Low-temperature ultrasonic measurements were performed for direct observation of the vacancies in Czochralski-grown Si crystals. Elastic softening, similar to that recently found for float-zone Si crystals was also observed for the vacancy-rich region of the defect-free zone in the Czochralski-grown Si crystal. It was further shown that both the interstitial-rich region in the defect-free zone and the region of the ring-like oxidation-induced stacking faults of the same crystal ingot exhibited no such elastic softening of detectable magnitude, confirming the previous conclusion that the defects responsible for the low-temperature softening were the vacancies. It was observed how the vacancy concentration in the defect-free zone varied along the pulling direction.

Vacancies in Defect-Free Zone of Point-Defect-Controlled CZ Silicon Observed by Low-Temperature Ultrasonic Measurements. H.Yamada-Kaneta, T.Goto, Y.Saito, Y.Nemoto, K.Sato, K.Kakimoto, S.Nakamura: Materials Science and Engineering B, 2006, 134[2-3], 240-3