Low-voltage forward gated diode: an early monitor of hot-carrier degradations in scaled MOSFETs

A low-voltage gated diode biased in weak accumulation and forward mode exhibits a new potential in monitoring the hot-carrier induced degradations of MOSFETs. This is an ability to detect degradation much earlier than the other monitors currently utilized in the industry in terms of the drive capability I_dsat and transconductance g _m. The original abilities such as sensitive and nondestructive monitoring are preserved. These abilities are highlighted in 4.8 and 3.5 nm oxide CMOS manufacturing processes, eventually leading to a guideline using a forward gated-diode monitor for process evaluation with regard to hot-carrier robustness. The early degradation detection ability can be explained reasonably in that (i) the gated-diode forward current I_f and its degradation ΔI _f are both entirely constricted to a very localized zone near the drain junction; and (ii) ΔI_f/I_f increases at a rate ∝t^0.5 since the generated interface state density increase ∝t^0.3, whereas ΔI_dsat /I_dsat follows a lower rate which ∝t^0.15 and Δg_m/g_m∝t^0.3, each due to different aging mechanisms. In addition, oxide trap generation is essentially lacking in our stress experiment, as evidenced by the measured gate induced drain leakage (GIDL) due to band-to-band tunneling