CN-112786631-B - Image sensor

Abstract

An image sensor includes a pixel array having a first pixel and a second pixel, each of the first pixel and the second pixel including a photodiode, a sampling circuit detecting a reset voltage and a pixel voltage from the first pixel and the second pixel and generating an analog signal, an analog-to-digital converter obtaining image data from the analog signal, and a signal processing circuit generating an image using the image data. Each of the first pixels includes a first-conductivity-type well separating the photodiodes and having impurities of a first conductivity type. The photodiode has an impurity of a second conductivity type different from the first conductivity type. Each of the second pixels includes a second-conductivity-type well separating the photodiodes and having impurities of the second conductivity type different from the first conductivity type. The potential of the well of the second conductivity type is higher than the potential of the well of the first conductivity type.

Inventors

• SHEN YINXIE
• LI JINGGAO
• CUI XINGZHU

Assignees

• 三星电子株式会社

Dates

Publication Date

20260508

Application Date

20200927

Priority Date

20191105

Claims (19)

1. 1. An image sensor, comprising: A pixel array including a plurality of first pixels and a plurality of second pixels, Wherein each of the plurality of first pixels and the plurality of second pixels includes a microlens, a plurality of photodiodes spaced apart from each other in at least one of a first direction and a second direction perpendicular to the first direction, and a plurality of transfer transistors, and Wherein each transfer transistor of the plurality of transfer transistors is connected to a respective photodiode of the plurality of photodiodes; A sampling circuit configured to detect a reset voltage and a pixel voltage from the plurality of first pixels and the plurality of second pixels, and output a difference between the reset voltage and the pixel voltage as an analog signal; An analog-to-digital converter configured to compare the analog signal with a ramp voltage to convert a result of the comparison into a digital signal and output the digital signal as image data, and A signal processing circuit configured to generate an image using the image data, Wherein each of the plurality of first pixels includes a well of a first conductivity type separating the plurality of photodiodes and having impurities of the first conductivity type, Wherein the plurality of photodiodes have impurities of a second conductivity type different from the first conductivity type, Wherein each of the plurality of second pixels includes a well of a second conductivity type separating the plurality of photodiodes and having impurities of the second conductivity type different from the first conductivity type, Wherein the potential of the well of the second conductivity type is higher than the potential of the well of the first conductivity type, and Wherein the full well capacity of each of the plurality of second pixels is greater than the full well capacity of each of the plurality of first pixels.
2. 2. The image sensor of claim 1, Wherein the image sensor is configured to perform an auto-focus function in a low-light environment using each of the plurality of first pixels and the plurality of second pixels.
3. 3. The image sensor of claim 2, Wherein the image sensor is further configured to generate an image using each of the plurality of first pixels and the plurality of second pixels in the low-light environment.
4. 4. The image sensor of claim 1, Wherein the image sensor is configured to generate an image using each of the plurality of second pixels and perform an auto-focus function using each of the plurality of first pixels in a high-illuminance environment.
5. 5. The image sensor of claim 4, Wherein the image sensor is further configured to perform a bad pixel correction operation in the high illumination environment to generate an image using each of the plurality of first pixels.
6. 6. The image sensor of claim 1, Wherein a ratio of the number of the first pixels to the number of the second pixels is 1:3 or less.
7. 7. The image sensor of claim 1, Wherein when a first transfer transistor of the plurality of transfer transistors is in an off state, a potential of a channel region disposed under a gate electrode of the first transfer transistor is lower than a potential of a well of the second conductivity type.
8. 8. The image sensor of claim 1, Wherein the potential of the second conductivity type well varies according to the doping concentration of the second conductivity type impurity in the second conductivity type well.
9. 9. The image sensor of claim 1, Wherein when the plurality of photodiodes are spaced apart from each other in the first direction, the potential of the second-conductivity-type well varies according to the width of the second-conductivity-type well in the second direction.
10. 10. The image sensor of claim 1, Wherein the plurality of photodiodes generate electrons as main carriers in response to light, and the lower the potential of the well of the first conductivity type, the higher the energy of the electrons.
11. 11. An image sensor, comprising: A pixel array including a first pixel and a second pixel, and A controller configured to receive a pixel signal from each of the first pixel and the second pixel and to generate an image using the pixel signal, Wherein the first pixel comprises a first photodiode, a second photodiode and a first microlens, Wherein the first photodiode and the second photodiode are both arranged below the first microlens, Wherein the second pixel comprises a third photodiode, a fourth photodiode and a second microlens, Wherein the third photodiode and the fourth photodiode are both arranged below the second microlens, Wherein the sum of the number of electrons accumulated in the first photodiode and the number of electrons accumulated in the second photodiode increases linearly to a first full well capacity, which corresponds to the maximum number of electrons output by the first photodiode and the second photodiode, during a first time portion of the exposure time, Wherein, during a second time portion of the exposure time, a sum of the number of electrons accumulated in the third photodiode and the number of electrons accumulated in the fourth photodiode increases linearly to a second full well capacity corresponding to a maximum number of electrons output by the third photodiode and the fourth photodiode during the second time portion, and Wherein the second full well capacity of the second pixel is greater than the first full well capacity of the first pixel.
12. 12. The image sensor of claim 11, Wherein, within the first time portion of the exposure time, the number of electrons accumulated in the first photodiode and the number of electrons accumulated in the second photodiode increase, and Wherein after the first time portion, the number of electrons accumulated in at least one of the first photodiode and the second photodiode does not increase.
13. 13. The image sensor of claim 11, Wherein during a first period of the second time portion, the number of electrons accumulated in the third photodiode and the number of electrons accumulated in the fourth photodiode increase, Wherein during a second period of time of the second time portion after the first period of time, the number of electrons accumulated in the third photodiode does not increase, but the number of electrons accumulated in the fourth photodiode increases, and Wherein during a third period of time of the second time portion after the second period of time, the number of electrons accumulated into the third photodiode and the fourth photodiode increases.
14. 14. The image sensor of claim 13, Wherein once the third photodiode is saturated, electrons accumulated in the third photodiode and electrons accumulated in the fourth photodiode mix during the second period of time of the second time portion.
15. 15. The image sensor of claim 13, Wherein electrons added during the third period of the second time portion and electrons contained in the saturated third photodiode are released when the image sensor reads a pixel voltage from the third photodiode.
16. 16. An image sensor, comprising: A pixel array including a first pixel and a second pixel, wherein each of the first pixel and the second pixel includes a microlens, a plurality of photodiodes, a plurality of transfer transistors, and a floating diffusion region, Wherein each transfer transistor of the plurality of transfer transistors includes a first electrode connected to a corresponding photodiode of the plurality of photodiodes and a second electrode connected to the floating diffusion region, and A controller configured to receive a pixel signal from at least one of the first pixel and the second pixel and to generate an image using the pixel signal, Wherein the plurality of photodiodes of the first pixel generate charges in response to light having illuminance higher than a reference illuminance during an exposure time, the charges moving to the floating diffusion region through a first path between the plurality of photodiodes and the floating diffusion region, Wherein a first photodiode of the plurality of photodiodes of the second pixel generates a charge during the exposure time in response to light having an illuminance higher than the reference illuminance, the charge moving to a second photodiode of the plurality of photodiodes through a second path between the first photodiode of the plurality of photodiodes and the second photodiode of the plurality of photodiodes, and Wherein the full well capacity of the second pixel is greater than the full well capacity of the first pixel.
17. 17. The image sensor of claim 16, Wherein the first pixel includes a well of a first conductivity type separating the plurality of photodiodes, Wherein the second pixel includes a well of a second conductivity type separating the plurality of photodiodes, an Wherein the potential of the well of the second conductivity type is higher than the potential of the well of the first conductivity type.
18. 18. The image sensor of claim 17, Wherein when a first transfer transistor of the plurality of transfer transistors is in an off state, a potential of a channel region disposed under a gate electrode of the first transfer transistor is lower than a potential of a well of the second conductivity type.
19. 19. The image sensor of claim 17, Wherein when a first transfer transistor of the plurality of transfer transistors is in an off state, a potential of a channel region disposed under a gate electrode of the first transfer transistor is higher than a potential of a well of the first conductivity type.

Description

Image sensor Cross Reference to Related Applications The present application claims the benefit of priority from korean patent application No.10-2019-0140188 filed in the korean intellectual property agency on 11/5 of 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical Field Example embodiments of the inventive concepts relate to image sensors. Background The image sensor is a semiconductor-based sensor that can generate an electrical signal in response to light. The image sensor may include a pixel array having a plurality of pixels, logic configured to drive the pixel array and generate an image, and other components. The plurality of pixels may include a photodiode that generates electric charges in response to light, and a pixel circuit that converts the electric charges generated by the photodiode into an electric signal. The image sensor may be widely applied to a camera to obtain a still image or video, and may also be applied to a smart phone, a tablet PC, a laptop computer, a television, a vehicle, and the like. Disclosure of Invention Example embodiments of the inventive concepts provide an image sensor that may improve image quality. According to an exemplary embodiment of the inventive concept, an image sensor includes a pixel array including a first pixel and a second pixel, wherein each of the first pixel and the second pixel includes a microlens, a photodiode spaced apart from each other, and a transfer transistor, and wherein each of the transfer transistors is connected to the corresponding photodiode, a sampling circuit detecting a reset voltage and a pixel voltage from the first pixel and the second pixel and outputting a difference between the reset voltage and the pixel voltage as an analog signal, an analog-to-digital converter comparing the analog signal with a ramp voltage, converting a result of the comparison into a digital signal, and outputting the digital signal as image data, and a signal processing circuit generating an image using the image data. Each of the first pixels includes a well of a first conductivity type separating the plurality of photodiodes and having impurities of the first conductivity type. The photodiode has an impurity of a second conductivity type different from the first conductivity type. Each of the second pixels includes a well of a second conductivity type separating the photodiodes and having impurities of the second conductivity type different from the first conductivity type. The potential of the well of the second conductivity type is higher than the potential of the well of the first conductivity type. According to an exemplary embodiment of the inventive concept, an image sensor includes a pixel array including a first pixel and a second pixel, and a controller receiving a pixel signal from each of the first pixel and the second pixel and generating an image using the pixel signal. The first pixel includes a first photodiode, a second photodiode, and a first microlens. The first photodiode and the second photodiode are both disposed under the first microlens. The second pixel includes a third photodiode, a fourth photodiode, and a second microlens. The third photodiode and the fourth photodiode are both disposed under the second microlens. The sum of the number of electrons accumulated in the first photodiode and the number of electrons accumulated in the second photodiode increases linearly to a first full well capacity corresponding to the maximum number of electrons output by the first photodiode and the second photodiode during a first time portion of the exposure time. In a second time portion of the exposure time, a sum of the number of electrons accumulated in the third photodiode and the number of electrons accumulated in the fourth photodiode increases linearly to a second full well capacity corresponding to a maximum number of electrons output by the third photodiode and the fourth photodiode in the second time portion. The second full well capacity of the second pixel is greater than the first full well capacity of the first pixel. According to an exemplary embodiment of the inventive concept, an image sensor includes a pixel array including a first pixel and a second pixel, wherein each of the first pixel and the second pixel includes a microlens, a plurality of photodiodes, a plurality of transfer transistors, and a floating diffusion region, wherein each of the plurality of transfer transistors includes a first electrode connected to a corresponding photodiode of the plurality of photodiodes and a second electrode connected to the floating diffusion region, and a controller receiving a pixel signal from at least one of the first pixel and the second pixel and generating an image using the pixel signal. The photodiodes of the first pixel generate charges in response to light having illuminance higher than a reference illuminance during an exposure time, the charges moving to the floating diff