利用电导技术研究快速热氮化二氧化硅与硅界面的性质

本文介绍了尼科里安-科兹伯格(Nicollian-Goetzberger)电导技术及其基本原理,建立了采用双相锁相放大器的测试系统,利用它测量了常规热氮化和快速热氮化SiO_2薄膜与Si衬底的界面性质,包括界面态密度,空穴俘获截面,表面势起伏,以及界面态时间常数等,并对它们进行了分析和讨论。研究结果表明:氮化会增加界面态的密度和平均时间常数,会增强表面势起伏,但只是轻微地改变空穴俘获截面.特别地,氮化还导致界面态密度在禁带中央以下0.2-0.25eV处出现峰值以及削弱了空穴俘获截面对能带能量的依赖关系.利用一个阵列模型,可以较好地模拟表面势起伏的标准偏差并可由此推断表面势起伏是由长波形式的界面态电荷非均匀性所引起.这个结果和氮化会导致高密度氧化层电荷的事实相一致.而以上所有界面态的性质,都与氮化的时间和温度有关.

Investigation of Rapid Thermally Nitrided-SiO_2/Si Interface with Conductance Technique

The device-quality SiO_2 films with a thickness of 15 nm have been nitrided in NH_3 byrapid thermal processing technique.The properties of the interface between these films andSi substrate were investigated by conductance technique using a measurement system equippedwith precision lock-in amplifier. The results show that the nitridation increases the densityand time constant of interface states,enhances the fluctuation of surface potential, but chang-es the hole capture cross-section only slightly.Especially, nitridation introduces a peak of in-terface states at 0.25 eV below midgap and the energy dependency of hole capture cross-sec-tion is suppressed. Using a patchwork model, the surface potential fluctuation can be well si-mulated and a surface charge nonuniformity with a long-way length distribution may exist.These are consistent with the fact that nitridation induces a high oxide charge density.Theexperimental data show that all these properties depend on nitridation time and temperature.