New approaches for scatterometry-based metrology for critical distance and overlay measurement and process control

Communication between lithography and metrology is becoming increasingly demanding in advanced nodes. This is where the requirements for metrology become extremely tight. This work is dedicated to the search for "clean" metrology that is required to address these requirements. Metrology measurements are obtained via an angle-resolved scatterometry-based platform (called YieldStar). Details of the technology behind YieldStar were thoroughly discussed by Vanoppen et al. in 2010. In this current work, measurement limits are challenged to test resolution and measurement uncertainty for overlay, critical dimension (CD), and sidewall angle (focus). Results indicate an atomic-scale performance of deep subnanometers. Two different sizes of scatterometry-based overlay targets are evaluated and compared using a technique called the similarity index. A CD reconstruction model is tested for cross talk of underlying thin-film layers, specifically the case where one of the underlying layers is anisotropic. A systematic approach is taken to increase the complexity of a CD reconstruction model in steps to evaluate the capability of handling birefringence effects of anisotropic material in the model. CD metrology data (1-D and 2-D/hole layers) are compared to CD scanning electron microscope data. Focus measurements are also extended for product wafers, and focus precision is evaluated. In addition, CD metrology monitor wafer applications, such as hotplate monitoring and overlay metrology monitor wafer application for scanner stability and matched machine overlay, are tested.