JP2003301265A - Ito thin film free from spike-shaped protrusion, manufacturing method therefor and target used in it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ITO thin film having low resistance, no spike-shaped protrusion on the surface, and superior smoothness, which is suitable for a transparent anode of an organic electroluminescence element. <P>SOLUTION: The ITO sputtering target made of an ITO sintered compact comprises a composition of indium, tin and oxygen, a sintered density of 99.5% or higher by relative density, a bulk specific resistance of 70-100 μΩcm, and an integrated intensity of an X-ray diffraction peak for the (220) plane of an In<SB>4</SB>Sn<SB>3</SB>O<SB>12</SB>phase, which is an intermediate compound of stannic oxide and indium oxide, in quantity of less than 30% with respect to that for the (211) plane of an In<SB>2</SB>O<SB>3</SB>phase. The manufacturing method is characterized by forming the film with a sputtering method using the target, in an oxygen partial pressure of 0.5-1.0%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ITO thin film having no spike-like protrusion and excellent in surface smoothness, and a method for manufacturing the same. The ITO thin film is an organic EL (Ele
It is particularly excellent as a transparent anode used for a ctro Luminescence display.

[0002]

2. Description of the Related Art With the development of information society in recent years, the technical level required for a display device which is a man-machine interface is increasing. Above all, organic EL
The (Electro Luminescence) panel has excellent visibility because it emits light by itself, and has features such as thinness, light weight, high-speed response, high viewing angle, and high contrast. As shown in FIG. 1, the organic EL element has a structure in which a transparent anode 2, a hole transport layer 3, a light emitting layer 4, an electron transport layer 5, and a metal cathode 6 are sequentially stacked on a glass substrate 1. . The panel structure is roughly classified into an XY matrix structure (passive type) composed of strip-shaped orthogonal transparent anodes and back electrodes and a structure using a thin film transistor (TFT) (active type). In either case, the transparent anode 2 is used for high definition and high speed response.
Low resistivity is required for ITO (Indium T
in Oxide) thin films have been used.

As a method for producing an ITO thin film, a sputtering method is mainly used because it is easy to increase the area of the thin film and a high performance film can be obtained. As a sputtering target for forming an ITO thin film, a target made of an alloy of metallic indium and tin, or a complex oxide (ITO) target containing indium oxide and tin oxide is used. Among them, the ITO target is mainly used because the resistance value and the transmittance of the obtained film do not change with time and the film formation conditions can be easily controlled.

When an ITO thin film is formed by sputtering at room temperature, an amorphous film can be obtained.
Since the TO thin film has a high resistivity, it is necessary to crystallize the thin film in order to reduce the resistivity of the ITO thin film.
It is necessary to form a crystalline ITO thin film by a sputtering method at a substrate temperature of 150 ° C. or higher, but conventionally, a crystalline ITO thin film formed by sputtering under such conditions has a spike-like shape. There is a problem that the protrusions are formed on the ITO thin film. IT with the spike-like protrusion
When an O thin film is used as a transparent anode of an organic EL display, a dark spot defect occurs, and it has been desired to reduce it. The dark spot defect is a phenomenon in which a non-light emitting point (black point) appears and the display quality is deteriorated when the organic EL element emits light for a long time.

Generally, when forming an ITO thin film by a sputtering method, argon and oxygen are used as a sputtering gas. The resistivity of the thin film obtained by changing the amount of oxygen in the gas changes, and shows a minimum value at a certain oxygen partial pressure value (see FIG. 2). Since it is preferable that the ITO thin film used as a transparent anode for a display element such as an organic EL has a low resistance, the ITO thin film is generally formed at an oxygen partial pressure at which the resistivity shows a minimum value. However, when the ITO thin film was formed before and after the oxygen partial pressure, many spike-like protrusions were always formed.

In order to reduce spike-like protrusions on the ITO thin film, it is conceivable to lower the temperature of the substrate on which the film is formed to form an amorphous thin film. But amorphous ITO
Thin films can reduce the formation of spike-like protrusions, but IT
Since the O thin film has a high resistivity, it was not sufficient for use as a transparent anode of a display element.

On the other hand, it has been proposed so far to form an ITO thin film by using various ITO targets. We have also proposed an ITO target characterized by a sintered density, an oxygen content, and an intermediate compound amount (for example, Patent Document 1).
reference). However, although the patent document discloses that a low resistance ITO thin film can be obtained without generating nodules on the target in a wide oxygen partial pressure (oxygen partial pressure in argon is in the range of 0 to 1%), There has been no suggestion of a method for forming an ITO thin film without spike-like protrusions.

As a method for forming a flat ITO thin film, various ITO thin films containing indium, tin, and a different element component other than oxygen have been proposed (see, for example, Patent Documents 2 to 8). However, IT containing these different elements
The O thin film cannot completely eliminate the spike-like protrusions, and there is a problem that a different element increases the resistivity of the ITO thin film. Furthermore, when an ITO thin film containing different elements is used for a display element, those elements may adversely affect the display element as impurities, which is not preferable in practice.

[0009]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-233969

[Patent Document 2] Japanese Patent Laid-Open No. 2000-129432

[Patent Document 3] Japanese Patent Laid-Open No. 2000-169219

[Patent Document 4] Japanese Patent Laid-Open No. 2000-169220

[Patent Document 5] Japanese Unexamined Patent Publication No. 2000-185968

[Patent Document 6] Japanese Unexamined Patent Application Publication No. 2001-151572

[Patent Document 7] Japanese Patent Laid-Open No. 2001-307553

[Patent Document 8] Japanese Unexamined Patent Application Publication No. 2002-050231

[0010]

As described above, in the case of an ITO thin film composed of indium, tin, and oxygen, a flat ITO thin film having no spike-like protrusions has been desired so far. No ITO thin film was obtained. The present invention provides an ITO thin film suitable for a transparent anode used for a display element such as an organic EL and having a low resistance and no spike-like protrusions on the surface, and a method for producing the same.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on a method of reducing spike-like protrusions on the surface of an ITO thin film having low resistance and excellent transmittance, and as a result, using an ITO target satisfying a specific condition. , And the ratio of argon gas and oxygen gas pressure within a limited range (oxygen partial pressure: O ₂
/ Ar), the spike-like protrusions on the surface of the ITO thin film are remarkably reduced, and the present invention has been completed.

The ITO thin film of the present invention will be described below.

The ITO thin film of the present invention is composed of indium, tin and oxygen, and the surface shape of which is a bearing curve of 0.
ITO whose difference between 1% value Rb and 50% value Rb is less than 15 nm
It is a thin film.

The ITO thin film in the present invention is a thin film composed of indium, tin and oxygen, and does not intentionally contain other different elements. However, it does not exclude an ITO thin film containing impurities that can be usually considered.

The bearing curve referred to in the present invention means IT
When the O thin film is sliced horizontally with respect to the substrate, the presence state of the surface protrusions is evaluated by the change in the sum of the sectional areas of the protrusions protruding above the sliced surface,
This is common in the evaluation of the surface condition of thin films.

For example, in the case of the ITO thin film having the surface projection shape shown in FIG. 3, when it is sliced in the horizontal direction, the total cross-sectional area (k + l + m +) of the portions k, l, m and n in the drawing is (k + 1 + m +
n) is the protrusion cross-sectional area at the slice position, and the bearing curve is obtained by plotting the change in the cross-sectional area by moving the slice surface up and down. The bearing curve has the profile shown in Fig. 4 (total cross-sectional area of each surface protrusion at a certain height)
/ (Measured total area) x 100 is% of Rb of the slice surface
It is a value. That is, the 50% value Rb of the bearing curve is the position where the protrusion above the slice surface corresponds to 50% of the cross-sectional area of the measurement film, and the 0.1% Rb value is the protrusion above the slice surface. It corresponds to a position near the film surface corresponding to 0.1% of the cross-sectional area of the film. The ITO thin film of the present invention is a thin film in which the interval between Rb of 50% and 0.1% is narrower than 15 nm, that is, there is no protrusion and the surface smoothness is excellent. Here, in the film which is completely smooth and has no spike-like protrusions, the positions of the 50% value Rb and the 0.1% value Rb coincide with each other, and the difference between them is 0 nm. The ITO thin film of the present invention corresponds to a more general surface roughness Ra of about 1 to 2 nm,
The lower limit of the interval between the 50% value Rb and the 0.1% value Rb is about 2 nm.

The bearing curve is the atomic force microscope (A
It can be evaluated by performing a three-dimensional measurement using FM) or the like.

The resistivity of the ITO thin film of the present invention is not particularly limited, but it is preferably in the range of 100 to 200 μΩ · cm. The resistivity of ITO thin film is 200μΩ ・ c
If it is larger than m, it is insufficient as a transparent anode of a display element. On the other hand, the lower limit of the resistivity of the ITO thin film obtained by the method of the present invention is substantially the lower limit of about 100 μΩ · cm, and most is in the range of 130 to 150 μΩ · cm.

Next, the method for producing the ITO thin film of the present invention will be described.

The ITO thin film of the present invention comprises indium, tin and oxygen, has a sintered density of 99.5% or more in relative density, a bulk resistivity of 70 to 100 μΩ · cm, and an intermediate compound of indium oxide and tin oxide. In ₄ Sn ₃
The integrated intensity of the X-ray diffraction peak of the (220) plane of the O ₁₂ phase is I
When forming a film by sputtering using an ITO sputtering target made of an ITO sintered body having an integrated intensity of the X-ray diffraction peak of the (211) plane of the n ₂ O ₃ phase of less than 30%,
Oxygen partial pressure in the sputtering atmosphere is 0.5 to 1.0%
It is manufactured by forming a film with oxygen in a limited range of oxygen.

The ITO target used for producing the ITO thin film of the present invention can be produced, for example, by the following method.

Indium oxide powder and tin oxide powder are used as raw materials for the ITO sintered body, and the maximum particle size of the indium oxide powder and tin oxide powder is 1 μm or less and the median diameter is 0.4 μm using a crushing device such as a ball mill. It is desirable to use the one crushed below. In the present invention, the particle size means the secondary particle size, and the median size means the particle size of the powder corresponding to 50% of the cumulative distribution in the volume of the particle size.

The content of tin oxide in the mixed powder is preferably 5 to 11% by weight at which the resistivity becomes the lowest when the ITO thin film is formed by sputtering.

Then, the obtained mixed powder is molded by a molding method such as a pressing method or a casting method to obtain an ITO molded body. In the case of manufacturing a molded body by press molding, the above-mentioned mixed powder is filled in a mold of a predetermined size and then pressed at a pressure of 100 to 300 kg / cm ² using a pressing machine to obtain a molded body. On the other hand, in the case of forming into a molded product by cast molding, the mixed powder is mixed with water, a binder and a dispersant to form a slurry, which is poured into a mold for cast molding to form a molded product and then dried.

The obtained ITO molded body may be subjected to a consolidation treatment by a cold isostatic pressing (CIP) if necessary. At this time, the CIP pressure is preferably ² ton / cm ² or more in order to obtain a sufficient consolidation effect.

Next, the ITO molded body thus obtained is sintered in a sintering furnace, and the atmosphere in the sintering furnace is from room temperature to at least 1 atmosphere.
An oxidizing atmosphere is used up to 500 ° C. Hold temperature is 150
The temperature is higher than 0 ° C, preferably 1550 ° C or higher, more preferably 1600 ° C or higher. To prevent evaporation of tin oxide, the upper limit is 1650 ° C. By doing so, it becomes possible to obtain an ITO sintered body having a relative density of 99.5% or more in relative density.

Next, in order to reduce the ITO sintered body of the present invention, the atmosphere is switched from the oxidizing atmosphere to the non-oxidizing atmosphere at a temperature higher than 1600 ° C. when the temperature is raised. This makes it possible to remove lattice oxygen in the sintered body and reduce the intermediate compound phase. When the oxidizing atmosphere is used up to a temperature exceeding 1500 ° C., the density increasing effect can be obtained, but the reducing effect of the sintered body may be difficult to obtain.

Further, the temperature decreasing rate up to at least 800 ° C. is a rate exceeding 100 ° C./hour, preferably 200 ° C.
/ Set to more than an hour. This makes it possible to further reduce the amount of intermediate compounds. When the rate of temperature decrease is less than 100 ° C./hour, it may be difficult to obtain the effect of reducing intermediate compounds.

The oxidizing atmosphere may have an oxygen concentration of 20% by volume or more, and specific examples thereof include an air atmosphere, an air pressure atmosphere, a pure oxygen atmosphere and an oxygen pressure atmosphere. It is preferably in a pure oxygen atmosphere. Further, the ratio of the oxygen flow rate (L / min) of the pure oxygen gas and the charged amount (kg) of the compact (charged weight / oxygen flow rate) during sintering in a pure oxygen atmosphere should be 1.0 or less and be introduced into the sintering furnace. Is more desirable.

The non-oxidizing atmosphere is preferably a vacuum atmosphere, an inert gas atmosphere, or a nitrogen gas atmosphere. When sintering in an inert gas atmosphere or nitrogen gas atmosphere, the introduced gas is sintered at a ratio (charge weight / inert gas flow rate) of the inert gas flow rate (L / min) to the compact body charge amount (kg) of 1.0 or less. It is preferably introduced into the furnace.

The sintering time is preferably 3 hours or more after reaching the desired holding temperature.

The sintered density obtained by the above method is 99.5% or more in relative density, and the bulk resistivity is 70 to 100 μm.
The integrated intensity of the X-ray diffraction peak of the (220) plane of the In ₄ Sn ₃ O ₁₂ phase, which is an intermediate compound of Ωcm and indium oxide and tin oxide, is the X-ray diffraction peak of the (211) plane of the In ₂ O ₃ phase. It is possible to obtain an ITO sintered body having an integrated strength of less than 30%.

The In ₄ Sn ₃ O ₁₂ phase (2
The X-ray diffraction peak of the (20) plane is 2θ = 50.x when an X-ray diffractometer in which the target of the X-ray tube is Cu.
It is a peak that appears around 7 ° (d value is 1.797).
Further, the X-ray diffraction peak of the (211) plane of the In ₂ O ₃ phase is 2θ = when an X-ray diffractometer similar to the above is used.
It is a peak appearing near 21.4 ° (d value is 4.151).

A normal ITO target contains a cubic bixbyite structure of indium oxide and a fluorite structure of an intermediate compound (In ₄ Sn ₃ O ₁₂ ) of indium oxide and tin oxide. IT using such ITO target
In order to reduce the spike-like protrusions of the O thin film, it is necessary to reduce both the intermediate compound in the ITO target and the lattice oxygen of the bixbyite structure. In the cubic bixbyite structure, oxygen ions are six-coordinated with indium ions, and the remaining two anion sites are empty, and these empty sites are called quasi-ion sites.
When oxygen enters this empty site, an intermediate compound (In ₄ Sn ₃ O ₁₂ ) of indium oxide and tin oxide having a fluorite structure is formed. Therefore, oxygen in the sintered body can be reduced by reducing the amount of the intermediate compound. The amount of the intermediate compound can be evaluated by X-ray diffraction of the ITO sintered body.

The integrated intensity of the X-ray diffraction peak of the (220) plane of the In ₄ Sn ₃ O ₁₂ phase was calculated from the X-ray intensity of the (211) plane of the In ₂ O ₃ phase.
The integrated intensity of the line diffraction peak is preferably less than 30%, and particularly preferably 26% or less.

It is important that the bulk resistivity of the ITO sintered body used as the target in the present invention is 70 to 100 μΩ · cm. This is because if the resistivity of the target is high, the discharge during sputtering film formation is not stable, abnormal discharge occurs, and the surface of the obtained ITO thin film becomes rough and does not fall within the range of the present invention. The resistivity of the ITO sintered body can be measured by a general four-point probe method or the like.

Further, IT used as a target in the present invention
The sintered density of the O sintered body must be 99.5% or more. Even if the amount of oxygen in the sintered body is reduced, if the sintering density is low, abnormal discharge is likely to occur during sputtering, and if Splats adheres to the substrate when abnormal discharge occurs, spikes will start from the adhesion part. A protrusion is formed. Here, the relative density of 100% of the ITO sintered body is 7.156 g / cm ³ when tin oxide is 10% by weight. IT
The relative density of the O sintered body can be measured by a general Archimedes method.

The ITO sintered body thus obtained is ground into a desired shape and used as an ITO sputtering target. The obtained processed ITO sintered body can be easily targeted by bonding it to a backing plate made of oxygen-free copper or the like using indium solder or the like.

The obtained target is placed in a sputtering apparatus, and an inert gas such as argon and an oxygen gas are used as a sputtering gas, and a direct current (dc) or a high frequency (rf) or both electric fields are applied to perform sputtering. By doing so, an ITO thin film can be obtained on a glass substrate or a film substrate.

The substrate temperature in sputtering film formation is not particularly limited, but it is preferably 150 ° C. or higher, particularly 200 ° C. or higher in order to obtain a crystalline and low-resistance ITO thin film.

In the present invention, spattering film formation is carried out using the above ITO target, but by setting the oxygen partial pressure during film formation to an extremely limited range of 0.5 to 1.0%, there is no spike-like protrusion. An ITO thin film is obtained.

We have reported a target in which generation of nodules and particles is small in Japanese Patent Laid-Open No. 2000-233969. However, the target used in the above publication has an intermediate compound amount of 30% or more when the density exceeds 99.5%, and a density of less than 99.5% when the intermediate compound amount is less than 30%. It was only. Therefore, no nodules and particles were generated by the method of the publication, but an ITO thin film without spike-like protrusions could not be obtained. Therefore, the publication does not mention the formation of an ITO thin film having no spike-like protrusion.

The reason for the difference between the ITO target used in the present invention and the target used in the above publication is considered to be the influence of the final sintering temperature and the temperature lowering rate.

On the other hand, in the present invention, an ITO target in which the density and the amount of the intermediate compound are further limited is used, and in addition, the oxygen concentration is 0.5 to 1.0%, particularly preferably 0.5 to 0.7%. The inventors have found that an ITO thin film having no spike-like protrusion can be obtained in the extremely limited oxygen concentration range.

IT without spikes by the method of the present invention
The reason why the O thin film is obtained is not clear, but it can be considered as follows, for example. In the method of the present invention, by using an ITO target with a low oxygen content and a small amount of intermediate compounds, the total amount of oxygen released from the target during film formation is reduced,
The amount of oxygen introduced by the sputtering gas supplements the lack of oxygen. In such a film formation, many free oxygen ions exist near the surface of the substrate on which the ITO thin film is deposited, and it is considered that the cluster particles containing the intermediate compound scattered from the target easily react with the oxygen ions. To be Therefore, suppression of local abnormal growth of film structure due to direct deposition of the clusters,
That is, it is considered that formation of spike-like protrusions can be suppressed.

If the effect of the present invention is due to the above-mentioned mechanism, when the oxygen concentration is low outside the range of the present invention and sufficient oxygen ions for decomposing scattered clusters are not supplied, spike-like protrusions The generation cannot be suppressed. On the other hand, if the oxygen concentration is further increased, the discharge during sputtering becomes unstable and abnormal discharge is likely to occur, so that spike-like protrusions cannot be suppressed even under the condition that the oxygen partial pressure exceeds 1%.

The purpose of the present invention is not achieved only by using a reduced target, and since it is essential to use a target having a high density and a small amount of intermediate compounds, the present invention uses a conventional reduced ITO target with a high oxygen content. This technique is also different from the method of forming a film by sputtering by pressure.

[0048]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

The density of the ITO target defined in the present invention is measured by the Archimedes method, the bulk resistivity is measured by the four-point probe method, and the bearing curve of the thin film is measured by an atomic force microscope (AFM) in an evaluation area (20 μm × 20 μm). It was measured. The X-ray diffraction spectrum of the ITO sintered body target was measured under the following conditions. X-ray source: Cukα was used to measure the diffraction peak only by Kα1 Power: 50 kV, 200 mA Measurement method: 2θ / θ, continuous scan Scan speed: 2 ° / min (scan range (2θ):
20 to 60 degrees) Example 1 900 g of indium oxide powder and 100 g of tin oxide powder having a maximum particle diameter of 1 μm or less and a median diameter of 0.4 μm or less.
Was put in a polyethylene pot and mixed by a dry ball mill for 72 hours to prepare a mixed powder. Next, the mixed powder was put into a mold and pressed at a pressure of 300 kg / cm ² to obtain a molded body. The molded body is 3 ton / c by CIP
Densification treatment was performed at a pressure of m ² .

Next, the obtained ITO molded body was sintered under the following conditions. (Sintering conditions) Temperature rising rate: 50 ° C./hr, sintering temperature: 1600 ° C., holding time: 5 hours, temperature dropping rate: 150 ° C./hr, sintering atmosphere: switching from oxygen atmosphere to nitrogen atmosphere when reaching 1510 ° C. Same atmosphere up to 400 ° C., (charged weight / oxygen flow rate): 0.8 Bulk resistivity, density, In ₄ Sn ₃ O _{12 of the} obtained sintered body
Table 1 shows the diffraction intensity ratios of the (220) plane of the phase and the (211) plane of the In ₂ O ₃ phase.

The obtained ITO sintered body was 100 mm × 18
It was cut to 0 mm × 6 mmt, bonded to a backing plate made of oxygen-free copper using indium solder to form an ITO target, and sputtering film formation was performed under the following conditions. (Sputtering film forming conditions) Device: DC magnetron sputtering device, magnetic field strength: 1000 Gauss (directly above target, horizontal component), substrate temperature: 200 ° C., sputtering gas: mixed gas of Ar and O ₂ , sputtering gas pressure: 5 mTorr, oxygen content Pressure: 0.0-1.0%, DC
Power: 600 W, film thickness: 150 nm The resistivity of the obtained ITO thin film was measured by the four-point probe method,
FIG. 5 shows the oxygen partial pressure dependence of the resistivity, and Table 1 shows the film resistivity and the oxygen partial pressure at which the film resistivity becomes minimum.

As a result of forming an ITO thin film with an oxygen partial pressure in the range of 0 to 1.1%, the oxygen partial pressure was 0.5%, 0.7%,
The ITO thin film obtained at 0.9% had no spike-like protrusions, but the oxygen partial pressure was 0%, 0.1%, 0.3%, 1.
At 1%, spike-like protrusions were recognized. Oxygen partial pressure 0.
The result of observing the surface condition of the ITO thin film prepared with 5% by AFM is shown in FIG.
Table 1 shows the difference between the value Rb and the 50% value Rb. IT obtained
The O thin film does not have spike-like protrusions and has a low resistivity
The ITO thin film was suitable as a transparent anode for the L element.

Example 2 An ITO sintered body was produced in the same manner as in Example 1 except that the sintering atmosphere switching condition of the ITO sintered body was switched from the oxygen atmosphere to the nitrogen atmosphere when the temperature reached 1600 ° C.

Bulk resistivity, density, I of the obtained sintered body
The (220) plane of the n ₄ Sn ₃ O ₁₂ phase and the (21) of the In ₂ O ₃ phase
The diffraction intensity ratio of the 1) plane is shown in Table 1.

Next, a thin film was prepared by the same method as in Example 1. FIG. 5 shows the oxygen partial pressure dependence of the resistivity, and Table 1 shows the film resistivity and the oxygen partial pressure at which the film resistivity becomes minimum.

As a result of forming an ITO thin film with an oxygen partial pressure in the range of 0 to 1.1%, the oxygen partial pressure was 0.5%, 0.7%,
The ITO thin film obtained at 0.9% had no spike-like protrusions, but the oxygen partial pressure was 0%, 0.1%, 0.3%, 1.
At 1%, spike-like protrusions were recognized. Oxygen partial pressure 0.7
FIG. 7 shows the result of observing the surface condition of the ITO thin film prepared by using AFM with AFM, and Table 1 shows the difference between the 0.1% value Rb and the 50% value Rb obtained from the bearing curve.

The ITO thin film thus obtained had no spike-like protrusions, had a low resistivity, and was an ITO thin film suitable as a transparent anode of an organic EL device.

Comparative Example 1 A sintered body was produced in the same manner as in Example 1 except that the sintering temperature was 1500 ° C. and the temperature lowering rate was 100 ° C./hour.

Bulk resistivity, density, I of the obtained sintered body
The (220) plane of the n ₄ Sn ₃ O ₁₂ phase and the (21) of the In ₂ O ₃ phase
The diffraction intensity ratio of the 1) plane is shown in Table 1. The density of the obtained sintered body was 99.5% or more, but the amount of the intermediate compound was 30.
It was a large percentage.

Next, an ITO thin film was prepared by the same method as in Example 1. FIG. 4 shows the oxygen partial pressure dependence of the resistivity, and Table 1 shows the film resistivity and oxygen partial pressure.

As a result of forming an ITO thin film with an oxygen partial pressure in the range of 0 to 1.1%, spike-like protrusions were observed in the ITO thin film at all oxygen partial pressures from 0 to 1.1%. Was given. FIG. 8 shows the results of observing the surface condition of the sample prepared with an oxygen partial pressure of 0.5% by AFM. Table 1 shows the difference between the 0.1% value Rb and the 50% value Rb obtained from the bearing curve.

Since an ITO target containing many intermediate compounds was used, spike-like protrusions were observed, and the ITO thin film was insufficient for use in an organic EL device.

Comparative Example 2 Sintering was carried out in the same manner as in Example 1 except that the sintering temperature was 1500 ° C., the temperature lowering rate was 100 ° C./hour, and the sintering atmosphere was switched from the oxygen atmosphere to the nitrogen atmosphere when reaching 1300 ° C. The body was made.

The bulk resistivity, density, and I of the obtained sintered body
The (220) plane of the n ₄ Sn ₃ O ₁₂ phase and the (21) of the In ₂ O ₃ phase
The diffraction intensity ratio of the 1) plane is shown in Table 1. The amount of the intermediate compound in the sintered body was small, but the density was lower than 99.5%.

Next, an ITO thin film was prepared by the same method as in Example 1. FIG. 5 shows the oxygen partial pressure dependence of the resistivity, and Table 1 shows the film resistivity and oxygen partial pressure.

As a result of forming an ITO thin film with an oxygen partial pressure in the range of 0 to 0.9%, spike-like protrusions were observed in the ITO thin film at all oxygen partial pressures from 0 to 0.9%. Was given.

FIG. 9 shows the results of observing the surface condition of the sample prepared at an oxygen partial pressure of 0.3% with the minimum resistivity with AFM.
Shown in. Table 1 shows the difference between the 0.1% value Rb and the 50% value Rb obtained from the bearing curve. Although a target with a small amount of the intermediate compound was used, since the target had a low density, many spike-like protrusions were observed in the obtained ITO thin film, and an ITO thin film insufficient for use in an organic EL device was obtained. There wasn't.

Comparative Example 3 A sintered body was produced in the same manner as in Example 1 except that the sintering temperature was 1500 ° C., the temperature lowering rate was 100 ° C., and gas switching was not performed.

Bulk resistivity, density, I of the obtained sintered body
The (220) plane of the n ₄ Sn ₃ O ₁₂ phase and the (21) of the In ₂ O ₃ phase
The diffraction intensity ratio of the 1) plane is shown in Table 1. The sintered body had a high density, but the amount of the intermediate compound was extremely large.

Next, a thin film was formed by the same method as in Example 1. FIG. 5 shows the oxygen partial pressure dependence of the resistivity, and Table 1 shows the film resistivity and oxygen partial pressure.

As a result of forming an ITO thin film with an oxygen partial pressure in the range of 0 to 0.7%, spike-like protrusions were observed in the ITO thin film at all oxygen partial pressures from 0 to 0.7%. Was given.

FIG. 1 shows the result of observing the surface condition of the sample prepared with the oxygen partial pressure of 0.1% at which the resistivity became the minimum with AFM.
It shows in 0. 0.1% value Rb calculated from the bearing curve
Table 1 shows the difference between the Rb and the 50% value Rb. Density is high enough
Although a TO target was used, since a target containing an extremely large amount of intermediate compound was formed at a low oxygen partial pressure, many spike-like protrusions were observed and only an ITO thin film unsuitable for use in an organic EL device was obtained.

[0073]

[Table 1]

[0074]

As described above, the ITO thin film of the present invention has a low resistivity and does not have spike-like projections.
Excellent as an ITO thin film used for the transparent anode of the L element.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an organic EL element.

FIG. 2 is a diagram showing the relationship between the resistivity of a thin film and the oxygen partial pressure. In the figure, the X-axis (horizontal axis) is the oxygen partial pressure (arbitrary unit a.
u. ), And the Y axis (vertical axis) is the resistivity (arbitrary unit au).
Indicates.

FIG. 3 is a diagram showing an image when a film is cut on an arbitrary surface in order to obtain a surface shape of the ITO thin film and a bearing curve of the ITO thin film.

FIG. 4 is a diagram showing an image of a bearing curve obtained by the method of FIG.

FIG. 5 is a diagram showing the relationship between the resistivity and oxygen partial pressure of the ITO thin films obtained in Examples and Comparative Examples. Example 1 is indicated by a black square (■), Example 2 is indicated by a black circle (●), Comparative Example 1 is indicated by a white square (□), Comparative Example 2 is indicated by a white circle (◯), and Comparative Example 3 is indicated by a white triangle (Δ). In FIG. 3, the X axis (horizontal axis) represents oxygen partial pressure (unit%), and the Y axis (vertical axis) represents resistivity (unit μΩ · cm).

FIG. 6 is an image of the surface state of the sample manufactured in Example 1 observed by AFM. In FIG. 6, the X axis (horizontal axis) represents the length of the observed portion (unit is μm), and the Y axis (vertical axis) represents the length in the thickness direction of the observed portion (unit is nm). No spike-like protrusion is observed.

FIG. 7 is an image obtained by observing the surface state of the sample manufactured in Example 2 with an AFM. In the figure, the X-axis (horizontal axis) shows the length of the observed portion (unit is μm), and the Y-axis (vertical axis) shows the length of the observed portion in the thickness direction (unit is nm). No spike-like protrusion is observed.

FIG. 8 is an image of the surface condition of the sample manufactured in Comparative Example 1, observed by AFM. In the figure, the X-axis (horizontal axis) shows the length of the observed portion (unit is μm), and the Y-axis (vertical axis) shows the length of the observed portion in the thickness direction (unit is nm). The white wedge-shaped part in the figure is a spike-shaped protrusion.

FIG. 9 is an image obtained by observing the surface state of the sample manufactured in Comparative Example 2 with an AFM. In the figure, the X-axis (horizontal axis) shows the length of the observed portion (unit is μm), and the Y-axis (vertical axis) shows the length of the observed portion in the thickness direction (unit is nm). The white wedge-shaped part in the figure is a spike-shaped protrusion.

FIG. 10 shows the surface condition of the sample prepared in Comparative Example 3 by AFM.
It is the image observed in. In the figure, the X-axis (horizontal axis) shows the length of the observed portion (unit is μm), and the Y-axis (vertical axis) shows the length of the observed portion in the thickness direction (unit is nm). The white wedge-shaped part in the figure is a spike-shaped protrusion.

[Explanation of symbols]

1: Glass substrate 2: Transparent anode 3: Hall transport layer 4: Light emitting layer 5: Electron transport layer 6: Metal cathode

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/28 C04B 35/00 R (72) Inventor Yuichi Nagasaki 2-11-16 Sakuradahigashi, Yamagata City, Yamagata Prefecture F Term ( Reference) 3K007 AB05 AB08 AB17 CB01 DB03 FA01 4G030 AA34 AA39 BA02 BA15 CA01 GA04 GA11 GA22 GA24 GA27 4K029 BC09 BD00 CA05 DC01 DC05 DC09 EA03 EA05

Claims (3)

[Claims] 1. An ITO comprising indium, tin and oxygen
It is a thin film and the surface shape is 0.1 of the bearing curve.
IT in which the difference between the% value Rb and the 50% value Rb is less than 15 nm
O thin film. 2. Sintering density is 99.5% or more in relative density, bulk resistivity is 70 μΩ · cm or more and 100 μΩ · cm or less, and substantially consisting of indium, tin and oxygen.
In ₄ S, an intermediate compound of indium oxide and tin oxide
ITO composed of an ITO sintered body in which the integrated intensity of the X-ray diffraction peak of the (220) plane of the n ₃ O ₁₂ phase is less than 30% of the integrated intensity of the X-ray diffraction peak of the (211) plane of the In ₂ O ₃ phase When forming a film by sputtering using a sputtering target, the oxygen partial pressure in the sputtering atmosphere is 0.5 to 1.
I in the range of 0% according to claim 1, characterized in that
Method of manufacturing TO thin film. 3. Sintering density is 99.5% or more in relative density, bulk resistivity is 70 μΩ · cm or more and 100 μΩ · cm or less, and substantially consisting of indium, tin and oxygen.
In ₄ S, an intermediate compound of indium oxide and tin oxide
An ITO calcination characterized in that the integrated intensity of the X-ray diffraction peak of the (220) plane of the n ₃ O ₁₂ phase is less than 30% of the integrated intensity of the X-ray diffraction peak of the (211) plane of the In ₂ O ₃ phase. An ITO sputtering target consisting of a unit.