Specular spectroscopic scatterometry

Scatterometry is one of the few metrology candidates that has true in situ/in-line potential for deep submicrometer critical dimension (CD) and profile analysis. Most existing scatterometers are designed to measure multiple incident angles at a single wavelength on periodic gratings. We extend this idea by deploying specular spectroscopic scatterometry. Specular spectroscopic scatterometry (SS) is designed to measure the zeroth-order diffraction response at a fixed angle of incidence and multiple wavelengths. This mechanism allows the use of existing thin-film metrology equipment, such as spectroscopic ellipsometers, to accurately extract topographic profile information from one-dimensional (1-D) periodic structures. In this work, we developed the grating tool-kit (gtk), which implements several variants of rigorous coupled-wave analysis (RCWA) to accurately and efficiently simulate diffraction behavior of 1-D gratings. Theoretical simulations using this package show that specular spectroscopic scatterometry can be applied in the current semiconductor manufacturing technology, and can be easily extended to the 0.07-μm generation. We have also applied a library-based profile extraction methodology to resist and poly focus-exposure matrices patterned using 0.25and 0.18-μm lithography and etch technology, respectively, to extract their cross-sectional profiles. Discrepancies between CD-SEM, CD-AFM, and SSS measurements are discussed and explained