Kang Di, Sio Hang Cheong, Stuckelberger Josua, Liu Rong, Yan Di, Zhang Xinyu, Macdonald Daniel
School of Engineering, The Australian National University (ANU), Canberra, ACT 2601, Australia.
SIMS and Microscopy Facility, Western Sydney University, Sydney, NSW 2753, Australia.
ACS Appl Mater Interfaces. 2021 Nov 24;13(46):55164-55171. doi: 10.1021/acsami.1c17342. Epub 2021 Nov 12.
It has previously been shown that ex situ phosphorus-doped polycrystalline silicon on silicon oxide (poly-Si/SiO) passivating contacts can suffer a pronounced surface passivation degradation when subjected to a firing treatment at 800 °C or above. The degradation behavior depends strongly on the processing conditions, such as the dielectric coating layers and the firing temperature. The current work further studies the firing stability of poly-Si contacts and proposes a mechanism for the observed behavior based on the role of hydrogen. Secondary ion mass spectrometry is applied to measure the hydrogen concentration in the poly-Si/SiO structures after firing at different temperatures and after removing hydrogen by an anneal in nitrogen. While it is known that a certain amount of hydrogen around the interfacial SiO can be beneficial for passivation, surprisingly, we found that the excess amount of hydrogen can deteriorate the poly-Si passivation and increase the recombination current density parameter . The presence of excess hydrogen is evident in selected poly-Si samples fired with silicon nitride (SiN), where the injection of additional hydrogen to the SiO interlayer leads to further degradation in the , while removing hydrogen fully recovers the surface passivation. In addition, the proposed model explains the dependence of firing stability on the crystallite properties and the doping profile, which determine the effective diffusivity of hydrogen upon firing and hence the amount of hydrogen around the interfacial SiO after firing.
先前已经表明，氧化硅上的异位磷掺杂多晶硅（多晶硅/二氧化硅）钝化接触在800°C或更高温度下进行烧制处理时，会遭受明显的表面钝化退化。退化行为强烈依赖于加工条件，如介电涂层和烧制温度。当前工作进一步研究了多晶硅接触的烧制稳定性，并基于氢的作用为观察到的行为提出了一种机制。应用二次离子质谱法测量在不同温度下烧制后以及在氮气中退火去除氢之后多晶硅/二氧化硅结构中的氢浓度。虽然已知界面二氧化硅周围一定量的氢有利于钝化，但令人惊讶的是，我们发现过量的氢会使多晶硅钝化恶化并增加复合电流密度参数。在选用氮化硅（SiN）烧制的多晶硅样品中，过量氢的存在很明显，其中向二氧化硅中间层注入额外的氢会导致进一步退化，而完全去除氢则能使表面钝化完全恢复。此外，所提出的模型解释了烧制稳定性对微晶特性和掺杂分布的依赖性，这决定了烧制时氢的有效扩散率，从而决定了烧制后界面二氧化硅周围的氢量。
