JP7738689B2 - Sputtering Target - Google Patents

Description

The present invention relates to a sputtering target.

A conventional method for joining sputtering targets is described in Japanese Patent Laid-Open Publication No. 6-114549 (Patent Document 1). In this sputtering target joining method, a molten brazing filler metal coating is formed on each of the target material and backing plate, and the target material and backing plate are then moved relative to each other while being rubbed together until they are overlapped. This removes any oxides that have formed on the coating surface, and the brazing filler metal coating is united without any oxides or air bubbles becoming trapped. The brazing filler metal is then cooled and solidified to complete the brazing process.

Japanese Patent Application Publication No. 6-114549

However, it has been discovered that the conventional sputtering target bonding method described above does not adequately bond the target material to the backing plate, potentially resulting in peeling of the target material during sputtering. After extensive research, the inventors noticed that with conventional methods, the ratio (bonding rate) of the actual bonded area (bonding area) to the area where the target material and backing plate should be bonded (bonding area) is small, and that the area of the largest area (maximum defect area) of the areas between the target material and backing plate where no bonding material is present (unbonded areas) is large. They discovered a relationship between the bonding rate, maximum defect area, and peeling of the target material.

The objective of the present invention is to provide a sputtering target that can realize a sputtering target in which the target material is less likely to peel off during sputtering.

In order to solve the above problem, one embodiment of the sputtering target comprises:
A backing plate;
a target material bonded to a bonding region of the backing plate (a region of the backing plate where the target material is to be bonded) via a bonding material,
a bonding area of a bonding portion (bonded portion) between the target material and the backing plate is 97% or more of an area of the bonding region;
The maximum defect area of the unbonded portion between the target material and the backing plate is 0.6% or less of the area of the bonded region.

According to the above embodiment, it is possible to improve the bonding rate, reduce the maximum defect area, and produce a sputtering target in which the target material is less likely to peel off.

In one embodiment of the sputtering target, the length of the target material is 1000 mm or more and 4000 mm or less.

According to the above embodiment, it is possible to manufacture sputtering targets in which the target material is less likely to peel off, even when the target is long.

Also, one embodiment of a method for joining a target material and a backing plate includes:
A method for bonding a target material and a backing plate with a bonding material, comprising:
applying a bonding material to a region (bonding region) on a main surface of the backing plate where the target material is to be bonded;
a step of sliding and moving the target material in the first direction along the main surface of the backing plate so that an edge (first edge) of the target material moves from a first edge side of the bonding region of the backing plate to a position beyond a second edge of the bonding region of the backing plate that faces the first edge in a first direction;
and sliding the target material along the major surface of the backing plate in a second direction opposite to the first direction to align the target material with the bonding area of the backing plate.
Hereinafter, moving the target material by sliding it in a first direction will also be referred to as "slide," and moving the target material by sliding it in a second direction will also be referred to as "reverse."

In the above embodiment, the target material is slid relative to the backing plate in a first direction and then reversed in a second direction, aligning the target material with the bonding area of the backing plate. This improves the bonding rate when bonding the target material to the backing plate, and also reduces the size of the maximum defect area, which is the largest area among unbonded areas. This makes it possible to manufacture a sputtering target in which the target material is less likely to peel off.

In addition, in one embodiment of the method for joining the target material and the backing plate,
The target material and the backing plate are formed to be elongated,
The edge of the target material is formed along the longitudinal direction of the target material,
the first end edge and the second end edge of the bonding region of the backing plate are formed along a longitudinal direction of the backing plate and are opposed to each other in a lateral direction of the backing plate,
The target material is moved relative to the backing plate by sliding it in the lateral direction of the backing plate.

According to the above embodiment, for long target materials and backing plates, the distance the target material needs to move relative to the backing plate can be reduced, shortening the working time.

In addition, in one embodiment of the method for joining the target material and the backing plate,
a step of arranging a plurality of wires on the main surface of the backing plate before the step of applying the bonding material;
When the target material is moved in the first direction and the second direction, the target material is moved by sliding it on the wire.

In the above embodiment, the target material slides on the wire, allowing the target material to be easily moved while maintaining the surface of the target material to be joined (joining surface) and the surface of the backing plate to be joined (joining surface) approximately parallel, thereby improving the joining rate. Furthermore, because the wire functions as a spacer, the thickness of the joining layer formed by the joining material between the target material and the backing plate can be made constant.

Furthermore, in one embodiment of the method for joining a target material and a backing plate, the diameter of the wire is 0.05 mm or more and 0.5 mm or less.

According to the above embodiment, wire breakage can be prevented and unevenness in the thickness of the bonding layer formed by the bonding material can be prevented.

Furthermore, one embodiment of the method for joining a target material and a backing plate includes a step of replenishing the first edge side of the joining area of the backing plate with joining material between the step of moving the target material in the first direction and the step of moving the target material in the second direction.

In the above embodiment, bonding material is replenished on the first edge side of the bonding area of the backing plate, which makes it possible to replenish bonding material on the first edge side of the bonding area, where bonding material is likely to run short, thereby further improving the bonding rate and further reducing the maximum defect area.

Furthermore, in one embodiment of the method for joining a target material and a backing plate, when the edge (first edge) of the target material is moved to a position beyond the second edge of the joining area of the backing plate in the step of moving the target material in the first direction, the distance in the first direction from the second edge of the joining area of the backing plate to the edge (first edge) of the target material is A, and the width of the joining area in the first direction is W, where A is the distance in the first direction from the second edge of the joining area of the backing plate to the edge (first edge) of the target material, and W is the width of the joining area in the first direction, the relationship is 0.03≦A/W<1.0.

According to the above embodiment, the moving distance of the target material relative to the backing plate can be reduced, while improving the joining rate and reducing the maximum defect area.

Furthermore, in one embodiment of the method for joining a target material and a backing plate, when the edge (first edge) of the target material is positioned on the first edge side of the joining region of the backing plate in the step of moving the target material in the first direction, the distance in the first direction from the first edge of the joining region of the backing plate to the edge (first edge) of the target material is B, and the width of the joining region in the first direction is W, then 0≦B/W<2.0.

According to the above embodiment, the moving distance of the target material relative to the backing plate can be reduced, and the target material can be placed on the backing plate and then slid, thereby improving the joining rate and reducing the size of the maximum defect area.

In one embodiment of the sputtering target manufacturing method, the target material and the backing plate are joined using the joining method to manufacture a sputtering target.

According to the above embodiment, the bonding rate can be improved when bonding the target material to the backing plate, and the size of the maximum defect area, which is the largest area among unbonded areas, can be reduced. Therefore, it is possible to manufacture a sputtering target in which the target material is less likely to peel off.

The sputtering target of the present invention makes it possible to produce a sputtering target in which the target material is less likely to peel off.

1A and 1B are explanatory views showing an embodiment of a method for joining a target material and a backing plate according to the present invention. 1A and 1B are explanatory views showing an embodiment of a method for joining a target material and a backing plate according to the present invention. 1A and 1B are explanatory views showing an embodiment of a method for joining a target material and a backing plate according to the present invention. 1A and 1B are explanatory views showing an embodiment of a method for joining a target material and a backing plate according to the present invention. 1A and 1B are explanatory views showing an embodiment of a method for joining a target material and a backing plate according to the present invention. FIG. 10 is a simplified cross-sectional view showing a state in which no bonding material is present in the bonding layer present between the target material and the backing plate. FIG. 10 is a simplified cross-sectional view showing a state in which no bonding material is present in the bonding layer present between the target material and the backing plate. FIG. 2 is a simplified diagram showing the state of a bonding material between a target material and a backing plate of the sputtering target of the present invention. FIG. 10 is a simplified diagram showing the state of a bonding material between a target material and a backing plate of a sputtering target of a comparative example.

The present invention will now be described in detail with reference to the illustrated embodiments.

(Embodiment)
1A to 1E are explanatory diagrams showing one embodiment of a method for bonding a target material and a backing plate (hereinafter referred to as the "bonding method") of the present invention. As shown in Fig. 1A to 1E, this method bonds a target material 2 and a backing plate 3 with a bonding material 4.

As shown in FIG. 1A, a target material 2 and a backing plate 3 are prepared. The target material 2 is formed in the shape of a long plate. The length of the long side of the target material 2 is, for example, 1,000 mm to 4,000 mm, preferably 1,500 mm to 3,500 mm, more preferably 2,000 mm to 3,200 mm, and even more preferably 2,200 mm to 3,000 mm. The length of the short side of the target material 2 is, for example, 100 mm to 2,000 mm, preferably 120 mm to 1,000 mm, more preferably 130 mm to 500 mm, and even more preferably 150 mm to 300 mm. The lengths of the long side and short side may be the same or different. The thickness of the target material 2 is, for example, 5 mm to 40 mm, preferably 10 mm to 30 mm, and even more preferably 12 mm to 25 mm. With this invention, it is possible to improve the bonding rate and reduce the maximum defect area, even when using target materials for large flat panel displays.

The aspect ratio of the length of the long side to the length of the short side of the sputtering target (length of long side/length of short side) is 1 or more and 30 or less, preferably 5 or more and 25 or less, more preferably 6 or more and 20 or less, even more preferably 7 or more and 18 or less, and particularly preferably 8 or more and 15 or less. This results in a long, slender shape for the sputtering target, but it is easier to achieve the effects of the reverse process, and it is possible to produce a sputtering target with a high bonding rate and a small maximum defect area.

The target material 2 has a sputtering surface 2a on its upper surface. When viewed from the top, the target material 2 has a first edge 21 and a second edge 22 corresponding to the long sides. The first edge 21 and the second edge 22 are formed along the longitudinal direction of the target material 2, and the first edge 21 and the second edge 22 are arranged facing each other in the lateral direction of the target material 2.

The target material 2 has a surface (bonding surface) to be bonded to the backing plate on the back side of the sputtering surface 2a, which is the upper surface. The size of the bonding surface is usually substantially the same as the size of the target material 2, but it may be smaller than the area of the target material 2 (length in the long side direction x length in the short side direction; area in the plan view if it has a rounded portion) due to the removal of burrs that occur on the bonding surface during machining and the removal of corners that could cause abnormal discharge. The area of the bonding surface may usually be at least 95%, preferably at least 98%, and more preferably at least 99% of the area of the target material 2.

When the target material 2 is sputtered, an inert gas ionized by sputtering collides with the sputtering surface 2a. Target atoms contained in the target material 2 are ejected from the sputtering surface 2a that is struck by the ionized inert gas. These ejected atoms are deposited on a substrate placed opposite the sputtering surface 2a, forming a thin film on the substrate.

The material from which target material 2 is made is not particularly limited, as long as it is made of a material composed of a ceramic or sintered body, such as a metal, alloy, oxide, or nitride, that is typically used in film formation by sputtering. An appropriate target material may be selected depending on the application and purpose. For example, target material 2 can be made from a material selected from the group consisting of metals such as aluminum, copper, chromium, iron, tantalum, titanium, zirconium, tungsten, molybdenum, niobium, indium, silver, cobalt, ruthenium, platinum, palladium, nickel, and their alloys, as well as tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and In-Ga-Zn composite oxide (IGZO). The materials constituting target material 2 are not limited to these. For example, Al or Al alloys are preferred as materials for the target material 2 for electrodes and wiring materials, and it is particularly preferable to use Al with a purity of 99.99% or higher, more preferably 99.999% or higher, or Al alloys (Al-Cu, Al-Si, Al-Cu-Si) that use these as their base material. High-purity Al has a relatively large linear thermal expansion coefficient, making it prone to warping due to the heat it receives during sputtering, and peeling from the backing plate. However, the present invention can improve the bonding rate, reduce the maximum defect area, and prevent peeling from the backing plate.

The backing plate 3 is formed in the shape of a long plate. The length of the long side of the backing plate 3 is, for example, 1000 mm or more and 4500 mm or less, preferably 1500 mm or more and 4000 mm or less, more preferably 2000 mm or more and 3500 mm or less, and even more preferably 2500 mm or more and 3200 mm or less. The length of the short side of the backing plate 3 is, for example, 100 mm or more and 2000 mm or less, preferably 150 mm or more and 1200 mm or less, more preferably 180 mm or more and 750 mm or less, and even more preferably 200 mm or more and 350 mm or less. Here, one direction along the short sides of the backing plate 3 is referred to as the first direction D1, and the other direction along the short sides of the backing plate 3 opposite to the first direction D1 is referred to as the second direction D2.

The backing plate 3 has a bonding area 30 (shown hatched) on its upper main surface 3a. The bonding area 30 is the area where the target material 2 is to be bonded. The shape of the bonding area 30 corresponds to the shape of the target material 2. In other words, the size of the bonding area 30 is substantially the same as the size of the bonding surface of the target material 2, preferably the size of the target material 2.

When viewed from above, the bonding area 30 has a first edge 31 and a second edge 32 corresponding to the long sides. The first edge 31 and the second edge 32 are formed along the longitudinal direction of the backing plate 3, and the first edge 31 and the second edge 32 are arranged facing each other in the lateral direction of the backing plate 3. The second edge 32 is located in the first direction D1 of the first edge 31.

The backing plate 3 is made of a conductive material, such as a metal or its alloy. Examples of metals include copper, copper alloys, aluminum, aluminum alloys, titanium, and stainless steel.

The bonding surface of the target material 2 and the bonding region 30 of the backing plate 3 are preferably flat, with a flatness of 1.0 mm or less, preferably 0.5 mm or less, and more preferably 0.3 mm or less, to facilitate slippage when sliding or reversing the target material 2 and to reduce the maximum defect area. Flatness is a numerical value indicating the smoothness (uniformity) of a plane, and refers to the degree of deviation from a geometrically correct plane of a planar shape. Furthermore, to prevent the bonding material from flowing over the bonding region 30 of the backing plate 3 during bonding, the backing plate 3's upper main surface 3a and its back surface should be approximately parallel, preferably parallel. To facilitate the application of a consistent force to the target material 2 when sliding or reversing the target material 2, the target material 2's upper sputtering surface 2a and its back surface, the bonding surface, should be approximately parallel, preferably parallel.

The bonding step is performed while the target material 2, backing plate 3, and bonding material 4 are heated. As shown in FIG. 1B , the bonding material 4 is applied to the entire bonding area 30 of the backing plate 3. The amount of the applied bonding material 4 is 1.5×10 ⁻⁶ kg/mm ² or more, preferably 2.5×10 ⁻⁶ kg/mm ² or more, more preferably 4.5×10 ⁻⁶ kg/mm ² or more, even more preferably 10×10 ⁻⁶ kg/mm ² or more, and still more preferably 14×10 ⁻⁶ kg/mm ² or more. There is no particular upper limit, but from the viewpoint of workability in the bonding step, it is preferably 50×10 ⁻⁶ kg/mm ² or less, more preferably 35×10 ⁻⁶ kg/mm ² or less, and even more preferably 25×10 ⁻⁶ kg/mm ² or less. The bonding material 4 is made of a metal with a low melting point (for example, 723K or less) such as solder or brazing filler metal, and the solder material is, for example, a metal such as indium, tin, zinc, lead, silver, copper, bismuth, cadmium, or antimony, or an alloy thereof, such as In material, In-Sn material, Sn-Zn material, Sn-Zn-In material, In-Ag material, Sn-Pb-Ag material, Sn-Bi material, Sn-Ag-Cu material, Pb-Sn material, Pb-Ag material, Zn-Cd material, Pb-Sn-Sb material, Pb-Sn-Cd material, Pb-Sn-In material, or Bi-Sn-Sb material, and it is generally preferable to use a solder material such as In, an In alloy, Sn, or an Sn alloy, which has a low melting point. The bonding is performed at a temperature equal to or higher than the melting point of the bonding material 4, preferably 140°C or higher, more preferably 150°C or higher and 300°C or lower, and the viscosity of the molten bonding material 4 is 0.5 mPa·s or higher, preferably 1.0 mPa·s or higher, more preferably 1.5 mPa·s or higher, and 5 mPa·s or lower, preferably 3 mPa·s or lower, more preferably 2.5 mPa·s or lower, to improve the bonding rate and reduce the maximum defect area. Furthermore, before bonding the target material 2 and the backing plate 3, a pretreatment (metallization treatment) can be performed on the bonding surface of the target material 2 with the backing plate 3 and the bonding surface of the backing plate 3 with the target material 2 to improve wettability with the bonding material 4. Pretreatment can include surface roughening, hairline finishing, texturing, and metallization, such as polishing and grinding. The bonding surfaces of the target material 2 and the backing plate 3 can be provided with textured surfaces, such as polished, ground, hairline, and textured surfaces, or metallized layers. For example, polishing can be performed manually or with a grinding machine equipped with an abrasive, using a paper or fiber substrate coated with abrasive grains. Metallization can be performed by applying a metallization material to the bonding surfaces and then subjecting them to ultrasonic irradiation. The metallization material can be selected from the same materials as the bonding material 4, such as In and Sn—Zn. The thickness of the metallization layer is 1 μm to 100 μm. This range facilitates ensuring wettability with the bonding material 4 and improving the bonding rate. The non-bonded areas of the target material 2 and the backing plate 3 can be masked with heat-resistant tape in advance to prevent adhesion of the bonding material 4 and the formation of a metallized layer.

As shown in Figure 1C, the first edge 21 of the target material 2 is then placed on the first edge 31 side of the bonding area 30 of the backing plate 3. At this time, the first edge 21 of the target material 2 is preferably positioned so that it overlaps the bonding area 30.

As shown in FIG. 1D, the target material 2 is then slid along the main surface 3a of the backing plate 3 in the first direction D1 so that the first edge 21 of the target material 2 moves from the first edge 31 side of the bonding area 30 of the backing plate 3 to a position beyond the second edge 32 of the bonding area 30 of the backing plate 3.

As shown in Figure 1E, the target material 2 is then slid along the main surface 3a of the backing plate 3 in the second direction D2 until it is aligned with the bonding area 30 of the backing plate 3. The target material 2 and backing plate 3 are then precisely aligned and fixed in place by placing a weight or clamping them with a vice, vise, or clamp. The bonded assembly of the target material 2 and backing plate 3 is then cooled and the bonding material 4 is solidified. In this way, the target material 2 and backing plate 3 are bonded together by the bonding material 4, producing a sputtering target 1.

According to the above-described joining method, the target material 2 is slid relative to the backing plate 3 in the first direction D1 and then reversed in the second direction D2, thereby aligning the target material 2 with the joining area 30 of the backing plate 3. In this way, by not only sliding the target material 2 but also reversing it, the joining material 4 can be pulled back in the second direction D2 by surface tension as the target material 2 reverses, reducing the space between the target material 2 and the backing plate 3 where no joining material 4 exists and making the unjoined areas smaller.

Therefore, in bonding the target material 2 and the backing plate 3, the bonding rate can be improved and the maximum defect area can be reduced.
The bonding rate refers to the ratio of the bonding area of the bonding portion between the target material 2 and the backing plate 3 to the area of the bonding region 30 .
Specifically, the bonding area refers to the total area of the portion where no region without bonding material is detected when viewed from the thickness direction of the bonding layer between the target material 2 and the backing plate 3 .
The maximum defect area refers to the area of the largest portion between the target material 2 and the backing plate 3 where no bonding material 4 is present. Here, the portion where no bonding material 4 is present (unbonded portion) refers to a region in the thickness direction of the bonding layer where no bonding material is present, i.e., a space, or a portion where foreign matter other than the bonding material, such as an oxide of the bonding material, is detected. This may include a portion where no bonding material is present, not just the entire thickness direction of the bonding layer. For example, as shown in FIG. 2A , the bonding layer 6 between the target material 2 and the backing plate 3 may have a space S where no bonding material 4 is present in a portion of the thickness direction of the bonding layer 6 (vertical direction in the figure). Alternatively, as shown in FIG. 2B , the bonding layer 6 between the target material 2 and the backing plate 3 may have a space S where no bonding material 4 is present throughout the entire thickness direction of the bonding layer 6 (vertical direction in the figure). The region where no bonding material is present can be detected using the measurement method described below. For example, when using ultrasonic flaw detection, if there is a space where no bonding material is present in the bonding layer, incident ultrasonic waves are reflected at the interface, allowing the defect to be recognized.

Accordingly, the present invention makes it possible to increase the bonding rate between the target material 2 and the backing plate 3 and reduce the maximum defect area, thereby making it possible to manufacture a sputtering target 1 in which areas with low bonding strength are less likely to form and the target material 2 is less likely to peel off.

In this way, the present invention has discovered that by focusing on both the bonding rate and the maximum defect area, the target material 2 is less likely to peel off during sputtering. Specifically, with regard to the bonding rate, as the bonding rate increases, the area where the bonding material 4 is not present can be reduced, making the target material 2 less likely to peel off.

On the other hand, with regard to the maximum defect area, if the maximum defect area becomes large, large localized defects will occur, which will impair electrical and thermal conductivity in that area, causing heat to concentrate in that area and melting the bonding material 4, making the target material 2 more likely to peel off. Therefore, if the maximum defect area becomes small, large localized defects will not occur and the target material 2 will be less likely to peel off.

Furthermore, with this joining method, the target material 2 is moved by sliding it relative to the backing plate 3 in the short direction of the backing plate 3. This reduces the movement distance of the target material 2 relative to the backing plate 3 for long target materials 2 and backing plates 3, thereby shortening the working time.

Preferably, prior to the application of the bonding material 4 (see FIG. 1B), multiple wires 5 are arranged on the main surface 3a of the backing plate 3 as shown in FIG. 1A. The wires 5 are made of, for example, stainless steel or copper. Specifically, the wires 5 are arranged in the bonding region 30 so as to extend in the first direction D1, and the multiple wires 5 are spaced apart in a direction perpendicular to the first direction D1. The target material 2 then slides along the wires 5 as it moves in the first direction D1 and the second direction D2. This allows the target material 2 to slide along the wires 5, making it easy to move. Furthermore, by using the wires 5 as spacers, the thickness of the bonding layer formed by the bonding material 4 can be made uniform. The thickness of the bonding layer is typically 0.03 mm to 1.5 mm, preferably 0.05 mm to 1 mm, more preferably 0.08 mm to 0.5 mm, and even more preferably 0.1 mm to 0.35 mm.

Preferably, the diameter of the wire 5 is 0.05 mm or more and 0.5 mm or less, and more preferably 0.1 mm or more and 0.3 mm or less. This makes it less likely for the wire 5 to break and reduces variation in the thickness of the bonding layer.

Preferably, bonding material 4 is replenished on the first edge 31 side of the bonding region 30 of the backing plate 3 between the step of moving the target material 2 in the first direction D1 (see FIG. 1D ) and the step of moving the target material 2 in the second direction D2 (see FIG. 1E ). Specifically, in the state shown in FIG. 1D , bonding material 4 is added to the portion of the bonding region 30 that is not covered by the target material 2. This replenishes bonding material 4 on the first edge 31 side of the bonding region 30 of the backing plate 3, so that bonding material 4 can be replenished on the first edge 31 side of the bonding region 30, where bonding material 4 is likely to become insufficient as the target material 2 moves, thereby further improving the bonding rate and further reducing the maximum defect area. The amount of replenished bonding material 4 is preferably 0.5×10 ⁻⁶ kg/mm ² or more, more preferably 0.8×10 ⁻⁶ kg/mm ² or more, and even more preferably 1.0×10 ⁻⁶ kg/mm ² or more. There is no particular upper limit, but from the viewpoint of workability in the joining step, it is preferably 20×10 ⁻⁶ kg/mm ² or less, more preferably 10×10 ⁻⁶ kg/mm ² or less, and even more preferably 7.0×10 ⁻⁶ kg/mm ² or less.

Preferably, during the step of moving the target material 2 in the first direction D1, as shown in FIG. 1D , when the first edge 21 of the target material 2 is moved to a position beyond the second edge 32 of the bonding region 30 of the backing plate 3, where A is the distance in the first direction D1 from the second edge 32 of the bonding region 30 of the backing plate 3 to the first edge 21 of the target material 2 and W is the width of the bonding region 30 in the first direction D1, the following relationship holds: 0.03≦A/W<1.0, preferably 0.05≦A/W≦0.8, and more preferably 0.06≦A/W≦0.6. Specifically, the relationship holds: 10 mm≦A≦150 mm, preferably 12 mm≦A≦120 mm, and preferably 150 mm≦W≦300 mm. This allows for a shorter movement distance of the target material 2 relative to the backing plate 3, while improving the bonding rate and reducing the maximum defect area.

Preferably, during the step of moving the target material 2 in the first direction D1, as shown in FIG. 1C , when the first edge 21 of the target material 2 is positioned toward the first edge 31 of the bonding region 30 of the backing plate 3, the distance in the first direction D1 from the first edge 31 of the bonding region 30 of the backing plate 3 to the first edge 21 of the target material 2 is B, and the width of the bonding region 30 in the first direction D1 is W. The following relationship holds: 0≦B/W<2.0, preferably 0≦B/W≦1.5, more preferably 0.03≦B/W≦1.2, and even more preferably 0.10≦B/W≦1.0. Specifically, the relationship holds: 0 mm≦B≦300 mm, preferably 5 mm≦B/W≦200 mm, and preferably 150 mm≦W≦300 mm. This reduces the moving distance of the target material 2 relative to the backing plate 3, improves the bonding rate, and reduces the maximum defect area.

The speed of movement (sliding) of the target material 2 in the first direction D1 and movement (reverse) in the second direction D2 is preferably 100 mm/sec or less, more preferably 50 mm/sec or less, and even more preferably 30 mm/sec or less, from the viewpoint of preventing excessive movement or escape of the joining material placed in the joining area. There is no particular lower limit, but from the viewpoint of productivity, it is 1 mm/sec or more, preferably 5 mm/sec or more.

It is preferable to provide a step of applying vibration to the top surface of the target material 2 to remove any air that may be present in the bonding layer when the edge of the target material 2 is positioned on the first edge side of the bonding area of the backing plate and/or when the movement (sliding) of the target material 2 in the first direction D1 is completed. Vibration can be applied by lightly tapping the top surface of the target material or by applying vibration in a direction parallel to the top surface of the target material 2. The vibration is preferably applied to the entire bonding layer between the target material and the backing plate (the bonding area where the target material is placed) when the edge of the target material 2 is positioned on the first edge side of the bonding area of the backing plate, and to the leading end of the movement (reverse) in the second direction D2 when the movement (sliding) of the target material 2 in the first direction D1 is completed. The vibration is preferably applied from the center toward the periphery of the bonding layer between the target material and the backing plate (the bonding area where the target material is placed). This allows air present in the bonding layer to be removed, improving the bonding rate and reducing the maximum defect area. In particular, when the edge of the target material 2 is positioned on the first edge side of the bonding area of the backing plate, there is a high possibility of air pockets being present in the bonding layer between the target material and the backing plate (the bonding area on which the target material rests). Therefore, by providing an air removal process, it is possible to further improve the bonding rate and reduce the maximum defect area.

Next, we will explain the manufacturing method of the sputtering target 1. As described above, the target material and the backing plate are joined using the joining method to manufacture the sputtering target.

In the manufacturing method of the present invention, the target material can be processed into a roughly plate-like shape, but the method for processing it into a plate-like shape is not particularly limited. Target material made from a metallic material can be produced, for example, by subjecting rectangular, cylindrical, or columnar target material obtained by melting and casting to plastic processing such as rolling, extrusion, or forging, followed by mechanical processing such as cutting, grinding, or polishing (such as cutting, milling, or end milling) to produce target material of the desired size and surface condition. Rolling processing is described, for example, in JP 2010-132942 A and WO 2011/034127 A. Extrusion processing is described, for example, in JP 2008-156694 A. Forging processes are described, for example, in JP 2017-150015 A, JP 2001-240949 A, and the Aluminum Technology Handbook (edited by the Aluminum Technology Handbook Editorial Committee of the Japan Light Metal Association, Karos Publishing, New Edition, published November 18, 1996). Using the joining method of the present invention, a machined plate-shaped target material is joined to a backing plate to produce a sputtering target. The target material may be purchased and machined to a specified size. Alternatively, the target material may be a sputtering target that has not met the product specifications due to an abnormality in the joining with the backing plate during the manufacturing process of the sputtering target 1. The backing plate may then be removed, and the joining material removed. If necessary, the surface of the joined sputtering target may be finished by cutting or polishing.

The sputtering target manufacturing method of the present invention uses the joining method of the present invention, making it possible to obtain sputtering targets of improved quality.

Next, we will explain the sputtering target 1 bonded using the above bonding method.

As shown in Figure 1E, the sputtering target 1 has a backing plate 3 and a target material 2 bonded to the bonding region 30 of the backing plate 3 via a bonding material 4.

Figure 3A is a simplified diagram showing the state of the bonding material 4 between the target material 2 and the backing plate 3 of the sputtering target 1. In Figure 3A, defective areas (unbonded areas) 10, where no bonding material 4 is present in the bonding region 30, are indicated by hatching. The defective areas 10 can be measured using, for example, ultrasonic flaw detection or transmission X-ray observation. However, when the area of the bonding region is large, ultrasonic flaw detection is preferable. Examples of ultrasonic flaw detection devices that can be used include the FS LINE and FS LINE Hybrid manufactured by Hitachi Power Solutions Co., Ltd., and the PDS and ADS71000 phased array ultrasonic flaw detection imaging systems manufactured by KJTD Corporation. Furthermore, when determining the bonding rate or maximum defect area using ultrasonic flaw detection, it is necessary to use a pseudo-defect sample with a flat-bottom hole of a specified size and adjust the ultrasonic flaw detection measurement conditions to recognize the reflected waves from the defect. Because the propagation speed of ultrasonic waves differs depending on the material, it is preferable that the pseudo-defect sample be made from the same material as the ultrasonic wave incident side of the sputtering target 1 in order to match the measurement sensitivity and conditions. It is also preferable that the distance from the ultrasonic wave incident surface of the pseudo-defect sample to the bottom surface of the flat-bottom hole be the same as the distance from the ultrasonic wave incident surface of the sputtering target 1 to the bonding layer.

As shown in FIG. 3A , the area of the portion between the target material 2 and the backing plate 3 where no defect locations 10 are detected is 97% or more of the area of the bonding region 30. In other words, the bonding rate is 97% or more, preferably 98% or more, and more preferably 98.5% or more. Furthermore, the maximum defect area of the defect locations 10 in the bonding layer between the target material 2 and the backing plate 3 is 2% or less of the area of the bonding region 30, preferably 1% or less, more preferably 0.6% or less, even more preferably 0.3% or less, even more preferably 0.1% or less, and particularly preferably less than 0.05%. For example, when the area of the bonding region 30 is 200 mm × 2300 mm, the maximum defect area is 2000 ^mm² or less.

The present invention makes it possible to manufacture a sputtering target 1 that improves the bonding rate, reduces the maximum defect area, and is less likely to peel off the target material 2. Preferably, the length of the target material 2 is 1,000 mm or more and 4,000 mm or less, making it possible to manufacture a sputtering target 1 in which the target material 2 is less likely to peel off even when using a long sputtering target 1.

Although the upper limit of the bonding rate is 100%, from the viewpoint of ease of peeling off the target material when removing the backing plate from a sputtering target that has become out of specification due to an abnormality that occurred during bonding or from a sputtering target that has been used in sputtering, the bonding rate is preferably 99.99% or less, more preferably 99.95% or less, and even more preferably 99.90% or less. Note that the target material can be peeled off from the sputtering target by applying heat to the sputtering target to a temperature equal to or higher than the melting point of the bonding material used for bonding, softening or melting the bonding layer, and physically destroying the bonding layer as necessary.
The lower limit of the ratio of the maximum defect area to the area of the bonding region 30 is not particularly limited, but from the viewpoint of further suppressing warpage of the sputtering target due to heat generated during sputtering, it is 0.001% or more, preferably 0.003% or more, more preferably 0.005% or more, and even more preferably 0.008% or more. When the lower limit of the maximum defect area ratio is above the above range, deformation of the target material caused by heat during sputtering is mitigated by the local defects, and warpage of the sputtering target is reduced.

In contrast, Figure 3B shows a comparative example sputtering target 100 when the target material and backing plate are bonded together simply by sliding the target material in the first direction D1, illustrating the state of the bonded material between the target material and backing plate. As shown in Figure 3B, compared to Figure 3A, the proportion of defective areas 10 is higher, the bonding rate is lower, and the maximum defect area of the defective areas 10 is larger. Thus, simply sliding the target material results in a poor bond between the target material and backing plate, making the target material more susceptible to peeling. This tendency is particularly pronounced when the target material is long or the bonding area is large.

In a preferred embodiment of the sputtering target of the present invention, a wire may be present between the target material and the backing plate, i.e., in the bonding layer. Having a wire in the bonding layer makes it easier to ensure the thickness of the bonding layer and make the thickness of the bonding layer more consistent, thereby increasing the bonding rate of the sputtering target 1 and reducing the maximum defect area, making it possible to produce a sputtering target 1 in which the target material 2 is less likely to peel off.

Example 1
A rolled plate made of high-purity aluminum with a purity of 99.999% was prepared and machined using a gantry machining center to produce a target material measuring 200 mm x 2,300 mm x 16 mm (the area of the bonding region was 4.5 x 10 ⁵ mm ² ). A backing plate made of oxygen-free copper with a purity of 99.99% was also prepared. The width W of the bonding region in the first direction D1 during the target material movement process (the so-called target material width) was 200 mm.

The target material and backing plate were heated on a hot plate to a temperature above the melting point of the bonding material.

The Sn-Zn-In alloy material was melted on the bonding surface of the target material, and the In material was melted on the bonding surface of the backing plate, and the bonding surfaces of both materials were metallized using an ultrasonic soldering iron. After the metallization process, oxides of the Sn-Zn-In alloy material and In material, as well as excess Sn-Zn-In alloy material and In material, were removed with a spatula from the bonding surfaces of the target material and the backing plate.

Ten 0.2 mm diameter SUS wires were placed at approximately equal intervals on the bonding surface of the metallized backing plate in a direction perpendicular to the longitudinal direction of the backing plate, and then an In bonding material was applied to the bonding surface from above the SUS wires. The amount of In bonding material applied to the bonding surface from above the SUS wires was 7.80 kg.

The target material was then oriented so that its bonding surface was parallel to and facing the bonding surface of the backing plate, and placed on the wire so that one of its long sides overlapped one of the long sides of the backing plate (target material placement position B = 0). The target material was then slid toward the designated bonding position. The ratio A/W of the overrun distance (overrun amount) A from the designated bonding position to the target material's width W was 0.1625, and the leading edge of the target material moving in the second direction D2 (reverse) was lightly struck from above to expel the air.

The target material was then slid to the desired joining position. The target material's position was fine-tuned so that it was in the desired joining position, a weight was placed on top of the target material to secure the target material and backing plate, and the assembly was then cooled to produce a sputtering target.

After the In material solidified, the warping caused by the difference in linear expansion coefficient between the target material and the backing plate was corrected to obtain the target. The bonding rate and maximum defect area were measured using an FS-LINE ultrasonic flaw detector manufactured by Hitachi Power Solutions Co., Ltd.

The bonding rate and maximum defect area were measured using the following procedure. First, a rolled plate made of high-purity Al with a purity of 99.999% was used. Both sides of the rolled plate were chamfered to create parallel surfaces, and then a pseudo-defect sample was prepared by drilling a flat-bottom hole with an equivalent circle diameter (diameter) of 2 mm and a counterbore hole with a diameter of 6 mm on one side. The distance from the un-drilled sample surface to the flat-bottom hole was set to the same as the thickness of the target material.

In preparation for measurement, an ultrasonic flaw detector "I3-1006-T S-80mm" (frequency 10MHz, focal length 80mm) was attached to the measuring device.

The pseudo-defect sample was then placed on the measuring device, the focus was adjusted to the countersunk hole, and measurement began. First, the countersunk hole was confirmed, and then, with the focus on the countersunk hole, the flat-bottom hole was confirmed. Then, the focus was adjusted to the flat-bottom hole. In this state, ultrasonic flaw detection (C-scan) was performed, and the sensitivity was adjusted so that the detected flat-bottom hole diameter matched the flat-bottom hole diameter of the pseudo-defect sample. As a result, the measurement conditions were a gain (sound wave strength) of 12 dB, a measurement pitch of 2 mm, and a defect level of 38. As a result, the program sensitivity was adjusted so that reflected echo strengths of 38 or higher would be detected as defects.

Next, the pseudo-defect sample was removed from the measuring device, and the bonded sputtering target was placed in the measuring device with the target material side facing up. The ultrasonic flaw detector height was set so that the focal position height of the program created with the pseudo-defect sample was the bonded layer of the sputtering target, and the ultrasonic flaw detector scanning range was set so that the measurement field of view covered the entire bonded surface, and an ultrasonic flaw detection measurement (C-scan) was performed on the bonded sputtering target. Ultrasonic waves were incident from the target material side.

The data obtained was analyzed using the analysis program attached to the ultrasonic flaw detector to obtain information on the joining rate and maximum defect area. The surface was then finished by polishing and blasting.

The results for the sputtering targets bonded as in Example 1 are shown in Table 1.

Examples 2 to 12
Examples 2 to 12 were carried out in the same manner as Example 1, except that the amount of bonding material, wire diameter, bonding material type, target material placement position B, and overrun amount A shown in Table 1 were used, and after the target material was placed on the bonding surface of the backing plate, substantially the entire surface of the bonding layer (contact portion, bonding area on which the target material rests) between the target material and the backing plate was lightly tapped from above to remove air from the bonding layer. In Examples 2 to 12, the target material was slid in a first direction and then reversed in a second direction, in the same manner as Example 1.
Example 13
In Example 13, a sputtering target was produced in the same manner as in Example 2, except that the bonding surface of the backing plate was metallized with a Sn—Zn material, Sn—Zn (containing 9% Zn) was used as the bonding material, and the air in the bonding layer was not knocked out, and the bonding rate and the maximum defect area were determined.
(Comparative Example 1)
In Comparative Example 1, the target material was only slid in the first direction, and was not reversed in the second direction, but otherwise the same procedures as in Examples 2 to 12 were carried out.
(Comparative Example 2)
In Comparative Example 2, the target material was neither slid nor reversed, nor air was hammered out, and a sputtering target was produced under the conditions shown in Table 1 without sliding or reversing the target material.

In Table 1, "amount of applied bonding material" refers to the amount of bonding material applied to the bonding area 30 of the backing plate 3 in Figure 1B. "Amount of replenished bonding material" refers to the amount of bonding material replenished to the bonding area 30 of the backing plate 3 through which the target material has passed in Figure 1D. "Wire type" refers to the type of wire 5 installed in the bonding area 30 of the backing plate 3 in Figure 1A, and stainless steel is used. "Wire diameter" refers to the diameter of the wire 5. "Type of bonding material" refers to the material of the bonding material, and solder made of In or Sn-Zn is used. "Target material installation position" refers to the position where the target material 2 is installed in Figure 1C, and is the distance B in the first direction D1 from the first edge 31 of the bonding area 30 of the backing plate 3 to the first edge 21 of the target material 2. "Air striking" refers to striking the top surface of the target material 2 to remove air between the target material 2 and the backing plate 3 when the edge of the target material 2 is positioned on the first edge side of the bonding area of the backing plate in Figure 1C, or when the movement (sliding) of the target material 2 in the first direction D1 has finished in Figure 1D. "Target material overrun amount" refers to the amount by which the target material 2 extends beyond the bonding area 30, and is the distance A in the first direction D1 from the second edge 32 of the bonding area 30 of the backing plate 3 to the first edge 21 of the target material 2 in Figure 1D. "Bonding material replenishment" refers to whether or not bonding material is replenished.

As can be seen from Table 1, in Examples 1 to 13, the bonding rate was 97% or more, and the maximum defect area was 2000 ^mm2 or less (i.e., the ratio of the maximum defect area to the area of the bonded region was 0.6% or less). In Examples 1 to 13, the target material was less likely to peel off, and no peeling of the target material was observed even after use in a sputtering device.

In contrast, in Comparative Example 1, the bonding rate was 90.70% and the maximum defect area was 11,628 ^mm2 , and in Comparative Example 2, the bonding rate was 96.27% and the maximum defect area was 1,948 ^mm2 . In Comparative Examples 1 and 2, the target material was prone to peeling.

The present invention is not limited to the above-described embodiments, and design modifications are possible without departing from the spirit of the present invention.

In the above embodiment, the target material and backing plate are formed to be long, but the target material and backing plate may have short and long sides of the same length.

REFERENCE SIGNS LIST 1 sputtering target 2 target material 2a sputtering surface 21 first edge 22 second edge 3 backing plate 3a main surface 30 bonding area 31 first edge 32 second edge 4 bonding material 6 bonding layer 5 wire 10 defect location D1 first direction D2 second direction

Claims (2)

A backing plate;
a target material bonded to the bonding region of the backing plate via a bonding material,
the target material is a material selected from the group consisting of aluminum and its alloys;
a bonding area of a bonding portion between the target material and the backing plate is 97% or more of an area of the bonding region;
a maximum defect area of a portion where no bonding material exists between the target material and the backing plate in the entire bonding region is 0.6% or less with respect to the entire area of the bonding region. The sputtering target of claim 1, wherein the length of the target material is 1000 mm or more and 4000 mm or less.