In semiconductor and photovoltaic
industries numerous process steps
deal with etching and silicon surface modification. The present study
focuses on the reactivity of HF-H2O2-based mixtures
toward silicon surfaces in a wide range of concentrations. The generally
very moderate reactivity is investigated regarding kinetic aspects
and the silicon dissolution reactions. The activation energy of silicon
dissolution in HF-H2O2 mixtures is determined
to be ∼50 kJ/mol, which supports a surface reaction controlled
mechanism. This interpretation is checked by oxidation experiments
of Si surfaces with HF-free H2O2 solutions.
Resulting silicon surfaces were characterized by means of diffuse
reflection Fourier transform infrared spectroscopy and photoelectron
spectroscopy. Surface properties give hints for an “electrochemical”
silicon oxidation. Furthermore, the oxidation behavior of different
H2O2 solutions is compared to that of HNO3 solutions. All results suggest kinetically limited silicon
dissolution in HF-H2O2 mixtures and hole injection
into the silicon surface to be the rate-determining part of the reaction
process.
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