Surface Damage and Copper Precipitation in Silicon

Abstract

AbstractMechanical polishing of silicon introduces considerable damage into the surface. Heating in air causes this damage to be annealed both by dislocation movement and by the formation of stacking faults. The dislocations are rearranged in planes parallel to the surface and stacking faults are formed in the slip planes which lie at an angle to the surface. Prolonged heating causes the defects to be removed by the oxide layer.Copper is preferentially precipitated at these defects. The type of precipitation depends on the copper concentration which is determined by the temperature at which the copper is diffused into the silicon: below 1000 °C the precipitates lie along dislocation lines; between 1000 °C and 1150 °C the precipitates lie as discrete particles parallel to {110} planes; at higher temperatures the precipitates are platelets which lie on the surface. Once a precipitate forms it grows preferentially and removes copper from the surrounding region.