JP2000345326A - Divided ito sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amt. of nodules to be generated in the surroundings of a divided part by controlling the relative density of each sintered body to the value equal to or above a specified one, controlling the width of the divided part formed by the adjacent sintered bodies to a specified range and moreover controlling the average line center roughness of each sintered body relative in the divided part to a specified range. SOLUTION: The relative density of ITO sintered bodies 2 to be used is controlled to >=99%. The plural pieces of ITO sintered bodies 2 are arranged side by side on a backing plate 1 to form into a divided ITO target. Individual ITO sintered bodies 2 are respectively arranged with the width (the width 4 of the divided part) of 0.05 to 0.2 mm each other. At the time of subjecting the ITO sintered bodies 2 to grinding working to form into desired dimensions, the average line center roughness (Ra) of the faces composing the divided part is worked into 0.5 to 1 μm. Moreover, the edge part 3 in which the sputtering face and the face composing the divided part are crossed is worked preferably to R 0.5 to 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ITO sputtering target used for producing a transparent conductive thin film,
In particular, the present invention relates to an ITO sputtering target having a divided portion in which a plurality of target materials are arranged on a single backing plate.

[0002]

2. Description of the Related Art Indium Tin Oxide (I
TO) thin film has features such as high conductivity and high transmittance,
Further, since fine processing can be easily performed, they are used in a wide range of fields such as display electrodes for flat panel displays, window materials for solar cells, and antistatic films. In particular, in the field of flat panel displays such as liquid crystal display devices, in recent years, the size and definition have been advanced, and the demand for ITO thin films as display electrodes has been rapidly increasing.

The method of producing such an ITO thin film can be roughly classified 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 evaporation method and a sputtering method. Among them, the sputtering method is used in various fields because it is a film forming method that can easily increase the area and obtain a high-performance film.

When an ITO thin film is produced by a sputtering method, an alloy target composed of indium metal and tin (IT target) or a composite oxide target composed of indium oxide and tin oxide (ITO target) is used as a sputtering target. . Among them, the method using an ITO target has a smaller change with time in the resistance value and transmittance of the obtained film than the method using an IT target, and the film forming conditions can be easily controlled. Has become mainstream.

[0005] In recent years, the size of mother glass for producing liquid crystal panels has increased in order to increase the size of liquid crystal panels and improve productivity. Generally, the size of the mother glass, which was 360 mm × 460 mm at the beginning of the second phase of the liquid crystal panel manufacturing, is changed to 410 mm × 520 mm in the second half of the second phase.
The period is 550 mm x 650 mm. Along with this, the size of the ITO target used when forming the ITO thin film on the glass substrate also gradually increases. For example, in the third stage, about 300 mm × 800 mm by an in-line type sputtering apparatus, and by a single-wafer sputtering apparatus. It is about 800 mm x 840 mm.

However, the I target used for the ITO target
The TO sintered body is a ceramic, and it is difficult to produce such a large sintered body with a good yield, and it is expensive due to a low yield. Therefore,
When manufacturing a large target as described above, a method is adopted in which a plurality of small sintered bodies are arranged on one backing plate to form a large target. For example, in the case of manufacturing a large target of 800 mm × 840 mm, this is a method of obtaining a large target by arranging three relatively small sintered bodies of 800 mm × 280 mm on one backing plate.

[0007] An ITO sputtering target formed by arranging a plurality of ITO sintered bodies side by side on a single backing plate can produce a large-sized target with good yield, but increases the use time of the target. Accordingly, a new problem is caused in that a large amount of nodules is generated in an adjacent portion between the sintered bodies (hereinafter, referred to as a “divided portion”) and around the divided portion.

[0008] The nodule means a black substance generated on the target surface as the cumulative sputtering time increases when the ITO target is continuously sputtered in a mixed gas atmosphere of argon gas and oxygen gas. It is known that this black deposit, which is considered to be a lower oxide of indium, is likely to cause abnormal discharge during sputtering, and itself is a source of foreign matter (particles). Therefore, when sputtering is performed continuously, foreign matter defects occur in the formed thin film, which causes a reduction in the manufacturing yield of flat panel displays such as liquid crystal display devices.

In the case of a single-piece target having no split portion, the density of the target is set to 6.4 g / cm ³ or more and the surface roughness of the target is controlled as disclosed in, for example, JP-A-08-060352. It has been reported that this can reduce the generation of nodules. However, when a target having a split portion is formed by combining a plurality of sintered bodies, it is difficult to suppress the generation of nodules around the split portion and the split portion.

Further, in order to reduce the nodules generated in the divided portion, the density of the divided sintered body is set to 6.4 g / cm ³ or more and the width of the divided portion as disclosed in Japanese Patent Application Laid-Open No. H11-061395. Is set to 0.05 mm or more and 0.4 mm or less, and among the edge portions of the divided ITO sintered body, the edge portions existing on the sputtering surface are R1 to R1.
A method for processing into R2 has been proposed.

However, in recent years, in order to improve the performance of a thin film formed with higher definition and higher performance of a liquid crystal display element, a film forming method of discharging with a low applied power has been adopted. It has become. Due to the film formation at the low applied voltage, nodules are generated even when a target adopting each of the above-described methods is used, which is becoming a problem. In particular, nodules generated around the divided portion are disclosed in JP-A-08-060352 and JP-A-Hei.
It cannot be reduced by the technique described in 1-061395, which is an important problem to be solved.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to carry out recent sputtering with a low applied power by using an ITO sputtering target having a split portion which is a single target by combining a plurality of ITO sintered bodies. Even in such a case, an object of the present invention is to provide an ITO sputtering target in which the amount of nodules generated around the division is reduced.

[0013]

Means for Solving the Problems The present inventors have conducted a detailed study on the causes of the formation of nodules around the split part in order to reduce the amount of nodules around the split part of the ITO sputtering target. As a result, nodules generated in the vicinity of the split part are such that the metal indium remaining as the solder material at the bottom of the split part adheres to the erosion part on the target surface during sputtering, and the target is formed with the adhered metal indium as a core. I found it to be a nodule. Although the cause of the metal indium serving as a nucleus for generating digging residue is not yet clear, the metal indium attached to the target surface reacts with oxygen contained in the sputtering gas to form indium oxide, and this indium oxide is ITO
It is thought that the digging remains because the resistivity is much higher than that of.

The present inventors have conducted detailed studies on measures to prevent the solder material existing at the bottom of the split portion from adhering to the target surface during sputtering, and as a result, the relative density of each sintered body was set to 99% or more. The width of the divided portion is 0.05 mm or more and 0.2 mm or less, and the average line center roughness (Ra) of the surfaces of the respective sintered bodies facing each other in the divided portion is 0.5 μm or more and 2 μm or less. As a result, it has been found that the amount of nodules generated in the vicinity of the dividing portion can be reduced, and the present invention has been completed.

That is, according to the present invention, in a divided ITO sputtering target in which a plurality of ITO sintered bodies substantially consisting of indium, tin and oxygen are bonded on a single backing plate, the relative density of each sintered body is set to 99. % Or more, the width of the divided part formed by the adjacent sintered bodies is set to 0.05 mm or more and 0.2 mm or less, and the average line center roughness of the surfaces of the respective sintered bodies facing each other in the divided part ( Ra) is set to 0.5 μm or more and 2 μm or less, and relates to a split ITO sputtering target.

Hereinafter, the present invention will be described in detail.

FIG. 1 is a perspective view showing an example of the split ITO sputtering target of the present invention, and FIG.
It is sectional drawing cut | disconnected by the surface orthogonal to the long side and the sputtering surface of O sintered compact. This example is a divided ITO target in which three ITO sintered bodies 2 are arranged side by side on one backing plate, and each of the ITO sintered bodies 2 constituting the target is 0.05 mm or more and 0.2 mm or more. They are arranged side by side on the backing plate 1 while maintaining the following width 4 (width of the divided portion).

An edge portion 3 at which the sputtering surface of the ITO sintered body intersects with the side surface of the ITO sintered body constituting the divided portion.
Is to suppress the generation of nodules and abnormal discharge,
To have a radius of 0.5-2 mm radius, ie
Processing to R0.5 to R2 is preferred. In addition, IT
Other edges present on the sputtering surface of the O-sintered body 2 are not necessarily required, but may be subjected to appropriate rounding.

The split ITO sputtering target of the present invention is not particularly limited in the number and shape of the split ITO sputtering target as long as a plurality of sintered bodies are arranged on one backing plate. As shown in FIG. 1, three sintered bodies of the same size may be joined, or as shown in FIG. 3, three sintered bodies of different sizes may be joined. Further, in the case of four divisions, the image may be divided into the shape of a “ta”.

The density of the ITO sintered body used in the present invention is 99% or more. Preferably it is 99.5% or more. By doing so, it is possible to suppress the abnormal discharge generated in the pores of the ITO sintered body and the generation of nodules due to the abnormal discharge.

As a method for producing an ITO sintered body having a sintered density of 99% or more, the relative density of the obtained sintered body is 99% or more.
Although it is not particularly limited as long as it is the above, for example, it can be manufactured 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 or the like, and the mixture is molded by a molding method such as a press method or a casting method to produce an ITO molded body. At this time, if the average particle diameter of the powder used is large, the density after sintering may not be sufficiently increased, and a sintered body having a relative density of 99% or more may not be obtained.
The average particle size of the powder used is preferably 1.5 μm or less, more preferably 0.1 to 1.5 μm.

The content of tin oxide in the mixed powder or the ITO powder is desirably 5 to 15% by weight at which the specific resistance decreases when a thin film is produced by a sputtering method.

Next, if necessary, CI
A consolidation process such as P is performed. At this time, the CIP pressure is desirably ² ton / cm ² or more, preferably ² to 3 ton / cm ^{2 in} order to obtain a sufficient consolidation effect. When the initial molding is performed by a casting method, a binder removal treatment may be performed for the purpose of removing water and organic substances such as a binder remaining in the molded body after the CIP. Also,
Even when the initial molding is performed by a press method, it is desirable to perform the same debinding treatment when a binder is used at the time of molding.

The compact thus obtained is put into a sintering furnace and sintered. As the sintering method, any method may be used as long as the relative density of the sintered body is 99% or more, but sintering in the air is preferable in consideration of the cost of production equipment and the like. However, it goes without saying that other conventionally known sintering methods such as the HP method, the HIP method and the oxygen pressure sintering method can be used.

As for the sintering conditions, it is possible to appropriately select the sintering conditions at which the relative density of the sintered body is 99% or more. However, in order to obtain a sufficient density increasing effect, and to suppress the evaporation of tin oxide. Therefore, the sintering temperature is 1450-1650
C. is desirable. The atmosphere during sintering is preferably air or a pure oxygen atmosphere. Also, the sintering time is desirably 5 hours or more, preferably 5 to 30 hours, in order to obtain a sufficient density increasing effect.

Subsequently, the ITO sintered body having a relative density of 99% or more manufactured by the above method is ground to a desired size. Since the ITO sintered body has a high hardness and cracks easily occur inside the sintered body during the grinding process, it is desirable to perform the process by wet processing. Here, among the respective surfaces of the sintered body subjected to the grinding processing, the average line center roughness (Ra) of the surface constituting the divided portion is 0.5 μm or more and 2 μm or less, preferably 0.1 μm or less.
Work to 5 μm or more and 1 μm or less. If the roughness of the surface constituting the divided portion is smaller than the above range, it is difficult to obtain the effects of the present invention, and if it is larger than the above range, a part of the sintered body is easily cut off from the rough surface, and particles and It is not preferable because it may be attached to the substrate.

Further, the sputtering surface of the ITO sintered body is polished, and the surface roughness (Ra) of the sputtering surface is set to 0.8.
It is preferable to process so that the maximum height (Rmax) is 7.0 μm or less and the maximum height (Rmax) is 7.0 μm or less. More preferably, Ra is 0.1 μm or less and Rmax is 2 μm or less. By doing so, it is possible to effectively suppress abnormal discharge generated in the uneven portion on the target surface and formation of nodules due to abnormal discharge.

The plurality of ITOs thus obtained are
The sintered body is joined on one backing plate. The backing plate and the metal bonding agent used in the present invention are not particularly limited. Examples of the backing plate include oxygen-free copper and copper phosphate, and examples of the metal bonding agent include indium solder.

The joining can be performed, for example, according to the following steps. First, the plurality of ground ITO sintered bodies and the backing plate are heated to a temperature equal to or higher than the melting point of the metal bonding agent used.

Next, a metal bonding agent is applied to the bonded surface of the heated ITO sintered body and the backing plate. The bonding surfaces of the ITO sintered body coated with the metal bonding agent thus obtained and the backing plate are bonded together. At this time, when the sintered body is subjected to the R processing, the edge portion is arranged so as to face the sputtering surface of the divided portion, and the width of the divided portion after cooling is 0.05 mm or more and 0.2 mm or less. So that If the width of the divided portion exceeds 0.2 mm, the metal bonding agent remaining in the divided portion adheres to the target surface around the divided portion during sputtering, which causes nodules, which is not preferable.
If the thickness is less than 0.05 mm, the ITO sintered body increases due to thermal expansion when installed in a vacuum apparatus and actually sputtered, and adjacent sintered bodies may collide with each other and be damaged. Not preferred.

The width of the divided portion heated for bonding depends on the material of the backing plate used, the melting point of the metal bonding agent used, the size of the ITO sintered body used, and the final target size. What is necessary is just to select suitably according to it.

For example, when bonding three sintered bodies of 800 mm × 280 mm on one backing plate to form one target, oxygen-free copper is used for the backing plate, and indium solder is used as a metal bonding agent. When used, the width of the divided portion is set to 0.53 mm while the sintered body and the backing plate are heated to 156 ° C., so that the width of the joined portion after cooling is 0.2 mm.

The actual control of the width of the divided portion can be performed, for example, as follows. First, a jig having a thickness of 0.53 mm is inserted into the divided portion, and the backing plate and the sintered body are joined. After aligning the sintered body and the backing plate and solidifying the indium solder, which is the metal bonding material, pull out the jig inserted into the joint,
Cool to room temperature.

The jig to be inserted into the division is not particularly limited as long as it can withstand the temperature at the time of joining.
Examples include stainless steel, iron, brass, carbon, Teflon, and polyimide resin. Since a resin such as Teflon or polyimide is soft, it is preferable because the jig after the solidification of the metal bonding agent can be easily removed.

The variation in the density between the sintered bodies bonded on one backing plate is ±± in relative density.
Desirably, it is within 0.3%. By doing so, the film thickness distribution of the thin film formed on the substrate is improved. Further, it is desirable that the structure of each sintered body, for example, the particle size, the dispersibility of tin, and the like have little variation among the sintered bodies. By doing so, the film quality (resistivity, transmittance) distribution of the thin film formed on the substrate is improved.

According to the present invention, the ITO sputtering target can be used without particular limitation on the sputtering method. The magnet disposed below the target may be a fixed type or a swing type,
It can be used regardless of the strength of the magnet.

As a sputtering gas, an oxygen gas or the like is added as necessary to an inert gas such as argon and the like, and discharge is performed while controlling the gas pressure to 2 to 10 mTorr. As a power application method for discharging, DC, RF or a combination thereof can be used. However, considering the stability of discharge, DC or RF with RF superimposed is preferable. There is no particular limitation on the power density applied to the target,
The target of the present invention is a low-power discharge (2.0 W /
cm ² or less).

The thus obtained divided IT of the present invention
The O sputtering target can reduce the amount of nodules generated around the divided portion even when a recent film forming method with low applied power is used.

The sputtering target according to the present invention is also effective for a target to which a third element is added for the purpose of imparting an additional function to ITO. As the third element, for example, Mg, Al, Si, T
i, Zn, Ga, Ge, Y, Zr, Nb, Hf, Ta and the like can be exemplified. The addition amount of these elements is not particularly limited. However, in order not to deteriorate the excellent electro-optical characteristics of ITO, (the total amount of oxides of the third element)
0% at // (ITO + sum of oxides of third elements) / 100
Over 20%.

[0041]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Indium oxide powder having an average particle diameter of 1.3 μm and tin oxide powder having an average particle diameter of 0.7 μm were put into a ball mill pot, and nylon balls having a diameter of 10 mm were added thereto, followed by dry ball mill mixing for 5 hours. To produce a mixed powder. Next, the obtained mixed powder was mixed with water, a dispersing agent, and a binder to form a slurry, and this was poured into a resin mold for casting to produce three molded articles of 130 mm × 80 mm × 10 mm.

Next, these compacts were placed in a drying furnace and subjected to a drying treatment, and then subjected to a CIP treatment at a pressure of 3 ton / cm ² . These compacts were placed in a degreasing furnace and heated at 450 ° C. for 10 hours in an air atmosphere to remove organic substances remaining on the compacts. Subsequently, these compacts were placed in an atmospheric sintering furnace and Sintering was performed under the conditions.

Sintering temperature: 1500 ° C. Heating rate: 25 ° C./Hr Sintering time: 10 hours When the density of the obtained sintered body was measured by the Archimedes method, all were 7.10 g / cm ³ (relative density: 99) .2
%)Met.

The sintered body is 100 mm × 58 mm × 6 m
m. Among the surfaces of the obtained sintered body, Ra of the surface constituting the divided portion is 0.53 μm, and R of the sputtering surface is
a and Rmax are 0.08 μm and 1.0 μm, respectively.
Was machined using a polishing machine. Further, R1 processing was performed on an edge portion to be a sputtering surface.

After the thus obtained sintered body and the backing plate were heated to 156 ° C., indium solder was applied to each joint surface. Next, after arranging these sintered bodies so that the width of the divided portion was 0.11 mm, the sintered bodies were cooled to room temperature to obtain a target. The width of the divided portion after cooling was 0.10 mm.

The obtained target was set in a vacuum apparatus, and sputtering was performed under the following conditions.

DC power: 1.3 w / cm ² Sputter gas: Ar + O ₂ gas pressure: 5 mTorr O ₂ / Ar: 0.1% A sputtering test was continuously performed for 60 hours under the above conditions. Image processing was performed on the external appearance photograph of the target after discharge using a computer, and the nodule generation amount was examined. As a result, nodules were generated on 7% of the target surface.

Example 2 Indium oxide powder having an average particle diameter of 1.3 μm and tin oxide powder having an average particle diameter of 0.7 μm were put into a ball mill pot, and nylon balls having a diameter of 10 mm were added thereto, followed by dry ball mill mixing for 5 hours. To produce a mixed powder. Next, the obtained mixed powder is mixed with water, a dispersing agent, and a binder to form a slurry, which is then poured into a resin mold for casting to form a 165 mm × 300 mm × 10 mm molded body 2.
Sheets were manufactured.

Next, these compacts were placed in a drying furnace and subjected to a drying treatment, and then subjected to a CIP treatment at a pressure of 3 ton / cm ² . These compacts were placed in a degreasing furnace and heated at 450 ° C. for 10 hours in an air atmosphere to remove organic substances remaining on the compacts. Sintering was performed under the same conditions as in Example 1.

When the density of the obtained sintered body was measured by the Archimedes method, the densities were 7.10 (relative density: 99.2%) and 7.11 g / cm ³ (relative density: 99.4), respectively. %)Met.

Each of these sintered bodies was 127 mm × 228.5.
It was processed into a sintered body of mm × 6 mm. Of the surfaces of the obtained sintered body, Ra of the surface constituting the divided portion was 1.8 μm, and Ra and Rmax of the sputtering surface were 0.08, respectively.
The workpiece was machined to a thickness of 1.1 μm using a polishing machine. Also, R2 is applied to the edge portion serving as the sputtering surface.
Was processed.

After the thus obtained sintered body and the backing plate were heated to 156 ° C., indium solder was applied to each joint surface. Next, after arranging these sintered bodies so that their joints became 0.43 mm, they were cooled to room temperature to obtain targets. The width of the divided portion after cooling was 0.2 mm.

The obtained target was set in a vacuum apparatus, and sputtering was performed under the same conditions as in Example 1. After continuously performing the sputtering test for 60 hours, the external appearance photograph of the target was subjected to image processing in the same manner as in Example 1. As a result, nodules were generated on 8% of the target surface.

Comparative Example 1 Three ITO sintered bodies were manufactured under the same conditions as in Example 1. When the density of the obtained sintered bodies was measured by the Archimedes method, all were 7.10 g / cm ³ . Next, these sintered bodies were processed into 100 mm × 58 mm × 6 mm. Of the surfaces of the obtained sintered body, Ra of the surface constituting the divided portion was 0.52 μm, and Ra and Rmax of the sputtering surface were obtained.
Were machined to 0.08 μm and 1.1 μm, respectively, using a polishing machine. Further, R1 processing was performed on an edge portion to be a sputtering surface.

After the thus obtained sintered body and the backing plate were heated to 156 ° C., indium solder was applied to each joint surface. Next, after arranging these sintered bodies so that the width of the divided portion was 0.27 mm, the sintered bodies were cooled to room temperature to obtain a target. The width of the divided part after cooling was 0.24 mm.

The obtained target was set in a vacuum apparatus, and sputtering was performed under the same conditions as in Example 1. After the sputtering test was continuously performed for 60 hours, the external appearance photograph of the target was subjected to image processing in the same manner as in Example 1. As a result, nodules were formed on 46% of the target surface.
Had occurred.

Comparative Example 2 Three ITO sintered bodies were manufactured under the same conditions as in Example 1. When the density of the obtained sintered bodies was measured by the Archimedes method, all were 7.10 g / cm ³ . Next, these sintered bodies were processed into 100 mm × 58 mm × 6 mm. Of the surfaces of the obtained sintered body, Ra of the surface constituting the divided portion was 0.3 μm, and Ra and Rmax of the sputtering surface were machined to 0.08 μm and 1.0 μm, respectively, using a polishing machine. Further, R1 processing was performed on an edge portion to be a sputtering surface.

After the thus obtained sintered body and the backing plate were heated to 156 ° C., indium solder was applied to each joint surface. Next, after arranging these sintered bodies so that the width of the divided portion was 0.11 mm, the sintered bodies were cooled to room temperature to obtain a target. The width of the divided portion after cooling was 0.10 mm.

The obtained target was set in a vacuum apparatus, and sputtering was performed under the same conditions as in Example 1. After the sputtering test was continuously performed for 60 hours, the external appearance photograph of the target was subjected to image processing in the same manner as in Example 1. As a result, nodules were formed on 40% of the target surface.
Had occurred.

[0061]

According to the split ITO sputtering target of the present invention, the amount of nodules generated around the split portion can be reduced even when a recent method of forming a film with low applied power is used.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a split ITO sputtering target of the present invention.

FIG. 2 is a diagram showing a cross section of the split ITO sputtering target shown in FIG.

FIG. 3 is a perspective view showing another example of the split ITO sputtering target of the present invention.

[Explanation of symbols]

 1: backing plate 2: ITO sintered body 3: edge part 4: width of division part

Claims (3)

[Claims] In a split ITO sputtering target in which a plurality of ITO sintered bodies substantially consisting of indium, tin and oxygen are joined on a single backing plate, the relative density of each sintered body is set to 99% or more. The width of the divided part formed by the adjacent sintered bodies is set to 0.05 mm or more and 0.2 mm or less, and the average line center roughness (Ra) of the surfaces of the respective sintered bodies facing each other in the divided part is determined. A split ITO sputtering target having a thickness of 0.5 μm or more and 2 μm or less. 2. An edge portion where the sputtering surface of the sintered body and the side surface of the sintered body constituting the divided portion intersect with each other is R0.5 to R0.5.
The split ITO sputtering target according to claim 1, wherein the target is processed into R2. 3. The sputtering surface of the ITO sintered body has a center line average roughness (Ra) of 0.8 μm or less and a maximum height (Rmax) of 7.0 μm or less. The split ITO sputtering target according to claim 1 or 2.