Investigation of single cell delay and delay mismatch in ring oscillator based test structure

Abstract

In previous work, we presented a test structure based on ring oscillator (RO) to measure single cell delay and delay mismatch, which can provide reliable information on intra-die and inter-die parameter variations. A delay cell of the configurable RO in the test structure considered for the computation technique consists of an inverter and a conducting transmission gate between adjacent cells. This paper will analyze the effects on delay cells of the transmission gates connecting to the output of inverters included in the active RO and investigate in depth delay mismatch in this RO based test structure. Monte Carlo simulation results reveal that the computation technique is applicable to derive delay mismatch between delay cells. A large number of post-layout simulations for different layout structures with different number of cells and different transistor sizes have been performed to analyze delay mismatch related to interconnect and device parameter variations