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MEMS stress sensor - QuickField simulation example

MEMS sensor changes its shape under mechanical stress. The electrode plates come close and the variation in electrical capacitance is detected.

Engineering question

How to find MEMS stress sensor capacitance?

Answer
Set up a plane-parallel QuickField Stress Analysis problem for a MEMS stress sensor and evaluate capacitance variation from computed field results.

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Typical applications
MEMS stress sensors, capacitive MEMS sensors, microstructure stress detectors

MEMS stress sensor

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Simulation problem

Problem Type
Plane-parallel problem of electrostatics and stress analysis .

Geometry
MEMS stress sensor Microelectromechanical system sensor changes its shape under mechanical stress Silicon Copper Copper Force 20μ 14μ

Given

Young's
modulus
Poisson's
ratio
Silicon 130 GPa 0.1
Copper 140 GPa 0.34

Task
Calculate the sensor deformation and electrical capacitance in initial and deformed states.

Solution
Initially the electrostatic problem is simulated to calculate the native capacitance of the sensor.
Then deformed sensor profile is calculated in stress analysis problem. The profile is exported into the separate geometry model file using Stress Deform tool. That deformed shape model is then used to run another electrostatic analysis to calculate the deformed state capacitance.

Results
Initial capacitance value 0.0026 pF
Capacitance in deformed state 0.0028 pF (+10%)

Electric field distribution in the deformed stress sensor
Electric field distribution in the deformed stress sensor

Video

  • MEMS stress sensor. Watch on YouTube.
    Calculation of deformed shape using QuickField Stress Analysis module
    Translation of the deformed shape to the geometry model using the StressDeform tool
    Initial capacitance calculation using Electrostatics module.
    Deformed state capacitance calculation
  • View simulation report in PDF

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