Method for recycling target material

Abstract

To provide a recycling method of a target material capable of improving treatment efficiency.SOLUTION: A flying body 5 made of stainless steel is made to collide with the back surface of the target material 1 separated from the backing plate 2. The flying body 5 is made to collide so as to satisfy "Ek / Sa> 2.0" and "Sa <260", where Ek (mJ) is its motion energy, V (mm3) is the volume of the flying body, Sa (mm2) is the average cross-sectional area of the flying body, and Sa = V ^ (2 / 3).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for recycling a target material, and more particularly to a method for recycling a target material bonded to a backing plate by a bonding material. [Background technology]

[0002] The sputtering target is formed by bonding, for example, a target material made of high-purity aluminum and a backing plate made of a metal different from the target material.

[0003] The backing plate is bonded to the target material to cool the target material when it is used for sputtering and to ensure the strength of the sputtering target. One method for bonding is to use a brazing filler metal (for example, a brazing filler metal made of tin-zinc or indium).

[0004] It should be noted that the target material is not completely consumed even when used in sputtering, and is therefore recovered and reused after use in sputtering.

[0005] Specifically, used sputtering targets are reused by separating the target material from the backing plate, removing foreign matter such as dust that may have been introduced from the surrounding environment during storage, transportation, handling, and separation, and removing the brazing material. The clean target material is then melted and cast.

[0006] Here, regarding the reuse of sputtering targets, "the first surface where the target material and the support member (backing plate) were joined must have a new Mohs hardness of 3 or more and a bulk density of 2 g / cm 3 A technique has been proposed in which an abrasive material such as that described below is sprayed onto the surface (see Patent Document 1).

[0007] Furthermore, with regard to the reuse of sputtering targets, a technique has been proposed in which "at least the bonding surface of the target material separated from the support member (backing plate) with the support member (backing plate) is treated with a base" (see Patent Document 2). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-132997 [Patent Document 2] Japanese Patent Application Publication No. 2018-172797 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the technology described in Patent Document 1 uses a lightweight, low-hardness abrasive to prevent residue from being pushed into the bonding surface, making it difficult to improve processing efficiency per unit time. Also, when a lightweight, low-hardness abrasive is used, it is difficult to sufficiently remove thick residue.

[0010] Furthermore, in the technology described in Patent Document 2, residual materials, aluminum derived from the target material, and salts and ions of solute elements are mixed into the treatment liquid, which can cause severe deterioration of the treatment liquid depending on the amount of residual materials attached, and can also require a long treatment time.

[0011] The present invention has been made in view of the above points, and has as its object to provide a method for recycling target materials that can improve processing efficiency. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides a target material recycling method for reusing a sputtering target having a target material mainly made of aluminum and a backing plate joined to the back surface of the target material with a joining material after the target material has been used for sputtering, the method comprising the steps of: peeling off the backing plate; and colliding a projectile having a Brinell hardness of 20 or more with the joining surface of the target material with the backing plate; defining the kinetic energy of the projectile as Ek (mJ); defining the volume of the projectile as V (mm 3 ), and the average cross-sectional area of ​​the projectile is Sa (mm 2 )year, When using TIFF2026001694000002.tif1230, Ek / Sa > 2.0 (Equation 1) The projectile is caused to collide under the condition that satisfies the following.

[0013] Here, by colliding a projectile with a Brinell hardness of 20 or more with the bonding surface of the target material with the backing plate, the back surface of the target material (the Brinell hardness of aluminum is approximately 20) can be thinly scraped off, and the bonding material adhering to the bonding surface can be efficiently removed.

[0014] In other words, by colliding a high-hardness projectile with the bonding surface between the target material and the backing plate, the bonding material is destroyed and removed, and the back surface of the target material to which the bonding material is attached is thinly scraped off, making it possible to efficiently remove the bonding material adhering to the bonding surface.

[0015] Metal materials with a "Brinell hardness of 20 or more" include copper (Brinell hardness 35), carbon steel (Brinell hardness 100 to 450), and stainless steel (generally Brinell hardness of about 120 to 190).

[0016] On the other hand, if a projectile with a Brinell hardness of less than 20 is collided with the bonding surface of the target material and backing plate, the projectile will be scraped by the target material (aluminum) and become smaller. As the projectile becomes smaller, its removal ability decreases, making it difficult to efficiently remove the bonding material adhering to the bonding surface.

[0017] An example of a material with a "Brinell hardness of less than 20" is wood (generally with a Brinell hardness of about 1 to 7).

[0018] Also, the kinetic energy of the projectile is Ek (mJ), and the volume of the projectile is V (mm 3 ), the average cross-sectional area of ​​the projectile is Sa (mm 2 )year, TIFF2026001694000003.tif1230, by satisfying "Ek / Sa > 2.0 ··· (Equation 1)", in other words, by making the kinetic energy per unit cross-sectional area exceed 2.0, the bonding material can be destroyed and removed, and the back surface of the target material to which the bonding material is attached can be thinly scraped away, thereby efficiently removing the bonding material attached to the bonding surface.

[0019] In other words, by colliding a projectile with a large amount of kinetic energy (kinetic energy per unit cross-sectional area) with the bonding surface between the target material and the backing plate, the back surface of the target material and the bonding material adhering to the back surface of the target material can be scraped off in a short period of time, making it possible to efficiently remove the bonding material adhering to the bonding surface.

[0020] The value of Ek / Sa is larger when the speed is faster, the projectile is heavier, and the projectile is smaller. A larger value of Ek / Sa means that a large amount of stress can be concentrated in a small area.

[0021] On the other hand, if "Ek / Sa > 2.0 (Equation 1)" is not satisfied, in other words, if the kinetic energy per unit cross-sectional area is 2.0 or less, the kinetic energy of the projectile (kinetic energy per unit cross-sectional area) is insufficient, and the ability to scrape (destroy) the "back surface of the target material" or the "bonding material adhering to the back surface of the target material" decreases, and as a result, it becomes difficult to efficiently remove the bonding material adhering to the bonding surface.

[0022] Here, when "Ek / Sa > 5.5 (Equation 2)" is satisfied, in other words, when the kinetic energy per unit cross-sectional area exceeds 5.5, the target material (aluminum) and the joining material can be further destroyed, and the joining material adhering to the joining surface can be sufficiently and efficiently removed.

[0023] In other words, by colliding a projectile with a greater kinetic energy (kinetic energy per unit cross-sectional area) with the bonding surface between the target material and the backing plate, the "back surface of the target material" and the "bonding material adhering to the back surface of the target material" can be scraped off in a shorter time, and the bonding material adhering to the bonding surface can be removed sufficiently efficiently.

[0024] Furthermore, if "Sa < 260 (Equation 3)" is satisfied, in other words, the average cross-sectional area of ​​the projectile is equal to or greater than the threshold value of 260 (mm 2 ), it is possible to prevent the bonding material from penetrating (being pushed into) the back surface of the target material due to the collision of the projectile, and it is possible to sufficiently and efficiently remove the bonding material adhering to the bonding surface.

[0025] On the other hand, if "Sa < 260 (Equation 3)" is not satisfied, in other words, the average cross-sectional area of ​​the projectile is less than the threshold value of 260 (mm 2 In the above cases, the target material (aluminum) is deformed due to the collision of the projectile, and the bonding material penetrates (is pushed into) the back surface of the target material, making it impossible to sufficiently and efficiently remove the bonding material adhering to the bonding surface.

[0026] In addition, if "Sa < 260 (Equation 3)" is not satisfied, in other words, the average cross-sectional area of ​​the projectile is less than the threshold value of 260 (mm 2 ) In the above cases, the kinetic energy of the projectile is consumed in "deformation of the target material" which does not contribute to the removal of the bonding material, rather than in "destruction of the target material" or "destruction of the bonding material" which contributes to the removal of the bonding material, resulting in a decrease in processing efficiency.

[0027] Here, if a process is included in which the target material is treated with at least one of an acid and a base chemical solution after the projectile has collided, it is possible to remove foreign matter caused by the environment and dust generated when the projectile impacts. Furthermore, even if the bonding material penetrates into the back surface of the target material due to the collision of the projectile, the foreign matter can be removed by the chemical treatment process. The target material may be masked with general-purpose masking tape or the like before being treated with the chemical solution.

[0028] Furthermore, when an acid treatment is performed as the chemical treatment, foreign matter on the target material after the backing plate is separated (removed) is dissolved and removed. Furthermore, when base treatment is performed as the chemical treatment, foreign matter on the target material after the backing plate is separated (removed) is dissolved and removed, and the target material into which the foreign matter has entered is thinly dissolved, causing the foreign matter to separate from the target material.

[0029] An example of chemical treatment is treatment with 10% to 15% by weight of a base (e.g., sodium hydroxide) for 30 minutes or more, followed by treatment with 10% to 15% by weight of an acid (e.g., nitric acid) for 720 minutes or more.

[0030] Furthermore, when the chemical treatment uses a treatment solution containing nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, aqua regia, or a mixed acid containing any of these, or an aqueous solution of any of these, and the treatment solution contains 3000 wtppm or more of aluminum ions, even in the following cases: (1) zinc ions are subsequently released into the treatment solution (for example, zinc ions are released in the current treatment batch) or (2) zinc ions have already been released into the treatment solution (for example, zinc ions were released in a treatment batch prior to the current treatment batch), the zinc ion substitution reaction (cementation) can be suppressed and contamination of the target material by zinc can be reduced.

[0031] That is, when target material with zinc attached or embedded therein is subjected to acid treatment, the zinc is released as ions into the treatment solution.The zinc ions released into the treatment solution then undergo a substitution reaction (cementation) with the target material (aluminum), causing zinc to precipitate on the target material, resulting in zinc contamination of the target material. Therefore, by using a treatment solution containing 3000 wtppm or more of aluminum ions and increasing the aluminum ion concentration in the treatment solution, the dissolution rate of the target material (aluminum) can be slowed down (in other words, by slowing down the rate of cementation, which is a substitution reaction), thereby reducing the precipitation of zinc ions in the treatment solution onto the target material.

[0032] Furthermore, a "treatment liquid containing 3000 wtppm or more of aluminum ions" can be obtained by adding a specified acid (nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, aqua regia, etc.) to used treatment liquid ("used treatment liquid" means that it has been used to treat target material) that has come to contain 3000 wtppm or more of aluminum ions by treating target material made of aluminum, and adjusting the hydrogen ion exponent to a specified concentration.

[0033] Furthermore, the "treatment solution containing 3000 wtppm or more of aluminum ions" can also be obtained by adding metallic aluminum, an aluminum salt, or a hydrate thereof to nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, aqua regia, or a mixed acid containing these, or to an aqueous solution of these.

[0034] Even if the treatment liquid contains more than 7000 wtppm of aluminum ions, the effect of slowing down the dissolution rate of the target material (aluminum) (in other words, the effect of slowing down the rate of cementation, which is a substitution reaction) will reach a plateau, so the aluminum ions contained in the treatment liquid may be 7000 wtppm or less.

[0035] Here, if the temperature is below 15°C (too low), the reaction rate is slow and it takes a long time to obtain a treatment solution with a concentration of 3000 wtppm or more. Furthermore, if the temperature exceeds 65°C (excessively high temperature), the reaction rate will be too fast and excessive heat of reaction will be generated, causing the reaction to proceed at an accelerated rate and the liquid temperature to rise, resulting in dangers such as boiling of the treatment liquid and generation of acid-containing mist. Furthermore, for metallic aluminum (or metallic aluminum alloy), its surface area is Sm (cm 2 ), and the volume is Vm (cm 3 ), even if the relationship Sm / Vm < 3.0 (equation 4) is not satisfied, in other words, if the surface area per unit volume is 3.0 or more, the surface area is too large compared to the weight of the aluminum (or aluminum alloy) being dissolved, and the contact area between the aluminum and nitric acid, etc. becomes excessive, causing the reaction rate to be too fast and creating a danger.

[0036] Therefore, by producing a "treatment solution containing 3000 wtppm or more of aluminum ions" (by adding metallic aluminum to nitric acid, etc.) in the "optimal temperature range of 15°C to 65°C" and under the condition that "Sm / Vm < 3.0 (Equation 4)" is satisfied, it is possible to achieve both safety and efficiency.

[0037] Furthermore, when the temperature of the treatment solution is low (excessively low), the reaction rate of the acid or base decreases, and the treatment takes a long time. On the other hand, if the temperature of the treatment liquid is high (excessively high), the reaction will proceed rapidly, causing the temperature of the treatment liquid to rise further due to the heat of reaction, resulting in bumping and the generation of mist containing acid or base, which will deteriorate the working environment and create danger. Therefore, the temperature of the treatment solution must be controlled within a specified temperature range (optimum temperature range). For acidic chemical treatment, the temperature condition is preferably "5°C or higher and 45°C or lower," and for basic chemical treatment, the temperature condition is preferably "20°C or higher and 60°C or lower." [Effects of the Invention]

[0038] The present invention realizes an improvement in the processing efficiency of the method for recycling target materials. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram for explaining a sputtering target. [Figure 2] FIG. 1 is a schematic diagram for explaining a method for regenerating a sputtering target. [Figure 3] FIG. 2 is a schematic diagram for explaining the measurement of the substrate density in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, a mode for carrying out the invention (hereinafter referred to as "embodiment") will be described.

[0041] [Sputtering target composition] FIG. 1 is a schematic diagram illustrating an example of a sputtering target that is a target of the target material recycling method of the present invention.

[0042] The sputtering target a shown in FIG. 1 has a target material 1 and a backing plate 2, and the backing plate 2 is joined to the back surface (the lower surface side in FIG. 1) of the target material 1 with a brazing material (jointing material) 3.

[0043] The target material 1 is made of aluminum with a purity of 99.9990 wt %, has a rectangular flat plate shape in plan view, and is 19 mm high. A backing plate is joined to the back surface of the target material 1 via a brazing material 3 .

[0044] The backing plate 2 is made of copper, and the target material 1 is bonded to its surface via a brazing material 3 .

[0045] The brazing material 3 can be any metal or alloy that can bond the target material 1 and the backing plate 2 and has a lower melting point than the target material 1 and the backing plate 2, and can be used without any particular restrictions. In this embodiment, tin-zinc was used. Other examples include indium and indium alloys, tin and tin alloys, which have low melting points.

[0046] [Reuse of sputtering target a] Hereinafter, a method for recycling (reusing) the target material 1 after using the above-mentioned sputtering target a will be described. That is, an example of a method for recycling a target material to which the present invention is applied will be described.

[0047] In one example of a target material recycling method to which the present invention is applied, first, as shown in FIG. 2(a), a used sputtering target a is placed on a heater 4, and the brazing filler material 3 is melted by heating with the heater 4 (in FIG. 2, the "solid brazing filler material" is given the symbol 3, while the "liquid" brazing filler material is given the symbol 3').

[0048] Here, in the present embodiment, an example is described in which the brazing material 3 is melted using the heater 4, but it is sufficient if the brazing material 3 can be melted, and it is not necessarily required to use the heater 4. For example, the brazing material 3 may be melted using a burner (not shown) or the like.

[0049] Next, as shown in FIG. 2(b), the target material 1 is separated (peeled) from the backing plate 2.

[0050] At this time, at least a part of the brazing material remains attached to the rear surface of the target material 1 after separation (the surface that was joined to the backing plate 2 via the brazing material). Therefore, before the brazing material 3' solidifies and becomes solid, the brazing material remaining on the back surface is scraped off with a predetermined tool (for example, a silicone spatula) or the like (the process of scraping off with a jig is not shown).

[0051] Next, as shown in FIG. 2(c), a projectile 5 is collided (driven) into the back surface of the target material 1 as indicated by the symbol X, thereby removing the brazing material 3 (which has become solid at this stage) that could not be removed by scraping it off using a jig.

[0052] Specifically, in this embodiment, shots made of SUS304 stainless steel (Brinell hardness: approximately 150) are used as projectiles.

[0053] Also, the kinetic energy of the projectile is Ek (mJ), and the volume of the projectile is V (mm 3 ), the average cross-sectional area of ​​the projectile is Sa (mm 2 )year, When using TIFF2026001694000004.tif1230, Ek / Sa > 5.5 (Equation 2) Sa < 260 (Equation 3) The projectiles are collided under the condition that

[0054] In this embodiment, stainless steel shot is used, but it is sufficient if the shot is harder than the target material 1 (aluminum). In other words, any material with a Brinell hardness of 20 or more is sufficient (the Brinell hardness of aluminum and aluminum alloys used in the target material 1 is approximately 20), and the shot does not necessarily have to be made of stainless steel.

[0055] Furthermore, in this embodiment, the flying objects 5 are caused to collide under the condition that "Ek / Sa > 5.5 (Equation 2)" is satisfied, but it is sufficient to cause the flying objects 5 to collide under the condition that "Ek / Sa > 2.0 (Equation 1)" is satisfied, and it is not necessarily necessary to cause the flying objects 5 to collide under the condition that "Ek / Sa > 5.5 (Equation 2)" is satisfied. However, in order to sufficiently and efficiently remove the brazing material 3 remaining on the back surface of the target material 1, it is preferable to collide the projectile 5 under the condition that "Ek / Sa > 5.5 (Equation 2)" is satisfied.

[0056] Furthermore, in this embodiment, the flying object 5 is caused to collide under the condition that "Sa < 260... (Equation 3)" is satisfied, but it is not necessary that the flying object 5 is caused to collide under the condition that "Sa < 260... (Equation 3)" is satisfied. However, in order to consume the kinetic energy of the projectile 5 in "destruction of the target material 1" and "destruction of the brazing material 3" and improve the processing efficiency, it is preferable to collide the projectile 5 under the condition that "Sa < 260... (Equation 3)" is satisfied.

[0057] After the projectile 5 is collided with the back surface of the target material 1, flakes (sputter deposits) adhering to the side surface of the target material 1 are removed as needed by rubbing with a spatula, grinding with a grinder, cutting with a saw blade, or the like.

[0058] Thereafter, chemical treatment is carried out as shown in FIG. 2(d). Specifically, as follows, "treatment with sodium hydroxide" is carried out, followed by "treatment with nitric acid."

[0059] In the chemical treatment, first, the target material 1 is immersed in a "sodium borate aqueous solution with added surfactant" at room temperature for 30 minutes or more to degrease it, then washed with water, and then subjected to a liquid treatment with 10 to 15% by weight of sodium hydroxide for 30 minutes or more. In this embodiment, the temperature of the treatment liquid is kept between 20°C and 60°C during the chemical treatment using sodium hydroxide. After the liquid treatment with sodium hydroxide, the substrate is washed with water.

[0060] Here, treatment with sodium hydroxide (base) can dissolve and remove those that dissolve in sodium hydroxide, including "brazing materials," "foreign matter from the environment," and "foreign matter from flying objects." Furthermore, treatment with sodium hydroxide (base) also dissolves the aluminum itself in the target material 1, so that aluminum that has entered the target material 1 or that is insoluble in sodium hydroxide (base) can also be removed as the aluminum itself is dissolved.

[0061] Next, a liquid treatment is carried out for 720 minutes or more with 10 wt % to 15 wt % nitric acid containing 3000 wt ppm or more and 7000 wt ppm or less of aluminum ions. In this embodiment, during the liquid treatment with nitric acid, the temperature of the treatment liquid is maintained at 5°C to 45°C. After the liquid treatment with nitric acid, the substrate is washed with water.

[0062] Here, treatment with nitric acid (acid) can dissolve and remove "brazing materials," "environmental contaminants," "aircraft-derived contaminants," and other substances that dissolve in nitric acid. Furthermore, the residues that adhere due to the above-mentioned "treatment with sodium hydroxide (base)" (residues that cannot be removed by washing with water) can also be neutralized and removed. Furthermore, since treatment with nitric acid (acid) hardly dissolves aluminum, there is no deterioration in yield.

[0063] An example of a method for producing the "treatment liquid comprising nitric acid" used in this embodiment is to add new acid to a used treatment liquid that has come to contain 3000 wtppm or more of aluminum ions as a result of liquid treatment of a target material (aluminum), thereby adjusting the hydrogen ion exponent to a predetermined concentration.

[0064] In addition, as another example of a method for producing the "treatment solution made of nitric acid" used in this embodiment, the surface area of ​​metallic aluminum or metallic aluminum alloy is reduced to Sm (cm 2 ), and the volume is Vm (cm 3 ), adding aluminum or an aluminum alloy that satisfies "Sm / Vm < 3.0" to nitric acid in the range of 15°C to 65°C is one example.

[0065] [effect] In one example of a target material recycling method to which the present invention is applied, shot made of SUS304 stainless steel having a Brinell hardness of approximately 150 is used as projectiles 5, and the projectiles are caused to collide with target material 1 under the condition that "Ek / Sa > 5.5... (Equation 2)" and "Sa < 260... (Equation 3)" are satisfied, thereby making it possible to efficiently and sufficiently remove the brazing material adhering to the back surface of target material 1.

[0066] Furthermore, even if a phenomenon occurs in which foreign matter enters the back surface of the target material 1 (for example, crushed brazing material enters, the projectile 5 enters, foreign matter from the environment enters, etc.) by colliding the target material 1 with the projectile 5, the foreign matter will be removed from the back surface of the target material 1 by subsequent chemical treatment.

[0067] Furthermore, since the "treatment liquid consisting of nitric acid" contains 3000 wtppm or more of aluminum ions, it is possible to suppress the substitution reaction (cementation) of zinc ions that hinders chemical treatment, and to prevent the deposition of zinc on the target material 1 (contamination of the target material 1 by zinc).

[0068] [Example 1] The first embodiment will be described below. In Example 1, for a used sputtering target a, the target material 1 is separated (peeled) from the backing plate 2, and a projectile 5 is made to collide with the back surface of the target material 1 (see FIGS. 2(a), (b), and (c)).

[0069] Specifically, the shot blast furnace was made of SUS304 stainless steel (Brinell hardness: approximately 150, density: 7.93 × 10) with the dimensions shown in Table 1. -6 kg / mm 3 ) is used as a projectile 5 and is made to collide under the conditions of a speed of 50.5 m / sec, a discharge rate of 60.0 kg / min, and a processing time of 2.8 sec. Here, "φ" indicates the diameter of the projectile 5, and "L" indicates the length of the projectile 5.

[0070] [Table 1] JPEG2026001694000005.jpg3694

[0071] In addition, the "volume V (mm)" of the projectile 5 can be calculated from the "diameter φD (mm)" and "length L (mm)" of the projectile 5. 3 ) can be calculated (V=(D / 2) 2 ×π×L). Furthermore, the volume V (mm 3 )" to calculate the "average cross-sectional area Sa (mm 2 ) can be calculated (Sa=V 2 / 3 (It is). In addition, the "kinetic energy Ek (mJ)" of the flying object 5 can be calculated from the "mass m (kg)" and "velocity v (m / sec)" of the flying object 5 (Ek = 1 / 2 × m × v 2 (J)=1 / 2×m×V 2 × 1000 (mJ). Since the projectile 5 is plastically deformed into a flattened sphere upon colliding with the target material 1, it will assume a substantially identical shape (spherical) during use, regardless of its initial shape (cylindrical in this embodiment). Therefore, regardless of the initial shape of the projectile 5, the average cross-sectional area Sa is defined as the 2 / 3 power of the volume V.

[0072] The volume V (mm 3 )” “Average cross-sectional area Sa (mm 2 ) and kinetic energy Ek (mJ) are shown in Table 2. Also, Ek / Sa (mJ / mm 2 ) are also shown in Table 2.

[0073] [Table 2] JPEG2026001694000006.jpg40158

[0074] Next, the target material 1 is degreased and subjected to a liquid treatment with 15 wt % sodium hydroxide for 30 minutes. The temperature of the liquid treatment is kept at 50°C.

[0075] Next, a liquid treatment was carried out with 15% by weight nitric acid for 720 minutes. The temperature of the liquid treatment was maintained at 25°C. Here, aluminum nitrate nonahydrate was added to the nitric acid solution to prepare the treatment liquid. In addition, when aluminum is difficult to dissolve because it forms a passive state, such as when dissolving metallic aluminum in nitric acid, the aluminum may be dissolved in a small amount of another acid and then mixed with a large amount of nitric acid to form a treatment solution.

[0076] In Example 1, the concentration of zinc (Zn), which is likely to remain among the components of the brazing filler metal (tin-zinc) 3, is measured, and the influence of Ek / Sa on the recycling method of the target material 1 is evaluated. Therefore, in Example 1, the "substrate concentration" and "dissolution analysis value" are measured by the method described below, and the "Zn contamination value (=dissolution analysis value - substrate concentration)" is calculated.

[0077] Here, the Zn contamination value is a value that indicates how much the dissolution analysis value of each of samples 1 to 6 has increased from the base concentration.If the brazing material 3 can be completely removed by recycling, then the "base concentration = dissolution analysis value" and the Zn contamination value (dissolution analysis value - base concentration) will be 0.

[0078] The dissolution analysis value also detects zinc (Zn) contained in the base material of the target material. Since the components of the target material vary from one material to another, it is not appropriate to evaluate the success or failure of recycling based on the dissolution analysis value. Therefore, in Example 1, the success or failure of recycling is evaluated based on the Zn contamination value.

[0079] (Measurement of substrate density) As shown in FIG. 3(a), the used sputtering target a is placed on a heater 4, and the brazing material 3 is melted by heating with the heater 4 (as in FIG. 2, the "liquid" brazing material is denoted by the symbol 3').

[0080] Next, as shown in FIG. 3(b), the target material 1 is separated (peeled) from the backing plate 2.

[0081] Next, as shown in Figure 3(c), the target material 1 is cut to completely remove the remaining brazing material adhering to the back surface of the target material 1 (the surface that was joined to the backing plate 2 via the brazing material 3), thereby exposing the aluminum portion.

[0082] The zinc (Zn) concentration of the aluminum portion of the target material 1 thus exposed (portion indicated by symbol A in FIG. 3(c)) is measured by glow discharge mass spectrometry. The zinc concentration obtained by such measurement is referred to as the "base concentration."

[0083] (Dissolution analysis value) For each of Samples 1 to 6, the target material 1 that has undergone the liquid treatment is dissolved, a solid sample is collected, and the zinc (Zn) concentration of the solid sample is measured by glow discharge mass spectrometry. The zinc concentration obtained by such measurement is referred to as the "dissolution analysis value." The crucible used for melting should be one that does not use a zinc-based coating.

[0084] (evaluation) The "Zn contamination values" of Samples 1 to 6 are shown in Table 3. 2 )" are also shown in Table 3. Furthermore, Table 3 also shows the results for the untreated case (a case in which, after the target material 1 was separated (peeled) from the backing plate 2 of a used sputtering target a, only liquid treatment was performed without colliding with the projectile 5).

[0085] [Table 3] JPEG2026001694000007.jpg4491

[0086] As is clear from Table 3, the Zn contamination value of untreated target material 1 was 51.00 wtppm, while the Zn contamination value of all samples 1 to 6 was below 0.15 wtppm. This means that the Zn contamination value is 3 / 1000 or less compared to the untreated case, and it can be seen that contamination by the brazing material component (Zn) has been improved.

[0087] Furthermore, as is clear from Table 3, the Zn contamination values ​​of samples 2 to 6 were below 0.05 wtppm, which was less than 1 / 1000 of the untreated case (less than 1 / 3 of sample 1), indicating that contamination by the brazing material component (Zn) had been significantly improved. That is, it can be seen that when the condition "Ek / Sa>5.5" is satisfied, contamination by the brazing material component (Zn) is significantly improved.

[0088] [Example 2] The second embodiment will be described below. In Example 2, for a used sputtering target a, the target material 1 is separated (peeled) from the backing plate 2, and a projectile 5 is made to collide with the back surface of the target material 1 (see FIGS. 2(a), (b), and (c)).

[0089] Specifically, a SUS304 stainless steel shot (Brinell hardness approximately 150) with a diameter of 1.5 mm and a length of 1.5 mm is used as the projectile 5, and is collided under the conditions of a speed of 50.5 m / sec, a discharge rate of 60.0 kg / min, and a processing time of 2.8 sec.

[0090] Next, the target material 1 is degreased and subjected to a liquid treatment with 15 wt % sodium hydroxide for 30 minutes. The temperature of the liquid treatment is kept at 50°C.

[0091] Next, a liquid treatment was carried out for 720 minutes using 15 wt% nitric acid, which contains copper ions (cementation source) and aluminum ions as shown in Table 4, and the temperature of the liquid treatment was maintained at 25°C.

[0092] [Table 4] JPEG2026001694000008.jpg40114

[0093] In Example 2, the concentration of copper (Cu) deposited on the target material 1 is measured, and the effect of aluminum ion concentration on cementation is evaluated. Therefore, in Example 2, the "substrate concentration" and "dissolution analysis value" are measured by the method described below, and the "Cu contamination value (=dissolution analysis value - substrate concentration)" is calculated.

[0094] Here, the Cu contamination value is a value that indicates how much the dissolution analysis value of each of samples 7 to 12 has increased from the base concentration.If cementation does not occur due to liquid treatment with nitric acid, the ``base concentration = dissolution analysis value'' and the Cu contamination value (dissolution analysis value - base concentration) will be 0.

[0095] The dissolution analysis value also detects copper (Cu) contained in the target material before the liquid treatment with nitric acid. Since the components of target materials vary from one another, it is not appropriate to evaluate the occurrence or severity of cementation based on the dissolution analysis value. Therefore, in Example 2, the occurrence or severity of cementation is evaluated based on the Cu contamination value.

[0096] (Measurement of substrate density) As in Example 1, the target material 1 is separated from the backing plate 2 of the used sputtering target a, and the target material 1 is cut to expose the aluminum portion, and the copper (Cu) concentration is measured by glow discharge mass spectrometry. The copper concentration obtained by such a measurement is referred to as the "base concentration."

[0097] (Dissolution analysis value) For each of Samples 7 to 12, the target material 1 that has been subjected to the liquid treatment is dissolved, a solid sample is collected, and the copper (Cu) concentration of the solid sample is measured by glow discharge mass spectrometry. The copper concentration obtained by such measurement is called the "dissolution analysis value."

[0098] (evaluation) The "Cu contamination values" of Samples 7 to 12 are shown in Table 5. Table 5 also shows the "AL ion content (wtppm)." Furthermore, Table 5 also shows target materials 1 that have not undergone liquid treatment (liquid treatment with sodium hydroxide and liquid treatment with nitric acid) after the projectile 5 has collided with the rear surface thereof.

[0099] [Table 5] JPEG2026001694000009.jpg44110

[0100] From Table 5, it can be seen that all of samples 7 to 12 showed Cu contamination values ​​greater than 0, in other words, the amount of copper precipitated was greater than that of target material 1, which was not subjected to liquid treatment, and that cementation occurred due to liquid treatment with nitric acid.

[0101] Furthermore, as is clear from Table 5, the Cu contamination values ​​of Samples 9 to 12 are below 19.61 wtppm (the Cu contamination value of Samples 7 and 8), indicating that the Cu contamination value has decreased. In other words, it can be seen that when the condition "Al ion content is 3000 wtppm or more" is met, Cu contamination is alleviated and cementation can be suppressed.

[0102] Furthermore, as is clear from Table 5, the Cu contamination value of Sample 12 is approximately the same as that of Sample 11, and it is understood that the rate of decrease in the Cu contamination value has plateaued. In other words, it is clear that in order to prevent cementation, it is sufficient to meet the condition that the AL ion content is 7000 wtppm or less.

[0103] Both Cu ions and Zn ions tend to undergo substitution reactions with aluminum and precipitate (comparing their ionization tendencies, Cu and Zn are more noble than Al). Furthermore, Cu has a more noble ionization tendency than Zn, and Cu tends to precipitate more easily than Zn. Therefore, if cementation can be suppressed by Cu, which precipitates more easily, it can be considered effective in suppressing cementation by Zn as well. [Explanation of symbols]

[0104] 1. Target material 2 Backing Plates 3. Brazing material 4 Heater 5 Projectile

Claims

1. A method for recycling a sputtering target having a target material mainly made of aluminum and a backing plate joined to a back surface of the target material with a joining material, for reusing the target material after the target material has been used for sputtering, comprising: a step of impacting a projectile having a Brinell hardness of 20 or more against a bonding surface of the target material with the backing plate after peeling off the backing plate, The kinetic energy of the flying object is Ek (mJ), and the volume of the flying object is V (mm ３ ), the average cross-sectional area of ​​the projectile is Sa (mm ２ )year, When Ek / Sa > 2.0 (Formula 1) The projectile is collided under the condition that satisfies the following: How to recycle target materials.

2. Ek / Sa > 5.5 (Formula 2) The projectile is collided under the condition that satisfies the following: The method for recycling a target material according to claim 1 .

3. Sa < 260 (Equation 3) The projectile is collided under the condition that satisfies the following: The method for recycling a target material according to claim 1 .

4. After the projectile is collided, the target material is treated with at least one of an acid and a base.

4. The method for recycling a target material according to claim 1, claim 2 or claim 3.

5. The chemical treatment is A treatment solution containing nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, aqua regia, or a mixed acid containing these, or an aqueous solution of these, containing 3000 wtppm or more of aluminum ions is used. The method for recycling a target material according to claim 4.

6. The treatment liquid is This is obtained by adding a specified acid to the used processing solution that has come to contain 3000 wtppm or more of aluminum ions due to the processing of a target material made of aluminum, and adjusting the hydrogen ion exponent to a specified concentration. The method for recycling a target material according to claim 5 .

7. The chemical treatment is Use the treatment solution containing 7000 wtppm or less of aluminum ions. The method for recycling a target material according to claim 5 .

8. The treatment liquid is The aluminum alloy is obtained by adding metallic aluminum or metallic aluminum alloy to nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, aqua regia, or a mixed acid containing any of these, or to an aqueous solution of any of these, at a temperature in the range of 15°C to 65°C, The aluminum or aluminum alloy has a surface area of ​​Sm (cm ２ ), and the volume is Vm (cm ３ ) and Sm / Vm < 3.0 (Formula 4) fulfill The method for recycling a target material according to claim 5 .

9. The acid treatment is carried out at a temperature of 5°C or higher and 45°C or lower. The method for recycling a target material according to claim 4.

10. The chemical treatment with a base is carried out at a temperature of 20°C or higher and 60°C or lower. The method for recycling a target material according to claim 4.

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