Performance enhance of CMOS-MEMS thermoelectric infrared sensor by using sensing material and structure design

This study presents the micro thermoelectric infrared (IR) sensor consisting of the heat transduction absorber and the serpentine structure with embedded thermocouple using the TSMC 0.18 mu m 1P6M standard CMOS process and the in-house post-CMOS MEMS process. The proposed IR absorber design has an umbrella-like structure with a post anchor to the serpentine suspension with embedded thermocouple. Compared to the reference design (IR sensor consisted of only the serpentine structure with embedded thermocouple), a better heat-flow path is achieved and the temperature difference between the hot and cold junctions is increased. Moreover, the umbrella-like structure has higher IR absorption area compared with the serpentine structure. In addition, the Seebeck coefficients of poly-Si films with and without silicide are respectively characterized. The poly-Si with no silicide has a much higher Seebeck coefficient (56-fold), and is employed in this study as the thermocouple material. Experiment results indicate the detectivity of proposed design is 2-2.6 fold higher than that of the reference one at 200 mTorr. Experiment also show that the responsivity enhancement of proposed design is further increased as the sensor size is reduced in area.