Micro-electromechanical systems (MEMS) has proven to be a feasible way to produce miniaturized mechanical devices based on silicon as a mechanical support element for functional materials as thin films. Until now mainstream MEMS technology has been restricted to readily available semiconductor friendly materials as Si, poly-Si, SiO2, Si3N4 and SiC. The main reason for this is that the same fabrication facilities are often used for both MEMS and microelectronics, making any materials with fast diffusing ions prohibited. However, seeing the potential of functional materials as tools to cover a larger range of physical phenomena for making e.g. sensors and actuators it is now more common that new labs are build or measures are taken, so that they can be included.
PiezoMEMS
In SINTEF we have a special focus on ferroelectric thin films as they possess several properties that may be exploited. For MEMS, the most important among these are the piezoelectric effect (piezoMEMS). Beside from this, there are two other domains that are used in microelectronics, namely the pyroelectric (infrared detectors) and ferroelectric (memory) effects.
To fabricate a piezoMEMS device a thin film of piezoelectric material is deposited on silicon substrates that are often micromachined to form geometrical structures as beams, bridges and membranes. Such structures, with an integrated piezoelectric thin film, are used to fabricate a variety of devices in our cleanroom MiNaLab in Oslo. Examples of such devices categorized after how the material is used is shown in Table 1
Piezoelectric MEMS microphones using thin membranes of Si and an active layer of piezoelectric PZT as the functional elements (SINTEF/ SONITOR ).
|
Direct effect:
Sensors, energy conversion
(AC coupled) |
Converse effect:
Linear Actuators |
Converse effect with
Resonant ultrasound excitation |
Both effects in resonance:
resonant transducer |
|
· Vibration sensor /accelerometer.
· microphone.
· photoacoustic sensors.
· energy scavenging from vibrations. |
· Optical scanner.
· Optical switch.
· Micro, nano probe
· Switch – Relay, RF switch.
· Valve. |
· Ultrasonic stator for micromotor.
· Droplet ejector, inkjet. |
· Thickness Bulk waves: RF filters. transformers.
· Plate waves in pMUTs: ultrasonic imaging, proximity sensors. |
|
Active damping |
|
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Table 1: Classification of applications of thin film piezoelectrics
SINTEF is offering feasibility studies and fabrication of small scale device series of piezoMEMS using a standardized process called MoveMEMS through the microBuilder service.
SINTEF can offer:
Related projects:
MEMS-pie (EU FP6)
NORD-pie (Nordic Innovations Centre)
Contact person: Frode Tyholdt
