New overlay pattern design for real-time focus and tilt monitor

Chin-Yu Ku; Tan Fu Lei; Jia-Min Shieh; Tsann-Bim Chiou; Hwang-Kuen Lin

doi:10.1117/12.410087

23 August 2000 New overlay pattern design for real-time focus and tilt monitor

Chin-Yu Ku, Tan Fu Lei, Jia-Min Shieh, Tsann-Bim Chiou, Hwang-Kuen Lin

Proceedings Volume 4182, Process Control and Diagnostics; (2000) https://doi.org/10.1117/12.410087
Event: Microelectronic Manufacturing, 2000, Santa Clara, CA, United States

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.

Citation Download Citation

Chin-Yu Ku, Tan Fu Lei, Jia-Min Shieh, Tsann-Bim Chiou, and Hwang-Kuen Lin "New overlay pattern design for real-time focus and tilt monitor", Proc. SPIE 4182, Process Control and Diagnostics, (23 August 2000); https://doi.org/10.1117/12.410087

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