2011 年 54 巻 4 号 p. 241-247
In very shallow silicon transistor, it has been required to detect individual dopant atoms. High angle annular dark field (HAADF) image is a powerful tool for composition analysis at an atomic level, but it has been two-dimensional information. Recently, aberration corrected electron microscope has been developed, which enable us to have an electron probe with large convergent angle. Such a probe has been pointed out to improve not only transverse resolution but also depth resolution on a nanometer scale. We found that the column intensity in the HAADF image depended on the z-position of arsenic (As) dopant atoms on the condition that the specimen was very thin and the incident electron beam was irradiated along the  direction of the silicon crystal. It means that the position of As dopant atom can be determined three-dimensionally. This is an advantage of obtaining three dimensional distribution of As dopant atoms in the silicon crystal and also finding which type of dopant cluster is formed.