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On-chip stress relaxation testing method for freestanding thin film materials
M Coulombier1, G Guisbiers, M-S Colla
1Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, 1348 Louvain-la-Neuve, Belgium.
The Review of Scientific Instruments
|November 7, 2012
Summary
A new microtensile testing method enables stress relaxation measurements in freestanding thin films at low strain rates. This technique reveals unexpectedly high room temperature relaxation in aluminum-silicon and palladium films.
Area of Science:
- Materials Science
- Mechanical Engineering
- Nanotechnology
Background:
- Freestanding thin films are crucial in microelectronics and MEMS.
- Characterizing their mechanical properties, especially stress relaxation, is challenging.
- Existing methods are often time-consuming and require specialized equipment.
Purpose of the Study:
- To develop a novel on-chip method for measuring stress relaxation in freestanding thin films.
- To determine the strain rate sensitivity of very thin films at low strain rates (<10⁻⁶/s).
- To demonstrate the technique's efficiency by testing thousands of specimens simultaneously.
Main Methods:
- Utilizing microfabrication techniques (cleaning, deposition, lithography, release) to create on-chip test structures.
- Applying uniaxial tension to released thin film specimens.
- Monitoring load decay during deformation to quantify stress relaxation.
- Adapting the setup for ultra-low strain rate testing.
Main Results:
- Successfully developed and validated an on-chip stress relaxation testing method.
- Demonstrated the capability to measure strain rate sensitivity at strain rates below 10⁻⁶/s.
- Observed unexpectedly high room temperature stress relaxation in 205-nm AlSi(0.01) and 350-nm Pd films.
- The method allows simultaneous testing of numerous specimens over extended periods.
Conclusions:
- The developed on-chip microtensile testing setup is effective for studying stress relaxation in thin films.
- The technique offers a high-throughput and efficient approach for mechanical characterization.
- The observed high relaxation in AlSi and Pd films warrants further investigation into their deformation mechanisms.
