Plasma and vacuum ultraviolet induced charging of SiO2 and HfO2 patterned structures

The authors compare the effects of plasma charging and vacuum ultraviolet (VUV) irradiation on oxidized patterned Si structures with and without atomic-layer-deposited HfO2. It was found that, unlike planar oxidized Si wafers, oxidized patterned Si wafers charge up significantly after exposure in an electron-cyclotron resonance plasma. The charging is dependent on the aspect ratio of the patterned structures. This is attributed to electron and/or ion shading during plasma exposure. The addition of a 10 nm thick HfO2 layer deposited on top of the oxidized silicon structures increases the photoemission yield during VUV irradiation, resulting in more trapped positive charge compared to patterns without the HfO2 dielectric.