Positive charge generation in metal-oxide-semiconductor capacitors

Abstract

This work examines the electrical behavior of metal-oxide-semiconductor capacitors in which positive charge has been generated in the silicon dioxide layer using either avalanche hole injection, avalanche electron injection, or Fowler-Nordheim Tunneling injection. It is concluded on the basis of flatband voltage measurements made as a function of time following charge injection that two distinct species of positive charge are generated in the oxide layer, depending on the nature of charge generation. In particular, avalanche hole injection results in the generation of trapped holes, while avalanche electron injection and Fowler-Nordheim Tunneling result in so-called ‘‘slow-states’’ or anomalous positive charge centers. The electrical behavior of these two species is discussed. In addition, interface trap density measurements following avalanche hole injection show that both a background level of interface traps and a peak at approximately 0.8 eV above the valence band edge build with time following injection. Further, the dependence of the interface trap density on injection fluence and time supports a model in which a neutral species is released from the bulk of the oxide during hole injection and subsequently generates an interface defect.