Effects of HF cleaning and subsequent heating on the electrical properties of silicon (100) surfaces

Abstract

Changes in surface-band bending of both boron-doped and phosphorus-doped silicon (100) samples by exposure (40 s) to hydrofluoric acid (HF) with varying HF concentrations were studied by x-ray photoelectron spectroscopy. Effects of subsequent thermal annealing was investigated by in situ heating in vacuum. Hydrogen termination of the dangling bonds on silicon was found to be an effective means to reduce surface gap states on silicon. Near-flatband surfaces were observed on both n- and p-Si by the HF exposure when the doping concentration was not less than 1×1016/cm3, and when the HF concentration was not higher than 5%. A higher HF concentration promoted hydrogen diffusion and the formation of an H-B species in p-Si. As such, band bending increased on p-Si. However, the deactivation of boron could be recovered by annealing for less than 1 h at a temperature as low a 120 °C.