Resistive RAM variability monitoring using a ring oscillator based test chip

Common problems with Oxide-based Resistive Random Access Memory (so-called OxRRAM) are related to high variability in operating conditions and low yield. Although research has taken steps to resolve these issues, variability remains an important characteristic for OxRRAMs. In this paper, a test structure consisting of an OxRRAM matrix where each memory cell can be configured as a ring oscillator is introduced. The oscillation frequency of each memory cell is function of the cell resistance. Thus, the test structure provides within-die accurate information regarding OxRRAM cells variability. The test structure can be used as a powerful tool for process variability monitoring during a new process technology introduction but also for marginal cells detection during process maturity.