JP2001210812A - Solid-state image pickup device and solid-state image pickup system provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup device which will not cause nonuniformity in light-receiving sensitivity. SOLUTION: In a solid-state image pickup device, which has condensing lenses for condensing incident light and a photoelectric conversion element for converting the light condensed by the lenses into an electrical signal and is provided with a plurality of pixels, each of the pixel being constituted into a structure such that the optical axes of the condensed lights coincide with the center of gravity of the light-receiving part of the photoelectric conversion element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device and a solid-state imaging system having a plurality of pixels for converting collected light into an electric signal.

[0002]

2. Description of the Related Art Conventionally, a solid-state imaging device includes a photoelectric conversion element such as a photodiode for converting received light into an electric signal and a photoelectric conversion element as described in Japanese Patent Application Laid-Open No. 05-040201. And a microlens for condensing light to make the light incident.

Here, the microlenses are provided to prevent a decrease in light reception sensitivity of the photodiode due to a decrease in light reception in the photodiode due to recent miniaturization of pixels. It is.

FIG. 7A is a plan view of a conventional solid-state imaging device. FIG. 7B is a cross-sectional view of each pixel of the solid-state imaging device shown in FIG. FIGS. 7A and 7B
Here, 1 is a pixel having a photodiode 5 on a silicon substrate (Si substrate) 7, 2 is a light-shielding layer that blocks a region other than the photodiode 5 in the pixel 1, and 3 is a light-shielding layer for the photodiode 5 of the pixel 1. Open area for incidence 4
Is a micro lens for condensing light on the photodiode 5,
Reference numeral 6 denotes a color filter layer for, for example, blue, red, and green.

As shown in FIG. 7A, a plurality of pixels 1 are arranged in a conventional solid-state imaging device. Also, as shown in FIG. 7B, the aperture regions 3 and the micro lenses 4 are formed at the same pitch in accordance with the position of the light receiving portion of the photodiode 5 of each pixel 1, and the light is condensed by the micro lenses 4. The optical axis of the emitted light coincides with the center of gravity of the aperture region 3. As a result, the light passing through the microlens 4 is focused on almost the center of the light receiving portion of the photodiode 5.

As described above, since the position of the microlens 4 is conventionally determined in accordance with the position of the photodiode 5 of each pixel 1, even if the opening area of the opening region 3 is reduced by the downsizing of the pixel 1, In addition, the light is condensed by the micro lens 4 to prevent the light receiving sensitivity from lowering.

[0007]

However, in the prior art, a part of the light condensed by the microlens does not reach the photodiode depending on the arrangement position of the pixels of the solid-state imaging device. In some cases, the light receiving sensitivity of the solid-state imaging device varies.

FIGS. 8A and 8B are explanatory diagrams of the principle in which the above problem occurs. 8A and 8B, reference numeral 10 denotes a subject imaged by the solid-state imaging device;
Reference numeral 11 denotes an imaging lens that forms light from the subject 10 on a solid-state imaging device. In FIGS. 8A and 8B, the same parts as those shown in FIGS. 7A and 7B are denoted by the same reference numerals.

In FIGS. 8 (a) and 8 (b),
(Ii) is a pixel arranged near the center of the solid-state imaging device. (I) and (iii) are pixels arranged around the solid-state imaging device.

As shown in FIG. 8A, light from a subject 10 is imaged on a solid-state imaging device via an imaging lens 11. Here, for example, light from the subject 10 sent to the pixels shown in FIGS. 8B and 8B enters the photodiode 5 via the microlens 4.

On the other hand, FIGS. 8 (b) (i) and 8 (b) (i)
The light from the subject 10 sent to the pixel shown in i) passes through the microlens 4 and is partially blocked by the light-blocking region of the light-blocking layer 2 and does not enter the photodiode 5. For this reason, it has not been possible to eliminate variations in light receiving sensitivity between a pixel close to the photographing lens and a pixel far from the photographing lens.

FIG. 9 is a diagram showing output signals of the solid-state imaging device shown in FIG. As shown in FIG. 9, the difference between the maximum value and the minimum value of the output signal of the conventional solid-state imaging device is 10% or more.

That is, when the average value of the output signal of the conventional solid-state imaging device is 100 mV, the maximum value of the output signal is 105 mV or more and the minimum value is 95 mV or less. In general, the output signal of the solid-state imaging device is considered to have a level that does not affect the reproduced image if the difference between the maximum value and the minimum value with respect to the average value is smaller than 10%.

Accordingly, an object of the present invention is to provide a solid-state imaging device having a small variation in light receiving sensitivity so as not to affect a reproduced image.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a condensing lens for condensing incoming and outgoing light, and a photoelectric conversion for converting light condensed by the condensing lens into an electric signal. In a solid-state imaging device including a plurality of pixels each including an element, each of the plurality of pixels is configured such that an optical axis of the collected light coincides with a center of gravity of a light receiving unit of the photoelectric conversion element. I have.

The present invention also includes the solid-state imaging device, an imaging lens for transmitting light from a subject to the solid-state imaging device, and storage means for storing an output signal of the solid-state imaging device.

[0017]

(Embodiment 1) FIG. 1A is a plan view of a pixel group of a solid-state imaging device according to Embodiment 1 of the present invention. FIG. 1B shows one of the pixel groups shown in FIG.
It is sectional drawing of the pixel of the 3rd column and the 5th column. FIG.
1A and 1B, reference numeral 1 denotes a silicon substrate (Si
A pixel having a photodiode 5 which is a photoelectric conversion element on a substrate 7, a light-shielding layer 2 having a light-shielding region that shields a region other than the photodiode 5 in the pixel 1, and a light-shielding layer 3 provided in the light-shielding layer 2. An opening area for allowing light to enter the photodiode 5, a microlens 4 for condensing light on the photodiode 5, and a color filter layer 6 for blue, red, and green, for example.

FIG. 1A shows, for convenience of explanation, 5
Although an example of × 5 pixels is shown, usually, for example, Equation 1
Ten thousand to several million pixels are arranged two-dimensionally.

As shown in FIGS. 1A and 1B, in the present embodiment, the center of gravity of the light receiving portion of the photodiode 5 is closer to the pixel 1 located closer to the periphery than the center of the pixel group.
It is configured to be located on the peripheral side of the center of gravity of the micro lens 4 and the opening region 3 so that the optical axis of the light condensed by the micro lens 4 and the center of gravity of the light receiving part of the photodiode 5 coincide. ing.

That is, as shown in FIG. 1B, in the pixels 1 in the first column, the center of gravity of the microlens 4 and the center of the aperture region 3 are located rightward in the drawing with respect to the center of the light receiving portion of the photodiode 5. The pixel 1 in the third column is configured so that the center of gravity of the light receiving portion of the photodiode 5 and the center of gravity of the microlens 4 and the opening region 3 coincide with each other. The configuration is such that the center of gravity of the microlens 4 and the opening area 3 is located to the left of the drawing with respect to the center of gravity of the light receiving unit. Here, the center of gravity of the opening region 3 refers to a position that becomes the center of gravity of an arbitrary substance when the substance is disposed in the opening region 3.

As described above, in the present embodiment, the center of gravity of the light receiving portion of the photodiode 5 is set closer to the periphery of the pixel 1 than the center of the microlens 4 and the center of the opening region 3 for the pixel 1 arranged closer to the periphery than the center of the pixel group. 1B, light incident on the photodiode 5 via the microlens 4 is not blocked by the light-blocking region of the light-blocking layer 2 as shown in FIG. 1B. .

FIG. 2 is a diagram showing output signals of the solid-state imaging device shown in FIG. As shown in FIG. 2, in the solid-state imaging device according to the present embodiment, the difference between the maximum value and the minimum value of the output signal is smaller than 10% with respect to the average value of the output signal. This is because variation in the light receiving sensitivity can be reduced by preventing the light condensed on the photodiode 5 from being blocked by the light shielding layer 2.

Embodiment 2 FIG. 3A is a plan view of a pixel group of a solid-state imaging device according to Embodiment 2 of the present invention. FIG.
FIG. 3B shows the first column and the third column in the pixel group shown in FIG.
It is sectional drawing of the pixel of a 5th column. Note that FIG.
(A), FIG. 3 (b), FIG. 1 (a), FIG. 1 (b)
Are denoted by the same reference numerals.

As shown in FIGS. 3A and 3B, in the present embodiment, the center of gravity of the light receiving portion of the photodiode 5 is closer to the pixel 1 located closer to the periphery than the center of the pixel group.
The center of gravity of the microlens 4 is located on the peripheral side with respect to the center of gravity of the microlens 4.
, The optical axis of the light condensed by the microlens 4, the center of gravity of the light receiving portion of the photodiode 5, and the center of gravity of the aperture region 3 respectively match. Like that.

In the configuration of the pixel 1 as shown in FIGS. 3A and 3B, for example, when the thickness of the color filter layer 6 is large, that is, the distance between the light shielding layer 2 and the microlens 4 is large. It is effective in the case.

As described above, the center of gravity of the aperture region 3 and the center of gravity of the light receiving portion of the photodiode 5 are shifted from the center of gravity of the microlens 4 in each of the pixels 1 arranged closer to the periphery than the center of the pixel group. As a result, FIG. 1 (a), FIG.
The variation in the light receiving sensitivity can be further reduced as compared with the solid-state imaging device shown in FIG.

(Embodiment 3) FIG. 4 is a sectional view of a pixel of a solid-state imaging device according to Embodiment 3 of the present invention.
3 is a diagram corresponding to the pixel in the first column and the pixel in the third column.
In FIG. 4, reference numeral 8 denotes a light-shielding black filter layer made of an organic material or the like, and reference numeral 9 denotes a flattening layer for forming the color filter layer 6 flat.

The black filter layer 8 is formed in a process of manufacturing the color filter layer 6 so that light incident on a portion having no microlens 4 does not cause adverse effects such as stray light and crosstalk due to light. .
Further, in FIG. 4, the same parts as those shown in FIGS. 1A and 1B are denoted by the same reference numerals.

In the present embodiment, as shown in FIG. 4, the center of gravity of the light receiving section of the photodiode 5 and the center of gravity of the opening area of the black filter layer 8 are closer to the pixel 1 located closer to the periphery than the center of the pixel group. , The microlens 4 and the opening area 3 are located on the peripheral side of the center of gravity of the opening area,
The optical axis of the light condensed by the microlens 4, the center of gravity of the light-receiving portion of the photodiode 5, and the center of gravity of the opening region of the black filter layer 8 match.

When the light-shielding layers 2 are displaced as shown in FIG. 3B, variations in the light receiving sensitivity can be further reduced.

(Embodiment 4) FIG. 5 is a plan view of a pixel group of a solid-state imaging device according to Embodiment 4 of the present invention. As shown in FIG. 5, in the solid-state imaging device according to the present embodiment, rectangular pixels 1 are arranged in a curved shape. In this manner, by changing the aperture ratio of the aperture region where the photoelectric conversion is performed for each arrangement position, the aperture ratio can be applied to a solid-state imaging system such as an autofocus camera as an autofocus sensor. The same parts as those of the solid-state imaging device shown in FIG. 1A are denoted by the same reference numerals.

In this embodiment, as shown in FIG. 5, the closer the pixel 1 is located to the periphery than the center of the pixel group, the more the center of gravity of the light receiving portion of the photodiode 5 is shifted to the microlens 4 and the aperture region 3. Is arranged on the peripheral side with respect to the center of gravity of the opening region, so that the optical axis of the light condensed by the microlens 4 and the center of gravity of the light receiving portion of the photodiode 5 coincide with each other.

Therefore, the solid-state imaging device shown in FIG. 5 can reduce the variation in the light receiving sensitivity similarly to the solid-state imaging device shown in FIG. The light-shielding layer 2 is formed as shown in FIG.
By displacing them as shown in (b), variations in light receiving sensitivity can be further reduced. Further, as shown in FIG. 4, a black filter layer may be provided.

Embodiment 5 FIG. 6 is a plan view of a pixel group of a solid-state imaging device according to Embodiment 5 of the present invention. The pixel group illustrated in FIG. 6 illustrates an arrangement example in a case where an imaging lens (not illustrated) has a so-called barrel aberration. That is, when light enters the imaging lens having barrel-shaped aberration, the light is distorted and condensed on the microlens 4. Therefore, the solid-state imaging device according to the present embodiment corrects the aberration generated in the optical system as described above on the solid-state imaging device side.

In FIG. 6, the same parts as those of the solid-state imaging device shown in FIG. 1A are denoted by the same reference numerals. Also in this embodiment, similarly to FIG. 1, the optical axis of the light condensed by the microlens 4 and the center of gravity of the light receiving portion of the photodiode 5 match.

By the way, if the light shielding layer 2 is displaced as shown in FIG. 3B, the variation in the light receiving sensitivity can be further reduced. Also, as shown in FIG.
A black filter layer may be provided.

In the first to fifth embodiments, the solid-state image pickup device having a microlens has been described as an example.
SIS, CMOS sensor, SIT sensor, CMD, AM
Any type of sensor, such as I, can be applied. Also, the case where the sensors are arranged in a plurality of rows × a plurality of columns has been described as an example, but the sensors may be arranged in a row × a plurality of columns, for example.

Further, the solid-state imaging device according to any one of the first to fifth embodiments has an imaging lens for causing light from a subject to enter the solid-state imaging device, and a storage such as a memory for storing an output signal from the solid-state imaging device. The present invention can also be applied to a solid-state imaging system such as a video camera or a still video camera having the means.

[0039]

As described above, according to the solid-state imaging device of the present invention, the optical axis of the light condensed by the condensing lens and the light receiving portion of the photoelectric conversion element for converting the condensed light into an electric signal. Is configured to coincide with the center of gravity of the photodetector, so that the variation in the light receiving sensitivity can be eliminated.

Further, a solid-state imaging system such as a video camera and a still video camera provided with the above-mentioned solid-state imaging device can improve the image quality.

[Brief description of the drawings]

FIG. 1 is a plan view and a cross-sectional view of a pixel group of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating output signals of the solid-state imaging device of FIG. 1;

FIG. 3 is a plan view and a cross-sectional view of a pixel group of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a pixel group of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 5 is a plan view of a pixel group of a solid-state imaging device according to a fourth embodiment of the present invention.

FIG. 6 is a plan view of a pixel group of a solid-state imaging device according to a fifth embodiment of the present invention.

FIG. 7 is a plan view and a sectional view of a pixel group of a conventional solid-state imaging device.

FIG. 8 is an explanatory diagram of a problem of a conventional solid-state imaging device.

FIG. 9 is a diagram illustrating output signals of the solid-state imaging device illustrated in FIG. 8;

[Explanation of symbols]

 Reference Signs List 1 pixel 2 light shielding layer 3 opening area 4 micro lens 5 photodiode 6 color filter layer 7 Si substrate 8 black filter layer 9 flattening layer 10 subject 11 imaging lens

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Claims (8)

[Claims] 1. A solid-state imaging device comprising a plurality of pixels each having a condensing lens for condensing incident light shielding and a photoelectric conversion element for converting light condensed by the condensing lens into an electric signal. Wherein the optical axis of the condensed light and the center of gravity of the light receiving section of the photoelectric conversion element coincide with each other. 2. The method according to claim 1, wherein the center of gravity of the light receiving unit of the photoelectric conversion element is located closer to the periphery of the pixel group having a plurality of pixels than the center of the pixel group. The solid-state imaging device according to claim 1. 3. The pixel according to claim 1, further comprising a light-shielding layer including an opening area for illuminating the condensed light on the photoelectric conversion element and a light-shielding area for shielding an area other than the photoelectric conversion element. 3. The solid-state imaging device according to claim 1, wherein each of the light-emitting elements is configured such that an optical axis of the condensed light coincides with a center of gravity of an opening region of the light-shielding portion. 4. 4. The solid-state imaging device according to claim 1, wherein a color filter layer is provided in an optical path of the collected light. 5. A filter layer comprising an opening area for allowing the condensed light to enter the photoelectric conversion element and a light shielding area for shielding an area of the pixel where the microlenses are not provided. 5. The method according to claim 1, wherein each of the plurality of pixels is configured such that an optical axis of the collected light coincides with a center of gravity of an opening region of the filter layer. 6. 2. The solid-state imaging device according to claim 1. 6. The solid-state imaging device according to claim 2, wherein the pixel group includes the plurality of pixels arranged one-dimensionally or two-dimensionally. 7. The solid-state imaging device according to claim 6, wherein the pixel group includes the plurality of pixels arranged in a curved shape. 8. A solid-state imaging device according to claim 1, an imaging lens for transmitting light from a subject to the solid-state imaging device, and a storage for storing an output signal of the solid-state imaging device. And a solid-state imaging system.