Improvement of punchthrough-induced gate-oxide breakdown in n-channel metal-oxide-semiconductor field-effect transistors using rapid thermal nitridation

Gate-dielectric breakdown in small n-channel metal-oxide-semiconductor field-effect transistors has been investigated. It is found that such breakdown is accelerated by large channel current when the devices operate in punchthrough conditions. The situation can be greatly improved by rapid thermal nitridation (RTN) of the gate oxide in the transistors. In addition, the time-dependent dielectric breakdown of the devices operating beyond punchthrough is also considerably improved by RTN. The results indicate that the charge to breakdown Q_bd is increased by three orders of magnitude as compared to conventional-oxide devices. All these improvements can be attributed to the nitridation-induced hardening of SiO₂/Si interface.