Heat management strategy for hybrid-bonded wafers using MgO interlayer dielectric

As the features of metal oxide semiconductor field-effect transistor (MOSFET) devices are aggressively scaled down, 3-dimensional (3D) integration is receiving significant attention for further semiconductor technology development. While hybrid bonding is a promising solution for 3D integration because it can achieve high interconnect density, thermal management of bonded dies would be a potential problem. The thermal conductivity of the interlayer dielectric is crucial for effective thermal management. With high thermal conductivity and low fabrication temperature, magnesium oxide (MgO) is one of the attractive dielectric interlayers. However, due to the high dielectric constant, crosstalk degradation is a major challenge for MgO implementation. This study proposes various strategies for MgO implementation. 2-dimensional technology, computer-aided-design, and transient thermal simulation have been utilized to investigate MgO performance as an interlayer dielectric. At the same time, the finite element method has been used to study the tradeoff with crosstalk performance. The simulated results reveal that the device operating temperature can be reduced to 7 °C by applying a MgO layer in SiO₂ intermetal dielectric, with a thickness ratio ranging from 20 to 40%. MgO single-layer implementation as a heat-conducting channel has also been studied. M4, M5, or M6 are recommended for high thermal conductivity and low crosstalk tradeoff. This study demonstrates that an optimized usage of MgO layer in the back-end-of-line can minimize crosstalk degradation while maintaining heat dissipation enhancement. These results suggest that MgO interlayer can be an attractive solution to the local heating issue in high-performance applications.