CHARACTERIZATION OF THE SILICON NITRIDE-THERMAL OXIDE INTERFACE IN OXIDE-NITRIDE-OXIDE STRUCTURES BY ELS, XPS, ELLIPSOMETRY, AND NUMERICAL-SIMULATION

This work studies the properties of the SiO2-Si3N4 interface in oxide- nitride-oxide (ONO) structures by using energy loss spectroscopy, X-ra y photoelectron spectroscopy, ellipsometry measurements and numerical simulation. By oxidation the as-deposited Si3N4, silicon-silicon bonds at Si3N4-thermal SiO2 interface are found. These excess Si-Si bonds a re produced by replacing nitrogen with oxygen during the oxidation of Si3N4. We further propose that the Si-Si bonds are the major trap cent er at the Si3N4-SiO2 interface. With MINDO/3 numerical simulation, we have found that the Si-Si bonds can capture both electrons and holes a t the top Si3N4-SiO2 interface. These bonds are proposed to be the res ponsible candidate for the positive charge accumulation in re-oxidized nitrided oxide. (C) 1998 Elsevier Science Ltd. All rights reserved.