Self-elimination of phase noise in coherence scanning interferometry for nano-scale measurement

Coherence scanning interferometry (CSI) has been a powerful non-contact technique. In this work, a novel surface recovery algorithm based on phase noise self-correction is proposed for nano-scale measurements. Through spectrum analysis, the surface height is coarsely retrieved from the linear relationship between phase and angular wavenumber. Afterwards, the phase noise is modeled, and a correction array is designed to compensate the noises in surface height. A coefficient is defined to assess the accuracy of correction array, then the surface height is automatically corrected with the coefficient minimized. In the experiments, three step height standards are tested to prove the measurement accuracy, and additional comparisons with a commercial white light profiler and an AFM are provided as well to testify the measurement noise level. At last, a nano-scale grids matrix is measured, where the nano-topography is accurately recovered. All investigations have verified the effectiveness of the proposed method in nano-scale measurements.