ON ELECTRON CONDUCTION AND TRAPPING IN SIMOX DIELECTRIC

We present experimental and theoretical evidence that the high field c onduction mechanism for buried oxide prepared by the technique of sepa ration by implanted oxygen (SIMOX) is due to Fowler-Nordheim (F-N) inj ection aided by field intensification at interfacial asperities. The a sperities are believed to be the pyramidal protusions thought to be st acking faults, observed in electron microscopy (XTEM) studies. The sta ndard F-N theory is modified to include field intensification (k(FI)) and reduced area (k(A)) factors to account for the presence of these d efects. Fitting of the model to experimental current-voltage data yiel ds a value for k(A) which predicts an average asperity separation in a greement with XTEM and defect etching studies. This work therefore cha llenges an existing theory which considers that the high field conduct ion involves tunnelling between Si clusters arising from the excess Si known to exist in SIMOX. We present arguments based on experimental o bservations relating to constant voltage stressing experiments, that o ur model can explain the observed behavior and, in addition, the anoma lies relating to the excess Si tunneling model.