a1 Hewlett-Packard Laboratories, Palo Alto, California 94304.
a2 Siltec Corporation, Mountain View, California 94043
The process of oxygen precipitation in Czochralski silicon materials has been studied using high resolution transmission electron microscopy. The resulting structure depends strongly on the thermal history of the material. The initial stages of precipitation involve the formation of clusters exhibiting strain fields which are coherent and isotropic at intermediate temperatures (∼7000°C). Incoherent defects are formed when the interstitial oxygen precipitates into substitutional sites in the silicon lattice. For long-time anneals, the quasi-equilibrium defect structure ranges from needle-like coesite (450–600°C), silica platelets (600–1000°C) to polyhedral silica precipitates (900–1200°C).
c1 Present address: Xerox Palo Alto Research Center, Palo Alto, CA 94304, USA.