Electron holography for analysis of deep submicron devices: Present status and challenges
(a) Schematic of the electron optical geometry for electron holography in TEM. (b) Hologram of a MOSFET. The inset shows interference fringes.
Schematic of ion milling in a cross-sectional specimen prepared from a MOSFET device. In the present experiment, low-energy Ar-ion milling was used instead of conventional FIB. The Ar ion energy was and the irradiation was only from the back side (substrate side) of the specimens.
Electron holography phase maps of specimens prepared by using low-energy back side milling: (a) MOSFET without SD implantation and (c) -MOSFET. (e) shows a phase map of an FIB-prepared -MOSFET specimen. (b), (d), and (f) show line profiles of phases measured along the dashed lines in (a), (c), and (e), respectively. Dotted horizontal lines in (d) and (f) show phase values averaged over the regions denoted by the dotted lines. The phase of the MOSFET without SD implantation is uniform over the observation area [(a) and (d)], while the phase of the -MOSFET [(b) and (e)] is clearly different in the -and -type regions. The background of the measured phase is smaller in specimens prepared using low-energy ion milling than that in the FIB-prepared specimen. rms values of the fluctuations in the measured phase were in the former and in the latter.
Measured potential maps (left column) and simulated potential contour maps (right column) of the samples. In the measured potential maps, dark and bright regions correspond to -and -type regions. Solid lines indicate equipotential lines. In the simulated maps, black lines show metallurgical junction positions. Simulated equipotential lines are superimposed on the experimental images [dashed lines in (a), (c) and (e)]. The experimental and simulated equipotential lines agree with each other in each sample. Arrows in (d) indicate protrusions of SD regions produced by B channeling during implantation.
Line profiles of potential along line AB in Fig. 4(a). Closed circles and dashed curve show the measured and simulated potentials, which agree well with each other.
Effect of increasing the variables is shown in the left column on the experimental parameters in the top row. A plus (+) sign indicates an increase, a minus (−) sign indicates a decrease, and (nc) indicates no change in the parameters.
Sample preparation conditions.
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