Effects of Thermal Donor Generation and Annihilation Upon Oxygen Precipitation
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EFFECTS OF THERMAL DONOR GENERATION AND ANNIHILATION UPON OXYGEN PRECIPITATION S. HAHN, S. C. SHATAS, and H. J. STEIN *Siltec Corporation, Mountain View, CA 94043 Peak Systems, Fremont, CA 94358 *Sandia National Laboratories, Alburquerque,
NM
87185
ABSTRACT Rapid thermal annealing and furnace annealing steps have been combined to investigate the effects of thermal donor generation and annihilation upon oxygen precipitation in low and high carbon content silicon wafers. Thermal donors were formed by furnace annealing at 450°C. Rapid thermal annealing was performed in 10 s periods at temperatures between 6000 and 1000*C and was followed by two step furnace annealing at 700° and 950 0 C. Rapid thermal annealing separates the annealing stage for thermal donor removal from that for removal of oxygen precipitate nuclei, and a marked dependence upon carbon is observed for nuclei stability under RTA. Implications of these observations for models of precipitate nuclei are considered. I.
INTRODUCTION
Thermal donors, TD's, in Si are of technological interest and have been studied extensively over a number of years [1]. Thanks to new techniques, such as infrared absorption, deep level transient spectroscopy and electron paramagnetic resonance, electrical characterization of this defect is relatively well-established. One of the important issues related to TD's is their role in oxygen precipitation, especially during nucleation stages near 700°C. Although various researchers 0 have found a 450 C pre-anneal significantly enhances precipitation rates, the path or paths from TD formation to oxygen precipitation are not completely known. Thermal donors form upon furnace annealing between 300-500 0 C and are removed by furnace annealing near 650°C. Because oxygen in Si goes through various stages of precipitation and phase segregation, these stages tend to overlap in furnace annealing. Rapid thermal annealing (RTA) can help separate processes which may not be separated in furnace annealing studies. In this study, we combined RTA and furnace annealing steps to investigate effects of TD generation and annihilation upon oxygen precipitation in low and high carbon content crucible-grown Si wafers. II.
EXPERIMENTAL
Materials used in this study were low carbon (less than instrument sensititivity 0.05 ppma) and high carbon content (1.2-1.8 ppma) P-type 100 mm diameter (100) Si wafers with resistivities of 6-10 ohm-cm. Oxygen concentrations, Oi, in these wafers were 17±0.5 ppma (ASTM F121-81).
Mat. Res. Soc. Symp. Proc. Vol. 59. c1986 Materials Research Society
Downloaded from https://www.cambridge.org/core. Access paid by the UCSB Libraries, on 21 Jul 2018 at 08:50:18, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/PROC-59-287
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Some of these wafers were initially subjected to 450 5 C/52 h furnace furnace annealing which generated -1016 TD's/cm3 and 7x10 1 5 TD's/cm3 respectively, for low and high carbon content Si. These wafers were annealed at temperatu
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