Study of excess silicon at Si3N4 thermal SiO2 interface using ellipsometric measurements

The chemical composition and structure of the Si(3)N(4/)thermal SiO2 interf ace in silicon/oxide/nitride/oxide (SONO) structures were studied by using electron energy loss spectroscopy (EELS) and ellipsometric measurements. Bo th experiments show the existence of excess silicon at the Si3N4/fhermal Si O2 interface, in the form of Si-Si bonds in the Si-rich silicon oxynitride. Wet oxidation of the as-deposited Si3N4 has profound effects on the interl aces in SONO structure. Mechanisms responsible for these observations are p roposed based on the chemical reactions during the synthesis of the SONO st ructure. Particularly, we propose that the Si-Si bonds are produced by repl acing nitrogen with oxygen during the oxidation of Si3N4 These bonds should be the responsible candidates for the positive charge accumulation in re-o xidized nitrided oxide at the hot hole injection and ionizing radiation. (C ) 1999 The Electrochemical Society. S0013-4651(98)06-067-4. All rights rese rved.