Non-contact surface profiling using optical interferometric microscopy

Abstract

We report the use of non-contact optical interferometric microscopy (OIM) for surface topographic profiling. A Linnik optical configuration is used to create interferograms of an object surface. When the coherence condition between the two beams is met the phase information of the object surface can be extracted to establish its topographic contour image. Using a four-image phase-shifted algorithm with the synchronization of a piezoelectric actuator reference mirror positioning, the present single camera OIM can reconstruct a surface topography with a field of view of 312 µm × 234 µm, axial resolution of 3.31 nm, and lateral resolution of 488 nm, and an estimated maximum topography depth of 270 nm.

Noncontact surface profiling using optical interferometric microscopy

“…PZA hysteresis is mapped to differential phase shifts between interferograms, and the maximum phase shift error is determined. 10 Four interferograms, each π∕4 radian apart, are obtained to create a phase map of the object. Simulations of a step plane were used to determine the necessary phase difference between interferograms for the four-image PSA to properly function.…”

“…We report a noncontact OIM surface profiler using a four-image PSA and fixed step PZA motions. PZA hysteresis is mapped to differential phase shifts between interferograms, and the maximum phase shift error is determined 10 . Four interferograms, each π/4 radian apart, are obtained to create a phase map of the object.…”