Evaluation of Thin Silicon Dioxide Layers by Beam Assisted Scanning Tunneling Microscope

Abstract

The electronic structure of thin thermal silicon dioxide ( SiO2) layers are evaluated by beam assisted scanning tunneling microscope (BASTM). The BASTM operation principle is that an insulator sample is exposed with an electron beam, which excites electron-hole pairs in the insulator and makes the sample conductive. 100 nm wide line and space patterns are delineated by electron beam lithography and dry etching in a 10 nm thick thermally grown silicon dioxide layer, and are observed by BASTM to ascertain the capability. Current-voltage (I-V) characteristics are measured for silicon dioxide layers with thicknesses between 1.8 and 4.5 nm by tunneling spectroscopy. The results indicate that both the band gap and barrier height have no dependence on the silicon dioxide layer thicknesses.