Trial Shape-Sensitive Linewidth Measurement System
John S. Villarrubia, Andras Vladar, Michael T. Postek
This is a report for a project to develop a scanning electron microscope (SEM) based shape-sensitive linewidth measurement system by improving the method by improving the method by which SEM data are analyzed. We report significant developments in algorithms that perform critical dimension (CD) measurements by matching SEM images to a library of modeled images. The method is similar to that employed by scatterometry. The system is intended to obtain a line''s or gate''s width and information about the shape of its edges (e.g., corner radii, wall angles) from a top-view SEM image or line-scan. Upon completion of the software its results were compared to cross section results on a polycrystalline silicon test line. Corner radii, which have only a subtle effect on SEM images, were in poor agreement between the two techniques. However, linewidth and wall angles were both in good agreement. The new technique exhibited better accuracy and more than a factor of 3 improved measurement repeatability compared to the regression to baseline method.
CD, critical dimension metrology, linewidth metrology, SEM library-based metrology