Relaxation of FN stress induced V/sub th/ shift at NMOSFETs with HfSiON gate dielectric and TiN gate electrode

Hafnium based materials like hafnium silicate (HfSiON) have been studied intensively for replacing conventional SiO/sub 2/, as gate dielectrics. In addition to dielectric breakdown and other wearout characteristics, threshold voltage shift (Vth) caused by electrical stress is one of the major reliability concerns. In this work, it has been found that a significant portion of V/sub th/ shift, induced by Fowler-Nordheim (FN) stress, is actually reversible. The origin of this V/sub th/ instability has been investigated and its implications on conventional reliability tests are discussed.