MEMS and sensors

In surface micromachining, what problem occurs if a structural thin film such as polysilicon has large internal residual stress?

  1. AThe film's resistance becomes zero
  2. BWhen the sacrificial layer is removed to release the structure, it warps or buckles
  3. CThe film becomes transparent
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Answer: B. When the sacrificial layer is removed to release the structure, it warps or buckles

Large residual stress built up during deposition causes released structures to buckle under compressive stress or to curl if the stress varies through the thickness, so they do not take the designed shape or characteristics. Controlling stress through deposition conditions and annealing is important.

  • A. The resistance does not become zero.
  • B. Correct. Warping or buckling occurs.
  • C. Stress does not make the film transparent.
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More MEMS and sensors questions

  1. In a MEMS electrostatic actuator, if the voltage between two parallel electrodes is doubled, by roughly what factor does the electrostatic attraction between them change? (Assume the gap is unchanged.)
  2. When choosing the measurement range of a MEMS accelerometer (for example, ±2 g versus ±16 g), which reasoning is correct?
  3. In a parallel-plate electrostatic actuator, what is the phenomenon called in which, as the voltage rises, the movable electrode suddenly snaps to the fixed electrode once it passes a certain position?
  4. Which method is widely used to evaluate the bias stability (slow drift of the output) of MEMS gyroscopes?
  5. What is the damping called that arises when a MEMS movable plate moves toward a nearby fixed surface and squeezes out the gas between them?