A SOI-based CMOS-MEMS IR image sensor with partially released reference pixels

Abstract

We have developed a 22 µm pitch and 320 × 240 pixel uncooled IR (infrared) image sensor. For IR detection, we utilized single crystal silicon series p–n junctions, which were fabricated on a SOI (silicon on insulator) wafer utilizing 8 inch CMOS technology and MEMS processes. The p–n junctions were passivated with buried and laminated oxide layers from wet crystalline etching of the silicon substrate. The oxide layers were also utilized to absorb the IR radiation and to form supporting beams. The partially released pixels were utilized as thermal black pixels (TBs) instead of optical black pixels (OBs) for correlated double sampling. The IR image sensor utilizing TBs obtained a thermal image of the human body stably without the smearing phenomenon.

Low-Cost Microbolometer Type Infrared Detectors

“…The reason is that the thermal IR detectors are considered to be much slower and less insensitive than the photon IR detectors [ 6 ]. In 1992, both Texas Instruments and Honeywell published their uncooled IRFPAs (infrared focal plane array) based on pyroelectric type and microbolometer type thermal detector, respectively, with fascinating performance [ 10 , 11 ], successfully encouraging a sustained effort to further reduce the pixel size, improve the device performance, and reduce the production cost [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ].…”

“…Not only does the high-integration process lower the production cost of the detectors, but also it provides mature approach with small feature size and high uniformity to benefit the pixel size and the device performance. Especially, the complementary metal oxide semiconductor (CMOS) microbolometer technology is developed for long-wavelength IR (LWIR, 8–14 μm) FPAs via CMOS foundry compatible approaches [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ]. During the fabrication process, the layer structures of the absorber and the thermal sensor are formed with CMOS process, and then post-CMOS micro-electro-mechanical system (MEMS) process are used to form suspended microbridge structures in purpose of thermal isolation.…”

Micromechanical IR thermal detector using torsional oscillation: Improvement of resonator profile for high sensitivity

“…The typical detectors are bolometers, 4) thermopiles, [5][6][7][8] bimetals, [9][10][11][12][13] and thermal diodes. 14,15) Generally, the thermal detectors are less sensitive than quantum detectors. One of the methods used to increase the sensitivity of a thermal detector is to enhance the thermal isolation of the IR-irradiating area from the surrounding.…”

Design optimization and performance analysis of deformed optical readout focal plane array

“…There are basically two kinds of FPA classified by the readout method: the electrical readout FPA; and optical readout FPA. The studies on electrical readout FPAs have been carried out extensively [4][5][6], and an IR imaging system cored by an electrical readout FPA has already been commercialized. Although an electrical readout FPA has achieved excellent properties, several key issues such as the requirement of a high-sensitivity signal processing unit for each pixel, and thermal noise from the readout circuit, limited the further improvement of its performance.…”