YieldStar: a new metrology platform for advanced lithography control

As leading edge lithography is moving to 2x-nm design rules, lithography control complements resolution as one of the main drivers and enablers to meet the very stringent overlay, focus and CD requirements. As part of ASML's holistic lithography roadmap, ASML is developing several application-specific optimization and control applications, such as LithoTuner Pattern Matcher and BaseLiner. These applications are all explicitly designed to improve the scanner process window (overlay, focus, CDU and matching). All these applications have in common that they require vast amounts of precise, accurate and process robust wafer data (either taken on product stacks or on so-called monitor wafers). To provide such essential data in a cost-effective manner, ASML developed a metrology platform, called YieldStar. This platform is based on an angle-resolved high-NA scatterometer. It is versatile, as YieldStar's sensor can measure overlay, CD and focus in a single measurement. Thanks to its high speed, large amounts of measurements can be quickly collected. In this paper the latest generation YieldStar is presented, the so-called 200 platform. This YieldStar 200 can be used in a stand-alone configuration (S-200) or as an integrated module in a lithography track (T-200). First overlay results show good TMU results without comprising speed. Furthermore, data is shown that demonstrate YieldStar's capability to reconstruct 3D CD patterns as well.