Study Of Diffraction Simulation Algorithm Of Periodic Structures And Applications

Scatterometry is one of the most important methods for process control and critical dimensions(CD) measurement in semiconductor manufacturing, and as a result it is widely used in the microelectronics manufacturing industry. According to the International Technology Roadmap for Semiconductors(ITRS) in 2011, scatterometry, as one of the online, real-time, non-destructive and cost-effective measurement methods, is supposed to play an important role in measurement of new material or structures under the new technology node. As an important part of scatterometry, the diffraction simulation algorithms for periodic materials have an immediate impact on the measurement efficiency. As a result, researche on the improvement and application of the diffraction simulation algorithms is the focus of this paper.The main content of this paper plays a key role in the software part of the OCD(Optical Critical Dimensions) measurement system, which is an enterprise-funded latitudinal project based on the key national project for industrialization of the OCD system. This paper is mainly about two topics: algorithms and application. The former includes modification of the rigorous coupled-wave analysis(RCWA) method and combination of the Slice Absorption Method and RCWA method(Fourier Modal Slice Absorption Method, FMSAM). And the latter is mainly about building up the module of diffraction simulation algorithms as the software part for the OCD measurement platform, as well as a successful application of overlay shift measurement method. The contents are detailed as below:1. In-depth study of all the research achievements in RCWA method and applying the implementation of the relevant achievements(considered as as core algorithms) to the simulation module of the OCD software platform, including the construction method for Toeplitz matrix of dielectric coefficient function of the typical structures, construction method for eigenvalue matrices(Lalanne empirical method and normal vector method), transfer matrix method for multi-slice structures based on the staircase approximation, and Matrix reduction method based on the symmetric techniques(the implementation of this method will be shown in the research results of research group, i.e. approximate rigorous coupled-wave analysis with a small angle). Finally, all these methods mentioned are fit for the FMSAM.2. A rapid normal vector field construction method for typical periodic structures with arbitrary analytical boundaries is presented and its empirical principle of normal vector’s priority selection, which, as for the typical periodic structures, can achive two orders of convergence higher than the normal vector field method without priority selection and the Lalanne empirical method.3. A complete implementation of the FMSAM combined with rigorous coupled-wave analysis method and the Slice Absorption Method. Improvements on the Cascading and Doubling Algorithm in the Slice Absorption Method, an introduction of two kinds of source types in Total field/Scattering field model and the difference analysis between them are given. Finally, a stepsize selction principle is presented on the numerical analysis of FMSAM. For these vertical profile structures, the computing efficeiency of RCWA is double of FMSAM; however, when the space grids number for FMSAM is compared with the slices number by staircase approximation in RCWA, FMSAM is much more efficient. Meanwhile, with no eigenvalue problem involved, which isn’t suited to parallel technology, the FMSAM is much more suitable for the GPU platform.4. Based on the aboved researches, the OCD software system’s module for diffraction simulation algorithms is shown in great detail, and a successful application of overlay shift measurement method is mentioned.