Photodetector circuit and semiconductor device

• US 9,887,232 B2
• Filed: 03/03/2015
• Issued: 02/06/2018
• Est. Priority Date: 09/12/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kurokawa, Yoshiyuki, Tsurume, Takuya
• Primary Examiner(s): PYO, KEVIN K
• Application Number:
  US14/636,996
• Publication Number:
  US 20150179696A1
• Time in Patent Office: 1,071 Days
• Field of Search: 2502081, 250214 R, 250214 C, 2502141, 250214 B, 348294, 348295, 348297, 348302, 348303, 348308
• CPC Class Codes: G01T 1/20184 Detector read-out circuitry, e.g. for clearing of traps, compensating for traps or compensating for direct hits
• CPC Class Codes: G01T 1/208 Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section
• CPC Class Codes: H01L 27/144 Devices controlled by radiation
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14678 Contact-type imagers
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

To provide a photodetector circuit capable of obtaining signals in different periods without being affected by characteristics of a photoelectric conversion element. The photodetector circuit has n signal output circuits (n is a natural number of 2 or more) connected to the photoelectric conversion element. Further, the n signal output circuits each include the following: a transistor whose gate potential varies in accordance with the amount of light entering the photoelectric conversion element; a first switching element which holds the gate potential of the transistor; and a second switching element which controls a signal output from the transistor. Thus, after data based on the amount of light entering the photoelectric conversion elements is held as the gate potentials of the transistors, the second switching elements are turned on, whereby signals in different periods can be obtained without being affected by characteristics of the photoelectric conversion element.

Claims

1. A photodetector circuit comprising:

a photoelectric conversion element;

a first transistor; and

a second transistor,

wherein the first transistor is configured to hold a first potential of a first node in accordance with an amount of light entering the photoelectric conversion element from a scintillator in a first period just before a start of the radiation emission, and

wherein the second transistor is configured to hold a second potential of a second node in accordance with an amount of light entering the photoelectric conversion element from the scintillator in a second period during the radiation emission.

2. The photodetector circuit according to claim 1,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor.

3. The photodetector circuit according to claim 1,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during a first output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during a second output period after the first output period.

4. The photodetector circuit according to claim 2,

wherein the first transistor is configured to hold the first potential from the first period to the first output period, and

wherein the second transistor is configured to hold the second potential from the second period to the second output period.

5. The photodetector circuit according to claim 2,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during an output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during the output period.

6. The photodetector circuit according to claim 5,

wherein the first transistor is configured to hold the first potential from the first period to the output period, and

wherein the second transistor is configured to hold the second potential from the second period to the output period.

7. An imaging device comprising:

a scintillator; and

a photodetector circuit comprising;

a photoelectric conversion element;

a first transistor; and

a second transistor,

wherein the first transistor is configured to hold a first potential of a first node in accordance with an amount of light entering the photoelectric conversion element from the scintillator in a first period just before a start of the radiation emission from a radiation source, and

wherein the second transistor is configured to hold a second potential of a second node in accordance with an amount of light entering the photoelectric conversion element from the scintillator in a second period during the radiation emission from the radiation source.

8. The imaging device according to claim 7,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor.

9. The imaging device according to claim 8,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during a first output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during a second output period after the first output period.

10. The imaging device according to claim 9,

wherein the first transistor is configured to hold the first potential from the first period to the first output period, and

wherein the second transistor is configured to hold the second potential from the second period to the second output period.

11. The imaging device according to claim 8,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during an output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during the output period.

12. The imaging device according to claim 11,

wherein the first transistor is configured to hold the first potential from the first period to the output period, and

wherein the second transistor is configured to hold the second potential from the second period to the output period.

13. An imaging device comprising:

a radiation source;

a scintillator; and

a photodetector circuit comprising;

a photoelectric conversion element;

a first transistor; and

a second transistor,

wherein the first transistor is configured to hold a first potential of a first node in accordance with an amount of light entering the photoelectric conversion element from the scintillator in a first period just before a start of the radiation emission from the radiation source, and

wherein the second transistor is configured to hold a second potential of a second node in accordance with an amount of light entering the photoelectric conversion element from the scintillator in a second period during the radiation emission from the radiation source.

14. The imaging device according to claim 13,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor.

15. The imaging device according to claim 14,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during a first output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during a second output period after the first output period.

16. The imaging device according to claim 15,

wherein the first transistor is configured to hold the first potential from the first period to the first output period, and

wherein the second transistor is configured to hold the second potential from the second period to the second output period.

17. The imaging device according to claim 14,

wherein the photoelectric conversion element is configured to generate first charge corresponding to the first potential during the first period,

wherein the photoelectric conversion element is configured to generate second charge corresponding to the second potential during the second period,

wherein the photodetector circuit is configured to output a signal corresponding to the first potential during an output period after the second period, and

wherein the photodetector circuit is configured to output a signal corresponding to the second potential during the output period.

18. The imaging device according to claim 17,

wherein the first transistor is configured to hold the first potential from the first potential to the output period, and

wherein the second transistor is configured to hold the second potential from the second period to the output period.