Electric-Current-Induced Phase Transformation in Cu6Sn5 Below Its Equilibrium Transition Temperature
Shih-Kang Lin1,2,3,4, Shubhayan Mukherjee1, Yu-Chen Liu4,5
1Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan.
Summary
Electric current drives a phase transformation in copper-tin (Cu$_{6}$Sn$_{5}$) below its equilibrium transition temperature. This current-induced change enhances the material's mechanical properties, impacting semiconductor reliability.
Area of Science:
- Materials Science
- Solid-State Physics
- Semiconductor Engineering
Background:
- Semiconductor interconnects face reliability challenges due to high current densities at sub-2 nm nodes.
- Traditional phase transformations are understood via thermal equilibrium, but electric current introduces non-equilibrium effects.
- Understanding current-driven structural evolution is crucial for advanced materials.
Purpose of the Study:
- To investigate the effect of electric current on the phase transformation of copper-tin (Cu$_{6}$Sn$_{5}$) below its equilibrium transition temperature.
- To determine if electric current can induce structural changes not observed under thermal aging alone.
- To evaluate the mechanical properties of the current-induced transformed phase.
Main Methods:
- Ex situ synchrotron X-ray diffraction series on current-stressed Cu$_{6}$Sn$_{5}$ samples.
- Transmission electron microscopy (TEM) for microstructural analysis.
- Controlled thermal aging experiments for comparison.
- Indentation testing to measure mechanical properties (modulus and hardness).
Main Results:
- A current-driven monoclinic-to-hexagonal transformation in Cu$_{6}$Sn$_{5}$ was observed at ~120°C, below the equilibrium transition temperature (186°C-189°C).
- Thermal aging alone did not induce the same transformation within the tested timeframe.
- Current stressing progressively converted the monoclinic (η') phase to the hexagonal (η) phase.
- The transformed hexagonal phase exhibited a higher indentation modulus and hardness compared to the monoclinic phase.
Conclusions:
- Electric current can drive unconventional structural evolution in Cu$_{6}$Sn$_{5}$ below its equilibrium transition temperature.
- Current-assisted phase stability is a significant factor in conductive intermetallics under high current densities.
- The findings provide insights into current-induced phase transformations relevant to semiconductor interconnect reliability.
Keywords:
Cu6Sn5electric‐current‐induced phase transformationelectromigrationintermetallicsphase stabilitysynchrotron x‐ray diffractionMore Related Videos
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