Characterization of thin oxide films for FET applications

Abstract

Electronic transport in thin silicon dioxide films used for field effect transistor (FET) devices is controlled by the metal-oxide barrier height rather than by bulk defect centers. The presence of charged ions (i.e., sodium) or interface states at the injecting electrode can lower the barrier height and thereby increase the electronic conduction. In addition, the transport of sodium ions is generally believed to be emission-limited from traps located at the metal-oxide interface. When present in large concentrations (>1012/cm2), Na ions can alter the internal space charge field, markedly enhance the current, and even lead to dielectric breakdown. Instabilities in the current at high electric fields (∼107V/cm) as a result of ionization processes were observed prior to breakdown. The degradation of metal-oxide-semiconductor capacitors as a result of electrothermal stressing can be retarded by the incorporation of hydrogen in the SiO2. © 1975 Academic Press, Inc.