| AVS 65th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology Division | Thursday Sessions |
| Session NS+AN+EM+MI+MN+MP+PS+RM-ThM |
| Session: | Nanopatterning and Nanofabrication |
| Presenter: | Erez Benjamin, Tel Aviv University, Israel |
| Authors: | J. Shklovsky, Tel Aviv University, Israel E. Mishuk, Weizmann Institute of Science, Israel Y. Berg, Orbotech Ltd, Israel N. Vengerovsky, Tel Aviv University, Israel Y. Sverdlov, Tel Aviv University, Israel I. Lubomirsky, Weizmann Institute of Science, Israel Z. Kotler, Orbotech Ltd S. Krylov, Tel Aviv University, Israel Y. Shacham-Diamand, Tel Aviv University, Israel E. Benjamin, Tel Aviv University, Israel |
| Correspondent: | Click to Email |
The integration of piezoelectric and electrostrictive materials into micromachined Si devices is viewed as an important technological milestone for further development of Microelectromechanical Systems (MEMS). Recently, it was demonstrated that gadolinium-doped ceria (CGO) exhibits very large electrostriction effect, which results in large electrostrictive strains and high energy densities under very low frequencies (0.01 – 1 Hz). Lead-free CGO is chemically inert with respect to Si, making it an attractive candidate for implementation in MEMS actuators. However, the integration of CGO into MEMS devices is challenging due problems associated with using conventional patterning techniques involving lithography and etching.
In this work, we have successfully created functional double-clamped beam micro-actuators made of CGO films confined between the top and bottom Al/Ti electrodes. The stack containing the electrodes and the ≈ 2 µm-thick CGO film was first blanket-deposited on top of the Si wafer. Cavities were then deep reactive ion etched (DRIE) in the wafer leading to forming of the free-standing rectangular membranes, 1.5 mm × 0.5 mm in size. Finally, ≈ 1.2 mm long and ≈ 100 µm wide the double-clamped beams were cut from the membranes using a femtosecond (fs) laser, demonstrating an unharmful technique for CGO patterning. Laser pulse energies, overlaps and number of line passes were varied during the experiments, to achieve successful cuts through the suspended layer by a clean ablation process. The optimized process conditions were found at a fluence of ~0.3 J/cm2 for a pulse width of 270 fs, where minimal damage and accurate processing was achieved with minimized heat-affected zones.
Resistivity measurements between the top and the bottom electrodes before and after fs laser cutting revealed that the cutting has no influence on the electric parameters of the device and no electrical shorts are introduced by the laser processing. Vertical displacement measurements under bipolar AC voltage (up to 10 V), at the frequency range of 0.03 – 2 Hz, demonstrated the functionality of the micro-actuator. A displacement of ≈ 45 nm at the voltage of 10 V at 50 mHz was achieved. The actuator didn’t show any mechanical or electrical degradation after continuous operation. Our data confirm that fs laser cutting is a useful technique for processing CGO films. The developed techniques may be expanded to other materials used for fabrication of MEMS devices, enabling fast, high yield and high-quality patterning of materials that are challenging to pattern using conventional etching-based methods.
*Three first authors contributed equally to this abstract.