Nature | Vol 582 | 25 June 2020 | 511Article
Ultralow-dielectric-constant amorphous
boron nitride
Seokmo Hong^1 , Chang-Seok Lee^2 , Min-Hyun Lee^2 , Yeongdong Lee3,4, Kyung Yeol Ma4,5,
Gwangwoo Kim^1 , Seong In Yoon4,5, Kyuwook Ihm^6 , Ki-Jeong Kim^6 , Tae Joo Shin1,7,
Sang Won Kim^2 , Eun-chae Jeon^8 , Hansol Jeon^3 , Ju-Young Kim^3 , Hyung-Ik Lee^9 ,
Zonghoon Lee3,4, Aleandro Antidormi^10 , Stephan Roche1 0,1 1, Manish Chhowalla^12 ✉,
Hyeon-Jin Shin^2 ✉ & Hyeon Suk Shin1,4,5,13 ✉Decrease in processing speed due to increased resistance and capacitance delay is a
major obstacle for the down-scaling of electronics^1 –^3. Minimizing the dimensions of
interconnects (metal wires that connect different electronic components on a chip) is
crucial for the miniaturization of devices. Interconnects are isolated from each other
by non-conducting (dielectric) layers. So far, research has mostly focused on
decreasing the resistance of scaled interconnects because integration of dielectrics
using low-temperature deposition processes compatible with complementary
metal–oxide–semiconductors is technically challenging. Interconnect isolation
materials must have low relative dielectric constants (κ values), serve as diffusion
barriers against the migration of metal into semiconductors, and be thermally,
chemically and mechanically stable. Specifically, the International Roadmap for
Devices and Systems recommends^4 the development of dielectrics with κ values of less
than 2 by 2028. Existing low-κ materials (such as silicon oxide derivatives, organic
compounds and aerogels) have κ values greater than 2 and poor thermo-mechanical
properties^5. Here we report three-nanometre-thick amorphous boron nitride films
with ultralow κ values of 1.78 and 1.16 (close to that of air, κ = 1) at operation frequencies
of 100 kilohertz and 1 megahertz, respectively. The films are mechanically and
electrically robust, with a breakdown strength of 7.3 megavolts per centimetre, which
exceeds requirements. Cross-sectional imaging reveals that amorphous boron nitride
prevents the diffusion of cobalt atoms into silicon under very harsh conditions, in
contrast to reference barriers. Our results demonstrate that amorphous boron nitride
has excellent low-κ dielectric characteristics for high-performance electronics.Modern high-performance logic and memory devices used in
multifunctional electronics are constructed using materials and designs
that have enabled a drastic reduction of transistor size and the packing
of more circuits in smaller areas^1 –^3 ,^6 –^11. However, the reduction in the
dimensions of metal interconnects and the increased packing density
have led to an increase in the resistance (R) and capacitance (C) delay,
which is becoming comparable to the operation speed of the devices.
Ideally, both R and C should be simultaneously reduced to achieve
continuous scaling of devices. However, the development of electri-
cally, mechanically and thermally robust low-κ materials (κ < 2) using
complementary metal–oxide–semiconductor (CMOS)-compatible
processes that are good inter-metal and inter-layer dielectrics and act
as diffusion barriers against electro-migration of metal atoms from
interconnects has been challenging.
State-of-the-art strategies for achieving low-κ dielectrics have
involved reducing the polarization strength and density of SiO 2
(κ = 4) by incorporating fluorine (κ = 3.7 for SiOF) or CH 3 (κ = 2.8 for
SiCOH) and introducing porosity (porous SiCOH or pSiCOH, κ = 2.4)^1 ,^12.
The recommendations of the International Roadmap for Devices and
Systems (IRDS) for 2028 call for the urgent development of ultralow-κ
dielectrics with κ values of less than 2 (refs.^13 ,^14 ). IRDS has also indi-
cated that the greatest challenge concerning interconnect develop-
ment is the introduction of new materials with reduced dielectric
permittivity. Boron-based compounds such as BCN and amorphoushttps://doi.org/10.1038/s41586-020-2375-9
Received: 16 November 2019
Accepted: 25 March 2020
Published online: 24 June 2020
Check for updates(^1) Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea. (^2) Inorganic Material Lab., Samsung Advanced Institute of Technology (SAIT), Suwon,
South Korea.^3 School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea.^4 Center for Multidimensional Carbon Materials,
Institute for Basic Science (IBS), Ulsan, South Korea.^5 Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea.^6 Pohang Accelerator
Laboratory, Gyeongbuk, South Korea.^7 UNIST Central Research Facilities, Ulsan, South Korea.^8 School of Materials Science and Engineering, University of Ulsan, Ulsan, South Korea.^9 Analytical
Engineering Group, Samsung Advanced Institute of Technology (SAIT), Suwon, South Korea.^10 Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Barcelona, Spain.
(^11) Institucio Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain. (^12) Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, UK. (^13) Low-Dimensional
Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea. ✉e-mail: [email protected]; [email protected]; [email protected]