JP2005175893A - Two-plate type color solid-state image pickup device and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute a small-sized and inexpensive digital camera excellent in color reproducibility. <P>SOLUTION: A two-plate type color solid-state image pickup device is provided with a color separation prism 35 for separating incident light from an object to light including blue and red, and green light; a solid-state image pickup element 36 which receives the blue and red incident light separated by the prism 35; and a solid-state image pickup element 37 which receives the green light separated by the prism 35. A color filter for transmitting blue or red is formed on each of a plurality of light-receiving parts provided on the solid-state image pickup element 36 in an array form. A color filter for transmitting green G1 or a color filter for transmitting green G2 whose wavelength region is deviated from that of the green G1 is formed on each of a plurality of light-receiving parts provided on the solid-state image pickup element 37 in an array form. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a two-plate color solid-state imaging device and a digital camera, and more particularly to a small and low-cost two-plate color solid-state imaging device and a digital camera excellent in color reproducibility.

  Conventionally, as a color solid-state imaging device using a solid-state imaging device, a three-plate type, a two-plate type, and a single-plate type are known.

  The three-plate color solid-state imaging device uses three solid-state imaging elements in which a large number of photoelectric conversion elements are formed in an array on the surface of a semiconductor substrate, as described in Patent Document 1 below, for example, and an optical image of a subject. The red optical image is received by the first solid-state imaging device, the green optical image is received by the second solid-state imaging device, and the blue optical image is received by the third solid-state imaging device. Yes. Therefore, a color separation prism that separates incident light from a subject into optical images of red (R), green (G), and blue (B) colors is used.

  FIG. 21 is a configuration diagram illustrating an example of a color separation prism. The illustrated color separation prism 1 includes a first prism member 1a, a second prism member 1b, a third prism member 1c, a blue reflecting dichroic film 2 provided between the members 1a and 1b, and the members 1b and 1c. It comprises a dichroic film 3 for red reflection provided.

  Of the R, G, and B optical images incident on the first prism member 1a, the blue (B) optical image is reflected by the dichroic film 2 and received by the third solid-state imaging device 4, and the dichroic film is received. Of the red (R) and green (G) color optical images transmitted through 2, the red (R) optical image is reflected by the dichroic film 3 and received by the first solid-state imaging device 5 and transmitted through the dichroic film 3. Then, the green (G) optical image straightly traveling through the third prism member 1 c is received by the second solid-state imaging device 4.

  This three-plate type solid-state image pickup device has the advantages that the color separation performance is high and incident light is not wasted, so that the color reproducibility of the picked-up image is excellent and the sensitivity is high. However, three solid-state imaging devices 4, 5, and 6 and a complicated color separation prism 1 are required, and R, G, and B images formed by a condensing lens (not shown) disposed in front of the prism 1. Since it is necessary to make the optical path lengths of the respective color rays reaching the respective solid-state imaging devices 4, 5, and 6 equal, there is a problem that the third prism member 1c cannot be omitted, which increases costs and increases the size of the apparatus.

  The two-plate type color solid-state imaging device is configured using two solid-state imaging devices and a color separation prism having a simpler structure than the prism 1 shown in FIG. Is done. FIG. 22 is a block diagram showing an example of a prism used in a two-plate color solid-state imaging device. The color separation prism 7 includes a first prism member 7a, a second prism member 7b, and a green (G) reflecting dichroic film 8 provided therebetween, and R, G incident on the first prism member 7a. , B optical images of green (G) are reflected by the dichroic film 8 and received by the first solid-state imaging device 9, and the red (R) and blue (B) optical images transmitted through the dichroic film 8 are transmitted. Each optical image is received by the second solid-state imaging device 10.

  The second solid-state imaging device 10 is provided with a color filter 11 on the front surface of the device 10 in order to separately receive a red (R) optical image and a blue (B) optical image. In this color fill 11, red (R) color filters and blue (B) color filters are alternately provided in stripes, and a photoelectric conversion element disposed on the back side of the red color filter detects the amount of received red light. The photoelectric conversion element arranged on the back side of the blue color filter detects the amount of blue light received.

  This two-plate type color solid-state imaging device requires only two solid-state imaging elements as compared with the three-plate type color solid-state imaging device, and the prism 7 can be configured at a low cost, so that the cost can be reduced. However, since the red (R) and blue (B) incident light beams travel straight and are received by the solid-state imaging device 10, the thickness of the second prism member 7b is further reduced in order to reduce the size of the apparatus. There is a need to.

  The single-plate color solid-state imaging device is configured to receive R, G, and B color optical images with one solid-state imaging device without using a color separation prism. For this reason, a color filter 11 in which a red (R) color filter, a green (G) color filter, and a blue (B) color filter are arranged in a mosaic according to a predetermined rule is formed on the front surface of the solid-state imaging device. Each of the large number of photoelectric conversion elements formed in (1) is configured to receive an optical image of one color of R, G, and B. An example of this color filter is shown in FIG. This color filter array is called a Bayer array, and is described in Patent Document 4 below.

  The single-plate color solid-state imaging device has the advantage that the cost is low and the device can be downsized because only one solid-state imaging device is required and no color separation prism is required. However, the green (G) and blue (B) light incident on the red (R) color filter is not photoelectrically converted, and the red (R) and blue (B) light incident on the green (G) color filter. Similarly, light is not photoelectrically converted, and similarly, red (R) and green (G) light incident on the blue (B) color filter is not photoelectrically converted. Therefore, only about 1/3 of the incident light is photoelectrically converted, and there is a problem that sensitivity is poor.

  As described above, there are advantages and disadvantages in the three-plate type, two-plate type, and single-plate type color solid-state imaging device, so which type of color solid-state imaging device to be mounted on the digital camera should be determined. It depends on the manufacturing cost and performance and the size of the digital camera. In a small digital camera such as a digital still camera, a single plate type camera that can reduce the size of the solid-state imaging device is often used.

  However, single-plate color solid-state image sensors with advanced pixel miniaturization as in recent years have reached the limits of the manufacturing technology for miniaturization, resulting in a decrease in manufacturing yield and manufacturing costs of color solid-state image sensors. Has become a problem. The reason is as follows.

  A color filter, flattening film, microlens, etc. must be stacked on the upper part of the light receiving part formed on the surface of the semiconductor substrate of the single-plate color solid-state image sensor. Between the light receiving part and the microlens (top lens) The distance (the height of each pixel) cannot be shortened. On the other hand, in the solid-state imaging device in which the increase in the number of pixels has progressed, the size of the opening of each pixel has been reduced to the wavelength order of incident light. For this reason, from the top lens to the photoelectric conversion element in each pixel. The incident optical path is an elongated path. In addition, since the incident angle of incident light at the peripheral portion is oblique with respect to the central portion of the solid-state imaging device, in order to avoid insufficient light quantity, that is, color shading in the peripheral portion, the peripheral pixels are matched to the incident angle. Therefore, a color filter, a flattening film, a microlens, and the like must be laminated so that each incident light path is inclined.

  Furthermore, precise layering of color filters has become difficult due to pixel miniaturization. Since users of digital cameras have come to desire faithful color reproducibility, for example, as described in Patent Documents 5 and 6 below, a wavelength of 460 to 530 nm that human visual cells feel as negative sensitivity. In order to detect the amount of light received in the vicinity, in addition to the three color filters of red (R), green (G), and blue (B), the amount of light received in the wavelength region having negative sensitivity is detected. 4 color filters must also be laminated. That is, in a single-plate solid-state imaging device, when such four color filters are arranged on the device, the incident light component that is not effectively photoelectrically converted in each pixel further increases. The problem of sacrificing resolution arises. In addition, the size of the pigment particle shape used in the color filter layer is relatively large in pixels that have become finer, and there is a problem that the shadow of the pigment particle shape affects the amount of light received by each pixel. . On the other hand, when using a dye-based color filter, it is necessary to make the film thickness of the color filter thicker than that of the pigment-based color filter in order to secure a sufficient spectral transmittance, which makes it difficult to miniaturize the pixels. There is a problem. For the above reasons, the production yield of the single-plate color solid-state imaging device is low, which is one factor that increases the production cost of digital cameras.

JP-A-5-244613 JP-A-5-244610 JP-A-3-274523 U.S. Pat. No. 3,971,065 JP 49-131025 A Japanese Patent No. 2872759

  A color solid-state image sensor mounted on a small digital camera has reached a limit in terms of technology and cost to realize this in a single plate type. However, when the color solid-state imaging device is realized by a three-plate system, an expensive and complicated color separation prism is required, which causes a problem that the device becomes large and the manufacturing cost increases.

  Therefore, it is most realistic to construct a compact, low-cost digital camera capable of faithful color reproduction with a two-plate color solid-state imaging device. It is necessary to optimize the combination with the color separation prism.

  An object of the present invention is to provide a small and low-cost two-plate color solid-state imaging device capable of faithful color reproduction and a digital camera equipped with the same.

  The two-plate color solid-state imaging device of the present invention includes a color separation prism that separates incident light from a subject into light including a first color and a second color and light including a third color and a fourth color, and the color separation A first solid-state imaging device that receives incident light of the first color and the second color separated by the prism, and a second that receives incident light of the third color and the fourth color separated by the color separation prism. In a two-plate color solid-state imaging device including a solid-state imaging device, a color filter that transmits the first color or the second color is provided in each of a plurality of light receiving units provided in an array on the first solid-state imaging device. A color filter that transmits the third color or the fourth color is formed in each of the plurality of light receiving portions that are formed and provided in an array on the second solid-state imaging device.

  With this configuration, the size of one pixel (light receiving unit) can be increased as compared with a single-plate solid-state image pickup device having the same resolution, and the color filters of each solid-state image pickup device need only have two colors. The production yield can be increased, and the cost can be reduced. In addition, since the image reproduction is performed with the first to fourth colors, faithful color reproduction is possible. In addition, since a color separation prism that is smaller than the color separation prism used in the three-plate type is used, an increase in the size of the apparatus can be avoided.

  In the two-plate color solid-state imaging device of the present invention, the color filter that transmits the first color and the color filter that transmits the second color are alternately arranged in the upper, lower, left, and right directions in each light receiving portion of the first solid-state imaging device. And / or a color filter that transmits the third color and a color filter that transmits the fourth color are alternately arranged vertically and horizontally in each light receiving portion of the second solid-state imaging device. .

  Although the arrangement of the color filters is arbitrary, the color reproducibility is further improved by the above arrangement.

  In the two-plate color solid-state imaging device of the present invention, the first color and second color light received by the first solid-state imaging device are blue and red light of three primary colors, respectively, and the second solid-state imaging The light of the third color and the fourth color received by the element is light in an intermediate wavelength range of the blue and the red.

  A primary color filter R or a complementary color filter Ye (yellow) may be used as long as it is a color filter that transmits a red (R) component, and a primary color system is used if it is a color filter that transmits a blue (B) component. Color filter B or complementary color filter Cy (cyan) may be used.

  The two-plate color solid-state imaging device of the present invention detects the amount of incident light having a wavelength of 460 nm to 530 nm from the difference between the third color detection signal and the fourth color detection signal output from the second solid-state imaging device. The color filters of the third color and the fourth color are formed as described above, and the color filter of the third color formed on the second solid-state image sensor emits light having a wavelength of 460 nm to 530 nm. It is formed so as to be transparent.

  With this configuration, it is possible to easily detect the negative sensitivity portion for red in human visual cells.

  The two-plate color solid-state imaging device of the present invention is formed such that the third color filter and the fourth color filter formed in the second solid-state imaging device divide the green wavelength range into two. It is characterized by.

  With this configuration, it is possible to faithfully reproduce the green color of the image.

  The two-plate color solid-state imaging device according to the present invention is characterized in that each light-receiving portion of the second solid-state imaging device is arranged so as to be shifted by 1/2 pitch with respect to each light-receiving portion of the first solid-state imaging device. And

  In this way, by arranging the two solid-state imaging elements in a pixel shift arrangement, it is possible to increase the resolution of the image.

  The two-plate color solid-state imaging device according to the present invention is characterized in that each light-receiving unit of the first solid-state imaging device is arranged at the same sampling point as each light-receiving unit of the second solid-state imaging device.

  With this configuration, false colors and color moire can be reduced.

  The two-plate color solid-state imaging device of the present invention is characterized in that the first solid-state imaging device and the second solid-state imaging device are each composed of a CCD, and the first solid-state imaging device and the second solid-state imaging device Each element is formed of a MOS image sensor. Furthermore, the arrangement of the light receiving portions of the first solid-state imaging device and the second solid-state imaging device is a honeycomb arrangement.

  The two-plate color solid-state imaging device of the present invention can be realized by a CCD or a MOS type, and each pixel (light receiving portion) can be realized by a square lattice arrangement or a honeycomb pixel arrangement.

  The color separation prism used in the two-plate color solid-state imaging device of the present invention separates the incident light from the subject into light including the first color and the second color and light including the third color and the fourth color. In addition, the two-plate color solid-state imaging in which the incident light of the first color and the second color is incident on the first solid-state image sensor and the separated incident light of the third color and the fourth color is incident on the second solid-state image sensor. In the color separation prism of the apparatus, a prism member that reflects incident light of the first color and the second color and enters the first solid-state image sensor, and reflects incident light of the third color and the fourth color And a prism member incident on the second solid-state imaging device.

  With this configuration, the thickness of the (spectral) optical system composed of the color separation prism can be reduced.

  The two-plate type color solid-state imaging device of the present invention is characterized by using the above-described color separation prism.

  With this configuration, further downsizing of the apparatus can be realized.

  A digital camera according to the present invention includes the two-plate color solid-state imaging device described above.

  With this configuration, a faithful color reproduction is possible, and a small, low-cost digital camera can be provided.

  A digital camera according to the present invention includes a two-plate color solid-state imaging device and signal processing for correcting red sensitivity detected by the first solid-state imaging device based on a detection signal having a wavelength of 460 nm to 530 nm detected by the two-plate color solid-state imaging device. Means.

  With this configuration, it is possible to provide a digital camera that can reproduce an image faithful to human visibility.

  According to the present invention, a faithful color reproduction is possible, and a low-cost, small-sized digital camera can be configured.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram of a digital camera (in this example, a digital still camera) according to an embodiment of the present invention. This digital camera is disposed between the optical system 21 equipped with a lens and a diaphragm for collecting incident light from a subject, the two-plate CCD module 22 according to the present embodiment, and the optical system 21 and the module 22. An infrared cut filter 23 is provided.

  The digital camera according to the present embodiment also takes in a red (R) signal, a blue (B) signal and a green (G1, G2) signal, which will be described later, from the two-plate CCD module 22 and performs a correlated double sampling process or the like. A circuit 24, a preprocess circuit 25 that takes in an output signal of the CDS circuit 24 and performs gain control processing, and the like, and an analog signal R, G1, G2, B output from the preprocess circuit 25 is converted into a digital signal. The D / D conversion circuit 26 and the R, G1, G2, and B image signals output from the A / D conversion circuit 26 are used to perform signal processing such as white balance correction, gamma correction processing, and color sensitivity correction processing, and imaging. A circuit 27 that performs image signal compression and expansion processing, an image memory 28 connected to the circuit 27, and an external image (not shown) of captured image data processed by the circuit 27 And a recording / display circuit 29 to or displayed on the liquid crystal display unit provided on recorded in memory or the camera back or the like.

  The digital camera further includes a system control circuit 30 that performs overall control of the entire digital camera, a synchronization signal circuit 31 that generates a synchronization signal according to an instruction signal from the system control circuit 30, and each of the components in the CCD module 22 based on the synchronization signal. And a CCD drive circuit 32 for outputting a drive signal to the CCD.

  In the digital camera according to the present embodiment, the lens focal point and the aperture of the optical system 21 are controlled based on the instruction signal from the system control circuit 30, and the two CCDs in the module 22 pass through the optical system 21 and the infrared cut filter 23. An optical image is formed. Then, a red (R) signal, a blue (B) signal, and a green (G1, G2) signal are output from each CCD according to the received optical image, and the preprocess circuit 25 performs R, B, G1 according to the synchronization signal. , G2 signal gain control and the like, and the circuit 27 performs signal processing and the like based on an instruction from the system control circuit 30, thereby imaging based on the R, B, G1, and G2 signals output from the CCD module 22. The image is reproduced, and the image data compressed into data such as JPEG format is recorded in the external memory.

  FIG. 2 is a configuration diagram of the two-plate CCD module 22 shown in FIG. The two-plate CCD module includes a color separation prism 35 and two CCDs, a first CCD 36 and a second CCD 37. The color separation prism 35 is formed on the first prism member 35a, the second prism member 35b, the green (G = G1 + G2) reflecting dichroic film 38 formed therebetween, and the end surface of the second prism member 35b. And a dichroic film 39 for total reflection. The film 39 need not be a dichroic film, and may be any film that totally reflects incident light.

  As shown in FIG. 2, the first prism member 35a has a triangular cross section, a light incident surface 35c on which incident light is incident substantially perpendicularly, and a dichroic film disposed obliquely with respect to the light incident surface 35c. 38 is provided with an interface formed by vapor deposition, and a third surface facing the CCD 37.

  The second prism member 35b also has a triangular cross section, and is a reflection surface in which the total reflection film 39 is formed by vapor deposition on the interface in contact with the first prism member 35a (dichroic film 38) and the interface. And a third surface on which the CCD 36 faces.

  Incident light from the subject first enters perpendicularly to the light incident surface 35a of the first prism member 35a, and the green (G = G1 + G2) incident light is reflected by the dichroic film 38, and then is incident on the light incident surface 35a. Totally reflected and imaged on the second CCD 37. The red (R) and blue (B) incident light that has passed through the dichroic film 38 from the first prism member 35a and entered the second prism member 35b is reflected by the total reflection film 39, and further, the first prism member 35a. It is totally reflected at the interface and forms an image on the first CCD 36.

  In the color separation prism 35 of the embodiment shown in FIG. 2, green (G = G1 + G2) incident light incident on the first prism member 35a is reflected twice to form an image on the second CCD 37, and the second prism member 35b has a red color. Since the incident light of (R) and blue (B) is reflected twice to form an image on the first CCD 36, the image formed by the second CCD 37 is mirror-inverted with respect to the image formed by the first CCD 36. Never become.

  Further, the color separation prism 35 of the present embodiment can be shortened in size in the light incident direction because it is not necessary to provide the prism member 7b of FIG. 22, and the CCD module can be reduced in size, weight, and thickness. it can. However, if the CCD module is mounted on a digital camera that does not need to be thin, the color separation prism shown in FIG. 22 can be used.

  FIG. 3 is a schematic diagram of the surface of the CCD 36. In the CCD 36, a large number of light receiving portions 44 (each light receiving portion is also referred to as a “pixel” hereinafter) indicated by a rectangle in the illustrated example are formed on the surface portion of the semiconductor substrate 43. Each light receiving portion 44 is arranged in a square lattice pattern on the surface of the semiconductor substrate 43, a vertical transfer path 45 is formed on the right side of each column of the light receiving portions 44, and a lower side portion of the semiconductor substrate 43 is A horizontal transfer path (HCCD) 46 for transferring the signal charges read from each light receiving portion 44 and transferred through the vertical transfer path 45 in the horizontal direction is formed.

  “R” and “B” in each light receiving unit 44 in FIG. 3 indicate the color of the color filter provided on each light receiving unit (red is “R” and blue is “B”). That is, red (R) light and blue (B) light separated by the color separation prism 35 enter the CCD 36 according to the present embodiment, and the red (R) color filter in the light receiving unit 44. The light receiving unit 44 on which 57 is stacked detects the incident light quantity of red, and the light receiving unit 44 on which the blue (B) color filter 57 is stacked detects the incident light quantity of blue.

  FIG. 4 is an enlarged view of the light receiving unit 44 shown in FIG. 3 by four pixels, and shows the transfer electrode. The transfer electrodes 47, 48, and 49 of this embodiment have a three-layer polysilicon structure, and constitute an interline CCD that can read all pixels. In the example shown in the figure, the third polysilicon electrode 49 also serves as a read gate electrode for reading out a red (R) signal charge or a blue (B) signal charge. Each pixel R, B connected in the vertical direction is defined by a comb-like element isolation band 42 as viewed from above.

5 is a cross-sectional view taken along line VV in FIG. In the n-type semiconductor substrate 43, a P well layer 50 is formed on the surface side, and an N ⁺ layer 51 is formed on the surface portion in the P well layer 50. The signal charge generated by the incident light is accumulated in the N ⁺ layer 51. The N ⁺ layer 51 (impurity (phosphorus or arsenic (P or As)) concentration forming this signal charge storage portion has a concentration of about 5 × 10 ^{16 to 17} / cm ³ ) extends under the read gate electrode 49, Electric charges generated according to the amount of incident light are read out to the vertical transfer path 45 through the gate portion.

A shallow P ⁺ layer 53 is provided on a part of the surface of the semiconductor substrate 43 provided with the N ⁺ layer 51, and an SiO ₂ film 54 is provided on the outermost surface. The impurity (boron) concentration of the P ⁺ layer 53 is about 1 × 10 ¹⁸ / cm ³ and the depth is about 0.1 to 0.2 μm, and the defect level at the oxide film-semiconductor interface on the surface of the light receiving portion is reduced. It contributes to. Further, the transfer electrodes 47, 48 and 49 described above are formed on the upper surface of the SiO ₂ film 54 at a position avoiding the light receiving region, and a light shielding film 55 having an opening 55a in the light receiving region is further provided thereon. Further, a flattening film 56a is formed on the upper part, and a color filter 57 is further provided thereon, and a top lens (microlens) 58 is formed on the upper part via the flattening film 56b.

  FIG. 6 is a schematic diagram of the surface of the CCD 37. The CCD 37 has the same structure as the CCD 36 and is different from the CCD 36 in that the color filter provided on each light receiving portion 44 is green (G). As the green (G) color filter, two types G1 and G2 are used.

  FIG. 7 is a graph showing the difference in spectral characteristics between the color filters G1 and G2. This graph also shows the spectral characteristics of the red (R) and blue (B) color filters used in the CCD 36. Although the long wavelength side cannot be cut with a red (R) color filter, this long wavelength portion is cut by the infrared cut filter 23 shown in FIG. In FIG. 7, the spectral sensitivities of R and B are normalized with the peak sensitivity of G1.

  The characteristic of G1 and the characteristic of G2 are the same at the long wavelength end (the part where the characteristic falls), but a difference (hatched part) occurs at the short wavelength end side. By detecting this difference (G1-G2), it is possible to detect an incident light component in a wavelength range of 460 nm to 530 nm. This difference (G1-G2) corresponds to the negative sensitivity r (FIG. 7) in the photoreceptor that detects human red (R), and the received light amount indicating this negative sensitivity r is determined by the color filter R of the CCD 36. By subtracting from the amount of light received by the light receiving section, color reproduction faithful to human visibility can be achieved.

  Since the difference between G1 and G2 in the present embodiment is small, the circuit 27 shown in FIG. 1 may process both as green (G) signals particularly in image processing when generating a luminance signal. = G1 or G = G2 may be processed, and further G = (G1 + G2) / 2 may be processed.

  FIG. 8 is a layout diagram of CCDs in the two-plate CCD module 22. In contrast to the CCD 36 in which R pixels and G pixels are alternately arranged in a square lattice, a CCD 37 in which G1 pixels and G2 pixels are alternately arranged in a square lattice is shown in the lower right diagram of FIG. By adopting a so-called pixel shift arrangement in which the pixel pitch is shifted by 1/2 in the vertical and horizontal directions, the resolution can be further increased, and an existing signal processing IC for honeycomb pixel arrangement can be used. Image processing can be performed.

  However, it is not essential to arrange the two-plate CCDs 36 and 37 in a pixel shift arrangement, and as shown in the lower left diagram of FIG. 8, the pixels of the CCD 36 and the pixels of the CCD 37 are arranged at the same sampling point. You may do it. With this arrangement, false colors and color moire can be further reduced.

[Modification of First Embodiment]
In the first embodiment, as described with reference to FIG. 7, the difference G1-G2 between the color filters G1 and G2 is set to have a negative visibility r. However, the setting of G1 and G2 is not limited to this. For example, instead of obtaining the negative visibility r by the difference between G1 and G2, as shown in FIG. 9, a color filter g (= G2) that directly detects the negative visibility r and the same green as in the conventional case. The color filter G (= G1) to be detected may be alternately formed on each pixel of the CCD 37.

  Further, the G1 and G2 color filters may be configured by setting the characteristics of G1 and G2 so as to divide the intermediate wavelength range of red (R) and blue (B) into almost two as shown in FIG. , Faithful color reproduction becomes possible. In the case of FIG. 10, light with a wavelength of 460 nm to 620 nm is reflected by the dichroic film 38 of FIG. 2 and enters the CCD 37, of which light with a wavelength of 460 nm to 540 nm is received by a pixel having a G1 filter. Light is received by a pixel having a G2 filter.

[Second Embodiment]
In the above-described embodiment, a CCD in which each pixel is arranged in a square lattice shape has been described as an example. However, a so-called honeycomb pixel arrangement in which each pixel of the CCD is divided by 1/2 pitch for each row (Japanese Patent Laid-Open No. 10-136391). The present invention can also be realized with a CCD), and high resolution can be achieved.

  FIG. 11 is a schematic diagram of the surface of the first CCD 60 having a honeycomb pixel arrangement, and FIG. 12 is a schematic diagram of the surface of the second CCD 70 having a honeycomb pixel arrangement. Each pixel 61 provided in the CCD 60 has the same cross-sectional structure as FIG. The pixels 61 are shifted by ½ pitch for each row, and vertical transfer paths 62 meander between the pixels 61 adjacent in the horizontal direction. The cross-sectional structure of each pixel 71 of the CCD 70 that detects a green (G) color signal by the color filters G1 and G2 is the same as that in FIG. 5 (the color of the color filter is G1 and G2), and is adjacent in the horizontal direction. A vertical transfer path 72 is arranged between the pixels 71 in a meandering manner.

  FIG. 13 is an enlarged view of four pixels of the CCD 70, and FIG. 14 is a detailed view showing transfer electrodes in the circle XIV of FIG. The CCD 60 has the same structure. Each pixel 71 is defined by the element isolation band 73 formed in a diamond shape, and signal charges are read from the gate portion 74 provided in the element isolation band 73 to the vertical transfer path 72 provided between the pixels. On the vertical transfer path 72, transfer electrodes having a two-layer polysilicon structure are provided so as to overlap each other, and four transfer electrodes 81, 82, 83, 84 are associated with one pixel. Accordingly, the CCD having the honeycomb pixel arrangement is a CCD which can read out all pixels (progressive operation) with the transfer electrode having a two-layer polysilicon structure.

  As in the second embodiment, even when two CCDs 60 and 70 having the same number of pixels and having a honeycomb pixel arrangement are used, the same effect as in the first embodiment can be obtained, and by using a CCD having a honeycomb pixel arrangement, Compared to the first embodiment, the number of pixels can be further increased, and the transfer operation with the two-layer polysilicon structure can be performed, so that the manufacturing cost can be reduced and the manufacturing yield can be improved. Become. As the G1 and G2 color filters, any of the G1 and G2 filters described in FIGS. 7, 9, and 10 is used.

  FIG. 15 is a layout diagram of CCDs in the two-plate CCD module used in the present embodiment. Compared with the CCD 60 in which R pixels and G pixels are arranged in a honeycomb shape, a CCD 70 in which G1 pixels and G2 pixels are arranged in a honeycomb shape has a pixel position of 1/2 as shown in the lower right diagram of FIG. A so-called pixel shift arrangement in which the pixels are displaced in the horizontal direction by the pitch is adopted. As a result, higher-resolution imaging is possible, and each of the R, G1, G2, and B pixel arrangements is a square lattice arrangement, and image processing is performed using an existing signal processing IC having a square lattice pixel arrangement. Can be performed.

  However, in the present embodiment as well, it is not always necessary to dispose the two CCDs 60 and 70 in a pixel shift manner. As shown in the lower right diagram of FIG. 15, each pixel of the CCD 60 and each pixel of the CCD 70 have the same sampling point. It may be arranged as follows. With this arrangement, false colors and color moire can be further reduced.

[Third Embodiment]
In each of the above-described embodiments, the example in which the CCD is used as the solid-state imaging device has been described. However, the present invention can be realized even if another solid-state imaging device, for example, a CMOS image sensor is used.

  FIG. 16 is a schematic view of the surface of the first CMOS image sensor. The first CMOS type image sensor 90 is formed on the surface portion of the n-type semiconductor substrate 91 and has a vertical scanning circuit 92 formed on the side of the light receiving region, a horizontal scanning circuit formed on the bottom side of the semiconductor substrate 91, and the like ( Signal amplification circuit, A / D conversion circuit, synchronization signal generation circuit, etc.) 93.

  In the light receiving region, a large number of light receiving portions 94 are arranged in a two-dimensional array, in this example, a square lattice. 17 is a schematic sectional view taken along line XVII-XVII in FIG. Each pixel of the first CMOS image sensor 90 also has a red (R) or blue (B) color filter 97 (FIG. 17), as in the above-described embodiment.

In each light receiving portion 94 of the first CMOS type image sensor 90, as shown in FIG. 16, a P well layer 95 is formed on the surface side of the n type semiconductor substrate 91, and an N ⁺ layer 99 is formed on the surface portion in the P well layer 95. Is formed. In this example, the N ⁺ layer 99 has an impurity (phosphorus or arsenic (P or As)) concentration of about 5 × 10 ^{16 to 17} / cm ³ .

The N ⁺ layer 99 is connected to the color signal detection amplifier 106 through an ohmic contact 105. In order to perform this ohmic contact 105 satisfactorily, the impurity concentration of this contact portion in the N ⁺ layer 99 is set to 1 × 10 ¹⁹ / cm ³ or more in this example. An equivalent circuit of the amplifier 106 is shown in FIG.

With such a cross-sectional structure of the light receiving portion, the reset transistor is turned on before color image capturing, and a predetermined amount of charge is accumulated in each PN junction portion of the N ⁺ layer 99. The accumulated charge in the PN junction of the N ⁺ layer 99 is discharged by the amount of photocarriers generated according to the amount of incident light reaching the light receiving unit, and the amount of change in charge at the PN junction of the N ⁺ layer 99 is It is read by the amplifier 106 as a color signal.

  FIG. 19 is a schematic view of the surface of the second CMOS image sensor. The second CMOS type image sensor 98 has the same structure as the light receiving portions shown in FIGS. 16 and 17, and only the color filter formed on each light receiving portion is different. That is, in the second CMOS image sensor 98, any one of the G1 filters and G2 filters described in FIGS. 7, 9, and 10 is alternately used as the color filter 97 (FIG. 17) formed on each light receiving portion. Be placed.

  Although not shown in FIG. 17, in the first and second CMOS type image sensors 90 and 98, a light shielding film, a planarizing layer, a wiring layer, a microlens, and the like are laminated on the surface of the semiconductor substrate.

  FIG. 20 is a two-dimensional plan view corresponding to one pixel of the first and second CMOS type image sensors 90 and 98. On the surface of the semiconductor substrate 91, each light receiving portion 94 is separated like a grid by element separation bands 110 by LOCOS extending vertically and horizontally, and in the example shown, each light receiving portion 94 has a substantially square shape. .

The N ⁺ layer 99 described above is formed in most of each light receiving area, and a strip-shaped peripheral circuit section 111 is provided at the upper right end. The peripheral circuit unit 111 is provided with the amplifier (source follower amplifier) 106 described above, and the color signal is read from the N ⁺ layer 99 connected through the contact hole 105 provided in the light receiving unit.

  In the drawing, a signal output line 112 and a reset line 114 are laid on an element isolation band 110 provided in the vertical direction, and a selection signal line 115 and a power supply line are provided on the element isolation band 110 provided in the horizontal direction. 113 is provided. The signal output line 112 is connected to the output of the amplifier 106. In FIG. 20, the connection line to the peripheral circuit is omitted, but the power supply voltage is applied to the power supply line 113, and the reset signal is applied to the reset line 114.

  These selection signals and reset signals are controlled by the vertical scanning circuit 92 and the horizontal scanning circuit 93 shown in FIGS. The dotted rectangular frame 107 described on the light receiving portion indicates the position of the opening of the light shielding film, and light passes only inside this, and the outside, that is, the peripheral circuit portion 111 and the contact hole 105 are shielded from light. . As shown in this figure, since the number of signal wirings and the number of peripheral circuits that need to be provided in one light receiving portion is small, the CMOS image sensor of this embodiment can widen the light receiving portion area, A bright image can be captured.

  Thus, even when the two-plate color solid-state imaging device is configured using the first CMOS image sensor 90 and the second CMOS image sensor of the present embodiment, the same effects as those of the first and second embodiments can be obtained. Can do.

  Note that the third embodiment described above is an example in which the light receiving portions are arranged in a square lattice pattern. For example, as described in US Pat. No. 4,558,365, the light receiving portions in each row are arranged at 1/2 pitch. Needless to say, an NMOS type image sensor having a so-called honeycomb pixel arrangement may be used. Further, the present invention is not limited to the CMOS type and the NMOS type, but may be other types of MOS type image sensors.

  According to the two-plate color solid-state imaging device and the digital camera equipped with the two-plate color solid-state imaging device of each embodiment described above, full-color imaging is possible, and 1 in comparison with the case where a single-plate solid-state imaging device having the same resolution is used. Since the size of the pixel can be increased, the manufacturing yield of the solid-state imaging device can be increased, and the cost can be reduced even with the two-plate type.

  The two-plate color solid-state imaging device according to the present invention can be reduced in size and cost, and is useful for mounting on a digital camera such as a digital still camera or a digital video camera.

It is a block block diagram of the digital still camera which concerns on one Embodiment of this invention. FIG. 2 is a configuration diagram of a two-plate CCD module according to the first embodiment shown in FIG. 1. FIG. 3 is a schematic surface view of the first CCD shown in FIG. 2. FIG. 4 is an enlarged view of four pixels of the first CCD shown in FIG. 3. FIG. 6 is a cross-sectional view taken along line VV in FIG. 5. It is a surface schematic diagram of the 2nd CCD shown in FIG. It is a graph which shows the spectral characteristics of color filter R, G1, G2, B used for 1st CCD and 2nd CCD. FIG. 3 is an explanatory diagram of arrangement of a first CCD and a second CCD shown in FIG. 2. It is a graph which shows the modification of the spectral characteristic of the color filters G1 and G2 used for 2nd CCD. It is a graph which shows another modification of the spectral characteristic of the color filters G1 and G2 used for 2nd CCD. It is the surface schematic diagram of 1st CCD which concerns on 2nd Embodiment of this invention. It is the surface schematic diagram of 2nd CCD which concerns on 2nd Embodiment of this invention. FIG. 12 is an enlarged view of four pixels of the first CCD shown in FIG. 11. It is an enlarged view in the circle XIV of FIG. It is arrangement | positioning explanatory drawing of 1st CCD shown in FIG. 11, and 2nd CCD shown in FIG. It is a surface schematic diagram of the 1st CMOS type image sensor which concerns on 3rd Embodiment of this invention. FIG. 17 is a schematic cross-sectional view taken along line XVII-XVII in FIG. 16. FIG. 18 is an equivalent circuit diagram of the amplifier shown in FIG. 17. It is a surface schematic diagram of the 2nd CMOS type image sensor concerning a 3rd embodiment of the present invention. FIG. 20 is a schematic plan view for one pixel shown in FIGS. 16 and 19. It is a block diagram of the conventional 3 plate-type color solid-state imaging device. It is a block diagram of the conventional 2 plate type color solid-state imaging device. It is a top view of the color filter used for the conventional single plate type color solid-state imaging device.

Explanation of symbols

22 Two-plate CCD module 35 Color separation prism 36, 60 First CCD
37,70 2nd CCD
38 Green reflective dichroic film 39 Total reflective dichroic film 44, 61, 71 Light receiving portions 45, 62, 72 Vertical transfer paths 51, 99 N ⁺ layer 90 First CMOS image sensor 98 Second CMOS image sensor

Claims (16)

  A color separation prism that separates incident light from a subject into light including a first color and a second color and light including a third color and a fourth color, and the first color and the first color separated by the color separation prism A two-plate color solid-state imaging device comprising: a first solid-state imaging device that receives incident light of two colors; and a second solid-state imaging device that receives incident light of the third color and the fourth color separated by the color separation prism. In the apparatus, a color filter that transmits the first color or the second color is formed in each of a plurality of light receiving portions provided in an array on the first solid-state image sensor, and the array is arranged on the second solid-state image sensor. A two-plate type color solid-state imaging device, wherein a color filter that transmits the third color or the fourth color is formed in each of a plurality of light receiving portions provided in a shape.   The color filter that transmits the first color and the color filter that transmits the second color are alternately arranged vertically and horizontally on each light receiving portion of the first solid-state imaging device. The two-plate color solid-state imaging device described.   2. The color filter that transmits the third color and the color filter that transmits the fourth color are alternately arranged vertically and horizontally in each light receiving portion of the second solid-state imaging device. The two-plate color solid-state imaging device according to claim 2.   The first and second color lights received by the first solid-state image sensor are blue and red lights of the three primary colors, respectively, and the third and fourth colors received by the second solid-state image sensor. The two-plate color solid-state imaging device according to any one of claims 1 to 3, wherein the color light is light in an intermediate wavelength range between the blue and the red.   The third color and the fourth color are detected so as to detect the amount of incident light having a wavelength of 460 nm to 530 nm from the difference between the third color detection signal and the fourth color detection signal output from the second solid-state imaging device. The two-plate color solid-state imaging device according to claim 4, wherein a color filter is formed.   5. The two-plate color solid-state image pickup device according to claim 4, wherein the third color filter formed on the second solid-state image pickup element is formed to transmit light having a wavelength of 460 nm to 530 nm. .   5. The color filter of the third color and the color filter of the fourth color formed on the second solid-state imaging device are formed so as to divide the green wavelength range into two. The two-plate color solid-state imaging device described.   8. The light receiving portion of the first solid-state imaging device is disposed so that the light receiving portions of the second solid-state imaging device are shifted by ½ pitch. A two-plate color solid-state imaging device according to claim 1.   8. The two-plate type according to claim 1, wherein each light receiving portion of the first solid-state imaging device is disposed at the same sampling point as each light receiving portion of the second solid-state imaging device. Color solid-state imaging device.   The two-plate type color according to any one of claims 1 to 9, wherein each of the first solid-state imaging device and the second solid-state imaging device is constituted by a charge coupled device (hereinafter referred to as a CCD). Solid-state imaging device.   10. The two-plate color solid-state imaging device according to claim 1, wherein each of the first solid-state imaging device and the second solid-state imaging device is configured by a MOS image sensor.   The two-plate color solid-state image pickup device according to any one of claims 1 to 11, wherein an arrangement of light receiving portions of the first solid-state image pickup element and the second solid-state image pickup element is a honeycomb arrangement.   The incident light from the subject is separated into light including the first color and the second color and light including the third color and the fourth color, and the separated incident light of the first color and the second color is the first solid. In a color separation prism of a two-plate color solid-state image pickup device that enters the image pickup device and makes the incident lights of the third color and the fourth color separated incident on the second solid-state image pickup device, the first color and the second color A prism member that reflects incident light to be incident on the first solid-state image sensor; and a prism member that reflects incident light of the third color and the fourth color and is incident on the second solid-state image sensor. A color separation prism for a two-plate color solid-state imaging device.   13. The two-plate color solid-state imaging device according to claim 1, wherein the color separation prism according to claim 13 is used as the color separation prism.   A digital camera comprising the two-plate color solid-state imaging device according to any one of claims 1 to 12.   The two-plate color solid-state imaging device according to claim 6 or 7, and the red sensitivity detected by the first solid-state imaging device by a detection signal of light having a wavelength of 460 nm to 530 nm detected by the two-plate color solid-state imaging device. A digital camera comprising signal processing means for performing correction.

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