KR20120062341A - Indium zinc oxide transparent condutive layer for an electrode and the preparing method thereof - Google Patents

Abstract

PURPOSE: An IZO(Indium Zinc Oxide) transparent conductive film and a manufacturing method thereof are provided to obtain a thin film with enhanced etching properties and to obtain an amorphous or nano crystalline thin film at low temperatures. CONSTITUTION: An IZO transparent conductive film comprises indium oxide, zinc oxide, and titanium oxide. The IZO transparent conductive film is formed from an IZO sputtering target expressed as the following formula, InxZny(TiO2-a)z, where x+y<=1, 0.0001<=z<0.002, x:y=8.5-9.5:1.5-0.5, and 0.5<=a<=1.

Description

Indium zinc oxide transparent conductive film and its manufacturing method {INDIUM ZINC OXIDE TRANSPARENT CONDUTIVE LAYER FOR AN ELECTRODE AND THE PREPARING METHOD THEREOF}

The present invention relates to an indium zinc oxide transparent conductive film having a titanium oxide dopant added thereto, and having improved etching characteristics, and a method of manufacturing the same.

With the development of the display device field, liquid crystal display devices, electroluminescent display devices, field emission displays, and the like have been widely applied to home appliances or office equipment. These displays mainly use indium tin oxide (hereinafter, referred to as "ITO") as a transparent conductive film. This is because the ITO film not only has excellent transparency and conductivity (specific resistance: 2 × 10 ⁻⁴ Ω · cm), but also excellent adhesion to a substrate and workability by an etching solution. As a method of manufacturing such an ITO thin film, there are generally a sputtering method, an ion plating method, a CVD (chemical vapor deposition) method, and the like. However, in spite of these advantages, since ITO has a protrusion-like structure due to crystal growth, when applied to organic EL, localized current concentration occurs, making uniform display difficult. In addition, since the light transmittance in the short wavelength band (visible light short wavelength region) of about 380-400 nm is especially low in the visible region, there exists a problem that the light extraction efficiency of the specific wavelength from a light emitting layer is not good.

On the other hand, the organic electroluminescent device uses an amorphous transparent conductive film having a very flat film surface, and in particular, the use of a transparent conductive film having a high light transmittance in a short wavelength of visible light is required. In addition, electronic paper, which is characterized by flexibility, requires a transparent conductive film which is difficult to be cracked against bending. In general, the oxide crystal film has a weak grain boundary and is easily cracked. Therefore, application of a strong amorphous transparent conductive film against bending has been proposed. Such amorphous transparent conductive films include combinations other than ITO, for example, zinc oxide and tin oxide as the main raw materials, aluminum added to zinc oxide, or indium zinc oxide as the main component of indium oxide and zinc oxide. ). Among them, IZO, which is mainly composed of indium oxide and zinc oxide, has attracted attention for its advantages of higher etching rate than ITO. However, since the etching rate cannot be adjusted to date, it is difficult to apply to a device or the like. Therefore, the development of a new IZO transparent conductive film capable of improving such etching characteristics is continuously requested in the field.

The inventors of the present invention have shown that when a titanium oxide dopant material is used as a constituent of an indium zinc oxide target, the electrochemical characteristics are excellently exhibited due to the crystallinity improvement by the dopant, and the etching characteristics of the transparent thin film formed from the target are significantly improved. I found out.

Accordingly, an object of the present invention is to provide a transparent conductive film formed from an indium zinc oxide target including the dopant material, which has excellent electrical conductivity and improved etching characteristics, and a method of manufacturing the same.

The present invention (a) indium oxide; (b) zinc oxide; And (c) titanium oxide (TiO _{2 -a} ), and a transparent conductive film formed from an indium zinc oxide (IZO) sputtering target represented by the following formula (1).

[Formula 1]

In _x Zn _y (TiO _{2 -a} ) _z

Wherein x + y ≦ 1, 0.0001 <z <0.002, where x: y = 8.5 to 9.5: 1.5 to 0.5, and 0.5 ≦ a ≦ 1 to be.

In this case, the content of the titanium oxide is 1 to 10 atomic% based on the weight of the target. It is preferably in the range, and more preferably in the range of 1 to 2 atomic%.

In addition, the sputtering target preferably further comprises +1 or + trivalent titanium oxide.

The sputtering target may have a specific resistance of less than 1 × 10 ⁻³ Ωcm through a ratio adjustment of In: Zn: TiO _{2 -a} .

It is preferable that the light transmittance of the said transparent conductive film is 80 to 90%, and a sheet resistance value is 10-40 ohm / sq.

On the other hand, the transparent conductive film of the present invention for achieving the technical problem is prepared using the above-described indium zinc oxide (IZO) target as the oxygen and argon deposition gas, the oxygen gas partial pressure is mixed in the range of 1 to 5% Or in an argon gas atmosphere controlled to less than 30%.

The transparent conductive film of the present invention is preferably applied to information transmission devices such as flat panel displays or smart windows, surface light source illumination devices, and touch panels.

Since the indium zinc oxide target of the present invention is a metal oxide of a single composition in which impurities are well dissolved, DC resistance is possible because the resistance of the target is low.

In addition, it is possible to form a thin film having improved etching properties by improving the crystallinity by the dopant, and to form an amorphous or nanocrystalline thin film at a low temperature.

In addition, the transparent conductive film formed by depositing the indium zinc oxide target of the present invention not only exhibits high light transmittance and low surface resistance (<20 ohm / Sq.) But also has excellent etching property and flatness, and thus may be useful industrially. have.

1 is a graph showing light transmittance results according to heat treatment changes of a transparent conductive thin film formed by depositing an indium zinc oxide target at room temperature (RT) according to an embodiment of the present invention.
FIG. 2 is an enlarged graph of the light transmittance result of FIG. 1.
3 is a graph showing X-ray diffraction results of a transparent conductive thin film (IZO) of Comparative Example 1 formed using a conventional indium zinc oxide target.
FIG. 4 is a graph showing X-ray diffraction results of a transparent conductive thin film (IZO: Ti) formed using an indium zinc oxide target added with a titanium oxide dopant according to Example 1. FIG.
5 is an electron micrograph of a transparent conductive thin film (IZO) formed after heat treatment of the transparent conductive thin film of Comparative Example 1.
6 is an electron micrograph of a transparent conductive thin film (IZO: Ti) formed after heat-treating the transparent conductive thin film of Example 1. FIG.
7 is an electron micrograph showing a result of etching characteristics by patterning a transparent conductive thin film (IZO) formed after the heat treatment of the transparent conductive thin film of Comparative Example 1. FIG.
FIG. 8 is an electron micrograph showing the results of etching characteristics by patterning a transparent conductive thin film (IZO: Ti) formed after the heat treatment of the transparent conductive thin film of Example 1. FIG.

Hereinafter, the present invention will be described in detail.

Indium zinc oxide target

In the present invention, as a constituent of an indium zinc oxide (IZO) target, a titanium oxide-based dopant material capable of improving the etching characteristics of a thin film is used.

In this case, the titanium oxide dopant material is composed of a material different from the conventional titanium dioxide (TiO ₂ ) and the oxygen composition ratio, that is, TiO _{2 -a} . Here, a may be set to 0.5 to 1.

Titanium oxide-based dopant material used in the present invention is a kind of oxygen divided by one oxygen while forming a new chemical bond to partially remove the oxygen from the titanium oxide-based material (TiO ₂ ), or to supplement the oxygen bond removed It is a substance that causes structural deformation. When the titanium oxide-based material is used as a dopant material, the titanium oxide-based material partially deforms the crystal structure of the indium zinc oxide target so as to freely grow crystallinity. Therefore, the etching characteristics may be significantly improved due to an increase in the degree of crystalline freedom of the transparent thin film formed from the indium zinc oxide target.

In addition, the dopant is added in the target to generate an electron carrier such as oxygen vacancies or electrons in the indium zinc oxide lattice to allow electricity to flow through the target. Therefore, it is possible to minimize the degradation of the electrochemical properties of the sputtering target by the use of the dopant material.

A dopant material that can be used in the present invention is TiO _{2 -a} (0.5 ≦ a ≦ 1) as a titanium oxide based material. The titanium oxide-based material may also be expressed as TiO _a , in which the range of a is not particularly limited and may be the same as the above-mentioned range. In addition, materials that can exert the above-described crystallinity improvement and etching improvement effects due to different TiO ₂ and oxygen composition ratios are also within the scope of the present invention.

The content of the titanium oxide dopant may be included in the range of 1 to 10 atomic% with respect to the weight of the entire target, preferably 1 to 2 atomic%. When smaller than the content range, the etching property due to the addition of the dopant may appear insignificant. When the content exceeds the content range, the conductivity property may be reduced to limit the use of the transparent conductive thin film.

The indium zinc oxide sputtering target of the present invention may further include titanium oxide of +1 or +3. At this time, the amount of the titanium oxide of +1 or + trivalent is not particularly limited and may be appropriately adjusted according to the titanium oxide-based dopant content.

In the sputtering target of the present invention, the maximum particle diameter of indium zinc oxide may range from 0.1 to 10 μm. The indium zinc oxide has a small grain size, thereby suppressing the generation of nodules generated on the target surface when forming the transparent conductive film, so that sputtering can be performed with good stability.

The density of the indium zinc oxide target according to the present invention may be 95% or more. In addition, by adjusting the ratio of In: Zn: TiO _{2 -a in} the target, the bulk resistance can be adjusted to 1 x 10 ^-3 ohm cm or less.

In the present invention, except for using the above-described titanium oxide dopant, it is possible to produce an indium zinc oxide target according to a conventional method known in the art.

For one preferred embodiment thereof, indium oxide powder, zinc oxide powder, and the above-described titanium oxide dopant are mixed to prepare a slurry, followed by milling, drying and pulverizing, forming the pulverized product, and sintering the molding. It can be made to the process.

The indium oxide or zinc oxide may be used without limitation conventional components known in the art. For example, these are In ₂ O ₃ May be ZnO.

The indium oxide powder and zinc oxide powder may be in a state in which the particle size is pulverized to several μm or less before mixing. In this case, the average particle diameter of indium oxide may be in the range of 0.1 to 1 μm, and the average particle diameter of zinc oxide may be in the range of 1 to 5 μm. In addition, the mass ratio of indium oxide and zinc oxide may be in a range of 85:15 to 95: 5, and preferably 90 to 91:10 to 9. Titanium oxide-based powder mixed with these may have an average particle diameter of 1 to 10 ㎛ range.

Upon mixing the aforementioned powders, it may further comprise conventional additives known in the art, such as binders, dispersants, antifoams, etc., as needed.

The dispersant is added to satisfy the purpose for the finely ground particles to be pulverized while the ground raw particles maintain an evenly stable dispersion in the solution for a long time. Non-limiting examples of the dispersant that can be used include organic acid series with carboxyl groups such as citric acid, polyacrylic acid (PAA) or salts thereof, copolymers, or combinations thereof. The dispersant may be used 0.5 to 3% by weight based on the weight of the powder in the slurry.

In addition, the binder is added to maintain the molding strength of the molded body in the process of drying the slurry to powder and then molding. Non-limiting examples thereof include polymers such as polyvinyl alcohol and polyethylene glycol. The amount of the binder used may range from 0.01 wt% to 5 wt% with respect to the powder in the slurry.

The antifoaming agent is for removing bubbles in the slurry, and typically silicone oil, octyl alcohol, boron, or the like can be used. The amount of the antifoaming agent may be in the range of 0.001 to 0.01% by weight relative to the powder in the slurry.

The slurry prepared by mixing the indium oxide powder, tin oxide powder, titanium oxide powder (TiO _{2 -a} ), water and an additive is milled and dried to prepare a dry powder.

The milling can then be carried out using conventional ball mills, bead mills and the like known in the art. The viscosity of the slurry obtained through milling is preferably adjusted to 100 cps or less.

The dried powder is spray-dried using a spray dryer or the like to obtain a dry powder.

Thereafter, the drying powder is subjected to a molding step of producing a molded body having a predetermined shape. In manufacturing the molded body, it is preferable to use a cold isostatic press (CIP) in consideration of process convenience and the like.

After the forming step described above, an indium zinc oxide sintered body is manufactured through a sintering step. The sintering step may be performed under an oxygen gas atmosphere, an inert gas atmosphere, or a mixed atmosphere of oxygen and an inert gas. The sintering step may be carried out in an oxygen gas, inert gas atmosphere in the range of 900 ~ 1350 ℃, or may be prepared by sintering the molded product in the range of 900 ~ 1350 ℃ under pressure conditions of oxygen or inert gas atmosphere. In this case, the pressurization condition may be in the range of 2 to 3 ton / cm ² using CIP.

The produced sintered body is processed into a constant size and shape and attached to a cooling metal plate or a backing plate to be used as a sputtering target.

<Transparent Conductive Film>

The present invention provides a transparent conductive film deposited using the indium zinc oxide target described above.

The transparent conductive film may have a difference in components depending on the deposition atmosphere, but is manufactured by sputtering the above-described indium zinc oxide (IZO) target, and thus the composition is substantially the same as the target. Therefore, a conductive film having excellent crystallinity and high conductivity (low resistivity) can be formed. Here, the transparent conductive film is (a) indium oxide; (b) zinc oxide; And (c) titanium oxide (TiO _{2 -a} ), and may be formed from an indium zinc oxide (IZO) sputtering target represented by the composition of Chemical Formula 1.

The transparent conductive film formed using the indium zinc oxide target may be in an amorphous form. In this case, the temperature of the substrate forming the film may range from room temperature to 200 ° C., but is not limited thereto. As described above, in the amorphous transparent conductive film, etching residues hardly occur. In addition, since the crystallinity of the transparent conductive film is excellent, high light transmittance may be exhibited in the 500 to 600 nm region.

The amorphous transparent conductive film may be crystallized by heat treatment at a temperature in the range of 200 to 350 ° C. after forming the film. In this case, whether an amorphous or crystalline film is formed may be confirmed by X-ray diffraction.

The light transmittance of the transparent conductive film of this invention is 80 to 90%, and a sheet resistance value is 10-40 ohm / sq. It can be a range. In particular, the light transmittance of the transparent conductive film of the present invention is more preferably 90% or more in the 500 to 600 nm light region.

For example, a method of manufacturing a transparent conductive film according to the present invention may be formed while mounting the indium zinc oxide sputtering target and supplying oxygen and argon gas at a rate of 80 sccm in a vacuum chamber. At this time, the substrate and the sputtering apparatus used may be any conventional one known in the art without limitation.

In addition, the deposition gas is used by mixing oxygen and argon, preferably the oxygen gas partial pressure is mixed in the range of 1 to 5%, or is formed under an argon gas atmosphere controlled to less than 30%.

The transparent conductive film obtained as described above is excellent in transparency and has high conductivity and improved etching characteristics in the light region around wavelength 550nm of about 80-90%, and thus has an electron injection layer of an organic electroluminescent device. The connection resistance can be kept low. Therefore, the transparent conductive film can be used as a transparent electrode of various display devices such as a liquid crystal display device or an organic electroluminescent display device which requires etching, high transparency and conductivity. In addition, information transmission devices such as flat panel displays such as LCD, PDP, OLED, LED, transparent, opaque smart window; Surface light source lighting device touch panels such as OLED and LED; And / or information transmission apparatus using the same.

Hereinafter, an indium zinc oxide target and a method of manufacturing the same according to the present invention will be described in detail through examples. However, the following examples are merely illustrative of the indium zinc oxide target of the present invention and its preparation method for the purpose of understanding the invention, and the scope of the present invention is not limited thereto.

Example 1

An indium oxide (In ₂ O ₃ ) powder having an average particle diameter of 1 μm or less and a tin oxide (SnO ₂ ) powder having an average particle diameter of 3 μm or less were blended in a weight ratio of 9: 1. Next, a mixed powder was prepared by mixing titanium oxide-based powder (TiO _{2 -a} , a = 0.5) with 1 atomic% of the total powder in a slurry tank. Pure water, dispersion and binder components were added to the mixed powder and wet milling using a hard zirconia ball mill. Milling and mixing time was 1 hour, and it grind | pulverized so that the average slurry particle size might be 1 micrometer or less. The slurry made by the above-described method was made in the form of dried granule powder by using a spray dryer (Spray Dryer), and was formed by cold hydrostatic press at a high pressure of about 100 to 500 MPa. Subsequently, the molded body was sintered at an elevated temperature of about 900 to 1350 ° C. for 1 hour in an air atmosphere to prepare an indium zinc oxide sintered body for sputtering containing a dopant. The sputtering surface of the sintered body was polished by a polishing machine, and a copper backing plate was bonded using an indium metal powder to prepare a sintered body target capable of thin film evaluation.

The indium zinc oxide target prepared above was mounted on a direct current magnetron sputtering apparatus, and oxygen and argon gas were added at room temperature to prepare a transparent conductive film having a thickness of 150 nm on a glass substrate. As a result of measuring the light transmittance in the light having a wavelength of 380 ~ 780 nm with respect to the glass substrate with a transparent conductive film is as shown in FIG. It can be seen that it exhibits a high transmittance of 88% or more.

Comparative Example 1

A transparent conductive film having a thickness of 150 nm was prepared on the glass substrate by the same method as Example 1, except that the film was deposited using a conventional indium zinc oxide (IZO) target without adding a dopant.

Experimental Example 1. Evaluation of optical properties of the transparent conductive film

The light transmittance results of before and after the heat treatment of the transparent conductive thin film were evaluated.

At this time, the thin film prepared in Example 1 and the heat treatment of the thin film of Example 1 were used as samples. In addition, a heat treatment of the IZO thin film of Comparative Example 1 and the IZO thin film of Comparative Example 1 was used as a control.

As a result, all the heat treated or untreated thin film samples showed excellent light transmittance of about 85 to 90% in the 550 nm wavelength region (see FIGS. 1 and 2). In particular, it was confirmed that the heat-treated thin film of Example 1 had better optical properties than the heat-treated thin film of Comparative Example 1 (see Table 1 below). It is estimated that the crystallinity of the thin film is improved due to the titanium oxide-based material added as a dopant.

IZO: Ti Thin Film of Example 1
(140nm thickness after heat treatment) IZO thin film of Comparative Example 1
(140 nm thick after heat treatment) Transmittance (550 nm) 89.8% 89%

Experimental Example  2. Transparent Conductive  Crystallinity and Electrochemical Characterization

X-ray diffraction (XRD) was used to evaluate the crystallinity of the thin film according to the oxygen partial pressure. At this time, the thin film prepared in Example 1 and the heat treatment of the thin film of Example 1 were used as samples. In addition, a heat treatment of the IZO thin film of Comparative Example 1 and the IZO thin film of Comparative Example 1 was used as a control.

As a result of the experiment, it was confirmed that the characteristic peaks of indium zinc oxide were observed in the heat treated Example 1 and Comparative Example 1 (see FIGS. 3 to 4).

Meanwhile, the electrical properties were evaluated by Hall measurement at room temperature using the samples.

As a result, it was found that both the amorphous thin film of Example 1 and the heat-treated crystalline thin film of Example 1 exhibited much better electrical properties than the conventional IZO thin film, which was heat treated or untreated (see Table 2 below). As a result, it was confirmed that the crystallinity of the indium zinc oxide thin film is improved according to the use of the titanium oxide dopant material, and the electrical properties are improved.

Sheet Resistance (ohm / sq.) Example 1 IZO: Ti as-depo. 32.17 Example 1 (heat treatment) IZO: Ti annealing 28.54 Comparative Example 1 IZO as-depo. 57.02 Comparative Example 1 (heat treatment) IZO annealing 52.04

Experimental Example  3. Transparent Conductive  Etching Characteristic Evaluation

Surface characteristics and etching characteristics were evaluated using the thin film of Example 1 to which the dopant was added and the conventional IZO thin film, respectively.

As a result of confirming the surface properties by SEM, it was found that both the IZO thin film of Example 1 and the conventional IZO thin film had a uniform surface morphology (see FIGS. 5 to 6).

In addition, by etching the heat-treated Example 1 thin film and the conventional IZO thin film was confirmed the etching characteristics. As a result, it was confirmed that the thin film of Example 1 to which the titanium oxide dopant was added shows very excellent etching characteristics compared to the conventional IZO thin film (see FIGS. 7 to 8).

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below but also by the equivalents of the claims.

Claims (1)

(a) indium oxide; (b) zinc oxide; And (c) a transparent conductive film containing titanium oxide (TiO _{2 -a} ) and formed from an indium zinc oxide (IZO) sputtering target represented by the composition of Formula 1 below:
[Formula 1]
In _x Zn _y (TiO _{2 -a} ) _z
Wherein x + y ≦ 1, 0.0001 ≦ z <0.002, where x: y = 8.5 to 9.5: 1.5 to 0.5, and a is 0.5 ≦ a ≦ 1.

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