Distinguishing dose from defocus for in-line lithography control

Christopher P. Ausschnitt

doi:10.1117/12.350800

14 June 1999 Distinguishing dose from defocus for in-line lithography control

Christopher P. Ausschnitt

Proceedings Volume 3677, Metrology, Inspection, and Process Control for Microlithography XIII; (1999) https://doi.org/10.1117/12.350800
Event: Microlithography '99, 1999, Santa Clara, CA, United States

Abstract

Manufacturing control of a lithographic process must guarantee that the pattern features on a masking level stay within a common process window, the focus-exposure space over which all pattern tolerances are met. To do so at focus latitudes below 1 micrometers , simultaneous determination and correction of dose and defocus error is required. In-line metrology practice has been to measure a single pattern attribute, usually the dimension of the smallest feature, at each of several locations on a wafer. Since the measurement of one pattern attribute, regardless of its accuracy or precision, cannot distinguish two variables - this approach is inherently inadequate for lithography control. We demonstrate how dose and defocus can be derived from the attributes of dual-tone, optically measurable targets on product wafers. Our method is applied to the in-line control of sub-0.25 micrometers step-and-scan lithography.

Citation Download Citation

Christopher P. Ausschnitt "Distinguishing dose from defocus for in-line lithography control", Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); https://doi.org/10.1117/12.350800

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