磁控溅射工艺引起硅表面超薄钝化层电子结构变化
摘要
During fabrication of TCO/SiO<italic><sub>x</sub></italic>/n-Si (SIS) photovoltaic devices, deposition of TCO films by sputtering damages the electronic structure of the SiO<italic><sub>x</sub></italic>/c-Si interface, leading to higher interface recombination rate and lower open circuit voltage of the obtained photovoltaic device. Enhancing the interface recombination rate is equivalent to decreasing the diffusion length in the bulk and reducing the short circuit current. It is obvious that damage to the interface can seriously affect the overall performance of the device. Usually, researchers are only concerned with the effect of passivation before TCO film deposition by sputtering, or with the overall performance of the fabricated device; thus, the damage incurred by sputtering during device fabrication is often overlooked. The damage incurred by sputtering on the efficient silicon-based heterojunction solar cells, especially the SIS devices, is rarely considered. In this letter, we report the investigations of the damage incurred by the energetic particle beams in the plasma (atoms/ions and UV glow) on the atomic bonding and electronic states in both ultra-thin silicon oxides and SiO<italic><sub>x</sub></italic>(1.5-2.0 nm)/c-Si(150 μm) sample's interface. The analysis was performed by using vacuum thermal annealing, effective minority carrier lifetime measurements (by using μ-PCD), and surface X-ray photoemission spectroscopy (XPS). The damage was observed in the process of magnetron sputtering deposition of the ITO thin film. We also investigated the effective passivation function of the ITO thin film's silicon surface. The results show that the samples' lifetime was reduced by more than 90% (from 105 μs to 5 μs) after the sputtering deposition of the ITO thin film. However, vacuum annealing at 100-400°C for 30 min partially eliminated the damage to the SiO<italic><sub>x</sub></italic>/c-Si interface and improved the passivation effect of the thin oxide layer