On-off switching of edge direct tunneling currents in metal-oxide-semiconductor field-effect transistors

On-off switching behaviors or two-level random telegraph signals (RTS) are measured in the low voltage (-1.4 0V<V-G<-0.88 V) edge direct tunneling currents in ultrathin gate stack (10 angstrom oxide + 10 angstrom nitride) n-channel metal-oxide-semiconductor field-effect transistors. The plausible origin is the process-induced defects in terms of localized gate stack thinning (or equivalently the conductive filament). In such extrinsic case, the current trapping-detrapping theories can adequately elucidate the data, particularly the RTS magnitude as large as 18%. The current-voltage characteristic associated with a certain defective spot is assessed straightforwardly, showing remarkable compatibility with existing oxide thinning case. Systematic measurements of RTS in the terminal currents allow for determining the occurrence probability as well as locations of defects, and may be treated as a sensitive process monitor. 0 2002 American Institute of Physics.