JP4560170B2 - Solid phase diffusion bonding sputtering target assembly and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a solid phase diffusion bonded sputtering target assembly, in particular, a target material constituting a cathode used in a sputtering apparatus for forming a thin film and a backing plate material as a supporting member thereof by solid phase diffusion bonding. The present invention relates to a method for manufacturing an integrated target assembly.
[0002]
[Prior art]
The sputtering target serves as a sputtering source for forming a thin film on a substrate when manufacturing various thin film devices including a semiconductor. In the case of a semiconductor, the shape is mostly a disk-like plate. Sputtering targets are usually used in the state of a target assembly integrated with a supporting member called a backing plate for the purpose of supporting and cooling the target material. When the target assembly is attached to the sputtering equipment and power is applied, the target surface will rise in temperature due to the heat of the load, but the backing plate side will be cooled by bringing cooling water into contact with the back surface of the backing plate, for example. The heat is removed and the temperature rise on the target surface is suppressed. As the backing plate material, metals and alloys such as oxygen-free copper, copper alloy, aluminum, aluminum alloy, titanium, and titanium alloy are used.
[0003]
Conventionally, as one method for joining a target material and a backing plate material, a brazing method using a low melting point brazing material such as In or Sn alloy or a high melting point brazing material has been performed. However, at high power loads for the purpose of improving throughput (increasing the deposition rate during sputtering), the temperature of the target material rises due to heat generation due to large currents despite the cooling of the backing plate side. As a result, a rise in the temperature at the joining interface is unavoidable, resulting in a reduction in joining strength due to the rise in temperature, and a problem such as peeling of the target material due to melting of the brazing material. For this reason, depending on the target material, a transition to an integrated joining method that does not use a brazing material is progressing.
[0004]
This integrated bonding method is a method of bonding in the expectation of formation of an intermetallic compound or a eutectic alloy by diffusion of atoms between bonding materials. That is, (1) a diffusion bonding method in which a bonding surface between a target material and a backing plate material is machined to a predetermined surface roughness, and both surfaces are heated and pressed together, or (2) the same as (1) above The mating surface may be machined to a predetermined surface roughness as described above, but a bonding aid called an insert material is sandwiched between the mating surfaces, and a diffusion bonding method using an insert material that heats and pressurizes in that state, etc. There is.
[0005]
For example, Japanese Patent Laid-Open No. 1-283367 (Japanese Patent No. 283356) discloses that “a target body made of metal and a backing plate made of metal are manufactured separately, and these are directly pressed without using a bonding material. Technology is described. Explosive pressure welding method and seam welding method are shown as examples, and further, good bonding strength is obtained, and hot welding is performed by hot roll rolling method and diffusion bonding method. The result of the case is shown. In this technique, the joint surface is buffed.
[0006]
As another direct bonding method, Japanese Patent Laid-Open No. 9-143704 discloses that “a titanium target material and an aluminum backing plate material are brought into contact with each other and diffusion bonding is performed by hydrostatic pressing under conditions of 300 to 450 ° C. and a pressure of 50 to 200 MPa. Technology "is described. In this case, the bonding strength is obtained by performing diffusion bonding using a surface roughened with 6S to 12S (ie, corresponding to a surface roughness of 6 to 12 μm) on the surface to be bonded to the backing plate material of the titanium target material. Is described as increasing.
[0007]
In addition, as a joining method using an insert material, Japanese Patent Laid-Open No. 6-108246 discloses a method for obtaining a “target assembly in which a target material, an insert material, and a backing plate material each have a solid phase diffusion joining interface”. Has been. In this case, when an insert material made of Ag, Cu, Ni or the like is used and solid phase diffusion bonding is performed at a temperature of 200 to 600 ° C. and a load of 0.1 to 20 kg / mm ² , a desired assembly is obtained. In the embodiment, an assembly is obtained by joining a Ti target material and an oxygen-free copper backing plate under the conditions of a temperature of 250 ° C. and a load load of 8 kg / mm ² using 100 μm Ag foil as an insert material. It has gained.
[0008]
[Problems to be solved by the invention]
Each of the above conventional techniques is partially useful. However, in the case of Japanese Patent Laid-Open No. 1-283367 (Patent No. 2831356), when the bonding temperature is lowered (450 ° C.), the bonding strength of the target obtained is There is a problem that it drops rapidly.
When this conventional diffusion bonding method was applied to a combination of Ti (target material) / Al (backing plate material) and a bonding test was performed, a practical load was applied under the condition of a bonding temperature of 450 ° C. The target obtained with the pressure and time had a bonding strength of 5 to 8 kg / mm ² , the fracture surface was the bonding interface itself, and the bonding soundness was poor.
[0009]
In the case of Japanese Patent Laid-Open No. 9-143704, there is a problem that material deformation occurs due to a heavy load, and there is also a problem that the bonding strength of the object does not increase. In other words, although the conditions for enabling bonding under low temperature conditions are disclosed, excessive loads and long bonding times at low temperatures are unavoidable, and if a load higher than this is applied, the target shape will be deformed. There is a problem of end. Moreover, in the Example which performed the roughening process, the joined body is obtained on the joining conditions of 140 Mpa and 400 hours at 400 degreeC, and the joining strength in this case is only less than 10.0 kg / mm < ² >. .
[0010]
Further, there is a problem that an assembly with high bonding strength cannot be obtained by inserting an insert material as disclosed in JP-A-6-108246. The joint strength of the assembly is only described as 6 kg / mm ² (shear strength).
[0011]
Although there are various known techniques for joining the target material and the backing plate material, including those described above, for example, diffusion bonding between Ti (target material) and Al (backing plate material) has sufficient joint strength. That is, in order to obtain bonding sound, it is necessary that sufficient atomic diffusion occurs at the interface. This is because a bonding strength of 10 kg / mm ² or more can be obtained.
[0012]
In the present invention, when the target material and the backing plate material are overlapped and diffusion-bonded, the surfaces thereof are smoothed to increase the contact area of the joint surface between the two materials, and the target material and the backing plate material. It is an object of the present invention to provide a sputtering target assembly and a method for manufacturing the same.
[0013]
[Means for Solving the Problems]
In order to increase the contact (adhesion) area of the bonding material among the various bonding conditions in diffusion bonding, the present inventors fill the surface recess with fine powder having a specific particle size range, It has been found that when the target material and the backing plate material are diffusion bonded, the bonding strength is improved, and the present invention has been completed.
[0014]
In the sputtering target assembly manufacturing method of the present invention, when a target material and a backing plate material that is a supporting member thereof are diffusion bonded, a dent on at least one of the joining surfaces of both materials to be superimposed is filled with fine powder, After smoothing and widening the contact surface when the two materials are superposed, diffusion bonding is performed by heating and pressing to obtain a target assembly having a solid phase diffusion bonding interface.
[0015]
The titanium target material used as a target material, aluminum or aluminum alloy backing plate material used as the backing plate material, Ag as a finely divided powder, Ru with fines Cu or Ni. Above recess filled with fine powder of at least one of the bonding surfaces of the wood overlaying, surface roughness 3μm or less. If the thickness exceeds 3 μm, the resulting target assembly has low bonding strength, which is not practical. You use a less average grain size 1.0μm as fines. When the average particle size exceeds 1.0 μm, when the surface roughness of the joint surface is 3 μm or less, there is a problem in filling the recess of the joint surface, and since the joint strength of the obtained target assembly is low, it is not practical. Absent. The particle size range of the fine powder can vary depending on the degree of surface roughness of the joint surface. In the case of fine powder, the numerical value indicates an average particle size, and the particle size distribution is before and after the average particle size, but it is not preferable to mix particles having a particle size of 3 μm or more as large particles.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
When the target material made of metal and the backing plate material made of metal are overlapped and diffusion bonded, the main bonding conditions are the surface roughness and surface cleanliness requirements of the bonded surface before bonding, At the time of bonding, it is desirable that requirements such as atmospheric conditions (degree of vacuum, reactive harmful impurity gas partial pressure), heating temperature and heating holding time, and applied pressure are within desired ranges. Of these requirements, the higher the surface cleanliness, the better. Since diffusion bonding utilizes the phenomenon of diffusion of atoms between bonding materials on the bonding surface, it is not preferable that impurities exist on the interface surface. Similarly, when a reactive impurity gas is present in the atmosphere during bonding, the bonding interface and the bonding material in the vicinity thereof react with the impurity gas and absorb the impurity gas at a high temperature. Reduce the bonding strength of the target assembly. As for the surface roughness of the joining surfaces, for example, the joining surfaces of both joining materials are finished as smooth as possible by machining or the like, and when both joining materials are overlapped, the contact area is as large as possible. It is desirable to be As a result, when spreading and bonding smooth surfaces at the time of diffusion bonding by heating and pressurization, compared to bonding with overlapping surfaces with rough surfaces and small contact areas The heating temperature can be lowered with the same pressure, and a predetermined diffusion bonding can be achieved even if the heating time is further shortened. In the present invention, the average roughness is preferably ≦ 3 μm as the smoothness of the bonding surfaces.
[0017]
Recently, large diameter target assemblies have tended to be used, for example titanium targets with a diameter of 14 mm (355 mm) or more. It is quite difficult to finish such a large-diameter disk to a surface roughness with an average roughness ≦ 3 μm, for example, by cutting with a lathe, and practical processing accuracy is up to about 6 μm. For this reason, in order to obtain a smooth surface of ≦ 3 μm, a grinding / polishing process using a grindstone, a polishing agent, a buff or the like is required after the lathe processing up to about 6 μm. Adding this step increases the processing time, increases the processing cost, and if the processed material is a metal with low hardness such as Al or Cu, each fine particle generated by grinding / polishing is added. It is not preferable because the metal surface is hardened and remains as a foreign substance on the joint surface. As a solution to this, in the present invention, after finishing the surface to an average grade of about 6 μm by lathing and cleaning the surface, for example, fine powder having an average particle size of 1.0 μm or less is filled in a recess having a surface roughness of 6 μm. As a result, the surface roughness is ≦ 3 μm, and the contact area of the joint surface is increased.
That is, the filling of fine powder serves to smooth the surface.
[0018]
According to the present invention, each joint surface of the target material and the backing plate material is processed into a surface as shown in FIG. In FIG. 1, 11 (13) indicates a target material and a backing plate material. The surface roughness of the joint surface is usually about 6 μm, but may naturally vary depending on the processing method. A fine powder having an average particle diameter of 1.0 μm or less is uniformly dispersed on the joint surface thus processed, and the respective recesses are filled as shown in FIG. As a result, the surface roughness is ≦ 3 μm, and the joint surface between the target material and the backing plate material is in contact with a wide area. In the present invention, compared with the case of normal diffusion bonding (FIG. 2), the fine powder to be used acts as shown in FIG. Then, an alloy layer containing the fine powder, an intermetallic compound layer, a fine powder diffusion layer, and the like are formed. 2 and 3, 11 is a target material, 12 is fine powder, 13 is a backing plate material, and 14 is a target assembly.
[0019]
In the present invention, for example, Ti, Ta, Nb, Mo, Cr, W, Co, Ni, Si and alloy compounds thereof can be used as the target material, and as the backing plate material, for example, Al, Al alloy, Cu And Cu alloy etc. can be used. Moreover, fine powders, such as Ag, Cu, Ni, can be used as a fine powder, for example. As the material of the fine powder, a preferable material is appropriately determined according to the combination of the target material and the backing plate material. For example, when the target material is made of Ti and the backing plate material is made of Al (Al alloy), fine powders such as Ag, Cu, and Ni are suitable as the fine powder as the smooth filler.
[0020]
The fine powder filling method is not limited as long as the fine powder can be uniformly filled in the recesses of the joint surface. For example, the fine powder is sprayed on the joint surface of the surface-treated target material and backing plate material. The fine particles may be rubbed together with a smooth Ti alloy disk to fill the dents on the joint surface, and a dispersion medium such as ethanol is added to the fine powder to form a paste, and the fine powder paste is applied to the joint surface to disperse the dispersion medium. After evaporating and drying, the fine powder adhering to the surfaces of both materials may be peeled off, and the fine powder may be filled in the recesses. In addition, as a method for uniformly dispersing the fine powder dispersed on both joint surfaces over the entire surface, a method may be adopted in which vibration is applied to the bonding material interface on one of the superposed surfaces using an ultrasonic vibration device.
[0021]
When fine powder having a high oxygen content is used, it is desirable to reduce the surface of the fine powder, for example, in an Ar—H ₂ mixed gas atmosphere in order to reduce the oxygen level.
[0022]
【Example】
Examples of the present invention will be described below.
[0023]
A titanium (Ti) target material and an aluminum alloy (Al alloy, A6061) backing plate material were joined together to produce a Ti target assembly as follows. A Ti target material having an outer diameter of 12 mm (305 mm) and a thickness of 6 mm was used, and an Al alloy backing plate material having the same outer diameter and a thickness of 20 mm was used. Each bonding surface was processed to an average roughness of about 6 μm by lathing. The surface was cleaned by ultrasonic degreasing with acetone, and then dried. 2.2 g of Ag fine powder having an average particle size of 500 nm (0.5 μm) was sprayed almost evenly on the surfaces of the joint surfaces of both materials. Next, using a disc-shaped Ti alloy (Ti-6Al-4V) jig having a diameter of 100 mm and a height of 100 mm, the surface of one end surface of which is finished to a roughness of ≦ 2 μm. Then, the surfaces of both materials on which Ag fine powder was dispersed were rubbed together. The reason for using a Ti alloy for the jig is that it is necessary to use a material harder than the mating material. The roughness of the joint surface of both materials became ≦ 3 μm by rubbing such Ag fine powder.
[0024]
Since the filling amount of the Ag fine powder is 2.2 g on one side, it is 4.4 g on both sides, whereas in the method using Ag foil as an insert material among the methods of the prior art, for example, Ag foil to be used If the thickness is 20 μm and it is used as a target material with a diameter of 12 mm (305 mm), the weight of the sandwiched Ag will be 15.2 g, and if the cutting material generated for circular use is added, it will increase by about 25%. To do. Therefore, in the case of the present invention, the amount of use is ¼ to ５ compared with the case of the prior art.
[0025]
Next, the joint surfaces of both materials processed as described above were superposed and set in a hot press apparatus. The inside of the apparatus was evacuated to 0.01 Pa or less, heated to 470 ° C. and held for 1 hour. At that time, a pressure of 20 MPa was applied to both materials, and so-called hot pressing was performed to join both materials to obtain a Ti target assembly.
[0026]
Ultrasonic flaw inspection was performed on the entire surface of the joint portion of the obtained assembly, but no defects such as unbonded were found. A tensile test piece was cut out from this assembly, and the breaking strength was determined by a tensile test. The average value of the tensile strength of 10 test pieces was 11.3 kg / mm ² , which was higher than 10 kg / mm ² , and was sufficient as the joint strength of the target assembly.
[0027]
In the above-described embodiment, the target assembly is composed of a Ti target material and an Al alloy backing plate material, which are representative configurations. In addition, Ta, Nb, Mo, Cr, and W can be used as target materials. Co, Ni, Si and their alloy compounds, etc., and Cu and Cu alloys as the backing plate material can also be obtained with high joint strength. Further, even when fine powder such as Cu or Ni is used instead of Ag fine powder, a material having a high bonding strength can be obtained.
[0028]
In the above embodiment, Ag fine powder was sprayed on the joint surfaces of the target material and the backing plate material, and then the surfaces were rubbed with a Ti alloy disk having a smooth surface to fill the dents in the joint surface with Ag fine powder. Add ethanol solution to make a paste, apply the Ag fine powder paste to the joint surface, evaporate ethanol and dry, then peel off the extra Ag fine powder adhering to the surface of both materials, In the case where the dent is filled, a material having a high bonding strength can be obtained. Further, as a method of uniformly dispersing the fine powder dispersed on both joint surfaces, the tip of the ultrasonic vibration device is used as a roller on one of the superimposed surfaces, for example, ultrasonic frequency: 30 kHz, ultrasonic output: 0.5 kW. The roller may be pressed lightly on the entire surface of the bonding material to apply vibration to the bonding material interface.
[0029]
Since the Ag fine powder having an average particle diameter of 500 nm used in the examples has an oxygen content of 0.02%, it is not necessary to reduce the oxygen level when used as a smooth filler, but Cu fine powder (for example, When using an average particle size of 500 nm and an oxygen content of 1.3%), Ni fine powder (for example, an average particle size of 200 nm and an oxygen content of 3.2%), it is necessary to lower their oxygen level. For that purpose, before raising the temperature in the hot press apparatus for bonding, the inside of the apparatus is replaced with 80 vol% Ar-20 vol% H ₂ mixed gas, heated to 300 ° C. and held for 10 minutes, It is desirable to perform surface reduction.
[0030]
The particle size of the fine powder used in the above examples is 1 μm or less. However, in the case of fine powder, the numerical value indicates the average particle size, and the particle size distribution is before and after the average particle size, but it is not preferable to mix particles having a particle size of 3 μm or more as large particles.
[0031]
【The invention's effect】
According to the present invention, among various bonding conditions in diffusion bonding, in order to increase the contact (adhesion) area of the bonding material, in addition to surface processing, the surface recess is filled with fine powder having a specific particle size range. Therefore, the time required for surface processing can be shortened. Therefore, the method of the present invention is useful not only for joining the target material of the sputtering target assembly and the backing plate material, but also widely for joining mechanical and electronic parts.
[0032]
Moreover, according to this invention, there exists an advantage that the usage-amount of a smooth filler can be less compared with the case of the method of using the insert material of a prior art.
[0033]
Furthermore, the filled fine powder has an average thickness of approximately 1 to 2 μm, and may diffuse in a short time during joining by hot pressing, and between the target material and the backing plate material and the metal. Even if the compound is formed, its thickness is thin, and a good bonding strength can be obtained as a structure of the bonding boundary.
[Brief description of the drawings]
FIG. 1A is a schematic cross-sectional view showing the surface roughness of a surface-treated target material and backing plate material.
(B) A schematic cross-sectional view showing a state in which fine powder is filled in the dents on the surfaces of the target material and the backing plate material shown in FIG.
FIG. 2A is a schematic cross-sectional view showing a bonding surface state of a target material and a backing plate material before heating and pressurization in conventional diffusion bonding.
(B) Typical sectional drawing which shows the process in which the unevenness | corrugation of a joint surface deform | transforms during heating and pressurization in the conventional diffusion bonding.
(C) Schematic sectional view showing a process in which grain boundaries move during heating and pressurization and voids disappear in conventional diffusion bonding (D) Process in which most voids disappear in conventional diffusion bonding FIG.
FIG. 3A is a schematic cross-sectional view showing a bonding surface state of a target material and a backing plate material before heating and pressing in diffusion bonding using fine powder according to the present invention.
(B) Typical sectional drawing which shows the state of the alloy layer (intermetallic compound) or fine powder diffusion layer containing the fine powder which arises during the heating and pressurization by this invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Target material 2 Backing plate material 3 Target assembly 11 Target material 12 Fine powder 13 Backing plate material 14 Target assembly

Claims (3)

In the method of manufacturing a sputtering target assembly, when a target material and a backing plate material that is a supporting member thereof are diffusion bonded, an average particle size of 1 μm or less and a maximum particle size are formed in a recess in at least one of the joining surfaces of both materials to be overlapped. Filled with fine powder of Ag, Cu or Ni with a diameter of less than 3 μm, smoothed the surface roughness to 3 μm or less, widened the contact surface when the two materials were overlapped, then fixed by diffusion bonding by heating and pressing. A target assembly having a phase diffusion bonding interface, a Ti target material as the target material, an Al or Al alloy backing plate material as the backing plate material, and a bonding strength between the target material and the backing plate material. The manufacturing method of the sputtering target assembly characterized by being 10 kg / mm < ² > or more . After applying the paste made by mixing the fine powder and ethanol to at least one joint surface of both the materials to be overlapped, the fine powder is filled in the concave portion of the joint surface by evaporating the ethanol The manufacturing method of the sputtering target assembly of Claim 1 characterized by the above-mentioned . A sputtering target assembly manufactured by the manufacturing method according to claim 1 or 2 .

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