Carbon nanotube (CNT) interconnects are emerging as the ultimate choice for next generation ultra large scale integrated (ULSI) circuits. Significant progress in precise growth of aligned CNTs and integration of multiwalled CNT interconnects into a test chip make them promising candidates for future nanoelectronic chips. Tremendous research efforts were made on silicon based ultra-low-k dielectrics for Cu interconnects, but, the most recent advancements in polymer based composites as dielectric materials open up fresh challenges in the use of low-k dielectrics for CNT interconnects. This paper reviews the emerging polymer composites like Boron Nitride Nanotubes, Graphene/Polyimide composites, Metal Organic Frameworks and small diameter CNTs. Many reviews are already exists on the synthesis, fabrication, dielectric, mechanical, chemical and thermal properties of these materials. In this review, we have explained the specific properties of these materials and the necessities for integrating them into CNT interconnects to meet the requirements of future IC designers.Keywords: low-k dielectric materials, ultra low-k dielectrics, carbon nanotubes, interconnects, dielectric constant,

Uma Sathyakam P

Department of Instrumentation

School of Electrical Engineering

Vellore Campus

Partha Sharathi Mallick

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Journal of Nano Research

Triangular carbon nanotube (T-CNT) bundles are proposed as long interconnects for subthreshold VLSI circuits. The performance of subthreshold interconnects depends on the intrinsic quantum and electrostatic coupling capacitances of the interconnects. Proposed T-CNT bundles have the most optimum geometry that give least possible coupling capacitance between adjacent wires in an IC. First, we describe the T-CNT bundle models and of traditionally used square/rectangular CNT bundles for comparison. The subthreshold output current of an inverter is modelled, and hence, we find the optimum transistor widths for nFET and pFET that drives the subthreshold interconnects. This is carried out by the current-over-capacitance ratio approach, where the subthreshold current and the transistor output capacitance are considered. Then, we model the interconnects using equivalent single conductor models and find their propagation delay and power dissipated. The performance factors such as crosstalk-induced delay, power delay product and victim noise levels of capacitive coupled interconnects of T-CNT bundles are compared to traditionally used square/rectangular CNT bundles for lengths ranging from 500&nbsp;μm to 2000&nbsp;μm. We find that T-CNT bundles outperform square/rectangular CNT bundles.

Fulltext

Journal of Electronic Materials

Triangular Carbon Nanotube Bundle Interconnects for Subthreshold VLSI Circuits

Current mode signaling (CMS) is found to be advantageous than voltage mode signaling (VMS) in VLSI interconnects. So, we propose the use of triangular carbon nanotube bundles as VLSI interconnects for CMS in VLSI circuits. T-CNT bundles have inherent advantages of lesser propagation delay and crosstalk delay than traditionally proposed square CNT bundle interconnects. We analyze the propagation delays of both the types of bundles in voltage and current mode signalling schemes and compare the improvement of propagation delay in both the cases. We find that T-CNT bundles perform better than square bundles in both the signalling schemes. © 2019 IEEE.

2019 Innovations in Power and Advanced Computing Technologies (i-PACT)

Analysis of triangular CNT bundle interconnects for current mode signalling

2019 IEEE 21st Electronics Packaging Technology Conference (EPTC)

On the Applicability of Triangular Carbon Nanotube Bundles as VLSI interconnects

This paper presents single walled carbon nanotube (SWCNT) interconnects with air as dielectric medium. We treat CNT interconnects as a discrete (fractal) media for the first time where continuum based differential equations fail to capture the physics at nanoscale and hence, we use discrete partial differential equations in this work. We have analyzed the effect of air gaps (AG) on performance factors like temperature dependent resistance R(T) of CNTs and hence the R(T)C delay of the interconnects. We have first calculated the temperature coefficient of resistance (TCR) of CNTs and analyzed the trend of changing resistance at different ambient temperatures. The R(T)C delay shows that CNT/AG interconnects can operate satisfactorily up to 500K. We then compare the R(T)C delay with ITRS predictions from 17nm to 8nm technology nodes. We have also calculated the chip area used by CNT/air-gap interconnects and found that they take up to 83% lesser area than the conventional Cu/low-k interconnects.

Carbon Nanotube Interconnects with Air-Gaps: Effect on Thermal Stability, Delay and Area

Journal of Materials Science: Materials in Electronics

Study of conjugated polymer/graphene oxide nanocomposites as flexible dielectric medium

Performance of mixed carbon nanotube bundle interconnects are analyzed for subthreshold circuits. As voltage scaling in ULSI ICs lead to performance challenges in delay, power dissipation and the overall performance of interconnects, we simulate two mixed CNT bundle configurations, MCB-1 and MCB-2, to analyze their propagation delay, power dissipated and energy delay product for 500μm interconnect length and at 20nm technology noce. Further, we do crosstalk analysis of the proposed bundles using a driver-interconnect-load model. One line is aggressor and another line is victim. Simulated results shows that MCB that has MWCNTs at the periphery and SWCNTs at the core is ideal for intermediate level interconnect applications.

2016 International Conference on Information Communication and Embedded Systems (ICICES)

Mixed CNT bundle interconnects for subthreshold circuits

This paper investigates the multi equivalent single conductor (MESC) model for mixed CNT bundles (MCBs) which contains metallic single and double walled CNTs at the core and semiconducting single walled CNTs at the periphery. This structure shows the least delay due to crosstalk.

2014 International Conference on Advances in Electrical Engineering (ICAEE)

Reduction of crosstalk in mixed CNT bundle interconnects for high frequency 3D ICs and SoCs

In this letter, we present a new method to reduce crosstalk of carbon nanotube (CNT)-based VLSI interconnects. For this, proper integration of semiconducting CNTs (s-CNTs) and a new contact geometry, where metallic CNTs are in the core and s-CNTs are in the periphery of the CNT bundle, is proposed. The coupling capacitance between adjacent interconnects is modeled and compared with and without s-CNTs in the CNT bundle periphery. SPICE analysis and EM simulations are carried out which show that the coupling capacitance can be reduced by 82.5% and the resulting delay by 8.41%. We suggest that the crosstalk effect between neighboring wires can be reduced by using s-CNTs in the design.

Journal	Journal of Nano Research
Publisher	Trans Tech Publications, Ltd.
ISSN	16619897
Open Access	No