JP3571982B2 - Solid-state imaging device and solid-state imaging system having the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device and a solid-state imaging system including a plurality of pixels that convert collected light into an electric signal.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 05-040201, a solid-state imaging device includes a photoelectric conversion element such as a photodiode for converting received light into an electric signal, and a light-emitting element for making light incident on the photoelectric conversion element. A microlens for focusing.
[0003]
Here, the microlens is provided to prevent a decrease in light reception sensitivity of the photodiode due to a decrease in light reception by the photodiode accompanying the recent miniaturization of pixels.
[0004]
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. 7A and 7B, reference numeral 1 denotes a pixel having a photodiode 5 on a silicon substrate (Si substrate) 7, reference numeral 2 denotes a light-shielding layer for shielding a region other than the photodiode 5 in the pixel 1, Reference numeral 3 denotes an opening region for allowing light to enter the photodiode 5 of the pixel 1, 4 denotes a microlens for condensing light on the photodiode 5, and 6 denotes a color filter layer of, for example, blue, red, or green.
[0005]
As shown in FIG. 7A, a plurality of pixels 1 are arranged in a conventional solid-state imaging device. Further, 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 applied light coincides with the center of gravity of the opening region 3. As a result, the light passing through the microlens 4 is focused on almost the center of the light receiving section of the photodiode 5.
[0006]
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 due to the miniaturization of the pixel 1, the microlens 4 By condensing the light by 4, the light receiving sensitivity is prevented from lowering.
[0007]
[Problems to be solved by the invention]
However, in the conventional technology, some 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, and therefore, the light receiving sensitivity of the solid-state imaging device varies. May occur.
[0008]
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, and reference numeral 11 denotes an imaging lens that forms light from the subject 10 on the solid-state imaging device. 8 (a) and 8 (b), the same parts as those shown in FIGS. 7 (a) and 7 (b) are denoted by the same reference numerals.
[0009]
8A and 8B, (ii) is a pixel disposed near the center of the solid-state imaging device. (I) and (iii) are pixels arranged around the solid-state imaging device.
[0010]
As shown in FIG. 8A, light from the subject 10 is imaged on the solid-state imaging device via the imaging lens 11. Here, for example, the light from the subject 10 sent to the pixels shown in FIGS. 8B and 8B enters the photodiode 5 through the microlens 4.
[0011]
On the other hand, the light from the subject 10 sent to the pixels shown in FIGS. 8B, 8I and 8B And is not incident on the photodiode 5. For this reason, it has not been possible to eliminate the variation in the light receiving sensitivity between a pixel close to the photographing lens and a pixel far from the photographing lens.
[0012]
FIG. 9 is a diagram illustrating output signals of the solid-state imaging device illustrated in FIG. As shown in FIG. 9, the difference between the maximum value and the minimum value of the output signal is 10% or more of the average value of the output signal of the conventional solid-state imaging device.
[0013]
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%.
[0014]
Therefore, an object of the present invention is to provide a solid-state imaging device with less variation in light receiving sensitivity so as not to affect a reproduced image.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a condenser lens for condensing incident light, a photoelectric conversion element for converting light condensed by the condenser lens into an electric signal, and a photoelectric conversion element In a solid-state imaging device including a plurality of pixels each having an opening area for receiving the condensed light and a light-shielding layer including a light-shielding area that shields an area other than the photoelectric conversion element, a pixel group including the plurality of pixels is provided. In the pixels arranged in the peripheral part from the center, the center of gravity of the opening area is located on the peripheral side with respect to the center of gravity of the condenser lens, and each of the plurality of pixels is the collected light. Is configured to pass through the center of gravity of the light receiving portion surface of the photoelectric conversion element, and the optical axis of the collected light is configured to pass through the center of gravity of the opening region of the light shielding layer.
[0016]
Further, in the solid-state imaging device of the present invention, a plurality of condenser lenses for condensing incident light, a pixel group including a plurality of photoelectric conversion elements for converting light incident from the condenser lens into an electric signal, A plurality of aperture regions for guiding light from an optical lens to the photoelectric conversion element, and in a pixel located at least in a peripheral portion of the pixel group, the condenser lens and the aperture region correspond to the photoelectric conversion element. Is shifted toward the center of the pixel group, and the center of gravity of the aperture region is shifted in the peripheral direction with respect to the center of gravity of the condenser lens, and the optical axis of light incident from the condenser lens is The pixel is configured so that it passes through the center of gravity of the light receiving portion surface of the photoelectric conversion element and the optical axis of the light incident from the condenser lens passes through the center of gravity of the opening region.
Further, a camera according to the present invention includes any one of the solid-state imaging devices described above, an imaging lens that transmits light from a subject to the solid-state imaging device, and a storage unit that stores an output signal of the solid-state imaging device.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
FIG. 1A is a plan view of a pixel group of the solid-state imaging device according to the first embodiment of the present invention. FIG. 1B is a cross-sectional view of the pixels in the first, third, and fifth columns of the pixel group shown in FIG. 1A and 1B, reference numeral 1 denotes a pixel having a photodiode 5 as a photoelectric conversion element on a silicon substrate (Si substrate) 7, and reference numeral 2 denotes a light-shielding region of the pixel 1 other than the photodiode 5. A light-shielding layer having a light-shielding region, 3 is an opening region provided in the light-shielding layer 2 for making light incident on the photodiode 5 of the pixel 1, 4 is a microlens for condensing light on the photodiode 5, and 6 is, for example, blue・ Color filter layer for red, green, etc.
[0018]
Although FIG. 1A shows an example in which 5 × 5 pixels are provided for convenience of description, normally, for example, several hundred thousand to several million pixels are arranged two-dimensionally.
[0019]
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 microlens 4 for the pixel 1 disposed closer to the periphery than the center of the pixel group. In addition, 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.
[0020]
That is, as shown in FIG. 1B, the pixels 1 in the first column are configured such that 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 gravity of the light receiving portion of the photodiode 5. The pixel 1 in the third column is configured such that the center of gravity of the light receiving portion of the photodiode 5 coincides with the center of gravity of the microlens 4 and the opening region 3. 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. 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 arranged in the opening region 3.
[0021]
As described above, in the present embodiment, the center of gravity of the light receiving portion of the photodiode 5 is positioned closer to the peripheral side than the center of gravity of the microlens 4 and the opening region 3 in the pixel 1 disposed closer to the periphery of the center of the pixel group. With this configuration, as shown in FIG. 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.
[0022]
FIG. 2 is a diagram illustrating output signals of the solid-state imaging device illustrated 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.
[0023]
(Embodiment 2)
FIG. 3A is a plan view of a pixel group of the solid-state imaging device according to Embodiment 2 of the present invention. FIG. 3B is a cross-sectional view of the pixels in the first, third, and fifth columns in the pixel group shown in FIG. 3 (a) and 3 (b), the same reference numerals are given to the same parts as those shown in FIGS. 1 (a) and 1 (b).
[0024]
As shown in FIGS. 3A and 3B, in the present embodiment, 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 micro lens 4. And the center of gravity of the aperture region 3 is also located on the periphery side of the center of gravity of the microlens 4, and the light is collected by the microlens 4. The optical axis of the light, the center of gravity of the light receiving portion of the photodiode 5, and the center of gravity of the aperture region 3 are respectively matched.
[0025]
The configuration of the pixel 1 as shown in FIGS. 3A and 3B is effective, for example, when the thickness of the color filter layer 6 is large, that is, when the distance between the light shielding layer 2 and the microlens 4 is large. It is.
[0026]
As described above, the closer the pixel 1 is located to the periphery than the center of the pixel group is, the more the center of gravity of the aperture region 3 and the center of gravity of the light receiving section of the photodiode 5 are shifted from the center of gravity of the microlens 4. The variation in the light receiving sensitivity can be further reduced as compared with the solid-state imaging device shown in FIGS. 1A and 1B.
[0027]
(Embodiment 3)
FIG. 4 is a cross-sectional view of a pixel of the solid-state imaging device according to Embodiment 3 of the present invention, and is a diagram corresponding to the pixel in the first column and the pixel in the third column in FIG. 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.
[0028]
The black filter layer 8 is formed in a process of manufacturing the color filter layer 6 so that light incident on a portion without the 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.
[0029]
In this embodiment, as shown in FIG. 4, 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 and the center of gravity of the opening area of the black filter layer 8 are the micro lens. 4 and the opening region 3 are located on the peripheral side of the center of gravity of the opening region, and 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 black filter layer The center of gravity of the opening area 8 is matched with the center of gravity.
[0030]
When the light-shielding layers 2 are displaced as shown in FIG. 3B, variations in the light receiving sensitivity can be further reduced.
[0031]
(Embodiment 4)
FIG. 5 is a plan view of a pixel group of the 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 photoelectric conversion is performed for each arrangement position, the present invention can be applied to a solid-state imaging system such as an autofocus camera as an autofocus sensor. The same parts as those in the solid-state imaging device shown in FIG. 1A are denoted by the same reference numerals.
[0032]
Further, in the present embodiment, as shown in FIG. 5, the center of gravity of the light receiving portion of the photodiode 5 is closer to the microlens 4 and the opening area of the opening area 3 for the pixel 1 arranged closer to the periphery than the center of the pixel group. And the optical axis of the light condensed by the microlens 4 coincides with the center of gravity of the light-receiving portion of the photodiode 5.
[0033]
Therefore, the solid-state imaging device illustrated in FIG. 5 can reduce variation in light receiving sensitivity, similarly to the solid-state imaging device illustrated in FIG. When the light-shielding layers 2 are displaced as shown in FIG. 3B, variations in the light receiving sensitivity can be further reduced. Further, as shown in FIG. 4, a black filter layer may be provided.
[0034]
(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 shown in FIG. 6 shows an arrangement example in the case where an imaging lens (not shown) has a so-called barrel aberration. That is, when light enters the imaging lens having barrel 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.
[0035]
Note that, in FIG. 6, the same parts as those of the solid-state imaging device shown in FIG. 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.
[0036]
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. Further, as shown in FIG. 4, a black filter layer may be provided.
[0037]
As described above, in the first to fifth embodiments, the solid-state imaging device having a microlens has been described as an example, but the photoelectric conversion device may be any other than a photodiode, such as a CCD, a BASIS, a CMOS sensor, a SIT sensor, a CMD, and an AMI. A type of sensor can also be applied. Further, 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.
[0038]
The solid-state imaging device according to any one of Embodiments 1 to 5 includes an imaging lens that causes light from a subject to enter the solid-state imaging device, and a storage unit such as a memory that stores 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 provided with the camera.
[0039]
【The invention's effect】
As described above, in the solid-state imaging device of the present invention, the optical axis of the light condensed by the condensing lens coincides with the center of gravity of the light receiving unit of the photoelectric conversion element that converts the condensed light into an electric signal. Therefore, variations in light receiving sensitivity can be eliminated.
[0040]
In addition, a solid-state imaging system such as a video camera or a still video camera provided with the solid-state imaging device can improve image quality.
[Brief description of the drawings]
FIG. 1 is a plan view and a 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 microlens 5 photodiode 6 color filter layer 7 Si substrate 8 black filter layer 9 flattening layer 10 subject 11 imaging lens

Claims (8)

A condensing lens for condensing incident light, a photoelectric conversion element for converting the light condensed by the condensing lens into an electric signal, an opening area for making the condensed light incident on the photoelectric conversion element, and In a solid-state imaging device including a plurality of pixels having a light-shielding layer consisting of a light-shielding region that shields an area other than the photoelectric conversion element,
Pixels arranged at a peripheral portion from the center of the pixel group composed of the plurality of pixels, the center of gravity of the opening region is located on the peripheral side with respect to the center of gravity of the condenser lens,
Each of the plurality of pixels is configured such that an optical axis of the collected light passes through a center of gravity of a light receiving portion surface of the photoelectric conversion element, and an optical axis of the collected light is the light shielding layer. A solid-state imaging device configured to pass through the center of gravity of the opening region. As the pixels are provided closer to the periphery than the center of the pixel group of the solid-state imaging device, the center of gravity of the surface of the light receiving unit of the photoelectric conversion element is more advanced with respect to the condensing lens in a direction away from the center of the pixel group. The solid-state imaging device according to claim 1, wherein: The solid-state imaging device according to claim 1, wherein a color filter layer is provided in an optical path of the collected light. An aperture region for allowing the collected light to enter the photoelectric conversion element, and a filter layer including a light-shielding region that shields a region of the pixel where the light-collecting lens is not provided,
4. The device according to claim 1, wherein each of the plurality of pixels is configured such that an optical axis of the collected light passes through a center of gravity of an opening region of the filter layer. 5. The solid-state imaging device according to any one of the preceding claims. The solid-state imaging device according to claim 1, wherein the pixel group includes the plurality of pixels arranged one-dimensionally or two-dimensionally. The solid-state imaging device according to claim 5, wherein the pixel group includes the plurality of pixels arranged in a curved shape. A plurality of condenser lenses for condensing incident light, a pixel group including a plurality of photoelectric conversion elements for converting light incident from the condenser lens to an electric signal, and light from the condenser lens to the photoelectric conversion elements A plurality of opening areas for guiding,
At least the pixels located at the periphery of the pixel group have the condensing lens and the aperture region deviated in the center direction of the pixel group with respect to the corresponding photoelectric conversion element, and the center of gravity of the aperture region Are shifted in the peripheral direction with respect to the center of gravity of the condenser lens, and the optical axis of light incident from the condenser lens passes through the center of gravity of the light receiving portion surface of the photoelectric conversion element, and is incident from the condenser lens. A pixel configured such that an optical axis of the light passes through a center of gravity of the opening region. A solid-state imaging device according to any one of claims 1 to 7 ,
An imaging lens that sends light from a subject to the solid-state imaging device side;
Camera comprising: a storage means for storing an output signal of the solid-state imaging device.

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