Oxygen '96

Early Stages of Oxygen Precipitation in Silicon

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GENERATION OF THERMAL DONORS, NITROGEN-OXYGEN COMPLEXES AND HYDROGEN-OXYGEN PAIRS IN Si

M. Suezawa

Institute for Material Research, Tohoku University, Sendai 980-77, Japan

Keywords: thermal donor, oxygen, nitrogen, hydrogen, silicon, cluster

Clusters of impurities may be precursors of precipitation. Since the number of constituent atoms included in clusters is essential for determining the nature of clusters, the processes by which thermal donors, nitrogen-oxygen complexes, and hydrogen-oxygen pairs are generated were studied based on the measurement of optical absorption associated with them after isothermal annealing of Si. The number of constituent atoms can be determined by the analysis of the generation process of clusters.

We measured optical absorption due to six types of thermal donors, namely TD-1 through TD-6, generated due to isothermal annealing of Czochralski-grown Si at 471 degrees C. We analysed these data with a method which was extended from Kaiser et al.'s treatment with chemical reaction equations. The number of oxygen atoms included in TD-3 through TD-6 were determined to be 5 through 8 and those of TD-1 and TD-2 are proposed to be 3 and 4. The activation energies for the generation of TD-1, TD-2 and TD-3 are 1.4, 1.7, and 2.1 eV, which are small compared to that (2.54 eV) of oxygen migration.

We also studied the generation processes of nitrogen-oxygen (N-O) complexes, which acted as shallow donors, from the isothermal annealing of nitrogen-doped Czochralski-grown Si. We analysed the processes by which those donors are generated with a modification of Kaiser et al.'s method since there are two kinds of constituent atoms, nitrogen and oxygen. The N-O-6 and N-O-3 complexes, the ground state energies of which are 36.21 and 37.02 meV, are known to include 2 and 3 pairs of nitrogen atoms, respectively, and one oxygen atom.

We found that a hydrogen atom made a pair with an oxygen atom at around 50 degrees C. A peculiar characteristic of this pair is that the vibrational frequency (1075.0 cm^-1) of a hydrogen-oxygen pair is smaller than that (1076.3 cm^-1) of a deuterium-oxygen pair.

Last modified: Mon Feb 19 17:21:20 GMT 1996 JG