In-situ variability characterization of individual transistors using topology-reconfigurable ring oscillators

We propose a variability characterization methodology using a topology-reconfigurable ring oscillator (RO) which enables in-situ characterization of individual transistors in the RO. By configuring the topology-reconfigurable RO into several nMOSFET and pMOSFET-sensitive topologies, local variation of each of the MOSFETs can be estimated. Measurement and estimation results from a 65 nm test chip confirm the validity of our proposed technique. We have successfully characterized static variation as well as RTN induced threshold voltage fluctuation of individual transistors. The proposed methodology can be used for fast and accurate characterization of variability.