Enhanced performances of CMOS-MEMS thermopile infrared detectors using novel thin film stacks

This paper presents the design, fabrication and experimental results of two CMOS-compatible micromachined thermopile infrared (IR) detectors. A preliminary interferometric absorber structure and modified interferometric absorber structure with Ge anti-reflection layer is used to enhance the absorptance, respectively. The reference thermopile IR detector only consisting of thermocouple embedded structure is provided with a characteristic interferometric absorber structure composed of passivation layers (Si(3)N(4 )and SiO2) and Al/Npolysilicon thermocouples. Compared to the reference thermopile IR detector, the thermopile IR detector modified by anti-reflection layer (Ge) has a higher IR absorptance and increased temperature difference between the hot and cold junctions. The responsivity and specific detectivity of the reference thermopile IR detector are similar to 256.6 V W-1 and 1.47 x 10(8) cm Hz(1/2) W-1, while those of the modified detector after applying the anti-reflection layer arrive at similar to 302.3 V W-1 and 1.73 x 10(8) cm Hz(1/2) W-1, which increase by similar to 18%.