JP2010174339A - Method of treating metal surface and method of manufacturing field effect transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of simultaneously carrying out an anodization treatment of metal containing a valve metal and a hydrophobizing treatment of the surface of a formed film and a field effect transistor using the same method. <P>SOLUTION: In the method, a coupling agent having a phosphonic acid group and an organic group is contained in an electrolyte. The coupling agent is expressed by R(OH)2PO (wherein R expresses 1C-20C hydrocarbon, 1C-20C alkyl, aryl, phenyl, ether, a derivative of thiophene, pyrrole or aniline, a derivative having vinyl, epoxy, styryl, methacryloxy, acryloxy, amino, ureido, chloropropyl, mercapto, sulfide or isocyanate). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal surface treatment method for anodizing a metal surface containing a valve metal in an electrolytic solution and a method for manufacturing a field effect transistor.

  Some of the valve metals are used in various industrial fields in various forms. For example, aluminum is used as an electrode of a transistor or a support for a lithographic printing plate. Further, tantalum is used as an electrode of a transistor or an electrode of a capacitor like aluminum.

  A metal oxide film such as aluminum oxide or tantalum oxide is formed on the surface of the valve metal such as aluminum or tantalum by anodic oxidation in an aqueous electrolyte containing sulfuric acid or phosphoric acid. The quality of the metal oxide film thus formed depends on processing parameters such as electrolysis time, electrolysis voltage, current density, electrolyte temperature, and acid concentration. Therefore, the quality of the metal oxide film can be adjusted by selecting these parameters.

  In Patent Document 1, in the formation of the surface layer of aluminum used for printing purposes, the support surface can be made hydrophilic by adding polyvinylphosphonic acid to the aqueous electrolyte, and good printability. Has been reported to be obtained. However, such a method always has the disadvantage that the quality of the printed product and the number of plate-making are lowered due to the precipitation of the polyvinylphosphonic acid / aluminum complex.

  Patent Document 2 discloses a technique for anodizing the surface of aluminum in an aqueous electrolytic solution to which a silane coupling agent is added. According to this method, remarkable hydrophilicity can be imparted to the surface layer, high chemical and physical stability can be obtained, and excellent ink induction characteristics can be obtained during printing.

  In Patent Document 3, a method is proposed in which a surfactant is added to an electrolytic solution for anodizing, and the anode of the electrolytic capacitor is anodized and simultaneously surface-treated.

  In any of the above conventional methods, the oxide layer on the metal surface is made hydrophilic by adding an additive. As a method of treating the surface of the metal oxide layer to be hydrophobic, Non-Patent Document 1 reports a method of treating the surface of the gate insulating film of a transistor using a coupling agent. The surface free energy is reduced by surface treatment using a silane coupling agent having an alkyl group having a high water-repellent effect or an alkyl fluoride group as an organic functional group, and the grain size of the organic semiconductor layer formed thereon By increasing, the boundaries between grains that cause carrier traps are reduced and the mobility is increased.

  However, the above method has a problem that an anodizing process and a process of treating the surface of the metal oxide film formed by the anodizing process are necessary, and the manufacturing process becomes complicated.

European Patent Application No. 048909 Japanese Patent Laid-Open No. 1-188694 JP 2005-175015 A

S. C. Lim, S. H. Kim, J. H. Lee, M. K. Kim, D. J. Kim and T. Zyung, Synthetic Metals, Vol.148, p. 75, 2005

  An object of the present invention is to provide a metal surface treatment method capable of simultaneously performing an anodizing treatment for forming a metal oxide film on the surface and a surface treatment for making the surface of the formed metal oxide film hydrophobic, and the treatment method. It is an object to provide a method of manufacturing a field effect transistor that can manufacture a field effect transistor excellent in mobility, on / off ratio, and subthreshold slope.

  The metal surface treatment method of the present invention is a metal surface treatment method in which a metal surface containing a valve metal is anodized in an electrolyte solution, and a coupling agent having a phosphonic acid group and an organic group is contained in the electrolyte solution. It is characterized by being included.

  According to the present invention, an anodizing treatment for forming a metal oxide film on the surface and a surface treatment for making the surface of the formed metal oxide film hydrophobic can be performed simultaneously.

  Further, according to the present invention, since the anodizing treatment and the surface treatment are performed simultaneously, the surface treatment is performed while applying a voltage to the metal. For this reason, the coupling agent can be present uniformly and in a large amount by reacting the phosphonic acid groups on the surface of the metal oxide film and in the film.

  Examples of the coupling agent used in the present invention include those represented by the following general formula.

  (In the formula, R is a hydrocarbon group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aryl group, a phenyl group, an ether group, a thiophene derivative, a pyrrole derivative, an aniline derivative, a derivative having a vinyl group, Derivatives having epoxy group, derivatives having styryl group, derivatives having methacryloxy group, derivatives having acryloxy group, derivatives having amino group, derivatives having ureido group, derivatives having chloropropyl group, derivatives having mercapto group, sulfide A derivative having a group and a derivative having an isocyanate group.)

  Examples of the derivative having an epoxy group include an epoxycyclohexyl group and a glycidoxypropyl group. Examples of the derivative having an amino group include N-aminoethylaminopropyl group, aminopropyl group, dimethylbutylidene, propylamine group, N-phenylaminopropyl group, N-vinylbenzylaminoethylaminopropyl group and the like. Examples of the derivative having a ureido group include a ureidopropyl group. Examples of the derivative having a mercapto group include a methyl mercaptopropyl group. Examples of the derivative having a sulfide group include a tetrasulfide group. Examples of the derivative having an isocyanate group include an isocyanate propyl group.

  The organic group R is preferably hydrophobic. From such a viewpoint, the organic group R is preferably a hydrocarbon group having 1 to 20 carbon atoms and an alkyl group having 1 to 20 carbon atoms, and more preferably a hydrocarbon having 6 to 18 carbon atoms. And an alkyl group having 6 to 18 carbon atoms.

  The electrolytic solution in the present invention preferably contains water or an aqueous acid solution and a polar solvent. In order to function as an electrolytic solution, it is necessary to include water or an aqueous acid solution. In addition, by including a polar solvent in the electrolytic solution, a coupling agent having a phosphonic acid group and an organic group can be dissolved, and surface treatment that makes the surface of the metal oxide film hydrophobic can be effectively performed. it can. Polar solvents include polar protic solvents and polar aprotic solvents. Examples of the polar protic solvent include acetic acid, 1-butanol, 2-propanol, 1-butanol, 2-propanol (isopropyl alcohol), 1-propanol, ethanol, methanol, formic acid and the like. Examples of polar aprotic solvents include tetrahydrofuran, acetone, acetonitrile, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like. The polar solvent is preferably one having excellent compatibility with water or an acid aqueous solution, and polar protic solvents such as alcohols are preferably used from this viewpoint, and alcohols such as methanol, ethanol and isopropyl alcohol are particularly preferable. Is preferably used. The volume ratio of water or aqueous acid solution to alcohol (water or aqueous acid solution: alcohol) is preferably in the range of 90:10 to 10:90.

  The electronic component of the present invention is manufactured by treating a metal surface by the metal surface treatment method of the present invention.

  Since the electronic component of the present invention is produced by treating a metal surface by the above-described treatment method of the present invention, an anodizing treatment for forming a metal oxide film and a surface for making the surface of the metal oxide film hydrophobic The treatment can be performed at the same time. For this reason, a manufacturing process can be simplified and manufactured.

  Examples of the electronic component include a field effect transistor and an electrolytic capacitor.

  The field effect transistor manufacturing method of the present invention includes a step of forming a gate electrode including at least a valve metal on a substrate on a substrate, and a gate insulating film is formed by treating the surface of the gate electrode by the method of the present invention. A step of forming an organic semiconductor layer on the gate insulating film, and a step of forming a source electrode and a drain electrode for forming a channel region in the organic semiconductor layer on the gate insulating film. It is said.

  According to the field effect transistor manufacturing method of the present invention, the step of anodizing the surface of the gate electrode to form a gate insulating film and the step of surface treatment for making the surface of the gate insulating film hydrophobic are performed simultaneously. Can do. For this reason, a manufacturing process can be simplified.

  In addition, according to the present invention, the anodizing treatment and the surface treatment are simultaneously performed, and the surface treatment is performed in a state where a voltage is applied to the gate electrode. It is attached to the surface of the film. Therefore, characteristics such as mobility, on / off ratio, and subthreshold slope in the field effect transistor can be improved.

  According to the present invention, an anodizing process for forming a metal oxide film on the surface and a surface process for making the surface of the formed metal oxide film hydrophobic can be performed simultaneously. For this reason, a manufacturing process can be simplified.

  The electronic component of the present invention can be manufactured by simplifying the process because the anodizing treatment for forming the metal oxide film on the metal surface and the surface treatment for making the surface of the formed metal oxide film hydrophobic can be performed simultaneously. can do. Further, since the anodic oxidation treatment and the surface treatment are performed at the same time, the coupling agent can be adhered uniformly and in large quantities to the surface of the metal oxide film.

  The field effect transistor manufacturing method of the present invention can simultaneously perform the step of forming the gate insulating film by anodizing the surface of the gate electrode and the surface treatment for making the surface of the gate insulating film hydrophobic. The manufacturing process can be simplified. In addition, since the coupling agent can be adsorbed uniformly and in large amounts on the gate insulating film, the adhesion and adhesion between the semiconductor layer and the gate insulating film are excellent, and the mobility, on / off ratio, and subthreshold are excellent. A field effect transistor having excellent characteristics such as slope can be manufactured.

Typical sectional drawing for demonstrating the processing method of the metal surface in the Example according to this invention. The typical sectional view for explaining the processing method of the metal surface in a comparative example. The figure which shows the relationship between the content rate of the alcohol in electrolyte solution, and the contact angle with respect to the pure water of the metal oxide surface after a process. Sectional drawing which shows the field effect transistor produced in one Example according to this invention. Sectional drawing which shows the field effect transistor produced in the other Example according to this invention. The figure which shows typically the vapor deposition apparatus for forming a source electrode and a drain electrode on a gate insulating film in the Example according to this invention. The figure which shows typically the vapor deposition apparatus for forming a source electrode and a drain electrode on a gate insulating film in the Example according to this invention. The typical sectional view showing the bottom field type horizontal field effect transistor produced in the example according to the present invention. The typical sectional view showing the top contact type horizontal field effect transistor produced in the example according to the present invention.

  Hereinafter, the present invention will be described with reference to specific embodiments, but the present invention is not limited to the following embodiments.

<Metal surface treatment>
FIG. 1 is a schematic cross-sectional view for explaining a metal surface treatment method according to an embodiment of the present invention. As shown in FIG. 1A, an electrode 2 made of a valve metal is provided on a substrate 1. Examples of the valve metal include tantalum, niobium, titanium, aluminum, hafnium, and zirconium. The electrode 2 may be an alloy containing a valve metal as a main component.

  In the present embodiment, the electrode 2 is anodized in an electrolytic solution containing a coupling agent having a phosphonic acid group and an organic group according to the present invention.

  By this anodic oxidation, a metal oxide film 3 is formed on the surface of the electrode 2 by anodic oxidation of the electrode 2 as shown in FIG. Further, the coupling agent layer 4 is formed on the surface of the metal oxide film 3 or in the film by the reaction of the phosphonic acid group of the coupling agent with the metal oxide. In this embodiment, the coupling agent layer 4 is also formed on the substrate 1. By forming such a coupling agent layer 4, hydrophobicity is imparted to the surface of the metal oxide film 3.

  In the present invention, the metal oxide film 3 is formed by anodizing the surface of the electrode 2 and the surface of the formed metal oxide film 3 is surface-treated. Since the voltage is applied to the electrode 2 when the surface treatment is performed with the coupling agent, the coupling agent is adsorbed on the surface of the metal oxide film 3 more uniformly and in a larger amount than the surface treatment by the comparative coupling agent treatment. And the amount of coupling agent adsorbed can be increased. For this reason, compared with the comparative processing method, the hydrophobicity by the coupling agent layer 4 on the surface of the metal oxide film 3 can be improved. In an organic field effect transistor, by treating the surface of the gate electrode according to the present invention, a gate insulating film is formed and a coupling agent layer is adsorbed on the surface of the gate insulating film to make the surface hydrophobic. it can. As a result, the adhesion with the organic semiconductor layer provided on the gate insulating film can be improved and the crystal growth of the organic semiconductor can be promoted, and the mobility, on / off ratio, subthreshold of the organic field effect transistor can be promoted. Characteristics such as slope can be improved.

  Further, the surface of the anode of the solid electrolytic capacitor is anodized by the treatment method of the present invention, thereby forming a dielectric layer on the surface of the anode and adsorbing the coupling agent layer on the surface of the dielectric layer to make the surface hydrophobic. Can increase the sex. In general, since a conductive polymer layer and a cathode layer are laminated on a dielectric layer, a hydrophobic coupling agent layer is formed on the surface of the dielectric layer. Adhesion with the polymer layer can be enhanced, and a coupling agent layer can be present in the defective portion of the dielectric layer, so that insulation between the anode and the conductive polymer layer can be enhanced. . For this reason, the leakage current in a solid electrolytic capacitor can be reduced.

  As described above, according to the present embodiment, the metal oxide film 3 is formed on the surface of the electrode 2 by anodic oxidation, and at the same time, the coupling agent layer 4 is formed on the surface of the metal oxide film 3. The surface can be made hydrophobic. Therefore, the anodizing process for forming the metal oxide film 3 and the surface process for making the surface of the formed metal oxide film 3 hydrophobic can be performed simultaneously.

  FIG. 2 is a cross-sectional view showing a comparative metal surface treatment method. As shown in FIG. 2A, an electrode 2 made of a valve metal is provided on a substrate 1.

  By performing anodic oxidation in an electrolytic solution not containing a coupling agent, a metal oxide film 3 is formed on the surface of the electrode 2 as shown in FIG.

  Next, the coupling agent layer is adsorbed on the surface of the metal oxide 3 by adhering the solution containing the coupling agent to the metal oxide 3 by immersing it in a solution containing the coupling agent. 4 is formed.

  According to the comparative metal surface treatment method shown in FIG. 2, as described above, the anodizing treatment for forming the metal oxide film 3 and the coupling agent layer are adsorbed on the surface of the metal oxide film 3 to make it hydrophobic. It is necessary to perform the surface treatment as a separate process.

Example 1
As shown in FIG. 1A, an electrode 2 was formed on a substrate 1. As the substrate 1, a glass substrate was used. As the electrode 2, an electrode made of tantalum was formed. The electrode 2 was formed in a rectangular parallelepiped shape having a length of 1.5 cm × width 1.5 cm × height 0.7 cm.

  As an electrolytic solution for anodizing, octadecylphosphone as a coupling agent is mixed in a mixed solvent in which isopropyl alcohol and ultrapure water are mixed in a volume ratio (isopropyl alcohol: superpure water) at a ratio of 50:50. An electrolytic solution containing 0.5 mmol / liter of acid was used. Octadecylphosphonic acid was dissolved in isopropyl alcohol and added.

  The electrode 2 was anodized using the above electrolytic solution. Specifically, the anode 2 was immersed in an electrolytic solution at 25 ° C., a constant voltage of 36 V was applied to the anode 2, and anodization was performed for 20 minutes.

  Thereafter, it was washed with isopropyl alcohol and dried at 60 ° C. for 10 minutes.

(Examples 2 to 5)
As a solvent used in the electrolytic solution, the volume ratio of isopropyl alcohol to ultrapure water (isopropyl alcohol: ultrapure water) is 90:10 (Example 2), 70:30 (Example 3), and 30:70 (implementation). Example 4) The electrode 2 was anodized in the same manner as in Example 1 except that 10:90 (Example 5) was used. The content of octadecylphosphonic acid was 0.5 mmol / liter in all cases, and octadecylphosphonic acid was dissolved in isopropyl alcohol to prepare an electrolytic solution.

(Comparative Example 1)
The volume ratio of isopropyl alcohol to ultrapure water (isopropyl alcohol: ultrapure water) was set to 100: 0. That is, anodization was performed using a solution in which octadecylphosphonic acid was dissolved only in isopropyl alcohol. Since no water is contained in the solution, the phosphonic acid group of the coupling agent is not dissociated and is not an electrolyte solution.

(Comparative Example 2)
The electrode 2 was treated in the same manner as in the above example except that the volume ratio of isopropyl alcohol to ultrapure water in the electrolyte solution (isopropyl alcohol: superpure water) was set to 0: 100. Therefore, the electrolyte contained no alcohol, and octadecylphosphonic acid was emulsified or suspended in a state separated from water.

(Example 6)
An electrode 2 made of aluminum instead of tantalum was formed on the glass substrate 1. Further, as an electrolytic solution, isopropyl alcohol and 0.1 wt% phosphoric acid aqueous solution are mixed so as to have a volume ratio (50:50), and octadecylphosphonic acid is contained so as to be 0.5 mmol / liter. The electrolyte solution was used. Octadecylphosphonic acid was previously dissolved in isopropyl alcohol, and an isopropyl alcohol solution in which octadecylphosphonic acid was dissolved was mixed with a phosphoric acid aqueous solution to prepare an electrolyte solution. Note that the 0.1 wt% phosphoric acid aqueous solution is used because an electrolytic solution in which isopropyl alcohol and pure water are mixed and octadecylphosphonic acid is contained can anodize aluminum. Because there was not.

  Except for the above, anodization was performed in the same manner as in Example 1.

(Examples 7 to 9)
Isopropyl alcohol and 0.1 wt% phosphoric acid aqueous solution in a volume ratio (isopropyl alcohol: phosphoric acid aqueous solution) at 70:30 (Example 7), 30:70 (Example 8), 10:90 (Example) Except for 9), the electrode 2 was anodized in the same manner as in Example 6 above.

(Comparative Example 3)
Isopropyl alcohol and 0.1% by weight phosphoric acid aqueous solution in a volume ratio (isopropyl alcohol: phosphoric acid aqueous solution) to be 100: 0, that is, octadecylphosphonic acid is added to isopropyl alcohol alone at 0.5 mmol / liter. The electrode 2 was anodized in the same manner as in Example 6 except that the solution so dissolved was used for anodization.

(Comparative Example 4)
The volume ratio of isopropyl alcohol and 0.1 wt% phosphoric acid aqueous solution (isopropyl alcohol: phosphoric acid aqueous solution) is 0: 100, that is, octadecylphosphonic acid is added to only 0.1 wt% phosphoric acid aqueous solution. The electrode 2 was anodized in the same manner as in Example 6 except that anodization was performed using a solution added to a concentration of 0.5 mmol / liter.

(Measurement of contact angle)
The contact angle with respect to the pure water of the surface of the electrode 2 processed in Examples 1-9 and Comparative Examples 1-4 was measured.

  FIG. 3 is a diagram showing the relationship between the measurement result for the contact angle with respect to pure water and the alcohol content (volume%) in the solution used for anodization. As is apparent from FIG. 3, the alcohol content in the electrolytic solution is preferably in the range of 10 to 90% by volume, and more preferably in the range of 20 to 80% by volume.

  In FIG. 3, ◇ indicates Examples 1 to 5 and Comparative Examples 1 and 2 in which electrodes made of tantalum were anodized, and Δ represents Examples 6 to 9 and Comparative Example 3 in which electrodes made of aluminum were treated. ~ 4 are shown.

[Evaluation of anodizing treatment]
About Examples 1-5 and Comparative Examples 1-2, it evaluated about whether the anodic oxidation process was made | formed. Evaluation of the anodizing treatment was performed because tantalum was colored when anodized. Evaluation was made according to the following criteria.

◯: The surface of tantalum is colored.
X: The surface of tantalum is not colored.

  The evaluation results are shown in Table 1.

  Further, Examples 6 to 9 and Comparative Examples 3 to 4 which were anodized with respect to aluminum were similarly evaluated. In the case of aluminum, when anodized, the surface becomes whitish.

◯: The surface of aluminum is whitish.
X: The surface of aluminum is not whitish.

  The evaluation results are shown in Table 2.

  As shown in Tables 1 and 2, the anodic oxidation treatment was performed in Examples 1 to 9 and Comparative Example 4, but the anodic oxidation treatment was not performed in Comparative Examples 1 to 3.

  The reason why Comparative Example 1 was not anodized was probably because the coupling agent that seems to contribute to the anodizing treatment was not sufficiently dissolved in the aqueous solution. It is considered that Comparative Examples 2 and 3 did not function as an electrolyte solution because they contained almost no water.

<Analysis of metal oxide film surface by XPS>
(Example 10)
In Example 1, the electrode 2 was anodized in the same manner as in Example 1 except that the voltage application time for forming the anodic oxide film was 60 minutes.

(Example 11)
In Example 1, a 0.1 wt% phosphoric acid aqueous solution was used instead of ultrapure water, and the voltage application time for forming the anodic oxide film was set to 60 minutes. 2 was anodized.

Example 12
In Example 6, the electrode 2 was anodized in the same manner as in Example 6 except that the voltage application time for forming the anodic oxide film was 60 minutes.

(Comparative Example 5)
Anodization was performed in the same manner as in Example 1 except that the electrode 2 was anodized using a 0.1 wt% phosphoric acid aqueous solution containing no octadecylphosphonic acid (ODPA) as an electrolyte.

(Comparative Example 6)
After anodizing in the same manner as in Comparative Example 5, it was immersed in an isopropyl alcohol solution at 25 ° C. containing 0.5 mmol / liter of octadecylphosphonic acid (ODPA) for 1 hour, then pulled up, washed with isopropyl alcohol, and 60 A surface treatment for attaching ODPA was performed by heat treatment at 10 ° C. for 10 minutes.

(Comparative Example 7)
Anodization was performed in the same manner as in Example 6 except that the electrode 2 was anodized using a 0.1 wt% phosphoric acid aqueous solution containing no octadecylphosphonic acid (ODPA) as an electrolyte.

(Comparative Example 8)
After anodizing in the same manner as in Comparative Example 7, it was immersed in an isopropyl alcohol solution at 25 ° C. containing 0.5 mmol / liter of octadecylphosphonic acid (ODPA) for 1 hour, then pulled up, washed with isopropyl alcohol, and 60 A surface treatment for attaching ODPA was performed by heat treatment at 10 ° C. for 10 minutes.

  The surface of the metal oxide film of the electrode obtained as described above was analyzed by XPS.

  Tables 3 and 4 show the C (carbon) count (C1s), O (oxygen) count (O1s), P (phosphorus) count (P2s), and Al (aluminum) obtained by XPS analysis. Count number (Al2p) and Ta (thallium) count number (Ta4f).

  “O / Ta” and “P / Ta” shown in Table 3 are values of O1s and P2p with respect to Ta4f, respectively.

  Further, “O / Al” and “P / Al” shown in Table 4 are values of O1s and P2s with respect to Al2p, respectively. Table 3 also shows the results of the anodized electrode in Example 6.

As shown in Table 3, in Example 10 and Example 11, and Comparative Example 5 and Comparative Example 6, the value of O / Ta is O / Ta calculated from Ta ₂ O ₅ which is a Ta oxide film composition. It is about the same as 2.5 or higher. Therefore, it can be seen that the surface of Ta is anodized and a metal oxide film is formed.

Similarly, in Table 4, the value of O / Al is higher than O / Al = 1.5 in Al ₂ O ₃ which is the oxidation number of Al. Therefore, it can be seen that in Examples 6 and 12, and Comparative Examples 7 and 8, the surface of Al was oxidized to form a metal oxide film.

  In Table 3, the ratio of Ta and O is less in Example 10 and Example 11 than in Comparative Example 6 in which the anodizing treatment and the surface treatment for hydrophobization were sequentially performed, and instead of this, the proportion of C Has increased. Therefore, by simultaneously performing the anodizing treatment and the surface treatment for hydrophobization according to the present invention, the amount of ODPA adsorbed increases, and the surface of the tantalum metal oxide film is covered more with the alkyl groups of ODPA. You can see that

  Further, as is apparent from Table 4, Examples 6 and 12 in which the anodizing treatment and the surface treatment for hydrophobizing were simultaneously performed according to the present invention were performed in the order of the anodizing treatment and the surface treatment for hydrophobizing. It can be seen that the proportion of Al and O is reduced compared to the comparative example 8 performed, and the proportion of C is increased instead. From this, according to the present invention, the amount of ODPA adsorbed can be increased by simultaneously performing anodization treatment and surface treatment for hydrophobization, and the surface of the aluminum metal oxide film is formed by the alkyl group of ODPA. It can be seen that more is coated.

<Vertical organic field effect transistor>
FIG. 4 is a schematic diagram showing a vertical organic field effect transistor according to an embodiment of the present invention.

  As shown in FIG. 4, a gate electrode 12 made of a valve metal is formed on an insulating substrate 11. In the present embodiment, the gate electrode 12 is made of aluminum. The gate electrode 12 has a height of 0.5 μm and a width of 10 μm.

  The gate electrode 12 is made of an oxide of aluminum on the side surfaces 12a and 12b and the upper surface 12c by anodizing with an electrolyte containing a coupling agent having a phosphonic acid group and an organic group in accordance with the present embodiment. A first gate oxide film 13 is formed. Furthermore, a second gate insulating film 14 is formed on the first gate insulating film 13. The second insulating film 14 is also formed on the substrate 11 on both sides of the gate electrode 12. The second gate insulating film 14 is an insulating film formed mainly by adsorbing a coupling agent.

  A first electrode 15 is formed on the second gate insulating film 14 on the upper surface 12 c of the electrode 12. A second electrode 16 is formed on the second gate insulating film 14 on the substrate 11 on one side of the gate electrode 12. A third electrode 17 is formed on the second gate insulating film 14 of the substrate 11 on the other side of the gate electrode 12. An organic semiconductor layer 18 is formed on the first electrode 15, the second electrode 16, the third electrode 17, and the second gate insulating film 14 corresponding to the side surfaces 12 a and 12 b of the gate electrode 12. Yes.

  In the organic field effect transistor shown in FIG. 4, the first electrode 15 is a floating electrode, the second electrode 16 is one of the source / drain electrodes, and the third electrode 17 is the other of the source / drain electrodes. The channel region is formed between the end 15b of the first electrode 15 and the end 16a of the second electrode 16 and between the end 15a of the first electrode 15 and the end 17a of the third electrode 17. Thus, an organic field effect transistor can be formed.

  As the organic material for forming the organic semiconductor layer in the present invention, a material having an electron accepting function (n-type semiconductor) and a material having an electron donating function (p-type semiconductor) can be used. For example, the materials exemplified below can be used.

  Examples of the material having an electron-accepting function include oligomers and polymers having pyridine and derivatives thereof as skeletons, oligomers and polymers having quinoline and derivatives thereof as skeletons, ladder polymers using benzophenanthrolines and derivatives thereof, cyano -Low polymers such as polyphenylene vinylene, fluorinated metal-free phthalocyanines, fluorinated metal phthalocyanines and derivatives thereof, perylene and derivatives thereof (PTCDA, PTCDI, etc.), naphthalene derivatives (NTCDA, NTCDI, etc.), bathocuproin and derivatives thereof Molecular organic compounds can be used. In addition, since a material obtained by substituting a fluorine group for a material having an electron donating function exhibits an electron accepting property, a material into which these fluorine groups are introduced can also be used.

  Materials having an electron-donating function include oligomers and polymers having thiophene and its derivatives in the skeleton, oligomers and polymers having phenylene-vinylene and its derivatives in the skeleton, oligomers and polymers having fluorene and its derivatives in the skeleton, benzofuran, and Oligomers and polymers having derivatives as skeletons, oligomers and polymers having thienylene-vinylene and derivatives thereof as skeletons, oligomers and polymers having aromatic tertiary amines such as triphenylamine and derivatives thereof, and carbazole and derivatives thereof Oligomers and polymers with skeletons, oligomers and polymers with skeletons of vinylcarbazole and its derivatives, oligomers and polymers with pyrrole and its derivatives, acetylene and its derivatives Oligomers and polymers having a skeleton, oligomers and polymers having a skeleton of isothiaphene and its derivatives, polymers such as oligomers and polymers having a skeleton of heptadiene and its derivatives, metal-free phthalocyanines, metal phthalocyanines and their derivatives, diamines , Phenyldiamines and derivatives thereof, acenes such as rubrene and pentacene and derivatives thereof, porphyrin, tetramethylporphyrin, tetraphenylporphyrin, tetrabenzporphyrin, monoazotetrabenzporphyrin, diazotetrabenzporphine, triazotetrabenzporphyrin , Octaethylporphyrin, octaalkylthioporphyrazine, octaalkylaminoporphyrazine, hemiporphyrazine, chlorophyll, etc. Low molecular organic compounds such as metal porphyrins, metal porphyrins and derivatives thereof, cyanine dyes, merocyanine dyes, squarylium dyes, quinacridone dyes, azo dyes, anthraquinones, benzoquinones, naphthoquinones, and other quinone dyes can be used. As the central metal of metal phthalocyanine and metal porphyrin, magnesium, zinc, copper, silver, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tin, platinum, lead and other metals, metal oxides, Metal halides can be used.

  As the organic semiconductor layer, the above material may be used alone, or a material obtained by dispersing and mixing the above material in an appropriate binder material may be used. Moreover, you may use the material which incorporated the said low molecular weight organic compound in the principal chain or side chain of a suitable high molecular organic compound. Examples of the binder organic material or the high molecular organic compound as the main chain include polycarbonate resin, polyvinyl acetal resin, polyvinyl phenol resin, polyester resin, modified ether type polyester resin, polyarylate resin, phenoxy resin, polyvinyl chloride resin, and polyacetic acid. Vinyl resin, polyvinylidene chloride resin, polystyrene resin, acrylic resin, methacrylic resin, cellulose resin, urea resin, polyurethane resin, silicone resin, epoxy resin, polyamide resin, polyacrylamide resin, polyvinyl alcohol resin, and their copolymers Or a crosslinked product, or a photoconductive polymer such as polyvinyl carbazole or polysilane.

  Depending on the material constituting the organic semiconductor layer, the organic semiconductor layer can be formed by physical vapor deposition (PVD method) exemplified by vacuum deposition or sputtering, various chemical vapor deposition methods ( CVD method), spin coating method; printing method such as screen printing method and ink jet printing method; air doctor coater method, blade coater method, rod coater method, knife coater method, squeeze coater method, reverse roll coater method, transfer roll coater method And various coating methods such as gravure coater method, kiss coater method, cast coater method, spray coater method, slit orifice coater method, calendar coater method, dipping method, spray method and the like.

  The first electrode, the second electrode, and the third electrode can be formed of a conductive material, for example, platinum, gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium , Palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin oxide / antimony, indium tin oxide (ITO), fluorine doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon Paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesi Chrome / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, lithium / aluminum mixture, etc. are used, and platinum, gold, silver, copper, aluminum, indium, ITO and carbon are particularly preferable. . Alternatively, a known conductive polymer whose conductivity is improved by doping or the like, for example, conductive polyaniline, conductive polypyrrole, conductive polythiophene, a complex of polyethylenedioxythiophene and polystyrenesulfonic acid, or the like is also preferably used.

  In addition, as a method of forming these electrodes, a combination of a PVD method and an etching technique exemplified in a vacuum deposition method and a sputtering method, a combination of various CVD methods and an etching technology, a spin coating method and an etching technology are included. A combination, a printing method such as a screen printing method and an ink jet printing method using a conductive paste and a solution of various conductive polymers described above, a lift-off method, a shadow mask method, a combination of the various coating methods described above and an etching technique, and A combination of spraying and etching techniques can be mentioned.

  FIG. 5 is a schematic cross-sectional view showing an organic field effect transistor of another embodiment according to the present invention.

  In the present embodiment, as shown in FIG. 5, the second electrode 16 is formed so as to extend onto the second gate insulating film 14 on the upper surface 12 c of the gate electrode 12. Therefore, in the present embodiment, the first electrode 15 used as the gate electrode is not formed. Other configurations are formed in the same manner as the embodiment shown in FIG.

  In the present embodiment, the second electrode 16 is used as one of the source / drain electrodes, and the third electrode 17 is used as the other of the source / drain electrodes. The organic field effect transistor 10 is configured with a channel region between the electrode 17 and the end 17a.

(Example 13)
The organic field effect transistor shown in FIG. 4 was produced.

  A gate electrode 12 made of aluminum was formed on the insulating substrate 11. As described above, the gate electrode 12 has a height of 0.5 μm and a width of 10 μm. The gate electrode 12 was formed by depositing aluminum on the insulating substrate 11 by vapor deposition or sputtering, forming a mask with a resist film, and patterning by wet etching.

  Next, anodizing treatment was performed according to the present invention using the gate electrode 12 as an anode. The electrolyte used was a mixture of isopropyl alcohol and 0.1 wt% phosphoric acid aqueous solution in a volume ratio (isopropyl alcohol: phosphoric acid aqueous solution) of 50:50. A coupling agent, octadecylphosphonic acid (ODPA), was contained in the electrolyte so as to be 0.5 mmol / liter. ODPA was added by dissolving in isopropyl alcohol.

  Using this electrolytic solution, anodization treatment was performed for 20 minutes at an applied voltage of 36 V using the gate electrode 12 as an anode. Thereafter, the gate electrode 12 was taken out from the electrolytic solution, washed with isopropyl alcohol, and dried at 60 ° C. for 10 minutes. By this anodic oxidation treatment, a first gate insulating film 13 and a second gate insulating film 14 were formed on the gate insulating film 12.

  Next, gold was formed on the side surfaces 12a and 12b and the upper surface 12c of the gate electrode 12 and the second insulating film 14 on the substrate 11 on both sides of the gate electrode 12 so as to have a film thickness of 80 nm by vacuum deposition. . The film was formed using a mask so that the channel width was 3 mm.

  Since it is necessary to deposit gold also on the second insulating film 14 on the side surfaces 12a and 12b of the gate electrode 12, gold was deposited using the vacuum deposition apparatus shown in FIG. 6 or FIG.

  In the vacuum vapor deposition apparatus shown in FIG. 6, a vapor deposition source 21 is disclosed in the vapor deposition chamber 20, and the substrate 11 is installed in an inclined state. By installing the vapor deposition source 21 at a location away from the center of the substrate 11, the side surface of the gate electrode 12 on the vapor deposition source 21 and the substrate 11 becomes an angle close to vertical, and film formation is possible on the side surface of the gate electrode 12. . The angle can also be set by shortening the distance between the substrate 11 and the vapor deposition source 21.

  In the vacuum deposition apparatus shown in FIG. 7, a deposition source 21 is disposed in the vacuum chamber 20, the substrate 11 is installed in the horizontal direction, and deposition is performed while rotating the substrate 11. By controlling the distance between the evaporation source 21 and the substrate 11 and the position of the evaporation source 21, a film can be formed on the side surface of the gate electrode 12.

  Returning to FIG. 4, the subsequent steps will be described. The film deposited on the second gate insulating film on the side surfaces 12a and 12b of the gate electrode 12 is removed by wet etching. As an etchant solution, a trade name “AURUM302” manufactured by Kanto Chemical Co., Inc. was used. The first electrode 15, the second electrode 16, and the third electrode 17 are formed by removing the gold thin film attached to the second gate insulating film 14 on the side surfaces 12a and 12b of the gate electrode 12 by etching. Is done.

  Next, a semiconductor layer 18 is formed so as to cover the first electrode 15, the second electrode 16, the third electrode 17, and the second gate insulating film 14 on the side surfaces 12 a and 12 b of the gate electrode 12. To do. The semiconductor layer 18 was formed by vacuum deposition using pentacene and rotating the substrate 11 to a film thickness of 120 nm. The semiconductor layer 18 can be formed using the vacuum evaporation apparatus shown in FIGS.

(Comparative Example 9)
Anodization of the gate electrode 12 was performed using a 0.1 wt% phosphoric acid aqueous solution not containing ODPA. Thereafter, the first gate insulating film 13 was formed by washing with pure water for 1 hour. Next, after immersing in an isopropyl alcohol solution containing 0.5 mmol / liter of ODPA for 1 hour, the first gate insulation is pulled up, washed with isopropyl alcohol, and heat-treated at 60 ° C. for 10 minutes. A second gate insulating film 14 was formed on the film 13.

  An organic field effect transistor was fabricated in the same manner as in Example 13 except for the above treatment.

[Evaluation of transistor characteristics]
The transistor characteristics of the organic field effect transistors fabricated in Example 13 and Comparative Example 9 were evaluated. The evaluation results are shown in Table 5.

  As shown in Table 5, the organic field effect transistor of Example 13 manufactured according to the present invention was improved by increasing the on / off ratio by about 3.4 times compared to the organic field effect transistor of Comparative Example 9. Further, the organic field effect transistor of Example 13 had the same mobility as the organic field effect transistor of Comparative Example 9, but the threshold voltage (Vth) and subthreshold slope (SS) were improved. .

  From the above, by forming the gate insulating film by anodizing the gate electrode according to the present invention, the manufacturing process can be simplified, and an organic electric field excellent in mobility, on / off ratio, and subthreshold slope can be obtained. It can be seen that an effect transistor is obtained.

<Horizontal organic field effect transistor>
FIG. 8 is a cross-sectional view illustrating a lateral organic field effect transistor according to an embodiment of the present invention. The lateral organic field effect transistor shown in FIG. 8 is a bottom contact transistor.

  As shown in FIG. 8, a gate electrode 32 made of a valve metal is formed on the insulating substrate 31. In the present embodiment, the gate electrode 32 is made of aluminum, and has a height of 1.0 μm and a width of 10 μm.

  By anodizing the gate electrode 32 according to the present invention, a first gate insulating film 33 is formed on the surface of the gate electrode 32, and a second gate insulating film 34 is formed on the first gate insulating film 33. Is formed. The first gate insulating film 33 is a metal oxide film formed by oxidizing the surface of the gate electrode 32. The second gate insulating film 34 is an insulating film formed by adsorption of a coupling agent.

  A first source / drain electrode 36 and a second source / drain electrode 37 are provided on the second gate insulating film 34, and an end portion 36 a of the first source / drain electrode 36, A channel region is formed between the two source / drain electrodes 37 and the end 37a.

  An organic semiconductor layer 38 is formed so as to cover the first source / drain electrode 36 and the second source / drain electrode 37 and between them.

  FIG. 9 is a schematic cross-sectional view showing a top contact type horizontal organic field effect transistor.

  In the present embodiment, similarly to the embodiment shown in FIG. 8, a gate electrode 32 is formed on a substrate 31, and the first gate insulating film is formed on the gate electrode 32 by anodic oxidation according to the present invention. 33 and a second gate insulating film 34 are formed.

  An organic semiconductor layer 38 is formed on the second gate insulating film 34. A first source / drain electrode 36 and a second source / drain electrode 37 are formed on the organic semiconductor layer 38 at a predetermined distance. A channel region is formed between the end portion 36 a of the first source / drain electrode 36 and the end portion 37 a of the second source / drain electrode 37.

(Example 14)
The bottom contact type horizontal organic field effect transistor shown in FIG. 8 was produced as follows.

  A gate electrode 32 (height: 1.0 μm, width: 10 μm) made of aluminum was formed on the insulating substrate 31. The gate electrode 32 was formed of aluminum by a vapor deposition method or a sputtering method. Thereafter, using the resist film as a mask, patterning was performed by wet etching to form the gate electrode 32.

  Anodization was performed according to the present invention using the gate electrode 32 as an anode. As the electrolytic solution, a mixture of isopropyl alcohol and 1 wt% phosphoric acid aqueous solution in a volume ratio (isopropyl alcohol: phosphoric acid aqueous solution) of 50:50 was used, and octadecylphosphonic acid (ODPA) was 0. It was contained so as to be 5 mmol / liter. Using this electrolytic solution, the gate electrode 32 was anodized at an applied voltage of 36 V for 20 minutes. Thereafter, the first gate insulating film 33 and the second gate insulating film 34 were formed on the gate electrode 32 by washing with isopropyl alcohol and drying at 60 ° C. for 10 minutes.

  Next, gold was deposited on the second gate insulating film 34 by vacuum deposition so as to have a thickness of 80 nm. During film formation, a first source / drain electrode 36 and a second source / drain electrode 37 were formed using a mask so that the channel width was 3 mm and the channel length was 0.1 mm.

  Next, the organic semiconductor layer 7 was formed so as to cover the first source / drain electrode and the second source / drain electrode 37 and the portion between them. The organic semiconductor layer 7 was formed by vacuum vapor deposition using pentacene so as to have a film thickness of 120 nm.

  As described above, the lateral field effect transistor of this embodiment was manufactured.

(Comparative Example 10)
In the same manner as in Example 14, after forming the gate electrode 32 on the substrate 31, anodization was performed in the same manner as described above using a 0.1 wt% phosphoric acid aqueous solution not containing ODPA as the electrolytic solution. Then, the first gate insulating film 33 was formed. Thereafter, running water was washed with pure water for 1 hour.

  Next, the gate electrode 32 on which the first gate insulating film 33 is formed is immersed in an isopropyl alcohol solution containing 0.5 mmol / liter of ODPA for 1 hour, and then pulled up and washed with isopropyl alcohol. Heat treatment was performed at 60 ° C. for 10 minutes, and a second gate insulating film 34 was formed on the first gate insulating film 33.

  Except for the above, a horizontal organic field effect transistor was produced in the same manner as in Example 14.

[Evaluation of transistor characteristics]
The transistor characteristics of the lateral field effect transistors of Example 14 and Comparative Example 10 were evaluated. The evaluation results are shown in Table 6.

  As shown in Table 6, the mobility of the field effect transistor of Example 14 manufactured according to the present invention and the field effect transistor of Comparative Example 10 were approximately the same, but the on / off ratio and the subthreshold slope (SS) ), Example 14 was superior.

  As for the output characteristics, Example 14 showed better saturation characteristics and rising at the same driving voltage.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Electrode 3 ... Metal oxide film 4 ... Coupling agent layer 10 ... Vertical organic field effect transistor 11 ... Insulating substrate 12 ... Gate electrode 12a, 12b ... Side surface of gate electrode 12c ... Upper surface of gate electrode 13 ... 1st gate insulating film 14 ... 2nd gate insulating film 15 ... 1st electrode 16 ... 2nd electrode 17 ... 3rd electrode 18 ... Organic-semiconductor layer 20 ... Deposition chamber 21 ... Deposition source 31 ... Substrate 32 ... Gate electrode 33 ... first gate insulating film 34 ... second gate insulating film 36 ... first source / drain electrode 37 ... second source / drain electrode 38 ... organic semiconductor layer

Claims (5)

A metal surface treatment method for anodizing a metal surface including a valve metal in an electrolyte solution,
A method for treating a metal surface, wherein the electrolyte contains a coupling agent having a phosphonic acid group and an organic group. The method for treating a metal surface according to claim 1, wherein the coupling agent is represented by the following general formula.

(In the formula, R is a hydrocarbon group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aryl group, a phenyl group, an ether group, a thiophene derivative, a pyrrole derivative, an aniline derivative, a derivative having a vinyl group, Derivatives having epoxy group, derivatives having styryl group, derivatives having methacryloxy group, derivatives having acryloxy group, derivatives having amino group, derivatives having ureido group, derivatives having chloropropyl group, derivatives having mercapto group, sulfide A derivative having a group and a derivative having an isocyanate group.)   The method for treating a metal surface according to claim 1 or 2, wherein the electrolytic solution contains water or an acid aqueous solution and alcohol.   An electronic component produced by treating a metal surface by the method according to claim 1. A method of manufacturing a field effect transistor comprising:
Forming a gate electrode on the substrate at least on the surface of which contains the valve metal;
Forming a gate insulating film by treating the surface of the gate electrode with the method according to claim 1;
Forming an organic semiconductor layer on the gate insulating film;
Forming a source electrode and a drain electrode for forming a channel region in the organic semiconductor layer on the gate insulating film.

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