Comparisons of six different intrafield control paradigms in an advanced mix-and-match environment

Joseph C. Pellegrini

doi:10.1117/12.275926

7 July 1997 Comparisons of six different intrafield control paradigms in an advanced mix-and-match environment

Joseph C. Pellegrini

Proceedings Volume 3050, Metrology, Inspection, and Process Control for Microlithography XI; (1997) https://doi.org/10.1117/12.275926
Event: Microlithography '97, 1997, Santa Clara, CA, United States

Abstract

The introduction of DUV step-and-scan exposure tools into a mix-and-match manufacturing environment with traditional i- line step-and-repeat systems has presented many unique challenges to lithographic process engineers. One of these challenges has been the development and selection of reliable methods for controlling intrafield patten overlay registration. We examined a spectrum of overlay control methods and compared the benefits and costs of each. We analyzed six different intrafield overly control approaches including: (1) traditional static tuning to a fixed archive wafer; (2) dedicated stepper routing; (3) static LEMSYS matching; (4) static cluster sorting; (5) global feedforward control, and; (6) combined cluster sorting with feed-forward control. In traditional static tuning, each stepper is calibrated to an arbitrary fixed reference and wafers are allowed to flow freely within the entire stepper population. Dedicated stepper routing imposes a restriction that wafers must return to the same stepper during critical layer processing. With static LEMSYS matching each stepper is calibrated to an ideal reference that is generated to minimize higher order intrafield errors. Static cluster sorting uses LEMSYS data to divide steppers into clusters then critical layer exposures for a given wafer are kept within a local cluster. Feedforward control attempts to aggressively adapt magnification offsets based upon the known lens signatures of steppers used to print previous layers. Our comparisons were based upon data from 12 actual exposure systems. The result showed that significant gains in overlay control can be achieved with incremental costs in dollars and complexity. Cost-benefits analysis showed that the more aggressive control techniques, involving feed- forward control, were best suited to large fabs operating near the physical limits of their steppers.

Citation Download Citation

Joseph C. Pellegrini "Comparisons of six different intrafield control paradigms in an advanced mix-and-match environment", Proc. SPIE 3050, Metrology, Inspection, and Process Control for Microlithography XI, (7 July 1997); https://doi.org/10.1117/12.275926

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