Influence of Cobalt Contamination in the Measurement of Diffusion Length of Silicon Wafers

Abstract

Si bulk lifetime techniques are really sensitive to Co after drive-in step performed by RTP: the bulk diffusion length is strongly reduced, even at very low level of contamination. In case of p-type silicon, we point out that low energy photodissociation enhances this decrease, showing a pairing behavior of Co that has demonstrated to be with Boron, as for the well known Fe-B pairs. A detailed study of the interaction of Co with Si which has been focused on the detection of Co in Si using bulk lifetime methods, especially the SPV technique has been carried out. Evidence of recombination centers related to Co by Deep Level Transient Spectroscopy (DLTS) is shown, along with the activation of Co, its recovery kinetics in p-type Si and the low limit of detection of the SPV technique.All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net.

Proof of Interstitial Cobalt Defects in Silicon Float Zone Crystals Doped during Crystal Growth

“…It can be recognized that the equations ( 7) and (7a) describe very well the experimental results. According to the relation (8) for t → ∞ one obtains (N D -N P )/N P = A/B = 0.76 which is in fair agreement with the experimental value.…”

Ultra-High Sensitivity Surface Photovoltage Measurement of Heavy Metal Contamination in Silicon Wafers with Fast Metal Identification

“…Due to large differences in diffusivity values between different metals, the metals are distinguished and identified based on the value of p. For the fastest diffusing Co, the p is in the range of minutes at room temperature [9]. For Fe it is in the range of hours [8] and in the range of days and weeks for the slowest diffusing Cr [10].…”

Niobium Contamination in Silicon

“…The optical activation is based on the evidence that some contaminants increase their electrical activity upon illumination with light of sufficient intensity. Examples of this sort are iron (13) and cobalt (14), and for these contaminants the optical activation is due to the dissociation of the metal-boron pair. For both iron and cobalt, the equilibrium state at room temperature is the metal-boron pair.…”