Nucleation of Oxygen Precipitates in a Quenched Czochralski Silicon Crystal
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NUCLEATION OF OXYGEN PRECIPITATES IN A QUENCHED CZOCHRALSKI SILICON CRYSTAL A. IKARI*, H. HAGA*, 0. YODA**, A. UEDONO*** AND Y. UJIHIRA*** *Electronics Research Labs., Nippon Steel Corp., 3434 Shimata Hikari 743, Japan "**TakasakiRadiation Chemistry Research Establishment, JAERI,, Takasaki, Gunma 370-12, Japan '*Department of Industrial Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
ABSTRACT We have studied the nucleation of oxygen precipitates in Czochralski(Cz) Si crystal quenched from high temperature (1390°C). We observed that the oxygen precipitation was enhanced by the quenching treatment. We found the density of precipitates in the quenched crystal depended on quenching temperature and that nuclei for oxygen precipitates were introduced during quenching. We studied these nuclei using infrared absorption (IR) and positron annihilation techniques. In order to clarify the state of the nuclei, the quenched specimens were irradiated with 3-MeV electrons at a dose of 1x10 18 e-/cm2 and vacancy-oxygen complexes were introduced. Positron lifetime spectra and IR absorption spectra for these specimens were measured as a function of isochronal annealing temperature. From the annealing behavior of the vacancy-oxygen complexes, it was found that oxygen clusters are introduced by the quenching and these clusters are the nuclei for the enhanced precipitation of the quenched Si crystal.
Introduction The control of oxygen precipitation in Czochralski (Cz) Si crystals is one of the most important technology in the current ULSI processes. In spite of many studies in this field [1], the nuclei for oxygen precipitation have not been made clear. Nucleation of oxygen precipitates is strongly affected by the thermal history during the crystal growth process. Harada et al. [2] reported the oxygen precipitation was enhanced in a rapidly into cooled crystal by detaching from the melt. Hara et al. [3] also reported the enhancement of oxygen precipitation in quenched wafers. In order to understand these nuclei, we have studied the behavior of oxygen precipitation in quenched Cz-Si. In order to find constituent elements of the nuclei, we irradiated the quenched specimens with electrons and introduced vacancy-oxygen complexes to the specimens. Introduction of these irradiation defects and their annealing behavior were measured by infrared absorption (IR) technique and positron annihilation techniques. The positron annihilation techniques have been established as a non-destructive and sensitive tool for the study of point defects in semiconductors. Details of these technique can be found in ref. [4]. Introduction and annealing of vacancy-oxygen complexes were intensively studied by electron paramagnetic resonance [5]. By comparing their behavior of the specimen with and without quenching, we analyzed what was introduced by quenching.
Mat. Res. Soc. Symp. Proc. Vol. 262. 01992 Materials Research Society
70
Experiment The specimens used in the present experiments were p-type (10 Q)cm) C
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