Process-sensitive Monitor Circuits for Estimation of Die-to-Die Process Variability

In this paper, we propose a set of ring oscillators (ROs) to estimate D2D variation of MOS threshold voltage and gate length. First, we show a design guideline on designing ROs with enhanced process sensitivities. We propose a set of ROs for process parameter estimation. We then develop an estimation method using a linear model to extract the variations from the measured frequencies. Simulation results confirm that our proposed circuits are able to extract process parameters in the conditions of error in the measurement. We build test chips to confirm the validity of our proposed ROs. We extracted process parameter variation using our monitor circuits. Variation results satisfy the variation range in Process Control Module (PCM) data and are within the corner model. The proposed ROs can be built on-chip to monitor process parameter variation in real time.