Formation Mechanisms and Structures of Thin Buried Layers of SiO2 Fabricated Using Ion Beam Synthesis

The effects of variations in the implanted dose Φ1 and the annealing temperature TA during the formation of buried layers of SiO2 produced by ion beam synthesis (IBS) are discussed. It is found that when specimens implanted with oxygen doses below 0,3 x 10l80+cm-2 are annealed at 1405°C for 30 minutes a buried layer consisting of two discontinuous rows of SiO2 precipitates is produced. For higher doses these two layers coalesce to give a single continuous layer of SiO2. The interfacial irregularity of this layer is found to decrease with increasing dose such that for doses of ≧ 1.8 x 10l80+cm-2 the interfaces are almost planar. Studies of these higher dose specimens annealed in the temperature range 1280–1300°C for times of 2–20 hours show that the crystal quality of the silicon overlay improves with increasing temperature and time. The oxygen concentration in the silicon overlayer also appears to increase with annealing time and mechanisms are proposed to explain the observed phenomena.