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Study of copper-refractory metal interfaces via solid-state wetting for emerging nanoscale interconnect applications

Published online by Cambridge University Press:  01 January 2006

Oscar van der Straten ,
Yu Zhu ,
Jonathan Rullan ,
Kathleen Dunn  and
Alain E. Kaloyeros
Oscar van der Straten
Affiliation:
College of Nanoscale Science and Engineering, The University at Albany—State University of New York, Albany, New York 12203
Yu Zhu
Affiliation:
College of Nanoscale Science and Engineering, The University at Albany—State University of New York, Albany, New York 12203
Jonathan Rullan
Affiliation:
College of Nanoscale Science and Engineering, The University at Albany—State University of New York, Albany, New York 12203
Kathleen Dunn
Affiliation:
College of Nanoscale Science and Engineering, The University at Albany—State University of New York, Albany, New York 12203
Alain E. Kaloyeros*
Affiliation:
College of Nanoscale Science and Engineering, The University at Albany—State University of New York, Albany, New York 12203
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

Solid-state wetting experiments were carried out to derive the work of adhesion (adhesion energy) of pertinent Cu/liner interfaces via the Young–Dupré equation using contact-angle measurements of the Cu equilibrium crystal shape on Ta and TaNx liners. Four types of liner surfaces were examined: untreated sputtered Ta (uSp-Ta), untreated sputtered TaNx (uSp-TaN), untreated atomic layer deposited (ALD) TaNx (uALD-TaN), and indium surfactant-treated ALD TaNx (tALD-TaN). All Cu-liner stacks were subsequently annealed at 600 °C for 48 h in a forming gas (95% Ar/5% H2) ambient. For Cu/uSp-Ta, the work of adhesion was found to be 2170 mJ/m2, corresponding to an average contact angle of 74°, while for Cu/uSp-TaN, the work of adhesion amounted to 1850 mJ/m2 for an average contact angle of 85°. Alternatively, the work of adhesion for Cu/uALD-TaN was determined to be 1850 mJ/m2, corresponding to an average contact angle of 85°, while for Cu/tALD-TaN, the work of adhesion was 2280 mJ/m2, at an average contact angle of 70°. These findings indicate that the highest degree of surface wetting occurs for the indium surfactant-treated ALD TaNx. It is thus suggested that surfactant treatment causes a reduction in the energy barrier to Cu nucleation, resulting in an enhancement in Cu wetting characteristics and a more uniform concentration of Cu nucleation sites. A critical potential outcome is the formation of atomically smooth Cu-liner interfaces with enhanced adhesion characteristics.

Keywords

Cluster assemblyScanning electron microscopy (SEM)Transmission electron microscopy (TEM)
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 1 , January 2006 , pp. 255 - 262
Copyright
Copyright © Materials Research Society 2006

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