““Carbon Nanotubes for Carbon Nanotubes for Interconnect Applications”Interconnect Applications”

Franz Kreupl, Andrew P. Graham, Maik Liebau, Georg S. Duesberg, Robert Seidel, Eugen Unger

Presented at IEDM 2004

EE C235 Presentation by Zachery JacobsonMarch 5, 2007

OutlineOutline

Overview of InterconnectsOverview of InterconnectsWhy Carbon Nanotube interconnects?Why Carbon Nanotube interconnects?Growth strategiesGrowth strategiesResultsResultsIssuesIssuesConclusionsConclusions

Overview of InterconnectsOverview of Interconnects

Increased resistance and decreased current carrying Increased resistance and decreased current carrying capability due to electromigration are two critical capability due to electromigration are two critical issues affecting the use of copper interconnectsissues affecting the use of copper interconnects

Ron Ho, SLIP 2005ITRS Roadmap, 2005

Why Carbon Nanotube Interconnects?Why Carbon Nanotube Interconnects?

Metallic Carbon Nanotubes are Metallic Carbon Nanotubes are potentially viable for use as potentially viable for use as interconnects due to their large mean-interconnects due to their large mean-free path (which leads to low free path (which leads to low resistance) and low electromigration resistance) and low electromigration (which increases current carrying (which increases current carrying capability)capability)

A. Naeemi, et al, IEDM 2004F. Kreupl, et al, IEDM 2004

Growth StrategiesGrowth Strategies

Two major growth strategiesTwo major growth strategies Bottom-up, where CNTs are grown before Bottom-up, where CNTs are grown before

ILD depositionILD deposition Buried catalyst, where CNTs are grown Buried catalyst, where CNTs are grown

after ILD depositionafter ILD deposition

J. Li, et al, Appl. Phys. Lett. 82, 2491 (2003)F. Kreupl, et al, IEDM 2004

ResultsResults

Nanotube quality is better Nanotube quality is better than PECVD grown than PECVD grown nanotubes, but variability is nanotubes, but variability is still highstill high

F. Kreupl, et al, IEDM 2004

ResultsResults

Relatively high annealing Relatively high annealing temperature needed to reduce temperature needed to reduce resistance due to contact issuesresistance due to contact issuesLarge variability in resistance Large variability in resistance between viasbetween vias

F. Kreupl, et al, IEDM 2004

IssuesIssuesContact resistance eliminates any advantage seen versus “bulk” Cu Contact resistance eliminates any advantage seen versus “bulk” Cu interconnectsinterconnectsTo make a good low resistance contact, high annealing temperatures are To make a good low resistance contact, high annealing temperatures are required which exceed the thermal budgetrequired which exceed the thermal budgetVariability of grown nanotubes continues to be an issueVariability of grown nanotubes continues to be an issueLarge diameter nanotubes underperform Cu vias even under ideal conditionsLarge diameter nanotubes underperform Cu vias even under ideal conditions

F. Kreupl, et al, IEDM 2004

ConclusionsConclusionsCarbon Nanotubes have theoretically higher Carbon Nanotubes have theoretically higher performance than Copper interconnects in some performance than Copper interconnects in some applicationsapplicationsUsing a buried catalyst method, vias were Using a buried catalyst method, vias were fabricated using single MWCNTs down to 20 nm fabricated using single MWCNTs down to 20 nm in diameterin diameterVariability was high among the nanowires Variability was high among the nanowires grown, which has a strong effect on performancegrown, which has a strong effect on performanceIf good contacts can be achieved with a low If good contacts can be achieved with a low temperature process, carbon nanotubes have a temperature process, carbon nanotubes have a chance at replacing copper vias at very small chance at replacing copper vias at very small process nodesprocess nodes

Thank you for your time! Questions?