JP6930558B2 - Manufacturing method of sputtering target - Google Patents

Description

The present invention relates to a method for manufacturing a sputtering target, which is formed by joining a target material and a backing material via a solder layer.

A sputtering method using a sputtering target is widely used as a means for forming a thin film such as a metal film or an oxide film.
Generally, the sputtering target has a structure in which a target material formed according to the composition of the thin film to be formed and a backing material holding the target material are joined via a solder layer.
Examples of the solder material forming the solder layer interposed between the target material and the backing material include In solder, Sn-Pb solder, and the like, as shown in Patent Documents 1 and 2. However, since Pb is an environmentally hazardous substance, the use of Sn-Pb solder is currently avoided, and In solder is widely used.

Here, as the above-mentioned sputtering target, for example, a flat plate type sputtering target and a cylindrical type sputtering target have been proposed.
The flat plate type sputtering target has a structure in which a flat plate-shaped target material and a flat plate-shaped backing material (backing plate) are laminated.
Further, the cylindrical sputtering target has a structure in which a cylindrical backing material (backing tube) is inserted on the inner peripheral side of the cylindrical target material. In addition, it has been proposed that the axial length of the cylindrical target is set to be relatively long, for example, 1 m or more.

Since the outer peripheral surface of the cylindrical sputtering target is a sputtering surface and sputtering is performed while rotating the target, the cylindrical sputtering target is more suitable for continuous film formation than the case where a flat plate type sputtering target is used. It has the advantage of excellent usage efficiency of the sputtering target.

Here, the backing material is arranged for holding the target material, supplying electric power to the target material, and cooling the target material. In the above-mentioned sputtering target, the target material and the backing material are used. Must be well joined.
As a means for inspecting the bonding state between the target material and the backing material, for example, in Patent Document 3, an ultrasonic inspection is performed in water, and a bonding defect such as a bubble (void) is obtained from the peak intensity of the reflected wave of the ultrasonic wave at the bonding interface. A method for determining the presence or absence of is proposed.

As described in Patent Document 3, when the above-mentioned sputtering target is inspected by ultrasonic inspection in water, the oscillated ultrasonic waves are the water / target material interface, the target material / solder layer interface, and the solder layer. It is mainly reflected at the four interfaces of / backing material interface and backing material / water interface. Here, since the acoustic impedance of defects such as voids is almost 0, the peak intensity is much higher than that of the reflected wave at the interface, and the defects can be detected.

Japanese Unexamined Patent Publication No. 2003-042975 Japanese Unexamined Patent Publication No. 10-280137 Japanese Unexamined Patent Publication No. 08-218166

By the way, for example, in the above-mentioned cylindrical sputtering target, a cylindrical backing material (backing tube) is inserted on the inner peripheral side of the cylindrical target material, and the axial length thereof is relatively long, 1 m or more. Since it may be set, the thickness of the solder layer tends to be as thick as 0.75 mm or more from the viewpoint of dimensional accuracy at the time of assembly.

Here, when the thickness of the solder layer becomes thicker than the wavelength of ultrasonic waves (for example, several tens of μm), the peak of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface. Since the intensity tends to be high, the S / N ratio of the signal when a defect is present becomes small, and there is a possibility that the defect cannot be detected accurately. In particular, when In solder is used as the solder material, the peak intensity of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface becomes higher, which makes it more difficult to detect defects. was there.

The present invention has been made in view of the above circumstances, and even when the solder layer is formed to be relatively thick, reflection at the target material / solder layer interface and the solder layer / backing material interface. It is an object of the present invention to provide a method for manufacturing a sputtering target, which can suppress the peak intensity of a wave to a low level and can accurately detect defects in a solder layer by ultrasonic flaw detection.

In order to solve the above problems, the method for manufacturing a sputtering target of the present invention is a method for manufacturing a sputtering target having a solder layer between a target material and a backing material, and the target material contains Cu or Ni. The backing material is made of any of stainless steel, copper or copper alloy, and titanium alloy, and the solder layer contains In—Sn alloy, and the acoustic impedance of the target material is X kg / (. m ² · s), with respect to the backing material of acoustic impedance ^{Ykg / (m 2 · s)} , the acoustic impedance of the solder layer Zkg / (m ² · s) is, Z ≧ 0.5 × (X + Y) - to meet 26.3 × 10 ^6, and the peak intensity of the reflected wave in the reflected wave and the solder layer / backing material interface in the target material / solder layer interface, and the peak intensity of the reflected wave when a defect is present In order to make the ratio (S / N ratio) 2.00 or more, the solder material is selected so that the difference in acoustic impedance between the target material and the backing material and the solder layer becomes small, and the solder layer is used. At the time of forming, three or more wires having the same diameter as the target thickness of the solder layer are inserted between the target material and the backing material as spacers, and the average thickness _{save of the} solder layer is 0.75 mm. The range is 2.0 mm or less, and when the standard deviation of the measured values at 10 points of the solder layer is σ, the above is made so that _{3 × σ is within the range of 0.2 × save or less.} It is characterized by forming a solder layer.

According to such a configuration and process for the preparation of a sputtering target of the present invention, the average thickness t _ave of the solder layer is in the range of less 2.0mm or 0.75 mm, thicker than the wavelength of the ultrasonic wave Therefore, the peak intensity of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface tends to be high. ^{Here, Xkg / (m 2 · s} ) of the acoustic impedance of the target material, the acoustic impedance of the backing material when the ^{Ykg / (m 2 · s)} , the acoustic impedance of the solder layer Zkg / (m ² · s) is, Z ≧ 0.5 × (X + Y) - 26.3 by satisfying × 10 ^6, the difference in acoustic impedance between the target material and the backing material and the solder layer is small, the target material / solder layer interface , And the peak intensity of the reflected wave at the solder layer / backing material interface can be suppressed to a low level. As a result, the S / N ratio of the signal when a defect is present becomes large, and the defect can be detected with high accuracy.

Further, the average thickness t _ave of the solder layer is in the range of less 2.0mm or 0.75 mm, when the standard deviation of the measurements at 10 points of the solder layer sigma, 3 × sigma 0 Since it is within the range of .2 × _save or less, the variation in the thickness of the solder layer is suppressed, and the position where the reflected wave is generated at the target material / solder layer interface and the solder layer / backing material interface ( The time) becomes stable, the influence of the reflected wave at the interface can be reliably suppressed, and defects can be detected with high accuracy.
Here, the average thickness t _ave of the solder layer, the sputtering target of less than 0.75mm is very difficult to produce in terms of dimensional accuracy, easily can bubbles when pouring the solder exceeds 2.0mm Therefore, the heat transfer property, which is an important property of the sputtering target, is inferior. Therefore, in the present invention, the average thickness t _ave of the solder layer is in the range of less 2.0mm or 0.75 mm.

Here, in the method for manufacturing a sputtering target of the present invention, the target material and the backing material may have a cylindrical shape.
In this case, when the target material and the backing material have a cylindrical shape, the thickness of the solder layer becomes relatively thick. Therefore, as described above, depending on the acoustic impedance of the target material and the backing material. By selecting the material of the solder layer so that the acoustic impedance of the solder layer is within the above range, the peak intensity of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface is lowered. It can be suppressed and defects can be detected with high accuracy.

Further, in the method for manufacturing a sputtering target of the present invention, the acoustic impedance of the solder layer is 17.5 × 10 ⁶ kg / (m ² · s) or more and 24.3 × 10 ⁶ kg / (m ² · s) or less. It is preferably within the range of.
In this case, the difference in acoustic impedance between the target material and backing material made of metal such as copper, copper alloy, and stainless steel and the solder layer can be reduced, and the bonding state between the target material and the backing material can be determined by ultrasonic flaw detection. It can be inspected accurately.

As described above, according to the present invention, even when the solder layer is formed relatively thick, the peak intensity of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface is lowered. It is possible to provide a method for manufacturing a sputtering target, which can be suppressed and can accurately detect defects in the solder layer by ultrasonic flaw detection.

It is the schematic explanatory drawing of the sputtering target which concerns on one Embodiment of this invention. (A) is a cross-sectional view orthogonal to the axis O direction, and (b) is a cross-sectional view along the axis O direction.

Hereinafter, the sputtering target according to the embodiment of the present invention will be described with reference to the attached drawings.

As shown in FIG. 1, the sputtering target 10 according to the present embodiment includes a cylindrical target material 11 extending along the axis O and a cylindrical backing material inserted on the inner peripheral side of the target material. (Backing tube) 12 is provided.
Then, the target material 11 and the backing material 12 are joined via the solder layer 13.

The target material 11 has a composition corresponding to the composition of the thin film to be formed, and is composed of various metals, oxides, and the like. In this embodiment, it is assumed that it is composed of, for example, Cu or Nb. At this time, the speed of sound in the target material 11 is 3000 to 5000 m / sec. Will be.
The size of the target material 11 is, for example, an outer diameter D1 within a range of 100 mm ≦ D1 ≦ 300 mm, an inner diameter d1 within a range of 50 mm ≦ d1 ≦ 200 mm, and an axis O-direction length L1 within a range of 50 mm ≦ L1 ≦ 3000 mm. It is said to be inside.

The backing material 12 is provided to hold the target material 11 and secure mechanical strength, and further has an action of supplying electric power to the target material 11 and cooling the target material 11. be. Therefore, the backing material 12 is required to have excellent mechanical strength, electrical conductivity, and thermal conductivity. For example, the backing material 12 is made of stainless steel such as SUS304, copper or a copper alloy, a titanium alloy, or the like. There is. In the present embodiment, the backing material 12 is made of SUS304, and at this time, the speed of sound of the backing material 12 is 5790 m / sec. Will be.
The size of the backing material 12 is, for example, an outer diameter D2 within a range of 30 mm ≦ D2 ≦ 200 mm, an inner diameter d2 within a range of 20 mm ≦ d2 ≦ 195 mm, and an axis O-direction length L2 within a range of 50 mm ≦ L2 ≦ 3000 mm. It is said to be inside.

The solder layer 13 interposed between the target material 11 and the backing material 12 is formed when the target material 11 and the backing material 12 are joined using the solder material.
The sputtering target 10 of the present embodiment is configured to insert the backing material 12 on the inner peripheral side of the cylindrical target material 11, and further, the backing material is inserted into the axial length L1 of the target material 11 and the backing material. Since the length L2 of the axis 12 in the O direction is set to be relatively long, the solder layer 13 is formed to be relatively thick from the viewpoint of dimensional accuracy at the time of assembly.

In the present embodiment, the average thickness t _ave of the solder layer 13 is within a range of 2.0mm or 0.75 mm, when the standard deviation of the measurements at 10 points of the solder layer 13 sigma, 3 × σ is within the range of _{0.2 × tave or less.}
Specifically, the thickness of the solder layer 13 is measured at five points in one cross section of the cylindrical sputtering target 10 orthogonal to the axis O direction, and further, in another cross section orthogonal to the axis O direction of the sputtering target 10. The thickness of the solder layer 13 is measured at five points. _{Then, the average thickness save} of the solder layer 13 calculated from the measured values at these 10 points is within the range of 0.75 mm or more and 2.0 mm or less, and the standard deviation of the measured values at the 10 points is defined as σ. When this is done, 3 × σ is within the range of _{0.2 × tave or less.}

When forming the solder layer 13, a wire having the same diameter as the target thickness (for example, Cu, SUS, Ti, etc.) is inserted between the target material 11 and the backing material 12 as a spacer. At this time, the number of wires to be inserted is set to 3 or more, and the wires are arranged so that the intervals between the wires are about the same. As a result, variation in the thickness of the solder layer 13 is suppressed, and when the standard deviation of the measured values at 10 points is σ, 3 × σ can be within the range of _{0.2 × save or less.} Become.

The material of the solder layer 13 is the acoustic of the solder layer 13 when the acoustic impedance of the target material 11 is X kg / (m ² · s) and the acoustic impedance of the backing material 12 is Y kg / (m ² · s). The impedance Zkg / (m ² · s) is selected so as to satisfy Z ≧ 0.5 × (X + Y) −27.

In the present embodiment, the acoustic impedance X of the target material 11 made of Cu is 41.8 × 10 ⁶ kg / (m ² · s), and the acoustic impedance Y of the backing material 12 made of SUS304 is 45.8 × 10 ⁶ kg / (m 2 · s). Since it is (m ² · s), the material of the solder layer 13 is selected so that its acoustic impedance Z is Z ≧ 16.8 × 10 ⁶ kg / (m ² · s).

Specifically, the solder layer 13 is an In—Sn alloy and has a Sn content of 20 mass% or more. The acoustic impedance Z of the solder layer 13 is ^{within the range of 17.5 × 10 6} kg / (m ² · s) or more and 24.3 × 10 ⁶ kg / (m ² · s) or less. Further, in the present embodiment, the melting point of the solder material constituting the solder layer 13 is set to 200 ° C. or lower.

Next, a method of ultrasonically inspecting the bonding state between the target material 11 and the backing material 12 in the sputtering target 10 of the present embodiment will be described.
The above-mentioned sputtering target 10 is placed in water, ultrasonic waves are oscillated from the surface of the target material 11 toward the stacking direction of the target material 11, the solder layer 13, and the backing material 12, and the presence or absence of defects is determined by the peak intensity of the reflected waves. Inspect.

The ultrasonic waves oscillated in the laminating direction of the target material 11, the solder layer 13, and the backing material 12 are the water / target material interface, the target material / solder layer interface, the solder layer / backing material interface, the backing material / water interface, and the like. It will be mainly reflected at the four interfaces of.
When a defect such as a gap exists between the target material 11 and the backing material 12, a reflected wave is generated due to this defect. Therefore, the presence or absence of the defect is evaluated by evaluating the peak intensity of the reflected wave. To judge.

In the present embodiment, the average thickness t _ave of the solder layer 13 are relatively thick in the range of less 2.0mm or 0.75 mm, the thickness of the solder layer 13 is higher than the wavelength of the ultrasonic wave Therefore, the peak intensities of the reflected wave at the target material / solder layer interface and the reflected wave at the solder layer / backing material interface tend to be high. Therefore, even if a defect exists between the target material and the backing material, the peak intensity of the reflected wave due to this defect, the reflected wave at the target material / solder layer interface, and the peak of the reflected wave at the solder layer / backing material interface. The difference from the strength becomes small, and there is a risk that defects cannot be detected accurately.

Therefore, in the present embodiment, when the acoustic impedance of the target material 11 is X kg / (m ² · s) and the acoustic impedance of the backing material 12 is Y kg / (m ² · s), the acoustic impedance of the solder layer 13 is Z kg. / (M ² · s),
Z ≧ 0.5 × (X + Y) -27
By selecting the material of the solder layer 13 so as to satisfy the above conditions, the peak intensities of the reflected wave at the target material / solder layer interface and the reflected wave at the solder layer / backing material interface are suppressed.

As a result, in the present embodiment, the ratio (S / N ratio) of the peak intensity of the reflected wave at the target material / solder layer interface and the reflected wave at the solder layer / backing material interface to the peak intensity of the reflected wave due to the defect is 2 It is said to be .00 or more.
Further, when the peak intensity of the water / target material is 100, the peak intensity of the reflected wave at the normal target material / solder layer interface and the reflected wave at the solder layer / backing material interface is 0.3 or less. That is, the peak intensities of the reflected wave at the normal target material / solder layer interface and the reflected wave at the solder layer / backing material interface are suppressed to be sufficiently low.

According to the sputtering target 10 of the present embodiment having the above configuration, the material of the solder layer 13 is selected in consideration of the acoustic impedance of the target material 11 and the backing material 12 as described above. Therefore, the difference in acoustic impedance between the target material 11 and the backing material 12 and the solder layer 13 becomes small, and the peak intensity of the reflected wave at the target material / solder layer interface and the solder layer / backing material interface can be suppressed to a low level. can. As a result, the S / N ratio of the signal when a defect is present becomes large, and the defect can be detected with high accuracy. Specifically, in the present embodiment, since the S / N ratio of the signal when a defect is present is 2.00 or more, it is possible to accurately detect the defect.

Further, in the present embodiment, the average thickness t _ave of the solder layer 13 is within a range of 2.0mm or 0.75 mm, when the standard deviation of the measurements at 10 points of the solder layer 13 sigma, Since 3 × σ is _{within the range of 0.2 × save} or less, the thickness variation of the solder layer 13 is suppressed, and the target material / solder layer interface and the solder layer / backing material interface are suppressed. The position (time) at which the reflected wave is generated becomes stable, the influence of the reflected wave at the interface can be reliably suppressed, and defects can be detected with high accuracy.

Further, in the sputtering target 10 of the present embodiment, since the target material 11 and the backing material 12 have a cylindrical shape, the thickness of the solder layer 13 becomes relatively thick, but as described above, the target material 11 By selecting the material of the solder layer 13 so that the acoustic impedance of the solder layer 13 is within the above range according to the acoustic impedance of the backing material 12, the target material / solder layer interface and the solder layer / backing The peak intensity of the reflected wave at the material interface can be suppressed to a low level, and defects can be detected with high accuracy.

Further, in the sputtering target 10 of the present embodiment, the acoustic impedance of the solder layer 13 is 17.5 × 10 ⁶ kg / (m ² · s) or more and 24.3 × 10 ⁶ kg / (m ² · s) or less. Since it is within the range of, the difference in acoustic impedance between the target material 11 made of Cu and the backing material 12 made of stainless steel and the solder layer 13 can be reduced, and the backing with the target material 11 is performed by ultrasonic flaw detection. The state of bonding with the material 12 can be accurately inspected.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.
In the present embodiment, a cylindrical sputtering target has been described as an example, but a sputtering target having another shape may be used. Further, the description has been made assuming that the solder layer is composed of an In—Sn alloy, but the present invention is not limited to this, and the acoustic impedance of the solder layer is within the above range according to the acoustic impedance of the target material and the backing material. It suffices if it is set to be.

The result of the confirmation experiment which confirmed the action and effect of the sputtering target which concerns on this invention will be described.
The target material and backing material shown in Table 1 were joined using the solder material shown in Table 1 to manufacture various sputtering targets.
In the examples of the present invention and Comparative Examples 1-3, in order to adjust the thickness of the solder layer, a wire having the same diameter as the target thickness (for example, Cu, SUS, Ti, etc.) is used as a spacer and backed with the target material 11. It was inserted between the material 12 and the material 12. At this time, the number of wires to be inserted was set to 3 or more, and the wires were arranged so that the intervals between the wires were about the same.
On the other hand, in Comparative Example 4, two wires having the same diameter as the target thickness were inserted between the target material 11 and the backing material 12.

This sputtering target was placed in water, ultrasonic waves were oscillated from the surface of the target material toward the stacking direction of the target material, the solder layer and the backing material, and the presence or absence of defects was inspected by the peak intensity of the reflected wave. The evaluation results are shown in Table 2.

In Comparative Example 1-3 in which the acoustic impedance of the solder layer is out of the range of the present invention with respect to the acoustic impedance of the target material and the backing material, the interface between the target material / the solder layer and the interface between the solder layer / the backing material The S / N ratio was less than 2.00 in either one or both. Therefore, there is a possibility that the defect cannot be detected with high accuracy.
Further, when the standard deviation of the measured values at 10 points of the solder layer is σ, in _{Comparative Example 4 in which 3 × σ exceeds 0.2 × save} , the variation in the thickness of the solder layer is large, and ultrasonic waves are used. The reflection intensity of the solder became unstable and the measurement could not be performed.

On the other hand, the example of the present invention in which the acoustic impedance of the solder layer is within the range of the present invention with respect to the acoustic impedance of the target material and the backing material, and the thickness and variation of the solder layer are within the range of the present invention. The S / N ratio was 2.00 or more at both the target material / solder layer interface and the solder layer / backing material interface. As a result, it was confirmed that, according to the example of the present invention, it is possible to detect defects with high accuracy.

10 Sputtering target 11 Target material 12 Backing material 13 Solder layer

Claims (3)

A method for manufacturing a sputtering target having a solder layer between the target material and the backing material.
The target material is assumed to contain Cu or Ni, the backing material is composed of any of stainless steel, copper or copper alloy, and titanium alloy, and the solder layer contains In—Sn alloy.
^{The acoustic impedance of the solder layer is Z kg / (m 2} · s) with respect to the acoustic impedance X kg / (m ² · s) of the target material and the acoustic impedance Y kg / (m ² · s) of the backing material.
Z ≧ 0.5 × (X + Y) -26.3 × 10 ⁶
The ratio (S / N ratio) of the peak intensity of the reflected wave at the target material / solder layer interface and the reflected wave at the solder layer / backing material interface to the peak intensity of the reflected wave when a defect is present. ) Is 2.00 or more, the solder material is selected so that the difference in acoustic impedance between the target material and the backing material and the solder layer becomes small.
When forming the solder layer, three or more wires having the same diameter as the target thickness of the solder layer are inserted as spacers between the target material and the backing material.
_{When the average thickness save} of the solder layer is within the range of 0.75 mm or more and 2.0 mm or less, and the standard deviation of the measured values at 10 points of the solder layer is σ, 3 × σ is 0.2. A method for manufacturing a sputtering target, which comprises forming the solder layer so as to be within the range of × t _{ave or less.} The method for manufacturing a sputtering target according to claim 1, wherein the target material and the backing material have a cylindrical shape. The claim is characterized in that the acoustic impedance Z of the solder layer is in the range of 17.5 × 10 ⁶ kg / (m ² · s) or more and 24.3 × 10 ⁶ kg / (m ² · s) or less. 1 or the method for manufacturing a sputtering target according to claim 2.

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