JP2007021580A - Solder alloy for producing sputtering target, and sputtering target using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solder alloy used for producing a sputtering target by joining a target material and a backing plate made of Cu or made of a Cu alloy and having high joining strength even at high temperature, and in which the erosion amount of the backing plate caused by the joining is extremely small, and to provide a sputtering target produced using the same. <P>SOLUTION: The solder alloy is used for joining a target material and a backing plate made of Cu or made of a Cu alloy upon the production of a sputtering target, and comprises 3 to 9 wt.% Zn, and the balance Sn with inevitable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solder alloy for producing a sputtering target and a sputtering target using the same. More specifically, the present invention is used when a sputtering target is manufactured by bonding a target material and a backing plate, has high bonding strength even at high temperatures, and is extremely eroded against a Cu or Cu alloy backing plate. The present invention relates to a small amount of a solder alloy and a sputtering target manufactured using the same.

Conventionally, a sputtering method is known as one of thin film forming methods.
Since the target material used for sputtering continues to be bombarded by high energy particles such as ions during sputtering, heat accumulates inside and becomes a high temperature. For this reason, a cooling plate called a backing plate made of a material having good thermal conductivity, usually Cu or Cu alloy, is joined to the target material, and the heat of the target material is released by cooling the backing plate.

The target material and the backing plate are bonded via a bonding material or diffusion bonding, but the former method using a bonding material is more common.
As a bonding material, conventionally, In which has a low melting point and In alloy containing In as a main component have been widely used (see Patent Document 1).

  However, the bonding material made of In or In alloy has a problem that it cannot cope with the increase in the area and thickness of the target material in accordance with the recent demand for larger mother glass in the flat panel display industry. Specifically, the problem of the target material peeling off from the backing plate due to the warpage of the target material itself due to the increase in the area of the target material, as well as the temperature rise of the target material due to the increase in input power density during sputtering, and When the bonding material layer becomes hot due to deterioration of cooling efficiency during sputtering due to the thickening of the target material, there is a problem that the target material peels from the backing plate due to insufficient bonding strength of the bonding material. Yes. In addition, there is a problem that In is disadvantageous in terms of cost because the price is soaring.

  In order to solve such a problem, a method of joining using pure Sn as a joining material is generally performed. However, pure Sn reacts with Cu or Cu alloy, which is a backing plate material, and erodes the backing plate.

  In general, the backing plate is repeatedly used by peeling off the used target material that has been joined and then joining a new target material. However, if the backing plate is eroded each time it is joined, the thickness of the backing plate gradually increases. It becomes thinner and weakens its own strength. As a result, warping due to strength reduction is caused, and finally, problems such as warping and cracking of the bonded target material occur. Moreover, since many backing plates are provided with cooling water passages therein, there is a risk of water leakage due to a decrease in strength or warping.

  In order to deal with such a problem of erosion of the backing plate, a method of plating the backing plate with Ni is known. However, since this method also erodes the plated Ni, it is necessary to periodically apply the Ni plating to repeatedly use the backing plate, which is not a preferable solution in terms of production efficiency and cost.

Patent Document 2 describes a sputtering target joined with a solder alloy, which is made of In (30 to 60% by weight) -Sn (30 to 60% by weight) -Zn (0.1 to 10% by weight). Has been. However, when In is contained in an amount of 27% by weight or more as described above, β-In ₃ Sn, which is an intermetallic compound, is generated and the melting point is lowered, leading to insufficient bonding strength at high temperatures,
The problem of peeling between the target material and the backing plate cannot be solved.

  Patent Document 3 describes a sputtering target in which two bonding material layers are provided between a target material and a chromium copper backing plate. Among these, Sn (90 to 70 wt%)-Zn (10 to 30 wt%) alloy is described as the bonding material of the first bonding material layer that contacts the target material, and the second bonding that contacts the backing plate. An In—Au—Sn alloy is described as a bonding material for the material layer. However, since the first bonding material contains a large amount of Zn, there is a problem that an oxide is easily generated and the bonding strength is lowered, and further, the second bonding material contains 1000 ppm or more of Pb. Therefore, it cannot be used in practice because it has a large impact on the environment and is against legal regulations such as the RoHS directive.

  Patent Document 4 describes a sputtering target in which an Al-based target and an Al-based backing plate are joined with an Sn—Pb—Ag solder alloy for the purpose of providing a sputtering target that is unlikely to peel off. However, since the solder alloy contains 1000 ppm or more of Pb, it cannot be actually used for the same reason as described above.

Patent Document 5 discloses Al (0.01 to 3.0 wt%)-In (0.1 to 50 wt%)-Ag (0.1 to 6.0 wt%)-Cu (0 to 6.0). A lead-free solder consisting of (wt%)-Zn (0-10.0 wt%)-Sn (balance) is described. As described above, multi-component (ternary, quaternary, or even ternary or higher) alloys are generally used as lead-free solders for electronic components such as printed circuit boards. It is necessary to do this, and costs such as equipment costs. For example, in the case of Patent Document 5, facilities such as a high-temperature furnace and Ag raw material costs for melting Ag having a melting point of 962 ° C. without segregation are required. Further, when these solder alloys are used as a bonding material for bonding a target material having a large area (for example, 1.5 m square or more), solder composition segregation and strength unevenness easily occur in the bonding surface. There is a problem. Also, depending on the content of Ag or In in the solder alloy, Ag and Cu contained in the backing plate react to generate an intermetallic compound to reduce the bonding strength, or In and Sn react to react with the intermetallic compound. (For example, β-In ₃ Sn) is generated to lower the melting point, and the bonding strength at high temperature is insufficient, so that the problem of peeling between the target material and the backing plate cannot be solved.

  Patent Document 6 describes that Sn—Zn (9 wt%) alloy is known as a lead-free solder for electronic components for printed circuit boards and the like, and Zn (3 to 5 wt%) — Bi ( A solder alloy composed of 10 to 23% by weight) -Sn (remainder) has been proposed. However, these are lead-free solders for electronic parts such as printed circuit boards, and there is no description about a bonding material used for manufacturing a sputtering target. Further, when the latter amount of Bi is added, the melting point of the solder is remarkably lowered and the bonding strength at high temperature is insufficient, so that the problem of peeling between the target material and the backing plate cannot be solved.

  Patent Document 7 discloses a lead-free solder alloy composed of Sn (85 to 92% by weight) -Ag (1 to 6% by weight) -In (4 to 10% by weight), and Patent Document 8 describes Sn (92 A lead-free solder alloy consisting of -97 wt%)-Ag (3-6 wt%)-Cu (0.1-2.0 wt%) is described. However, such a composition containing no Zn cannot solve the problem of erosion of the Cu or Cu alloy backing plate. Furthermore, in the said composition, since Ag is contained 2000ppm or more, Ag and Cu contained in a backing plate react, produce | generate an intermetallic compound, and there exists a possibility that joining strength may fall.

  Patent Document 9 describes that a lead-free solder of Sn (91.2% by weight) -Zn (8.8% by weight) is known. This is a solder for optical devices and microelectronic devices. There is no description of a bonding material used for manufacturing a sputtering target, which is a lead-free solder used for attachment.

  Patent Document 10 describes that when a sputtering target is manufactured, a target material is bonded to a backing plate made of Cu or the like with a low melting point brazing material (Sn—Zn solder or the like). However, no specific composition of the Sn—Zn solder is described.

Conventionally, when the wettability between the target material and the bonding material is poor, a Cu film or a Ni—Cu alloy film called a backing film is formed on the bonding surface of the target material by sputtering or vapor deposition to increase the wettability. However, such a method has a problem that a film forming apparatus is required and costs are increased, and the number of processes is increased, resulting in a decrease in productivity.
JP-A-7-48667 JP-A-7-227690 JP-A-8-269704 Japanese Patent Laid-Open No. 10-46327 Japanese Unexamined Patent Publication No. 2000-141078 JP-A-8-164495 JP-A-8-87591 Japanese Patent Laid-Open No. 9-326554 JP-A-8-118067 Japanese Patent Laid-Open No. 2001-340959

  The present invention is used when a sputtering target is manufactured by bonding a target material and a Cu or Cu alloy backing plate, and has a high bonding strength even at high temperatures, and the backing plate erosion due to bonding is extremely small. It is an object of the present invention to provide a solder alloy and a sputtering target manufactured using the same.

  Furthermore, another object of the present invention is to provide a solder alloy and a sputtering target manufactured using the same that have excellent wettability with a target material to the extent that a backing film is unnecessary.

  As a result of intensive studies in view of the above circumstances, the present inventors join a binary solder alloy containing Sn as a main component and containing a specific amount of Zn to a target material and a Cu or Cu alloy backing plate. When used as a bonding material, the bonding strength can be maintained high even when the temperature of the bonding material layer rises under severe sputtering conditions, and the target material can be prevented from peeling from the backing plate. According to this, it was found that the amount of erosion of the backing plate can be remarkably reduced and the wettability with the target material can be improved, and the present invention has been completed.

That is, the present invention relates to the following matters.
The solder alloy according to the present invention is a solder alloy used for joining a target material and a Cu or Cu alloy backing plate in the production of a sputtering target, and contains 3 to 9 wt% of Zn, with the balance being Sn and It consists of inevitable impurities.

In the present invention, the target material is preferably made of a metal or an alloy, and more preferably made of Al or an Al alloy.
The sputtering target according to the present invention is obtained by joining the target material and a Cu or Cu alloy backing plate using the solder alloy.

  According to the solder alloy of the present invention, since a bonding material layer having high bonding strength can be formed even at high temperatures, it is possible to prevent the target material from peeling off from the backing plate even under severe sputtering conditions. The amount of Cu erosion of the plate can be significantly reduced, and strength deterioration due to repeated use of the backing plate can be prevented.

  In addition, the solder alloy of the present invention has excellent wettability with the target material to the extent that no backing film is required, so the equipment and processes necessary for producing the backing film can be omitted, greatly increasing the productivity of the sputtering target. It can be improved.

  Further, according to the sputtering target of the present invention, it is possible to stably form a thin film with a large area in accordance with a request for increasing the size of the mother glass.

Hereinafter, the present invention will be specifically described.
<Solder alloy for sputtering target production>
The solder alloy of the present invention is a bonding material used for bonding a target material and a Cu or Cu alloy backing plate in the production of a sputtering target, and contains Zn in an amount of 3 to 9% by weight, and the balance Consists of Sn and inevitable impurities. Here, the unavoidable impurities mean a very small amount of elements other than Zn and Sn that are inevitably contained in the alloy. In other words, the solder alloy of the present invention substantially consists of Sn and Zn.

Since the solder alloy contains Sn as a main component, high bonding strength can be maintained even at high temperatures. Specifically, the bonding strength at 150 ° C. when the target material and a Cu or Cu alloy backing plate are bonded using the solder alloy is 2.5 kgf / mm ² or more, preferably 3.0 kgf / mm. Can reach ² or more. In this case, the upper limit value of the bonding strength is not particularly limited. Since the solder alloy has such a high bonding strength at a high temperature, after bonding the target material and a Cu or Cu alloy backing plate using the solder alloy, the bonding material layer is formed under severe sputtering conditions. Even when the temperature rises, the target material can be prevented from peeling from the backing plate.

  Further, since the solder alloy contains Zn in an amount within the above specific range, the reaction between Sn in the solder alloy and Cu, which is a main element constituting the backing plate, is suppressed, and bonding is performed. The amount of erosion of the backing plate at the time can be remarkably reduced, the melting point of the solder alloy can be adjusted to a preferable range, and the wettability with the target material can be improved.

  When the Zn content of the solder alloy is less than the above lower limit value, the amount of Cu erosion of the backing plate may increase at the time of joining, and the wettability with the target material, particularly the Al target material, tends to decrease. is there. On the other hand, when the Zn content exceeds the above upper limit, oxides are likely to be generated, and the bonding strength tends to be reduced.

As a material of the backing plate to which the solder alloy of the present invention can be applied as a bonding material, Cu and Cu alloy are preferable, and Cu is more preferable, since the wettability with the solder alloy is good and the bonding strength is particularly high. Examples of the Cu alloy include alloys containing Cu as a main component, such as chromium copper. According to the solder alloy of the present invention, when the Cu or Cu alloy backing plate and the target material are joined with the solder alloy, the amount of Cu erosion of the backing plate can be significantly reduced. It is possible to prevent strength deterioration due to

  The melting point of the solder alloy is desirably 198 to 220 ° C. (the eutectic point of the Sn—Zn alloy is 198 ° C.). When the melting point of the solder alloy exceeds 220 ° C., the oxidation of the solder alloy and the backing plate is promoted, and there is a fear that the bonding strength is lowered, and the workability cannot be ensured due to the high temperature, and the productivity and the yield are lowered.

  The material of the target material to which the solder alloy of the present invention can be applied as a bonding material is not particularly limited, but specifically, any one of Al, Ti, Mo, Ta, Nb, Cu, Cr, and Ag Or an alloy containing at least one of these metals as a main component.

  Examples of the alloy include Al alloys such as Al—Ni alloys, Al—Nd alloys, Al—Cu alloys, and Al—Ti alloys; Ti alloys such as Ti—W alloys; Mo alloys such as Mo—W alloys; Ag -Ag alloys such as Pd alloy and Ag-Au alloy; Cu alloys such as Cu-Ni alloy; Cr alloys such as Cr-Ni alloy. These alloy compositions can be appropriately determined according to the composition of the thin film to be obtained by sputtering, and are not particularly limited.

  Among these, an Al target material or an Al alloy target material is preferable from the viewpoint that the temperature easily rises when a large amount of power is applied by sputtering and the effects of the present invention can be more effectively exhibited. In general, when In or Sn is used as a bonding material for bonding such Al or Al alloy target materials, since the wettability with the target material is poor, the bonding surface of the target material is called a backing film. A method of forming a film or a Ni—Cu alloy film by sputtering or vapor deposition to ensure wettability has been adopted. However, such a method is not desirable because it requires a film forming apparatus and is costly, and also increases the number of steps, which reduces productivity.

  On the other hand, the solder alloy of the present invention has good wettability even when joining Al or Al alloy target materials, so it is not particularly necessary to form the backing film, which contributes to cost reduction and productivity improvement. be able to.

  The solder alloy of the present invention can be obtained by measuring, adding, stirring, mixing, heating, melting, cooling, and the like by a known method so that each component described above is included in the above amount, and its manufacture The method is not particularly limited.

<Sputtering target>
The sputtering target of this invention can be manufactured by joining the target material and backing plate which were mentioned above through the joining material layer formed from the solder alloy of this invention by a normal method.

  The shape of the target material and the backing plate is not particularly limited as long as their joint surfaces are substantially parallel to each other. In addition, as needed, in order to improve the wettability with a solder alloy to the joint surface of the said target material, you may perform a roughening process by a well-known method.

  Specifically, for example, the joint surface of the target material is processed by a milling machine, a lathe, a surface grinder, etc., subjected to a roughening treatment as necessary, and then degreased by washing with an organic solvent or the like. In a state where the target material is heated to the melting point of the solder alloy or higher, the solder alloy is applied to the bonding surface of the target material by dipping to form a bonding material layer, and the backing plate is similarly degreased to obtain the melting point of the solder alloy. By heating as described above, these bonding surfaces may be combined with each other via a bonding material layer and appropriately pressed. Although the pressure at the time of pressurization is not specifically limited, Usually, it is good in it being 0.0001-0.1 MPa with respect to a target area.

  In addition, when necessary, a bonding material layer was formed on the bonding surface of the target material in the same manner, and a solder alloy was applied to the bonding surface of the degreasing and heated backing plate in the same manner to form a bonding material layer. Thereafter, these bonded surfaces may be combined and pressed together with a bonding material layer in a state heated to the melting point of the solder alloy or higher.

  The bonding material layer of the sputtering target obtained in this manner usually has a thickness of 2 mm or less, preferably 0.1 to 1 mm, considering the resistance of the solder alloy. Further, the obtained sputtering target may be cooled to room temperature and then subjected to straightening finishing.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

[Examples 1 and 2, Comparative Examples 1 to 6]
Using Sn (purity 99.99%) and Zn (purity 99.99%) as raw materials, these are Sn /
Sn—Zn solder alloys containing Zn (wt%) = 97/3 and 91/9 (referred to as samples No. 1 and No. 2 in that order) were prepared.

  As a comparative control, Sn—Zn solder alloy containing the same raw material at a ratio of Sn / Zn (wt%) = 100/0, 99/1, 90/10, 85/15 (referred to as sample Nos. 3 to 6) Was prepared.

Further, as a comparative control, a solder alloy containing In (Purity 99.99%) and Sn (Purity 99.99%) as raw materials at a ratio of In / Sn (wt%) 100/0 and 15/85 ( Samples No. 7 and 8) were prepared in this order.

Using the obtained sample Nos. 1 to 8, the following methods were used to (1) melting point, (2) temperature dependence of bonding strength, (3) erosion amount of the backing plate (Cu), and (4) Al target The wettability with the material was evaluated.

The evaluation results are shown in Table 1.
(1) Melting point measurement method For each of the above sample Nos. 1-8, endothermic reaction peaks when heated to 300 ° C with a differential thermal analyzer TG-DTA2000S (manufactured by MAC Science) at a heating rate of 20 ° C / hour. The value was measured, and the temperature of the peak value was taken as the melting point.

(2) Measuring method of bonding strength Using the above sample Nos. 1 to 8, a φ10mm x 50mm cylindrical Al target material without a backing film and a 20mm x 20mm x 5mmt Cu backing plate were joined. The bonding strength at room temperature (23 ° C.) was measured using a tensile test apparatus Autograph AGS-500B (manufactured by Shimadzu Corporation). Further, the vicinity of the joint was heated with a Heating Gun (manufactured by Hakuko Co., Ltd.) while measuring the temperature with a thermocouple, and the joint strength at the time of temperature rise (60, 90, 120, 150 ° C.) was also measured in the same manner.

(3) Measuring method of erosion amount of backing plate (Cu) Each of the above sample Nos. 1 to 8 was primed using an ultrasonic soldering iron in a Cu backing plate 50 × 50 mm □ heated to 260 ° C. on a hot plate. . After undercoating, the solder alloy on the backing plate was scraped with a silicon rubber brush, and the scraped solder alloy was analyzed using ICP (SPS5100; manufactured by SII Nano Technology) to quantify the amount of Cu.

(4) Evaluation method of wettability with Al target material Sample Nos. 1 to 8 were each heated for 10 seconds in an Al target material 50 × 50 mm □ heated to 260 ° C. on a hot plate using an ultrasonic soldering iron. Primed. Next, the Al target material was once cooled to room temperature and heated again to 260 ° C., and then the solder alloy on the Al target material was scraped with a silicon rubber brush. Then, visually observe whether the solder alloy remains uniformly on one side on the Al target material without peeling off, the wettability is good, the solder alloy remains uniformly on one side, and what is not peeled off is ○ The case where the wettability was poor and the solder alloy was peeled off was evaluated as x.

From Table 1, Examples 1 and 2 (Sample Nos. 1 and 2) are Comparative Examples 2 to 6 (Sample Nos. 3 to 8).
), The bonding strength at high temperatures is high, the amount of Cu erosion from the backing plate is significantly reduced, and the wettability with the Al target material is also good.

Moreover, it turns out that Example 1 and 2 (sample No. 1, 2) have the melting | fusing point in the preferable range, when raising the efficiency of a sputtering target manufacturing operation.
[Examples 3 to 17]
Using the solder alloy of sample No. 2 (Sn / Zn (weight%) = 91/9) of Example 2 above, various target materials (Al alloy, Ti, Ti, φ10 mm × 50 mm) without a backing film Alloy, Mo, Mo alloy, Ta, Si, Nb, Cu, Cr, Ag, Ag alloy) and a 20 mm x 20 mm x 5 mmt Cu backing plate are joined together, and tensile test equipment Autograph AGS
The bonding strength at room temperature (23 ° C.) was measured using -500B (manufactured by Shimadzu Corporation). Further, the vicinity of the joint was heated with a Heating Gun (manufactured by Hakuko) while measuring the temperature with a thermocouple, and the joint strength at the time of temperature rise (60, 90, 120, 150 ° C.) was also measured.

The results are shown in Table 2.
In addition, when the amount of erosion of each backing plate (Cu) was measured by the same method as in Example 2, it was almost the same as the result of Example 2.

  From Table 2, when the target material and the Cu backing plate are bonded using the solder alloy of the present invention, the bonding strength at high temperature is maintained high regardless of the type of the target material. Recognize.

Claims (4)

  A solder alloy used for joining a target material and a Cu or Cu alloy backing plate in the production of a sputtering target, comprising 3 to 9% by weight of Zn, with the remainder consisting of Sn and inevitable impurities Solder alloy.   The solder alloy according to claim 1, wherein the target material is made of a metal or an alloy.   The solder alloy according to claim 1, wherein the target material is made of Al or an Al alloy.   A sputtering target obtained by joining a target material and a Cu or Cu alloy backing plate using the solder alloy according to claim 1.