SPUTTERING TARGET-BACKING PLATE ASSEMBLY

Abstract

A sputtering target-backing plate assembly obtained by bonding a sputtering target and a backing plate using a brazing material, wherein a braze bonding layer which bonds the sputtering target and the backing plate contains a material having thermal conductivity that is higher than that of the brazing material in an amount of 5 vol % or more and 50 vol % or less, and a thickness of the braze bonding layer is 100 m or more and 700 m or less. An object is to prevent the seepage of the brazing material while maintaining the thickness of the braze bonding layer.

Claims

1. A sputtering target-backing plate assembly obtained by bonding a sputtering target and a backing plate using a brazing material, wherein a braze bonding layer which bonds the sputtering target and the backing plate contains a material having thermal conductivity that is higher than that of the braze material in an amount of 5 vol % or more and 50 vol % or less, and a thickness of the braze bonding layer is 100 m or more and 700 m or less.

2. The sputtering target-backing plate assembly according to claim 1, wherein the material having high thermal conductivity is comprised of a metal powder having an average grain size (D.sub.50) of 1.0 m or more and 100 m or less.

3. The sputtering target-backing plate assembly according to claim 1, wherein the material having high thermal conductivity is comprised of a metal foil having a thickness of 20 m or more and 100 m or less.

4. The sputtering target-backing plate assembly according to claim 3, wherein the metal foil is inserted as a single layer between the brazing materials, or laminated alternately with the brazing material.

5. The sputtering target-backing plate assembly according to claim 4, wherein the metal foil is inserted within the brazing material in an island shape or a ring shape.

6. The sputtering target-backing plate assembly according to claim 5, wherein, when the metal foil is inserted as a single layer between the brazing materials, an area ratio of an area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 100% or less.

7. The sputtering target-backing plate assembly according to claim 5, wherein, when the metal foil is laminated alternately with the brazing material, an area ratio of a total area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 400% or less.

8. The sputtering target-backing plate assembly according to claim 4, wherein, when the metal foil is inserted as a single layer between the brazing materials, an area ratio of an area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 100% or less.

9. The sputtering target-backing plate assembly according to claim 4, wherein, when the metal foil is laminated alternately with the brazing material, an area ratio of a total area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 400% or less.

10. The sputtering target-backing plate assembly according to claim 3, wherein the metal foil is inserted within the brazing material in an island shape or a ring shape.

11. The sputtering target-backing plate assembly according to claim 10, wherein, when the metal foil is inserted as a single layer between the brazing materials, an area ratio of an area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 100% or less.

12. The sputtering target-backing plate assembly according to claim 10, wherein, when the metal foil is laminated alternately with the brazing material, an area ratio of a total area of one surface of the metal foil relative to an area of a bonding surface of the sputtering target is 50% or higher and 400% or less.

13. The sputtering target-backing plate assembly according to claim 1, wherein a diameter of the sputtering target is 420 mm or more.

14. The sputtering target-backing plate assembly according to claim 1, wherein the sputtering target is made from a material having a thermal expansion coefficient of 1.010.sup.6/K or higher and 1510.sup.6/K or less.

15. The sputtering target-backing plate assembly according to claim 1, wherein the material having high thermal conductivity is comprised of copper, silver, gold, or an alloy thereof.

16. The sputtering target-backing plate assembly according to claim 1, wherein the brazing material is comprised of indium or indium alloy.

17. The sputtering target-backing plate assembly according to claim 3, wherein a surface of the metal foil is embossed.

Description

DETAILED DESCRIPTION

[0023] When bonding a sputtering target having a low coefficient of thermal expansion to a backing plate via brazing bonding, the brazing material is sometimes applied thickly to prevent the warping of the target. Nevertheless, for instance, when using indium as the brazing material, since the thermal conductivity of indium is low at a 82 W/m.Math.K, when the brazing material is thick, there was a problem in that the cooling efficiency from the backing plate side is low, and the temperature of the sputtering target or the brazing material would tend to increase during sputtering.

[0024] In order to solve the foregoing problem, the present disclosure is based on a basic technical concept of introducing a material having high thermal conductivity into a brazing material which is used for bonding a sputtering target and a backing plate, and thereby improving the thermal conductivity while maintaining the buffer effect of a thick brazing material (braze bonding layer), reducing the temperature increase of the sputtering target and the brazing material during sputtering, and preventing the outflow of the brazing material. Note that, in this disclosure, since other materials are introduced into the brazing material, the overall bonding material between the sputtering target and the backing plate is referred to as a braze bonding layer.

[0025] The present disclosure is particularly effective in a sputtering target having a low coefficient of thermal expansion to which the brazing material needs to be applied thickly. In particular, the present disclosure is effective when the sputtering target is made from a material having a low coefficient of thermal expansion of 1510.sup.6/K or less relative to copper (coefficient of thermal expansion: 16.810.sup.6/K), copper alloy, or aluminum (coefficient of thermal expansion: 2310.sup.6/K), or aluminum alloy which are used as a general backing plate material. As that kind of materials, considered may be single elements such as Si (coefficient of thermal expansion: 2.610.sup.6/K) and Ge (coefficient of thermal expansion: 6.110.sup.6/K), or compounds of these elements and chalcogenide elements or compounds of other metals and chalcogenide elements (including oxides such as SiO.sub.2 and Al.sub.2O.sub.3, GST, etc.).

[0026] The thickness of the braze bonding layer is preferably set to 100 m or more and 700 m or less. If the thickness of the braze bonding layer is less than 100 m, it is not possible to maintain the buffer effect of the braze bonding layer, and the target tends to become warped during sputtering. Meanwhile, when the thickness of the braze bonding layer exceeds 700 m, heat will become accumulated in the brazing material during sputtering, and the risk of the brazing material melting will increase.

[0027] The present disclosure is characterized in containing a material having thermal conductivity that is higher than that of the brazing material, such as indium (82 W/m.Math.K) or tin (67 W/m.Math.K), in the braze bonding layer which bonds the sputtering target and the backing plate, and, consequently, since the thermal conductivity of the braze bonding layer will increase and the cooling efficiency is improved, it is possible to reduce the melting of the brazing material and prevent the outflow thereof in comparison to a case where only the brazing material is used. As a material having high thermal conductivity, for instance, copper (402 W/m.Math.K), silver (429 W/m.Math.K), gold (318 W/m.Math.K), or their alloys can be listed. Note that the values of thermal conductivity described above have all been compared at around room temperature. Moreover, the braze bonding layer preferably contains a material having high thermal conductivity in an amount of 5 vol % or higher and 50 vol % or less. When this amount is less than 5 vol %, there are cases where the effect of preventing the elution of the brazing material and the effect of suppressing the warping of the target after bonding cannot be obtained. Meanwhile, when this amount exceeds 50 vol %, there are cases where the adhesion ratio of the brazing material decreases.

[0028] As the methods of introducing the foregoing material having high thermal conductivity, there are 1) a method of adding a metal powder such as a copper powder or a silver powder, and 2) a method of introducing a flexible metal foil such as a copper foil or a silver foil. With either method, it is possible to increase the thermal conductivity of the braze bonding layer in comparison to a case where only the brazing material is used. In the method of 1) above, the average grain size D.sub.50 of the powder is preferably 1.0 m or more and 100 m or less. When the average grain size D.sub.50 is less than 1.0 m, the powders become aggregated and the uniform dispersion thereof becomes difficult. Meanwhile, when the average grain size D.sub.50 exceeds 100 m, the overlapping of grains will occur in the brazing material, and the adhesion ratio may decrease.

[0029] In the method of 2) above, a metal foil such as a silver foil or a copper foil may be inserted as a single layer between the brazing materials, or the brazing material and the foil may be laminated alternately (metal foils are inserted in the form of a laminae in the same manner as a mille-feuille). When the metal foil is inserted as a single layer, in addition to using a single foil, a plurality of foils may be used as a single layer. Similarly, when laminating the metal foils, a plurality of foils may be used within a single layer. For example, a plurality of foils in an island shape (any shape such as a circle or square may be used) or in a ring shape may be placed to increase the area ratio. When alternately laminating the brazing material and the metal foil, the part that comes into contact with the sputtering target and the backing plate will obviously include the brazing material for bonding the sputtering target and the backing plate. The thickness of the metal foil (1 layer) is preferably set to 20 m or more and 100 m or less. When the thickness of the metal foil is less than 20 m, the handling thereof becomes difficult. Meanwhile, when the thickness of the metal foil exceeds 100 m, the adhesion ratio of the brazing material may decrease.

[0030] Moreover, in the method of 2) above, when the metal foil is inserted as a single layer between the brazing materials, preferably, the area ratio of the area of the metal foil (one surface) relative to the area of the bonding surface of the sputtering target is 50% or higher and 100% or less. For instance, when the diameter of the sputtering target is 400 mm and one copper foil having a diameter of 360 mm is inserted, the area ratio will be 81% (=(180180)/(200200)100). In other words, when the diameter of the sputtering target is 400 mm, the area ratio being 50% means that the diameter of the copper foil is approximately 228 mm, and the area ratio being 100% means that the diameter of the foil is the same as the diameter of the sputtering target.

[0031] Meanwhile, in the method of 2) above, when the metal foil is laminated alternately with the brazing material between the brazing materials, preferably, the area ratio of the area of the metal foil (total area when a plurality of metal foils are inserted) relative to the area of the bonding surface of the sputtering target is 50% or higher and 400% or less. For instance, when foils are introduced in the following manner; namely, In layer 120 m/copper foil 70 m/In layer 120 m/copper foil 70 m/In layer 120 m, and the diameter of the sputtering target is set to 400 mm and the diameter of the copper foil is set to 360 mm, since the area ratio of one copper foil is 81%, when two copper foils are inserted in the manner described above, the area ratio of the total area will be 162%.

[0032] Moreover, in the method of 2) above, preferably, both surfaces of the metal foil have undergone surface treatment, and in particular embossing, which forms a regular concave-convex pattern, is preferably performed. It is thereby possible to improve the adhesion of the brazing material and the metal foil, and consequently improve the overall bonding strength of the braze bonding layer.

[0033] The brazing material may be any material that melts at a temperature that is lower than the melting point of the material configuring the sputtering target and the backing plate, and in particular In (indium), indium alloy, Sn (tin), or tin alloy is preferably used. However, the indium alloy or tin alloy described above, and indium or tin to which a copper or silver powder has been added, should be clearly differentiated. Moreover, the adhesion ratio can be increased by performing ultrasonic welder treatment or vapor deposition treatment after applying the brazing material to the sputtering target and the backing plate. While there is no particular limitation regarding the size of the sputtering target to which the present disclosure can be applied, since the problem of warping of the target becomes notable and the necessity of thickening the brazing material (braze bonding layer) will increase when the diameter of the sputtering target is 420 mm or more, the present disclosure is particularly effective in the foregoing case.

EXAMPLES

[0034] The present disclosure is now explained with reference to the following Examples and Comparative Examples. Note that the following Examples are merely illustrative, and the present disclosure shall in no way be limited thereby. In other words, the present disclosure is limited only by the scope of the claims, and various modifications other than the Examples are also covered by the present disclosure.

Example 1

Cu Powder 20 Vol %

[0035] An In brazing material, to which a copper powder having a grain size of 70 m was mixed therein in an amount of 20 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding was small with a convex of 0.18 mm, and the adhesion ratio based on ultrasonic flaw detection inspection was high at 99.7%, and adhesiveness was favorable. Next, as a simulation method of evaluating prolonged sputtering acceleratingly, the sputtering target side was heated for 3 minutes using a halogen lamp heater, and the backing plate was cooled at a water temperature of 20 C. to evaluate having or not having the elution of the brazing material. As a result, elution of the brazing material was not observed. The foregoing measurement of the warping of the sputtering target, measurement of the adhesion ratio, and elution evaluation of the brazing material were also performed in the same manner in the following Examples and Comparative Examples.

Example 2

Cu Powder 50 Vol %

[0036] An In brazing material, to which a copper powder having a grain size of 70 m was mixed therein in an amount of 50 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding was small with a convex of 0.15 mm, and the adhesion ratio was high at 99.4%, and adhesion was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 3

Cu Powder 50 Vol %, Thin Brazing Material

[0037] An In brazing material, to which a copper powder having a grain size of 70 m was mixed therein in an amount of 50 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 300 m. The warping of the target after the bonding was small with a convex of 0.24 mm, and the adhesion ratio was high at 98.1%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 4

Ag Powder 20 Vol %

[0038] An In brazing material, to which a silver powder having a grain size of 10 m was mixed therein in an amount of 20 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 300 m. The warping of the target after the bonding was small with a convex of 0.20 mm, and the adhesion ratio was high at 99.2%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 5

Fine Powder

[0039] An In brazing material, to which a copper powder having a grain size of 0.8 m was mixed therein in an amount of 20 vol %, was applied to a Si sputtering target (114.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding was small with a convex of 0.23 mm, and the adhesion ratio decreased to 96.6%. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 6

Large Grain Size Powder

[0040] An In brazing material, to which a copper powder having a grain size of 200 m was mixed therein in an amount of 20 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding increased to a convex of 0.38 mm, and the adhesion ratio decreased to 91.3%. Meanwhile, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed. Note that the foregoing warping amount and adhesion ratio are within an acceptable range.

Comparative Example 1

Only Brazing Material

[0041] Only an In brazing material was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding increased to a convex of 0.48 mm. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was observed.

Comparative Example 2

Copper Powder Ratio 5 vol % or less

[0042] An In brazing material, to which a copper powder having a grain size of 70 m was mixed therein in an amount of 3 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding increased to a convex of 0.40 mm. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was observed.

Comparative Example 3

Copper Powder Ratio 50 vol % or Higher

[0043] An In brazing material, to which a copper powder having a grain size of 70 m was mixed therein in an amount of 70 vol %, was applied to a Si sputtering target (444.7 mm) and an oxygen-free copper backing plate, and the target and the backing plate were thereby bonded. The thickness of the braze bonding layer was set to 500 m. The warping of the target after the bonding was small with a convex of 0.25 mm, but the adhesion ratio decreased to 89.5%. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed. However, the foregoing adhesion ratio is insufficient as the adhesion of the target and backing plate in order to be used as a target, and there is a possibility that the In brazing material will melt due to the deterioration in the cooling efficiency during sputtering, and cause the separation of the target.

[0044] The results of using a metal powder are summarized in Table 1.

TABLE-US-00001 TABLE 1 Thickness of braze Volume ratio Target warping Overview Detailed structure bonding layer (vol %) In seepage after bonding Adhesion rate Example 1 Cu powder 20 vol % Brazing material material + 500 um 20 vol % None 0.18 mm convex 99.7% copper powder (70 um) Example 2 Cu powder 50 vol % Brazing material material + 500 um 50 vol % None 0.15 mm convex 99.4% copper powder (70 um) Example 3 Cu powder 50 vol % + Brazing material material + 300 um 50 vol % None 0.24 mm convex 98.1% thin brazing material copper powder (70 um) Example 4 Ag powder 20 vol % Brazing material material + 300 um 20 vol % None 0.20 mm convex 99.2% silver powder (10 um) Example 5 Fine powder Brazing material material + 500 um 20 vol % None 0.23 mm convex 96.6% copper powder (0.8 um) Example 6 Large grain size Brazing material material + 500 um 20 vol % None 0.38 mm convex 91.3% powder copper powder (200 um) Comparative Only brazing material Only brazing material material 500 um 0 vol % Observed 0.48 mm convex 99.8% Example 1 Comparative Metal powder ratio Brazing material material + 500 um 3 vol % Observed 0.40 mm convex 99.5% Example 2 5 vol % or less copper powder (70 um) Comparative Metal powder ratio Brazing material material + 500 um 70 vol % None 0.25 mm convex 89.5% Example 3 50 vol % or more copper powder (70 um) Sputtering target material: Si; Brazing material: In; Backing plate material: OFC; Target shape: 444.7 mm

Example 7

Foil 2 Layers

[0045] A Si sputtering target (114.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 nun) was placed. A more spacer was disposed thereon and then a second copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 120 m, the foil material thickness (1 layer) was set to 70 m, and the braze bonding layer thickness was set to 500 m. The warping of the target after the bonding was small with a convex of 0.15 mm convex, and the adhesion ratio was high at 99.5%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 8

Foil 3 Layers

[0046] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 nun) was placed. A more spacer was disposed thereon and then a second copper foil was placed, another spacer was disposed thereon and then a third copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 80 m, the foil material thickness (1 layer) was set to 70 m, and the braze bonding layer thickness was set to 530 m. The warping of the target after the bonding was small with a convex of 0.09 mm convex, and the adhesion ratio was high at 99.3%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 9

Large Diameter Foil 2 Layers

[0047] A Si sputtering target (114.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (440 mm) was placed. A more spacer was disposed thereon and then a second copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 120 m, the foil material thickness (1 layer) was set to 70 m, and the braze bonding layer thickness was set to 500 m. The warping of the target after the bonding was small with a convex of 0.13 mm convex, and the adhesion ratio was high at 98.1%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 10

Foil 4 Layers

[0048] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 mm) was placed. A more spacer was disposed thereon and then a second copper foil was placed, another spacer was disposed thereon and then a third copper foil was placed, another spacer was disposed thereon and then a fourth copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 60 m, the foil material thickness (1 layer) was set to 35 m, and the braze bonding layer thickness was set to 440 m. The warping of the target after the bonding was small with a convex of 0.09 mm convex, and the adhesion ratio was high at 98.3%, and adhesiveness was favorable. Next, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed.

Example 11

Thick Foil

[0049] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 mm) was placed. A more spacer was disposed thereon and then a second copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 90 m, the foil material thickness (1 layer) was set to 105 m, and the braze bonding layer thickness was set to 480 m. The warping of the target after the bonding was small with a convex of 0.17 mm convex, and the adhesion ratio decreased to 94.5%. Meanwhile, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was not observed. Note that the foregoing adhesion ratio is within an acceptable range.

Comparative Example 4

Foil Area Ratio Less Than 50%

[0050] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and a copper foil were prepared, a spacer of an intended thickness was thereafter disposed, and a copper foil (400 mm) was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 210 m, the foil material thickness (1 layer) was set to 70 m, and the braze bonding layer thickness was set to 590 m. The warping of the target after the bonding was large with a convex of 0.45 mm convex. As a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was observed.

Comparative Example 5

Thin Foil

[0051] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 mm) was placed. A more spacer was disposed thereon and then a second copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 160 m, the foil material thickness (1 layer) was set to 9 m, and the braze bonding layer thickness was set to 498 m. The warping of the target after the bonding was large with a convex of 0.46 mm convex. As a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was observed.

Comparative Example 6

Thick Braze Bonding Layer

[0052] A Si sputtering target (444.7 mm), an oxygen-free copper backing plate, and copper foils were prepared, a spacer of an intended thickness was thereafter disposed, and a first copper foil (400 mm) was placed. A more spacer was disposed thereon and then a second copper foil was placed, another spacer was disposed thereon and then a third copper foil was placed, and a molten brazing material was thereafter poured therein to bond the target and the backing plate. The brazing material thickness (1 layer) was set to 120 m, the foil material thickness (1 layer) was set to 105 m, and the braze bonding layer thickness was set to 795 m. The warping of the target after the bonding was small with a convex of 0.25 mm convex. Meanwhile, as a result of conducting an elution evaluation test of the foregoing brazing material, elution of the brazing material was observed.

[0053] The results of using a metal foil are summarized in Table 2.

TABLE-US-00002 TABLE 2 Thickness of braze Overview Detailed structure bonding layer Example 7 Foil 2 layers Brazing material + copper foil + 500 um brazing material + copper foil + brazing material Example 8 Foil 3 layers Brazing material + copper foil + 530 um brazing material + copper foil + brazing material + copper foil + brazing material Example 9 Large diameter foil 2 layers brazing material + copper foil + 500 um brazing material + copper foil + brazing material Example 10 Foil 4 layers Brazing material + copper foil + brazing material + 440 um copper foil + brazing material + copper foil + brazing material + copper foil + brazing material Example 11 Thick foil - Reduced Brazing material + copper foil + 480 um adhesion rate brazing material + copper foil + brazing material Comparative Foil area ratio 50% or less Brazing material + copper foil + brazing material 590 um Example 4 Comparative Thin foil - Reduced warping Brazing material + copper foil + 498 um Example 5 suppression effect brazing material + copper foil + brazing material Comparative Thick brazing material Brazing material + copper foil + 795 um Example 6 (800 um) brazing material + copper foil + brazing material + copper foil + brazing material Brazing Volume material Foil material ratio thickness Foil thickness Target warping (vol %) (1 layer) diameter (1 layer) Area ratio In seepage after bondng Adhesion rate Example 7 23% 120 um 400 70 um 162% None 0.15 mm convex 99.5% Example 8 32% 80 um 400 70 um 243% None 0.09 mm convex 99.3% Example 9 27% 120 um 440 70 um 196% None 0.13 mm convex 98.1% Example 10 31% 60 um 440 35 um 324% None 0.09 mm convex 98.3% Example 11 43% 90 um 400 105 um 162% None 0.17 mm convex 94.5% Comparative 2% 210 um 200 70 um 20.2% Observed 0.45 mm convex 99.8% Example 4 Comparative 3% 160 um 400 9 um 162% Observed 0.46 mm convex 97.2% Example 5 Comparative 32% 120 um 400 105 um 243% Observed 0.25 mm convex 97.5% Example 6 Sputtering target material: Si; Brazing material: In; Backing plate material: OFC, Target shape: 444.7 mm

[0054] Since the overall braze bonding layer has high thermal conductivity and the cooling efficiency is improved in the sputtering target-backing plate assembly of the present disclosure, the present disclosure yields a superior effect of being able to reduce the melting of the brazing material, and consequently prevent the outflow of the brazing material from the bonded interface of the sputtering target and the backing plate. The present disclosure is particularly effective upon bonding a sputtering target made from a semiconductor material such as silicon (Si) or germanium (Ge), or an oxide material such as PZT (Pb(Zr, Ti)O.sub.3), HfO.sub.2, La.sub.2O.sub.3, or MgO.