First Look at Across-chip Performance Variation Using Non-Contact, Performance-Based Metrology

We report on the first non-contact, non-destructive performance measurements of embedded ring oscillators. Measurements are made on inside the die active area as early as metal 1. A 90nm logic CMOS technology was used for this work. We have measured residual across-field performance variation separate from and of opposite sense to wafer uniformity. This effect cannot be extrapolated from scribe measurements