Semiconductor device

• US 9,985,069 B2
• Filed: 06/16/2015
• Issued: 05/29/2018
• Est. Priority Date: 03/12/2010
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kurokawa, Yoshiyuki, Ikeda, Takayuki, Tamura, Hikaru, Kozuma, Munehiro
• Primary Examiner(s): VU, HUNG K
• Application Number:
  US14/740,720
• Publication Number:
  US 20150279896A1
• Time in Patent Office: 1,078 Days
• Field of Search: 257 43, 257 57, 257 72
• CPC Class Codes: G02F 1/13312 Circuits comprising photodetectors for purposes other than feedback
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• 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 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

An object is to achieve low-power consumption by reducing the off-state current of a transistor in a photosensor. A semiconductor device including a photosensor having a photodiode, a first transistor, and a second transistor; and a read control circuit including a read control transistor, in which the photodiode has a function of supplying charge based on incident light to a gate of the first transistor; the first transistor has a function of storing charge supplied to its gate and converting the charge stored into an output signal; the second transistor has a function of controlling reading of the output signal; the read control transistor functions as a resistor converting the output signal into a voltage signal; and semiconductor layers of the first transistor, the second transistor, and the read control transistor are formed using an oxide semiconductor.

Claims

1. A semiconductor device comprising:

a photodiode;

a first transistor, a gate thereof electrically connected to the photodiode;

a second transistor; and

a read control circuit including a third transistor,

wherein;

one of a source and a drain of the second transistor is electrically connected to one of a source and a drain of the first transistor,

the other of the source and the drain of the second transistor and one of a source and a drain of the third transistor are electrically connected to a photosensor output line,

each of the first transistor, the second transistor and the third transistor comprises an oxide semiconductor layer in a channel formation region thereof, and

the photodiode is positioned over the first transistor and the second transistor with an insulating layer therebetween.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises at least one of indium, gallium, tin, and zinc.

3. The semiconductor device according to claim 1, wherein the photodiode is selected from a PN diode, a PIN diode, a Schottky diode, and an avalanche diode.

4. The semiconductor device according to claim 1, wherein a plurality of photosensors each comprising the photodiode, the first transistor and the second transistor is arranged in row and column directions over a substrate.

5. The semiconductor device according to claim 4, wherein the plurality of photosensors is configured to concurrently perform a reset operation and a storage operation in all the rows, and sequentially perform a read operation in each row.

6. The semiconductor device according to claim 1, wherein an off-state current of each of the first transistor, the second transistor and the third transistor is less than or equal to 100 aA per 1 μ

m in a channel width.

7. The semiconductor device according to claim 1, wherein the photosensor output line is electrically connected to a photosensor reading circuit.

8. The semiconductor device according to claim 1, wherein:

the first transistor is electrically connected to a first wiring supplied with a first reference potential, and

the third transistor is electrically connected to a second wiring supplied with a second reference potential lower than the first reference potential.

9. The semiconductor device according to claim 1, wherein the other of the source and the drain of the third transistor is connected to a first wiring which is configured to be supplied with a first reference potential,

wherein the other of the source and the drain of the first transistor is connected to a second wiring which is configured to be supplied with a second reference potential, and

wherein the first reference potential is different from the second reference potential.

10. A semiconductor device comprising:

a photodiode;

a first transistor, a gate thereof electrically connected to the photodiode;

a second transistor, one of a source and a drain thereof electrically connected to a source or a drain of the first transistor; and

a read control circuit,

wherein;

the other of the source and the drain of the second transistor and the read control circuit are electrically connected to a photosensor output line,

the read control circuit is electrically connected between the other of the source and the drain of the second transistor and a first wiring configured to be supplied with a first reference potential,

each of the first transistor and the second transistor comprises an oxide semiconductor layer in a channel formation region thereof, and

the photodiode is positioned over the first transistor and the second transistor with an insulating layer therebetween.

11. The semiconductor device according to claim 10, wherein the oxide semiconductor layer comprises at least one of indium, gallium, tin, and zinc.

12. The semiconductor device according to claim 10, wherein the photodiode is selected from a PN diode, a PIN diode, a Schottky diode, and an avalanche diode.

13. The semiconductor device according to claim 10, wherein a plurality of photosensors each comprising the photodiode, the first transistor and the second transistor is arranged in row and column directions over a substrate.

14. The semiconductor device according to claim 13, wherein the plurality of photosensors is configured to concurrently perform a reset operation and a storage operation in all the rows, and sequentially perform a read operation in each row.

15. The semiconductor device according to claim 10, wherein an off-state current of each of the first transistor and the second transistor is less than or equal to 100 aA per 1 μ

m in a channel width.

16. The semiconductor device according to claim 10, wherein the photosensor output line is electrically connected to a photosensor reading circuit.

17. The semiconductor device according to claim 10,

wherein the other of the source and the drain of the first transistor is connected to a second wiring which is configured to be supplied with a second reference potential, and

wherein the first reference potential is different from the second reference potential.