin, Vanguard International Semiconductor Corp. (Taiwan)


Published in SPIE Proceedings Vol. 4182:
Process Control and Diagnostics
Michael L. Miller; Kaihan A. Ashtiani, Editor(s)

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