E. Oda

No image lag photodiode structure in the interline CCD image sensor

An undesirable image lag with a long time constant was found in the interline CCD image sensor having N+P-junction photodiode (PD). This paper clarifies the image lag mechanism and proposes a new photodiode structure having no image lag. The image lag measurement method and the experimental results are also given. The experimental results quantitatively agreed with the analytical model, in which signal electrons are assumed to be transferred from the PD to the vertical CCD as a small subthreshold current. To eliminate the image lag, a P+NP-structure PD with low donor concentration was proposed, where all the signal electrons can be quickly transferred before the subthreshold condition begins. As a result, the decay lag values of the 1st and the 2nd fields were reduced to half and the decay lags after the 3rd field were not observed.

Interline CCD image sensor with an anti blooming structure

A ⅔-in 384 (H) × 490 (V) element interline CCD image sensor with a new antiblooming structure was developed. Blooming was suppressed without sacrificing photosensitivity and dynamic range by means of a vertical overflow drain positioned under (rather than beside) a photodiode. For 10-percent vertical height illumination the smear signal was reduced to 0.05 percent of the illumination signal. Well-balanced performance, namely, large dynamic range (72 dB), low random noise (65 rms noise electrons per charge packet), high-contrast transfer functions for horizontal and vertical directions, and a spectral response similar to the luminous efficiency curve were obtained under moderate operating conditions.

Interline CCD image sensor with an antiblooming structure

A ⅔-in 384 (H) × 490 (V) element interline CCD image sensor with a new antiblooming structure was developed. Blooming was suppressed without sacrificing photosensitivity and dynamic range by means of a vertical overflow drain positioned under (rather than beside) a photodiode. For 10-percent vertical height illumination the smear signal was reduced to 0.05 percent of the illumination signal. Well-balanced performance, namely, large dynamic range (72 dB), low random noise (65 rms noise electrons per charge packet), high-contrast transfer functions for horizontal and vertical directions, and a spectral response similar to the luminous efficiency curve were obtained under moderate operating conditions.

An interline CCD image sensor with reduced image lag

An undesirable image lag with a long time constant was found in the interline CCD image sensor having an n+-p-junction photodiode (PD). This paper clarifies the image lag mechanism and proposes a new photodiode structure having very little image lag. The image lag measurement method and the experimental results are also given. The experimental results quantitatively agree with the analytical model, in which signal electrons are assumed to be transferred from the PD to the vertical CCD as a small subthreshold current. To eliminate the image lag, a p+-n-p-structure PD with low donor concentration is proposed, in which all the signal electrons can be quickly transferred before the subthreshold condition begins. As a result, decay lag values for the first and the second fields were reduced to half and no decay lags were observed after the third field.

Blooming suppression mechanism for an interline CCD image sensor with a vertical overflow drain

The blooming suppression mechanism for a vertical overflow drain (VOD) structure for an interline CCD image sensor(1) was quantitatively analyzed. An analytical formula, describing photodiode potential VPDchange as a function of integration time and light intensity, was obtained using VOD structure punch-through characteristics. Calculated results at strong light intensity, for which blooming suppression is required, indicate that (1) at a fixedV_{SUB}, V_{PD}after integration time decreases linearly with an exponential increase in the light intensity. This fact implies that a slight VVDdecrease remarkably increases punch-through current, which overflows excess signal charge into the drain. (2) VVDafter integration time markedly increases with VSUB. By combining this fact with (1), it can be deduced that VSUB, necessary for blooming suppression, increases only slightly even for several orders of incident light increase. Experimental results for both VOD image sensor cell and an actual interline sensor verified the analytical results. Therefore, the VOD image sensor has an excellent blooming suppression capability.

New low noise output amplifier for high definition CCD image sensor

A novel low-noise CCD (charge coupled device) output amplifier, the RJG detector, has been developed. The RJG detector incorporates a JFET having an electrically floating ring-junction gate (RJG). The operating principle is that signal charges, transferred from CCD into the RJG, directly modulate the drain current in the detection JFET. Test devices were fabricated and evaluated with 37-MHz clock frequency. By introducing JFET and achieving complete charge transfer in reset operation, 1/f noise has been reduced and reset noise has been completely eliminated. As a result, input referred noise equivalent electrons within the 18.5 MHz baseband were reduced to 17 (electrons). The RJG detector is confirmed to be suitable for a high-definition CCD image sensor, which requires high-speed operation.<<ETX>>

A 1920(H)*1035(V) pixel high-definition CCD image sensor

A 1920(H) × 1035(V) pixel high definition CCD image sensor has been developed. In order to follow up 74.25 MHz high sampling frequency, as well as to avoid the necessity for ultra fine patterning work for horizontal CCD register electrode formation, the device adopts a dual channel configuration for the horizontal CCD register. To accomplish both vertical signal charge transfer in the V-CCD register and signal charge distribution from the V-CCD registers into the dual channel horizontal CCD registers simultaneously within a 3.77 ¿s short horizontal blanking period, the 1H memory electrode between the V-CCD and H-CCD is introduced. The device operates successfully and a 1000 TV line limiting resolution has been obtained.

A new concept silicon homojunction infrared sensor

A novel silicon photovoltaic infrared sensor is proposed. It consists of three regions with a homojunction structure that has a flexibility designed barrier height corresponding to the cutoff wavelength. The operation of the sensor is based on infrared absorption and internal photoemission by free-electrons in a conduction band in a degenerated n/sup ++/-type silicon. Results obtained with fabricated sensors have verified the basic operating principle and have shown that the detectable wavelength range extends past 12 mu m.<<ETX>>

324*487 Schottky-barrier infrared imager

A standard TV-compatible PtSi Schottky-barrier infrared imager is described. The imager is a 324*487 element area array and has an electronic shutter function. Although the pixel is 42*21 mu m, a large fill factor of 42% is obtained, using a 1.5- mu m minimum design rule and a two-level polysilicon layer, and two-level aluminum layer structure. Using face-down bonding technology, it was possible to reduce the package size to 60% of the conventional ceramic package size. Due to optimization of the Schottky-barrier diode process and the diode structure, the noise equivalent temperature difference is as small as 0.1 K at f/1. >

New technologies in dual channel read-out registers for high-density CCD image sensor

New technologies has been developed for dual channel read-out registers. The mechanism for fixed pattern noise, associated with charge transfer between two horizontal CCD registers, has been clarified and optimum design has been proposed. Furthermore, a new dual channel read-out technique has been developed.