Characterization and Modeling of RF-Performance $(f_{T})$ Fluctuation in MOSFETs

The fluctuation of RF performance (particularly for f
_T
: cutoff frequency) in the transistors fabricated by 90-nm CMOS technology has been investigated. The modeling for f
_T
fluctuation is well fitted with the measurement data within approximately 1% error. Low-V
_t
transistors (fabricated by lower doping concentration in the channel) show higher f
_T
fluctuation than normal transistors. Such a higher f
_T
fluctuation results from C
_gg
(total gate capacitance) variation rather than g
_m
variation. More detailed analysis shows that C
_gs
+ C
_gb
(charges in the channel and the bulk) are predominant factors over C
_gd
(charges in LDD/halo region) to determine C
_gg
fluctuation.