Special Issue: Modern Sensing Technologies

Vol. 90, April 2008, pp. 302-309

A Micromachined Infrared Senor for an Infrared Focal Plane Array

Seong M. Cho, Woo Seok Yang, Ho Jun Ryu, Sang Hoon Cheon, Byoung-Gon Yu, Chang Auck Choi

IT Convergence & Components Laboratory (ICCL), Electronics and Telecommunications Research Institute (ETRI), 161 Gajeong-dong, Yuseong-gu, Daejeon, Korea

Tel.: +82-42-860-6237, fax: +82-42-860-6205

E-mail: smcho@etri.re.kr, www.etri.re.kr

 Received: 15 October 2007   /Accepted: 20 February 2008   /Published: 15 April 2008

Abstract: A micromachined infrared sensor for an infrared focal plane array has been designed and fabricated. Amorphous silicon was used as a sensing material, and silicon nitride was used as a membrane material. To get a good absorption in infrared range, the sensor structure was designed as a l/4 cavity structure. A Ni-Cr film was selected as an electrode material and mixed etching scheme was applied in the patterning process of the Ni-Cr electrode. All the processes were made in 0.5 μm iMEMS fabricated in the Electronics and Telecommunication Research Institute (ETRI). The processed MEMS sensor had a small membrane deflection less than 0.15 μm. This small deflection can be attributed to the rigorous balancing of the stresses of individual layers. The efficiency of infrared absorption was more than 75% in the wavelength range of 8 ~ 14 μm. The processed infrared sensor showed high responsivity of ~230 kV/W at 1.0V bias and 2 Hz operation condition. The time constant of the sensor was 8.6 msec, which means that the sensor is suitable to be operated in 30 Hz frame rate.

Keywords: Infrared Sensor, MEMS, Focal Plane Array

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