14 June 1999 Measuring fab overlay programs
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Abstract
This paper presents a methodology for measuring and improving the effectiveness of stepper overlay management on product wafers in the semiconductor industry. The research that supports this measurement approach encompasses over 12 fabs with over 30 technologies. Overlay performance, stepper deployment, stepper productivity and die yield loss due to overlay error were studied. To provide an objective measurement of a fab overlay methodology and performance, measurements were made of the overall overlay design rule compliance and distribution and of the overlay variance and distribution by stepper field location. Modeled data analysis was used to assess and validate the effectiveness of the stepper control methodology, sampling level and field/target locations. Balancing stepper productivity and overlay results is a problem in most fabs. An overlay 'opportunity box' is defined that allows a fab to explore overlay error ranges, lost stepper productivity, and product overlay design rule requirement by stepper deployment. Stepper deployment decision tend to be digital - 'engineering' or 'manufacturing' - quantification of die yield loss as a function of overlay error is usually required to make deployment changes. Several examples of die yield loss, as a function of overlay error and distribution, are presented. A brief introduction of the yield analysis technique used is provided.
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Richard J. Martin, Richard J. Martin, Xuemei Chen, Xuemei Chen, Itzik Goldberger, Itzik Goldberger, } "Measuring fab overlay programs", Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350871; https://doi.org/10.1117/12.350871
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