用三光束干涉法测量薄膜厚度

Film Thickness Measurement with the Three Beam Interferoraetric Method

本文用三光束干涉法非接触地测量了薄膜厚度.该方法把位于中间的零级光作为测试光束,位于两侧的±1级光作为参考光束,不但具有精度高的特点,而且稍作改进还能用于其它多种参数的测量.

The basic principle of the three beam interferometer is analyzed. The relationships between parameters are described and the method of attaining high sensitivity by optimization is given. An experimental optical path for film thickness measurement with reflective type three beam interfer-ometry is also given. The relationship between the detecting signals and optical path difference is obtained. The sample is placed on a parallelo-grammatic mechanism and the film thickness is measured with high accuracy using 40 line-pairs/mm gratings. A method for precision measurement of very small path differences is suggested, by which path differences as small as 500 and 1000 have been measured.