阅读说明：本技术 光传感器电路、光传感器装置及显示装置 (Optical sensor circuit, optical sensor device, and display device ) 是由 津吹将志 纲岛贵德 盐川真里奈 于 2019-03-08 设计创作，主要内容包括：本发明的课题在于提供能够进行稳定的动作的、使用了氧化物半导体晶体管的光传感器电路。光传感器电路包含受光晶体管、第1开关晶体管、第2开关晶体管及电容元件。受光晶体管包含：与第1布线连接的栅极；与第2布线连接的源极；以及漏极。第1开关晶体管具有：与第3布线连接的栅极；与第4布线连接的源极；以及与受光晶体管的漏极连接的漏极。电容元件包含：与受光晶体管的漏极连接的第1端子；以及与第1开关晶体管的源极连接的第2端子。第2开关晶体管包含：与栅极线连接的栅极；与信号线连接的源极；以及电容元件的第1端子连接的漏极。受光晶体管、第1开关晶体管及第2开关晶体管分别包含氧化物半导体层来作为沟道层。(The invention provides a photosensor circuit using an oxide semiconductor transistor, which can perform stable operation. The photosensor circuit includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor, and a capacitive element. The light receiving transistor includes: a gate connected to the 1 st wiring; a source electrode connected to the 2 nd wiring; and a drain electrode. The 1 st switching transistor has: a gate connected to the 3 rd wiring; a source connected to the 4 th wiring; and a drain connected to the drain of the light receiving transistor. The capacitor element includes: a 1 st terminal connected to a drain of the light receiving transistor; and a 2 nd terminal connected to a source of the 1 st switching transistor. The 2 nd switching transistor includes: a gate electrode connected to the gate line; a source electrode connected to the signal line; and a drain to which the 1 st terminal of the capacitor is connected. The light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.)

1. A light sensor circuit, characterized in that,

includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor and a capacitor,

the light receiving transistor includes:

a gate connected to the 1 st wiring;

a source electrode connected to the 2 nd wiring; and

a drain electrode formed on the substrate,

the 1 st switching transistor includes:

a gate connected to the 3 rd wiring;

a source connected to the 4 th wiring; and

a drain connected to the drain of the light receiving transistor,

the capacitance element includes:

a 1 st terminal connected to the drain of the light receiving transistor; and

a 2 nd terminal connected to the source of the 1 st switching transistor,

the 2 nd switching transistor includes:

a gate electrode connected to the gate line;

a source electrode connected to the signal line; and

a drain connected to the 1 st terminal of the capacitive element,

The light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

2. The light sensor circuit of claim 1, comprising:

a 1 st period in which the light receiving transistor and the 2 nd switching transistor are turned on and the 1 st switching transistor is turned off;

a 2 nd period in which the light receiving transistor and the 2 nd switching transistor are turned off and the 1 st switching transistor is turned on after the 1 st period;

a 3 rd period in which the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor are turned off after the 2 nd period, and charges generated by light irradiation are accumulated in the capacitor element; and

in the 4 th period, after the 3 rd period, the light receiving transistor and the 1 st switching transistor are turned off, the 2 nd switching transistor is turned on by the gate line, and the electric charge accumulated in the capacitor element is read from the signal line in the 4 th period.

3. The light sensor circuit of claim 2,

having a reset circuit comprising a 3 rd switching transistor,

the 3 rd switching transistor has:

a gate connected to the 5 th wiring;

a source connected to the 4 th wiring; and

a drain electrode connected to the signal line,

the 3 rd switching transistor includes an oxide semiconductor layer as a channel layer.

4. The light sensor circuit of claim 3,

in the 1 st period, the 3 rd switching transistor is turned on.

5. The light sensor circuit of claim 1,

the gate electrodes of the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor are provided in one of a lower portion and an upper portion of the oxide semiconductor layer of the corresponding transistor,

the 1 st switch transistor and the 2 nd switch transistor each have a back gate,

the back gate is provided on the other of the lower portion and the upper portion of the oxide semiconductor layer of the corresponding switch transistor.

6. The light sensor circuit of claim 5,

the back gate is connected to the source of the corresponding switch transistor.

7. The light sensor circuit of claim 3,

the gate of the 3 rd switching transistor is provided in one of a lower portion and an upper portion of the oxide semiconductor layer of the 3 rd switching transistor,

the 3 rd switch transistor has a back gate,

the back gate of the 3 rd switch transistor is provided on the other of the lower portion and the upper portion of the oxide semiconductor layer of the 3 rd switch transistor.

8. A light sensor device, comprising:

a plurality of gate lines;

a plurality of signal lines;

a plurality of photosensor circuits connected to the plurality of gate lines and the plurality of signal lines such that 1 photosensor circuit is connected to 1 gate line and 1 signal line,

the plurality of photosensor circuits respectively include:

a light receiving transistor;

a 1 st switching transistor;

a 2 nd switching transistor; and

a capacitive element for generating a capacitive voltage in the semiconductor device,

the light receiving transistor includes:

a gate connected to the 1 st wiring;

a source electrode connected to the 2 nd wiring; and

a drain electrode formed on the substrate,

the 1 st switching transistor includes:

a gate connected to the 3 rd wiring;

a source connected to the 4 th wiring; and

a drain connected to the drain of the light receiving transistor,

The capacitance element includes:

a 1 st terminal connected to the drain of the light receiving transistor; and

a 2 nd terminal connected to the source of the 1 st switching transistor,

the 2 nd switching transistor includes:

a gate electrode connected to the corresponding gate line;

a source electrode connected to the corresponding signal line; and

a drain connected to the 1 st terminal of the capacitive element,

the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

9. The light sensor device of claim 8, comprising:

a 1 st period in which the light receiving transistor and the 2 nd switching transistor are turned on and the 1 st switching transistor is turned off;

a 2 nd period in which the light receiving transistor and the 2 nd switching transistor are turned off and the 1 st switching transistor is turned on after the 1 st period;

a 3 rd period in which the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor are turned off after the 2 nd period, and charges generated by light irradiation are accumulated in the capacitor element; and

In the 4 th period, after the 3 rd period, the light receiving transistor and the 1 st switching transistor are turned off, the 2 nd switching transistor is turned on by the gate line, and the electric charge accumulated in the capacitor element is read from the signal line in the 4 th period.

10. The light sensor device of claim 9,

having a reset circuit comprising a 3 rd switching transistor,

the 3 rd switching transistor has:

a gate connected to a 5 th wiring to which a reset signal is supplied;

a source connected to the 4 th wiring; and

a drain electrode connected to the corresponding signal line,

the 3 rd switching transistor includes an oxide semiconductor layer as a channel layer.

11. The light sensor device of claim 10,

in the 1 st period, the 3 rd switching transistor is turned on based on the reset signal.

12. The light sensor device of claim 10,

the gate of each of the light receiving transistor, the 1 st switching transistor, the 2 nd switching transistor, and the 3 rd switching transistor is provided in one of a lower portion and an upper portion of the oxide semiconductor layer of the corresponding transistor,

The 1 st switch transistor, the 2 nd switch transistor, and the 3 rd switch transistor each have a back gate,

the back gate is provided on the other of the lower portion and the upper portion of the oxide semiconductor layer of the corresponding switch transistor.

13. The light sensor device of claim 12,

the back gate is connected to the source of the corresponding switch transistor.

14. A display device is characterized in that a display panel is provided,

having a display panel with a display area,

the display area includes display pixels and photosensor circuits,

the light sensor circuit includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor, and a capacitor,

the light receiving transistor includes:

a gate connected to the 1 st wiring;

a source electrode connected to the 2 nd wiring; and

a drain electrode formed on the substrate,

the 1 st switching transistor includes:

a gate connected to the 3 rd wiring;

a source connected to the 4 th wiring; and

a drain connected to the drain of the light receiving transistor,

the capacitance element includes:

a 1 st terminal connected to the drain of the light receiving transistor; and

a 2 nd terminal connected to the source of the 1 st switching transistor,

The 2 nd switching transistor includes:

a gate electrode connected to the gate line;

a source electrode connected to the signal line; and

a drain connected to the 1 st terminal of the capacitive element,

the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

15. The display device according to claim 14, comprising:

a 1 st period in which the light receiving transistor and the 2 nd switching transistor are turned on and the 1 st switching transistor is turned off;

a 2 nd period in which the light receiving transistor and the 2 nd switching transistor are turned off and the 1 st switching transistor is turned on after the 1 st period;

a 3 rd period in which the light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor are turned off after the 2 nd period, and charges generated by light irradiation are accumulated in the capacitor element; and

in the 4 th period, after the 3 rd period, the light receiving transistor and the 1 st switching transistor are turned off, the 2 nd switching transistor is turned on by the gate line, and the electric charge accumulated in the capacitor element is read from the signal line in the 4 th period.

16. The display device according to claim 14 or 15,

having a reset circuit comprising a 3 rd switching transistor,

the 3 rd switching transistor includes:

a gate connected to the 5 th wiring;

a source connected to the 4 th wiring; and

a drain electrode connected to the signal line,

the 3 rd switching transistor includes an oxide semiconductor layer as a channel layer.

Technical Field

The present invention relates to an optical sensor circuit, and more particularly, to an optical sensor circuit, an optical sensor device, and a display device using an oxide semiconductor transistor.

Background

As a photo sensor circuit and a photo sensor element using an oxide semiconductor transistor, japanese patent application laid-open publication No. 2011-.

Disclosure of Invention

The oxide semiconductor transistor has a degradation mode in which a negative bias voltage applied while light irradiation is performed is degraded, and a threshold voltage is greatly changed. In addition, when light irradiation is performed on the oxide semiconductor transistor, there is a characteristic that the drain current is very slowly reduced even when the light irradiation is stopped. Therefore, there is a problem that it is difficult to apply the oxide semiconductor transistor to the photosensor element.

The purpose of the present invention is to provide a photosensor circuit using an oxide semiconductor transistor, which can perform stable operation.

Other objects and novel features will be apparent from the description of the specification and the accompanying drawings.

Brief description of representative embodiments of the invention an overview of a representative embodiment of the invention is as follows.

That is, the photosensor circuit includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor, and a capacitive element. The light receiving transistor includes: a gate connected to the 1 st wiring; a source connected to the 2 nd wiring; and a drain electrode. The 1 st switching transistor includes: a gate connected to the 3 rd wiring; a source connected to the 4 th wiring; and a drain connected to the drain of the light receiving transistor. The capacitance element includes: a 1 st terminal connected to the drain of the light receiving transistor; and a 2 nd terminal connected to the source of the 1 st switching transistor. The 2 nd switching transistor includes: a gate electrode connected to the gate line; a source electrode connected to the signal line; and a drain connected to the 1 st terminal of the capacitor element. The light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

In addition, the optical sensor device includes: a plurality of gate lines; a plurality of signal lines; and a plurality of photosensor circuits connected to the plurality of gate lines and the plurality of signal lines such that 1 photosensor circuit is connected to 1 gate line and 1 signal line. Each of the plurality of photosensor circuits includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor, and a capacitive element. The light receiving transistor includes: a gate connected to the 1 st wiring; a source electrode connected to the 2 nd wiring; and a drain electrode. The 1 st switching transistor includes: a gate connected to the 3 rd wiring; a source connected to the 4 th wiring; and a drain connected to the drain of the light receiving transistor. The capacitance element has: a 1 st terminal connected to the drain of the light receiving transistor; and a 2 nd terminal connected to the source of the 1 st switching transistor. The 2 nd switching transistor includes: a gate electrode connected to the corresponding gate line; a source electrode connected to the corresponding signal line; and a drain connected to the 1 st terminal of the capacitor element. The light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

In addition, the display device has a display panel with a display area. The display area includes display pixels and photosensor circuits. The photosensor circuit includes a light receiving transistor, a 1 st switching transistor, a 2 nd switching transistor, and a capacitive element. The light receiving transistor includes: a gate connected to the 1 st wiring; a source electrode connected to the 2 nd wiring; and a drain electrode. The 1 st switching transistor includes: a gate connected to the 3 rd wiring; a source connected to the 4 th wiring; and a drain connected to the drain of the light receiving transistor. The capacitance element includes: a 1 st terminal connected to the drain of the light receiving transistor; and a 2 nd terminal connected to the source of the 1 st switching transistor. The 2 nd switching transistor includes: a gate electrode connected to the gate line; a source electrode connected to the signal line; and a drain connected to the 1 st terminal of the capacitor element. The light receiving transistor, the 1 st switching transistor, and the 2 nd switching transistor each include an oxide semiconductor layer as a channel layer.

Drawings

Fig. 1 is a cross-sectional view schematically illustrating an exemplary configuration of an oxide semiconductor transistor used in a photosensor device of an embodiment.

Fig. 2 is a cross-sectional view schematically illustrating an exemplary structure of the light receiving transistor of fig. 1.

Fig. 3 is a cross-sectional view schematically illustrating an exemplary configuration of the switching transistor of fig. 1.

Fig. 4 is a graph showing characteristics of the drain current of the light receiving transistor in the case of no light irradiation.

Fig. 5 is a graph showing characteristics of drain current of the light receiving transistor in the case where light is irradiated.

Fig. 6 is a circuit diagram illustrating an exemplary configuration example of the light sensor circuit of the embodiment.

Fig. 7 is a block diagram showing an exemplary overall configuration of the optical sensor device of the embodiment.

Fig. 8 is a timing chart illustrating an example of the operation of the optical sensor device according to the embodiment.

Fig. 9 is a characteristic diagram for explaining characteristics of a photocurrent of the oxide semiconductor transistor of the comparative example.

Fig. 10 is a diagram for explaining the photocurrent of the oxide semiconductor transistor of the comparative example.

Fig. 11 is a diagram for explaining a photocurrent of the oxide semiconductor transistor of the embodiment.

Fig. 12 is a diagram exemplarily showing a gate bias potential (Vg) of the gate electrode of the oxide semiconductor transistor at the time of application of the reset pulse of fig. 11.

Fig. 13 is a diagram exemplarily showing a drain bias potential (Vd) of the drain electrode of the oxide semiconductor transistor at the time of application of the reset pulse of fig. 11.

Fig. 14 is a plan view schematically showing the display device of application example 1.

Fig. 15 is a plan view schematically showing the display device of application example 2.

Fig. 16 is a plan view schematically showing a display device of a modification.

Fig. 17 is a circuit diagram showing an example of the configuration of a display pixel and a photosensor circuit that can be employed in the display device of the modification.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

The present disclosure is merely an example, and it is needless to say that appropriate modifications and conceivable arrangements that are made by those skilled in the art while keeping the gist of the present invention are included in the scope of the present invention. In the drawings, the width, thickness, shape, and the like of each part are schematically shown as compared with the actual case in order to make the description more clear, but the present invention is not limited to the explanation.

In the present specification and the drawings, the same elements as those described above with reference to the appearing drawings are denoted by the same reference numerals, and detailed description thereof may be omitted as appropriate.