Investigation and Modeling of Hot Carrier Effects on Performance of 45- and 55-nm NMOSFETs With RF Automatic Measurement

Effects of hot carriers on dc and RF reliabilities for both 45- and 55-nm negative metal-oxide-semiconductor field-effect transistors with in-line ground-signal-signal-ground test-pad structures were investigated in detail. The investigations were evaluated by an RF automatic testing system with a proprietary control program in Agilent's Integrated Circuit Characterization and Analysis Program software. After a hot carrier stress, we found that the increase in C
_gs
is larger than the decrease in C
_gd
for 55- and 45-nm devices, and the difference increases as the process technology keeps advancing. Thus, the degradations of cutoff frequency f
_T
and maximum oscillation frequency f
_max
are dependent on transconductance g
_m
and gate capacitance C
_gg
(= C
_gs
+ C
_gd
) for 45- and 55-nm devices. This is different than many conventional studies that used low-frequency equipment. We propose a surface channel resistance model to comprehensively interpret the observations and verify it by the slope changes in the curves of measured f
_T
versus g
_m
.