CMOS-SOI-MEMS Thermal Antenna and Sensor for Uncooled THz Imaging

We report the design (electrical, mechanical, and thermal) and characterization of an improved performance uncooled thermal sensor for THz radiation based on thermal antenna. The 2-D imager pixel array provides the periodicity and constitutes a frequency-selective surface tuned to the desired THz wavelength band. The focal-plane array is first fabricated in a matured 0.18-μm CMOS-Silicon Over Insulator (SOI) process. By applying MEMS postprocessing using the CMOS metallization layers as built-in masks, micromachined-suspended directly absorbing resistive antennae integrated with thermal sensors are obtained, thus achieving good thermal isolation as well as low thermal mass. Characterization is performed using blackbody operating at 900-1200 K and THz filters. In contrast to the earlier published results, the reported device is characterized with a fully blocking set of three THz filters. With the current responsivity of ∼ 2.6 A/W, Noise Equivalent Power (NEP) of the order of NEP Hz |1Hz= 6.1 pW Hz, D of 0.41 10¹⁰ cm Hz/W, this uncooled THz sensor in the standard CMOS-SOI technology may enable monolithic uncooled passive THz imagers.