On-Wafer Characterization of HCI/BTI-induced Threshold Voltage Degradation based Measured Frequency Shift of Ring-Oscillator Circuits

This paper presents an on-wafer characterization method for transistor threshold voltage degradation caused by hot-carrier injection and bias temperature instability using conventional Ring-Oscillator configurations. One of the key advantages of our proposed method is its ability to estimate the threshold voltage shift of each individual transistor within the gate while operating under AC stress conditions. Additionally, our approach effectively eliminates transistor variability. By employing a method that monitors the collective behavior of multiple transistors simultaneously, we can mitigate the impact of variability—such as differences arising from manufacturing processes and operational conditions. This enhancement not only improves the accuracy of estimations for transistor threshold voltage shift by aging but also leads to more reliable predictions regarding the long-term degradation mechanisms of the circuits. Thus, this characterization method serves as a valuable tool for actual manufacturing processes in terms of both cost and time efficiency.