Thin Film Measurement Method Based On White Light Scanning Interferometry

As thin film is widely used in the field of optical communication,aerospace,biomedicine,new energy and other frontier fields,the research on thin film is becoming increasingly important.The thickness of thin film directly affect the properties.Therefore,there is an important significance to detect film thickness.As a kind of optical detection method,white light scanning interferometry has the advantages of non-destruction and high precision,which is widely used in the field of micro-nano detection.The research topic is the white light scanning interferometry used for the measurement of the thickness of thin film.The main work of this paper is as follows:1.The reflection characteristics of thin film were analyzed,and the commonly used detection methods of thin film were introduced.The development of the white light scanning interferometry and the related basic theory were also analyzed.2.The model of the white light interference signal was established.Several coherent peak detection algorithms of measuring film thickness were analyzed,and the measurement accuracy and anti-noise capability of different step lengths or at different noise levels were simulated and analyzed.Simulation results showed that the whitelight phase-shifting interferometry has the highest accuracy and the best anti-noise ability.3.The intensity curve fitting method was proposed.For the local optimization algorithm,two methods of initial estimation were proposed,which were based on the phase and the results of coherent peak detection algorithms,respectively.The effective range of initial value was also studied.4.Frequency analysis of measuring film thickness was studied.The method of initial estimation based on the nonlinear phase of thin film was analyzed.Simulation results showed superiority in measuring ultrathin film of this method.5.A Michelson microscopic white light scanning interferometry was developed.The reliability of the system was verified by testing the performance.The feasibility of the above methods was verified by measuring the standard thin film.Experimental results showed that the measurement accuracy can reach the nanometer scale.