Interferometer -based Technology for Optical Nanoscale Inspection

We demonstrate the interferometer-based approach for nanoscale grating Critical Dimension (CD) measurements and prove the possibility to achieve no worse than 10 nm accuracy of measurements for 100 nm pitch gratings. The approach is based on phase shift measurement of light fields specularly reflected from periodical pattern and adjacent substrate with subsequent comparison between experimental and simulation results. RCWA algorithm is used to fit the measured results and extract the CD value. It is shown that accuracy of CD value measurement depends rather on the grating’s CD/pitch ratio than its CD value