High-speed lateral scanning white-light phase shift interferometry.

In this study, we present lateral scanning white light interferometry (LS-WLI), where phase-shifting algorithms are applied to inspect the topography of a large field of view (FOV) with high-speed measurements. At a point, the interference signal must be acquired with a specific condition to adapt the phase-shifting algorithm. This means that all points have two points, of which the phase difference is π/2, when the number of points acquired in a phase period is multiple of 4, despite increasing the data points in a period. Consequently, stretching the fringe spacing in LS-WLI facilitates the application of phase-shift techniques, thereby enhancing stage speed, even with a fixed camera speed. Using the proposed method, we can successfully obtain a laterally expended topographic image as 5.25 mm × 1.25 mm, where the step height of the microstructure is 140 nm.