Usage of profile information obtained with Scatterometry

Scatterometry, a non-destructive optical metrology, provides information on cross-sectional pattern profiles, including pattern height, sidewall angle and linewidth. Compared with other non-destructive metrology tools, such as the atomic force microscope (AFM) and CD-SEM, scatterometry offers the advantages of high throughput and superior repeatability. We have applied scatterometry to the monitoring of the depth of Shallow Trench Isolation (STI) for the analysis of complicated stack. We obtained sufficient measurement accuracy by optimizing a model. In addition, we propose the application of scatterometry to post-lithography monitoring for advanced process control (APC). A regression model was established to derive effective dose and focus from the change of photoresist profile monitored by means of scatterometry. In our experiment using an ArF scanner, we obtained sufficient measurement repeatability of dose and focus.