Dislocation locking was investigated in Czochralski Si with various O concentrations at 350 to 850C. Specimens containing well-defined arrays of dislocation half-loops were subjected to isothermal anneals of controlled duration, during which O diffused to the dislocations. The stress required to bring about dislocation motion was then measured at 550C. The dislocation unlocking stress as a function of annealing time was found to obey distinct regimes. For all annealing temperatures investigated, the unlocking stress initially rises approximately linearly before taking a constant value. The unlocking stress data were analyzed to give values for the binding energy of O to a dislocation and the effective diffusion coefficient of O in Si. At 650 to 850C, the diffusion coefficient of O was found to be in agreement with established values. At 350 to 650C, O transport was found to be strongly enhanced, with an activation energy of approximately 1.5eV and a pre-factor which depends on O concentration. For given annealing conditions, the dislocation unlocking stress was found to depend on the temperature at which the unlocking process was carried out at 450 to 700C. Furthermore, the dislocation locking technique was used to study the effect of high concentrations of shallow dopants on O diffusion at 350 to 550C. Oxygen transport was found to be unaffected by a high Sb concentration (about 3 x 1018/cm3), but was found to be enhanced by a factor of approximately 44 in material with a high B concentration (about 5 x 1018/cm3).

Oxygen Transport in Czochralski Silicon Investigated by Dislocation Locking Experiments. J.D.Murphy, S.Senkader, R.J.Falster, P.R.Wilshaw: Materials Science and Engineering B, 2006, 134[2-3], 176-84