Hot-electron-induced traps studied through the random telegraph noise

Random telegraph signal (RTS) measurements have been used to study individual hot-carrier-induced traps in nMOSFETs. It is shown that single filling and emptying can cause 0.1% step noise in channel current. Trap location (3-10 A from interface), time constant ( approximately 10 ms), and energy are found to be quite different from those of prestress (process-induced) traps. The type (acceptor or donor) of the traps can also be identified by RTS measurements; both the process and stress-induced traps with energies near the conduction band edge are found to be of the acceptor type for nMOSFETs and trap levels near the valence band edge are found to be of the donor type for pMOSFETs. Using RTS as a characterization tool, it is found that the stress-induced interface traps are located closer to the interface, resulting in shorter time constants and a stronger influence on the surface mobility than the process-induced traps.>