Investigation of Native Oxide Layers on Untreated and Chemically Treated InAlN Surfaces by X-ray Photoelectron Spectroscopy
Investigation of Native Oxide Layers on Untreated and Chemically Treated InAlN Surfaces by X-ray Photoelectron Spectroscopy
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DOI：
10.1149/2.004201ssl
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发表时间：
2012
影响因子：
--
通讯作者：
M. Akazawa;T. Nakano
中科院分区：
文献类型：
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作者：
M. Akazawa;T. Nakano
用X射线光电子能谱（XPS）研究了未处理和化学处理的氮化铝表面的自然氧化层的特征。使用氨（NH 4 OH）、盐酸（HCl）和氢氟酸（HF）进行化学处理。未处理的InAlN表面上的原生氧化物层被发现主要由氢氧化物组分组成。这些氢氧化物被HF处理完全去除，而其他处理导致不完全去除。NH 4 OH处理增加了In相关的氢氧化物组分的强度，表明氧化已经发生。这是证实了连续的NH 4 OH/HF处理施加到一个Al 2 O3 InAlN层，导致蚀刻。© 2012电化学学会。(DOI：10.1149/2.004201ssl）版权所有。为了提高器件的性能，应该根据对表面自然氧化层的理解，采用适当的制造工艺来控制金属-半导体和绝缘体-半导体界面。然而，本机氧化物层的化学成分还没有被详细研究InAlN。因此，应研究原生氧化物层的特性以找到去除方法，特别是使用用于制造半导体器件的生产线所熟悉的普通酸的方法，作为界面形成之前的适当预处理。此外，表面原生氧化物层的分析可以导致对器件制造工艺有用的知识。以前，氢氟酸（HF）处理被发现是有用的，用于消除表面自然氧化物层的影响，测量带偏移在InAlN-GaN异质结构的XPS。5，6然而，尚未实现对自然氧化层中化学键合的详细分析。此外，没有研究或比较用于去除InAlN自然氧化物层的任何其他普通的危险性较小的化学品。在这里，我们调查的天然氧化层的组成，并比较使用氨（NH 4 OH），盐酸（HCl），和HF溶液的处理之间的氧化物去除的效率。我们通过X射线光电子能谱（XPS）分析化学处理前后的原生氧化物组分。采用金属有机物气相外延（MOVPE）技术在蓝宝石（0001）衬底上的GaN缓冲层上生长了In 0.17Al 0.83N层。通过X射线衍射（XRD）证实了InAlN层的In摩尔分数为0.17，用于本XPS测量的全部3英寸晶片被分成块。因此，所研究的所有样品的摩尔分数是均匀的。每次处理前的初始表面称为未处理表面，是从生长室中取出样品后InAlN的空气暴露表面。HF和HCl处理在室温下进行，而NH 4 OH处理在50 ℃下进行。每次化学处理之后，用去离子（DI）水（18 Mcm -质量）冲洗，并用纯氮气吹扫，然后将样品立即引入真空中。需要用去离子水冲洗，以防止残留化学品污染真空系统。使用单色化的Al-Kα X射线源（1486.6 eV）进行XPS。通过调整样品表面C1 scorelevel的峰位置至285.0eV，校正了由绝缘衬底充电引起的结合能位移。必要时，通过倾斜样品来改变光电子出射角θ（定义为相对于样品表面的仰角），以改变样品表面C1 scorelevel的峰位置。
ThecharacteristicsofnativeoxidelayersonuntreatedandchemicallytreatedInAlNsurfaceswereinvestigatedbyX-rayphotoelectron spectroscopy (XPS). Ammonia (NH4OH), hydrochloric acid (HCl), and hydrofluoric acid (HF) were used for chemical treatment. The native oxide layer on an untreated InAlN surface was found to mainly consist of hydroxide components. These hydroxides were completely removed by HF treatment, whereas the other treatments resulted in incomplete removal. NH4OH treatment increased the intensity of the In-related hydroxide component, indicating that oxidation had occurred. This was confirmed by successive NH4OH/HF treatments applied to an ultrathin InAlN layer, which resulted in etching. © 2012 The Electrochemical Society. (DOI: 10.1149/2.004201ssl) All rights reserved. improve the device performance, an appropriate fabrication process should be applied to control the metal-semiconductor and insulator- semiconductor interfaces based on an understanding of the surface native oxide layer. However, the chemical composition of the native oxide layer has not been investigated in detail for InAlN. Therefore, the characteristics of the native oxide layer should be investigated to find a removal method, particularly one using ordinary acids familiar to the production lines used to fabricate semiconductor devices, as an appropriate pretreatment prior to interface formation. In addition, the analysis of surface native oxide layers may lead to knowledge useful for the device fabrication process. Previously, the hydrofluoric acid (HF) treatment was found to be useful for eliminating the effect of surface native oxide layers on measuring band offset at the InAlN- GaN hetero structures by XPS. 5,6 However, the detailed analysis of chemical bonding in native oxide layers have not been achieved. In addition, any other ordinary less dangerous chemicals to remove the InAlN native oxide layers were not investigated or compared. Here we investigate the composition of the native oxide layer and compare the efficiency of oxide removal among treatments using ammonia (NH4OH), hydrochloric acid (HCl), and HF solutions. We analyze the native oxide components before and after the chemical treatments by X-ray photoelectron spectroscopy (XPS). In0.17Al0.83N layers were grown on GaN buffer layers on sapphire (0001) substrates by metal-organic vapor phase epitaxy (MOVPE). The In molar fraction 0.17 of the InAlN layer was confirmed by X-raydiffraction(XRD)foralloverthe3-inchwafertobedividedinto pieces for the present XPS measurements. Consequently, the molar fraction was uniform for all samples under investigation. The initial surface before each treatment referred to as the untreated surface, was the air-exposed surface of InAlN after taking out the sample from the growth chamber. The HF and HCl treatments were carried out at room temperature, whereas the NH4OH treatment was carried out at 50 ◦ C. Each chemical treatment was followed by rinsing with deionized (DI) water (18 Mcm - quality), and blowing with pure nitrogen, then the samples were immediately introduced into vacuum. DI water rinsing was necessary to prevent pollution of the vacuum system by residual chemicals. XPS was performed using a monochromated Al-Kα X-ray source (1486.6 eV). The binding energy shift induced by the charging oftheinsulatingsubstratewascalibratedbyadjustingthepeakposition oftheC1scorelevelto285.0eVforeachsamplesurface.Ifnecessary, the photoelectron exit angle, θ, (defined as the elevation angle respect to the sample surface) was changed by tilting the sample to vary the