Hidetoshi Nozaki

A 2-million-pixel CCD image sensor overlaid with an amorphous silicon photoconversion layer

A highly sensitive 2-million-pixel high-definition charge-coupled device (CCD) image sensor was developed that features an overlaid amorphous silicon photoconversion layer on an interline transfer-type CCD scanner. The device is adapted to the 16:9 aspect ratio. 1125 scanning lines and 2:1 interlace high-definition TV system. A dual-channel horizontal CCD register is used to reduce the operating frequency to one half of the 74.25-MHz readout frequency. A horizontal period signal storage memory (1H line memory) is provided between the vertical CCD register and the horizontal CCD register to provide the signal distribution from the vertical CCD to the horizontal CCD register during the 3.77- mu s short horizontal blanking interval. This device realized a 1000 TV line horizontal limiting resolution 210 nA/1x high sensitivity. Total random noise was found to be 52 electrons RMS and a 72-dB dynamic range was achieved. >

Improvement of Hydrogenated Amorphous Silicon n-i-p Diode Performance by H2 Plasma Treatment for i/p Interface

Hydrogenated amorphous silicon (a-Si:H) n-i-p diodes in which the intrinsic (i-type) layer surfaces were exposed to an H2 plasma before depositing the p-type layer (H2 plasma treatment of the i/p interface) were prepared. The effects of this H2 plasma treatment of the i/p interface were observed by dark I-V, photo-I-V under 450 nm illumination, and quasistatic C-V measurements. It has been found that the defect density at the i/p interface is reduced by this treatment. It has also been determined that the performance of a-Si:H diodes is improved by this treatment of the interface.

A 2/3-inch 2M-pixel STACK-CCD imager

Shrinking pixel size in conventional CCD imagers degrades device performance. Unsatisfactory smear noise of -90 dB is attained in a 2/3-inch 2M pixel CCD imager. The STACK-CCD imager has a great advantage regarding this problem. A 100% aperture ratio and low smear noise are maintained regardless of future pixel shrinking, because CCD scanning circuits are overlaid with an amorphous silicon (a-Si) photoconversion layer.<<ETX>>

A 3.7/spl times/3.7 /spl mu/m/sup 2/ square pixel CMOS image sensor for digital still camera application

Systems such as digital still cameras, robots, etc. require low-cost, low-power and high-resolution. This CMOS image sensor has reduced cell size. The sensor is fabricated using 0.6 /spl mu/m, triple-poly-silicon, double-metal CMOS process technology. The sensor has 3.7/spl times/3.7 /spl mu/m/sup 2/ pixels. It operates with one 3.3V power supply and has less than 30mW power dissipation.

A 2/3-in 2 million pixel STACK-CCD HDTV imager

A 2/3-in optical format 2 M pixel STACK-CCD imager has been developed. The STACK-CCD imager, overlaid with an amorphous silicon photoconversion layer, realizes a large signal charge handling capability of 1.0/spl times/10/sup 5/ electrons, a -140 dB smear noise and a 90 dB dynamic range with a newly introduced device configuration and its unique operation. The 5.0 /spl mu/m(H)/spl times/5.2 /spl mu/m(V) unit pixel imager with sufficiently low image lag has been realized by a novel bias charge injection scheme These device performances are the best ever achieved by a CCD HDTV imager. This is the first such imager satisfying the device performances required for a practical use 2/3-in 2 M pixel HDTV imager. >

Measurement and analysis of photocurrent transient characteristics for hydrogenated amorphous-silicon photodiodes

The relations between the photocurrent transient after the end of steady-state illumination for hydrogenated amorphous silicon photodiodes and the related film properties for undoped hydrogenated amorphous silicon prepared by mercury-sensitized photochemical vapor deposition are investigated. The photocurrent transient characteristic indicates significant correlations with the film properties, such as electron drift mobility ( mu /sub d/), silicon dangling bond density (N/sub s/), a minimum in the density of states near the Fermi level (N/sub min/), and space-charge density (N/sub i/). The photocurrent transient decay decreases with increasing mu /sub d/ and with decreasing N/sub s/, M/sub min/, and N/sub i/. This result was confirmed by a model analysis. >

Characteristics for a-Si:H Films Prepared by Mercury-Sensitized Photochemical Vapor Deposition

The density of states in a-Si:H, prepared by mercury-sensitized photo-CVD, was measured by the space-charge-limited current method. The density of Si dangling bonds (Ns) was measured by the electron spin resonance method. Ns and a minimum of the density-of-state near the Fermi level (Nmin) indicated the same tendency versus substrate temperature, which showed a good correlation between Ns and Nmin. Both Ns and Nmin showed a minimum value near substrate temperature of 200°C. Photosensitivity reached more than 1×106 for the sample.

Mercury-Sensitized Hydrogen Radical Photoetching of Undoped Hydrogenated Amorphous Silicon and Crystalline Silicon

An etching study for undoped a-Si:H films and c-Si has been carried out by using Hg-sensitized H radicals in H2 gas under UV-light irradiation with a low pressure mercury lamp. It has been found that the etch rate of undoped a-Si:H increases with decreasing substrate temperature and H2 flow rate, as well as with increasing UV-light intensity. Concerning H2 gas pressure dependence, a maximum etch rate was observed at around 0.1 Torr. An adsorbed layer, composed of H2 molecules, H radicals, Hg atoms and photoexcited Hg atoms, can be considered to be formed on the surface. The adsorbed layer irradiated with UV light may supply a sufficient number of H radicals near the surface to rapidly cut off the Si network, leading to the formation of volatile SiHx.

Correlation between Si-H2 bond density and electron drift mobility in a-Si:H films prepared by photochemical vapor deposition

The correlation between Si-H2 bond density and electron drift mobility in a-Si:H films has been investigated by using the dependence of the film properties on the silane gas pressure in mercury-sensitized photochemical vapor deposition. It was found that the electron drift mobility decreased with increasing the Si-H2 bond density, when the hydrogen contents were about the same amount.

Hg-Sensitized Photochemical Vapor Deposition Application to Hydrogenated Amorphous Silicon Photoconversion Layer Overlaid on Charge Coupled Device

An Hg-sensitized photochemical vapor deposition method has been developed which has enabled a hydrogenated amorphous silicon photoconversion layer to be overlaid on a charge coupled device (CCD) imager, without a pixel separation structure. This chemical vapor deposition (CVD) method has been used to realize imaging devices with high sensitivity and high resolution for high-definition TV.