Process monitoring of semiconductor thin films and interfaces by spectroellipsometry

摘要

Abstract: Real-time monitoring by multiwavelength phase modulated ellipsometry (PME) of the growth of plasma deposited microcrystalline Silicon ($mu@c-Si) is presented. Several growth models for process-monitoring are reviewed, and in particular the inhomogeneity in the $mu@c-Si layer is treated by allowing graded-index profile in the bulk. By also using the Bruggeman effective medium theory to describe the optical properties of $mu@c-Si, the monitoring of the crystallinity in the upper and lower part of the layer, together with the thickness is demonstrated. The inversion algorithms is very fast, with calculation times within 5 seconds using a standard Pentium computer. This opens up for precise control of surface roughness, bulk thickness, and crystallization of both the top and bottom interfaces of the layer during the elaboration of devices such as solar cells and thin film transistors. !17