We study the pattern of oxidation induced stacking faults ͑OISF͒ on heavily boron doped silicon wafers. The measured radii of the OISF pattern are compared with V/G simulations and the dependence of the critical V/G value ͑͒ on boron concentration is constructed. The value for undoped silicon ͑ 0 ͒ is assumed to be close to 0.13 mm 2 /min K. The critical value rises steadily with boron concentration following a logarithmic dependency. The OISF ring located in the P band, commonly observed in lightly doped silicon, is not detected. We observe the banded OISF pattern, which reflects the residual vacancy profile according to the qualitative model for microdefects formation proposed by Voronkov and Falster ͓J. Cryst. Growth, 204, 462 ͑1999͔͒. Such OISF distribution is not reported so far. As an explanation, abnormal oxygen precipitation during crystal growth due to heavy boron doping and high oxygen content is assumed. Consequently, the grown-in oxygen precipitates, whose density corresponds to the residual vacancy concentration, are stable at the temperature above 1050°C and serve as the OISF nuclei. Furthermore, we observe fine structure of the L band and a strong dependence of the OISF pattern appearance on the oxygen content and the crystal thermal history.
Modern Aspects of Bulk Crystal and Thin Film Preparation 44 2.1 Czochralski growth of silicon crystals Today´s Czochralski (CZ) grown silicon single crystals are produced in a mass scale in diameters of up to 300 mm, but the 150 mm and 200 mm processes are still considered as standard. A typical CZ puller is shown in Fig. 1. The puller consists of an upper and lower chamber formed by steel water-cooled shells. The lower chamber contains a graphite hot zone with active central part and thermally insulating outer parts. A silica crucible is placed in the heart of the hot zone which is supported by a graphite susceptor on the pedestal attached to the lower shaft. The seed holder is fastened onto the upper shaft (or affixed to a cable). The heater is a meandering-coil element heated by high electric current. Both chambers are piped to a vacuum system. The puller is typically purged with inert gas (usually argon). In the beginning of the process the quartz crucible is loaded with a charge of polysilicon chunks and the single crystalline seed is fitted into the seed holder. After closing the puller the chambers are evacuated and refilled by inert gas to the desired process pressure. The process starts with melting the polysilicon charge by applying high power to the heater. Once the charge is molten, the melt flow is stabilized under steady conditions and the seed is lowered towards the melt. After the seed is dipped into the melt, the system is adjusted to achieve a stable interface between the melt and the seed crystal. Pulling the seed upwards crystallizes the melt at the solid-liquid interface and the crystal proceeds to grow.
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