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The spurious contribution of oxide precipitates to the infrared absorption of interstitial oxygen in silicon is determined from spectra collected at 7 K for samples with different initial interstitial oxygen O-i concentration subjected to a three-step thermal treatment. These data can be used to correct the residual O-i values determined at room temperature following the standard procedure from the intensity of the 1107 cm(-1) absorption band. The error in residual O-i is found to reach values on the order of 2x10(17) atoms/cm(3) for samples with initial O-i content higher than 6.5x10(17) atoms/cm(3). (C) 2001 American Institute of Physics

Interstitial oxygen profile across an epitaxial silicon and Czochralski silicon interface has been studied using high-spatial-resolution Fourier transform infrared spectroscopy. Systematic transmission measurements performed on a transversal wafer cross section evidenced oxygen contamination of the epilayer. This was due to solid-state outdiffusion from the substrate occurring during epilayer deposition. Oxygen diffusivity values resulting from the experiments suggest a mechanism scarcely influenced by the interface. Oxygen contamination is strictly related to the type of dopant present in the substrate and not to that present in the epilayer. The oxygen contamination of the epilayer (significant in n-type substrate samples) could explain the structural defects often observed in epitaxial layers by different techniques.

Gettering of Cr during the growth of silicon sheets from a Cr-doped melt is observed when the solid/liquid interface region is exposed to CO or CO2 gases. The gettering occurs within a region about 1-mum wide at the surface of the crystal, where a large accumulation of carbon and oxygen is detected. Mechanisms for carbon and oxygen participation in forming gettering sites for Cr are examined

Carbon complex formation during annealing in the temperature range from 450 to 1150-degrees-C is studied in a carbon-rich polycrystalline edge-defined film-fed grown (EFG) silicon sheet. The result is compared with that obtained in Czochralski (CZ) single-crystal silicon. Infrared (IR) spectroscopy reveals that carbon removal from substitutional sites above 600-degrees-C is greatly inhibited in EFG silicon with respect to that seen in the CZ material. A broad IR peak attributed to C-O complexes appears only after annealing at highest temperatures, while there is no evidence for appearance of the sharp band at 794 cm-1 usually assigned to SiC precipitation. The suppression of carbon complex formation in EFG material is attributed to decreased availability of silicon self-interstitials necessary to promote removal of carbon from substitutional sites and to enhance its diffusivity

High-spatial resolution Fourier transform infrared spectroscopy permitted us to study the effects of incident light polarization on the absorption band related to aggregates of SiO2 disk-shaped precipitates present in annealed (100) Czochralski silicon samples. This is the first report documenting the strong dependence of such a band intensity on light polarization. Experimental results were compared with the simulation obtained using the effective medium theory. From this comparison we deduce that the precipitates only lie on the planes among {100} which are parallel to the wafer surface. This result can be related to the difference between the 〈100〉 direction and those crystallographically equivalent, introduced by the ingot growth process.