We have developed a low-cost uncooled infrared radiation focal plane array (FPA) requiring no thermoelectric cooler
(TEC), which has 320 x 240 detection pixels with 22 um pitch. The silicon single-crystal series p-n junction diodes and
the low-noise readout circuit on the same SOI wafer fabricated by 0.13 um CMOS technology were utilized for infrared
(IR) detection. The temperature dependence in the readout circuit was eliminated by correlated double sampling (CDS)
operation with reference pixel that was insensitive to infrared radiation.
In order to reduce the temperature dependence, we improved the reference pixel and the readout circuit. Although the
reference pixels should be completely insensitive to IR radiation, prior reference pixels showed measurable sensitivity.
The improved reference pixel was formed by partially releasing with bulk-micromachining and was verified to be
insensitive to IR radiation by an object of 400°C. The readout circuit had a differential amplifier instead of a singletransistor
amplifier and an analog-to-digital converter (ADC). In each portion, CDS was applied to reduce temperature
dependence. The first CDS operation was used for eliminating the pixel output variation and the second operation was
used for canceling the variation of the differential amplifier. The output variation referred to input was reduced to 1/30
compared with that of the prior circuit. Moreover, the residual variation of output voltage was reduced by CDS operation
in ADC and stable output data was obtained with ambient temperature variation.
With these improvements, the sensitivity variation of the FPA was improved to 10% in the range of -30 degrees to 80
degrees and noise equivalent temperature difference (NETD) of 40 mK was achieved.
We have developed an uncooled infrared radiation focal plane array (IR-FPA) with 22 μm pitch and 320 × 240 pixels
utilizing silicon p-n junction diodes, which were fabricated by 0.13 μm CMOS technology and bulk-micromachining.
The thermal time response of cells was lowered to be 16msec by reduction of thermal capacity of cells. In addition to
increase the sensitivity of cells by extending the length of supporting beams, p-n junction diode was scaled down as
small as 20% in area compared to previous one. Micro-holes were formed in the cell to reduce only thermal capacity,
which were negligibly small compared to incident IR wavelength. This method needs no additional process step and is
considered as suitable for low cost and mass-productive IR-FPA.
We have developed a 22um pitch and 320 × 240 pixel uncooled infrared radiation focal plane array on the silicon-oninsulator
(SOI) substrate by means of 0.35um CMOS technology and bulk-micromachining. For IR detection, we use
silicon single-crystal series p-n junctions that can realize high uniformity of sensitivity and low voltage drift. The
supporting beam shrinkage enabled the pixel pitch shrinkage from 32um to 22um and 320 × 240 pixel number without
deteriorating NETD. We also developed a SOI low-noise CMOS readout circuit that can calibrate chip temperature and
introduced a noise canceling digital algorithm to cancel the reset noise generated in the readout circuit. The dominant
noise source, SOI MOSFET noise, was decreased by optimizing the gate design. Finally the FPA has realized noise
equivalent temperature difference (NETD) of 0.12K and requires no thermo-electric cooler (TEC) and is mounted on a
low-cost standard ceramic package.
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.
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