Micromachined thermoelectric IR sensors fabricated by a self-aligned process

Abstract

In this paper, we report the fabrication and characterization of micromachinedthermoelectric IR sensors through a self-aligned technique. Unlike most conventionalfront-etched thermoelectric IR sensors, etching windows in the self-aligned process aredetermined by the spacing between polysilicon thermocouple legs. Due to etchingwindows for structure release being patterned by a self-aligned process ratherthan as a last photolithography step, the fabrication complication is reducedand narrow etching windows can be patterned. Using the self-aligned process,three types of thermoelectric IR sensors are fabricated and characterized. WithSiO2/Si3N4 as absorber layer, the sensor with rectangular structure shows the highest responsivity of43.5 V W − 1, and the circular-shaped sensor with polysilicon strips patterned in the absorber areashows the fastest response and the highest specific detectivity of . This self-aligned technique is also directly applicable to other MEMS devices withpolysilicon as the structure material, and also makes it possible to manufacture ultrasmallgaps.