KR100754356B1 - ITO sputtering target - Google Patents

Abstract

The ITO sputtering target which can reduce the amount of nodules which generate | occur | produced on the target surface also when using the film-forming method which generate | occur | produces a nodule easily and discharges with low applied electric power is used.

An ITO sputtering target and the ITO sintered body formed by joining an ITO sintered body consisting essentially of indium, tin, and oxygen to a metal backing plate such as oxygen-free copper by an indium-tin solder containing 3 to 15% by weight of tin, and the backing plate In an ITO sputtering target formed by joining with a metal bonding agent such as indium solder, a part or all of the exposed portion of the metal bonding agent is covered with an alloy made of indium and tin.

ITO Sputtering Targets, Nozzles, Backing Plates, Indium-Tin Solder, Metal Bonders

Description

Ito sputtering target

The present invention relates to an ITO sputtering target used when producing a transparent conductive thin film.

ITO (Indium Tin Oxide) thin film is characterized by high electrical conductivity and high transmittance, and can be easily processed in particular, so that a wide range of display electrodes for flat panel displays, window materials for solar cells, antistatic films, etc. It is widely used in the field. In particular, in the field of flat panel displays, including liquid crystal displays, in recent years, large-scale and high-definition have been progressing, and the demand for ITO thin films as the display electrodes has also increased.

Such an ITO thin film manufacturing method can be roughly divided into a chemical film forming method such as a spray pyrolysis method and a CVD method, and a physical film forming method such as an electron beam deposition method and a sputtering method. Among them, the sputtering method has been used in various fields because it is a film forming method which is easy to enlarge a large area and obtains a higher performance film.

When manufacturing an ITO thin film by the sputtering method, as a sputtering target to be used, the alloy target (IT target) which consists of metal indium and metal tin, or the composite oxide target (ITO target) which consists of indium oxide and tin oxide is used. . In particular, the method using the ITO target has a small change over time in the resistance value and the transmittance of the obtained film compared to the method using the IT target, and the ITO thin film manufacturing method is mainstream because it is easy to control the film forming conditions. It is becoming.

When the ITO target is sputtered continuously in a mixed gas atmosphere of argon gas and oxygen gas, black deposits called nidules are precipitated on the target surface with an increase in accumulated sputtering time. Since black deposits, which are considered to be lower oxides of indium, are precipitated around the erosion part of the target, they are likely to cause abnormal discharge during sputtering, and these are themselves foreign particles. It is known to be the source of occurrence.

As a result, if sputtering is performed continuously, foreign material adsorption will generate | occur | produce in the formed thin film, and these have become a cause of manufacture suspension or fall of flat panel displays, such as a liquid crystal display device. In particular, in the field of flat panel displays in recent years, high-definition has progressed, and since foreign material adsorption in such thin films causes malfunction of the device, it has become a problem to be solved in particular.

In order to solve such a problem, for example, as in Japanese Patent Application Laid-Open No. 08-060352, the density of the target is set to 6.4 g / cm ³ or more, and the surface roughness of the target is controlled to generate nodules. It is reported that this can be reduced.

However, in recent years, a film forming method of discharging at low applied power has been adopted for the purpose of improving the performance of thin films formed with high definition and high performance of liquid crystal display devices. Due to the film formation as the low applied power, generation of nodules is a problem even when a target adopting the above-described method is used. It is thought that this is due to an increase in the probability that the nuclei of the once-generated nodules become nuclei of the remaining ones due to the decrease in the applied electric power, and become nuclei of the residue.

An object of the present invention is to provide an ITO sputtering target which easily reduces the generation of nodules and reduces the amount of nodules generated on the target surface even when a film forming method for discharging at a low applied voltage is used.

In order to reduce the amount of nodules generated by the ITO sputtering target, the present inventors conducted detailed inspection on the cause of the generation of the nodules. As a result, some nodules include metal indium, which is a solder material used for joining an ITO sintered body and a backing plate, to be attached to an erosion portion of the target surface during sputtering, and the attached metal indium is used as a nucleus. It was found that the target surface became jagged and notched. It is not yet clear what causes the metal indium to become a nucleus that generates deposits, but the metal indium attached to the target surface reacts with oxygen contained in the sputtering gas to form indium oxide, which is compared with ITO. Since the resistivity is very high, it is considered to be a rough residue.

Therefore, the present inventors performed detailed examination about the structure of the solder material and ITO sputtering target used as a bonding agent of an ITO sintered compact and a backing plate. As a result, in the first invention of the present invention, after using the indium-tin alloy as the solder material, or in the second invention of the present invention, after bonding the ITO sintered body and the backing plate using indium solder on the backing plate, By covering a part or all of the exposed portion of the solder material with an alloy made of indium and tin, it has been found that the generation of nodules due to the solder material can be reduced, and the present invention has been reached.

That is, the present invention is substantially the indium in the ITO sputtering target and the second invention formed by bonding an ITO sintered body made of indium, tin, or oxygen to a metal backing plate by indium tin solder as a first invention. In an ITO sputtering target formed by bonding an ITO sintered body consisting of tin and oxygen to a backing plate by a metal bonding agent, a part or all of the exposed portion of the metal bonding agent is coated with an alloy made of indium and tin. It relates to an ITO sputtering target.

Hereinafter, the present invention will be described in detail.

Although it does not specifically limit as a manufacturing method of the ITO sintered compact used by this invention, For example, it can manufacture by the following method.

First, a binder or the like is added to a mixed powder of indium oxide powder and tin oxide powder or ITO powder, and molded by a molding method such as a press method or an injection method to produce an ITO molded body. At this time, when the average particle diameter of the powder to be used is large, the density after sintering may not sufficiently increase, and the particle diameter of the powder to be used is preferably 1.5 μm or less, and particularly preferably 0.1 to 1.5 μm. By doing in this way, it becomes possible to obtain a sintered compact with a larger sintered density.

The tin oxide content in the mixed powder or ITO powder is preferably 5 to 15% by weight in which the specific resistance decreases when the thin film is produced by the sputtering method. When necessary for the molded product obtained later, condensation treatment such as CIP is performed. At this time, the CIP pressure is preferably 2 ton / cm ² or more, preferably ² to 3 ton / cm ² , in order to obtain a sufficient consolidation effect. Therefore, when the first molding is performed by the injection method, a debinding treatment may be performed for the purpose of removing organic matters such as moisture and binder remaining in the molded body after CIP. Alternatively, even when the first molding is performed by the press method, when the binder is used during molding, it is preferable to perform the above binder removal treatment.

The molded article thus obtained is introduced into a sintering furnace and sintered. Although any method can be used as a sintering method, in consideration of cost of a production facility, sintering in air | atmosphere is preferable. However, it goes without saying that other conventionally known sintering methods such as hot press (HP) method, hot isostatic press (HIP) method and oxygen pressurization sintering method can be used.

Moreover, although it can select suitably also about sintering conditions, in order to acquire sufficient density synergy effect or to suppress evaporation of tin oxide, it is preferable that sintering temperature is 1450-1650 degreeC. In addition, it is preferable that the atmosphere at the time of sintering is air | atmosphere or pure oxygen atmosphere. Moreover, also in sintering time, in order to acquire sufficient density increase effect, it is preferable to set it as 5 hours or more, Preferably it is 5 to 30 hours.

By doing in this way, an ITO sintered compact with a high sintered density can be obtained.

In the present invention, the density of the ITO sintered compact to be used is not particularly limited, but in order to suppress abnormal discharge due to electric field concentration at the edge of the pores of the sintered compact and the idea of nodules, It is preferable to make relative density into 99% or more, More preferably, it is 99.5% or more.

The relative density (D) used in the present invention represents a relative value with respect to the theoretical density (d) that can be obtained from the additive average of the true densities of In ₂ O ₃ and SnO ₂ . The theoretical density (d), which can be obtained from the average of the averages, refers to the true density of In ₂ O ₃ and SnO ₂ when the mixed amount (g) of In ₂ O ₃ and SnO ₂ powder is a and b in the sintered body composition, respectively. Using 7.18, 6.95 (g / cm ³ ),

It can obtain | require by d = (a + b) / ((a / 7.18) + (b / 6.95)). Therefore, if the measured density of a sintered compact is d1, the relative density D (%) can be calculated | required by Formula: D = (d1 / d) * 100.

The ITO sintered compact manufactured by the method mentioned above is ground to desired size. It is preferable that an ITO sintered compact has high density and high limit hardness, and cracks are likely to occur inside the sintered compact during grinding, and the machining is preferably performed by wet processing.

In addition, the sputtering surface of the ITO sintered compact is mechanically polished, and in the first invention, the surface roughness of the sputtering surface is adjusted so that the average line center roughness Ra is 0.8 μm or less, and the maximum height Rmax is 7.0 μm or less. It is preferable to process. More preferably, Ra is 0.1 micrometer or less, and Rmax is 2.0 micrometers or less. In 2nd invention, it is preferable to process average line center roughness Ra of a sputtering surface at 0.8 micrometer or less, and maximum height Ry to 6.5 micrometers or less. More preferably, Ra is 0.1 micrometer or less, and Ry is 2 micrometers or less.

In addition, the definition and the measuring method of Ra and Ry said by this invention are the methods of JISB0601-1994, The definition and the measuring method of Rmax are based on what was described in JIS-B0601-1982. This makes it possible to more effectively suppress the abnormal discharge occurring at the convex portion of the target surface and the formation of the nodules due to the abnormal discharge.

The ITO sintered compact thus obtained is bonded onto the backing plate. Although the backing plate used for this invention is not specifically limited, For example, anoxic copper, phosphorus copper, etc. are mentioned.

In joining, in the 1st invention of this invention, it can carry out according to the following processes, for example. First, it heats more than melting | fusing point of the solder material which uses an ITO sintered compact and a backing plate. After heating, indium tin solder is applied to the bonding surface of the ITO sintered body and the backing plate. As the solder coating method, for example, coating by ultrasonic solder or directly dissolving the solder may be applied, and the coating thickness is preferably 0.1 to 0.6 mm, for example.

By using the solder material as an indium-tin alloy, the solder material becomes ITO even if it is oxidized after adhering to the erosion part of the target during sputtering, so that the resistivity is almost the same as that of the surrounding sintered body, and no deposits are formed so that nodules are produced. It doesn't work. On the other hand, in the case of using indium as in the prior art, since it adheres to the erosion part and then oxidizes, it becomes high resistivity compared with the ITO sintered body, and thus it becomes easy to be a nucleus for producing nodules.

 Therefore, even when an indium-tin alloy is used as the solder material, it is preferable to set the tin concentration (tin / (indium + tin) x 100) in the solder material at a weight ratio of 3 to 15% so that the resistivity decreases when the oxide is used. desirable.

Subsequently, the ITO target of this invention can be obtained by joining the joining surfaces of a solder material application | coating ITO sintered compact and a backing plate, and cooling to room temperature.

In the second invention of the present invention, indium solder or the like is preferable as the metal bonding agent. This is because indium solder is flexible and has an effect of preventing cracking of the sintered compact when the ITO sintered compact portion is heated and expanded during sputtering.

What is necessary is just to perform the joining method in this case by the process similar to what is demonstrated below, for example. That is, the ITO sintered compact and the backing plate are heated above the melting point of the metal bonding agent to be used. A bonding agent is apply | coated to the bonding surface of the heated ITO sintered compact and a backing plate. After joining the ITO sintered compact after bonding agent application and the bonding surface of a backing plate, and arrange | positioning in a desired position on a backing plate, cooling of a target-backing plate bonding body is performed.

Although the present invention is characterized by coating part or all of the exposed (obvious) binder portion with an alloy consisting of indium and tin when bonding, the coating is carried out by cooling the target-backing plate assembly. This is preferable because the operation of heating the joined body again can be omitted due to the coating.

Specifically, when the temperature of the bonding body is 1 to 5 占 폚 higher than the melting point of the indium-tin alloy, the indium-tin alloy is heated at a temperature of 1 to 5 占 폚 higher than the melting point, and applied to the bonding agent exposed portion. To cover. At this time, if the indium-tin alloy is applied more than necessary, the alloy is prominently protruded from the target member, and the protruding portions are separated by plasma during sputtering, and when the separated particles reach the substrate, particles ), And the ratio of the product to the raw material may be reduced, so it is preferably 1 mm or less. Then, the ITO target which is this invention can be obtained by cooling to room temperature.

As the indium-tin alloy, 3 to 15% by weight of Sn / (In + Sn), which is a suitable composition capable of obtaining a low resistivity similar to that of the ITO sintered body, is preferred, so that a rugged residue does not occur when forming an oxide. Preferably, 4 to 12% by weight is preferred.

The ITO sputtering target by this invention can be used especially without being limited to the sputtering method. The magnet disposed under the target may be of fixed type or of swing type, and may be used regardless of the strength of the magnet.

As a sputtering gas, oxygen gas etc. can be added to inert gas, such as argon, etc. as needed, and discharge can be normally performed, controlling gas pressure at 2-10 mTorr. DC, RF or a combination thereof can be used as a power application method for discharging, but in consideration of the stability of the discharge, it is preferable to superimpose RF on DC or DC. Although there is no restriction | limiting in particular about the power density applied to a target, The target of this invention is especially effective under the conditions of the recent low power discharge (2.0 W / cm <^2> or less).

Moreover, the sputtering target by this invention is effective also in the target which added the 3rd element so that ITO may have an additional function. As a 3rd element, Mg, Al, Si, Ti, Zn, Ga, Ge, Y, Zr, Nb, Hf, Ta etc. can be illustrated, for example. The amount of such elements added is not particularly limited, but in order not to degrade the excellent electro-optical properties of ITO, (totalization of oxides of the third element) / (totalization of oxides of the third element) / 100 is more than 0%. It is preferable to set it as 20% or less (weight ratio).

<Example>

Hereinafter, one exemplary embodiment of the present invention will be described in detail, but the present invention is not limited thereto.

Example 1

900 g of indium oxide powder having an average particle diameter of 1.3 µm and 100 g of tin oxide powder having an average particle diameter of 0.7 µm were placed in a polyethylene pot and mixed for 72 hours by a dry ball mill to prepare a mixed powder. It was 2.0 g / cm <^{3> when} the tap density of the said mixed powder was measured.

This mixed powder was put into a mold and pressed at a pressure of 300 kg / cm ^{2 to obtain} a molded body. The compact was subjected to densification by CIP at a pressure of 3 ton / cm ² . Thereafter, the molded body was placed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering condition)

Sintering temperature: 1500 degreeC, Temperature rising rate: 25 degreeC / Hr, Sintering time: 10 hours, Introducing gas into an sintering furnace: Oxygen, Introducing gas flux: 2.6 cm / min.

The density of the obtained sintered compact was measured by the Archimedes method and found to be 7.11 g / cm ³ (relative density: 99.4%).

This sintered compact was processed into the 4 inch x 7 inch sintered compact of 6 mm by the wet processing method, and the surface roughness of the sputtering surface of the sintered compact was machined by Ra: 0.7 micrometer, Rmax: 5.5 micrometer.

Thereafter, an indium-tin solder containing 10% by weight of tin was applied to each of the bonding surfaces of the ITO sintered body and the backing plate made of oxygen-free copper, and then bonded to form an ITO target.

Sputtering was performed on this target under the following sputtering conditions.

DC power: 1.3 w / cm ²

Sputter Gas: Ar + O ₂

Gas Pressure: 5 mTorr

O ₂ / Ar: 0.1%

Under the above conditions, sputtering experiments were continuously performed for 60 hours. The external appearance photograph of the target after discharge was image-processed using a computer, and the generation amount of nodules was investigated. As a result, nodules occurred in 14% of the target surface.

Example 2

An ITO sintered body was manufactured under the same conditions as in Example 1. It was 7.11 g / cm <^{3> when} the density of the obtained sintered compact was measured by the Archimedes method.

This sintered compact was processed into the 4 inch x 7 inch sintered compact of 6 mm by the wet processing method, and the surface roughness of the sputtering surface of the sintered compact was machined by Ra: 0.1 micrometer and Rmax: 1.0 micrometer.

Subsequently, an indium-tin solder containing 5% by weight of tin was applied to each of the bonding surfaces of the ITO sintered body and the backing plate made of oxygen free copper, and then bonded to form an ITO target.

This target was sputtered under the same sputtering conditions as in Example 1. After 60 hours of continuous sputtering experiments, the image of the target was imaged in the same manner as in Example 1, and nodules occurred in 6% of the target surface.

Example 3

An ITO sintered body was manufactured under the same conditions as in Example 1. It was 7.11 g / cm <^{3> when} the density of the obtained sintered compact was measured by the Archimedes method.

This sintered compact was processed into the 4 inch x 7 inch sintered compact of 6 mm by the wet processing method, and the surface roughness of the sputtering surface of the sintered compact was machined by Ra: 0.1 micrometer and Rmax: 1.0 micrometer.

Subsequently, an indium-tin solder containing 12% by weight of tin was applied to each bonding surface of the ITO sintered body and the backing plate made of oxygen-free copper, and then bonded to form an ITO target.

This target was sputtered under the same sputtering conditions as in Example 1. After the sputtering experiment was continuously performed for 60 hours, the image of the target was imaged in the same manner as in Example 1, and nodules occurred at 6% of the target surface.

Comparative Example 1

An ITO sintered body was manufactured under the same conditions as in Example 1. It was 7.11 g / cm <^{3> when} the density of the obtained sintered compact was measured by the Archimedes method.

This sintered compact was processed into the 4 inch x 7 inch sintered compact of 6 mm by the wet processing method, and the surface roughness of the sputtering surface of the sintered compact was machined by Ra: 0.1 micrometer and Rmax: 1.0 micrometer.

Subsequently, indium solder was applied to each bonding surface of the ITO sintered body and the backing plate made of oxygen-free copper, and then bonded to form an ITO target.

This target was sputtered under the same sputtering conditions as in Example 1. After the sputtering experiment was continuously performed for 60 hours, the external photograph of the target was imaged in the same manner as in Example 1, and nodules occurred in 38% of the target surface.

Example 4

900 g of indium oxide powder having an average particle diameter of 1.3 µm and 100 g of tin oxide powder having an average particle diameter of 0.7 µm were placed in a tub made of polyethylene, and mixed by a dry ball mill for 72 hours to prepare a mixed powder. It was 2.0 g / cm <^{3> when} the tap density of the said mixed powder was measured.

This mixed powder was put into a mold and pressed at a pressure of 300 kg / cm ^{2 to obtain} a molded body. The compact was subjected to densification by CIP at a pressure of 3 ton / cm ² . Thereafter, the molded body was placed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering condition)

Sintering temperature: 1500 ° C, Heating rate: 25 ° C / Hr, Sintering time: 10 hours, Gas introduced into the sintering furnace: Oxygen, Introducing gas flux: 2.6 cm / min.

It was 7.11 g / cm <^3> (relative density: 99.4%) when the density of the obtained sintered compact was measured by the Archimedes method based on JISR1634-1998.

The sintered compact is processed into a sintered compact of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet working method, and the surface roughness of the sputtering surface of the sintered compact is machined to Ra: 0.7 µm and Ry: 5.2 µm.

Then, after heating this sintered compact and backing plate to 156 degreeC, indium solder was apply | coated to each joining surface. Then, the sintered compact was arrange | positioned in the desired position of a backing plate, and it cooled to 149 degreeC. Thereafter, an indium-tin alloy (melting point: about 145 ° C) containing 10% by weight of tin and heated up to 149 ° C was applied over the entire periphery of the exposed portion of the indium solder material on the side of the joint, and then cooled to room temperature. An ITO target was obtained.

This target was sputtered on the following sputtering conditions.

DC power: 300 w

Sputter Gas: Ar + O ₂

Gas Pressure: 5 mTorr

O ₂ / Ar: 0.1%

Under the above conditions, sputtering experiments were continuously performed for 60 hours. The external appearance photograph of the target after discharge was image-processed using the computer, and the generation amount of nodules was investigated. As a result, only 12% of the target surface had nodules.

Example 5

An ITO sintered body was obtained in the same manner as in Example 4. The density of the obtained sintered compact was measured and found to be 7.11 g / cm ³ (relative density: 99.4%).

The sintered compact is processed into a sintered compact of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet working method, and the surface roughness of the sputtering surface of the sintered compact is machined to Ra: 0.08 µm and Ry: 0.8 µm.

Then, after heating this sintered compact and backing plate to 156 degreeC, indium solder was apply | coated to each joining surface. Then, the sintered compact was arrange | positioned in the desired position of a backing plate, and it cooled to 150 degreeC. Thereafter, an indium-tin alloy containing 10% by weight of tin and heated to 150 ° C was applied to the exposed part over the entire periphery of the exposed portion of the indium solder material on the side of the joint, and then cooled to room temperature to obtain an ITO target. .

This target was sputtered for 60 hours under the same conditions as in Example 4. The external appearance photograph of the target after discharge was image-processed using the computer, and the amount of nodules was investigated. As a result, only 5% of the target surface had nodules.

Comparative Example 2

An ITO sintered body was manufactured in the same manner as in Example 4. The density of the obtained sintered compact was measured by the Archimedes method and found to be 7.11 g / cm ³ (relative density: 99.4%).

The sintered compact is processed into a sintered compact of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet working method, and the surface roughness of the sputtering surface of the sintered compact is machined to Ra: 0.7 µm and Ry: 5.2 µm.

After heating the sintered compact and backing plate obtained in this way to 156 degreeC, indium solder was apply | coated to each joining surface. Then, the sintered compact was arrange | positioned in the predetermined position of a backing plate, and then cooled to room temperature and made into a target.

This target was sputtered continuously for 60 hours under the same conditions as in Example 4. The external appearance photograph of the target after discharge was image-processed using the computer, and the amount of nodules was investigated. As a result, nodules occurred in 59% of the target surface.

The ITO sputtering target of the present invention can reduce the amount of nodules even in the case of using the film forming method of low applied power in recent years.

Claims (3)

ITO sputtering target formed by joining an ITO sintered body consisting substantially of indium, tin and oxygen to a metal backing plate with 3 to 15% by weight of indium-tin solder at a tin amount of (tin) / (indium + tin) × 100. . The ITO sputtering target according to claim 1, wherein the relative density of the ITO sintered body consisting substantially of indium, tin, and oxygen is set to 99% or more. The ITO sputtering target according to claim 1 or 2, wherein the average line center roughness Ra of the sputtering surface of the ITO sintered compact is 0.8 µm or less and the maximum height Rmax is 7.0 µm or less.