Fabrication and packaging of a resonant infrared sensor integrated in silicon

A novel integrated infrared (IR) sensor is described that incorporates a resonant silicon/silicon dioxide microbridge. The resonance frequency of the microbridge is sensitive to the incident IR power as a result of the thermally induced stress variation resulting from the absorption of the IR radiation. A merged process including on-wafer stress-free packaging, NMOS circuitry and bulk silicon micromachining is illustrated. One-port electrostatic excitation and capacitive detection was used, the resonator being electrically floating. Relative responsitivities of 450 ppm/μW of absorbed power were obtained.