KR20170123517A - Transition metal molybdenum disulfide based photosensor array structure - Google Patents

Abstract

A transition metal molybdenum disulphide optical sensor array structure includes a plurality of optical sensor pixels sequentially selected. The optical sensor pixels include a first thin film transistor, a second thin film transistor, a light blocking part, a sensor element gate voltage supply part, and a switch element gate voltage supply part. The switch element gate voltage supply part supplies a preset switch element gate voltage to a gate electrode of a transistor set as a switch element. The sensor element gate voltage supply part supplies a preset sensor element gate voltage, in which the amount of drain current changed by incident light is larger than that in the switch element gate voltage, to a gate electrode of a transistor set as a sensor element. At this point, the gate electrode of the transistor set as the sensor element is connected to a switch element gate voltage supply part of an optical sensor pixel selected at the next turn.

Description

TECHNICAL FIELD [0001] The present invention relates to a transition metal disulfide-

The present invention relates to an optical sensor element based on a transition metal molybdenum disulfide, and more particularly to an optical sensor element array structure including a thin film transistor (TFT) using a two-dimensional transition metal molybdenum disulfide material.

Recently, researches on flexible displays, transparent displays, 3D displays and high-resolution displays have been actively studied as researches on next generation displays.

Thin film transistors (TFTs) using thin film films such as amorphous silicon (a-Si) and low temperature poly silicon (LTPS) as channel materials are currently used for realizing the next generation display.

However, the TFT using such a channel material has problems such as mechanical deformation of the flexible substrate during high-temperature deposition, easy breaking property and opacity during bending, and most of all, since the mobility of the material, which is the biggest disadvantage, is low, It is the limit to be.

Recently, researches on bidirectional large-area display that can increase communication between users and devices are actively under way. The bidirectional display means a display device such as an electronic blackboard or a TV including a remote touch screen function. In order to realize this, an optical sensor array structure capable of effectively recognizing an optical input performed by a user Is required.

Such an optical sensor array structure may be provided on a plate different from the TFT for performing image display, but may be provided on the same plate, and includes a pixel structure composed of an optical sensor element and a switch element for selecting an optical sensor element Both the individual elements as well as the array structure as a whole require excellent performance and efficient fabrication characteristics. 1 is an illustration showing an example in which a display transistor and a sensor transistor are formed together in a liquid crystal display backplane.

In order to meet such a demand, an attempt has recently been made to implement a photosensor using a thin film transistor (TFT) based on a transition metal chalcogenide compound. Transition metal chalcogen compound-based photosensor TFT devices exhibit a dark-to-dark photocurrent characteristic when exposed to light. 2 is a graph showing the light exposed state and the dark state photocurrent characteristic of the transition metal chalcogenide compound thin film transistor.

When a negative voltage is applied to a gate for use in an optical sensor having such a high photoconductive characteristic, an effective read operation can be performed due to a high dark to light photocurrent characteristic ratio. FIG. 3 is a graph illustrating an example of performing a read operation of an optical sensor using photocurrent characteristics of a transition metal chalcogen compound-based TFT.

However, in the case where the transition metal chalcogenide compound-based TFT is applied with light by applying a negative voltage to the gate and applying a positive voltage to the ground and drain to the source, It exhibits excellent photocurrent characteristics against dark, and maintains its photoconductivity even after blocking light. 4 is a graph showing photoconduction retention characteristics in a transition metal chalcogenide compound-based TFT.

The persistent photoconductivity (PPC) characteristic of the optical sensor device, which takes a few tens of seconds to several days to recover from its original state, has emerged as a technical issue that must be solved in optical sensor devices requiring high-speed operation.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide an optical sensor array structure capable of suppressing retention of photoelectric conductivity occurring upon optical detection of a molybdenum disulfide- .

In order to achieve the above object, a transition metal disulfide molybdenum photosensor array structure according to the present invention includes a plurality of photosensor pixels sequentially selected, and the photosensor pixel includes a first thin film transistor, a second thin film transistor, , A sensor element gate voltage supply section, and a switch element gate voltage supply section.

The first thin film transistor includes a first source electrode, a first drain electrode, and a first channel region of transition metal molybdenum disulfide formed between the first source electrode and the first drain electrode, and the second thin film transistor includes a first source electrode, And a second channel region of transition metal molybdenum disulfide formed between the second source electrode and the second drain electrode, wherein the shielding portion includes a first thin film transistor and a second thin film transistor The light incident on the channel region of the transistor set as the switch element is cut off and the light incident on the channel region of the transistor set as the sensor element is passed.

The switch element gate voltage supply unit supplies a predetermined switch element gate voltage to the gate electrode of the transistor set as the switch element, and the sensor element gate voltage supply unit supplies the switch element gate voltage to the switch element gate voltage supply unit such that the magnitude of the drain current changed by the incident light is larger A predetermined sensor element gate voltage is supplied to the gate electrode of the transistor set as the sensor element. At this time, the gate electrode of the transistor set as the sensor element is connected to the switch gate voltage supplier of the photosensor pixel selected in the following order.

According to such a configuration, it is possible to fabricate an optical sensor array structure with excellent manufacturing efficiency while effectively suppressing the photoconductivity retention phenomenon that occurs in the optical detection of the transition metal molybdenum disulfide-based optical sensor.

At this time, the shielding portion may include a layer of opaque material formed on the transistor channel region material layer set as the switching element. According to this structure, the light incident on the channel region of the transition metal molybdenum disulfide-based thin film transistor can be easily and selectively blocked.

In addition, the opaque material layer may include an opaque electrode material layer and an insulating material layer formed between the opaque electrode material layer and the channel region material layer. According to this structure, it is possible to attempt to change the characteristics of the switch transistor by using the voltage applied to the electrode material layer formed.

Further, the light-shielding portion may further include a transparent material layer formed on the transistor channel region material layer set as the sensor element, wherein the transparent material layer includes a transparent electrode material layer, an insulating material formed between the transparent electrode material layer and the channel region material layer Layer. According to this structure, it is possible to attempt to change the characteristics of the sensor transistor by using the voltage applied to the electrode material layer formed.

The light blocking portion includes a first thin film transistor and a transparent panel positioned above the second thin film transistor. The transparent panel includes a black matrix layer formed in a predetermined region for blocking light incident on a channel region of a transistor set as a switching element . ≪ / RTI > According to this configuration, the transition metal disulfide disulfide-based thin film transistors having the same structure can be selectively applied to the sensor or switch element by a simple method of applying a black matrix to a certain region of the glass panel employed in a display device including a sensor element array .

Further, the shielding portion may include an opaque gate electrode of the transistor set as the switching element and a transparent gate electrode of the transistor set as the sensor element. According to this configuration, the sensor array structure can be realized with a simpler structure for the transition metal molybdenum disulfide-based thin film transistor of the top gate type.

According to the present invention, it is possible to fabricate an optical sensor array structure having excellent manufacturing efficiency while effectively suppressing the photoconductivity retention phenomenon that occurs upon optical detection of the transition metal molybdenum disulfide-based optical sensor.

Further, the light incident on the channel region of the transition metal-based molybdenum disulfide-based thin film transistor can be easily and selectively blocked.

Further, it is possible to attempt to change the characteristics of the switch transistor by using the voltage applied to the electrode material layer formed.

Further, it is possible to attempt to change the characteristics of the sensor transistor using the voltage applied to the electrode material layer formed.

In addition, it is possible to selectively use the transition metal disulfide disulfide-based thin film transistors of the same structure selectively as a sensor or a switch element by a simple method of applying a black matrix to a certain region of a glass panel employed in a display device including a sensor element array do.

Further, for the transition metal molybdenum disulfide-based thin film transistor of the top gate type, the sensor array structure can be realized with a simpler structure.

1 shows an example in which a display transistor and a sensor transistor are formed together in a liquid crystal display backplane;
2 is a graph showing the light exposed state and the dark state photocurrent characteristic of a transition metal chalcogenide compound thin film transistor.
3 is a graph illustrating an example of performing a read operation of an optical sensor using photocurrent characteristics of a transition metal chalcogenide compound-based TFT.
4 is a graph showing photoconduction retention characteristics in a transition metal chalcogenide compound-based TFT.
5 is a schematic cross-sectional view of a pixel structure of a transition metal molybdenum disulfide light sensor according to a first embodiment of the present invention.
Figure 6 is a schematic circuit diagram of the pixel structure of the transition metal disulfide molybdenum photosensor of Figure 5;
7 is a graph comparing optical characteristics of a sensor element and a switch element.
8 is a graph showing the ratio of photocurrent / dark current of a transition metal molybdenum disulfide-based phototransistor.
9 is a graph showing the photoconductivity retention characteristics of a transition metal disulfide molybdenum optical sensor element.
10 is a view for explaining the photoelectric conductivity-maintaining property in a molybdenum disulfide-based optical sensor;
11 is a graph depicting the photoconductive properties of a resettled molybdenum disulfide optical sensor element.
12 is a view for explaining the photoconductivity characteristics in the reset molybdenum disulfide-based optical sensor.
13 is a waveform diagram showing waveforms of drain voltages and gate voltages applied to photosensor pixels;
FIG. 14 is a schematic circuit diagram showing a pixel composed of a sensor TFT and a select TFT; FIG.
15 is a waveform diagram of the gate voltage applied to each pixel in the photosensor array including the light pixels of Fig.
16 is a schematic cross-sectional view of a molybdenum disulfide light sensor array structure according to a second embodiment of the present invention.
Fig. 17 is a schematic circuit diagram of a molybdenum disulfide light sensor array structure of Fig. 16; Fig.
18 is a schematic cross-sectional view of a molybdenum disulfide light sensor array structure according to a third embodiment of the present invention.
19 is a schematic circuit diagram of a molybdenum disulfide light sensor array structure of Fig. 18;
20 is a schematic cross-sectional view of a molybdenum disulfide light sensor array structure according to a fourth embodiment of the present invention.
Fig. 21 is a schematic circuit diagram of the molybdenum disulfide light sensor array structure of Fig. 20; Fig.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 5 is a schematic cross-sectional view of a pixel structure of a transition metal disulfide molybdenum photosensor according to a first embodiment of the present invention, and FIG. 6 is a schematic circuit diagram of a pixel structure of a transition metal disulfide molybdenum photosensor of FIG.

5 and 6, the pixel structure of the transition metal disulfide molybdenum photosensor includes a first thin film transistor 110, a second thin film transistor 120, a light shield section 130, a switch element gate voltage supply section 140, And a device gate voltage supply unit 150.

The first thin film transistor 110 includes a first source electrode 112, a first drain electrode 114 and a first source electrode 112 and a first drain electrode 114 formed between the first source electrode 112 and the first source electrode 112, A channel region 116, and an etch stopper 118.

The second thin film transistor 120 includes a second drain electrode 124 and a second source electrode 122 connected to the first source electrode 112 and a second drain electrode 122 between the second source electrode 122 and the second drain electrode 124 A second channel region 126 of the transition metal molybdenum disulfide formed in the second channel region 126, and an etch stopper 128.

Although the etch stoppers 118 and 128 are formed on the channel regions 116 and 126 of the thin film transistors 110 and 120 in FIG. 5, the etch stoppers 118 and 228 may not be included in the other embodiments.

The light shielding part 130 blocks the light incident on the channel region of the transistor 120 set as the switch element of the first thin film transistor 110 and the second thin film transistor 120, To pass the light incident on the region.

5 and 6, the first thin film transistor 110 is set as the switch element and the second transistor 120 is set as the sensor element. In another embodiment, the second thin film transistor 120 is used as the switch element, 1 thin film transistor 110 may be respectively set.

According to such a configuration, the transition metal disilicide-based molybdenum disulfide thin film transistors having excellent characteristics such as high sensitivity light response characteristic and omnidirectional visible light reactivity are realized by the optical sensor element and the switch element, respectively, So that a pixel structure can be produced.

The switch element gate voltage supplier 140 supplies a preset switch element gate voltage to the gate electrode of the transistor set as the switch element, and the sensor element gate voltage supplier 150 controls the amount of the drain current, And supplies a predetermined sensor element gate voltage higher than the transistor element gate voltage to the gate electrode of the transistor set as the sensor element. In FIG. 6, it can be seen that the gate elements of the sensor element and the switch element are connected to different voltage supply lines.

According to this configuration, the transition metal disulfide molybdenum-based thin film transistor implemented with a sensor transistor can apply a gate voltage in a region having a more sensitive characteristic to incident light, thereby enhancing the performance of the optical sensor array.

5, in order to realize different sensitivities to light while using the same semiconductor material, in a transition metal disulfide molybdenum-based thin film transistor array structure of a bottom gate TFT structure, the sensor region is directly exposed to light and opaque An electrode is formed.

Sensor and a switch using the same semiconductor material. However, in the case of a switch device, a non-transparent electrode (sheild metal) is used to realize a dark current state irrespective of exposure to light. 7 is a graph comparing optical characteristics of a sensor element and a switch element.

In implementing a sensor array based on a thin film transistor, a sensor and a switch element constituting a sensor pixel must have different sensitivities to light when exposed to light. However, a transition metal molybdenum disulfide-based phototransistor exhibits a high photocurrent / dark current ratio when exposed to light in the dark state of the off current state (negative voltage application). 8 is a graph showing the photocurrent / dark current ratio of a transition metal molybdenum disulfide-based phototransistor.

Accordingly, the sensor element applies the gate voltage in the positive voltage region where the photocurrent / dark current ratio is high, and the switching element in the positive voltage region where the photocurrent / dark current ratio is low.

However, as mentioned above, there is a PPC phenomenon in the transition metal molybdenum disulfide-based optical sensor device. 9 is a graph showing photoconductivity retention characteristics of a transition metal disulfide molybdenum optical sensor element. In FIG. 9, it is possible to observe the PPC characteristic that is maintained even after the light is removed from the actual data.

Therefore, in a state where a negative voltage is applied to the gate at the time of reading, the light does not return to the original dark level, as shown in FIG. 10, due to the photoconductive property which is maintained even after the light is shrouded. 10 is a view for explaining the photoconductivity maintenance characteristics in a molybdenum disulfide-based optical sensor.

To solve this problem, after the read operation is completed, a positive voltage may be applied to the gate to reset the photosensor element. FIG. 11 is a graph showing the photoconductive characteristic of the resettable molybdenum disulfide optical sensor element, and FIG. 12 is a diagram for explaining the photoconductive characteristic in the resetted molybdenum disulfide-based photosensor.

That is, in order to remove the PPC phenomenon of the molybdenum disulfide-based photo-TFT, a reset pulse is applied to the gate of the photo-TFT after the read operation of the photosensor to solve the PPC problem.

13 is a waveform diagram showing waveforms of drain voltages and gate voltages applied to photosensor pixels. 13, when the switch transistor 110 is turned on, it can be confirmed that the first gate voltage Low is applied to the sensor transistor 120. When the switch transistor 110 is turned off, It can be confirmed that the second gate voltage Hi is applied to the sensor transistor 120 for suppressing the development.

13, the detection of the incident light is performed when light is incident on the switch transistor 110 in the ON state and the first gate voltage is applied to the sensor transistor, and the reset of the drain current is performed after the detection of the incident light Lt; RTI ID = 0.0 > 120 < / RTI >

However, in the optical sensor array including a plurality of optical sensor pixels sequentially selected, it is possible to implement without providing a switch element gate voltage supplier 140 and a sensor element gate voltage supplier 150 for every optical sensor pixel .

FIG. 14 is a schematic circuit diagram showing a pixel made up of a sensor TFT and a select TFT, and FIG. 15 is a waveform diagram of a gate voltage applied to each pixel in the photosensor array including the light pixel in FIG.

In Fig. 14, it can be seen that the gate n is connected to the gate of the select TFT and the gate n + 1 is connected to the gate of the n photo TFTs. In Fig. 15, When adopting the addressing method which sequentially performs the digital operation, it can be confirmed that the negative voltage is applied to the other gate when the positive voltage is applied to the gate n.

Gate n is selected. When the nth select TFT is selected, a read operation is performed because a negative voltage is applied to the gate of the nth photo sensor TFT. If the (n + 1) th gate is selected, The gate of the TFT is selected, and a positive voltage is applied to the gate of the n-th photo sensor TFT, whereby the reset is automatically performed.

The light-shielding portion 130 includes a layer of opaque material 132 formed on a material layer of the transistor channel region 126, which is set as a switching element. According to this structure, the light incident on the channel region of the transition metal molybdenum disulfide-based thin film transistor can be easily and selectively blocked.

5, the opaque material layer 132 at this time includes an opaque electrode material layer 133 and an insulating material layer 134 formed between the opaque electrode material layer 133 and the channel region 116 material layer . According to this structure, it is possible to attempt to change the characteristics of the switch transistor by using the voltage applied to the electrode material layer formed.

The opaque electrode material layer 133 may be implemented in a floating state when no additional characteristic changes are desired in the thin film transistor through the opaque electrode material layer 133, but for the more stable characteristics, It will be common practice to put them in a grounded state.

The shielding part 130 may further include a transparent material layer 136 formed on a material layer of a transistor channel region 116 that is set as a sensor element. The transparent material layer 136 may include a transparent electrode material layer 137 And an insulating material layer 138 formed between the transparent electrode material layer 137 and the channel region 116 material layer. According to this structure, it is possible to attempt to change the characteristics of the sensor transistor by using the voltage applied to the electrode material layer 137 formed.

FIG. 16 is a schematic cross-sectional view of a molybdenum disulfide optical sensor array structure according to a second embodiment of the present invention, and FIG. 17 is a schematic circuit diagram of the molybdenum disulfide optical sensor array structure of FIG. 16 shows an example in which transparent electrodes are formed on the sensor region and opaque electrodes are formed on the switch region in the transition metal disulfide molybdenum-based thin film transistor array structure of the bottom gate TFT structure.

The light shielding part 130 includes a first thin film transistor and a transparent panel 200 located on the second thin film transistor. The transparent panel 200 shields light incident on a channel region of a transistor The black matrix layer 210 may be formed in a predetermined area. According to this configuration, the transition metal disulfide disulfide-based thin film transistors having the same structure can be selectively applied to the sensor or switch element by a simple method of applying a black matrix to a certain region of the glass panel employed in a display device including a sensor element array .

FIG. 18 is a schematic cross-sectional view of a molybdenum disulfide optical sensor array structure according to a third embodiment of the present invention, and FIG. 19 is a schematic circuit diagram of the molybdenum disulfide optical sensor array structure of FIG. 18, a black matrix is not applied on the upper side of the sensor region of the transparent panel 200 located on the upper side of the transition metal disulfide molybdenum-based thin film transistor array structure of the bottom gate TFT structure, and a black matrix is formed on the upper side of the switch region A coated example is shown.

In addition, the light-shielding portion 130 may include the opaque gate electrode 160 of the transistor set as the switch element and the transparent gate electrode 170 of the transistor set as the sensor element. According to this configuration, the sensor array structure can be realized with a simpler structure for the transition metal molybdenum disulfide-based thin film transistor of top gate type.

FIG. 20 is a schematic cross-sectional view of a molybdenum disulfide optical sensor array structure according to a fourth embodiment of the present invention, and FIG. 21 is a schematic circuit diagram of the molybdenum disulfide optical sensor array structure of FIG. FIG. 20 shows an example in which the gate electrode of the transition metal disulfide-based thin film transistor array structure of the top gate TFT structure is not coated with the black matrix on the upper side of the sensor region but the black matrix is coated on the upper side of the switch region.

The present invention is applied to an optical sensor-based electronic device using a two-dimensional transition metal molybdenum disulfide (MoS ₂ ) -based thin film transistor (TFT) structure. It can be applied to the remote touch screen of the electronic whiteboard, and it is applicable to the remote touch screen suitable for the cable TV.

2-Dimensional Transition Metals Optical sensors based on molybdenum disulfide-based TFT-type devices are ultimately designed for display response in response to high-sensitivity photoreaction characteristics and omnidirectional visible light. They are used not only for communication between devices and users, Lt; RTI ID = 0.0 > and / or < / RTI >

Transition metal molybdenum disulfide with a low energy band gap (1.3-1.8 eV) reacts with omni-directional visible light (1.8-3.2 eV), and the TFT using this material can replace the existing amorphous silicon or oxide semiconductor based optical sensor technology It is expected to be.

According to the present invention, by implementing a bidirectional large-area display having high sensitivity light response characteristics and optical sensing characteristics responsive to full-direction visible light, it is possible to contribute to securing the core sensor technology of a bidirectional large- .

Although the present invention has been described in terms of some preferred embodiments, the scope of the present invention should not be limited thereby but should be modified and improved in accordance with the above-described embodiments.

110: first thin film transistor
112: first source electrode
114: first drain electrode
116: first channel region
118, 128: etch stopper
120: second thin film transistor
122: second source electrode
124: second drain electrode
126: second channel region
130:
132: Opaque material layer
133: Opaque electrode material layer
134, 138: Insulation material layer
136: transparent material layer
137: transparent electrode material layer
140: Switch element gate voltage supplier
150: Sensor element gate voltage supply
160: opaque gate electrode
170: transparent gate electrode
200: Transparent panel
210: black matrix layer

Claims (9)

A first thin film transistor including a first source electrode, a first drain electrode, and a first channel region of transition metal molybdenum disulfide formed between the first source electrode and the first drain electrode;
A second thin film transistor including a second drain electrode connected to the first source electrode, a second source electrode, and a second channel region of molybdenum disulfide formed between the second source electrode and the second drain electrode;
A light shielding part for shielding light incident on a channel region of a transistor set as a switching element among the first thin film transistor and the second thin film transistor and for passing light incident on a channel region of a transistor set as a sensor element;
A switching element gate voltage supplier for supplying a predetermined switching element gate voltage to the gate electrode of the transistor set as the switching element; And
And a sensor element gate voltage supply section for supplying a predetermined sensor element gate voltage whose magnitude of a drain current changed by the incident light is larger than the switch element gate voltage to the gate electrode of the transistor set to the sensor element, A plurality of light sensor pixels,
Wherein the gate electrode of the transistor set to the sensor element is connected to the switch gate voltage supplier of the photosensor pixel selected in the following order.
The method according to claim 1,
Wherein the shielding portion comprises an opaque material layer formed on the transistor channel region material layer set as the switching element.
3. The method of claim 2,
Wherein the opaque material layer comprises an opaque electrode material layer and an insulating material layer formed between the opaque electrode material layer and the channel region material layer.
3. The method of claim 2,
Wherein the shielding portion further comprises a transparent material layer formed on the transistor channel region material layer set as the sensor element.
5. The method of claim 4,
Wherein the transparent material layer comprises a transparent electrode material layer and an insulating material layer formed between the transparent electrode material layer and the channel region material layer. ≪ RTI ID = 0.0 > 18. < / RTI >
The method according to claim 1,
The light-shielding portion includes a first thin-film transistor and a transparent panel positioned above the second thin-film transistor, and the transparent panel is formed in a predetermined region for blocking light incident on a channel region of the transistor set as the switching element And a black matrix layer. ≪ Desc / Clms Page number 18 >
The method according to claim 1,
Wherein the shielding part comprises an opaque gate electrode of the transistor set as the switching element and a transparent gate electrode of the transistor set as the sensor element.
A sensor thin film transistor including a source electrode, a drain electrode, a gate electrode, and a channel region of transition metal molybdenum disulfide formed between the source electrode and the drain electrode;
A switch thin film transistor having a gate electrode connected to a gate voltage supply unit different from the sensor thin film transistor and connected in series with the sensor thin film transistor;
A switching element gate voltage supplier for supplying a predetermined switching element gate voltage to the gate electrode of the switch thin film transistor; And
And a sensor element gate voltage supplier for supplying a predetermined sensor element gate voltage to the gate electrode of the sensor thin film transistor,
Wherein the gate electrode of the transistor set to the sensor element is connected to the switch gate voltage supplier of the photosensor pixel selected in the following order.
9. The method of claim 8,
The switch thin film transistor is a molybdenum disulfide-based transistor having the same structure as that of the sensor transistor. The light sensor pixel blocks light incident on the channel region of the switch thin film transistor and transmits light incident on the channel region of the sensor thin film transistor Wherein the light-shielding portion comprises a light-shielding portion for the molybdenum disulfide-based optical sensor array.

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