High-field transport in SiO2 on silicon induced by corona charging of the unmetallized surface

Abstract

A study has been made of high-field electronic transport in thermally grown SiO2 in which the injection and transport of carriers were induced by charging the exposed surface of the insulator with ions extracted from a corona discharge. This technique totally avoids destructive breakdown through weak spots in the insulator. Auxiliary developments included a comparison technique for measuring the steady-state potential difference across the unmetallized insulator and a p-n junction method for determining the sign of the principal charge carrier in the oxide. Using a corona discharge in dry air, breakdown fields of approximately 6.5 and 13.5 MV/cm were obtained for charging with positive and negative ions, respectively. Electrons were identified as the current carriers for both polarities of applied field. Measurements of the discharge of the samples, made with a Kelvin probe, yield results that are consistent with Fowler-Nordheim tunneling of electrons from the silicon into the oxide, with an electron effective mass in the oxide m*ox=0.48m. Positive charge accumulation was observed in the oxide after charging with negative corona to fields above 11 MV/cm.