EFFECTS OF DISSOLVED-OXYGEN IN HF SOLUTION ON SILICON SURFACE-MORPHOLOGY

Surface morphology changes on atomically flat hydrogen-terminated Si(111) in various dissolved oxygen concentration (DOC) hydrofluoric acid (HF) solutions were studied using Fourier-transformed IR attenuated total reflection spectroscopy (FT-IR-ATR). The sharp absorption peak attributed to silicon monohydrides at the surface terraces decreases and the absorption peaks attributed to silicon monohydrides at the surface steps, dihydrides and trihydrides increase with immersion time in HF solutions at any DOC. These results indicate that the atomically flat hydrogen-terminated surfaces were roughened in HF solutions and the rate of such spectral change, i.e., surface morphology change, decreased as the DOC of HF solution decreased. Such surface morphology change implies that the HF solution etches silicon surface, therefore, the dissolved oxygen in an HF solution plays an important role in the silicon etching.