No abstract

Using two-step annealing of wafers containing mechanically induced back-surface damage, we have shown that the presence of stabilized damage regions controls the development of front-surface defect denudation zones and internal SiOx nucleation. Using data from transmission electron microscopy, secondary ion mass specrometry profiling, and secondary ion microscopy measurements we have demonstrated that little or no direct correlation exists between measured (front-surface) oxygen depletion widths and defect denudation zone widths. Primary anneals at temperatures <600 °C have also been shown to produce no significant or measurable depletion of oxygen at the front surface of wafers.

Motion and gettering of oxygen into damage regions created by back-surface mechanical abrasion in Si has been investigated using transmission electron microscopy (TEM), scanning electron microscopy, secondary-ion mass spectrometry profiling and secondary-ion microscopy. Redistribution and gettering of oxygen have been detected along dislocation lines after annealing at 600 °C by both TEM and direct ion imaging. Subsequent annealing at 1050 °C produces additional gettering, SiOx nucleation, and a dramatic increase in dislocation-line density within the initial damage region. Secondary dislocation lines extending to a depth ≃ 40 μm are also generated by the two-stage anneal, resulting in additional gettering sites for oxygen and other impurities. In comparison, single anneals at 1050 °C produce rapid defect annihilation, oxygen outdiffusion, and loss of additional gettering efficiency.