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Gettering of FE By Aluminum In P-Type Cz Silicon

Published online by Cambridge University Press:  15 February 2011

S. H. Ahn ,
S. Zhao ,
A. L. Smith ,
L. L. Chalfoun ,
M. Platero ,
H. Nakashima  and
L. C. Kimerling
S. H. Ahn
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
S. Zhao
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
A. L. Smith
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
L. L. Chalfoun
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
M. Platero
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
H. Nakashima
Affiliation:
Advanced Science and Technology Center for Cooperative Research, Kyushu University, Kasuga Fujuoka 816 Japan.
L. C. Kimerling
Affiliation:
Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139.
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Abstract

In this study, we investigate the gettering process of Fe in p-type Cz silicon after iron has been introduced at the solubility limit at 1000°C. Deep Level Transient Spectroscopy (DLTS) was used to measure [FeB], a fingerprint of [Fei], at the center of samples. The minority carrier diffusion length and lifetime were calculated from Electron Beam Induced Current (EBIC) measurements. The fact that [FeB] is proportional to the negative second power of the minority carrier diffusion length at the high [FeB] regime confirms that FeB donors are the dominant recombination centers limiting solar cell performance with high Fe contamination. By quenching after heat treatment, we can maintain and measure the kinetics and thermodynamics of gettering exclusively. The getter/silicon interface was studied by comparison of the gettering rates of molten Al at 620°C, 700°C, and 800°C, and iron silicide at 700°C. We model Fe gettering with respect to temperature, time, solubility and precipitate nuclei density. In the early stage of Fe gettering, the process is dominated by precipitate formation around oxygen precipitate nuclei. The precipitate density is estimated to be on the order of 5×108cm−3. In later stages, Fe outdiffusion contributes to the [Fei] reduction. The early stage precipitation limits [Fei] reduction after short time to the solubility at the gettering temperature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 442: Symposium E – Defects in Electronic Materials II , 1996 , 169
Copyright
Copyright © Materials Research Society 1997

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