KR20010098806A - Transparency conduction film, manufacturing method and the usage thereof - Google Patents

Abstract

The present invention provides a transparent conductive film having a flat film surface and low resistivity suitable for large high-precision EL panels, and a method and a use thereof.

The transparent conductive film of the present invention has a resistivity of 250 μΩ · Cm or less and a maximum height difference (Z-max) / thickness (t) of surface irregularities is 10% or less. For example, a sputtering target made of indium, tin, germanium, and oxygen may be used. It is manufactured by sputtering with sputter power superimposed on rf in dc.

Description

Transparent conductive film and its manufacturing method and use {TRANSPARENCY CONDUCTION FILM, MANUFACTURING METHOD AND THE USAGE THEREOF}

The present invention relates to a low resistance transparent conductive film with improved surface flatness, and more particularly to a crystallized transparent conductive film.

ITO (Indium Tin Oxide) thin film has characteristics of high conductivity and high transmittance, and also can be easily processed finely, so that it is a display electrode for flat panel display and a resistive touch panel. ), A solar cell window material, an antistatic film, an electromagnetic wave prevention film, an antifogging film, a sensor, and is widely used in a wide range of fields.

Such an ITO thin film manufacturing method can be roughly divided into chemical film forming methods such as spray pyrolysis and CVD, and physical film forming methods such as electron beam evaporation, ion plating, and sputtering. Among them, sputtering has been used in various fields because it is a film forming method that makes it possible to easily form a uniform film in a large area and obtain a high-performance film.

In order to increase the stability of the discharge during sputtering, and to reduce the amount of nodules (black foreign matter formed on the target surface when sputtering the ITO target in the mixed atmosphere of argon gas and nitrogen gas continuously), Attempts have been made to add elements. For example, a method of containing silicon oxide and / or germanium oxide in the ITO sintered body as in Japanese Patent Laid-Open No. 62-202415, a method in which 1 to 15% by weight of germanium oxide is contained in the ITO sintered body as in Japanese Patent Application Laid-Open No. 5-98436, etc. Is proposed.

Recently, with the development of the information society, the level of technology required for the flat panel display is increasing. As shown in FIG. 1, an inorganic electroluminescent panel (EL) is formed of a light emitting layer 3 sandwiched by an insulating layer 2 through a transparent electrode 1 and a metal back electrode 4. A strong electric field of cm is applied to the light emitting layer to emit light. Because it is self-luminous, the visibility is high, and because it is an all-solid, it has excellent characteristics of being resistant to vibration. The panel structure has an X-Y matrix structure composed of a transparent electrode and a back electrode that are orthogonal in a band shape. Therefore, as the panel becomes larger and more precise, there is a demand for a technology for lowering the resistivity of the transparent conductive film used for the transparent electrode.

In addition, when a light emitting layer emits light, a strong electric field of 10E8V / cm is applied, so that if there is a large uneven portion on the surface of the transparent electrode 1, electric field concentration occurs at that portion, and insulation breakdown is likely to occur. When insulation breakdown occurs, the display of the pixel portion becomes impossible and the display quality of the display becomes poor. Therefore, the unevenness of the electrode surface needs to be reduced.

On the other hand, when an ITO thin film is formed at room temperature, an amorphous film is obtained unless special conditions are applied. However, in order to lower the resistivity of the thin film, it is preferable to crystallize the film. The crystallization temperature of ITO is around 150 ° C. (depends on the film forming conditions). In order to obtain a crystal film, it is necessary to form the film at a film forming temperature equal to or higher than this temperature. However, when the crystalline ITO thin film is formed using the sputtering method, protrusions and domain structures of the film characteristic to the ITO thin film are formed.

In general, when the ITO film is formed by the sputtering method, argon and oxygen are used as the sputtering gas. As the amount of oxygen in the gas is changed, the resistivity of the obtained thin film changes, showing a minimum value at a specific oxygen partial pressure value. Thus, when the film is formed at the oxygen partial pressure value where the resistivity of the thin film has a minimum value as described above, the projections and domain structures of the thin film surface are remarkably revealed, resulting in a poor surface flatness. In such a film, the maximum height difference (Z-max) of surface irregularities may reach 100 nm at a film thickness of 200 nm.

On the other hand, in order to pursue the flatness of the thin film, a film may be formed in a range deviating from the optimum oxygen partial pressure value, or an amorphous method may be used by lowering the substrate temperature at the time of film formation. However, in either case, the resistivity increases as the flatness of the thin film is secured.

As such, development of a transparent conductive film that satisfies two characteristics of flatness and low resistivity has been required.

An object of the present invention is to provide a crystalline transparent conductive film suitable for a large high precision EL panel and having a flat film surface and low resistivity.

1 is a diagram showing the structure of an inorganic EL panel.

2 is a diagram showing the resistivity and Z-max / t of the film obtained in Example 1. FIG.

3 is a diagram showing an X-ray diffraction spectrum (XRD) of the thin film obtained in Example 1. FIG.

4 is a graph showing the resistivity and Z-max / t of the film obtained in Example 2. FIG.

5 is a diagram showing an X-ray diffraction spectrum (XRD) of the thin film obtained in Example 2. FIG.

<Description of Symbols for Major Parts of Drawings>

1 transparent electrode 2 insulating layer

3: light emitting layer 4: back electrode

5: glass substrate

The present inventors have conducted extensive studies on conductive metal oxides doped with different elements in ITO, and have resulted in resistivity of 250 μΩ · Cm and Z-max / t of 10% or less, thereby increasing the size and precision of the panel. Correspondingly, it was found that a transparent conductive film having high reliability was obtained even in an EL panel to which a strong electric field was applied. In addition, such a thin film was found to be achieved by an ITO thin film containing germanium as a dopant, and completed the present invention.

The present invention relates to a transparent conductive film having a resistivity of 250 μΩ · Cm or less and at the same time satisfying that Z-max / t is 10% or less, except that the transparent conductive film is substantially made of indium, tin, potassium, and oxygen. Such a conductive film is achieved by, for example, a film substantially composed of indium, tin, germanium, and oxygen. Here, "substantially" means "except inevitable impurities."

In the present invention, Z-max is a parameter representing the degree of irregularities of the surface of the material, and means the difference between the highest peak of the highest acid and the lowest valley depth within a specific area of the surface. As a measuring method, the measurement by atomic force microscopy (AFM) is common. An atomic force microscope is a device for measuring the surface irregularities by converting the minute lever (closer) to the surface of the material in a specific area in the longitudinal and horizontal direction, and converting the bending of the lever to the height in the vertical direction of the sample surface. In the present invention, using the atomic force microscope (trade name: SPI 3700) of Seiko Electronics Industrial Co., Ltd. was measured by scanning the lever in the region of 3㎛ 3㎛.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The thin film concerning this invention and the apparatus containing this thin film are manufactured, for example by the following method.

First, the sputtering target for thin film formation is manufactured. As a sintered compact for using as a sputtering target, it is good that the sintered compact obtained is 95% or more, More preferably, it is 98% or more.

This is because when the sintered density is less than the above density, abnormal discharge easily occurs during sputtering, and since abnormal growth particles are formed using the generated splat as a nucleus, it is difficult to obtain a flat film.

Further, the relative density (D) according to the present invention exhibit a relative value of the theoretical density (d) obtained in the additive average of the true density of the In ₂ O _3, SnO ₂ and GeO _2. The theoretical density (d) obtained from the average of the averages means that when the mixed amounts of In ₂ O ₃ , SnO ₂ and GeO ₂ powders in the target composition are a, b and c (g), respectively, the true density is 7.179, 6.95, Using 6.239 (g / cm ³ ), d = (a + b + c) / ((a / 7.179) + (b / 6.95) + (c / 6.239)). When the measured density of a sintered compact is d1, the relative density is obtained by Formula D = d1 / d * 100 (%).

A sintered compact having a sintered density of 95% or more can be produced, for example, by the following method.

First, for example, indium oxide powder, tin oxide powder and germanium oxide powder are mixed as the raw powder. Instead of indium oxide powder and tin oxide powder, tin oxide solid solution indium oxide powder may be used. In this case, if the average particle diameter of the powder to be used is large, the density after sintering does not sufficiently increase, so that it is difficult to obtain a sintered body having a relative density of 95% or more, so that the average particle diameter of the powder to be used is preferably 1.5 μm or less, and more preferably 0.1 to 1.5 μm. It is good. The powder may be mixed by dry mixing or wet by a ball mill or the like.

Here, the mixing amount of tin oxide is 5 to 20% by an atomic ratio of Sn / (Sn + In). More preferably, it is 8 to 17%, More preferably, it is 10 to 14%. This is because when the ITO thin film is manufactured using the target of the present invention, the resistivity of the thin film is the lowest.

The mixed amount of germanium oxide is preferably 1 to 6% by an atomic ratio of Ge / (In + Sn + Ge). More preferably, it is 2 to 5%, More preferably, it is 3 to 5%. When the amount of germanium oxide added is less than the above range, the planarization effect of the thin film is small, so that a film having large unevenness can be obtained, and when the above range is exceeded, the resistivity can be high.

A molded article is produced by adding a binder or the like to the mixed powder obtained as described above and molding by a press method or an injection method. In the case of producing a molded article by the pressing method, after filling the powder with a predetermined mold, the powder is pressed at a pressure of 100 to 300 kg / cm ² using a powder press machine. When the moldability of powder is bad, you may add finders, such as a paraffin and polyvinyl argon, as needed.

When the molded article is prepared by the injection method, a slurry for preparing the injection molded article is prepared by adding a binder, a dispersant, ion-exchanged water to the ITO mixed powder, and mixing with a ball mill. Subsequently, injection is performed using the obtained slurry. It is advisable to remove the bubbles from the slurry before pouring the slurry into the mold. Degassing | defoaming may be performed, for example in a vacuum by adding the polyalkylene glycol type defoamer to a slurry. The injection molded body is then dried.

Next, a crimping process is performed on the obtained molded object by a cold hydrostatic press (CIP) etc. as needed. At this time, the CIP pressure is 1 ton / cm ² or more, preferably ² to 5 ton / cm ² to obtain a sufficient compression effect. In the case where the initial molding is performed by the injection method, the binder removal treatment may be performed for the purpose of removing organic matter such as moisture and binder present in the molded body after CIP. Further, even when the initial molding is performed by the press method, when the binder is used at the time of molding, it is preferable to perform the binder removal treatment in the same manner.

The molded article thus obtained is introduced into the sintering furnace and sintered. Any method may be used as the sintering method, but sintering in the air is preferable considering the cost of the production equipment. However, other conventionally known sintering methods such as hot press (IIP), hot hydrostatic press (HIP) and oxygen pressure sintering may also be used.

Moreover, although it can select suitably also in sintering conditions, in order to acquire sufficient density synergy effect, and to suppress evaporation of tin oxide, it is good that it is 1450-1650 degreeC. In addition, the atmosphere at the time of sintering should be an atmosphere or an oxygen atmosphere completely. The sintering time is 5 hours or more, preferably 5 to 30 hours in order to obtain a sufficient density synergistic effect. In this way, the germanium-containing ITO sintered body can be produced.

Next, after processing the obtained sintered compact with desired improvement, a sputtering target is manufactured by joining to the packing plate which consists of oxygen-free copper using indium solder etc. as needed.

Using the obtained sputtering target, the transparent conductive thin film of this invention can be formed on board | substrates, such as a gas substrate and a film substrate. At this time, as a method of manufacturing the thin film, it is preferable to use a sputtering method using 50 to 500 W of power (however, it depends on the size of the cathode) in which rf is superimposed on dc for reducing the resistivity and planarization of the thin film. Here, the ratio of rf superimposed on dc should be 50-100% of rf / dc as applied power. As rf, a high frequency of 13.56 MHz ± 0.05% is preferable.

The substrate temperature at the time of film formation is preferably 200 ° C. or higher, more preferably 300 ° C. or higher in order to crystallize the thin film.

In addition, a film may be produced by sputtering at the same time using a sputtering target consisting of three kinds of indium oxide, tin oxide and germanium oxide, or two kinds of mixed oxides of these three kinds and the remaining oxides. In addition, you may replace and use one part or all part of each sputtering target with a metal or an alloy.

At the time of film formation, argon and oxygen are introduced into the vacuum apparatus as sputtering gas to perform sputtering. In order to lower the resistivity of the membrane, the flow rate of these introduced gases is controlled to appropriately set the value at which the resistivity is lowered.

The thin film thus obtained has a resistivity of 250 μΩ · Cm or less, preferably 220 μΩ · Cm or less, and at the same time Z-max / t of 10% or less, preferably 6% or less, which is very flat and has low resistivity. In addition, the thickness of the film to form is good to be 100-500 nm.

On the other hand, the thin film formed on the substrate can be etched in a desired pattern as necessary, and can constitute a device according to claim 4 of the present application.

In order to have an additional function in the thin film according to the present invention, a fourth element may be added. As a 4th element, Mg, Al, Si, Ti, Zn, Y, Zr, Nb, Hf, Ta, etc. are mentioned, for example. The amount of these elements added is not limited thereto, but in order not to weaken the excellent electrical properties and flatness of the thin film according to the present invention (total amount of oxide of the fourth element) / (In ₂ O ₃ + SnO ₂ + GeO ₂ The total amount of oxide of the fourth element) / 100 is preferably 0% or more and 20% or less (weight ratio).

EXAMPLE

Hereinafter, embodiments of the present invention will be described in more detail. However, the present invention is not limited thereto.

Example 1

440 g of indium oxide powder, 60 g of tin oxide powder, and a predetermined amount of germanium oxide powder were placed in a polyethylene pot, and mixed with a dry ball mill for 72 hours to prepare a mixed powder.

This powder was put into a mold and pressed at a pressure of 300 Kg / Cm ² to prepare a molded article. The molded body was refined by CIP at a pressure of 3 ton / Cm ² , and then the molded body was placed in a complete oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering condition)

Sintering temperature: 1500 ° C., Heating rate: 25 ° C./hour, Sintering time: 6 hours, Oxygen pressure: 50 mmH ₂ O (gauge pressure), Oxygen flux: 2.7 cm / min.

It was 95% or more when the density of the obtained sintered compact was measured in accordance with the Archimedes method. The sintered compact was processed into a sintered compact having a diameter of 4 inches and a thickness of 6 mm according to a wet working method, and bonded to a packing plate made of an oxygen-free copper material using indium solder, which was then used as a target.

This target was sputtered under the following sputtering conditions to evaluate the thin film.

(Sputtering condition)

Substrate: a glass substrate, the applied electric power: dc150W + rf100W, gas pressure: 1.1mTorr, sputtering gas: Ar + O _2, O ₂ / Ar: resistivity to a value which is a minimum control, substrate temperature: 200 ℃, film thickness: 200nm.

The composition of the obtained film was analyzed by EPMA (Electron Prove Micro Analysis), and the results obtained by measuring the resistivity and Z-max / t of the thin film are shown in FIG. 2. Preferred results were obtained when the content of Ge / (In + Sn + Ge) was 1 to 6%.

The crystallinity of the thin film when Ge / (In + Sn + Ge) was 3% was investigated using XRD, and the results are shown in FIG. 3. It was the film which orientated and crystallized on the (100) plane.

Example 2

450 g of indium oxide powder, 50 g of tin oxide powder, and a predetermined amount of germanium oxide powder were placed in a polyethylene pot, and mixed with a dry ball mill for 72 hours to prepare a mixed powder.

Using this powder, a target was prepared in the same manner as in Example 1. The thin film was manufactured on the conditions similar to Example 1 using the obtained target.

The composition of the obtained film was analyzed by EPMA (Electron Prove Micro Analysis), and the resistivity and Z-max / t of the thin film were measured. The obtained result is shown in FIG. When the content of Ge / (In + Sn + Ge) is 1 to 6%, preferable results were obtained.

The crystallinity of the thin film when Ge / (In + Sn + Ge) is 5% was investigated using XRD. The results are shown in FIG. Although there was no particularly strong orientation surface, it was a crystallized film.

Example 3

Among the targets prepared in Example 1, a thin film having a thickness of 500 nm was prepared by sputtering under the same conditions as in Example 1 except for the sputtering time using a target having a Ge composition of 3 atomic%. The resistivity and Z-max / t of the obtained film were measured, and the resistivity was 195 µΩ · Cm and Z-max / t = 6.1%.

Comparative Example 1

After sputtering in the following sputtering conditions using the target whose Ge composition of the thin film was 3 atomic% among the target prepared in Example 1, the thin film was evaluated.

(Sputtering condition)

Substrate: a glass substrate, the applied electric power: dc200W, gas pressure: 1.1mTorr, sputtering gas: Ar + O _2, O ₂ / Ar: resistivity to a value which is a minimum control, substrate temperature: 200 ℃, film thickness: 200nm.

When the resistivity and Z-max / t of the obtained film were measured, the resistivity was 260 µΩ · Cm and Z-max / t = 6.9%.

Comparative Example 2

After sputtering in the following sputtering conditions using the target whose Ge composition was 5 atomic% of the thin film among the targets prepared in Example 2, the thin film was evaluated.

(Sputtering condition)

Substrate: a glass substrate, the applied electric power: dc200W, gas pressure: 1.1mTorr, sputtering gas: Ar + O _2, O ₂ / Ar: resistivity to a value which is a minimum control, substrate temperature: 200 ℃, film thickness: 200nm.

When the resistivity and Z-max / t of the obtained film were measured, the resistivity was 280 µΩ · Cm and Z-max / t = 8.5%.

According to the present invention, a transparent conductive film having a flat film surface and low resistivity can be obtained so as to be suitable for a large high precision EL panel.

Claims (7)

A transparent conductive film having a resistivity of 250 μΩ · Cm or less and having a maximum height difference (Z-max) / film thickness (t) of surface irregularities of 10% or less, provided that the transparent conductive film is substantially indium, tin, gallium and oxygen. Unless it consists of). The method of claim 1, A substantially transparent conductive film comprising indium, tin, germanium and oxygen. The method of claim 2, Germanium is contained in the ratio of 1.0%-6.0% by the atomic ratio of Ge / (In + Sn + Ge), The transparent conductive film characterized by the above-mentioned. The method according to any one of claims 1 to 3, A transparent conductive film, wherein the structure of the thin film is a crystal film. An apparatus comprising the transparent conductive film according to any one of claims 1 to 4. The sputtering target consisting substantially of indium, tin, germanium and oxygen is sputtered with sputtering power with rf superimposed on rf, and the resistivity is 250 μΩ · Cm or less, and the maximum height difference of surface irregularities (Z-max) / The manufacturing method of the transparent conductive film whose film thickness t is 10% or less. The method of claim 6, A method for producing a transparent conductive film, wherein germanium is contained in an amount of 1.0% to 6.0% by an atomic ratio of Ge / (In + Sn + Ge).