Dissolution of electrically inactive phosphorus by low temperature annealing
In this study we investigate the dissolution of electrically inactive phosphorus complexes by low temperature annealing after the POCl3 diffusion process. This has the immediate consequence that the existing near-surface emitter volume SRH recombination can be reduced. Thereby, a significant reduction of emitter saturation current density j0E is achieved without driving the emitter further into the silicon substrate. For short-term temperature treatments well below the POCl3 diffusion temperature, a reduction of up to -60 fA/cm2 has been achieved. This study increases our understanding of the formation and dissolution of electrically inactive phosphorus complexes during post-annealing processes.
Electrically-inactive phosphorus re-distribution during low temperature annealing
An increased total dose of phosphorus (P dose) in the first 40 nm of a phosphorus diffused emitter has been measured after Low Temperature Annealing (LTA) at 700 °C using the Glow Discharge Optical Emission Spectrometry technique. This evidence has been observed in three versions of the same emitter containing different amounts of initial phosphorus. A stepwise chemical etching of a diffused phosphorus emitter has been carried out to prepare the three types of samples. The total P dose in the first 40 nm increases during annealing by 1.4 × 1015 cm–2 for the sample with the highly doped emitter, by 0.8 × 1015 cm–2 in the middle-doped emitter, and by 0.5 × 1015 cm–2 in the lowest-doped emitter. The presence of surface dislocations in the first few nanometers of the phosphorus emitter might play a role as preferential sites of local phosphorus gettering in phosphorus re-distribution, because the phosphorus gettering to the first 40 nm is lower when this region is etched stepwise. This total increase in phosp...
Phosphorus diffusion into silicon from chemically vapour-deposited phosphosilicate glass
Abstract The diffusion coefficient of phosphorus in phosphosilicate glass in the temperature range 940–1050°C was determined on the basis of etch rate measurements. Higher diffusivity values and a lower activation energy than the corresponding values for the thermal oxide are obtained. For diffusion of phosphorus into silicon we have shown that, within experimental error and for concentrations lower than the solubility value, the whole of the dopant is electrically active. This is in disagreement with the hypothesis of the existence of compensated phosphorus in the form of E centres in equilibrium with substitutional phosphorus. Moreover, it is shown that the dopant concentration profile predicted by the model of Fair and Tsai is in disagreement with experimental data.