Wet-chemical passivation of Si(111)- and Si(100)-substrates

Abstract

The influence of preparation-induced surface roughness, as well as the hydrogen and oxide coverage on electronic properties of Si(111) and Si(100) surfaces was investigated by combining various surface-sensitive techniques. Simultaneous surface photovoltage (SPV) and spectroscopic ellipsometry (SE) measurements, both in the ultraviolet/visible (UV–VIS) and the infrared (IR) spectroscopic region, yielded detailed information about intrinsic and extrinsic surface states on hydrogen (H)-terminated Si(111) and Si(100) surfaces, immediately after the wet-chemical preparation as well as during the initial oxidation. The energetic distributions of interface states D it( E) on Si(100) and Si(111) surfaces were correlated to the surface roughness 〈 d r〉, the change of hydrogen coverage and the oxide growth on an atomic scale. As shown by these experiments, generally higher interface state densities D it, min were observed on Si(100) surfaces in comparison to Si(111). However, on Si(100) substrates a faster oxide growth and a significantly thicker final native oxide layer were found. The wet-chemical preparation methods of hydrogen or oxide passivated surfaces on Si(100) substrates were carefully optimized, resulting in smooth H-terminated surfaces (〈 d r〉≈4 Å and D it, min<5×10 10 cm −2 eV −1) and passivating oxide layers in the thickness range of 1–3 nm ( D it, min <5×10 11 eV −1 cm −2).