Absolute pressure sensors by air-tight electrical feedthrough structure

A new electrical feedthrough structure for silicon absolute pressure sensors has been developed, and has been applied to an integrated capacitive pressure sensor, a piezoresistive pressure sensor and a piezoresistive force sensor array for tactile imaging. The feedthrough structure is constructed from Pyrex glass, which has narrow through-holes engraved by electrochemical discharge drilling, and silicon, which has the diffused electrical feedthrough from the reference cavity. The reference cavity is hermetically sealed by glass-silicon anodic bonding. The metal contacts to the diffused feedthrough at the bottom of glass holes are made by CrCuAu evaporation through a metal mask. Using this structure, an electrical feedthrough from the reference cavity can be made without any air leakage. This structure is useful for the fabrication of absolute pressure sensors, acceleration sensors and so on.