Anomalous hot-carrier behavior for LDD p-channel transistors

It has previously been reported that gradual junction p-channel transistors can have shorter lifetimes under hot-carrier stress conditions than abrupt junction devices (see IEEE Trans. Electron Devices, vol. 39, p. 2290-98, 1992). Here, the work is extended to LDD (lightly doped drain) structures. p-MOS hot-carrier effects are examined for deep submicron structures with abrupt and LDD junctions. It is shown that, contrary to the case of n-MOS transistors, the lifetimes for hot-carrier stress of the LDD p-MOS transistors are actually shorter than their abrupt junction counterparts, in the range of LDD dopings examined here. This is explained in terms of two competing mechanisms, gate electronic injection, which decreases for the LDD junctions, and the size of the damage region in the oxide, which increases for the LDD junctions. It is concluded that using LDD-type structures for hot-carrier control does not automatically guarantee longer lifetimes.<
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