Parametric failure modeling and yield analysis for STT-MRAM

The emerging Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) is a promising candidate to replace conventional on-chip memory technologies due to its advantages such as non-volatility, high density, scalability and unlimited endurance. However, as the technology scales, yield loss due to extreme parametric variations is becoming a major challenge for STT-MRAM because of its higher sensitivity to process variations as compared to CMOS memories. In addition, the parametric variations in STT-MRAM exacerbates its stochastic switching behavior, leading to both test time fails and reliability failures in the field. Since an STT-MRAM memory array consists of both CMOS and magnetic components, it is important to consider variations in both these components to obtain the failures at the system level. In this work, we model the parametric failures of STT-MRAM at the system level considering the correlation among bit-cells as well as the impact of peripheral components. The proposed approach provides realistic fault distribution maps and equips the designer to investigate the efficacy of different combinations of defect tolerance techniques for an effective design-for-yield exploration.