GATE-OXIDE BREAKDOWN ACCELERATED BY LARGE DRAIN CURRENT IN N-CHANNEL MOSFETS

The time-dependent dielectric breakdown of thin gate oxides in small n-channel MOSFET's operated beyond punchthrough has been investigated. It has been discovered that catastrophic gate-oxide breakdown is considerably accelerated when holes generated by the large drain current are injected into the gate oxide. More specifically, the gate-oxide breakdown in a MOSFET (gate length = 1.0-mu-m, gate width = 15-mu-m) occurs in approximately 100 s at an applied gate oxide field of approximately 5.2 MV/cm during the high drain current stress, while it occurs in approximately 100 s at an applied gate oxide field of approximately 10.7 MV/cm during a conventional time-dependent dielectric breakdown (TDDB) test. The results indicate that the gate oxide lifetime is much shorter in MOSFET's when there is hot-hole injection than that expected using the conventional TDDB method.