Thermal conductivity measurement of amorphous dielectric multilayers for phase-change memory power reduction

In this work, we investigate the temperature-dependent thermal conductivities of few nanometer thick alternating stacks of amorphous dielectrics, specifically SiO₂/Al₂O₃ and SiO₂/Si₃N₄. Experiments using steady-state Joule-heating and electrical thermometry, while using a micro-miniature refrigerator over a wide temperature range (100-500 K), show that amorphous thin-film multilayer SiO₂/Si₃N₄ and SiO₂/Al₂O₃ exhibit through-plane room temperature effective thermal conductivities of about 1.14 and 0.48 W/(m × K), respectively. In the case of SiO₂/Al₂O₃, the reduced conductivity is attributed to lowered film density (7.03 → 5.44 × 10²⁸m^-3 for SiO₂ and 10.2 → 8.27 × 10²⁸m^-3 for Al₂O₃) caused by atomic layer deposition of thin-films as well as a small, finite, and repeating thermal boundary resistance (TBR) of 1.5 m² K/GW between dielectric layers. Molecular dynamics simulations reveal that vibrational mismatch between amorphous oxide layers is small, and that the TBR between layers is largely due to imperfect interfaces. Finally, the impact of using this multilayer dielectric in a dash-type phase-change memory device is studied using finite-element simulations.