Semiconductor device

• US 20080078923A1
• Filed: 09/17/2007
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hirose, Atsushi
• Granted Patent: US 7,791,012 B2
• Time in Patent Office: Days
• US Class Current: 250/214.1
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 2003/2836 Programming unit, i.e. source and date processing
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H04N 23/65 Control of camera operation in relation to power supply
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation

Abstract

To suppress a decrease in photosensitivity of a photoelectric conversion element provided in a semiconductor device by reducing the parasitic resistance of an amplifier circuit. In addition, the amplifier circuit which amplifies the output current of the photoelectric conversion element is operated stably. A semiconductor device includes a photoelectric conversion element, a current mirror circuit having at least two thin film transistors, a high-potential power supply electrically connected to each of the thin film transistors, and a low-potential power supply electrically connected to each of the thin film transistors. When a reference thin film transistor is an n-type, the reference thin film transistor is placed closer to the low-potential power supply than an output thin film transistor is. When a reference thin film transistor is a p-type, the reference thin film transistor is placed closer to the high-potential power supply than an output thin film transistor is.

Claims

1. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and an output thin film transistor, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the output thin film transistor are n-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode through the photoelectric conversion element,

wherein one of source and drain electrodes of the output thin film transistor is electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode,

wherein the other of the source and drain electrodes of the output thin film transistor is electrically connected to the low-potential electrode, and

wherein the reference thin film transistor is placed closer to the low-potential electrode than the output thin film transistor is.

2. The semiconductor device according to claim 1,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

3. The semiconductor device according to claim 1,

wherein a gate electrode of the output thin film transistor is electrically connected to a gate electrode and the one of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the output thin film transistor through the photoelectric conversion element, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the output thin film transistor.

4. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and an output thin film transistor, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the output thin film transistor are n-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode through the photoelectric conversion element,

wherein one of source and drain electrodes of the output thin film transistor is electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode,

wherein the other of the source and drain electrodes of the output thin film transistor is electrically connected to the low-potential electrode, and

wherein a current path between the reference thin film transistor and the low-potential electrode is shorter than a current path between the output thin film transistor and the low-potential electrode.

5. The semiconductor device according to claim 4,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

6. The semiconductor device according to claim 4,

wherein a gate electrode of the output thin film transistor is electrically connected to a gate electrode and the one of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the output thin film transistor through the photoelectric conversion element, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the output thin film transistor.

7. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and a plurality of output thin film transistors, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the plurality of the output thin film transistors are n-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode through the photoelectric conversion element,

wherein one of source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode,

wherein the other of the source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the low-potential electrode, and

wherein the reference thin film transistor is placed closer to the low-potential electrode than each of the plurality of the output thin film transistor is.

8. The semiconductor device according to claim 7,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

9. The semiconductor device according to claim 7,

wherein gate electrodes of the plurality of the output thin film transistors are electrically connected to a gate electrode and the one of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the plurality of the output thin film transistors through the photoelectric conversion element, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the plurality of the output thin film transistors.

10. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and a plurality of output thin film transistors, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the plurality of the output thin film transistors are n-type thin film transistor,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode through the photoelectric conversion element,

wherein one of source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode,

wherein the other of the source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the low-potential electrode, and

wherein a current path between the reference thin film transistor and the low-potential electrode is shorter than a current path between each of the plurality of the output thin film transistors and the low-potential electrode.

11. The semiconductor device according to claim 10,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

12. The semiconductor device according to claim 10,

wherein gate electrodes of the plurality of the output thin film transistors are electrically connected to a gate electrode and the one of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the plurality of the output thin film transistors through the photoelectric conversion element, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the plurality of the output thin film transistors.

13. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and an output thin film transistor, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the output thin film transistor are p-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode,

wherein one of source and drain electrodes of the output thin film transistor is electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode through the photoelectric conversion element,

wherein the other of the source and drain electrodes of the output thin film transistor is electrically connected to the low-potential electrode, and

wherein the reference thin film transistor is placed closer to the high-potential electrode than the output thin film transistor is.

14. The semiconductor device according to claim 13,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

15. The semiconductor device according to claim 13,

wherein a gate electrode of the output thin film transistor is electrically connected to a gate electrode and the other of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the output thin film transistor, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the output thin film transistor through the photoelectric conversion element.

16. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and an output thin film transistor, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the output thin film transistor are p-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode,

wherein one of source and drain electrodes of the output thin film transistor is electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode through the photoelectric conversion element,

wherein the other of the source and drain electrodes of the output thin film transistor is electrically connected to the low-potential electrode, and

wherein a current path between the reference thin film transistor and the high-potential electrode is shorter than a current path between the output thin film transistor and the high-potential electrode.

17. The semiconductor device according to claim 16,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

18. The semiconductor device according to claim 16,

wherein a gate electrode of the output thin film transistor is electrically connected to a gate electrode and the other of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the output thin film transistor, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the output thin film transistor through the photoelectric conversion element.

19. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and a plurality of output thin film transistors, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the plurality of the output thin film transistors are p-type thin film transistors,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode,

wherein one of source and drain electrodes of the plurality of the output thin film transistor are electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode through the photoelectric conversion element,

wherein the other of the source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the low-potential electrode, and

wherein the reference thin film transistor is placed closer to the high-potential electrode than each of the plurality of the output thin film transistors is.

20. The semiconductor device according to claim 19,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

21. The semiconductor device according to claim 19,

wherein gate electrodes of the plurality of the output thin film transistors are electrically connected to a gate electrode and the other of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the plurality of the output thin film transistors, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the plurality of the output thin film transistors through the photoelectric conversion element.

22. A semiconductor device comprising:

a photoelectric conversion element;

a current mirror circuit including a reference thin film transistor and a plurality of output thin film transistors, the current mirror circuit amplifying an output of the photoelectric conversion element; and

a power supply including a high-potential electrode and a low-potential electrode,

wherein both the reference thin film transistor and the plurality of the output thin film transistors are n-type thin film transistor,

wherein one of source and drain electrodes of the reference thin film transistor is electrically connected to the high-potential electrode,

wherein one of source and drain electrodes of the plurality of the output thin film transistor are electrically connected to the high-potential electrode,

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the low-potential electrode through the photoelectric conversion element,

wherein the other of the source and drain electrodes of the plurality of the output thin film transistors are electrically connected to the low-potential electrode, and

wherein a current path between the reference thin film transistor and the high-potential electrode is shorter than a current path between each of the plurality of the output thin film transistors and the high-potential electrode.

23. The semiconductor device according to claim 22,

wherein a drop in gate voltage of the reference thin film transistor is suppressed.

24. The semiconductor device according to claim 22,

wherein gate electrodes of the plurality of the output thin film transistors are electrically connected to a gate electrode and the other of the source and drain electrodes of the reference thin film transistor,

wherein the one of the source and drain electrodes of the reference thin film transistor is electrically connected to the one of the source and drain electrodes of the plurality of the output thin film transistors, and

wherein the other of the source and drain electrodes of the reference thin film transistor is electrically connected to the other of the source and drain electrodes of the plurality of the output thin film transistors through the photoelectric conversion element.