ANOMALOUS HOT-CARRIER BEHAVIOR FOR LDD P-CHANNEL TRANSISTORS

It has previously been reported that gradual junction p-channel transi stors can have shorter lifetimes under hot-carrier stress conditions t han abrupt junction devices [1]. Here, the work is extended to LDD (li ghtly doped drain) structures. p-MOS hot-carrier effects are examined for deep submicron structures with abrupt and LDD junctions. It is sho wn that, contrary to the case of n-MOS transistors, the lifetimes for hot-carrier stress of the LDD p-MOS transistors are actually shorter t han their abrupt junction counterparts, in the range of LDD dopings ex amined here. This is explained in terms of two competing mechanisms, g ate electronic injection, which decreases for the LDD junctions, and t he size of the damage region in the oxide, which increases for the LDD junctions. It is concluded that using LDD-type structures for hot-car rier control does not automatically guarantee longer lifetimes.