Laser-Machined Interposer with Diamond-Coated Capillary Surfaces for Hotspot Mitigation in 3D Heterogeneous Integration (3DHI) Packaging

The continued increase in localized power density in advanced semiconductor systems has made hotspot formation a primary limitation in 3D Heterogeneous Integration (3DHI) packages, where heat must be removed through vertically constrained and thermally resistive pathways. This work presents a laser-manufactured interposer concept that integrates capillary-driven, two-phase cooling within the packaging layer to mitigate hotspots and enable higher power operation within a fixed footprint.The proposed architecture incorporates three-dimensional wick pillar arrays formed via advanced laser manufacturing, creating a capillary network capable of sustaining liquid delivery and thin-film evaporation. A key limitation in such wick structures is the low thermal conductance of dielectric materials, such as alumina, which restricts vertical heat transport from the device to the evaporating interface. To address this, the wick pillars are selectively coated with diamond, introducing high-conductivity pathways that enhance the effective vertical thermal conductivity of the wick and reduce local temperature gradients at the hotspot.To evaluate the viability and performance limits of the proposed approach, coupled thermomechanical and thermohydraulic models are developed in COMSOL Multiphysics. The framework resolves heat conduction within composite wick structures, capillary-driven liquid transport, and evaporation dynamics, while also capturing thermomechanical stresses arising from material heterogeneity and thermal gradients. The results demonstrate that enhancing vertical thermal transport within the wick significantly reduces hotspot intensity, delays dry out, and increases the maximum sustainable heat flux without exceeding mechanical reliability constraints.These findings establish the feasibility of integrating laser-manufactured, diamond-enhanced wick structures within interposer platformsand provide quantitative guidance on design trade-offs between thermal performance and structural integrity. The proposed concept offers a scalable pathway for hotspot mitigation in next-generation 3DHI systems and supports continued increases in chip-level power density.