Oxygen '96

Early Stages of Oxygen Precipitation in Silicon

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OXYGEN PRECIPITATION IN ANNEALED CZ. AND FZ. SILICON DETECTED BY S.I.R.M., F.T.I.R. AND L.B.I.C.

C. Veve and N. Gay

Laboratoire de Photoélectricité des Semi-Conducteurs F. A. 882 ``Defauts dans les Semi-conductoeurs et leurs Oxydes'' Faculté des sciences et techniques de Marseille-St.Jérome 13397 MARSEILLE Cedex 20 - FRANCE
Fax: 91 28 88 52

Keywords: oxygen, silicon, precipitates, SIRM, FTIR, LBIC

A Scanning Infrared Microscope (S.I.R.M.), a Light Beam Induced Current mapping (L.B.I.C.), a Fourier Transform Infrared spectrometer (F.T.I.R.) and a minority carrier diffusion length (L) measurement tool have been associated to detect and to evaluate the recombination strength of precipitates in annealed Cz and FZ silicon wafers (in oxygen rich and in oxygen poor samples).

Samples were submitted to two step annealing treatments at 750 degrees C for 16h (a) and/or at 900 degrees C for 24h (b) in pure Ar, in order to nucleate and to grow oxygen related precipitates. When treatments (a) and/or (b) are applied to Cz silicon wafers dark spots are detected by S.I.R.M., and F.T.I.R. indicates that they could be related to oxygen precipitates. L.B.I.C. maps detect ring like distribution of recombination centres and diffusion length collapses to 20 micro-m! Conversely, in FZ wafers the treatments of (a) and (a)+(b) do not have such a harmful effect on (L).

Phosphorus diffusion at 900 degrees C for few hours leads to the disappearance of precipitates detected by the S.I.R.M. in annealed ((a)+(b)) Cz samples.

Surface oxidation at 900 degrees C on Cz samples produces a similar effect because like phosphorus diffusion it leads to an injection of self-interstitials which are known to be able to shrink precipitates, but new defects identified as stacking faults are detected by S.I.R.M.

S.I.R.M., F.T.I.R. and L.B.I.C. are non destructive techniques, able to detect the presence of precipitates in silicon wafers, and to lead to an evaluation of their recombination strength.

Last modified: Mon Feb 19 12:10:49 GMT 1996 JG