Optical ellipsometry for SiON gate production monitoring

We report the use of single wave ellipsometry for accurate thickness measurements, combined with deep ultraviolet broadband ellipsometry measurement of the refractive index and extinction coefficient to extract nitrogen fraction from a single optical measurement. We demonstrate the effectiveness of laser desorption in removing airborne molecular contamination before measurement, and a method to compensating for time-dependent composition changes. Superior tool matching and long-term stability show that optical measurements can provide a reliable and high-throughput method for SiON gate dielectric production control.