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

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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.