To enable the continued scaling of integrated circuits, the semiconductor industry faces ongoing struggles to implement better low‐dielectric‐constant (low‐k) materials within the interconnect system. One of the biggest challenges to integrating new dielectrics is overcoming the low‐k death curve—that is, the fatal falloff in mechanical properties associated with the low material densities required to achieve low k values. It is shown that amorphous hydrogenated boron carbide (a‐BC:H) films exhibit Young's modulus (E) values between two and ten times greater than those of state‐of‐the‐art Si‐based dielectric materials across a wide range of k values. In particular, optimized a‐BC:H films with moderate k values in the range of 3–4, in addition to possessing outstanding stiffness (E ≈ 100–150 GPa), simultaneously exhibit excellent electrical properties (leakage current of <10–8 A cm–2 at 2 MV cm–1 and breakdown voltage of >5 MV cm–1). Films in this range also demonstrate resistance to Cu diffusion to at least 600 °C, as well as chemical stability and etch properties suitable for low‐k diffusion barrier/etch stop applications.

A multiresponse 2 5 full factorial experiment is performed to investigate the effects of growth conditions (temperature, power, pressure, total flow rate, partial precursor flow rate) on the chemical, mechanical, dielectric, electronic, and charge transport properties of thin-film amorphous hydrogenated boron carbide (a-B x C:H y ) grown by plasma-enhanced chemical vapor deposition (PECVD) from orthocarborane. The main and interaction effects are determined and discussed, and the relationships between properties are investigated via correlation analysis. The process condition with the strongest influence on growth rate is pressure, followed by partial precursor flow rate, with low pressure and high partial flow rate conditions yielding the highest growth rates. The atomic concentration of hydrogen (at.% H) and density are controlled primarily by temperature and power, with low temperature and power conditions leading to relatively soft, hydrogen-rich, low-density, porous films, and vice versa. The B/C ratio is controlled by temperature, power, pressure, and the power*pressure interaction, and is uncorrelated to hydrogen concentration. Thin-film dielectric and electronic structure properties, including high-frequency dielectric constant (ε 1 ), low-frequency/total dielectric constant (κ), optical band gap (E Tauc /E 04 ), and Urbach energy (E U ), are correlated strongly with at.% H, and weakly to moderately with B/C ratio. These properties are dominated by the influence of temperature, with a second significant influence from the power*pressure interaction. The interaction of power and pressure leads to two opposite growth regimes-high power and high pressure or low power and low pressure-that can produce a-B x C:H y films with similar dielectric or electronic structure properties. Charge transport properties also show a correlation with at.% H and B/C, but not with the electronic structure and disorder parameters, which suggests a complicated relationship between the two. The range of properties measured highlights the potential of thin-film a-B x C:H y for low-κ dielectric and neutron detection applications, and suggests clear pathways for future material property optimization.

Thin-film carborane-based amorphous hydrogenated boron carbide (a-B x C:H y ), grown by plasma-enhanced chemical vapor deposition (PECVD), has emerged as a promising semi-insulating, low-dielectric-constant (low-κ) (κ < 3.5) material for intra/interlayer dielectric (ILD) and/or copper diffusion barrier/etch stop applications. Of the many integration challenges faced by candidate materials for low-κ ILDs or more specialized layers, one of the most important is the need for extremely low leakage currents up to high electric fields. In the case of a-B x C:H y , the leakage current at a given field can span nearly ten orders of magnitude, depending on the fabrication conditions and resulting physical properties of a given film. In order to go beyond a brute force process–property approach toward optimizing the electrical properties in thin-film a-B x C:H y , we explore their origin and relationship to electronic, dielectric, and disorder properties. This contribution will describe the charge transport mechanisms in a-B x C:H y films in different electric field regimes, which include Ohmic, space-charge-limited-current, and Poole–Frenkel behavior. These mechanisms, and the underlying electrical properties that define these mechanisms (e.g., resistivity, mobility, trapping), are related to individual and combined electronic (band gap), dielectric (electronic and atomic/distortion polarization), and disorder (Urbach energy, Tauc parameter, dispersion energy) parameters. We further discuss how balancing the contributions of these different parameters via hydrogen and carbon content, through varying growth parameters, allows us to control the underlying charge transport mechanisms at both low and high fields, to ultimately obtain leakage currents on the order of 10–8 A/cm2or lower at 2 MV/cm. Figure 1. (a) Leakage current density (J) as a function of electric field (E) for a selection of a-B x C:H y films. (b) and (c) Correlations between charge transport and disorder parameters: zero-field mobility extracted from steady-state space-charge-limited current measurements (μ 0(SS-SCLC)) as a function of E g E u B –1/2 disorder parameter, and resistivity (ρ) extracted in Ohmic regime as a function of dispersion energy (E d). Figure 1