3-D On-Chip Integration of GaN Power Devices on Power Delivery Network (PDN) With Direct Heat Spreading Layer Bonding for Heterogeneous 3-D (H3D) Stacked Systems

Heterogeneous 3-D (H3D) stacked systems offer numerous advantages for high-performance computing (HPC) and artificial intelligence/machine learning (AI/ML) applications. However, implementing H3D systems requires a re-designed power delivery network (PDN) for efficient power delivery in 3-D stacked systems and thermal management solutions. To develop an efficient PDN for the H3D system, a 3-D integrated on-chip power device is recommended. In this work, we demonstrate an H3D-integrated GaN power device on the PDN of a CMOS chip with direct heat-spreading layer bonding. The GaN power devices were designed to integrate both E-mode and D-mode with ${L}_{\text {G}}$ of $1.5~\mu $ m and ${L}_{\text {GD}}$ of $15~\mu $ m, and achieve a ${R}_{\scriptscriptstyle{\mathrm {on}}}$ of $22.3~\Omega $ mm and ${V}_{\text {BD}}$ of 137 V. These results surpass the limitation of silicon-based power devices. In addition, we experimentally demonstrated that direct heat spreading layer bonding effectively relaxed the thermal effect of H3D-integrated GaN power devices using a thermoreflectance microscopy (TRM) system for the first time. By introducing a heat spreading layer, the thermal resistance ( ${R}_{\text {TH}}$ ) of the GaN power device was reduced by 48.8% compared to GaN power devices without a heat spreading layer. These findings mark a substantial advancement in PDN technology, setting the stage for vertically integrated active PDNs that support efficient power delivery and effective thermal management in H3D stacked systems.