Passivation mechanism of the high-performance titanium oxide carrier-selective contacts on crystalline silicon studied by spectroscopic ellipsometry

Variable-angle spectroscopic ellipsometry analysis is performed to study the impact of post-deposition annealing on the passivation performance of the heterocontacts consisting of titanium oxide and silicon oxide on crystalline silicon (c-Si) prepared by atomic layer deposition (ALD) for the development of high-performance ALD-TiO x /SiO y /c-Si heterocontacts. The highest lifetime of 1.8 ms is obtained for the TiO x /SiO y /c-Si heterocontacts grown at 175 °C after annealing at 275 °C for 3 min. With increasing annealing temperature, the TiO x layers of the TiO x /SiO y /c-Si heterocontacts become dominant. Furthermore, the amplitude of dielectric functions of the ALD-TiO x layer decreases as annealing temperature increases, which suggests that enhanced diffusion of Ti into SiO y interlayers at higher annealing temperature. The sufficient diffusion of Ti atoms into SiO y interlayers is caused by annealing at 275 °C for 3 min, yielding high-quality interface passivation.