Surface treatment effects on Si(111) and (100) surface structures and Si/SiO2 interface state

Surface treatment effects on microscopic morphology of Si(111) and (100) surfaces have been investigated by atomic force microscope (AFM). Well-ordered atomic steps and flat terraces have been clearly observed on the Si(111) surfaces treated in 40% NH4F solution. Then, SiO2 films were deposited on these atomically flat substrates at 300 degrees Celsius by photo-CVD method. Interface state density of the Si/SiO2 structure with this flat surface is smaller than that of the substrate with disordered surface. On the other hand, in the case of Si(100) wafers, atomically flat structures have not been observed in the surfaces treated by 1% HF, 40% BHF, and HF/H2O2 solutions, and a lot of small and random unevennesses have been observed on each surface. Si/SiO2 interface state density decreases with decreasing average roughness of Si surface.