JP4815765B2 - Method for manufacturing organic semiconductor device - Google Patents

Description

  The present invention relates to an organic semiconductor pattern and an organic semiconductor layer patterning method, an organic semiconductor device, a manufacturing method thereof, and a display device.

  Conventionally, inorganic semiconductor materials such as silicon Si, gallium arsenide GaAs, and indium gallium arsenide InGaAs have been used for various semiconductor devices (transistors, diodes, photoelectric conversion devices, etc.).

  The basis of the manufacturing method is patterning of a semiconductor layer by photolithography and etching. That is, first, a solution containing a photoresist is applied to the surface of the semiconductor layer, the solvent is evaporated, and a photoresist layer is formed. Subsequently, this photoresist layer is patterned by photolithography into a shape corresponding to the electronic circuit pattern to be produced. Next, unnecessary portions of the semiconductor layer are removed by etching using the photoresist pattern as a mask, thereby forming an electronic circuit pattern.

  Organic semiconductor devices, on the other hand, can be increased in area at a lower cost than inorganic semiconductor devices, can be formed on flexible plastic substrates, and are stable against mechanical shocks. Research that assumes application to the environment is being actively conducted.

  However, when an organic semiconductor thin film such as pentacene is exposed to a solvent after film formation, its electrical properties are likely to change. Therefore, like an inorganic semiconductor, when a photoresist solution is applied to an organic semiconductor layer to form a photoresist layer and patterned, the solvent of the photoresist solution damages the organic semiconductor layer, and the organic semiconductor There arises a problem that the leakage current in the layer increases or the mobility in the organic semiconductor layer decreases.

  Therefore, in Patent Document 1 described later, a method for patterning an organic thin film is proposed in which a protective layer is provided on an organic thin film made of an organic semiconductor material and the like, and a photoresist layer is formed on the protective layer and patterned. Yes.

  FIG. 9 is a flowchart showing the organic thin film patterning method disclosed in Patent Document 1.

  In this method, first, as shown in FIG. 9A, a thin film 102 made of an organic semiconductor material such as pentacene is formed on a substrate 101 by a normal method, and then a protective material is formed on the organic thin film 102. The protective layer 103 to be formed is laminated. Any protective material may be used as long as it is chemically stable with respect to the solvent and the like and can prevent the solvent and the like from entering the organic thin film 102. However, parylene, especially parylene-N is described as being most preferable. Yes.

  Next, as shown in FIGS. 9B and 9C, after a photoresist layer 104 is formed by a normal method, a resist pattern 105 having a predetermined shape is formed by photolithography.

  Next, as shown in FIG. 9D, the protective layer 103 is etched using the resist pattern 105 as a mask, and then the organic thin film 102 is etched using the resist pattern 105 and the patterned protective layer 106 as a mask. After the patterning is completed, the resist pattern 105 is removed. The resist pattern 105 may be left as it is without being removed. The organic thin film pattern 107 thus obtained is subsequently subjected to processing for producing an organic thin film transistor or the like.

  Further, Patent Document 2 described later shows an organic FET (field effect transistor) in which a mask made of a photoresist is directly formed on an organic semiconductor layer and the photoresist is left after patterning.

  FIG. 10 is a cross-sectional view of an organic FET formed as a pixel transistor of a liquid crystal display device disclosed in Patent Document 2.

  In this organic FET 110, a gate electrode 112 is formed on an insulating substrate 111, and a gate insulating layer 113 is formed thereon. A drain electrode 114 and a source electrode 115 are formed in contact with the gate insulating layer 113, and a portion of the drain electrode 114 and the source electrode 115 overlaps the drain electrode 114 and the source electrode 115 while being tetrahedral. An organic semiconductor layer 116 made of thiotetracene is formed, and these constitute the organic FET 110.

  A pixel electrode 119 is provided on the right side of the organic FET 110 in contact with the gate insulating layer 113, and the source electrode 115 is connected to the pixel electrode 119. The organic FET 110 controls the operation of a liquid crystal display element (not shown) by turning on and off the drive voltage applied to the pixel electrode 119.

  The organic semiconductor layer 116 patterned as described above is formed by etching using an organic semiconductor layer deposited on the entire surface by vapor deposition as a mask with a resist 117 patterned corresponding to the shape of the organic semiconductor layer 116. The At this time, photosensitive benzocyclobutene (BCB) is used as a material for the resist 117, and the resist 117 is not removed even after the etching step and remains on the organic semiconductor layer 116. Further, the BCB layer is formed as a protective material layer 118 so as to wrap the entire organic FET 110.

  Patent Document 2 does not describe a solvent or the like when forming the resist 117 made of BCB, and describes whether the organic semiconductor layer 116 is damaged by forming the resist 117 directly on the organic semiconductor layer 116. It has not been. Further, it is described that by leaving the resist 117 without being removed, damage to the organic semiconductor layer 116 that occurs when the resist 117 is removed can be prevented.

US Pat. No. 6,600,604 (columns 3-5, FIG. 1) JP 2000-66233 A (pages 4 and 5, FIGS. 3 and 6)

  In Patent Document 1, regarding a protective material for forming a protective layer, a general description that it is chemically stable with respect to a solvent of a photoresist and the like and can prevent the solvent from entering the organic thin film 102, and parylene. In particular, only Parylene-N is described as being most preferable. For example, there is no description specifically indicating why Parylene-N is optimal, in other words, what conditions are more desirable as a protective material. For this reason, it cannot be said that the problem of the invention of Patent Document 1 has been completely solved by the invention of Patent Document 1. The reason is as follows.

  In order to form the optimal protective layer made of parylene, at least the evaporation zone for performing the process of evaporating the parylene dimer, the thermal decomposition zone for performing the process of decomposing the parylene dimer, and the parylene vapor fed to the substrate are adjusted. After the process is performed, a special vacuum deposition apparatus having a pyrolysis zone and a deposition zone for performing a process of depositing and polymerizing a parylene monomer on a substrate and forming a parylene polymer is required. Further, unlike mature semiconductor manufacturing technology, a technology for producing a parylene polymer by optimizing conditions such as temperature and pressure in each of the above processes has been established, and it is difficult to say that it is widely used (Special Table 2002). 505803).

  That is, at present, many users who want to use the invention of Patent Document 1 are not in a state where parylene can be used as a protective material. Then, when trying to obtain the same effect as the invention of Patent Document 1 using a protective material other than Parylene, Patent Document 1 does not describe anything that can be referred to in order to select the protective material.

  The same applies to the handling of the photoresist after patterning. Patent Document 1 shows an example in which the resist pattern 105 is removed after completion of patterning in FIG. 1, but the other is that the resist pattern 105 may be left without being removed. There is also. Since there is no description about the pros and cons in each case, it is not possible to obtain from Patent Document 1 what can be referred to regarding the handling of the photoresist after patterning.

  Patent Document 2 shows an example in which a photoresist 117 made of benzocyclobutene is directly provided as a mask on an organic semiconductor layer 116 made of tetrathiotetracene formed by a vapor deposition method. However, as described above, whether or not the organic semiconductor layer 116 is damaged by forming the photoresist 117 on the organic semiconductor layer 116 is not described because it is not described.

  Even if the damage to the organic semiconductor layer 116 is acceptable, there is no description about the solvent used in forming the resist 117 made of benzocyclobutene, and the cause is due to the solvent used. Whether it is special to benzocyclobutene, special to tetrathiotetracene formed by vapor deposition, or a combination of these cannot be determined.

  Whatever the cause, it is an exception that even if a photoresist is formed directly on the organic semiconductor layer, no significant damage is caused to the organic semiconductor layer. This is not true for the case of using a photoresist.

  The present invention has been made in view of such a situation, and the object thereof can be applied to a general organic semiconductor layer or a photoresist without using a special protective material such as parylene, and an organic semiconductor by patterning. To provide a method for patterning an organic semiconductor layer and a method for manufacturing an organic semiconductor device capable of suppressing degradation of the performance of the layer, and to provide an organic semiconductor pattern, an organic semiconductor device, and a display device manufactured based on this method is there.

That is, the present invention includes a step of forming an organic semiconductor layer, a step of stacking and forming a protective layer for protecting the organic semiconductor layer from the mask layer on the organic semiconductor layer, and the mask layer having a predetermined pattern. In the method for patterning an organic semiconductor layer, the method includes a step of laminating and forming the protective layer, and a step of patterning the protective layer and further the organic semiconductor layer in the same shape by etching using the mask layer as a mask.
The mask layer is formed of a material different from the mask layer, and the protective layer is formed of a hydrophilic organic polymer compound or an insulating inorganic compound.
A step of forming an organic semiconductor layer, a step of stacking a protective layer for protecting the organic semiconductor layer from the mask layer on the organic semiconductor layer, and a step of stacking the mask layer having a predetermined pattern on the protective layer. And forming the protective layer by etching using the mask layer as a mask, and further patterning the organic semiconductor layer in the same shape.
The protective layer is formed of an organic polymer compound or an insulating inorganic compound having a different material from the mask layer and having hydrophilicity,
The present invention relates to a method for manufacturing an organic semiconductor device, wherein the protective layer and the mask layer are left after the patterning.

  Furthermore, the organic semiconductor layer and the mask layer are made of different materials, and the protective layer made of a hydrophilic organic polymer compound or insulating inorganic compound and the mask layer are laminated in the same pattern in this order. It relates to an organic semiconductor pattern, and the organic semiconductor layer and the mask layer are made of different materials, and the protective layer made of a hydrophilic organic polymer compound or insulating inorganic compound and the mask layer are the same in this order. The present invention relates to an organic semiconductor device stacked in a pattern, and at least the organic semiconductor layer constituting the channel portion and the mask layer are made of different materials and are made of a hydrophilic organic polymer compound or insulating inorganic compound. A protective layer and the mask layer are laminated in the same pattern in this order, and an organic field effect transistor having source and drain electrodes in contact with the channel portion. Those related to the display device having the Njisuta as a drive unit.

  The organic semiconductor device of the present invention has a laminated structure in which an organic semiconductor layer, a protective layer, and a mask layer are laminated in this order, and the organic semiconductor layer is formed by the protective layer from a solvent or the like when forming the mask layer. Isolated. In addition, as a first feature, a hydrophilic organic polymer compound or an insulating inorganic compound is selected as a material for forming the protective layer. Therefore, the protective layer is used when forming the mask layer. In addition to being stable to the organic solvent, the organic solvent can prevent the organic solvent from entering the organic semiconductor layer. Further, the protective layer may be formed using a polar solvent such as water that is not compatible with the organic semiconductor layer, or may be formed by a method that does not use a solvent, such as chemical vapor deposition (CVD). Therefore, damage to the organic semiconductor due to the solvent when forming the protective layer can be suppressed or eliminated.

  Further, as compared with the case where only the mask layer is provided, the protective layer and the mask layer are separately provided and the functions are separated, so that each layer limits the function to one of the protective action and the mask forming action. be able to. As a result, an optimal material and manufacturing method can be selected for each of the protective layer and the mask layer from a wider range of options. Further, if the protective layer and the mask layer are formed of materials having different solubility in a solvent, the protective layer can have durability against the solvent used when forming the mask layer.

  As a result, the thin and dense protective layer can be formed without using a special material such as parylene and a special apparatus for forming the material. For example, the hydrophilic organic polymer compound includes polyvinyl alcohol, and the protective layer can be easily formed by applying an aqueous solution thereof by spin coating or the like and then evaporating the solvent. . Insulating inorganic compounds include silicon nitride and aluminum oxide, and the protective layer can be formed using established semiconductor technology such as CVD and sputtering, and existing equipment. In this way, the organic semiconductor layer can be reliably patterned with little damage using already established and widespread technology and equipment.As a result, the mobility in the organic semiconductor layer is high, An organic semiconductor device having a small leakage current and a large ratio of on-current to off-current can be manufactured at low cost.

  The second feature is that the protective layer and the mask layer remain after the patterning of the organic semiconductor layer, so that the passivation effect of the protective layer and the mask layer on the organic semiconductor layer can be improved. In addition to expectation, damage to the organic semiconductor layer that occurs when these layers are removed can be prevented. In addition, since the step of removing the protective layer and the mask layer can be omitted, the number of steps of manufacturing the organic semiconductor device can be reduced and the production efficiency can be improved.

  The organic semiconductor pattern of the present invention should be regarded as an intermediate product in the process of manufacturing the organic semiconductor device, and is a structure obtained by patterning the organic semiconductor layer. Like the organic semiconductor device, the organic semiconductor device has the stacked structure in which the organic semiconductor layer, the protective layer, and the mask layer are stacked, and has the first feature and the effect thereof.

  The organic semiconductor layer patterning method and the organic semiconductor device manufacturing method of the present invention are a method of manufacturing the organic semiconductor pattern and the organic semiconductor device, respectively. This has an integral relationship with the characteristics and effects of the organic semiconductor device.

  The display device of the present invention has the organic semiconductor device configured as an organic field effect transistor in which the organic semiconductor layer forms at least a channel portion as a driving unit, so that a display with a high response speed and a high contrast ratio is provided. Is possible.

  In the present invention, at least one of the organic polymer compound selected from the group consisting of polyvinyl alcohol and pullulan, and the insulating inorganic compound selected from the group consisting of silicon nitride, silicon oxide, silicon carbide, and aluminum oxide. The protective layer is preferably formed.

  Since polyvinyl alcohol and pullulan have a hydroxyl group and have hydrophilicity, as described above, they do not have affinity with the organic solvent used when forming the mask layer, and are stable to this organic solvent. In addition, the organic solvent can be prevented from entering the organic semiconductor layer. Moreover, since it can form using polar solvents, such as water, with which the said organic-semiconductor layer is not compatible, the damage to the said organic-semiconductor by the solvent at the time of forming the said protective layer can be suppressed.

  Silicon nitride, silicon oxide, silicon carbide, and aluminum oxide form a crystalline film and can prevent the organic solvent used in forming the mask layer from entering the organic semiconductor layer. Moreover, since it can be formed by a method that does not use a solvent, such as a CVD method or a sputtering method, damage to the organic semiconductor due to the solvent when forming the protective layer can be eliminated.

  Moreover, it is preferable that the single-layered or laminated protective layer is formed by the organic polymer compound and / or the insulating inorganic compound. With a single layer, the structure is simple and easy to manufacture, and with a laminated structure, the structure is complicated and time-consuming to manufacture, but the combination of each layer has the advantage of realizing functions that cannot be realized with a single layer. is there.

  The mask layer may be formed of an organic material. The material of the mask layer is not limited to an organic material, but when the protective layer is a hydrophilic organic polymer compound, the protective layer is formed by forming the mask layer with a hydrophobic organic material. The influence of the mask layer and the solvent on the can be suppressed.

  The organic semiconductor layer may be formed of pentacene. Pentacene is known to exhibit excellent semiconductor properties such as high mobility.

  The organic semiconductor device of the present invention is preferably configured as an organic field effect transistor having the patterned organic semiconductor layer at least in a channel portion, and having a source and a drain electrode in contact with the channel portion. And this organic field effect transistor is good to be used as a pixel transistor of a liquid crystal display device.

  In the organic semiconductor layer patterning method and the organic semiconductor device manufacturing method of the present invention, the mask layer is preferably formed by patterning a photoresist layer. According to this method, the mask layer can be formed with high accuracy by applying mature semiconductor manufacturing technology.

  Alternatively, the mask layer may be formed by printing. According to this method, for example, the mask layer can be formed with a small number of steps by applying a printing technique such as inkjet printing, screen printing, or microprinting. Further, the size can be easily increased.

  In the method for manufacturing an organic semiconductor device of the present invention, the organic semiconductor layer may be annealed after the patterning step. Thereby, defects due to reversible changes that occur in the organic semiconductor layer when the protective layer is formed, for example, damage to the organic semiconductor layer such as plasma damage that occurs when the protective layer is formed by sputtering are repaired. be able to.

  Next, a preferred embodiment of the present invention will be described specifically and in detail with reference to the drawings.

Embodiment 1
In the first embodiment, the mask layer is formed by patterning a photoresist layer by photolithography and etching. The patterned organic semiconductor layer is used as a channel portion, and source and drain electrodes are provided in contact with the channel portion to produce an organic field effect transistor, which is used as a pixel transistor of a liquid crystal display device.

  FIG. 1 is a flowchart showing a patterning process of the organic semiconductor layer 2 based on the first embodiment.

  First, as shown in FIG. 1A, an organic semiconductor layer 2 is formed on a substrate 1. For example, if the organic semiconductor material is a low molecular weight compound such as pentacene or oligothiophene, the organic semiconductor layer 2 is formed by a vapor deposition method using a resistance heating type vapor deposition source, and the organic semiconductor material is made of polythiophene or polyfluorene. If it is a high molecular weight compound, it is formed by dissolving in a solvent, applying the solution by spin coating or capillary coating, and then evaporating the solvent.

  Subsequently, the protective layer 3 is formed by being stacked on the organic semiconductor layer 2. The protective layer 3 is formed by CVD or sputtering if the protective material is silicon nitride, silicon dioxide, silicon carbide or aluminum oxide. If the protective material is polyvinyl alcohol or pullulan, an aqueous solution is applied by spin coating or capillary. After coating by a coating method, the solvent is formed by evaporating water.

  At this time, since silicon nitride, silicon dioxide, silicon carbide, or aluminum oxide can be formed by a method that does not use a solvent, such as a CVD method or a sputtering method, the organic semiconductor layer is formed by a solvent when the protective layer 3 is formed. 2 damage can be eliminated. In addition, since polyvinyl alcohol and pullulan can be formed from a solution using a polar solvent such as water to which the organic semiconductor layer 2 is incompatible as a solvent, the organic semiconductor layer 2 depends on the solvent used when the protective layer 3 is formed. Damage received can be reduced.

  In this manner, the thin and dense protective layer 3 can be formed without using a special material such as parylene and a special apparatus for forming the material. The protective layer 3 made of an insulating inorganic compound such as silicon nitride can be formed using established semiconductor technology such as a CVD method or a sputtering method and existing equipment. Further, the protective layer 3 made of a hydrophilic organic polymer compound such as polyvinyl alcohol can be easily formed by applying an aqueous solution thereof by spin coating or the like and then evaporating the solvent.

  The thickness of the protective layer 3 is desirably 50 nm to 1 μm, and more desirably 200 nm. This is because the thickness of 50 nm or more is necessary to form the protective layer 3 which is excellent in homogeneity and flatness and has a sufficient protective action. On the other hand, if the thickness is too thick, the driving voltage becomes too high. This is because in order to keep the driving voltage of the liquid crystal display element low, it is necessary to suppress the thickness to 1 μm or less.

  Next, as shown in FIG. 1B, a photoresist layer 4 is formed on the protective layer 3 by a coating method. As a material for the photoresist, for example, polyvinyl alcohol doped with a polymerization initiator, polymethyl methacrylate, polystyrene, or the like can be used. The polymerization initiator used here is a substance that initiates polymerization of a monomer upon irradiation with ultraviolet light.

  At this time, if the material of the protective layer 3 is silicon nitride, silicon oxide, silicon carbide or aluminum oxide, they form a crystalline film, and the organic solvent used when forming the photoresist layer 4 is organic. Intrusion into the semiconductor layer 2 can be prevented. Further, if the material of the protective layer 3 is polyvinyl alcohol or pullulan, these have a hydroxyl group and have hydrophilicity, so that they do not have an affinity for the organic solvent used when forming the photoresist layer 4 and are themselves In addition to being stable to the organic solvent, the organic solvent can be prevented from entering the organic semiconductor layer 2.

  Next, as shown in FIG. 1C, the photoresist layer 4 is patterned by photolithography into the same pattern as a predetermined circuit pattern to be formed on the organic semiconductor layer 2 to form a mask layer 5. According to this method, the mask layer 5 can be formed with high accuracy by applying mature semiconductor manufacturing technology.

  As a method of forming the mask layer 5, there is a method of locally depositing a vapor deposition film by vapor deposition from the opening of the metal mask, but this method is difficult to perform fine processing.

Next, as shown in FIG. 1 (d), the protective layer 3 is etched using the mask layer 5 as a mask and patterned to the same shape as the mask layer 5. At this time, when the protective layer 3 is made of silicon nitride, wet etching using a solution containing phosphoric acid is performed, or dry etching using sulfur hexafluoride SF ₆ , perfluorohydrocarbon C _x F _y, or the like is performed. . When the protective layer 3 is made of silicon dioxide, wet etching with a solution containing hydrofluoric acid or dry etching using sulfur hexafluoride SF ₆ or perfluorohydrocarbon C _x F _y is performed. Do. When the protective layer 3 is made of an organic material such as polyvinyl alcohol or pullulan, etching using oxygen O ₂ plasma is performed.

  Next, as shown in FIG. 1E, using the mask layer 5 and the patterned protective layer 6 as a mask, the organic semiconductor layer 2 is etched by oxygen plasma and patterned into the same shape as the mask layer 5 to perform patterning. Thus obtained organic semiconductor layer (organic semiconductor pattern) 7 is obtained. After the patterning is completed, the mask layer 5 is not removed with a resist stripping solution, but is left as it is as a protective film of the organic semiconductor pattern 7. The organic semiconductor pattern 7 is subsequently subjected to processing for producing an organic thin film transistor and the like.

  Note that when the protective layer 3 and the organic semiconductor layer 2 are etched by oxygen plasma, the mask layer 5 is also etched. Accordingly, it is assumed that the photoresist layer 4 is formed thicker by the reduced amount due to the etching so that the thickness after the reduction by the etching becomes a predetermined thickness.

  2 to 4 are a cross-sectional view (FIG. 2), a perspective view (FIG. 3), and a layout view (FIG. 4) of the main part of the liquid crystal display device according to the first embodiment. However, the cross-sectional view is a cross-sectional view at the position of line 4A-4A shown in the layout diagram, and the perspective view is an interlayer insulating film so that the relationship between the organic field effect transistor 10 and its surroundings can be easily understood at the same position. 24 and a part of the liquid crystal 26 are omitted. In this liquid crystal display device, the organic semiconductor layer 7 is formed as a channel portion in contact with the source electrode 15 and the drain electrode 16 to produce the organic field effect transistor 10 and used as a pixel transistor of the liquid crystal display device.

  As shown in FIGS. 2 and 3, in the organic FET 10, a barrier layer 12 is provided on a substrate 11, and a gate electrode 13 and a gate insulating layer 14 are formed thereon. A source electrode 15 and a drain electrode 16 are formed in contact with the gate insulating layer 14. A part of the source electrode 15 and the drain electrode 16 overlaps the source electrode 15 and the drain electrode 16 while being patterned. A laminated structure of the patterned organic semiconductor layer 7, the patterned protective layer 6, and the mask layer 5 is formed, and a bottom gate type organic FET 10 is constituted by these.

  A pixel electrode 23 is provided on the gate insulating layer 14 on the right side of the organic FET 10, and the drain electrode 16 is electrically connected to the pixel electrode 23. The organic FET 10 controls the operation of the liquid crystal display element 20 by turning on and off the drive voltage applied to the pixel electrode 23.

  The liquid crystal display element 20 includes a backlight 21, a polarizing plate 22, a substrate 11, a barrier layer 12, a gate insulating layer 14, a pixel electrode 23, an interlayer insulating film 24, an alignment film 25, a liquid crystal layer 26, an alignment film 27, and a pixel electrode 28. A transmissive liquid crystal display element including a substrate 29 and a polarizing plate 30.

  Hereinafter, each part including the manufacturing method will be described with emphasis on the organic FET 10.

  The substrate 11 may be anything as long as it is normally used as a substrate. For example, a plastic substrate made of an organic polymer is preferable because a flexible screen can be formed and it is inexpensive and lightweight.

  When an organic polymer substrate is used as the substrate 11, gas may be released from the substrate 11 during the processing process, which may cause a deterioration in the quality of the liquid crystal display device. The barrier layer 12 is for suppressing the release of this gas, and is formed by depositing a layer made of silicon dioxide or silicon nitride on the surface of the substrate 11 to a thickness of several hundred nm.

  Next, a gate electrode 13 made of a metal thin film such as aluminum Al or copper Cu or metal fine particles such as silver fine particles Ag or gold fine particles Au is formed on the substrate 11 on which the barrier layer 12 is formed. The electrode made of a metal thin film is formed by vapor deposition of a metal thin film and lithography patterning, and the electrode made of metal fine particles is formed by a printing method.

  Next, a gate insulating layer 14 made of an inorganic material or an organic polymer material is formed on the gate electrode 13 and on the barrier layer 12 where the gate electrode 13 is not formed. Specifically, the gate insulating layer 14 made of an inorganic material is formed by CVD or sputtering using a layer made of silicon dioxide or silicon nitride, and the gate insulating layer 14 made of an organic polymer material is made of polyvinylphenol (PVP). ), Polymethyl methacrylate (PMMA), polyimide, or the like is deposited by coating or printing, and then the solvent is evaporated.

  Next, on the gate insulating layer 14, in the same manner as the gate electrode 13, a source electrode 15 and a drain electrode 16 made of a metal thin film such as aluminum Al or copper Cu, or metal fine particles such as silver fine particles Ag or gold fine particles Au. And form.

  Next, in the same manner as shown in FIG. 1A, the organic semiconductor layer 2 and the protective layer 3 are laminated on the entire surface of the gate insulating layer 14 including the source electrode 15 and the drain electrode 16. . The organic semiconductor layer 2 is formed, for example, by vapor-depositing pentacene or oligothiophene by a resistance heating method, or by applying a solution such as polythiophene or polyfluorene by a spin coating method or a capillary coating method and then evaporating the solvent. To do. The protective layer 3 is formed by, for example, forming silicon nitride, silicon dioxide, aluminum oxide, or the like by CVD or sputtering, or applying an aqueous solution such as polyvinyl alcohol or pullulan by spin coating or capillary coating, and then using a solvent. Formed by evaporating some water.

  Next, in the same manner as shown in FIG. 1B, a photoresist layer 4 is formed on the protective layer 3 by coating. As the material of the photoresist, for example, polyvinyl alcohol, polymethyl methacrylate, polystyrene, or the like doped with a polymerization initiator that starts polymerization of a monomer when irradiated with ultraviolet light can be used.

  Next, in the same manner as shown in FIG. 1C, the mask layer 5 is formed by patterning the photoresist layer 4 into the shape of the organic FET 10 by photolithography.

  Next, in the same manner as shown in FIG. 1 (d), the protective layer 3 is etched using the mask layer 5 as a mask and patterned to the same shape as the mask layer 5. At this time, the protective layer 3 made of silicon nitride is subjected to wet etching using a phosphoric acid solution or dry etching. The protective layer 3 made of silicon dioxide is subjected to wet etching with hydrofluoric acid or dry etching. The protective layer 3 made of an organic material is etched by oxygen plasma.

  Next, as shown in FIG. 1 (e), the organic semiconductor layer 2 is etched by oxygen plasma using the mask layer 5 and the patterned protective layer 6 as a mask, and patterned into the same shape as the mask layer 5. Thereby, the organic semiconductor layer 2 is separated for each pixel, and a channel portion of each organic FET is formed. After the patterning is completed, the mask layer 5 is left as it is as a protective film for the organic semiconductor layer pattern 7.

  The organic semiconductor pattern 7 thus obtained is subsequently subjected to processing for producing an organic thin film transistor and the like. For example, after an aqueous polyvinyl alcohol solution is applied by spin coating or capillary coating, the solvent is evaporated to form an interlayer insulating film 24 made of polyvinyl alcohol, and the organic FET 10 is formed in the laminated structure constituting the liquid crystal display element 20. Can be incorporated.

  On the other hand, the liquid crystal display element 20 is not limited to this, but is a transmissive liquid crystal display element having a backlight 21, and alignment films 25 and 27, ITO ( Pixel electrodes 23 and 28 made of transparent electrodes such as indium tin oxide, light-transmitting substrates 11 and 29, and polarizing plates 22 and 30 are provided. The alignment directions of the two alignment films 25 and 27 and the polarization directions of the two polarizing plates 22 and 30 are orthogonal to each other, and the liquid crystal display element 20 is a TN (Twisted Nematic) type that maximizes the amount of transmitted light when no voltage is applied. This is a liquid crystal display element.

  In terms of circuit, the pixel electrodes 23 and 28 constitute a pixel capacitor (pixel capacitor) having a liquid crystal layer 26 or the like sandwiched therebetween as a dielectric layer. The pixel electrode 23 is connected to the drain electrode 16 of the organic FET 10, and the pixel capacitance is configured to be charged / discharged through the organic FET 10.

  As shown in FIG. 4, in this liquid crystal display device, one pixel is formed by each one of the organic FET 10 and the liquid crystal display element 20, and a large number of pixels are arranged in a matrix. A data line 31 connected to the source electrode 15 of the organic FET 10, a gate scanning line 32 connected to the gate electrode 13, a common line 33 connected to the common electrode and forming an effective ground potential, Are provided in a grid pattern.

  During the operation of the liquid crystal display device, a signal voltage is applied to one of the data lines 31 and a selection signal is applied to one of the gate scanning lines 32. As a result, the pixel at the intersection is selected, and the pixel capacitance of the pixel is charged / discharged by the signal voltage applied to the source electrode 15 through the organic FET 10 that is turned on. The data line 31 to which the signal voltage is applied and the gate scanning line 32 to which the selection signal is applied are sequentially changed during one cycle, whereby all the pixels are accessed one after another. The pixel's organic FET 10 is in an off state for one cycle after the pixel in one cycle is accessed until the pixel is accessed again in the next cycle, and the pixel capacitance was applied during access. The signal voltage is held, and the liquid crystal display element 20 is configured to maintain a certain gradation.

  Each pixel may be provided with an auxiliary capacitor 35 in parallel with the pixel capacitor. This is to suppress a decrease in the voltage of the pixel capacitor during one cycle due to the off-state current of the organic FET 10.

  As described above, in the first embodiment, the organic semiconductor layer 2 can be surely patterned with little damage using the technology and equipment already established and spread, and as a result, the patterning is performed. In addition, an organic semiconductor device having high mobility in the organic semiconductor layer 7 and low leakage current and a large ratio of on-current to off-current can be manufactured at low cost.

  In addition, since the protective layer 6 and the mask layer 5 are left after the patterning of the organic semiconductor layer 2, the passivation effect of the protective layer 6 and the mask layer 5 on the organic semiconductor layer 7 can be expected. The damage to the organic semiconductor layer 7 that occurs when these layers are removed can be prevented in advance. Moreover, since the process of removing the protective layer 6 and the mask layer 5 can be omitted, the number of steps of the manufacturing process of the organic semiconductor device can be reduced and the production efficiency can be improved.

  Further, in the liquid crystal display device, an organic field effect transistor is formed using the organic semiconductor layer 7 as a channel portion, and this is used as a pixel transistor. Therefore, a high-quality display with a high response speed, a large contrast ratio, and a small flicker. Is possible.

Embodiment 2
FIG. 5 is a layout diagram (a) of the liquid crystal display device according to the second embodiment and a sectional view (b) of the organic FET portion. The cross-sectional view (b) is a cross-sectional view at the position indicated by the line 5A-5A in the layout diagram (a).

  The liquid crystal display device shown in FIG. 5 differs from the liquid crystal display device according to the first embodiment shown in FIGS. 2 to 4 only in that the source electrode 45 and the drain electrode 46 are formed as comb electrodes. Yes. As in the first embodiment, the comb electrodes 45 and 46 are formed by forming a metal thin film by a vapor deposition method or a sputtering method and patterning the thin film by lithography.

  As shown in the cross-sectional view of FIG. 5B, the organic semiconductor layer 7 is formed so as to wrap the entire comb electrodes 45 and 46. By making the source electrode 45 and the drain electrode 46 comb-shaped electrodes, the substantial cross-sectional area of the channel portion formed by the organic semiconductor layer 7 is increased, and even the organic semiconductor layer 7 having a low mobility is sufficient. A large charge or discharge current can be obtained.

  Since the rest is the same as that of the liquid crystal display device according to the first embodiment, it is needless to say that the same effect can be obtained. That is, in the liquid crystal display device according to the present embodiment, an organic field effect transistor is formed using the organic semiconductor layer 7 as a channel portion, and this is used as a pixel transistor. Therefore, the response speed is fast, the contrast ratio is large, High-quality display with little flicker is possible.

Embodiment 3
The third embodiment is different from the first embodiment only in that the mask layer is formed by a printing method instead of forming the mask layer by patterning a photoresist layer.

  FIG. 6 is a flowchart showing the patterning process of the organic semiconductor layer 2 based on the third embodiment.

  First, as in the first embodiment, as shown in FIG. 6A, the organic semiconductor layer 2 is formed on the substrate 1, and the protective layer 3 is formed thereon. The organic semiconductor layer 2 is formed by a resistance heating vapor deposition method if the organic semiconductor material is a low molecular weight compound such as pentacene or oligothiophene. If the organic semiconductor material is a high molecular weight compound such as polythiophene or polyfluorene, After dissolving in a solvent and applying the solution by spin coating or capillary coating, the solvent is evaporated. If the protective material is silicon nitride or silicon dioxide, the protective layer 3 is formed by CVD or sputtering. If the protective material is polyvinyl alcohol or pullulan, an aqueous solution is applied by spin coating or capillary coating. It is formed by evaporating water as a solvent.

  Next, as shown in FIG. 6B, a mask layer 8 is formed on the protective layer 3 by printing. As a printing method, inkjet printing, screen printing, microprinting method, or the like is used. For example, a circuit of an organic semiconductor layer to be formed by depositing a solution of polyvinyl alcohol or pullulan in a polar solvent such as water on the protective layer 3 by the above printing method and then evaporating the solvent. A mask layer 8 having the same pattern as the pattern is formed. According to this method, the mask layer 8 can be formed with a small number of steps by applying the printing technique. Further, the size can be easily increased.

Next, as shown in FIG. 6C, the protective layer 3 is etched using the mask layer 5 as a mask, as in FIG. At this time, when the protective layer 3 is made of silicon nitride, wet etching using a solution containing phosphoric acid is performed, or dry etching using sulfur hexafluoride SF ₆ , perfluorohydrocarbon C _x F _y, or the like is performed. . When the protective layer 3 is made of silicon dioxide, wet etching with a solution containing hydrofluoric acid or dry etching using sulfur hexafluoride SF ₆ or perfluorohydrocarbon C _x F _y is performed. Do. When the protective layer 3 is made of an organic material such as polyvinyl alcohol or pullulan, etching using oxygen O ₂ plasma is performed.

  Next, as shown in FIG. 2D, the organic semiconductor layer 2 is etched by oxygen plasma using the mask layer 8 and the patterned protective layer 6 as a mask, as in FIG. And pattern in the same shape. After the patterning is completed, the mask layer 8 is not removed and is left as it is as a protective film of the organic semiconductor pattern 7.

  Thereafter, in the same manner as in the first embodiment, the patterned organic semiconductor layer 7 is used as a channel portion, and source and drain electrodes are provided in contact with the channel portion to produce an organic field effect transistor. Used as a pixel transistor or the like.

  As described above, since the mask layer is formed by printing in this embodiment, the mask layer can be formed by a small number of steps by applying a printing technique. Further, the size can be easily increased.

  Since the method other than the mask manufacturing method is the same as that of the first embodiment, it is needless to say that the same effects as those of the first embodiment can be obtained with respect to common points.

  In other words, the organic semiconductor layer 2 can be reliably patterned with little damage using the technology and facilities already established and spread, and as a result, the mobility in the patterned organic semiconductor layer 7 is high, In addition, an organic semiconductor device having a small leakage current and a large ratio of on-current to off-current can be manufactured at low cost.

  In addition, since the protective layer 6 and the mask layer 5 are left after the patterning of the organic semiconductor layer 2, the passivation effect of the protective layer 6 and the mask layer 5 on the organic semiconductor layer 7 can be expected. The damage to the organic semiconductor layer 7 that occurs when these layers are removed can be prevented in advance. Moreover, since the process of removing the protective layer 6 and the mask layer 5 can be omitted, the number of steps of the manufacturing process of the organic semiconductor device can be reduced and the production efficiency can be improved.

  Further, in the liquid crystal display device, an organic field effect transistor is formed using the organic semiconductor layer 7 as a channel portion, and this is used as a pixel transistor. Therefore, a high-quality display with a high response speed, a large contrast ratio, and a small flicker. Is possible.

Embodiment 4
In the fourth embodiment, after patterning the organic semiconductor layer in the same manner as in the first or third embodiment, the step of annealing the organic semiconductor layer is only performed. Is different. However, in the present embodiment, the organic semiconductor layer 2 made of pentacene is formed by a vapor deposition method, and a silicon nitride thin film is formed as the protective layer 3 by a sputtering method.

  When the organic semiconductor layer 2 is made of pentacene, for example, annealing is performed at 80 ° C. for 16 hours immediately after the organic semiconductor layer 2 is patterned. The leakage current flowing through the organic semiconductor layer 7 patterned in this step can be returned to the state of the organic semiconductor layer 2 before the patterning step.

FIG. 7 is a graph showing the relationship between the gate voltage V _g and the drain current I _d in the organic FET based on the fourth embodiment. A dotted line is a graph of Comparative Example 1 in which an organic FET is configured using an as-deposited pentacene thin film, and a broken line is a pentacene thin film formed by vapor deposition and then patterned using a silicon nitride thin film as the protective layer 3 In the graph corresponding to the embodiment 3 in which the organic FET is configured, the solid line is formed by vapor deposition, patterned using the silicon nitride thin film as the protective layer 3, and then subjected to the annealing treatment described above. It is a graph of organic FET based on this Embodiment which constituted organic FET by the pentacene thin film.

  In the above organic FET, the gate length is 5 μm, the gate width is 47.2 μm, and the drain voltage is −7 V, which are constant.

According to FIG. 7, in Comparative Example 1 using the pentacene thin film as it is formed, the drain current I _d changes from about 10 ⁻³ A in the on state to about 10 ⁻¹⁰ A in the off state, and the on current and the off current. The ratio reaches about 10 ⁷ . On the other hand, in Embodiment 3 using the pentacene thin film patterned under the silicon nitride protective layer, the drain current I _d changes from about 5 × 10 ⁻⁴ A in the on state to about 5 × 10 ⁻⁷ A in the off state. However, the ratio of on-current to off-current is reduced to about 10 ³ . However, in the fourth embodiment using the pentacene thin film annealed after patterning, the drain current I _d changes from about 3 × 10 ⁻⁴ A in the on state to about 3 × 10 ⁻¹⁰ A in the off state, and the on current And the off-current ratio recover to about 10 ⁶ .

  FIG. 8 shows an example in which the same measurement as in FIG. 7 was performed on another pentacene thin film for comparison. A dotted line is a graph of Comparative Example 1 in which an organic FET is configured using a pentacene thin film as it is formed, and a broken line is an organic FET formed using a pentacene thin film that is formed by vapor deposition and then patterned without a protective layer. It is the graph of the comparative example 2 comprised, and a continuous line is formed into a film by vapor deposition, and after patterning without a protective layer, the organic FET was comprised using the pentacene thin film which performed the annealing process similar to the above. It is a graph.

According to FIG. 8, in Comparative Example 1, as in FIG. 7, the drain current I _d changes from about 10 ⁻³ A in the on state to about 10 ⁻¹⁰ A in the off state, and the ratio of the on current to the off current. Reaches about 10 ⁷ . On the other hand, in Comparative Example 2 using a pentacene thin film patterned without a protective layer, the drain current I _d changes from about 5 × 10 ⁻⁴ A in the on state to about 5 × 10 ⁻⁶ A in the off state. The ratio of current to off current is reduced to about 10 ² . And in the comparative example 3 by the pentacene thin film annealed after patterning without a protective layer, the drain current I _d changes from about 4 × 10 ⁻⁴ A in the on state to about 3 × 10 ⁻⁵ A in the off state. However, the ratio of on-current to off-current is rather deteriorated to about 10 ¹ .

  Comparing Embodiments 3 and 4 with Comparative Examples 2 and 3, there are two possible mechanisms by which the off-current increases due to damage received by the pentacene thin film, with different annealing effects.

  That is, as seen in Comparative Examples 2 and 3, the damage caused by patterning without a protective layer is large and is a damage that does not recover even after annealing. This is considered to be caused by irreversible changes such as the formation of a new current path at the interface between pentacene and the resist due to, for example, an irreversible interaction (for example, a chemical reaction) with the resist. It is done.

  On the other hand, as can be seen in the third and fourth embodiments, the damage in the case where the protective layer 3 is present is relatively small, and most of the damage is recovered by the annealing treatment. In this embodiment, this damage is known to be plasma damage caused by sputtering when the silicon nitride protective layer is formed by sputtering, and damage caused by a reversible change recovered by annealing treatment Conceivable.

As described above, according to the present embodiment, the provision of the protective layer 3 causes large and irreversible damage to the organic semiconductor layer that does not recover even after annealing, which occurs when patterning is performed without the protective layer. And reversible damage such as plasma damage generated in the organic semiconductor layer 2 during the formation of the protective layer 3 by the annealing treatment after the patterning, so that the on-current in the patterned organic semiconductor layer 7 is reduced. The ratio with the off-current is about 10 ^6, and it can be recovered to a value close to about 10 ⁷ before patterning. The leakage current is smaller than those in the first and third embodiments, and the on-current and off-current An organic semiconductor device with a large ratio can be manufactured. In the liquid crystal display device, an organic field effect transistor is formed using the organic semiconductor layer 7 as a channel portion, and this is used as a pixel transistor. Therefore, the response speed is faster than those in the first and third embodiments, A high-quality display with high contrast ratio and less flickering is possible.

  In other respects, there is essentially no difference from the first and third embodiments, and it goes without saying that the same effects as in the first and third embodiments can be obtained. That is, since the protective layer 6 and the mask layer 5 are left after the patterning of the organic semiconductor layer 2, the passivation effect of the protective layer 6 and the mask layer 5 on the organic semiconductor layer 7 can be expected. The damage to the organic semiconductor layer 7 that occurs when these layers are removed can be prevented in advance. Moreover, since the process of removing the protective layer 6 and the mask layer 5 can be omitted, the number of steps of the manufacturing process of the organic semiconductor device can be reduced and the production efficiency can be improved.

  As mentioned above, although this invention was demonstrated based on embodiment, it cannot be overemphasized that this invention is not limited to these examples at all, and can be suitably changed in the range which does not deviate from the main point of invention.

  The organic semiconductor pattern and organic semiconductor layer patterning method, organic semiconductor device and method for manufacturing the same, and display device of the present invention are thin film transistors that are widely used as switching elements for various electronic circuits, particularly active matrix circuits for displays. It is used as a semiconductor device such as TFT) and a manufacturing method thereof, and can contribute to the development of new uses such as cost reduction and application to a flexible substrate having no heat resistance such as plastic.

It is a flowchart which shows the patterning process of the organic-semiconductor layer based on Embodiment 1 of this invention. It is sectional drawing of a liquid crystal display device principal part. It is a perspective view of the principal part of a liquid crystal display device same as the above. 2 is a layout diagram of the liquid crystal display device. FIG. It is the layout figure (a) and sectional drawing (b) of the liquid crystal display device based on Embodiment 2 of this invention. It is a flowchart which shows the patterning process of the organic-semiconductor layer based on Embodiment 3 of this invention. The relationship between the gate voltage V _g and the drain current I _d of the organic FET based on the fourth embodiment of the present invention is a graph showing. Is a graph showing the relationship between a gate voltage V _g and the drain current I _d of the organic FET of the comparative example. It is a flowchart which shows the method of patterning the organic thin film easy to be influenced by the solvent shown by patent document 1. FIG. It is sectional drawing of organic FET used as a pixel transistor of the liquid crystal display device shown by patent document 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Organic-semiconductor layer, 3 ... Protective layer, 4 ... Photoresist layer, 5 ... Mask layer,
6 ... patterned protective layer,
7 ... patterned organic semiconductor layer (organic semiconductor pattern), 8 ... mask layer,
10 ... Organic FET, 11 ... Substrate, 12 ... Barrier layer, 13 ... Gate electrode,
14 ... gate insulating layer, 15 ... drain electrode, 16 ... source electrode, 20 ... liquid crystal display element,
21 ... Backlight, 22, 30 ... Deflection plate, 23, 28 ... Pixel electrode, 24 ... Interlayer insulating film,
25, 27 ... alignment film, 26 ... liquid crystal, 29 ... substrate, 31 ... data line, 32 ... gate scanning line,
33 ... Common wire, 35 ... Auxiliary capacitance, 40 ... Organic FET,
45 ... Source electrode (comb electrode), 46 ... Drain electrode (comb electrode),
DESCRIPTION OF SYMBOLS 101 ... Board | substrate, 102 ... Organic thin film, 103 ... Protective layer, 104 ... Photoresist layer,
105 ... resist pattern, 106 ... patterned protective layer,
107 ... Organic thin film pattern, 110 ... Organic FET, 111 ... Insulating substrate,
112 ... Gate electrode, 113 ... Gate insulating layer, 114 ... Drain electrode,
115 ... Source electrode, 116 ... Organic semiconductor layer, 117 ... Resist, 118 ... Protective material layer,
119: Pixel electrode

Claims (7)

The organic semiconductor layer is protected from a mask layer formed of an organic material and a step of forming an organic semiconductor layer, and the mask layer is made of an organic polymer compound or an insulating inorganic compound having a different material and hydrophilicity. The protective layer is formed by laminating the protective layer on the organic semiconductor layer, the step of laminating and forming the mask layer having a predetermined pattern on the protective layer, and etching using the mask layer as a mask. And further, patterning the organic semiconductor layer into the same shape,
After the patterning, leaving the mask layer together with the protective layer, the organic semiconductor layer is annealed to repair the damage the organic semi conductor layer is subjected, and the mask layer together with the protective layer Leave it in the semiconductor device,
A method of manufacturing an organic semiconductor device.   The organic polymer compound selected from the group consisting of polyvinylphenol, polyvinyl alcohol and pullulan, and at least one of the insulating inorganic compound selected from the group consisting of silicon nitride, silicon oxide, silicon carbide and aluminum oxide. The manufacturing method of the organic-semiconductor device of Claim 1 which forms a protective layer.   The method for producing an organic semiconductor device according to claim 1, wherein the protective layer of a single layer or a stacked layer is formed by the organic polymer compound and / or the insulating inorganic compound. The method of manufacturing an organic semiconductor device according to claim 1 , wherein the mask layer is formed by patterning a photoresist layer. The method for manufacturing an organic semiconductor device according to claim 1 , wherein the mask layer is formed by printing.   The method for manufacturing an organic semiconductor device according to claim 1, wherein the organic semiconductor layer is formed of pentacene.   2. The method of manufacturing an organic semiconductor device according to claim 1, wherein an organic field-effect transistor having the patterned organic semiconductor layer at least in a channel portion and having source and drain electrodes in contact with the channel portion is manufactured.

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