Trigger-When-Charged: A Technique for Directly Measuring RTN and BTI-Induced Threshold Voltage Fluctuation Under Use- ${V}_{dd}$

Low-power circuits are important for many applications, such as Internet of Things. Device variations and fluctuations are challenging their design. Random telegraph noise (RTN) is an important source of fluctuation. To verify a design by simulation, one needs assessing the impact of fluctuation in both driving current ΔI
_d
and threshold voltage ΔV
_th
. Many early works, however, only measured RTN-inducedAId. ΔV
_th
was not directly measured because of two difficulties: its average value is low and it is highly dynamic. Early works often estimated ΔV
_th
from ΔI
_d
/g
_m
(V
_g
= V
_dd
), where g
_m
is the transconductance, without giving its accuracy. The objective of this paper is to develop a new Trigger-When-Charged (TWC) technique for directly measuring the RTN-induced ΔV
_th
. By triggering the measurement only when a trap is charged, measurement accuracy is substantially improved. It is found that there is a poor correlation between ΔI
_d
/g
_m
(V
_g
= V
_dd
) and the directly measured ΔV
_th
(V
_g
= V
_th
). The former is twice of the latter on average. The origin for this difference is analyzed. For the first time, the TWC is applied to evaluate deviceto-device variations of the directly measured RTN-induced ΔV
_th
without selecting devices.