Dresden 2006 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 18: Thin semiconducting films

DS 18.1: Vortrag

Donnerstag, 30. März 2006, 09:30–09:45, GER 38

Characterisation of Si and SiGe layers with different strain by spectroscopic ellipsometry — •Jürgen Moers, Dan Mihai Buca, and Siegfried Mantl — Institute for Thin Films and Interfaces; Research Center Jülich; D-52425 Jülich; Germany

For further improvement of MOSFET devices high mobility materials as strained silicon are under investigation. Strained silicon is produced by growing thin silicon layers on relaxed SiGe-buffers, where the Ge-content determines the in-plane lattice constant and the incorporated strain. For process characterization it is mandatory to measure the thickness of the epitaxially grown layers and the homogeneity of the Ge-content. In order to provide a non-destructive characterization method, spectroscopic ellipsometry was investigated for thickness and composition measurement, as well as for wafer mapping.

Measurements were performed with a SENTECH SE800 spectroscopic ellipsometer and the appendant SpectraRay software was used for data analysis and simulation. The accuracy of the method is strongly dependent on the provided optical indexes. For SiGe as well as for the strained silicon an extended 4-oscilator-Leng-Model was used to describe analytically the refractive indexes and the absorption coefficient of the materials. SiGe-buffers with different Ge-content and strain were used to investigate the dependence of the model-parameters. Similar measurements were done with strained silicon layers directly on insulator. With the acquired optical data simulations where done to estimate the limits of spectroscopic ellipsometry as characterization method for strained silicon and SiGe layers.