WO2014087926A1 - Molybdenum cylindrical body and method of producing molybdenum cylindrical body - Google Patents

Abstract

The purpose of the present invention is to overcome the problem of the necessity for large-scale equipment in order to produce a molybdenum cylindrical body for use as a large target. According to the present invention, a molybdenum cylindrical body for use as a large target is obtained by joining together a plurality of low-density molybdenum cylindrical bodies having density between 7.1 g/cm³ (relative density 70%) and 8.7 g/cm³ (relative density 85%), inclusive, in which oxygen has been controlled to 100 ppm or less.

Description

Molybdenum cylinder and method for producing molybdenum cylinder

The present invention relates to a molybdenum (Mo) product used as a sputtering target material and a method for manufacturing the same.

Generally, a molybdenum target is often used as a sputtering target for manufacturing a semiconductor device. As such a molybdenum target, a plate-shaped material has been frequently used, but due to the problem of use efficiency, it is changing to a highly efficient cylindrical material, and the required dimensions tend to increase. However, since the molybdenum material is a difficult-to-process material, manufacturing a large molybdenum target having a complicated shape increases the size of the device itself, so that facilities that can be processed in the world are limited.

Patent Document 1 discloses a method of manufacturing a molybdenum and molybdenum alloy tubular target. Specifically, Patent Document 1 describes that a flexible mold is filled with Mo powder having a particle size of 0.5 to 10 μm as measured by the Fisher method and having a metal purity of 99.9 wt% or more. A method is disclosed in which a green compact is obtained by placing it in a cold isostatically pressurized pressure vessel and compressing and solidifying it at a pressure of 100 to 500 MPa. Thereafter, in the method of Patent Document 1, the green compact is sintered and machined at a temperature of 1600 to 2500 ° C. to obtain, for example, a tube material having an outer diameter of 243 mm, an inner diameter of 123 mm, and a length of 1060 mm. Finally, an extrusion tube having a length of 2700 mm, an outer diameter of 170 mm, and an inner diameter of 129 mm is manufactured by performing extrusion processing or the like.

Patent Document 2 describes a method of obtaining a molybdenum pipe having a small hollow using fibers. Further, Patent Document 3 discloses a method for producing a low-density molybdenum sintered body by performing two-stage sintering.

Japanese Patent No. 4896032 JP-A-6-174970 Japanese Patent No. 3869057

Since the manufacturing method disclosed in Patent Document 1 requires a complicated and large-scale machining process, there are many problems in terms of economy, and an increase in size of the equipment is inevitable. Further, Patent Document 2 is a method of manufacturing a molybdenum pipe, but it is a technique for making a small hollow using fibers and cannot be applied to a technique for manufacturing a large cylinder. Furthermore, the molybdenum sintered body obtained by the method of Patent Document 3 discloses a technique for obtaining a Mo product having a high porosity and performing impregnation, etc., and obtaining a cylindrical target in which voids are likely to remain. Because of the final true density molybdenum cannot be obtained.

An object of the present invention is to obtain a large molybdenum product that is economically inexpensive and has a complicated cylindrical shape without using a large facility.

Another object of the present invention is to produce a target product having a complicated shape using powder metallurgy.

Furthermore, the subject of this invention is providing the molybdenum low density cylindrical body used as the prototype (intermediate body) for performing HIP shaping | molding especially.

According to the first aspect of the present invention, the molybdenum molded body has a tubular form, and the density is 7.1 g / cm ³ (relative density 70%) or more and 8.7 g / cm ³ (relative density 85%). A molybdenum low-density cylindrical body characterized in that oxygen is 100 ppm or less is obtained below.

According to a second aspect of the present invention, in the first aspect, the ratio of the inner diameter to the outer diameter is 1: 1.1 to 1: 3, the inner diameter is 50 mm or more, and the length is 100 mm or more. A molybdenum low density cylindrical body is obtained.

According to the third aspect of the present invention, a plurality of tubular tubes having a density of 7.1 g / cm ³ (relative density 70%) or more, 8.7 g / cm ³ (relative density 85%) or less, and oxygen of 100 ppm or less. After the molybdenum molded body is prepared by cold isostatic pressing (CIP), the plurality of the tubular molybdenum molded bodies are laminated and then subjected to hot isostatic pressing (HIP). A target molybdenum cylindrical body obtained by joining the tubular molybdenum molded bodies is obtained.

Furthermore, according to the fourth aspect of the present invention, the molybdenum molybdenum body for a target according to the third aspect, wherein the tubular molybdenum molded body is obtained by the cold isostatic pressing at a press pressure of 147 MPa or more. The manufacturing method is obtained.

According to a fifth aspect of the present invention, in the fourth aspect, the tubular molybdenum molded body is obtained by heat treatment in a reducing atmosphere at a heat treatment temperature of 1000 ° C. or higher and lower than 1600 ° C. A method for producing a target molybdenum cylinder is obtained.

According to the present invention, a molybdenum low-density cylindrical body can be obtained by pressing, sintering, and pressure sintering without requiring special machining such as extrusion, and industrially and inexpensively. Is obtained.

It is a figure which shows the molybdenum low density cylindrical body which concerns on the Example of this invention with a comparative example. It is a figure which shows the molybdenum low density cylindrical body which concerns on the other Example of this invention with a comparative example.

Principle of the invention:
The present inventors have applied hot isostatic pressing (HIP), hot pressing, etc. to a plurality of tubular molybdenum low-density cylindrical bodies (ie, tubular green compacts) once formed by pressure treatment or the like. By applying the process, it was intended to join a plurality of tubular molybdenum low density cylinders to produce a long target molybdenum cylinder.

In this way, when joining a plurality of tubular molybdenum low density cylindrical bodies in a subsequent step, the density of the tubular molybdenum low density cylindrical body is set to 7.1 g / cm ³ to 8.7 g / cm ³ (that is, relative density 70 % To 85%) was found to be necessary for joining in the subsequent process. Accordingly, the present inventors have density of molybdenum ^{7.1g / cm 3 ~ 8.7g / cm} 3 ( i.e., a relative density of 70% to 85%) the condition for realizing the range of, case where the target The present invention has been found together with the necessary conditions to achieve the present invention. That is, it has been found that a molybdenum cylinder having a relative density of 90% or more cannot be joined by hot isostatic pressing (HIP) or hot pressing.

First, the present inventors used an isostatic press for molding and investigated the change in density due to the molding pressure. However, with only the isostatic press, the density of molybdenum is too low, and HIP bonding is performed in a subsequent process. It has been found that the yield due to the deformation of time decreases.

Therefore, when heat treatment was performed in a heating furnace in a hydrogen atmosphere, higher density was achieved. However, if the relative density exceeds 85%, it becomes impossible to bond in a subsequent process (for example, HIP or hot press), and therefore a relative density of 70% or more and 85% or less is appropriate. It was also found that the target relative density can be realized by performing heat treatment at a true temperature of around 1250 ° C. in order to achieve the target relative density.

On the other hand, it was also found that abnormal discharge or the like can be prevented during sputtering by reducing the oxygen content to 100 ppm or less.

It has also been found that when the oxygen content exceeds 1500 ppm, nests and internal defects, which are poor sintering due to molybdenum oxide, are generated.

Based on the above knowledge, the results of manufacturing the molybdenum low density cylindrical body according to the present invention are shown as Examples 1 to 3 in FIG. FIG. 1 also shows Comparative Examples 1 to 4.

Next, the manufacturing process of the molybdenum low density cylindrical body shown in FIG. 1 will be described.

First, the powder particle size was measured by the Fischer method, and the molybdenum powder having a particle size of 3.2 μm was used in Examples 1 to 3 and Comparative Examples 1 to 3. The heat treatment was performed in hydrogen at a heating rate of 10 ° C./min and kept at the maximum temperature for 1 hour. A test article having an outer diameter of about 300 mm, an inner diameter of about 150 mm, and a height of about 200 mm was prepared. For the measurement of low density, either calculation from the shape or Archimedes method by paraffin coating can be used.

Subsequently, these molybdenum powders are sealed in a cylindrical capsule and subjected to CIP (cold isostatic pressing), whereby molybdenum low density cylinders according to Examples 1 to 3 and Comparative Examples 1 to 4 as shown in FIG. Got the body. Further, a plurality of molybdenum low-density cylinders were joined by HIP to obtain a target molybdenum cylinder.

As shown in Examples 1 to 3, a general molybdenum powder is controlled to a heat treatment temperature of 1200 ° C. to 1400 ° C. and a density of 7.1 to 8.7 g / cm ³ (relative density of 70% to 85%). Thus, a molybdenum cylindrical body suitable for use as a prototype (also referred to as an intermediate) of a cylindrical target could be produced. In Comparative Examples 1 and 2, the relative density was low, and defects were generated during bonding by HIP. Also, as in Comparative Example 4, a problem occurred during bonding even when the relative density exceeded 90%. In addition, according to experiments by the present inventors, it was confirmed that the heat treatment temperature may be increased to 1500 ° C.

Further, when a similar test was performed using powder having an average particle size of 1.8 to 7.5 μm, when the particle size was fine (1.8 μm), the maximum pressing pressure could be reduced by 40%. When the diameter was large (7.5 μm), the oxygen content value was lower, and the heat treatment temperature could be lowered to a minimum of 1000 ° C.

In either case, even if the particle diameter of molybdenum changes, the yield of cylindrical targets can be improved by adjusting the temperature and pressure so that the relative density of the cylindrical body is 70% to 85% and the oxygen analysis value is 100 ppm or less. I could do it well.

When the density was less than 7.1 g / cm ³ (relative density less than 70%), that is, when the density was too low, deformation occurred in HIP bonding, and bonding could not be performed. It was also observed that when the density was greater than 9.3 g / cm ³ (91%), the amount of deformation at the time of HIP bonding was insufficient, and a gap was formed in the target, resulting in failure.

Furthermore, a defect that a gap was generated in the joint even when the oxygen analysis value exceeded 100 ppm was also observed.

When manufacturing a low-density molybdenum cylindrical body, in addition to CIP, by performing heat treatment, the molded body has a bending strength of about 10 MPa as a CIP body, and by performing heat treatment, a bending strength of 50 MPa or more is obtained. By increasing the strength during transportation, it is possible to greatly improve the yield of defects during transportation.

Also, there is a possibility of a cylindrical target intermediate using only CIP that does not perform heat treatment unless the oxygen content is high.

Furthermore, it was also found that the proper design of the shape becomes important in taking this CIP process when manufacturing the intermediate of the cylindrical target.

Here, when the powder was molded at a particle size of 3.2 μm and a molding pressure of 225 MPa, the result shown in FIG. 2 was obtained. FIG. 2 shows Comparative Examples 5 and 6 together with Examples 4 to 6. As shown in FIG. 2, it has been found that the inner diameter / outer diameter ratio affects the CIP molding result.

That is, in the molybdenum low density cylindrical body, the ratio of the inner diameter to the outer diameter was required to be 1: 1.1 to 1: 3. Even when molybdenum is mixed with a binder, moldability and shape retention may be improved, but it is desirable not to add a binder in consideration of high density during use.

Furthermore, when considering the practicality of the molybdenum low density cylindrical body, the molybdenum low density cylindrical body needs to have an inner diameter of 50 mm or more and an outer diameter of 100 mm or more.

In the present invention, if the inner diameter does not exceed 50 mm, there is no opportunity for use as a target molybdenum cylindrical body, and if the length does not exceed 100 mm, an industrially subsequent joining step is included. In addition, the productivity of molybdenum cylinders for targets is greatly limited.

Although the embodiments of the present invention described above have been described with respect to molybdenum low-density cylinders, the present invention can also be applied to target molybdenum cylinders obtained by joining these molybdenum low-density cylinders.

This application claims the benefit based on the priority from Japanese Patent Application No. 2012-268069 filed on Dec. 7, 2012, the disclosure of which is hereby incorporated herein in its entirety Incorporated as a reference.

Claims (5)

1. The molybdenum molded body has a tubular shape, has a density of 7.1 g / cm ³ (relative density 70%) or more and 8.7 g / cm ³ (relative density 85%) or less, and oxygen is 100 ppm or less. Characteristic molybdenum cylinder.
2. 2. The molybdenum cylinder according to claim 1, wherein the ratio of the inner diameter to the outer diameter is 1: 1.1 to 1: 3, the inner diameter is 50 mm or more, the outer diameter is 100 mm or more, and the length is 100 mm or more. .
3. Cold isostatic pressing of a plurality of tubular molybdenum compacts having a density of 7.1 g / cm ³ (relative density 70%) or more, 8.7 g / cm ³ (relative density 85%) or less, and oxygen of 100 ppm or less. (CIP) After preparing the plurality of tubular molybdenum compacts, the target molybdenum cylinder joined with the plurality of tubular molybdenum compacts by applying hot isostatic pressing (HIP). A method for producing a molybdenum cylinder, comprising obtaining a body.
4. The method for producing a molybdenum cylindrical body according to claim 3, wherein the tubular molybdenum molded body is obtained by the cold isostatic pressing at a press pressure of 147 MPa or more.
5. The method for producing a molybdenum cylindrical body according to claim 4, wherein the tubular molybdenum molded body is obtained by further heat treatment in a reducing atmosphere at a heat treatment temperature of 1000 ° C or higher and lower than 1600 ° C.

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