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Tantalum-Nitride Diffusion Barrier Studies Using the Transient-Ion-Drift Technique for Copper Detection

Published online by Cambridge University Press:  17 March 2011

T. Heiser
Affiliation:
University Louis Pasteur, Laboratoire de Physique et Applications des Semiconducteurs, CNRS, BP20 F67037 Strasbourg Cedex 2, France
C. Brochard
Affiliation:
University Louis Pasteur, Laboratoire de Physique et Applications des Semiconducteurs, CNRS, BP20 F67037 Strasbourg Cedex 2, France
M. Swaanen
Affiliation:
at ST Microelectronics, 850, rue Jean Monnet B.P. 16, F-38921 Crolles cedex, on leave of absence from Philips Electronics, Eindhoven, Netherlands
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Abstract

The permeability of 5 nm thick TaN, Ta and TiN diffusion barriers has been studied by monitoring the bulk copper concentration in silicon after isothermal and isochronal annealing experiments with a transient-ion-drift (TID) technique. The method estimates quantitatively the bulk copper concentration in silicon from capacitance transients of a Schottky barrier which arise when copper ions drift out of the depletion region towards the quasi-neutral region. The correlation between the copper lateral distribution and the position of the copper metal is used to distinguish between background contamination and copper originating from barrier leakage. The TID detection limit is found lower than 1012at/cm3, which makes this technique particularly well adapted for quantitative diffusion barrier studies. Isothermal and isochronal annealing experiments show that TaN fails at a higher temperature than Ta barriers. The copper concentration does not exceed the solubility limit, indicating that copper precipitates nucleate rapidly at the interface. The opposite is found in TiN covered samples where a large copper supersaturation is obtained even after short annealing times.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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