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JP-2026075395-A - Light detection device

JP2026075395AJP 2026075395 AJP2026075395 AJP 2026075395AJP-2026075395-A

Abstract

[Challenge] To completely cancel out noise charge and enable pixel miniaturization. [Solution] The light detection device comprises a first pixel having a first photoelectric conversion element that accumulates a charge corresponding to the amount of incident light, and a first charge holding unit that holds a signal charge transferred from the first photoelectric conversion element and a noise charge due to parasitic photosensitivity; a second pixel having a second photoelectric conversion element that accumulates a charge corresponding to the amount of incident light, and a second charge holding unit that holds the noise charge without holding the signal charge transferred from the second photoelectric conversion element; and signal lines that transmit a first pixel signal corresponding to the signal charge and the noise charge held in the first charge holding unit, and a second pixel signal corresponding to the noise charge held in the second charge holding unit, at different timings. [Selection Diagram] Figure 4

Inventors

  • 日向野 駿

Assignees

  • ソニーセミコンダクタソリューションズ株式会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (20)

  1. A first pixel having a first photoelectric conversion element that accumulates charge according to the amount of incident light, and a first charge holding unit that holds signal charge transferred from the first photoelectric conversion element and noise charge due to parasitic light sensitivity, A second pixel having a second photoelectric conversion element that accumulates charge corresponding to the amount of incident light, and a second charge holding unit that holds the noise charge without holding the signal charge transferred from the second photoelectric conversion element, The device comprises signal lines that transmit a first pixel signal corresponding to the signal charge and noise charge held in the first charge holding unit, and a second pixel signal corresponding to the noise charge held in the second charge holding unit, at different timings. Light detection device.
  2. The device comprises a floating diffusion region that holds the signal charge and noise charge transferred from the first charge holding unit, or the noise charge transferred from the second charge holding unit at a timing different from that of the first charge holding unit, The light detection device according to claim 1.
  3. A pixel circuit that generates a first pixel signal corresponding to the signal charge and noise charge transferred from the first charge holding unit to the floating diffusion region, and a second pixel signal corresponding to the noise charge transferred from the second charge holding unit to the floating diffusion region, at different timings. The system includes a signal processing circuit that generates a digital signal corresponding to the difference between the first pixel signal and the second pixel signal. The light detection device according to claim 2.
  4. A first floating diffusion region that holds the signal charge and noise charge transferred from the first charge holding unit, The device comprises a second floating diffusion region that holds the noise charge transferred from the second charge holding unit, The light detection device according to claim 1.
  5. A first pixel circuit that generates a first pixel signal corresponding to the signal charge and noise charge transferred to the first floating diffusion region, A second pixel circuit that generates a second pixel signal corresponding to the noise charge transferred to the second floating diffusion region at a different timing than the first pixel circuit, The system includes a signal processing circuit that generates a digital signal corresponding to the difference between the first pixel signal and the second pixel signal. The light detection device according to claim 4.
  6. The first pixel has a first discharge transistor that is temporarily turned on after the exposure period of the first photoelectric conversion element has ended and before the reading of the first pixel signal begins to discharge the charge accumulated in the first photoelectric conversion element to a reference voltage node. The second pixel has a second discharge transistor that remains on for the duration of the exposure period of the second photoelectric conversion element and the readout period of the second pixel signal to discharge the charge accumulated in the second photoelectric conversion element to the reference voltage node. The light detection device according to claim 1.
  7. A first pixel group including two or more of the first pixels arranged in a first direction, It has a second pixel group including two or more of the second pixels arranged in the first direction, The first pixel group and the second pixel group are arranged in a second direction that intersects the first direction. The light detection device according to claim 6.
  8. A plurality of the first pixel groups arranged in the second direction, A plurality of the second pixel groups arranged in the second direction, The light detection device according to claim 7.
  9. Each of the plurality of first pixel groups and each of the plurality of second pixel groups are arranged alternately in the second direction. The light detection device according to claim 8.
  10. It comprises a plurality of pixel groups arranged in a second direction, each including two or more first pixels or second pixels arranged in the first direction, Each of the aforementioned plurality of pixel groups operates selectively as either the first pixel group or the second pixel group based on an external signal. The arrangement of the first and second pixel groups, which are alternately arranged in the second direction, changes from frame to frame. The light detection device according to claim 9.
  11. A plurality of pixels, including two or more of the first or second pixels, are arranged in a Bayer array in which pixel blocks containing two or more of the pixels included in the first pixel group and the second pixel group, which are arranged adjacent to each other in the second direction, are the same color. The light detection device according to claim 8.
  12. The system comprises multiple on-chip lenses that concentrate incident light onto individual pixels within the pixel block, or that concentrate incident light onto each pixel block. The light detection device according to claim 11.
  13. Each of the aforementioned on-chip lenses is divided into multiple parts corresponding to each pixel in the pixel block. Each pixel within the aforementioned pixel block is an image plane phase-difference pixel. The light detection device according to claim 12.
  14. Two or more first pixel groups arranged adjacent to each other along the second direction, and two or more second pixel groups arranged adjacent to each other along the second direction, are arranged alternately along the second direction. The light detection device according to claim 8.
  15. One second pixel group is arranged between two or more first pixel groups that are arranged adjacent to each other in the second direction. The light detection device according to claim 8.
  16. The noise charge is canceled by taking the difference between each of the multiple first pixel signals output from each of the two or more first pixel groups and the corresponding second pixel signal output from one second pixel group. The light detection device according to claim 15.
  17. During the exposure period of the second pixel and the readout period of the second pixel signal, the second output transistor in the second pixel is kept on, and the transfer transistor in the second pixel and the pixel transistor used to generate the second pixel signal are kept off, while the second pixel signal is output to the signal line. The light detection device according to claim 6.
  18. The semiconductor layer comprises a plurality of photoelectric conversion regions on which a plurality of photoelectric conversion elements, including the first photoelectric conversion element and the second photoelectric conversion element, are arranged; a plurality of charge holding portions, including the first charge holding portion and the preceding second charge holding portion; and a plurality of pixel separation regions that separate the plurality of photoelectric conversion regions. The length in the depth direction of at least some of the pixel separation regions is shallower than the length in the depth direction of the multiple photoelectric conversion regions. The light detection device according to claim 1.
  19. The depth of the pixel isolation region located on the transfer path for transferring the charge accumulated in each of the plurality of photoelectric conversion elements to the corresponding charge holding portion is shallower than the depth of the semiconductor layer of the pixel isolation region not located on the transfer path. The light detection device according to claim 18.
  20. The semiconductor layer comprises an insulating layer disposed on the side opposite to the light incident surface, Of the plurality of pixel isolation regions, at least the pixel isolation region located on the transfer path is arranged so as not to come into contact with the insulating layer. The light detection device according to claim 19.

Description

This disclosure relates to a photodetector. When strong light is incident on a photodiode while a floating diffusion region (floating diffusion) is holding signal charge, stray light (hereinafter referred to as noise charge), which is proportional to the amount of incident light, mixes into the floating diffusion region. As a result, the floating diffusion region holds charge in which the signal charge and noise charge are superimposed. Therefore, the pixel signal generated by the voltage level of the floating diffusion region contains a component of noise charge, leading to a decrease in the image quality of the captured image. Solutions to this image quality degradation due to noise charge have been proposed (see Patent Documents 1 and 2). In Patent Document 1, the pixel signal is read out while a charge with noise charge superimposed on the signal charge is held in a floating diffusion region. Then, the pixel signal is read out again while only the noise charge is held in the floating diffusion region. The noise charge component is then canceled out by taking the difference between these pixel signals. In Patent Document 2, a second discharge transistor is provided separately from the first discharge transistor that discharges the charge accumulated in the photodiode. In the first state, with the second discharge transistor turned off, signal charge and noise charge are accumulated in the MEM and the pixel signal is read out. In the second state, with the second discharge transistor turned on, only noise charge is accumulated in the MEM and the pixel signal is read out. By taking the difference between these pixel signals, the noise charge component is canceled out. Japanese Patent Publication No. 2017-076899Japanese Patent Publication No. 2021-125716 A block diagram showing the schematic configuration of an electronic device 2 equipped with a light detection device 1 according to this disclosure.A block diagram showing the schematic configuration of the light detection device 1 related to this disclosure.A perspective view of the light detection device 1 relating to this disclosure.Circuit diagram of the pixel 10 and pixel circuit 20 according to this embodiment.A plan view of the light detection device 1 according to this embodiment.Cross-sectional view of line A-A' in Figure 5.A flowchart illustrating the processing operation of the light detection device 1 according to this embodiment.A planar layout diagram showing an example in which a first pixel group (first pixel column) 31, in which a plurality of first pixels 10a are arranged in the first direction X, and a second pixel group (second pixel column) 33, in which a plurality of second pixels 10b are arranged in the first direction X, are alternately arranged in the second direction Y.A timing diagram of the light detection device 1 according to this embodiment.Potential diagrams of the first pixel 10a and the second pixel 10b in the light detection device 1 according to this embodiment.A timing diagram of the light detection device 1 according to a first modified example of this embodiment.This is a cross-sectional view of the photoelectric conversion region 42 and the charge holding unit MEM in the light detection device 1 according to this embodiment.A cross-sectional view of the photoelectric conversion region 42 and the charge holding section MEM in a photodetector 1 according to one comparative example.A plan view of the light detection device 1 according to a second modified example of this embodiment.Cross-sectional view of line A-A' in Figure 14.A circuit diagram of the pixel 10 and pixel circuit 20 of the light detection device 1 according to a third modified example of this embodiment.This figure illustrates the interlacing drive performed by the optical detection device 1 according to this embodiment.This figure shows a first example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a second example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a third example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a fourth example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a fifth example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a sixth example of the pixel arrangement of the light detection device 1 according to this embodiment.This figure shows a typical arrangement example of the second direction Y of the first and second pixel rows.A block diagram showing an example of a general configuration of a vehicle control system.An explanatory diagram showing an example of the installation location of the external information detection unit and the imaging unit. The following description will focus on the main components of the photodetector, with reference to