JP2015081355A - Sputtering target and method for manufacturing sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target that does not need an extra-manufacturing facility and is excellent in post-sputtering property, and to provide a method for manufacturing the same.SOLUTION: The sputtering target is integrally formed from a plurality of parts that are divided into small pieces of single metal to be a target material by hot isostatic press (HIP) and diffused junction. There is also provided the method for manufacturing the sputtering target.

Description

The present embodiment relates to a sputtering target for forming a thin film and a method for manufacturing the sputtering target.

In the process of forming thin films, such as semiconductor manufacturing, wafers with a diameter of 300 mm are the mainstream from the viewpoint of productivity, and in the future, manufacturing with larger wafers such as wafer lines with a diameter of 450 mm will be performed. Is being considered.

In connection with this, the sputtering target used for the sputtering apparatus at the time of thin film formation needs to enlarge larger than 400 mm in diameter.

Conventionally, Japanese Patent Application Laid-Open No. 2003-193225 (Patent Document 1) and Japanese Patent Application Laid-Open No. 05-222525.
As shown in Japanese Patent Publication (Patent Document 2), these sputtering targets are obtained by machining a sintered body manufactured by hot pressing or hot isostatic pressing to a finished dimension, or by sintering or melting these sintered bodies. The ingot manufactured by the above method is made into a predetermined size by a combination of plastic working (forging and rolling) and heat treatment, and finished by machining.

In order to reduce impurities in a thin film formed by sputtering and improve EM (electromigration) characteristics and the like, these sputtering targets are required to have high purity and fine crystal grains. However, with the increase in size, the manufacturing itself becomes difficult with conventional manufacturing equipment, and even if it can be manufactured, the metal structure over the entire surface of the target (crystal grain size, crystal orientation) to obtain uniform sputtering characteristics as a target. , Internal defects, etc.) are difficult to control. Therefore, in order to manufacture a large target, new capital investment such as a large firing furnace, a forging device, a rolling mill, and a heat treatment furnace is required, and the manufacturing cost is greatly increased.

Furthermore, when a large target is manufactured as an integrated product, it is difficult to control the metal structure over the entire surface as described above, so that local defects are likely to remain. Not only will it cause fine metal pieces called dust to fall off, but also the uniformity of the target will be impaired, resulting in non-uniform sputtering behavior and non-uniform film thickness on the product after film formation. There are concerns about adverse effects such as short lifetime in EM characteristics and the like, and non-constant electrical resistance of the deposited film.

JP 2003-193225 A Japanese Patent Laid-Open No. 05-222525

The problem to be solved by the present embodiment is to provide a sputtering target and a method for manufacturing the same that do not require new manufacturing equipment and are excellent in characteristics after sputtering.

In order to solve the above-mentioned problems, the sputtering target of the embodiment is integrated with a plurality of parts divided into single metal pieces as a target material by diffusion bonding with a hot isostatic press (HIP). It is the sputtering target characterized by having performed, and its manufacturing method.

FIG. 3 is an explanatory diagram of a state in which metal pieces according to the first embodiment are diffusion bonded. FIG. 3 is an explanatory diagram for creating a disk-shaped target according to the first embodiment by machining.

The present invention relates to a high-purity metal sputtering target used in a sputtering apparatus for forming an electrode / wiring material such as an LSI or a memory by sputtering, and a method for manufacturing the sputtering target.

In the high-purity metal sputtering target and the method for producing the same according to the present invention, high purity refers to a metal having a purity of 99.95% or more excluding impurity metals other than nitrogen, oxygen, carbon, hydrogen, and sulfur.

99.95% or more of high-purity metal powder is die pressed or cold isostatic pressed (CIP)
After being molded, etc., it is sintered in hydrogen at a temperature higher than the primary recrystallization temperature, and small pieces are created from these sintered bodies by machining, and multiple pieces of those small pieces are organic components or metal components, etc. Using a mold release agent that does not contain a component harmful to the thin film characteristics of the metal foil having a melting point exceeding the HIP temperature (for example, Nb or Ta) is 1.3 × 10 ⁻³ Pa or less, preferably 1.0x
After degassing canning at a vacuum of 10 ⁻³ Pa or less (at this time, degassing is preferably performed at 200 ° C. or more for 2 hours or more), and at a temperature higher than the primary recrystallization temperature for 3 hours or more, preferably 5 hours or more. Hot isostatic pressing (HIP) at a pressure of 175 MPa or more, preferably 184 MPa or more
Processing was performed, and the small pieces were diffused and joined together.

A disk-shaped target was created from the integrated metal by machining as shown in Fig.2.

According to the sputtering target and the manufacturing method thereof described above, hot isostatic pressing (HIP) is performed at a temperature higher than the primary recrystallization temperature with parts obtained by dividing a single metal as a target material.
Because it is an integral type by diffusion bonding, since it is the joining of small piece-like divided parts, there is no need for new large manufacturing equipment, and there are almost no defects in the joint after diffusion bonding, so the characteristics after sputtering It is possible to have excellent uniformity.

Hot isostatic pressing is performed at a temperature higher than the primary recrystallization temperature. In this temperature range, lattice defects in the metal structure disappear, crystal rearrangement, and recrystallization proceed. This is because the number of pores (vacancies) that cause dust during sputtering is reduced.

However, when the primary recrystallization temperature exceeds 500 ° C., the crystal grains grow due to the secondary recrystallization and the grain size is locally coarsened, so that the metal structure in the sputtering surface becomes non-uniform, and the sputtering behavior Becomes non-uniform, which adversely affects the film characteristics (film thickness, electrical resistance, etc.) after film formation.

The pressure applied in the hot isostatic pressing is preferably a pressure higher than the yield stress of the metal in a temperature range higher than the recrystallization temperature in order to reduce defects at the bonding interface.

However, if the fracture strength of the base metal is exceeded, defects such as cracks and pores (voids) may occur in the crystal grains and cause dust during sputtering. Adversely affects electrical resistance, electromigration, etc.).

As a bonding pressure method at the time of diffusion bonding, in the case of hot pressing, since the pressure is uniaxial (for example, a direction perpendicular to the target surface), defects are likely to occur on a specific surface such as the outer periphery of the target. If a hydraulic press is used, the directionality of such pressure is small, and pressure is applied in all directions, so that defects in the base material and the bonding interface are reduced.

Metals having a melting point exceeding the HIP temperature using a release agent that does not contain components harmful to thin film properties of organic components or metal components in hot isostatic pressing (HIP) (for example, Nb or Ta
Etc.) is degassed and canned with a metal foil of 1.3 × 10 ⁻³ Pa or less when using a mold release agent containing these, C, O, Al, Fe, Ni, etc. during hot pressing This element may diffuse into the base metal and adverse effects such as increasing the resistance value of the thin film after sputtering when a target using these elements is sputtered may occur.

When there are bonding defects having a size of 1 μm or more in the bonding interface region within 10 mm on both sides from the bonding interface of the diffusion bonded target as described above, these defective portions are minute metal pieces called dust when the target is sputtered, etc. It will cause the dropout.

The size of the defect is preferably less than 1 μm, more preferably 0.1 μm or less, and most preferably is a state in which there is no defect (0 μm).

In addition, when it is difficult to discriminate the bonding interface, a sample having a target diameter x width of 20 mm may be cut out and cut every 20 mm in the length direction to measure the relative density, the three-point bending strength, and the average particle diameter. .

Since the target of the embodiment is homogenized with the base material at the bonding interface, the same result as that of the base material can be obtained even if the method as in the previous period is used.

The relative density is defined as a percentage of the element density of the density measured by “Method for measuring density and specific gravity by weighing method in liquid” in Section 8 of JISZ8807. The element density is the density of each element described in the “Metal Data Book” edited by the Japan Institute of Metals. For the relative density, the relative density of the base material is A (%), and the relative density of the bonding interface region within 10 mm on both sides from the bonded interface is B (
%) And calculated by B / A, and this value is 0.978 or more. If it is less than 0.978, there are many defective parts such as pores, which cause dropping of fine metal pieces called dust when sputtered. 1.000 equivalent to the base material is preferable.

The average particle diameter is defined as the average (average cut length) of the lengths (intercept lengths) intersecting the grain boundaries on two orthogonal straight lines calculated from a metallographic photograph of a plane parallel to the target surface. Its average particle size is 100
When the average particle size of the base material is C (μm) and the average particle size of the bonding interface region is D (μm), D / C is 0.726 to 1.378. When the average particle size exceeds 100 μm, uniform sputtering is difficult. In addition, when D / C is less than 0.726 and exceeds 1.378, the average crystal grain variation between the base material and the bonding region is too large, and uniform sputtering is difficult.

The three-point bending strength is determined by a three-point bending test according to JIS R1601. When the three-point bending strength of the three-point bending test according to JIS R1601 of the three-point bending test base material is E (MPa) and the three-point bending strength of the bonding interface region is F (MPa), F / E is 0.793. That's it. 0.7
If it is less than 93, the bonding interface region is not sufficiently bonded because the strength is lower than that of the base material, so that uniform sputtering is difficult.

The number of defects is such that the seam of the interface is 200 in the bonded interface region within 10 mm on both sides from the bonded interface.
This is the number of junction defects having a size of 1 μm or more on a double scanning electron microscope (SEM) photograph.

The base material is a sputtering target characterized in that it is formed of one of the 3a group, 4a group, 5a group, 6a group, 7a group, 8 group, and 1b group metal.

As Group 3a metal, Sc, Y, Group 4a metal as Ti, Zr, Hf, Group 5a metal as V, Nb, Ta, Group 6a metal as Cr, Mo, W, Group 7a as Mn, Re, Group 8 metal mainly refers to Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, and Group 1b metal metal mainly refers to Cu, Ag, Au. Preferably, high melting point metals (W, Mo, Ta, Nb,
A metal produced from a sintered body with Cr, V, Zr, Hf, Ru, Re, Ir, Pt) is desirable.

Hereinafter, an example of tungsten will be described as the present embodiment.

After 99.99% or more of high-purity tungsten powder (particle size: 2.0 to 4.0 μm) was molded to 207 mm x 207 mm x 13 mm with a mold press, it was kept in hydrogen at 1750 ° C for 8 hours in hydrogen. Sintering was performed, and 9 p small pieces having a size of 168 mm × 168 mm × 10 mm were formed by machining.

A vacuum of 1.3 × 10 ⁻³ Pa or less with an Nb metal thin plate using a release agent that does not contain components harmful to thin film characteristics such as organic components or metal components, arranged in 3 × 3. After deaeration-canning at a temperature, the piece is diffused and bonded by hot isostatic pressing (HIP) at 1600 ° C to 1900 ° C for 5 hours or more and at a pressure of 175 MPa or more, and integrated as shown in Fig. 1 did.

A target of φ440 mm was created from the integrated metal by machining as shown in FIG.

For this target, the relative density of the bonding interface and the integral part (base material), the metal structure (average crystal grain size), the three-point bending strength, the amount of impurities, the amount of C, and the short leak defect after sputtering were investigated. The results are shown in Table-1.

As is apparent from Table 1, the sputtering target which is one of the present embodiments is such that the bonding interface has an integral part (base material) and relative density, metal structure (average crystal grain size), three-point bending strength, There was no difference in either the amount of impurities or the amount of C.

According to the sputtering target and the manufacturing method thereof according to at least one embodiment described above, diffusion bonding is performed by hot isostatic pressing (HIP) at a temperature equal to or higher than the recrystallization temperature at a part obtained by dividing a single metal serving as a target material. Because it is an integrated type, it does not require a new large-scale manufacturing facility because it is a joining of small piece parts, and it has excellent post-sputtering characteristics because there are almost no defects in the joint after diffusion bonding. Is possible.

Hot isostatic pressing is performed at a temperature higher than the recrystallization temperature. In this temperature range, lattice defects in the metal structure disappear, crystal rearrangement, and recrystallization progress. This is because the number of pores (vacancies) that cause dust during sputtering is reduced.

The pressure applied in the hot isostatic pressing is preferably a pressure equal to or higher than the yield stress of the metal at a temperature equal to or higher than the recrystallization temperature in order to minimize defects at the bonding interface.

The hydrostatic press is used as the bonding method because the pressure applied during diffusion bonding is higher than the uniaxial pressure in all directions unlike the uniaxial hot press. It is.

Vacuum degassing canning with Nb metal foil using a release agent that does not contain organic components or metal components harmful to thin film properties such as aluminum in hot isostatic pressing (HIP) When an agent is used, elements such as C, O, and Al may diffuse into the base metal during hot pressing, which may cause adverse effects such as increasing the resistance value of the thin film after sputtering.
(Comparative Example 1)

After 99.99% or more of high-purity tungsten powder (particle size: 2.0 to 4.0 μm) is formed into about φ400 mm by cold isostatic pressing (CIP), it is heated at 1750 ° C. for 8 hours in hydrogen. Sintered in hydrogen and vacuum degassed with an Nb metal sheet using a release agent that does not contain organic components or metal components that are harmful to thin film properties such as aluminum, and then 185 MPa at 1800 ° C. for 5 hours. Hot isostatic pressing (HIP) treatment at a pressure of φ320 by machining
A target of mm was produced.

For this target, the relative density, metal structure (average crystal grain size), three-point bending strength, impurity content, C content, number of defects, and short leak defects after sputtering were investigated, and the results are shown in Table-1.

Thus, comparing the comparative example 1 and the example 1, in this embodiment, it is possible to manufacture a target having almost the same density, strength, and impurity amount as the integrated target, and further, the crystal grain size It can be seen that it is possible to miniaturize the film and to reduce the short leak defect after sputtering.

Although some of the present embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Sputtering target 2 ... Base material 3 ... Bonding interface area | region

Claims (13)

In a sputtering target in which a plurality of divided base metals made of a high-purity metal having a purity of 99.95% or more are joined and integrated, a defect having a size of 1 μm or more in a joining interface region within 10 mm on both sides from the joined interface There is no sputtering target. In a sputtering target in which a plurality of divided base metals made of a high-purity metal having a purity of 99.95% or more are joined together, the joint of the interface is 200 times in the joined interface region within 10 mm on both sides from the joined interface. The sputtering target according to claim 1, which cannot be confirmed on a photograph of a scanning electron microscope (SEM). JIS Z 8807 8 Density measured by weighing method in liquid and specific gravity measured by the density measurement method The percentage of the density relative to the element density is A (%). The relative density of the base material is A (%). The sputtering target according to claim 1, wherein B / A is 0.978 or more when the relative density of the bonding interface region is B (%). The sputtering target according to any one of claims 1 to 3, wherein the diameter is 300 mm or more. The sputtering target according to any one of claims 1 to 4, wherein the base material is a sintered body. 6. The base material according to claim 1, wherein the base material is formed of one of a group 3a, 4a, 5a, 6a, 7a, 8 and 1b metals. The sputtering target according to item. The base materials are Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re
7, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au. Sputtering target. The average grain length of the grain boundary on the straight line calculated from the metal structure photograph of the plane parallel to the target plane is defined as the average grain size, the average grain size is 100 μm or less, and the average grain size of the base material is C (μm). ,
The sputtering target according to any one of claims 1 to 7, wherein D / C is 0.726 to 1.378 when the average particle size of the bonding interface region is D (µm). . The three-point bending strength of a three-point bending test according to JIS R1601 of the base material is E (MP
The F / E is 0.793 or more when the three-point bending strength of the joining interface region is F (MPa), and the f / E is any one of claims 1 to 8. Sputtering target. 10. The unit according to claim 1, wherein a plurality of base materials are integrally formed by diffusion bonding with a hot isostatic press (HIP) at a temperature equal to or higher than a recrystallization temperature. Sputtering target and manufacturing method thereof. After hot isostatic pressing (HIP), vacuum degassing canning using a release agent that does not contain components harmful to thin film properties after sputtering of organic components or metal components, followed by hot isostatic pressing (
11. The method according to claim 1, wherein diffusion bonding is performed by performing a HIP process.
2. The sputtering target according to item 1 and a method for producing the sputtering target. C, O, Al, Fe, N harmful to thin film properties after sputtering during hot isostatic pressing (HIP)
12. A vacuum degassing canning using a mold release agent that does not contain i and Cr components, followed by diffusion bonding by hot isostatic pressing (HIP) treatment. 2. The sputtering target according to item 1 and a method for producing the sputtering target. After performing vacuum degassing canning using a release agent that does not contain components harmful to thin film properties after sputtering of organic components or metal components during hot isostatic pressing (HIP), at a temperature above the recrystallization temperature, The sputtering target according to any one of claims 1 to 12, wherein the pressure is subjected to hot isostatic pressing (HIP) treatment under conditions higher than the yield stress of the base metal and diffusion bonding. Method.

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