Reliable 3D characterization of pressure sensors
MEMS pressure sensors are some of the very first micro-electro-mechanical devices (MEMS) manufactured in series production and today exist in various types (e.g. relative or absolute pressure measurement) for different applications, many of them safety critical. Pressure sensors are used in a multitude of applications such as medical and biomedical use, in diaphragms, in wearables, diagnostic imaging and more.
How do pressure sensors work?
The basic working principle of MEMS pressure sensors lies in the conversion of phyiscal load and pressure into an analog electrical signal. Changes in pressure causes the pressure sensor membrane to change its shape and the electrical voltage signal is proportional to the membrane's deflection. To ensure the functionality and product quality especially in safety critical applications a comprehensive assessment and characterization of MEMS pressure sensors is key. Due to its size and sensitivity, MEMS pressure sensors call for non-contact optical testing methods.
Measure 3D topography of MEMS pressure sensors
Some performance relevant parameters of pressure sensors cannot be measured electrically, which is why the industry relies on additional approaches. One such approach is 3D topography measurement of the thin and sensitive pressure sensor membrane including membrane thickness measurement. Optical surface profilers of the TopMap series of white-light interferometers precisely reveal form parameters and curvature of the pressure sensor membrane at different applied pressures, thus avoiding unwanted stress and ensuring that the etching process works as desired. Resistors applied to the pressure sensor membrane can be measured as well to confirm and optimize the positioning and attachment.
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Testing pressure sensor dynamics and performance
The resonance frequency and vibration amplitude of MEMS pressure sensor membrane can be detected precisely using microscope-based laser Doppler vibrometry. For each resonance the operational deflection shape of the membrane can be compared with the predicted mode shapes of a finite elements (FE) simulation. When combining the vibrometer measurement data with FE simulation data, the correlation allows to determine parameters such as boundary conditions, thickness, stiffness and stress. Optical testing solutions from Polytec allow the membrane thickness measurement of a 300 nm thick pressure sensor membrane with an accuracy below 1%. For in-line quality control, wafer-level automation helps detect defective MEMS pressure sensor membrane units before packaging, which saves rejects and money.
Membrane thickness, film & layer thickness measurement
Related products
TopMap Pro.Surf
Ideal for quick and precise 3D surface characterization. The areal measurement of the TopMap Pro.Surf ensure to not miss any details when inspecting your workpiece surface. Short measuring times and a large field-of-view characterize the TopMap Pro.Surf.
TopMap Micro.View
TopMap Micro.View® is an easy to use and compact optical profiler. Choose Micro.View® as the cost-effective quality control solution for surface analysis of precision-engineering, for inspecting roughness, microstructures and more surface details.
TopMap Micro.View+
TopMap Micro.View®+ is the next generation optical surface profiler in a modular design to reliably measure the most challenging analysis tasks regarding surface finish and microstructures with utmost precision. Focus Finder and Focus Tracker assist in keeping samples focused at all times, with fully motorized positioning units ready for automation. Find out more!
MSA-600 Micro System Analyzer
The all-in-one optical measurement solution for static and dynamic 3D characterization of MEMS and microstructures- now for up to 6 GHz! The MSA-600 enhances microsystem development and quality inspections - also allowing testing on wafer-level when integrated into commercially available probe stations.
MSA-650 IRIS Micro System Analyzer
The innovative and patented MSA-650 IRIS Micro System Analyzer with IR capability allows for measuring true MEMS dynamics up to 25 MHz by characterizing both in-plane and out-of-plane motions through silicon encapsulation without contact, without need for preparing nor decapping the device.
Further applications in microtechnology and nanotechnology
- Vertical interconnect access (VIA)
![Microstructure inspection of VIA on an integrated circuit (IC)]()
- Die bonding
![Elektrisch leitendes Kleben in der Elektronik]()
- Flexible electronics
![Surface analysis and and quality control on flexible electronics and printed electronics]( "Surface analysis and and quality control on flexible electronics and printed electronics")
Surface analysis and and quality control on flexible electronics and printed electronics - Surface roughness
![Surface roughness masurement and measuring Ra, Rz roughness parameters]( "Surface roughness masurement and measuring Ra, Rz roughness parameters")
Surface roughness masurement and measuring Ra, Rz roughness parameters - Layer thickness
![Optical and areal step edge test showing a 75.2 nm thick coating]( "Optical and areal step edge test showing a 75.2 nm thick coating")
Optical and areal step edge test showing a 75.2 nm thick coating - Surface parameters
![Surface parameter characterizing the form, waviness and texture of a workpiece]( "Surface parameter characterizing the form, waviness and texture of a workpiece")
Surface parameter characterizing the form, waviness and texture of a workpiece
