Efficient simulation of light diffraction from 3-dimensional EUV-masks using field decomposition techniques

As the opportunities for experimental studies are still limited, a predictive simulation of EUV lithography is very important for a better understanding of the technology. One of the most critical issues in modeling of EUV lithography is the description of the mask. Typical absorber heights in the range between 80 and 100 nm are more than 5 times larger than the wavelength of the used EUV radiation. Therefore, it is virtually impossible to perform parameter studies for 3D EUV masks, such as arrays of contacts or posts, with nowadays standard computers by straightforward application of finite-difference time-domain (FDTD) algorithms, which are used for the rigorous electromagnetic field simulation of optical masks. This paper discusses the application of field decomposition techniques for an efficient simulation of 3D EUV-masks with FDTD algorithms. Comparisons with full 3D simulations are used to evaluate the accuracy and the performance of the proposed approach. The application of the new QUASI 3D rigorous electromagnetic field simulation for EUV masks reduces memory requirements and computing time by a factor of at least 100. The implemented simulation approach is applied for a first exploration of mask induced imaging artifacts such as placement errors, telecentricity errors, Bossung asymmetries, and focus shifts for 3D EUV masks.