ABSTRACT
Numerous applications of scatterometry have been demonstrated in the semiconductor manufacturing process. Major processes include mask processing, lithography, etch, and chemical mechanical polishing. Near-field optical techniques can provide a new way to obtain highly spatially resolved images of both topographic and chemical changes for improved characterization and control of the entire lithography process. Because a typical lithography area in a fab is equipped with several overlay metrology tools, tool-to-tool matching is a significant metric, attesting to the accuracy of the tools as well as to the ability to use the tools interchangeably. A number of different focus systems have been implemented in commercially available overlay metrology tools, including interferometric, astigmatic, and contrast-based methods. Metrology tools had been used in acquiring quality management data and determining the optimum dose, focus position, and overlay offset in order to increase the manufacturing yield as much as possible.
