Defect formation in high dose oxygen implanted silicon

Abstract

The effect of dose (1 × 10 16 to 9 × 10 17 cm −2) and annealing temperature (700 to 1300°C) on the strain state and defect microstructure of oxygen implanted silicon were investigated by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM). At the lowest dose a unidirectional lattice expansion perpendicular to the surface occurred as a result of excess implantation-induced self-interstitials and interstitial clusters in the vicinity of the projected range while at doses of 1 × 10 17 and 3 × 10 17 cm −2, an association of lattice vacancies and oxygen atoms in the near-surface region gave rise to a unidirectional lattice contraction at the surface. The biaxial tensile stress in this surface layer provided a climb force for the development of large prismatic 1 2 〈110〉 extrinsic dislocation half-loops in the near surface region. At higher doses the oxygen precipitated as SiO 2 and was no longer associated with vacancies in the surface layer. The precipitates provided an additional interstitial source for extrinsic Frank loops which apparently unfaulted upon annealing at ⩾ 1050°C, and were pinned by existing precipitates resulting in a high threading dislocation (TD) density. It was concluded that controlling near-surface precipitation is a significant factor in reducing TD densities. This may be accomplished by ensuring that the near-surface oxygen is accommodated by cavities rather than as SiO 2 precipitates.