JP2007324453A - Organic field effect transistor and integrated circuit using the same and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic field effect transistor having an excellent semiconductor characteristic and capable of suppressing an off-current flowing through an edge, even when the edge of an organic semiconductor layer is deteriorated by patterning, in the organic field effect transistor having a patterned organic semiconductor layer. <P>SOLUTION: An organic field effect transistor 101 has a gate insulating layer 4a, a patterned organic semiconductor layer 5a, a gate electrode 3 separated from this organic semiconductor layer 5a by the gate insulating layer 4a, and a source electrode 1 and a drain electrode 2a provided in contact with the organic semiconductor layer 5a. The edge 5'a of the organic semiconductor layer is disposed so as not to be brought into contact with at least one of the source electrode 1 and the drain electrode 2a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic field effect transistor, an integrated circuit using the same, and an electronic device.

  Field effect transistors (FETs) are widely used as important switches and amplifying elements along with bipolar transistors. A field effect transistor has a structure in which a gate electrode is provided on a semiconductor material via a source electrode, a drain electrode, and an insulator layer. Basically, one of p-type and n-type carriers transports charges. This is a typical unipolar element.

  Conventionally, an inorganic material such as silicon has been widely used as a material for a semiconductor layer of a field effect transistor. Recently, however, attempts have been made to use organic semiconductor materials. Specifically, an example using a conductive polymer and a conjugated polymer (Patent Document 1), an example using a low molecular compound (Patent Document 2), and the like have been reported.

Field effect transistors using organic semiconductor materials (referred to as “organic field effect transistors” or “organic FETs” as appropriate) are mostly manufactured at a lower temperature than inorganic semiconductors. A film can be used, and an element that is light and hard to break can be manufactured.
Organic semiconductor materials are abundant in their variations, and the material properties can be easily changed fundamentally by changing the molecular structure. Therefore, by combining different functions, functions and elements that are impossible with conventional inorganic semiconductors such as silicon can be realized.

  The organic semiconductor layer of the organic field effect transistor is patterned by an etching process after being formed using a solution coating method or by a printing method. As the fine processing technique of the etching process, a plasma etching method (electron cyclotron resonance method, high frequency method, etc.), a sputter etching method, a chemical dry etching method, or the like is used. From the above, the organic semiconductor layer obtained is superior in terms of layer formation cost compared to conventional methods such as vapor deposition using inorganic materials such as silicon, and large-area devices can be manufactured at low cost. It is.

Examples of conventionally known organic field effect transistors include the configurations shown in FIGS. 8 (a) and 8 (b). FIG. 8A is a schematic plan view of a conventional organic field effect transistor as viewed from above, and FIG. 8B is a schematic cross-sectional view taken along the plane aa ′ in FIG. The organic field effect transistor 100 in FIGS. 8A and 8B includes a source electrode 1, a drain electrode 2, a gate electrode 3, a gate insulating layer 4, a patterned organic semiconductor 5, and a substrate 6. Prepare.
The source electrode 1 and the drain electrode 2 are provided so as not to contact each other and to contact the organic semiconductor layer 5. The gate electrode 3 is provided so as to be separated from the source electrode 1, the drain electrode 2, and the organic semiconductor layer 5 by the gate insulating layer 4. Furthermore, these components are supported by the substrate 6.

  In the conventional organic field effect transistor 100 configured as described above, when a voltage equal to or higher than a certain voltage (hereinafter referred to as “threshold voltage” or “threshold voltage”) is applied to the gate electrode 3, Carriers are generated in the channel portion to form a storage layer, and the conductivity between the source electrode 1 and the drain electrode 2 is increased.

  The accumulation layer is formed depending on the voltage of the gate electrode 3 (hereinafter referred to as “gate voltage”), and the conductivity of the organic field effect transistor 100 is changed by changing the thickness of the accumulation layer. On the other hand, when the gate voltage 3 is lower than the threshold voltage, the accumulation layer is not formed and the conductivity is lost. That is, the organic field effect transistor 100 operates like a variable switch that controls the current between the source electrode 1 and the drain electrode 2 depending on the gate voltage.

JP-A 61-202469 Japanese Patent No. 2984370

  As described above, the organic field effect transistor has an effective feature that is not available in a transistor using an inorganic semiconductor material, and can be manufactured by a low-temperature process using a solution.

  However, the edge portion of the patterned organic semiconductor layer has a problem that it is likely to deteriorate even if it is patterned under mild conditions such as a printing method. Furthermore, in any of the above-described microfabrication techniques, there is a possibility that the edge portion of the organic semiconductor layer may be deteriorated if the formed organic semiconductor layer is exposed to a process atmosphere when etching is performed. there were.

  The edge portion 5 ′ of the organic semiconductor layer 5 deteriorated by the etching process or the like (region portion outside the alternate long and short dash line shown in FIG. 8A) is deteriorated even when no voltage is applied to the gate electrode 3. As a result, the carrier density increases, so that a highly conductive layer is formed. The edge portion 5 ′ in which the highly conductive layer is always formed due to this deterioration short-circuits the source electrode 1 and the drain electrode 2, whereby the source electrode 1 -drain in a state where no voltage is applied to the gate electrode 3. The current between the electrodes 2 (hereinafter referred to as “off current”) is increased. That is, there is a problem that the off-current increases due to the path shown by the arrows X1 and X2 in FIG. 8A, and the semiconductor characteristics are deteriorated.

  The present invention has been made in view of the above problems. That is, according to the present invention, in an organic field effect transistor having a patterned organic semiconductor layer, even when the edge portion of the organic semiconductor layer deteriorates due to patterning, the off-current flowing through the edge portion is suppressed, and good semiconductor characteristics are obtained. It is an object to provide an organic field effect transistor having an integrated circuit and an electronic device using the same.

  As a result of intensive studies in view of the above circumstances, the present inventor has arranged the edge portion of the organic semiconductor layer and at least one of the source electrode and the drain electrode so as not to contact each other, or the substrate surface is a projection surface. In such a case, all the paths connecting the projection pattern of the source electrode and the projection pattern of the drain electrode along the edge portion of the projection pattern of the organic semiconductor layer and the projection pattern of the gate electrode cross each other. The present inventors have found that the off-current flowing through the edge portion of the organic semiconductor deteriorated by the patterning process can be suppressed, and the present invention has been completed.

  That is, the gist of the present invention is a gate insulating layer, a patterned organic semiconductor layer, a gate electrode separated from the organic semiconductor layer by the gate insulating layer, and a source electrode provided in contact with the organic semiconductor layer And an organic field effect transistor having a drain electrode, the organic field effect transistor being disposed so that an edge portion of the organic semiconductor layer does not contact at least one of the source electrode and the drain electrode It exists in an effect transistor (Claim 1).

  In this case, it is preferable that at least one of the source electrode and the drain electrode is disposed so as to be separated from the edge portion of the organic semiconductor layer through the gate insulating layer.

  Further, an insulating part provided in contact with the organic semiconductor layer is further provided, and at least one of the source electrode and the drain electrode is separated from an edge part of the organic semiconductor layer through the insulating part. It is preferable to arrange (claim 3).

  Further, when the substrate surface is a projection surface, all paths connecting the projection pattern of the source electrode and the projection pattern of the drain electrode along the edge portion of the projection pattern of the organic semiconductor layer, and the gate electrode It is preferable that the projection pattern is arranged so as to intersect with the projection pattern.

  Another gist of the present invention is a gate insulating layer, a patterned organic semiconductor layer, a gate electrode separated from the organic semiconductor layer by the gate insulating layer, and a source electrode provided in contact with the organic semiconductor layer And an organic field effect transistor having a drain electrode, wherein the projection pattern of the source electrode and the projection pattern of the drain electrode along the edge portion of the projection pattern of the organic semiconductor layer when the substrate surface is a projection plane The organic field effect transistor is characterized in that it is arranged so that all the paths connecting the two and the projected pattern of the gate electrode intersect each other (claim 5).

  Further, the projection pattern of the organic semiconductor layer is arranged so that the projection pattern of the gate electrode intersects with the closed curve around the projection pattern of the organic semiconductor layer at two or more locations. Preferably, the organic semiconductor layer is divided into two or more partial projection patterns including a partial projection pattern of the organic semiconductor layer including the partial projection pattern of the organic semiconductor layer including a projection pattern of the drain electrode. .

  Another subject matter of the present invention lies in an integrated circuit comprising at least the organic field effect transistor described above (claim 7).

  Another subject matter of the present invention lies in an electronic device comprising at least an electronic circuit including the organic field effect transistor described above (claim 8).

  According to the present invention, it is possible to obtain an organic field effect transistor having excellent semiconductor characteristics by suppressing off-current flowing through the edge portion of the organic semiconductor layer deteriorated by the patterning process.

[I. Embodiment of the Invention]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and may be arbitrarily modified without departing from the gist of the present invention. Can be implemented.

  In the present invention, the “edge portion of the organic semiconductor layer” refers to a region in the vicinity of the end portion of the organic semiconductor layer where deterioration due to patterning may occur. Although the region varies depending on the material of the organic semiconductor layer and the patterning technique, it generally refers to a region within 0.1 μm, preferably within 1 μm, from the end of the patterned shape of the organic semiconductor layer. .

  In addition, the degree of deterioration of the edge portion of the organic semiconductor layer due to the patterning process varies depending on the type of patterning process. Examples of the patterning process include a printing method, an etching process, a stamping method, and the like. Among them, when an etching process is used, the edge portion of the obtained organic semiconductor layer tends to be easily deteriorated. Therefore, the effect obtained by applying the present invention becomes more remarkable.

[I-1. First Embodiment]
[Basic configuration]
FIG. 1A is a schematic plan view of the organic field effect transistor 101 according to the first embodiment of the present invention as viewed from above, and FIG. 1B is a bb ′ plane of FIG. It is typical sectional drawing in. In FIGS. 1A and 1B, the same components as those shown in FIGS. 8A and 8B are denoted by the same reference numerals, and the description thereof is omitted. . The same applies to FIGS. 2 to 7 described below unless otherwise specified.

  The configuration of the organic field effect transistor 101 shown in FIGS. 1A and 1B is the same as that of the conventional organic field effect transistor 100 shown in FIGS. 8A and 8B. In addition to the drain electrode 2a to be described, the shapes of the gate insulating layer 4 and the organic semiconductor layer 5 are partially changed in accordance with the change (these are referred to as the gate insulating layer 4a and the organic semiconductor layer 5a, respectively). .

  That is, the drain electrode 2a is formed such that a part thereof is bent, and the gate insulating layer 4a is interposed between the bent part and the edge part 5'a of the organic semiconductor layer. However, even in this case, it is assumed that the drain electrode 2a is provided in contact with the organic semiconductor layer 5a at the left end portion in the drawing. Thus, the drain electrode 2a is configured to be in contact with the organic semiconductor layer 5a and isolated from the edge portion 5'a. According to such a configuration, the physical contact between the edge portion 5 ′ a of the organic semiconductor layer and the drain electrode 2 a is interrupted, so that it is possible to avoid a short circuit between the source electrode 1 and the drain electrode 2 a.

  Note that, instead of the drain electrode, the source electrode may be separated from the edge portion of the organic semiconductor layer through the gate insulating layer. In this case, similarly to the drain electrode 2a of FIGS. 1A and 1B, a part of the source electrode is bent, and a gate insulating layer is formed between the bent portion and the edge portion of the organic semiconductor layer. Is configured to intervene. According to such a configuration, since the physical contact between the edge portion of the organic semiconductor layer and the source electrode is blocked, it is possible to avoid a short circuit between the source electrode and the drain electrode.

[First Modification]
Furthermore, you may comprise so that both a drain electrode and a source electrode may be separated from the edge part of an organic-semiconductor layer through a gate insulating layer.

  FIG. 2 is a schematic cross-sectional view of the organic field effect transistor 102 according to the first modification of the first embodiment of the present invention as seen from the side. In the organic field effect transistor 102 shown in FIG. 2, the source electrode 1a and the drain electrode 2a are formed so that a part thereof is bent, and between the bent part and the edge part 5′b of the organic semiconductor layer. The gate insulating layer 4b is interposed. However, even in this case, it is assumed that the source electrode 1a is provided in contact with the organic semiconductor layer 5a at the right end portion in the drawing and the drain electrode 2a is provided at the left end portion in the drawing. Thereby, both the source electrode 1a and the drain electrode 2a are configured to be in contact with the organic semiconductor layer 5b and isolated from the edge portion 5'b.

  According to such a configuration, since the edge portion 5′b of the organic semiconductor layer is separated from both the source electrode 1a and the drain electrode 2a, the deterioration width of the edge portion 5′b of the organic semiconductor layer is not uniform. Even in this case, it is possible to more reliably suppress an increase in off current.

  The bent shape of the source electrode 1a and / or the drain electrode 2a shown in FIGS. 1A, 1B and 2 is merely an example. If the source electrode and / or the drain electrode are isolated from the edge portion of the organic semiconductor layer through the gate insulating layer, the bent shape of the source electrode and / or the drain electrode can be arbitrarily set.

[Second Modification]
Further, by providing an insulating portion on the organic semiconductor layer, the source electrode and / or the drain electrode can be isolated from the edge portion of the organic semiconductor layer.

  FIG. 3 is a schematic cross-sectional view seen from the side of the organic field effect transistor 103 according to the second modification of the first embodiment of the present invention. The configuration of the organic field effect transistor 103 shown in FIG. 3 is the same as that of the conventional organic field effect transistor 100 shown in FIG. 8 except that an insulating portion 7a is provided on the drain electrode 2 and the organic semiconductor layer 5 is formed accordingly. A part of the shape is changed (this is referred to as an organic semiconductor layer 5c).

The insulating portion 7a shown in FIG. 3 is provided so as to be interposed between the drain electrode 2 and the edge portion 5′c of the organic semiconductor layer. However, the insulating portion 7a does not completely separate the drain electrode 2 and the organic semiconductor layer 5c, and the drain electrode 2 is provided in contact with the organic semiconductor layer 5c in the vicinity of the left end portion in the drawing. Accordingly, the drain electrode 2 is configured to be isolated from the edge portion 5′c while being in contact with the organic semiconductor layer 5c. Even with such a configuration, the physical contact between the edge portion 5 ′ c of the organic semiconductor layer and the drain electrode 2 is blocked by the insulating portion 7 a, thereby avoiding a short circuit between the source electrode 1 and the drain electrode 2. it can.
Further, since there is no need to bend the source electrode 1 and the drain electrode 2, it can be easily configured using conventional electrodes.

  Note that the source electrode instead of the drain electrode may be isolated from the edge portion of the organic semiconductor layer by an insulating portion provided on the organic semiconductor layer. In this case, an insulating portion similar to the insulating portion 7a in FIG. 3 is provided so as to be interposed between the source electrode and the edge portion of the organic semiconductor layer. Even with such a configuration, the physical contact between the edge portion of the organic semiconductor layer and the source electrode is interrupted, so that it is possible to avoid a short circuit between the source electrode and the drain electrode.

  Moreover, you may comprise so that both a drain electrode and a source electrode may be isolated from the edge part of an organic-semiconductor layer by the insulation part provided on the organic-semiconductor layer. According to such a configuration, since the edge portion of the organic semiconductor layer is separated from both the source electrode and the drain electrode, even when the deterioration width of the edge portion of the organic semiconductor layer is not uniform, the off-current is more reliably ensured. It is possible to suppress the rise of In this case, an insulating part that isolates the drain electrode from the edge part of the organic semiconductor layer and an insulating part that isolates the source electrode from the edge part of the organic semiconductor layer may be provided separately. You may comprise so that both a drain electrode and a source electrode may be isolated from the edge part of an organic-semiconductor layer.

[Third Modification]
Furthermore, the source electrode and / or drain electrode can be bent and formed, and an insulating part can be provided on the organic semiconductor layer to isolate the source electrode and / or drain electrode from the edge portion of the organic semiconductor layer. It is.

  FIG. 4 is a schematic cross-sectional view of an organic field effect transistor 104 according to a third modification of the first embodiment of the present invention as seen from the side. The configuration of the organic field effect transistor 104 shown in FIG. 4 is the same as the configuration of the organic field effect transistor 103 shown in FIG. 3, except that the insulating portion 7a is changed to the insulating portion 7b and the drain electrode 2 is changed to the drain electrode 2b. A part of the shape of the organic semiconductor layer 5c is changed in accordance with the change (this is referred to as an organic semiconductor layer 5d).

  The drain electrode 2b shown in FIG. 4 is formed to be bent so that a part thereof protrudes upward (opposite to the gate insulating layer 4) of the organic semiconductor layer 5d, and the bent portion and the organic semiconductor layer An insulating portion 7b is provided between the edge portion 5'd. However, even in this case, it is assumed that the drain electrode 2b is provided in contact with the organic semiconductor layer 5b at the left end portion in the drawing. Thereby, the drain electrode 2b is configured to be in contact with the organic semiconductor layer 5d and isolated from the edge portion 5'd. Even with such a configuration, the physical contact between the edge portion 5′d of the organic semiconductor layer and the drain electrode 2b is blocked by the insulating portion 7b, so that a short circuit between the source electrode 1 and the drain electrode 2b is avoided. it can.

  In FIG. 4, the drain electrode 2b is formed by being bent and further provided with an insulating portion 7b so that the drain electrode 2b is isolated from the edge portion 5′d of the organic semiconductor layer. The source electrode may have the same configuration instead of the electrode, or both the drain electrode and the source electrode may have the same configuration.

  The material of the insulating portions 7a and 7b is not particularly limited as long as it has insulating properties and has resistance to the voltage between the source electrode 1 and the gate electrodes 2 and 2b. As an example, the same material as that of the gate insulating layer described later can be given. In addition, since the voltage applied to the insulating portions 7a and 7b is lower than that of the gate insulating layer, a material having an insulating performance lower than that of the gate insulating layer can be used. In addition, the material of the insulation parts 7a and 7b may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  The shape of the insulating portions 7a and 7b is not particularly limited. The physical contact between the drain electrode 2 and the edge portions 5′c and 5′d of the organic semiconductor layer can be cut off, and the contact between the drain electrode 2 and the organic semiconductor layers 5c and 5d can be allowed. If possible, any shape can be used. Preferably, the shapes of the insulating portions 7a and 7b are determined in consideration of the closest distance between a source electrode and / or drain electrode, which will be described later, and an edge portion of the organic semiconductor layer.

[Others]
According to the first embodiment of the present invention described above and the modifications thereof, the source electrode and / or the drain electrode and the edge portion of the organic semiconductor layer are configured to be isolated. At this time, if the physical contact between the source electrode and / or the drain electrode and the edge portion of the organic semiconductor layer is interrupted, the source electrode and the drain electrode may be any of the first embodiment and its modifications. You may apply combining two or more types of composition. With this configuration, it is possible to avoid a short circuit between the source electrode and the drain electrode. As a result, abnormalities in the final product due to an increase in off-current are reduced and yield is improved, which is preferable.

  In the above-described first embodiment and its modifications, the closest distance between the source electrode and / or drain electrode and the edge portion of the organic semiconductor layer is usually 0.1 μm or more, particularly 1 μm or more, It is preferable to be 2 μm or more. If the closest distance between the source electrode and / or drain electrode and the edge portion of the organic semiconductor layer is too short, the shielding from the edge portion of the organic semiconductor layer, that is, the portion where the highly conductive layer can be formed due to deterioration is incomplete. Tend to be.

[I-2. Second Embodiment]
FIG. 5 is a schematic plan view of the organic field effect transistor 105 according to the second embodiment of the present invention as viewed from above. The configuration of the organic field effect transistor 105 of FIG. 5 is the same as that of the conventional organic field effect transistor 100 shown in FIG. 8 except that the gate electrode 3 is changed to a gate electrode 3a described below, and the gate is changed accordingly. The shape of the insulating layer 4 is partially changed (this is referred to as a gate insulating layer 4c).

  As shown in FIG. 5, the gate electrode 3a is provided so as to intersect the arrow X3 and the arrow X4 along the edge portion 5 'of the organic semiconductor layer. Here, the arrows X3 and X4 represent paths through which a short circuit from the source electrode 1 to the drain electrode 2 may occur due to the deteriorated edge portion 5 ′ of the organic semiconductor layer 5. This path corresponds to a path connecting the projection pattern of the source electrode 1 and the projection pattern of the drain electrode 2 along the edge portion 5 ′ of the projection pattern of the organic semiconductor layer 5 when the surface of the substrate 6 is the projection plane. . That is, the off-current increases due to the current flowing through this path. In FIG. 5, the gate electrode 3a is arranged so that the projected pattern of the gate electrode 3a intersects all of these paths X3 and X4.

  When the organic field effect transistor 105 configured as described above is operated, voltage control of the gate electrode 3a is performed as follows. That is, when a current is passed from the source electrode 1 to the drain electrode 2, a voltage is applied to the gate electrode 3 a so as to form a storage layer in the organic semiconductor layer 5. On the other hand, when the current from the source electrode 1 to the drain electrode 2 is interrupted, a voltage opposite to the voltage for forming the normal accumulation layer is applied to the gate electrode 3a. Thereby, carriers in the highly conductive layer that is always formed at the edge portion 5 ′ of the organic semiconductor layer due to deterioration can be canceled out, and a short circuit between the source electrode 1 and the drain electrode 2 can be avoided.

  That is, the off-current flows along paths X3 and X4 connecting the projection pattern of the source electrode 1 and the projection pattern of the drain electrode 2 along the degraded portion of the organic semiconductor layer 5, that is, the edge portion 5 ′. Even if the semiconductor layer 5 is patterned in any shape, if all of these paths X3 and X4 can be blocked, it is possible to control an increase in off-current. The path is blocked by applying a voltage opposite to the voltage for forming the normal storage layer by the gate electrode 3a at one or more of the paths X3 and X4 along the edge portion 5 'of the organic semiconductor layer. .

  The shape and arrangement position of the gate electrode 3a are not limited to the shape shown in FIG. When the substrate surface is the projection surface, all the paths connecting the projection pattern of the source electrode and the projection pattern of the drain electrode intersect the projection pattern of the gate electrode along the edge portion of the projection pattern of the organic semiconductor layer. As long as it is possible, it can be in any shape and can be placed in any position.

In particular, when a closed curve around the projection pattern of the organic semiconductor layer is considered, the projection pattern of the organic semiconductor layer is arranged so that the closed curve and the projection pattern of the gate electrode intersect at two or more locations. 2 or more partial projection patterns including a projection pattern portion of the organic semiconductor layer including the projection pattern (hereinafter referred to as “partial projection pattern”) and a partial projection pattern of the organic semiconductor layer including the projection pattern of the drain electrode. It is preferable to set the arrangement position and shape so as to be divided.
That is, in the case of FIG. 5, the projection pattern of the organic semiconductor layer including the projection pattern of the source electrode refers to a portion on the left side of the projection pattern left edge of the gate electrode 3 a among the projection patterns of the organic semiconductor layer 5. The projection pattern of the organic semiconductor layer including the projection pattern of the drain electrode refers to a portion on the right side of the projection pattern of the gate electrode 3a in the projection pattern of the organic semiconductor layer 5. Note that the present invention is not limited to FIG.

  The width of the gate electrode 3a intersecting with the edge portion 5 ′ of the organic semiconductor layer is not particularly limited, and may be appropriately adjusted according to the configuration or use of the organic field effect transistor 105. The range is usually 1 μm or more, preferably 2 μm or more, more preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less. If the width of the gate electrode 3a is too narrow, there is a possibility that the off-current cannot be effectively cut off, and if it is too wide, there is a possibility that it becomes an obstacle to miniaturization.

  The gate voltage applied to the gate electrode when the off-state current is cut off is not particularly limited, and is adapted to the configuration and application of the organic field effect transistor 105, the state of deterioration of the edge portion 5 ′ of the organic semiconductor layer, and the like. What is necessary is just to adjust suitably. If a voltage that shifts from an off state to an on state when a gate voltage is applied is a threshold voltage (Vt), the value of Vt generally changes due to deterioration of the semiconductor. Therefore, the gate voltage when the off-current is cut off may be adjusted according to the change in the value of Vt.

  In the present embodiment, unlike the first embodiment, it is not necessary to bend the shape of the source electrode or the gate electrode, and it is not necessary to provide a new component such as an insulating portion. In a conventional organic field effect transistor, it can be realized only by making some changes to the shape of the gate electrode. For this reason, there is no need to use special means or the like when molding or laminating each component of the organic field effect transistor, and there is an advantage that a high off-current suppressing effect can be realized easily and at low cost.

[I-3. Third Embodiment]
In the organic field effect transistor 101 (shown in FIG. 6) of the first embodiment described above, the edge portion 5′a of the organic semiconductor layer is deteriorated, and the highly conductive layer is always formed on the edge portion 5′a. When the region is enlarged, the source electrode 1 and the drain electrode 2a may be short-circuited along the paths indicated by arrows X5 and X6 in FIG. In this case, in order to avoid an increase in off-state current, it is possible to adopt a configuration in which the technical features of the second embodiment described above are further combined with the configuration of the first embodiment.

  FIG. 7 is a schematic plan view of an organic field effect transistor 106 according to the third embodiment of the present invention as viewed from above. The configuration of the organic field effect transistor 106 in FIG. 7 has a configuration that combines the technical features of the first embodiment and the second embodiment. Specifically, the drain electrode 2a is formed so that a part thereof is bent, and the gate insulating layer 4d is interposed between the bent part and the edge part 5′a of the organic semiconductor layer. Thus, the organic semiconductor layer is separated from the edge portion 5′a of the organic semiconductor layer. Further, the gate electrode 3 a connects the projection pattern of the source electrode 1 and the projection pattern of the drain electrode 2 along the edge portion 5 ′ a of the projection pattern of the organic semiconductor layer 5 a when the substrate 6 surface is the projection surface. It is arranged so as to intersect all of the routes.

  In the organic field effect transistor 106 having the above configuration, the physical contact between the edge portion 5′a of the organic semiconductor layer and the drain electrode 2a is cut off, and as a result, a short circuit occurs between the source electrode 1 and the drain electrode 2a. Can be avoided. Further, as the deterioration of the organic semiconductor layer progresses and the highly conductive layer region that is always formed on the edge portion 5′a expands, the edge portion 5′a of the organic semiconductor layer and the drain electrode 2a come into contact with each other. Even in this case, by applying a voltage opposite to the voltage for forming the normal storage layer on the gate electrode 3a to the gate electrode, the high voltage that is always formed on the edge portion 5′a of the organic semiconductor layer due to deterioration. The conductive layer can be canceled out. Therefore, a short circuit between the source electrode 1 and the drain electrode 2a can be avoided.

  Note that the configuration for separating the drain electrode 2a from the edge portion 5'a of the organic semiconductor layer via the gate insulating layer 4d is basically the same as that of the first embodiment, and thus detailed description thereof is omitted. Further, the configuration of the gate electrode 3a, the gate voltage when the off-current is cut off, and the like are basically the same as those in the second embodiment, and thus detailed description thereof is omitted.

  Moreover, the combination of 1st Embodiment and 2nd Embodiment is not necessarily restricted to the combination shown by FIG. 7, It is possible to add a deformation | transformation arbitrarily and to combine.

  For example, FIG. 7 shows a configuration in which the edge portion 5′a of the organic semiconductor layer is separated from the drain electrode 2a, but the source electrode is separated from the edge portion of the organic semiconductor layer instead of the drain electrode. Alternatively, both the source electrode and the drain electrode can be isolated from the edge portion of the organic semiconductor layer.

  FIG. 7 shows a configuration in which the edge portion 5′a of the organic semiconductor layer is separated from the drain electrode 2a via the gate insulating layer 4d. However, by providing an insulating portion on the organic semiconductor layer, the organic semiconductor layer The edge portion may be separated from the source electrode and / or the drain electrode.

[I-4. Others]
The organic field effect transistors according to the first to third embodiments described above have a configuration in which a gate electrode, a gate insulating film, a source electrode and a drain electrode, and an organic semiconductor layer are stacked in this order on a substrate. The layer structure of the organic field effect transistor to which the present invention is applicable is not limited to this. An organic field effect transistor having a gate insulating layer, a patterned organic semiconductor layer, a gate electrode separated from the organic semiconductor layer by the gate insulating layer, and a source electrode and a drain electrode provided in contact with the organic semiconductor layer If it is, the present invention can be applied to an organic field effect transistor having an arbitrary layer configuration.

[II. Common Items of Each Embodiment]
All of the organic field effect transistors of the present invention described above with reference to the embodiments are separated from the organic semiconductor layer by the gate insulating layer, the patterned organic semiconductor layer, and the gate insulating layer as basic components. A gate electrode and a source electrode and a drain electrode provided in contact with the organic semiconductor layer are provided. In addition, these components are typically provided on and supported by the substrate.

  Details of these components (materials, forming methods, etc.) are described in [I. Except for the matters described in the section “Embodiments of the Present Invention”, this is the same as the conventional organic field effect transistor. Therefore, in the following description, the above [I. Common items other than those described in the section “Embodiments of the present invention” will be described together.

[II-1. substrate〕
The material of the substrate is not particularly limited as long as it can support each component of the organic field effect transistor provided thereon. Examples include known substrates such as glass and polysiloxane, and organic substrates such as various organic polymers. Among these, organic polymers such as vinyl polymers such as polyester, polycarbonate, polyimide, polyamide, polyether sulfone, epoxy resin, polybenzoxazole, polybenzothiazole, polyparabanic acid, polysilsesquioxane, and polyolefin are preferable. is there. Among them, polyesters such as polyethylene terephthalate, polycarbonate, polyimide, polyamide, polybenzoxazole, polybenzothiazole, polyparabanic acid and other condensed polymers, and crosslinked products such as polyvinylphenol are preferable from the viewpoint of heat resistance and solvent resistance. Polyester, polycarbonate, polyimide, and polybenzoxazole are more preferable, and polyester such as polyethylene terephthalate or polyimide is particularly preferable. Any of these materials may be used alone, or two or more of these materials may be used in any ratio and combination.

  Further, the substrate may contain components such as fillers and additives as necessary in addition to the main material described above. These components may also be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Note that the substrate material preferably has a glass transition point of 40 ° C. or higher. When the glass transition point is lower than 40 ° C., the fluidity is too high, and therefore, it tends to be difficult to maintain the substrate by being softened when other layers are laminated or heated.

Further, the material of the substrate preferably has a linear expansion coefficient of usually 25 × 10 ⁻⁵ cm / cm · ° C. or less, and more preferably 10 × 10 ⁻⁵ cm / cm · ° C. or less. If the linear expansion coefficient is greater than 25 × 10 ⁻⁵ cm / cm · ° C., dimensional changes are likely to occur during heat treatment during production, and the performance of the organic field effect transistor tends to be unstable.

  In addition, the material of the substrate is preferably one that exhibits solvent resistance against the solvent used when forming each component of the organic field effect transistor, and the component provided in contact with the substrate (in each of the above embodiments) In the structure, those having high adhesion to the gate insulating film and the gate electrode are preferable.

The thickness of the substrate is usually 0.01 mm or more, preferably 0.05 mm or more, and usually 10 mm or less, preferably 2 mm or less, and more preferably 1 mm or less.
Specifically, for example, in the case of a substrate mainly made of an organic polymer, the thickness is about 0.05 to 0.1 mm, and in the case of a substrate mainly made of glass, silicon or the like, it is about 0.1 to 10 mm. Is preferred.

[II-2. (Gate electrode)
The constituent material of the gate electrode is not particularly limited as long as it is a conductive material, and any known material can be selected and used. Examples of gate electrode materials include platinum, gold, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium, sodium, and other metals, InO ₂ , SnO ₂ , ITO, and other conductive metal oxides, camphor Conductive materials in which doped conductive polymers such as polyaniline doped with sulfonic acid and polyethylenedioxythiophene doped with paratoluenesulfonic acid, and carbon black, graphite powder, metal fine particles, etc. are dispersed in a binder. Composite materials and the like. Any of these materials may be used alone, or two or more of these materials may be used in any ratio and combination.

  The gate electrode is formed by, for example, a vacuum deposition method, a sputtering method, a coating method, a printing method, a sol-gel method, or the like. As the patterning method, for example, a photolithographic method combining photoresist patterning and etching with an etchant or reactive plasma, ink-jet printing, screen printing, offset printing, letterpress printing and other printing methods, microcontact printing method, etc. Soft lithography techniques such as these, and a technique combining a plurality of these techniques. It is also possible to directly form a pattern by irradiating an energy beam such as a laser or an electron beam to remove the material or changing the conductivity of the material.

  The thickness of the gate electrode is not particularly limited, but is preferably in the range of usually 0.01 μm or more, particularly 0.02 μm or more, and usually 2 μm or less, especially 1 μm or less.

[II-3. (Gate insulation layer)
The gate insulating layer is a layer having a function of maintaining an overlapping region between the gate electrode, the source electrode, and the drain electrode and a channel region on the gate electrode as an electrically insulating region. Here, “electrical insulation” means that the electric conductivity is 10 ⁻⁹ S / cm or less.

The material of the gate insulating layer is not particularly limited as long as it is an insulating material. For example, polymethyl (meth) acrylate, polystyrene, polyvinylphenol, polyimide, polycarbonate, polyester, polyvinyl alcohol, polyvinyl acetate, polyurethane, polysulfone, polyimide Polymers such as resins, polyamide resins, epoxy resins, phenol resins and copolymers thereof, oxides such as silicon dioxide, aluminum oxide and titanium oxide, ferroelectric oxides such as SrTiO ₃ and BaTiO ₃ , silicon nitride And dielectrics such as nitrides, sulfides and fluorides, or polymers in which particles of these dielectrics are dispersed. Any of these materials may be used alone, or two or more of these materials may be used in any ratio and combination.

Since the gate insulating layer is related to leakage current to the gate electrode and low gate voltage driving of the field effect transistor, the electric conductivity at room temperature is usually 10 ⁻⁹ S / cm or less, particularly 10 ⁻¹⁴ S / cm. The following is preferable. The relative dielectric constant is usually 2.0 or more, preferably 2.5 or more.

  The gate insulating layer is treated with a solution by a known method such as spin coating, solution casting, stamp printing, screen printing, or jet printing, and dried to form an uncrosslinked polymer layer, and then irradiated with ultraviolet rays or heat treated. Is formed by forming a crosslinked structure by forming a crosslinked polymer layer. In addition, for example, patterning is possible by using a photomask or the like during the crosslinking treatment by ultraviolet irradiation, and the uncrosslinked polymer portion not irradiated with ultraviolet rays can be easily removed with an organic solvent or the like. By performing this patterning process, it becomes easy to construct a via hole structure in an electronic circuit.

  The thickness of the gate insulating layer is preferably 0.01 μm or more, particularly 0.1 μm or more, more preferably 0.2 μm or more, and usually 4 μm or less, especially 2 μm or less, more preferably 1 μm or less.

[II-4. Organic semiconductor layer)
The organic semiconductor used as the material of the organic semiconductor layer is not particularly limited as long as it is a semiconductor mainly composed of an organic substance, and any material can be used. Specific examples include condensed aromatic hydrocarbons such as naphthacene, pentacene, pyrene and fullerene, oligomers such as α-sexithiophene, macrocyclic compounds such as phthalocyanine and porphyrin, α-sexithiophene and dialkylsexithiophene. Typically, oligothiophenes containing 4 or more thiophene rings, or thiophene ring, benzene ring, fluorene ring, naphthalene ring, anthracene ring, thiazole ring, thiadiazole ring, benzothiazole ring combined in total 4 or more, Condensed thiophenes such as anthradithiophene, dibenzothienobisthiophene, α, α′-bis (dithieno [3,2-b ′: 2 ′, 3′-d] thiophene) and derivatives thereof, naphthalenetetracarboxylic anhydride, Naphthalenetetracarboxylic sandiimide, perylenetetracarboxylic Aromatic carboxylic acid anhydrides and imidized products such as anhydrides, perylenetetracarboxylic sandiimide, macrocyclic compounds such as copper phthalocyanine, perfluoro copper phthalocyanine, tetrabenzoporphyrin and metal salts thereof, polythiophene, polyfluorene, polythieny Lembinylene, polyphenylene vinylene, polyphenylene, polyacetylene, polypyrrole, polyaniline, especially those showing self-organization such as regioregular polythiophene, and polymers showing liquid crystallinity represented by polyfluorene and its copolymers It is done. Any of these organic semiconductor materials may be used alone, or two or more thereof may be used in combination in any ratio and combination. Moreover, although only an organic semiconductor material may be used, it can also be used by mixing with materials other than an organic semiconductor material. Furthermore, it can also be used as a laminated structure of a plurality of layers made of different materials.

Among them, as the material for the organic semiconductor layer, an azaannulene compound is preferable, and a compound having a porphyrin skeleton (hereinafter abbreviated as “porphyrin compound”) or a compound having a phthalocyanine skeleton (hereinafter abbreviated as “phthalocyanine compound”). Is more preferable. As specific examples of the porphyrin-based compound, benzoporphyrin and its metal complex such as Cu and Zn are particularly preferable. Specific examples of the phthalocyanine compound include copper phthalocyanine, halogenated phthalocyanine such as F ₁₆ CuPC, and the like.

  The organic semiconductor layer can be formed by depositing a material such as the above-described organic semiconductor material by various methods. For example, a material having a certain degree of solubility can be formed by coating. As a method of application, a casting method that only drops a solution, a coating method such as spin coating, dip coating, blade coating, wire bar coating, spray coating, etc., a printing method such as inkjet printing, screen printing, offset printing, letterpress printing, A soft lithography technique such as a microcontact printing method, or a combination of these techniques can be used. Furthermore, as a technique similar to coating, a Langmuir-Blodgett method in which a monomolecular film formed on a water surface is transferred to a substrate and laminated, a liquid crystal or a melt state is sandwiched between two substrates or introduced between substrates by capillary action. A method etc. are also mentioned.

  Alternatively, an organic semiconductor layer can be formed by forming a highly soluble organic semiconductor precursor by the above coating method and converting it into an organic semiconductor film by heat treatment or the like. As examples of such organic semiconductor precursors, tetrabenzoporphyrin and pentacene have been reported so far.

The organic semiconductor layer can also be formed by a vacuum process. In this case, it is possible to use a vacuum vapor deposition method in which an organic semiconductor material is put in a crucible or a metal boat, heated in a vacuum, and attached to a substrate or the like. At this time, the degree of vacuum is 1 × 10 ⁻³ Torr or less, preferably 1 × 10 ⁻⁵ Torr or less. Note that 1 Torr≈133 Pa. Further, since the transistor characteristics change depending on the substrate temperature, it is necessary to select an optimum substrate temperature, but a range of 0 ° C. or higher and 200 ° C. or lower is usually preferable. Further, the deposition rate is usually 0.01 Å / second or more, preferably 0.1 Å / second or more, and usually 100 Å / second or less, preferably 10 Å / second or less. As a method for evaporating the material, a sputtering method in which ions such as accelerated argon collide can be used in addition to heating.

  If the thickness of the organic semiconductor layer is too thin, the current flowing portion is limited and the characteristics tend to be insufficient, and if it is too thick, more materials are required for film formation and the film formation time is longer. As a result, the cost increases, and the off-current tends to flow, and the on / off ratio tends not to be increased. Accordingly, the preferable thickness of the organic semiconductor layer is usually 5 nm or more, particularly 10 nm or more, more preferably 30 nm or more, and usually 10 μm or less, especially 1 μm or less, and further 500 nm or less.

[II-5. Source electrode and drain electrode)
The constituent material of the source electrode and the drain electrode is not particularly limited as long as it is a material exhibiting conductivity, as in the case of the gate electrode, and a known material can be arbitrarily selected and used. Examples of materials for the source and drain electrodes include metals such as platinum, gold, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium, sodium, and conductive metal oxides such as InO ₂ , SnO ₂ , and ITO. , Doped conductive polymer such as polyaniline doped with camphorsulfonic acid, polyethylenedioxythiophene doped with paratoluenesulfonic acid, carbon black, graphite powder, metal fine particles, etc. are dispersed in binder And conductive composite materials. Any of these materials may be used alone, or two or more of these materials may be used in any ratio and combination.

  Similar to the gate electrode, the source electrode and the drain electrode are formed by, for example, a vacuum deposition method, a sputtering method, a coating method, a printing method, a sol-gel method, or the like. As the patterning method, for example, a photolithographic method combining photoresist patterning and etching with an etchant or reactive plasma, ink-jet printing, screen printing, offset printing, letterpress printing and other printing methods, microcontact printing method, etc. Soft lithography techniques such as these, and a technique combining a plurality of these techniques. It is also possible to directly form a pattern by irradiating an energy beam such as a laser or an electron beam to remove the material or changing the conductivity of the material.

  The thickness of the source electrode and the drain electrode is not particularly limited, but is preferably 0.01 μm or more, particularly 0.02 μm or more, and usually 2 μm or less, particularly 1 μm or less.

[II-6. channel〕
The organic field effect transistor performs switching or amplification operation by controlling the current in the channel portion sandwiched between the source electrode and the drain electrode by the gate electrode. The length of this channel portion (gap interval between the source electrode and the drain electrode) generally increases as the transistor becomes narrower, but if it is too narrow, the off-current increases or the on / off ratio decreases. There is a tendency to have an effect. Further, it is preferable that the channel width (the width between the source electrode and the drain electrode) is large in terms of allowing a large current to flow. It may become. Note that a long channel length can be obtained by using a comb electrode for the source electrode and the drain electrode.

Therefore, the channel length is preferably in the range of usually 100 nm or more, especially 500 nm or more, more preferably 1 μm or more, and usually 300 μm or less, especially 100 μm or less, and more preferably 50 μm or less.
The width of the channel is preferably in the range of usually 500 nm or more, especially 5 μm or more, more preferably 10 μm or more, and usually 20 mm or less, especially 5 mm or less, more preferably 1 mm or less.

[II-7. Others]
The field effect transistor of the present invention may have an arbitrary layer, if necessary, in addition to the above-described layers.
For example, a protective film can be provided on the uppermost layer (an organic semiconductor layer or the like in each of the above embodiments) on the side opposite to the substrate. The material of the protective layer is not particularly limited. For example, films made of various resins such as acrylic resin such as epoxy resin and polymethyl methacrylate, polyurethane, polyimide, polyvinyl alcohol, fluororesin, polyolefin, silicon oxide, aluminum oxide, and nitride A film made of a dielectric such as silicon or an inorganic oxide film or a nitride film is preferably used. In particular, a resin (polymer) having a low oxygen and moisture permeability and a low water absorption rate is desirable. For example, a metal such as aluminum, a metal having a small gas permeability such as silicon oxide, silicon nitride, or SiON, or a polymer film having an inorganic oxide film can be suitably used for the polymer film.

[II-8. Field effect transistor)
The mobility of the field effect transistor of the present invention is usually 10 ⁻³ cm ² / Vs or higher, preferably 10 ⁻² cm ² / Vs or higher.
The on / off ratio depends on the application and the like, but is generally 10 ² or more, preferably 10 ³ or more, more preferably 10 ⁴ or more.

  The field effect transistor of the present invention may be configured as a single element or may be configured as a part of an integrated circuit. In the latter case, most or all of the transistors included in the integrated circuit are preferably the field effect transistors of the present invention. By integrating transistors into an integrated circuit, a digital element or an analog element can be realized. Examples of these elements include logic circuits such as AND, OR, NAND, NOT, memory elements, oscillation elements, amplification elements, and the like. Further, an IC card or an IC tag can be manufactured by combining these elements.

  The application of the field effect transistor of the present invention is not particularly limited, and can be used for various electronic devices. Examples of the electronic device include an active matrix of a display and an IC element such as an IC tag or a driver IC of a display.

  For example, when the field effect transistor of the present invention is used for an active matrix of a display, it can be used as a switching element. This utilizes the fact that the current between the source and drain can be switched by the voltage applied to the gate, so that the switch is turned on only when a voltage is applied to or supplied to a certain display element, and the circuit is disconnected at other times. By doing so, a high-speed, high-contrast display is performed. Examples of the display element to be applied include a liquid crystal display element, a polymer dispersed liquid crystal display element, an electrophoretic display element, an electroluminescent element, and an electrochromic element.

  An electronic device such as an active matrix using the field effect transistor of the present invention (electronic device of the present invention) can be manufactured by a low-temperature process, and cannot withstand high-temperature processing of a plastic substrate, plastic film, paper, or the like. A substrate can be used. In addition, since the device can be manufactured by a coating or printing process, it is suitable for application to a large area display, for example. Further, as an alternative to the conventional active matrix, it is advantageous as an element capable of an energy saving process and a low cost process.

  According to the organic field effect transistor of the present invention, even in the case where the edge portion of the organic semiconductor layer deteriorates due to patterning in the organic field effect transistor, the organic field having good semiconductor characteristics is suppressed by suppressing the off-current flowing through the edge portion. An effect transistor and an integrated circuit and an electronic device using the effect transistor can be obtained and are extremely useful.

(A) is the typical top view which looked at the organic field effect transistor which concerns on 1st Embodiment of this invention from upper direction, (b) is the model in the bb 'surface of the organic field effect transistor shown to (a). FIG. It is typical sectional drawing which looked at the organic field effect transistor which concerns on the 1st modification of 1st Embodiment of this invention from the side. It is the typical sectional view which looked at the organic field effect transistor concerning the 2nd modification of a 1st embodiment of the present invention from the side. It is the typical sectional view which looked at the organic field effect transistor concerning the 3rd modification of a 1st embodiment of the present invention from the side. It is the typical top view which looked at the organic field effect transistor which concerns on 2nd Embodiment of this invention from upper direction. It is a figure explaining the subject which 3rd Embodiment of this invention tends to solve, and is the typical top view which looked at the organic field effect transistor which concerns on 1st Embodiment of this invention from upper direction. It is the typical top view which looked at the organic field effect transistor which concerns on 3rd Embodiment of this invention from upper direction. (A) is the typical top view which looked at the conventional organic field effect transistor from the upper part, (b) is typical sectional drawing in the a-a 'plane of the organic field effect transistor shown to (a).

Explanation of symbols

1, 1a Source electrode 2, 2a, 2b Drain electrode 3, 3a Gate electrode 4, 4a, 4b, 4c, 4d Gate insulating layer 5, 5a, 5b, 5c, 5d Organic semiconductor layer 6 Substrate 7a, 7b Insulating part 100, 101, 102, 103, 104, 105, 106 Organic field effect transistor

Claims (8)

An organic electric field having a gate insulating layer, a patterned organic semiconductor layer, a gate electrode separated from the organic semiconductor layer by the gate insulating layer, and a source electrode and a drain electrode provided in contact with the organic semiconductor layer An effect transistor,
An organic field effect transistor, wherein an edge portion of the organic semiconductor layer and at least one of the source electrode and the drain electrode are not in contact with each other. The organic field effect according to claim 1, wherein at least one of the source electrode and the drain electrode is disposed so as to be separated from an edge portion of the organic semiconductor layer through the gate insulating layer. Transistor. An insulating portion provided in contact with the organic semiconductor layer;
3. The device according to claim 1, wherein at least one of the source electrode and the drain electrode is disposed so as to be separated from an edge portion of the organic semiconductor layer through the insulating portion. Organic field effect transistor. When the substrate surface is a projection surface, all paths connecting the projection pattern of the source electrode and the projection pattern of the drain electrode along the edge portion of the projection pattern of the organic semiconductor layer, and the projection pattern of the gate electrode The organic field effect transistor according to claim 1, wherein the organic field effect transistor is disposed so as to intersect with each other. An organic electric field having a gate insulating layer, a patterned organic semiconductor layer, a gate electrode separated from the organic semiconductor layer by the gate insulating layer, and a source electrode and a drain electrode provided in contact with the organic semiconductor layer An effect transistor,
When the substrate surface is a projection surface, all paths connecting the projection pattern of the source electrode and the projection pattern of the drain electrode along the edge portion of the projection pattern of the organic semiconductor layer, and the projection pattern of the gate electrode An organic field effect transistor, wherein the organic field effect transistor is disposed so as to intersect with each other. The projected pattern of the organic semiconductor layer includes the projected pattern of the source electrode by arranging the projected pattern of the gate electrode so as to intersect the closed curve around the projected pattern of the organic semiconductor layer at two or more places. 6. The method according to claim 5, wherein the organic semiconductor layer is divided into two or more partial projection patterns including a partial projection pattern of the organic semiconductor layer and a partial projection pattern of the organic semiconductor layer including a projection pattern of the drain electrode. Organic field effect transistor. An integrated circuit comprising at least the organic field effect transistor according to claim 1. An electronic device comprising at least an electronic circuit including the organic field effect transistor according to claim 1.

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