High Thermal Conductivity in Back-End-of-Line Compatible AlN Thin Films

TL;DR

This study demonstrates that low-temperature deposited AlN thin films exhibit high thermal conductivity across various substrates, making them suitable for heat dissipation in advanced integrated circuits.

Contribution

The paper presents the fabrication and characterization of BEOL-compatible AlN thin films with high thermal conductivity on multiple substrates, supported by experimental and simulation data.

Findings

AlN films have thermal conductivity >45 W/m·K on various substrates.

Finite element analysis shows up to 44% reduction in device temperature.

AlN is practical as a high-TC heat spreader in ICs.

Abstract

With thermal issues becoming a major challenge to the development of integrated circuits (ICs), high-thermal-conductivity (high-TC) materials are gaining interest from both the industry and academia, especially for high-density back-end-of-line (BEOL) structures. Aluminum nitride (AlN) is an insulating material with high TC, suitable for thermal management in electronic devices. Furthermore, polycrystalline AlN thin films can be deposited at BEOL-compatible low temperatures (lower than 400 C) while retaining relatively high TC, rendering AlN a promising candidate for BEOL heat dissipation. Still, AlN deposition should aim at achieving high TC on a variety of substrates used in IC processes. In this work, we obtained 600- and 1200-nm BEOL-compatible AlN thin film samples on Si, SiO, SiN, and Al2O3 substrates for structural and thermal characterizations. Specifically, time-domain thermoreflectance (TDTR) measurements revealed consistently high TC (higher than 45 W m-1 K-1) on different substrates. Moreover, finite element analysis (FEA) simulations of AlN capped on top of an indium-tin-oxide (ITO) transistor showed a reduction of up to 44% in peak device temperature. Our work provided experimental and calculational evidence for the practicality of leveraging AlN as a high-TC, BEOL-compatible heat spreader material.