Influence of the annealing temperature of (n) poly-Si/SiOx passivating contacts on their firing stability

Several works have been published recently regarding firing stability of passivating contacts featuring P-doped polysilicon on an interfacial oxide (poly-Si/SiOx). Therein, a degradation was reported if the (n) poly-Si/SiOx structure was capped by a dielectric passivation layer during firing due to creation of additional defects in the interfacial oxide. In part A of this study it is shown, that P-doped (n) poly-Si/SiOx structures capped by a SiNy or SiNy/AlOz stack only degrade during firing at moderate temperatures if they previously have been annealed below the optimum annealing temperature Topt. It was found that this degradation is stronger the colder the annealing temperature was below Topt. In part B of this study it is shown, that at excess firing temperatures also samples annealed at or above Topt degrade. Again, this degradation depends on the initial annealing temperature in a similar way that the degradation is stronger the colder the annealing temperature was below Topt. Furthermore, a saturation of the measured surface recombination density was observed for set firing temperatures above 900°C, which points to a saturation of the underlying defect creation mechanism in the interfacial oxide.