AbstractWe present a new IR absorption technique of measuring the dissolved interstitial oxygen concentration [Oi] and its reduction Δ [Oi] due to oxygen precipitation of the heavily-doped silicon crystal with doping level of about 1019 atoms/cm3. The method consists of the three steps: bonding the silicon wafer to a thick FZ silicon substrate by heat-treatment, thinning the wafer, and measuring the height of the 1136-cm−1 absorption peak of Oi at a temperature below 5 K. For a heavily doped wafer and the heavily doped substrate of an epitaxial wafer, we demonstrate examples of measuring the initial [Oi] and Δ [Oi] due to heat-treatment. Using this method, we investigate oxygen precipitation characteristics of the wafer heavily doped with boron. We found that the enhanced oxygen precipitation due to heavy boron-doping is expected if we perform preanneal at temperatures below 700°C.