JP2018172797A - Method for cleaning target material, method for manufacturing target material, method for manufacturing recycled ingot, and recycled ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of simply removing impurities derived from a joint material and a supporting member from a used target material, and simply recovering the joint material remaining in the target material, a method for manufacturing a used target material substantially not containing such impurities and a recycled ingot, and such a recycled ingot.SOLUTION: The present invention can provide: a target material cleaning method including a step of treating a coupling surface of a target material separated from a support member to at least the support member with base after using a sputtering target made by coupling the target material mainly made of metal and the support member with a joint material in sputtering; a used target material manufacturing method; a method for manufacturing a recycled ingot using the target material treated by the cleaning method; and a recycled ingot.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for collecting and cleaning a target material in recycling of a sputtering target after use, a method for producing a target material, a method for producing a recycled ingot, and a recycled ingot.

  In a sputtering target, a target material generally composed of ceramics such as metal, alloy, and oxide and a support member such as a backing plate or backing tube composed of metal or alloy are bonded with a bonding material such as solder material (bonding). A thin film such as a metal or an oxide can be formed on the substrate by subjecting such a sputtering target to sputtering. Regardless of the type of target material, it is not completely consumed by sputtering, but is recovered after its use. For example, a metal such as aluminum or copper is again melted and cast to produce an ingot (slab, ingot). ) Can be reused (recycled).

  Regarding the reuse of the collected used target material, for example, Patent Documents 1 to 3 disclose the removal of surface deposits on a sputtering target with an acid.

JP 2005-23350 A JP 2005-23349 A International Publication No. 2015/151498 Pamphlet

  In most cases, the thickness of the bonding material remaining on the used target material is not uniform, and if the used target material is simply treated with an acid as in the past, the components derived from the bonding material such as solder material are not used. It cannot be completely removed. In particular, in a target material for a flat panel display having a large size, the risk that a bonding material remains in a part is very high. In addition, metal elements contained in a supporting member such as a backing plate and a backing tube may be mixed in the target material by diffusion, and it is difficult to remove such impurities by treating with an acid as in the conventional case. For this reason, when the used target material processed by the conventional method is melted and cast again, impurities derived from the bonding material and the support member are mixed, and the target material having the same quality as the original target material It was difficult to play. In general, In, In alloy, Sn, Sn alloy, etc. are used for bonding the target material and the support member as the bonding material, and these bonding materials are made of, for example, an inorganic acid such as nitric acid. Since it can be dissolved, it is desirable to collect and recycle particularly expensive In, but it is recovered from an acid aqueous solution, and such recovery is very complicated.

  Therefore, the present invention provides a method that can easily remove impurities derived from the bonding material and the support member from the used target material, and can easily recover the bonding material remaining in the target material, such impurities. An object of the present invention is to provide a used target material and a method for producing a recycled ingot, which are substantially free of selenium, and such a recycled ingot.

  As a result of diligent research, the present inventor used a sputtering target formed by bonding a target material and a support member with a bonding material by sputtering, and then separated the used target material from the support member, thereby supporting the target material. It was found that impurities such as a bonding material adhering to the target material can be easily peeled and removed from the target material by treating the bonding surface with the base with the base, and the present invention has been completed.

The present invention provides the following, but the present invention is not limited to the following.
[1]
After a sputtering target formed by bonding a target material mainly composed of metal and a support member with a bonding material is used in sputtering, at least a bonding surface of the target material separated from the support member is bonded to the support member. A method for cleaning the target material, comprising treating with a base.
[2]
The method according to [1] above, comprising treatment with an acid after the treatment with the base.
[3]
The method according to [1] or [2] above, wherein the metal is aluminum.
[4]
The manufacturing method of a used target material including processing a target material by the method of any one of said [1]-[3].
[5]
The manufacturing method of the recycle ingot using the used target material obtained by the manufacturing method as described in said [4].
[6]
A recycled ingot containing aluminum as a main component and having a total amount of impurities derived from the bonding material and the support member of less than 10 ppm by weight.

According to the present invention, at least the bonding surface of the used target material with the support member is treated and washed with a base, so that the target material is eroded by the base and the bonding material remaining on the target material is easily peeled off. Can be removed. Therefore, according to the present invention, it is possible to provide a used target material that is substantially free of impurities derived from the bonding material and the support member, by such a treatment with a base.
In addition, by using the target material that has been subjected to such treatment, a recycled ingot that substantially does not contain impurities derived from the bonding material and the support member can be manufactured. Therefore, according to the present invention, a target material having substantially the same composition as the original target material can be manufactured again from such a recycled ingot. Furthermore, according to the present invention, the bonding material remaining on the used target material can be easily recovered in a solid state.

It is the schematic which shows typically an example of processing of the target material according to this invention, and reproduction | regeneration of the target material using the same. It is the schematic which shows the coupling | bonding of the target material of a sputtering target, and a supporting member. It is the schematic which shows the coupling | bonding of the target material and support member of another sputtering target. It is the schematic which shows the coupling | bonding of the target material and support member of another sputtering target.

  The present invention relates to a method for cleaning a target material separated from a used sputtering target, a method for producing the target material, and an ingot (hereinafter referred to as “recycled ingot”) that uses the target material treated by the cleaning method as a raw material. ) And a recycled ingot produced by the production method.

  In the present invention, the “sputtering target” is a target material mainly composed of a metal (element) and a support member bonded by a bonding material, and is not particularly limited as long as it can be used for sputtering. Absent. When the sputtering target is a flat plate type, a flat backing plate can be used as the support member. When the sputtering target is cylindrical, a cylindrical backing tube can be used as the support member. Here, a cylindrical backing tube can be inserted into the cylindrical target material, and the inner peripheral portion of the cylindrical target material and the outer peripheral portion of the backing tube can be joined by a bonding material.

  The “target material” can be mainly composed of a metal (element), for example, aluminum (Al), copper (Cu), chromium (Cr), iron (Fe), tantalum (Ta), titanium (Ti ), Zirconium (Zr), tungsten (W), molybdenum (Mo), niobium (Nb), silver (Ag), cobalt (Co), ruthenium (Ru), platinum (Pt), palladium (Pd), gold (Au ), Rhodium (Rh), iridium (Ir), and nickel (Ni), and a metal (element) selected from the group consisting of the above metals may be used. It is preferably composed of aluminum (purity 99.99% (4N) or more, preferably 99.999% (5N) or more) or copper (purity 99.99% (4N) or more). There. There are no particular restrictions on the size, shape and structure of the target material. It is preferable to use a plate-like material as the target material.

When the support member is a “backing plate”, mainly copper (Cu), chromium (Cr), aluminum (Al), titanium (Ti), tungsten (W), molybdenum (Mo), tantalum (Ta), niobium It includes a metal (element) selected from the group consisting of (Nb), iron (Fe), cobalt (Co) and nickel (Ni), and may be an alloy including the above metals, Copper (oxygen-free copper), chromium copper alloy, aluminum alloy and the like are preferable. If it is a plate-like thing which can arrange | position a target material, there will be no restriction | limiting in particular in the dimension of a backing plate, a shape, and a structure.
When the support member is a “backing tube”, the constituent metal is the same as in the case of the above-described backing plate, and among these, stainless steel (SUS), titanium, titanium alloy, and the like are preferable. Since the dimensions of the backing tube are inserted and joined inside the cylindrical target material, it is usually longer than the cylindrical target material, and the outer diameter of the backing tube is preferably slightly smaller than the inner diameter of the cylindrical target material. .

  The “bonding material” is not particularly limited as long as it can be used to form a sputtering target by contributing to the bonding between the target material and the support member (FIG. 2). Examples of the bonding material include solder material and brazing material.

The “solder material” is a material containing a metal or alloy having a low melting point (for example, 723 K or less), for example, indium (In), tin (Sn), zinc (Zn), lead (Pb), silver (Ag). , Copper (Cu), bismuth (Bi), cadmium (Cd) and antimony (Sb), or a material containing a metal or an alloy thereof. More specifically, In, In—Sn, Sn—Zn, Sn—Zn—In, In—Ag, Sn—Pb—Ag, Sn—Bi, Sn—Ag—Cu, Pb—Sn, Pb—Ag, Zn-Cd, Pb-Sn-Sb, Pb-Sn-Cd, Pb-Sn-In, Bi-Sn-Sb, and the like can be given.
As the “brazing material”, a target material and a support member can be bonded, and any metal or alloy having a melting point lower than that of the target material and the support member can be used without any particular limitation.
As the bonding material, it is preferable to use a solder material such as In or In alloy, Sn or Sn alloy which generally has a low melting point.

  For example, the solder material can be bonded by forming a diffusion layer (alloy layer) with a metal (element) contained in the target material on the bonding surface with the target material by heating. In addition, the solder material can be bonded by forming a diffusion layer (alloy layer) with a metal (element) contained in the support member in the same manner also on the bonding surface with the support member. Therefore, a solder layer can be formed by using such a solder material, and a target material and a support member can be combined (FIG. 3).

  In general, if only the solder material is placed on the target material or the support member, an oxide film that may be present on the surface of the target material or the support member is affected, so that sufficient bonding strength may not be obtained. Therefore, first, a metallized layer may be provided in order to improve the wettability of the solder material with respect to those surfaces.

  “Metallization” is a processing method that can be generally used to form a metal film on a non-metallic surface. In the present invention, for example, when a target material or a support member has an oxide film, solder for metallization is used. A metallized layer is formed by bonding with a target material or a support member using a material. The metallized layer, for example, using an ultrasonic soldering iron, while destroying the oxide film of the target material and the support member by ultrasonic vibration energy (cavitation effect), by heating, along with oxygen atoms in the oxide film, It can be formed by chemically bonding metal atoms contained in the metallization solder material and metal atoms contained in the target material or the support member.

  The metallized layers (5, 5 ′) (see FIG. 4) that can be formed in this way can be joined to the solder layer (4), and between the target material (1) and the solder layer (4). Position between the support member (2) and the solder layer (4) to firmly bond the target material (1) and the solder layer (4) and the support member (2) and the solder layer (4) Can be fulfilled.

The thickness of the solder layer is, for example, in the range of 50 μm to 500 μm for the flat plate type and 250 μm to 1500 μm for the cylindrical type.
The thickness of the metallized layer is, for example, in the range of 10 μm to 100 μm for both the flat plate type and the cylindrical type.

  Solder materials that can be used for metallization include, for example, indium (In), tin (Sn), zinc (Zn), lead (Pb), silver (Ag), copper (Cu), bismuth (Bi), cadmium ( A material including a metal selected from the group consisting of Cd) and antimony (Sb) or an alloy thereof, and more specifically, In, In—Sn, Sn—Zn, Sn—Zn—In, In—Ag. Sn-Pb-Ag, Sn-Bi, Sn-Ag-Cu, Pb-Sn, Pb-Ag, Zn-Cd, Pb-Sn-Sb, Pb-Sn-Cd, Pb-Sn-In, Bi-Sn -Sb etc. are mentioned. What is necessary is just to select a material with high affinity with a target material or a supporting member suitably.

  In this invention, after using a sputtering target by sputtering, a target material is isolate | separated (peeled) from a supporting member. There is no particular limitation on the method for separating the target material from the support member. For example, heat (for example, 180 ° C. to 300 ° C.) is applied to a bonding layer (or bonding layer) that can be formed from the bonding material described above, and the bonding layer is physically formed as necessary while softening or melting the bonding layer. The target material can be separated from the support member by breaking.

  In the case where the target material is a flat plate type, in the target material after separation, the surface on the side that is bonded (or bonded) to the support member (hereinafter sometimes referred to as “bonded surface” or “bonded surface”) At least a part of the bonding material remains attached. Note that even if the bonding material adhering to the bonded surface after separation is scraped off with a spatula (for example, a silicone spatula), the adhering bonding material cannot be completely removed. In addition, the bonding material may adhere and remain on the sputtering surface of the target material. As the cause, for example, the bonding material melted at the time of separation of the target material adheres to the sputtering surface, and the separated used target materials are stacked and stored so that the bonding surface and the sputtering surface are in contact with each other. For example, the bonding material on the bonding surface may adhere to the sputtering surface. Therefore, the treatment may be applied also to the sputtering surface.

  When the target material is a cylindrical type, the cylindrical target material can be bonded to the outer periphery of the cylindrical backing tube using a bonding material. Therefore, as in the case of the above-described plate target material, The bonding material adheres to the bonding surface (inner peripheral portion) and cannot be completely removed. In addition, the bonding material may adhere and remain on the sputtering surface of the target material. Furthermore, components derived from the backing tube may be mixed as impurities. Therefore, the cleaning method may be applied to the outer peripheral portion and the inner peripheral portion, which are sputtering surfaces, also in the cylindrical target material.

  The presence of bonding material adhering to the target material after separation can be confirmed by, for example, energy dispersive X-ray fluorescence analysis (EDXRF). In addition, a metal element may diffuse from the support member to the target material, and such a metal element can be similarly confirmed by EDXRF. In addition, wavelength dispersive X-ray fluorescence analysis (WDXRF), electron probe microanalysis (EPMA), Auger Electron Spectroscopy (AES), X X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), laser irradiation type inductively coupled plasma mass spectrometry (LA-) Impurities originating from the bonding material and the support member can be confirmed by analysis methods such as ICP-MS: Laser Ablation Inductively Coupled Plasma Mass Spectrometry (XRD) and X-ray Diffraction Analysis (XRD). Confirmation with EDXRF or WDXRF is preferred because of its simplicity and wide analysis range.

  Here, an ingot (hereinafter sometimes referred to as “slab” or “ingot”) is manufactured by melting and casting in the subsequent recycling process using the separated target material to which the bonding material has adhered. When the target material is manufactured again from the ingot, impurities derived from the attached bonding material components are mixed. In some cases, a metal element diffuses from the support member to the target material and is mixed as an impurity, and such a metal element may also be mixed into the ingot as an impurity.

  Therefore, in the present invention, as will be described in detail below, after the used target material is separated from the support member, at least the bonding surface to which the bonding material of the target material adheres and remains is treated with a base and washed. Thereby, since the base erodes the target material, the bonding material is peeled off and removed from the target material, and at the same time, impurities derived from the support member can be easily removed (FIG. 1).

(Cleaning method of used target material)
Base treatment The present invention is characterized in that at least the bonding surface of the target material separated from the support member is treated with a base.

  Examples of the base that can be used in the present invention include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, and alkaline earths such as calcium hydroxide, strontium hydroxide, and barium hydroxide. Examples thereof include metal hydroxide, sodium carbonate, ammonia, guanidine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and the like. If necessary, a combination of two or more bases may be used.

  In addition to the above-described base, a chelating agent that forms a complex with metal ions constituting the target material may be added. For example, when the target material is aluminum, heptogluconic acid, gluconic acid, citric acid, tartaric acid, an alkali metal salt of ethylenediaminetetraacetic acid, and the like can be given. Moreover, you may add commercially available alkali etching processing agents, such as arsatin. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular in the density | concentration of a base, For example, it is 5 to 50 weight%, Preferably it is 8 to 40 weight%, More preferably, it is 10 to 35 weight%. If the concentration is too low, the reaction rate with the target material may be slow, and sufficient cleaning effect may not be obtained. If the concentration is too high, the oxide layer on the surface of the target material may become thick or the cost may increase. . Moreover, when using combining a base, the density | concentration of one base may be 5 weight% or less, for example, and may be 1 weight% or less.

  There is no restriction | limiting in particular also in the temperature of the base to be used, for example, 10 to 80 degreeC, Preferably it is 15 to 70 degreeC, More preferably, it is 20 to 60 degreeC. If the temperature is too low, the reaction rate with the target material is slow, and a sufficient cleaning effect may not be obtained. If the temperature is too high, the oxide layer on the surface of the target material may be thick.

  There is no restriction | limiting in particular in the processing time by a base, For example, 3 minutes or more, Preferably it is 3 minutes-12 hours, More preferably, they are 5 minutes-5 hours, More preferably, they are 5 minutes-120 minutes. What is necessary is just to determine suitably according to the density | concentration and temperature of a base.

  Examples of the treatment with a base include application of a base solution (preferably an aqueous solution) to the target material and immersion of the target material in a base solution (preferably an aqueous solution).

-Acid treatment If necessary, after the above-mentioned base treatment, at least the bonding surface of the target material with the support member may be treated with an acid (FIG. 1). By treatment with such an acid, in some cases, the treatment with the above-mentioned base can dissolve the impurities derived from the bonding material and the support member that cannot be sufficiently peeled off and remain, and such impurities can be removed. Further, it can be removed.

  Examples of the acid that can be used in the present invention include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid (hydrofluoric acid), phosphoric acid, perchloric acid, chloric acid, perbromic acid, bromic acid, periodic acid, iodine. Examples include acids, hydroiodic acid, permanganic acid, and tetrafluoroboric acid. If necessary, two or more acids may be used in combination. For example, aqua regia or hydrofluoric acid can be used.

  There is no restriction | limiting in particular in the density | concentration of an acid, For example, they are 1 weight%-50 weight%, Preferably they are 5 weight%-45 weight%, More preferably, they are 10 weight%-40 weight%. However, in the case of a mixed acid such as hydrofluoric acid, the concentration of one acid may be 1% by weight or less.

  There is no restriction | limiting in particular also in the temperature of the acid to be used, for example, 10 to 50 degreeC, Preferably it is 15 to 45 degreeC, More preferably, it is 20 to 40 degreeC.

  There is no restriction | limiting in particular in the processing time by an acid, For example, 3 minutes or more, Preferably it is 3 minutes-12 hours, More preferably, they are 5 minutes-120 minutes, More preferably, they are 10 minutes-90 minutes. What is necessary is just to determine suitably according to the density | concentration and temperature of an acid.

  Examples of the treatment with an acid include application of an acid solution (preferably an aqueous solution) to the target material and immersion of the target material in an acid solution (preferably an aqueous solution).

・ Processing process When processing a large amount of used target materials at the same time, it is preferable to place the target materials in a bowl-shaped container and immerse the whole bowl-shaped container in a base solution or an acid solution. Insertion and removal operations can be performed easily.

  The container may be made of any material that has high chemical resistance and can withstand the weight of the used target material contained therein. Examples include metals and alloys such as stainless steel, titanium, titanium alloys, nickel, nickel alloys, inconel, and aluminum alloys, resins such as vinyl chloride resins, fluororesins, polyethylene, and polypropylene, and are selected as appropriate according to the base or acid used. do it. When processing a used target for a flat panel display having a length exceeding 1 m, it is preferable to use stainless steel such as SUS304 and SUS316 from the viewpoint of strength, durability, and chemical resistance. When a metal container is selected, a material coated with the above resin or the like may be used in order to prevent dissolution of the metal in the solution.

  In order to immerse the entire bowl-shaped container in the solution, the bowl is preferably in the form of a net, mesh, punching, expanding, or grating. Since the base or acid can diffuse inside and outside the container, a decrease in the reaction rate can be suppressed. In addition, when using a metal cage, the amount of the metal component dissolved in the solution can be suppressed by reducing the area of the portion that comes into contact with the solution, and the metal component is deposited on the target material. The risk of contamination can be reduced.

There is no particular restriction on the posture of the used target material immersed in the base or acid. However, in the case of a flat target material, the side surface of the target material faces downward, and the angle of the target joining surface with respect to the lower surface of the container is It is preferable to remove the bonding material and the like more efficiently by dipping at an angle of 60 ° to 120 ° so as to stick. When the used target material is immersed in a base or acid, a gas is generated in the form of bubbles due to the reaction of the bonding material or target material with the base or acid, and the gas rises along the surface of the treated surface. In addition to stirring the solution, peeling of the bonding material can be promoted by the collision of bubbles.
In the case of a cylindrical target material, when the outer peripheral surface of the target material faces downward and the immersion surface is immersed preferably at an angle of 2 ° to 45 ° so that the joint surface of the target material is inclined with respect to the lower surface of the container, an air pocket is generated. Can be suppressed, and the risk that the bonding material remains can be reduced.

  Further, immediately after the base treatment or the acid treatment, jet cleaning with a high-pressure fluid of 3 MPa or more, preferably 5 MPa or more may be performed. Although there is no restriction | limiting in particular in the kind of fluid, When using a base and an acid, it is preferable to use water. The thickness of the bonding material remaining on the used target material that has been peeled off from the support member is not uniform, and part of the bonding material that remains thick or the bonding material that has melted in the peeling process hangs down on the target material and is present in islands or spots There are often parts. There is a risk that the bonding material may remain after the above-mentioned treatment, but a part of the bonding material adhering thereto can be physically removed by performing jet cleaning, and there is a risk that the bonding material remains. Can be reduced.

-Detection of impurities According to the method for cleaning a used target material of the present invention, the detection limit of EDXRF (normally, the detection limit varies depending on the element, but for example, the detection limit of impurities derived from a bonding material is 0.01. The amount of impurities derived from the bonding material and the support member can be reduced to a value lower than that of, for example, 0.01% by weight for indium, and the processed target material is a bonding material. And impurities substantially derived from the support member. Here, “substantially free of impurities derived from the bonding material and the support member” means that the amount of impurities is smaller than the lower limit of detection of EDXRF and reduced to such an extent that it cannot be detected by EDXRF.

  In addition, the cleaning method of the present invention is different from the cleaning method with a conventional acid solution, and the used target material is more actively dissolved to peel the bonding material adhering to the surface in a solid state. This is a method that can be removed. Therefore, since the bonding material can be easily recovered from the solution used for the treatment, it has many advantages over the conventional acid cleaning method.

(Manufacturing method of recycled ingot)
The target material processed according to the cleaning method of the present invention can produce a recycled ingot by melting and casting, for example, as shown in FIG.

  As a method for producing the recycled ingot, a known method may be used, which can be produced through a melting and casting process. As a melting method, it may be melted in the atmosphere or in a vacuum in an electric furnace or a combustion furnace, and as a casting method, a continuous casting method, a semi-continuous casting method, a die casting method, a precision casting method, a hot top A casting method, a gravity casting method, or the like can be employed. Moreover, you may perform a degassing process and an inclusion removal process between a melt | dissolution and a casting process.

  What is necessary is just to determine suitably the manufacturing conditions of recycling ingot, especially temperature according to the metal (element) mainly contained in a target material.

  For example, when the metal contained as the main component in the target material is aluminum, the target material after the treatment is carbonized at 670 to 1200 ° C., preferably 750 to 850 ° C. under vacuum (for example, 0.03 Torr) or air. A recycled ingot can be manufactured by dissolving in a crucible such as aluminum or alumina, stirring in the air as necessary to remove dross, and then cooling in the air.

  For the production of the recycled ingot, it may be produced only with the target material after washing, or a mixture of conventional raw metal and the target material after washing may be used together. When the raw material metal and the target material after cleaning are mixed, the mixing ratio of the target material after cleaning is usually 20% by weight or more, and is 50% by weight or more for suppressing the ratio of the raw material cost in the manufacturing cost. It is preferable.

(Recycled ingot)
As described above, the recycled ingot that can be manufactured according to the method of the present invention is substantially free from impurities derived from the bonding material and the support member, and is substantially different from the original (unused) target material. Can have the same composition. Therefore, a target material having substantially the same composition as the original target material can be manufactured again from such a recycled ingot. Here, “having substantially the same composition as the original target material” means that the main metal (element) is the same, and may contain impurities in the same amount as the impurities originally contained in the original target material. Means that. For example, the total amount of impurities that can be derived from the bonding material and the support member is less than 10 ppm on a weight basis, preferably 0.1 ppm to 8 ppm, more preferably 5 ppm or less (or less), and even more preferably 0.1 ppm to 5 ppm. Even more preferably, it is 0.1 ppm to 3.5 ppm, and the total amount of impurities is less than 50 ppm, preferably 0.1 ppm to 20 ppm, more preferably 0.1 ppm to 10 ppm, still more preferably 0.1 ppm to 7 ppm. For example, it is within the range. The impurities originally contained in the original target material and the amount thereof can depend on the type of metal contained in the target material as a main component and the method of manufacturing the original target material. In addition, the recycled ingot may be used for applications other than the target material. For example, it may be used as a raw material for products that require high purity such as aluminum electrolytic capacitors, hard disk substrates, corrosion resistant materials, and high purity alumina. it can.

  For example, when the metal contained as the main component in the target material is aluminum, the total amount of impurities derived from the bonding material and the support member contained in the recycled ingot is, for example, less than 10 ppm on a weight basis, preferably 0. 0.1 ppm to 8 ppm, more preferably 5 ppm or less (or less), further preferably 0.1 ppm to 5 ppm, and even more preferably 0.1 ppm to 3.5 ppm is within an acceptable range. Although it depends on the application, it is known that an aluminum target material for flat display, for example, can usually contain about 10 ppm of impurities, and if the amount of impurities is this level, there is no particular problem in sputtering. .

  In addition, since the amount of impurities contained in the recycled ingot is extremely small, the amount of such impurities can be measured using glow discharge mass spectrometry (GDMS). Although the lower limit of quantification of GDMS varies depending on the main element of the target material and the element to be detected, for example, when the metal contained as the main component of the target material is aluminum, it is usually 0.001 ppm to 0.1 ppm. For example, indium is 0.01 ppm.

  As described above, according to the present invention, the used target material can be easily cleaned, and the target material after cleaning does not substantially contain impurities derived from the bonding material and the support member. By using the target material processed by the method, a recycled ingot having substantially the same composition as the original target material can be obtained. From such a recycled ingot, a target material having substantially the same composition as the original target material can be easily produced. Moreover, according to the present invention, the bonding material can be easily recovered in a solid state after the base treatment.

  EXAMPLES Hereinafter, although an Example of this invention is given and this invention is demonstrated in detail, this invention is not limited to a following example.

(Examples 1 to 9 and Comparative Example 1)
A flat plate target material made of aluminum (purity: 99.999%, dimensions: 2000 mm × 200 mm × 15 mm) and an oxygen-free copper backing plate (purity: 99.99%, dimensions: 2300 mm × 250 mm × 15 mm), Sputtering targets formed by bonding with In or Sn—Zn solder materials (solder layer thickness: 350 μm) shown in Tables 1 to 3 below (use Sn—Zn—In solder materials for metallization of the target materials). After being used for sputtering, the target material was separated from the backing plate by heating (280 ° C.) the bonding layer. The solder material adhering to the joint surface of the target material was scraped off with a silicone spatula, and the solder material was recovered as much as possible. After separation from the backing plate, the target material was cut to a size of about 100 mm × 200 mm × 15 mm.

The above target materials were each washed and treated by dipping under the conditions shown in Tables 1 to 3 below (Examples 1 to 9 and Comparative Example 1), and the EDXRF analyzer (EDX-700L, detection limit: manufactured by Shimadzu Corporation): The bonding surface of the used target material after cleaning was analyzed (semi-quantitative analysis) under the following conditions using about 0.01 wt% of In.
At that time, the presence or absence of X-ray peak detection was also confirmed for the elements of the components of the bonding material and the backing plate. As a result, it was also confirmed that no peak was detected when the analysis result was 0 wt%.
The analysis results of EDXRF are shown in Tables 1 to 3 below together with the analysis results of the used target material (before cleaning) and the unused target material (before bonding).
<Analysis conditions>
X-ray irradiation diameter: 10mmφ
Excitation voltage: 10 kV (Na to Sc), 50 kV (Ti to U)
Current: 100 μA
Measurement time: 200 seconds (100 seconds measurement at each excitation voltage)
Atmosphere: He
Tube: Rh target Filter: None Measurement method: Fundamental parameter method Detector: Si (Li) semiconductor detector

As the results of Examples 1 to 9 show, the used target material substantially free of impurities derived from the bonding material and the backing plate could be obtained by the cleaning method of the present invention.
On the other hand, in Comparative Example 1 in which only the treatment with acid was performed, copper (Cu) derived from the backing plate could not be removed even though the treatment was performed for 20 hours. Moreover, in Examples 1-9, although the solder material which is a joining material was able to be collect | recovered in the solid state in the stage of a base treatment, in the comparative example 1 which processed with the acid, solder material is in acid aqueous solution. It melt | dissolved and it was not able to collect | recover joining materials.

  Next, a part of the target material obtained in Examples 2, 6, 7, 8 and Comparative Example 1 was collected, and the target material treated at 850 ° C. under vacuum (for example, 0.03 Torr) was dissolved in the atmosphere. About 3 kg of recycled ingots were produced by removing the dross by stirring in the air and then cooling in the air.

  The amount of impurities contained in the recycled ingot and the unused target material was subjected to microanalysis for In, Sn, Zn, and Cu, respectively, using GDMS (VG Elemental, VG9000). The results are shown in the following Tables 4 and 5 together with the analysis results of the ingot produced by the same method from the used target material (before cleaning) and the target material of Comparative Example 1 and the unused target material (before joining).

  As the results of Examples 2, 6, 7, and 8 show, the total amount of impurities (ie, In, Sn, Zn, Cu) derived from the bonding material and the backing plate is 5 ppm by weight by the cleaning method of the present invention. Thus, a recycled ingot having substantially the same composition as that of the original target material could be obtained.

  On the other hand, in Comparative Example 1 in which only the treatment with the acid was performed, the total amount of impurities (that is, In, Sn, Zn, Cu) derived from the bonding material and the backing plate despite the treatment for 20 hours was It was about 19 ppm on the weight basis, and a recycled ingot having substantially the same composition as the original target material could not be obtained.

(Example 10)
The used flat plate type target material (2t) was processed under the same conditions as in Example 7. However, the size of the used target material that was washed was 1000 mm × 200 mm × 15 mm (size obtained by cutting the target material peeled off from the backing plate in half), and was placed in a net-like cage made of SUS304 and immersed in the cleaning liquid. At that time, the used target material was placed in the basket so that the long side of the target faced downward and the joint surface stood (60 ° to 120 °) with respect to the lower surface of the container. Further, after immersion in a base and an acid, the joint surface was jet cleaned with high-pressure water of about 5 MPa. After washing, 10 of the treated target materials were randomly selected and cleaned using an EDXRF analyzer (EDX-700L, detection limit: about 0.01 wt% in In) manufactured by Shimadzu Corporation. The joint surface of the target material was analyzed (semi-quantitative analysis). At that time, the presence or absence of X-ray peak detection was confirmed for the elements of the bonding material and the backing plate component. As a result of analysis, it was also confirmed that no peak was detected when the content was 0%.
Next, the entire amount (2t) of the cleaned target material is melted in the atmosphere at 750 ° C., dross is removed using a flux in the atmosphere, the molten metal is poured into the mold in the atmosphere, and the molten metal is cooled. Recycled ingots were manufactured.
The amount of impurities contained in the recycled ingot was measured using GDMS (VG9000 manufactured by VG Elemental). The results are shown in Table 5 above.
As the result of Example 10 shows, the cleaning method of the present invention is not affected by the variation in the thickness of the solder material of the used target, and it is clear that it is suitable for processing a large amount of the used target material. It was.
Further, when the used target material was treated for 2 tons, about 4 kg of the solder material could be recovered in a solid state (film shape).
About the said Example and the comparative example, although the flat type target material was demonstrated, the same result can be obtained by performing the same process also about the cylindrical type target material joined using a joining material to a backing tube. it can.

  According to the present invention, it is possible to obtain a target material that is substantially free of impurities derived from a bonding material and a supporting member such as a backing plate and a backing tube by washing the used target material with at least a base. A recycled ingot having substantially the same composition as the original target material substantially free of impurities derived from the bonding material and the support member can be obtained by manufacturing the ingot again using a new target material as a raw material. it can. According to the present invention, a target material having substantially the same composition as the original target material can be produced from such a recycled ingot, and the joining material can be easily recovered in a solid state. Useful for recycling target materials.

1 target material 2 support member 3 bonding material (or bonding layer)
4 Solder layer 5, 5 ′ Metallized layer 10, 20, 30 Sputtering target

Claims (6)

  After a sputtering target formed by bonding a target material mainly composed of metal and a support member with a bonding material is used in sputtering, at least a bonding surface of the target material separated from the support member is bonded to the support member. A method for cleaning the target material, comprising treating with a base.   The method of claim 1, comprising treating with an acid after the treatment with the base.   The method according to claim 1, wherein the metal is aluminum.   The manufacturing method of a used target material including processing a target material by the method of any one of Claims 1-3.   The manufacturing method of the recycle ingot using the used target material obtained by the manufacturing method of Claim 4.   A recycled ingot containing aluminum as a main component and having a total amount of impurities derived from the bonding material and the support member of less than 10 ppm by weight.

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