Local Anodic Oxidation Induced by Electric Fields of MV/cm at AFM Silicon Nitride Tips on Silicon Surfaces

Local anodic oxidation of silicon using Atomic Force Microscopy (AFM) was investigated by applying a negative voltage between a silicon nitride tip and p+doped Si (111) surfaces. Numerical simulations of the electric field at the silicon nitride tip apex on the silicon presented values next to 1x106 V/cm, which is ten times lower than that obtained from conductive tips. In addition, a last ammonium-based cleaning known as standard cleaning 1 (SC1) was a necessary pre-conditioning for anodic oxidation to occur using negative applied potentials (Vtip) ranging from -15 to -22.5V. The anodic oxidation was performed from 0 to 144 hours after SC1. Localized squares patterns of oxide, 0.25 μm2 in area, were formed by growing parallel lines with constant interlinear spacing and length and several scans in the same area. It was noteworthy that oxide thickness increased with the applied negative voltage, number of scans and interval of time after SC1. As a result, the high hydrophilic characteristic of the SC1-last cleaning allowed establishing a local oxidation process assisted by lower electric fields (1x106 V/cm) and by diffusion of ionic species generated from adsorbed water after SC1.