Based On Afm And Interference Spectra Of Thin Film Thickness Measurement System

With the rapid development of film technology, the film technology is widely applied in many fields like micro-electronics technology, polymer technology, aerospace technology, biological engineering, food science, etc. As the thickness definitively influence the optical, mechanical, electromagnetic performance of films, exact measurement of the film thickness has become a significant technology.There are some types of the film thickness measurement methods. For the porous film, a typical method of the thickness measurement is to observe the section of porous film in the use of SEM. However, the SEM is most suitable for conductor materials, when used to measure thickness of non-conductor films, the films need to be gilt generally. This method is destructive and introduces great error. Moreover, in this method, thickness of a small part of film is measured and it is not sure the section is vertical to the surface. So it is necessary to find a method of non-distructive, convenient, precise measurement of porous film thickness.The issue of this project is produced in this background. We introduced a new method of film thickness measurement based on the combination of AFM and interference spectrum. With this method, some current problems and limitations existed in many methods have been avoided. In our film thickness measurement system, it needs not to cut the film to observe the section and ensures the film's integrity. And it is a precise, simply-manipulated and non-distructive film thickness measurement method. It contains the effective refractive index arithmetic of porous film, so we can measure the effective refractive index and thickness of porous film.For this project, research is developed in theoretical methods, system design and establishment and measurement experiment technologies. The research work is as follows:Theoretically, a new method of film thickness measurement based on the combination of AFM and interference spectrum was brought forward. The effective refractive index isdetermined by AFM high resolution image, and then the real thickness is determined by interference spectrum gained from fiber spectrometer.On the system design and establishiment, we constructed the film thickness measurement system based on the combination of AFM and interference spectrum. The system contains AFM instrument system, high resolution fiber spectrometer, control circuit, interface with computer and software system. The system is of high stabilization and advantage, and it provides high resolution orientation for the sample. The AFM used in system is designed and developed by ourselves, whose measurement range is 4000nm×4000nm and the precision is 1nm. This system's measurement range is 0.5 μm～200μm. The film thickness measurement software is included, which contains the function of AFM scanning and imaging control, image processing, computation of the porosity and effective refractive index, capture of interference spectrum, measurement of film thickness, etc.In the end, some experiments of film thickness measurement for the polarized glass, ITO and porous alumina film have been carried out. Their AFM images of film surface microstructure and film thickness are attained, which proves the feasibility of the film thickness system we designed and developed.On the research work of the film thickness measurement system, the innovations as follows:A new method of film thickness measurement based on AFM and interference spectrum was introduced for the first time, which is especially applicable in the measurement of porous film. This method combines the advantages of AFM and film thickness measurement by interference spectrum. It could determine the film thickness and the effective refractive index of porous film. Furthermore, it could gain precise nanometer structure image of film.We take the lead in development the system of film thickness measurement based on AFM and interference spectrum. The system realizes the measurement of film thickness, moreover, it contains the function of porosity, effective refractive index of porous filmmeasurement, and AFM scanning surface of film.The AFM in this film thickness measurement system can be used in liquid. So this system could measure the film thickness and observe the microstructure of film when the film is being produced. It provides the real-time control of film preparation. Moreover, it is a non-distructive and non-damaging film thickness measurement system.