Method of thin film thickness measurement based on laser heterodyne interferometry

For the difficulty of measuring thin film thickness, a method of thin film thickness measurement based on laser heterodyne interferometry is proposed. Thin film difference of this method is generated by the relative optical path difference of Michelson interference light path with principle of heterodyne interference. The thickness is got by precision displacement table in line-by-line scaning. The shift of measurement system is about 8nm with constant temperature. Average deviation of measuring results is about 5nm. The comparison with ellipsometer shows the correctness of the method.