Roles for A Precursor Oxide Phase in The Siting, Shaping, and Shrinking of Oxygen Precipitates
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ROLES FOR A PRECURSOR OXIDE PHASE IN THE SITING, SHAPING, AND SHRINKING OF OXYGEN PRECIPITATES P. Fraundorf Monsanto Electronics Materials Company, St. Louis MO 63167
ABSTRACT Three separate "anomalous" effects in the precipitation of oxygen in silicon may be explained if typical poorly-crystallized platelet oxygen precipitates begin as tiny crystalline clusters. The first anomaly, sometimes referred to as the induction effect, may be explained if one postulates the existence of kinetically stable precipitate embryos (seeds) containing no more than one or two oxygen atoms. We show here that such a postulate, coupled with observations, places rather specific constraints on binding energy as a function of size for such tiny clusters. The second and third anomalies, arising in precipitate shape and retrogrowth behavior dependences, respectively, may be explained if one postulates the existence of a relatively dense precursor phase which undergoes first order phase transition, following otherwise classical rules, to the final-stage amorphous oxide normally found. In this case, both precipitate shape and strain field can ambient during be interpreted as a barometer of the interstitial key periods in a precipitate's history.
INTRODUCTION It has been previously suggested that several anomalies in the precipitation of oxygen in silicon may be explained by the properties of a phase which acts as precursor to the poorlycrystallized platelet oxygen precipitates commonly found in late stages of oxygen precipitation in silicon [1,2,3]. If this is the case, then it should be possible to work backwards and infer some properties of the precursor phase from observed anomalies. In this paper, we present some theory concerning: (a) precipitate phase changes, and (b) the early stages of impurity clustering in solids, which allows one to do just that.
ANOMALY
1: INDUCTION EFFECT.
One of the "classic" anomalies in the theory of oxygen precipitation in silicon involves the ability of prior low temperature (
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