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Three-dimensional imaging of individual hafnium atoms inside a semiconductor device

van Benthem, K., A. R. Lupini, M. Kim, H. S. Baik, S. Doh, J. H. Lee, M. P. Oxley, S. D. Findlay, L. J. Allen, J. T. Luck and S. J. Pennycook

Appl. Phys. Lett., 87, Art. No. 034104 (2005)

Aberration correction allows the probe-forming aperture of the microscope to be larger, improving image resolution not only in the transverse plane but also in depth. The greatly reduced depth of focus is now less than the typical thickness of a microscope specimen and three-dimensional reconstruction is possible through optical sectioning. A focal series of images has become a depth series. In this work, individual Hf atoms were located in the nanometer wide gate region of a Si/SiO2/HfO2 high dielectric constant device structure to a precision of around 0.1x0.1x0.5 nm. The nanometer depth resolution and single atom sensitivity represents two orders of magnitude higher volume resolution than tilt series tomography. At the same time this method was also being applied to catalysts, see
Borisevich, A. Y., A. R. Lupini and S. J. Pennycook, "Depth sectioning with the aberration-corrected scanning transmission electron microscope," Proc. Nat. Acad. Sci. USA, 103, 3044-3048 (2006).


A sequence of frames from a through-focal series of Z-contrast images of a Si/SiO2/HfO2 high dielectric constant device structure showing an individual Hf atom coming in and out of focus (circled). The HfO2 is seen brightly on the left, the Si lattice dimly on the right, and the Hf atoms are in the SiO2 gate oxide region. Results obtained with a VG Microscopes HB603U operating at 300 kV with a Nion aberration corrector.
   
 

1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge,
TN 37831, USA
2Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
3Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

   
 

 Oak Ridge National Laboratory