ANALYSIS OF THE HOT-CARRIER DEGRADATION OF DEEP-SUBMICROMETER LARGE-ANGLE-TILT-IMPLANTED DRAIN (LATID) MOSFETS

The hot carrier degradation of large-angle-tilt implanted drain (LATID ) and standard LDD N-MOSFETs has been investigated thoroughly using th e combination of I-V characterization, charge-pumping and profiling of the damaged region. Although the LATID structure exhibits a good curr ent drivability and net improvement in the hut-carrier immunity, the g ate-voltage dependence of the transistor degradation shows significant differences compared to the LDD structure. The distinct time-dependen ce of the transconductance degradation and the filling of acceptor-lik e (neutral) oxide traps were emphasized. It is shown that the degradat ion in LATID is less sensitive to the gate-voltage V-g governing hole or electron injection, which leads to a ''flat'' V-g-dependence where holes are less efficient to create acceptor-like oxide traps. The char ge-pumping analysis has shown a similar V-g-dependence between the int erface trap generation and the acceptor-like oxide traps in both struc tures. Less positive and negative trapped charges are found in LATID t han in LDD with a larger difference in the high V-g-stress region (whe re the trapping of negative charge largely dominates the interface tra p generation). This was confirmed by profiling measurements which have shown that the density of the negative trapped charges in LATID is on e half of that in LDD, but in contrast presents a significant extensio n from the n-region into the channel. Finally, though the LATID N-MOSF ET is one of the best structures able to exceed a DC lifetime of 10 ye ars, lifetime experiments have shown that accepter-like oxide traps cl early reduce the device lifetime in LATID in the same way as in LDD, w hich could lead to enhanced hot-carrier degradation in some cases of A C operation for these structures. (C) 1997 Elsevier Science Ltd.