Study of tunneling current oscillation dependence on SiO2 thickness and Si roughness at the Si/SiO2 interface

Abstract

The tunneling current through tin (∼50 Å) silicon dioxide films is observed to have a small oscillatory component at high electric fields. Three main results involving the oscillatory component of the tunneling current are reported. First, a new and improved analysis for obtaining the oscillatory component from the current measurements is described. Then, using this analysis, the dependence of the oscillatory component on oxide thickness and SiO2/Si interface roughness is studied. The thickness study shows that the oscillation amplitude decreases exponentially as the distance traveled by the electron in the conduction band of SiO2 increases. This decrease is attributed to the scattering effects and the mean free path of the electron in SiO2 is estimated to be 6 Å, in agreement with previous reports. The roughness study is performed on thermally oxidized purposely roughened Si surfaces, and the roughness is characterized by the atomic force microscopy. The oscillations in the tunneling currents show no dependence on the interface roughness, indicating that the roughness at the Si surface has little effect on the thickness uniformity of thermally grown thin oxide films and that oxide films grow uniformly over the roughened Si surfaces for at least the first 50 Å or so.