JP2005260318A - Two-board type color solid-state imaging apparatus and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and small-sized two-board type color solid-state imaging apparatus carrying out color imaging with high sensitivity, high resolution and high image quality. <P>SOLUTION: In the two-board type color solid-state imaging apparatus provided with: a color separation prism 35 for separating a three-primary color incident light into green, red and blue colors; a first solid-state imaging element 36 for receiving the red and blue color incident light beams separated by the prism 35 and providing outputs of a red signal in response to the luminous quantity of red color and a blue signal in response to the luminous quantity of blue color; and a second solid-state imaging element 37 for receiving the green incident light separated by the prism 35 to provide an output of a green signal in response to the luminous quantity of green color, an yellow filter for transmitting through the red light is provided to an upper part of each of red color detecting light receiving sections and a cyan filter for transmitting through the blue light is provided to an upper part of each of blue color detecting light receiving sections among a plurality of light receiving sections of the solid-state imaging element 36. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a two-plate color solid-state imaging device and a digital camera.

  As a color solid-state imaging device used for a digital camera, there are known a single-plate type using one solid-state imaging device and a multi-plate type using a plurality of solid-state imaging devices (Patent Document 1, Patent Document 2).

  The former is a discrete (mosaic) arrangement of a plurality of color filters on a single solid-state imaging device, and is cheaper but inferior to the latter in terms of sensitivity, resolution, and color reproducibility. Further, in the single-plate solid-state image sensor, the problem of a decrease in manufacturing yield due to high pixel (miniaturization) has become serious, which causes an increase in the cost of the solid-state image sensor.

  The latter, for example, a three-plate type color solid-state imaging device, as shown in FIG. 16, has dedicated solid-state imaging elements 1 and 2 for each of three color components (for example, red (R), green (G), and blue (B)). , 3 are used exclusively for TV cameras for broadcasting stations that are excellent in resolution, color reproducibility, etc. and require high image quality. However, since a plurality of image sensors (solid-state imaging devices) 1, 2 and 3 and a large color separation prism 4 are required, there is a problem that the system cost increases and the digital camera increases in size.

  In recent years, an example in which a three-plate color solid-state imaging device is applied to a relatively low-cost digital still camera or camcorder is increasing. The reason is that the adverse effects associated with the increase in the number of pixels of a single-plate solid-state imaging device have become prominent. That is, there is a concern that the manufacturing yield and performance of the solid-state imaging device itself will rapidly decrease due to pixel miniaturization and the like.

  For this reason, multi-plate imaging systems have been constructed using high-yield, high-performance solid-state imaging devices. If the manufacturing yield of the solid-state imaging device is high, the cost of the multi-plate imaging device is simply doubled or tripled, even if the cost of the color separation prism is taken into consideration. It will not be.

  In recent years, the resolution of image sensors has been increasing (multiple pixels). In the future, as the number of pixels increases, that is, the unit pixel size becomes finer, there are concerns about image quality degradation such as a decrease in sensitivity, false signals, false colors, and shading.

  In general, when a color image is taken using a single-plate solid-state image sensor, the color of the subject, that is, the color component of light incident on the imaging system, is discretely arranged in a two-dimensional array on the surface of a single solid-state image sensor Each color signal needs to be detected as a different color signal (for example, R, G, B).

  Therefore, in a single-plate color solid-state image pickup device, a color filter is generally disposed on each pixel, and in the entire solid-state image pickup device, three or four color filters are arranged in a mosaic shape (Patent Document 1) or a stripe shape. It is the target.

  The color filter includes a primary color system (R, G, B) and a complementary color system (Ye, Cy, Mg, etc.) filter composed of its complementary colors. Conventionally, from the viewpoint of emphasizing color reproducibility, primary color (R, G, B) color filters are often used in digital cameras and the like. On the other hand, the complementary color filter (Cy, Ye, Mg, etc.) includes two primary color components in its color signal component (for example, Mg includes blue B and red R). Although the sensitivity is higher than when a filter is used, there is a problem that the S / N is lowered in the process of color separation processing, and faithful color reproduction is difficult.

  Regarding color filters, the following problems have become more apparent. Color filter materials include so-called pigments and dyes. The pigment system uses a pigment as a coloring material, so it has excellent light resistance and heat resistance and is often used in digital cameras and the like. However, as the pixels become finer, the granularity of the pigment has begun to affect the image quality, and since the thickness of the color filter cannot be reduced, the distance between the microlens and the light receiving portion can be shortened. There are problems such as difficulty.

  On the other hand, the dye-based color filter, unlike the pigment-based one, needs to improve light resistance and heat resistance, but has no problem of graininess and can be easily thinned. Therefore, with the miniaturization of pixels, dye-based color filters are being reviewed instead of pigment-based color filters.

  However, in order to adopt a dye-based color filter, in addition to light resistance and heat resistance, the spectral transmittance of each color component is controlled, the amount of overlap of spectral spectra of different color components is reduced, and color reproduction by color mixing is performed. It is not easy to obtain a color resist material that prevents functional deterioration and at the same time has functional performance as a resist material (for example, fine pattern formation is possible and development processing is equivalent to that of a conventional photoresist).

U.S. Pat. No. 3,971,065 JP-A-3-274523

  As described above, a color solid-state imaging device mounted on a digital camera has reached a limit in terms of technology and cost in order 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 small and low-cost digital camera that can faithfully reproduce colors with a two-plate type color solid-state imaging device. In this case, the color filter material to be stacked on the solid-state image sensor and the combination with the color separation prism can be optimized, and high-sensitivity, high-resolution, high-quality color images can be captured. It is necessary to reduce costs.

  An object of the present invention is to provide a two-plate color solid-state imaging device and a digital camera that are capable of capturing a small, high-sensitivity, high-resolution, high-quality color image at low cost.

  The two-plate color solid-state imaging device of the present invention receives a color separation prism that separates incident light of three primary colors into green, red, and blue, and receives the incident light of red and blue separated by the color separation prism. A first solid-state imaging device that outputs a red signal corresponding to a red light amount and a blue signal corresponding to a blue light amount, and receiving the green incident light separated by the color separation prism, and according to the green light amount In the two-plate color solid-state imaging device including a second solid-state imaging device that outputs a green signal, a complementary color that transmits red light above the red-detecting light-receiving portion among the plurality of light-receiving portions of the first solid-state imaging device. A first color filter of the first color filter is provided, and a second color filter of a complementary color system that transmits blue light is provided above the blue light receiving unit among the plurality of light receiving units of the first solid-state imaging device. To do.

  As described above, by combining the color separation prism and the complementary color filter, a two-plate color solid-state imaging device capable of capturing a color image with a small size, high sensitivity, high resolution, and high image quality at low cost can be obtained. .

  In the two-plate color solid-state imaging device of the present invention, the first color filter is a yellow (Ye) filter, and the second color filter is a cyan (Cy) filter.

  Blue color is separated by a yellow filter that has a broader characteristic than the red spectral characteristic and separated into the red detection light receiving part, and blue is separated by a cyan filter that has a broader spectral characteristic than the blue spectral characteristic. Since the light is incident on the portion, the light absorption of the color filter itself can be minimized, so that the sensitivity can be maintained higher than that of the primary color filter.

  In the two-plate color solid-state imaging device of the present invention, the first color filter and the second color filter are constituted by a dye system.

  When a dye-based color filter is used, adjacent color filters of different colors may be mixed in the boundary region. However, the first solid-state imaging device (B, R detection) according to the present invention is originally in the middle. Since light of the G component that is the wavelength does not enter, even if the color filter is mixed, a decrease in color reproducibility due to the entrance of the incident light of the G component is minimized. Therefore, the range of material selection for the dye-based color filter is expanded.

  In the two-plate color solid-state imaging device of the present invention, the first color filter and the second color filter are formed in a mosaic shape or a stripe shape.

  Thus, it does not depend on the shape of the color filter, and any color filter arrangement in a mosaic shape or a stripe shape can be used.

In the two-plate color solid-state imaging device of the present invention, the PN junction depth Xj (B) of the blue color detection light receiving unit, the PN junction depth Xj (R) of the red color detection light receiving unit, and the second solid state imaging device. The PN junction depth Xj (G) of the green light detecting light receiving portion provided in the element is Xj (B) <Xj (G) <Xj (R)
It is manufactured so as to satisfy the relationship.

  Since Xj (R), Xj (G), and Xj (B) are manufactured in consideration of the optical absorption coefficient for each color of incident light, the sensitivity of each color can be maximized.

  In the two-plate color solid-state imaging device according to the present invention, the color separation prism includes a dichroic mirror that reflects green light and transmits red and blue light in incident light.

  With this configuration, it is possible to perform color separation with reduced incident light loss.

  In the two-plate color solid-state imaging device of the present invention, the color separation prism includes a green trimming filter at the green light exit, and a magenta (Mg) trimming filter at the red and blue light exits. It is characterized by providing.

  With this configuration, the spectral characteristics of the light incident on the first and second solid-state imaging elements are almost ideal incident light spectra.

  In the two-plate color solid-state imaging device of the present invention, the light receiving portions provided in each of the first solid-state imaging device and the second solid-state imaging device are both arranged in a square lattice shape or a honeycomb shape. .

  The present invention can be applied to a solid-state imaging device having any pixel arrangement.

  The two-plate color solid-state imaging device of the present invention is characterized in that each of the first solid-state imaging device and the second solid-state imaging device is a CCD type or MOS type image sensor.

  The present invention can be applied regardless of CCD type or MOS type.

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

  This makes it possible to capture a color image with high sensitivity, high resolution, and high image quality.

  According to the present invention, high-sensitivity, high-resolution, high-quality color imaging is possible, and the imaging apparatus can be reduced in size and cost. In particular, since a dye-based color filter can be used as a complementary color-based color filter, the selection range of the color filter material can be widened and the image quality can be improved.

  In addition, one of the solid-state image sensors does not require a color filter, and the other solid-state image sensor requires only two color filters, so the manufacturing process of the solid-state image sensor itself can be simplified and the production yield is improved. Cost reduction can be achieved.

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

  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 includes an optical system 21 equipped with a lens and a diaphragm for collecting incident light from a subject, a two-plate color solid-state imaging device 22 according to the present embodiment, and the optical system 21 and a two-plate color solid-state imaging device 22. And an infrared cut filter 23 disposed between the two.

  The digital camera according to the present embodiment also receives a red (R) signal, a green (G) signal, and a blue (B) signal output from the two-plate color solid-state imaging device 22 and performs a correlated double sampling process and the like. A preprocess circuit 25 that takes in an output signal of the CDS circuit 24 and performs gain control processing, and an A / D conversion circuit that converts R, G, and B analog signals output from the preprocess circuit 25 into digital signals. 26 and signal processing for taking R, G, and B image signals output from the A / D conversion circuit 26 and performing signal processing such as white balance correction and gamma correction processing, and signal compression and expansion processing of the captured image The circuit 27, the image memory 28 connected to the signal processing circuit 27, and the captured image data processed by the signal processing circuit 27 are recorded in an external memory (not shown) And a recording / display circuit 29 to or displayed on the liquid crystal display unit provided on the 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 in response to an instruction signal from the system control circuit 30, and a color solid-state imaging device 22 based on the synchronization signal. And a solid-state image sensor drive circuit 32 that outputs a drive signal to each solid-state image sensor.

  In the digital camera of the present embodiment, the lens focus and diaphragm of the optical system 21 are controlled based on an instruction signal from the system control circuit 30, and the two solid-state image sensors in the module 22 are passed through the optical system 21 and the infrared cut filter 23. An optical image of the subject is formed. Then, a red (R) signal, a green (G) signal, and a blue (B) signal are output from each solid-state imaging device according to the received optical image, and the preprocess circuit 25 performs R, G, B according to the synchronization signal. Signal gain control or the like is performed, and the signal processing circuit 27 performs image processing or the like based on an instruction from the system control circuit 30, thereby imaging based on the R, G, and B signals output from the color solid-state imaging device 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 color solid-state imaging device 22 shown in FIG. The two-plate color solid-state imaging device includes a color separation prism 35 and two solid-state imaging elements, a first solid-state imaging element 36 and a second solid-state imaging element 37. The color separation prism 35 includes a first prism member 35a, a second prism member 35b, a green (G) reflecting dichroic mirror 38 formed therebetween, and a total reflection formed on an end surface of the second prism member 35b. Dichroic mirror 39. The film 39 does not need to be a dichroic mirror, and may be any film that totally reflects incident light.

  Since mixed light of red and blue is incident on the first solid-state imaging device 36, a color filter is formed on the top of each pixel of the first solid-state imaging device 36 to separate red and blue. As this color filter, in this embodiment, a complementary color Ye (yellow) color filter is used to separate red, and a complementary color Cy (cyan) color filter is used to separate blue.

  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 mirror disposed obliquely with respect to the light incident surface 35c. 38 is provided with an interface formed by vapor deposition and a third surface on which the solid-state imaging device 37 faces. A trimming filter 40 that adjusts the waveform of the green light is formed on the third surface, that is, the green (G) light emission port, so that the solid-state imaging device 37 does not include the green color filter.

  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 contacting the first prism member 35a (dichroic mirror 38) and the interface. And a third surface on which the solid-state imaging device 36 faces. An Mg (magenta) trimming filter 41 that adjusts the waveform of the incident light to the solid-state image sensor 36 is formed on the third surface, that is, the red and blue light emission ports.

  Incident light from the subject first enters the light incident surface 35a of the first prism member 35a perpendicularly, and the green (G) incident light is reflected by the dichroic mirror 38, and then totally reflected by the light incident surface 35a. Then, an image is formed on the second solid-state imaging device 37. The red (R) and blue (B) incident light that has passed through the dichroic mirror 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 solid-state image sensor 36.

  In the color separation prism 35 of the embodiment shown in FIG. 2, the green (G) incident light incident on the first prism member 35a is reflected twice to form an image on the second solid-state image sensor 37, and the second prism member 35b. In addition, since the incident light of red (R) and blue (B) is reflected twice to form an image on the first solid-state image sensor 36, the second solid is formed with respect to the image formed by the first solid-state image sensor 36. The image formed by the image sensor 37 is not mirror-inverted.

  Since the color separation prism 35 of this embodiment can shorten the dimension in the light incident direction, the color solid-state imaging device can be reduced in size, weight, and thickness. Further, since the light is reflected twice as described above, there is an advantage that the focal length of the optical system 21 can be increased.

  The shape of the prism that splits the incident light into green light and red and blue light is not limited to that shown in FIG. 2, and for example, as shown in FIG. A simple structure having a dichroic mirror 43 that reflects green light and transmits red and blue light on the surface may be used. Even in this case, the Cy color filter 45 or the Ye color filter 46 is mounted on the light receiving portion of the first solid-state image sensor 36, and no color filter is mounted on the second solid-state image sensor 37. do not do.

  FIG. 4 shows how the spectral spectrum changes until the light incident on the optical system reaches the surfaces of the solid-state imaging devices 36 and 37. As shown in FIGS. 2 and 3, since the IR cut filter 23 is inserted in the camera lens system, the long wavelength side of R is steep at 700 nm or more as shown by the broken line in FIG. The light intensity has dropped.

The green G light reflected from the dichroic mirror (FIG. 4 (a)) or the transmitted red R and blue B light (FIG. 4 (b)) passed through the conventional R, G, B primary color filters. It shows sharp spectral characteristics compared to the characteristics. However, there are problems such as leakage of components on the short wavelength side or the long wavelength side, and the boundary wavelength changing depending on the incident light angle. For example, in FIG. 4A, it has spectral characteristics at a wavelength of 500 nm or less or a wavelength of 600 nm or more.

  In order to improve this, a trimming filter is usually inserted into the prism. In the embodiment shown in FIG. 2, the G trimming filter 40 is used for green (G) light, and the magenta (Mg) trimming filter 41 is used for red (R) and blue (B) light. I am using it. The spectral characteristics of the trimming filters 40 and 41 are shown in FIGS.

  As shown in FIGS. 6A and 6B, the spectral characteristics of light that passes through the trimming filters 40 and 41 and finally enters the solid-state imaging devices 37 and 36 are almost ideal incident light spectra.

  In particular, the solid-state image sensor 36 has a feature that the probability that red R and blue B are mixed with green G is extremely low because there is no G component in the incident light.

  In the two-plate color solid-state imaging device of the present embodiment, all the solid-state imaging elements 37 are assigned to green (G) signals, which is extremely advantageous for generation of luminance signals, and high resolution is realized. In particular, green (G) has sensitivity over almost the entire surface of the solid-state imaging device 37, so that there is almost no insensitive portion of incident light of green (G), and there is an effect that generation of false signals can be suppressed.

  Regarding color reproducibility, color reproduction can be performed using a red (R) signal and a blue (B) signal obtained from the solid-state image sensor 36 at the same sampling point as the green (G) signal of the solid-state image sensor 37. There is an effect that the problem of color misregistration and false color can be reduced. Since only green (G) light is incident on the solid-state imaging device 37, no color filter is necessary in the first place.

  On the other hand, since red (R) light and blue (B) light are incident on the solid-state image sensor 36, as described above, cyan (Cy) and yellow (Ye), which are complementary color filters, are replaced with the solid-state image sensor. 36 are arranged in a mosaic on the surface and separated. In order to separate red (R) and blue (B), a primary color filter may be used. However, for the reason described later, complementary color filters, particularly cyan (Cy) and yellow (Ye) are preferable.

  FIG. 7 shows how the spectral spectrum changes before the light that has reached the surface of the solid-state imaging device reaches the pixel light receiving unit. FIG. 7A is a reprint of FIG. 6B, showing the spectral characteristics of the light reaching the solid-state imaging device 36, and includes red (R) and blue (B) light.

  FIG. 7B is a graph showing the spectral characteristics of the cyan (Cy) filter. The cyan filter is a color filter that transmits blue (B) with a short wavelength and green (G) with a medium wavelength, and has a broader characteristic on the longer wavelength side than a primary color blue filter. However, since the light incident on the solid-state image sensor 36 does not include green (G), when the light having the spectral characteristics shown in FIG. 7A enters the cyan filter, as shown in FIG. Only the light of (B) is transmitted without being obstructed by the cyan filter and reaches the light receiving section.

  Similarly, FIG. 7C is a graph showing the spectral characteristics of the yellow (Ye) filter. The yellow filter is a color filter that transmits green (G) having a medium wavelength and red (R) having a long wavelength, and has a broader characteristic on the lower wavelength side than a primary color red filter. For this reason, when the light having the spectral characteristics shown in FIG. 7A that does not include green (G) is incident on the yellow filter, red (R) is disturbed by the yellow filter as shown in FIG. 7E. All pass through and reach the light receiving part.

  FIG. 8 is an enlarged view of the color filter array for four pixels of the solid-state image sensor 36. In this example, the cyan filter and the yellow filter are mosaic-shaped, that is, the cyan filter and the yellow filter are alternately arranged in the vertical direction and the horizontal direction. Accordingly, the color filters of different colors are formed in such a state that the end portions are in contact with each other.

  This is done by first applying a color resist of one color and patterning it, then removing the unnecessary part and then applying another color filter to fill the part where the first color filter does not exist and the other color filter. This is because is patterned. Dye-type color filters have the advantage of having no graininess and being easy to form a thin film. However, when different colors come into contact with each other in this way, there is a concern that the dyes are mixed with each other over time.

  However, as in the present embodiment, the solid-state image sensor 36 detects only blue (B) and red (R) light, and the solid-state image sensor 36 does not receive green (G) light. Even if the color mixture of the dyes progresses in the color filter boundary region 8 and the cut-off wavelength on the long wavelength side of the cyan filter in FIG. 7B slightly moves, or on the short wavelength side of the yellow filter shown in FIG. Even if the cut-off wavelength moves slightly, there is an advantage that red (R) light and blue (B) light are hardly affected.

  For this reason, room for material design or material selection of the dye-based color filter material is widened, and optimization of exposure and development processing conditions becomes easy.

  The two-plate color solid-state imaging device according to the above-described embodiment uses the first solid-state imaging device 36 and the second solid-state imaging device 37. As the solid-state imaging devices 36 and 37, CMOS image sensors and other MOSs are used. A type image sensor may be used, or an image sensor using a charge coupled device (CCD) may be used.

  Further, there is no limitation on the pixel arrangement in each of the solid-state image pickup devices 36 and 37, and each pixel is arranged at a ½ pixel pitch for each row as described in a square lattice arrangement or as described in JP-A-10-136391. It may be a pixel arrangement shifted so-called, a so-called honeycomb arrangement. The present embodiment is applicable to both interline type and frame transfer type CCDs.

  Furthermore, in the embodiment, the cyan filter and the yellow filter provided in the solid-state image sensor 36 are arranged in a mosaic shape, but each color filter may be arranged in a stripe shape.

  FIG. 9A is a schematic diagram of the surface of a CCD 36a used as the solid-state imaging device 36 described above, and FIG. 9B is a schematic diagram of the surface of a CCD 37a used as the solid-state imaging device 37 in the same manner. In the figure, R, G, and B indicate pixels that detect a red (R) signal, pixels that detect a green (G) signal, and pixels that detect a blue (B) signal. A color filter is not stacked on a pixel that detects a G signal, a cyan (Cy) color filter is stacked on a pixel that detects a B signal, and a yellow (Ye) pixel is detected on a pixel that detects an R signal. Color filters are stacked.

  In the CCD 36a, the cyan color filter and the yellow color filter are arranged in a mosaic pattern. For example, as shown in FIGS. 10A and 10B, the stripe-like cyan color filter and the stripe-like yellow color filter are alternately arranged. The structure provided in may be sufficient.

  In FIG. 9, a vertical transfer path (VCCD) 51 is formed on the right side of the pixels 50 in each column, a horizontal transfer path (HCCD) 52 is formed on the lower side, and an amplifier 53 is provided at the exit of the horizontal transfer path 52. The provided configuration is the same as that of a general CCD.

  11A is a schematic diagram of the surface of a CCD 36b used as the solid-state image sensor 36, and FIG. 11B is a schematic diagram of the surface of a CCD 37b used as the solid-state image sensor 37. In this embodiment, the pixel arrangement is a honeycomb arrangement, and the cyan filter and the yellow filter are alternately provided by the CCD 36b as in the first embodiment. A vertical transfer path 62 is meandered on the right side of each pixel column arranged in the vertical direction of each pixel 61, a horizontal transfer path 63 is formed at the lower side, and an amplifier 64 is provided at the outlet of the horizontal transfer path 63. Yes.

  In the case of the honeycomb arrangement, as shown in FIGS. 12A and 12B, stripe-like cyan (Cy) filters 45 and yellow filters 46 can be alternately formed with widened portions on the pixels. However, color filters having different colors may be separated for each pixel and formed in a mosaic shape.

  13A is an enlarged view of four pixels of the CCD 36b, and FIG. 13B is an enlarged view of four pixels of the CCD 37b. In each of the CCDs 36b and 37b, each pixel 61 is shifted by ½ pitch for each row, and a vertical transfer path 62 meanders between the pixels 61 adjacent in the horizontal direction.

  FIG. 14 is a detailed view showing the transfer electrode in each circle XIV of FIGS. 13 (a) and 13 (b). Each pixel 61 is defined by the element separation band 65 formed in a diamond shape, and the color signal charge is read from the gate portion 66 provided in the element separation band 65 to the vertical transfer path 62 provided between the pixels.

  On the vertical transfer path 62, transfer electrodes having a two-layer polysilicon structure are provided so as to overlap each other, and four transfer electrodes 67a, 67b, 67c, 67d 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.

  In the CCD 36b having the honeycomb pixel arrangement, the blue (B) signal generated through the Cy filter and the red (R) signal generated through the yellow filter are transferred through separate vertical transfer paths 62. There is an advantage that the signal charge of the R signal and the signal charge of the B signal are not mixed in each vertical transfer path 62. As a result, there is a feature that false colors, vertical stripes, and the like that degrade image quality do not occur.

  The CCDs 36b and 37b of the present embodiment have the same structure of each pixel except that only the color of the color filter and the presence or absence of the color filter layer are different. Thereby, the CCDs 36b and 37b can be manufactured by the same semiconductor process, and the manufacturing cost can be reduced. The same applies to the square lattice array CCD shown in the first embodiment.

  The surface structure of the CCD according to this embodiment is the same as that of the CCD shown in FIGS. 13A and 13B of the second embodiment, but the cross-sectional structure of the pixel is different from that of the second embodiment. FIG. 15A is a cross-sectional view of Example 3 corresponding to red (R) and blue (B) corresponding to the cross section along the line aa in FIG. 13A. FIG. 15B is a cross-sectional view of FIG. It is sectional drawing equivalent to the bb sectional view of b).

  IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL.ED-15, NO.1, JANUARY 1968 "A Planar Silicon Photosensor with an Optimal Spectral Response for Detecting Printed Material" PAUL A.GARY and JOHN G.LINVILL It has been reported that the properties, that is, the photoelectric conversion characteristics of the photoelectric conversion element (photodiode) constituting the light receiving portion depend on the wavelength of the incident light and the position in the depth direction of the semiconductor substrate.

Therefore, in this embodiment, a pixel structure that utilizes the optical properties of the semiconductor is employed. That is, as will be described later, in order to optimize the sensitivity and white balance of each pixel for detecting R, G, and B color signals, the structure of the N ⁺ region, particularly the junction depth (Xj) is changed.

FIG. 15A is a cross-sectional view of a pixel for detecting red (R) and a pixel for detecting blue (B) in the CCD 36c used as the solid-state imaging device 36 of FIG. In the n-type silicon substrate 70, a P well layer 71 is formed on the surface side, and N ⁺ layers 72 R and 72 B are formed on the surface portion in the P well layer 71. Signal charges generated by the incident light are accumulated in the N ⁺ layers 72R and 72B.

In the pixel for detecting red, the N ⁺ layer 72R takes the optical absorption coefficient of red in the silicon substrate 70 into consideration and sets the depth Xj to about 0.8 to 2.0 μm to maximize the sensitivity to red. ing. In the pixel that detects blue, the N ⁺ layer 72B has a depth Xj of about 0.1 to 0.3 μm to maximize the sensitivity to blue.

The N ⁺ layers 72R and 72B (impurity (phosphorus or arsenic (P or As)) concentration serving as signal charge storage portions are about 5 × 10 ^{16 to 17} / cm ³ ) extend below the read gate electrode 73, respectively. The charges generated according to the amount of incident light are read out to the vertical transfer path 74 through the gate portion.

A shallow P ⁺ layer 75 is provided on a part of the surface of the semiconductor substrate 70 provided with the N ⁺ layers 72R and 72B, and an SiO ₂ film 76 is provided on the outermost surface. The P ⁺ layer 75 has an impurity (boron) concentration of about 1 × 10 ¹⁸ / cm ³ and a depth of about 0.1 μm, which contributes to the reduction of the defect level at the oxide film-semiconductor interface on the surface of the light receiving portion. Yes. The red detection pixel and the blue detection pixel are separated by an element separation band 77.

Further, a light shielding film 78 having an opening 78a in the light receiving region is provided on the upper surface of the SiO ₂ film 76, and a planarizing film (protective film) 79 is formed thereon, and further, a color filter layer is formed thereon. 80 is provided, and a top lens (microlens) 82 is formed thereon via a planarization film 81. The top lens 82 is preferably a gapless top lens with no gap between adjacent top lenses 82.

  In order to reduce the false color of the captured image, the horizontal and vertical distances between the pixels that are discretely arranged on the two-dimensional plane (on the surface of the solid-state image sensor) can be shortened, or insensitive areas between adjacent pixels. It is effective to eliminate As described above, further miniaturization of the pixels is required to shorten the distance between the pixels beyond the current level, and it has become technically difficult. Therefore, in this embodiment, the top lens 82 is a gapless lens, so that the insensitive area between adjacent pixels is eliminated, and the red (R) light receiving surface and the blue (B) light receiving surface adjacent to each other in the left and right directions are continuous. Therefore, the false color due to the aliasing distortion is further reduced.

  FIG. 15B is a cross-sectional view of a pixel of the CCD 37c used as the solid-state imaging device 37 of FIG. 2, that is, a pixel for detecting green (G). Since it is almost the same as the cross-sectional structure of FIG. 15 (a), the same members are denoted by the same reference numerals, description thereof is omitted, and only differences are described.

In a pixel that detects green (G) light, the depth of the N ⁺ region 72G is set to about 0.3 to 0.8 μm in consideration of the green optical absorption coefficient in the silicon substrate 70. The sensitivity to green is maximized.

  Further, since only green (G) light is incident on the CCD 37 c by the photolytic prism, the color filter layer 80 shown in FIG. 15A is not provided, and the planarizing film 79 is formed up to the bottom of the top lens 82.

In this embodiment, since the depth of the N ⁺ layer, that is, the PN junction depth Xj of the photodiode is Xj (B) <Xj (G) <Xj (R), the signal charge corresponding to the red incident light amount Can be stored in the N ⁺ layer 72R with high sensitivity, the signal charge corresponding to the green incident light amount can be stored in the N ⁺ layer 72G with high sensitivity, and the signal charge corresponding to the blue incident light amount can be stored in the N ⁺ layer 72B with high sensitivity. It has the effect of being able to.

  The above-described embodiments are all examples of CCDs, but it goes without saying that the present invention can also be applied to MOS image sensors by making the color filter structure the same as in Embodiments 1-3. Absent.

  The two-plate color solid-state imaging device according to the present invention can be reduced in size and cost, and can capture a color image with high resolution, high image quality, and high sensitivity. It is useful for mounting on digital cameras.

It is a block block diagram of the digital camera which concerns on one Embodiment of this invention. FIG. 2 is a configuration diagram of the two-plate color solid-state imaging device shown in FIG. 1 shown in FIG. 1. It is a figure which shows another example of the photolysis prism shown in FIG. (A) is a figure which shows wavelength distribution of the light of the green (G) reflected by the dichroic mirror shown in FIG. (B) is a figure which shows wavelength distribution of the light of the blue (B) and red (R) which permeate | transmitted with the dichroic mirror shown in FIG. (A) is a graph which shows the spectral characteristics of the green trimming filter shown in FIG. (B) is a graph showing the spectral characteristics of the magenta (Mg) trimming filter shown in FIG. (A) is a graph which shows wavelength distribution of the green light which injects into the solid-state image sensor for green detection of FIG. (B) is a graph showing the wavelength distribution of red and blue light incident on the solid-state image sensor for detecting red and blue in FIG. (A) is a graph which shows the wavelength distribution of the red and blue light which injects into the solid-state image sensor for red and blue detection of FIG. (B) is a graph showing spectral characteristics of a cyan (Cy) filter. (C) is a graph which shows the spectral characteristic of the blue light which passed the cyan filter. (D) is a graph which shows the spectral characteristic of a yellow (Ye) filter. (E) is a graph which shows the spectral characteristic of the red light which passed the yellow filter. It is explanatory drawing of the color mixing problem which generate | occur | produces in the boundary part of an adjacent color filter. (A) It is the surface schematic diagram of CCD for red and blue detection which concerns on Example 1 of this invention. (B) It is the surface schematic diagram of CCD for green color detection concerning Example 1 of the present invention. (A) is a figure which illustrates the striped color filter extended in the vertical direction. (B) is a figure which illustrates the striped color filter extended in a horizontal direction. (A) It is the surface schematic diagram of CCD for red and blue detection which concerns on Example 2 of this invention. (B) It is the surface schematic diagram of CCD for green color detection concerning Example 2 of the present invention. (A) is a figure which illustrates the striped color filter extended in the vertical direction used with CCD of a honeycomb arrangement | sequence. (B) is a figure which illustrates the stripe-shaped color filter extended in the horizontal direction used with CCD of a honeycomb arrangement | sequence. FIG. 12A is a schematic plan view of four pixels of the CCD shown in FIG. FIG. 12B is a schematic plan view of four pixels of the CCD shown in FIG. It is an enlarged view in circle XIV of Drawing 13 (a) (b). (A) is sectional drawing of Example 3 of this invention corresponded in the AA line cross section of Fig.13 (a). FIG. 13B is a sectional view of the third embodiment of the present invention corresponding to the section taken along line BB in FIG. It is a block diagram of the conventional 3 plate-type color solid-state imaging device.

Explanation of symbols

22 Two-plate color solid-state imaging device 35 Color separation prism 36 First solid-state imaging device (for R and B detection)
37 Second solid-state imaging device (for G detection)
36a, 36b, 36c First CCD (for R, B detection)
37a, 37b, 37c Second CCD (for G detection)
38 Green reflective dichroic mirror 39 Total reflective dichroic mirror 70 n-type silicon substrates 72R, 72G, 72B N ⁺ layer 78 light shielding film 80 complementary color system color filter layer 82 Gya press microlens Cy cyan filter Ye yellow filter

Claims (10)

  A color separation prism that separates incident light of the three primary colors into green, red, and blue, and receives the red and blue incident light separated by the color separation prism and receives a red signal and a blue signal according to the amount of red light A first solid-state imaging device that outputs a blue signal corresponding to the amount of light, and a second solid-state imaging device that receives the green incident light separated by the color separation prism and outputs a green signal corresponding to the amount of green light A complementary color system first color filter that transmits red light is provided above the red detection light-receiving unit among the plurality of light-receiving units of the first solid-state image sensor; A two-plate color solid-state imaging device, wherein a complementary color second color filter that transmits blue light is provided above a blue-detecting light-receiving unit among a plurality of light-receiving units of one solid-state imaging device.   2. The two-plate color solid-state imaging device according to claim 1, wherein the first color filter is a yellow (Ye) filter, and the second color filter is a cyan (Cy) filter.   3. The two-plate color solid-state imaging device according to claim 1, wherein the first color filter and the second color filter are formed of a dye system. 4.   4. The two-plate color solid-state imaging device according to claim 1, wherein the first color filter and the second color filter are formed in a mosaic shape or a stripe shape. 5. The PN junction depth Xj (B) of the blue detection light-receiving unit, the PN junction depth Xj (R) of the red detection light-receiving unit, and the green detection light-receiving unit provided in the second solid-state imaging device PN junction depth Xj (G) of Xj (B) <Xj (G) <Xj (R)
5. The two-plate color solid-state imaging device according to claim 1, wherein the two-plate color solid-state imaging device is manufactured so as to satisfy the relationship.   6. The two-plate color solid according to claim 1, wherein the color separation prism includes a dichroic mirror that reflects green light and transmits red light and blue light in incident light. Imaging device.   2. The color separation prism includes a green trimming filter at the green light exit and a magenta (Mg) trimming filter at the red and blue light exits. The two-plate color solid-state imaging device according to claim 6.   8. The light receiving portion provided in each of the first solid-state imaging device and the second solid-state imaging device is arranged in a square lattice shape or a honeycomb shape. The two-plate color solid-state imaging device described.   9. The two-plate color solid-state image pickup device according to claim 1, wherein each of the first solid-state image pickup element and the second solid-state image pickup element is a CCD type or MOS type image sensor. .   A digital camera comprising the two-plate color solid-state imaging device according to any one of claims 1 to 9.

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