Spectroellipsometric Method for Process Monitoring of Semiconductor Thin Films and Interfaces

摘要

Real time monitoring by multiwavelength phase modulated ellipsometry (PME) of the growth of plasma deposited microcrystalline Silicon (μc-Si) is presented. The construction of a growth model for process-monitoring is discussed, and in particular the inhomogeneity in the μc-Si layer is modelled by using an approximation of the reflection coefficient known as the Wentzel Kramers Brillouin Jeffreys (WKBJ) approximation. By also using the Bruggeman effective medium theory to describe the optical properties of μc-Si, monitoring of the crystallinity in the upper and lower part of the layer, together with the thickness is demonstrated. The inversion algorithms remain thus extremely fast, with calculation times within 5 seconds on a standard Pentium computer. This opens up for precise control of thickness, and crystallisation of both the top and bottom interfaces of the layer during the production of devices such as solar cells and thin film transistors.