JPH02143561A - Color image sensor - Google Patents

Abstract

PURPOSE:To make a solid-state image sensing element nearly equal in sensitivity to different colors and to obtain a color image sensing device capable of enlarging a dynamic range by a method wherein an optical shield layer is provided on a photodetective surface of the solid-state image sensing element high in sensitivity to colors to control the volume of incident light. CONSTITUTION:An optical shield layer 30 is provided onto a transparent electrode 22 so as to cover a photosensitive section (on a pixel electrode) in the same ratio for each pixel, where the shield layer 30 is arranged on a pixel electrode 20 excluding a gap 23 between the electrodes 20, and an opening 30a is formed on the center of each pixel electrode 20. When the photosensitive section is shielded with the optical shield layer 30 by 50% in light incident areas the light incident volume is reduced by 50% as compared with that when it is not shielded and the number of electrons generated through photoelectric conversion is also reduced by 50%, so that the sensitivity of each pixel is reduced to 50% of that when it is not shielded. Consequently, the sensitivity of the pixel can be controlled by varying its shielded area. By this setup, the relative sensitivity of a color image sensing device of this design can be nearly equal to colors (R, G, and B) to detect.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a color imaging device using a solid-state imaging device, and particularly to a color imaging device that improves the color sensitivity characteristics of the solid-state imaging device. It relates to an imaging device.

(Conventional technology) Traditionally, electronic color cameras have a single-panel configuration.

It is classified into 2-plate type, 3-plate type, etc. For example, in a three-panel color camera as shown in FIG.
The light is separated into three primary colors, G) and blue (B), and is incident on the corresponding stacked solid-state image sensors 63a, 63b, and 63c for photoelectric conversion. After the outputs of the elements 63a, 63c are amplified by amplifiers 64a, 64b, and 64c, the signals are processed by a color encoder 65 to obtain color signals.

Here, the stacked solid-state image sensor has a large optical aperture ratio per cell and can obtain higher sensitivity than the conventional CCD type, so it is indispensable for high-resolution electronic color cameras.

However, this type of device has the following problems. That is, as is clear from FIG. 7, the spectral sensitivity characteristics of the stacked solid-state image sensor have a dependence on the wavelength of incident light, and the sensitivity to red is higher than the sensitivity to blue.

Therefore, if this device was used as it was in a three-chip color camera, there was a drawback that the afterimage would have a blue color due to poor R-G-B sensitivity balance. In addition, since the dynamic range is determined by the difference in illuminance that gives the maximum amount of charge and the minimum amount of charge (noise) that can be collected in the potential well, conventional laminated layers, which have a large difference in sensitivity between R-G-B, Another problem with solid-state image sensors is that the R sensitivity is too high, which limits the expansion of the dynamic range.

(Problems to be Solved by the Invention) Conventionally, in a color imaging device using a stacked solid-state imaging device, due to the characteristics of the photoconductor film, there is a large difference in sensitivity depending on R-G-B. Because of its high sensitivity, G,
There is a problem in that the signal reaches saturation at such low illuminance that the B signal current does not reach saturation, making it impossible to increase the dynamic range.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a color imaging device in which the sensitivity of a solid-state imaging device to different colors can be made approximately equal, and the dynamic range can be expanded. It is about providing.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to provide a light shielding layer that regulates the amount of incident light on the light receiving surface of a solid-state image sensor for colors with high sensitivity.

That is, the present invention provides a color imaging device that captures a color image by independently detecting the amounts of light of different colors using solid-state imaging devices, in which the sensitivities to the colors to be detected are adjusted so that the sensitivities to the respective colors are approximately equal. A light shielding portion is provided on a portion of the photosensitive portion depending on the situation.

Further, the present invention detects the amount of light of different colors using three solid-state image sensors, and uses three solid-state image sensors to capture a color image.
In the plate-type color imaging device, in order to make the sensitivities of the three solid-state imaging devices approximately equal to each other, on the photosensitive portion of at least one solid-state imaging device, depending on the sensitivity of the device to the color to be detected, The light shielding portions are provided at a constant ratio to the area of one pixel.

More specifically, on the photosensitive part of a solid-state image sensor with high absolute sensitivity (sensitivity per unit area), a certain amount of light is applied to one pixel area, depending on the absolute sensitivity of the solid-state image sensor to the color to be detected. A light shielding portion is provided at a certain ratio, so that the relative sensitivity (sensitivity per pixel) of the solid-state imaging device approaches the relative sensitivity of the solid-state imaging device having the lowest absolute sensitivity.

(Function) According to the present invention, by providing the light shielding portion according to the absolute sensitivity to the color to be detected, the relative sensitivity to each color to be detected can be made equal. For example, in a three-panel color camera, if a light shielding section is provided in the R- device, and a 50% light shielding section is formed for each pixel, the sensitivity of R can be reduced by 50% compared to the conventional device. By changing the area ratio of the light shielding part, it is possible to balance the RGB sensitivity, and the dynamic range can be increased. Furthermore, inconveniences such as coloring of afterimages can be avoided. Furthermore, depending on the formation position of the light shielding part, it is possible to suppress moiré and reduce smear, and if the light shielding part is formed only for a limited number of pixels, it is possible to suppress moiré and reduce smear. It can also be applied to cameras.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing an R solid-state image sensor used in a three-panel color camera according to a first embodiment of the present invention. The overall configuration of the device is the same as that shown in FIG. 6, and the difference between this embodiment and the conventional device lies in the configuration of the solid-state image sensor.

In FIG. 1, reference numeral 11 denotes a p-type St substrate, and a p+-type element isolation layer 12°n+-type channel (
A vertical CCD channel) 13 and an n++ type storage diode 14 are formed, on which a transfer gate 15, 16 is formed.

Here, a part of the transfer gate 15 becomes a signal readout gate. Further, after forming a first insulating film 17 such as 5i02 on this, a contact hole is made in the insulating film 17, and a pixel electrode wiring 18 is formed. Furthermore, BPS for flattening
A solid-state image sensor chip 10 is fabricated by depositing a second insulating film 19 made of a G film (borophosphosilicate glass), making contact holes in this insulating film 19, and forming pixel electrodes 20.

A photoconductive film 21 made of amorphous hydrogenated silicon (a-3i:H) or the like is deposited on the solid-state image sensor chip 10, and a transparent electrode 22 made of ITO or the like is formed thereon. The configuration up to this point is the same as the conventional one, and the G and B solid-state image sensors in this embodiment are also the same. However, the R solid-state image sensor in this example is provided with a light shielding section in addition to the above configuration. That is, the light shielding layer 30 is provided on the transparent electrode 22 so as to cover the photosensitive area (on the pixel electrode) in the same proportion for one pixel. This light shielding layer 30
is made of Al1, for example, and the shielding area is, for example, 50% of the area of one pixel.

In the configuration shown in FIG. 4, the light incident from the transparent electrode 22 is photoelectrically converted by the photoconductive film 21, thereby converting the light into electrons.
A hole pair is formed. Since the potential of the pixel electrode 20 electrically connected to the storage diode 14 is higher than that of the transparent electrode 22, electrons move toward the pixel electrode 20 and holes move toward the transparent electrode 22. Holes are transparent electrode 2
2 to an external circuit, and the electrons are stored in a storage diode 14 connected to the pixel electrode 20. Then, the signal charge (
When a signal charge readout pulse is applied to the signal charge readout gate 15, the electrons are transferred from the storage diode 14 to the vertical C
The signal is read out to the OD channel 13. Note that the charges read out and transferred to the vertical COD channel 13 are transferred to the horizontal COD channel (not shown).
It will be output via the CD channel.

FIG. 2 is a plan view of the solid-state image sensing device shown in FIG. 1 viewed from above, and shows more pixels equivalent than in FIG. 1. The light shielding layer 30 is arranged on the pixel electrodes 20 excluding the gaps 23 between the pixel electrodes 20, and has an opening 3 in the center above each pixel electrode 20.
0a is formed. Here, if 50% of the incident area of the photosensitive part is shielded by the light shielding layer 30, the amount of incident light will be reduced to 50% of that without shielding, and the number of electrons generated by charge conversion will also be reduced by 50%. The sensitivity per pixel is reduced by 50% compared to when there is no shielding part. Sensitivity can be controlled by changing the area of this shielding part, and if the ratio of area to one pixel is the same for each pixel, there is no equivalent restriction on the nine positions of the light shielding layer 30.

If a device with this structure is used as the R taper and chair of a three-panel color camera and the R sensitivity is controlled to alleviate the R-G-B sensitivity difference, the dynamic range will be larger than before. be able to. Note that the area of the light shielding portion may be determined depending on the difference between the absolute sensitivity of the element provided with the shielding portion and that of the element having the lowest absolute sensitivity, as well as the characteristics of the color filter used for each element.

Thus, according to this embodiment, each color to be detected (R-G
-B) The relative sensitivity (sensitivity per pixel) can be made approximately equal. In other words, it is possible to balance the RGB sensitivities, thereby increasing the dynamic range. Furthermore, inconveniences such as coloring of afterimages can be avoided. In addition, since the solid-state image sensor is a stacked type, a sufficient light-receiving area can be obtained even if a light shielding part is provided, and further advantages include the fact that it can be realized with a simple configuration simply by adding a light shielding part to the conventional structure. There is also.

Further, as a second example, a case will be described in which the formation position of the light shielding portion is set to exist above the gap between two pixels. In the example shown in FIGS. 3(a) and 3(b), the light shielding layer 30 is provided not only on the pixel electrode 20 but also on the pixel electrode 20.
A device is also provided on the gap 23 between them. In this case, the light shielding layer 30 is used not only for sensitivity control, but also because light enters the gap 23 between the pixel electrodes 20 and prevents electrons from directly entering the vertical CCD, resulting in the effect of reducing smear.

By the way, when pixels are arranged in K rows and L columns, n
rows and (n+1) rows in the A field period, then (n
When operating in the field accumulation mode in which the +1)th row and the (n+2)th row are added and read out during the B field period, in the arrangement of the light shielding part as in Embodiment 1 and Embodiment 2, after adding the signals, Within that row, areas where a signal is present and areas where it is absent always appear alternately, causing a problem in which moiré occurs on the playback screen. FIG. 4 shows a third embodiment in which a light shielding portion is formed to suppress the moire.

As in Examples 1 and 2, in order to make the sensitivity the same for each pixel, the ratio of the light shielding portion to the area of one pixel is kept constant.

In the n-th and (n+1)-th rows, the formation positions of the light shielding portions are shifted by 180° or around 180 degrees, as shown in FIG. 4, so that the light incident portions form a checkered pattern. Originally, in order to form this checkered pattern without adding a light shielding layer, it is necessary to arrange the pixel electrodes in every other row by shifting them by 1800 degrees, but in this example, by adding the light shielding layer 30, the pixel electrodes are shifted by 1800 degrees. It is possible to reduce the amount (only the width of the electrode 23 between the pixel electrodes 20 or the vicinity thereof).

With this arrangement, when reading, as shown in FIG. 5, the nth row and (n+1) row (solid arrow) are added in the A field, and (n+1) is added in the B field.
Since the row and the (n+2)th row (broken line arrow) are added and read, a signal is always present from one end of the row to the other, and the occurrence of moiré can be suppressed.

Note that the present invention is not limited to the embodiments described above. For example, the solid-state imaging device provided with the light shielding portion is not limited to the one that has the highest absolute sensitivity for the color to be detected, but by providing the light shielding portion in other than the solid-state imaging device with the lowest absolute sensitivity, it is possible to It is possible to bring the relative sensitivity of the image sensor closer to each other. Further, in the embodiment, a three-plate type using three solid-state image sensors has been described, but it is also possible to apply the present invention to a one-plate type in which one solid-state image sensor is provided with filters of different colors. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by providing a light shielding layer that regulates the amount of incident light on a part of the light-receiving surface of the solid-state image sensor for colors with high sensitivity, different types of solid-state image sensors can be used. It is possible to realize a color imaging device in which the sensitivity to colors can be made substantially equal and the dynamic range can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic structure of a solid-state image sensor used in a color image sensor according to a first embodiment of the present invention, FIG. 2 is a plan view showing the arrangement of a light shielding part of the device, and FIG. 4 and 5 are for explaining the second embodiment of the present invention and are a plan view showing the arrangement of the light shielding parts, and FIGS. 4 and 5 are for explaining the third embodiment of the present invention. Figure 4 is a plan view showing the arrangement of the light shielding part, Figure 5 is a schematic diagram showing the signal readout state, Figures 6 and 7 are for explaining the conventional problems, and Figure 6 is a three-plate type. A schematic configuration diagram showing a color camera, and FIG. 7 is a characteristic diagram showing the wavelength dependence of sensitivity of a solid-state image pickup device used therein. 11... St substrate, 12... element isolation layer, 13...
- CCD channel, 14...Storage diode, 15.
16... Transfer gate, 17. 19... Insulating film, 1... Pixel electrode wiring, 20... Pixel electrode, 21... Photoconductive film, 22... Transparent electrode, 23... Pixel electrode gap, 30... Light shielding layer, a... Opening.

Claims (4)

[Claims] (1) In a color imaging device that captures a color image by independently detecting the amount of light of different colors using a solid-state imaging device, the sensitivity to the color to be detected is adjusted so that the sensitivity to each color is approximately equal. A color imaging device characterized in that a light shielding section is provided on a part of a photosensitive section. (2) In a three-chip color imaging device that detects the amount of light of different colors using three solid-state imaging devices to capture a color image, the sensitivity of each of the three solid-state imaging devices to each color is approximately equal. According to the present invention, a light shielding portion is provided on the photosensitive portion of at least one solid-state image sensing device at a constant ratio to the area of one pixel, depending on the sensitivity of the device to the color to be detected. Imaging device. (3) The color imaging device according to claim 1 or 2, wherein the solid-state imaging device includes the light shielding portion between adjacent pixels. (4) The solid-state image sensor has a signal charge storage diode, a signal charge readout section, and a signal charge transfer section formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage diode formed at the top. It is a photoconductive film-stacked solid-state imaging device comprising a solid-state imaging device chip, a photoconductive film stacked on the chip, and a transparent electrode formed on the photoconductive film. Claim 1 or 2
The color imaging device described.