Three-dimension RCWA Method And Its Application In Integrated Circuit

In the process of integrated circuit production, the complex micro structure on the surface of circuit is equivalent to a collection of small periodic gratings. Rigorous coupled-wave analysis(RCWA), which was put forward by M. G. Moharam and T. K. Gaylord in 1981, is a method can precisely solve diffraction problem of periodic gratings. It has been widely used in the research of diffraction analysis for all kinds of periodic gratings. If applying optimization methods such as regression algorithm at the same time and comparing spectrum calculated with experimental reflectance spectrum of samples, we can indirectly get the critical dimension(CD) and profile of the grating structure. Optical critical dimension(OCD) device, used to measure critical dimension by feedback while etching in the workmanship of integrated circuit production, is based on the principle.According to the views above, this paper regard the three-dimension RCWA method and its application in the integrated circuit production as the objects studied. With understanding the theory and technology principles available now scrupulously, it is integrated into the software system of OCD, used to measure CD in the workmanship of integrated circuit production. The work of this paper is summarized as follows:First of all, the data processing of three-dimension RCWA is cognized and summarized from the integral view. Through understanding the RCWA method scrupulously, including plane diffraction, conical diffraction and multi-layer uniform film diffraction, this paper has summarized the introduced process of Fourier series. Then, a grating model with round corner in the x-y plane has been given based on methods available now to solve the Fourier coefficients. And the additional terms of the corresponding Fourier coefficients are found out at the same time.Nextly, the numerical simulation of three-dimension grating diffraction by RCWA method has been realized using C++, and as a conclusion, the results of simulation are consistent with those of another RCWA software available now. After the simulation function is integrated into the OCD software system, the theoretical reflectance spectrum can be got just by inputing corresponding model parameters of grating in the graphic user interface.Then the function of building database for three-dimension RCWA has been realized based on postgre SQL. The calculation of simulation for getting reflectance spectrum of three-dimension RCWA takes a lot of time. By introducing database of reflectance spectrum, the simulation process can be skipped while testing samples online. It can improve the matching efficiency between sample and model and make it possible to measure CD of three-dimension gratings online in the workmanship of integrated circuit production.Finally, the three-dimension RCWA is used to analyze a model of shallow trench isolation structure, then compare the results with those of analysis by two-dimension RCWA which has achieved good application in practice and find they are consistent as a result.