Discrepancies between roughness measurements obtained with phase-shifting and white-light interferometry

Discrepancies between phase-shifting and white-light interferometry have been observed in step-height and surface roughness measurements. The discrepancies have a strong relation to the roughness average parameter of the surface. The skewing effect, which mainly occurs in the vicinity of peaks, valleys, and edges of the sample, causes this problem in white-light interferometry of step height. For roughness, two possible sources of the discrepancy are considered.