3D anisotropic semiconductor grooves measurement simulations (scatterometry) using FDTD Methods

摘要

In this paper, we analyze the finite-difference time-domain (FDTD) method for the anisotropic medium mounts that are put on the silicon substrate periodically. FDTD is useful for analyzing the light scattering from arbitrary shape anisotropic grooves and mounts. We consider anisotropic conductive films which have a uniaxial anisotropy, a biaxial anisotropy and off-diagonal dielectric constants tensor components. First, the FDTD formulation is obtained from Maxwell equation for the anisotropic medium. Next, we show light propagation aspects and reflection coefficients in the structure of anisotropic flat layer put on the silicon substrate. The electric field polarized in the y direction is perpendicularly emitted to the x-y plane. In this case, only the Ey scattered components appear in the isotropic medium, the uniaxial anisotropy and the biaxial anisotropy. However, we show that the Ex components also slightly appear in the off-diagonal anisotropic case, since there are off-diagonal dielectric components. The reflection coefficients are compared with the RCWA results calculated by approximating that the refractive indices are isotropy. Then, we confirmed that the anisotropy calculation is right. Finally, we calculated the reflection coefficients from the anisotropic periodic mounts put on the silicon substrate.