KR20060044750A - Fluorine-containing indium-tin-oxide sintered body and the method of preparation of the same - Google Patents

Abstract

The present invention aims to provide a new technique capable of producing a high-density sintered compact for an F-ITO target at a low temperature and in a short time in order to form a transparent conductive film having excellent surface smoothness. The present invention provides a method for producing a fluorine-containing indium-tin oxide sintered body, wherein a direct current pulse current is applied to a powder raw material containing indium, tin, oxygen, and fluorine under pressure; Fluorine-containing indium-tin oxide sintered body obtained by this method; Sputtering target material containing this fluorine-containing indium tin oxide sintered compact; Thin film manufactured using this sputtering target material; Provided said thin film in which the ratio (surface smoothness; ΔZ / d) of the height difference (ΔZ; difference between the maximum value and minimum value of the film thickness) due to unevenness of the thin film to the average value d of the thin film thickness does not exceed 10%. .

Fluorine-containing indium-tin oxide sintered body, target, energized sintering, surface smoothness

Description

Fluorine-containing indium-tin oxide sintered body and its manufacturing method {Fluorine-Containing Indium-Tin-Oxide Sintered Body and the Method of Preparation of the Same}

1 is a graph showing the sintering temperature dependency of density in the sintered body manufactured by the energized sintering method in Example 1. FIG.

2 is a chart showing X-ray diffraction patterns of the sintered bodies obtained in Example 1 and Comparative Example 1. FIG.

[Document 1] Japanese Unexamined Patent Publication No. 60-121272

J. N. Avaritsiotis and R. P. Howson, Thin Solid Films, vol. 80, pp. 63-66 (1981).

[Document 3] Japanese Unexamined Patent Publication No. 2000-273618

[Document 4] Japanese Unexamined Patent Publication No. 10-72253

The present invention provides a fluorine-containing indium-tin oxide useful as a material for forming a transparent conductive film ("Fluorine-containing Indium-Tin-Oxide": represented by the formula In _1-x Sn _x F _y O _z ; hereinafter referred to as "F-ITO"). The present invention relates to a sintering method for quickly producing a sintered body.

Since the ITO thin film has high conductivity and excellent light transmittance, it is widely used as a transparent conductive film in various display devices such as liquid crystal displays.

As a method for producing an ITO thin film, there are a spray method, an immersion method, a vacuum deposition method, and a sputtering method. However, sputtering methods that are relatively superior in terms of manufacturing cost, productivity, film quality, and film properties (conductivity, light transmittance) are the current mainstream production technologies. It became.

The sputtering method includes a method using an alloy target (IT target) of In and Sn, and a method using an oxide target (ITO target) containing a sintered body of In ₂ O ₃ and SnO ₂ . In the method using the IT target, it is difficult to obtain a uniform film on a large-area substrate because the film conductivity has a large dependence of the film conductivity on the variation of the amount of oxygen introduced during thin film production and the poor reproducibility of film formation. Therefore, a method using an ITO target is advantageous in terms of large area, homogeneous film production, and the like.

In recent years, in order to make display of a display panel high quality in a liquid crystal display, an organic electroluminescent display, etc., not only high electroconductivity and high light transmittance but also high surface smoothness is calculated | required by a transparent conductive film. In order to meet such demands, attempts have been made to replace a portion of oxygen of a metal oxide as a target material with fluorine.

For example, Japanese Unexamined Patent Application Publication No. 60-121272 discloses a method for producing a transparent conductive film by plasma-reacting oxygen and the like using indium fluoride, tin fluoride and the like as starting materials. In addition, a study (J. N. Avaritsiotis and R. P. Howson, Thin Solid Films, vol. 80, pp. 63-66 (1981)) using a gas such as carbon tetrafluoride as a raw material of the fluorine component has also been reported. However, as disclosed in these well-known documents, in the reaction film forming method using gas as a thin film forming raw material, a variation occurs in the amount of fluorine obtained in the film as in the case of producing the oxygen gas introduction film using the IT target described above. Moreover, since the quantity is not enough, the thin film which expresses a predetermined characteristic is not obtained as a result. Therefore, as in the case of using the ITO target, it is predicted that it is preferable to produce a film by the sputtering method using the target containing fluorine. In fact, Japanese Unexamined Patent Application Publication No. 2000-273618 discloses a method for producing a sputtered film using a target containing indium fluoride and indium oxide, and it has been reported that a highly conductive thin film is conventionally obtained.

However, little is reported about the method for producing the fluorine-containing ITO target. Japanese Unexamined Patent Application Publication No. 2000-273618 discloses an embodiment using a tablet press-molded with indium fluoride and indium oxide powder as a target. By the way, since the tablet obtained by shaping | molding has low density and low electroconductivity, it has a big difficulty, such as the discharge voltage during film formation rises and a film formation rate is low. Therefore, it is speculated that it is preferable to use a sintered high density target, but there is no report on the production of the F-ITO target by the sintering method. This is due to the fact that ITO is a sinterable ceramic. ITO targets are usually produced by molding a powder containing indium, tin and oxygen and heat-treating for about 10 hours at a high temperature of 1450 to 1650 ° C. with an electric furnace or the like (for example, Japanese Patent Laid-Open No. 10-72253). report). However, when this method is applied to the production of an F-ITO target using a fluorine-containing indium-tin oxide powder as it is, only the ITO target containing no fluorine is released from the raw material powder due to high temperature and long time heat treatment. Not obtained. In order to suppress the release of fluorine, for example, a method of encapsulating a raw material powder in a closed system and performing heat treatment at a relatively low temperature and for a short time is considered, but a report example in which a F-ITO target was produced in such a manner. There is no.

In conclusion, it is indispensable to develop a technology for manufacturing F-ITO sputter targets in a simple and short process for manufacturing and distributing high quality displays.

Therefore, a main object of the present invention is to provide a new technique capable of producing a high-density sintered compact for an F-ITO target at a low temperature and in a short time in order to form a transparent conductive film having excellent surface smoothness.

As a result of intensive research in view of the problems of the prior art as described above, the present inventors have found that when a direct current pulse current is applied (sintering and sintering) while pressurizing a mixed powder containing indium, tin, oxygen, and fluorine, The high-density F-ITO sintered compact can be manufactured within a short time, and the obtained sintered compact was found to be suitable as a target for transparent conductive film manufacture, and came to complete this invention.

That is, the present invention provides the following fluorine-containing indium-tin oxide sintered compact and a sputtering target material using the same.

1. A method for producing a fluorine-containing indium-tin oxide sintered body, wherein a direct current pulse current is applied to a powder raw material containing indium, tin, oxygen, and fluorine under pressure.

2. The powder according to claim 1, wherein the powder raw material is (1) a powder obtained by reacting indium-tin oxide with hydrofluoric acid, (2) a powder obtained by mixing tin oxide with a powder obtained by reacting indium oxide with hydrofluoric acid, (3 A powder obtained by reacting tin oxide with hydrofluoric acid; (4) a powder mixed with indium oxide, indium fluoride, and tin oxide, (5) a powder mixed with indium oxide, tin oxide, and tin fluoride, ( 6) A group consisting of a powder obtained by reacting indium oxide and hydrofluoric acid, (7) a mixed powder of indium oxide and indium fluoride, and (8) a powder further heat-treated with the mixed powder shown in (1) to (7). The manufacturing method of the fluorine containing indium tin oxide sintered compact which is 1 or more types chosen from.

3. A fluorine-containing indium-tin oxide sintered body obtained by the method according to the above 1 or 2.

4. The target material for sputtering containing the fluorine-containing indium tin oxide sintered compact of the said 3rd term | claim.

5. Thin film manufactured using the sputtering target material of the said 4th term.

6. The ratio (surface smoothness; ΔZ / d) of the above item 5, wherein the ratio (surface smoothness; ΔZ / d) of the height difference (ΔZ; difference between the maximum value and minimum value of the film thickness) due to unevenness of the thin film to the average value (d) of the film thickness is 10%. Thin film not exceeding.

According to this invention, a high density F-ITO sintered compact can be manufactured stably in a short time.

When using the high-density F-ITO sintered compact by this invention as a target material for sputtering, the transparent conductive film which is excellent in surface smoothness and exhibits high electrical conductivity and high light transmittance can be manufactured.

The method of the present invention can also be applied to the production of sputter target materials for producing fluorine-containing transparent conductive films having various compositions, for example, fluorine-containing ZnO-based target materials. That is, according to the method of the present invention, it is possible to stably produce a fluorine-containing high-density target that was difficult to manufacture in the external thermal sintering method by a conventional electric furnace in a short time.

Best Mode for Carrying Out the Invention

Hereinafter, the starting raw material, the sintering method, the sintered compact obtained, etc. which are used by the method of this invention are demonstrated in detail.

Starting raw materials

There is no restriction | limiting in particular as each component raw material powder for starting raw material manufacture. For example, indium oxide, indium chloride, indium nitrate, indium sulfate, indium fluoride, indium bromide, etc. are mentioned. Examples of the tin source include tin oxide, tin chloride, tin nitrate, tin sulfate, tin fluoride, and tin bromide. Examples of the fluorine source include hydrofluoric acid, indium fluoride, tin fluoride, and acetyl fluoride.

As a starting material, the mixture which mix | blended each of these component raw materials, the reaction product between these each raw material of components, or the powder which heat-treated or hydrothermally processed these reaction products, etc. can be used.

The ratio of the fluorine component, indium component and tin component in the starting material can be appropriately selected according to the required composition of the target material determined by the thin film composition.

The starting material is not particularly limited, but as a more preferable mixed powder, (1) powder obtained by reacting indium-tin oxide with hydrofluoric acid, and (2) powder obtained by mixing tin oxide with powder obtained by reacting indium oxide with hydrofluoric acid (3) a powder obtained by reacting tin oxide and hydrofluoric acid with indium oxide, (4) indium oxide, indium fluoride, and tin oxide powders, (5) indium oxide, tin oxide, and tin fluoride Further heat treatment (usually a powder, (6) a powder obtained by reacting indium oxide and hydrofluoric acid, (7) a mixed powder of indium oxide and indium fluoride, and (8) the mixed powder shown in the above (1) to (7). Powder or the like) heat-treated at about 100 to 600 ° C. By performing the heat treatment described above, unreacted residues and the like remaining in the mixed powder can be removed to improve the properties of the sintered body. For example, since the powder of (1) is a reaction product powder using an aqueous solution, a residue such as a hydroxyl group is likely to exist, and since this is later gasified during energizing sintering, a dense sintered compact may not be obtained. In such a case, when the powder is heat-treated at about 100 to 600 ° C. before sintering and the residue is removed in advance, the amount of gas generated during energizing sintering becomes small, and a dense sintered body is easily obtained.

The mixing ratio of indium and tin is about 0 to 30%, more preferably about 0 to 20%, based on the total weight of the two. The mixing ratio of oxygen and fluorine is about 1 to 30%, preferably about 2 to 20%, based on the total weight of the two.

The particle diameter of the mixed powder is not particularly limited, but in order to achieve high density of the sintered compact, the particle size is usually about 0.01 to 10 m, more preferably about 0.05 to 5 m.

Energized sintering

In the present invention, the starting raw material powder is sintered by pulse energization, and a high-density F-ITO sintered body can be produced by a sintering operation of about 100 minutes or less (about 10 to 100 minutes) from the start of temperature rise to completion of sintering. Can be.

The energization sintering method is a method of sintering by applying a pulse current to the raw material powder under pressure heating. More specifically, in the present invention, by using the sintering method by on-off pulse energization, such as energized sintering (or pulse energized sintering, pulsed high current sintering, discharge plasma sintering, discharge sintering, etc.), first, it is accommodated in a predetermined mold. One raw material powder is compressed to be a green compact, and a compact current can be supplied to the green compact, and the peak current and the pulse width can be controlled to control compression of the material while controlling the material temperature.

In the present invention, for the mixed raw material powder compact containing indium, tin, oxygen and fluorine, for example, a DC pulse current of about 2,000 to 10,000 A, more preferably about 5,000 to 8,000 A, for example, is usually used. It can be applied under a pressure of about 10 to 60 MPa, more preferably about 20 to 50 MPa to produce a high-density F-ITO sintered body in a short time of about 100 minutes or less from the start of the temperature rise to the completion of the sintering. The temperature at the time of sintering may be selected in consideration of the composition of the raw material, the particle size and particle size distribution of the raw material powder, the size of the sintered body, the pressing pressure, the amount of applied current, and the like, but is usually about 900 to 1400 ° C, more preferably 1000 to 1300 ° C. It is enough.

In a more preferred embodiment of the present invention, sintering of raw powder compacts containing indium, tin, oxygen and fluorine using an apparatus for energizing sintering ("discharge plasma sintering" or "Spark-Plasma-Sintering", SPS) Is done. The discharge plasma sintering machine for implementing this SPS method, its operation principle, and the like are disclosed in, for example, Japanese Patent No. 3,007,929 (Japanese Patent Application Laid-Open No. H10-251070).

In the method of this invention, when graphite is used as a jig, for example, the surface vicinity of the sintered compact obtained may contain graphite which is a component of a jig. Impurities such as graphite contained in the vicinity of the sintered compact can be easily removed by polishing the surface of the sintered compact or performing heat treatment in air.

The fluorine-containing indium-tin oxide sintered body obtained by the method of the present invention has a composition represented by the composition formula In _1-x Sn _x F _y O _z . In this composition formula, x and y are usually in a range of about 0 ≦ x ≦ 1 and 0 <y ≦ 0.3, respectively, and z is a value defined by z = (x−y + 3) / 2.

 <Example>

Examples and comparative examples are shown below to further clarify the features of the present invention.

In Examples and Comparative Examples below, indium oxide (In ₂ O ₃ ) powder having a particle size of about 1 to 5 μm is used as the In source, and tin oxide (SnO ₂ ) powder having a particle size of about 1 to 5 μm is used as the Sn source. Used.

Example 1

Preparation of Starting Raw Powder

Further, about 305 g of In ₂ 0 ₃ and about 46 g of Sn 0 ₂ were sufficiently mixed, and then calcined at 1400 ° C. for 2 hours in an electric furnace. The calcined product was put into about 700 mL of a 10-fold diluted solution of a commercially available HF solution (concentration of about 47%), heated to about 80 ° C. while stirring in a draft with an exhaust system, and evaporated to dryness. The obtained solid was heat-treated at 500 ° C. for 2 hours in an electric furnace, and then ground and mixed to obtain starting material powder.

Manufacture of Sintered Body

A discharge plasma sintering apparatus (manufactured by Sumitomo Sekitan Kogyo Co., Ltd., " SPS-3.20MK-IV &quot;) was used for energizing sintering. In addition, the jig | tool used the thing made of graphite and the cylindrical shape of inner diameter 10cm. About 350 g of the starting raw material powder obtained above was uniformly put in this jig, about 10 g of Al ₂ O ₃ powder was packed up and down, and a pressure of about 30 MPa was applied to degas the inside of the sintering chamber to about 10 Pa. . Subsequently, by applying a DC pulse current of about 1000 to 6000 A to the jig, the periphery of the raw material was heated to a predetermined temperature of 1000 to 1200 ° C. at a heating rate of about 20 ° C./min. After maintaining this state for about 30 minutes, current application and pressurization application were stopped, the produced sintered compact was cooled to room temperature, the inside of the sintering chamber was returned to atmospheric pressure, and the sintered product was extracted.

All obtained sintered products were disk shape of diameter about 10 cm and thickness about 7 mm. Subsequently, Al ₂ O ₃ layers present on the upper and lower surfaces of each of the sintered products were removed by polishing to obtain a dark blue-green desired discotic sintered body.

As shown in FIG. 1, the density of each obtained sintered compact was 6.4 g / cm <^{3> as} a sintered compact of 1200 degreeC, for example, and was about 90% based on the theoretical density (about 7.1 g / cm <^3> ) of ITO. This sintered compact at 1200 degreeC was a mixture (IT-ITO) of IT0 and InOF, as is evident from the X-ray diffraction pattern of FIG. As a result of analyzing the element of this sintered compact, as shown in following Table 1, tin content (Sn / Sn + In) was about 10%, and fluorine content (F / F + O) was about 4%.

Sn / (In + Sn) F / (O + F) Example 1 10.4% 3.9% Comparative Example 1 9.0% 0.0%

As is clear from these results, according to the present invention, a high-density F-ITO sintered body can be produced.

Formation of a thin film

In the above, the film was formed on the glass substrate by the sputtering method using the F-ITO sintered compact manufactured at the sintering temperature of 1200 degreeC as a target. Substrate temperature during film formation was 200 degreeC or 300 degreeC, and sputter power = DC: 200W, film formation pressure = 3 mTorr, and film formation time = 15 minutes.

The thickness, specific resistance, surface elevation, surface smoothness and light transmittance of the obtained film are shown in Table 2 below. The resistivity was about 2-6 × 10 ⁻⁴ Ωcm and the transmittance at 550 nm was 89-90%, and these values were reported values of thin films using conventional ITO targets (1 × 10 ⁻⁴ Ωcm and 91%; R. Latz, K. Michael, and M. Scherer, Jpn. J. Appl. Phys., 30, L149 (1991)].

Film formation temperature Thin film thickness d (nm) Resistivity ρ (10 ^-4 Ωcm) Surface elevation difference ΔZ (nm) Surface smoothness ΔZ / d (%) Transmittance T (%) (550 nm) 300 ℃ 147.9 2.829 13.235 8.9 89.84 200 ℃ 148.7 5.884 6.179 4.2 88.92

Comparative Example 2

Film formation temperature Thin film thickness d (nm) Resistivity ρ (10 ^-4 Ωcm) Surface elevation difference ΔZ (nm) Surface smoothness ΔZ / d (%) Transmittance T (%) (550 nm) 300 ℃ 153.9 1.731 54.981 35.7 89.92 200 ℃ 151.6 3.214 45.898 30.3 86.47

In addition, the ΔZ / d value (surface smoothness) of the obtained thin film was about 4 to 9%, and the surface smoothness was remarkably improved as compared with the value (about 20% or more) of the thin film by the usual IT0 target material.

From the above result, it was clear that the F-ITO sintered compact obtained by the method of this invention exhibits the outstanding effect as a sputter target for manufacturing the transparent conductive film with very high surface smoothness.

Example 2

After reacting indium oxide powder (about 305 g) with hydrofluoric acid (solution diluted 10 times with a solution of 47% concentration, about 3500 mL), the powder was prepared by evaporating to dryness at about 80 ° C to oxidize it. Tin (about 46 g) was mixed and the mixture was heat treated at 500 ° C. for 2 hours in an electric furnace.

Using the heat processing product obtained above as a starting material, it sintered for 30 minutes at 1200 degreeC by the same electric current sintering method as Example 1, and obtained the sintered compact.

Elemental analysis of the obtained sintered compact showed Sn / (In + Sn) = 10.9% and F / (O + F) = 18.5%.

The said sintered compact was formed into a film on the glass substrate by the same method as Example 1 as a target material. The properties of the obtained film were as shown in Table 3.

Film formation temperature Thin film thickness d (nm) Resistivity ρ (10 ^-4 Ωcm) Surface elevation difference ΔZ (nm) Surface smoothness ΔZ / d (%) Transmittance T (%) / 550 nm 100 ℃ 153.8 10.974 8.097 5.3 89.14

Example 3

After the indium oxide powder (about 290 g), the indium fluoride powder (about 25 g) and the tin oxide powder (about 46 g) were sufficiently mixed, a starting raw material powder was prepared by heat treatment at 500 ° C. for 2 hours in an electric furnace. This raw material powder was sintered at 1200 degreeC for 30 minutes by the same electric current sintering method as Example 1, and the sintered compact was obtained.

As a result of elemental analysis of the sintered compact, it was confirmed that Sn / (In + Sn) = 10.4% and F / (0 + F) = 8.4%.

The said sintered compact was formed into a film on the glass substrate by the same method as Example 1 as a target material. The properties of the obtained film were as shown in Table 4.

Film formation temperature Thin film thickness d (nm) Resistivity ρ (10 ^-4 Ωcm) Surface elevation difference ΔZ (nm) Surface smoothness ΔZ / d (%) Transmittance T (%) / 550 nm 100 ℃ 150.9 9.830 7.017 4.6 87.85

Example 4

After reacting indium oxide powder (about 250 g) with hydrofluoric acid (solution diluted 10-fold with a solution of 47% concentration, about 400 mL), evaporated to dryness at about 80 ° C. to prepare a powder, which was then heated in an electric furnace. It heat-treated at 500 degreeC for 2 hours.

The heat processing product obtained above was sintered at 1200 degreeC for 30 minutes by the same electric current sintering method as Example 1, and the sintered compact was obtained.

Elemental analysis of the obtained sintered compact showed Sn / (In + Sn) = 0.0% and F / (0 + F) = 8.0%.

 The said sintered compact was formed into a film on the glass substrate by the same method as Example 1 as a target material. The properties of the obtained film were as shown in Table 5.

Film formation temperature Thin film thickness d (nm) Resistivity ρ (10 ^-4 Ωcm) Surface elevation difference ΔZ (nm) Surface smoothness ΔZ / d (%) Transmittance T (%) / 550 nm 100 ℃ 145.0 3.674 12.75 8.8 88.75

Comparative Example 1

About 350 g of the mixed powder of In ₂ O ₃ and about 46 g of SnO ₂ was heat-treated at 1400 ° C., added to an aqueous HF solution (concentration of 4.7%), evaporated to dryness, and then about 350 g of the raw material mixture heat-treated at 500 ° C. Was uniformly placed in a cylindrical jig having a diameter of 10 cm, press-molded at about 50 MPa, and then the molded body was extracted from the jig and sintered at 1400 ° C. for 2 hours in a normal electric furnace.

The obtained sintered compact had a disk shape of about 10 cm in diameter and about 1.4 cm in thickness, and the density was a low value of 3.2 g / cm ³ , which corresponds to about 45% of the theoretical density (about 7.1 g / cm ³ ) of IT0. This sintered compact was comprised only in ITO, as is clear from the X-ray-diffraction pattern shown in FIG.

In addition, as a result of elemental analysis of the sintered compact, it was found that almost no fluorine was contained as shown in Table 1 above. This was thought to be due to fluorine release during sintering at 1400 ° C.

From the above result, it was clear that the F-ITO sintered compact could not be manufactured by the normal sintering method by an electric furnace.

Comparative Example 2

Using a conventional ITO target (density 6.7 g / cm ³ , relative density about 94%) containing no fluorine, a film was formed on the glass substrate under the same conditions as in Example 1. The properties of the obtained membrane are shown in Table 2 above.

The resistivity and light transmittance of the film showed almost the same values as those of the film obtained in Example 1, but the surface smoothness (ΔZ / d) was 30% or more. All of them could not obtain a high thin film.

According to this invention, a high density F-ITO sintered compact can be manufactured stably in a short time.

Claims (6)

A method for producing a fluorine-containing indium-tin oxide sintered body, wherein a direct current pulse current is applied to a powder raw material containing indium, tin, oxygen, and fluorine under pressure. The powder raw material according to claim 1, wherein the powder raw material is (1) powder obtained by reacting indium-tin oxide with hydrofluoric acid, (2) powder obtained by reacting indium oxide with hydrofluoric acid, and (3) oxidation Indium oxide mixed with powder obtained by reacting tin and hydrofluoric acid, (4) Indium oxide, indium fluoride, and tin oxide powders, (5) Indium oxide, tin oxide, and tin fluoride powders, (6) A powder obtained by reacting indium oxide with hydrofluoric acid, (7) a mixed powder of indium oxide and indium fluoride, and (8) a powder obtained by further heat-treating the mixed powder shown in (1) to (7). The manufacturing method of the fluorine-containing indium tin oxide sintered compact which is 1 or more types. The fluorine-containing indium-tin oxide sintered compact obtained by the method of Claim 1 or 2. The target material for sputtering containing the fluorine-containing indium tin oxide sintered compact of Claim 3. The thin film manufactured using the sputtering target material of Claim 4. The ratio (surface smoothness; ΔZ / d) of the height difference (ΔZ; difference between the maximum value and the minimum value of the film thickness) due to unevenness of the thin film to the average value (d) of the film thickness does not exceed 10%. Do not thin film.

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