Determination of best focus and exposure dose using CD-SEM side-wall imaging

We use CD-SEM side-wall imaging using the Applied Materials VeraSEM 3d system as a destruction free and quick method to determine side-wall profiles. The system allows the reconstruction of profiles by tilting the SEM beam up to 6 degrees. Using two different tilt angles the reconstruction of side-wall profiles is possible in a quick and destruction free way even for negatively sloped profiles. The use of the profile analysis utility is believed to reduce cycle time significantly especially for process development and troubleshooting in production. We compare profiles obtained from the profile analysis utility of the VeraSEM 3D to X-SEM measurements to qualify this method for use in development and high volume production. For selected examples containing resist lines we investigate process windows determined from top-down CD measurements, X-SEM measurements and the profile analysis utility and compare the best stepper focus and exposure dose values obtained from these methods. It is shown how the results from the profile analysis utility can be used for process monitoring by comparing the obtained data to reference data from FEM wafers.