High Thermal Conductivity Near Phonon Ballistic Transport of Nanoscale Aln Thin Films Prepared by Atomic Layer Annealing

Abstract

With the aggressive shrinking size and increasing density of nanoscale transistors in advanced integrated circuits, effective dissipation of heat from hot spots has become a critical concern. To address this issue, aluminum nitride (AlN) has emerged as a promising material due to its high thermal conductivity. By introducing atomic layer annealing (ALA) into each cycle of atomic layer deposition, the crystalline quality of the resulting AlN thin film can be greatly enhanced. Furthermore, the ALA technique enables the establishment of an epitaxial connection with the sapphire substrate, even at a low deposition temperature of only 300oC. The time-domain thermoreflectance analysis reveals that the thermal conductivity of the nanoscale AlN layers prepared with the ALA treatment is linearly dependent on the film thickness, and the values are close to those predicted by the ab-initio calculation under the ballistic transport condition. The result demonstrates that the ALA technique can significantly improve the crystallinity of AlN, thereby reducing phonon scattering caused by structural imperfections as phonons travel ballistically through the nanoscale AlN thin film.

Keywords: Aluminum nitride, ballistic transport, Thermal conductivity, atomic layer deposition