System exploration and technology demonstration of 3D Wafer-to-Wafer integrated STT-MRAM based caches for advanced Mobile SoCs

This paper analyzes the most feasible 3D integration and partitioning scheme for STT-MRAM based caches in an advanced Mobile SoC based on the process demonstration of the first ever functional 3D integrated STT devices. We present 3D partitioning schemes from a design -architecture perspective and Power Performance and Area (PPA) analysis is carried out for the 2D and 3D SoC designs with both SRAM and STT-MRAM caches. Our work shows that the PPA benefits from 3D Memory on Logic partitioning are magnified when it can be exploited to accommodate larger caches in general. We also show that STT-MRAM based 3D partitioned caches can exploit this potential increase in capacity to improve performance even more than SRAM. These 3D Wafer-to-Wafer (W2W) integrated STT-MRAM caches can result in up-to 30% performance improvement at 17% power and 15% footprint reduction for our target SoC.