The purpose of this work is to develop a new model for LDD
n-MOSFET degradation in drain current under long-term AC use
conditions for lifetime projection which includes a self-limiting
effect in the hot-electron induced device degradation.
Experimental results on LDD n-channel MOSFETs shows that the
maximum drain current degradation is a function of the AC
average substrate current under the various AC stress conditions
but not a function of frequency or waveforms or different
measurement configurations. An empirical model is constructed
for circuit applications. It is verified that the self-limiting in drain
current is due to the thermal re-emission of a trapped-hot-electron
in the oxide. Results show that self-heating during AC
stress releases trapped electrons, which in turn limits the
maximum amount of drain current degradation. Moreover,
tunneling to and from traps model is employed to visualize the
internal mechanism of thermal recovery of electrons under
different bias conditions. Although the LDD device structure can
reduce the hot electron effect, various processing technologies can
also affect the device reliability. A carbon doped LDD device with
the first and the second level metal and passivation layer but
without any final anneal shows that a significant reduction in the
shifts of the threshold voltage of MOSFETs with time can be
achieved. However, the long-term reliability projection of nMOSFETs
based on DC stress tests alone is shown to be overly
pessimistic. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36673 |
| Date | 08 November 1991 |
| Creators | Or, Siu-shun Burnette |
| Contributors | Forbes, Leonard |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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