KrF resist pattern monitoring by ellipsometry

This is a report on a rapid and accurate optical method for monitoring line widths by ellipsometry. Samples with a KrF chemically amplified positive resist (TDUR-P009) were exposed by a KrF stepper with 0.35-mu m dense line/space patterns (0.70 mu m pitch) and 0.30-mu m sparse line patterns (2.0 mu m pitch), and measured by ellipsometry. Ellipsometry was found to be effective in monitoring changes in resist line widths and cross-sectional shapes due to variations in focus and dose. Multivariable regression analysis was adopted to predict the line width and the focus position of a stepper. Good agreement (3 sigma = 4.3 nm) between CD-SEM measured and predicted widths was achieved. Also, focus positions were accurately predicted. The results of spectroscopic ellipsometry, which provides many ellipsometric parameters in a short period, are shown.