High-resolution SEM observation at the atomic level using a dedicated STEM with aberration correction

Abstract

We have developed a high-resolution secondary electron (SE) imaging technique using a dedicated scanning transmission electron microscope (STEM) instrument with a high efficiency SE detector (Hitachi HD-2700) in order to investigate the structural characterization at the atomic level without thin film processing. The HD-2700 is equipped with a CEOS GmbH spherical aberration (Cs) corrector and can routinely achieve 1Å spatial resolution in SE and STEM imaging. We applied this technique for high accuracy critical dimension measurements of semiconductor materials using aberration corrected SE imaging. We have observed the cross sectional SE image of a semiconductor transistor along the Si[011] zone axis. The specimen thickness was 1μm and an accelerating voltage of 200 kV was used to observe the semiconductor structures, such as a metal gate. Under these conditions the high-k gate insulating layer, source, and drain structures can be clearly seen. The higher magnification SE images show that it is possible to resolve the Si111 plane, which has a spacing of 0.314 nm, and these images can be used for magnification calibration. These results indicate the ability to perform high precision measurements of crystal lattices for the structural characterization of semiconductor materials.