In this study we focus on the aluminium nitride (AlN). This material shows a large number of advantages associated with
good piezoelectric properties. Therefore, AlN is an excellent candidate for MEMS actuation where low dielectric loss,
low thermal drift and high signal-to-noise ratios are required. In this paper, the case of AlN driven cantilevers composed
of three thin layers deposited on the silicon substrate will be considered. Precise knowledge of physical and material
parameters of AlN applied in these simple elements are necessary for their further applications. However, up to now,
AlN still represents a technological challenge and many of its micromechanical and piezoelectric properties are not
precisely described. That is why, our study has been concentrated on determination of such parameters like the residual
thin film stresses, thermal expansion coefficient α and piezoelectric coefficient d31. In this paper the interactions between
the theoretical solution, the numerical FEM simulations and experimental results were performed. This hybrid
methodology allows to identify the main source of behaviors discrepancy between the physical and numerical model of
tested cantilevers. Obtained knowledge leads to optimization of the technological process and required parameters of
actuator functionality achievement by better understanding of the tested microdevices properties. In experimental
procedure, it was used nanoindentation tests for obtaining an elastic properties of AlN, interferometric techniques for
performing the static and dynamic measurements of cantilevers and scanning electron microscope for measuring
topography.
In this paper vibration characterization of MEMS cantilevers are presented using lens-less in-line digital holographic
microscope (LDHM). In-line digital holography provides larger information capability with higher phase sensitivity,
and full CCD sensor area is utilized for real image reconstruction. In lensless in-line digital holographic microscope, a
highly diverging beam replaces the conventional microscope objectives to provide the required magnification. The
diverging wave geometry also reduces the effect of twin-image wave caused by the in-line holographic geometry. For
vibration analysis, the time averaged holograms were recorded corresponding to different vibration states of the
cantilevers. Direct numerical evaluation of the amplitude and phase information from single time averaged hologram
provides the full-field real time quantitative analysis. The experimental study of vibration measurements of Aluminum
nitride (AlN) driven cantilevers is performed. The full field study shows the simultaneous vibration behavior of many
cantilevers corresponding to same input conditions. Our study shows the shift in the resonant condition of cantilevers
both for first and second resonant frequencies. This kind of analysis is most suitable to optimize and monitoring the
fabrication process of cantilevers.
The subject of this paper is the use of aluminum nitride (AlN) as an actuation layer in MEMS/MOEMS systems. This
material shows a good piezoelectric properties related to deposition conditions. AlN is a promising candidate for the
acoustic wave devices, MEMS applications and sensors what have been already proposed. Up to now, AlN is still a
technological challenge and many of its micromechanical and piezoelectric properties are not precisely described. That is
why our study has been focused on the determination of the material parameters like Young's modulus, residual thin film
stress, piezoelectric coefficient d31 and mechanical behaviour of especially designed cantilevers. To ensure the optimum
design, functionality and reliability of those actuators the theoretical solution and the numerical simulations of
mechanical performance by the Finite Element Method (FEM) were performed. The created model of device takes into
account multiple film stacking. For the characterization it was chosen a full-field optical technique applied in a
multifunctional interferometric platform. Proposed set-up performs the measurement in static and dynamic regimes with
nanometer sensitivity and high spatial resolution. The hybrid method of analysis combining the experimental and
numerical results has been used to better understand the properties of these microdevices, facilitate their designing and to
optimize their technological process. The optimum goal is a developing of the high quality and reliable AlN-driven
cantilevers for use in MEMS/MOEMS.
This study presents static and dynamic characterisation by Twyman Green interferometry of two active MEMS actuators driven by a thin film transducer of aluminium nitride (AlN). Firstly, we report on the testing results of thin film AlN/Si piezoelectric micro-machined ultrasonic transducers. These devices are expected to exhibit sensing capabilities for monitoring fluid property changes. The goal of second case study is the development of reliable AlN driven cantilevers working as actuation elements in Micro-Electro-Mechanical Systems (MEMS).
We discuss on-going reliability studies of micro-optical components and assemblies as conducted in the EU FP6 Network of Excellence on Micro-Optics "NEMO". We focus on three case studies including first biaxial fatigue testing of micro-optical components, second reliability testing and quality control of MEMS and third micro-interferometric tomography for measuring optical fibre refractive index changes. For each of these case studies we discuss the dedicated measurement and characterization methods as well as first results and the perspectives for future research.
The goal of this study was the investigation of reliability of AlN driven cantilevers, operating as MEMS actuators. Some of the fabrication steps being critical in regards to reliability issues, these steps have been firstly optimized. Then the monitoring of fatigue effects produced by thermal loading (130° C) of cantilevers, introducing the evolution of micromechanical parameters has been obtained by Twyman-Green interferometry. The measurements of evolution of resonance frequencies and displacement amplitudes permit the estimation of the long-term stability of such AlN based actuators.
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