Scanning white-light interferometry for microstructures geometrical characterization

Scanning white-light interferometry (SWLI) surface profiling for geometrical characterization and device inspection is described in this paper, which is quick, non-destructive, non-contact, and easy to carry out at the wafer scale with sub-micrometer lateral resolution and nanoscale vertical resolution. The measurement system is based on a Mirau microscopic interferometer, using a piezo objective nano-positioner to realize accurate scanning in vertical direction in the range of one hundred micrometers. It employs the method called centroid algorithm to extract the envelope peak position. Comparing with phase shifting interferometry, it has a large measurement range. The measurement accuracy of the system is calibrated by a step height standard which is certificated by NIST. A micro resonator is employed to illustrate the capabilities of SWLI as a measurement and process characterization tool.