Shrinking on-product overlay (OPO) budgets in advanced technology nodes require more accurate overlay measurementand better measurement robustness to process variability. Pupil-based accuracy flags have been introduced to thescatterometry-based overlay (SCOL?) system to evaluate the performance of a SCOL measurement setup. WavelengthHoming? is a new robustness feature enabled by the continuous tunability of advanced SCOL systems using asupercontinuum laser light source in combination with a flexible bandpass filter. Inline process monitoring using accuracyflags allows for detection, quantification and correction of shifts in the optimal measurement wavelength. This workdemonstrates the benefit of Wavelength Homing in overcoming overlay inaccuracy caused by process changes andrestoring the OPO and residual levels in the original recipe.
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