Prospects of graphene and carbon nanotube for nanoscale interconnects

Abstract

Interconnects are the channels that provide power and carry signals between various components on an integrated circuit. As technology is shrinking to nano scale the thickness of the interconnect wire is also decreasing. Currently, copper (Cu) is being used as interconnect material but with the scaling in nanometer regime, it exhibits much difficulties in terms of IC performance and reliability. Which is the bottleneck for improving IC performance in future. When the thickness of the copper wire reduces to 41nm its resistivity becomes approximately 1.5 times of the bulk resistivity[56]. When this thickness is 10nm the resistivity is infinite. Not only this to keep pace with the current technology node of interconnets a large amount of current has to flow within a very thick wire. for this reason the wire has to withstand with a high current density. But copper at nanometer range only sustain in 106A/cm2[81] of current densities with some structural defects. Also in this current density copper wire exhibits very high joule heating consequently degrades the IC’s performance. Progressively high curent density leads to electromigration faliure which degrades wire life time. As a result IC lose its longevity. To tackle this challenges and difficulties faced by copper wires it is high time to think of another material which can be used as interconnect for future devices. The new material have to have sustainability in nanoscale with higher breakdown current density, Elecromigration antagonist and joule heating preventive which leads to high performance IC’s. Also the new material need to be reliable which makes the interconnect lifetime higher. In this paper we are proposing two new material named graphene and carbon nanotube(CNT) which can be the effective replacement of copper. Graphene and CNT can be implemented in nanoscale interonnects for their magical characteristics. Both of this material have nanoscale physical configuaration. Graphene has low resistivity (1u cm)[72] is even lower compared to other good conductor like silver (1.5u cm). Not only this CNT’s and Graphene can withstand current densities up to 109A/cm2[81] which make them electromigration antagonist. But The only challenge for graphene is schottkey barrier it creates at the junction of the metal and semiconductor which causes a barrier height for electron to pass through. Another compound mixing where the barrier height is less can solve the problem of graphene. If this issue is resolved, we may then directly use Graphene and CNT for nano scale interconnects. This paper extensively illustrates why Graphene and CNT can be the best alternative for replacing copper. In the beginning of the paper different kinds of interconnect has been described. Later that the paper delivers a comprehensive review of the previous, existing materials used for interconnects v and then described the new materials for interconnects. The paper also elaborates the major limitations of copper in nanoscale interconnects and then successfully delineate the major advantages we may get from graphene and carbon nanotube as interconnect material. After that the production route of graphene has been described. In this dissertation we tried to establish the major issues of copper and the best alternative for that. Further study is needed for the capping material of graphene which will increase the lifetime of the interconnect.