Inhomogeneous ring oscillator for WID variability and RTN characterization

We propose an inhomogeneous ring oscillator (RO) whose performance is strongly influenced by a small set of transistors for characterizing transistor-by-transistor variability. Performance sensitivities of the transistors are enhanced by inserting a “singular point” into a homogeneous RO. Proposed ROs have been embedded in a 65nm RO-array test structure, and it is verified that the proposed ROs are highly sensitive to Within-Die (WID) local variability and Random Telegraph Noise (RTN). The amounts of random variation in threshold voltages(V
_thN
and V
_thP
) and channel length(L) are extracted from the WID frequency variation. Temporal variation of oscillation frequency due to RTN is observed in the inhomogeneous RO.