JPH0240742B2 - KODODENSEIHAKUMAKUSEIZOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a highly conductive thin film using an organic indium compound, an organic tin compound, or an organic indium compound. (Prior art and its problems) Highly conductive thin film manufacturing methods can be roughly divided into two types: solution methods and non-solution methods. Non-solution methods include physical methods such as vapor deposition or sputtering, and so-called CVD (chemical vapor deposition). Although it is possible to produce highly conductive (low resistance) thin films using such non-solution methods, either method requires a high vacuum system or precise atmosphere control, and requires special electromagnetic energy conversion equipment. As a result, the manufacturing equipment becomes complicated and large, and the equipment is cumbersome, which inevitably increases the manufacturing cost. Furthermore, it has been difficult to increase the area of the conductive film or to form a film with a complicated shape. Solution methods include chemical methods such as spray methods, dip methods, and coating methods. Among the chemical methods mentioned above, the spray method and the so-called CVD method have poor efficiency in using the film raw material, which is a metal component, and it has been difficult to control the film forming conditions. In addition, the dip method and conventional coating method do not require vacuum equipment and are simple, but the electrical properties of the conductive film (low resistance,
There was a problem that the high conductivity was poor. (Means for Solving the Problems) The present inventors have conducted intensive research to solve the above problems and to develop a method for easily manufacturing highly conductive thin films, which have one or more metal-oxygen bonds. The present invention was achieved by applying a p-xylene solution containing an organic indium compound as a main solute onto a substrate and then heating and baking the solution. That is, the present invention comprises 2 to 10% by weight of an organic indium compound having at least one indium-carbon bond and further having at least one indium-oxygen bond, and an organic indium compound having at least one tin-oxygen bond. A solvent solution containing 0 to 0.5% by weight of a tin compound is used as a coating solution, the coating solution is uniformly applied onto a substrate, the substrate is heated and dried to evaporate the solvent, and a film is formed. In the air atmosphere,
The present invention relates to a highly conductive thin film production method characterized by thermally decomposing an organometallic compound containing the above-mentioned organic indium compound as a main component by heating and baking at a temperature of 300 to 600°C. The present invention will be explained below based on the configuration. The organic indium compound used in the present invention is synthesized by mixing and stirring easily available trialkylindium and the corresponding oxygen-containing bond in ether. In the present invention, the trialkylindium that can be used in the synthesis of organic indium compounds has the formula R ₃ In (R in the formula is CH ₃ , CH ₃ CH ₂ , CH ₃ CH ₂ CH ₂ ,
It is represented by a saturated straight-chain alkyl group such as CH ₃ CH ₂ CH ₂ CH ₂ , a branched alkyl group, or an aralkyl group such as benzyl. In general, trialkylindium with fewer carbon atoms has higher reactivity with oxygen-containing compounds, so it is easier to synthesize the organic indium compound R ₂ InX ₂ .
Similarly, trialkylindium having fewer carbon atoms generally has a property that it is more effective because the effective In content in R ₂ InX or RInX ₂ becomes higher. However, small alkyl derivatives such as CH ₃ and CH ₃ CH ₂ have low stability and are difficult to handle. Therefore, butyl group, i.e. 4 carbon atoms
The alkyl group is preferred. For example, the synthesis of R ₃ In described above can be carried out by F. Pung, D.
F. Pung, W. Zimmermann, H. Pfeiffer and I.
Pfeiffer et al., Z.anorg.allgem.Chem 267 , 39
(1951), and is represented by the following general formula: Incl ₃ 6RMgCl --------→ R ₃ In (1). In the present invention, the oxygen-containing compounds that can be used in the synthesis of organic indium compounds include formula HX (where X is alcohols (X=R'O), phenols (X=
R′=O), carboxylic acids (X=R′COO), 1,
3-diketones, etc.). For alcohols (X=R′O), R′ is C ₁ to _{C 6}
Those representing alkyl or aralkyl groups are used, such as methanol, ethanol, isopropanol, tert-butanol, allyl alcohol,
There are hexyl alcohols, etc., but alcohols with a carbon number of about R′ = C ₁ to C ₃ can be synthesized.
Since the stability of Bu ₂ InX is low, it is preferable to use one having a carbon number of R′≧C ₄ . As the phenols (X=R'O), those in which R' represents a phenyl group, an alkyl-substituted phenyl group, a naphthyl group, or an aromatic hydrocarbon group are used. For carboxylic acids (X=R′COO), R′ is C ₁
Those representing ~ _C7 or ~ _C12 alkyl groups (including branched and unsaturated groups) or aryl groups (aromatic hydrocarbon groups) are used, such as acetic acid, propionic acid, benzoic acid, oxalic acid, tartaric acid, acrylic acid, etc. There are acids etc. 1,3-ditokenes (

[Formula], etc.) are carbonyl compounds that tend to form enolates, such as acetylacetone,
and its derivatives. Organic indium compound (BuInX or BuInX ₂ )
Regarding the synthesis of
and ALPickard et al., J.Organoment.Chem. 8 , 427
(1967)], and the reaction formula is shown as R ₃ In+HX→R ₂ InX+H (2) R ₃ In+2HX→RInX ₂ +2H (3). The mixing ratio of tributylindium and oxygen-containing compound is 1:1 or 1:2; in the former case, Bu _{2 InX is produced by the reaction shown in equation (2), and in the latter case, Bu 2} InX is produced by the reaction shown in equation (3). BuInX ₂ is obtained. Organic indium compounds are n in R _o InX _(3-o)
=1 or 2. When n=0, that is, InX ₃ , organic metal salts (so-called indium trialkoxide (In(OR) ₃ ), indium triacylate (In(O ₂ CR) ₃ ), indium trisacetylacetonate (In(acac) ₃ ) and other metal organics). Organometallic salts (metal organics) are metal compounds containing organic residues and do not have a direct metal-carbon bond, but the organoindium compounds used in the present invention are organometallic compounds. It is a metal compound having at least one metal-carbon bond. n=
3, that is, R ₃ I _o , MOCVD (metal organic
included in the scope of the chemical vapor deposition method. The synthesis of organic indium compounds will be explained below using Bu ₂ InX as an example. All operations in the synthesis method for Bu ₂ InX are performed under a nitrogen atmosphere. First, 0.03 mol of distilled tributyl indium (Bu ₃ In.bp114℃/3mmHg) is added to 100
Dissolve in 50 ml of dehydrated ether in a 50 ml flask and cool on ice. The solution is then added with an oxygenate (e.g.
0.03 mol of propionic acid) was added dropwise while stirring under ice cooling. At this time, butane is slowly generated. After the dropwise addition is completed, stirring is continued for another 1 to 2 hours, and after the reaction is completed, the solvent is distilled off under _N2 atmosphere. When the product is an oil, it is distilled under reduced pressure, and when it is a solid product, it is recrystallized from ether to obtain an organic indium compound. The properties of the organic indium compound (Bu ₂ InX) thus obtained are shown in Table 1, and the thermal analysis results are shown in Table 2 and Figures 2A to 2C.

【table】

[Table] BuInX ₂ is synthesized in the same manner as for Bu ₂ InX, using twice the molar amount of oxygen-containing compound as compared to Bu ₃ In, but the reaction temperature needs to be raised to around the ether reflux temperature. Carry out under reflux. A method for producing the highly conductive thin film of the present invention will be described below, in which a p-xylene solution containing the obtained organic indium compound as a main solute is applied onto a substrate and then heated and baked. As the solvent for the coating solution, hydrocarbon-based solvents and oxygen-containing solvents (especially,
Examples include aromatic hydrocarbons such as benzene, toluene, and xylene, and higher alcohols such as hexanol, with p-xylene having a high boiling point being particularly preferred. Although it is possible to use a commercially available solvent as it is, in such a case, the solution may not be completely homogeneous, so it is desirable to dehydrate and dry it in advance. The organic indium compound is dissolved in p-xylene so that the coating solution contains 2 to 10% by weight of the organic indium compound. If the organic indium compound is less than 2% by weight in the coating solution, film formation will not be excellent, and if it is more than 10% by weight, the viscosity will become high and operation will be difficult. Bu ₂ SnO is added to this in an amount of 0 to 0.5% by weight in the coating solution, and heated to form a uniform solution. When the amount added is more than 0.5% by weight, the membrane resistance value increases. If the solution is not uniform, the solution is further heated to the reflux temperature or a small amount of higher alcohol such as hexyl alcohol is added to make the solution uniform. Organotin compounds are used as dopants. The coating solution thus obtained is stable to air and moisture and can be stored as is for a long period of time. When applying the above-mentioned coating liquid to a substrate, a method is used in which the substrate is immersed or the liquid is dropped onto the substrate and spread uniformly over the entire substrate by tilting the substrate or using a spinner. Soda glass, pyrex or quartz is generally used as the substrate. The substrate is heated and dried to evaporate the solvent and obtain a film. The obtained film is placed in an electric furnace, for example, and heated to 300 -
About 30 minutes at a temperature of 600℃, preferably 350-550℃
A highly conductive thin film is obtained by baking for about 1 hour. Firing is
At temperatures below 300℃, organic components cannot be completely decomposed and released, making it impossible to obtain high conductivity.
If the temperature exceeds 600℃, the substrate material will melt or deform, so care must be taken. The thickness of the film after firing is preferably about 200 to 3,500 Å; if it is less than 200 Å, a uniform film cannot be obtained, and if it is more than 3,500 Å, the transparency will decrease and the film will crack or peel. The highly conductive film using an organotin compound is an ITO thin film, and when not used, an indium oxide thin film is obtained. The highly conductive thin film according to the present invention can be applied to liquid crystal or electrochromic display elements, touch panels, and other transparent electrode applications. (Example) The present invention will be explained by the following example. Various properties of the highly conductive thin film according to the present invention were measured using the following method and equipment. (1) Visible light transmittance Using Shimadzu UV-200S, wavelength range 300~
Measured by reflection method at 900 nm (2) Film thickness A highly conductive thin film is etched with dilute nitric acid to form a step, and measured using a repeated reflection interferometer (3) Surface resistance Measured by 4-probe method (Example) Book The invention will be illustrated by the following examples. Example 1 Dibutylindium 2 _- ethylhexanoate ( _Bu2InO2CCHP (Et)( _CH2 ) _3CH3 ) and dibutyltin oxide ( _Bu2SnO ) as _a dopant
A p-xylene solution containing 5% by weight and 0.25% by weight, respectively, was uniformly applied onto a slide glass, and the glass plate was dried at 100° C. for 40 minutes to obtain a transparent film.
By further heating the film at 450°C for 1 hour,
A highly conductive ITO film with a thickness of 1400 Å, a resistivity of 1.9×10 ^-3 Ωcm, and a visible transmittance of over 90% was obtained. obtained when only the firing temperature was changed under similar conditions.
Figure 1 shows the change in surface resistance of the ITO film. Also,
Table 3 shows the properties of ITO films produced using various organic indium compounds under similar firing conditions.

[Table] Example 2 P containing 5% by weight of dibutylindium 2-ethylhexanoate (Bu ₂ InO ₂ CCH(Et) (CH ₂ ) ₃ CH ₃ ) and not containing dibutyltin oxide (Bu ₂ SnO) as a dopant - A highly conductive thin film was obtained using a xylene solution under the same conditions and method as in Example 1.
The film has a thickness of 1000 Å, a resistivity of 2×10 ^-2 Ωcm,
The transmittance in the visible range was over 90%. FIG. 1 shows the change in surface resistance of the film obtained when only the firing temperature was changed. (Effect) The organic indium compound used in the present invention is
It is easy to synthesize, can be easily purified by distillation or recrystallization, is stable against air or moisture, has good storage properties for coating solutions, and has a thermal decomposition temperature of 400°C.
Due to its low temperature below ℃ and thermal reaction in solution.
Because a disproportionation reaction occurs with Bu ₂ SnO and it is easy to form an In-OrSn chain, the tin atoms as a dopant are highly dispersed on the film surface, and exhibits high conductivity even at low temperature firing. It is possible to
Furthermore, the coating and baking method is suitable for producing large-area ITO films, and screen printing has the effect of making it possible to form fine patterns.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the sheet resistance and firing temperature of the ITO film of the present invention, and Figure 2A is a thermogravimetric analysis and differential thermal analysis curve diagram of the organic indium compound Bu ₂ In (acac) used in the present invention. , FIG. 2B is a thermogravimetric analysis and differential thermal analysis curve diagram of the organic indium compound Bu ₂ InO ₂ CEt used in the present invention, and FIG. 2C is a thermogravimetric analysis and differential thermal analysis curve of the organic indium compound Bu ₂ InOPh used in the present invention. It is a curve diagram.

Claims (1)

[Claims] 1. At least one indium-carbon bond and at least one indium-carbon bond.
A solvent solution containing 2 to 10% by weight of an organic indium compound having an oxygen bond and 0 to 0.5% by weight of an organic tin compound having at least one tin-oxygen bond is used as a coating solution, and the coating solution is uniformly spread over a substrate. The substrate is heated and dried to evaporate the solvent to form a film, and then the film is heated in an air atmosphere for 300 min.
A method for producing a highly conductive thin film, which comprises thermally decomposing the organometallic compound containing the organoindium compound as a main component by heating and baking at a temperature of ~600°C. 2. The production method according to claim 1, wherein the organic indium compound is synthesized from trialkylindium represented by the general formula R ₃ In and an oxygen-containing compound. 3 R of the above trialkylindium (R ₃ In)
The manufacturing method according to claim 2, wherein is a _C1 to _C8 straight chain and branched alkyl or aralkyl group. 4. The method according to claim 2, wherein the oxygen-containing compound is an alcohol, a phenol, a carboxylic acid, or a 1,3-diketone.