JP4264248B2 - Color solid-state imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single-plate color solid-state imaging device and a digital camera equipped with the color solid-state imaging device.
[0002]
[Prior art]
As a typical color reproduction means in a solid-state imaging device such as a CCD, three or four different spectral characteristics are provided for a large number of photodiodes (pixels, pixels) arranged in a two-dimensional array on the surface of the imaging device. 2. Description of the Related Art A micro-color filter (single-plate color solid-state imaging device) in which a micro color filter is arranged in a mosaic shape is known.
[0003]
Micro color filters are roughly classified into two types, primary color systems (R, G, B) and complementary color systems (G, Ye, Cy, Mg). Depending on the arrangement method, stripe patterns and Bayer patterns (USP 3,971, 065: Patent Document 1) and the like have been proposed.
[0004]
However, since each photodiode is discretely distributed on a two-dimensional plane, and each photodiode corresponds to one of three to four different spectral sensitivities, the following is achieved. There is a problem.
[0005]
(1) When an image having a spatial frequency higher than the Nyquist frequency determined by the arrangement pitch of the photodiodes is projected onto the color solid-state imaging device, this high spatial frequency component is folded back to the low frequency side, so-called moire. A false signal is generated, and the quality of the captured image is deteriorated.
[0006]
(2) Color filters having different spectral sensitivities correspond to signals at different locations on the two-dimensional plane, and the Nyquist domains (spatial frequency distributions) of the colors do not match due to the distribution patterns of the color filters. As a result, a phenomenon called so-called false color or color moire is caused, and the image quality of the photographed image is deteriorated.
[0007]
Therefore, conventionally, as one method of reducing moire, a method of inserting an optical low-pass filter (OLPF) between a condensing optical system (lens system) and a single-plate color solid-state imaging device has been adopted. By using this method, high spatial frequency components are attenuated and moire is improved.
[0008]
However, the moire improvement effect using the optical low-pass filter is insufficient, and the optical low-pass filter is configured by combining birefringent optical materials such as a quartz plate, so that it can be used as a package for protecting a solid-state imaging device such as a CCD. In the structure in which the optical low-pass filter is attached, there is a problem that the optical low-pass filter is easily broken and the manufacturing cost is increased due to mechanical stress applied to the package.
[0009]
On the other hand, in recent single-plate color solid-state imaging devices, the pixel size (photodiode size) is miniaturized, that is, the number of pixels is increased, and the resolution is drastically improved. The Nyquist frequency is also increased by making the pixel arrangement pitch finer. For this reason, the generation of moire tends to be suppressed in principle.
[0010]
However, since many photodiodes of several million pixels are integrated on one chip, the following different problems (A) and (B) have become apparent.
[0011]
(A) With the miniaturization of the size of the photodiode, it is also necessary to reduce the microlens diameter. In this case, since the thickness of the microlens is relatively thick and the focal length of the microlens is shortened, the focal point is formed in front of and above the photodiode. Therefore, in order to adjust the focal length, another lens (in-layer lens) needs to be formed in the lower part, the structure becomes complicated, and it is difficult to obtain a stable manufacturing yield.
[0012]
Further, a light shielding film having an opening above each photodiode is laminated on the entire photodiode and other peripheral circuits. The opening size formed in the light shielding film is simultaneously reduced with the miniaturization of the photodiode. For example, when the opening size becomes 1 μm or less, depending on the wavelength of the incident light, the light passes through this opening. The light intensity is greatly attenuated. Therefore, for example, since the wavelength of red (R) light is about 0.650 μm, it is necessary to consider the wave optical effect when the aperture size becomes 1 μm or less.
[0013]
For this reason, if the photodiodes are miniaturized with the arrangement of the conventional photodiodes separated for each color, the on-chip condensing optical system (microlens) is simultaneously formed with the miniaturization of the photodiodes and readout circuits formed on the semiconductor substrate. , Color filters, light-shielding film openings) must be miniaturized, and the intensity of light entering the light-receiving section is greatly reduced by the wave optical effect, and sufficient sensitivity cannot be obtained even when a bright subject is imaged. Arise.
[0014]
(B) Phenomena with different sensitivities and color reproducibility occur in the central part and the peripheral part of the light receiving area of the solid-state imaging device. This is a so-called (luminance, color) shading phenomenon. In particular, as the condensing optics (camera lens) system becomes smaller and the focal length becomes shorter, the fluctuation in sensitivity due to the difference between the incident angle of the incident light near the center of the light receiving area and the peripheral part cannot be ignored. Yes.
[0015]
Means for improving the problem (B) include the following.
(A) The arrangement of the microlens is shifted by a predetermined amount toward the center as it goes to the periphery.
(B) A microlens (inner lens) is provided below the microlens (top lens), and the light once collected by the top lens is again aligned with each photodiode by the inner lens and condensed. Let
(C) In the peripheral signal processing circuit (external circuit), the sensitivity variation is electrically corrected.
[0016]
The improvement means (b) and (b) above are becoming difficult to adopt because the microlens shape and its arrangement position control have become difficult with the miniaturization of photodiodes. . In any of the above measures (a), (b), and (c), if the lens system is different (for example, the lens system of a digital still camera and the lens system of a mobile phone camera), the appearance of shading differs. A design change is required for each imaging system to be applied.
[0017]
In contrast to the conventional color solid-state imaging device having such a problem, US Pat. No. 5,965,875 (Patent Document 2) discloses a photodiode for detecting blue color, detecting green color, and detecting red color with a depth of a semiconductor substrate. A CMOS image sensor formed by overlapping in the direction is proposed. This CMOS image sensor is an 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 ( The principle described in Non-Patent Document 1), that is, the principle that the photoelectric conversion characteristic of each photodiode has wavelength dependency (spectral sensitivity) depending on the depth of the PN junction of the photodiode from the surface of the semiconductor substrate is used. is doing.
[0018]
[Patent Document 1]
US Pat. No. 3,971,065
[Patent Document 2]
US Pat. No. 5,965,875
[Non-Patent Document 1]
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
[0019]
[Problems to be solved by the invention]
The above-described CMOS image sensor of Patent Document 2 utilizes the fact that the light absorption in the depth direction of each pixel, that is, a photodiode, and the visible light wavelength have a corresponding relationship, and the pixel, that is, each color (R, G, B, etc.). ), The Nyquist domain does not differ, and it is considered that false colors and color moiré are less likely to occur.
[0020]
However, in order to obtain the spectral spectrum of each color component based on the wavelength dependence of the photoelectric conversion efficiency in the depth direction of the light incident on the silicon substrate, ohmic contacts are provided for the photodiode structures corresponding to light having different wavelengths. However, there is a problem that the structure in which the electric signal is directly read out is taken, the area of the light receiving portion of the photodiode is relatively reduced, and multilayer metal wirings need to be provided in the X and Y directions on the element surface. .
[0021]
An object of the present invention is to provide an inexpensive single-plate color solid-state imaging device that enables high-sensitivity, high-resolution, and faithful color reproduction with suppressed generation of false signals (moire) and false colors.
[0022]
[Means for Solving the Problems]
  The color solid-state imaging device of the present invention is a color solid-state imaging device including a plurality of photoelectric conversion regions arranged in an array on the surface of a semiconductor substrate, and the surface of the semiconductor substrate corresponds to each of the photoelectric conversion regions. And each of the openings is covered with a light-shielding film having one opening, and the photoelectric conversion region is divided into a plurality of sections for outputting a plurality of photoelectric conversion signals having different spectral sensitivities. Divided into planesWherein the diameter or diagonal length of each of the openings is t, and the wavelength of red light is 0.650 μm, and t is λ to 2λ, and the plurality of different spectral sensitivities are the primary color system. The spectral sensitivity of the three colors red, green and blueIt is characterized by that.
  The color solid-state imaging device according to the present invention is the color solid-state imaging device described above, wherein the plurality of different spectral sensitivities have a peak in a negative portion of a color matching function in addition to the three primary color systems. It is characterized by including sensitivity.
  The color solid-state imaging device of the present invention is a color solid-state imaging device including a plurality of photoelectric conversion regions arranged in an array on the surface of a semiconductor substrate, and the semiconductor substrate surface is one of the photoelectric conversion regions. Corresponding to each of the plurality of openings, each of which is covered by a light-shielding film, and inside each of the openings, the photoelectric conversion region outputs a plurality of photoelectric conversion signals having different spectral sensitivities. Each of the plurality of different spectrums is divided into planes, where t is the size of λ-2λ, where t is the diameter or diagonal length of each of the openings, and λ is the wavelength of red light 0.650 μm. The sensitivity is characterized by the spectral sensitivities of three complementary colors of yellow, cyan, magenta and green.
[0023]
  With this configuration, the sections having different spectral sensitivities are arranged close to each other on the two-dimensional surface, generation of false signals and false colors is suppressed, and image data with high sensitivity and high resolution and excellent color reproducibility is obtained. This color solid-state imaging device can be manufactured at low cost..
[0024]
The color solid-state imaging device of the present invention is a color solid-state imaging device including a plurality of photoelectric conversion regions arranged in an array on the surface of a semiconductor substrate, and each inside of the photoelectric conversion region has a plurality of different spectral sensitivities. And is divided into a plurality of sections for storing the signal charges, and a transfer path for transferring the signal charges read from each of the plurality of sections is formed on the side of the photoelectric conversion region. Features.
[0025]
With this configuration, the sections having different spectral sensitivities are arranged close to each other on the two-dimensional surface, generation of false signals and false colors is suppressed, and image data with high sensitivity and high resolution and excellent color reproducibility is obtained. In addition, the color solid-state imaging device can be manufactured at low cost.
[0030]
Furthermore, in the color solid-state imaging device of the present invention, the spectral sensitivity of at least one of the sections is determined by a color filter disposed above each section.
[0031]
With this configuration, the spectral sensitivity can be easily set and desired spectral characteristics can be easily obtained.
[0032]
Furthermore, in the color solid-state imaging device of the present invention, the spectral sensitivity of at least one section of the photoelectric conversion region is determined by an impurity distribution in the depth direction of the section.
[0033]
With this configuration, a color solid-state imaging device can be formed without using a color filter.
[0034]
In the color solid-state imaging device of the present invention, the spectral sensitivity of at least one of the sections is determined by a color filter disposed above the section and an impurity distribution in the depth direction of the section.
[0035]
This configuration uses spectral characteristics that combine the spectral characteristics of the color filter and the spectral characteristics determined by the impurity distribution, so that the spectral characteristics of the section using the color filter are improved and the color of the color image captured by the color solid-state imaging device is improved. Reproducibility is improved.
[0036]
Furthermore, in the color solid-state imaging device of the present invention, the section includes a P well layer provided on an N type semiconductor substrate and an N type impurity layer formed on the P well layer, and the depth of the P well layer is increased. And the spectral sensitivity of the section is determined by changing the depth of the N-type impurity layer.
[0037]
With this configuration, sections having different spectral sensitivities can be formed without using a color filter, the manufacturing process can be simplified, and the manufacturing yield can be improved.
[0038]
Furthermore, in the color solid-state imaging device of the present invention, the depth of the P-well layer in the section having the blue spectral sensitivity, the depth of the P-well layer in the section having the green spectral sensitivity, and the section having the red spectral sensitivity. The depth of the P well layer in is formed deeper in order.
[0039]
With this configuration, the photoelectric charge generated by the light on the long wavelength side of each spectral sensitivity flows out to the substrate, and the long wavelength side of each spectral characteristic is attenuated.
[0040]
Furthermore, in the color solid-state imaging device of the present invention, the depth of the N-type impurity layer provided in the P well layer of the section having the blue spectral sensitivity and the P well layer in the section having the green spectral sensitivity are provided. The depth of the N-type impurity layer and the depth of the N-type impurity layer provided in the P-well layer in the section having red spectral sensitivity are formed in order.
[0041]
With this configuration, light incident on the semiconductor substrate of the color solid-state imaging device can be detected by being distinguished by the length of the wavelength, that is, the penetration depth into the semiconductor substrate.
[0048]
  Furthermore, in the color solid-state imaging device of the present invention,In the negative part of the color matching functionProcessing is performed using a signal read from a section having spectral sensitivity with a peak, and color reproduction that approximates a color matching function is performed.
[0049]
With this configuration, an image close to an image seen by a person can be obtained.
[0050]
Furthermore, the color solid-state imaging device according to the present invention includes a configuration in which the arrangement of sections having the same spectral sensitivity is different between adjacent photoelectric conversion regions.
[0051]
With this configuration, it is possible to further suppress the occurrence of moire.
[0052]
Furthermore, in the color solid-state imaging device of the present invention, the area of at least one of the sections in the photoelectric conversion region is different from the areas of the other sections.
[0053]
With this configuration, the spectral sensitivity, that is, the signal intensity of each section can be made uniform, and the color balance can be optimized.
[0054]
Furthermore, in the color solid-state imaging device of the present invention, the area of each section in the photoelectric conversion region is inversely proportional to the relative size per unit area of the spectral sensitivity.
[0055]
With this configuration, the sensitivity balance for each color is optimized, and good image data can be generated.
[0056]
A digital camera according to the present invention includes any one of the color solid-state imaging devices described above.
[0057]
With this configuration, generation of false signals and false colors is suppressed, and an image with high sensitivity and high resolution and excellent color reproducibility can be taken.
[0058]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0059]
(First embodiment)
FIG. 1 is a schematic diagram of a single-plate color solid-state imaging device according to the first embodiment of the present invention. On the surface of the semiconductor substrate constituting the single-plate color solid-state imaging device 1 according to the present embodiment, a photoelectric conversion region 10 (hereinafter, each photoelectric conversion region is referred to as a pixel portion), which will be described in detail later, is square in this example. It is formed in a grid pattern arranged vertically and horizontally.
[0060]
The inside of each pixel unit 10 is divided into a plurality of sections having different spectral sensitivities (hereinafter, each section is also referred to as a small pixel), and the pixel units 10 adjacent in the horizontal direction in FIG. The accumulated charge of each small pixel is sequentially read out to the vertical transfer path formed in the vertical direction, and the charge transferred through the vertical transfer path is then transferred through the horizontal transfer path (HCCD) 11. Output from the color solid-state imaging device 1.
[0061]
FIG. 2 is an enlarged plan view of four pixels of the pixel unit 10 of the single-plate color solid-state imaging device shown in FIG. Each pixel unit 10 has a spectral spectrum different from that of a small pixel having red spectral sensitivity (denoted as “R” in the drawing) and a small pixel having blue spectral sensitivity (denoted as “B” in the drawing). A total of four small pixels of two small pixels having two types of green spectral sensitivities (denoted as “G1” and “G2” in the figure) are divided into four vertically and horizontally by an element separation band 12.
[0062]
The single-plate color solid-state imaging device 1 shown in FIG. 2 shows a state covered with a light shielding film 13, and each light shielding film 13 has an opening 13 a for each pixel portion 10. Are provided, and no opening is provided for each small pixel R, G1, G2, B in the pixel unit 10. Therefore, even if the pixel unit 10 and the small pixels R, G1, G2, and B are miniaturized (higher pixels), the size of the opening 13a can be made larger than the wavelength of light, and the sensitivity is good. A simple image can be captured.
[0063]
  FIG. 3 is a cross-sectional view of one pixel of the pixel 10 of the single-plate color solid-state imaging device 1 in which the microlens is arranged, and corresponds to a cross section taken along line III-III in FIG. A P well layer 3 is formed on the surface of the N-type substrate 2, and an element isolation band 1 is formed on the surface of the P well layer 3.2Thus, N-type impurity layers 4a and 4b are formed which are separated from each other. A PN junction formed between the P-well layer 3 and each of the N-type impurity layers 4a and 4b forms a photodiode (photoelectric conversion unit), and photocharge corresponding to incident light is applied to the N-type impurity layers 4a and 4b. Accumulated.
[0064]
The surface of each N-type impurity layer 4a, 4b has a high concentration P-type impurity layer (surface P⁺Layers) 5a and 5b are formed, and the semiconductor surface is covered with an oxide film 5c. N-type impurity layers 15 formed beside each N-type impurity layer 4a, 4b constitute a vertical transfer path, and a transfer electrode 18 is provided above the vertical transfer path 15 via an oxide film 5c.
[0065]
Further, a flattening film 7a is provided thereon, and a light shielding film 13 having an opening 13a and covering the transfer electrode and the vertical transfer path is provided on the upper surface of the flattening film 7a, and the color filter layer 8 is formed thereon. Further, one microlens 14 is provided for one opening of the light shielding film 13 through the planarizing film 7b.
[0066]
Note that the small pixels R, G1, G2, and B shown in FIG. 2 and the subsequent FIG. 4 do not indicate the respective color portions of the color filter layer 8, but the N-type impurity layer 4a in FIG. , 4b, and “R”, “G1”, “G2”, and “B” depend on the color of the color filter layer 8 of the photodiode formed by the N-type impurity layers 4a and 4b and the P-well layer 3, respectively. The spectral sensitivity is shown.
[0067]
One microlens (top lens) 14 according to the present embodiment is provided for one pixel unit 10, so that all the light incident from the microlens 14 enters the corresponding opening 13 a of the light shielding film 13. Designed.
[0068]
In the present embodiment, the incident light collected by the top lens 14 does not need to be accurately imaged on any small pixel, and it is only necessary to collect the luminous flux in the opening 13a. It becomes easy.
[0069]
FIG. 4 is a plan view showing two pixel portions in a state where the light shielding film 13 is removed from the state shown in FIG. Vertical transfer paths 15 extending in the vertical direction are formed on both sides of each pixel portion 10. In this embodiment, as shown in FIG. 5 (cross-sectional view taken along the line VV in FIG. 4), polysilicon is formed from polysilicon. The transfer electrodes 16, 17 and 18 having a three-layer structure are stacked on the buried channel (vertical transfer path) 15 via the oxide film 5c and driven by, for example, a three-phase transfer pulse. The vertical transfer path 15 and the electrodes 16, 17, 18 are formed so as to be between the pixel portions 10 while avoiding the element isolation band 12 between the adjacent small pixels R, G 1, G 2, B in the pixel portion 10. Is done.
[0070]
That is, when the light shielding film 13 covers the semiconductor surface of the solid-state imaging device, not only the vertical transfer path 15 but also the electrodes 16, 17 and 18 are hidden by the light shielding film 13, and as shown in FIG. The vertical transfer path 15 and the electrodes 16, 17, 18 are not exposed. For this reason, the distance between adjacent small pixels in one pixel unit 10 can be set to the minimum processing size necessary for element separation, and the same manufacturing process, design rule, and chip size are the same as the conventional one. The distance between the small pixels in the pixel portion can be shortened, and the occurrence of false colors is suppressed.
[0071]
In addition, a plurality of small pixels having different spectral sensitivities are concentrated and arranged as a pixel portion, and each small pixel is formed adjacent to each other with only the element separation band 12 interposed therebetween. Compared to a solid-state imaging device, the chip utilization rate is improved.
[0072]
In the single-plate color solid-state imaging device 1 having such a configuration, first, the accumulated charges of the small pixel R and the small pixel G1 are read out to the vertical transfer path 15 respectively, and then the horizontal transfer path 11 ( 1), and then transferred along the horizontal transfer path 11 and output from the solid-state imaging device 1. Then, the accumulated charges of the small pixel G2 and the small pixel B are respectively read out to the vertical transfer path 15 and then transferred along the vertical transfer path 15 to the horizontal transfer path 11, and then along the horizontal transfer path 11 It is transferred and output from the solid-state imaging device 1.
[0073]
As described above, according to the present embodiment, a plurality of small pixels are concentrated and arranged in one place to form one pixel unit, and the distance between the small pixels in one pixel unit is set to the small pixel in the adjacent pixel unit. Since the distance is smaller than the distance, the opening 13a of the light-shielding film 13 can be made large even if the resolution is increased and each small pixel is miniaturized, and a highly sensitive image can be taken. The opening diameter (diameter or diagonal length) t of each opening 13a is 3 colors or 4 colors corresponding to each color component even if the wavelength is reduced to, for example, t = λ to 2λ with respect to the red wavelength λ (nm). The output signal is not attenuated.
[0074]
In the present embodiment, since the two small pixels G1 and G2 having different spectral spectra are provided as the green small pixels, it is possible to perform faithful color reproduction as compared with the case where only the small green pixel G is provided. Furthermore, the resolution can be increased and the arrangement period of small pixels with the same spectral sensitivity can be reduced, so that the occurrence of moire is suppressed, color reproducibility is improved, and high-quality images can be obtained. It becomes.
[0075]
(Second Embodiment)
FIG. 6 is an enlarged plan view of a main part of the color solid-state imaging device according to the second embodiment of the present invention, and illustrates four pixels with a light shielding film. In the first embodiment, the arrangement of the small pixels in the pixel unit 10, that is, the arrangement of the small pixels R, G1, G2, and B is the same in all the pixel units. The arrangement of the small pixels R, G1, G2, B is regularly changed between the parts. This is to reduce periodic false signals caused by the color filter array.
[0076]
When changing the arrangement of small pixels with different spectral sensitivities in the pixel part,
(1) The upper, lower, left, and right color arrangements are exchanged alternately for each column or row of the pixel portion.
(2) The arrangement of the color filter (B) corresponding to the short wavelength and the color filter (R) corresponding to the long wavelength at the light receiving central portion and the peripheral portion of the solid-state imaging device is changed, and the light around the light receiving portion or the light shielding opening is changed. Improve vignetting (shading).
And so on.
[0077]
As described above, by periodically changing the arrangement of the small pixels in the pixel unit, it is possible to obtain an image with better image quality than in the first embodiment.
[0078]
(Third embodiment)
FIG. 7 is an enlarged plan view of a main part of a color solid-state imaging device according to the third embodiment of the present invention, and illustrates a pixel portion of four pixels provided with a light shielding film. In the first embodiment, a primary color filter is used, and two types of green color filters G1 and G2 are used. However, in this embodiment, complementary color filters Ye (yellow) and Mg (magenta) are used. , Cyan (Cy) and green (G) color filters are used.
[0079]
Since the complementary color system is composed of four colors, when the pixel portion is formed of four small pixels as in this embodiment, it is convenient to assign each color to each small pixel. In this embodiment as well, it is preferable to periodically change the arrangement of the small pixels Ye, Cy, Mg, and G in each pixel unit, as in the second embodiment.
[0080]
(Fourth embodiment)
FIG. 8 is an enlarged plan view of a main part of a color solid-state imaging device according to the fourth embodiment of the present invention, and illustrates a pixel portion of four pixels provided with a light shielding film. In each of the above-described embodiments, the pixel unit 10 is divided into four small pixels having the same area. However, in this embodiment, the pixel unit 10 is divided into four small pixels having different areas, and different spectral sensitivities R, G1, and G2 and B are allocated. By changing the area of each small pixel, it is possible to easily adjust the color balance and optimize the light sensitivity.
[0081]
The area of each small pixel in the pixel unit 10 is preferably inversely proportional to the relative spectral sensitivity per unit area of each small pixel. That is, the small pixel area is reduced for colors with high sensitivity, and the small pixel area is increased for colors with low sensitivity.
[0082]
(Fifth embodiment)
FIG. 9 is an enlarged plan view of a main part of a color solid-state imaging device according to the fifth embodiment of the present invention, and illustrates four pixels with a light shielding film. In this embodiment, in addition to the small pixels having the R, G, B spectral sensitivities of the primary color system, the small pixel having the smallest area has a fourth spectral sensitivity different from R, G, B. .
[0083]
The fourth spectral sensitivity in the present embodiment is, for example, a spectral sensitivity having a peak near a wavelength of 520 nm as shown in FIG. FIG. 11 is a graph showing the color matching function. In red (R), there is a negative portion A near 520 nm. If this is not realized, faithful color reproduction cannot be performed. Therefore, in the present embodiment, the signal charge amount corresponding to the light amount in the vicinity of the wavelength of 520 nm is detected by the small pixel having the fourth spectral sensitivity, and this is subtracted from the signal charge amount with respect to the light amount of red R, so that the same color Spectral sensitivity corresponding to the negative part A of the function is realized, and color reproduction as perceived by human eyes can be performed.
[0084]
(Sixth embodiment)
FIG. 12 is an enlarged plan view of a main part of a color solid-state imaging device according to the sixth embodiment of the present invention, and illustrates four pixels with a light shielding film. In each of the above-described embodiments, one pixel unit is formed by intensively arranging four small pixels. In this embodiment, one pixel unit is composed of three small pixels of R, G, and B. Is different.
[0085]
(Seventh embodiment)
FIG. 13 is a schematic diagram of a color solid-state imaging device according to the seventh embodiment of the present invention. In each of the above-described embodiments, the pixel units 10 are arranged in a square lattice pattern. However, in the present embodiment, the pixel unit 20 is shifted by ½ pitch between the odd-numbered rows and the even-numbered rows to form a so-called honeycomb arrangement. Different.
[0086]
Since the pixel portion 20 has a honeycomb arrangement, the vertical transfer paths (not shown in FIG. 13) provided on both sides of the pixel portion 20 have a meandering arrangement. The signal charges transferred from the vertical transfer path to the horizontal transfer path 22 (accumulated charges of the small pixels constituting the pixel unit 20) are then transferred through the horizontal transfer path 22 and output from the solid-state imaging device 21. The
[0087]
FIG. 14A is an enlarged plan view of the pixel portion 20 with the light shielding film removed, and FIG. 14B is a plan view of the light shielding film for four pixel portions. FIG. 15 is an enlarged view inside broken line circle XV in FIG.
[0088]
On both sides of the pixel portion 20, meandering vertical transfer paths 23 are formed, and polysilicon transfer pulse electrodes 24 and 25 are provided so as to overlap the vertical transfer paths 23. Further, adjacent small pixels R, G1, G2, and B constituting the pixel unit 20 are separated by the element separation band 26, but each small pixel in the pixel unit 20 is the same as in the first embodiment. The pixels R, G1, G2, and B are divided into planes with minimum processing dimensions necessary for element isolation.
[0089]
In the example shown in the figure, the rectangular pixel portion 20 inclined by 45 degrees is divided into four small pixels R, G1, G2, and B by two diagonal lines, and each accumulation is performed in the vertical transfer path 23 where each small pixel faces. The charge is read out. A light-shielding film provided with one opening corresponding to each of the pixel portions 20 (the opening 27a is shown by a virtual line only for one pixel portion 20 in FIG. 14A because the drawing is complicated) 27, since the transfer pulse electrodes 24 and 25 are provided so as to overlap the vertical transfer path 23 as described above, the electrodes 24 and 25 and the vertical transfer are provided in the opening 27a of the light shielding film 27. The path 23 is not exposed, and only the small pixels R, G1, G2, and B separated by the element isolation band 26 manufactured with the minimum processing size are exposed.
[0090]
Also in the present embodiment, since the distance between the small pixels in one pixel unit 20 is smaller than the distance to the small pixel in the adjacent pixel unit, the same effect as in the first embodiment can be obtained. By adopting a honeycomb arrangement for the portion 20, there is no wiring area for the vertical CCD transfer electrode (ineffective area that is neither a light receiving part nor a charge transfer part) compared to a square lattice arrangement, so that the surface area of the image sensor can be used effectively. Further, higher sensitivity and higher resolution can be achieved.
[0091]
Although the small pixels R, G1, G2, and B have been described, complementary color small pixels G, Cy, Ye, and Mg may be used. Alternatively, a small pixel having the three primary colors R, G, and B and the small pixel having the fourth spectral sensitivity described with reference to FIG. 9 may be used.
[0092]
Also in this honeycomb arrangement, color reproducibility and high image quality can be achieved by periodically changing the arrangement of small pixels in the pixel portion in the same manner as in the second embodiment.
[0093]
(Eighth embodiment)
Whether the pixel portions are arranged in a square lattice shape or a honeycomb shape, how to divide the surface of each pixel portion is arbitrary, and the shape of the pixel portion is also arbitrary. FIG. 16 illustrates various pixel portion shapes and small pixel surface dividing methods. In the figure, the first spectral sensitivity is CF1, the second spectral sensitivity is CF2,... The sixth spectral sensitivity is CF6.
[0094]
The number of small pixels constituting one pixel portion is at least three for the three colors R, G, and B in the primary color system, but by increasing the number of small pixels to four to five, It is possible to provide various pixels such as a small pixel having a spectral sensitivity of 4 or a small pixel having other types of spectral sensitivity, and various images for improving image quality using detection signals of these small pixels. Processing is possible.
[0095]
(Ninth embodiment)
FIG. 17 is an enlarged plan view of a main part of a color solid-state imaging device according to the ninth embodiment of the present invention. The small pixels R, G, and B in each of the embodiments described above have a configuration in which spectral sensitivity is given by a color filter, whereas in the present embodiment, the color filter is not used and the small pixel photodiode structure itself is used. The spectral sensitivity R, G, B is provided. This embodiment shows an example in which a plurality of pixel portions 10 are arranged in a square lattice pattern.
[0096]
18A, 18B, and 18C are diagrams showing the photodiode structures of the small pixels B, G, and R according to this embodiment. FIG. 18A is a cross-sectional view of a small pixel having a spectral sensitivity of blue (B), showing a cross section along line aa in FIG. FIG. 18B is a cross-sectional view of a small pixel having a spectral sensitivity of green (G), showing a cross section taken along the line bb of FIG. Similarly, FIG. 18C is a cross-sectional view of a small pixel having a red (R) spectral sensitivity, showing a cross section taken along the line cc of FIG.
[0097]
In the color solid-state imaging devices according to the first to eighth embodiments described above, the photodiode structure constituting each small pixel has the same structure, and a color filter is used so that each small pixel has spectral sensitivity. . On the other hand, in the small pixel of the present embodiment, the spectral sensitivity is given by changing the PN junction depth of the photodiode constituting each small pixel, and the depth of the P well layer is also changed according to the spectral sensitivity. Yes.
[0098]
A small pixel (FIG. 18A) having a spectral sensitivity of blue (B) has a P-well layer 31 having a depth d = 1 to 3 μm formed on an N-type silicon substrate (N-Sub) 30 to form a P-well. An N-type impurity layer 32 having a depth d = 0.2 to 0.4 μm is formed on the surface side of the layer 31, and a high-concentration P-type impurity layer (surface P) having a required depth is further formed on the surface.⁺) A layer 33 is formed, and the outermost surface is covered with a transparent oxide film 34.
[0099]
A small pixel (FIG. 18B) having a spectral sensitivity of green (G) is formed by forming a P-well layer 31 having a depth d = 3 to 4 μm on an N-type silicon substrate (N-Sub) 30 to form a P-well. An N-type impurity layer 32 having a depth d = 0.4 to 1.0 μm is formed on the surface side of the layer 31, and a surface P having a required depth is further formed on the surface.⁺The layer 33 is formed, and the outermost surface is covered with a transparent oxide film 34.
[0100]
A small pixel (FIG. 18C) having a red (R) spectral sensitivity is formed by forming a P-well layer 31 having a depth d = 4 to 6 μm on an N-type silicon substrate (N-Sub) 30 to form a P-well. An N-type impurity layer 32 having a depth d = 1.0 to 2.0 μm is formed on the surface side of the layer 31, and a surface P having a required depth is further formed on the surface.⁺The layer 33 is formed, and the outermost surface is covered with a transparent oxide film 34.
[0101]
When light is incident on the PN junctions constituting the small pixels R, G, and B, charges are accumulated in the N-type impurity layer 32 of the PN junction. The longer the wavelength of light, the deeper the penetration distance into the substrate. Therefore, charges corresponding to the amount of blue light are accumulated in the small pixels (FIG. 18A) having a shallow PN junction surface, and the intermediate depth. The small pixels (FIG. 18B) accumulate charges corresponding to the amount of green light, and the deepest small pixels (FIG. 18C) accumulate charges corresponding to the amount of red light.
[0102]
It is important for faithful color signal processing that the spectral characteristics (see FIG. 19) of each small pixel have a characteristic that attenuates also on the long wavelength side. Therefore, in the present embodiment, the depth of the P well layer 31 is also varied corresponding to each spectral characteristic. That is, the P well layer 31 is deepened in the order of FIGS. 18A, 18B, and 18C.
[0103]
As a result, in the photodiode structure shown in FIG. 18A, photoelectric charges generated by light having a wavelength longer than green (G) flow out to the N-type substrate 30, and in the photodiode structure shown in FIG. , The photocharge generated by the wavelength longer than red (R) flows out to the N-type substrate 30, and similarly, in the photodiode structure shown in FIG. 18C, it is generated by the light of the infrared wavelength outside the visible wavelength range. Photoelectric charges flow out to the N-type substrate 30 and an attenuation characteristic is realized on the long wavelength side of each spectral characteristic.
[0104]
As a result, the wavelength dependence (spectral characteristics) of the signal charges accumulated in each of the small pixels R, B, and G becomes a mountain shape in which the long wavelength side falls in each of R, G, and B, as shown in FIG. And the color reproducibility by the color signal detected by the small pixels having these spectral characteristics is improved.
[0105]
In the present embodiment, each small pixel R, G, B has a surface P.⁺Although the thickness of the layer 33 is the same dimension, the surface P of each small pixel R, G, B⁺Layer 33 may have different thicknesses.
[0106]
Needless to say, in this embodiment as well, as in each of the above-described embodiments, the arrangement positions and surface division methods of the small pixels R, G, and B in the pixel unit 10 are arbitrary. May be periodically changed, and the area of each small pixel may be different. Furthermore, the pixel portion may be arranged in a honeycomb arrangement.
[0107]
(Tenth embodiment)
20A, 20B, and 20C are cross-sectional views of a color solid-state imaging device according to the tenth embodiment of the present invention. Although basically the same as the color solid-state imaging device according to the ninth embodiment shown in FIGS. 18A, 18B, and 18C, the difference is that as shown in FIG. A blue (B) color filter 36 is also placed on a small pixel having sensitivity, and the spectral characteristics of B that can be possessed by the photodiode structure itself are further sharpened by the color filter 36. When the spectral characteristics of one of R, G, and B become sharp, the color reproducibility becomes better. Note that a green color filter may be placed on the small pixel G.
[0108]
(Eleventh embodiment)
21A, 21B, and 21C are sectional views of a color solid-state imaging device according to the eleventh embodiment of the present invention. Although basically the same as the color solid-state imaging device according to the tenth embodiment shown in FIGS. 20A, 20B, and 20C, the difference is that as shown in FIG. The small pixel diode structure (the depth of the P well layer 31 and the depth of the N-type impurity layer 32) having the same sensitivity is the same as the structure of the small pixel G (FIG. 21B). The photodiode structure is optimized to have a spectral sensitivity of G. Even if the small pixel B is optimized to have the spectral sensitivity of G, the blue color filter 36 accumulates charges according to the blue light quantity. According to this embodiment, since the small pixel B and the small pixel G can be manufactured in the same structure, there is an advantage that the manufacturing process becomes easy.
[0109]
(Twelfth embodiment)
FIG. 22 is a block diagram of a digital camera according to an embodiment of the present invention. A digital camera such as a digital still camera, a digital video camera, or a camera mounted on a small electronic device such as a cellular phone receives an optical signal of a subject image formed by a condensing optical system (not shown) and converts it into an electrical signal. The single-plate color solid-state imaging device 1 according to any one of the embodiments described above, the analog signal processing circuit 102 such as CDS for analog processing of the image signal output from the single-plate color solid-state imaging device 1, and the analog signal An analog-to-digital conversion circuit 103 that converts the image signal processed by the processing circuit 102 into a digital image signal, and a digital processing circuit that takes the digitized image signal and performs JPEG compression or expansion, or performs DRAM control 104, a DRAM 105 connected to the digital processing circuit 104, It includes a system microcomputer 106 for generally controlling the entire Tarukamera, a recording medium 107 for recording the image data captured, and a bus 108 for connecting these to each other.
[0110]
In the digital camera according to the present embodiment, each color signal component of R, G, and B is output from each of the above-described small pixels of the color solid-state imaging device 1, and thus high sensitivity with suppressed generation of false signals (moire) and false colors. , It is possible to capture a color image capable of high-resolution and faithful color reproduction.
[0111]
【The invention's effect】
According to the present invention, it is possible to obtain a single-plate color solid-state imaging device that enables high-sensitivity, high-resolution, and faithful color reproduction with reduced generation of false signals (moire) and false colors.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a color solid-state imaging device according to a first embodiment of the present invention.
FIG. 2 is an enlarged plan view of a main part of the color solid-state imaging device shown in FIG.
3 is a cross-sectional view of the pixel portion shown in FIG.
4 is a schematic plan view of four pixel portions from which the light shielding film of FIG. 2 is removed. FIG.
5 is a cross-sectional view taken along line VV in FIG.
FIG. 6 is a plan view of an essential part of a color solid-state imaging device according to a second embodiment of the present invention.
FIG. 7 is a plan view of an essential part of a color solid-state imaging device according to a third embodiment of the present invention.
FIG. 8 is a plan view of an essential part of a color solid-state imaging device according to a fourth embodiment of the present invention.
FIG. 9 is a plan view of an essential part of a color solid-state imaging device according to a fifth embodiment of the present invention.
FIG. 10 is an explanatory diagram of a fourth spectral sensitivity used in the fifth embodiment of the present invention.
FIG. 11 is a graph showing color matching functions of R, G, and B.
FIG. 12 is a plan view of an essential part of a color solid-state imaging device according to a sixth embodiment of the present invention.
FIG. 13 is a schematic diagram of a color solid-state imaging device according to a seventh embodiment of the present invention.
14A is an enlarged plan view of a main part of the color solid-state imaging device shown in FIG.
(B) It is a top view of the light shielding film for four pixel parts.
FIG. 15 is an enlarged view inside a broken line circle XV shown in FIG.
FIG. 16 is a diagram illustrating a surface division example of a pixel portion of a color solid-state imaging device according to an eighth embodiment of the present invention.
FIG. 17 is an enlarged plan view of a main part of a color solid-state imaging device according to a ninth embodiment of the present invention.
18A is a cross-sectional view taken along line aa in FIG.
(B) is a sectional view taken along line bb of FIG.
(C) is a sectional view taken along the line cc of FIG.
FIG. 19 is a graph illustrating spectral characteristics of small pixels R, G, and B of a color solid-state imaging device according to a ninth embodiment of the present invention.
FIG. 20 is a cross-sectional view of small pixels B, G, and R of a color solid-state imaging device according to a tenth embodiment of the present invention.
FIG. 21 is a cross-sectional view of small pixels B, G, and R of a color solid-state imaging device according to an eleventh embodiment of the present invention.
FIG. 22 is a configuration diagram of a digital camera according to an embodiment of the present invention.
[Explanation of symbols]
1 Color solid-state imaging device
10,20 Pixel part (photoelectric conversion area)
11, 22 Horizontal transfer path
12, 26 element isolation band
13, 27 Light shielding film
13a, 27a opening
14 Micro lens (top lens)
15, 23 Vertical transfer path
16, 17, 18, 24, 25 electrodes
30 N-type silicon substrate
31 P well layer
32 N-type impurity layer
33 Surface P⁺layer

Claims (15)

A color solid-state imaging device including a plurality of photoelectric conversion regions arranged in an array on a surface of a semiconductor substrate, wherein the semiconductor substrate surface has one opening corresponding to each one of the photoelectric conversion regions. The photoelectric conversion region is divided into a plurality of sections for outputting a plurality of photoelectric conversion signals having different spectral sensitivities, inside each of the openings .
When the diameter or diagonal length of each of the openings is t and the wavelength of red light is 0.650 μm, λ is t λ to 2λ,
The color solid-state imaging device, wherein the plurality of different spectral sensitivities are red, green, and blue spectral sensitivities of three primary colors . 2. The color solid-state imaging device according to claim 1, wherein the plurality of different spectral sensitivities include spectral sensitivities having a peak in a negative portion of a color matching function in addition to the three primary colors. Color solid-state imaging device. A color solid-state imaging device including a plurality of photoelectric conversion regions arranged in an array on a surface of a semiconductor substrate, wherein the semiconductor substrate surface has one opening corresponding to each one of the photoelectric conversion regions. The photoelectric conversion region is divided into a plurality of sections for outputting a plurality of photoelectric conversion signals having different spectral sensitivities, inside each of the openings .
When the diameter or diagonal length of each of the openings is t and the wavelength of red light is 0.650 μm, λ is t λ to 2λ,
The color solid-state imaging device, wherein the plurality of different spectral sensitivities are spectral sensitivities of three complementary colors of yellow, cyan, magenta, and green . 4. The color solid-state imaging device according to claim 1 , wherein a transfer path that transfers the signal charges read from each of the plurality of sections is formed on a side of the photoelectric conversion region. A color solid-state imaging device. 5. The color solid-state imaging device according to claim 1, wherein the spectral sensitivity of at least one of the sections is determined by a color filter disposed above each section. Imaging device. 3. The color solid-state imaging device according to claim 1 , wherein the spectral sensitivity of at least one section of the photoelectric conversion region is determined by an impurity distribution in a depth direction of the section. Color solid-state imaging device. 3. The color solid-state imaging device according to claim 1, wherein the spectral sensitivity of at least one of the sections is determined by a color filter disposed above the section and an impurity distribution in a depth direction of the section. A color solid-state imaging device. 8. The color solid-state imaging device according to claim 6 , wherein the section includes a P well layer provided on an N type semiconductor substrate, and an N type impurity layer formed on the P well layer. A color solid-state imaging device, wherein the spectral sensitivity of the section is determined by changing a depth of the P-well layer and a depth of the N-type impurity layer. 9. The color solid-state imaging device according to claim 8 , wherein the depth of the P-well layer in the section having blue spectral sensitivity, the depth of the P-well layer in the section having green spectral sensitivity, and the red spectral sensitivity. A color solid-state imaging device, wherein the depth of the P-well layer in the section having a depth is formed in order. 10. The color solid-state imaging device according to claim 8 , wherein a depth of an N-type impurity layer provided in the P well layer of the section having a blue spectral sensitivity and the section having a green spectral sensitivity. The depth of the N-type impurity layer provided in the P well layer and the depth of the N-type impurity layer provided in the P well layer in the partition having the red spectral sensitivity are formed in order. A color solid-state imaging device. 3. The color solid-state imaging device according to claim 2 , wherein processing is performed with a signal read from a section having spectral sensitivity having a peak in a negative portion of the color matching function, and color reproduction approximating the color matching function is performed. A color solid-state imaging device. The color solid-state imaging device according to any one of claims 1 to 11, wherein the solid-state imaging device includes an arrangement in which sections having the same spectral sensitivity are different between adjacent photoelectric conversion regions. apparatus. The color solid-state imaging device according to any one of claims 1 to 12, wherein an area of at least one of the sections in the photoelectric conversion region is different from an area of another section. Color solid-state imaging device. 14. The color solid-state imaging device according to claim 13 , wherein the area of each section in the photoelectric conversion region is inversely proportional to the relative size per unit area of the spectral sensitivity. Color solid-state imaging device. A digital camera comprising the color solid-state imaging device according to any one of claims 1 to 14 .

Images