JPH09209136A - Production of titanium target assembled body for sputtering and titanium target assembled body for sputtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain a joined target of titanium and a backing plate small in the generation of particles and capable of releasing sputtered grains of the same direction. SOLUTION: In a state in which a titanium stock subjected to cold working a backing plate essentially consisting of aluminum are mutually brought into contact, hydrostatic pressing treatment followed by heating is executed. In this hydrostatic pressing treatment, the titanium stock and backing plate member are diffusedly joined, and furthermore, the recrystallization of the titanium stock is executed. As for the conditions of the hydrostatic pressing, preferably, the temp. is regulated to 300 to 450 deg.C, and the pressure is regulated to 50 to 200MPa. Moreover, the titanium stock is preferably subjected to roughening treatment from 6S to 12S in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a titanium target assembly for sputtering used for forming a thin film mainly composed of titanium by sputtering, and a titanium target assembly for sputtering.

[0002]

2. Description of the Related Art In recent years, a thin film has been widely formed by a sputtering method in the field of manufacturing semiconductor elements, magnetic disks used as recording media for personal computers, or precision parts such as liquid crystal displays.
The target used for sputtering is usually an assembly in which a packing plate is bonded to the target material. This is because the backing plate serves as a member for fixing the target material when it is mounted on the sputtering apparatus, as a heat conducting member for preventing overheating of the target material during sputtering, or for dissipating the charge accumulated in the target material. This is because it is effective as a conductive member for

From the viewpoint of thermal conductivity, oxygen-free copper is mainly used as a backing plate material satisfying the above-mentioned high thermal conductivity and high electrical conductivity. Also,
Backing plates of pure aluminum or aluminum-based alloys such as duralumin may also be used. Usually, the target material and the backing plate are joined by using an indium-based or tin-based brazing material. Recently, in order to improve the efficiency of film formation, the titanium target material has been increased in size, and the power input for sputtering tends to increase more and more. For example, a pure titanium target material used in an LSI manufacturing process may be supplied with high electric power of several tens of kilowatts in order to compensate for the decrease in the deposition rate of a thin film due to the use of a collimator. Therefore, the target material is overheated more intensely than in the past, and securing the reliability of bonding with the backing plate at high temperature has become a major issue.

A method of using a brazing material having a high melting point is known as a means for ensuring the reliability of the joint at high temperature. However, there is a limit to the high temperature of the brazing material, and when using the brazing material. There is a problem that the target material is contaminated by the flux agent used. In order to solve such a problem, there is a case in which a target material is directly introduced into the apparatus and sputtering is performed without using a backing plate, but in this case, as described above, the target material during sputtering is It is not possible to obtain the advantage of mounting the backing plate such that overheat can be prevented or the charge up can be easily dissipated.

As a new method for solving the above-mentioned problems, a method of joining a target material and a backing plate by solid phase diffusion has been proposed. For example, according to Japanese Patent Application Laid-Open No. 6-65733, a titanium target and an aluminum backing plate are diffusion-bonded at 500 ° C. for 24 hours under a load of 800 tons to obtain tensile strengths of 9.7 to 11. 9 kgf / mm
It is disclosed that a bond strength of ² (95.1 to 116.6 MPa) can be obtained. In addition, JP-A-6-1082
According to Japanese Patent Publication No. 46, a method of inserting an insert material having a melting point lower than that of the target and performing diffusion bonding is disclosed.

The above-described method of joining the target material and the backing plate by diffusion can obtain about 10 to 20 times stronger joining than the joining by the normal brazing material, and increase the input power even during sputtering. It is expected that the reliability of the joint can be secured even if the temperature rises due to the above.

[0007]

In recent years, with the high integration of semiconductor elements typified by LSI, the diameter of contact holes formed in the semiconductor element tends to become smaller and the aspect ratio tends to increase. When a film is formed in a contact hole having such a high aspect ratio, there is a problem that the film is hard to deposit on the bottom of the contact hole. Therefore, in order to sufficiently deposit the film on the bottom of the contact hole, it is necessary for the sputtered particles to be incident on the contact hole as vertically as possible. Conventionally, a method in which a collimator is provided between the target material and the substrate on which a film is to be formed, and the directions of sputtered particles reaching the substrate are aligned,
Alternatively, a method for aligning the directions of sputter particles has been put into practical use by improving the apparatus, such as long-distance sputtering in which the directions of sputter particles reaching the substrate are aligned by separating the target material and the substrate. According to the study of the present inventors, the average crystal grain size in the structure of the titanium target material that is usually used is about 50 μm, but it has an extremely fine recrystallized structure with the average crystal grain size of 10 μm or less. It was found that the directions of sputtered particles can be aligned by using a titanium target.

Further, in recent years, due to the miniaturization of wiring widths and the increase in the number of laminated films accompanying the high integration of LSIs, there is a problem that the yield of products is reduced due to the generation of foreign particles, so-called particles, in the sputtering film forming process. . For example, for a titanium target material used to form an ohmic contact portion of an LSI, argon sputter for forming a pure titanium layer and argon and nitrogen for forming a titanium nitride (TiN) layer are usually used. And reactive sputtering under mixed atmosphere are alternately applied. The present inventors investigated the relationship between the shape change of the titanium target material surface in such a sputtering process and the generation of particles.

As a result, a titanium nitride (TiN) layer is formed on the surface of titanium during the reactive sputtering process.
It was found that peeling of the N layer is one of the causes of particle generation. As one of the causes of peeling of the TiN layer, unevenness is formed in the erosion portion, and the edge portion of this unevenness serves as the starting point of arcing, and the TiN film is peeled and scattered by the impact of abnormal discharge, and particles are generated. Was estimated. The present inventors have confirmed that the above-mentioned generation of particles can be reduced by adjusting the crystal grain size of the titanium target material to be fine. This is because by making the crystal grain size of the structure fine, irregularities in the erosion part are small and smooth, abnormal discharge is unlikely to occur, and the film stress of the TiN layer is also dispersed, so that the generation of particles due to peeling is suppressed. It is considered to be a thing.
It should be noted that the fact that a titanium target material having small crystal grains can reduce the generation of particles as compared with a titanium target material having coarse crystal grains is also reported in JP-A-6-10107 or JP-A-6-280009. Has been done.

The inventor of the present invention is effective for the purpose of aligning the directions of sputtered particles with a titanium target material adjusted to a structure having finer crystal grains than before, and at the same time, generation of particles during the sputtering period. It was concluded that it is also effective for suppression. The present inventor has disclosed in Japanese Patent Application Laid-Open No. 6-65733, instead of a method of joining a backing plate by brazing so that a titanium target material having such a fine recrystallized structure can withstand high power during sputtering. An attempt was made to obtain a titanium target assembly by the method of joining the target material and the backing plate by the method of diffusion joining described.

However, when a titanium target assembly in which a fine structure is adjusted is manufactured by the method described in JP-A-6-65733, the crystal grains in the target structure become coarse due to heating during diffusion bonding, It has been found that there are cases where it is not possible to maintain a structure capable of forming a sufficient film at the bottom of the contact hole. An object of the present invention is to provide a target assembly in which the generation of particles is small and sputtered particles in a uniform direction can be emitted, and a manufacturing method capable of efficiently obtaining the target assembly.

[0012]

Means for Solving the Problems The inventors of the present invention have carried out a process of adjusting the structure of a titanium material necessary for obtaining a target material,
A process for directly diffusion bonding a titanium material and a backing plate member mainly composed of aluminum was examined. The present inventor has found that titanium and aluminum are easily diffused, and that it is possible to perform diffusion bonding at a low temperature of 500 ° C. or lower by using a hydrostatic press. Titanium also depends on the degree of strain due to cold working. It was found that recrystallization can occur even at 500 ° C or lower. That is, under the specific conditions of the present invention using a hydrostatic press, the titanium material and aluminum can be diffusion bonded even at a low temperature below the melting point of aluminum, and the structure can be adjusted by recrystallization simultaneously in the same temperature range. It was found that Focusing on this point, the present inventor performed a heat treatment for structure adjustment by recrystallization of a titanium material,
They found that it can be used as a heat treatment for diffusion bonding.

That is, according to the present invention, a hydrostatic pressing process involving heating is performed in a state where a cold-worked titanium material and a backing plate member mainly made of aluminum are in contact with each other, and the hydrostatic pressing process is performed. Titanium target assembly for sputtering to obtain an assembly in which a titanium material and a backing plate member are diffusion-bonded and the titanium material is recrystallized, and a target material made of titanium having a recrystallized structure and a backing plate are diffusion-bonded. Is a manufacturing method.

Preferably, the isostatic pressing conditions are 30
A temperature of 0 to 450 ° C is applied. Further, for the purpose of aligning the directionality of sputtered particles in sputtering and reducing the generation of particles, titanium is adjusted to a finer recrystallized structure, and in particular, the target material has a structure with an average crystal grain size of 10 μm or less. It is preferably applied to the manufacture of the target assembly of the present invention having
Further, in order to further increase the bonding strength, it is effective to perform a roughening treatment of 6S to 12S on the surface of the titanium material to be bonded to the backing plate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION One feature of the present invention is that the structure of titanium material is adjusted and the titanium material and the backing plate are joined by hydrostatic pressing accompanied by heating. According to the present inventor, the size of the recrystallized grains of titanium largely depends on the temperature, but with respect to time, within the range of several hours for performing diffusion bonding, the crystal grains are not significantly coarsened. Turned out not. Therefore, it has become possible to perform the structure adjustment of the titanium material and the joining of the titanium material and the backing plate simultaneously with the hydrostatic pressing accompanied by heating. By doing so, it is not necessary to adjust the structure of the titanium material in advance, and it is possible to omit the steps and improve the production efficiency. Further, by setting the hydrostatic pressing condition to a condition for adjusting the structure of the titanium material, it is possible to eliminate the problem of coarsening of crystal grains due to heating after the structure adjustment. In addition, the fact that the diffusion bonding process and the recrystallization occur at the same time makes it easy for the atoms to move along with the release of the strain during the recrystallization of titanium, even when a heating condition lower than the conventional one is applied. However, an advantage that diffusion bonding is easier than in the case of simple heating can be expected.

Further, the application of a hydrostatic press is also a feature of the present invention. In uniaxial press molding, although pressure is applied perpendicularly to the joint interface between the titanium target material and the backing plate, there is a problem in that even if the axis deviates even a little, pressure irregularity may occur at the joint interface. When bonding is performed in a low temperature region to prevent the coarsening of the structure, the diffusion of atoms at the bonding interface largely depends on the pressure applied to the bonding interface. Therefore, the generation of the pressure unevenness directly leads to the generation of the unbonded portion, which makes it unusable as a target assembly that needs to secure thermal conductivity and electrical conductivity. On the other hand, the hydrostatic press can apply isotropic pressure to the target material and the backing plate, and can prevent pressure unevenness from occurring on the joint surface.

In the present invention, 300 to 450 ° C. is preferable as the condition for isostatic pressing,
This is because if the temperature is lower than 0 ° C, it is difficult to carry out diffusion bonding even after holding for a long time, and if the temperature exceeds 450 ° C, the structure tends to become coarse due to the growth of crystal grains. In particular, when it is desired to obtain a structure finer than the average crystal grain size of 10 μm, the conditions of a total cold rolling rate of 75% or more and a hydrostatic pressing treatment of 450 ° C. or less are applied. Further, as the condition of the hydrostatic press, the pressure was changed from 50 MPa to 200 MPa,
At a pressure lower than 50 MPa, it is difficult to obtain a good bonding state, and on the other hand, applying a pressure of 200 MPa or higher is not practical in terms of the performance of the hydrostatic pressing device.

By the method described above, a titanium target for sputtering can be obtained in which a titanium material having a recrystallized structure is diffusion-bonded to a backing plate mainly made of aluminum. In the present invention, the aluminum-based backing plate means a backing plate made of pure aluminum or an aluminum-based alloy such as duralumin. From the viewpoint of thermal conductivity, pure aluminum is preferable, but since the backing plate is required to have strength as the target becomes larger, Si, Cu, Mn,
An alloy containing 10% by weight or less of a strengthening element such as Mg, Cr, Zn, Ti or Zr can be used.

In the present invention, since low temperature and high pressure are applied as described above, it is desirable that the container for transmitting the pressure used in the hydrostatic press is one which is easily deformed at the lowest temperature. Specifically, it is desirable to use a container made of aluminum that is easily deformed, or to use a metal foil having a plate thickness of 0.5 mm or less as a container for transmitting pressure. As the metal foil, a foil of pure iron, stainless steel, aluminum or the like can be used, and in particular, niobium or molybdenum foil which is a refractory metal can be selected in order to prevent contamination of the target material. Also, when the container is mainly made of aluminum, without preparing a separate backing plate, the container is used as a backing plate member, the container and the titanium material are diffusion-bonded by a hydrostatic press treatment, and a hydrostatic press treatment is performed. The container can then be processed into a backing plate.

Further, in the present invention, it is desirable that the surface of the titanium material to be joined to the backing plate is subjected to a roughening treatment of 6S to 12S in advance. This is because the hardness of titanium is higher than that of aluminum, so if unevenness is formed, the unevenness bites into the backing plate at the time of joining due to the setting of high-pressure hydrostatic pressing conditions, and an anchor effect can be obtained. This is because the contact area at the interface is increased, mass transfer due to diffusion is facilitated, and the bonding strength can be increased. That is, it becomes possible to join at a lower temperature. Further, when such an uneven portion is formed, the oxide layer that is likely to be formed on the surface of the backing plate is pierced at the time of bonding and the active surface is exposed, so that mass transfer is facilitated. This will further increase the bonding strength.

[0021]

【Example】

(Example 1) A titanium ingot of 5N (99.999% purity) grade was cold-forged and cold-rolled under the conditions shown in Table 1 to obtain a titanium material. The obtained titanium material was machined to have a size of φ300 × 8 mmt and a joint surface roughness of 3.
Adjusted to 2S. On the other hand, from a pure aluminum plate material of JIS alloy No. 1050 and duralumin of JIS alloy No. 2017, a size φ300 × 2 is obtained by machining.
A backing plate having a surface roughness of 5 t and a joint surface roughness of 2S was obtained. The joining surface of the titanium material and the backing plate,
The surface was washed with 10% hydrofluoric nitric acid to remove the oxide film and dirt on the surface. Then, it was washed with pure water and dried by argon blow.

[0022]

[Table 1]

Next, in the combinations shown in Table 2, the joining surfaces of the titanium material and the backing plate were overlapped and encapsulated in a pure aluminum capsule having a thickness of 3 mm. The capsule was placed in a furnace of a hot isostatic press machine, the pressure was reduced to 5 × 10 -3 Pa, and then the capsule was sealed. Next, the temperature in the furnace of the hot isostatic press was raised, and diffusion bonding and recrystallization of the titanium material were performed under the treatment conditions of 400 ° C. and 140 MPa for 5 hours. After the treatment was completed, the aluminum capsule was removed by lathing to obtain a target assembly in which the titanium target material and the aluminum backing plate were joined. In the measurement by the ultrasonic flaw detection method, all the target samples had a bonding rate of 100%. At the stage of machining, a tensile test piece of 30 mm square and 12 mm thick is cut out from the bonded body of the target material and the backing plate, and a load is applied in a direction perpendicular to the bonded surface to measure the bonding strength. The average crystal grain size of the target material was measured. Table 2 shows the results.

[0024]

[Table 2]

As shown in Table 2, the backing plate made of duralumin was able to obtain a sufficiently high bonding strength of 50 MPa or more, although the bonding strength was slightly lower than that of the pure aluminum backing plate. Further, as shown in Table 2, in the joining of the target material and the backing plate by the hydrostatic pressing performed under the condition of 400 ° C., coarsening of crystal grains in the target material structure does not occur, and the target material structure is adjusted and diffused. The joining could be achieved at the same time. Using the obtained target assembly, the ultimate vacuum of 5 × 10−5 Pa, argon pressure of 5 Pa, power supply (per unit area of target) 1
The film formation was evaluated under the conditions of 5 W / cm ² and the substrate temperature of 200 ° C. The results are shown in Table 3. The number of particles shown in Table 3 is the number of particles of 0.3 μm or more in a 6-inch wafer. The bottom coverage ratio is calculated by measuring the top film thickness and the bottom film thickness when forming a film in a contact hole having a hole diameter of 0.5 μm and an aspect ratio of 1.5, and calculating the bottom film thickness / top film thickness. .

[0026]

[Table 3]

As shown in Table 3, each sample had a bottom coverage of 20% or more, and the number of particles could be 20 or less. High bottom coverage means that more sputtered particles have reached the bottom of the contact hole.
It is an index that indicates that the sputtered particles protruding from the target material are aligned in the same direction. In addition, as a target material, T1 which can be adjusted to have an average crystal grain size of 10 μm or less
It can be seen that the target materials from T6 to T6 have a smaller number of particles and a higher bottom coverage than the target material of T7 having an average crystal grain size of more than 10 μm, which is preferable.

(Comparative Example) A titanium material was obtained in the same manner as the sample T1 of Example 1, and then heat treatment for recrystallization was performed at 400 ° C. to obtain a titanium target material having a fine structure with an average crystal grain size of 8 μm. Got The obtained titanium target material and a backing plate made of pure aluminum were enclosed in a pure aluminum capsule having a thickness of 3 mm. After reducing the pressure to 5 × 10 -3 Pa, sealing the capsule, and then raising the temperature in the furnace of the hot isostatic press,
Diffusion bonding treatment was carried out at 500 ° C. under the condition of 120 MPa for 5 hours. After the diffusion bonding treatment, the aluminum capsule was removed to obtain a target assembly in which the titanium target and the aluminum backing plate were bonded.
The bonding rate was 100% as measured by the ultrasonic flaw detection method.

Further, in the machining stage, from the joined body of the target material and the backing plate, a 30 mm square and a thickness of 1
A 2 mm tensile test piece was cut out and weighted in a direction perpendicular to the joint surface to measure the joint strength and the average crystal grain size of the target material after the diffusion joint treatment.
As a result, the bonding strength was as good as 94 MPa. However, the average crystal grain size was 25 μm, which was coarser than that of the material before the diffusion bonding treatment. A photograph of the metal microstructure of the target of the comparative example is shown in FIG. When this target was subjected to film formation evaluation in the same manner as in Example 1, the number of particles was 6
As compared with the target of the present invention described in Example 1 having a fine structure, 24 in 0.3 inch or more in an inch wafer and a bottom coverage rate of 20%,
It became inferior.

(Example 2) Titanium materials T1 and T3 similar to those used in Example 1 and a backing plate made of pure aluminum similar to Example 1 were prepared. The respective joint surfaces were overlapped and encapsulated in a pure aluminum capsule. The capsule was placed in a furnace of a hot isostatic press machine, the pressure was reduced to 5 × 10 -3 Pa, and then the capsule was sealed. Next, the temperature inside the furnace of the hot isostatic press was raised, and the pressure and temperature were changed to set the conditions for holding for 5 hours so that the influence of the temperature and pressure in the hydrostatic press could be confirmed.

The capsule has a wall thickness of 3 mm when a temperature of 400 ° C. or higher is applied in a hydrostatic press.
In the case of using a pure aluminum can of No. 1 and applying a temperature of less than 400 ° C., a 0.1 mm pure molybdenum foil was used. After processing, remove the aluminum capsule by lathe processing,
A target assembly in which a titanium target material and an aluminum backing plate were joined was obtained. In the measurement by the ultrasonic flaw detection method, all the target samples had a bonding rate of 100%. At the stage of machining, a tensile test piece of 30 mm square and 12 mm thick is cut out from the bonded body of the target material and the backing plate, and a load is applied in a direction perpendicular to the bonded surface to measure the bonding strength. The average crystal grain size of the target material was measured. Table 2 shows the results. A micrograph of a typical metal microstructure of the present invention is shown in FIG.

[0032]

[Table 4]

As shown in sample 15 of Table 4, the titanium material and the backing plate could not be bonded at a pressure of 150 MPa at 280 ° C. Also, 3
At 00 ° C. or higher, the bond between the target material and the backing plate was good, but as shown in Samples 20 and 25, it was found that when the temperature was raised to 500 ° C., the crystal grains became considerably large. Further, as shown in Sample 26, it can be seen that when the pressure of the hydrostatic press is lower than 50 MPa, the bonding strength becomes low. As shown in Table 4, the adjustment of the target material structure and the diffusion bonding can be achieved at the same time, and the bonding strength and the average crystal grain size of the titanium structure can be adjusted by changing the conditions of the hydrostatic pressing. I know that I can do it.

Example 3 Target material T1 of Example 1
A target material similar to that of Example 1 was manufactured, and an aluminum backing plate similar to that of Example 1 was prepared. The joint surfaces of the target material and the backing plate were processed into the surface roughness shown in Table 5. These are treated at 400 ° C. as in Example 1.
Then, the diffusion-bonded titanium material was recrystallized under the processing conditions of 140 MPa for 5 hours. A titanium target having the same size and grade as the aluminum backing plate and an aluminum backing plate were prepared. Here, with respect to Ti, as shown in Table 1, the roughness of the joint surface is 1S, 2S, 6.3S, 12
S was changed, and the remaining conditions were diffusion bonding by the same procedure as in Example 1, and a target was manufactured by machining.

In the obtained target, the target material had an average particle size of 10 μm, and it was confirmed that the crystal grains did not become coarse. The bonding strength was measured by the same method as in Example 1 in order to confirm the influence of the surface roughness applied to the bonding surface of the target material and the bonding strength. Table 5 shows the results
Shown in As shown in Table 5, it can be seen that the bond strength can be increased by increasing the target material roughness.

[0036]

[Table 5]

[0037]

EFFECTS OF THE INVENTION According to the present invention, by hydrostatic pressing with heating, the structure of the titanium material is adjusted and the joining of the titanium material and the backing plate is performed at the same time.
Since it is not necessary to adjust the structure of the titanium material in advance, the process can be omitted and the production efficiency can be improved. Further, by setting the hydrostatic pressing condition to a condition for adjusting the structure of the titanium material, it is possible to eliminate the problem of coarsening of crystal grains due to heating after the structure adjustment.
As a result, a fine titanium structure, which is effective for the purpose of suppressing the generation of particles and aligning the directions of sputtered particles, can be accurately obtained, and is industrially effective.

[Brief description of drawings]

FIG. 1 is a micrograph showing a metal microstructure of a target material of the present invention.

FIG. 2 is a micrograph showing a metal microstructure of a target material of a comparative example.

Claims (5)

[Claims] 1. A hydrostatic pressing process involving heating is performed in a state where a cold-worked titanium material and a backing plate member mainly made of aluminum are in contact with each other, and the titanium material is subjected to the hydrostatic pressing process. A titanium target for sputtering, characterized by performing diffusion bonding of a backing plate member and recrystallization of a titanium material to obtain an assembly in which a target material made of titanium having a recrystallization structure and a backing plate are diffusion bonded. Assembly manufacturing method. 2. The hydrostatic pressing process is performed at 300 to 450.
The method of manufacturing a sputtering target assembly according to claim 1, wherein the condition is a temperature of 50 ° C. and a pressure of 50 to 200 MPa. 3. The production of a titanium target assembly for sputtering according to claim 1, wherein the structure of the titanium material is adjusted to a recrystallized structure having an average crystal grain size of 10 μm or less by isostatic pressing. Method. 4. The titanium target assembly for sputtering according to claim 1, wherein the surface of the titanium material to be joined to the backing plate is subjected to a surface roughening treatment of 6S to 12S. Production method. 5. A sputtering titanium target assembly in which a target material made of titanium and a backing plate mainly made of aluminum are diffusion-bonded,
The target material made of titanium has an average crystal grain size of 10
A titanium target assembly for sputtering characterized by having a thickness of not more than μm.