Sputtering target and method for producing same

Abstract

Provided are: an integrated sputtering target in which both a target section and a backing plate section contain copper and unavoidable impurities, the sputtering target having a Vickers hardness (Hv) of 90 or more, and a crystal grain flatness ratio of 0.35-0.65 in a cross section orthogonal to the sputtering surface;

Description

[0001] This application is a divisional application of the following application:

[0002] Invention Name: Sputtering target and method for manufacturing the same International Application Date: March 16, 2018 International Application Number: PCT / JP2018 / 010629

[0003] National application number: 201880004416.7 Technical Field

[0004] The present invention relates to a sputtering target and a method for manufacturing the same. Background Art

[0005] In recent years, the miniaturization of the wiring of semiconductor elements has been advancing. As the miniaturization progresses, copper with lower resistance has been used as the material of the wiring instead of aluminum used so far. The formation of such copper wiring is sometimes performed by, for example, forming a diffusion barrier layer containing Ta / TaN or the like on the concave portion of the contact hole or wiring groove, and then performing copper electroplating. Among them, a thin film of copper or copper alloy is usually formed by sputtering as the base layer of the electroplating.

[0006] As a sputtering target of copper or copper alloy which can be used for such sputtering and a method for producing the same, there are those described in Patent Documents 1 to 5, for example.

[0007] However, the above-mentioned sputtering target including copper or copper alloy is usually composed of a target component having a sputtering surface for sputtering and a backing plate having a function of cooling the target material and sputtering electrode during sputtering. In order to manufacture the sputtering target, the backing plate and the target are bonded to each other using an adhesive, and the target is made of a predetermined material different from the backing plate and is separately made from the backing plate by melt casting, etc.

[0008] However, as described above, when a sputtering target is manufactured by bonding a backing plate and a target material that are separately manufactured, the manufacturing man-hours increase due to the separate manufacturing of the backing plate and the target material and bonding them together, and the target member is reduced in thickness by the thickness of the backing plate, resulting in a short life.

[0009] In view of this situation, a one-piece sputtering target in which both the target part and the backing plate part are made of the same copper or copper alloy, a so-called monolithic target, has been proposed, as described in Patent Documents 6 and 7. According to this one-piece sputtering target, the target part and the backing plate part can be made into one piece at the same time, so there is no need to bond them to each other, which can help reduce manufacturing man-hours and reduce the cost of the target user due to the increased use time during sputtering.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Publication No. 2015-61943

[0013] Patent Document 2: U.S. Patent Application No. 2014 / 0158532

[0014] Patent Document 3: Japanese Patent No. 4118814

[0015] Patent Document 4: U.S. Patent Application No. 2005 / 0121320

[0016] Patent Document 5: Japanese Patent No. 5277808

[0017] Patent Document 6: Japanese Patent No. 4976013

[0018] Patent Document 7: U.S. Patent Application No. 2004 / 0072009 Summary of the invention

[0019] Problem that the invention aims to solve

[0020] In an integrated sputtering target in which both the target part and the backing plate part are made of copper or a copper alloy, the backing plate part must be made of the same material and properties as the target part, and the target part has a predetermined material and properties for forming a predetermined thin film by sputtering. Therefore, the hardness of the integrated sputtering target is reduced compared to a split sputtering target in which a high-hardness backing plate of another material can be used.

[0021] Due to this reduction in target hardness, the sputtering target is prone to warping during the sputtering process.

[0022] Currently, Patent Documents 6 and 7 state that "the copper alloy sputtering target according to the present invention can have a Brinell hardness of at least about 40 HB. Depending on the circumstances, the target of the present invention can have a hardness of about 60 HB or more." Sputtering targets with such low hardness may warp during the sputtering process and become difficult to use afterwards.

[0023] In order to solve this problem, the present invention proposes a sputtering target and a method for manufacturing the same, wherein the sputtering target is an integral sputtering target in which the target portion and the backing plate portion both contain the same copper and inevitable impurities, or an integral sputtering target in which the target portion and the backing plate portion both contain predetermined elements and the remaining portion contains copper and inevitable impurities, which can effectively prevent the reduction of target hardness which can cause warping during sputtering.

[0024] Solutions for solving problems

[0025] The inventors have conducted careful research on methods for improving the hardness of a sputtering target in which the target portion and the backing plate portion are integrated, and found that in the manufacturing method to date, the ingot obtained by melt casting is sequentially forged, rolled and heat treated, and then further subjected to predetermined cold plastic processing after the heat treatment, thereby introducing strain and increasing the hardness of the manufactured sputtering target.

[0026] Based on such knowledge, the sputtering target disclosed in the present invention is an integrated sputtering target in which both the target portion and the backing plate portion contain copper and inevitable impurities, the Vickers hardness of the sputtering target is greater than Hv 90, and the flatness of the grains in the cross section perpendicular to the sputtering surface is greater than 0.35 and less than 0.65.

[0027] The manufacturing method of the sputtering target disclosed in the present invention is a method for manufacturing an integrated sputtering target in which both the target part and the backing plate part contain copper and inevitable impurities, and the method includes: melting the raw materials and casting an ingot containing copper and inevitable impurities; and sequentially performing hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging on the ingot, and performing the second cold rolling or second cold forging at a change rate of 20% to 40%.

[0028] In addition, the sputtering target disclosed in the present invention is an integrated sputtering target in which both the target part and the backing plate part contain 0.1 mass % to 8 mass % of at least one element selected from aluminum, manganese, nickel and cobalt, and the rest contains copper and unavoidable impurities, the Vickers hardness Hv of the sputtering target is greater than 90, and the flatness of the grains in the cross section perpendicular to the sputtering surface is greater than 0.35 and less than 0.85.

[0029] In addition, the manufacturing method of the sputtering target disclosed in the present invention is a method for manufacturing an integrated sputtering target in which both the target part and the backing plate part contain 0.1 mass % to 8 mass % of at least one element selected from aluminum, manganese, nickel and cobalt, and the rest contains copper and inevitable impurities. The method includes: the steps of melting the raw materials and casting an ingot containing the elements and containing copper and inevitable impurities; and the steps of sequentially performing hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging on the ingot, and performing the second cold rolling or second cold forging at a change rate of 20% to 60%.

[0030] Effects of the Invention

[0031] According to the above-mentioned sputtering target, the sputtering target is an integral sputtering target in which the target part and the backing plate part both contain the same copper and inevitable impurities, or the target part and the backing plate part both contain predetermined elements and the remaining part contains copper and inevitable impurities, and by making the sputtering target have a predetermined Vickers hardness Hv, the occurrence of warping during the sputtering process can be effectively prevented.

[0032] Furthermore, according to the above-mentioned method for producing a sputtering target, a sputtering target having high hardness can be produced by performing the second cold rolling or the second cold forging after the heat treatment and setting the change rate of the second cold rolling or the second cold forging within a predetermined range. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram showing a method for measuring the average grain size and the flatness of the grains. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below.

[0035] (Sputtering target and manufacturing method according to first embodiment)

[0036] The sputtering target of the present embodiment comprises: a target portion in the shape of a circular plate or the like; and a backing plate portion, which is substantially the same shape as the target portion and is formed integrally with the target portion, and the target portion and the backing plate portion both contain the same copper and inevitable impurities. The Vickers hardness Hv of the sputtering target is greater than 90, and the flatness of the grains in the cross section orthogonal to the sputtering surface is greater than 0.35 and less than 0.65. In addition, in the present embodiment, the sputtering target generally has a plate shape such as a circular plate, but also includes sputtering targets of shapes other than this. Whether it is an integral sputtering target can be determined by confirming whether the blanks on the surface and the reverse side of the sputtering target are the same. Since it is a sputtering target containing copper, it can be confirmed by measuring the electrical conductivity.

[0037] (composition)

[0038] The target part and the backing plate part of the sputtering target of this embodiment both contain copper as a main component, and may contain elements other than copper at least within the range that the Vickers hardness Hv described in detail later is maintained at or above 90. The copper content of the target part and the backing plate part is preferably 99.99 mass % or more, and more preferably 99.9999 mass % or more. If the copper content is too low, there is a concern that major defects may occur when used in semiconductor products.

[0039] The target part and the backing plate part may both contain only copper, but as the above-mentioned impurities, for example, a total of 0.01 mass % or less, preferably 0.005 mass % or less of one or more elements selected from the group consisting of Fe, Cr, Ni, Si, Ag, S and P may be contained. When the total content of the above-mentioned elements exceeds 0.01 mass %, serious defects may occur when used in semiconductor products.

[0040] However, the present invention is not limited to the elements listed here, and other elements may be contained as long as a Vickers hardness Hv of 90 or more can be ensured.

[0041] (Vickers hardness)

[0042] The Vickers hardness Hv of the sputtering target of this embodiment is 90 or more. Thus, even if it is a sputtering target having a backing plate portion mainly containing copper like the target portion, and even if it is such a sputtering target, for example, such a sputtering target having a diameter exceeding 400 mm, the occurrence of warping during the sputtering process can be suppressed. As a result, effective sputtering can be performed until the second half of the life of the sputtering target. From this perspective, the Vickers hardness Hv of the sputtering target is 90 or more, and particularly preferably 97 or more.

[0043] On the other hand, if the hardness is too high, there is a concern that recrystallization may occur due to the heat generated by sputtering during the sputtering process, and softening may occur. Therefore, the Vickers hardness Hv may be, for example, 125 or less, preferably 118 or less.

[0044] The Vickers hardness Hv is measured in accordance with JIS Z2244 (2009). In a sputtering target in which the target portion and the backing plate portion are integrated, the Vickers hardness Hv of the target portion and the backing plate portion are substantially the same.

[0045] Such a Vickers hardness Hv can be obtained by, for example, manufacturing according to a manufacturing method described later.

[0046] (Average grain size)

[0047] In the sputtering target of the present embodiment, the average crystal grain size is preferably 10 μm or more and 60 μm or less. When the average crystal grain size is less than 10 μm, there is a possibility that the erosion rate during sputtering decreases. In addition, when the average crystal grain size exceeds 60 μm, there is an undesirable situation that the uniformity of the film during sputtering deteriorates. Therefore, the average crystal grain size is more preferably 20 μm or more and 50 μm or less, and further preferably 25 μm or more and 45 μm or less.

[0048] The average crystal grain size is measured by observation using an optical microscope. Figure 1 As shown, for the sputtering surface, two straight lines are drawn in the longitudinal and transverse directions, for a total of four straight lines (refer to Figure 1 The average grain size in the target thickness direction and the average grain size in the direction perpendicular to the target thickness direction are measured using the number of grain boundaries intersecting the straight line. The average of the average grain sizes in the above directions is taken as the average crystal grain size.

[0049] (Grain flatness)

[0050] The flatness of the crystal grains present in the cross section along the plane perpendicular to the sputtering surface of the sputtering target of the present embodiment is 0.35 or more and 0.65 or less.

[0051] The flattening ratio is determined as follows: draw four arbitrary straight lines, two each in the target thickness direction and in the direction perpendicular to the target thickness direction, of the crystal grain observed on the cross section using an optical microscope (see Figure 1 The average grain size in the target thickness direction and the average grain size at right angles to the target thickness direction are measured, and then the flatness is calculated by taking the average grain size in the target thickness direction as the short side and the average grain size at right angles to the target thickness direction as the long side using the flatness = (1 - short side / long side).

[0052] When the flatness is less than 0.35, insufficient strength may be caused due to insufficient processing deformation of the recrystallized structure. On the other hand, when the flatness exceeds 0.65, there is a possibility that the erosion rate decreases due to the excessively fine grain size in the thickness direction. In addition, when the flatness in pure copper exceeds 0.65, the recrystallization temperature decreases due to processing deformation, so there is a concern that softening due to sputtering heat may occur during the sputtering process.

[0053] Therefore, in the sputtering target of the present embodiment, the flatness of the crystal grains present in the cross section of the plane perpendicular to the sputtering surface is 0.35 to 0.65, preferably 0.40 to 0.60, and more preferably 0.45 to 0.55.

[0054] Such a flattening ratio of the crystal grain in the cross section can be obtained by, for example, manufacturing according to the manufacturing method described later.

[0055] (Manufacturing method)

[0056] The sputtering target of the present embodiment can be produced, for example, as follows.

[0057] First, high-purity copper with a purity of 4N or 6N is melted at 1080°C to 1280°C for 0.5 to 6 hours, and cooled and solidified in a predetermined mold, thereby casting an ingot containing copper and inevitable impurities to serve as a blank for a sputtering target with a target portion and a backing plate portion as one piece.

[0058] Next, the ingot is subjected to hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging.

[0059] Among them, hot forging is preferably performed at a temperature of 300° C. to 900° C. This is because: if the temperature during forging is lower than 300° C., there is a risk of cracks occurring in the ingot during forging, and on the other hand, if the temperature during forging exceeds 900° C., in addition to the risk of abnormal softening of copper, abnormal grain growth may occur during forging due to the high temperature.

[0060] In addition, here, from the perspective of fully destroying the casting structure, the rate of change of the first cold rolling or the first cold forging is preferably 70% or more. In addition, the rate of change R (%) refers to the ratio of the dimensional change in the thickness direction expressed by the formula R = (T1-T2) / T1×100, when the thickness of the target blank before rolling or forging is T1 and the thickness of the target blank after rolling or forging is T2. Especially in the case of rolling, the above-mentioned rate of change is equivalent to the so-called rolling rate, which is also calculated by the same formula. The same is true for the rate of change of the second cold rolling or the second cold forging described later. The measurement of the thickness of the target blank when calculating the rate of change is carried out as follows: on the basis of confirming that the surface of the target blank such as a disc has become a sufficiently flat surface using a flat rod as a reference, the thickness of four parts is measured circumferentially at a position on the central side of 50 mm from the periphery of the target blank.

[0061] The temperature of the first cold rolling or the first cold forging is set to about 10°C to 100°C, for example.

[0062] Preferably, the heat treatment after the first cold rolling or the first cold forging is performed at a temperature of 200°C to 500°C for 0.5 to 3 hours. This is because: at a low temperature below 200°C, recrystallization cannot be fully promoted, and strain will remain locally. On the other hand, at a high temperature exceeding 500°C, the grains will become abnormally coarse. In addition, when the heat treatment time is short, recrystallization cannot be fully promoted, and there is a concern that strain will remain locally. When the heat treatment time is long, the grains may become abnormally coarse.

[0063] Then, after the heat treatment, a second cold rolling or a second cold forging is further performed. The change rate of the second cold rolling or the second cold forging is set to 20% to 40%. As a result, strain can be introduced into the target blank, effectively improving the hardness of the manufactured sputtering target. In addition, by performing the second cold rolling or the second cold forging, the grains are squeezed in the thickness direction, as a result, the flatness of the grains in the above-mentioned cross section of the sputtering target becomes greater than 0.35 and less than 0.65.

[0064] When the change rate of the second cold rolling or the second cold forging is less than 20%, the hardness of the sputtering target cannot be sufficiently increased, and the possibility of warping during sputtering cannot be eliminated. On the other hand, when the change rate of the second cold rolling or the second cold forging is greater than 40%, the drop in recrystallization temperature due to the introduction of strain becomes significant, and the sputtering target softens due to the heat during sputtering, and there is also a concern that the sputtering target may warp in this case.

[0065] From this viewpoint, the change rate of the second cold rolling or the second cold forging is set to 20% to 40%, and particularly preferably to 25% to 35%.

[0066] The temperature of the second cold rolling or the second cold forging is set to about 10°C to 100°C, for example.

[0067] In the second cold rolling or the second cold forging, in order to prevent relaxation of the introduced strain due to working heat of rolling or forging, water cooling is preferably performed in each process of rolling or forging or in each rolling or forging.

[0068] Thereafter, finishing such as cutting is performed as necessary, whereby a sputtering target can be manufactured.

[0069] (Sputtering target and manufacturing method of the second embodiment)

[0070] The sputtering target of the present embodiment comprises: a target portion in the shape of a circular plate or the like; and a backing plate portion, which is substantially the same shape as the target portion and is formed integrally with the target portion, and the sputtering target is an integral sputtering target in which the target portion and the backing plate portion both contain the same copper alloy, the Vickers hardness Hv of the sputtering target is above 90, and the flatness of the grains in the cross section orthogonal to the sputtering surface is above 0.35 and below 0.85. In addition, in the present embodiment, the sputtering target generally has a plate shape such as a circular plate, but also includes sputtering targets of shapes other than this. Whether it is an integral sputtering target can be determined by confirming whether the blanks on the surface and the reverse side of the sputtering target are the same. Since it is a sputtering target containing copper, it can be confirmed by measuring the electrical conductivity.

[0071] (composition)

[0072] The target part and the backing plate part of the sputtering target of the present embodiment both contain copper as a main component, and contain 0.1 mass % to 8 mass % of at least one element selected from aluminum, manganese, nickel and cobalt as a subcomponent, and may contain elements other than the above at least within a range where the Vickers hardness Hv described in detail later is maintained at or above 90. The target part and the backing plate part both contain a copper alloy of the same composition.

[0073] The content of the secondary components of the copper alloy constituting the target part and the backing plate part is 0.1 mass % to 8 mass % in total when the secondary components are multiple elements. If the content of the secondary components is too much, the conductivity is greatly reduced and it is difficult to use as a wiring material. On the other hand, if the content of the secondary components is too little, it is worried that it will be difficult to make a target with uniformly dispersed alloy components. From this point of view, the content of the secondary components is set to 0.1 mass % to 8 mass %, preferably 0.1 mass % to 6 mass %, and more preferably 0.2 mass % to 6 mass %. The content of the secondary components is 0.1 mass % or more, preferably 0.2 mass % or more as the lower limit, and 8 mass % or less, preferably 6 mass % or less, more preferably 5 mass % or less as the upper limit, and particularly preferably 4 mass % or less as the upper limit. As a sputtering target with two or more copper alloys as secondary components, there are sputtering targets containing manganese and aluminum, etc.

[0074] The target portion and the backing plate portion may further contain, as impurities, for example, a total of 0.01 mass % or less, preferably 0.005 mass % or less of one or more elements selected from the group consisting of Fe, Cr, Si, Ag, S and P. When the total content of the above elements exceeds 0.01 mass %, serious defects may occur when used in semiconductor products.

[0075] However, the present invention is not limited to the elements listed here, and other elements may be contained as long as a Vickers hardness Hv of 90 or more can be ensured.

[0076] (Vickers hardness)

[0077] The Vickers hardness Hv of the sputtering target of this embodiment is 90 or more. Thus, even if it is a sputtering target having a backing plate portion containing the same copper alloy as the target portion, and such a sputtering target, even if it is such a sputtering target with a diameter exceeding 400 mm, the occurrence of warping during the sputtering process can be suppressed. As a result, effective sputtering can be performed until the second half of the life of the sputtering target. From this perspective, the Vickers hardness Hv of the sputtering target is 90 or more, and particularly preferably 97 or more.

[0078] Furthermore, if warping occurs in the sputtering target, the uniformity of the formed thin film decreases and causes problems such as plasma shedding. However, in the present embodiment, since the target has the above-mentioned Vickers hardness Hv, such problems do not occur.

[0079] The Vickers hardness Hv is measured in accordance with JIS Z2244 (2009). In a sputtering target in which the target portion and the backing plate portion are integrated, the Vickers hardness Hv of the target portion and the backing plate portion are substantially the same.

[0080] Such a Vickers hardness Hv can be obtained by, for example, manufacturing according to a manufacturing method described later.

[0081] (Average grain size)

[0082] In the sputtering target of the present embodiment, the average crystal grain size is preferably 5 μm or more and 50 μm or less. When the average crystal grain size is less than 5 μm, there is a possibility that the erosion rate during sputtering decreases, and when the average crystal grain size exceeds 50 μm, there is an undesirable situation that the uniformity of the film during sputtering deteriorates. Therefore, the average crystal grain size is more preferably 20 μm or more and 50 μm or less, and further preferably 25 μm or more and 45 μm or less.

[0083] The average crystal grain size is measured by observation using an optical microscope. Figure 1 As shown, for the sputtering surface, two straight lines are drawn in the longitudinal and transverse directions, for a total of four straight lines (refer to Figure 1The average grain size in the target thickness direction and the average grain size in the direction perpendicular to the target thickness direction are measured using the number of grain boundaries intersecting the straight line, and the average of the average grain sizes in the above directions is taken as the average crystal grain size.

[0084] (Grain flatness)

[0085] The flatness of the crystal grains present in the cross section along the plane perpendicular to the sputtering surface of the sputtering target of the present embodiment is 0.35 or more and 0.85 or less.

[0086] The flattening ratio is obtained by drawing four arbitrary straight lines, two each in the target thickness direction and in the direction perpendicular to the target thickness direction, of the crystal grain observed on the cross section using an optical microscope (see Figure 1 The average grain size in the target thickness direction and the average grain size at right angles to the target thickness direction are measured, and then the flatness is calculated by taking the average grain size in the target thickness direction as the short side and the average grain size at right angles to the target thickness direction as the long side using the flatness = (1 - short side / long side).

[0087] When the above-mentioned flatness is less than 0.35, insufficient strength will be caused due to insufficient processing deformation of the recrystallized structure; on the other hand, when the above-mentioned flatness exceeds 0.85, during sputtering, the voltage will become too high due to the large internal stress of the sputtering target, which may shorten the life of the sputtering target.

[0088] Therefore, in the sputtering target of the present embodiment, the flatness of the crystal grains existing in the cross section along the plane perpendicular to the sputtering surface is 0.35 to 0.85, preferably 0.40 to 0.60, and more preferably 0.45 to 0.55.

[0089] Such a cross-sectional grain flatness can be obtained by, for example, manufacturing according to a manufacturing method described later.

[0090] (Manufacturing method)

[0091] The sputtering target of the present embodiment can be produced, for example, as follows.

[0092] First, at least one element selected from aluminum, manganese, nickel and cobalt is added to high-purity copper with a purity of 4N or 6N to achieve the above-mentioned predetermined composition, and is melted at 1080°C to 1280°C for 0.5 hour to 6 hours, and then cooled and solidified in a predetermined mold, thereby casting an ingot containing the above-mentioned elements, copper and inevitable impurities to serve as a blank for a sputtering target with a target portion and a backing plate portion as an integral part.

[0093] Next, the ingot is subjected to hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging.

[0094] Among them, hot forging is preferably performed at a temperature of 300° C. to 900° C. This is because: if the temperature during forging is lower than 300° C., there is a risk of cracks occurring in the ingot during forging, and on the other hand, if the temperature during forging exceeds 900° C., in addition to the risk of abnormal softening of copper, abnormal grain growth may occur during forging due to the high temperature.

[0095] In addition, here, from the perspective of fully destroying the casting structure, the rate of change of the first cold rolling or the first cold forging is preferably set to 70% or more. In addition, the rate of change R (%) refers to the ratio of the dimensional change in the thickness direction expressed by the formula R = (T1-T2) / T1 × 100 when the thickness of the target blank before rolling or forging is T1 and the thickness of the target blank after rolling or forging is T2. In particular, in the case of rolling, the above-mentioned rate of change is equivalent to the so-called rolling rate, which is also calculated by the same formula. The same is true for the rate of change of the second cold rolling or the second cold forging described later. The measurement of the thickness of the target blank when calculating the rate of change is carried out as follows: on the basis of confirming that the surface of the target blank such as a disk has become a sufficient plane using a flat rod as a reference, the thickness of four parts is measured circumferentially at a position on the central side of 50 mm from the periphery of the target blank.

[0096] The temperature of the first cold rolling or the first cold forging is set to about 10°C to 100°C, for example.

[0097] Preferably, the heat treatment after the first cold rolling or the first cold forging is performed at a temperature of 200°C to 500°C for 0.5 to 3 hours. This is because: at a low temperature below 200°C, recrystallization cannot be fully promoted, and strain will remain locally. On the other hand, at a high temperature exceeding 500°C, the grains will become abnormally coarse. In addition, when the heat treatment time is short, recrystallization cannot be fully promoted, and there is a concern that strain will remain locally. When the heat treatment time is long, the grains may become abnormally coarse.

[0098] Then, after the heat treatment, a second cold rolling or a second cold forging is further performed. The rate of change of the second cold rolling or the second cold forging is set to 20% to 60%. As a result, strain can be introduced into the target blank, effectively improving the hardness of the manufactured sputtering target. In addition, by performing the second cold rolling or the second cold forging, the grains are squeezed in the thickness direction, as a result, the flatness of the grains in the above-mentioned cross section of the sputtering target becomes greater than 0.35 and less than 0.85. Moreover, by controlling the amount of strain introduced into the target blank in the second cold rolling or the second cold forging, the increase in the sputtering voltage caused by the internal stress during sputtering can be suppressed, thereby extending the service life of the sputtering target.

[0099] When the change rate of the second cold rolling or the second cold forging is less than 20%, the hardness of the sputtering target cannot be sufficiently increased, and the possibility of warping during sputtering cannot be fully eliminated. On the other hand, when the change rate of the second cold rolling or the second cold forging is greater than 60%, the voltage becomes too high during sputtering due to the large internal stress of the sputtering target, thereby shortening the life of the sputtering target.

[0100] From this viewpoint, the change rate of the second cold rolling or the second cold forging is set to 20% to 40%, particularly preferably 25% to 35%.

[0101] The temperature of the second cold rolling or the second cold forging is set to about 10°C to 100°C, for example.

[0102] In the second cold rolling or the second cold forging, in order to prevent relaxation of strain introduced by working heat of rolling or forging, water cooling is preferably performed in each process of rolling or forging or in each rolling or forging.

[0103] Thereafter, finishing such as cutting is performed as necessary, whereby a sputtering target can be manufactured.

[0104] (Example)

[0105] Next, a sputtering target was produced by trial and its effect was confirmed, so it will be described. However, the description here is only exemplary, and the present invention is not limited to this.

[0106] (Test Example 1)

[0107] High-purity copper with a purity of 6N was melted in a crucible at a temperature of 1100°C for 1 hour, and then the molten metal was poured into a mold to produce an ingot with a diameter of 220 mm and a thickness of 210 mm. Next, the ingot was hot forged at a temperature of 500°C to form a size of 160 mm in diameter and 250 mm in thickness, and then the first cold forging or the first cold rolling was performed to obtain a target blank with a diameter of 470 mm and a thickness of 45 mm. The target blank was heat treated at 300°C for 1 hour, then cooled, and then subjected to a second cold rolling or a second cold forging based on the change rate shown in Table 1, and then cut to produce a sputtering target in which the target portion and the backing plate portion are integrated.

[0108] As shown in Table 1, Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2 were manufactured under the same conditions except that the change rate of the second cold rolling or the second cold forging after the heat treatment was different.

[0109] For each of Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2, the Vickers hardness of the test samples of the prepared sputtering targets, the Vickers hardness after the test samples were further heated at 140° C. for 1 hour, the average crystal grain size, and the flatness of the cross-sectional grains were determined.

[0110] In addition, sputtering targets of Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2 were used to perform sputtering up to 2500 kWhr according to the recommended recipe, and target warpage was measured at the end of sputtering. Target warpage was determined by measuring the back surface of the target using a three-dimensional measuring instrument.

[0111] The results are also shown in Table 1.

[0112] (Table 1)

[0113]

[0114] The results shown in Table 1 show that the measured values ​​of Vickers hardness of Examples 1-1 to 1-3, which were subjected to second cold rolling or second cold forging within a range of 20% to 40% after heat treatment, were large, and as a result, the occurrence of warpage during sputtering was effectively suppressed.

[0115] On the other hand, in Comparative Example 1-1 in which the change rate of the second cold rolling or the second cold forging was less than 20%, the measured value of the Vickers hardness became small, thereby causing a large warp to occur during the sputtering process.

[0116] Although the measured value of the Vickers hardness of Comparative Example 1-2, in which the change rate of the second cold rolling or the second cold forging was greater than 40%, increased, a large warp occurred during the sputtering process. Considering that the Vickers hardness of Comparative Example 1-2 decreased after heating, the recrystallization temperature of Comparative Example 1-2 decreased when the strain was introduced, and when a large strain with a change rate of about 50% was applied at this time, softening due to the heat during sputtering occurred, resulting in a large warp.

[0117] (Test Example 2)

[0118] High-purity copper with a purity of 6N and aluminum or manganese are added to a crucible in a manner to achieve a specified composition, melted at a temperature of 1100°C in the crucible for 1 hour, and then the molten metal is poured into a mold to produce an ingot with a diameter of 220 mm and a thickness of 210 mm. Next, the ingot is hot forged at a temperature of 500°C to form a size of 160 mm in diameter and 250 mm in thickness, and then the first cold forging or the first cold rolling is performed to obtain a target blank with a diameter of 470 mm and a thickness of 45 mm. The target blank is heat treated at 300°C for 1 hour, then cooled, and then subjected to a second cold rolling or a second cold forging based on the rate of change shown in Table 2. It is then subjected to cutting processing to produce a sputtering target in which the target portion and the backing plate portion are integrated.

[0119] As shown in Table 2, Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-6 were manufactured under the same conditions except that the change rate of the second cold rolling or the second cold forging after the heat treatment was different.

[0120] Regarding each of Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-6, the Vickers hardness, the average crystal grain size, and the flatness of the cross-sectional crystal grains of the produced sputtering targets were determined.

[0121] Furthermore, using the sputtering targets of Examples 2-1 to 2-9 and Comparative Examples 2-1 to 2-6, sputtering was performed up to 3200 kWhr according to the recommended recipe, and the target life and target warpage at the end of sputtering were measured.

[0122] The target life is calculated as the power consumption during sputtering (power x time). The more power consumption, the longer the sputtering can be performed at high power, which means the longer the life of the sputtering target. In addition, the warping of the target is calculated by measuring the back surface of the target using a three-dimensional measuring instrument.

[0123] These results are also shown in Table 2. In addition, since the target life depends largely on the sputtering conditions, Table 2 also shows the index normalized with respect to Example 2-1.

[0124] (Table 2)

[0125]

[0126]

[0127] The results shown in Table 2 show that the measured values ​​of Vickers hardness of Examples 2-1 to 2-9, which were subjected to second cold rolling or second cold forging within a range of 20% to 60% after heat treatment, were large, and as a result, the occurrence of warpage during sputtering was effectively suppressed.

[0128] On the other hand, in Comparative Examples 2-1, 2-3, and 2-5, in which the change rate of the second cold rolling or the second cold forging was less than 20%, the measured values ​​of the Vickers hardness became small, and thus large warping occurred during the sputtering process.

[0129] In Comparative Examples 2-2, 2-4, and 2-6, where the change rate of the second cold rolling or second cold forging was greater than 60%, the measured values ​​of Vickers hardness increased, but the flatness of the cross-sectional crystal grains also increased. As a result, the voltage during sputtering increased due to the increase in internal stress, and as a result, the device reached its limit in the second half of its life.

[0130] It can be seen from the above embodiments that the sputtering target of the present invention is an integrated sputtering target that can be manufactured at low cost, and can improve the target hardness and effectively suppress warping during the sputtering process.

Claims

1. A sputtering target, which is an integrated sputtering target in which both a target portion and a backing plate portion contain copper and inevitable impurities, wherein: The sputtering target has a Vickers hardness Hv of 90 or more, and an oblateness of a crystal grain in a cross section perpendicular to a sputtering surface of 0.35 or more and 0.65 or less.

2. The sputtering target according to claim 1, wherein The average crystal grain size of the sputtering target is 10 μm or more and 60 μm or less.

3. A method for manufacturing a sputtering target, wherein: The sputtering target is an integrated sputtering target in which both the target portion and the backing plate portion contain copper and inevitable impurities. The method comprises: a step of melting the raw materials and casting an ingot containing copper and inevitable impurities; and The ingot is sequentially subjected to the steps of hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging, The second cold rolling or the second cold forging is performed at a change rate of 20% to 40%.

4. The method for producing a sputtering target according to claim 3, wherein: The heat treatment is performed at a temperature of 200° C. to 500° C. for 0.5 to 3 hours.

5. The method for producing a sputtering target according to claim 3 or 4, wherein: The first cold rolling or the first cold forging is performed at a change rate of 70% or more.

6. The method for producing a sputtering target according to claim 3 or 4, wherein: The hot forging is performed at a temperature of 300°C to 900°C.

7. A sputtering target, wherein: The sputtering target is an integrated sputtering target in which the target part and the backing plate part each contain 0.1 mass % to 8 mass % of at least one element selected from aluminum, manganese, nickel and cobalt, and the remainder contains copper and inevitable impurities. The sputtering target has a Vickers hardness Hv of 90 or more, and an oblateness of crystal grains in a cross section perpendicular to a sputtering surface of 0.35 or more and 0.85 or less.

8. The sputtering target according to claim 7, wherein: The average crystal grain size of the sputtering target is 5 μm or more and 50 μm or less.

9. A method for manufacturing a sputtering target, wherein: The sputtering target is an integrated sputtering target in which the target part and the backing plate part each contain 0.1 mass % to 8 mass % of at least one element selected from aluminum, manganese, nickel and cobalt, and the remainder contains copper and unavoidable impurities. The method comprises: The step of melting the raw materials and casting an ingot containing the elements and copper and inevitable impurities; and The ingot is sequentially subjected to the steps of hot forging, first cold rolling or first cold forging, heat treatment, and second cold rolling or second cold forging, The second cold rolling or the second cold forging is performed at a change rate of 20% to 60%.

10. The method for producing a sputtering target according to claim 9, wherein: The heat treatment is performed at a temperature of 200° C. to 500° C. for 0.5 to 3 hours.

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