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Thermally conductive ultra-low-k dielectric layers based on two-dimensional covalent organic frameworks

Nature Materials volume 20, pages 1142–1148 (2021)Cite this article

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Abstract

As the features of microprocessors are miniaturized, low-dielectric-constant (low-k) materials are necessary to limit electronic crosstalk, charge build-up, and signal propagation delay. However, all known low-k dielectrics exhibit low thermal conductivities, which complicate heat dissipation in high-power-density chips. Two-dimensional (2D) covalent organic frameworks (COFs) combine immense permanent porosities, which lead to low dielectric permittivities, and periodic layered structures, which grant relatively high thermal conductivities. However, conventional synthetic routes produce 2D COFs that are unsuitable for the evaluation of these properties and integration into devices. Here, we report the fabrication of high-quality COF thin films, which enable thermoreflectance and impedance spectroscopy measurements. These measurements reveal that 2D COFs have high thermal conductivities (1 W m−1 K−1) with ultra-low dielectric permittivities (k = 1.6). These results show that oriented, layered 2D polymers are promising next-generation dielectric layers and that these molecularly precise materials offer tunable combinations of useful properties.

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Fig. 1: Templated colloidal polymerization of boronate ester-linked COF films.
Fig. 2: Optoelectronic properties of COF films.
Fig. 3: COF-5 dielectric layer impedance measurements.
Fig. 4: Thermal properties of 2D COF thin films.
Fig. 5: Meta-analysis of thermal conductivities in low-k dielectrics.

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Source data are provided with this paper. Additional data are available from the corresponding authors upon request.

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Acknowledgements

W.R.D., J.-L.B. and F.W. thank the Army Research Office of the United States for a Multidisciplinary University Research Initiatives (MURI) award under grant no. W911NF-15-1-0447. A.M.E. is supported by a National Science Foundation (NSF) Graduate Research Fellowship under grant no. DGE-1324585. N.P.B. also acknowledges an NSF Graduate Research Fellowship. A.G. and P.E.H. appreciate support from the Office of Naval Research (grant no. N00014-20-1-2686). M.B., J.A.M. and A.J.H.M. gratefully acknowledge support from the Army Research Office, grant W911NF-17-1-0397. The electron microscopy work was supported by the United States Department of Energy (DOE DE-SC0019356), and the impedance spectroscopy work was supported by the NSF (DMR-1720139). This study made use of the Integrated Molecular Structure Education and Research Center (IMSERC) and the Electron Probe Instrumentation Center (EPIC) at Northwestern University, both of which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205 and NSF ECCS1542205, respectively), the Materials Research Science and Engineering Center (NSF DMR-1720139), the State of Illinois, and the International Institute for Nanotechnology. Portions of this work were performed at the DuPont–Northwestern–Dow Collaborative Access Team (DND-CAT) located at Sector 5 and Sector 8 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co. and the Dow Chemical Company. This research used resources of the Advanced Photon Source and Center for Nanoscale Materials, both of which are DOE Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. Resources at the Advanced Photon Source were funded by the NSF under award no. 0960140. This research used resources of the Advanced Light Source, a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.

Author information

Author notes

  1. These authors contributed equally: Austin M. Evans, Ashutosh Giri.

Authors and Affiliations

  1. Department of Chemistry, Northwestern University, Evanston, IL, USA

    Austin M. Evans, Edon Vitaku, David W. Burke, Mark C. Hersam & William R. Dichtel

  2. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, USA

    Ashutosh Giri & Patrick E. Hopkins

  3. Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI, USA

    Ashutosh Giri

  4. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA

    Vinod K. Sangwan, Carlos G. Torres-Castanedo, Matthew S. Rahn, Nathan P. Bradshaw, Michael J. Bedzyk & Mark C. Hersam

  5. School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA

    Sangni Xun

  6. Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA

    Sangni Xun

  7. College of Environmental Science and Engineering, Hunan University, Changsha, People’s Republic of China

    Sangni Xun

  8. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

    Matthew Bartnof, Jonathan A. Malen & Alan J. H. McGaughey

  9. Department of Physics, University of California Berkeley, Berkeley, CA, USA

    Halleh B. Balch & Feng Wang

  10. Kavli Energy NanoScience Institute, University of California Berkeley, Berkeley, CA, USA

    Halleh B. Balch & Feng Wang

  11. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Halleh B. Balch & Feng Wang

  12. Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ, USA

    Hong Li & Jean-Luc Brédas

  13. Department of Physics and Astronomy, Northwestern University, Evanston, IL, USA

    Michael J. Bedzyk

  14. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

    Jonathan A. Malen & Alan J. H. McGaughey

  15. Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, USA

    Mark C. Hersam

  16. Simpson Querrey Institute, Northwestern University, Evanston, IL, USA

    Mark C. Hersam

  17. Department of Physics, University of Virginia, Charlottesville, VA, USA

    Patrick E. Hopkins

  18. Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, USA

    Patrick E. Hopkins

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Contributions

A.M.E. prepared and characterized all COF films. A.G. performed all thermal property characterization and simulations. V.K.S. prepared COF-5 devices and performed impedance spectroscopy. S.X. and H.L. performed and interpreted density functional theory calculations. M.B. performed thermal property characterization. C.G.T.-C. performed and interpreted the X-ray reflectivity experiments. H.B.B. performed synchrotron X-ray scattering experiments. M.S.R. prepared EG/SiC substrates used for COF devices. N.P.B. imaged the COF devices using scanning electron microscopy. E.V. assisted with monomer syntheses. D.W.B. assisted with synchrotron X-ray characterization. V.K.S., H.L., M.J.B., F.W., J.-L.B., J.A.M., A.J.H.M., M.C.H., W.R.D. and P.E.H. supervised this work. All authors contributed to the conception of the study, data interpretation and manuscript preparation.

Corresponding authors

Correspondence to William R. Dichtel or Patrick E. Hopkins.

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Northwestern University and the University of Virginia have filed a preliminary patent application (provisional application no. 6314014) related to the discoveries disclosed here.

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Evans, A.M., Giri, A., Sangwan, V.K. et al. Thermally conductive ultra-low-k dielectric layers based on two-dimensional covalent organic frameworks. Nat. Mater. 20, 1142–1148 (2021). https://doi.org/10.1038/s41563-021-00934-3

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