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Quantitative coverage and stability of hydrogen-passivation layers on HF-etched Si(1-x)Gex surfaces

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5 Author(s)
Wilde, M. ; Institute of Industrial Science, University of Tokyo, Komaba-4-6-1, Meguro-ku, 153-8505 Tokyo, Japan ; Fukutani, K. ; Koh, S. ; Sawano, K.
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This study investigates the stability of surface hydride layers passivating silicon-germanium alloys against contamination in ambient conditions after treatment in dilute hydrofluoric acid (HF), which is of central importance to the fabrication of SiGe-based semiconductor devices. We report quantitative hydrogen coverages on HF-etched Si(1-x)Gex surfaces (x=0,0.30,0.60,0.82), determined after air-to-vacuum transfer by H-specific 1H(15N,αγ)12C nuclear reaction analysis. Combination of this coverage information with analysis of the zero-point vibrational properties and 15N-ion-induced desorption kinetics of the surface H atoms enables the distinction of well-passivated SiGe surfaces terminated exclusively by hydrides of Si and Ge from those partially covered by contaminating adsorbates. It is found that the resistance of HF-etched Si(1-x)Gex alloys against recontamination is drastically reduced at increasing Ge contents. Pure Si(100)–H is stably passivated at least up to 1 week in air by a layer of 1.3±0.1 monolayer total H coverage. Si0.70Ge0.30 initially resembles H-passivated Si(100) but shows indications of moderate contamination after 1 week in air. The HF treatment does not produce stable passivation layers on Ge-rich alloys (x≥0.60), which suffer heavy recontamination within minutes after removal from the HF solution.

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Journal of Applied Physics  (Volume:98 ,  Issue: 2 )