PS3-RAM: A Fast Portable and Scalable Statistical STT-RAM Reliability/Energy Analysis Method

The development of emerging spin-transfer torque random access memory (STT-RAM) is facing two major technical challenges-poor write reliability and high write energy, both of which are severely impacted by process variations and thermal fluctuations. The evaluations on STT-RAM design metrics and robustness often require a hybrid simulation flow, i.e., modeling the CMOS and magnetic devices with SPICE and macro-magnetic models, respectively. Very often, such a hybrid simulation flow involves expensive Monte Carlo simulations when the design and behavioral variabilities of STT-RAM are taken into account. In this paper, we propose a fast and scalable semi-analytical method-PS3-RAM, enabling efficient statistical simulations in STT-RAM designs. By eliminating the costly macro-magnetic and SPICE simulations, PS3-RAM achieves more than 100(000boldsymbol {times }) runtime speedup with excellent agreement with the result of conventional simulation method. PS3-RAM can also accurately estimate the STT-RAM write error rate and write energy distributions at both magnetic tunneling junction switching directions under different temperatures, demonstrating great potential in the analysis of STT-RAM reliability and write energy at the early design stage of memory or micro-architecture.