A design of integrated CMOS-MEMS infrared emitter arrays

Abstract

This paper presents a new design of complementary metal-oxide-semiconductor microelectromechanical systems (CMOS-MEMS) infrared (IR) emitter arrays. The infrared emitter array is a key radiation source for various gas sensors. In this work, an IR emitter array has been implemented using the standard CSMC 0.5 µm 2P3M CMOS process. Three different shapes of micro emitters are designed. Heating resistor in each emitter is a moderate resistor composed of tungsten via-chain laminated in the micro structure, which is mechanically released from the substrate surface by the post-CMOS dielectric dry etching and aluminum sacrificial layer wet etching. This design shows a potential to vertically integrate CMOS circuits and MEMS IR emitter within a small footprint. In most CMOS-MEMS similar devices, on the other hand, polysilicon heating resistors were released by bulk silicon etching, which urges the IR emitter to be integrated in a coplanar CMOS circuit with a larger footprint. Thermal properties and radiation properties of the emitters under vacuum condition are calculated in a 2-step sequential simulation. Firstly, steady state temperature response and dynamic temperature response are calculated through multi-physics coupling finite element method (FEM) simulation, and thermal mass and thermal conductance of each micro emitter are derived. Secondly, dynamic radiation responses are also estimated with a Matlab program based on Plank’s radiation law. All simulation results supports the evidence that the designed devices are of power efficient and high speed. Read-in circuit is also designed and integrated within each of 8 × 8 emitter array elements.