Detection and mapping of oxygen in silicon wafers by scanning infrared absorption

Scanning Infrared Absorption (S.I.R.A.) setup was carried out for investigating and mapping of microdefects distribution in Czochralski silicon wafers. Using CO₂ laser, this non destructive, non contact test method allows transmitted beam local attenuation from oxygen precipitates to be determined. Transmitted intensity I_t maps from peak height of the 1080 cm⁻¹ absorption band were obtained. An inhomogeneous initial oxygen distribution is found in as-grown samples. The samples were then submitted to preannealing at 750°C for 16 hours, followed by annealing at 900°C for 24 hours. The obtained I_t fluctuations mapping depicts a ring-shaped distribution of oxygen precipitates.