Heavily tin (So) doped Si crystals in a concentration up to 4 x 1019 cm(-3) were grown by the Czochralski method. Variation of Sn concentration in the crystals was well expressed by the Pfann equation using a segregation coefficient of k=0.016. From the occurrence of growth interface instability and the appearance of Sn precipitates in the grown crystals, the solubility limit of Sn was considered to be around 5 x 10(19) cm(-3). Interstitially dissolved oxygen O-i was presented at a concentration of 8-9 x 10(17) cm(-3) in the grown Sn-doped crystals. The FT-IR absorption peak relating to a Si-O-i-Si quasi-molecule at 1106 cm(-1) showed preferential occupation of 0; at the bond-centered position of Si-Si. The O-i peak shifted to the lower wave number side with increasing Sn concentration in Si, implying expansion of the Si-Si bond. (C) 2014 Elsevier B.V. All rights reserved.