电子器件中铜及ITO薄膜电极的腐蚀行为研究

【作者】 曹思；

【导师】 李劲； 蒋益明；

【作者基本信息】 复旦大学 ， 物理电子学， 2011， 硕士

【摘要】 铜薄膜由于具有优良的电学、热学与力学综合性能,在电子器件中获得了广泛的应用。许多功能器件如传感器、光电存储器中大量涉及铜薄膜材料。随着电子器件尺寸减小,膜的大气隔层厚度降低,制造与使用中的腐蚀影响不容忽视,薄膜氧化就是其中的一个重要方面,因为这将导致薄膜的损伤,还有器件性能的降低或失效。在实际应用环境中,还不可避免有水汽的影响。澄清薄膜的氧化规律对特殊结构膜的制备、可控纳米结构的实现、薄膜结构的稳定性以及薄膜应用与失效分析等都具有重要意义。氧化铟锡(Indium Tin Oxide, ITO)透明导电薄膜,诞生五十多年以前,是一种重要的光电材料。ITO薄膜既有高导电性,又在可见光范围内有很高的透光性,且在红外光范围内有很高的反射性,在光电产业中有着广阔的应用前景。具体在太阳能电池、平板显示、气敏器件、节能建筑窗和航空航天领域它都已经得到了广泛的应用。在电子器件中ITO薄膜常常作为电极浸入相应的溶液体系里,或者电化学沉积其它物质构成太阳能电池,亦或作为基板电镀上需要进行光谱分析和电化学分析的反应物。因此它在上述体系中的电化学稳定性就是一个至关重要的问题。本文选取铜薄膜和ITO透明导电薄膜为研究对象。首先研究了金属铜薄膜体系在水汽中的氧化行为,利用同位素示踪法分析其氧化传质规律,构建了铜薄膜湿法氧化的传质模型。其次系统研究了ITO透明导电薄膜在碱性溶液中的阴极极化反应规律,运用电化学阻抗谱的方法分析了ITO薄膜阴极极化腐蚀的等效电路及其电极元件的各项参数在腐蚀过程中的变化,并了解了溶液各参数对ITO阴极极化反应速率和程度影响的规律。得到以下结论：1.同位素示踪法是一种有效且直接的探明材料氧化微观传质机制的方法。具体过程是,首先对Cu薄膜样品先后通H216O和H2180蒸汽,然后采用二次离子质谱(SIMS),分析同位素元素16O与18O氧化膜中的计数分布及其变化规律,最后根据SIMS谱图讨论Cu薄膜氧化微观传质机制。2.研究了铜薄膜体系在水汽中的氧化传质机制。由在H216O/H218O中各1.5小时接续氧化后的SIMS计数-溅射时间图可以看出,在对数坐标下随着溅射时间的增加,也即溅射深度的增加,16O原子在膜内分布缓慢下降,而18O原子计数则呈现上升的趋势。说明在300℃下,水汽环境中Cu的氧化机制为水分子短路扩散机制,也即同位素H218O通过氧化膜短路扩散进入内表面与Cu反应,在扩散过程中不会直接替换氧化膜网格上的160原子。3.确立了电化学阻抗谱在ITO薄膜电化学腐蚀表征方面的应用。利用电化学阻抗谱表征了ITO薄膜阴极极化腐蚀的过程。具体即选取时长3000s的ITO薄膜阴极极化J-t曲线中8个典型时间节点,通过这8个处于不同反应阶段的样品进行电化学阻抗谱分析,来了解ITO薄膜阴极极化腐蚀过程中其与溶液界面电极系统的各项参数,从而获得ITO薄膜阴极极化腐蚀反应的详细过程和机理。同时也证明了EIS可以用于ITO薄膜电化学腐蚀的表征。4.了解了ITO薄膜阴极极化的过程。根据电化学阻抗谱图建立了ITO薄膜阴极极化腐蚀样品的等效电路图。根据拟合结果可以看出,ITO薄膜极化腐蚀过程中,双电层电容不断增大,传递电阻不断减小,由薄膜表面吸附物即腐蚀产物金属态In的弛豫效应引起的电感也处于不断减小的过程。5.证实了ITO薄膜在碱性溶液中阴极极化腐蚀速度和程度受溶液pH值、温度、Cl-浓度等参数的影响。在溶液pH值为碱性的溶液内,由电化学阻抗谱的结果可以看出,溶液pH值的增加使得腐蚀速率加快,方块电阻的测量表明腐蚀程度也随之增强；在0.1mol/L的NaOH溶液体系下,温度的上升明显提高了ITO薄膜阴极极化的速度和程度；Cl-离子浓度的增加也能起到同样的影响。更多还原

【Abstract】 Copper thin film has gained tremendous application in electronic devices, thanks to its excellent electronic, thermal and mechanical properties. It can be found in many functional devices like sensors and photoelectric memorizers. As the size of electronic devices goes down and the thickness of thin films decreases, corrosion problems in manufacturing and processing are becoming severe, especially thin film oxidation. In real application environment, water vapor is also unavoidable. To clarify the law of transport in thin film will have great impact on both science and practice.Indium Tin Oxides (ITO) thin films are important optoelectronic materials, which are are both transparent to visible light and electrically conductive. ITO films have been widely used in the fields of flat panel display, solar cells, anti-frost glass, gas sensing devices, energy saving window, aeronautics and astronautics etc. In addtion, ITO films have a broad application as transparent electrodes for electrochemical deposition, with which transmission spectrums of reactants could be obtained after deposition. In these applications, the electrochemical stability turns to be a very significant scientific issue.In this paper, copper and ITO films are chosen to be studied. Firstly, the transport mechanism of copper thin film oxidation in water vapor is studied by using H216O/H218O isotopic labeling. Secondly, the electrochemical corrosion behaviors of ITO films during cathodic polarizations are investigated in sodium hydroxide solutions by means of Electrochemical Impedance Spectrums. The impacts of reaction parameters on corrosion rate and extent are also obtained. The results are as follows:1. Isotopic labeling was proved to be effective and direct in studying the transport mechanism of metal materials. Copper thin films were exposed to H216O and H218O vapor in succession. The distribution of 16O and 18O in the oxide film was then analysed by means of secondary ion mass spectroscopy (SIMS), according to which the transport mechanism of copper film oxidation was discussed.2. The SIMS results demonstrated that the transport mechanism of copper thin film oxidation is short circuit diffusion mechanism.3. Electrochemical impedance spectrums (EIS) had been built to characterize electrochemical corrosion of ITO thin films. In detail, cathodic polarization process of ITO thin films was studied by EIS. 4. According to EIS, the equivalent circuits of ITO film electrode were obtained. The parameters of equivalent circuit elements at different steps of the corrosion were calculated. With huge transfer resistance of solid-liquid interface between original ITO films and solutions, it decreased a lot during the corrosion process.That’s because the surface area of ITO electrode increased and metallic In was generated and absorbed to the surface, which made original semiconductor-solution interface turned to be metal-solution one.5. With the increased pH value, temperature of the solutions and the concentration of Cl+, both the rate and the extent of the ITO films’electrochemical corrosion were enhanced.更多还原