Metal contamination detection in nickel induced crystallized silicon by spectroscopic ellipsometry

The metal (Ni) contamination on crystallized silicon obtained by metal induced crystallizaion (MIC) was estimated by Spectroscopic Ellipsometry (SE) using a new simulation approach. The method employs the addition of Ni as reference for a Bruggeman Effektive Medium Approximation (BEMA) to simulate the optical response of the crystallized silicon. Samples with different initial metal/silicon ratios were annealed and crystallized. Besides determining thickness, surface roughness and crystalline fraction, this new approach using SE has shown to be sensible to changes on the initial metal thickness used on the crystallization process being able of determining in a quick and non destructive way the Ni concentration inside MIC poly-Si films. The effectiveness of the obtained results was confirmed by RBS. An accurate determination of the initial Ni thickness that is deposited onto the amorphous silicon prior to crystallization is not possible using a quartz oscillator due to the very low quantity of evaporated materials. A better relation between defferent metal amounts present inside the crystallized films can be obtained by integratingthe Ni distribution in the RBS spectra. The obtained values are proportional to the Ni volume fraction determined by SE ellipsometry proves to be sensible to a metal volume fraction as low as 0.24%, corresponding to an initial Ni average thickness of 0.05 nm.