A model for SIMOX buried-oxide high-field conduction

Abstract

A new model for SIMOX buried-oxide (BOX) high-field conduction which incorporates the role of silicon islands and BOX nonstoichiometry is presented. For single-implant SIMOX BOX high-field conduction, the onset E-field for both positive and negative applied bias is much lower than the expected onset E-field for that of thermal oxide. In addition, the onset E-field for injection from the substrate is lower than for injection from the top-silicon. We propose that conduction by electron injection from the top interface is due to Fowler-Nordheim tunneling with oxide nonstoichiometry induced modification of the effective barrier-height. Conduction by electron injection from the bottom interface is due to a two-step Fowler-Nordheim tunneling mechanism with cathode E-field enhancement caused by the presence of silicon islands located near the oxide-substrate interface of single-implant SIMOX. These mechanisms were verified using numerical simulation, electrical, and physical measurements. A modified Fowler-Nordheim equation can be used to model BOX conduction through the addition of three parameters, k/sub e/, k/sub a/, and o/sub BOX/. The E-field enhancement factors (k/sub e/ and k,/sub a/) can be directly correlated to silicon island shape, location and density, while the effective barrier-height (o/sub BOX/) can be correlated to BOX nonstoichiometry. Monitoring these parameters has potential use as a simple method for SIMOX BOX quality control.