JP2007288294A - Solid-state imaging apparatus and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single plate type solid-state imaging apparatus capable of attaining finer imaging pixels while maintaining the image quality such as a dynamic range and to provide a camera with the solid-state imaging apparatus as an imaging device. <P>SOLUTION: In the solid-state imaging apparatus, each of green color filer layers 240G is formed octagonal and each of red color filter layers 240R and each of blue color filter layers 240B are formed square. Further, the area of each of the green color filer layers 240G is selected greater than the area of the other color filter layers 240R, 240B, and the number of imaging pixel sections formed with the green color filer layers 240G is selected to be N/2, wherein N is the total number of pixels in the imaging region of the solid-state imaging apparatus. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device and a camera, and more particularly to an arrangement of color filters in a single-plate solid-state imaging device.

  Solid-state imaging devices such as CCD image sensors and CMOS image sensors are widely used as imaging devices such as digital still cameras and digital movie cameras. A CMOS image sensor as a solid-state imaging device is composed of an imaging region that receives light and photoelectrically converts it to a single semiconductor substrate, and a peripheral circuit region that extracts an image signal from the imaging region. In the imaging region, millions of photodiodes (light receiving portions) are arranged in the surface direction of the semiconductor substrate, and an imaging pixel is configured by each one. In addition to the photodiode, each imaging pixel is provided with transistor element regions for amplification, selection, and reset, and a wiring layer is formed over a plurality of layers (see Patent Document 1). ).

  Each imaging pixel is provided with a color filter that transmits only the required wavelength components (red component, green component, blue component) from the incident light above each photodiode, that is, upstream of the optical path of the incident light. Has been. As shown in FIG. 5A, in the solid-state imaging device, a red color filter 1000R, a green color filter 1000G, and a blue color filter 1000B are arranged in a grid pattern (see Patent Document 2). Note that the arrangement of the color filters 1000R, 1000G, and 1000B as shown in FIG. 5A is called a Bayer arrangement.

Each imaging pixel is formed with an on-chip lens that condenses incident light onto a photodiode at the most upstream side of the optical path. As the on-chip lens, a circular lens is generally used from the viewpoint of light collection efficiency. Therefore, the effective area in each imaging pixel is an inward area of inscribed circles 1001R, 1001G, and 1001B as shown in FIG. 5B, and has an area of 78.5 [%] as a ratio.
JP 2002-335455 A JP 2000-316163 A

  However, in the conventional solid-state imaging device, it is difficult to miniaturize imaging pixels while maintaining imaging quality such as a dynamic range. That is, for solid-state imaging devices, the area occupied per unit imaging pixel is required to be reduced in order to achieve higher resolution, and accordingly, the size of the photodiode must be reduced and dynamic It has become difficult to maintain sufficient image quality such as range.

  The present invention has been made to solve the above problems, and is a single-plate solid-state imaging device capable of miniaturizing imaging pixels while maintaining image quality such as a dynamic range and a camera including the same The purpose is to provide.

  In order to achieve the above object, the present invention provides a semiconductor substrate in which two or more imaging pixels each having a light receiving portion having a photoelectric conversion function are two-dimensionally formed in the surface direction, and in the thickness direction of the semiconductor substrate, A solid-state imaging device in which red, green, and blue color filters are arranged corresponding to each of the imaging pixels upstream of the light path of the incident light from the light receiving unit, and each of the green color filters It is characterized by being formed with a larger area than each of the color (red and blue) color filters.

  A camera according to the present invention includes the solid-state imaging device according to the present invention as an imaging device.

  As described above, in the solid-state imaging device and the camera including the same according to the present invention, the size of each of the green color filters is set larger than the size of each of the red and blue color filters. Even when the size of the imaging region is reduced, a high dynamic range can be maintained. This is based on the viewpoint that the spectral characteristics of the human eye have a peak near green, and it is effective to increase the size of the green imaging pixel in order to obtain a high dynamic range. It is. That is, in the solid-state imaging device according to the present invention, the green color filter is not set to the same size as the red and blue color filters, but is set larger than the size of the red and blue color filters. Even when the size of the entire imaging region is reduced, the dynamic range can be kept high from the viewpoint of the spectral characteristics of the human eye.

In the solid-state imaging device according to the present invention, the following variations can be employed.
In the solid-state imaging device according to the present invention, the area ratio of the green color filter to the red color filter or the blue color filter (area ratio in imaging pixel unit) is changed from the RGB color space to the YUV color space at the time of JPEG compression processing. It is possible to adopt a configuration in which the green luminance data is set based on a contribution ratio with respect to the luminance information in the conversion to.

In the solid-state imaging device according to the present invention, each of the green color filters has an octagonal shape when viewed in plan, and each of the red and blue color filters is viewed in plan. When it does, it can take the structure of becoming a square shape.
In the solid-state imaging device according to the present invention, when a virtual circle inscribed in each color filter is drawn, the diameter of the virtual circle inscribed in the green color filter is in the red or blue color filter. A configuration in which the diameter is 1.1 times or more and 2 times or less with respect to the diameter of the virtual circle to be in contact can be employed.

In the solid-state imaging device according to the present invention and the camera including the same, the number of imaging pixels formed with a green color filter is the same as the number of imaging pixels formed with a red color filter, and the blue The number of image pickup pixels formed with the color filter is substantially equal to the total number.
Further, in the solid-state imaging device and the camera including the same according to the present invention, each color filter in adjacent imaging pixels is formed in a state of abutting or overlapping so as not to generate a gap between each other. Can be adopted.

Moreover, in the solid-state imaging device according to the present invention, it is possible to adopt a configuration in which the area of the light receiving unit in each imaging pixel is set according to the area of the color filter in the imaging pixel.
In the solid-state imaging device and the camera including the same according to the present invention, an on-chip lens having a condensing function is disposed upstream of the color filter in each imaging pixel, and the on-chip in each imaging pixel. It is possible to adopt a configuration in which the lens size is set according to the area of the color filter in the imaging pixel.

  The camera according to the present invention includes a digital still camera and a digital movie camera.

The best mode for carrying out the present invention will be described below with reference to the drawings. It should be noted that each embodiment used below is merely an example for easily explaining the configuration of the present invention and the operations / effects produced therefrom, and the present invention is other than essential parts for achieving the effects. There is no limitation to these.
1. Configuration of Solid-State Imaging Device 1 The configuration of the solid-state imaging device 1 according to the embodiment will be described with reference to FIG.

First, the solid-state imaging device 1 according to the present embodiment is used as an imaging device in a digital still camera or a digital movie camera.
As shown in FIG. 1A, the solid-state imaging device 1 includes an imaging region 20 and a circuit region 30 that are formed based on a semiconductor substrate 10. Although not shown, a plurality of imaging pixel units 200 are two-dimensionally arranged in the imaging region 20 in the main surface direction of the semiconductor substrate 10 (see FIG. 1B).

  On the other hand, in the circuit region 30, a timing generation circuit unit 31, a vertical shift register unit 32, a pixel selection circuit unit 33, a horizontal shift register unit 34, and the like are formed. Among them, the vertical shift register unit 32 and the horizontal shift register unit 34 are both composed of dynamic circuits, and are sequentially driven from the timing generation circuit unit 31 to each imaging pixel unit 200 or pixel selection circuit unit 33 in the imaging region 20. (Switching) pulse is output. The pixel selection circuit unit 33 includes a switching element unit (not shown) formed corresponding to each imaging pixel unit 200 in units of rows, and sequentially receives pulses from the horizontal shift register unit 34. Turns on.

  The imaging pixel unit 200 in the imaging region 20 is an amplification type unit pixel each having an amplification unit. The photoelectrically converted signal charges are selected by the vertical shift register unit 32 and the pixel selection circuit unit 33. Is read out from the imaging pixel unit 200 intersecting with the row in which the ON state is ON. The timing generation circuit unit 31 applies a power supply voltage, a timing pulse, and the like to the vertical shift register unit 32 and the horizontal shift register unit 34.

2. Configuration of Imaging Area 20 The configuration of the imaging area 20 will be described with reference to FIG. In FIG. 1B, a part of the imaging pixel unit 200 in the imaging region 20 is illustrated.
As shown in FIG. 1B, each of the imaging pixel units 200 in the imaging region 20 is formed with a photodiode PD having a photoelectric conversion function from the surface of the semiconductor substrate 10 inward in the thickness direction. Yes. Further, in the region from the surface of the semiconductor substrate 10 toward the inside in the thickness direction, the floating diffusion layer 202 and the amplification transistor TR are spaced apart from the photodiode PD and spaced from each other. the drain of the _a 203, the amplification transistor TR source selection and _a transistor TR shared pole 205 also serves as a drain _S and the selection transistor TR _S of the source 207, are formed in this order toward the right from the left in the X-axis direction . In addition, a pixel separation layer 208 is formed between adjacent imaging pixel units 200.

A gate insulating film 210 is formed on the surface of the semiconductor substrate 10 except for the region where the pixel isolation layer 208 is formed. On the surface of the gate insulating film 210, a transfer gate 201 is formed in a region corresponding to between the photodiode PD and the floating diffusion layer 208, and an amplification transistor TR in a region corresponding to between the drain 203 and the shared electrode 205. _A gate 204 is formed. Further, on the surface of the gate insulating film 210, the corresponding region gate 206 of the selection transistor TR _S is formed between the source 207 of the selection transistor TR _S and a shared electrode 205.

  Further, wiring layers 211 and 212 are formed on the surface of the gate insulating film 210 with the planarization films 221 and 222 sandwiched therebetween, and a planarization film 223 is interposed on the wiring layer 212. A light shielding film 213 is formed in a sandwiched state. The wiring layers 211 and 212 are connected to the transfer gate 201, gates 204 and 206, the floating diffusion layer 202, the source 207, and the like by contact plugs 231.

Each of the wiring layers 211 and 212 and the light shielding film 213 is formed in a state where it does not extend upward in the Z-axis direction of the photodiode PD. Further, the color filter layer 240 is formed on the light shielding film 213 with the planarizing film 224 sandwiched therebetween, and the microlens 250 is formed thereon with the planarizing film 225 sandwiched therebetween. .
The color filter layer 240 is color-coded for each imaging pixel unit 200. This will be described later.

The imaging pixel unit 200 includes a transfer transistor, a reset transistor, and the like in addition to the amplification transistor TR _A and the selection transistor TR _S. However, the illustration is omitted in FIG. .
Light that has entered the imaging region 20 in the solid-state imaging device 1 from the outside is collected by the microlens 250 and selected by the color filter layer 240 (only the frequency component of the selected color of red, green, and blue is selected). Is transmitted to the photodiode PD. The optical path of incident light in the imaging region 20 is set in a direction from the upper side to the lower side in the Z-axis direction in FIG.

3. Configuration of Color Filter Layer 240 The configuration of the color filter layer 240 which is the most characteristic part of the configuration of the solid-state imaging device 1 in the present embodiment will be described with reference to FIG. FIG. 2 is a schematic plan view of a part of the color filter layer 240 in the solid-state imaging device 1 as viewed in a plan view (viewed downward from the Z-axis direction in FIG. 1B).

  As shown in FIG. 2, in the solid-state imaging device 1, the green color filter layer 240G is formed in an octagon, and the red color filter layer 240R and the blue color filter layer 240B are formed in a quadrangle. The green color filter layer 240G is set to have a larger area than the color filter layers 240R and 240B of other colors, and the number of image pickup pixel units 200 formed with the green color filter layer 240G is as follows. The total number of pixels N in the imaging region 20 of the solid-state imaging device 1 is set to N / 2. The numbers of pixels of the red color filter layer 240R and the blue color filter layer 240B are substantially the same, and are set to N / 4 with respect to the total number N of pixels.

  Further, as shown in FIG. 2, there is no gap between each of the color filter layers 240R, 240G, and 240B, and the color filter layers 240R, 240G, and 240B actually have a slight overlap. It is formed with. In this way, the color filter layers 240R, 240G, and 240B can be efficiently arranged without causing a gap between them. The green color filter layer 240G is an octagon, and the red color filter layer 240R and In the solid-state imaging device 1 according to the present embodiment, the blue color filter layer 240B is rectangular, and the entire color filter layer 240 is configured by combining the color filter layers 240R, 240G, and 240B. is there.

4). As described above, in the solid-state imaging device 1 according to the present embodiment, the area of the green color filter layer 240G is larger than that of the color filter layers 240R and 240B of other colors. Although the size is set large, details of the sizes of the color filter layers 240R, 240G, and 240B will be described with reference to FIG. FIG. 3 is a diagram schematically drawn by extracting two pixels of the green color filter layer 240G and one pixel of the red color filter layer 240R and the blue color filter layer 240B from the color filter layer 240 of the solid-state imaging device 1. It is.

First, the outlines of the color filter layers 1000R, 1000G, and 1000B in the Bayer array in the conventional solid-state imaging device are shown by two-dot chain lines in FIG. As described above, the effective areas of the color filter layers 1000R, 1000G, and 1000B according to the Bayer array are inward areas of the inscribed circles 1001R, 1001G, and 1001B. The diameters of the inscribed circles 1001R, 1001G, and 1001B are “D ₁ ”.

Next, as shown in FIG. 3, an inscribed circle 241G with respect to the contour of the green color filter layer 240G in the solid-state imaging device 1 according to the present embodiment is drawn, and its diameter is set to “D ₂ ”. Further, inscribed circles 241R and 241B with respect to the outlines of the red color filter layer 240R and the blue color filter layer 240B are drawn, and the diameter thereof is set to “D ₃ ”. In the present embodiment, the red color filter layer 240R and the blue color filter layer 240B have a rectangular shape of the same size.

In the present embodiment, the inscribed circle 1001R in a conventional Bayer array, 1001G, with respect to the diameter _{D 1} of the 1001B, the diameter _{D 2} and the inscribed circle 241R of the inscribed circle 241G, the diameter _{D 3} of 241B, respectively following It is set with the relationship.

The [Number 1] and from [Expression 2], the diameter _{D 2} of the inscribed circle 241G is inscribed circle 241R, for each diameter _{D 3} of 241B, it has a (0.707 / 0.293) times . Note that the ratio of the total area occupied by all the inscribed circles 241R, 241G, and 241B in the imaging region 20 to the entire imaging region 20 in the solid-state imaging device 1 is approximately 92 [%].
5). Setting the sizes of the color filter layers 240R, 240G, 240B In the solid-state imaging device 1 according to the present embodiment, the sizes of the color filter layers 240R, 240G, 240B are set as described above. The reason for setting is as follows.

  First, in the solid-state imaging device 1, an image processing procedure in which luminance information from the imaging pixel unit 200 having the green color filter layer 240G is acquired as a main element is generally adopted. In the Bayer array in the conventional solid-state imaging device, the green color filter layers 1000G are arranged in a staggered pattern based on the unit of 2 rows and 2 columns in the vertical and horizontal directions as shown in FIG. Further, the red color filter layer 1000R and the blue color filter layer 1000B are evenly arranged. As described above, in the conventional Bayer arrangement, a large number of imaging pixel units having symmetry and the green color filter layer 1000G are arranged, so that the area of the green color filter layer 1000G is doubled and high luminance reproducibility is achieved. It has gained.

  Next, in a digital camera or the like on which the solid-state imaging device 1 is mounted, an image format such as JPEG is mainly used, and information expressed in a YUV color space is used. In this format, the green allocated bits occupy half of the whole, and the amount of green information is increased to increase the information amount as a whole. In the conversion from the luminance data of the three primary colors of RGB in JPEG to the luminance / color difference data in the YUV color space, the following relationship is established.

  As shown in the above [Equation 3] to [Equation 5], the contribution ratio of the green luminance data G in the luminance information Y is about five times that of the blue luminance data B and about twice that of the red luminance data R. is there. That is, in the solid-state imaging device 1, as a measure for ensuring a wide dynamic range, the imaging pixel unit 200 having the green color filter layer 240G is set to preferentially occupy a large area, and the red color filter layer 240R. The area of the imaging pixel unit 200 having the blue color filter layer 240B is set small. That is, in the solid-state imaging device 1 according to the present embodiment, the relationship among the green color filter layer 240G, the red color filter layer 240R, and the blue color filter layer 240B is set by the above [Equation 1] and [Equation 2]. .

  Moreover, the conversion formula which becomes reverse with respect to said [Formula 3]-[Formula 5] is shown next.

  As shown in the above [Equation 6] to [Equation 8], each color can be generated on the basis of luminance data, and an imaging pixel unit 200 having a green color filter layer 240G is a main element of luminance information. Therefore, the resolution of the luminance information Y can be increased by increasing the resolution of the imaging pixel unit 200 having the green color filter layer 240G. This makes it possible to increase the resolution of the image.

From the above viewpoint, the solid-state imaging device 1 according to the present embodiment employs a layout in which the area occupied by each of the green color filter layers 240G is larger than that of the red color filter layers 240R and the blue color filter layers 240B. It is possible to increase the resolution of the sensor, particularly the luminance.
In addition, in the solid-state imaging device 1 according to this embodiment, the diameter _{D 2} of the inscribed circle 241G for the contour of the green color filter layer 240G, the red color filter layer 240R and the inscribed circle 241R of the blue color filter layer 240B, to the diameter D ₃ of 241B, are you set on the basis of the coefficients according to the data in the equation (3) is due to the following reasons.

  First, in order to establish the luminance information of the JPEG image represented by the above [Equation 6], it is necessary to satisfy the relationship of R: G: B = 0.5: 1: 0.2. Therefore, when considering reducing the sizes of the red color filter layer 240R and the blue color filter layer 240B, the shape of each color filter layer shown in FIG. 4 is assumed, and the area is expressed by the following equations [Equation 9] to [Equation 11]. ] Is established.

  Here, by performing the approximation of the above [Equation 9] to [Equation 11], the relations of the following equations are obtained, respectively.

Solving [Equation 12] to [Equation 14] provides a common solution of the two equations. As a result, one side of the red color filter layer 240R is reduced by 5 [%] and one side of the blue color filter layer 240B is 32 [ %] Decrease will be established.
When the above relationship is examined with reference to a virtual circle indicating an increase in the green color filter layer 240G, the decrease in the size of the red color filter layer 240R becomes the increase in the green color filter layer 240G as it is, and the green color filter layer 240G. The size ratio of each virtual circle between the red color filter layer 240R and the red color filter layer 240R is 1.1: 1. The same calculation is performed, and the size ratio of the virtual circle between the green color filter layer 240G and the blue color filter layer 240B is 2: 1.

In the present embodiment, drives out the above reason, are set as described above the diameter D ₂ in relation to the diameter D _3.
6). Other matters In the above description, the diameter D ₂ and the diameter D ₃ are set based on the coefficients of the above [Equation 3]. However, in the solid-state imaging device according to the present invention, (D ₂ / D ₃ ) It is possible to set the value in a range of 1.1 to 2 times.

  In the solid-state imaging device 1 according to the above-described embodiment, the green color filter layer 240G has an octagonal shape, and the color filter layers 240R and 240B of other colors have a rectangular shape. The shape and size of the photodiode PD are also set to follow the shape and size of the color filter layers 240R, 240G, and 240B. However, the shape is not necessarily the same or similar from the viewpoint of manufacturing and from the viewpoint of the light collecting performance of the microlens 250.

  In the solid-state imaging device 1 according to the above-described embodiment, the green color filter layer 240G has a regular octagonal shape and the color filter layers 240R and 240B of other colors have square shapes. It may be a distorted octagon and a quadrangle that is compressed or stretched in one direction. The solid-state imaging device according to the present invention is mainly characterized in that the area of the green color filter layer 240G is set larger than the areas of the red color filter layer 240R and the blue color filter layer 240B. The shape is not necessarily limited to that of the above embodiment.

Further, in the solid-state imaging device 1 according to the above-described embodiment, the configuration in which the adjacent color filter layers 240R, 240G, and 240B are slightly overlapped is adopted, but it is not always necessary to overlap, and they may be matched. .
Furthermore, although the MOS type solid-state imaging device has been described as an example in the above embodiment, the present invention can also be applied to a CCD type solid-state imaging device.

  The present invention is effective for realizing a digital still camera, a digital movie camera, and the like that are required to maintain high image quality such as a dynamic range even when the size of an image pickup pixel is reduced as the definition is increased.

(A) is a schematic block diagram which shows the structure of the solid-state imaging device 1 which concerns on embodiment, (b) is a schematic cross section which shows a part of structure of the imaging area 20 of the solid-state imaging device 1. FIG. 3 is a schematic plan view showing a color filter array in an imaging region 20 of the solid-state imaging device 1. FIG. FIG. 3 is a schematic plan view illustrating a size relationship of a part of a color filter array extracted from an imaging region. 3 is a schematic plan view showing a part of a color filter array used for determining the size of each color filter layer 240R, 240G, 240B of the solid-state imaging device 1. FIG. (A) is a schematic plan view which shows the Bayer arrangement | sequence employ | adopted with the conventional solid-state imaging device, (b) is a schematic top view which extracts and shows the part.

Explanation of symbols

1. Solid-state imaging device 10. Semiconductor substrate 20. Imaging region 30. Circuit area 31. Timing generation circuit section 32. Vertical shift register unit 33. Pixel selection circuit unit 34. Horizontal shift register unit 200. Imaging pixel unit 201. Transfer gate 202. Floating diffusion layer 203. Drains 204, 206. Gate 205. Common electrode 207. Source 208. Pixel separation layer 210. Gate insulating films 211 and 212. Wiring layer 213. Light shielding films 221, 222, 223, 224, 225. Planarization film 231. Contact plug 240. Color filter layer 240R. Red color filter layer 240G. Green color filter layer 240B. Blue color filter layer 250. Microlens PD. Photodiode TR _A. Amplifying transistor TR _S. Select transistor

Claims (9)

A plurality of imaging pixels each having a light receiving portion having a photoelectric conversion function are two-dimensionally formed in the surface direction of the semiconductor substrate,
In the thickness direction of the semiconductor substrate, a solid-state imaging device in which red, green, and blue color filters are arranged corresponding to each of the imaging pixels upstream of the optical path of incident light from the light receiving unit,
Each of the green color filters is formed with a larger area than each of the other color filters. In an imaging pixel unit, the area ratio of the green color filter to the red color filter or the blue color filter is the green luminance with respect to the luminance information in the conversion from the RGB color space to the YUV color space at the time of JPEG compression processing. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is set based on a ratio of data contribution. Each of the green color filters has an octagonal shape when viewed in plan,
The solid-state imaging device according to claim 1, wherein each of the red and blue color filters has a quadrangular shape when viewed in plan. When drawing a virtual circle inscribed in each of the color filters of each color,
The diameter of the virtual circle inscribed in the green color filter is 1.1 to 2 times the diameter of the virtual circle inscribed in the red or blue color filter. The solid-state imaging device according to claim 3. The number of imaging pixels formed with the green color filter is defined as the number of imaging pixels formed with the red color filter and the number of imaging pixels formed with the blue color filter. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is substantially equal to a number obtained by adding together. 6. Each color filter in an adjacent imaging pixel is formed in a state of butting or overlapping so as not to generate a gap between each other. Solid-state imaging device. The solid-state imaging device according to any one of claims 1 to 6, wherein an area of the light receiving unit in each imaging pixel is set according to an area of the color filter in the imaging pixel. Each imaging pixel is provided with an on-chip lens having a condensing function upstream of the color filter in the optical path,
8. The solid-state imaging device according to claim 1, wherein the size of the on-chip lens in each imaging pixel is set according to an area of the color filter in the imaging pixel. A camera comprising the solid-state imaging device according to claim 1 as an imaging device.

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