Thin Film Measurement Method Based On White Light Spectral Interferometry

As a kind of special structure, the thin film is widely used in optics, communication, biological, aerospace and other fields in recent years. The characteristic of the thin film decides whether it can work properly. So the thin film detection technology becomes more and more important.As a kind of typical optical detection method, white light spectral interferometry detection technology can realize non-contact and high precision measurement and is widely used in the field of film properties detection. This method can not only measure in the film thickness, refractive index, but also can measure the phase information. This research topic is the white light spectral interferometry detection technology used for the thin film characteristic detection. The system based on white light spectral interferometry detection technology has been built and complete the detection of thin film. The main achievements of this thesis are as follows:1. The development and application of thin film was introduced. And several methods for detection of the thin film detection were discussed and summarized. The state-of-the-art development of white light spectral interference detection technology was described in detail.2. White light spectral interferometry principle was described. White light interference characteristics, the theory of partially coherent light and properties of the thin film were also described in detail.3. Several phase extraction algorithms were studied. In order to select the appropriate algorithm, they were analyzed in the aspect of precision, measurement range, time consumption, ability of anti noise and error form.4. The optimization theory was elaborated. For the local optimization algorithm, two methods for initial estimates which were based on nonlinear phase and the relationship between reflectivity and signal visibility were put forward. Both of them can provide appropriate initial values for local optimization algorithm. For the global optimization algorithm, we designed simulated annealing and genetic algorithm for data processing. Both of them can obtain the ideal result without initial values. They were analyzed. Compared with the algorithm of global local algorithm, the results showed that the local optimization algorithm can get higher precision results in less time. However, the global optimization algorithm did not need initial values and could measure the film thickness and refractive index.5. The factors in the system that can influence the measurement results were analyzed. The equivalent thickness was studied and put forward equivalent wavelength to eliminate the error. Then the system was tested with the help of PZT, and the measuring range of the system was confirmed. The stability of the system was also tested. Furthermore, the standard thin film was tested for validating the methods. The results showed that the thin film phase and thin film thickness was acquired with high accuracy.