Thermal Analysis of Microfluidic cooling in Processing-in-3D-Stacked Memory

Recent 3D-stacked Processing-In-Memory (PIM) research investigates improved performance by transferring computation from the CPU into memory. Although PIM's integration in 3D-stacked memory can achieve better performance, it leads to higher power density than conventional memory operations. The increased power density causes 3D-stacked memory to exacerbate thermal issues. Traditional heat sink cooling on the top surface generates a mismatch between the 3D volumetric heat flux generation and a surface cooling capacity. In this study, we demonstrate a microfluidic cooling technique for PIM in 3D stacked memories. Our technique exploits gaps between the memory die and the gap between the logic die and interposer as cooling chambers. We model the thermal and fluidic characteristics of 3D stacked memory simultaneously. A 64 mm ² of memory, consuming 64W for PIM operation, can be cooled under 85 with a 16.5 ml/min rate of coolant flow. We also performed 2D and 3D COMSOL simulations of the thermal behavior and microfluidic cooling for die-stacked memories operating with PIM.