JP5724323B2 - Sputtering target - Google Patents

Description

  The present invention relates to a sputtering target containing indium oxide and tin oxide used in the production of a transparent conductive thin film.

  Indium Tin Oxide (ITO) thin film has features such as high conductivity and high transmittance, and can be easily finely processed. Therefore, it can be used in a wide range of fields such as display electrodes for flat panel displays and window materials for solar cells. It is used. Such an ITO thin film is formed by a sputtering method because it can be easily formed on a large area and a high-performance film can be obtained.

  When the ITO target is continuously sputtered in a mixed gas atmosphere of argon gas and oxygen gas, black deposits called nodules are deposited on the target surface as the integrated sputtering time increases. This nodule, which is considered to be a lower oxide of indium, is deposited around the erosion part of the target, so it is likely to cause abnormal discharge during sputtering, and it is known that it itself becomes a source of foreign matter. Yes.

  As a result, when sputtering is continuously performed, foreign matter defects are generated in the formed thin film, which causes a reduction in the manufacturing yield of flat panel displays such as liquid crystal display devices. In particular, in recent years, in the field of flat panel displays, high definition has progressed, and such a foreign substance defect in a thin film has caused an operation failure of the element, which has been an important problem to be solved.

The cause of the generation of nodules is broadly classified into those caused by the ITO sintered body used for the target member and those caused by the solder material used for joining the target material and the backing plate. As a result of the sintered body, the target density, surface state, and Sn dispersibility are affected. As a countermeasure, the target density is set to 6.4 g / cm ³ or more and the surface roughness of the target is controlled. Thus, it has been reported that generation of nodules can be reduced (see, for example, Patent Document 1).

  In addition, due to the solder material, not only the protrusion from the solder material used for joining one target member but also the protrusion from the exposed portion of the solder material existing in the gap between the targets when two or more target members are arranged. The influence of this has become impossible to ignore due to the recent increase in target size.

  As a countermeasure for the solder material, it has been reported that the nodule can be reduced by covering a part or all of the exposed portion of the solder material with an alloy made of indium and tin (for example, see Patent Document 2). .

  However, if the exposed part of the solder material is covered with an alloy made of indium and tin, the melting point of the alloy of indium and tin is lower than the melting point of indium, so it is easy to melt, and the molten alloy is placed at the opposite position. There has been a problem in that the yield of the product decreases due to adhesion to the film surface of flat panel displays and solar cells.

Japanese Patent Laid-Open No. 08-060352 JP 2001-081551 A

  An object of the present invention is to reduce the amount of nodules generated on the surface of an ITO target caused by a solder material, and at the same time reduce the decrease in product yield due to the molten solder material adhering to the film surface of a flat panel display or the like. The object is to provide an ITO sputtering target.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have adopted a melting point of 200 ° C. at a part or all of the exposed portion of the solder material when joining the ITO sintered body and the backing plate using indium solder. It has been found that the above problem can be solved by covering with the above metal. The present invention has been completed.

  That is, the present invention is a sputtering target formed by bonding one or more target members made of ITO containing indium oxide and tin oxide to a backing plate using an indium solder material, and is exposed from the target-backing plate assembly. The sputtering target is characterized in that a part or all of the indium solder material is covered with a metal plating film having a melting point of 200 ° C. or higher.

  Hereinafter, the present invention will be described in detail.

  Although the ITO sintered compact used for this invention is not specifically limited, For example, it can manufacture with the following method.

  First, a binder or the like is added to a mixed powder of indium oxide powder and tin oxide powder, ITO powder, or the like, and 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 size of the powder used is large, the density after sintering may not be sufficiently increased. Therefore, the average particle size of the powder used is preferably 1.5 μm or less, more preferably 0. .1 to 1.5 μm. By carrying out like this, it becomes possible to obtain a sintered compact with higher sintering density.

  Further, the tin oxide content in the mixed powder or ITO powder is not particularly limited, but is preferably 5 to 15% by weight in which the specific resistance decreases when a thin film is produced by a sputtering method.

Next, a compacting treatment such as CIP (cold isostatic pressing) is performed on the obtained molded body as necessary. Here CIP pressure to obtain a sufficient compaction effect 2 ton / cm ² or more, preferably 2~3ton / cm ^2. Here, when the first molding is performed by a casting method, a binder removal treatment may be performed for the purpose of removing moisture remaining in the molded body after CIP and organic substances such as a binder. Even when the first molding is performed by a press method, it is preferable to perform the same debinding process when a binder is used during molding.

  The molded body thus obtained is put into a sintering furnace and sintered. Any method can be used as the sintering method, but in view of the cost of production facilities and the like, sintering in the air is preferable. However, it goes without saying that other conventionally known sintering methods such as HP (hot press) method, HIP (hot isostatic pressing) method and oxygen pressure sintering method can be used.

  The sintering conditions can be selected as appropriate, but the sintering temperature is preferably 1450 to 1650 ° C. in order to obtain a sufficient density increasing effect and to suppress the evaporation of tin oxide. The atmosphere during sintering is preferably air or a pure oxygen atmosphere. Also, the sintering time is preferably 5 hours or more, and preferably 5 to 30 hours in order to obtain a sufficient density increasing effect.

  In the present invention, the density of the ITO sintered body to be used is not particularly limited, but in order to further suppress abnormal discharge and nodule generation due to electric field concentration at the pore edge portion of the sintered body, the relative density is 99% or more. Preferably, it is 99.5% or more.

  Further, the sputtering target of the present invention is effective even when a third element is added to the ITO sintered body for the purpose of giving the ITO an additional function. Examples of the third element include Mg, Al, Si, Ti, Zn, Ga, Ge, Y, Zr, Nb, Hf, Ta, and Sr. The addition amount of these elements is not particularly limited, but it does not deteriorate the excellent electro-optical characteristics of ITO. Therefore, (total of oxides of third elements) / (total of oxides of ITO + third elements) ) Is preferably over 0% and 20% or less (weight ratio).

  The obtained ITO sintered body is bonded onto the backing plate using an indium solder material. The material of the backing plate used in the present invention is not particularly limited, but oxygen-free copper, phosphor bronze and the like are preferable.

  When joining the ITO sintered body on the backing plate, first, the ITO sintered body and the backing plate are heated to the melting point or higher of the indium solder material using the ITO sintered body. Next, an indium solder material is applied to the joined surface of the heated ITO sintered body and the backing plate. Next, after joining the sintered surfaces of the ITO sintered body coated with the indium solder material and the backing plate at a desired position on the backing plate, the target-backing plate joined body is cooled to room temperature.

  Next, a part or all of the portion where the indium solder material is exposed from the target-backing plate assembly is covered with a metal plating film.

  The metal plating film is not particularly limited as long as it has a melting point of 200 ° C. or higher, but copper is preferable. One or more selected from tin, zinc, nickel, chromium, cobalt, titanium, silver, gold, platinum, and ruthenium may be added to copper in the range of 0.01 wt% to 20 wt%. .

  Whether to cover the entire exposed part of the indium solder material with a metal plating film, or to leave the part that is not necessarily all covered, such as the ease of covering due to the structure of the target, the covering method, etc. It may be determined according to the performance to be performed.

  Further, when two or more ITO sintered bodies are arranged and bonded, it is more effective to coat the solder material existing in the gap as necessary.

  The method of coating with a metal plating film is roughly classified into an electroplating method, an electroless plating method, and an oxidation-reduction plating method, but any method is effective in the present invention.

  The electroplating method is to connect the indium solder material to the negative side of the power source as a cathode, arrange a non-woven fabric impregnated with a metal plating solution on the exposed portion of the indium solder material, and further dispose a copper anode. In this method, the exposed portion of the indium solder material is coated with a metal plating film by performing electrolysis using a DC power source. It is also effective to take measures to remove the oxide film on the surface of the indium solder material before copper plating and to increase the activated state of the surface. For example, a non-woven fabric impregnated with sodium hydroxide is disposed on the exposed portion of the indium solder material, and further, electrolytic reduction is performed using the carbon electrode as an anode, thereby improving the adhesion of the copper plating film. In place of the copper electrode or the carbon electrode, an iridium oxide electrode with little oxidation and surface deterioration may be used.

  In electroless plating, an activator for electroless plating solution is previously attached to the exposed part of the indium solder material for a certain period of time, and then the electroless plating solution is applied to the indium solder material for a certain period of time at a certain temperature. In this method, the metal plating film is coated by adhering to the exposed portion of the metal.

  The oxidation-reduction plating method is a method in which a metal plating solution is attached to a portion where an indium solder material is exposed, and an indium reductant and a metal oxidant easily exchange electrons to deposit a metal. In this method, the exposed portion of the indium solder material is coated with a metal plating film.

  In this manner, the metal plating film is coated on the exposed portion of the indium solder material. At this time, if the metal plating film is coated more than necessary, the metal bonding film may be peeled off, so the thickness of the metal plating film is preferably 0.1 μm or more and 500 μm or less, more preferably 1 μm or more and 100 μm or less. is there.

  Although there is no restriction | limiting in particular about the conditions which sputter | spatter using the sputtering target of this invention, Oxygen gas etc. are added as needed to inert gas etc., such as argon, as sputtering gas, Usually 0.2-1. It is preferable to carry out while controlling these gas pressures at 0 Pa. As a power application method for sputtering, DC, RF, or a combination thereof can be used, and there is no particular limitation on the power density applied to the target.

  The nodules generated on the target surface can be reduced, and at the same time, the yield reduction of the product due to the metal deposits protruding from the solder material can be reduced.

1 is a diagram illustrating an embodiment described in Example 1. FIG. 6 is a diagram showing an embodiment described in Example 2. FIG. FIG. 6 is a diagram showing an embodiment described in Example 3. FIG. 10 is a diagram showing an embodiment described in Example 4.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

Example 1
An ITO target containing 10% by weight of tin oxide and having a relative density of 99.7% was prepared according to a conventional method. This sintered body was processed into a sintered body of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet processing method.

  Next, the ITO sintered body and the copper backing plate were heated to 170 ° C., and an indium solder material was applied to the bonded surfaces of the heated ITO sintered body and the backing plate.

  Next, the bonded surfaces of the ITO sintered body coated with the indium solder material and the backing plate were placed at a desired position on the backing plate, and then the target-backing plate joined body was cooled to room temperature.

  Next, the exposed portion of the indium solder material was coated with copper plating by an electrolytic plating method.

  FIG. 1 schematically shows an example of the electrolytic plating method. The backing plate 3 and the negative side of the DC power source 1 were connected, and the indium solder material 4 joined to the backing plate 3 was used as the cathode. The side of the ITO sintered body 2 and the vicinity of the portion where the indium solder material 4 of the backing plate 3 is exposed are masked with an insulating Kapton tape 7, and other than the portion where the indium solder material 4 is exposed. In this place, copper plating was not deposited. A non-woven fabric 5 impregnated with a copper plating solution was disposed on the portion where the indium solder material 4 was exposed, the copper plate 6 was connected to the positive side of the DC power source 1, and the copper plate was used as an anode.

Constant current electrolysis was performed for 5 minutes at a current density of 2 A / dm ² , and the copper plating film was coated on the indium solder material 4. The film thickness of the electrolytic plating film was 3.2 μm.

  In this way, an ITO target was obtained in which the copper plating film was coated by an electrolytic plating method on the portion where the indium solder material 4 was exposed.

This target was sputtered under the following sputtering conditions.
DC power: 300W
Sputtering gas: Ar + O ₂
Gas pressure: 5 mTorr
O ₂ / Ar: 0.1%
The sputtering test was continuously carried out for 50 hours under the above conditions. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were only generated in 12% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. No foreign matter was observed on the 10 glass substrates.

Example 2
In the same manner as in Example 1, an ITO sintered body containing 5% by weight of tin oxide and having a relative density of 99.4% was obtained. Next, the target material was joined to a copper backing plate in the same manner as in Example 1 to obtain an ITO target.

  The electroless plating method of the present invention was applied to the indium solder material of the ITO target, and the exposed portion of the solder material was coated with copper plating. FIG. 2 schematically shows an example of the electroless plating method of the present invention. In the vicinity of the side of the ITO sintered body 2 and the portion of the backing plate 3 where the indium solder material 4 is exposed, it is masked with an insulating Kapton tape 7 in advance, and the indium solder material 4 is exposed. The copper plating film was made not to adhere to the place other than the part which is. Then, the entire target was heated to 50 ° C. with the heating plate 8.

  Next, after the nonwoven fabric 5 impregnated with an activator of copper electroless plating solution is placed on the exposed portion of the indium solder material 1 for 1 minute and removed, the nonwoven fabric 5 impregnated with the plating solution is placed for 3 minutes, and the copper Plating was applied to the portion where the indium solder material 4 was exposed. The thickness of the obtained plating film was 2.3 μm.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were only generated in 12% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. No foreign matter was observed on the 10 glass substrates.

Example 3
In the same manner as in Example 1, an ITO sintered body containing 10% by weight of tin oxide and having a relative density of 99.8% was obtained. Next, the target material was joined to a copper backing plate in the same manner as in Example 1 to obtain an ITO target.

  The oxidation reduction plating method of the present invention was applied to the indium solder material of the ITO target, and the exposed portion of the solder material was coated with copper plating. FIG. 3 schematically shows an example of the oxidation-reduction plating method of the present invention. In the vicinity of the side of the ITO sintered body 2 and the portion of the backing plate 3 where the indium solder material 4 is exposed, it is masked with an insulating Kapton tape 7 in advance, and the indium solder material 4 is exposed. The copper plating was made not to adhere to the place other than the part where it is.

  Next, the nonwoven fabric 5 impregnated with the copper plating solution (copper sulfate aqueous solution) was placed for 5 minutes on the portion where the indium solder material 4 was exposed, and the copper plating was coated on the portion where the indium solder material 4 was exposed. The obtained plating film had a thickness of 0.5 μm.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were only generated in 12% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. No foreign matter was observed on the 10 glass substrates.

Example 4
Two ITO sintered bodies containing 10% by weight of tin oxide and having a relative density of 99.8% were obtained in the same manner as in Example 1. Next, two target materials were aligned and joined to a copper backing plate by the same method as in Example 1 to obtain an ITO target. The width of the divided part was 0.5 mm.

  Next, the exposed portion of the indium solder material was coated with copper plating by an electrolytic plating method.

FIG. 4 schematically shows an example of the electrolytic plating method. For the solder material in the gap formed between the target members, a thin copper plate 6 to which the non-woven fabric 5 and the Kapton tape 7 are bonded is inserted from above or from the side, and plating is performed. The current density was 2 A / dm ² and constant current electrolysis was performed for 5 minutes to coat the copper plating film on the portion where the indium solder material 4 was exposed. The film thickness of the electrolytic plating film was 3.1 μm.

  The exposed portion of the solder material other than the gap formed between the target members was plated by the same method as in Example 1, and the thickness of the electrolytic plating film was 3.1 μm.

  In this way, an ITO target in which the Cu plating film is coated on the exposed portion of the solder material other than the gap formed between the target members and the exposed portion of the solder material in the gap formed between the target members Obtained.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were only generated in 13% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. No foreign matter was observed on the 10 glass substrates.

Comparative Example 1
An ITO sintered body having a relative density of 99.8% containing 10% by weight of tin oxide was manufactured under the same conditions as in Example 1. This sintered body was processed into a sintered body of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet processing method.

  The sintered body and the copper backing plate thus obtained were heated to 156 ° C., and then indium solder was applied to each joint surface. Next, after placing the sintered body at a predetermined position on the backing plate, the sintered body was cooled to room temperature to obtain a target.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were generated in 59% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. Four foreign substances were observed on 10 glass substrates.

Comparative Example 2
An ITO sintered body having a relative density of 99.8% containing 10% by weight of tin oxide was manufactured under the same conditions as in Example 1. This sintered body was processed into a sintered body of 101.6 mm × 177.8 mm and a thickness of 6 mm by a wet processing method.

  The sintered body and the copper backing plate thus obtained were heated to 156 ° C., and then indium solder was applied to each joint surface. Next, after placing the sintered body at a predetermined position on the backing plate, the sintered body was cooled to room temperature to obtain a target.

  Next, after applying an indium-tin alloy (melting point: about 145 ° C.) containing 10% by weight of tin and heated up to 149 ° C. over the entire periphery of the portion where the indium solder material is exposed on the side surface of the joint. The ITO target was obtained by cooling to room temperature.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were only generated in 12% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. Eight foreign substances were observed on 10 glass substrates.

Comparative Example 3
Two ITO sintered bodies containing 10% by weight of tin oxide and having a relative density of 99.8% under the same conditions as in Example 4 were obtained. Next, two target materials were aligned and joined to a copper backing plate by the same method as in Example 1 to obtain an ITO target. The width of the divided part was 0.5 mm.

  The obtained target was sputtered in the same manner as in Example 1 for 50 hours. Image processing was performed on the appearance photograph of the target after discharge, and the amount of nodules was examined. As a result, nodules were generated in 59% of the target surface. Thereafter, an ITO film having a thickness of 150 nm was formed on a 150 mm square glass substrate, and the number of foreign substances made of metallic indium adhered to the substrate was examined. Six foreign substances were observed on 10 glass substrates.

  An ITO sputtering target capable of producing a transparent conductive thin film with high yield can be provided.

1 DC power supply 2 ITO sintered body 3 Backing plate 4 Indium solder material 5 Non-woven fabric 6 Copper plate 7 Kapton tape 8 Heating plate

Claims (5)

A sputtering target obtained by joining one or more target members made of ITO containing indium oxide and tin oxide onto a backing plate using an indium solder material, wherein the indium solder is exposed from the target-backing plate assembly. A sputtering target, wherein a part or all of the material is covered with a metal plating film having a melting point of 200 ° C. or higher and a thickness of 1 μm or more and 100 μm or less . In a sputtering target obtained by joining two or more target members on a backing plate using an indium solder material, a portion where the solder material is exposed in a gap formed between the target members is a metal having a melting point of 200 ° C. or higher. The sputtering target according to claim 1, wherein the sputtering target is covered with a plating film. The sputtering target according to claim 1 or 2, wherein the metal plating film having a melting point of 200 ° C or higher is a copper plating film. The sputtering target according to any one of claims 1 to 3, wherein the backing plate is made of copper. A method for manufacturing a sputtering target, wherein one or more target members made of ITO containing indium oxide and tin oxide are bonded to a backing plate using an indium solder material, and are exposed from the target-backing plate assembly. 5. The sputtering target according to claim 1, wherein a part or all of the indium solder material is coated with a metal plating film having a melting point of 200 ° C. or more and a thickness of 1 μm to 100 μm. Production method.

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