Carbon‐Enriched Amorphous Hydrogenated Boron Carbide Films for Very‐Low‐k Interlayer Dielectrics

Abstract

A longstanding challenge in ultralarge‐scale integration has been the continued improvement in low‐dielectric‐constant (low‐k) interlayer dielectric materials and other specialized layers in back‐end‐of‐the‐line interconnect fabrication. Modeled after the success of carbon‐containing organosilicate materials, carbon‐enriched amorphous hydrogenated boron carbide (a‐BxC:Hy) films are grown by plasma‐enhanced chemical vapor deposition from ortho‐carborane and methane. These films contain more extraicosahedral sp3 hydrocarbon groups than nonenriched a‐BxC:Hy films, as revealed by FTIR and NMR spectroscopy, and also exhibit lower dielectric constants than their nonenriched counterparts, notably due to low densities combined with a low distortion and orientation contribution to the total polarizability. Films with dielectric constant as low as 2.5 are reported with excellent electrical stability (leakage current of 10−9 A cm−2 at 2 MV cm−1 and breakdown voltage of >6 MV cm−1), good thermal conductivity of 0.31 ± 0.03 W m−1 K−1, and high projected Young's modulus of 12 ± 3 GPa. These properties rival those of leading SiOC:H materials, and position a‐BxC:Hy as an important complement to traditional Si‐based materials to meet the complex needs of next‐generation interconnect fabrication.

Ultralow‐k Amorphous Boron Nitride Based on Hexagonal Ring Stacking Framework for 300 mm Silicon Technology Platform

“…Such as, amorphous hydrogenated boron carbide (a-BC:H) film was reported to exhibit a low k value of 3.3 with high Young's modulus >100 GPa on Si substrate, [11] however, the gain on both properties reduced for k values further scaled down below 3. [12] Recently, an ultralow k value of 1.78 with density above 2.1 g cm -3 has been reported on a 3-nm-thick inductively coupled plasma chemical vapor deposition (ICP-CVD) grown amorphous boron nitride (aBN) film on n ++ -Si substrate at 400 °C using borazine as precursor. [13] Borazine (B 3 N 3 H 6 ) is believed to favor the formation of fused B-N hexagonal ring frameworks, [14] which in turn establish low net polarity regions within aBN film.…”

“…To lift possible ambiguities related to substrate effects on the measured effective k value, [15] remote plasma enhanced CVD (PECVD) system was used for aBN film fabrication through a mixture of excited gas stream and neutral borazine, to prevent the unintentional boron-doping on Si substrate with ICP-CVD direct application. [12] Finally, a novel full borazine-aBN film growth process with ultralow k of 2.11, high density of 2.1 g cm -3 , and intrinsic Young's modulus > 50 GPa on 300 mm on Si wafer by 400 °C PECVD process is lined out transferable into a practical semiconductor manufacturing facility setup.…”

Topological Constraint Theory Analysis of Rigidity Transition in Highly Coordinate Amorphous Hydrogenated Boron Carbide

“…In contrast, evidence from previous work suggests that the PECVD carborane a-BC:H product, while still based on icosahedral units, forms a very different disordered polymeric network comprised of orthocarborane B 10 C 2 H x units, cross-linked to varying degrees, either directly to each other or via extraicosahedral hydrocarbon linkers (e.g., B-CH 2 -B; Figure 1). Solid-state NMR and FTIR characterization (Paquette et al, 2011;Nordell et al, 2017) is consistent with the presence of hydrogenated ortho-carborane and sp 3 hydrocarbon functionalities within the network. We assume that all carborane vertices that are not crosslinked are terminated by hydrogen atoms.…”

“…Here, we apply rigidity theory to a unique and unusually coordinated material, boron carbide. This material has garnered interest for a variety of applications, including nuclear reactor coatings (Greuner et al, 2004;Buzhinskij et al, 2009), neutron detection (Robertson et al, 2002;Caruso, 2010;Gervino et al, 2013), low-k dielectrics and related layers for integrated circuits (Han et al, 2002;Nordell et al, 2016bNordell et al, , 2017, and various specialized coatings (Keski-Kuha et al, 1998;Chen et al, 2006;Hu and Kong, 2014;Azizov et al, 2015;Störmer et al, 2016). The particular amorphous hydrogenated boron carbide (a-BC:H) variant described here was produced in the form of thin films by plasma-enhanced chemical vapor deposition (PECVD) from a single-source molecular ortho-carborane (o-C 2 B 10 H 12 ) precursor to form a disordered polymeric carboranebased network.…”

Plasma CVD of B–C–N thin films using triethylboron in argon–nitrogen plasma

“…Since the composition and density of these films are nearly identical, they cannot explain the difference in permittivity, nor can the uncertainties due to the actual contact area on such samples. We suggest that this difference is due to the rigidity of the atomic network, as for a-Si x C:H 72 and a-B x C:H, 73 which in our case could be tuned by Ar ion bombardment. The nanowalls deposited at nitrogen-rich conditions suffer a rather mild bombardment, provided that the Ar partial pressure is low; hence they should have a permittivity in the same range as the smooth films.…”