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KINETIC COMPETITION DURING SOLID PHASE CRYSTALLIZATION IN ION-IMPLANTED SILICON

G.L. OLSON, J.A. ROTH, L.D. HESS, AND J. NARAYAN* Hughes Research Laboratories, Malibu, CA 90265 *Oak Ridge National Laboratory, Oak Ridge, TN 37830

ABSTRACT We report on an investigation of the temperature and concentration dependent kinetic competition between solid phase epitaxy and complex formation and precipitation in arsenic-implanted Si(100). Crystallization kinetics were monitored using time-resolved reflectivity during cw laser irradiation or furnace heating; microstructural changes were evaluated using cross-sectional TEM. At low temperatures and high As concentrations, complex formation and precipitation substantially alter the SPE kinetics. At higher temperatures competing interactions are less significant, and SPE becomes the dominant process. The kinetic competition between these processes is discussed with respect to the vacancy model for SPE.

INTRODUCTION It is well known that the kinetics of solid phase epitaxy (SPE) in amorphous silicon films can depend strongly on the presence of impurity atoms in the layers [1,2]. However, the rate enhancement and retardation produced by these impurities can cause the rate of SPE to become a complicated function of concentration and temperature. The investigation of these effects is important for the development of a comprehensive description of the mechanism of SPE and for an understanding of the role played by competing processes (e.g., complex formation, random crystallization, precipitate formation) during solid phase epitaxial crystallization of an amorphous Si film. In this paper we examine the temperature and concentration dependent interactions which control the solid phase crystallization kinetics in arsenic-implanted silicon. In previous studies of As-implanted silicon several interesting and unusual effects have been observed: (1) At moderate concentrations, arsenic enhances the SPE rate in Si relative to the intrinsic rate [1], at high concentrations, however, it acts to retard the SPE process [3]; (2) arsenic has been shown to form vacancy-diatom complexes (As+-V=-As+) [4] which, in the vacancy model for SPE [5,6], may produce rate-altering effects that are not usually associated with simple dopants in silicon; (3) has been suggested that polycrystalline nucleation and growth will dominate the crystallization kinetics at high temperatures in films containing high arsenic concentrations [7]; and (4) it has been shown that unusual solubility behavior is evident when metastable arsenic concentrations are produced by cw laser or rapid thermal annealing [8-11]. an attempt to understand the variety of effects which occur during recrystallization of As-implanted silicon we have studied the dependence of SPE rate on temperature and As concentration over a wide range using timeresolved reflectivity during furnace or laser heating. Cross-sectional transmission electron microscopy (TEM) is used for determination of microstructural changes which accompany crystallization of the