Infrared measurement and irradiation of ultra low carbon concentration silicon crystal

Vacancy-interstitial-oxygen-carbon (VIOC) complexes induced by electron irradiation in ultra-low and low carbon content (well below and around 1015/cm3) CZ silicon crystals were examined by highly sensitive infrared (IR) absorption spectroscopy at RT. Absorption lines of peak absorbance down to 5x10-6 were successfully delineated. Dose dependence and annealing temperature dependence were systematically investigated. Both major and minor groups were detected. Increase, saturation and decrease for the dose increase is mainly due to the chain reaction. Order estimate of complex concentration was performed. In addition to the established advantage of IR such as wide applicability to all complexes, reliable assignment and insensitivity to coexisting defects, high sensitivity down to 5x1012/cm3 was established. The problem of measuring carbon substitutional (Cs) concentration was discussed and reduction of [Cs] in the reference material by irradiation is demonstrated. These techniques will provide reliable measurement of oxygen, and nitrogen also and tool for analysis of the infrared defect dynamics in growing silicon crystals. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)