Characterization and Benchmarking of the Low Intertier Thermal Resistance of Three-Dimensional Hybrid Cu/Dielectric Wafer-to-Wafer Bonding

Abstract

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 intertier thermal resistance of wafer-pairs fabricated by three-dimensional (3D) hybrid Cu/dielectric wafer-to-wafer (W2W) bonding. The thermal test structures include heater elements and temperature sensors. The steady-state or transient measurement data are 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 for die-to-die (D2D) or die-to-wafer (D2W) stacking with microbumps. 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.