Keiichi Akagawa

410K pixel PtSi Schottky-barrier infrared CCD image sensor

We developed an 811 by 508-element monolithic focal plane array detector using a PtSi Schottky-barrier photodiode, which has the greatest number of pixels for the Standard TV format. This detector array uses an interlined CCD configuration and 1.0-micron design rules. The pixel size of this detector was 18 by 21 microns square. From many experiments, the process conditions needed for obtaining the high responsivity were determined. To obtain high responsivity, we focused on two important aspects. The first one was an effective fill factor, and the second one was the properties of the PtSi Schottky barrier. Applying the new procedure to the wafer fabrication process, we reduced the nonactive portion of the pixel and obtained the ideal optical cavity structure. This new procedure was also a damage-free process, so good PtSi Schottky-barrier properties were obtained, which is related to the second aspect. We investigated the dependence of Schottky-barrier height on Pt deposition substrate temperature. Based on the results of the investigation, typical (Phi) b (Schottky- barrier height) and typical C1 (quantum efficiency coefficient) of 0.22 eV and 0.28/eV, respectively, were obtained. The NETD (noise equivalent temperature difference), calculated as the ratio of noise to response, was 0.06 K. The responsivity nonuniformity was estimated to be 0.45%. These measurements were done for a scene temperature of 300 K, f/1.2 cold shield, a 3 micrometer- long-wavelength pass filter, and 1/60-second integration time. Excellent thermal imaging was obtained without uniformity correction. We also show that the combination of electrical shutter operation and ND filter is suitable for high-temperature measurement.

New high-performance PtSi IRCCD and its electrical shutter operation

In this work the design and performance of a 537 (H) x505 (V) -element PtSi Schottky-barrier diode (SBD) IRCCD are described. To downsize the JR camera, the pixel size of the IRCCD has been reduced to 15.2mx11.8jtm. The package size of the IRCCD is l4mmxl4mm. The reduction of the pixel size causes a decrease in thermal sensitivity. However, the noise equivalent temperature difference (NETD) of the IRCCD is less than 0.13°C, because the transfer conversion gain from the electrons to the voltage has been increased, by decreasing the capacitance of its FDA. Furthermore, the NETD can be decreased to 0.1 1°C by increasing the platinum deposition temperature to 340°C. The IRCCD has an electrical shutter function with which the exposure time can be varied from 1/500 second to 1/5000 second. In addition, the IRCCD has a mixed-signal-mode shutter function, which was developed to expand the dynamic range. The mixed-signal-mode shutter function is performed by mixing the signal electrons of two kinds of pixels, one shuttered and the other unshuttered. The IRCCD also has a temperature monitor diode on a chip to control the cooling system of the JR camera. However, inclusion of this diode causes an increase in the fixed pattern noise. To reduce this noise, the monitor diode is forward biased for only a moment for temperature measurement. Keywords: PtSi SBD IRCCD, downsizing, electrical shutter, temperature monitor diode

Construction and performance of an 811 x 508 element multiwavelength PtSi IR CCD imager

In this paper, we propose a method of constructing a multi- wavelength IR imager and investigate some of its applications. The optical cavity structure has been used to improve the sensitivity of the IR imager for a long time. However, it can also be used as an on-chip interference filter. We developed two kinds of multi-wavelength IR imagers based on the 410 k pixel PtSi IRCCD, which has been previously reported by us. The type A multi-wavelength IR imager is composed of three kinds of pixels. In the device, three kinds of pixels with different spectral responsivities are arranged in the form of a stripe in the vertical direction of the CCD. The type A device is used within the wavelength range of 3 - 5.5 micrometer. The type B device is a multi-wavelength IR imager in which four kinds of pixels with different spectral responsivities are arranged in the vertical direction in the form of a stripe. The type B device is used within the wavelength range of 1.5 - 2.5 micrometer. We report the structure, the characteristics and some applications of the multi-wavelength IR imagers.

Solid State Imaging Techniques. A 410k pixel PtSi Schottky-Barrier Infrared CCD Image Sensor.

A 811 × 508 pixel PtSi Schottky-barrier infrared CCD image sensor which has the greatest number of pixels for a Standard TV format was developed. We achieved a 38% fill-factor of 18 × 21μm size pixel for this image sensor by using 1.0μm design rules. The noise equivalent temperature difference with f/1.2 was 0.06 K at 300 K. The responsivity nonuniformity with a 300 K background signal was estimated at 0.45%. The sensor obtained execellent thermal imaging without uniformity correction.