Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 25: Poster 1

HL 25.43: Poster

Wednesday, September 7, 2022, 18:00–20:00, P2

Contactless mapping of the sheet resistance of GaAs samples — •Timo A. Kurschat, Arne Ludwig, and Andreas D. Wieck — Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, D-44780 Bochum

Measurements of the sheet resistance without the need to break the sample and integrate electrical contacts enable the evaluation of the homogeneity and quality of samples before further processing. Spatially resolved maps can be created without destroying or modifying the wafer.

The sheet resistance is measured by placing the sample on top of two circular electrodes. These couple capacitively with the conducting layer through the substrate. When applying a high frequency alternating voltage at one electrode, a signal can be measured at the other one. The sheet resistance is measured by sweeping the frequency from 1 MHz to 400 MHz and applying a fit. The setup works for sheet resistances between 300 Ω/ and 50 kΩ/.

The measured resistance and the coupling capacitances depend on the geometry of the sample and the electrodes. The changes at the edges of a sample are shown with line scans across a quarter 3" wafer and across a 5 mm wide sample. To show the effect of changes in the sheet resistance, the conducting layer was partly removed by etching. This shows artifacts especially if one electrode is completely below an isolating region. The spatial resolution depends strongly on the orientation of the electrodes.