Ultrathin silicon oxide prepared by in-line plasma-assisted N2O oxidation (PANO) and the application for n-type polysilicon passivated contact

• Published in: Solar energy materials and solar cells 2020-05, Vol.208 (C), p.110389, Article 110389
• Main Authors: Huang, Yuqing, Liao, Mingdun, Wang, Zhixue, Guo, Xueqi, Jiang, Chunsheng, Yang, Qing, Yuan, Zhizhong, Huang, Dandan, Yang, Jie, Zhang, Xinyu, Wang, Qi, Jin, Hao, Al-Jassim, Mowafak, Shou, Chunhui, Zeng, Yuheng, Yan, Baojie, Ye, Jichun
• Format: Article
• Language: English
• Subjects: Amorphous silicon; Annealing; Chemical vapor deposition; Circuits; Crystallization; MATERIALS SCIENCE; Nitric acid; Nitrous oxide; Open circuit voltage; Oxidation; Passivity; Plasma-assisted N2O oxidation; Polysilicon; Polysilicon passivated contact; Recombination; Silicon; Silicon oxide; Silicon oxides; SOLAR ENERGY; Substrates; Temperature; TOPCon; Transmission electron microscopy; Ultrathin silicon oxide
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2019.110389

We develop a plasma-assisted nitrous-oxide (N2O) gas oxidation (PANO) method to prepare the ultrathin silicon oxide (SiOx) for polysilicon (poly-Si) passivated contact. The effects of preparation conditions, including the substrate temperature, processing time, and plasma power, are studied. Afterwards, we integrate the PANO SiOx into the polysilicon passivated contact and optimize the passivation and contact performances. Excellent surface passivation with the n-type poly-Si and PANO SiOx on the n-type c-Si wafer is achieved by 880 °C annealing, which shows competitive passivation quality to the one with NASO SiOx. Champion implied open-circuit voltage (iVoc) and single-sided recombination saturated current (J0) reach 730 mV and 4.3 fA/cm2 after crystallization; and they are further improved to 747 mV and 2.0 fA/cm2 (3 × 1015cm−3) after subsequent AlOx/SiNx hydrogenation. Using transmission electron microscopy (TEM), we find that the thickness of PANO SiOx ranges 1.1–2.4 nm and the controlled nitric acid oxidized SiOx (NAOS) ranges 1.3–1.8 nm. The contact resistivity (ρc) is typically 820 °C. Also, the crystallinity, phosphorous in-diffusion profile, and current-leaking density of the passivated contacts are investigated. In general, the PANO SiOx and in-situ doping amorphous silicon precursor can be fabricated in one PECVD system without additional equipment or transfer procedures, which is favorable for the high-efficiency, low-cost industrial manufacture. •Ultrathin SiOx prepared by in-line plasma-assisted N2O oxidation (PANO) is used for passivated contact.•Passivated contact with PANO SiOx shows competitive quality to that with NASO SiOx.•Champion surface passivation reaches iVoc = 747 mV &J0 = 2.0 fA/cm2 after hydrogenation.•Contact resistivity becomes  820 °C.•Oxidation degree, thickness, and pinhole are characterized for robust passivated contact with PANO SiOx.