JP2007066962A - Color solid-state imaging device and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high sensitivity color solid-state imaging device capable of picking up a color image exhibiting excellent color reproducibility. <P>SOLUTION: The color solid-state imaging device comprises a plurality of first type and second type pixels arranged in two-dimensional array on the surface of a semiconductor substrate wherein each pixel outputs two different signals independently, and spectral sensitivity (Fig. 3(a)) of the first type pixel is different from spectral sensitivity (Fig. 3(b)) of the second type pixel. Each of the first type and second type spectral sensitivities suitably has one mountain projecting upward and one valley projecting downward wherein the mountain of one of the first and second types overlaps the valley of the other type. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color solid-state imaging device and a digital camera such as a CCD type image sensor and a CMOS type image sensor, and more particularly to a color solid-state imaging device and a digital camera suitable for achieving high sensitivity and high image quality.

  A color solid-state imaging device such as a CCD type or a CMOS type has color filters having different spectral characteristics stacked, for example, in a stripe shape or a mosaic shape, on each light receiving portion arranged in a two-dimensional array on the surface of a semiconductor substrate. Yes.

  In this case, for example, only light in the B wavelength region (incident light component having a wavelength shorter than about 480 nm) reaches the light receiving unit in which blue (B) color filters are stacked, and other wavelength components (for example, Green (G) and red (R)) are absorbed by the B color filter and do not reach the light receiving section. That is, among the incident light, the wavelength component of B is photoelectrically converted and used to generate image data, but wavelength components other than B (G and R) are not used to generate image data. .

  The above is an example of a primary color filter using R, G, and B as basic color filters. There is a problem that a color solid-state imaging device having a primary color filter can use only about 1/3 of incident light.

  As the color filter, a so-called complementary color filter is used in addition to the primary color filter. The complementary color filter is a spectral filter that transmits light in a wavelength region that has a complementary color relationship with each primary color component. For example, a complementary color filter that transmits color components (G and R) having a complementary color relationship of B is called a yellow filter (Ye). Similarly, the complementary color filter that transmits the color components (B and R) that have a complementary color relationship of G is a magenta filter (Mg), and the complementary color filter that transmits the color components (B and G) that have a complementary color relationship of R. Is a cyan filter (Cy).

  When the complementary color filter is used, for example, about 2/3 of the incident light is used because G and R of the incident light reach B and the B is blocked in the light receiving portion on which the yellow filter is laminated. That is, there is an advantage that the wavelength of the incident light can be used in a wide range, and the sensitivity is higher than when the primary color filter is used. For this reason, it is widely used in video movie cameras (moving image capturing) in which an auxiliary light source such as a flash is difficult to use.

  However, when the complementary color filter is used, the signals obtained from one light receiving unit are signals corresponding to G + R, G + B, and R + B. Therefore, after reading these signals G + R, G + B, and R + B from the solid-state imaging device, It is necessary to perform a color signal separation operation in the circuit and divide it into an R signal component, a G signal component, and a B signal component. As a result, there is a problem that the color reproducibility is inferior as compared with a solid-state image sensor equipped with a primary color filter that can directly read out each color component (R, G, B) from the solid-state image sensor. Accordingly, in a still camera (still image capturing) that places importance on image quality, a solid-state image sensor equipped with a primary color filter is often used.

  In recent years, as the resolution of a solid-state imaging device is increased, that is, the number of pixels is increased, and the area of the light receiving portion occupying one pixel is decreasing, it is becoming increasingly difficult to maintain the same sensitivity as before. On the other hand, there is an increasing demand for further increasing the sensitivity (ISO 800 or higher) of a conventional digital camera having a photographic sensitivity (ISO) of about ISO 100 to 400.

  The reason is that shooting a night scene without flash (auxiliary light source) emission, or so-called “image blurring due to moving subjects”, which was not effective in preventing powerful camera shake, is a high-speed shutter for the increased sensitivity. This is because the effect of preventing this can be expected.

  In order to achieve this high sensitivity, it is impossible for a primary color filter layered solid-state imaging device with low light utilization efficiency. However, in the solid-state imaging device in which the complementary color filters are stacked, it is necessary to solve the problem of color reproducibility degradation caused by the color signal separation calculation described above.

  There is a conventional technique in which color signals are separated by an element structure instead of an arithmetic process. For example, a plurality of photodiodes (photoelectric conversion elements) are provided in the depth direction of the semiconductor substrate, and a color-separated signal is extracted from each photodiode. This prior art utilizes the fact that the optical absorptance of the semiconductor substrate in the depth direction has wavelength dependency (Non-patent Document 1).

  FIG. 15 shows the wavelength dependence of the light absorptance inside the photodiode when the depth (thickness) of the photodiode (PD) that constitutes the light receiving unit that detects and accumulates the photoelectrically converted charge is changed. It is a graph which shows the simulation result shown. In a photodiode structure using a silicon (Si) substrate, the optical absorption coefficient of Si has wavelength dependence, so the longer the wavelength, the smaller the light absorption coefficient, and as a result, the absorption efficiency inside the photodiode tends to decrease. There is. Accordingly, as the photodiode depth (thickness) is increased (thickened), the absorption efficiency in the long wavelength light region can be increased.

FIG. 16 is a graph showing the relative sensitivity of three types of photodiodes having different photodiode depths using the above characteristics of a photodiode using an N-type Si substrate (the illustrated example is a photodiode having an N ⁺ PN structure). It is. As can be seen from this graph, the shorter the photodiode depth (Xj = 0.3 μm), the higher the short wavelength photosensitivity and the low long wavelength photosensitivity. On the contrary, the shorter the photodiode depth (Xj = 5 μm in the figure), the lower the short wavelength sensitivity and the higher the long wavelength photosensitivity.

  However, comparing the characteristics shown in FIG. 16 with the spectral characteristics of the primary color filter shown in FIG. 17, the characteristics shown in FIG. 16 have a wide half-value width and a large overlapping portion. For example, a photodiode with Xj = 0.3 μm that detects blue wavelength light and a photodiode with Xj = 1.6 μm that detects green wavelength light have a large overlap with each other, and blue and green color separation is not sufficient . However, the overlapping portion of the spectral spectrum of the photodiode of Xj = 0.3 μm that detects blue wavelength light and the photodiode of Xj = 5 μm that detects red wavelength light is relatively small.

  For this reason, from the spectral characteristics of these three types of signal output, signals of three colors R, G, and B are detected by three photodiodes provided in the depth direction of the semiconductor substrate, and a natural image is detected by the color signal processing circuit. However, there is a concern that the image quality of the color S / N and the like deteriorates due to the overlap of the spectral spectra even if these are reproduced (Patent Documents 1 and 2).

JP 58-103165 A Japanese Patent Laid-Open No. 1-134966 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

  As described above, in a solid-state imaging device capable of capturing a high-resolution color image, it is desired to capture a color image with excellent color reproducibility and to achieve high sensitivity. Is difficult.

  An object of the present invention is to provide a color solid-state imaging device and a digital camera that can capture a color image with excellent color reproducibility and that is highly sensitive.

  In the color solid-state imaging device of the present invention, a plurality of first-type and second-type pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate, and each pixel outputs two different signals independently. In the imaging apparatus, the spectral sensitivity of the first type of pixels and the spectral sensitivity of the second type of pixels are different from each other.

  The color solid-state imaging device of the present invention includes a first convexity and a second convexity, each of the first and second types of spectral sensitivities having one upward convexity and one downward convexity. One of the two types of mountains and the other valley overlap.

  In the color solid-state imaging device of the present invention, the pixel includes two photoelectric conversion units in the depth direction of the semiconductor substrate, and the first type of spectral sensitivity is realized on the first type of pixel. A color color filter is stacked, and a second color filter that realizes the second type of spectral sensitivity is stacked on the second type of pixel.

  In the color solid-state imaging device of the present invention, a plurality of first-type pixels on which a first color filter is stacked and a plurality of second-type pixels on which a second color filter is stacked are arranged on the surface of a semiconductor substrate. A color solid-state imaging device that is arranged in a dimensional array and each pixel includes two photoelectric conversion units in the depth direction of the semiconductor substrate, and has four imaging regions C1, C2 in the imaging wavelength range from the shorter wavelength , C3, and C4, the first color filter transmits light in the wavelength region of the regions C1 and C3, and the second color filter transmits light in the wavelength region of the regions C2 and C4. It is characterized by that.

  The color image pickup device of the present invention is characterized in that a main transmission wavelength region of the regions C1, C2, C3, and C4 is C1 <450 nm <C2 <540 nm <C3 <620 nm <C4.

  The color solid-state imaging device according to the present invention is characterized in that the main transmission wavelength region of the regions C1, C2, C3, and C4 is 400 nm <C1 <470 nm <C2 <560 nm <C3 <630 nm <C4.

  In the color solid-state imaging device of the present invention, the shallow photoelectric conversion unit of two photoelectric conversion units provided in the depth direction of the semiconductor substrate mainly absorbs incident light in the wavelength region of the region C1 or the region C2. The deep photoelectric conversion part is formed to a depth that mainly absorbs incident light in the wavelength region of the C3 or the region C4.

  The shallow photoelectric conversion unit of the color solid-state imaging device of the present invention is formed to a depth of 0.1 μm or more and 1.2 μm or less from the surface of the semiconductor substrate, and the deep photoelectric conversion unit is formed from the surface of the semiconductor substrate to 2 It is formed to a depth of not less than 0.0 μm and not more than 10 μm.

The color solid-state imaging device according to the present invention includes a shallow photoelectric conversion unit n1 and a deep photoelectric conversion unit n3 among the two photoelectric conversion units provided in the first type of pixels, and 2 provided in the second type of pixels. Of the two photoelectric conversion units, the shallow photoelectric conversion unit n2 and the deep photoelectric conversion unit n4 have a depth of n1, n2, n3, and n4 in order from the surface of the semiconductor substrate.

  The color solid-state imaging device according to the present invention has photoelectric characteristics within each range of 0 <n1 ≦ 0.3 μm, 0.1 μm ≦ n2 ≦ 1.0 μm, 1.0 μm ≦ n3 ≦ 5.0 μm, 2.0 μm ≦ n4 ≦ 10 μm. A conversion unit is formed.

  The color solid-state imaging device of the present invention is characterized in that the photoelectric conversion units n1 and n2 are formed at the same depth, and the photoelectric conversion units n3 and n4 are formed at the same depth.

  The color solid-state imaging device according to the present invention is characterized in that a signal readout circuit for reading out a captured image signal from the pixel is configured by a MOS transistor.

  The color solid-state imaging device according to the present invention is characterized in that the signal reading means for reading the captured image signal from the pixel includes a vertical charge transfer unit.

  The color image pickup apparatus of the present invention is characterized in that the pixels are arranged in a honeycomb shape on the surface of the semiconductor substrate.

  A digital camera of the present invention is a digital camera equipped with any of the color solid-state imaging devices described above, and is a cutoff on the long wavelength side of an infrared cut filter provided between a camera lens and the color solid-state imaging device. The wavelength is from 655 nm to 700 nm.

  A digital camera of the present invention is a digital camera equipped with any of the color solid-state imaging devices described above, and is a cutoff on the short wavelength side of an infrared cut filter provided between a camera lens and the color solid-state imaging device. The wavelength is 400 nm or more and 430 nm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the color image excellent in color reproducibility can be imaged, and also a highly sensitive color solid-state imaging device and digital camera can be provided.

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

(First embodiment)
FIG. 1 is a schematic view of a surface of a color solid-state imaging device according to an embodiment of the present invention. In the color solid-state imaging device 10 shown in FIG. 1, a large number of light receiving portions 12 (each light receiving portion is also referred to as a “pixel” hereinafter) indicated by a rectangle in the illustrated example on the surface portion of the semiconductor substrate 11. Is formed.

  Each light receiving unit 12 is arranged in a square lattice pattern on the surface of the semiconductor substrate 11, and a vertical transfer path 13 including a vertical charge transfer register (VCCD) is formed on the right side of each column of the light receiving unit 12. A horizontal transfer path (HCCD) 14 including a horizontal charge transfer register (HCCD) that horizontally transfers a signal charge read from each light receiving unit 12 and transferred through the vertical transfer unit 13 is provided on the lower side of the semiconductor substrate 11. Is formed.

  In the color solid-state imaging device 10 according to the present embodiment, the first color filter CF1 is stacked on the first group of light receiving units 12 arranged in a checkered pattern among the many light receiving units 12 arranged in a square lattice, and the rest. The second color filter CF2 is stacked on the second group of light receiving portions 12 arranged in a checkerboard pattern. In the present embodiment, the first color filter CF1 and the second color filter CF2 are arranged in a checkered pattern, that is, a mosaic pattern, but may be arranged in a stripe pattern.

  2 and 3 are explanatory diagrams of the first color filter CF1 and the second color filter CF2. In general, a digital camera is equipped with an infrared cut (IR) filter, and light in a wavelength region of 380 nm to 650 nm is transmitted and incident on the color solid-state imaging device 10.

  Therefore, in this embodiment, first, as shown in FIG. 2, the wavelength range 380 to 650 nm of incident light is divided into four regions C1, C2, C3, and C4 from the short wavelength side to the long wavelength side. Each wavelength range is, for example, 380 nm <C1 <450 nm <C2 <540 nm <C3 <620 nm <C4.

  Then, as shown in FIG. 3A, the first color filter CF1 is mixed with a dye or a pigment so that the wavelength of the region C1 and the wavelength of the region C3 separated from the region C1 are transmitted. To manufacture.

  Similarly, as shown in FIG. 3B, the second color filter CF2 is mixed with a dye or a pigment so that the wavelength of the region C2 and the wavelength of the region C4 separated from the region C2 are transmitted. To manufacture.

  The first color filter CF1 and the second color filter CF2 are configured so that the spectral spectrum overlap is minimized, that is, the peak of one spectral spectrum matches the valley of the other spectral spectrum. .

  As described above, in this embodiment, the imaging wavelength region is divided into approximately four parts, and only two colors (two types) are used as the color filter. Note that it is not always necessary to attenuate the short wavelength side (400 nm or less) of the spectral spectrum of the region C1, and similarly, it is not always necessary to attenuate the long wavelength side (650 nm or more) of the spectral spectrum of the region C4. A characteristic common to the color filters CF1 and CF2 is a spectral spectrum shape having a shape of at least one peak (convex upward) and at least one valley (convex downward).

  FIG. 4 is a graph showing the spectral spectra of the first and second color filters CF1 and CF2 instead of FIG. As described above, an infrared cut (IR) filter mounted on a normal digital camera transmits light in a wavelength range of 380 nm to 650 nm, and transmits light of other wavelengths (for example, long wavelength light of 650 nm or more). It is shut off. For this reason, long wavelength light of 650 nm or more does not contribute to photoelectric conversion, and therefore does not contribute to sensitivity improvement.

  However, it is effective to detect light having a long wavelength of 650 nm or more in order to increase sensitivity. Therefore, in the embodiment shown in FIG. 4, the wavelength range of light that passes through the infrared cut filter and enters the color solid-state imaging device is 400 to 700 nm, and this wavelength range is divided into four regions C1, C2, C3, and C4. Yes.

  The respective wavelength ranges are, for example, 400 nm <C1 <470 nm <C2 <560 nm <C3 <630 nm <C4. The first color filter CF1 transmits light in the wavelength range of the regions C1 and C3, and the second color filter CF2 transmits light in the wavelength range of the regions C2 and C4.

  In the present embodiment, the infrared cut filter is used to prevent in advance the incidence of light having a short wavelength of 400 nm or less. By blocking the incidence of ultraviolet rays on the short wavelength side, it can be expected that the dye color filter can be prevented from fading. In the present embodiment, the spectral spectrum of the first color filter CF1 in the region C1 is rapidly attenuated at 420 nm or less. As a result, an effect that the influence of the chromatic aberration of the camera lens, which becomes conspicuous with the rectangular wavelength light, is less likely to be expected.

  FIG. 5 is an enlarged view of four light receiving portions 12 shown in FIG. 1 and shows transfer electrodes. The transfer electrodes 17, 18, and 19 of this embodiment have a three-layer polysilicon structure and constitute an interline CCD that can read out all pixels. In the illustrated example, the third polysilicon electrode 19 and the second polysilicon electrode 18 also serve as read gate electrodes for reading signal charges from the photodiodes.

FIG. 6 is a schematic cross-sectional view taken along the line VI-VI of the light receiving unit 12 in which the first color filter CF1 shown in FIG. 5 is stacked. In the n-type semiconductor substrate 11, a P well layer 22 is formed on the surface side, an N ⁺ layer (n1 layer) 23 is shallow in the P well layer 22, and an N ⁺ layer (n3 layer) 24 is deep in the deep part. They are formed separately in the vertical direction. The N ⁺ layer 23 extends to below the read gate electrode (transfer electrode) 19.

The N ⁺ layer (n3 layer) 24 formed in the deep part has an N ⁺ region (charge path) 24a that rises to the surface of the semiconductor substrate 11 at the end, and this N ⁺ region 24a is formed from a part of the transfer electrode. The read gate electrode 18 is extended to below.

A shallow P ⁺ layer 25 is provided on a part of the surface of the semiconductor substrate 11 provided with two kinds of accumulation portions 23 and 24 having different depths, and an SiO ₂ film 26 is provided on the outermost surface. ing. The P ⁺ layer 25 contributes to the reduction of the defect level at the oxide film-semiconductor interface on the light receiving portion surface.

_On the upper surface of the SiO ₂ film 26, the transfer electrodes 17, 18, 19 described above are formed at positions avoiding the light receiving region, and a light shielding film 27 having an opening 27 a in the light receiving region is further provided on the upper surface. Further, a planarizing film 28 is formed thereon, a first color filter CF1 layer 29 is further laminated thereon, and a top lens (microlens) 30 is formed thereon via the planarizing film. .

FIG. 7 is a schematic cross-sectional view taken along the line VII-VII of the light receiving unit 12 in which the second color filter CF2 shown in FIG. 5 is laminated. Although the structure is the same as that shown in FIG. 6, the depth of the N ⁺ layer (n2 layer) 23 and the depth of the N ⁺ layer (n4 layer) 24 are only different from those in FIG.

  The depth relationships of the n1, n2, n3, and n4 layers are n1, n2, n3, and n4 in order from the surface of the semiconductor substrate.

For example,
0.1 μm <n1 ≦ 0.3 μm
0.1 μm ≦ n2 ≦ 1.0 μm
1.0 μm ≦ n3 ≦ 5.0 μm
2.0 μm ≦ n4 ≦ 10.0 μm
However, it is not limited to this.

  FIG. 8 is an explanatory diagram of the operation of the color solid-state imaging device according to this embodiment. When light from which unnecessary light is cut by the infrared cut filter enters the color solid-state imaging device 10, in the pixel shown in FIG. 6 in which the first color filter CF1 is stacked, as shown in FIG. The short wavelength light with a wavelength of 380 to 450 nm (wavelength 400 to 470 nm in FIG. 4) that passes through the region C1 shown in FIG. 4 and the long wavelength with a wavelength of 540 to 620 nm (wavelength 560 to 630 nm in FIG. 4) that passes through the region C3. Wavelength light reaches the light receiving area.

  The short wavelength light is absorbed on the surface of the semiconductor substrate to generate a photocharge, and the generated signal charge is accumulated in the n1 layer on the surface. The long-wavelength light reaches the deep part of the semiconductor substrate and generates photocharges, and the generated signal charges are accumulated in the deep n3 layer. In the present embodiment, the short wavelength light and the long wavelength light transmitted through the color filter CF1 are separated in the region C2 (wavelength 450 to 540 nm, wavelength 470 to 570 nm in FIG. 4), so that there is little overlap and n1 The color separation performance of the signal charges accumulated in the layers n3 and n3 increases.

  The same applies to the pixel shown in FIG. 7 in which the second color filter CF2 is laminated. As shown in FIG. 8B, the wavelength 450 to 540 nm (FIG. 4) that transmits the region C2 shown in FIG. 3 (FIG. 4). In this case, short-wavelength light having a wavelength of 470 to 560 nm and long-wavelength light having a wavelength of 620 to 650 nm (wavelength of 630 to 700 nm in FIG. 4) transmitted through the region C4 reach the light receiving region.

  The short wavelength light is absorbed on the surface of the semiconductor substrate to generate a photocharge, and the generated signal charge is accumulated in the n2 layer on the surface. The long-wavelength light reaches the deep part of the semiconductor substrate to generate a photocharge, and the generated signal charge is accumulated in the deep n4 layer. In the present embodiment, the short wavelength light and the long wavelength light transmitted through the color filter CF2 are separated in the region C3 (wavelength 540 to 620 nm, wavelength 560 to 630 nm in FIG. 4), so that there is little overlap and n2 The color separation performance of signal charges accumulated in the n4 and n4 layers is improved.

  In the present embodiment, the depths of the n1 layer and the n3 layer in the light receiving portion where the first color filter CF1 is stacked differ from the depths of the n2 layer and the n4 layer in the light receiving portion where the second color filter CF2 is stacked. Although the depth is set, the regions C1, C2, C3, and C4 are set so that the short-wavelength light and the long-wavelength light that are transmitted through the color filters CF1 and CF2 are sufficiently separated. Color separation performance is high without changing the depth of the provided photodiode.

For this reason, the depth of the n1 layer and the n2 layer can be made the same, the depth of the n3 layer and the n4 layer can be made the same, and the number of manufacturing steps can be reduced. In this case, for example,
0.1 μm <n1 = n2 <1.2 μm
2.0 μm <n3 = n4 <10 μm
It is good, but it is not limited to this.

(Second Embodiment)
FIG. 9 is a schematic surface view of a color solid-state imaging device according to the second embodiment of the present invention. While the first embodiment is a CCD color solid-state imaging device, the present embodiment is a MOS type color solid-state imaging device such as a CMOS type.

  The color solid-state imaging device 40 of the present embodiment is formed on the surface portion of an n-type semiconductor substrate 41, and is formed with a vertical scanning circuit 42 formed beside the light receiving region, and a horizontal scanning circuit formed on the bottom side of the semiconductor substrate 41. Etc. (signal amplification circuit, A / D conversion circuit, synchronization signal generation circuit, etc.) 43.

  In the light receiving region on the surface of the semiconductor substrate 41, a large number of light receiving portions 44 are arranged in a two-dimensional array, in this example, a square lattice. In each light receiving portion 44, the first color filter CF1 and the second color filter CF2 described in FIGS. 3 and 4 are arranged in a mosaic pattern. It is also possible to arrange the color filters CF1 and CF2 in a stripe shape.

FIG. 10 is a schematic cross-sectional view taken along the line XX of FIG. 9, and shows a cross section of the pixel on which the second color filter CF2 is mounted. The cross-sectional structure of the pixel on which the first color filter CF1 is mounted is the same, and only the portion where CF1 is laminated instead of CF2 in FIG. 10 is different. A P well layer 45 is formed on the surface side of the n-type semiconductor substrate 41, an N ⁺ layer (n 1 = n 2) 46 is formed in a shallow portion of the surface in the P well layer 45, and N is formed in a deep portion in the P well layer 95. ^{A +} layer (n 3 = n 4) 47 is formed separately from the N ⁺ layer 46. The N ⁺ layer 47 is provided with a charge passage 47a that rises to the surface at the end. 6 and 7, the depths of the photoelectric conversion units n1 and n3 of the pixel on which CF1 is mounted and the depths of the photoelectric conversion units n2 and n4 of the pixel on which CF2 is mounted are expressed as n1 ≠ n2, n3 ≠. It is good also as n4.

The N ⁺ layer 46 is connected to the short wavelength signal detection amplifier 52 by the ohmic contact 51, and the charge path 47 a of the N ⁺ layer 47 is connected to the long wavelength signal detection amplifier 54 by the ohmic contact 53.

  Each of the amplifiers 52 and 54 is constituted by a known three transistor or four transistor as a signal readout circuit of a CMOS type image sensor. That is, it has an output transistor, a reset transistor, a row selection transistor (3-transistor configuration) constituted by MOS transistors, or a row readout transistor in addition to these.

  A planarizing film and a wiring layer (not shown) are provided on the surface of the semiconductor substrate, and the color filters CF1 and CF2 described in FIGS. 3 and 4 are laminated thereon, and a microlens (not shown) is formed thereon. Is provided.

With such a configuration, the reset transistor constituting the amplifier 52 is turned on before the color image is captured, and a predetermined amount of charge is accumulated in the PN junctions of the N ⁺ layers 46 and 47, respectively. The accumulated charge at the PN junction of the N ⁺ layer 46 is discharged by the amount of photocharge generated according to the amount of incident light of short wavelength light among the light transmitted through the color filter CF1 (or CF2), and the N ⁺ layer 47 The accumulated charge at the PN junction is discharged by the amount of photocharge generated according to the amount of incident light of long wavelength light out of the light transmitted through the color filter CF1 (or CF2).

The amount of change in charge at each PN junction of each N ⁺ layer 46, 47 is independently determined by amplifiers 52, 54 provided for each light receiving unit in accordance with control instructions from the vertical scanning circuit 42 and horizontal scanning circuit 43 in FIG. Is read out.

(Third embodiment)
FIG. 11 is a schematic view of the surface of a CCD color solid-state imaging device having a honeycomb pixel arrangement. A large number of pixels 61 arranged in a two-dimensional array on the surface of the semiconductor substrate are shifted by ½ pitch for each row, and vertical transfer paths 62 meander between the adjacent pixels 61 in the horizontal direction. The

  The cross-sectional structure of each pixel 61 provided in the color solid-state imaging device 60 of the present embodiment is the same as that shown in FIGS. 6 and 7 (n1 = n2, n3 = n4 may be used), and a color filter. From the pixel 61 on which CF1 is laminated, signal charges corresponding to the amounts of light received in the regions C1 and C3 shown in FIG. 3 or 4 are separately output to the vertical transfer path 62, and the pixel 61 on which the color filter CF2 is laminated. The signal charges corresponding to the amounts of light received in the areas C2 and C4 are separately output to the vertical transfer path 62.

  FIG. 12 is an enlarged view of four pixels of the color solid-state imaging device 60. FIG. 13 is a detailed view showing the transfer electrode in the circle XIII in FIG. In the color solid-state imaging device 60 of the present embodiment, each pixel 61 is defined by the element separation band 63 formed in a diamond shape, and the vertical transfer provided between the pixels from the gate portion 64 provided in the element separation band 63. The signal charge is read out to the path 62.

  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 81, 82, 83, 84 are associated with one pixel.

  When signal charges are read out from the color solid-state imaging device 60, the signal charges in the region C3 are read out from the pixels 61 in which the color filters CF1 are stacked into the vertical transfer path 62 and the color filters CF2 are stacked in the first frame. The signal charge in the area C4 is read from the pixel 61 to the vertical transfer path 62, and the signal charge in the area C1 is read to the vertical transfer path 62 from the pixel 61 on which the color filter CF1 is stacked in the next second frame. The signal charges in the region C <b> 2 are read out from the pixel 61 in which are stacked to the vertical transfer path 62.

  The signal charges (C1, C2, C3, C4) on the vertical transfer path 62 are transferred to the horizontal transfer path, and then transferred on the horizontal transfer path and output. That is, in the CCD color solid-state imaging device 60 having the honeycomb pixel arrangement, all pixels can be read (progressive operation) with the transfer electrode having the two-layer polysilicon structure.

(Fourth embodiment)

FIG. 14 is a block diagram of a digital camera equipped with the color solid-state imaging device according to any one of the above-described embodiments. This digital camera includes an optical system 101 on which a lens and a diaphragm for collecting incident light from a subject, a color solid-state imaging device 102 according to any of the above-described embodiments, an optical system 101, and a color solid-state imaging device 102. And an infrared cut filter 103 disposed between the two.

  The digital camera of the present embodiment also takes in the C1 signal (a signal corresponding to the amount of light received in the region C1, hereinafter the same), the C2, C3, and C4 signals output from the color solid-state imaging device 102, and correlated double sampling. The CDS circuit 104 that performs processing, the preprocess circuit 105 that takes in the output signal of the CDS circuit 104 and performs gain control processing, and the analog signals C1, C2, C3, and C4 output from the preprocess circuit 105 are converted into digital An A / D conversion circuit 106 that converts the signals into signals, and C1, C2, C3, and C4 image signals output from the A / D conversion circuit 106, and R (red), G (green), and B (blue) signals Is connected to the circuit 107 and a circuit 107 that performs signal processing such as white balance correction and gamma correction processing, and performs signal compression and expansion processing of a captured image. Image comprises a memory 108, a recording / display circuit 109 which can be displayed on the liquid crystal display unit provided on the circuit 107 is processed and recorded in the external memory or a camera back (not shown) or the like captured image data.

  The digital camera further includes a system control circuit 110 that performs overall control of the entire digital camera, a synchronization signal circuit 111 that generates a synchronization signal in response to an instruction signal from the system control circuit 110, and a color solid-state imaging device 102 based on the synchronization signal. Are provided with a drive circuit 112 that outputs a drive control signal.

  In the digital camera of this embodiment, the lens focus and aperture of the optical system 101 are controlled based on an instruction signal from the system control circuit 110, and an optical image of a subject is displayed on the color solid-state imaging device 102 through the optical system 101 and the infrared cut filter 103. Forms an image. Then, the C1, C2, C3, and C4 signals are output from the color solid-state imaging device 102 in accordance with the received optical image, and the signal processing circuit 107 reproduces the R, G, and B signals from these C1 to C4 signals and performs imaging. Generate image data. The captured image data is compressed into data such as JPEG format and recorded in an external memory.

  According to each embodiment described above, the imaging wavelength region is divided into four regions (wavelength ranges) C1, C2, C3, and C4, and the two color signal components C1 and C3 are independent from the first light receiving unit (pixel). Since the other two color signal components C2 and C4 are detected independently from the second light receiving portion (pixel), incident light can be effectively converted into an electrical signal. While the light use efficiency of the primary color filter is approximately 1/3, the light use efficiency according to each embodiment of the present invention is 2/4 = 1/2, and the sensitivity is increased accordingly.

  Further, since it is substantially equivalent to mounting four color filters, high sensitivity and high image quality (high color S / N ratio) are possible.

  In addition, the wavelength dependence of the light absorption coefficient in the depth direction of the semiconductor substrate is combined with the color filter, and the detection wavelength range of the two photodiodes is separated by the color filter to reduce the overlap amount, so that the color separation performance is improved. Improves faithful color reproduction.

  Furthermore, since the color filters to be used are only two colors, CF1 and CF2, the manufacturing process of the color solid-state imaging device is simplified, and the manufacturing cost can be reduced.

  The color solid-state imaging device according to the present invention can achieve high sensitivity and high image quality, and is useful for mounting in digital cameras such as digital still cameras and digital video cameras.

It is a surface schematic diagram of the color solid-state imaging device concerning a 1st embodiment of the present invention. It is explanatory drawing of color filter CF1, CF2 shown in FIG. 2 is a graph showing each spectrum of color filters CF1 and CF2 shown in FIG. 4 is a graph showing spectral spectra of color filters CF1 and CF2 of an embodiment different from FIG. FIG. 2 is an enlarged schematic diagram for four adjacent pixels shown in FIG. 1. FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 5. FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG. 5. It is a figure which shows the transmitted light of color filter CF1, CF2 shown in FIG. 1, and the potential of a substrate depth direction. It is a surface schematic diagram of the color solid-state imaging device which concerns on the 2nd Embodiment of this invention. FIG. 10 is a schematic cross-sectional view taken along line XX in FIG. 9. It is a surface schematic diagram of the color solid-state imaging device which concerns on the 3rd Embodiment of this invention. It is an expansion schematic diagram for 4 adjacent pixels shown in FIG. FIG. 13 is an enlarged view in a circle XIII in FIG. 12. It is a block block diagram of a digital camera. It is a graph which shows the junction depth and wavelength dependence of the light absorption factor of a photodiode. It is a graph which shows the spectral sensitivity characteristic of a photodiode. It is a graph which shows the spectral characteristic of a primary color filter.

Explanation of symbols

10, 40, 60, 102 Color solid-state imaging device 11, 41 Semiconductor substrate 12, 44 Light receiving part (pixel)
13, 62 Vertical transfer path 14 Horizontal transfer paths 23, 24, 46, 47 N ⁺ areas C1, C2, C3, C4 Visible light area divided into four CF1 first color filter CF2 second color filter

Claims (16)

  A color solid-state imaging device in which a plurality of first-type and second-type pixels are arranged in a two-dimensional array on the surface of a semiconductor substrate, and each pixel independently outputs two different signals. The color solid-state imaging device, wherein the spectral sensitivity of the pixel of the seed and the spectral sensitivity of the pixel of the second type are different from each other.   Each of the spectral sensitivities of the first type and the second type has a peak that is one upward convex and a valley that is one downward convex, and the peak of one of the first and second types. The color solid-state imaging device according to claim 1, wherein the first and second valleys overlap each other.   The pixel includes two photoelectric conversion units in a depth direction of a semiconductor substrate, and a first color filter that realizes the first type of spectral sensitivity is stacked on the first type of pixel, 3. The color solid-state imaging device according to claim 2, wherein a second color filter that realizes the second type of spectral sensitivity is stacked on the two types of pixels. 4.   A plurality of first type pixels on which a first color filter is stacked and a plurality of second type pixels on which a second color filter is stacked are formed in a two-dimensional array on the surface of a semiconductor substrate, A color solid-state imaging device in which each pixel includes two photoelectric conversion units in the depth direction of the semiconductor substrate, and the imaging wavelength region is divided into four regions C1, C2, C3, and C4 from the shorter wavelength, Color image imaging, wherein the first color filter transmits light in the wavelength region of the regions C1 and C3 and the second color filter transmits light in the wavelength region of the regions C2 and C4 apparatus.   5. The color solid-state imaging device according to claim 4, wherein a main transmission wavelength region of the regions C1, C2, C3, and C4 is C1 <450 nm <C2 <540 nm <C3 <620 nm <C4.   5. The color solid-state imaging device according to claim 4, wherein a main transmission wavelength region of the regions C1, C2, C3, and C4 is 400 nm <C1 <470 nm <C2 <560 nm <C3 <630 nm <C4.   Of the two photoelectric conversion units provided in the depth direction of the semiconductor substrate, the shallow photoelectric conversion unit is formed to a depth that mainly absorbs incident light in the wavelength region of the region C1 or the region C2, and the deep photoelectric conversion unit is The color solid-state imaging device according to claim 4, wherein the color solid-state imaging device is formed to a depth that mainly absorbs incident light in a wavelength region of the C3 or the region C4.   The shallow photoelectric conversion part is formed at a depth of 0.1 μm to 1.2 μm from the surface of the semiconductor substrate, and the deep photoelectric conversion part is at a depth of 2.0 μm to 10 μm from the surface of the semiconductor substrate. The color solid-state imaging device according to claim 7, wherein the color solid-state imaging device is formed as follows.   The shallow photoelectric conversion unit n1 and the deep photoelectric conversion unit n3 among the two photoelectric conversion units provided in the first type of pixel, and the shallow photoelectric conversion of the two photoelectric conversion units provided in the second type of pixel. 9. The depth of each of the part n <b> 2 and the deep photoelectric conversion part n <b> 4 is n <b> 1, n <b> 2, n <b> 3, n <b> 4 in ascending order from the surface of the semiconductor substrate. Color solid-state imaging device.   That the photoelectric conversion part is formed in each range of 0 <n1 ≦ 0.3 μm, 0.1 μm ≦ n2 ≦ 1.0 μm, 1.0 μm ≦ n3 ≦ 5.0 μm, 2.0 μm ≦ n4 ≦ 10 μm The color solid-state imaging device according to claim 9.   The color solid-state imaging device according to claim 9, wherein the photoelectric conversion units n1 and n2 are formed at the same depth, and the photoelectric conversion units n3 and n4 are formed at the same depth.   The color solid-state imaging device according to any one of claims 1 to 11, wherein a signal readout circuit for reading a captured image signal from the pixel is configured by a MOS transistor.   The color image capturing apparatus according to claim 1, wherein a signal reading unit that reads a captured image signal from the pixel includes a vertical charge transfer unit.   The color solid-state imaging device according to claim 12 or 13, wherein the pixels are arranged in a honeycomb shape on a surface portion of a semiconductor substrate.   15. A digital camera equipped with the color solid-state imaging device according to claim 1, wherein a cutoff wavelength on a long wavelength side of an infrared cut filter provided between the camera lens and the color solid-state imaging device. Is a digital camera characterized by having a wavelength of 655 nm to 700 nm.   A digital camera equipped with the color solid-state imaging device according to any one of claims 1 to 15, wherein a cutoff wavelength on a short wavelength side of an infrared cut filter provided between a camera lens and the color solid-state imaging device Is a digital camera having a wavelength of 400 nm to 430 nm.

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