S. Suwazono

A 2/3-inch 2 M-pixel IT-CCD image sensor with individual p-wells for separate V-CCD and H-CCD formation

This 2/3-inch optical-lens-format, 2 M-pixel interline-transfer (IT) CCD image sensor achieves large charge handling capability in the vertical CCD (V-CCD), and at the same time ensures sufficient transfer efficiency in the horizontal CCD (H-CCD). A V-CCD/H-CCD connection eliminates the potential barrier caused by separate V-CCD/H-CCD formation. Image sensor performance includes a 40 k-electron charge-handling capability in the V-CCD, leading to a 71 dB dynamic range, and sufficient transfer efficiency in the H-CCD, with no deterioration in V-CCD to H-CCD transfer efficiency. The power consumption is 0.49 W, just 22% of that previously achieved in a 1-inch 2 M pixel frame interline transfer (FIT) CCD. This is possible because the p-well reduces the driving pulse amplitude in the V-CCD and the IT scheme decreases electrode capacitance and driving frequency.<<ETX>>

A 1/4 inch 380 k pixel IT-CCD image sensor employing gate-assisted punchthrough read-out mode

A newly developed 1/4-inch 380 k pixel IT-CCD image sensor features a novel cell structure in which signal charges are read out from a photodiode (PD) to a vertical-CCD (V-CCD) in a gate-assisted punchthrough mode. The cell structure, fabricated through the use of high energy ion implantation technology, enables both deep PD formation and transfer-gate (TG)/channel-stop (CS) length reduction. Deep PD formation helps increase sensitivity per PD unit area, and TG/CS length reduction widens both PD and V-CCD areas. Although the cell size is small (4.8 /spl mu/m (H)/spl times/5.6 /spl mu/m (V)), the sensor achieves both high sensitivity (35 mV/lx) and a high saturation signal (600 mV). >

Optical limitations to cell size reduction in IT-CCD image sensors

We have determined the practical limits of cell size reduction in interline-transfer CCD image sensors, limits resulting from diffraction occurring at the aperture above the photodiode. We have found that image cell size cannot be reduced to a level for which aperture width would fall below about 0.2 /spl mu/m. We have also found, however, that image cells with greater than 0.2 /spl mu/m aperture size are sensitive over the entire wavelength range of visible light, and that sensitivity can be increased by thinning the photoshield film.

A 1/2-in 1.3 M-pixel progressive-scan IT-CCD for digital still camera applications

A 1/2-in 1.3 M-pixel progressive-scan interline-transfer charge-coupled-device (IT-CCD) image sensor has been developed for small, low-power mega-pixel digital still cameras (DSCs). The pixel size as small as 5 /spl mu/m square makes small-size progressive-scan IT-CCD (8.3/spl times/7.1 mm/sup 2/) for the SXGA format. A two-phase-drive horizontal-CCD with phosphorus-implanted storage regions helps reduce the driving voltage to 2.5 V, resulting in the power consumption of the device being as low as 146 mW. A new source-follower amplifier with separate p-well driver transistors achieves 12% higher gain than that obtained using a conventional amplifier. An overflow drain with a self-adjusting potential barrier can instantly remove superfluous charges in vertical-CCDs just before an exposure period, which enables DSCs to perform such functions as quick auto-focusing and dark-current removal. New dual operation modes for still and motion pictures can provide not only high-resolution color signals in a 15-frame/s 1050-line progressive mode but also wide-dynamic-range color signals in a 30-frame/s 525-line progressive mode. The latter mode employs a pixel-exchange-and-mix readout operation that helps halve the number of scanning lines with no loss in sensitivity and color information.

A 30 frames/s 2/3-in 1.3 M-pixel progressive scan IT-CCD image sensor

A 30 frames/s 2/3-in 1.3 M-pixel progressive scan interline-transfer charge-coupled device (IT-CCD) image sensor has been developed for video and digital still-camera applications. To obtain high frame-rate images, a 49-MHz driving horizontal CCD (H-CCD) was developed. An 8-phase drive for vertical CCDs (V-CCDs) makes it possible to operate in a variety of modes, such as 1050 line progressive scan mode and 1049 line wide dynamic range interlaced scan mode. For digital still camera use, removing residual charges stored in the V-CCDs before exposure is essential, therefore new narrow-channel barrier over-flow drain (NCB-OFD) attached under the H-CCD was developed. The NCB-OFD automatically drains out extra charges and has the advantages of requiring neither an over-flow control gate nor any additional masks.

A 30 frame/s 2/3 inch 1.3M pixel progressive scan IT-CCD image sensor

For multimedia applications, 30Frame/s 2/3 inch 1.3M pixel progressive scan interline-transfer CCD (IT-CCD) image sensor employs an optimized well for the horizontal CCD (H-CCD) and a wide bandwidth amplifier for 49 MHz operation. An 8-phase drive for vertical CCDs (V-CCDs) makes it possible to carry out a variety of operations such as 1050 line progressive mode and 1049 line wide dynamic range interlaced mode. For still camera use, removing residual charges stored in the V-CCDs before exposure is essential. A narrow-channel barrier overflow drain attached under the H-CCD automatically drains extra charge and requires neither overflow control gate nor additional masks.

A 1/2 inch 1.3 M-pixel progressive-scan IT-CCD for still and motion picture applications

For still pictures, the sensor provides high-resolution color signals in a 15 frame/s 1050-line progressive mode. For motion pictures, it provides wide-dynamic range color signals in a 30 frame/s 525-line progressive mode. This latter mode employs a pixel-exchange-and-mix readout function that helps halve the number of scanning lines. A 5/spl times/5 /spl mu/m/sup 2/ pixel makes the 8.3/spl times/7.1 mm/sup 2/ IT-CCD the smallest yet applicable to the SXGA format. A two-phase drive horizontal CCD with phosphorus-implanted storage regions (PST-HCCD) with optimized wells so that they do not generate potential pockets under inter-electrode gaps helps reduce the driving voltage to 2.5 V. In still camera use, an overflow drain with self-adjusting potential barrier (SA-OFD) is attached to the HCCD to remove superfluous charges in the vertical CCD (VCCD) just before an exposure. A source-follower amplifier with separate p-well driver transistors with suppressed back-gate effects achieves a gain 11% higher than that obtained using a conventional amplifier. Green-sensitivity of the device is 190 mV (F8, 706 nt, 1/30 s), and the saturation signal is 400 mV (1050-line progressive mode).

A flattened-pear shaped photodiode structure for low smear and high sensitivity CCD image sensors

A new, flattened-pear shaped photodiode structure has been developed to reduce smear and to increase photo-sensitivity in CCD image sensors. The new structure features a wide, low-concentration N- layer formed below the conventional photodiode N layer. The new photodiode was designed by using a new parameter deduced from simulated potential-profiles to help optimize the Nlayer conditions. The new structure was applied to a 2/3-inch 2M pixel interline-transfer CCD (IT-CCD) image sensor, and it has achieved a low smear (-85 dB) as well as high sensitivity (35 nA/1x).<<ETX>>

1-million-pixel progressive-scan 60-fps IT-CCD image sensor

A 1M-pixel progressive-scan interline-transfer CCD image sensor has been developed.It features high resolution, real- time speed and square pixels. A real-time speed was obtained by a pair of H-CCDs, located at the upper and lower of the image area and driven at 43MHz. Charges of the upper and lower halves of the image area are output separately by using the upper and lower H-CCDs, respectively. This operation enables a 1024 by 1024 progressive scan at 60 frame/sec. The device can be operated in a 512 by 512 progressive scan at 120 frame/sec by combining the charges in each of two vertically-adjacent pixels and two horizontally-adjacent pixels. Furthermore, a 1024 by 1024 interlace scan at 120 field/sec is also acceptable for either frame-integration or field-integration. The device can also be operated in a 1024 by 1024 progressive scan at 30 frame/sec by using only one of the H-CCD.