Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 26: Interfaces/surfaces

HL 26.3: Vortrag

Dienstag, 27. März 2007, 16:30–16:45, H14

Noninvasive Detection of Alkali Metal Ion Contaminations of Si(100)/SiO₂ Interfaces by Optical Second-Harmonic Generation — •Armin Rumpel¹, Bastian Manschwetus¹, Gerhard Lilienkamp¹, Harald Schmidt², and Winfried Daum¹ — ¹Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstr. 4, D-38678 Clausthal-Zellerfeld — ²Institut für Metallurgie, TU Clausthal, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld

Optical second-harmonic generation (SHG) is demonstrated as a nondestructive probe of alkali metal ion contaminations in Si(100)/SiO₂ gate oxide systems. Accumulation of sodium or potassium ions in the near-interface region of the oxide leads to a strong resonant enhancement of the SHG signal between 3.2 eV and 3.8 eV. This enhancement is caused by dc-electric-field-induced SHG in a negatively charged space charge region of the semiconductor. The temperature dependence of the SHG signal from a potassium-contaminated Si(100)/SiO₂ system, measured for a two-photon energy of 3.3 eV, exhibits a slow initial decrease followed by a steep rise of the signal at a temperature of about 380 ^∘C. The decrease of the signal is caused by the temperature dependence of the E₁ interband resonance while the strong increase indicates the onset of potassium diffusion from the surface of the oxide to the near-interface region. The accumulation of potassium near the Si(100)/SiO₂ interface of the heated sample has been verified by SIMS measurements.