Improved scatterometry time-to-solution using virtual reference

Advanced nodes require precise detection and control of intricate profile details – scatterometry is tool of choice for such requirements. Scatterometry is a model-based technique, and needs extensive reference metrology for qualification. Such reference measurements are costly, time-consuming and often destructive causing delays in deployment. With increasing number of scatterometry steps in flow, and the requirement to collect more reference data points to statistically qualify shrinking metrology specifications, the cost and time for reference metrology is exponentially increasing. This work is aimed to significantly reduce this need. We developed a novel methodology whereby scatterometry spectral information itself is used to predict “virtual” reference data. We qualify this methodology on several key applications from 20nm and 14nm node. We find that performance of solution developed using proposed methodology is indeed similar to performance of solution obtained using real reference data, thereby significantly reducing the lead time to develop scatterometry solutions.