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.

Partha Sharathi Mallick

Department of Instrumentation

School of Electrical Engineering

Vellore Campus

Uma Sathyakam P

Sathyakam P.U

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

This paper proposes novel triangular cross-sectioned geometry of carbon nanotube (CNT) bundles for crosstalk and delay reduction in CNT bundle interconnects for VLSI circuits. First, we formulate the equivalent single conductor (ESC) transmission line models of the interconnects. Through SPICE analysis of the ESC circuits, we find the propagation delays of the proposed CNT bundles. Next, we model the capacitively coupled interconnects for crosstalk analysis. It is found that the coupling capacitance of triangular CNT bundle is 29% lesser than the traditionally used square CNT bundles. Further, the crosstalk-induced delay of triangular interconnects is found to be 30% lesser when compared to square bundle interconnects. The reduction in delay is found to increase as the number of CNTs in the bundle increases. So, we suggest that triangular CNT bundles are the most suitable candidates as global interconnects.

Fulltext

Journal of Circuits, Systems and Computers

Geometry-Based Crosstalk Reduction in CNT Interconnects

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.

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

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,

Future Dielectric Materials for CNT Interconnects - Possibilities and Challenges

2019 IEEE 21st Electronics Packaging Technology Conference (EPTC)

On the Applicability of Triangular Carbon Nanotube Bundles as VLSI interconnects

Interconnects plays an important role in integrated circuits. Copper is used as an interconnect material, but beyond 22[Formula: see text]nm technology node it faces many problems due to grain boundary scattering, and therefore carbon nanotubes are the most promising future interconnect materials. Various techniques and approaches such as driver sizing, repeater sizing, repeater insertion, wire sizing, wire spacing, shielding, boos table repeater were used by various researchers. Many of these techniques can be utilized for future CNT based VLSI interconnects as well. This paper presents a detailed discussion on the techniques and approaches of past, present and future relevant for interconnects of VLSI circuits.

Optimization Techniques for CNT Based VLSI Interconnects — A Review

Carbon nanotube based interconnect technology is becoming popular for its various merits over the current copper technology. The ability to conduct high current at high temperatures through the 1D structure is making the CNT interconnect technology an attractive one. Single wall and multi wall CNT interconnects have received greater interest initially when the mixed CNT bundles (MCBs) did not get much attention as VLSI interconnects. But, it was only in 2007 when the conductance study of mixed CNT bundles was done and since then many works have been reported. At this stage, it is essential to review the reports of MCB based interconnect technology. We present in this paper, the first review on MCB VLSI interconnects.

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