Carbon Nanotube ViasOutlineWhat Are Vias?Carbon Nanotubes for ViasCNT Damascene ProcessCharacterization ResultsIssues with Current EffortsThermal & Self-Heating IssuesSummary & ConclusionReferencesCarbon Nanotube ViasBy: Rhesa NathanaelOutlineWhat are vias?Why carbon nanotubes for vias?Fabrication sequence.Characterization results.Issues with current efforts.Summary & Conclusion.What Are Vias?ITRS, 2007Intel, IEDM 2007Carbon Nanotubes for ViasCopper:Resistance ↑ with scaling.Electromigration.Carbon Nanotubes:Ballistic transport.Very large resistance to electromigration.R = h/4e2 = 6.45kΩAllows current densities > 109 A/cm2CNT Damascene Processa) Via hole formationb) TaN/Ta barrier layer TiN contact layer Co catalyst nanoparticlesc) Nanotube growth•CVD (C2H2 + Ar at 1kPa, 450ºC)d) SOG coatinge) CMP nanotubes CMP TiN, TaN/Taf) Ti top contact layer Ta barrier layer Cu interconnectCharacterization ResultsCNT density = 3x1011 cm-2Mean free path = 80nm 32nm Technology Node (2013)Ballistic transportRc = contact resistance = 0.5kΩ RCNT = nanotube resistanceRQ = quantum resistancenCNT = number of shells = 7λCNT = electron mean free pathH = via heighth = Planck’s constante = electron chargeIssues with Current EffortsMost fabrication efforts MWCNT.Most characterization efforts electrical properties.CNT via resistance within an order of magnitude of Cu via has been demonstrated.More effort needed on SWCNT & thermal characterization.SWCNT vs. Cu MWCNTLocal interconnectThermal & Self-Heating IssuesThermal contact resistance + Joule heating at metal CNT contactMWCNT thermal properties inferior to Cu & SWCNTConclusion:Summary & ConclusionCarbon nanotube for vias:Ballistic transport.Electromigration resistance.Damascene process.Mean free path 80nm 32nm technology node.Efforts misplaced?SWCNT vs. MWCNT.More careful thermal characterization of CNT vias needed.Replace Cu?Dense SWCNT bundles.Good electrical and thermal contact.References[1] M. Nihei, et al., “Electrical performance of carbon nanotube via interconnects fabricated by novel damascene process,” International Interconnect Technology Conference 2007, pp. 204-206.[2] H. Li, et al., “Carbon nanotube vias: a reality check,” Inernational Electron Devices Meeting 2007 pp. 207-210.[3] B. Q. Wei, et al., “Reliability and current carrying capacity of carbon nanotubes,” App. Phys. Lett., vol. 79, no. 8, pp. 1172-1174,
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