JPH09143704A - Titanium target for sputtering and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium target and its production method low in generation of particles and having a backing plate capable of releasing sputtering particles made uniform in direction. SOLUTION: A titanium target material prepared previously into a recrystallization structure having <=20μm max. grain size and <=10μm average crystal grain size and the backing plate consisting essentially of aluminum are subjected to a hydrostatic press at a condition of 300-450 deg.C and 50-200MPa pressure in a contact state to obtain the target keeping a fine recrystallization structure. An aluminum vessel and a metallic foil having <=0.5mm thickness are used as a vessel for the hydrostatic press. A roughening treatment is preferably conducted on the titanium target material at the time of joining.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a titanium target for sputtering used for forming a thin film containing titanium by sputtering and a method for producing the same.

[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 sputtering target is usually formed by joining a packing plate to a target material. This is because the backing plate serves as a fixing member for the target material when it is attached to the sputtering device, as a heat conducting member for preventing overheating of the target during sputtering, or for discharging the charge accumulated in the target material. This is because it is effective as a conductive member.

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 aluminum or aluminum-based alloys such as duralumin may also be used. Usually, the target material and the backing plate are
Bonding is performed using an indium-based or tin-based brazing material. Recently, in order to improve the efficiency of film formation, the target material has been increased in size, and the power input for sputtering tends to increase more and more. For example, LSI
The pure titanium target used in the manufacturing process of
In order to compensate for the decrease in the deposition rate of the thin film due to the use of the collimator, a high electric power of tens of kilowatts may be applied. For this reason, the target is overheated more intensely than before, and it has become a major issue to secure the reliability of bonding with the backing plate at a high temperature.

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 is contaminated by the flux agent used. In order to solve such a problem, there is a case where a target material is directly introduced into the apparatus and sputtering is performed without using a backing plate. In this case, as described above, the target is overheated during sputtering. It is not possible to obtain the advantage of mounting the backing plate that can prevent the above-mentioned phenomenon or can easily dissipate the charge up.

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 Laid-Open No. 6-65733, a titanium target and an aluminum backing plate are directly connected to each other.
Tensile strength of 9.7 to 11.9 kgf / mm by diffusion bonding under load of 800 tons for 24 hours at ℃
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, due to the miniaturization of the wiring width and the increase in the number of laminated films accompanying the high integration of LSIs, the yield of products is reduced due to the generation of foreign matters, so-called particles, in the sputtering film forming process. It's a problem. For example, for a titanium target used to form an ohmic contact portion of an LSI, an argon sputter for forming a pure titanium layer and an argon and nitrogen for forming a titanium nitride (TiN) layer are usually used. Alternating with reactive sputtering in a mixed atmosphere. The present inventors investigated the relationship between the shape change of the titanium target 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 to a fine one. 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. In addition,
It is disclosed that the titanium target adjusted to have such fine crystal grains can reduce generation of particles as compared with a titanium target having coarse crystal grains.
It is also reported in Japanese Patent Laid-Open No. 0107 or Japanese Patent Laid-Open No. 6-280009.

Further, in recent years, with the high integration of semiconductor elements represented by LSI, the hole diameter of the contact hole 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 that the sputtered particles be incident on the contact hole as vertically as possible.

Conventionally, a collimator is provided between the target and the substrate on which a film is to be formed so that the directions of the sputtered particles that reach the substrate are aligned, or the sputtered particles that reach the substrate by separating the target from the substrate are used. A method for aligning the directions of sputtered particles has been put into practical use by improving the apparatus such as long-distance sputtering in which the directions are aligned. According to the study by the present inventors, the average crystal grain size is 10 μm.
It was found that a titanium target having an extremely fine recrystallized structure of m or less can reduce not only particles but also the direction of sputtered particles.

As described above, the titanium target adjusted to have a structure having fine crystal grains is effective for the purpose of suppressing the generation of particles during the sputtering period and aligning the directions of the sputtered particles. The present inventor replaces the method of joining a backing plate by brazing so that a titanium target having such a fine recrystallized structure can withstand a large power during sputtering,
An attempt was made to obtain a titanium target by a method of joining a target material and a backing plate by the method of diffusion joining described in JP-A-6-65733.

However, when a titanium target is manufactured by the method described in JP-A-6-65733, the directionality of sputtered particles is not as uniform as that of a target joined by brazing, and a sufficient film is formed at the bottom of the contact hole. I found that sometimes I could not. An object of the present invention is to provide a titanium target formed of a bonded body of a target material and a backing plate, which is capable of emitting sputtered particles in which the generation of particles is small and the directions thereof are uniform, and a manufacturing method thereof.

[0014]

The present inventors have investigated the relationship between the titanium target structure and the conditions under which a backing plate mainly made of aluminum is diffusion-bonded to a titanium target material and the titanium target structure. As a result, in a target adjusted to a recrystallized structure having fine crystal grains with a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less, even if the entire structure is filled with the recrystallized grains, a normal diffusion bonding is performed. It was found that when the heating and joining conditions of about 500 ° C. used for the above are applied, the crystal grains grow rapidly. Then, it was found that the rapid increase of crystal grains in the target material structure at the time of heat bonding causes the generation of particles and the spread of distribution in the direction of sputtered particles.

Based on these findings, the present inventors have studied a method capable of joining a titanium target material and a backing plate while maintaining a fine recrystallized structure.
Then, by focusing on the hot isostatic pressing device that heats the sealed gas and utilizes the pressure increase at that time, by generating a hydrostatic pressure of 50 MPa or more at a low temperature of 450 ° C. or less, an extremely fine target structure can be obtained. It was found that it is possible to bond with a backing plate mainly made of aluminum while keeping it.

That is, according to the method for producing a titanium target for sputtering of the present invention, a titanium target material and a backing plate mainly composed of aluminum are in contact with each other at 300 to 450 ° C. and a pressure of 50 to 200 M.
Hydrostatic pressing is performed under the condition of Pa to obtain a target in which a target material having a recrystallized structure having a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less and a backing plate are joined by diffusion.

More preferably, as the above-mentioned titanium target material, a titanium material obtained by cold working in advance is subjected to a heat treatment at 450 ° C. or lower to obtain a maximum particle size of 20 μm.
A titanium target material having a recrystallized structure of m or less and an average crystal grain size of 10 μm or less is used. In this way, by introducing strain by cold working and adjusting the crystal grains of the titanium target material in advance by heat treatment, some of the crystal grains become coarse due to heating during hydrostatic pressing. This is effective because it can be prevented. Preferably, the isostatic pressing conditions apply a temperature of 400 ° C. or lower.

As a container for transmitting pressure in the hot isostatic press of the present invention, a container made of aluminum which is easily deformable,
Alternatively, it is preferable to use a metal foil having a thickness of 0.5 mm or less. 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 target material to be bonded to the backing plate. A novel titanium target for sputtering of the present invention, which is obtained by diffusion-bonding a titanium target material having a recrystallized structure having a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less to a backing plate mainly containing aluminum by the above-described method. Can be obtained. In addition, the bonding strength of the titanium target of the present invention can be set to a tensile strength of 50 MPa or more by the method described above.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION One of the features of the manufacturing method of the present invention is that they are joined by a hydrostatic press.
In the uniaxial press molding, although pressure is applied perpendicularly to the joint interface between the titanium target and the backing plate, there is a problem in that even if the axis is slightly misaligned, the pressure cannot be uniformly applied to the joint interface.

When only a low temperature region can be used to maintain an extremely fine structure as in the present invention, the diffusion of atoms at the bonding interface largely depends on the pressure applied to the bonding interface, so that the bonding interface is uniform. If no pressure is applied to the joint, an unbonded portion will occur. In this case, it cannot be used as a target that needs to ensure thermal conductivity and electrical conductivity. The hydrostatic breath specified by the present invention is
Isotropic pressure can be applied to the target and the backing plate, and the pressure can be uniformly applied to the bonding interface, so that the generation of unbonded portions can be prevented.

In the present invention, the reason for isostatic pressing from 300 ° C. to 450 ° C. is that if it is less than 300 ° C., diffusion bonding is difficult even if it is held for a long time, and it is industrially used. This is because it cannot be done. Meanwhile 450
When the temperature exceeds ℃, crystal grains grow, especially the maximum grain size of 2
This is because a fine structure cannot be maintained when joining a target material having a grain size of 0 μm or less and an average crystal grain size of 10 μm or less. Further, as the condition of the hydrostatic press, the pressure was changed from 50 MPa to 200 MPa by 50
When the pressure is lower than MPa, the bonding strength is lowered, while applying the pressure of 200 MPa or higher is not realistic from the viewpoint of the performance of the hydrostatic press machine.

By the above-described method, the titanium target material having a recrystallized structure having a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less is diffusion-bonded to a backing plate mainly made of aluminum, which is a novel sputtering method of the present invention. Titanium target can be obtained. 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. In terms of thermal conductivity,
Pure aluminum is preferable, but as the target becomes larger, the backing plate is required to have strength. Therefore, Si, Cu, Mn, Mg, Cr, Zn, Ti, Zr is required.
It is possible to use an alloy, for example, duralumin, in which a strengthening element such as is selectively added by 10 wt% or less.

The reason why the maximum grain size is 20 μm or less and the average crystal grain size is 10 μm or less is not only for suppressing the generation of particles during the sputtering period as described above, but also for aligning the directions of sputtered particles. On the other hand, it is necessary to reduce the size to the level specified here. The maximum grain size in the structure where the above effects cannot be obtained exceeds 20 μm, and the average grain size is 10 μm.
For the target material exceeding μm, the crystal grains are not coarsened even at about 500 ° C., and it is not necessary to dare to apply the method of the present invention using low temperature conditions. In the present invention, in order to prevent the crystal grains of the target material from coarsening, the hydrostatic pressing is performed at a temperature of 400 ° C. or lower. By applying the low temperature and high pressure applied by the manufacturing method of the present invention described above, the bonding strength between the target material and the backing plate can be set to a tensile strength of 50 MPa or more.

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 that 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. In particular, in order to prevent the contamination of the target, it is effective to select a foil of high melting point metal such as niobium or molybdenum.

Further, in the present invention, it is desirable that the surface of the titanium target 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 will bite into the backing plate at the time of bonding, and the anchor effect can be obtained, and the contact area of the interface will increase. This is because the mass transfer due to diffusion becomes easy and the bonding strength can be increased. Moreover, if such an uneven portion is formed,
The oxide layer, which is likely to be formed on the surface of the backing plate at the time of bonding, is broken through to expose the active surface, which facilitates mass transfer. This will further increase the bonding strength.

[0026]

【Example】

Example 1 After cold forging a 5N (99.999% purity) grade titanium ingot, cold rolling was performed under the conditions shown in Table 1, and then heat treatment for recrystallization at 400 ° C. was performed. A target material having the indicated crystal grain size was obtained. The target material obtained is machined to a size of φ300 x
The target material was adjusted to 8 mmt and the joint surface roughness was adjusted to 3.2 S. 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 × 25 was obtained by machining.
A backing plate having a surface roughness t and a joint surface roughness of 2S was obtained.
1 for the joint surface of the target material and the backing plate
The surface was washed with 0% hydrofluoric acid to remove the oxide film and dirt on the surface. Then, it was washed with pure water and dried by argon blow.

[0027]

[Table 1]

Next, in the combinations shown in Table 2, the respective bonding surfaces of the target 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. Then, the temperature in the furnace of the hot isostatic pressing apparatus was raised, and diffusion bonding was 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 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%. Also, at the stage of machining,
3 from the joined body of the target material and the backing plate
A 0 mm square and 12 mm thick tensile test piece was cut out, and a load was applied in a direction perpendicular to the joint surface to measure the joint strength and the crystal grain size of the target material. Table 2 shows the results.

[0030]

[Table 2]

As shown in Table 2, the backing plate made of duralumin has a bonding strength slightly lower than that of the backing plate made of pure aluminum, but is 50 MPa.
The above sufficiently high bonding strength could be obtained. 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 a good target material structure is maintained. I was able to. Using the obtained target, the ultimate vacuum of 5 × 10
Minus 5th power Pa, Argon pressure 5Pa, power supply (per target unit area) 15W / cm ² , substrate temperature 2
The film formation was evaluated under the condition of 00 ° C. Table 3 shows the results
Shown in 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. .

[0032]

[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 showing that the directions of sputtered particles jumping out of the target are aligned. In addition, especially as a target material, the maximum grain size is 20 μm or less, and the average grain size is 10 μm.
In the target materials T1 to T6 adjusted below, the maximum grain size exceeds 20 μm and the average grain size is 10 μm.
It can be seen that the number of particles is small and the bottom coverage is high as compared with the target material of T7 exceeding m, which is preferable.

Example 2 Target materials T1 (average crystal grain size 8 μm) and T3 (average crystal grain size 4 μm) similar to those used in Example 1 and a backing made of pure aluminum similar to Example 1 were used. Prepared the plate. 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. As the capsule, a can of pure aluminum having a thickness of 3 mm was used when a temperature of 400 ° C. or higher was applied in the hydrostatic breath, and a foil of pure molybdenum of 0.1 mm was used when a temperature of less than 400 ° C. was applied. .

After the treatment was completed, the aluminum capsule was removed by lathing to obtain a target 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%. Also, at the stage of machining,
3 from the joined body of the target material and the backing plate
A 0 mm square, 12 mm thick tensile test piece was cut out, and a load was applied in a direction perpendicular to the joint surface to measure the joint strength and the average crystal grain size of the target material. Table 2 shows the results. In addition, as a typical metal microstructure of the present invention, the microstructure of Sample 17 is shown in FIG. As the metal microstructure of the comparative example, the microstructure of Sample 20 is shown in FIG.

[0036]

[Table 4]

As shown in Table 4, as shown in Sample 15, the target material and the backing plate could not be joined at a pressure of 150 MPa at 280 ° C. Further, at 300 ° C. or higher, the bonding between the target material and the backing plate was good, but as shown in Samples 20 and 25, when the temperature was raised to 500 ° C., the crystal grains became coarse. Recognize. That is, in order to obtain a target having a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less, which is capable of aligning the directions of sputtered particles, as well as suppressing the generation of particles during the sputtering period as in the present invention, It can be seen that it is necessary to set the condition of the hydrostatic pressing to 300 to 450 ° C. In addition, it can be seen from Sample 26 that a pressure of 50 MPa or higher needs to be applied to obtain a bonding strength of 50 MPa or higher.

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, diffusion bonding was performed under the processing conditions of 140 MPa and 5 hours of holding. A titanium target having the same size and grade as the aluminum backing plate and an aluminum backing plate were prepared. Here, for Ti, the roughness of the bonding surface was changed to 1S, 2S, 6.3S, 12S as shown in Table 1, and the remaining conditions were diffusion bonding by the same procedure as in Example 1. The target was manufactured by machining.

In the obtained target, it was confirmed that the target material maintained the average grain size of 8 μm and that the crystal grains were not coarsened. In order to confirm the effect of surface roughness and bonding strength applied to the bonding surface of the target material,
The bonding strength was measured by the same method as in Example 1. Table 5 shows the results. As shown in Table 5, it can be seen that the bond strength can be increased by increasing the target material roughness.

[0040]

[Table 5]

[0041]

EFFECTS OF THE INVENTION According to the present invention, a target material having an effect of reducing particles and having fine crystal grains capable of aligning the direction of sputtering can be used as an aluminum alloy without coarsening the fine crystal grains. It is possible to provide it as a target which is diffusion-bonded to a backing plate mainly composed of. As a result, a large amount of power can be applied to a titanium target having a fine recrystallized structure, and a high quality thin film can be produced with high efficiency, which is extremely effective for mass production of thin films.

[Brief description of the drawings]

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

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

Claims (8)

[Claims] 1. A maximum grain size of 20 μm or less and an average grain size of 1
A sputtering titanium target in which a titanium target material having a recrystallized structure of 0 μm or less is diffusion bonded to a backing plate mainly containing aluminum. 2. The titanium target for sputtering according to claim 1, wherein the diffusion bonding part has a bonding strength of 50 MPa or more in tensile strength. 3. A titanium target material and a backing plate mainly containing aluminum are contacted with each other.
Hydrostatic pressing is performed under the conditions of 00 to 450 ° C. and pressure of 50 to 200 MPa to obtain a target in which a target material having a recrystallized structure with a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less and a backing plate are joined by diffusion. A method of manufacturing a sputtering target, comprising: 4. The titanium material obtained by cold working is 45
After performing a heat treatment at 0 ° C. or less to obtain a titanium target material having a recrystallized structure with a maximum grain size of 20 μm or less and an average crystal grain size of 10 μm or less, the titanium target material and an aluminum-based backing plate are contacted with each other. The titanium for sputtering according to claim 3, wherein the target is obtained by performing isostatic pressing under the conditions of 300 to 450 ° C. and a pressure of 50 to 200 MPa in this state to bond the target material and the backing plate by diffusion to obtain a target. Target manufacturing method. 5. The method for producing a titanium target for sputtering according to claim 3, wherein the temperature of the hydrostatic press is 400 ° C. or lower. 6. The method for producing a titanium target for sputtering according to claim 3, wherein the hydrostatic pressing is performed by enclosing the target material and the backing plate in a container made of aluminum. 7. The hydrostatic press is performed by enclosing the target material and the backing plate in a container made of a metal foil having a thickness of 0.5 mm or less. Manufacturing method of titanium target for sputtering. 8. The titanium target for sputtering according to claim 3, wherein the surface of the titanium target material to be joined to the backing plate is subjected to a roughening treatment of 6S to 12S. Method.