Research on Uneven Profile of Transparent Film with High Precision

摘要

This paper discusses a kind of optical instru-ment, based on spectrum analysis, to outline un-even profile of transparent film. Methods usually used for film thickness distribution is divided into two groups, including contact ones and non-contact ones. The former introduces a sensing probe and inevitable results in damage to film detected. Sensing probe is expensive, and film must be coated on hard base surface, so the method is lim-ited in a small scope of metal film. For transparent film, method based on wide-band light inter-ference theory is efficient. When a beam with wide band wavelength is cast on a film , part of energy is absorbed by floor, and part of energy is reflected on both upper and lower surfaces, beams interference with each other. However. Having going through same path, rays w ith different frequency have identical displacement, but their phase difference is distinct. As a result, their intensities differ. The difference is related with thickness of detected film. It can be found that this method has a far higher precision than laser interferometer. In this paper, PbTiO_3 film coated on silicon floor is surveyea, and lesting error is less than 7nm. The paper describes principle, method, instrument and result completely and clearly. It is proved an improvement of film thickness test.