Control of Nanoplane Orientation in voBN for High Thermal Anisotropy in a Dielectric Thin Film: A New Solution for Thermal Hotspot Mitigation in Electronics

Abstract

High anisotropic thermal materials, which allow heat to dissipate in a preferential direction, are of interest as a prospective material for electronics as an effective thermal management solution for hot spots. However, due to their preferential heat propagation in the in-plane direction, the heat spreads laterally instead of vertically. This limitation makes these materials ineffective as the density of hot spots increases. Here, we produce a new dielectric thin film material at room temperature, named vertically ordered nanocrystalline h-BN (voBN). It is produced such that its preferential thermally conductive direction is aligned in the vertical axis, which facilitates direct thermal extraction, thereby addressing the increasing challenge of thermal crosstalk. The uniqueness of voBN comes from its h-BN nanocrystals where all their basal planes are aligned in the direction normal to the substrate plane. Using the 3ω method, we show that voBN exhibits high anisotropic thermal conductivity (TC) with a 16-fold difference between through-film TC and in-plane TC (respectively 4.26 and 0.26 W·m·K). Molecular dynamics simulations also concurred with the experimental data, showing that the origin of this anisotropic behavior is due to the nature of voBN's plane ordering. While the consistent vertical ordering provides an uninterrupted and preferred propagation path for phonons in the through-film direction, discontinuity in the lateral direction leads to a reduced in-plane TC. In addition, we also use COMSOL to simulate how the dielectric and thermal properties of voBN enable an increase in hot spot density up to 295% compared with SiO, without any temperature increase.

A thermal study of amorphous and textured carbon and carbon nitride thin films via transient grating spectroscopy

“…Also, TGS only computes the thermal diffusivity in the in-plane direction here, and as amorphous films are intrinsically anisotropic, this is not necessarily true for the NCG and flCN films. In these more ordered films some anisotropy is to be expected, as seen in another study with vertically ordered boron nitride thin films 23 . In addition to the phonon transport, thermal transport can also occur through the electrons, which can be quite dominant in electrically conductive materials such as metals where the empirical Wiedemann-Franz law 24 states the electrical and thermal conductivities are linearly related at constant temperature.…”

Graphene related materials for thermal management

“…In this technique, a thin metal wire is used to heat the specimen indirectly and the same wire serves both as a heater and thermometer. The 3ω technique, was developed by Cahill and Pohl in 1987 [317] and now it is a widely used technique for thermal conductivity measurement on bulk and thin film [109,[318][319][320]. The method used is based on heat diffusion in a semi-infinite solid as shown in figure 27(a).…”

Construction of low melting point alloy/graphene three-dimensional continuous thermal conductive pathway for improving in-plane and through-plane thermal conductivity of poly(vinylidene fluoride) composites

“…With the development of modern electronic devices towards multifunction, miniaturization, and high integration, large amounts of heat in a chip cannot opportunely dissipate and further accumulate, causing hot spots which threaten the lifetime and reliability of an electronic device [1,2]. In fact, the progress of electronic devices has been restricted by the absence of effective heat management methods within highpower-density electronic devices [3].…”