Impact of hydrogenation on the stability and mechanical properties of amorphous boron nitride

Abstract

Interconnect materials with ultralow dielectric constant, and good thermal and mechanical properties are crucial for the further miniaturization of electronic devices. Recently, it has been demonstrated that ultrathin amorphous boron nitride (aBN) films have a very low dielectric constant, high density (above 2.1 g/cm3), high thermal stability, and mechanical properties. The excellent properties of aBN derive from the nature and degree of disorder, which can be controlled at fabrication, allowing tuning of the physical properties for desired applications. Here, we report an improvement in the stability and mechanical properties of amorphous boron nitride upon hydrogen doping. With the introduction of a Gaussian approximation potential (GAP) for atomistic simulations, we investigate the changing morphology of amorphous boron nitride with varying H doping concentrations. We found that for 8 at\% of H doping, the concentration of $sp^3$-hybridized atoms reaches to a maximum which leads to an improvement of thermal stability and mechanical properties by 20\%. These results will be a guideline for experimentalists and process engineers to tune the growth conditions of amorphous boron nitride films for numerous applications.

Exploring dielectric properties in atomistic models of amorphous boron nitride

“…Equation ( 8) also substantiates our earlier remark about the local character of the momentum matrix elements, which in this tight-binding formulation can be seen to be a direct consequence of the local character of the tight-binding Hamiltonian (itself a consequence of the exponential decay of the atomic orbitals). Figure 7 displays the dielectric function for samples aBN1−x and aBN2 (the DOS of aBN1−0 and aBN2 are also shown in figure 6) 12 . As expected from the tendency of large systems to self-average, we find that at these scales (∼10 4 atoms) the dielectric properties of the system are essentially isotropic 13 .…”

“…It thus appears desirable to move towards more sophisticated tight-binding (or generally second principles) models. Finally, it is believed that amorphous BN materials also contain hydrogen or oxygen atoms in non-negligible quantity, impacting their structural stability and mechanical properties [12], so that one should also consider proper tight-binding modeling of these additional atomic species for accessing the full dielectric response of measured samples.…”

“…In this framework, we show the emergence of some correlations between the nature of the structural disorder and bonding character statistics inside the sample, and the resulting formation of mid-gap states and behavior of the dielectric constant (section 2). Second, we construct large scale atomic structural models (∼10 4 atoms) using molecular dynamics with such machine learning potentials, which enjoy ab-initio accuracy [11,12], and evaluate the electronic and dielectric properties of these large systems through a simple Slater-Koster tight-binding model. Although this latter model presents significant limitations, it allows us to get a first picture of the electronic and dielectric properties in large, highly complex three-dimensional geometries mixing boron and nitrogen atoms, linked together by sp 1 , sp 2 and sp 3 bonds.…”