Vibrometry

For efficient product development in micro- and nanotechnology
Precise, reliable and fast measuring technology for characterizing and monitoring the quality of devices is decisive to in developing and producing microsystems. This is all the more important since microsensors are increasingly taking over safety-related tasks too – placing high demands on reliability and functional safety. A robust design and high production precision play a key role in this regard.
Active microelectromechanical structural elements such as MEMS actuators or sensors need suitable optical measurement methods, since purely electrical characterization isn’t enough.
Polytec’s Micro System Analyzers are ideal for this. On the one hand, they enable determination of the surface topography with a high resolution and, on the other, they allow for precise characterization of the dynamic motion behaviour too. Dynamic measurement using laser Doppler vibrometry is characterized by a high frequency bandwidth and extremely good displacement amplitude resolution. This measuring technology even enables vibration measurements up to the high MHz range (and even the GHz range) – which is required for an ever-growing number of microtechnology applications.
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Wafer-level
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Test of prototypes
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cMUTs and pMUTs
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SAWs und BAWs
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FEM validation
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Micro mechanics
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MEMS reliability
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Bio MEMS
Efficiently measuring MEMS right on the wafer
Wafer-level testing prior to separating the chips allows the sorting out of bad dies early in the production process thus helping to keep MEMS production costs low while maintaining high yield and quality levels. While electrical test procedures are standard here, certain tasks are necessaryto verify directly the mechanical function, typically by optical measurement.
You can easily integrate Polytec’s measuring technology into virtually all commercially available wafer probes to do precisely that. By combining a (semi)-automatic probe station with a microscope-based scanning laser vibrometer such as the Polytec Micro System Analyzer, you can efficiently and quickly measure the dynamic behavior of MEMS right on the wafer. That way, you can achieve a high throughput and have a key tool for monitoring the production process.
Documents
A practical example:
Time domain measurement of RF-MEMS switches on wafer level


Microstructure characterization
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Change cookie settingsMEMS prototype verification for process optimization
The development of a new microelectromechanical system (MEMS) always requires a new production process, unlike with pure semiconductor devices. Process recipes and modules have to be revised at the very least, since at present you still can’t fall back on standard recipes for new micromechanical components, as is otherwise customary in semiconductor development.
Both the system design and an optimized process design are essential if a structural element determined primarily by mechanical properties is to work properly. Prototype verification thus not only enables the design to be confirmed, but allows for affirmation of the manufacturing process too. To determine unexpected mechanical behaviour and model deviations, a powerful optical measurement by Laser Vibrometry is often the method of choice.
Due to its high frequency bandwidth, high lateral resolution and excellent amplitude resolution, a laser vibrometer from Polytec should be the first tool you reach for so that you can reliably determine modal properties of MEMS such as transfer functions, resonance frequencies, damping and deflection shapes. The topographical analysis is also important for component development and process optimization. Surface data such as step heights and other dimensions provide you with valuable information about current process parameters, so you can reliably control the MEMS component manufacturing process.
Documents
A practical example:
CMOS / MEMS co-integrated flow microsensor
The figure illustrates the a characterization of the Topography of a CMOS / MEMS co-integrated flow microsensor carried out using the surface topography option of the MSA-500 Micro System Analyzer from Polytec. The flow microsensor had been realized using silicon-on-insulator (SOI) technology.

Microstructure characterization
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Change cookie settingsCharacterizing ultrasonic transducers in real time
Ultrasonic transducers produced using microsystems technology are promising for medical ultrasonic applications. Here, you essentially make a distinction between so-called pMUTs and cMUTs (piezoelectric Micromachined Ultrasonic Transducers and capacitive Micromachined Ultrasonic Transducers respectively).
cMUTs have unique properties compared with conventional elements. Thanks to the membrane’s bending mode deflection shape, the transducer’s mechanical impedance reduces, while energy transfer to the ambient medium improves at the same time. Microfabrication also enables affordable series production of cMUTs using semiconductor technology. The semiconductor switching circuit can be directly integrated on the same chip, so as to simply create even large-sized 1D or more complicated 2D array configurations.
A combination of different methods is often used to characterize new ultrasonic transducers. Finite element simulations predict the transducer’s behaviour, taking the surrounding medium into consideration too. You can then measure new transducer prototypes with microscope-based laser vibrometers such as the Polytec MSA Micro System Analyzer, to directly determine the mechanical frequency response of the sound transducer surface. In doing so, you will come to appreciate the large frequency bandwidth and real time capability that you use to reliably and accurately measure transient processes in particular.
Documents
A practical example:
IMEC in Belgium characterized a unique cMUT with the Polytec MSA and, based on the results, determined the spatial pressure field in the transfer medium using the Rayleigh integral method. The results were subsequently confirmed with independent hydrophone measurements.



Microstructure characterization
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Change cookie settingsContactlessly characterizing SAWs
As surface acoustic wave (SAW) filters are electronic components that work through surface acoustic waves they are in fact mechanical filters. Due to their superior properties, they are an integral part of high-frequency applications such as mobile telephony. Optimization of the SAW surface’s micro-acoustic properties is one of the key tasks involved in developing new SAW components.
Due to the high frequencies, short acoustic path lengths and small vibration amplitudes, the measurement and visualization of surface waves places particular demands on measuring technology. Using a laser vibrometer is one of the few solutions available for measuring vibration on such systems.
Polytec’s laser Doppler vibrometers enable you to conduct non-contact characterization operations across all frequencies, even when faced with broadband excitation. The deflection shapes are visualized in an impressive way. You can even examine transients and relaxation behaviour. Key results are determining properties such as the filter characteristics and performance losses (leakage).
Documents
A practical example:
In addition to their use as electronic filters, SAWs play a key role in microfluidic applications too. In this regard, SAWs are used for targeted droplet manipulation of biomaterials. When such lab-on-a-chip components are being developed, the surface dynamics are examined with high-frequency vibrometers such as the Polytec UHF-120 due to the non-contact optical measurement, the frequency bandwidth and the high resolution.

Microstructure characterization
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Change cookie settingsValidating models the easy and efficient way
It is hardly possible to imagine developing MEMS components without computer simulation. FE simulation models have to be tested and refined through comparisons with experimental data. Non-contact, optical measurement methods are essential to characterizing the mechanical properties with maximum precision.
Laser Doppler vibrometers from Polytec have proven to be the perfect technique for quickly, easily and optically detecting the mechanical movement of structures within MEMS components and correlating the modeled behavior with the measurement data.
This can be done on a single die or on wafer level by easy integration with any MEMS Wafer Probe Stations.
The broadband real time measurement, combined with the Polytec vibrometers’ excellent amplitude resolution, allows you to easily and efficiently determine the transfer functions for model validation.
Documents
A practical example:
Model validation of a micro mirror array.
The figure shows the comparison between the FEM model calculation and the vibrometer measurement on a MEMS micro mirror array.

Microstructure characterization
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Change cookie settingsRelated products

MSA-100-3D Micro System Analyzer
The 3D Micro System Analyzer records vibration components in all three spatial directions at once. The optical measurement system enables high-resolution 3D vibration analysis with amplitude resolutions in the sub-picometer range, for both in-plane and...
Conducting extensive and precise micromechanics analyses
The possibility to directly integrate microscopic, mechanical functional units with semiconductor electronics at silicon level gave rise to a multitude of different micromechanical sensors and actuators and to the huge success of MEMS and microstructures.
The sheer range of product types and areas of use is huge.
The variety of device type encompasses pressure and inertial sensor systems for automotive and aerospace applications, MEMS microphones, MEMS acceleration and gyroscope sensors for portable electronic devices, a wide range of micro mirror elements for light manipulation, energy harvesters for autonomous systems and microbalances for extremely small material quantities. And, lastly, there are pMUTs and cMUTs for generating ultrasonics in medical technology and micro-acoustic elements such as SAWs, which are increasingly being put to use as electronic filter elements, but are also deployed in lab-on-a-chip applications too.
Reliable and precise measurement of not only the electrical measuring technology, but also the direct mechanical function – in other words, the movement of the smallest silicon components – is absolutely essential to developing MEMS components such as this.
Using the microscope based single-point or scanning vibrometers from Polytec, you can measure displacements in the pm range, and acquire transfer functions and operational deflection shapes in either 1D or 3D, with a high frequency bandwidth and lateral resolution in the µm or sub-µm range. You also have the option of capturing your microsystem’s topography with the MSA Micro System Analyzer.
Documents
A practical example:
The MSA-100-3D Micro System Analyzer allows for a real 3D vibration measurement with pm path resolution for both out-of-plane (OOP) and in-plane (IP) components. Here, this is taking place on an MEMS cantilever.

Microstructure characterization
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Change cookie settingsRelated products

MSA-100-3D Micro System Analyzer
The 3D Micro System Analyzer records vibration components in all three spatial directions at once. The optical measurement system enables high-resolution 3D vibration analysis with amplitude resolutions in the sub-picometer range, for both in-plane and...
Testing the reliability and service life of MEMS
MEMS sensors and actuators are key functional elements in many devices and systems and, more and more often, they have safety-related functions too. Thus they have to be reliable and guaranteed throughout the system’s entire service life often under challenging operating conditions.
Therefore verification of new MEMS components has to take place under exactly these conditions. Vacuum or climatic test chambers are used to simulate the pressure loading or air humidity influences and stimuli like mechanical excitation or radiation are applied. The long time function stability is verified in accelerated aging tests.
Since, unlike conventional semiconductor elements, MEMS feature moving, micromechanical components as their key functional elements, the capability of measuring the dynamic, mechanical system behaviour is extremely important during reliability and service life tests.
Polytec’s Micro System Analyzer offers you all the relevant measuring modes for this purpose. The highly versatile measurement system can also be equipped with special lenses with large stand-off distancess to measure both static and dynamic component behavior from outside a test chamber.
Documents
A practical example:
Vibration measurements on MEMS in a vacuum chamber
The influence of ambient pressure on an MEMS module’s dynamic properties is measured with the Polytec MSA, which is used either in conjunction with a vacuum chamber or in combination with a vacuum probe station for measurements at wafer level.

Microstructure characterization
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Change cookie settingsRelated products

MSA-100-3D Micro System Analyzer
The 3D Micro System Analyzer records vibration components in all three spatial directions at once. The optical measurement system enables high-resolution 3D vibration analysis with amplitude resolutions in the sub-picometer range, for both in-plane and...
MEMS characterization for Biology and Medicine
MEMS and microstructures are key basic and cross-sectional technologies for an extremely wide range of medical and biological applications. The scope of use ranges from lab-on-a-chip applications with high-frequency surface waves for rapid medical diagnostics, to MEMS microphones for use in hearing aids, and ultrasonic transducers for medical imaging based on microsystems technology.
You can rely on the non-contact, microscope-based optical measuring technology from Polytec to determine the surface topography and dynamic properties of medical MEMS sensors and actuators. Microscope-based vibration measurement is also used in bionically inspired “technology transfer” from natural to technical systems to measure the biomechanics of insects’ hearing, for example.
Documents
A practical example:
Micromachined ultrasonic transducers (pMUTs & cMUTs) are pushing the boundaries of real-time 3D medical imaging (sonography) in applications such as IVUS (intravascular ultrasound) and echocardiography.
To characterize the micromechanics of these transducer elements, measurements must be performed at high frequencies (~10 MHz) and with a high spatial resolution (<1 μm). The various possibilities offered by Polytec’s Micro System Analyzer provide this information for pMUT and cMUT development with maximum precision and zero contact.

Microstructure characterization
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