Thermal characterization of the inter-die thermal resistance of hybrid Cu/dielectric wafer-to-wafer bonding

In this paper, we present the design of a passive test chip with thermal test structures in the Metal 1 layer of the back-end of Line (BEOL) for the experimental thermal characterization of the inter-die thermal resistance of wafer-pairs fabricated by hybrid Cu/dielectric wafer-to-wafer bonding. The thermal test structures include heater elements and temperature sensors. The measurement data is combined with a modeling study to extract the thermal resistance of the bonded interface for the fabricated bonded wafer pair. The extracted thermal resistance of the die-die interface created by hybrid wafer-to-wafer bonding is compared to literature data on µbump stacking. The low thermal resistance of the thin bonded dielectric interface indicates that hybrid Cu/dielectric bonding is a promising technology to create 3D chip stacks with a low thermal die-to-die resistance.