The dissolution mechanism of oxide precipitates in czochralski silicon degenerately doped with boron during high temperature annealing
The morphology of oxide precipitation induced defects in Czochralski silicon degenerately doped with boron and annealed at 800° and 1050°C, respectively, was examined using a transmission electron microscope. After an extended annealing at 800°C, the predominantly observed defects were the oxide precipitate platelets having the {001}-type habit planes and sides parallel to <110> and <112> crystallographic directions. The morphology of the oxide precipitates as derived from the residual oxygen calculation is suggested to be that of a thin octahedral shape. During a subsequent high temperature annealing, the octahedral precipitate platelets became thermodynamically unstable and dissolved. Based upon the defect morphology observed after a 1050°C anneal, it is suggested that the dissolving precipitate introduces a tensile strain into the surrounding silicon lattice. Contrary to precipitate growth, the lattice strain introduced by precipitate dissolution is relieved primarily through mechanisms involving vacancy injection from the precipitate interface and a condensation of excess silicon interstitials via a formation of an interstitial-type dislocation loop.