An Investigation of Bias Temperature Instability in Hydrogenated Low-Temperature Polycrystalline Silicon Thin Film Transistors

概要

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The instability mechanisms of the hydrogenated n-channel low-temperature polycrystalline silicon thin film transistors under on-state stress were investigated with various bias stress conditions and device channel widths. It was found that hot carrier degradation which originated from a high drain electric field and self-heating during high current operation were the two dominant mechanisms responsible for device degradation. An electrically reversible depassivation/passivation phenomenon was also found in devices under high current stress, but not in those under hot carrier stress. It was inferred that the self-heating effect would accelerate the bond breakage and diffusion of hydrogen ions, thus enhancing the rate of depassivation/passivation. Moreover, when the current in the hot carrier stress mode was sufficiently high, self-heating became the dominant degradation mechanism and hot carrier degradation phenomenon was also suppressed for devices with large channel width. Meanwhile, the electrically reversible depassivationlpassivation phenomenon also occurred in this case.
2002-09-15