Imaging device and method for driving the same

• US 9,972,655 B2
• Filed: 09/11/2014
• Issued: 05/15/2018
• Est. Priority Date: 08/23/2012
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kurokawa, Yoshiyuki, Ikeda, Takayuki
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Malevic, Djura
• Application Number:
  US14/483,457
• Publication Number:
  US 20150028335A1
• Time in Patent Office: 1,342 Days
• CPC Class Codes: A61B 6/4208 characterised by using a particular type of detector
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/14612 involving a transistor
• CPC Class Codes: H01L 27/14663 Indirect radiation imagers, e.g. using luminescent members
• CPC Class Codes: H01L 31/0376 including amorphous semiconductors H01L31/0392 takes precedence
• CPC Class Codes: H04N 23/30 for generating image signals from X-rays
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

An imaging device capable of obtaining image data with a small amount of X-ray irradiation is provided. The imaging device obtains an image using X-rays and includes a scintillator and a plurality of pixel circuits arranged in a matrix and overlapping with the scintillator. The use of a transistor with an extremely small off-state current in the pixel circuits enables leakage of electrical charges from a charge accumulation portion to be reduced as much as possible, and an accumulation operation to be performed substantially at the same time in all of the pixel circuits. The accumulation operation is synchronized with X-ray irradiation, so that the amount of X-ray irradiation can be reduced.

Claims

1. An imaging device comprising:

a first transistor, a second transistor, a third transistor, each comprising;

a gate electrode over an insulting surface;

an gate insulating film over the gate electrode;

an oxide semiconductor layer over the gate insulating film; and

a first electrode and a second electrode over the oxide semiconductor layer,

a first capacitor;

a resistor;

a second capacitor;

an operational amplifier circuit;

a first insulating film over at least the first transistor, the second transistor, the third transistor;

an optical sensor element;

a second insulating film over the first insulating film and the optical sensor element; and

a scintillator over the second insulating film,

wherein the first electrode of the first transistor is electrically connected to a first portion of the optical sensor element with a first wiring through an opening of the first insulating film and an opening of the second insulating film,

wherein the second electrode of the first transistor is electrically connected to a gate of the second transistor and the first capacitor,

wherein the first electrode of the second transistor is electrically connected to the first electrode of the third transistor,

wherein the second electrode of the third transistor is electrically connected to the resistor,

wherein the resistor is electrically connected to an inverting input terminal of the operational amplifier circuit, and

wherein an output terminal of the operational amplifier circuit is electrically connected to the inverting input terminal through the second capacitor.

2. The imaging device according to claim 1,

wherein a first potential and a second potential are applied to a second portion of the optical sensor element and the gate electrode of the first transistor substantially at the same time to reset a charge of the first capacitor.

3. The imaging device according to claim 1,

wherein the oxide semiconductor layer includes indium, gallium, and zinc.

4. The imaging device according to claim 1,

wherein the optical sensor element comprises an amorphous semiconductor.

5. The imaging device according to claim 1, wherein the first wiring is over the second insulating film.

6. An imaging device comprising:

a first transistor, a second transistor, a third transistor, each comprising;

a gate electrode over an insulting surface;

an gate insulating film over the gate electrode;

an oxide semiconductor layer over the gate insulating film; and

a first electrode and a second electrode over the oxide semiconductor layer,

a first capacitor;

a resistor;

a second capacitor;

an operational amplifier circuit;

a first insulating film over at least the first transistor, the second transistor, the third transistor;

a photodiode;

a second insulating film over the first insulating film and the photodiode; and

a scintillator over the second insulating film,

wherein the first electrode of the first transistor is electrically connected to an electrode of the photodiode with a first wiring through an opening of the first insulating film and an opening of the second insulating film,

wherein the second electrode of the first transistor is electrically connected to a gate of the second transistor and the first capacitor,

wherein the first electrode of the second transistor is electrically connected to the first electrode of the third transistor,

wherein the second electrode of the third transistor is electrically connected to the resistor,

wherein the resistor is electrically connected to an inverting input terminal of the operational amplifier circuit, and

wherein an output terminal of the operational amplifier circuit is electrically connected to the inverting input terminal through the second capacitor.

7. The imaging device according to claim 6,

wherein a first potential and a second potential are applied to a cathode of the photodiode and the gate electrode of the first transistor substantially at the same time to reset a charge of the first capacitor.

8. The imaging device according to claim 6,

wherein the oxide semiconductor layer includes indium, gallium, and zinc.

9. The imaging device according to claim 6,

wherein the photodiode comprises an amorphous semiconductor.

10. The imaging device according to claim 6, wherein the first wiring is over the second insulating film.

11. An imaging device comprising:

a first transistor, a second transistor, a third transistor, each comprising;

a gate electrode over an insulting surface;

an gate insulating film over the gate electrode;

an oxide semiconductor layer over the gate insulating film; and

a first electrode and a second electrode over the oxide semiconductor layer,

a resistor;

a capacitor;

an operational amplifier circuit;

a first insulating film over at least the first transistor, the second transistor, the third transistor;

an optical sensor element;

a second insulating film over the first insulating film and the optical sensor element; and

a scintillator over the second insulating film,

wherein the first electrode of the first transistor is electrically connected to a first portion of the optical sensor element with a first wiring through an opening of the first insulating film and an opening of the second insulating film,

wherein the second electrode of the first transistor is electrically connected to the gate electrode of the second transistor,

wherein the first electrode of the second transistor is electrically connected to the first electrode of the third transistor,

wherein the second electrode of the third transistor is electrically connected to the resistor,

wherein the resistor is electrically connected to an inverting input terminal of the operational amplifier circuit, and

wherein an output terminal of the operational amplifier circuit is electrically connected to the inverting input terminal through the capacitor.

12. The imaging device according to claim 11,

wherein a first potential and a second potential are applied to a second portion of the optical sensor element and the gate electrode of the first transistor substantially at the same time to reset a charge between the second electrode of the first transistor and the gate electrode of the second transistor.

13. The imaging device according to claim 11,

wherein the oxide semiconductor layer includes indium, gallium, and zinc.

14. The imaging device according to claim 11,

wherein the optical sensor element comprises an amorphous semiconductor.

15. The imaging device according to claim 11, wherein the first wiring is over the second insulating film.

16. An imaging device comprising:

a first transistor, a second transistor, a third transistor, each comprising;

a gate electrode over an insulting surface;

an gate insulating film over the gate electrode;

an oxide semiconductor layer over the gate insulating film; and

a first electrode and a second electrode over the oxide semiconductor layer,

a resistor;

a capacitor;

an operational amplifier circuit;

a first insulating film over at least the first transistor, the second transistor, the third transistor;

a photodiode;

a second insulating film over the first insulating film and the photodiode; and

a scintillator over the second insulating film,

wherein the first electrode of the first transistor is electrically connected to an electrode of the photodiode with a first wiring through an opening of the first insulating film and an opening of the second insulating film,

wherein the second electrode of the first transistor is electrically connected to a gate of the second transistor,

wherein the first electrode of the second transistor is electrically connected to the first electrode of the third transistor,

wherein the second electrode of the third transistor is electrically connected to the resistor,

wherein the resistor is electrically connected to an inverting input terminal of the operational amplifier circuit, and

wherein an output terminal of the operational amplifier circuit is electrically connected to the inverting input terminal through the capacitor.

17. The imaging device according to claim 16,

wherein a first potential and a second potential are applied to a cathode of the photodiode and the gate electrode of the first transistor substantially at the same time to reset a charge between the second electrode of the first transistor and the gate electrode of the second transistor.

18. The imaging device according to claim 16,

wherein the oxide semiconductor layer includes indium, gallium, and zinc.

19. The imaging device according to claim 16,

wherein the photodiode comprises an amorphous semiconductor.

20. The imaging device according to claim 16, wherein the first wiring is over the second insulating film.