JP2015153859A - Solid imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid imaging device capable of reducing deterioration of image quality even if output pixels are switched between a plurality of pixels having different sensitivity.SOLUTION: In a pixel cell 100 of a solid imaging device, a high sensitive pixel 1 having a large light-receiving area, and a low sensitive pixel 2 having a small light-receiving area are arranged. The high sensitive pixel 1 and the low sensitive pixel 2 are arranged so that the center O1 of a geometrical plane shape of the high sensitive pixel 1 and the center O2 of the geometrical plane shape of the low sensitive pixel 2 coincide with the center O of the pixel cell 100.

Description

  Embodiments described herein relate generally to a solid-state imaging device.

  As a method of expanding the dynamic range of the solid-state imaging device, a plurality of pixels having different sensitivities are arranged adjacent to each other, and an output pixel is selected according to the amount of incident light.

  The sensitivity of the pixel can be set by changing the light receiving area of the pixel. In this case, if the light receiving area is increased, a highly sensitive pixel can be obtained.

  However, in the conventional pixel arrangement, there is a shift in the optical pixel position between pixels with different sensitivities, so there is also a shift in the position of the subject that receives the light, and the image quality deteriorates when the output pixel is switched. There was a problem.

JP 2007-19251 A

  The problem to be solved by the present invention is to provide a solid-state imaging device capable of reducing image quality degradation even when output pixels are switched between a plurality of pixels having different sensitivities.

  In the solid-state imaging device according to the embodiment, a plurality of pixels having different light receiving areas are arranged in one pixel cell so that the centers of the respective geometric planar shapes are at the same position or in the vicinity.

FIG. 2 is a plan view illustrating a pixel arrangement example of the solid-state imaging device according to the first embodiment. The figure which shows the example of the sensitivity characteristic with respect to the input light quantity of a high sensitivity pixel and a low sensitivity pixel. FIG. 6 is a plan view showing another pixel arrangement example of the solid-state imaging device according to the first embodiment. FIG. 6 is a plan view illustrating an example of pixel arrangement of a solid-state imaging device according to a second embodiment. The top view which shows another pixel arrangement | positioning example of the solid-state imaging device of 2nd Embodiment. FIG. 9 is a plan view illustrating an example of pixel arrangement of a solid-state imaging device according to a third embodiment. The top view which shows another pixel arrangement | positioning example of the solid-state imaging device of 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(First embodiment)
FIG. 1A is a plan view illustrating a pixel arrangement example in pixel cells arranged in a matrix in the solid-state imaging device according to the first embodiment.

  In the pixel cell 100 of the solid-state imaging device according to the present embodiment, the high sensitivity pixel 1 and the low sensitivity pixel 2 are disposed, and the high sensitivity pixel 1 is disposed so as to surround the low sensitivity pixel 2.

  FIG. 1B is a plan view of the high-sensitivity pixel 1, and FIG. 1C is a plan view of the low-sensitivity pixel 2. In each figure, the hatched portion indicates the light receiving area of each pixel.

  The light receiving area of the high sensitivity pixel 1 is larger than the light receiving area of the low sensitivity pixel 2. Since the light receiving area is large, the sensitivity of the high sensitivity pixel 1 is higher than the sensitivity of the low sensitivity pixel 2.

  Here, the center of the geometric shape of the high-sensitivity pixel 1 in the annular form is represented as O1, and the center of the geometric shape of the low-sensitivity pixel 2 is represented as O2.

  In the present embodiment, as shown in FIG. 1A, the center O1 of the high sensitivity pixel 1 and the center O2 of the low sensitivity pixel 2 are arranged so as to coincide with the center O of the pixel cell 100.

  Further, the charge generated in the high sensitivity pixel 1 is read out by the read gate G1 and output as a pixel output signal. Similarly, the charge generated in the low sensitivity pixel 2 is read out by the read gate G2 and output as a pixel output signal.

  FIG. 2 shows an example of sensitivity characteristics representing the relationship of the pixel output signal with respect to the input light amount of the high sensitivity pixel 1 and the low sensitivity pixel 2.

  As shown in FIG. 2, the high-sensitivity pixel 1 exhibits a linear output characteristic in a low light amount region, and the low-sensitivity pixel 2 exhibits a linear output characteristic in a high light amount region.

  Therefore, in the present embodiment, the output pixel is switched according to the input light amount, with the low light amount region as the shared range of the high sensitivity pixel 1 and the high light amount region as the shared range of the low sensitivity pixel 2.

  At this time, in this embodiment, since the centers of the geometric shapes of the high-sensitivity pixel 1 and the low-sensitivity pixel 2 coincide with each other, even if the output pixel is switched, the deviation of the optical axis with respect to the subject is small. For this reason, it is possible to reduce the deterioration of image quality due to the switching of the output pixels.

  FIG. 3 is a plan view showing another example of the pixel arrangement in the pixel cell.

In the example illustrated in FIG. 3, four pixels having different sensitivities, that is, a high sensitivity pixel 11, a medium sensitivity pixel 12, a low sensitivity pixel 13, and an ultra low sensitivity pixel 14 are arranged in the pixel cell 110.

  Here, the high-sensitivity pixel 11, the medium-sensitivity pixel 12, the low-sensitivity pixel 13, and the ultra-low-sensitivity pixel 14 are arranged such that the centers of their geometric shapes coincide with the center O of the pixel cell 110.

  The high sensitivity pixel 11, the medium sensitivity pixel 12, and the low sensitivity pixel 13 have an annular shape, and the low sensitivity pixel 13 surrounds the ultra low sensitivity pixel 14, and the low sensitivity pixel 13 surrounds the medium sensitivity pixel 12. Are arranged so that the high sensitivity pixel 11 surrounds the middle sensitivity pixel 12.

  Further, the readout gate G11 for the high sensitivity pixel 11, the readout gate G12 for the medium sensitivity pixel 12, the readout gate G13 for the low sensitivity pixel 13, and the readout gate G14 for the ultra low sensitivity pixel 14. Is provided.

  In the example shown in FIG. 3 as well, four pixels having different sensitivities are arranged so that the centers of the geometric shapes coincide. Therefore, even if the output pixel is switched according to the input light amount, the deviation of the optical axis with respect to the subject is small.

  According to the present embodiment, a plurality of pixels having different sensitivities are arranged in one pixel cell so that the center of the geometric shape coincides with the center of the pixel cell. The deviation of the optical axis due to switching can be reduced. As a result, it is possible to reduce deterioration in image quality due to switching of output pixels.

(Second Embodiment)
For example, in the case of the high-sensitivity pixel 1 shown in FIG. 1 of the first embodiment described above, since the light receiving area is large, the charge generated at a position far from the pixel readout gate G1 takes time to reach the readout gate G1. It takes. In some cases, charges remain in the pixel, causing afterimages. Therefore, in this embodiment, an example of a solid-state imaging device capable of quickly reading out charges even with a highly sensitive pixel will be described.

  FIG. 4 is a plan view illustrating a pixel arrangement example in the pixel cell of the solid-state imaging device according to the second embodiment. In the example shown in FIG. 4, the arrangement area of the high-sensitivity pixel 1 shown in FIG. 1 is divided into four, and each area includes a high-sensitivity pixel 1a, a high-sensitivity pixel 1b, a high-sensitivity pixel 1c, and a high-sensitivity pixel 1d. It is said.

  As shown in FIG. 4, in the pixel cell 200 of the solid-state imaging device according to the present embodiment, the high sensitivity pixel 1a, the high sensitivity pixel 1b, the high sensitivity pixel 1c, and the high sensitivity pixel 1d are surrounded so as to surround the low sensitivity pixel 2. Is arranged.

  In the example shown in FIG. 4, the high sensitivity pixel 1a is provided with a read gate G1a, the high sensitivity pixel 1b is provided with a read gate G1b, the high sensitivity pixel 1c is provided with a read gate G1c, and the high sensitivity pixel 1d is provided with a read gate G1d. Therefore, compared to the high-sensitivity pixel 1 shown in FIG. 1, the distances to the read gates G1a to 1d are shorter in each of the high-sensitivity pixel regions 1a to 1d.

  Accordingly, the charges generated in the high sensitivity pixels 1a to 1d are quickly read from the read gates G1a to 1d. As a result, the charge reading speed can be improved and the residual charge can be suppressed.

  FIG. 5 is a plan view showing another example of pixel area division.

In the pixel cell 210 shown in FIG. 5, the high sensitivity pixel region is divided into the high sensitivity pixel 11a and the high sensitivity pixel 11b, and the medium sensitivity pixel region is divided into the medium sensitivity pixel 12a and the medium sensitivity pixel 12b. .

  The medium sensitivity pixel 12a and the medium sensitivity pixel 12b are disposed so as to surround the low sensitivity pixel 13, and the high sensitivity pixel 11a and the high sensitivity pixel 11b are disposed so as to surround the medium sensitivity pixel 12a and the medium sensitivity pixel 12b. .

  In the example shown in FIG. 5, the high sensitivity pixel 11a is provided with a read gate G11a, the high sensitivity pixel 11b is provided with a read gate G11b, the medium sensitivity pixel 12a is provided with a read gate G12a, and the medium sensitivity pixel 12b is provided with a read gate G12b. .

  Therefore, the pixels generated in the high sensitivity pixels 11a and 11b are quickly read out from the read gates G11a and 11b, and the pixels generated in the medium sensitivity pixels 12a and 12b are read out quickly from the read gates G12a and 12b.

  According to the present embodiment, a pixel having a large light receiving area and a high sensitivity is divided into a plurality of areas, and a read gate is provided in each area, so that the charge generated in each light receiving area can be read quickly. Can do. Thereby, the charge reading speed from the pixel can be improved, and the charge can be prevented from remaining in the pixel.

(Third embodiment)
In the first and second embodiments described above, low sensitivity pixels are formed by reducing the pixel size. However, it is difficult to reduce the pixel size while keeping the output characteristics with respect to the input light amount the same as that of the large pixel. Therefore, in this embodiment, an example of a solid-state imaging device in which low-sensitivity pixels can be easily manufactured is shown.

  FIG. 6 is a plan view illustrating a pixel arrangement example in the pixel cell of the solid-state imaging device according to the third embodiment.

In the pixel cell 300 shown in FIG. 6, a high sensitivity pixel 11a, a high sensitivity pixel 11b, a medium sensitivity pixel 12, and a low sensitivity pixel 13 are arranged.

  In the present embodiment, unlike the first and second embodiments, the medium sensitivity pixel 12 and the low sensitivity pixel 13 are arranged side by side. Further, the high sensitivity pixel 11 a and the high sensitivity pixel 11 b are arranged so as to surround the medium sensitivity pixel 12 and the low sensitivity pixel 13.

  Therefore, the position of the center O12 of the medium sensitivity pixel 12 and the position of the center O13 of the low sensitivity pixel 13 do not coincide with the position of the center O11 of the high sensitivity pixel arrangement region composed of the high sensitivity pixel 11a and the high sensitivity pixel 11b.

  That is, the center O12 of the medium sensitivity pixel 12 and the center O13 of the low sensitivity pixel 13 are arranged in the vicinity of the center O11 of the high sensitivity pixel arrangement region. However, since the positional deviation is small, the optical axis deviation due to the switching of the output pixel is small, and the image quality deterioration due to the switching of the output pixel is small.

  In the present embodiment, the pixel size itself of the low sensitivity pixel 13 is the same as the pixel size of the medium sensitivity pixel 12. However, a light shielding mask SM is provided in the low sensitivity pixel 13. Since incident light is blocked by the light shielding mask SM, the light receiving area contributing to the photoelectric conversion of the low sensitivity pixel 13 is smaller than that of the medium sensitivity pixel 12.

  The light receiving area of the low sensitivity pixel 13 can be arbitrarily adjusted by changing the light shielding area of the light shielding mask SM.

  FIG. 7 is a plan view showing another arrangement example of the medium sensitivity pixel 12 and the low sensitivity pixel 13.

In the pixel cell 310 shown in FIG. 7, the medium sensitivity pixel 12 and the low sensitivity pixel 13 are arranged vertically. Further, the high sensitivity pixels 1 a to 1 d are arranged so as to surround the medium sensitivity pixel 12 and the low sensitivity pixel 13.

  Also in the example shown in FIG. 7, the pixel size of the low-sensitivity pixel 13 is the same as the pixel size of the medium-sensitivity pixel 12, and the light-shielding mask SM is provided in the low-sensitivity pixel 13. The light receiving area contributing to the conversion is smaller than that of the medium sensitivity pixel 12.

  Also in the example shown in FIG. 7, the center O12 of the medium sensitivity pixel 12 and the center O13 of the low sensitivity pixel 13 are arranged in the vicinity of the center O11 of the high sensitivity pixel arrangement region. However, since the positional deviation is small, the optical axis deviation due to the switching of the output pixel is small, and the image quality deterioration due to the switching of the output pixel is small.

  According to the present embodiment as described above, the light receiving area can be adjusted by the light shielding mask, so that the low sensitivity pixel can be easily manufactured. In addition, since the low sensitivity pixel can be arranged in the vicinity of the medium sensitivity pixel, it is possible to suppress deterioration in image quality due to switching of the output pixel.

  According to the solid-state imaging device of at least one embodiment described above, it is possible to reduce image quality degradation even when output pixels are switched between a plurality of pixels having different sensitivities.

  Moreover, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1, 1a-1d, 11, 11a, 11b High-sensitivity pixels 12, 12a, 12b Medium-sensitivity pixels 2, 13 Low-sensitivity pixels 14 Ultra-low-sensitivity pixels G1, G2, G11-G14, G1a-G1d, G11a, G11b, G12a , G12b Read gates O, O1, O2, O11 to O13 Center SM Shading mask 100, 110, 200, 210, 300, 310 Pixel cell

Claims (5)

A plurality of pixels having different light receiving areas are
A solid-state imaging device, characterized in that each geometrical planar shape is arranged in one pixel cell so that the centers of the geometric plane shapes are at the same position or the vicinity. The plurality of pixels are:
The solid-state imaging device according to claim 1, wherein a pixel having a large light receiving area surrounds a pixel having a small light receiving area. A light receiving surface of a pixel having a large light receiving area is divided into a plurality of regions,
The solid-state imaging device according to claim 2, wherein a readout gate is disposed in each of the regions. Pixels with a small light receiving area are
The solid-state imaging device according to claim 2, wherein the light receiving area is adjusted by an opening size of the light receiving surface. Two pixels having the same pixel size but different aperture sizes are
The solid-state imaging device according to claim 4, wherein the solid-state imaging device is disposed adjacently.