JPS61273807A - Tramsparent conducting oxide thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention relates to a Cd--Sn (cadmium-tin) based oxide transparent conductive thin film.

[Problems to be solved by the prior art/invention] Transparent conductive Ill is one of the most useful display devices such as liquid crystal displays, electroluminescence, and electrochromic elements, and photoelectric conversion devices such as solar cells! The demand for it as a polar material or an infrared reflective film is increasing.

The compositions of these transparent conductive 3JIIs include a composition in which tin oxide is doped with antimony or fluorine (for example, NFSAIII) and a composition in which indium oxide is doped with tin (hereinafter abbreviated as ITO). It has the following characteristics.

In other words, tin oxide-based transparent conductive films can be manufactured by sputtering, but due to cost and performance reasons, they are manufactured by methods such as spraying and atmospheric CVD. is 1~6X10-3Ω
・Disadvantages include being slightly inferior to ITO films such as cm, having many pinholes in the film and poor surface smoothness, and being acid resistant, making it difficult to etch with acid and making precise pattern processing difficult. On the other hand, ITOII has a good conductivity of 2 to 5X10-4; pattern etching with acid is easy.However, it is manufactured by a process using a vacuum system such as vacuum evaporation or sputtering. Because of this, the manufacturing equipment is expensive, the productivity is low because a batch method is suitable for production, it is difficult to form a film over a large area, and the yield of the raw material target is low.
It is expected that indium resources will be depleted, and there will be disadvantages such as higher raw material costs, making products more expensive.

As mentioned above, although ITOm is expensive, it has good performance, and therefore ITOll is currently used for most of the applications of transparent conductive thin films for electronic devices. Therefore, it is desired to develop a transparent conductive material @II that is inexpensive and has high performance.

Examples of ITOH production methods other than the vacuum-based process include a spray method in which a metal salt solution is sprayed onto a heated glass substrate and thermally decomposed, and a coating method in which a metal salt solution is applied onto a substrate and then heated and thermally decomposed. have been proposed and considered. However, the spray method has problems such as the formation of a thin film with a smooth surface, which tends to cause cloudiness of Kuku, WIII, and the need for post-treatment with gases such as thermally decomposed halogens, which increases equipment costs. On the other hand, the coating method has problems such as the inability to produce an ITO film with the same level of surface resistance as ITOla made using a vacuum process.

On the other hand, Nozik has developed a cadmium-tin oxide film with a composition of Cdz Sno 4 using a sputtering method to create a transparent conductive thin film with the same level of SN property, visible light transmittance, and etching processability as an ITO film. We have discovered Product II (hereinafter referred to as CTOll) (U.S. Pat. No. 3,811,953). Also, the Cd
Although the conductivity is slightly inferior to 2Sno4 II, CdSn
It is known that Os-based material can also be used as a transparent conductive IWA and is attracting attention.

The disadvantages of these CTO films are: (1) they must be manufactured by sputtering, so the film formation rate is slow and productivity is low; and (2) they have good average visible light transmittance, but in the short wavelength range. Due to its high absorption, it is colored yellow, which may impair its aesthetic appearance.Furthermore, when used in large-fill ponds, it is difficult for high-energy, short-wavelength light to pass through the cell, reducing efficiency. .

The present inventors have already established a method for manufacturing cToWA by thermally decomposing a composite metal solution containing a cadmium compound on a substrate to solve the drawback (1), and have filed a patent application (Japanese Patent Application No. 58-248342). ).

The present invention has been made to roughly eliminate the above-mentioned drawback (2).

(Means for solving the problem) The present invention has an atomic ratio of Cd/Sn of 0.3 to 2.0, Ca,%, Ba%sr, B, Zn1NL, Fe, Cu
A Ctt-Sn-based oxide transparent conductor characterized by containing one or more metal elements selected from the group consisting of P and P in an atomic ratio of 0.01 to 1.0 to Sn (tin). The present invention relates to a CTO-based thin film (hereinafter referred to as a CTO-based thin film).

〔Example〕

The CTO-based thin film of the present invention has an atomic ratio of Cd/Sn of 0.3.
~2. O1 is preferably in the range of 0.8 to 1.8, and is formed by adding a third metal component thereto.

When the Cd/Sn atomic ratio is less than 0.3, the conductivity of the CTO-based thin film becomes less than about 100 CI-1, making it impossible to use it as a transparent conductive thin film and making it difficult to etch with acid. occurs. On the other hand, Cd
/Sn exceeds 2.0 in atomic ratio, tin and unreacted C
Due to the precipitation of dO, a single-phase thin film is not formed, and the film becomes brown, impairing its light transmittance.

The third metal component used in the present invention includes false, -1aa1
Examples include Sr, B, Zn, NL, Qi, F. or P, and these may be used alone or in combination of two or more.

The third metal component in the present invention has an atomic ratio of 0.01 to 1.01, preferably 0.03 to 0.5, relative to tin. When the atomic ratio is less than 0.01, the effect of using the third metal component hardly occurs, and the CTO formed
The translucency and conductivity of the system thin film are not sufficiently improved. On the other hand, when the atomic ratio exceeds 1.0, the light transmittance in the short wavelength range is improved, but the conductivity decreases, making it impractical.

1□9 If an alkaline earth metal such as -1Cm, Sr, Ba, B, or P is added as a third metal component, the CTO thin film formed will be improved compared to when it is not added. As the density increases and the hardness □ increases, the translucency of short wavelength visible light and near ultraviolet rays improves, and it becomes colorless with a bluish tinge compared to the additive-free yellowish transparent film. A similar CTO-based thin film can be obtained. The conductivity of the CTO-based thin film obtained is approximately the same as +1 when the third metal component is not used, or an improvement of nearly 50%.

1. When zI+ is used as the third metal component, CTO
The short-wavelength visible light and near-ultraviolet light transmittance of the PA-based thin film has been significantly improved, and the translucency in 4,000 people has been improved by 30 to 50% compared to the non-PA-added system. Moreover, conductivity is also improved.

, On the other hand, when F@, NL, or He is used as the third metal component, the light transmittance of the resulting CTO-based thin film is hardly improved, but the conductivity is improved, among which;・NL, cIL
The effect of adding is large.

When a CTO-based thin film is manufactured using the third metal component as described above, the short-wavelength visible light and near ultraviolet rays are 1;3!11!1 h1 compared to 1 h1 when the third metal component is not used.
13tFlcII! f! 5AJ='1. C0IIEI
3Ci.

0°゛rLtll$IfIsSatlIllghr°゛2°l/, CTOIIIi, since the three metal components are dissolved in solid solution, the band gap (Eg ,,)
It is thought that the number of free electrons increases due to the doping effect, which causes the basic absorption edge to shift to the shorter wavelength side and improves the conductivity.

Next, the method for manufacturing the CTO thin film of the present invention will be explained.

The CTO-based thin film may be manufactured by a sputtering method, but a manufacturing method similar to the manufacturing method described in patent application No. 58-248342 developed by the present inventors, that is, a cadmium compound, a tin compound, and a tin compound in an organic solvent is used. It may be manufactured by thermally decomposing a composite metal solution containing a third metal compound as a metal component on a substrate, and by this method, l'&lb゛%I:8n*Ual/%% production0111
4: You can wander around the target.

Cadmium compound used to form CTO system*m.

Generally, commercially available cadmium compounds can be used as □; however, organic compounds having 1 to 30 carbon atoms and 4. 1 Cadmium compound manufactured from cadmium:
: , j゛''13!L?t<, "°"UkltS'Pt&゛'''''-: Typical examples of such cadmium compounds include cadmium carboxylates, cadmium alkoxides, Examples include cadmium β-diketone complexes, cadmium α-keto acid complexes, cadmium α-keto acid complexes, cadmium α-keto-ester complexes, cadmium β-keto acid ester complexes, etc. The above-mentioned cadmium carboxylic acid salts Specific examples include cadmium formate, cadmium acetate, WMF!cadmium, cadmium lactate, cadmium maleate, cadmium oxalate, cadmium octylate, cadmium oleate, cadmium stearate, cadmium linoleate, cadmium naphthenate, etc. Salts with cadmium monovalent or polyvalent carboxylic acids having 1 to 30 carbon atoms are preferred.Specific examples of cadmium alkoxides include cadmium and cadmium carboxylic acids having 1 to 30 carbon atoms.
Cadmium alkoxide obtained by reaction with 20 monohydric or polyhydric alcohols is used. Specific examples of cadmium β-diketone complexes include cadmium acetylacetone, cadmium benzoylacetone, etc. Specific examples of cadmium α- or β-keto mt complexes include acetylformate, acetoacetate, bupionyl-1so
- Complex of W& acid, benzoyl acetic acid, etc. and cadmium,
Specific examples of cadmium α- or β-keto acid esters include complexes of esters of the above α- or β-keto acids with methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, etc., and cadmium; In addition to these, there are also complexes of esters of α- or β-oxy acids such as glycolic acid, lactic acid, α-oxyN acid, hydroacrylic acid, and salicylic acid with methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, and cadmium. etc., and condensates, multimers, and mixtures thereof may also be used. Among these, those that are soluble in organic solvents and decompose into inorganic cadmium compounds when heated at 400° C. or lower are particularly preferred.

As a tin compound used for forming a CTO-based thin film, a divalent tin alkoxylate represented by the general formula (1): % formula % [) (wherein R1 is a hydrocarbon group having 1 to 20 carbon atoms) Class, general formula (■)
: 5n(OR+)t(N) (wherein, R1 is the same as above), general formula: Sn(OR+)a<Y*(I] (wherein, R1 is the same as above) is the same as above, Y is a functional group having chelating ability or a halogen atom, and X is an integer of 1 to 3), or tetravalent tin partial alkoxides of general formula (1), general formula [11, Examples include condensation multimers of compounds represented by the general formula (to): 5n(OCORz)2[Vl (wherein, R2 is hydrogen or a hydrocarbon group having 1 to 30 carbon atoms) Examples include divalent tin carboxylates represented by the general formula M: Sn(OCOR2)a(Vl (in the formula, R2 is the same as above); β-diketone complexes that are reaction products of valent or tetravalent tin with acetylacetone, benzoylacetone, etc., tinoxy β-diketone complexes, alkyltins such as tetramethyltin and tetraethyltin, and organic tins such as tetraphenyltin. , and the general formula cvn: RKSnx4-xWD (wherein, R is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen atom such as a chlorine atom or a fluorine atom, an alkoxy group, a carboxylic acid residue, and Examples include, but are not limited to, compounds represented by (same as above).

Specific examples of the compound represented by the general formula (13) include:
Jetoxytin, dipropoxytin, di-2-ethylhexoxytin, dipropoxytin, etc., general formula (II)
Specific examples of compounds represented by the general formula include tetraethoxytin, tetrapropoxytin, tetrabutoxytin, tetrakis(2-ethylhexoxy)tin, tetrastearoxytin, etc. Specific examples of compounds represented by the general formula Y include tin. Specific examples of compounds represented by the general formula (2), such as butoxydichloride and tristearoxytin monochlorite, include stannous acetate, stannous oxalate, stannous tartrate, stannous octylate, and stannous oleate. , stannous linoleate, stannous stearate, etc. Specific examples of compounds represented by the general formula M include stannous acetate, stannous lactate, stannous II acid, stannous octylate, and linole. Specific examples of compounds represented by the general formula (capital) such as stannic acid include dioctyltin diacetate, diethyltin oxide, dibutyltin maleate,
Examples include diphenyltin dichloride, dibenzyltin dihydroxide, tributyltin laurate, dibutyltin dilaurate, dibutyltin propoxide, and dipinyltin dihydroxide.

These compounds may be used alone or in combination of two or more, but those that are soluble in organic solvents and decompose into inorganic tin compounds when heated at 400° C. or lower are particularly preferred.

It is important that the third metal compound used to form the CTO-based Ill be compatible with the solution containing the aforementioned cadmium and tin, and that the metal component should remain in the film after thermal decomposition; specific examples include Cm, -1Ba.

5r1B1Zn, NL, Cu, F., P and formic acid, acetic acid,
Propionic acid, milk m, *m, naphthenic acid, octylic acid,
Salts with carbonic acids such as acrylic acid and methacrylic acid or β゛...1 such as acetylacetone, -diketone complexes, or α or β-oxy1.
1...Acids, organometallic compounds such as complexes with β-ketonic acids,
3・:1・J products, or chlorides and nitrate compounds of the above metals are 1ゝ・. preferable.

,゛.

, as an organic solvent used for forming a cTo-based thin film, 11,
For example, monohydric alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, pentanol,
Pine glycol, glycerin, 1,4-butanedi-
Polyhydric alcohols such as alcohol; carboxylic acid esters such as ethyl acetate, propyl acetate, isoamyl acetate, and propyl formate; ketones such as acetone, acetylacetone, diethyl ketone, and methyl ethyl ketone; aromatic compounds such as benzene, toluene, and xylene. Solvents, dioxane, tetrabalance, ethers such as hydrofuran, glycol nylons such as methyl cellosolve, ethyl cellosolve, etc., ethyl compounds, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl Examples include, but are not limited to, nitrogen-containing organic solvents such as acetamide. These organic solvents 1 may be used alone,
It is good to use a mixture of two or more types. ,. -16 Yoe1. □
. . In the case of ethers such as alcohols, carboxylic acid esters, dioxane, and tetrahydrofuran, they can be widely used in various combinations of cadmium compounds, tin compounds, and third metal compounds; It is preferable to select it appropriately depending on the combination of the third metal compound.

A composite metal solution used for forming a CTO-based thin film is prepared by dissolving a cadmium compound, a tin compound, and a third metal compound in an organic solvent.

The concentration of the cadmium compound, tin compound, and third metal compound (hereinafter referred to as metal component) in the composite metal solution is usually about 0.01 to 40% (I amount %, hereinafter the same) as the metal content. , from the point of view of workability etc.
It is preferable to set it to 20%.

If necessary, an organic dehydrating agent such as an orthoformic acid ester may be added to the composite metal solution used for forming the CTO-based W-based film, if necessary.

In the present invention, a CTO-based thin film is formed by thermally decomposing a composite metal solution on a substrate made of quartz glass, transparent alumina, soda glass, or soda glass coated with silica to prevent alkali diffusion. be done.

, 13ji122""6°"OMIN! (7111tl
"1" 1゛Coral compound, tin compound and third metal compound i (0111@-Vc, hQ*e<a'b°■6.
0460゛In the combination, cadmium carboxylate, tin carboxylate, and carboxylate of the third metal component,
1,: 1 or acetylacetonate of a third metal component: PA-1, (combination with a complex, cadmium carboxylate and SP1) Dualkoxide and a carboxylate of a third metal component, or acetylacetonate of a third metal component: For reasons such as the combination of a metal component with an acetylacetonate complex, the combination of a cadmium β-diketone complex, a tin alkoxide, and a carboxylate of a third metal component or an acetylacetonate complex of a third metal component, etc. preferable. That is, the combination of cadmium carboxylic acid, tin carboxylate, and carboxylate of the third metal component or acetylacetonate complex of the third metal component is the cheapest raw material and is therefore useful. Furthermore, an unsaturated carboxylic acid that causes an oxidative curing reaction such as oleic acid, linoleic acid, and lyluic acid is added, or a curable group such as a cadmium salt, a third metal component salt, or a tin salt of these unsaturated carboxylic acids is added. When present in the liquid, a thin film with even better surface condition can be obtained. It is preferable that the compound having the curable group is contained in the composite metal solution in an amount of 0.1% or more.
It is more preferable that the content is 0%, and in such a case, a remarkable effect is produced. A combination of a cadmium carboxylate, a tin alkoxide and a carboxylate of a third metal component or an acetylacetonate complex of a third metal component, or a combination of a cadmium β-diketone complex, a tin alkoxide and a carboxylate of a third metal component or In the case of the combination with the acetylacetonate complex of the three metal components, the hydrolyzability of the added tin alkoxide is extremely weak compared to the case of tin alkoxide alone, and the mixture composition is not just 5. It is thought that a co-reaction occurs to form a coordination compound, and because of this hydrolyzability, the film forming property on the substrate is particularly excellent. Particularly favorable effects can be expected when azeotropically treating a solution to produce a target compound film.

In addition, in order to promote the co-reaction between these compounds, such a composite metal solution is coated on a substrate by dip coating, dried for 5 to 60 minutes at 70 to 150°C, and then exposed to air. Alternatively, secondary firing is performed by eJ culm heat treatment at about 400 to 700° C. for 15 minutes to 2 hours in an oxidizing atmosphere with adjusted oxygen partial pressure. Of course, the temperature may be higher than 700°C, but
Even if the temperature exceeds G'C, no special advantage can be obtained. It has been found from the results of sm X-ray diffraction that if the secondary calcination is performed at a temperature below about 600°C, it generally becomes amorphous, and when it is performed at a temperature below about 500°C, W!
It has been found that the entire III becomes almost amorphous and crystallizes at temperatures above about 600°C.

The thickness of the CTO-based thin film can be controlled by the concentration of the composite metal solution to be applied and, for example, in the case of dip coating, the pulling rate during dip coating. The temperature of the composite metal solution is as described above, but the temperature of 31 degrees can be adjusted arbitrarily and is not particularly limited, but for example, when using a carboxylic acid metal compound, A rough guideline is approximately 30c+e/min. The concentration of the composite metal solution, the pulling rate during dip coating, etc. may be appropriately determined depending on the combination of cadmium compound, tin compound, third metal compound, organic solvent, thermal decomposition method, desired film thickness, etc. The thickness of the film formed in this way may be selected as appropriate depending on the application, but it is usually 2.
00 to 20,000 people, preferably 50 to 20,000 people.
It is more preferable that it is about 0 to 1G, about 1.5G.

The CTO-based WI film obtained through the primary firing process usually has a conductivity of 10-1 to 102 Ω-1 (1-1, which is quite low, but the thin film can be irradiated with ultraviolet rays or subjected to the following annealing process). As a result, the conductivity is improved by about 1 to 2 orders of magnitude.

Annealing refers to heat-treating a thin film that has undergone primary firing for the purpose of decomposing the composite metal solution under a reducing atmosphere, an inert gas atmosphere, or under reduced pressure, usually about 50 imHg or less.

Heat treatment in a reducing atmosphere means, for example, heat treatment in a molecular active gas atmosphere for about 1 to 90 minutes at a temperature of about 50 to 400°C in a reducing gas such as hydrogen or carbon monoxide, for example, in a molecular active gas atmosphere. , nitrogen, helium, or other inert gas for about 5 to 180 minutes at about 200 to 700 °C.
This method is carried out at about 700° C. for about 5 minutes to about 3 hours.

Further, these annealing steps may be performed consecutively with the primary firing step. Through these annealing, CT
In addition to improving the thin film conductivity of O-based thin films, the translucent region shifts to the ultraviolet region.

- Even if wllI is irradiated with ultraviolet rays after the next firing, the same effect as annealing can be obtained. Conductivity and visible light transmittance can be improved by irradiating ultraviolet rays with a wavelength of about 2000 to 40 GOA for 1 minute to 10 hours under conditions such that the illuminance on the substrate is 500,000 to 1 million lux. It has the effect of improving.

Although the method for producing CTO-based 111I of the present invention has been described based on the dip coating method, coating methods other than the dip coating method, such as spin coating and doctor blade methods, can also be employed. It is also possible to form a CTO-based thin film by spraying a composite metal solution used for forming a CTO-based thin film onto a heated substrate and thermally decomposing the solution.

The CTO-based thin film produced in this manner can be suitably used as an electrode material for displays for liquid products, electroluminescence, solar cells, and the like.

Next, the CTO-based SGS of the present invention will be explained based on Examples, but the present invention is not limited to these Examples 1 to 10 and Comparative Examples 1 to 4. Cadmium octylate ethyl cellosolve solution 1s, og, metal tin containing ffi 28.0% tin octylate 8.21; l, and the third metal component in Table 1 so as to be 10 mol % with respect to the metal tin. In addition, linoleic acid IS, OQ, isoamyl acetate 21.81;
was added and subjected to azeotropic treatment for 4 hours to prepare a coating solution (metal content & about 8%, Cd/S atomic ratio 1.5).

A quartz glass plate with a thickness of 0.81 mm was immersed in this solution, and after being applied by pulling it up at a pulling rate of 10C1/Win,
It was dried in a dryer for 150''C x 3G minutes to form a transparent cured film on the quartz glass plate.

Next, this sample was fired at 600'CX for 1 hour in the air.
A transparent inorganic compound was obtained, and its surface resistance value, x11 diffraction, and visible light transmittance -j'□ were measured using a DC four-terminal method.

Subsequently, these substrates were annealed at 300° C. for 3 G minutes in a mixed gas with a Hi:Nz ratio of 1:1 (molar ratio), and the same rf4t* measurements as described above were performed.

In addition, these thin films were analyzed using fluorescent X-ray analysis to determine the
The composition ratio of the third metal was determined, and it was confirmed that the composition ratio was almost unchanged from the composition before annealing and the starting composition.

Further, the film was etched with acid to form a step, and the film thickness of each aim was measured using a step-type film thickness meter to determine the volume resistivity of each.

The results of these Examples are summarized in Table 1.

[Margin below]

Example 11 Ice-free cadmium acetate 23. After boiling OQ and tin tetrabutoxide 22.8a in 1 yogonia of ethyl alcohol, and adding a predetermined amount of anhydrous zinc acetate, the coating solution was refluxed for about 4 hours (the atomic ratio of cd/Sn was 1). .8)
.

After coating the solution on quartz glass in the same manner as in Example 1, it was baked in the air at 500°C for 30 minutes, and then heated at 200°C for 30 minutes.
When the conductivity was measured after annealing in a hydrogen atmosphere for 1 minute, the conductivity was improved by the addition of Zn, as seen in FIG.

Example 12 In the same manner as in Example 11, 0.1 mol of each of strontium acetate, nickel diacetylacetonate and zinc octylate was added to tin as the third metal component, and after refluxing, the mixture was coated on quartz glass E and fired. Further annealing treatment was performed to obtain transparent conductive material III. Note that the film thicknesses were all about 1100A. The transmittance of these nanometers in the visible light range was measured using a spectrophotometer, and the results are shown in FIG.

From the results shown in FIG. 2, it can be seen that in the sr and zη doped system, the transmittance in the short wavelength range is improved compared to the undoped system.

When we measured the visible light transmittance of Mg, Ba, and B%P added systems in the same way, we found that, similar to the Sr and Zn added systems, there was an improvement in the transmittance in the short wavelength region compared to the non-additive system. It was seen.

〔Effect of the invention〕

Cadmium-tin-based oxide transparent conductive film with improved conductivity and transparency by adding a specific metal as a component of the cadmium-tin-based oxide transparent conductive thin film itI1
You can get 1M.

[Brief explanation of drawings]

Figure 1 is a graph showing the volume resistivity of the film obtained in Example 11 as a function of the addition of zl to Sn, and Figure 2 is the relationship between wavelength and transmittance of the film obtained in Example 12. This is a graph showing.

Claims (1)

[Claims] 1 Cd/Sn has an atomic ratio of 0.3 to 2.0, and C
one or more metal elements selected from the group consisting of a, Mg, Ba, Sr, B, Zn, Ni, Fe, Cu and P are S
A Cd-Sn based oxide transparent conductive thin film, characterized in that the atomic ratio of n to n is 0.01 to 1.0.