JP2014190699A - Sensor device using organic thin film transistor - Google Patents

Abstract

The present invention provides a sensor device having a detection capability with high sensitivity and a wide dynamic range and capable of extracting sensing information as a voltage signal.
A complementary circuit is configured by first to fourth same-channel transistors Tr1 to Tr4, and any one of the transistors is configured by an organic TFT and used as a sensor element. Organic TFTs used as sensor elements function to change their electrical characteristics in response to physical changes or due to adsorption of specific substances, and the other transistor that constitutes the complementary circuit has no sensor sensitivity. The
Since the sensor device forms a complementary circuit, it can have a detection capability with a wide dynamic range, and since the sensor output is provided as a voltage value, it can contribute to simplifying the external circuit configuration.
[Selection] Figure 1

Description

  The present invention relates to a sensor device having a complementary circuit using an organic thin film transistor, and more particularly to a sensor device having a complementary circuit using a same-channel transistor.

Organic thin film transistors (organic TFTs), which can be formed on a flexible material such as a plastic film in a low temperature (room temperature) atmosphere, are attracting attention as a technology that can realize lightweight and flexible electronic devices. Yes.
It can also be applied to sensor devices, etc., using the function to output changes in the characteristics of organic transistors as electrical signals when physical changes are made to organic transistors or when specific substances are adsorbed. It is being considered.

That is, the organic transistor can be used as a sensor for detecting physical changes such as pressure, temperature, light, acceleration, strain, magnetism, and humidity, gas, ions, pH, or specific enzymes, DNA, proteins, etc. it can.
In particular, it can be used as a detection unit of a flexible sensor using a resin film as a substrate, such as a sensor array having a large area or a sheet-like sensor device that can be installed in a curved surface.

A conventional sensor using an organic transistor generally has a device form in which a single organic transistor functions as a sensor element and detects a current change (drain current) flowing through the organic transistor. This is disclosed in Patent Document 1. Yes.
As disclosed in Patent Document 1, the gate insulating film or the organic semiconductor contains a substituent that easily binds or reacts with the substance to be detected, and the change in current that flows through the organic transistor when the substance to be detected is adsorbed is used as an index. , Detecting substances.

JP 2006-258661 A

However, according to the sensor device disclosed in Patent Document 1, as described above, since the organic transistor alone functions as a sensor element and measures an electrical signal, the current change amount when sensing is as small as several times as small. The sensitivity is bad.
Also, with this measurement technique, it is difficult to detect changes that change with digits, and the problem is that the signal dynamic range is narrow. That is, although it can be identified whether or not the sensor has detected the target substance, it is difficult to quantitatively detect the amount or degree thereof.

Therefore, if the sensitivity as a sensor is improved and the dynamic range of the detected signal is widened, the above problem can be solved.
Further, when considering a practical circuit, it is easier to perform signal processing if the electrical signal at the time of sensing is detected as a voltage signal, and the S / N can be greatly increased. Furthermore, if sensing information can be detected as a voltage signal, the information can be easily digitally processed.

  The present invention has been made on the basis of the above-mentioned technical point of view. A complementary circuit is configured by using the same channel type transistor, thereby having a detection capability with high sensitivity and a wide dynamic range, and sensing. It is an object of the present invention to provide a sensor device that can directly extract information as a voltage signal.

  The sensor device according to the present invention, which has been made to achieve the above-mentioned object, includes first to fourth co-channel transistors, and each drain and source electrode of the first and second transistors are connected between operating power supplies. The drain and gate electrodes of the second transistor are connected and short-circuited, and the drain and source electrodes of the third and fourth transistors are connected in series between operating power supplies, and the fourth transistor The drain electrode of the second transistor is connected to the gate electrode of the transistor, the gate electrodes of the first and third transistors are used as input voltage terminals, the source electrode of the third transistor, the drain electrode of the fourth transistor, A complementary circuit is configured by making the connection point of At least one of the first to fourth transistors is formed of an organic thin film transistor and is used as a sensor element. A change in output voltage caused at the voltage output terminal with respect to an input voltage supplied to the input voltage terminal is as follows. It is a sensor output.

  In this case, the organic thin film transistor used as a sensor element functions to change its electrical characteristics in response to a physical change or due to adsorption of a specific substance, and the other transistors constituting the complementary circuit have no sensor sensitivity. Made up.

  In addition, in a desirable mode of the sensor device according to the present invention, a P-channel transistor is used as the first to fourth transistors, and the first transistor is configured as a sensor element.

According to the above-described sensor device according to the present invention, the pseudo complementary circuit (CMOS) is configured by using the first to fourth co-channel transistors, and at least one of the transistors is configured by the organic thin film transistor (organic TFT). Used as a sensor element.
The organic TFT used as the sensor element functions as a sensor by changing the electrical characteristics due to the target physical change or adsorption of a specific substance, and outputs the sensor output as voltage information from the output terminal of the complementary circuit. Can bring.

In this case, a detection output (sensor output) having a wide dynamic range can be output as a voltage value to the output terminal of the complementary circuit in accordance with operating voltages (Vdd and Vss described later) applied to the complementary circuit. . Accordingly, it is possible to provide a sensor device capable of quantitatively detecting a target physical change or a specific substance by using an organic TFT used as a sensor element.
In addition, since the sensor output information is provided as a voltage value, the sensor output information can be immediately digitally processed, which can contribute to simplifying the external circuit configuration.

FIG. 3 is a connection diagram showing a configuration of a first complementary circuit used in the sensor device according to the present invention. It is the schematic diagram which showed the laminated structural example of the P channel type organic TFT utilized for the complementary circuit shown in FIG. It is the diagram which showed the inversion output characteristic obtained by the complementary circuit shown in FIG. 1 corresponding to the bending degree of the board | substrate of organic TFT. It is the connection diagram which showed the structure of the 2nd complementary circuit utilized for the sensor device which concerns on this invention. FIG. 5 is a schematic diagram illustrating a stacked configuration example of an N-channel organic TFT used in the complementary circuit illustrated in FIG. 4.

Hereinafter, a sensor device according to the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a circuit configuration diagram showing a first form of a complementary circuit used in the sensor device according to the present invention. As the first to fourth transistors Tr1 to Tr4, all are P-channel organic TFTs. An example using (hereinafter also simply referred to as a P-type organic TFT) is shown.

As shown in FIG. 1, the drain and source electrodes of the first transistor Tr1 and the second transistor Tr2 are connected in series between the operating power supply Vdd and the operating power supply Vss. That is, the drain electrode of the first transistor Tr1 is connected to the operating power supply Vdd, and the source electrode of the first transistor Tr1 is connected to the drain electrode of the second transistor Tr2. The source electrode of the second transistor Tr2 is connected to the operating power supply Vss, and the drain and gate electrodes of the second transistor Tr2 are connected and short-circuited.
Therefore, the second transistor Tr2 forms a diode whose drain and gate electrodes serve as anode terminals and whose source electrode functions as a cathode terminal.

The drain and source electrodes of the third transistor Tr3 and the fourth transistor Tr4 are connected in series between the operation power supply Vdd and the reference potential point GND of the circuit.
That is, the drain electrode of the third transistor Tr3 is connected to the operating power supply Vdd, and the source electrode of the third transistor Tr3 is connected to the drain electrode of the fourth transistor Tr4. The source electrode of the fourth transistor Tr4 is connected to the reference potential point GND. Further, the drain electrode of the second transistor is connected to the gate electrode of the fourth transistor.

  The gate electrodes of the first transistor Tr1 and the third transistor Tr3 constitute an input voltage terminal Vin, and the connection point between the source electrode of the third transistor Tr3 and the drain electrode of the fourth transistor Tr4 is a voltage output terminal Vout. Thus, a complementary circuit is configured.

  That is, in the circuit configuration shown in FIG. 1, the fourth transistor Tr4 is substantially formed by the combination of the first transistor Tr1, the second transistor Tr2 functioning as a diode, and the P-type organic TFTs of the fourth transistor Tr4. The third transistor Tr3 and the fourth transistor Tr4 operate as a complementary circuit (CMOS). Therefore, the circuit configuration shown in FIG. 1 can also be called a pseudo-complementary circuit.

The pseudo-complementary circuit shown in FIG. 1 constitutes a logic circuit as an inverter, and the output voltage supplied to the output terminal Vout in accordance with the input voltage supplied to the input terminal Vin is the reference voltage for the operation power supply Vdd. Changes can be made within the range of the potential point GND.
Therefore, for example, when a P-type organic TFT functioning as the first transistor Tr1 is used as the sensor element described above, a change in electrical characteristics of the P-type organic TFT as the first transistor is brought to the output terminal Vout with a large dynamic range. be able to.

  FIG. 2 shows a stacked configuration example of P-type organic TFTs as the first to fourth transistors Tr1 to Tr4. This example is a general configuration of a field effect type organic transistor. To produce this transistor, as an example, first, a PEN film having a thickness of 125 μm is bonded to a glass plate using a heat-resistant double-sided tape, A substrate 1 for manufacturing a device is used.

  Aluminum to be the gate electrode 2 is vacuum-deposited on the substrate 1 to a film thickness of 30 nm, and then a cross-linkable polyvinyl phenol to be the gate insulating film 3 is formed thereon by spin coating so as to have a film thickness of 300 nm. Film. Next, after a gold electrode is formed on the entire surface, pattern forming is performed in the shape of the source electrode 4 and the drain electrode 5 using photolithography. Finally, as the P-type organic semiconductor layer 6, a P-type organic TFT can be obtained by vacuum-depositing pentacene with a film thickness of 50 nm.

  In the sensor device according to the present invention, the P-type organic TFT as the first transistor Tr1 shown in FIG. 1 is used as a sensor element, and the P-type organic TFT as the other second to fourth transistors Tr2 to Tr4 is a sensor element. It is made the structure which does not have the sensitivity as.

The second to fourth transistors Tr2 to Tr4 that do not require sensitivity as sensors optimize the device structure such as the channel length, channel width, gate insulating film thickness, electrode material, and organic semiconductor material. As a result, it is possible to reduce a change in electrical characteristics with respect to a target physical change or adsorption of a specific substance, and it is possible to eliminate sensitivity as a sensor.
In addition, as a transistor having no sensor sensitivity, a transistor using an oxide semiconductor, a silicon semiconductor, or a carbon nanotube can be used instead of the organic transistor.

  FIG. 3 shows output characteristics (inversion characteristics) of the voltage output terminal Vout obtained by a complementary circuit corresponding to the bending degree of the substrate 1 of the first transistor Tr1 constituting the sensor element. The inversion characteristics are shown when the input voltage Vin is swept from -10V to 30V in a state where 20V is applied as the operating voltage Vdd and -20V is applied as the operating voltage Vss.

  3 shows the input voltage Vin on the horizontal axis and the output voltage Vout on the vertical axis. When the substrate 1 of the first transistor Tr1 is bent on the front side (when the substrate is deformed in a convex direction), In addition, a case where the substrate 1 is bent with the substrate 1 inward (when the substrate is deformed in a concave direction) is shown.

In FIG. 3, the characteristics indicated by reference symbols a, b, and c indicate that the output voltage Vout is inverted when the substrate 1 is deformed in a convex direction and the bending radius (R) of the substrate 1 is 10 mm, 5 mm, and 3 mm. The characteristics are shown. The characteristics indicated by symbols d, e, and f indicate the inversion characteristics of the output voltage Vout when the substrate 1 is deformed in the concave direction and the bending radius (R) of the substrate 1 is 10 mm, 5 mm, and 3 mm. ing.
The characteristic indicated by the symbol g indicates a case where the substrate 1 is not subjected to a bending operation.

As shown in FIG. 3, when the substrate 1 is deformed in the convex direction, the inversion characteristics shift to the high voltage side, and when the substrate 1 is deformed in the concave direction, the inversion characteristics shift to the low voltage side. I understand that. Then, it is possible to detect the bending (deformation) direction of the substrate 1 and its curvature from the value of the input voltage Vin when the output voltage Vout is inverted by sweeping the input voltage Vin of the complementary circuit.
By using the detection means shown in FIG. 3, it is possible to digitally detect whether or not the substrate 1 is bent with a specific curvature.

In the first embodiment of the sensor device according to the present invention described above, a pseudo-complementary circuit is configured using four P-type organic TFTs. Similarly, a pseudo-complementary circuit is configured using four N-type organic TFTs. It can be configured as a sensor device.
FIG. 4 shows a second embodiment in which a pseudo-complementary circuit is configured using four N-channel organic TFTs (N-type organic TFTs) to form a sensor device.

As shown in FIG. 4, the drain and source electrodes of the first transistor Tr1 and the second transistor Tr2 are connected in series between the reference potential point GND of the circuit and the operating power supply Vss.
That is, the drain electrode of the first transistor Tr1 is connected to the reference potential point GND, and the source electrode of the first transistor Tr1 is connected to the drain electrode of the second transistor Tr2. The source electrode of the second transistor Tr2 is connected to the operating power supply Vss, and the drain and gate electrodes of the second transistor Tr2 are connected and short-circuited.
Therefore, the second transistor Tr2 forms a diode whose drain and gate electrodes serve as anode terminals and whose source electrode functions as a cathode terminal.

The drain and source electrodes of the fourth transistor Tr4 and the third transistor Tr3 are connected in series between the operating power supply Vdd and the reference potential point GND of the circuit.
That is, the drain electrode of the fourth transistor Tr4 is connected to the operation power supply Vdd, and the source electrode of the fourth transistor Tr4 is connected to the drain electrode of the third transistor Tr3. The source electrode of the third transistor Tr3 is connected to the reference potential point GND. Further, the drain electrode of the second transistor is connected to the gate electrode of the fourth transistor.

  The gate electrodes of the first transistor Tr1 and the third transistor Tr3 constitute an input voltage terminal Vin, and the connection point between the drain electrode of the third transistor Tr3 and the source electrode of the fourth transistor Tr4 is connected to the voltage output terminal Vout. As a result, a complementary circuit is formed.

  In the circuit configuration shown in FIG. 4, the fourth transistor Tr4 is substantially P by the combination of the N-type organic TFTs of the first transistor Tr1, the second transistor Tr2 functioning as a diode, and the fourth transistor Tr4. The third transistor Tr3 and the fourth transistor Tr4 operate as a complementary circuit (CMOS). Therefore, the circuit configuration shown in FIG. 4 can also be called a pseudo-complementary circuit.

The pseudo-complementary circuit shown in FIG. 4 also forms a logic circuit as an inverter. The output voltage supplied to the output terminal Vout according to the input voltage supplied to the input terminal Vin is the operating power supply Vdd. Changes can be made within the range of the reference potential point GND.
Therefore, for example, when an N-type organic TFT functioning as the first transistor Tr1 is used as the sensor element described above, a change in electrical characteristics of the N-type organic TFT as the first transistor is brought to the output terminal Vout with a large dynamic range. be able to.

  FIG. 5 shows an example of a stacked configuration of N-type organic TFTs used in the pseudo-complementary circuit shown in FIG. This example also constitutes a field effect type organic transistor, and the same procedure as that for the already described P type organic TFT is adopted in the production of the N type organic TFT.

As an example, a PEN film having a thickness of 125 μm is bonded to a glass plate using a heat-resistant double-sided tape to form a substrate 11 for manufacturing a device.
Aluminum which becomes the gate electrode 12 is vacuum-deposited on the substrate 11 with a film thickness of 30 nm, and then a cross-linkable polyvinyl phenol which becomes the gate insulating film 13 is formed thereon by spin coating so as to have a film thickness of 300 nm. Film.

  Next, after a gold electrode is formed on the entire surface, pattern formation is performed in the shape of the source electrode 14 and the drain electrode 15 using photolithography. Finally, an N-type organic TFT can be obtained by vacuum-depositing FPTBBT (Chemical Communication, Vo1.46, Page 3265) with a film thickness of 50 nm as the N-type organic semiconductor layer 16.

Also in the second embodiment of the sensor device shown in FIGS. 4 and 5, for example, when an N-type organic TFT as the first transistor Tr1 is used as a sensor element, the other second to fourth transistors Tr2 to Tr4 are used. The N-type organic TFT has a configuration that does not have sensitivity as a sensor.
For each transistor that does not require sensitivity as a sensor, this can be realized by optimizing the device structure such as the channel length and channel width in the same manner as the P-type organic TFT described above.

  And also in the 2nd form of the sensor device shown in FIG.4 and FIG.5, when using N-type organic TFT as 1st transistor Tr1 as a sensor element, and using this as a sensor which detects the bending degree of a board | substrate, Detection characteristics similar to those in the example shown in FIG. 3 can be obtained.

  As for the sensor device according to the present invention, the case where the degree of bending of the substrate or the like is detected as one example has been described. However, the sensor device according to the present invention can be applied to pressure, temperature, light, acceleration, strain, magnetism, humidity. It can also be used to detect physical changes. In the detection of this physical change, the sensor output can be obtained by arranging the entire sensor device in the measurement position or atmosphere.

Further, in order to detect gas, ions, pH, or a specific enzyme, DNA, protein, etc., it functions as a sensor element, for example, on the surface of the organic semiconductor layer 6 of the P-type organic TFT shown in FIG. It is desirable to form a layer capable of adsorbing a substance to be detected on the surface of the organic semiconductor layer 16 of the N-type organic TFT shown in FIG.
A change in the electrical characteristics of the organic TFT caused by the adsorption of a specific substance is brought about from the Vout terminal of the complementary circuit, which can perform a sensor function.

The organic transistors shown in FIGS. 2 and 5 have a bottom gate / top contact structure. However, the sensor device according to the present invention is not limited to this, and the bottom gate / bottom contact structure, the top gate / bottom contact are not limited thereto. A structure or the like can be employed as appropriate.
In addition, the insulating material, electrode, and base material used for the organic transistor are not particularly required, and general materials suitable for the organic transistor can be used.

  In the embodiments described above, the first transistor Tr1 constituting the pseudo-complementary circuit is used as the sensor element. However, any one of the second to fourth transistors Tr2 to Tr4 is used as the sensor element. It can also be used.

  In the second embodiment of the sensor device shown in FIG. 4 and FIG. 5, a pseudo-complementary circuit is configured using four N-type organic TFTs. Compared with a type organic transistor, the stability as a device is generally poor and easily deteriorated. Therefore, considering the durability and reproducibility of the sensor device, it is desirable to use the sensor device using the P-type organic transistor shown in the first embodiment at present.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Gate electrode 3 Gate insulating film 4 Source electrode 5 Drain electrode 6 P-type organic semiconductor layer 11 Substrate 12 Gate electrode 13 Gate insulating film 14 Source electrode 15 Drain electrode 16 N-type organic semiconductor layer Tr1 to Tr4 Transistor

Claims (3)

First to fourth same-channel transistors are provided, and the drain and source electrodes of the first and second transistors are connected in series between operating power supplies, and the drain and gate electrodes of the second transistor are connected. The drain and source electrodes of the third and fourth transistors are connected in series between the operating power supplies, and the drain electrode of the second transistor is connected to the gate electrode of the fourth transistor,
The gate electrodes of the first and third transistors are used as input voltage terminals, and the connection point between the source electrode of the third transistor and the drain electrode of the fourth transistor is used as a voltage output terminal. Is configured,
At least one of the first to fourth transistors is formed of an organic thin film transistor and used as a sensor element, and a change in output voltage provided to the voltage output terminal with respect to an input voltage supplied to the input voltage terminal Is a sensor output.   Organic thin-film transistors used as sensor elements function to change electrical characteristics in response to physical changes or by adsorption of specific substances, and other transistors that make up complementary circuits have no sensor sensitivity The sensor device according to claim 1.   The sensor device according to claim 1, wherein the first transistor is used as a sensor element.

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