Abrupt current increase due to space-charge-limited conduction in thin nitride-oxide stacked dielectric system

In this article, the conduction mechanisms in nitride-oxide stacked structu res on Si are investigated experimentally and theoretically. Amorphous sili con nitride films (3-5 nm thick) were deposited by low-pressure chemical va por deposition. The ultrathin oxide layers (1-1.5 nm thick) were formed by reoxidization of the nitride layer at about 900 degreesC in wet ambient. Th e current-voltage characteristics for negative and positive gate polarities are asymmetric. An abrupt current increase under negative gate bias prior to dielectric breakdown is reported for this structure. This current-voltag e phenomenon is attributed to trap-controlled single-carrier steady-state s pace-charge-limited conduction-the solid state analog of space-charge-limit ed current in a vacuum diode. Details of space-charge-limited conduction pa rameters depend on the thickness of the dielectric film and temperature. Th e study of those parameters can yield information about the traps inside ni tride-oxide films. Such information can provide considerable insight into c harge transport mechanisms and carrier trapping in these materials, which a re important in understanding the physical processes involved in the basic film properties. (C) 2001 American Institute of Physics.