Optical Thin Film Constants Calculation And Measurement Systems

It is a hot issue for the researchers on thin film tech to determine the parametersof thin film precisely and rapidly. For decades, there have been many methods fordetermination of the optical constants. Because of the convenient metrology system,the wide application, and high precision, the method based on reflection spectra turnout to be the most pervasive approach in temporal thin film metrology. There is farmore related theoretical literatures and applied devices abroad than Home does. Themain barrier is how to determine the optical parameters from the measured data bygetting rid of the problems such as the multiple solutions and the like.In this article, a complete analysis and discussion on the reflection spectrum andits metrology system is presented. The paper follows three steps. In the first one,based on the literature information, the reflectance expression including theparameters for film and stack deduced by classic electromagnetics is presented in themost simplified way. The second, the method for determining the optical constants ofthin film is explicated. By modifying the extremum point method and adopting themethod of bi-average, computational speed is improved and (n,k,d) is achieved. Then,the article presents another method based on reflectance spectrum and flexibletolerance method to approximate the optical constants by dwindling the polyhedron.One the one hand, the new method fix out the problem of multiple solutions well. Onanother hand, for there is no dependence on interferential spectrum and transparentarea, the method can be applied to diverse sorts of reflectance spectrum with a fastspeed, nice convergence, and high precision. In the last section, the optical solutionfor bi-layer thin film is put forward with the method of all-searching , and least-squaremethod. Meanwhile, the method is also extended to tri-layer thin film. Then thereflectance metrology system is discussed in a complete way. The article lay out someguiding reference such as intros for some pervasive commercial device in the world,the data information for those devices and the like to help choose the relatedmetrology device properly .Regarding the aspect of data processing , the comparisonsbetween different method are done. In the meantime, the measured date for samplethin film is compared to the standard one where the result shows a error degree about±5% .The results prove the method has a nice application value.