The team of Sun Bo of Shenzhen International Graduate School has made new progress in the thermal conduction mechanism of metal-semiconductor interface
Tsinghua News, October 12. With the increasing performance of semiconductor devices, especially the development of size miniaturization and high power density, heat dissipation has become one of the technical bottlenecks restricting the stability, reliability, and life of semiconductor devices. Especially for nanoscale semiconductor devices, increasing the thermal conductivity of the interface is a key part of improving the heat dissipation performance. Therefore, the study of interfacial heat transport has important application value and scientific significance for the heat dissipation of semiconductor devices.
Generally speaking, for the interface (semiconductor-semiconductor or metal-semiconductor) in semiconductor devices, the traditional diffusion mismatch model (DMM) considers the phonon transport at the interface to be an elastic process, that is, the phonon passing through the interface does not change in energy . Since the phonons are all excited at the Debye temperature, at high temperature (that is, the temperature is higher than the Debye temperature), the energy of phonons passing through the interface no longer changes with temperature, and the interface thermal conductivity shows a saturation trend. However, compared with the theoretical model, the conditions for improving the thermal conductivity of the interface are still insufficient experimentally.
In response to the above problems, Sun Bo's team from Shenzhen International Graduate School of Tsinghua University cooperated with Gu Xiaokun's team from Shanghai Jiaotong University and Wang Xinqiang's team from Peking University to try to explore the conditions for improving the thermal conductivity of the interface. The team used molecular beam epitaxy (MBE) to prepare two Al/Si interfaces with atomically flat and 1nm interdiffusion layers by precisely controlling the growth conditions. The interfacial thermal conductivity at different temperatures was accurately measured by time-domain thermal reflectometry (TDTR). It is found that the thermal conductivity of the rough interface tends to be saturated at high temperature, which is consistent with the traditional diffusion mismatch model; while the thermal conductivity of the flat interface increases with temperature at high temperature, which is deviating from the traditional theory, and is also observed on the flat Al/GaN interface. to a similar phenomenon. Theoretical calculations show that the thermal conductivity of the flat interface increases with temperature due to the inelastic transport process of phonons at the interface. At the flat interface, the transmission ability of phonons shows stronger frequency dependence, which makes the phonon nonequilibrium more pronounced at the interface, and promotes the inelastic transformation between phonons, so that the thermal conductivity of the interface exhibits a high temperature. Stronger temperature dependence. This study found an inelastic phonon transport process at the atomically flat Al/Si, Al/GaN interface, which is regarded as an additional phonon transport channel at the interface, which can improve the thermal conductivity of the interface, thereby Improve the thermal performance of the interface. This study resolves a long-standing debate on the mechanism of interfacial phonon inelasticity and has implications for thermal management in semiconductor devices.