JP2005272272A - Sintered compact of fluorine-containing indium-tin oxide and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide novel technology capable of manufacturing a high-density sintered compact for an F-ITO target in order to form a transparent conductive film having excellent surface smoothness. <P>SOLUTION: The method for manufacturing the sintered compact of the fluorine-containing indium-tin oxide comprising applying a DC pulse current under pressurization to powder raw materials containing indium, tin, oxygen and fluorine; the target material for sputtering composed of the sintered compact of the fluorine-containing indium-tin oxide obtained by the method described in the previous item; the thin film manufactured by using the target material for sputtering described in the previous item; the thin film, described in the previous item, wherein the ratio (surface smoothness; ΔZ/d) of the height difference (ΔZ; difference between the maximum value and minimum value of the film thicknesses) by the ruggedness of the thin film to the mean value (d) of the thin film thickness does not exceed 10%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is useful fluorine-containing indium as the material for forming the transparent conductive film - tin oxide ( "Fluorine-containing Indium-Tin -Oxide": represented by the composition formula _{In 1-x Sn x F y} O z; hereinafter The present invention relates to a sintering method for rapidly producing a sintered body (sometimes abbreviated as “F-ITO”).

  The ITO thin film is widely used as a transparent conductive film in various display devices such as a liquid crystal display because it has high conductivity and excellent translucency.

  Methods for producing ITO thin films include spraying, dipping, vacuum deposition, sputtering, etc., but relative in terms of manufacturing cost, productivity, film quality, film characteristics (conductivity, translucency), etc. Sputtering methods that are superior in quality are the current mainstream production technology.

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) made of a sintered body of In ₂ O ₃ and SnO ₂ . In the method using an IT target, the dependence of the film conductivity on the variation in the amount of oxygen introduced during the production of the thin film is extremely large, and the reproducibility of the film formation is inferior, so that a uniform conductive film is obtained on a large substrate. It is difficult. Therefore, a method using an ITO target is advantageous in terms of increasing the area and producing a homogeneous film.

  In recent years, in order to improve display panel display quality in liquid crystal displays, organic EL displays, etc., transparent conductive films are required to have high surface smoothness in addition to high conductivity and high translucency. It is becoming. In order to meet such a demand, an attempt has been made to substitute a part of oxygen of a metal oxide as a target material with fluorine.

  For example, Patent Document 1 discloses a method of manufacturing a transparent conductive film by using indium fluoride, tin fluoride or the like as a starting material, and causing plasma reaction with oxygen and the like. A study using a gas such as carbon tetrafluoride as a raw material for the fluorine component (Non-patent Document 1) has also been reported. However, as disclosed in these known documents, in the reactive film formation method using a gas as a thin film forming raw material, as in the case of the oxygen gas introduction film formation using the above-mentioned IT target, it is taken into the film. Since the amount of fluorine varies and the amount thereof is not sufficient, a thin film exhibiting desired characteristics cannot be obtained as a result. Therefore, as with the case of using an ITO target, it is predicted that it is preferable to form a film by sputtering using a target containing fluorine. In fact, Patent Document 2 discloses a sputtering film forming method using a target containing indium fluoride and indium oxide, and it is reported that a highly conductive thin film can be obtained.

  However, few methods have been reported for producing fluorine-containing ITO targets. Said patent document 2 has shown the Example which used the tablet which press-molded the indium fluoride and the indium oxide powder as a target. However, since the tablet obtained by molding has low density and low conductivity, the discharge voltage during film formation rises and the film formation rate is low. For this reason, it is presumed that it is preferable to use a sintered high-density target, but there is no report on the production of an F-ITO target by a sintering method. This is because ITO is a hardly sinterable ceramic. The ITO target is usually produced by molding a powder composed of indium, tin, and oxygen and heat-treating it at a high temperature of 1450-1650 ° C. for about 10 hours with an electric furnace or the like (for example, Patent Document 3). However, when this method is applied as it is to the production of an F-ITO target using fluorine-containing indium-tin oxide powder, fluorine is desorbed from the raw material powder by high-temperature and long-time heat treatment. Only ITO targets that do not contain can be obtained. In order to suppress the desorption of fluorine, for example, a method of confining the raw material powder in a closed system and subjecting it to a heat treatment at a relatively low temperature for a short time can be considered. There are no reports of production.

In conclusion, it is indispensable to develop a technology to manufacture F-ITO sputter targets in a simple and short process for producing high-quality displays and spreading them.
JP-A-60-121272 JN Avaritsiotis and RP Howson, Thin Solid Films, vol.80, pp.63-66 (1981). JP 2000-273618 A Japanese Patent Laid-Open No. 10-72253

  Therefore, the present invention mainly provides a new technique capable of producing a high-density sintered body for an F-ITO target at a low temperature in a short time in order to form a transparent conductive film having excellent surface smoothness. With a purpose.

  As a result of intensive studies in view of the above-described problems of the prior art, the present inventor applied a DC pulse current while applying pressure to a mixed powder containing indium, tin, oxygen, and fluorine (electric current firing). In this case, the present inventors have found that a high-density F-ITO sintered body can be produced within a short time, and that the obtained sintered body is suitable as a target for producing a transparent conductive film. It came to be completed.

That is, the present invention provides the following fluorine-containing indium-tin oxide sintered body 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 under pressure to a powder raw material containing indium, tin, oxygen and fluorine.
2. Powder raw materials were (1) powder obtained by reacting indium-tin oxide and hydrofluoric acid, and (2) tin oxide mixed with powder obtained by reacting indium oxide and hydrofluoric acid. Powder, (3) a powder obtained by reacting tin oxide and hydrofluoric acid, mixed with indium oxide, (4) mixed powder of indium oxide, indium fluoride and tin oxide, (5) indium oxide Mixed powder of tin oxide and tin fluoride, (6) powder obtained by reacting indium oxide and hydrofluoric acid, (7) mixed powder of indium oxide and indium fluoride, and (8) these 2. The method for producing a fluorine-containing indium-tin oxide sintered body according to item 1, which is at least one selected from the group consisting of powders obtained by further heat-treating the mixed powder shown in (1) to (7).
3. 3. A fluorine-containing indium-tin oxide sintered body obtained by the method according to item 1 or 2.
4). 4. A sputtering target material comprising the fluorine-containing indium-tin oxide sintered body according to item 3.
5). A thin film produced using the sputtering target material according to Item 4.
6). Item 5 above wherein 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 the unevenness of the thin film to the average value (d) of the film thickness does not exceed 10% A thin film according to 1.

  According to the present invention, a high-density F-ITO sintered body can be stably produced in a short time.

  When the high-density F-ITO sintered body according to the present invention is used as a sputtering target material, it is possible to produce a transparent conductive film that has excellent surface smoothness and exhibits high conductivity and high translucency. .

  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 has been difficult to produce by an external heating sintering method using a conventional electric furnace or the like in a short time.

Hereinafter, the starting material, the sintering method, and the obtained sintered body used in the method of the present invention will be described in more detail.
There is no restriction | limiting in particular as each component raw material powder for starting raw material preparation. For example, examples of the indium source include indium oxide, indium chloride, indium nitrate, indium sulfate, indium fluoride, and indium bromide. 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 the starting material, a mixture in which these component materials are blended, a reaction product between these component materials, a powder obtained by heat-treating or hydrothermally treating these reaction products, or the like can be used.

  The proportions 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 according to the thin film composition.

  The starting material is not particularly limited, but as a more preferable mixed powder, (1) a powder obtained by reacting indium-tin oxide and hydrofluoric acid, (2) indium oxide and hydrogen fluoride Powder obtained by mixing tin oxide with powder obtained by reacting with acid, (3) Powder obtained by mixing tin oxide and hydrofluoric acid with powder obtained by mixing indium oxide, and (4) Indium oxide and fluoride. Mixed powder of indium phosphide and tin oxide, (5) mixed powder of indium oxide, tin oxide and tin fluoride, (6) powder obtained by reacting indium oxide and hydrofluoric acid, (7) oxidation Examples thereof include mixed powders of indium and indium fluoride, and (8) powders obtained by further heat treatment (usually heat treatment at about 100 to 600 ° C.) of the mixed powders shown in (1) to (7). By performing the above heat treatment, unreacted residues remaining in the mixed powder are removed, and the properties of the sintered body can be improved. For example, since the powder of (1) is a reaction product powder using an aqueous solution, there is a high possibility that residues such as hydroxyl groups are present, and this is gasified during the subsequent current sintering, so a dense sintered body May not be obtained. In such a case, the powder is heat-treated at about 100 to 600 ° C. before sintering, and the residue is removed in advance, thereby reducing the amount of gas generated during current sintering and a dense sintered body. Is easy to obtain.

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

The particle size of the mixed powder is not particularly limited, but is usually about 0.01 to 10 μm, more preferably about 0.05 to 5 μm, in order to achieve high density of the sintered body.
In the present invention, in the present invention, the starting raw material powder is sintered by pulse energization, and is usually sintered for about 100 minutes or less (about 10 to 100 minutes) from the start of temperature rise to the completion of sintering. By operation, a high-density F-ITO sintered body can be produced.

  The electric current sintering method is a method in which a raw material powder is sintered by applying a pulse current under pressure and heating. More specifically, in the present invention, a sintering method by ON-OFF pulse energization such as current sintering (or pulse current sintering, pulse high current sintering, discharge plasma sintering, discharge sintering, etc.). First, the raw material powder contained in a predetermined mold is compressed into a green compact. A pulsed current is applied to the green compact, and the peak current and pulse width are controlled to control the material temperature. Compression and sintering can be performed while controlling.

  In the present invention, for a mixed raw material powder compact containing indium, tin, oxygen and fluorine, for example, usually about 10-60 MPa, more preferably about 20-50 MPa, for example, about 2,000-10,000 A. A high-density F-ITO sintered body can be produced in a short time of about 100 minutes or less from the start of temperature rise to the completion of sintering by applying a DC pulse current of about 5,000 to 8,000 A, more preferably about 5,000 to 8,000 A. . The temperature during 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 applied pressure, the amount of applied current, etc., but usually 900 to 1400 ° C. About 1000 to 1300 ° C.

  In a more preferred embodiment of the present invention, a raw material powder containing indium, tin, oxygen and fluorine using an apparatus for electric current sintering (also called “discharge plasma sintering” or “Spark-Plasma-Sintering” or SPS). The green compact is sintered. A discharge plasma sintering machine for operating this SPS method and its operating principle are disclosed in, for example, Japanese Patent No. 3,007,929 (Japanese Patent Laid-Open No. 10-251070).

  In the method of the present invention, for example, when graphite is used as a jig, the vicinity of the surface of the obtained sintered body may contain graphite as a component of the jig. Such impurities such as graphite contained in the vicinity of the surface of the sintered body can be easily removed by polishing or heat-treating the surface of the sintered body in the air.

Fluorine-containing indium obtained by the method of the present invention - tin oxide sintered body 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 the range of about 0 ≦ x ≦ 1 and 0 <y ≦ 0.3, respectively, and z is a value defined by z = (x−y + 3) / 2. .

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

In the following examples and comparative examples, 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 ) having a particle size of about 1 to 5 μm is used as the Sn source. ) Powder was used.
[Example 1]
Preparation of starting material powder First, about 305 g of In ₂ O ₃ and about 46 g of SnO ₂ were sufficiently mixed, and then baked in an electric furnace at 1400 ° C. for 2 hours. This calcined product was put into about 700 mL of a 10-fold diluted commercial HF aqueous solution (concentration: about 47%), and heated at about 80 ° C. while stirring in a fume hood equipped with an exhaust facility to evaporate to dryness. The obtained solid was heat treated in an electric furnace at 500 ° C. for 2 hours, and then pulverized and mixed to obtain a starting material powder.
A spark plasma sintering apparatus (“SPS-3.20MK-IV” manufactured by Sumitomo Coal Mining Co., Ltd.) was used for the electric current sintering of the sintered body . A jig made of graphite and having a cylindrical shape with an inner diameter of 10 cm was used. In this jig, uniformly put about 350 g of the starting raw material powder obtained above, spread about 10 g of Al ₂ O ₃ powder on the top and bottom, apply a pressure of about 30 MPa, and remove the inside of the sintering chamber to about 10 Pa. I worried. Next, 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 temperature rising rate of about 20 ° C./min. After maintaining this state for about 30 minutes, the application of current and pressure was stopped, the formed sintered body was cooled to room temperature, the inside of the sintering chamber was returned to atmospheric pressure, and the sintered product was taken out.

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

As shown in FIG. 1, the density of each obtained sintered body is 6.4 g / cm ³ for a sintered body at 1200 ° C., for example, based on the theoretical density of ITO (about 7.1 g / cm ³ ). About 90%. The sintered body at 1200 ° C. is a mixture of ITO and InOF (F-ITO), as is apparent from the X-ray diffraction pattern of FIG. When elemental analysis of this sintered body was conducted, as shown in Table 1, the tin content (Sn / Sn + In) was about 10% and the fluorine content (F / F + O) was about 4%. there were.

これらの結果から明らかな様に、本発明によれば、高密度F-ITO焼結体を作製することができる。
薄膜の形成
上記において、燒結温度1200℃で作製したF-ITO焼結体をターゲットとして用いて、ガラス基板上にスパッタ法により、成膜を行った。成膜中の基板温度は、200℃または300℃とし、スパッタパワー=DC：200W、成膜圧力=3mTorr、成膜時間=15分で行った。

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, a F-ITO sintered body produced at a sintering temperature of 1200 ° C. was used as a target, and a film was formed on a glass substrate by sputtering. The substrate temperature during film formation was 200 ° C. or 300 ° C., sputtering power = DC: 200 W, film formation pressure = 3 mTorr, and film formation time = 15 minutes.

Table 2 shows the film thickness, specific resistance, surface height difference, surface smoothness and translucency of the obtained film. The specific resistance is about 2-6 × 10 ⁻⁴ Ωcm, the transmissivity at 550 nm is 89-90%, and these values are the reported values for 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).).

また、得られた薄膜のΔZ／d値(表面平滑度)は、約4〜9％であり、通常のITOターゲットによる薄膜の値(約20％以上)に比べ、表面平滑性が著しく向上していた。

Moreover, the ΔZ / d value (surface smoothness) of the obtained thin film is about 4-9%, and the surface smoothness is remarkably improved compared to the value of the thin film (about 20% or more) with the normal ITO target. It was.

From the above results, it is clear that the F-ITO sintered body obtained by the method of the present invention exhibits an excellent effect as a sputtering target for producing a transparent conductive film having extremely high surface smoothness.
[Example 2]
After reacting indium oxide powder (approx. 305 g) with hydrofluoric acid (commercially diluted solution of 47% solution, approximately 3500 mL), the powder was prepared by evaporating to dryness at approximately 80 ° C. This was mixed with tin oxide (about 46 g), and the mixture was heat-treated in an electric furnace at 500 ° C. for 2 hours.

  Using the heat treatment product obtained above as a starting material, sintering was performed at 1200 ° C. for 30 minutes by the same electric current sintering method as in Example 1 to obtain a sintered body.

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

  Using the sintered body as a target material, a film was formed on a glass substrate in the same manner as in Example 1. The properties of the obtained film were as shown in Table 3.

［実施例３］
酸化インジウム粉末(約290g)とフッ化インジウム粉末(約25g)と酸化錫粉末(約46g)とを十分に混合した後、電気炉で500℃、2時間熱処理することにより、出発原料粉末を調製した。この原料粉末を実施例1と同様の通電焼結法により、1200℃で30分間焼結して、焼結体を得た。

[Example 3]
After mixing indium oxide powder (approx. 290 g), indium fluoride powder (approx. 25 g) and tin oxide powder (approx. 46 g), heat treatment is performed in an electric furnace at 500 ° C. for 2 hours to prepare a starting material powder. did. This raw material powder was sintered at 1200 ° C. for 30 minutes by the same electric current sintering method as in Example 1 to obtain a sintered body.

  From the elemental analysis results of the sintered body, it was confirmed that Sn / (In + Sn) = 10.4% and F / (O + F) = 8.4%.

  Using the sintered body as a target material, a film was formed on a glass substrate in the same manner as in Example 1. The properties of the obtained film were as shown in Table 4.

［実施例4］
酸化インジウム粉末(約250g)とフッ化水素酸(市販の濃度47％の溶液を10倍希釈した溶液、約400mL)とを反応させた後、約80℃で蒸発乾固させて粉末を調製し、これを電気炉で500℃、2時間熱処理した。

[Example 4]
After reacting indium oxide powder (approx. 250 g) with hydrofluoric acid (a solution obtained by diluting a commercially available 47% solution 10-fold, approx. 400 mL), the powder was prepared by evaporating to dryness at approx. 80 ° C. This was heat-treated in an electric furnace at 500 ° C. for 2 hours.

  Using the heat treatment product obtained above as a starting material, sintering was performed at 1200 ° C. for 30 minutes by the same electric current sintering method as in Example 1 to obtain a sintered body.

  Elemental analysis of the obtained sintered body revealed that Sn / (In + Sn) = 0.0% and F / (O + F) = 8.0%.

  Using the sintered body as a target material, a film was formed on a glass substrate in the same manner as in Example 1. The properties of the obtained film were as shown in Table 5.

［比較例１］
In₂O₃約305gとSnO₂約46gとの混合粉を1400℃で熱処理した後、HF水溶液(濃度約4.7％)に加え、蒸発乾固し、500℃で熱処理した原料混合物約350gを直径10cmの円筒型の治具に均一に入れて、約50MPaで加圧成型した後、成型体を治具から取り出し、通常の電気炉により1400℃で2時間焼結した。

[Comparative Example 1]
A mixed powder of approximately 305 g of In ₂ O ₃ and approximately 46 g of SnO ₂ is heat-treated at 1400 ° C, then added to an HF aqueous solution (concentration approximately 4.7%), evaporated to dryness, and approximately 350 g of the raw material mixture heat-treated at 500 ° C After uniformly putting it in a 10 cm cylindrical jig and press molding at about 50 MPa, the molded body was taken out from the jig and sintered at 1400 ° C. for 2 hours in a normal electric furnace.

The obtained sintered body has a disk shape with a diameter of about 10 cm and a thickness of about 1.4 cm, and the density is 3.2 g / cm corresponding to about 45% of the theoretical density of ITO (about 7.1 g / cm ³ ). It was a low value of ³ . As apparent from the X-ray diffraction pattern shown in FIG. 2, this sintered body was composed only of ITO.

  Further, when elemental analysis of the sintered body was performed, it was found that almost no fluorine was contained as shown in Table 1 above. This is thought to be due to the elimination of fluorine during sintering at 1400 ° C.

From the above results, it is clear that an F-ITO sintered body cannot be produced by a sintering method using an ordinary electric furnace or the like.
[Comparative Example 2]
Using a normal ITO target (density 6.7 g / cm ³ , relative density about 94%) containing no fluorine, a film was formed on a glass substrate under the same conditions as in Example 1. The properties of the obtained film are shown in Table 2 above.

  The specific resistance and translucency of the film showed almost the same values as those of the film according to Example 1, but the surface smoothness (ΔZ / d) was 30% or more, more than 3 times that of Example 1. It was lowered and it was not possible to obtain a thin film having high conductivity, translucency and surface smoothness.

In the sintered compact produced by the electric current sintering method in Example 1, it is a graph which shows the sintering temperature dependence of a density. 3 is a chart showing X-ray diffraction patterns of sintered bodies obtained in Example 1 and Comparative Example 1. FIG.

Claims (6)

A method for producing a fluorine-containing indium-tin oxide sintered body, wherein a direct current pulse current is applied under pressure to a powder raw material containing indium, tin, oxygen and fluorine. Powder raw materials were (1) powder obtained by reacting indium-tin oxide and hydrofluoric acid, and (2) tin oxide mixed with powder obtained by reacting indium oxide and hydrofluoric acid. Powder, (3) a powder obtained by reacting tin oxide and hydrofluoric acid, mixed with indium oxide, (4) mixed powder of indium oxide, indium fluoride and tin oxide, (5) indium oxide Mixed powder of tin oxide and tin fluoride, (6) powder obtained by reacting indium oxide and hydrofluoric acid, (7) mixed powder of indium oxide and indium fluoride, and (8) these The method for producing a fluorine-containing indium-tin oxide sintered body according to claim 1, which is at least one selected from the group consisting of powders obtained by further heat-treating the mixed powder shown in (1) to (7). A fluorine-containing indium-tin oxide sintered body obtained by the method according to claim 1 or 2. A sputtering target material comprising the fluorine-containing indium-tin oxide sintered body according to claim 3. A thin film produced using the sputtering target material according to 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 the unevenness of the thin film to the average value (d) of the film thickness does not exceed 10%. A thin film according to 1.

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