Characterization of Nickel Induced Crystallized Silicon by Spectroscopic Ellipsometry
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0910-A21-06
Characterization of Nickel Induced Crystallized Silicon by Spectroscopic Ellipsometry Luis Pereira1, Hugo Aguas1, Manfred Beckers2, Rui M. S. Martins2, Elvira Fortunato1, and Rodrigo Martins1 1 Materials Science Department, Faculty of Science and Technology, New University of Lisbon, Campus da Caparica, Caparica, 2829-516, Portugal 2 Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, P.O.B. 510119, Dresden, 01314, Germany ABSTRACT In this work Spectroscopic Ellipsometry (SE) was used to study metal induced crystallization (MIC) on amorphous silicon films in order to analyze the influence of different annealing conditions on their structural properties. The variation of the metal thickness has shown to be determinant on the time needed to full crystallize silicon films. Films of 100 nm thickness crystallize after 2h at 500ºC using 1 nm of Ni deposited on it. When reducing the average metal thickness down to 0.05 nm the same silicon film will need almost 10 hours to be totally crystallized. Using a new approach on the modelling procedure of the SE data we show to be possible to determine the Ni remaining inside the crystallized films. The method consists in using Ni as reference on the Bruggeman Effective Medium Approximation (BEMA) layer that will simulated the optical response of the crystallized silicon. Silicon samples and metal layers with different thicknesses were analyzed and this new method has shown to be sensible to changes on the initial metal/silicon ratio. The nickel distribution inside the silicon layers was independently measured by Rutherford Backscattering Spectroscopy (RBS) to check the data obtained from the proposed approach.
INTRODUCTION The SE has already proved to be a very effective tool in studying poly-Si films, in a quick and non-destructive way, having the possibility to be used in-situ. Through the analysis of the dielectric function of the poly-Si using a Bruggeman Effective Medium Approximation (BEMA) [1], SE makes possible to infer the physical properties of the material. Changes on the impurity doping, surface roughness or grains size/boundaries have a great influence on the dielectric function [2,3]. Several past works compared the results obtained by SE with the ones obtained by other techniques such as Atomic Force Microscopy (AFM) and Rutherford Backscattering Spectroscopy (RBS) [4,5], Transmission Electron Microscopy (TEM) [4], X-Ray Diffraction (XRD) [6], Raman Spectroscopy (RS) [7], confirming that SE gives reliable results in determining the thickness, surface roughness, crystalline fraction and composition. It is known that poly-Si films produced by Ni metal induced crystallization (MIC) will retain some metal embedded on it [8,9]. Although lowering the crystallization temperature when compared with conventional Solid Phase Crystallization (SPC) or being less expensive than laser processing, this crystallization method present some disadvantages, being the metal contamination the most limitative when aiming the application on dev
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