JP2000144395A - Ruthenium target and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure Ru target capable of improving filling density at the time of using hot isostatic pressing, also capable of preventing nonuniform deformation and cracking during hot isostatic pressing, and having excellent structure, and its manufacturing method. SOLUTION: As a manufacturing method for obtaining an Ru target composed of a powder sintered compact of >=99% relative density and >=99.99% purity, a reduced Ru powder is pulverized and sealed in a hermetically sealed vessel to undergo hot isostatic pressing, by which relative density is regulated to >=99%. In this manufacturing method of the Ru target, it is preferable that pulverizing treatment is performed to <=50 μm volume average diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a Ru target used for producing a Ru thin film used for an electrode material, for example, and a method for producing the same.

[0002]

2. Description of the Related Art With the increase in the degree of integration of semiconductors, oxide-based materials having a higher dielectric constant have been used for capacitors in semiconductor cells. A platinum group noble metal with low reducibility to oxides is used. Among these noble metals, a sputtered Ru film having a low specific resistance of an oxide of the noble metal itself formed in the bonding layer with the dielectric layer is particularly frequently used. The Ru target for such a film is manufactured by the following three methods. The method includes a melting method using an electron beam or an arc, a method in which an ingot manufactured by solidifying raw material powder by hot pressing is subjected to an electron beam melting treatment to be highly purified, and a method in which an ingot manufactured by a melting method is hot-rolled. It is.

However, each of the above three methods has its own advantages and disadvantages. First, although the melting method has the advantage that a high-density target is easily obtained,
There is a drawback that voids are easily generated in the tissue and adversely affect the film formation, for example, as described in Japanese Patent Application Laid-Open No. 8-311641.
No. In addition, depending on the dissolution conditions, there is an inherent danger that a solidified structure of dendrites appears.

The method of treating a hot-pressed ingot with an electron beam also has the advantage that the density can be increased. However, the post-process of electron beam treatment is required, which complicates the process. In addition, there is a problem that a solidified structure of dendrites appears as in the above-described dissolution method due to the accompanying dissolution.

In general, the solidification structure of dendrites is not preferable in terms of film uniformity, film formation characteristics such as abnormal discharge and generation of particles, and a uniform fine structure is preferable. It is widely known in tool materials and the like that the mechanical properties such as the transverse rupture strength are inferior to a simple structure, and also in this respect, a method in which a uniform fine structure cannot be obtained is not preferable. Furthermore, in the case of electron beam melting, a high-purity ingot block of a friend material, called a starting block, is indispensable to prevent contamination of the ingot, and the initial investment is large. Not.

[0006] The melt rolling method mentioned last has an advantage that a structure having few voids can be obtained by providing a rolling step. However, since a post-step of rolling is required, the step becomes complicated and the rolling is performed. Brings out the organization. The rolled structure has low isotropy of the structure and exhibits a crystallographically strong orientation to a specific surface, and thus may cause a non-uniform sputtered film or a decrease in the film forming rate. As mentioned above,
The current manufacturing method based on the dissolution method has a fundamental problem in the structure, defects, orientation, and the like.

[0007]

As a method for solving the above-mentioned problems, the present inventor has applied a sintered body target which does not involve melting after sintering. We paid attention to the fact that generation of microstructures and voids can be prevented, and that the influence of texture generated by rolling can be reduced. Then, the realization of a Ru target made of a sintered body was studied. Here, the biggest problems in realizing a Ru target by a sintered body are the target density and the target manufacturability.

According to the study of the present inventor, even if an attempt is made to obtain a sintered body by applying a hot isostatic press effective for preventing contamination of the Ru powder in the manufacturing process, the relative density is inevitably about 98%. I could only get it. When the density of the target is low, a large number of defects remain inside the target, and abnormal discharge and generation of particles due to the abnormal discharge become a problem. Also, Ru is applied by applying a hot isostatic pressing method.
When the powder is sintered under pressure, the deformation due to the pressure sintering is so large that the container filled with the powder cannot follow and may be broken. Further, the deformation tends to be extremely non-uniform, and the product yield is reduced. An object of the present invention is to solve the above problems and to provide a Ru target made of a high-purity and high-density sintered body and a method for manufacturing the same.

[0009]

Means for Solving the Problems The present inventors diligently studied to solve the above problems. As a result, it has been found that the reason why the density of the sintered body does not increase and the reason why the yield decreases during the manufacturing process are in the shape of the raw material powder.
Since high-purity Ru powder is usually produced by a reduction method, it is a coral-shaped amorphous, porous powder. This Ru powder has a problem that the specific gravity of the powder itself is low and the friction of the powder is large, so that crosslinking at the time of filling is liable to be caused, and it is difficult to increase the filling density. Was found to be the cause.

As a result of further study, it has been found that the above problem can be solved by pulverizing the reduced Ru powder before sintering, and the present invention has been achieved. That is, the present invention is a method for producing a Ru target in which a reduced Ru powder is pulverized, sealed in a closed container, and subjected to hot isostatic pressing to adjust the relative density to 99% or more. Preferably,
The pulverization treatment is to pulverize to a volume average diameter of 50 μm or less.

According to the above-described method for producing a Ru target of the present invention, a relative density of 99% or more and a purity of 99.degree.
It is possible to provide a Ru target composed of a powder sintered body of 99% or more.

[0012]

An important feature of the production method of the present invention is that a pulverization treatment is applied to reduced Ru powder. By applying this step, deformation by hot isostatic pressing can be suppressed, and a high-density Ru target of 99% or more of the present invention can be obtained without defects such as cracks.

Further, the application of a hot isostatic press using a sealed container can minimize external contamination during the manufacturing process, and is made of a sintered body having a purity of 99.99% or more. It is possible to realize the target. In addition, as a method of improving the packing density in the sealed container, it is possible to further improve the packing density by using a vibrator, a hammer shaker, a press, or the like in combination.

The relative density of the present invention is 99% or more, and the purity is 99.
Since the Ru target composed of a powdered sintered body of 99% or more is a powdered sintered body, the structure becomes uniform and fine, and does not have an orientation to a specific crystal plane. This makes it possible to suppress the occurrence of abnormal discharge while preventing a variation in the deposition rate of Ru during sputtering.

In the production method of the present invention, it is desirable that the raw material has as high a purity as possible.
Use 99.995% or more of raw material Ru powder. The reduced Ru
Pulverization of the powder is desirably pulverized to a volume average diameter of 50 μm or less from the viewpoint of ensuring high packing density and reducing the occurrence of cracks. As the conditions of the hot isostatic pressing, filling in a sealed container, degassing, sealing, and a temperature of 1150 ° C. or more, desirably 1400 ° C. or less, a pressure of 1000 atm or more, and a time of 45 minutes or more are desirable. .

When the temperature of the hot isostatic pressing is lower than 1150 ° C., the density of the target after hot isostatic pressing is 99%.
In some cases, the temperature cannot be reached, and 1150 ° C or higher is desirable. If the temperature exceeds 1400 ° C., the strength of the iron can normally used as a sealed container is insufficient when the temperature exceeds 1400 ° C., and the contamination from the container may progress. If the pressure is 1000 atm or more, it may be difficult to increase the density of the target to 99% or more.

In addition to the above-mentioned method, in order to prevent contamination at the time of pulverization, for example, in a pulverization treatment by a ball mill, reduced Ru powder is preliminarily pulverized in an argon atmosphere. It is preferable to form a coating of the reduced Ru layer to prevent contamination of the powder from the container. In the pulverization process, a pulverization process can be performed using a planetary ball mill, an attritor, a rod mill, or the like other than the ball mill described above.

As the shape of the Ru powder after pulverization, for example, when a reduced Ru powder having an average particle size of about 60 μm is ball-milled, at an initial stage (for example, several hours) after the commencement of the pulverization, the progress of the pulverization causes The percentage has increased,
The ultrafine powder having a particle diameter of 5 μm or less and the fine powder having a particle diameter of about 10 μm are bipolarized. However, if further pulverization is performed, the average particle diameter increases again due to the reagglomeration of the fine powder, and 10 μm to
The proportion of powder with a particle size of 50 μm increases to about 70%. The ratio of the powder having a particle size of 50 μm or less is about 10%, and the ratio of the fine powder having a particle size of 10 μm or less is about 20%. A powder having such a particle size distribution is particularly desirable from the viewpoint of improving the filling rate, and it is possible to achieve a higher packing density.

At this time, the volume average diameter is determined by the time required for the pulverizing treatment. For example, when the pulverization time in a ball mill is 4 hours or more, the volume average diameter is 50 μm.
m or less. Further, if the pulverization time in the above-mentioned ball mill is set to, for example, 12 hours or more, a powder shape which can be adjusted to a particle size distribution suitable for improving a filling rate in a closed container for hot isostatic pressing can be obtained. Here, an example in which a ball mill is used has been described.However, when a pulverizing device other than the ball mill is used, there is a difference in a particle size suitable for high filling and a required time for obtaining a particle size distribution. Needless to say.

[0020]

EXAMPLE First, a pure Ru raw material powder having a purity of 99.9 was used.
A 95% reduced Ru powder was prepared. The reduced Ru powder was pulverized using a ball mill. As the ball mill, both pods and balls made of stainless steel were used. At this time, the reduced Ru powder was preliminarily pulverized in an argon atmosphere to form a coating of the reduced Ru layer on the container wall surface and the ball surface, thereby preventing contamination of the powder from the container. Using the ball mill apparatus thus prepared, a pulverizing treatment was performed for 12 hours under an argon atmosphere.

To compare the powder shapes before and after the pulverizing treatment, an electron micrograph of the powder before the pulverizing treatment is shown in FIG. 3, and an electron micrograph of the powder after the pulverizing treatment is shown in FIG.
3 and 4, the powder is spheroidized by the pulverization treatment, the small holes existing in the powder disappear or are significantly reduced, and the powder has a shape suitable for improving the filling rate. FIG. 2 shows the particle size distribution of the powder in order to compare the change in the particle size of the powder before and after the pulverization. At the time of grinding for 12 hours, the particle size distribution is sharp. It was found that the powder having a sharp particle size distribution and a relatively large particle size was adjusted to a desirable particle size distribution from the viewpoint of improving the filling rate, and the volume average particle size was also 16.63 μm.

Subsequently, the above-mentioned powder was sealed in a closed container. Table 1 shows the packing ratio of the powder before and after the pulverization treatment, and Table 2 shows the results of impurity analysis of the powder to compare the composition of the powder before and after the pulverization treatment.

[0023]

[Table 1]

[0024]

[Table 2]

By the pre-grinding treatment, impurities other than oxygen remain unchanged at the analysis limit or less, and it can be said that contamination during the grinding is negligible. Further, the powder subjected to the pulverization treatment was filled in an iron can having an Nb foil applied thereto by applying a load of a surface pressure of 0.68 MPa.
The Nb foil has an effect of reducing the oxygen concentration increased by the pulverization process, in addition to the effect of releasing from the iron can and preventing the reaction.

The iron can filled with the powder is degassed and sealed.
Hot isostatic pressing was performed at 180 ° C. and 100 MPa for a holding time of 3 hours. The sintered body obtained by hot isostatic pressing was machined to obtain a Ru target. R
The u target had a relative density of 100% and was completely densified.

A cross section of the Ru target was observed with an optical microscope, and a photograph is shown in FIG. As shown in FIG.
The u target has a uniform and fine structure without dendrites.
Such a uniformly fine structure is generally preferable in terms of reducing particles and abnormal discharge during sputtering, improving the uniformity of the film, and the like. Table 3 shows the analysis results of impurities contained in the target. The oxygen concentration is lower than the impurities in the powder of Table 2. This is because oxygen was reduced by the movement of oxygen from the Ru powder to the Nb foil.

[0028]

[Table 3]

Table 4 shows a list of the main X-ray diffraction peaks of the target. It almost agrees with the peak intensity of powdered Ru shown on the JCPDS card, which is a standard database of diffraction data. Specifically, based on Equation 1,
Using the measured diffraction intensity I and the diffraction intensity R described on the JCPDS card, the main peaks (100), (002),
When X (I) is obtained for three of (101), 25
It is in the range of ４０40%, which is a random orientation.
Also, it can be seen that there are no extremely coarse grains.

[0030]

(Equation 1)

[0031]

[Table 4]

The target of the present invention has a low orientation and does not contain coarse particles. The target is preferable in terms of reduction of particles and abnormal discharge during sputtering, improvement of film uniformity, improvement of sputtering rate, and the like. Density 9
A pure Ru target composed of a powder sintered body of 9% or more can be obtained.

Comparative Example The same reduced Ru powder as in the example (FIG. 2 reduced powder (untreated)) was filled in an iron can without being subjected to pulverization treatment, degassed and sealed at 1320 ° C. and 185 MPa.
a, Hot isostatic pressing was performed with a holding time of 0.75 hours. The density of this sintered body was 97%. The amount of shrinkage and deformation during hot isostatic pressing was large, the iron can was abnormally deformed, and wrinkled cracks were generated in the sintered body, and a sintered body with good characteristics could not be obtained.

[0034]

According to the present invention, a pure Ru target with uniform fineness and no orientation can be produced in a drastically reduced number of steps, which is an indispensable technique for producing a pure Ru target.

[Brief description of the drawings]

FIG. 1 shows a microscopic photograph of a cross section of a target.

FIG. 2 is a diagram showing a particle size distribution of Ru powder before and after a pulverization process.

FIG. 3 is a micrograph showing an example of the shape of a Ru powder before a pulverization treatment.

FIG. 4 is a micrograph showing an example of the shape of the powder after the pulverization of the Ru powder.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C23C 14/14 B22F 3/14 MF term (reference) 4K017 AA03 BA02 CA07 DA09 4K018 AA02 BA01 BB04 BC08 EA13 KA29 4K029 AA02 BA02 DC03 DC09

Claims (3)

[Claims] 1. A relative density of 99% or more and a purity of 99.99%.
A Ru target comprising the above powder sintered body. 2. After the reduced Ru powder is pulverized, the reduced Ru powder is sealed in a closed container and subjected to hot isostatic pressing to obtain a relative density of 99%.
%. A method for manufacturing a Ru target, wherein the Ru target is adjusted to at least%. 3. The method for producing a Ru target according to claim 2, wherein the pulverization is performed by pulverization to a volume average diameter of 50 μm or less.