Film thickness and boundary characterization by interferometric profilometry

摘要

Two threshold parameters are used to identify the intensity modulation peaks corresponding to the interfaces of the two sides of a thin film with the adjacent media. The first parameter is used to distinguish modulation data from noise and is set on the basis of actual background noise data measured during the interferometric scan. The second parameter is used to separate actual contrast data from signals of relatively high modulation that satisfy the first parameter but do not in fact result from interference fringes. Data that satisfy both parameters are considered valid modulation data and the peak of each modulation envelope is then calculated using conventional means. The thickness of the film at each pixel is obtained by dividing the scanning distance corresponding to the two peaks by the group index of refraction of the film material.