Atomic transport in three-dimensional nanostructures of silicon and germanium

随着半导体器件小型化程度的提高，比表面积增大。因此，表面和界面的性质对于控制和设计纳米电子器件的电子性质将变得越来越重要。目前有关纳米物体中原子输运的实验结果非常有限。特别是，自扩散是凝聚态物质中最基本的质量输运过程，在纳米级的Si和Ge系统中还没有得到研究。在这个研究项目的框架内，我们将研究硅和锗纳米结构中自扩散的尺寸效应，以获得关于这些受限材料系统中本征点缺陷的性质的信息。为此，通过纳米压印光刻(NIL)或电子束光刻(EBL)，然后优先在低温下进行高各向异性反应离子刻蚀(RIE)，制备了不同宽度和直径的同位素调制的Si和Ge鳍片和柱状结构。同位素结构是研究结构尺寸、温度、掺杂浓度、环境和辐照条件下自扩散的理想测试结构。采用原子探针层析(APT)、二次离子质谱仪(SIMS)、中子反射仪(NR)、扫描扩展电阻显微镜(SSRM)、扫描开尔文探针显微镜(SKPM)和电化学电容电压谱(ECV)等技术，以高分辨率测量了标记基质和掺杂原子的分布。用扫描电子显微镜(SEM)和高分辨电子显微镜(HRTEM)分析了热处理前后硅和锗纳米物体的形貌和结构。将实验结果与计算机模拟进行比较，以建立考虑电子表面和界面态影响的纳米级Si和Ge系统中原子输运的有意义的物理模型。

With increasing downscaling of semiconductor devices the surface-to-volume ratio increases. Accordingly, the properties of surfaces and interfaces will become increasingly important to control and engineer the electronic properties of nanoelectronic devices. Present experimental results on atomic transport in nanoobjects are very limited. In particular, self-diffusion, that is the most fundamental process of mass transport in condensed matter, was not yet studied in nanoscaled Si and Ge systems. In the framework of this research project we will investigate size effects on self-diffusion in Si and Ge nanostructures to gain information on the properties of native point defects in these confined material systems. For this purpose isotopically modulated Si and Ge fin and pillar structures with different widths and diameters are prepared by means of nano imprint lithography (NIL) or electron beam lithography (EBL) followed by highly anisotropic reactive ion etching (RIE) preferentially performed at cryogenic temperatures. The isotope structures are ideal test structures for studying self-diffusion as function of the structure size, temperature, dopant concentration, ambient and irradiation conditions. The distribution of the labeled matrix and dopant atoms is measured with high resolution applying appropriate profiling techniques which involve atom probe tomography (APT), secondary ion mass spectrometry (SIMS), neutron reflectometry (NR), scanning spreading resistance microscopy (SSRM), scanning Kelvin probe microscopy (SKPM) and electrochemical capacitance voltage profiling (ECV). Scanning electron (SEM) and high resolution transmission electron microscopy (HRTEM) will be performed to analyze the morphology and structure of the Si and Ge nanoobjects before and after thermal treatments. The experimental results are compared to computer simulations to develop meaningful physical models of atomic transport in nanoscaled Si and Ge systems that consider the impact of electronic surface and interface states.