Imaging device

• US 9,035,301 B2
• Filed: 06/13/2014
• Issued: 05/19/2015
• Est. Priority Date: 06/19/2013
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Takahashi, Hironobu, Hosaka, Yasuharu, Tsubuku, Masashi, Shima, Yukinori, Obonai, Toshimitsu
• Primary Examiner(s): Le, Thao P
• Application Number:
  US14/303,629
• Publication Number:
  US 20140374745A1
• Time in Patent Office: 340 Days
• Field of Search: 257/43
• US Class Current: 257/43
• CPC Class Codes: H01L 27/14616 characterised by the channel of the transistor, e.g. channel having a doping gradient
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14663 Indirect radiation imagers, e.g. using luminescent members
• CPC Class Codes: H01L 27/14692 Thin film technologies, e.g. amorphous, poly, micro- or nanocrystalline silicon
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

An imaging device that is highly stable to irradiation with radial rays such as X-rays and can inhibit a decrease in electrical characteristics is provided. The imaging device takes an image with radial rays such as X-rays and includes pixel circuits arranged in a matrix and a scintillator overlapping the pixel circuits. The pixel circuits each includes a switching transistor with an extremely small off-state current and a light-receiving element which is configured to convert the radial rays to electrical charges. A gate insulating film of the switching transistor has a stacked structure including a silicon nitride film with a thickness of 100 nm to 400 nm and a silicon oxide film or a silicon oxynitride film with a thickness of 5 nm to 20 nm.

Claims

1. A semiconductor device comprising a light-receiving element and a first transistor connected to the light-receiving element, wherein the first transistor comprises:

a gate electrode over an insulating surface;

a gate insulating film comprising a first insulating film over the gate electrode and a second insulating film over the first insulating film; and

an oxide semiconductor layer over the second insulating film,

wherein the first insulating film comprises a silicon nitride,

wherein the second insulating film comprises a silicon oxide or a silicon oxynitride,

wherein the first insulating film has a thickness of 100 nm to 400 nm, and

wherein the second insulating film has a thickness of 5 nm to 20 nm.

2. The semiconductor device according to claim 1, wherein the semiconductor device is an imaging device using X-rays or gamma-rays.

3. The semiconductor device according to claim 1, wherein the light-receiving element is a photodiode.

4. The semiconductor device according to claim 1, wherein the light-receiving element is a variable resistive element.

5. The semiconductor device according to claim 1, further comprising a second transistor, a third transistor, and a charge storage portion,

wherein a first terminal of the first transistor is connected to the charge storage portion,

wherein a second terminal of the first transistor is connected to a first terminal of the light-receiving element,

wherein a gate of the second transistor is connected to the charge storage portion, and

wherein a first terminal of the second transistor is connected to a first terminal of the third transistor.

6. The semiconductor device according to claim 5, further comprising a fourth transistor comprising a first terminal connected to the charge storage portion.

7. A semiconductor device comprising a pixel and a scintillator overlapping the pixel, the pixel comprising:

a light-receiving element configured to receive light; and

a first transistor connected to the light-receiving element, wherein the first transistor comprises;

a gate electrode over an insulating surface;

a gate insulating film comprising a first insulating film over the gate electrode and a second insulating film over the first insulating film; and

an oxide semiconductor layer over the second insulating film,

wherein the first insulating film comprises a silicon nitride,

wherein the second insulating film comprises a silicon oxide or a silicon oxynitride,

wherein the first insulating film has a thickness of 100 nm to 400 nm,

wherein the second insulating film has a thickness of 5 nm to 20 nm, and

wherein the scintillator is configured to convert X-rays or gamma-rays to the light.

8. The semiconductor device according to claim 7, wherein the light-receiving element is a photodiode.

9. The semiconductor device according to claim 7, wherein the light-receiving element is a variable resistive element.

10. The semiconductor device according to claim 7, further comprising a second transistor, a third transistor, and a charge storage portion,

wherein a first terminal of the first transistor is connected to the charge storage portion,

wherein a second terminal of the first transistor is connected to a first terminal of the light-receiving element,

wherein a gate of the second transistor is connected to the charge storage portion, and

wherein a first terminal of the second transistor is connected to a first terminal of the third transistor.

11. The semiconductor device according to claim 10, further comprising a fourth transistor comprising a first terminal connected to the charge storage portion.

12. A semiconductor device comprising a light-receiving element and a first transistor connected to the light-receiving element, wherein the first transistor comprises:

a gate electrode over an insulating surface;

a gate insulating film comprising a first insulating film over the gate electrode and a second insulating film over the first insulating film;

an oxide semiconductor layer over the second insulating film, the oxide semiconductor layer overlapping with the gate electrode;

a source electrode layer and a drain electrode layer in contact with part of the oxide semiconductor layer; and

an insulating layer over the gate insulating film, the oxide semiconductor layer, the source electrode layer, and the drain electrode layer,

wherein the first insulating film comprises a silicon nitride,

wherein the second insulating film comprises a silicon oxide or a silicon oxynitride,

wherein the first insulating film has a thickness of 100 nm to 400 nm, and

wherein the second insulating film has a thickness of 5 nm to 20 nm.

13. The semiconductor device according to claim 12, wherein the semiconductor device is an imaging device using X-rays or gamma-rays.

14. The semiconductor device according to claim 12, wherein the light-receiving element is a photodiode.

15. The semiconductor device according to claim 12, wherein the light-receiving element is a variable resistive element.

16. The semiconductor device according to claim 12, further comprising a second transistor, a third transistor, and a charge storage portion,

wherein a first terminal of the first transistor is connected to the charge storage portion,

wherein a second terminal of the first transistor is connected to a first terminal of the light-receiving element,

wherein a gate of the second transistor is connected to the charge storage portion, and

wherein a first terminal of the second transistor is connected to a first terminal of the third transistor.

17. The semiconductor device according to claim 16, further comprising a fourth transistor comprising a first terminal connected to the charge storage portion.