{"46304":{"#nid":"46304","#data":{"type":"news","title":"Graphene May Have Advantages Over Copper for Future IC Interconnects","body":[{"value":"\u003Cp\u003EThe unique properties of thin layers of graphite -- known as graphene -- make the material attractive for a wide range of potential electronic devices.  Researchers have now experimentally demonstrated the potential for another graphene application: replacing copper for interconnects in future generations of integrated circuits.\u003C\/p\u003E\n\u003Cp\u003EIn a paper published in the June 2009 issue of the IEEE journal \u003Cem\u003EElectron Device Letters\u003C\/em\u003E, researchers at the Georgia Institute of Technology report detailed analysis of resistivity in graphene nanoribbon interconnects as narrow as 18 nanometers.\n\u003C\/p\u003E\n\u003Cp\u003EThe results suggest that graphene could out-perform copper for use as on-chip interconnects -- tiny wires that are used to connect transistors and other devices on integrated circuits.  Use of graphene for these interconnects could help extend the long run of performance improvements for silicon-based integrated circuit technology.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022As you make copper interconnects narrower and narrower, the resistivity increases as the true nanoscale properties of the material become apparent,\u0022 said Raghunath Murali, a research engineer in Georgia Tech\u0027s Microelectronics Research Center and the School of Electrical and Computer Engineering.  \u0022Our experimental demonstration of graphene nanowire interconnects on the scale of 20 nanometers shows that their performance is comparable to even the most optimistic projections for copper interconnects at that scale.  Under real-world conditions, our graphene interconnects probably already out-perform copper at this size scale.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EBeyond resistivity improvement, graphene interconnects would offer higher electron mobility, better thermal conductivity, higher mechanical strength and reduced capacitance coupling between adjacent wires.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Resistivity is normally independent of the dimension -- a property inherent to the material,\u0022 Murali noted.  \u0022But as you get into the nanometer-scale domain, the grain sizes of the copper become important and conductance is affected by scattering at the grain boundaries and at the side walls.  These add up to increased resistivity, which nearly doubles as the interconnect sizes shrink to 30 nanometers.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe research was supported by the Interconnect Focus Center, which is one of the Semiconductor Research Corporation\/DARPA Focus Centers, and the Nanoelectronics Research Initiative through the INDEX Center.\n\u003C\/p\u003E\n\u003Cp\u003EMurali and collaborators Kevin Brenner, Yinxiao Yang, Thomas Beck and James Meindl studied the electrical properties of graphene layers that had been taken from a block of pure graphite.  They believe the attractive properties will ultimately also be measured in graphene fabricated using other techniques, such as growth on silicon carbide, which now produces graphene of lower quality but has the potential for achieving higher quality.  \n\u003C\/p\u003E\n\u003Cp\u003EBecause graphene can be patterned using conventional microelectronics processes, the transition from copper could be made without integrating a new manufacturing technique into circuit fabrication.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We are optimistic about being able to use graphene in manufactured systems because researchers can already grow layers of it in the lab,\u0022 Murali noted.  \u0022There will be challenges in integrating graphene with silicon, but those will be overcome. Except for using a different material, everything we would need to produce graphene interconnects is already well known and established.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EExperimentally, the researchers began with flakes of multi-layered graphene removed from a graphite block and placed onto an oxidized silicon substrate.  They used electron beam lithography to construct four electrode contacts on the graphene, then used lithography to fabricate devices consisting of parallel nanoribbons of widths ranging between 18 and 52 nanometers.  The three-dimensional resistivity of the nanoribbons on 18 different devices was then measured using standard analytical techniques at room temperature.\n\u003C\/p\u003E\n\u003Cp\u003EThe best of the graphene nanoribbons showed conductivity equal to that predicted for copper interconnects of the same size.  Because the comparisons were between non-optimized graphene and optimistic estimates for copper, they suggest that performance of the new material will ultimately surpass that of the traditional interconnect material, Murali said.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Even graphene samples of moderate quality show excellent properties,\u0022 he explained.  \u0022We are not using very high levels of optimization or especially clean processes.  With our straightforward processing, we are getting graphene interconnects that are essentially comparable to copper.  If we do this more optimally, the performance should surpass copper.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThough one of graphene\u0027s key properties is reported to be ballistic transport -- meaning electrons can flow through it without resistance -- the material\u0027s actual conductance is limited by factors that include scattering from impurities, line-edge roughness and from substrate phonons -- vibrations in the substrate lattice.  \n\u003C\/p\u003E\n\u003Cp\u003EUse of graphene interconnects could help facilitate continuing increases in integrated circuit performance once features sizes drop to approximately 20 nanometers, which could happen in the next five years, Murali said.  At that scale, the increased resistance of copper interconnects could offset performance increases, meaning that without other improvements, higher density wouldn\u0027t produce faster integrated circuits.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This is not a roadblock to achieving scaling from one generation to the next, but it is a roadblock to achieving increased performance,\u0022 he said.  \u0022Dimensional scaling could continue, but because we would be giving up so much in terms of resistivity, we wouldn\u0027t get a performance advantage from that.  That\u0027s the problem we hope to solve by switching to a different materials system for interconnects.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Vogel (404-385-3364); E-mail: (\u003Ca href=\u0022mailto:avogel@gatech.edu\u0022\u003Eavogel@gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"New Material May Replace Traditional Metal at Nanoscale Widths"}],"field_summary":[{"value":"Georgia Tech researchers have experimentally demonstrated the potential for another application of graphene: replacing copper for interconnects in future generations of integrated circuits.","format":"limited_html"}],"field_summary_sentence":[{"value":"Graphene could replace copper for nanoscale IC interconnects"}],"uid":"27303","created_gmt":"2009-06-04 00:00:00","changed_gmt":"2016-10-08 03:03:14","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2009-06-04T00:00:00-04:00","iso_date":"2009-06-04T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"46305":{"id":"46305","type":"image","title":"Graphene interconnects","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894414","gmt_changed":"2016-10-08 02:40:14","alt":"Graphene interconnects","file":{"fid":"101083","name":"tyf17432.jpg","image_path":"\/sites\/default\/files\/images\/tyf17432_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tyf17432_0.jpg","mime":"image\/jpeg","size":890854,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tyf17432_0.jpg?itok=P0xy4pJx"}},"46306":{"id":"46306","type":"image","title":"Testing graphene","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894414","gmt_changed":"2016-10-08 02:40:14","alt":"Testing graphene","file":{"fid":"101084","name":"tai17432.jpg","image_path":"\/sites\/default\/files\/images\/tai17432_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tai17432_0.jpg","mime":"image\/jpeg","size":1304054,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tai17432_0.jpg?itok=FCpn2p9a"}},"46307":{"id":"46307","type":"image","title":"Microscope image","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894416","gmt_changed":"2016-10-08 02:40:16","alt":"Microscope image","file":{"fid":"101085","name":"tni17432.jpg","image_path":"\/sites\/default\/files\/images\/tni17432_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tni17432_0.jpg","mime":"image\/jpeg","size":158173,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tni17432_0.jpg?itok=TrysqtjE"}}},"media_ids":["46305","46306","46307"],"related_links":[{"url":"http:\/\/www.mirc.gatech.edu\/","title":"Microelectronics Research Center"},{"url":"http:\/\/www.mirc.gatech.edu\/raghu\/","title":"Raghunath Murali"},{"url":"http:\/\/ieeexplore.ieee.org\/xpl\/freeabs_all.jsp?arnumber=4968006\u0026count=43\u0026index=12\u0026isnumber=4968003","title":"Paper in Electron Device Letters"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"429","name":"graphene"},{"id":"433","name":"IC"},{"id":"430","name":"interconnects"},{"id":"432","name":"nanoribbon"},{"id":"431","name":"nanoscale"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}