Evaluation of Crystal Lattice Rotation around a Stress-Induced Twin in a Step-Graded SiGe / Si(110) Using STEM Moiré Observation and its Image Analysis
Evaluation of Crystal Lattice Rotation around a Stress-Induced Twin in a Step-Graded SiGe / Si(110) Using STEM Moiré Observation and its Image Analysis
复制标题
使用 STEM 莫尔条纹评估阶梯梯度 SiGe / Si(110) 中应力诱导孪晶周围的晶格旋转
DOI：
10.1017/s1431927619001946
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发表时间：
2019
影响因子：
2.8
通讯作者：
and Kazuo Ishizuka
中科院分区：
文献类型：
--
作者：
Junji Yamanaka;Chiaya Yamamoto;Mai Shirakura;Kosuke O. Hara;Keisuke Arimoto;Kiyokazu Nakagawa;Akimitsu Ishizuka;and Kazuo Ishizuka
弹性晶格应变对半导体材料的电学性能影响很大。例如，应变硅表现出比普通硅更高的载流子迁移率。SiGe虚拟衬底通常用于生产应变Si[1,2]。关键是SiGe晶格必须是松弛的，否则就不可能在SiGe上产生应变的Si。因此，分析应变Si和SiGe虚拟衬底的晶格应变是很重要的。当我们不需要纳米级空间分辨率时，拉曼光谱和x射线互反映射（XRM）对分析晶格应变是有用的。另一方面，TEM相关的方法，如高分辨率TEM/STEM图像和纳米束电子衍射，在空间分辨率很重要的情况下是有用的，尽管这些TEM相关的方法不适合获得微米级区域的数据。近年来，一些研究者报道了一种分析晶格应变的新方法[3,4]。这种新方法使用了一种STEM扫描线和晶格之间的moiririse。该方法可以获得大范围的数据，且具有良好的空间分辨率。我们也报道了这种技术的使用，特别是从不使用cs校正机器的角度来看[5,6]。我们报道了由于锗成分变化而导致SiGe晶格间距轻微变化的可行性研究。在这项研究中，我们重点研究了SiGe中应力诱导孪晶周围的局部晶格旋转。我们研究晶格间距的同一样品被用于本研究，因此我们展示了样品制备过程的本质[6]。采用MBE法制备了Si/SiGe/Si（110）异质结构。SiGe部分由1层厚（440 nm）层和9层薄（各40 nm）层组成。我们用XRM评估了厚SiGe层的Ge成分为22 at%。薄层的Ge含量分别为19.8、17.6、15.4、13.2、11、…、4.4、2.2 at%。在40和10 kV的加速电压下，用FIB制备了用于STEM观测的箔片。采用现场发射型STEM (FEI Tecnai Osiris)，没有任何Cs校正器，加速电压为200 kV。利用商用软件smoir<s:1> (HREM Research Inc.)来分析来自STEM moir<s:1>[4]的晶格旋转。
Elastic lattice strain strongly affects electric properties of semiconductor materials. For example, a strained Si exhibits higher carrier-mobility than an ordinary Si. SiGe virtual substrates are commonly used to produce the strained Si [1, 2]. The key point is that the SiGe lattice must be relaxed, otherwise it is impossible to produce the strained Si on the SiGe. Therefore, it is important to analyze lattice strain of both the strained Si and the SiGe virtual substrate. Raman spectroscopy and X-ray reciprocal mapping (XRM) are useful to analyze lattice strain when we don’t need nm-order spatial resolution. On the other hand, TEM related methods such as high resolution TEM/STEM images and nano-beam electron diffraction are useful in the case that the spatial resolution is important, although these TEM related methods are not suitable to acquire the data from micrometer order area. Recently a new method to analyze lattice strain was reported by some researchers [3, 4]. The new method uses a STEM moiré, a moiré between scanning lines of STEM and crystal lattice. This method can acquire data from a wide area with good spatial resolution. We also reported the usage of this technique, especially from the viewpoint of without using Cs-corrected machines [5, 6]. We reported our feasibility study about a slight change of lattice spacing of the SiGe due to Ge composition change [6]. In this study we focused on the local lattice rotation around a stress-induced twin in the SiGe.The same specimen which we had investigated lattice spacing was used for this study so we show just the essence of the specimen preparation procedure [6]. A Si/SiGe/Si (110) hetero-structure was produced using MBE. The SiGe part was composed of 1 thick (440 nm) layer and 9 thin (40 nm each) layers. We evaluated the Ge composition of the thick SiGe layer was 22 at% using XRM. The Ge composition of the thin layers were estimated to be 19.8, 17.6, 15.4, 13.2, 11,…, 4.4, 2.2 at%. The foil for the STEM observation was fabricated by using FIB with Ga+ ions acceleration voltage of 40 and 10 kV. A fieldemission type STEM (FEI Tecnai Osiris) without any Cs correctors was utilized with an acceleration voltage of 200 kV. Commercially available software sMoiré (HREM Research Inc.) was utilized in order to analyze the lattice rotation from the STEM moiré [4].