Governing Thermal Transport in Three-Dimensional Electronics.

Thermal management has emerged as a materials bottleneck for three-dimensional integrated circuits, which are being actively explored to enable dense vertical connectivity and mitigate interconnect delay and energy consumption. Unlike 2D-structure chips, stacked tiers confine dissipation within a boundary-rich back-end-of-line (BEOL) heterostructure. Heat must cross ultrathin dielectrics, porous interlayers, and numerous metal/dielectric and bonding interfaces. Consequently, interfacial resistance and thin-film size effects often determine temperature increase and reliability margins. This perspective highlights the materials physics underlying thermal limits and relates it to integration and design considerations. First, lattice heating is described by a carrier-phonon relaxation pathway in which the optical phonon bath serves as a transient energy reservoir and modulates ultrafast thermal responses. Second, heat transport in nanoscale BEOL multilayer stacks is discussed with emphasis on thickness-dependent conduction and finite thermal penetration that filters temperature transients across tiers. Then, vertical heat removal is governed by interfacial thermal boundary conductance (TBC) and via-network electrothermal coupling with parasitic Joule heating. Finally, thermal pathways are discussed, including thermally conductive insulating dielectrics and heat spreaders, TBC enhancing interlayers, low-temperature bonding and alternative metallization, and functional via architectures consistent with the BEOL thermal budget.