Improvement of Measurement Repeatability for White Light Phase Shifting Interferometry by Phase Compensation

Abstract

In this thesis, the measurement repeatability of White Light Phase Shifting Interferometry (WLPSI) is improved using phase compensation algorithm. In WLPSI, phases which include height information of a target can be obtained by calculating intensities of captured images. The mechanical vibration of a stage, however, could affect each phase of an image. In consequence of the vibration, phase errors are implicated at each phase and these errors could bring out the unstable repeatability. In order to enhance the repeatability, a phase compensation method is introduced based on the phase variation theory. At the ideal measurement, a set interval of PZT actuator is equal when scanning. Based on the theory, the phase variation is proportional to the scanning interval. Therefore, the phase compensation method can be applied using the relation between the phase variation and the interval. In order to verify the performance of the suggested method, measurement of three types of micro patterns and Standard Step Height Sample with vibration is carried out. As a result, the repeatability of measurement is improved by applying proposed phase compensation method.