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HL: Halbleiterphysik
HL 48: Preparation and characterization
HL 48.2: Talk
Thursday, March 30, 2006, 15:30–15:45, POT 151
Impact of Focussed Ion Beam (FIB) Preparation on the Potential Structure of Silicon Semiconductors — •Andreas Lenk1 and Uwe Mühle2 — 1Institute of Structure Physics, Triebenberg Laboratory, Dresden University, 01062 Dresden, Germany — 2Infineon Technologies Dresden GmbH & Co OHG, Germany
The electrical features of a semiconductor device are mainly determined by the dopant distribution in its matrix, which is not visible in a Transmission Electron Microscope (TEM). Electron holography, however, allows 2D mapping of electrical potentials. Since the inner electrical potential of a semiconductor is shifted in the doped regions, holography can provide 2D mappings of dopant distributions.
Because electron holography is very sensitive also against thickness variations, a homogeneously thick specimen is needed. The most efficient tool for a respective specimen preparation is the Focussed Ion Beam (FIB), which uses 30kV gallium ions for target cutting of a thin, electron transparent membrane. Unfortunately, those very ions work also as p-type dopants in silicon.
For quantitative measurement, the influence of such additional, preparation-induced dopants has to be considered. Therefore, FIB-lamellae have been cross-sectioned and investigated with electron holography. It is shown that the gallium ions of a FIB do not only amorphize the crystalline silicon laterally, but also decrease the electric potential near the surface of the lamella.