Optical metrology strategies for inline 7nm CMOS logic product control

In this paper we propose a "film on grating" (FoG) measurement technique using spectroscopic ellipsometry (SE) that can enable sub-angstrom ngstrom level precision for multi-layer film thickness measurement on topographies that closely approximate the device structure. FoG follows the industry trends to 'measure what matters' and provides thickness measurement data from patterned structures that has much stronger correlation to actual device performance. We also explore the impact of deviations in the film stack that can appreciably alter the device performance. One of the key device performance metrics that we will investigate is the leakage current, which is highly sensitive to process variations or defectivity. Measuring both the thickness and the bandgap of the HK dielectric permits excellent correlation with leakage current as determined by electrical testing of the device. The ability to predict electrical parameters effectively will greatly accelerate learning cycles during process development and can enable real time product control on existing inline metrology tools.