Point Defects, Diffusion Mechanisms, and the Shrinkage and Growth of Extended Defects in Silicon
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Semiconductors
POINT DEFECTS, DIFFUSION MECHANISMS, AND THE SHRINKAGE AND GROWTH OF EXTENDED DEFECTS IN SILICON
Ulrich Gosele* IBM Thomas J. Watson Research Center, Yorktown Heights, N.Y., USA Werner Frank MPI fur Metallforschung, Institut fur Physik, and Universitat Stuttgart, Institut fur Theoretische und Angewandte Physik, Stuttgart, Fed. Rep. Germany
ABSTRACT
The paper introduces the basic point-defect models proposed for silicon, which involve either vacancies or self-interstitials only, or both types of point defects simultaneously under thermal-equilibrium conditions. The growth and shrinkage kinetics of oxidation-induced stacking faults as well as oxidationenhanced or -retarded diffusion phenomena are discussed within the frame work of these models. Whereas no unambiguous conclusions on the dominant diffusion mechanism can be drawn from the available oxidation-related experiments, recent investigations on so-called anomalous diffusion phenomena (e.g., the 'emitter-push effect') and on the diffusion of gold in silicon demonstrate Si self-interstitials to be the point defects governing self- and impurity diffusion. The possibility of a coexistence of vacancies and self-interstitials in thermal equilibrium is discussed in this context. The paper concludes with speculations on how carbon in conjunction with self-interstitials may influence the nucleation process of oxygen precipitates in silicon.
INTRODUCTION
Point defects in silicon govern the diffusion of substitutional dopants and also the growth or shrinkage of extended defects such as oxidation-induced stacking faults (OISF), which in turn may adversely affect the yield of highly integrated silicon devices. Although most of the technically relevant effects induced by and related to point defects have been investigated thoroughly, no consistent and generally accepted picture has emerged. Even the simple and basic question which type of point defects (vacancies or self-interstitials) dominates self- and impurity diffusion in silicon under thermal-equilibrium conditions, is still a highly controversial matter. For this reason we will first present, in a simplified manner, the main point-defect models proposed for silicon and then discuss the shrinkage and growth kinetics of oxidation-induced stacking faults as well as oxidation-enhanced diffusion phenomena in terms of these models. Hereby we concentrate on areas in which either recent progress has been made or open questions can be defined properly. Subsequently we review investigations on the so-called anomalous diffusion effects (e.g., the 'emitter-push effect') which give a clear-cut answer on the diffusion mechanism of, at least, phosphorus and boron in silicon. The *On leave of absence from the Max-Planck-Institut Germany.
fur Metallforschung, Stuttgart, Fed. Rep.
56 possibility of a coexistence of vacancies and self-interstitials in silicon under thermal-equilibrium conditions is one of the topics of the following section which deals with the diffusion of Au and Ni in silicon. Finally we sh
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