Image sensor, method of forming pixel, pixel readout circuit and calibration method
Various example embodiments are directed to an image sensor, a method of forming a pixel, a pixel readout circuit, and a calibration method. The image sensor includes a substrate including a plurality of pixels, each pixel of the plurality of pixels configured to convert light into a corresponding electric signal, each pixel including a first photoelectric sensor and a second photoelectric sensor, a plurality of deep trench isolation (DTI) structures, each DTI structure of the plurality of DTI structures configured to isolate the first photoelectric sensor and the second photoelectric sensor of a corresponding pixel of the plurality of pixels, each DTI structure in the corresponding pixel in the substrate, a plurality of metal gates (MGs) on the plurality of DTI structures, and in each pixel of the plurality of pixels, the second photoelectric sensor is included inside the first photoelectric sensor.
1 . An image sensor, comprising:
a substrate including a plurality of pixels, each pixel of the plurality of pixels configured to convert light into a corresponding electric signal, each pixel including,
a first photoelectric sensor and a second photoelectric sensor, the second photoelectric sensor included inside the first photoelectric sensor;
a plurality of deep trench isolation (DTI) structures, each DTI structure of the plurality of DTI structures configured to isolate the first photoelectric sensor and the second photoelectric sensor of a corresponding pixel of the plurality of pixels, each DTI structure in the corresponding pixel in the substrate;
a plurality of metal gates (MGs) on the plurality of DTI structures, wherein
the first photoelectric sensor is configured to generate a signal corresponding to a first image, and
the second photoelectric sensor is configured to generate a signal corresponding to a second image that has less crosstalk than the first image; and
at least one processor configured to,
obtain a third image by combining the first image with the second image, and
calibrate the third image using the second image to compensate for the crosstalk in the first image.
2 . The image sensor of claim 1 , wherein
in each of the pixels of the plurality of pixels, the second photoelectric sensor is at a center of the pixel, the second photoelectric sensor is included inside the DTI structure, and the DTI structure is included inside the first photoelectric sensor; and
in each of the pixels, a center line corresponding to the first photoelectric sensor, a center line of the DTI structure, and a center line of the second photoelectric sensor overlap in at least one direction.
3 . The image sensor of claim 1 , wherein
each DTI structure of the plurality of DTI structures includes a first perimeter and a second perimeter, and the first perimeter and the second perimeter are concentric to one another;
the first perimeter and the second perimeter both have an oval shape;
a major axis of the first perimeter and a major axis of the second perimeter are both arranged in a same direction as a direction of a long side of a photosensitive area of a chip of the image sensor; and
a ratio of a length of the major axis to a length of a minor axis of the first perimeter and a ratio of a length of the major axis to a length of a minor axis of the second perimeter are same as a ratio of the length of the long side to a length of a short side of the photosensitive area.
4 . The image sensor of claim 3 , wherein
each MG of the plurality of MGs includes a third perimeter and a fourth perimeter, and the third perimeter and the fourth perimeter are concentric to one another;
a shape of each of the third perimeters and a shape of each of the fourth perimeters are same as the shapes of each of the first perimeters and each of the second perimeters; and
a center point of the third perimeter and a center point of the fourth perimeter overlap with a center point of the first perimeter and a center point of the second perimeter.
5 . The image sensor of claim 1 , further comprising:
a pinning layer on the substrate;
a high-K dielectric layer on the pinning layer;
a passivation layer on the high-K dielectric layer; and
the plurality of DTI structures extend towards the substrate from an upper surface of the high-K dielectric layer or a lower surface of the passivation layer.
6 . The image sensor of claim 1 , wherein the at least one processor is further configured to:
obtain the first image by reading a plurality of first output signals from the plurality of pixels, the reading the plurality of first output signals including reading a respective first output signal from the first photoelectric sensor of each pixel of the plurality of pixels; and
obtain the second image by reading a plurality of second output signals from the plurality of pixels, the reading the plurality of second output signals including reading a respective second output signal from the second photoelectric sensor of each pixel of the plurality of pixels.
7 . The image sensor of claim 6 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calculating a first average value of all pixel values of the second image.
8 . The image sensor of claim 7 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calculating a plurality of first ratios of each pixel value of the second image to the calculated first average value; and
calculating a second average value of all pixel values of the third image.
9 . The image sensor of claim 8 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
based on the calculated first ratio of a desired pixel value of the second image and the calculated second average value, calibrating a pixel value of a corresponding desired pixel of the third image such that a second ratio of a calibrated pixel value of the corresponding desired pixel of the third image to the calculated second average value is same as the calculated first ratio of the desired pixel value of the second image to the calculated second average value.
10 . The image sensor of claim 6 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
dividing the second image into a plurality of regions before calibrating the third image.
11 . The image sensor of claim 10 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calibrating the third image on a region-by-region basis of the second image.
12 . The image sensor of claim 11 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calculating a first average value of all regions of the second image;
calculating a plurality of first ratios of each of the regions of the second image to the calculated first average value; and
calculating a second average value of all regions of the third image.
13 . An image sensing device, comprising:
a first pass transistor connected to a first photoelectric sensor outside of a deep trench isolation (DTI) structure of a pixel, the DTI structure having an oval shape;
a second pass transistor connected to a second photoelectric sensor inside of the DTI structure of the pixel, the DTI structure configured to isolate the second photoelectric sensor; and
at least one processor configured to,
obtain a first image by reading a first output signal from the first photoelectric sensor using the first pass transistor,
obtain a second image that has less crosstalk than the first image by reading a second output signal from the second photoelectric sensor using the second pass transistor,
obtain a third image by combining the first image with the second image, and
calibrate the third image using the second image to compensate for the crosstalk in the first image.
14 . The image sensing device of claim 13 , wherein
the second photoelectric sensor is at a center of the pixel, the second photoelectric sensor included inside the DTI structure, and the DTI structure is included inside the first photoelectric sensor; and
a center line corresponding to the first photoelectric sensor, a center line of the DTI structure, and a center line of the second photoelectric sensor overlap in at least one direction.
15 . The image sensing device of claim 13 , wherein
the DTI structure includes a first perimeter and a second perimeter, and the first perimeter and the second perimeter are concentric to one another;
the first perimeter and the second perimeter both have an oval shape;
a major axis of the first perimeter and a major axis of the second perimeter are both arranged in a same direction as a direction of a long side of a photosensitive area of a chip of an image sensor included in the image sensing device; and
a ratio of a length of the major axis to a length of a minor axis of the first perimeter and a ratio of a length of the major axis to a length of a minor axis of the second perimeter are same as a ratio of the length of the long side to a length of a short side of the photosensitive area.
16 . The image sensing device of claim 15 , further comprising:
a metal gate (MG) on the DTI structure, the MG including a third perimeter and a fourth perimeter, the third perimeter and the fourth perimeter being concentric to one another;
a shape of the third perimeter and a shape of the fourth perimeter are same as the shapes of the first perimeter and the second perimeter; and
a center point of the third perimeter and a center point of the fourth perimeter overlap with a center point of the first perimeter and a center point of the second perimeter.
17 . The image sensing device of claim 13 , further comprising:
a pinning layer on a substrate;
a high-K dielectric layer on the pinning layer;
a passivation layer on the high-K dielectric layer; and
the DTI structure extending towards the substrate from an upper surface of the high-K dielectric layer or a lower surface of the passivation layer.
18 . The image sensing device of claim 13 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calculating a first average value of all pixel values of the second image;
calculating a plurality of first ratios of each pixel value of the second image to the calculated first average value;
calculating a second average value of all pixel values of the third image; and
based on the calculated first ratio of a desired pixel value of the second image and the calculated second average value, calibrating a pixel value of a corresponding desired pixel of the third image such that a second ratio of a calibrated pixel value of the corresponding desired pixel of the third image to the calculated second average value is same as the calculated first ratio of the desired pixel value of the second image to the calculated second average value.
19 . The image sensing device of claim 13 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
dividing the second image into a plurality of regions before calibrating the third image; and
calibrating the third image on a region-by-region basis of the second image.
20 . The image sensing device of claim 13 , wherein the at least one processor is further configured to calibrate the third image using the second image by:
calculating a first average value of all regions of the second image;
calculating a plurality of first ratios of each of the regions of the second image to the calculated first average value; and
calculating a second average value of all regions of the third image.