The impact of the carrier transport on the random dopant induced drain current variation in the saturation regime of advanced strained-silicon CMOS devices

The variation of saturation drain current (I
_d,sat
), induced by the random dopant variation (RDF), has been extensively studied by a new multivariate analysis method. It was found that the variation of I
_d,sat
is originated from V
_th,sat
and saturation velocity (V
_sat
), while the variation of V
_th,sat
comes from the drain induced barrier lowering (DIBL). However, the experimental results shows that V
_sat
dominates the variation of I
_d,sat
. From the transport theory, V
_sat
is further decomposed into V
_inj
and B
_sat
, showing that V
_inj
is the dominant factor of I
_d,sat
variation. The faster the V
_inj
is, the less the I
_d,sat
variation becomes. If one improves the injection velocity, then the variation of I
_d,sat
can be suppressed. This has been one of the significant benefits of strained silicon technology in CMOS device scaling.