反射法-椭偏法揭示了铜氧化过程中的厚度，生长速率和相组成,ACS Applied Materials & Interfaces

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反射法-椭偏法揭示了铜氧化过程中的厚度，生长速率和相组成
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2016-08-16 00:00:00 , DOI: 10.1021/acsami.6b06626
Juan J. Diaz Leon _{1,

2} , David M. Fryauf _{1,

2} , Robert D. Cormia ₃ , Min-Xian Max Zhang ₄ , Kathryn Samuels ₄ , R. Stanley Williams ₄ , Nobuhiko P. Kobayashi _{1,

2}

Affiliation

铜的氧化是一个复杂的过程。氧化铜在室温和标准压力（RTSP）下会形成两个稳定相：氧化亚铜（Cu ₂O）和氧化铜（CuO）。这两相具有不同的光学和电气特性，这使它们对于太阳能电池或电阻式开关设备等应用很有趣。对于给定的应用，必须有选择地控制氧化物的厚度和氧化铜/氧化亚铜相的体积分数。在铜表面上生长的氧化铜膜的厚度和组成在很大程度上取决于所沉积的铜的特性。在这篇研究文章中，研究了两种样品，即通过两种不同的沉积技术（电子束蒸发和溅射）制备的铜膜。作为研究的核心部分，使用光谱偏振偏光反射光谱法-椭圆偏振光谱法（RE）在253天的时间内常规分析了氧化铜的形成。使用有效的介质近似（EMA）模型拟合RE数据。通过使用X射线光电子能谱（XPS），原子力显微镜（AFM）和X射线衍射（XRD）对RE测量进行补充和验证。我们的结果表明，在相同的实验室环境条件（RTSP，平均相对湿度为87％）下氧化的两个样品，其反比对数的生长速率和厚度和成分随时间的变化而形成了独特的氧化膜。讨论的重点是稀土元素同时提取氧化铜膜的厚度（即生长速率）和组成的能力，以及在两个铜样品中观察到的独特氧化习惯的合理物理机制。似乎扩展了表面特性（即，表面粗糙度和晶界）以及沉积的多晶铜膜的优先晶体取向控制了氧化铜膜的生长动力学。基于非接触式和非破坏性测量（例如RE）的分析以提取关键材料参数，对于方便地了解最终使制造规模的氧化铜基器件得以实现的氧化过程而言，是非常有益的。

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Reflectometry–Ellipsometry Reveals Thickness, Growth Rate, and Phase Composition in Oxidation of Copper

The oxidation of copper is a complicated process. Copper oxide develops two stable phases at room temperature and standard pressure (RTSP): cuprous oxide (Cu₂O) and cupric oxide (CuO). Both phases have different optical and electrical characteristics that make them interesting for applications such as solar cells or resistive switching devices. For a given application, it is necessary to selectively control oxide thickness and cupric/cuprous oxide phase volume fraction. The thickness and composition of a copper oxide film growing on the surface of copper widely depend on the characteristics of as-deposited copper. In this Research Article, two samples, copper films prepared by two different deposition techniques, electron-beam evaporation and sputtering, were studied. As the core part of the study, the formation of the oxidized copper was analyzed routinely over a period of 253 days using spectroscopic polarized reflectometry-spectroscopic ellipsometry (RE). An effective medium approximation (EMA) model was used to fit the RE data. The RE measurements were complemented and validated by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD). Our results show that the two samples oxidized under identical laboratory ambient conditions (RTSP, 87% average relative humidity) developed unique oxide films following an inverse-logarithmic growth rate with thickness and composition different from each other over time. Discussion is focused on the ability of RE to simultaneously extract thickness (i.e., growth rate) and composition of copper oxide films and on plausible physical mechanisms responsible for unique oxidation habits observed in the two copper samples. It appears that extended surface characteristics (i.e., surface roughness and grain boundaries) and preferential crystalline orientation of as-deposited polycrystalline copper films control the growth kinetics of the copper oxide film. Analysis based on a noncontact and nondestructive measurement, such as RE, to extract key material parameters is beneficial for conveniently understanding the oxidation process that would ultimately enable copper oxide-based devices at manufacturing scales.

更新日期：2016-08-16

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