High-speed lateral-scanning white-light interferometry for etched arrays with vertical off-axis compensation

The growing demand for fast inspection and metrology for large-scale micro-nanostructures has stimulated the development of lateral-scanning white-light interferometry (LSWLI). However, it is challenging to maintain the accuracy comparable to vertical-scanning white-light interferometry (WLI) due to the straightness of the translation stage and environmental vibration. This Letter presents a high-speed LSWLI with vertical off-axis compensation for etched arrays. The flat substrate is utilized to extract the off-axis motion of the sample during high-speed scanning. A white-light phase shifting interferometry (WLPSI) algorithm for the non-uniformly sampled interference signal is provided to recover surface topography. The experimental results demonstrated a similar height measurement accuracy compared with WLI, even though the scanning speed is 1 mm/s and the off-axis motion range is 600 nm.