Development of a nanoscale point-defect analysis method using convergent-beam electron diffraction and its application to point-defect-induced properties

为了在纳米尺度空间分辨率下定量分析点缺陷的原子结构、分布及其周围区域的局域晶格应变，本研究以掺杂Si为点缺陷试件，在会聚束电子衍射（CBED）图的低阶反射摇摆曲线中发现了异常的强度增加现象.为了弄清点缺陷引起的反常强度与应变之间的关系，用透射电镜测量了不同掺杂量样品的反常摇摆曲线强度，确定了不引起反常强度的样品制备方法。同时发现，除了掺杂杂质原子外，离子注入产生的原子和小团簇也能引起强度的异常增加.基于平行-动力学衍射理论、多层切片法和Howie-Whelan方法，开发了摇摆曲线的模拟程序.利用不同的应变分布模型对摇摆曲线进行了模拟，并与实验数据进行了比较，结果表明，这种反常的CBED摇摆曲线可以用晶格弯曲的应变弛豫模型来解释。这意味着CBED低阶反射的摇摆曲线可以成功地用于确定具有纳米级空间分辨率的局部应变分布。到目前为止，半导体器件的局部晶格应变已经使用CBED高阶劳厄区（HOLZ）线图案进行了检查。本方法使我们能够分析这样的高应变区HOLZ线模糊或不清晰，HOLZ线方法不能应用。

The present research project aimed to develop a method to quantitatively analyze the atomic structure and distribution of point defects and the local lattice strain of their surrounding areas in a nanometer-scale spatial resolution.Impurity-doped Si was used as a test specimen containing point defects, in which anomalous intensity increase was found in rocking curves of low-order reflections of convergent-beam electron diffraction (CBED) patterns. In order to clarify the relationship between the anomalous intensity and the strain due to point defects, the intensities of the anomalous rocking curves were measured from specimens with various doping amounts using an energy-filter transmission electron microscope.The specimen preparation method not to cause the anomalous intensity was established. It was also found that the anomalous intensity increase can be caused by not only doped impurity atoms but also the atoms and small clusters induced by ion implantation.Simulation programs for the rocking curves was developed based on the statistical-dynamical diffraction theory, the multi-slice method and the Howie-Whelan's method. Simulations of rocking curves were performed using various strain distribution models and were compared with the experimental data.As a result, we have demonstrated that the anomalous CBED rocking curves can be explained by a strain-relaxation model with lattice bending. This implies that the CBED rocking curves of the low-order reflections can be successfully used for the determination of local strain distributions with a nanometer-scale spatial resolution.Local lattice strains of semiconductor devices have been so far examined using higher-order Laue zone (HOLZ) line patterns of CBED. The present method enables us to analyze such highly strained areas as HOLZ lines are blurred or unclear, to which the HOLZ line method cannot be applied.