JPS61133782A - Solid-state image pickup devcie - Google Patents

Abstract

PURPOSE:To eliminate the false signal caused by the picture beyond the Nyquist limit, by connecting plural vertical transmission electrodes to one photoelectric conversion means and by switching to one of the vertical transmission electrode to output the picture signal obtained from the photoelectric convertion means according to the field. CONSTITUTION:Vertical transmission electrodes 11-14 are driven at four phase, and at same time they can function as a lead-out gate of the electric charge sent from a photosensor 10. Since the threshold voltage of this lead-out gate part is set higher than the vertical transmission drive voltage, there is no possibility that the electric charge leaks in from the photosensor while the vertical transmission is executed. Thus, four photosensors are connected to one vertical transmission electrode, and by impressing the lead-out drive voltage VH to one of the four phases, the four phorosensors contacting the electrode of that phase are absorbed of their signal charge, and added together and transmitted under the electrode of one phase.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a solid-state imaging device equipped with a CCD type imaging device.

More specifically, the present invention relates to a solid-state imaging device configured to reduce the number of in-field sampling points and the number of vertical transfer electrodes, and to obtain high resolution.

[Prior Art and its Problems] In this type of solid-state imaging device that has been known in the past, the pixel aperture is made as large as possible in order to reduce false signals caused by images exceeding the Nyquist limit.

However, there is a limit to increasing the aperture ratio on the image sensor pattern, and for example, the pixel aperture has been made isometrically larger by (1) photoconductive film stacking type, (2) those using lenticular lenses, etc.

However, even if such measures are taken, there are limits, and it is naturally impossible to obtain an aperture larger than the pixel pitch. Alternatively, it is also known to equivalently enlarge the pixel aperture by vibrating the element, but this method is complicated as it involves mechanical movement.
Moreover, there is also the disadvantage that the stability, which is an advantage of solid-state devices, is lost.

Furthermore, a "field" accumulation mode is known as one of the driving methods for a CCD type image sensor.

This field accumulation mode transfers and outputs the sum signal of two pixels in the vertical direction, and although it can reduce false signals in the vertical direction, it cannot reduce the important false signals in the horizontal direction. I can't. In other words, this method is mainly used to reduce the afterimage caused by the "frame" accumulation method. Merely devising the method will not be of any use in improving horizontal false signals.

[Objective] In view of the above-mentioned points, a first object of the present invention is to provide a solid-state imaging device that almost eliminates false signals caused by images exceeding the Nyquist limit in both the vertical and horizontal directions.

The second object of the present invention is to achieve a simple element configuration,
It is an object of the present invention to provide a solid-state imaging device which has high resolution and which absorbs all electric charges for each field to form an image with little afterimage.

[Structure of the invention]

In order to achieve such an object, the present invention provides a solid-state imaging device including a CCD type solid-state imaging device.

A plurality of vertical transfer electrodes are connected to a single photoelectric conversion means, and the signal charge obtained from the photoelectric conversion means is switched and outputted to one of the plurality of vertical transfer electrodes according to the field. This is a characteristic feature.

To describe the configuration of the above invention from another perspective, the present invention attempts to remove false signals based on images exceeding the Nyquist limit by realizing a pixel aperture larger than the equivalent pixel pitch. It is something.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a diagram illustrating a pixel arrangement in an embodiment of the present invention.

1 to 4 in this figure each indicate the arrangement pattern of the pixel center of gravity, which has a checkerboard arrangement. In addition, in the conventional method, even if the aperture ratio is 100%, the shape of the aperture is shown as 5. In contrast, in the present invention, as will be described in detail later, the pixel aperture is set to 6.
This makes it possible to enlarge the aperture up to the aperture shown in .

FIG. 2 shows a pattern of a CCD type image pickup device included in an embodiment of the present invention. This figure is a pattern diagram drawn focusing on the impurity concentration on a semiconductor substrate. Note that this figure shows only the area for the sake of simplification, and does not show various wiring connections, overlapping electrodes, etc.

In FIG. 2, 11 to 14 are pixel centroids 1 to 4, respectively.
This is a vertical transfer electrode corresponding to (see FIG. 1). Here, electrodes having the same number are electrically connected to each other, and a four-phase electrode structure is adopted.

Therefore, the electrode 11 corresponds to the first phase electrode, and the electrodes 12 to 14 correspond to the second to fourth phase electrodes, respectively. Further, 10 is a photosensor, which is a photodiode.

It is formed using an MQS sensor or the like. Reference numeral 15 indicates a lead-out gate region, and each of the vertical transfer electrodes 11 to 14 in contact with this region covers the top thereof. 1B indicates a channel stop region. Note that during vertical transfer in which charges are transferred along the path shown by the broken line in the figure, the potential of the transfer section is the lowest and the potential of the readout gate region 15 is higher than that. This lead-out gate region 15 also serves as a channel stop.

FIG. 3 shows the arrangement of the electrodes 11 and 13 provided in the first layer among the vertical transfer electrodes 11 to 14 described above. These first layer electrodes 11 and 13 are formed using the same mask. Note that the sensor 10 indicated by a broken line in this figure is drawn for convenience to represent the positional relationship with the first layer electrodes 11 and 13.

FIG. 4 shows the arrangement of the electrodes 12 and 14 provided in the second layer among the vertical transfer electrodes 11 to 14 described above and the connection state of these electrodes. That is, 112 and 114 shown in the figure serve as wiring for interconnecting the same electrodes. Note that the sensor 10 indicated by a broken line in the figure
is drawn for convenience, similar to FIG. 3, to represent the positional relationship with the second layer electrodes 12 and 14.

FIG. 5 shows wiring for connecting the first layer electrodes 11 and 13 shown in FIG. 3, where 111 is a connection pattern for the electrode 11 and 113 is formed as a connection pattern for the electrode 13 at the same time. Further, 121 and 123 each indicate a contact hole portion for electrode connection.

Regarding the various patterns described so far, for example, the electrodes shown in FIGS. 3 and 4 are made of polysilicon,
Furthermore, the connection wiring shown in FIG. 5 can be formed using aluminum.

As is clear from the above-mentioned Figures 3 to 5, since the connection wiring is performed diagonally with respect to the scanning direction of the screen, it is possible to connect between each of the four-phase electrodes without covering the light-receiving surface of each photosensor. The degree of integration can be easily increased by wiring.

FIG. 6 shows a vertical transfer electrode 1 for vertical charge transfer.
Fig. 7 shows the charge addition process when the readout drive voltage Vu is applied to the electrode 11, and Fig. 8 shows the timing of the pulses to be applied to the electrodes 1 to 14. The operation of this embodiment will now be described with reference to these drawings.

As already mentioned, the vertical transfer electrodes 11 to 14 are driven in four phases and also function as lead-out gate electrodes for charges sent out from the photosensor 10 (in other words,
The same vertical transfer electrode is also used as the readout gate electrode), and the threshold voltage of this readout gate is higher than the drive voltage VM (e.g. 3V) during vertical transfer, so the voltage is lower than that of the photosensor during vertical transfer. There is no charge leakage.

In this way, four photosensors are in contact with one vertical transfer electrode, and by applying the readout drive voltage VH (for example, 10 ports) to the electrode of one of the four phases, the voltage of that phase can be changed. Signal charges can be absorbed and added from the four photosensors that are in contact with the outer periphery of the electrode, and transferred to the bottom of one phase of the electrode.

For example, when the readout drive voltage VH is applied to the electrode 11 during the field blanking period of the first field, charges are transferred as shown by the solid arrow in FIG. →Electrode 13→
sequentially transferred to the electrode 14 (see Figures 2 and 6)
.

Thus, only once for each field, one of the four phases
Tsunoden 7. By driving each pole to VH, the sum signal obtained from the four photosensors is sent to the transfer section (below the vertical transfer electrode). The combination of these four photosensors can be changed for each field, as is clear from FIGS. 7 and 8. In this way, the sum signal obtained from the four photosensors is transferred under one vertical transfer electrode, and the combination of the four photosensors is different for each phase electrode. It is a characteristic.

Note that with the configuration described above, it is possible to obtain significantly better image signal characteristics compared to the conventional technology, but in order to further increase the aperture ratio to increase sensitivity and reduce false signals, for example, It is preferable to increase the aperture ratio by attaching a conventionally known lenticule or lens or by adding multiple layers. As a result, it is also possible to create an ideal aperture like 6 shown in FIG.

[Effects] As explained above, according to the present invention, a high resolution image can be obtained even when a CCD type image sensor with a small number of vertical transfer electrodes is used.

Further, according to the present invention, the frequency of horizontal transfer lock can be lowered, and the frequency of vertical transfer lock can also be halved compared to the conventional one.

Further, according to the present invention, since the electrode connection wiring can be made oblique to the scanning direction of the screen, the degree of integration can be increased without covering the light receiving surface of the photosensor with electrodes.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the pixel arrangement in an embodiment of the present invention, FIG. 2 is a layout diagram showing the pattern of a CCD type image sensor included in an embodiment of the present invention, and FIG. 3 is a diagram illustrating the arrangement of the first layer. Figure 4 is a diagram showing the arrangement of vertical transfer electrodes provided in the second layer, Figure 5 is a diagram showing the arrangement of vertical transfer electrodes provided in the second layer, and Figure 5 is for connection of the first layer electrodes shown in Figure 3. Figure 6 is a diagram showing the wiring; Figure 6 is a timing diagram showing voltages applied to each vertical transfer electrode for readout driving and vertical transfer; Figures 7 and 8 are diagrams explaining the operation of this embodiment. It is. 1... Pixel centroid of the first field, 2... Pixel centroid of the second field, 3... Pixel centroid of the third field, 4... Pixel centroid of the fourth field, lO... Photo sensor , 11,. 12,13.14...Vertical transfer electrode, 111
．． 113... Connection pattern, hole part.

Claims (1)

[Claims] 1) In a solid-state imaging device equipped with a CCD type solid-state imaging device, a plurality of vertical transfer electrodes are connected to a single photoelectric conversion means, and an image signal obtained from the photoelectric conversion means is A solid-state imaging device characterized in that output is switched to one of the plurality of vertical transfer electrodes according to a field. 2) The solid-state imaging device according to claim 1, wherein each of the vertical transfer electrodes is in contact with a plurality of the photoelectric conversion means via a readout gate. 3) The solid-state imaging device according to claim 1, wherein the vertical transfer electrodes are arranged in a checkerboard pattern, and wiring for connecting the vertical transfer electrodes is provided obliquely to the scanning direction of the screen. Device.