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/SiO _x). Therein, a degradation was reported if the (n) poly-Si/SiO _x 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/SiO _x structures capped by a SiN _y or SiN _y/AlO _z stack only degrade during firing at moderate temperatures if they previously have been annealed below the optimum annealing temperature T _opt. It was found that this degradation is stronger the colder the annealing temperature was below T _opt. In part B of this study it is shown, that at excess firing temperatures also samples annealed at or above T _opt 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 T _opt. 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.