Nano-twinned copper for high strength and highly conductive micro/nanocomponents

• Forschungsstelle: COST
• Projektnummer: C15.0057
• Projekttitel Englisch: Nano-twinned copper for high strength and highly conductive micro/nanocomponents

Schlüsselwörter (Englisch)

nt Cu; UV.LIGA; electrodeposition; electrical conductivity; copper interconnect

Forschungsprogramme (Englisch)

COST-Action MP1407 - ELECTROCHEMICAL PROCESSING METHODOLOGIES AND CORROSION PROTECTION FOR DEVICE AND SYSTEMS MINIATURIZATION

Kurzbeschreibung (Englisch)

Nanotwinned metals have shown high strength and creep resistance as well as low electrical resistivity. In this project, we aim to investigate the mechanical and electrical properties of nanotwinned Cu especially in micro/nano-scale. To achieve this goal, we propose to fabricate micromechanical parts in nanotwinned Cu (nt-Cu) by the UV-LiGA process, which is a microfabrication technique using electrodeposition assisted by a micro-template patterned by UV-lithography. We will carry out the studies by utilizing accelerated materials design strategy that covers the entire paradigm of processing-structure-property-performance relations and by generating a microstructure based on well-ordered nanotwins to achieve high strength and creep re-sistance as well as low electrical resistivity.

Weitere Hinweise und Angaben (Englisch)

Full name of research-institution/enterprise: EMPA Laboratory for Mechanics of Materials and Nanostructures Head of Laboratory

Partner und Internationale Organisationen (Englisch)

AT; BE; BG; CZ; DK; FR; MK; DE; EL; HU; IE; IL; IT; LT; PL; PT; RO; RS; SI; ES; SE; TR; UK

Abstract (Englisch)

Compared to nanocrystalline metals, nanotwinned metals exhibit similar high strength, but improved ductility and lower electrical resistivity. The main objective of this project is to investigate the electrodeposition of nanotwinned copper into LIGA moulds to enable fabrication of micromechanical parts with controlled twin density and orientation. Highly-textured nanotwinned Cu (nt-Cu) films with different twin orientations were prepared by pulse electrodeposition in an acidic Cu sulfate bath containing a combination of conventional bath additives. The effects of bath composition, current-density, pulse cycles and convection on the microstructure and mechanical properties will be studied. The orientation of nanotwins was found to depend on the deposition potential. Copper deposits with horizontally oriented nanotwins were formed at an on-potential of -0.2 V vs. saturated calomel electrode (SCE), while deposits with vertically oriented nanotwins are obtained at -0.6 V vs. SCE. For horizontally oriented nt-Cu, the twin spacing decreases with an increase of pulse-off time. The mechanical properties of electrodeposited copper with highly-oriented nanoscale twins were investigated by in situ SEM microcompression of micropillars fabricated with a focused ion beam. Results show that the mechanical properties are highly sensitive to the twin orientation. When compared to a fine grained Cu sample, an increase of 44% and 130% in stress at 5% offset strain was observed in quasi-static tests for vertically and horizontally aligned twins, respectively. Inversely strain rate jump micro-compression testing reveals higher strain sensitivity for vertical twins. These observations are attributed to a change in deformation mechanism from dislocation pile-ups at the twin boundary for horizontal twins to dislocations threading inside the twin lamella for vertical twins. The findings offer the possibility of more flexible engineering of nanotwin structure in Cu electrodeposits to tailor their mechanical and electrical properties.

Datenbankreferenzen (Englisch)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C15.0057