Variable angle spectroscopic ellipsometry (VASE) has been used to monitor the deposition of silicon nitride (SiN_x) and polycrystalline silicon (poly-Si) by low pressure chemical vapor deposition. SiN_x 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 SiN_x, the Cauchy model and the parametric semiconductor model resulted in fits of comparable quality and the optical functions of SiN_x 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.

Date Published: 20 October 2000
PDF: 10 pages
Proc. SPIE 4230, Micromachining and Microfabrication, (20 October 2000); doi: 10.1117/12.404908

Published in SPIE Proceedings Vol. 4230:
Micromachining and Microfabrication
Kevin H. Chau; M. Parameswaran; Francis E.H. Tay, Editor(s)