Liquid junctions for characterization of electronic materials. III: Modulation spectroscopies of reactive ion etching of Si

Photoreflectance, electrolyte photoreflectance, and electrolyte electroreflectance (EER) were measured for various reactive ion etching (RIE) treatments of 〈100〉 n-Si that include CHF3/Ar, CF4, CClF3/H2, CClF3/H2, followed by O2 ash. For all the RIE-treated samples we observe a shift of the transition energy and splitting or broadening of the peaks. These spectral changes were interpreted in terms of tensile strain of the order of 1% caused by the surface damage. In all the cases except for CClF3/H2 the strain is two dimensional. The potential dependence of the EER shows that the CHF3/Ar and the CF4 treatments result in an accumulation of slow surface states that pin the dc potential but not the ac modulation. The CClF3/H2 results in a much smaller pinning that can be removed by O2 ash.