<title>Process monitoring of LPCVD silicon nitride and polysilicon by variable-angle spectroscopic ellipsometry</title>

Abstract

Variable angle spectroscopic ellipsometry (VASE) has been used to monitor the deposition of silicon nitride (SiNx) and polycrystalline silicon (poly-Si) by low pressure chemical vapor deposition. SiNx with different nitrogen content and poly-Si were deposited onto Si wafers with a thin layer of thermal oxide. Ellipsometric data was acquired over the spectral range 270 nm - 1700 nm at multiple angles of incidence. For each material, two optical function models were used for fitting of the ellipsometric spectra. In the case of SiNx, the Cauchy model and the parametric semiconductor model resulted in fits of comparable quality and the optical functions of SiNx depend on the flow ratio of the dichlorosilane and ammonia used for the deposition. For poly-Si, the parametric semiconductor model was found to give a better fit than the Bruggeman effective medium approximation. In addition, some of the poly-Si samples were diffusion doped and in-situ doped with phosphorus. Using the same optical function models, it was found that diffusion doping resulted in increased crystallinity of the poly-Si. For the in-situ doped poly-Si, there was little change in the optical functions before and after annealing at 1000 degree(s)C. These results demonstrate that VASE is useful for in-line monitoring of thin film deposition in microelectronic processing.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.