Precipitate and Defect Formation in Oxygen Implanted Silicon-on-Insulator Material

Abstract

AbstractThe formation and structure of defects and precipitates in high-dose oxygen implanted silicon-on-insulator material was directly studied by weak beam and high resolution electron microscopy. In as-implanted material, the edge of the oxygen implant profile contained 1.5 nm diameter precipitates at a density of 1019 cm2. Defects, including micrctwins, stacking faults, and (311) defects, were present in as-implanted material but no threading or loop dislocations were observed. This suggests that threading dislocations are formed in the thermal ramping and annealing cycle. In material annealed for different times and temperatures precipitate size was much more dependent on peak temperature rather than time-at-temperature indicating that oxygen diffusion distance is less important than thermodynamic factors in controlling precipitate size. Annealing from 1150°C to 1250°C produced threading dislocations and possible dislocation dipoles which extended through the superficial layer. Transient annealing of very low dose oxygen implanted Si produced loop and threading dislocations. This suggests that a high heating rate during precipitation will generate excess Si interstitials at a rate high enough to create high stresses at precipitates and form dislocations. A qualitative model for dislocation formation is proposed and processing conditions for reducing dislocation density are suggested.