Surface-micromachined pyroelectric infrared imaging array with vertically integrated signal processing circuitry

Abstract

Surface-micromachining techniques have been used in the fabrication of a 64/spl times/64 element PbTiO/sub 3/ pyroelectric infrared imager. Polysilicon microbridges of 1.2 /spl mu/m-thickness have been formed 0.8 /spl mu/m above the surface of a silicon wafer. Each of the 4096 polysilicon microbridges measures 50/spl times/50 /spl mu/m/sup 2/ and forms a low thermal mass support for a 30/spl times/30 /spl mu/m/sup 2/ PbTiO/sub 3/ pyroelectric capacitor with a thickness of 0.36 /spl mu/m. The air-bridge formed reduces the thermal conduction path between the detector element and substrate. An NMOS preamplifier cell is located directly beneath each microbridge element. The measured blackbody voltage responsivity at 30 Hz is 1.2/spl times/10/sup 4/ V/W. The corresponding measured normalized detectivity (unamplified) D* is 2/spl times/10/sup 8/ cm-Hz/sup 1/2/W at 30 Hz. The test chip fabricated measures 1/spl times/1 cm/sup 2/ and contains more than ten thousand transistors and 4096 micromechanical structures with integrated ferroelectric microsensors. The technique of stacking of microsensors and integrated circuits represents a new approach for achieving high-density and high-performance integrated pyroelectric microsensors through minimization of circuit to sensor interconnection with extremely small thermal crosstalk.<>