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.
We have developed a 32 μm pitch and 160 × 120 pixel uncooled infrared radiation focal plane array (IRFPA) on SOI by 0.35 μm CMOS technology and bulk-micromachining. For IR detection, we use silicon single crystal series p-n junctions which can realize high uniformity of temperature coefficient and low voltage drift. We have also developed a low-noise CMOS readout circuit on the same SOI which can calibrate the substrate temperature variation in every frame period, comparing two types of pixels, a bulk-micromachined infrared detection pixel and a non-micromachined reference pixel. Then the FPA requires no thermo-electric cooler (TEC) and is mounted on a low-cost standard ceramic package for the consumer products market.
This paper reports the implementation of a siliconbased infrared (IR) multiband pass filter (BPF) on an uncooled microbolometer IR focal plane array (IR-FPA), both of which are fabricated by the standard CMOS process. IR spectroscopy has been widely used as a sample identification technique, exploiting the fact that each molecule structure has a unique spectral feature. Using IR-BPF and IR-FPA, a low-cost and compact IRspectral imaging system is realized. The microbolometer IR-FPA exhibits broad spectral response sufficient to cover the IR-region from the mid-infrared (3 µm) to far-infrared (8 µm~), which is broader than the coverage of conventional non-silicon-based photodetectors such as mercury cadmium telluride. Single-band images of invisible gases such as ethanol vapor and CO 2 in breath are obtained with the IR-FPA. For multiband imaging, a guidedmode resonance IR filter is fabricated by patterning aluminum (Al) layer of 100 nm thickness on a silicon-on-insulator wafer.
Si-PIN photodiode type detector is one of the X-ray detectors which have recently shown significant improvement in resolution of FWHM of 250 eV at 5.9 keV which is worse only by 130 eV than that of a conventional type Si(Li) detector. The remarkable advantages of the SPINP detector are high operability with the thermoelectric cooling system and low voltage bias, and small volume including the preamplifier system. It is found that SPINP detector is applicable to the X-ray spectrometry and also PIXE in the X-ray energy range below about 15 keV with a reasonable efficiency. The pattern analysis method is feasible to analysis such bad resolution spectra obtained with this detector. Some techniques related to the Si-PIN photodiode type detector in Bio-PIXE are discussed.
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