Controllable shrinking of inverted-pyramid silicon nanopore arrays by dry-oxygen oxidation

A novel and simple technique for the controllable shrinkage of inverted-pyramid silicon (Si) nanopore arrays is reported. The Si nanopore arrays with sizes from 60 to 150 nm, made using a combination of dry and wet etching, were shrunk to sub 10 nm, or even closed, using direct dry-oxygen oxidation at 900 ° C. The shrinkage process of the pyramidal nanopore induced by oxidation was carefully modeled and simulated. The simulation was found to be in good agreement with the experimental data within most of the oxidation time range. Using this method, square nanopore arrays with an average size of 30 nm, and rectangular nanopores and nanoslits with feature sizes as small as 8 nm, have been obtained. Furthermore, focused ion beam cutting experiments revealed that the inner structure of the nanopore after the shrinkage kept its typical inverted-pyramid shape, which is of importance in many fields such as biomolecular sensors and ionic analogs of electronic devices, as well as nanostencils for surface nano-patterning.