Crystallite Dimensions and Strain in Poly-Si and Ti-Silicide Thin Films Measured with Grazing Incidence X-Ray Diffraction

Abstract

ABSTRACTThe present study describes the measurement of microcrystalline grain dimensions and crystallite strain for polycrystalline silicon (poly-Si) and titanium suicide, using grazing incidence X-ray diffraction (GIXRD). A variety of poly-Si sample configurations were synthesized by different low pressure chemical vapor deposition (LPCVD) processing techniques. Selected samples were subsequently processed by phosphorous diffusion doping and reaction with thin titanium layers. Characterization with GIXRD reveals differing crystallite grain dimensions, ranging from =80Å to =900Å. Crystal strain was measured in direction perpendicular to (111) lattice planes. Phosphorous diffusion doping is shown to remove this (111) strain, in addition to increasing crystallite grain dimensions. The GIXRD characterization, which measures a specific fraction of the sample crystal texture, indicates that deposition rate modulated poly-Si LPCVD reduces (111) microscopic strain in poly-Si films two-fold, compared to conventional poly-Si deposition. The crystallite dimensions of conventional poly-Si, are found to peak approximately in direction perpendicular to (110) planes. The same trend is observable for deposition rate modulated poly-Si, where grain dimensions, measured in [110] direction, are reduced by =30%. Larger crystallite dimensions were measured in direction perpendicular to (110) planes, for both cubic poly-Si and orthorhombic Ti-silicide layers, suggesting the presence of preferred crystallite growth directions, resulting in anisotropie crystallite grain dimensions.