Application Of Perturbation Method In The Analysis Of Diffraction Gratings

With the quickly development of science and technology, the position of the semiconductor industry in our national economy is increasingly important.In these years, due to the widely use of the smart phones, the moving Internet and the big data, the semiconductor industry have again been pushed to a new climax. We have come to a new information era as the dimension of chips in the integrated circuit has decreased to 20 nm. A smaller dimension must lead to the increased integration, which will be a new challenge to the microelectronic measurement technology. The scatterometry has been widely used due to a lot of advantages of it. The optical critical dimension(OCD) measurement technology,which is an important application of the scatterometry, has been used widespread-due to its nondestructiveness,convenience,and high efficience.The OCD measurement has become a mainstream technology for the CD measurement and analysis.The rigorous coupled-wave analysis(RCWA) is one of the most popular method in the OCD simulation analysis.It can well be used for the analysis and simulation of the simple structures,such as one-dimension diffraction gratings.But for the analysis of two-dimension diffraction gratings which is commonly used in the microelectronic structures,it usually takes a long time and a large memory to get a reliable result,and it is is even difficult to converge in some cases,especially for the configuration of non-rectangular gratings,which need to be devided into many slices to get a more accurate result,which requires huge memory and computing time.In this paper, a new approach by combination of perturbation method and RCWA has been developed.We made a further study of this improved RCWA method.We analyze the combination of perturbation method and scattering matrix method.In this way,the practicability of the perturbation method has been improved. The application of perturbation method for the analysis of one-dimension and two-dimension non-regular gratings has been made further study.By making use of the simulation software,the result has been simulated by coding based on above new approach.For the analysis of one-dimension gratings,it doesn’t limit to the gratings with a small slope angle.By increasing the times of solving the eigenvalue problem,the problem of bigger height and gradient gratings had been solved using the perturbation method.The new approach can be more effective by avoiding solving eigenvalue and eigenvetor problems,especially for the analysis of two-dimension gratings.In the research of two-dimension gratings,we obtain a good result,i.e. at the basis of achieving the accuracy,effectively improving the computing efficiency.The perturbation method mentioned in this paper should not be limited to the gratings which is involved in this article.It can be used in the analysis of other periodic structures, especially the application of higher timeliness requirements.