JP2006202907A - Image pickup element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To substantially improve influence of an aperture ratio of a micro lens and to suppress influence of color mixture, in an image pickup element. <P>SOLUTION: The image pickup element 50 having a plurality of pixels is provided with: photoelectric converters 2 provided for each of the plurality of pixels and converting a received light into an electric signal; the micro lenses 9 for collecting a light to be incident into the image pickup element into the photoelectric converter; and inner lenses 10 provided between the micro lens and the photoelectric converters and having a light collecting function. The micro lenses 9 are each disposed on pixels adjacent in the direction of a vertical angle of each pixel, of the plurality of pixels, and the inner lenses 10 are each disposed on a pixel in which the micro lenses are not disposed, of the plurality of pixels. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image sensor that captures a subject image.

  In recent years, solid-state image sensors used in digital still cameras and the like are roughly classified into CCD (Charge-Coupled Device) and CMOS (Complimentary Metal Oxide Semiconductor) image sensors (see Patent Document 1 and Patent Document 2).

  First, the structure of the CCD 1000 will be briefly described with reference to FIG.

  FIG. 10 is a sectional view of the CCD 1000.

10, 1001 is a semiconductor substrate made of silicon or the like, 1002 is a photoelectric conversion element made of a photodiode, 1003 is an oxide film formed on the semiconductor substrate 1001, 1004 is a charge transferred by the photoelectric conversion element 1002, etc. A three-layer wiring made of polysilicon or the like through which a clock signal is transmitted, 1006 is a light-shielding layer made of tungsten or the like, which mainly shields the charge transfer vertical CCD register 1005 provided below the wiring 1004; Reference numeral 1007 denotes a first protective film made of SiO ₂ or the like for protecting the photoelectric conversion element 1002 or the like from outside air (O ₂ , H ₂ O), impurity ions (K +, Na +), etc., and 1008 denotes a second protective film such as a SiON type. It is a membrane. Reference numeral 1009 denotes a planarizing layer made of an organic material for reducing unevenness of the second protective film 1008, and reference numeral 1010 denotes a microlens that collects light from a subject on the photoelectric conversion element 1002.

  The planarization layer 1009 eliminates the unevenness of the main surface 1011 of the CCD 1000 and also serves to adjust the focal length of the microlens 1010 so that the light passing through the microlens 1010 forms an image on the photoelectric conversion element 1002. . Therefore, the thickness of the planarization layer 1009 is determined by the curvature of the lens and the refractive index of the lens material.

  On the other hand, the structure of the CMOS image sensor 1050 will be briefly described with reference to FIG.

  FIG. 11 is a cross-sectional view of one pixel of the CMOS image sensor 1050.

In FIG. 11, reference numeral 1051 denotes a silicon substrate (Si substrate), which is provided with a light receiving portion 1052 serving as a photoelectric conversion element such as a photodiode. Reference numeral 1053 is formed between interlayer insulating films 1054 made of SiO ₂ or the like, and is a transfer electrode for transferring photocharge generated in the light receiving portion 1052 to a floating diffusion portion (FD portion) (not shown). is there. Reference numeral 1055 denotes a wiring electrode having a light-shielding action formed so that light is not incident on other than the light receiving portion 1052, and 1056 is formed on an uneven surface formed by an electrode or wiring (not shown) to provide a flat surface. A planarizing film 1057 is a color filter of, for example, red (R), green (G), and blue (B), and a micro lens 1059 is further formed through a planarizing layer 1058. The lens shape of the microlens 1059 is determined so that a light beam incident from a photographing lens (not shown) is condensed on the light receiving unit 1052.

  In recent years, an intra-layer lens structure in which a lens function is inserted between the microlens and the light receiving portion is mainly employed (see Patent Document 3).

This is generally used to more reliably guide light from the microlens by the light shielding film 1006 in the CCD 1000 and the wiring electrode 1055 in the CMOS image sensor 1050, and has the effect of increasing the substantial aperture ratio.
JP 2002-141488 A JP 2002-083948 A Japanese Patent Laid-Open No. 11-274443

  In general, the amount of light that is sensed by the photoelectric conversion element 1002 (light receiving unit 1052), that is, the so-called sensitivity characteristic inherent to the imaging element, is greatly influenced by the aperture ratio of the microlenses (1010, 1059).

  FIG. 12 is a view of four pixels of the CMOS image sensor 1050 as viewed from above, and the ratio (aperture ratio) of the aperture of the microlens to the square surface of one pixel is about 70%. In this case, about 30% of the area other than the microlens cannot be efficiently guided to the light receiving unit 1052, and is blocked by the wiring electrode 1055, or light passing through the color filter of the corresponding pixel is adjacent to the pixel. It causes the so-called color mixture to enter.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to substantially improve the aperture ratio of the microlens and to suppress the influence of color mixing in the imaging device. .

  In order to solve the above-described problems and achieve the object, an image pickup device according to the present invention is an image pickup device that includes a plurality of pixels, is arranged for each of the plurality of pixels, and photoelectrically converts received light into an electric signal. A conversion unit, a microlens for condensing the light incident on the image sensor on the photoelectric conversion unit, and an internal lens having a condensing function disposed between the microlens and the photoelectric conversion unit. The microlens is disposed in each of the plurality of pixels adjacent to each pixel in the diagonal direction, and the pixel in which the microlens is not disposed among the plurality of pixels. Are characterized in that the internal lenses are respectively arranged.

  Further, an image sensor according to the present invention includes, in an image sensor having a plurality of pixels, a photoelectric conversion unit that is arranged for each of the plurality of pixels and converts received light into an electric signal, and light incident on the image sensor. A microlens for condensing on the photoelectric conversion unit, and first and second internal lenses having a condensing function disposed between the microlens and the photoelectric conversion unit, each having an opening diameter Different first and second inner lenses are provided, and among the plurality of pixels, pixels adjacent to each pixel in the diagonal direction have smaller aperture diameters than the microlens and the first inner lens. A second internal lens is disposed, and the first internal lens is disposed in each of the plurality of pixels in which the microlens is not disposed.

  Further, an image sensor according to the present invention includes, in an image sensor having a plurality of pixels, a photoelectric conversion unit that is arranged for each of the plurality of pixels and converts received light into an electric signal, and light incident on the image sensor. A microlens for condensing on the photoelectric conversion unit, the first and second microlenses having different aperture diameters, and a condensing function disposed between the microlens and the photoelectric conversion unit First and second internal lenses having first and second internal lenses having different aperture diameters, and the pixels adjacent to each other in the diagonal direction among the plurality of pixels. A first microlens having a larger aperture diameter than the second microlens and a second inner lens having a smaller aperture diameter than the first inner lens are disposed, and the plurality of pixels ,in front The pixel in which the first microlens and the second inner lens is not disposed, characterized in that said second micro-lens and the first inner lens are disposed, respectively.

  According to the present invention, in the imaging device, the aperture ratio of the microlens can be substantially improved and the influence of color mixing can be suppressed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
This embodiment is a first embodiment in which the present invention is applied to a CMOS image sensor.

  FIG. 1 is a side sectional view showing a configuration of a CMOS image sensor 50 according to the first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a silicon substrate (Si substrate), which is provided with a light receiving portion 2 that becomes a photoelectric conversion element such as a photodiode. In addition, 5 is a wiring electrode having a light shielding effect formed so that light is not incident on other than the light receiving portion 2, and 6 is provided on an uneven surface formed by an electrode or a wiring (not shown) to provide a flat surface. For example, a planarizing film 7 is a color filter of, for example, red (R), green (G), and blue (B), and an intralayer lens 10 is formed via a planarizing layer 8. The intra-layer lens 10 has a lens effect based on the sum of refractive indexes with the interlayer material 11 having a relatively low refractive index, and the microlens 9 is disposed on the interlayer material 11 via the planarizing film 12. Yes. Each lens shape is determined so that a light beam incident from a photographing lens (not shown) can be condensed on the light receiving unit 2 by the microlens 9 or the in-layer lens 10.

  Here, the amount of light sensed by the light receiving unit 2, the so-called sensitivity characteristic specific to the imaging element, is greatly influenced by the aperture ratio of the microlens 9 and the in-layer lens 10.

  FIG. 2 is a view of the CMOS image sensor 50 shown in FIG. 1 as viewed from above, and shows the size and planar arrangement of the microlenses 9 and the intralayer lenses 10.

  As can be seen from FIG. 2, the microlens 9 is not disposed in the adjacent pixel, but is disposed only in the diagonal pixel region. The one-layer inner lens 10 is disposed only in the diagonal pixel region where the microlens 9 is not disposed.

  FIG. 3 is a diagram showing the total aperture ratio of the microlens and the in-layer lens for the square surface of one pixel in FIG. 2 corresponding to the Bayer array color filter.

  As can be seen from FIG. 3, the microlens 9 is arranged corresponding to the blue (B) and red (R) color filters, and the total aperture ratio of the lens slightly exceeds 100%. On the other hand, the in-layer lens 10 is arranged corresponding to a green (G) color filter, and the total aperture ratio of the lens is about 85%, which is significantly higher than the conventional configuration as shown in FIG. You can see that is going up. Further, the effective aperture ratio in the total of R, G, and B is very high, and the structure is not easily affected by color mixing.

  In the example of FIG. 3, the aperture ratios of the B and R color filters are different from those of the G color filter, but the spectral characteristics of the original color filters of R, G, and B are different. Is the product of the spectral characteristics of each color filter and the aperture ratio. Finally, since image processing with a single-plate image sensor performs white balance adjustment, it does not matter that the spectral characteristics differ for each of R, G, and B. Conversely, as in the present embodiment, the balance ratio including image processing is changed by changing the aperture ratio of each color filter on purpose and combining a lens with a small aperture ratio for a color with little correction (eg, G). It is possible to reduce the correction coefficient for performing.

(Second Embodiment)
FIG. 4 is a diagram showing a second embodiment of the present invention, and the same reference numerals are given to the same components as those in FIG.

  FIG. 5 is a view of the CMOS image sensor 60 shown in FIG. 4 as viewed from above, and shows the size and planar arrangement of the microlenses 9 and the intralayer lenses 10.

  As can be seen from FIGS. 4 and 5, the inner lens 13 having an aperture diameter smaller than that of the inner lens 10 is also disposed in the pixel in which the micro lens 9 is disposed. By using the in-layer lens 13 together, it is possible to correct spherical aberration that cannot be suppressed by the microlens 9 alone, and it is also possible to act so that light is not blocked by the wiring electrode 5.

  Also in this case, the total aperture ratio is almost the same as in FIG. 3, and the same effect as in the first embodiment can be obtained.

(Third embodiment)
FIG. 6 is a diagram showing a third embodiment of the present invention, and the same reference numerals are given to the same components as those in FIG.

  FIG. 7 is a view of the CMOS image sensor 70 shown in FIG. 6 as viewed from above, and shows the size and planar arrangement of the microlenses 9 and the intralayer lenses 10.

  As can be seen from FIGS. 6 and 7, in the pixel in which the microlens 9 is disposed, the inner lens 13 having an aperture diameter smaller than that of the inner lens 10 is disposed, and the inner lens 10 is disposed. The microlens 14 having an aperture diameter smaller than that of the microlens 9 is also disposed in the pixel that is formed. Thus, by using the microlenses 9 and 14 and the in-layer lenses 10 and 13 together, as in the second embodiment, spherical aberration is corrected and light is not blocked by the wiring electrode 5. Is possible.

(Fourth embodiment)
FIG. 8 is a diagram showing a fourth embodiment of the present invention, and the same reference numerals are given to the same components as those in FIG.

  In the CMOS image sensor 80 of the present embodiment, SiN having a high refractive index is used as the protective film 15 on the upper surface of the electrode, and the in-layer lens 16 made of SiN is formed only in the pixel corresponding to the green color filter. A color filter 7 is arranged on the upper surface of the planarizing film 6, and a microlens 9 is formed on the upper surface of the planarizing film 8. Each lens shape is determined so that a light beam incident from a photographing lens (not shown) can be condensed on the light receiving unit 2 by the microlens 9 or the in-layer lens 16.

  FIG. 9 is a diagram showing the total aperture ratio of the microlens and the in-layer lens with respect to the square surface of one pixel in FIG. 8 corresponding to the Bayer array color filter.

  As can be seen from FIG. 9, the microlens 9 is arranged corresponding to the blue (B) and red (R) color filters, and the total aperture ratio of the lens exceeds 100%. On the other hand, the in-layer lens 16 is arranged corresponding to a green (G) color filter, and the total aperture ratio of the lens is about 75%. In this case, the effective aperture ratio in total of R, G, and B is about 95%, and by making the shape of the color filter according to the in-layer lens, it is possible to make it less susceptible to the influence of color mixing.

  As described above, the embodiments of the present invention have been described based on the CMOS image sensor, but the same effect can be obtained even when applied to a CCD image sensor. In the above-described embodiment, examples of the upward convex microlens and the upward convex in-layer lens are shown. However, for example, an upward convex micro lens and a downward convex in-layer lens may be used. In addition, although the shape of the micro lens and the in-layer lens has been described as a circular shape, for example, an R, G, and B total can be obtained by applying an octagonal shape to the micro lens and the in-layer lens or changing the size of the circular shape. It is also possible to arbitrarily set the balance of the actual aperture ratio for each color of the color filter without lowering the effective aperture ratio at.

  As described above, according to the above embodiment, the aperture ratio of the microlens can be substantially improved, and the influence of color mixing can be suppressed.

  In addition, the aperture ratio of each color of the color filter can be changed according to the spectral characteristics of the color filter without lowering the total aperture ratio of the microlens and the in-layer lens. It is possible to adjust both the aperture ratio for each color of the color filter, and it is possible to improve color reproducibility and the like.

It is a sectional side view which shows the structure of the CMOS image sensor of the 1st Embodiment of this invention. It is the figure which looked at the CMOS image sensor shown in FIG. 1 from the top, and is a figure which shows the magnitude | size and planar arrangement | sequence of a microlens and an in-layer lens. It is a figure explaining the aperture ratio of 1st Embodiment. It is a figure which shows the 2nd Embodiment of this invention. It is the figure which looked at the CMOS image sensor shown in FIG. 4 from the top, and is a figure which shows the magnitude | size and planar arrangement | sequence of a microlens and an in-layer lens. It is a figure which shows the 3rd Embodiment of this invention. It is the figure which looked at the CMOS image pick-up element shown in FIG. 6 from the top, and is a figure which shows the magnitude | size and planar arrangement | sequence of a micro lens and an in-layer lens. It is a figure which shows the 4th Embodiment of this invention. It is a figure explaining the aperture ratio of the 4th Embodiment of this invention. It is a sectional side view which shows the schematic structure of the conventional CCD. It is a sectional side view which shows the schematic structure of the conventional CMOS image sensor. It is a figure explaining the aperture ratio of the conventional microlens.

Explanation of symbols

1,1051 Si substrate 2,1002,1052 Light receiving part 4,1054 Interlayer insulating film 5,1055 Wiring electrode 6,8,12 Flattening film 7,1057 Color filter 9,14,1059 Microlens 10,13 Intralayer lens 50 , 60, 70, 80, 1050 CMOS image sensor 1000 CCD
1053 Transfer electrode

Claims (9)

In an image sensor having a plurality of pixels,
A photoelectric conversion unit that is arranged for each of the plurality of pixels and converts received light into an electrical signal;
A microlens for condensing the light incident on the image sensor on the photoelectric conversion unit;
An internal lens having a light collecting function disposed between the microlens and the photoelectric conversion unit;
Among the plurality of pixels, pixels adjacent to each pixel in the diagonal direction are each provided with the microlens, and among the plurality of pixels, the pixels on which the microlens is not provided are An image pickup device in which internal lenses are arranged.   The microlens and the internal lens are disposed so as to partially overlap each other in a pixel in which the microlens is disposed adjacent to each other and a pixel in which the internal lens is disposed. The imaging device according to 1.   The pixel further includes a color filter that is arranged so that one color corresponds to one pixel of the plurality of pixels, and a plurality of types of colors are periodically arranged, and the pixel on which the microlens is arranged and the internal lens The image pickup device according to claim 1, wherein the pixels in which the color filter is arranged are arranged corresponding to different colors of the color filter. In an image sensor having a plurality of pixels,
A photoelectric conversion unit that is arranged for each of the plurality of pixels and converts received light into an electrical signal;
A microlens for condensing the light incident on the image sensor on the photoelectric conversion unit;
A first and a second internal lens having a condensing function disposed between the microlens and the photoelectric conversion unit, each including a first and a second internal lens having different aperture diameters;
Among the plurality of pixels, pixels adjacent to each pixel in the diagonal direction are each provided with the microlens and a second inner lens having an aperture diameter smaller than that of the first inner lens, The imaging device, wherein the first internal lens is disposed in each of the plurality of pixels in which the microlens is not disposed.   In the pixel where the microlens and the second internal lens are arranged adjacent to each other and the pixel where the first internal lens is arranged, the microlens and the first internal lens are partially The imaging device according to claim 4, wherein the imaging devices are arranged so as to overlap each other.   The microlens and the second internal lens further include a color filter that is arranged so that one color corresponds to one pixel of the plurality of pixels, and a plurality of types of colors are periodically arranged. The imaging device according to claim 4, wherein the arranged pixel and the pixel on which the first internal lens is arranged are arranged corresponding to different colors of the color filter. In an image sensor having a plurality of pixels,
A photoelectric conversion unit that is arranged for each of the plurality of pixels and converts received light into an electrical signal;
A first microlens and a second microlens for condensing light incident on the image sensor on the photoelectric conversion unit, each having a different aperture diameter;
A first and a second internal lens having a condensing function disposed between the microlens and the photoelectric conversion unit, each including a first and a second internal lens having different aperture diameters;
Among the plurality of pixels, pixels adjacent to each pixel in the diagonal direction have a smaller opening diameter than the first microlens and the first inner lens having a larger opening diameter than the second microlens. A second internal lens is disposed in each of the plurality of pixels, and the second micro lens and the first micro lens are not included in the pixels in which the first micro lens and the second internal lens are not disposed. And an internal lens of the image sensor.   In the pixel in which the first microlens and the second internal lens are arranged adjacent to each other, and the pixel in which the second microlens and the first internal lens are arranged, the first microlens is arranged. The imaging device according to claim 7, wherein the lens and the first inner lens are disposed so as to partially overlap each other.   The color filter further includes a color filter arranged so that one color corresponds to one pixel of the plurality of pixels, and a plurality of kinds of colors are periodically arranged, and the first microlens and the second interior The pixel in which the lens is arranged and the pixel in which the second microlens and the first inner lens are arranged are arranged corresponding to different colors of the color filter. The imaging device according to claim 7.

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