As the semiconductor industry rapidly approaches the 3nm technology node, on product overlay (OPO) requirements have become even tighter and, as a result, reduction of residual overlay errors have become more important and challenging. Metrology performance enhancements are required to meet these demands. Using angle-resolved pupil imaging, Scatterometry Based Overlay (SCOL®) is a unique overlay metrology architecture that includes massive multi-signal analysis to enable improved accuracy and residuals reduction. In this paper we present a new Rotated Quadrupole (RQ) illumination pattern for SCOL metrology systems designed to enable broad measurable landscape coverage, support additional target design pitches with smaller target dimensions, and improve tool-to-tool matching (TTTM). These improvements enable the SCOL measurement system to provide higher measurement accuracy, reduce residuals error, and improve robustness to process variation. In this paper we will cover theory, some use cases, and measured results.
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