Measurement of opaque film's surface profile by broadband-light interference methods

摘要

A new method based on the principle of broadband-light interference, which combines reflected spectrum analysis and optical fiber techniques, is proposed to measure surface profile of opaque film. The testing system mainly consists of a Michelson interferometer. Incident light is split into a reference beam and an input beam to the sample. When two lights reflected from the surface of film and mirror may interfere within the range of broadband light coherent length, the output of interference patterns is measured by a spectrograph. The optical path difference of the sample point and the reference mirror is tested by analyzing the interference pattern. When the reference mirror is fixed, the relative thickness value of different measuring points on the film's surface is achieved by scanning the film's surface. Its testing range is from 0.2 micron to less than 20 micron. According to the relative thickness data, the film's surface profile is obtained. The result shows that the testing error of this method is within 2 nm. This method has the advantages over the other measuring method, such as nondestructive, higher accuracy and simple structure.