  A MOSFET threshold voltage extraction method covering the entire range of
drain-to-source voltage, from linear to saturation modes, is presented.
Transconductance-to-current ratio is obtained from MOSFET transfer
characteristics measured at low to high drain voltage. Based on the
charge-based modeling approach, a near-constant value of threshold voltage is
obtained over the whole range of drain voltage for ideal, long-channel MOSFETs.
The method reveals a distinct increase of threshold voltage versus drain
voltage for halo-implanted MOSFETs in the low drain voltage range. The method
benefits from moderate inversion operation, where high-field effects, such as
vertical field mobility reduction and series resistances, are minimal. The
present method is applicable over the full range of drain voltage, is fully
analytical, easy to be implemented, and provides more consistent results when
compared to existing methods.
