Jalal Rouhi and colleagues at Universiti Sains Malaysia and Universiti Teknologi Petronas in Malaysia have demonstrated impressive levels of control over the shape and gap width of silicon electrodes using an approach that combines local anodic oxidation and wet etching.
Local anodic oxidation (LAO) lithography using an atomic force microscopy tip has proved a valuable technique for fabricating nanoscale electronics structures. Rouhi and colleagues applied a statistical system to LAO lithography of silicon wafers and made a comprehensive study of the effects of writing speed, voltage and relative humidity on the oxide dimensions, as well as the interdependence between these factors. The resulting precisely fabricated oxide-silicon structures acted as etching masks.
They then applied their understanding of anisotropic tetramethylammonium hydroxide (TMAH) wet-etching behaviour to determine the etched nanogap separations for a given TMAH concentration, etching time and mask geometry.
As the authors pointed out, "The current work showed for the first time that TMAH wet etching and LAO can be used together as appropriate methods for controlling the shape and gap values of electrodes."
The work is reported in Semiconductor Science and Technology.