WO2017018434A1 - Biosensor - Google Patents

Abstract

In a biosensor using a thin-film transistor including a semiconductor film made of an oxide semiconductor, the observation of a biologically derived substance with an optical microscope is made possible while making it easy to assess the relationship between the state of the biologically derived substance and a change in electrical characteristics of the thin-film transistor. This biosensor (10) comprises a thin-film transistor (12) and a semiconductor layer (14). The semiconductor layer is formed in a different region on a substrate from a channel layer (22) of the thin-film transistor. The semiconductor layer is made of the same material as the channel layer. As viewed from the normal direction to the substrate, a first region (32) is formed in the channel layer, and a second region (34) is formed in the semiconductor layer. The first region is a region to which a biologically derived substance adheres, and that affects the electrical characteristics of the thin-film transistor. The second region is a region that is made of the same material as the first region, and in which the adhering biologically derived substance can be observed with an optical microscope from the substrate side.

Description

Biosensor

The present invention relates to a biosensor, and more particularly, to a biosensor using a thin film transistor.

In recent years, biosensors using thin film transistors as field effect transistors have been proposed. In such a biosensor, it has been proposed to acquire an electrical signal related to a biological substance while observing the biological substance with an optical microscope (see, for example, Japanese Patent No. 5488372).

Japanese Patent No. 5488372

The biosensor described in the above publication has a semiconductor film made of an oxide semiconductor. Therefore, when a biological material is observed using a fluorescence microscope, the electrical characteristics of the thin film transistor are changed by irradiating the semiconductor film with excitation light. For this reason, there is a problem that it is difficult to determine how much the state of the biological substance affects the change in the electrical characteristics of the thin film transistor.

It is an object of the present invention to achieve a biosensor using a thin film transistor having a semiconductor film made of an oxide semiconductor while observing a biological material using an optical microscope, and to change the electrical characteristics of the thin film transistor and the biological material. It is to make the relationship with the state easy to understand.

The biosensor according to the embodiment of the present invention includes a thin film transistor and a semiconductor layer. The thin film transistor is a bottom gate type. The thin film transistor is formed over a substrate that transmits visible light and includes a gate electrode made of metal and a channel layer made of an oxide semiconductor. The semiconductor layer is formed in a region different from the channel layer included in the thin film transistor over the substrate. The semiconductor layer is made of the same material as the channel layer. As viewed from the normal direction of the substrate, a first region is formed in the channel layer, and a second region is formed in the semiconductor layer. The first region is a region that attaches a biological substance and affects the electrical characteristics of the thin film transistor. The second region is made of the same material as the first region, and is a region where the attached biological substance can be observed from the substrate side with an optical microscope.

In the biosensor according to the embodiment of the present invention, it is possible to easily understand the relationship between the change in the electrical characteristics of the thin film transistor and the state of the biological material while observing the biological material using an optical microscope. .

It is a top view which shows schematic structure of the biosensor by the 1st Embodiment of this invention. FIG. 2 is a cross-sectional view showing a schematic configuration of the biosensor according to the first embodiment of the present invention, which is a cross-sectional view taken along the line AA in FIG. FIG. 2 is a cross-sectional view showing a schematic configuration of the biosensor according to the first embodiment of the present invention, which is a cross-sectional view taken along the line BB in FIG. FIG. 2 is a cross-sectional view showing a schematic configuration of a biosensor according to a second embodiment of the present invention, which is a cross-sectional view corresponding to the AA cross section in FIG. FIG. 4 is a cross-sectional view showing a schematic configuration of a biosensor according to a second embodiment of the present invention, which is a cross-sectional view corresponding to a BB cross section in FIG. FIG. 5 is a cross-sectional view showing a schematic configuration of a biosensor according to a third embodiment of the present invention, which is a cross-sectional view corresponding to the AA cross section in FIG. FIG. 4 is a cross-sectional view showing a schematic configuration of a biosensor according to a third embodiment of the present invention, which is a cross-sectional view corresponding to a BB cross section in FIG. FIG. 8 is a cross-sectional view showing a schematic configuration of a biosensor according to an application example of the third embodiment of the present invention, and is a cross-sectional view corresponding to a cross section taken along line AA in FIG. FIG. 7 is a cross-sectional view showing a schematic configuration of a biosensor according to an application example of the third embodiment of the present invention, and is a cross-sectional view corresponding to a cross section taken along line BB in FIG.

The biosensor according to the embodiment of the present invention includes a thin film transistor and a semiconductor layer. The thin film transistor is a bottom gate type. The thin film transistor is formed over a substrate that transmits visible light and includes a gate electrode made of metal and a channel layer made of an oxide semiconductor. The semiconductor layer is formed in a region different from the channel layer included in the thin film transistor over the substrate. The semiconductor layer is made of the same material as the channel layer. As viewed from the normal direction of the substrate, a first region is formed in the channel layer, and a second region is formed in the semiconductor layer. The first region is a region that attaches a biological substance and affects the electrical characteristics of the thin film transistor. The second region is made of the same material as the first region, and is a region where the attached biological substance can be observed from the substrate side with an optical microscope.

The biosensor has a first region. The first region is formed in the channel layer as viewed from the normal direction of the substrate.

Here, “when viewed from the normal direction of the substrate, the first region is formed in the channel layer” not only when the first region is formed by the channel layer itself, but also when the first region is a channel layer. The case where it forms with the coating layer which covers a layer is also included.

When the biological material adheres to the first region, the electrical characteristics of the thin film transistor change. That is, in the biosensor, it is possible to detect a change in the electrical characteristics of the thin film transistor due to the biological substance adhering to the first region. Note that changes in electrical characteristics of the thin film transistor include, for example, changes in off-state current and threshold voltage.

The biosensor has a second region. The second region is formed in the semiconductor layer when viewed from the normal direction of the substrate.

Here, “when viewed from the normal direction of the substrate, the second region is formed in the semiconductor layer” not only when the second region is formed of the semiconductor layer itself, but also when the second region is a semiconductor layer. The case where it forms with the coating layer which covers a layer is also included.

The semiconductor layer is made of an oxide semiconductor. Therefore, the semiconductor layer transmits light. In the biosensor, the biological substance attached to the second region can be observed using an optical microscope.

Here, the second region is made of the same material as the first region. Therefore, the state of the biological substance adhering to the second region and the state of the biological substance adhering to the first region can be made the same. That is, in the biosensor, the state of the biological substance can be observed when the electrical characteristics of the thin film transistor are changed.

In the biosensor, the thin film transistor is a bottom gate type. Therefore, the gate electrode can suppress the channel layer from being irradiated with light from the light source used for microscopic observation. That is, change in electrical characteristics of the thin film transistor due to light irradiation to the channel layer can be suppressed. As a result, the relationship between the state of the biological substance and the change in the electrical characteristics of the thin film transistor at that time can be easily understood.

In the biosensor, when the first region is formed by the channel layer, the second region is formed by the semiconductor layer.

In such an embodiment, the biological substance adheres to the channel layer. Therefore, the change in the electrical characteristics of the thin film transistor when the biological substance adheres to the first region is larger than when the biological substance adheres to the insulating film covering the channel layer. As a result, it becomes easy to detect a change in electrical characteristics of the thin film transistor when the biological substance adheres to the first region.

The biosensor preferably further includes a passivation film. The passivation film covers the channel layer and the semiconductor layer. In this case, the first region is formed by a portion of the passivation film that overlaps the channel layer. The second region is formed by a portion of the passivation film that overlaps the semiconductor layer.

In such an embodiment, the channel layer can be protected by the passivation film. That is, the channel layer is not exposed to the solution containing the biological substance. Therefore, the operation of the thin film transistor can be stabilized.

In addition, the passivation film covers not only the channel layer but also the semiconductor layer. Therefore, the material forming the first region and the material forming the second region can be the same. The reason is as follows.

When the channel layer is made of an oxide semiconductor, heat treatment is performed after the passivation film is formed. At this time, hydrogen, oxygen, or the like moves between the passivation film and the channel layer. Here, in the above aspect, the semiconductor layer is formed of the same material (oxide semiconductor) as the channel layer and is covered with the same passivation film as the channel layer. Therefore, when hydrogen, oxygen, or the like moves between the passivation film and the channel layer by heat treatment after film formation, hydrogen, oxygen, or the like moves in the same manner between the passivation film and the semiconductor layer. As a result, the composition of the portion of the passivation film covering the channel layer and the portion covering the semiconductor layer can be made the same. That is, the material forming the first region can be made the same as the material forming the second region.

As described above, if the material forming the first region and the material forming the second region can be made the same, the state of the biological substance attached to the first region and the living body attached to the second region The state of the derived substance can be made the same. That is, also in the above aspect, the state of the biological substance can be observed when the electrical characteristics of the thin film transistor are changed.

The passivation film may include a first passivation film and a second passivation film. In this case, the first passivation film is formed in contact with the channel layer and the semiconductor layer. The second passivation film is formed in contact with the first passivation film.

In such an embodiment, preferably, the first passivation film is a silicon oxide film and the second passivation film is a silicon nitride film.

In this case, the waterproofness of the passivation film is further enhanced. As a result, the operation of the thin film transistor can be further stabilized.

In the biosensor, the passivation film may cover the source electrode and the drain electrode of the thin film transistor. In this case, the biosensor may further include a reference electrode formed on the passivation film.

In such an embodiment, a reference electrode may not be provided separately. Therefore, it is possible to reduce the size of the mechanism that detects a change in the electrical characteristics of the thin film transistor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[First embodiment]
A biosensor 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1, 2A, and 2B. FIG. 1 is a plan view showing a schematic configuration of the biosensor 10. 2A is a cross-sectional view taken along line AA in FIG. 2B is a cross-sectional view taken along the line BB in FIG.

As shown in FIG. 1, the biosensor 10 includes a thin film transistor 12 and a semiconductor layer 14. Hereinafter, these will be described.

The thin film transistor 12 is formed on the substrate 16 as shown in FIG. 2A. The substrate 16 transmits visible light. The substrate 16 is, for example, a glass substrate.

The thin film transistor 12 has a so-called bottom gate structure. The thin film transistor 12 includes a gate electrode 18, a gate insulating film 20, a semiconductor active layer 22, a source electrode 24, and a drain electrode 26.

The gate electrode 18 is formed in contact with the substrate 16. The gate electrode 18 may be a metal film made of a metal such as aluminum (Al), tungsten (W), molybdenum (Mo), tantalum (Ta), chromium (Cr), titanium (Ti), or copper (Cu). Alternatively, an alloy film made of an alloy containing any of these metals may be used. The metal film and the alloy film may have a single layer structure or a laminated structure.

The gate electrode 18 is covered with a gate insulating film 20. The gate insulating film 20 may be, for example, a silicon nitride film, a silicon oxide film, or a laminate of a silicon nitride film and a silicon oxide film.

The semiconductor active layer 22 is formed in contact with the gate insulating film 20. The semiconductor active layer 22 is located in the gate electrode 18 when viewed from the normal direction of the substrate 16. That is, the entire semiconductor active layer 22 overlaps the gate electrode 18 when viewed from the normal direction of the substrate 16.

The semiconductor active layer 22 is made of an oxide semiconductor. The oxide semiconductor may be, for example, a compound (In—Ga—Zn—O) composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O), or indium (In). , Tin (Tin), zinc (Zn), and oxygen (O) (In-Tin-Zn-O), indium (In), aluminum (Al), zinc (Zn), And a compound (In—Al—Zn—O) made of oxygen (O).

The source electrode 24 and the drain electrode 26 are formed in contact with the semiconductor active layer 22. The source electrode 24 and the drain electrode 26 are formed of the same material as the gate electrode 20.

The semiconductor layer 14 is formed in contact with the substrate 16 as shown in FIG. 2B. As shown in FIG. 1, the semiconductor layer 14 is formed at a position different from the gate electrode 18 included in the thin film transistor 12. That is, the semiconductor layer 14 does not overlap with the gate electrode 18 of the thin film transistor 12 when viewed from the normal direction of the substrate 16 (direction perpendicular to the paper surface of FIG. 1). The semiconductor layer 14 is made of the same material as the semiconductor active layer 22. The semiconductor layer 14 is formed in the same process as the semiconductor active layer 22.

The biosensor 10 is in contact with the solution 28 as shown in FIGS. 2A and 2B. The solution 28 is stored using, for example, a side wall (not shown) formed on the substrate 16. The solution 28 includes a biological substance 30. The biological substance 30 is, for example, DNA, sugar chain, or protein. The biological substance 30 is charged. The biological substance 30 exists in the solution 28 in an ionized state.

The biosensor 10 has a region 32 and a region 34 as shown in FIG. Hereinafter, these areas will be described.

As shown in FIG. 1, the region 32 is formed by a portion of the semiconductor active layer 22 located between the source electrode 24 and the drain electrode 26 when viewed from the normal direction of the substrate 16. That is, the region 32 is formed by a portion of the semiconductor active layer 22 that is not in contact with the source electrode 24 and the drain electrode 26 as shown in FIGS.

The living body-derived substance 30 adheres to the region 32. The region 32 is subjected to a treatment for facilitating the attachment of the biological substance 30. This treatment only needs to modify the functional group on the surface of the semiconductor layer 14. A conventionally well-known thing can be employ | adopted. For example, by treating the surface of the semiconductor layer 14 using an appropriate silane coupling agent, the target biological material 30 is easily attached. If the silane coupling agent is changed, the type of the biological material 30 to be attached can be changed. For example, when the surface of the semiconductor layer 14 is modified with biotin, it is treated with a silane coupling agent and then treated with a biotinylation reagent.

When the biological material 30 adheres to the region 32, the electrical characteristics of the thin film transistor 12 change. Specifically, for example, the threshold voltage changes as the IV characteristic shifts. Therefore, the difference between the threshold voltage when the biological material 30 is attached to the region 32 and the threshold voltage when the biological material 30 is not attached to the region 32 is the biological material 30 attached to the region 32. It can be detected as an electrical signal related to. That is, the biosensor 10 can detect a change in electrical characteristics of the thin film transistor 12 as an electrical signal related to the biological material 30.

When a change in electrical characteristics of the thin film transistor 12 is detected, a reference electrode (not shown) to which a predetermined potential (for example, 0 V) is applied is placed in the solution 28, and the potential of the reference electrode is changed to the solution potential. It is preferable to use the potential of 28. Thereby, the potential of the solution 28 can be set to a predetermined magnitude. As a result, it is possible to improve accuracy when detecting a change in electrical characteristics of the thin film transistor 12.

The region 34 is formed by the semiconductor layer 14 as shown in FIGS. 1 and 2B. That is, the region 34 is formed of the same material as the region 32.

As shown in FIG. 2B, the biological material 30 adheres to the region 34. The region 34 is subjected to the same processing as the region 32 in order to easily attach the biological material 30.

Here, the semiconductor layer 14 is made of an oxide semiconductor. Therefore, the semiconductor layer 14 transmits light. That is, in the biosensor 10, the biological material 30 attached to the region 34 can be observed from the substrate 12 side using an optical microscope.

As described above, the region 34 is made of the same material as the region 32. Therefore, the state of the biological substance 30 attached to the region 34 is the same as the state of the biological substance attached to the region 32. That is, in the biosensor 10, the state of the biological material 30 when the electrical characteristics of the thin film transistor 12 change can be observed.

The optical microscope includes, for example, a fluorescence microscope. When the biological material 30 is observed using a fluorescence microscope, the biological material 30 is irradiated with excitation light. When the semiconductor active layer 22 is irradiated with this excitation light, the electrical characteristics of the thin film transistor 12 change. Specifically, for example, the IV characteristic shifts.

The biosensor 10 has a bottom gate type thin film transistor 12. For this reason, irradiation of excitation light to the semiconductor active layer 22 is suppressed by the gate electrode 18. That is, changes in the electrical characteristics of the thin film transistor 12 due to the irradiation of the excitation light to the semiconductor active layer 22 are suppressed. As a result, the relationship between the state of the biological substance 30 and the change in the electrical characteristics of the thin film transistor 12 at that time can be easily understood.

In the biosensor 10, the biological substance 30 adheres to the semiconductor active layer 22. Therefore, the change in the electrical characteristics of the thin film transistor 12 is greater than when the biological material 30 is attached to the insulating film covering the semiconductor active layer 22. Therefore, in the biosensor 10, it becomes easy to detect a change in the electrical characteristics of the thin film transistor 12 due to the adhesion of the biological material 30 to the region 32.

[Second Embodiment]
A biosensor 10A according to a second embodiment of the present invention will be described with reference to FIGS. 3A and 3B. FIG. 3A is a cross-sectional view corresponding to the AA cross section in FIG. 3B is a cross-sectional view corresponding to the BB cross section in FIG.

The biosensor 10A further includes a passivation film 36 as compared to the biosensor 10. The passivation film 36 is a silicon oxide film. As shown in FIG. 3A, the passivation film 36 covers the semiconductor active layer 22, the source electrode 24, and the drain electrode 26. The passivation film 36 covers the semiconductor layer 14 as shown in FIG. 3B.

The biosensor 10A has a region 32A shown in FIG. 3A and a region 34A shown in FIG. 3B. Hereinafter, these areas will be described.

As shown in FIG. 3A, the region 32 </ b> A is formed by a portion of the passivation film 36 that is in contact with the semiconductor active layer 22. That is, the region 32 </ b> A is formed by a portion of the passivation film 36 that overlaps the semiconductor active layer 22 when viewed from the normal direction of the substrate 16.

The living body-derived substance 30 adheres to the region 32A. The region 32 </ b> A is subjected to a process for facilitating the adhesion of the biological material 30. This treatment only needs to modify the functional group on the surface of the semiconductor layer 14. A conventionally well-known thing can be employ | adopted. For example, an amino group is formed in the Si—OH bond on the surface of the passivation film 36 by a silane coupling reaction. The biological substance 30 is attached using the amino group. If the silane coupling agent is changed, the type of the biological material 30 to be attached can be changed. For example, when the surface of the semiconductor layer 14 is modified with biotin, it is treated with a silane coupling agent and then treated with a biotinylation reagent.

As shown in FIG. 3B, the region 34 </ b> A is formed by a portion of the passivation film 36 that is in contact with the semiconductor layer 14. That is, the region 34 </ b> A is formed in a portion of the passivation film 36 that overlaps the semiconductor layer 14 when viewed from the normal direction of the substrate 16. As is clear from this, the region 34A is formed of the same material as the region 32A.

In the biosensor 10A, similarly to the biosensor 10, the state of the biological material 30 can be observed with a microscope while detecting an electrical signal related to the biological material 30.

In the biosensor 10A, the semiconductor active layer 22 is covered with a passivation film 36. Therefore, exposure of the semiconductor active layer 22 to the solution 28 can be suppressed. As a result, the operation of the thin film transistor 12 can be stabilized.

In the biosensor 10 </ b> A, the passivation film 36 covers not only the semiconductor active layer 22 but also the semiconductor layer 14. Therefore, the material forming the region 32A can be the same as the material forming the region 34A. The reason is as follows.

When the semiconductor active layer 22 is made of an oxide semiconductor, heat treatment is performed after the passivation film 36 is formed. At this time, hydrogen, oxygen, or the like moves between the passivation film 36 and the semiconductor active layer 22.

Here, in the biosensor 10 </ b> A, the semiconductor layer 14 is formed of the same material (oxide semiconductor) as the semiconductor active layer 22 and is covered with the same passivation film 36 as the semiconductor active layer 22. Therefore, when hydrogen, oxygen, or the like moves between the passivation film 36 and the semiconductor active layer 22 due to the heat treatment after film formation, the hydrogen or oxygen is similarly transferred between the passivation film 36 and the semiconductor layer 14. Etc. move. As a result, the composition of the portion of the passivation film 36 that covers the semiconductor active layer 22 and the portion that covers the semiconductor layer 14 can be made the same. That is, the material forming the region 32A can be made the same as the material forming the region 34A.

Thus, if the material forming the region 32A and the material forming the region 34A can be made the same, the state of the biological substance 30 attached to the region 32A and the biological substance 30 attached to the region 34A The state can be made the same. That is, also in the biosensor 10 </ b> A, the change in the electrical characteristics of the thin film transistor 12 can be associated with the state of the biological material 30.

[Third embodiment]
A biosensor 10B according to a third embodiment of the present invention will be described with reference to FIGS. 4A and 4B. 4A is a cross-sectional view corresponding to the AA cross section in FIG. 4B is a cross-sectional view corresponding to the BB cross section in FIG.

The biosensor 10B further includes a passivation film 36A as compared to the biosensor 10. The passivation film 36 </ b> A includes a passivation film 361 and a passivation film 362.

The passivation film 361 is a silicon oxide film. As shown in FIG. 4A, the passivation film 361 covers the semiconductor active layer 22, the source electrode 24, and the drain electrode 26. The passivation film 361 covers the semiconductor layer 14 as shown in FIG. 4B.

The passivation film 362 is a silicon nitride film. The passivation film 362 covers the passivation film 361 as shown in FIGS. 4A and 4B.

The biosensor 10B has a region 32B shown in FIG. 4A and a region 34B shown in FIG. 4B. Hereinafter, these areas will be described.

As shown in FIG. 4A, the region 32 </ b> B is formed by a portion of the passivation film 362 that overlaps the semiconductor active layer 22 when viewed from the normal direction of the substrate 16.

The living body-derived substance 30 adheres to the region 32B. In the region 32B, a process for facilitating the attachment of the biological material 30 is performed. This treatment only needs to modify the functional group on the surface of the semiconductor layer 14. A conventionally well-known thing can be employ | adopted. For example, an amino group is formed on the Si—OH bond on the surface of the passivation film 362 by a silane coupling reaction. The biological substance 30 is attached using the amino group. If the silane coupling agent is changed, the type of the biological material 30 to be attached can be changed. For example, when the surface of the semiconductor layer 14 is modified with biotin, it is treated with a silane coupling agent and then treated with a biotinylation reagent.

As shown in FIG. 4B, the region 34 </ b> B is formed in a portion of the passivation film 362 that overlaps the semiconductor layer 14 when viewed from the normal direction of the substrate 16. That is, the region 34B is formed of the same material as the region 32B.

In the biosensor 10B, as in the biosensor 10, the state of the biological material 30 can be observed with a microscope while detecting an electrical signal related to the biological material 30.

In the biosensor 10B, the semiconductor active layer 22 is covered with a passivation film 36A. Therefore, exposure of the semiconductor active layer 22 to the solution 28 can be suppressed. As a result, the operation of the thin film transistor 12 can be stabilized.

In the biosensor 10B, the uppermost layer (passivation film 362) of the passivation film 36A is a silicon nitride film. Therefore, the waterproofing effect by the passivation film 36A can be further enhanced.

In the biosensor 10B, the passivation film 36A covers not only the semiconductor active layer 22 but also the semiconductor layer 14. Therefore, the material forming the region 32B can be the same as the material forming the region 34B. The reason is as follows.

When the semiconductor active layer 22 is made of an oxide semiconductor, heat treatment is performed after the formation of the passivation film 36A. At this time, hydrogen, oxygen, or the like moves between the passivation film 361 and the semiconductor active layer 22 and between the passivation film 361 and the passivation film 362.

Here, in the biosensor 10B, the semiconductor layer 14 is formed of the same material (oxide semiconductor) as the semiconductor active layer 22, and is covered with the same passivation film 36A as the semiconductor active layer 22. Therefore, in the case where hydrogen, oxygen, or the like moves between the passivation film 361 and the semiconductor active layer 22 and between the passivation film 361 and the passivation film 362 by heat treatment after film formation, the passivation film 361 and the semiconductor layer 14 and between the passivation film 361 and the passivation film 362 also move hydrogen, oxygen, and the like. As a result, the composition of the portion of the passivation film 362 that overlaps the semiconductor active layer 22 and the portion that overlaps the semiconductor layer 14 can be made the same as viewed from the normal direction of the substrate 16. That is, the material forming the region 32B and the material forming the region 34B can be the same.

Thus, if the material forming the region 32B and the material forming the region 34B can be made the same, the state of the biological substance 30 attached to the region 32B and the biological substance 30 attached to the region 34B The state can be made the same. That is, also in the biosensor 10B, the change in the electrical characteristics of the thin film transistor 12 and the state of the biological material 30 can be associated.

[Application example of the third embodiment]
A biosensor 10B1 according to an application example of the third embodiment of the present invention will be described with reference to FIGS. 5A and 5B. In the biosensor 10B1, the reference electrode 38 is formed on the passivation film 362 as compared to the biosensor 10B. For example, the reference electrode 38 is formed of the same material as that of the gate electrode 18. As shown in FIG. 5A, the reference electrode 38 does not cover the region 32B. As shown in FIG. 5B, the reference electrode 38 does not cover the region 34B.

A predetermined potential (for example, 0 V) is applied to the reference electrode 38. When detecting a change in the electrical characteristics of the thin film transistor 12, the potential of the reference electrode 38 is used as the potential of the solution 28.

In the biosensor 10B1, as in the biosensor 10, the state of the biological material 30 can be observed with a microscope while detecting an electrical signal related to the biological material 30.

In the biosensor 10B1, the reference electrode 38 is formed on the passivation film 362. Therefore, the mechanism for detecting the electrical signal related to the biological material 30 can be reduced in size.

The above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

10: Biosensor, 12: Thin film transistor, 14: Semiconductor layer, 16: Substrate, 18: Gate electrode, 22: Semiconductor active layer (channel layer), 30: Biological material, 32: Region (first region), 34: Region (second region), 36: passivation film, 361: passivation film (first passivation film), 362: passivation film (second passivation film), 38: reference electrode

Claims (7)

A substrate that transmits visible light;
A bottom-gate thin film transistor formed on the substrate and having a gate electrode made of metal and a channel layer made of an oxide semiconductor;
A semiconductor layer made of the same material as the channel layer, formed in a region different from the channel layer of the thin film transistor on the substrate;
When viewed from the normal direction of the substrate, a first region is formed in the channel layer by attaching a biological substance and affecting the electrical characteristics of the thin film transistor. A biosensor which is made of the same material as that of the first region and has a second region in which the attached biological substance can be observed with an optical microscope from the substrate side. The biosensor according to claim 1, wherein
The first region is formed by the channel layer;
The second region is a biosensor formed by the semiconductor layer. The biosensor according to claim 1, further comprising:
A passivation film covering the channel layer and the semiconductor layer;
The first region is formed by a portion of the passivation film that overlaps the channel layer,
The second region is a biosensor formed by a portion of the passivation film that overlaps the semiconductor layer. The biosensor according to claim 3, wherein
The biosensor according to claim 1, wherein the passivation film is a silicon oxide film. The biosensor according to claim 3, wherein
The passivation film is
A first passivation film formed in contact with the channel layer and the semiconductor layer;
A biosensor comprising: a second passivation film formed in contact with the first passivation film. The biosensor according to claim 5, wherein
The first passivation film is a silicon oxide film;
The biosensor, wherein the second passivation film is a silicon nitride film. The biosensor according to claim 3, wherein
The passivation film covers a source electrode and a drain electrode of the thin film transistor,
The biosensor further comprises:
A biosensor comprising a reference electrode formed on the passivation film.

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