Capacitive sensors are exceptionally well suited to the measurement of displacements and deflections of micro-components such as (cantilever) beams and membranes. In this case, the capacitive sensing principle was used to measure the displacement of a membrane.
The capacitive pressure sensor is made up of two chambers, which are separated by a thin membrane. The membrane is fabricated on a silicon substrate using wet etching with KOH. Also on the silicon substrate, there is a glass substrate with metallization.
The membrane and the metal layer patterned on the glass constitute a parallel plate capacitor. When a differential pressure arises between the two chambers, the membrane bends. This displacement leads to a change in the capacitance of the sensor, which can then be measured electrically.
- Membrane dimensions: 12 x 12 mm
- Membrane thickness: 50 µm
- Electrode spacing: 14 µm
- Capacitance: 100 … 190 pF
- Measurement range (patm-pref): 0 … 1000 Pa
- Resolution: 0.1 … 0.5 Pa
This sensor is fabricated as part of the Workshop Hands-on-MEMS.