AVS 46th International Symposium
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuP

Paper AS-TuP12
Characterisation of Oxide on GaAs Wafer Surfaces with TOF-SIMS and ARXPS

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: B. Burkhardt, Universität Münster, Germany
Authors: B. Burkhardt, Universität Münster, Germany
O. Brox, Universität Münster, Germany
W. Fliegel, Freiberger Compound Materials GmbH, Germany
L. Wiedmann, Universität Münster, Germany
A. Kleinwechter, Freiberger Compound Materials GmbH, Germany
A. Benninghoven, Universität Münster, Germany
Correspondent: Click to Email
Molecular-beam epitaxy (MBE) on GaAs requires a thermally removable oxide. Therefore reliable techniques are needed to control oxides on the GaAs wafer surface in the production process. The quantitative oxide characterization (thickness and stoichiometry) can presently only be achieved by ARXPS. In this paper we compare results achieved with TOF-SIMS and ARXPS. The experiments were performed in a reflectron based TOF instrument equipped with an 8'' manipulator for macroscanning and a dual beam source for depth profiling (sputter beam: 500eV Cs@super +@, analysis beam: 10kV Ar@super +@). For ARXPS we used a spherical electron analyzer with multichannel detector and monochromator X-ray source (Al K@alpha@: 1486,6 eV). For ARXPS data interpretation we assumed a 4-layer-system for the GaAs oxide. Separating the XPS signal into different oxide states we determined thickness and stoichiometry of each layer. Dual beam depth profiling was used to characterize the oxide layer by means of SIMS. The integrals of the secondary ions AsO@sub n@@super -@ and GaO@sub n@@super -@ over the sputter depth can be correlated to the oxide thickness and the various oxide phases as identified by ARXPS. The use of SF@sub 5@@super +@ primary ions allowed the detection of Ga@sub m@As@sub n@@super ±@ cluster ions with more than 40 atoms. The Ga/As ratio of these clusters changes with storage time and can be taken as a measure of stoichiometry changes in the uppermost atomic layer. Using ARXPS for calibration TOF-SIMS has shown to be a suitable technique to control the oxide layer on GaAs wafer.