Scatterometry for shallow trench isolation (STI) process metrology

摘要

Scatterometry is a non-destructive optical metrology based on the analysis of light scattered form a periodic sample. In this research angular scatterometry measurements were performed on three wafers processed using shallow trench isolation (STI) technology. The periodic features that were measured on these wafers were composite etched gratings comprised of SiN on oxide on Si. The wafers were processed at three different etch times in order to generate different etch depths (shallow, nominal and deep). It was at this point in the process that the scatterometry measurements were performed. The scatterometry model was comprised of four parameters: Si thickness, SiN thickness, linewidth and sidewall angle. For comparison purposes measurements were also performed using a critical dimension scanning electron microscope (CD-SEM), a cross-section SEM and an atomic force microscope (AFM). The results show good agreement between the scatterometry measurements and the other technologies.