Design solutions of capacitive sensors

• Capacitive pressure sensor with the membrane etched from a silicon wafer
  using isotropic or anisotropic etching

• Gap of the capacitor is usually defined on the silicon wafer
• Thickness of the membrane usually varies from 1 to 2 ?m
• Thickness of the gap varies from 1 to 5 ?m
• Silicon diaphragm is electrostatically bonded to the Pyrex glass, or other substrate
• If the substrate is an electrically non-conductive material, as a glass, a metal layer,
  serving as a capacitor fixed electrode must be deposited on it

• Capacitive pressure sensor using a structure with an ultra-thin diaphragm with a centre boss

• This solution offers very high sensitivity by using an ultra-thin diaphragm
• A nearly parallel capacitor obtained by using the centre boss enlarges the operating range
  and yields improved linearity