JP2002170944A - Solid state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sensitivity of a solid state imaging device and reduce the light shading. SOLUTION: The solid state imaging device comprises color filters and imaging lenses 16 corresponding to pixel areas thereof. In each pixel area, the center of an opening of a shape layer 2 and the center of a microlens 4 are offset at every pixel from the center of a photoelectric conversion region of each pixel. The offset value thereof is seat so as to be greater for a pixel nearer the peripheral side of a microchip. The shape layer 2 is laid so as not to obstruct the condensation of the microlens 4.

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 having a microlens, and more particularly to a compound-eye solid-state imaging device that performs color imaging using a plurality of imaging lenses and a plurality of imaging areas.

[0002]

2. Description of the Related Art Conventionally, a solid-state imaging device having a microlens has a planar layout as shown in FIG. In FIG. 11, reference numeral 1 denotes a pixel including a photodiode for performing photoelectric conversion, 2 denotes a light-shielding layer for shielding a region other than the photodiode, and 3 denotes an opening region (opening) formed in the light-shielding layer 2 for receiving light. Reference numeral 4 denotes a microlens for collecting light for each pixel 1, and reference numeral 5 denotes a photoelectric conversion region (photodiode region) where photoelectric conversion is performed.

As shown in FIG. 11, in a conventional solid-state imaging device, pixels 1 are uniformly arranged in a two-dimensional direction on a substrate, and the center of an opening region 3 of a photoelectric conversion region 5 of the pixel 1 is the same. The micro lenses 4 are formed at the same pitch, and the micro lenses 4 formed thereon are also formed at the same pitch.

Here, the layout is made such that the center of light condensing by the microlens 4 and the center of the opening of the pixel coincide with each other in the vertical direction. In addition, the curvature of the microlens 4 is designed so that the light is focused on the photoelectric conversion region 5 in order to maximize the light collection efficiency. As described above, by optimally designing the micro lens 4, even if the pixel size becomes small, the micro lens 4 is designed so as not to cause an extreme decrease in sensitivity.

[0005]

However, it has been found that the mere miniaturization of pixels in the plane direction causes a decrease in sensitivity of the solid-state imaging device and non-uniform sensitivity (light shading). The cause will be described with reference to FIGS. That is, since the opening area of the pixel cannot be sufficiently obtained due to the reduction in the size of the pixel, a reduction in sensitivity occurs because a part of the light beam condensed by the microlens is blocked by the light shielding layer. Then, the ratio of being blocked by the light-shielding layer increases as the incident angle of the principal ray of the imaging lens increases and the photoelectric conversion region in the peripheral pixel increases.
Light shading is also a problem.

[0006] Further, since the incident angle becomes steeper in the peripheral portion, light having an angle condensed in a region other than the photoelectric conversion region also exists, which also causes shading due to a decrease in sensitivity. .

The present invention has been made based on the above circumstances, and a first object of the present invention is to realize a solid-state imaging device free from light shading due to a decrease in sensitivity.

A second object of the present invention is to shorten the design period of a solid-state imaging device and reduce the design cost.

[0009]

In order to achieve the above object, according to the present invention, there are provided a plurality of imaging areas in which photoelectric conversion regions are two-dimensionally arranged, and a plurality of light-receiving areas provided corresponding to the respective photoelectric conversion regions. A microlens for condensing light, and an opening for allowing light to enter the photoelectric conversion unit provided corresponding to each photoelectric conversion region, and the microlens in a peripheral portion of the imaging area. And a position of the opening is shifted from a corresponding photoelectric conversion area toward a center of the imaging area.

A plurality of imaging areas each having a two-dimensional array of photoelectric conversion regions, a microlens provided for each photoelectric conversion region for condensing light, and a peripheral portion of the imaging area. Wherein the position of the microlens is shifted from the corresponding photoelectric conversion region toward the center of the imaging area, and at least 2
A solid-state imaging device is characterized in that a shift amount between the microlens and the corresponding photoelectric conversion region is different in one imaging area.

[0011] Further, light provided corresponding to each of the photoelectric conversion regions formed on the layer planarized in the CMP process and the imaging area in which the photoelectric conversion regions are arranged two-dimensionally is collected. A solid-state imaging device, wherein a position of the microlens is shifted from a corresponding photoelectric conversion region in a center direction of the imaging area in a peripheral portion of the imaging area. I will provide a.

An imaging area in which photoelectric conversion regions are two-dimensionally arranged, a micro lens provided for each photoelectric conversion region for condensing light, and a photoelectric conversion region corresponding to each photoelectric conversion region. And an opening for allowing light to be incident on the photoelectric conversion unit provided. In the periphery of the imaging area, the position of the microlens and the opening is smaller than that of the corresponding photoelectric conversion region. In addition to the arrangement shifted in the center direction of the area, the pitch of the microlenses in the first area including the plurality of microlenses is different from the pitch of the microlenses in the second area including the plurality of microlenses. A featured solid-state imaging device is provided.

[0013] Also, there is provided an imaging system comprising the solid-state imaging device described above, a lens for forming an image of light on the solid-state imaging device, and a signal processing unit for processing a signal from the solid-state imaging device. I do.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic diagram of a plane layout according to an embodiment which best illustrates the features of the present invention. FIG. 2 specifically shows a layout in which one of a plurality of pixel areas formed in the solid-state imaging device is enlarged. Actually, the pixels are arranged in an area of several hundred thousand to several million, but here, for simplicity, a 5 × 5 pixel area will be described. Also,
FIG. 3 shows a plan view and a cross-sectional view of one pixel of the solid-state imaging device including a microlens.

1 to 3, reference numeral 1 denotes a pixel, 2
Denotes a light-shielding layer (light-shielding region) for shielding light from a region other than the photoelectric conversion region (photodiode region) 5 of each pixel; 3, an opening provided in the light-shielding layer 2 (opening region); Is a microlens for condensing light, 6 is a silicon (Si) substrate, 7 is a planarized SiN protective film,
Reference numeral 8 denotes a microlens flattening film using an organic material, 9a denotes an R pixel area, 9b denotes a G pixel area, 9c denotes a G pixel area, 9d denotes a B pixel area, and 15 denotes a wiring layer.

This embodiment has a configuration corresponding to a four-eye type compound-eye solid-state imaging device, and has a G region (9 region).
b, 9c) are for improving the resolution. Therefore, when high resolution is not required, a so-called three-eye type compound-eye solid-state imaging device having one G region may be used.

FIG. 4 shows an imaging device for compound eye imaging including an optical system of an imaging lens. Here, a color filter 16 and an imaging lens 17 are provided corresponding to each pixel area of the solid-state imaging device.

In each pixel area, the center of the opening 3 of the light shielding layer 2 and the center of the microlens 4 are shifted for each pixel with respect to the center of the photoelectric conversion region of each pixel. , The larger the pixel is on the outer peripheral side of the microchip. This shift amount is determined by the imaging lens 17 to be used, and the layout on the substrate is set so that the center of the optical axis between the imaging lens 17 and the microlens 4 substantially matches the center of the photoelectric conversion region.
Further, the light shielding layer 2 is laid out so as not to block the light condensing of the microlenses 4.

FIGS. 5 and 6 are disclosed to clarify the operation and effect of this embodiment. That is, as shown in FIG. 5, the microlenses 4 are arranged so that the main optical axis of the imaging lens 17 coincides with the center of the photoelectric conversion region, and the light shielding layer 2 blocks the light flux of the microlenses 4. By arranging them so as not to have, as shown in FIG. 6, good characteristics with little light shading could be obtained.

The four pixel areas may have the same layout in order to reduce the design load. However, the layout taking into account the refractive index of the wavelength of each color, that is, a layout in which the shift amount is changed for each pixel area is adopted. It is more preferable in practice.

In this embodiment, the surface protective film 7 is formed by chemical mechanical polishing (CMP).
ishing). Therefore, conventionally,
It is possible to reduce the thickness of the flattening film 10 which was required to be about μm to 0.2 μm or less. Therefore, conventionally, 4-5 μm
m required photoelectric conversion area (photodiode area)
The distance from to the microlens 4 can be made 2 to 3 μm.

FIG. 7 shows an equivalent circuit diagram for one pixel area of the solid-state imaging device according to this embodiment. FIG.
, 11 is a horizontal shift register, 12 is a vertical shift register, 13 is a readout circuit, and 14 is an output amplifier.

In general, the CMP process is often a standard process of the CMOS process.
When the present invention is applied to an OS sensor, it is not necessary to significantly change the process standard, so that the effect of shortening the development period and the effect of reducing the development cost are great.

In this embodiment, a high-sensitivity output signal with less shading can be obtained, and in particular, a thin, compound-eye solid-state imaging device can be easily realized. In addition, the present invention
Not only CMOS sensors but also solid-state imaging devices having microlenses, such as CCD, BASIS, SIT, C
It can be applied to MD, AMI, etc.

(Second Embodiment) FIG. 8 shows a plurality of pixel areas in a second embodiment according to the present invention.
2 shows a planar layout of one pixel area. In the first embodiment, the center of the opening of the microlens and the light-shielding layer 2 is shifted for each pixel, but in this embodiment, the group is grouped for each of a plurality of pixels and the center of the layout is shifted with respect to the center of the layout. The center of the opening of the microlens and the light shielding layer 2 is shifted. In FIG. 8, the layout is changed to a 2 × 2 pixel unit as one group. That is, the pitch of the plurality of microlenses included in a certain predetermined group is different from the pitch of the plurality of microlenses included in another group.

In the case of this embodiment, for each of a plurality of pixels,
Since the layout is enabled, the work load of the layout is reduced as compared with the previous embodiment. That is, when the number of pixels to be grouped is increased, the layout load is reduced, but on the other hand, the number of pixels in which the center of the optical axis is shifted from the center of the photodiode increases, so that the light shading slightly increases. Therefore, it is desirable to group the optical shading to such an extent that the shading falls within an allowable range. For example, if the pixels are grouped so that the deviation of the optical axis falls within 0.1 μm, the adverse effect on the reduction of the light shading is substantially negligible. Thus, the load on the layout can be reduced. That is, it is possible to realize a high-sensitivity solid-state imaging device in which design cost is suppressed and light shading is small.

In the first and second embodiments, the center of the microlens and the center of the opening are configured to coincide with each other. However, as shown in FIG. However, the configuration may be such that the microlens is shifted toward the center of the imaging area with respect to the opening while being shifted toward the center of the imaging area.

In this case, in the first and second embodiments,
Although it is more difficult to adjust the positions of the microlens, the opening, and the photoelectric conversion region as compared with, the light collection rate to the photoelectric conversion region in the peripheral portion is improved.

(Third Embodiment) Referring to FIG.
An imaging system using the solid-state imaging device described in Embodiments 1 and 2 described above will be described.

In FIG. 10, reference numeral 101 denotes a barrier which functions both as protection of the lens and as a main switch; 102, a lens for forming an optical image of a subject on the solid-state image sensor 4;
Is an aperture for changing the amount of light passing through the lens 102, and 1
Reference numeral 04 denotes the solid-state imaging device according to the first or second embodiment for capturing a subject formed by the lens 102 as an image signal;
Reference numeral 05 denotes an imaging signal processing circuit including a variable gain amplifier for amplifying an image signal output from the solid-state imaging device 104, a gain correction circuit for correcting a gain value, and the like.
Reference numeral 6 denotes an A / D converter for performing analog-to-digital conversion of an image signal output from the solid-state imaging device 104;
A signal processing unit that performs various corrections on the image data output from the / D converter 6 and compresses the data; 108 is a solid-state imaging device 104, an imaging signal processing circuit 105, an A / D converter 106, and a signal processing unit 107 A timing generator for outputting various timing signals; 109, an overall control / arithmetic unit for controlling various operations and the entire still video camera; 110, a memory unit for temporarily storing image data; 111, a recording medium; An interface unit for performing recording or reading; 112, a detachable recording medium such as a semiconductor memory for recording or reading image data;
Is an interface unit for communicating with an external computer or the like.

Next, the operation of the still video camera at the time of shooting in the above configuration will be described.

When the barrier 101 is opened, the main power is turned on, the power of the control system is turned on, and the power of the imaging system circuit such as the A / D converter 106 is turned on. Then, in order to control the exposure amount, the overall control / arithmetic unit 109 opens the aperture 103, and the solid-state imaging device 10
The signal output from 4 is converted by the A / D converter 106 and then input to the signal processing unit 107.

Based on the data, the exposure calculation is totally controlled.
The calculation is performed by the arithmetic unit 109.

The brightness is determined based on the result of the photometry, and the overall control / calculation unit 109 controls the aperture according to the result.

Next, based on the signal output from the solid-state imaging device 104, a high-frequency component is extracted, and the overall control / calculation unit 109 calculates the distance to the subject. Thereafter, the lens is driven to determine whether or not the lens is in focus. When it is determined that the lens is not focused, the lens is driven again to perform distance measurement.

Then, after the focusing is confirmed, the main exposure starts.

When the exposure is completed, the image signal output from the solid-state imaging device 104 is A / D converted by the A / D converter 106, passes through the signal processing unit 107, and is controlled by the overall control / operation unit 10.
9 is written to the memory unit.

Thereafter, the data stored in the memory unit 110 passes through the recording medium control I / F unit under the control of the overall control / arithmetic unit 109 and is recorded on a removable recording medium 112 such as a semiconductor memory.

Further, the image may be processed by inputting it directly to a computer or the like through the external I / F unit 113.

[0041]

As described above, according to the present invention,
Light shading due to the non-uniformity of light condensing of the microlenses accompanying the miniaturization of pixels and the increase in the number of pixels can be significantly reduced, and this solid-state imaging device can be used in imaging systems such as video cameras and still video cameras. ,
The image quality of the reproduced image can be improved.

Further, by applying the present invention to a compound-eye solid-state imaging device, the device can be reduced in size, particularly, the thickness can be reduced, so that a thin card size camera having a thickness of about 3 mm is realized. You can.

[Brief description of the drawings]

FIG. 1 is a plan layout diagram showing a first embodiment according to the present invention.

FIG. 2 is an enlarged view of one imaging area.

FIG. 3 is a plan view and a cross-sectional view of a pixel of the present invention.

FIG. 4 is a cross-sectional view of a compound-eye solid-state imaging device according to the present invention.

FIG. 5 is a diagram for explaining the effect of the present invention.

FIG. 6 is an output waveform diagram of the solid-state imaging device of the present invention.

FIG. 7 is an equivalent circuit diagram of one imaging area according to the present invention.

FIG. 8 is an enlarged view of one imaging area according to the second embodiment of the present invention.

FIG. 9 is a plan view and a cross-sectional view of a pixel of the present invention.

FIG. 10 is a diagram illustrating an imaging system.

FIG. 11 is a conventional plan layout diagram.

FIG. 12 is a diagram illustrating a conventional problem.

FIG. 13 is a diagram illustrating conventional light shading.

[Explanation of symbols]

 1, 220 pixels 2, 216, 240 Light-shielding layer (light-shielding area) 3 Opening (opening area) 4, 212 microlens 5 Photoelectric conversion area (photodiode area) 6, 230 Silicon (Si) substrate 7 SiN protective film 8 micro Lens flattening films 9a to 9d Imaging area (color filter layer) 11 is a horizontal shift register (HSR) 12 is a vertical shift register (VSR) 13 is a readout circuit 14 is an output amplifier 15 is a wiring layer 16 a color filter 17 an imaging lens

Claims (10)

[Claims] A plurality of imaging areas each having a two-dimensional array of photoelectric conversion regions; a microlens provided for each photoelectric conversion region for condensing light; and a plurality of microlenses corresponding to each photoelectric conversion region. And an opening for allowing light to be incident on the photoelectric conversion unit, provided in the periphery of the imaging area, wherein the position of the microlens and the opening is larger than that of the corresponding photoelectric conversion region. A solid-state image pickup device, wherein the arrangement is shifted toward the center of the image pickup area. 2. The solid-state imaging device according to claim 1, wherein the center of the micro lens and the center of the opening substantially coincide with each other. 3. The solid-state imaging device according to claim 1, wherein the microlens is formed on a layer planarized in a CMP process. 4. The imaging device according to claim 1, wherein the microlenses are arranged in a peripheral portion of the imaging area so as to be shifted from a corresponding opening in a center direction of the imaging area. A solid-state imaging device, comprising: 5. A plurality of imaging areas each having a two-dimensional array of photoelectric conversion regions, a microlens provided corresponding to each photoelectric conversion region for condensing light, and a peripheral portion of the imaging area. In the above, the position of the micro lens is arranged to be shifted in the center direction of the imaging area from the corresponding photoelectric conversion area, and in at least two imaging areas, the micro lens and the corresponding photoelectric conversion area A solid-state imaging device having different amounts of displacement. 6. The solid-state imaging device according to claim 1, wherein the same color filter is arranged for each of the plurality of imaging areas. 7. An imaging area in which photoelectric conversion regions are arranged two-dimensionally, and light provided corresponding to each photoelectric conversion region formed on a layer planarized in a CMP process. A solid-state imaging device, wherein a position of the microlens is shifted from a corresponding photoelectric conversion region toward a center direction of the imaging area in a peripheral portion of the imaging area. . 8. The micro-lens according to claim 7, further comprising an opening for allowing light to enter the photoelectric conversion unit provided corresponding to each photoelectric conversion region, wherein a center of the microlens and a center of the opening are arranged. A solid-state imaging device, which substantially matches. 9. An imaging area in which photoelectric conversion regions are arranged two-dimensionally, a micro lens provided for each photoelectric conversion region for condensing light, and a microlens corresponding to each photoelectric conversion region. And an opening for allowing light to enter the photoelectric conversion unit provided in a peripheral portion of the imaging area, wherein the position of the microlens and the opening is smaller than that of the corresponding photoelectric conversion region. The pitches of the microlenses in the first region including the plurality of microlenses are set to be shifted from each other in the center direction of the area,
A solid-state imaging device, which is different from the pitch of the microlenses in the region of (1). 10. The method according to claim 1, wherein
9. An imaging system comprising: the solid-state imaging device according to item 1; a lens for forming an image of light on the solid-state imaging device;