SPECTROELLIPSOMETRIC METHOD FOR PROCESS MONITORING SEMICONDUCTOR THIN-FILMS AND INTERFACES

Real-time monitoring by multiwavelength phase-modulated ellipsometry o f the growth of plasma-deposited microcrystalline Silicon (mu c-Si) is presented. We discuss the construction of a growth model for process monitoring, and, in particular, we treat the inhomogeneity in the mu c -Si layer by using an approximation of the reflection coefficient know n as the WKBJ method. By also using the Bruggeman effective medium the ory to describe the optical properties of mu c-Si, we demonstrate moni toring the crystallinity in the upper and the lower part of the layer together with the thickness. The inversion algorithms thus remain very fast, with calculation times within 5 s on a standard Pentium compute r. This makes possible precise control of the thickness and the crysta llization of both the top and the bottom interface of the layer during the elaboration of devices such as solar cells and thin-film transist ors. (C) 1998 Optical Society of America.