The Determinations Of Optical Parameters Of Semiconductor Film

It is always be studied by thin film workers that how to determinate the thin film parameters with high degree accuracy. In this paper, I studied the present methods for analyzing the optical parameters of thin film purposively to solve the problem of semiconductor thin film. Among so many methods, I pick up the reflection method to combine with the genetic algorithm, which is entitled the modern optimizing algorithm. And a new method of simultaneous determination the multi-parameters of semiconductor thin film has been presented.At the first step, considering the probabilities of absorbing and dispersive film or substrate, two different theoretical models were compared, the method of equivalent complex refractive index and of applying Fresnel coefficient, which are both used to calculate index of reflection. The former was chosen to combine with the Forouhi-BIoomer model to present the relationship of wavelength and corresponding index of reflection. Based on this relationship, genetic algorithm was introduced to gain the optical parameters of material by the method of inversion. Simultaneously, a simple and good working measurement system was set up and index of reflection of samples were measured in certain spectra range. By the theoretical method mentioned above, I gained the physical thickness and distribution of refraction index n(λ) and extinction coefficient κ(λ) . In the end, error analysis of the system was present.In this paper, a relative small fitting error was obtained by means of proper selection of theoretical model and design of genetic algorithm. It has been certified through experiment that by applying this model and algorithm, relative accurate and full optical parameters of samples can be get simply from the information of reflection spectra.