Abstract
We performed tensile tests on highly <111>-oriented nanotwinned copper (nt-Cu) foils with different columnar grain structures. For a systematic study, we altered the microstructure of the foils by tuning the electroplating electrolyte and annealing temperatures under a nitrogen atmosphere. The results show that the yield strength ranges from 300 to 700 MPa, and elongation spans from 5% to 25%. Knowing the measured twin spacing and average grain size, and combining the confined layer slip with the Hall–Petch equation, we calculated the theoretical yield strength of the nt-Cu with different microstructures, and the theoretic values match the experiment results. Owing to the unique crystal orientation properties of <111>-oriented columnar grains, dislocations induced by slip are very limited. The Schmid factor of grains along the tensile axis direction is highly identical, so the plastic deformation is much more suitably explained by the Schmid factor model. Thus, we replace the Taylor factor with the Schmid factor in the slip model of nt-Cu.
Highlights
Copper has been the most important conductor in microelectronic devices owing to its high ductility and conductivity
The and grain orientation was observed by electron backscattered diffraction (EBSD) equipped in Discussions a JEOL JSM-7800F Prime Scanning Electronic Microscopy (SEM, JEOL JSM-7800F, Akishima, Tokyo, JAPAN), the crystallographic texture and statistical image maps were analyzed by Tuning and of Microstructure
The average grain size and twin spacing were modified in two different ways
Summary
Copper has been the most important conductor in microelectronic devices owing to its high ductility and conductivity. It is discovered that by introducing nano-scale twins into the microstructure of copper, the mechanical strength, ductility, and electromigration resistivity can be improved, with nearly identical conductivity as bulk copper [1,2,3]. Nanotwinned copper is generally achieved in two ways—sputtering and electroplating deposition [2,4,5,6,7,8,9]. The advantage of sputtering is the high purity in the copper film, with the ability to control the preferred orientation of grains. Sputtered -oriented nanotwinned copper is shown to have high thermal stability and strength [2,10]. Lu et al [1,8]
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