Opportunities and challenges of 2D materials in back-end-of-line interconnect scaling

As the challenges in continued scaling of the integrated circuit technology escalate every generation, there is an urgent need to find viable solutions for both the front-end-of-line (transistors) and the back-end-of-line (interconnects). For the interconnect technology, it is crucial to replace the conventional barrier and liner with much thinner alternatives so that the current driving capability of the interconnects can be maintained or even improved. Due to the inherent atomically thin body thicknesses, 2D materials have recently been proposed and explored as Cu diffusion barrier alternatives. In this Perspective article, a variety of 2D materials that have been studied, ranging from graphene, h-BN, MoS2, WSe2 to TaS2, will be reviewed. Their potentials will be evaluated based on several criteria, including fundamental material properties as well as the feasibility for technology integration. Using TaS2 as an example, we demonstrate a large set of promising properties and point out that there remain challenges in the integration aspects with a few possible solutions waiting for validation. Applications of 2D materials for other functions in Cu interconnects and for different metal types will also be introduced, including electromigration, cobalt interconnects, and radio-frequency transmission lines.

[1]  G. Henkelman,et al.  A climbing image nudged elastic band method for finding saddle points and minimum energy paths , 2000 .

[2]  Tetsuya Osaka,et al.  Advanced nanoscale ULSI interconnects : fundamentals and applications , 2009 .

[3]  Moon J. Kim,et al.  Enhancing Interconnect Reliability and Performance by Converting Tantalum to 2D Layered Tantalum Sulfide at Low Temperature , 2019, Advanced materials.

[4]  Robert Rosenberg,et al.  Reduced electromigration of Cu wires by surface coating , 2002 .

[5]  Andrew H. Simon,et al.  Comparison of Cu electromigration lifetime in Cu interconnects coated with various caps , 2003 .

[6]  F. Zahid,et al.  Resistivity of thin Cu films coated with Ta, Ti, Ru, Al, and Pd barrier layers from first principles , 2010 .

[7]  M. Chaigneau,et al.  Synthesis of conducting transparent few-layer graphene directly on glass at 450 °C , 2012, Nanotechnology.

[8]  Moon J. Kim,et al.  Comparison of graphene growth on arbitrary non-catalytic substrates using low-temperature PECVD , 2015 .

[9]  Michael Lane,et al.  Relationship between interfacial adhesion and electromigration in Cu metallization , 2003 .

[10]  Moon J. Kim,et al.  MoS2 for Enhanced Electrical Performance of Ultrathin Copper Films. , 2019, ACS applied materials & interfaces.

[11]  E. Liniger,et al.  The effect of Cu diffusion on the TDDB behavior in a low-k interlevel dielectrics , 2006, Microelectron. Reliab..

[12]  Stefan Grimme,et al.  Semiempirical GGA‐type density functional constructed with a long‐range dispersion correction , 2006, J. Comput. Chem..

[13]  J. Narayan,et al.  Copper diffusion characteristics in single-crystal and polycrystalline TaN , 2002 .

[14]  Suppression of conductivity deterioration of copper thin films by coating with atomic-layer materials , 2017 .

[15]  Chuan-Pu Liu,et al.  Effect of crystallinity and preferred orientation of Ta2N films on diffusion barrier properties for copper metallization , 2006 .

[16]  D. Edelstein,et al.  Characterization of Copper Electromigration Dependence on Selective Chemical Vapor Deposited Cobalt Capping Layer Thickness , 2011, IEEE Electron Device Letters.

[17]  Jen Fin Lin,et al.  1-nm-thick graphene tri-layer as the ultimate copper diffusion barrier , 2014 .

[18]  O. Singh,et al.  The phase transition in 2H-TaS2 at 75 K , 1974 .

[19]  R. K. Smith,et al.  Thin dielectric films: Uncorrelated breakdown of integrated circuits , 2002, Nature.

[20]  T. Wong.  Time Dependent Dielectric Breakdown in Copper Low-k Interconnects: Mechanisms and Reliability Models , 2012, Materials.

[21]  Seong Jun Yoon,et al.  Ultrathin graphene and graphene oxide layers as a diffusion barrier for advanced Cu metallization , 2015 .

[22]  David T. Read,et al.  Resistivity dominated by surface scattering in sub-50 nm Cu wires , 2010 .

[23]  Chandreswar Mahata,et al.  Graphene as an atomically thin barrier to Cu diffusion into Si. , 2014, Nanoscale.

[24]  J. Shapter,et al.  Accurate thickness measurement of graphene , 2016, Nanotechnology.

[25]  Diederik Verkest,et al.  Impact of Wire Geometry on Interconnect RC and Circuit Delay , 2016, IEEE Transactions on Electron Devices.

[26]  Tuo-Hung Hou,et al.  Large‐Area 2D Layered MoTe2 by Physical Vapor Deposition and Solid‐Phase Crystallization in a Tellurium‐Free Atmosphere , 2017 .

[27]  Philippe Benech,et al.  Cu Nanolines for RF Interconnects: Electrical Characterization , 2015, IEEE Transactions on Electron Devices.

[28]  S. Kodambaka,et al.  Near room-temperature synthesis of transfer-free graphene films , 2012, Nature Communications.

[29]  T. Kuan,et al.  Alteration of Cu conductivity in the size effect regime , 2004 .

[30]  Eric Eisenbraun,et al.  Ultrathin Diffusion Barriers/Liners for Gigascale Copper Metallization , 2000 .

[31]  D. Chi,et al.  Growth of wafer-scale MoS2 monolayer by magnetron sputtering. , 2015, Nanoscale.

[32]  Taesung Kim,et al.  Low‐Temperature Synthesis of Large‐Scale Molybdenum Disulfide Thin Films Directly on a Plastic Substrate Using Plasma‐Enhanced Chemical Vapor Deposition , 2015, Advanced materials.

[33]  Hui Long,et al.  Mass transport mechanism of cu species at the metal/dielectric interfaces with a graphene barrier. , 2014, ACS nano.

[34]  K. Croes,et al.  Electromigration Activation Energies in Alternative Metal Interconnects , 2019, IEEE Transactions on Electron Devices.

[35]  Chun-Li Lo,et al.  Large-Area, Single-Layer Molybdenum Disulfide Synthesized at BEOL Compatible Temperature as Cu Diffusion Barrier , 2018, IEEE Electron Device Letters.

[36]  J. W. McPherson,et al.  Time dependent dielectric breakdown physics - Models revisited , 2012, Microelectron. Reliab..

[37]  Laurence Moquillon,et al.  65-, 45-, and 32-nm Aluminium and Copper Transmission-Line Model at Millimeter-Wave Frequencies , 2010, IEEE Transactions on Microwave Theory and Techniques.

[38]  J. Michelon,et al.  Challenges in the implementation of low-k dielectrics in the back-end of line , 2005 .

[39]  Three-dimensional resistivity and switching between correlated electronic states in 1T-TaS2 , 2016, Scientific reports.

[40]  S. Ciraci,et al.  Graphene coatings: An efficient protection from oxidation , 2012, 1203.2580.

[41]  A. Turak,et al.  Synergistic oxidation of CVD graphene on Cu by oxygen plasma etching , 2017 .

[42]  G. Kresse,et al.  Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set , 1996 .

[43]  E. Vogel,et al.  Low-temperature, plasma assisted, cyclic synthesis of MoS2 , 2018 .

[44]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[45]  Blöchl,et al.  Projector augmented-wave method. , 1994, Physical review. B, Condensed matter.

[46]  W. Steinhögl,et al.  Size-dependent resistivity of metallic wires in the mesoscopic range , 2002 .

[47]  S. Datta,et al.  Two-dimensional tantalum disulfide: controlling structure and properties via synthesis , 2018 .

[48]  Daniel C. Edelstein,et al.  Copper Metallization for High Performance Silicon Technology , 2000 .

[49]  M. Murakami,et al.  Diffusion barrier property of TaN between Si and Cu , 1996 .

[50]  A. Wee,et al.  Study of copper diffusion into Ta and TaN barrier materials for MOS devices , 2004 .

[51]  Chun-Li Lo,et al.  Incorporating Niobium in MoS2 at BEOL‐Compatible Temperatures and its Impact on Copper Diffusion Barrier Performance , 2019, Advanced Materials Interfaces.

[52]  M. J. Kim,et al.  Diffusion Studies of Copper on Ruthenium Thin Film A Plateable Copper Diffusion Barrier , 2004 .

[53]  G. Ardila,et al.  High frequency characterization and modeling of single metallic nanowire , 2013, 2012 International Semiconductor Conference Dresden-Grenoble (ISCDG).

[54]  N. J. Chou.  Application of Triangular Voltage Sweep Method to Mobile Charge Studies in MOS Structures , 1971 .

[55]  R. Mehta,et al.  Transfer-free multi-layer graphene as a diffusion barrier. , 2017, Nanoscale.

[56]  G. Kresse,et al.  From ultrasoft pseudopotentials to the projector augmented-wave method , 1999 .

[57]  Han Li,et al.  Modulating crack propagation in a multilayer stack with a super-layer , 2015 .

[58]  A. Strachan,et al.  Novel doping alternatives for single-layer transition metal dichalcogenides , 2017, 1703.10745.

[59]  J. P. Tidman,et al.  Resistivity of thin TaS2 crystals , 1976 .

[60]  A. Lamperti,et al.  Large-area patterning of substrate-conformal MoS2 nano-trenches , 2019, Nano Research.

[61]  S. Rossnagel.  Characteristics of ultrathin Ta and TaN films , 2002 .

[62]  B. Fraisse,et al.  Copper diffusion in TaN-based thin layers , 2008 .

[63]  L. Mattheiss.  Band Structures of Transition-Metal-Dichalcogenide Layer Compounds. , 1973 .

[64]  J. Noguchi,et al.  Dominant factors in TDDB degradation of Cu interconnects , 2005, IEEE Transactions on Electron Devices.

[65]  Sunny Chugh,et al.  Enhanced electrical and thermal conduction in graphene-encapsulated copper nanowires. , 2015, Nano letters.

[67]  San-Yuan Chen,et al.  Phase formation behavior and diffusion barrier property of reactively sputtered tantalum-based thin films used in semiconductor metallization , 1999 .

[68]  H. Wong,et al.  In-Situ Grown Graphene Enabled Copper Interconnects With Improved Electromigration Reliability , 2019, IEEE Electron Device Letters.

[69]  T. Siegmund,et al.  A modified 4-point bend delamination test , 2008 .

[70]  J. Vlassak,et al.  Water Diffusion and Fracture Behavior in Nano-Porous Low-K Dielectric Film Stacks , 2009 .

[71]  Ping-Chuan Wang,et al.  Electromigration threshold in copper interconnects , 2001 .

[72]  Moshe Eizenberg,et al.  Copper ion diffusion in porous and nonporous SiO2-based dielectrics using bias thermal stress and thermal stress tests , 2008 .

[73]  Eric Pop,et al.  Studies of two-dimensional h-BN and MoS2 for potential diffusion barrier application in copper interconnect technology , 2017, npj 2D Materials and Applications.

[74]  Christopher J. Wilson,et al.  Direct observation of the 1/E dependence of time dependent dielectric breakdown in the presence of copper , 2011 .

[75]  E. Pop,et al.  Intrinsic electrical transport and performance projections of synthetic monolayer MoS2 devices , 2016, 1608.00987.

[76]  Jing Sun,et al.  A long-term oxidation barrier for copper nanowires: graphene says yes. , 2015, Physical chemistry chemical physics : PCCP.

[77]  Sungjoo Lee,et al.  Controlled Layer-by-Layer Etching of MoS₂. , 2015, ACS applied materials & interfaces.

[78]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[79]  Junyong Kang,et al.  Oxidation resistance of graphene-coated Cu and Cu/Ni alloy. , 2011, ACS nano.

[80]  Hasan Sahin,et al.  Monolayers of MoS2 as an oxidation protective nanocoating material , 2014 .

[81]  Jing‐Cheng Lin,et al.  Grain Boundary Diffusion of Copper in Tantalum Nitride Thin Films , 1999 .

[82]  Lain-Jong Li,et al.  Recent advances in controlled synthesis of two-dimensional transition metal dichalcogenides via vapour deposition techniques. , 2015, Chemical Society reviews.

[83]  S. Xiao,et al.  Layer-by-layer thinning of MoSe 2 by soft and reactive plasma etching , 2017 .