Self-Aligned Thermoelectric Infrared Sensors With Post-CMOS Micromachining

In this letter, we report the fabrication and characterization of CMOS-compatible self-aligned thermoelectric infrared (IR) sensors. Since etching windows for structure release are patterned by a self-aligned process, the fabrication complication is reduced and a narrow etching window can be patterned. Additionally, the self-aligned process reduces the thermal conductance of the thermopile structure, since the film thickness around the sidewall of the thermocouple is reduced. Two self-aligned thermoelectric IR sensors with rectangular and circular structures are fabricated. The responsivity, detectivity, and time constant are 43.5 V/W, 2.51 ?? 10⁷ cm ?? Hz^1/2/W, and 14.1 ms for the rectangular IR sensor and 31.8 V/W, 3.25 ?? 10⁷ cm ?? Hz^1/2/W, and 12.6 ms for the circular IR sensor, respectively.