Phenomena and mechanism of local oxidation microlithography of 4H–SiC via electrochemical jet anodisation

Local oxidation microlithography (LOM) of 4H–SiC wafers based on the spatial confinement of electrochemical oxidation inside a microelectrolyte jet, namely, electrochemical jet anodisation (EJA), is presented. EJA enables selective growth of the oxide layer on a micro-scale local area with no masks because the anodic reaction occurs exclusively in the jet-substrate interaction area. The shape and height profile of the oxide layer were highly dependent on the anodising conditions. The change in the current density resulted in two distinct oxidation regimes, leading to the formation of either Gaussian-type or doughnut-shaped oxide spots. The oxide growth mechanism was revealed by SEM, AFM and XTEM characterisation of the oxide at the micro/nanoscale. A flat oxide layer with uniform thickness was obtained by applying parametric control. Following a chemical etching process, microstructures were readily created at the patterned oxide locations, demonstrating EJA as a potential lithography technique for microfabrication.