Currently, phase-shifting interferometry is widely used in MEMS (micro-electro-mechanical system) microsurface topography measurements, and an expensive and high-precision piezoelectric transducer (PZT) is often necessary to realize phase-shift operation. Because of the feature of a MEMS structure which always has a flat substrate, a practical algorithm to calculate phase shifts by fast Fourier transformation (FFT) from gathered interference fringes of the substrate is presented, then microsurface topography can be reconstructed according to the obtained phase shifts. By means of the presented algorithm, an expensive and high-precision PZT is unnecessary and the phase-shift operation can even be carried out by rotating the fine focus adjustment knob. The accuracy and feasibility of the method have been verified by experiments. Experiments indicated that the presented method can satisfy the needs of in situ MEMS topography measurements and is very simple.
A novel optical MEMS pressure sensor with a SU-8, microstructure is proposed. SU-8 photoresist is used to form the
high aspect ratio structure on silicon wafer. The advantage of the novel structure mainly lies in the design of separating
sensing membrane deformation with the length change of Fabry–Perot cavity. The principle of the pressure measurement
has been introduced. The mechanical model is analyzed and parameters of SU-8 structure are determined by simulation.
The fabrication process is described. Experimental results demonstrate that the sensor has a reasonable linearity,
sensitivity under micro-pressure measurement range from 0 to 0.1 MPa.
An electrostatically actuated in-situ measuring method for average stress gradient of a MEMS film was proposed based
on pull-in voltages of a set of cantilevers. The key of the measuring method is to realize accurate calculation of pull-in
voltages of the cantilevers. To increase the accuracy of the measurement, bending of the cantilevers along the width
direction due to the stress gradient was considered. Actual simulations indicate that the calculating speed and the
accuracy of the measuring method are ideal, and the method can be applied to in-situ measurement.
A novel pressure sensor with a mesa structure diaphragm based on microelectromechanical systems
(MEMS) techniques is presented. The operating principle of the MEMS pressure sensor is expatiated
by the Fabry-Parot (F-P) cavity model and the relation between pressure and interference light intensity
is deduced in the sensor. The mechanical model of the mesa structure diaphragm is validated by
simulation, which declares that the mesa structure diaphragm is superior to the planar one on the depth
of parallelism. Experimental system is also introduced.
A novel pressure sensor based on Fabry-Perot interferometry and micro-electromechanical system
(MEMS) technology is proposed and demonstrated. Basic micro-electromechanical technique has been
used to fabricate the pressure sensor. Fabrication process and packaging configuration are proposed.
The loaded pressure is gauged by measuring the spectrum shift of the reflected optical signal. The
experimental results show that high linear response in the range of 0.2-1.0 Mpa and a reasonable
sensitivity of 10.07 nm/MPa (spectrum shift/pressure) have been obtained for this sensor.
An optical MEMS pressure sensor based on multi-layer circular diaphragm has been analyzed by utilizing the shell theory and characteristic matrix methods. Finite element methods are used to analyze the deflection of circular diaphragm with the residual stress effect considered. Simulation results are given by using FEM software tools ANSYS. The analytic expressions for the absolute reflectance of multi-layer circular diaphragm structure are derived. The results are valid for the most optical MEMS pressure sensors based on Fabry-Perot interferometer.
System-level simulation is an important phase for shortening design cycle and reducing design costs of MEMS devices, while the key to do this is to create macromodels for the MEMS devices. An equivalent circuit macromodel for beam-structure electromechanical systems is presented in force-current (F-I) analogy. It is appropriate for small-signal time and frequency domain analysis. Comparing with the existed macormodel created by force-voltage (F-V) analogy, the F-I analogy macromodel has the following advantage: the topology of the electric network of a F-I analogy macromodel is the same one as its original mechanical network. So it is very convenient to create an equivalent circuit macromedel for a complicated MEMS in F-I analogy. Simulating results show that the F-I analogy macromodel has high accuracy.