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Formation of Aluminum Oxide Films on Silicon Surface by Aluminum Evaporation in Oxygen Gas Atmosphere

Published online by Cambridge University Press:  10 May 2012

Y. Nagatomi ,
S. Yoshidomi ,
M. Hasumi ,
T. Sameshima  and
A. Kohno
Y. Nagatomi
Affiliation:
Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
S. Yoshidomi
Affiliation:
Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
M. Hasumi
Affiliation:
Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
T. Sameshima
Affiliation:
Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
A. Kohno
Affiliation:
Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
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Abstract

We report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.

Keywords

passivationAloxidation
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1426: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology—2012 , 2012 , pp. 421 - 426
Copyright
Copyright © Materials Research Society 2012

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