KR100936016B1 - Method of fabricating a sputtering target of molybdenum having ultrafine crystalline and sputtering target of molybdenum prepared thereby - Google Patents

Abstract

The present invention relates to a method for producing an ultra-fine grain Mo sputtering target, and to a Mo sputtering target thus obtained, and more particularly, to producing a sputtering target using nano-sized Mo powder as a raw material powder, at a high temperature for a short time and at a low temperature. The present invention relates to a method for producing an ultrafine grain Mo sputtering target that performs a two-stage sintering process for a long time, and a Mo sputtering target obtained thereby.

The method inhibits rapid grain growth that occurs during sintering of nanopowders, thereby enabling the production of sputtering targets having ultrafine grains of 500 nm or less.

Sputtering Target, Ultra Fine Grain, Two Stage Sintering

Description

METHOD OF FABRICATING A SPUTTERING TARGET OF MOLYBDENUM HAVING ULTRAFINE CRYSTALLINE AND SPUTTERING TARGET OF MOLYBDENUM PREPARED THEREBY}

The present invention relates to a method for producing an ultrafine grain Mo sputtering target, which suppresses rapid growth of particles during sintering of a nanopowder and enables the production of a sputtering target having ultrafine grains, and a Mo sputtering target obtained thereby.

Molybdenum (Mo) has been applied to a variety of industrial materials such as high temperature high strength structural materials, electrical contact materials. Sintering of the molybdenum in the case of powder metallurgy has been performed for a long time and high temperature of 1800~2000 ℃ (P. Garg, Park SJ, German RM, Int. J. Refract. Met. Hard Mater . 25 (2007) 16).

Republic of Korea Patent Publication No. 2007-57225 proposes the production of molybdenum sputtering target, specifically, after molding the molybdenum powder at a high temperature of 1780 ~ 2175 ℃, heat treatment at a temperature of 815 ~ 1375 ℃ to form a tubular sputtering target Manufacture.

The high-temperature sintering using such a micro-sized molybdenum powder is not only a problem of deterioration of mechanical properties due to grain growth, but also when the crystal grain size is large, the thin film formed by sputtering using the target does not have a desired uniform texture and / or film thickness. Will not.

Generally, nano-sized powders have a significantly increased specific surface area compared to micron-sized powders, which means an increase in sintering drive. In this regard, the use of nanopowders has the advantage of being able to sinter at low energy. However, in general, the driving force of sintering is proportional to the size of the surface area of the powder particles, so that the nanoparticles have a high possibility of rapid grain growth during sintering (Cameron, CP & Raj, R. Grain growth transition during sintering of colloidally prepared alumina powder compacts J. Am . Ceram . Soc . 71, 1031-1035 (1988); Brook, RJ in Treatise on Materials Science and Technology Vol. 9 (ed. Wang, FFY) 331-363 (Academic, New York, 1976)). . This grain growth implies grain growth, and as a result, it is very difficult to keep the microstructure of the final sintered compact in nanometer scale (J. Horvath, R. Birringer, and H. Gleiter, Solid State Comm. , 62 (5) (1987) 319; RS Averback, HJ Hofler, and Tao, M ater.Sci . & Eng ., A166 (1993) 169.)

In other words, sintering through the nanopowder deviates from the equilibrium state of a typical polycrystalline material of the same composition due to the randomly increased interface of the nanopowder and the many atoms located within the interface. For this reason, the diffusivity and sinterability are improved compared to the general powder, but the thermal stability is decreased. This decrease in thermal stability causes rapid grain growth and abnormal grain growth during sintering, which makes it difficult to produce sintered bodies having ultrafine grains. Therefore, the general sintering method cannot produce a sintered body having ultrafine grains in a single phase metal-based material.

Therefore, in order to maintain the properties of the nano-powder even in the bulk material, a sintering process in which grain growth is suppressed is required.

Two-step sintering has been reported to be applicable to ceramic materials such as Y ₂ O ₃ to produce dense bodies with reduced grain growth (Chen IW, Wang XH.Sintering dense nanocrystalline ceramics without final -stage grain growth Nature 2000; 404: ...... 168~171 .; Lee YI, Kim YW, Mitomo M, Kim DY Fabrication of dense nanostructured silicon carbide ceramics through two-step sintering J. Am Ceram Soc 2003; 86 (10): 1803-1805)

The present inventors applied a two-stage sintering method to solve the problem of the molybdenum nano-powder that causes rapid grain growth.

An object of the present invention is to provide a method for producing a Mo sputtering target having a high density and ultrafine grains using a nano-size Mo raw material powder and the Mo sputtering target produced thereby.

In order to achieve the above object, the present invention when manufacturing a sputtering target using a nano-size Mo powder as a raw material powder,

Provided is a method for producing an ultrafine grain Mo sputtering target that performs a two-stage sintering process for a short time at a high temperature and a long time at a low temperature.

The present invention also provides a Mo sputtering target prepared by the above method.

The two-stage sintering method according to the present invention solves the problem of grain growth in the sintering process when using a powder having a particle size of nano size as a raw material powder, thereby enabling the production of a sputtering target having a relatively high density of ultrafine grains.

Hereinafter, the present invention will be described in more detail.

In the present invention, when producing a sputtering target using a Mo powder having a nanoparticle size as a raw material powder, Mo sputtering target is manufactured through a two-sinter sintering process for a short time at a high temperature and a long time at a low temperature.

Specifically, the Mo sputtering target

Iii) molding the Mo nanopowder to prepare a molded article,

Ii) The molded product is first sintered to 1000 to 1100 ° C at a heating rate of 5 to 15 ° C / min,

Iii) The first sintered sintered body is produced through a second sintering process at 900 to 950 ° C.

First, a molded article is manufactured by molding Mo nanopowder.

The Mo nano powder uses a nano size powder having a particle size of 20 to 200 nm. These nano-sized raw powders can be applied to various fields compared to micron-sized powders.

The Mo nano powder may be purchased and used commercially, or may be prepared by using a micron-level powder through a direct ball mill process. In the case of direct production as an example, the MoO ₃ raw material powder is injected into a ball and a ball mill, followed by ball milling under an argon atmosphere, followed by reduction.

The ball is not particularly limited in the present invention, a known stainless steel ball is used, wherein the ball is a raw material powder and a loading ratio (weight ratio) of 14: 1 to: 18: 1, preferably a weight ratio of 16: 1. The ball mill is performed smoothly by mixing with.

At this time, the ball mill apparatus that can be used is not particularly limited in the present invention, typically an attritor, a 3-D mixer, a planetary ball mill, a vibratory ball mill, a horizontal ball mill ( Various ball mill devices such as horizontal ball mills are possible.

The MoO ₃ raw material powder was carried out in the above-described ball mill apparatus at a speed of 100 to 500 rpm for 1 to 24 hours, and the powder obtained after the ball mill process was heated up to a temperature of 700 to 900 ° C. in a hydrogen atmosphere, without being maintained. Cooling produces Mo nanopowders.

Such Mo nano powder performs a conventional molding process for producing a sputtering target. The molding process is not limited in the present invention, a process that is commonly used is possible, and preferably isoaxial uniaxial molding of the Mo nanopowder under a pressure of 200 to 300 MPa to prepare a molded body.

Next, the molded article prepared above is subjected to a primary sintering process up to 1000 to 1100 ° C. at a temperature increase rate of 5 to 15 ° C./min.

At this time, if the temperature increase rate is lower than the above problem occurs that the particles grow during the temperature rise, on the contrary, if the problem exceeds the above, the problem of density decrease occurs, it is carried out within the above range. In addition, when the sintering temperature is less than the above range, it is difficult to achieve densification during the secondary sintering process due to the low sintering density, and when the sintering temperature is exceeded, the problem of grain growth occurs.

Next, Mo sputtering target is manufactured through the second sintering of the first sintered sintered body at 900 to 950 ° C.

At this time, when the secondary sintering temperature is lower than the above problem occurs that the density is lowered, on the contrary, if it exceeds the above problem occurs that the particles grow, it is carried out within the above range.

This secondary sintering is carried out for 3 to 20 hours. At this time, if the sintering time is less than the above range, the particle size is fine, but there is a fear that the density may be lowered.

According to Experimental Example 1 of the present invention, the Mo sputtering target has a density of 80% or more, preferably 84 to 95%, and a Vickers hardness of 2.0 GPa or more, preferably 2.5 to 3.5 GPa. In addition, the crystal grains have ultrafine grains of 500 nm or less, preferably 200 to 500 nm.

The Mo sputtering target can be used in all fields where Mo can be used, and can be applied in the form of a thin film through various sputtering methods.

For example, Mo sputtering targets are used in all fields of manufacturing molybdenum sintered products having ultrafine grains, that is, high-temperature high-strength structural materials, electrical contact materials, shaped charge liners of missiles, anode grids and supports of electron tubes. , Electrical circuit contacts, high-temperature parts of heat-resistant materials, special alloys, electrode materials for electric bulbs, heating wires, hydrogenated catalysts, glass melting electrodes for glass electric furnaces, and mandrel for the manufacture of various filaments. Is also used.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

Preparation Example 1 Preparation of Nano Molybdenum (Mo) Powder

Molybdenum oxide (MoO ₃ ) powder was charged to the Attrittor equipment with a stainless ball (Stainless Ball, 4.5 mm) in a 1:16 weight ratio, and milled for 20 hours at a speed of 400 rpm. The powder obtained after milling was put in an alumina pot, heated to 800 ° C. in a hydrogen atmosphere in a furnace, and cooled without holding time. A powder was obtained.

1 is a scanning electron microscope (SEM) photograph of the nano Mo powder prepared in Preparation Example 1. Referring to Figure 1, the prepared Mo powder was confirmed that the particle size has a particle size of less than 100 nm level.

Examples 1 to 6: Ultrafine Grain Mo Preparation of Sputtering Target

Nano Mo prepared in Example 1 A molded body was prepared by injecting 2.5 g of powder in a 9 mm die and isotropically uniaxially molding at 250 MPa. In the high temperature furnace of hydrogen atmosphere, the molded body is divided into the temperature of the first step to 1050 ° C., and the temperature of the second step to different temperature conditions of 900 ° C. and 950 ° C., respectively, for 3 hours, 10 hours, and 20 hours. The two stage sintering was carried out by holding. In this case, the conditions of each two-stage sintering process are shown in Table 1 and FIG. 2.

1st stage sintering (temperature, temperature increase rate) 2 stage sintering (temperature, holding time) Example 1 1050 ℃ (10 ℃ / min) 900 ° C, 3 hours Example 2 1050 ℃ (10 ℃ / min) 900 ° C, 10 hours Example 3 1050 ℃ (10 ℃ / min) 900 ° C, 20 hours Example 4 1050 ℃ (10 ℃ / min) 950 ° C, 3 hours Example 5 1050 ℃ (10 ℃ / min) 950 ° C, 10 hours Example 6 1050 ℃ (10 ℃ / min) 950 ° C, 20 hours

Comparative Example 1: Mo Preparation of Sputtering Target

A sputtering target was prepared in the same manner as in Example 1 except that the temperature was raised to 1200 ° C. during sintering and then cooled as it is without additional holding time.

Comparative Example 2: Mo Preparation of Sputtering Target

A sputtering target was prepared in the same manner as in Example 1 except that the temperature was increased to 1300 ° C. during sintering and then cooled as it is without a separate holding time.

Experimental Example 1: Characterization

Density measurement

The relative densities of the sputtering targets (sintered bodies) prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were measured by the Archimedes method (Archimedes' principle), and the results are shown in Table 2 and FIG. 3.

Relative Density (%) Example 1 74.33% Example 2 77.38% Example 3 83.60% Example 4 83.98% Example 5 86.97% Example 6 90.01% Comparative Example 1 84.27% Comparative Example 2 89.35%

Comparing Examples 1, 3 and 4 and 6 in Table 2, it can be seen that the relative density increases as the holding time increases in the second sintering process in the two-sintering process.

In addition, when comparing the Examples 1, 4, Examples 2, 5 and Examples 3, 6, it can be seen that the relative density also increases as the temperature of the secondary sintering increases during the two-stage sintering.

Microstructure Observation

The microstructures of the sputtering targets prepared in Examples 3 and 6 and Comparative Examples 1 and 2 were measured by scanning electron microscopy and are shown in FIGS. 4 to 7.

4 is a scanning electron micrograph of the sputtering target prepared in Example 3, Figure 5 is a scanning electron micrograph of the sputtering target prepared in Comparative Example 1.

4 and 5, it can be seen that the particles of the sputtering target subjected to the two-sinter sintering process according to the present invention are more fine than the sputtering target of Comparative Example 1.

6 is a scanning electron microscope photograph of the sputtering target prepared in Example 6, and FIG. 7 is a scanning electron microscope photograph of the sputtering target prepared in Comparative Example 2. FIG.

6 and 7, as in the results of FIGS. 4 and 5, it can be seen that the particles of the sputtering target subjected to the two-sinter sintering process according to the present invention are more fine than the sputtering target of Comparative Example 2.

Hardness measurement

The hardness of the sputtering targets prepared in Examples 3 and 6 and Comparative Examples 1 and 2 was measured, and the results obtained are shown in Table 3 below. At this time, the process conditions, the size of the grains are shown for comparison.

General Sintering Law 2-step sintering method General Sintering Method 2-step sintering method Comparative Example 1 Example 3 Comparative Example 2 Example 6 Processing conditions 1200 ℃ 1050 ℃ → 900 ℃, 20 hours 1300 ℃ 1050 ° C → 950 ° C, 20 hours Relative density 84.27% 83.60% 89.35% 90.01% Grain size 800 nm 300 nm 1 μm 500 nm Hardness 2.06 GPa 2.58 GPa 2.43 GPa 3.15 GPa

Referring to Table 3, it can be seen that in the case of Comparative Examples 1 and 2, although the same raw material powder as in Example was used, the grain size was large, and the grains were greatly grown in the sintering process.

That is, in the case of Comparative Example 1 and Example 3 having the same relative density, the size of the crystal grains differ by more than two times, and in the case of performing two-stage sintering not only in the size of the grain but also in the hardness, 2.06 GPa (Comparative Example 1) It can be seen that the mechanical properties are also significantly improved to 2.58 GPa (Example 3). This is a very good mechanical property considering the hardness value of general commercial molybdenum is 2.4 GPa. It can be seen that the physical properties of the sintered body are also increased.

1 is a scanning electron microscope (SEM) photograph of the molybdenum nano powder prepared in Preparation Example 1.

2 is a graph showing the two-step sintering process conditions of Examples 1 to 6.

3 is a graph showing the densities of Examples 1 to 6 and Comparative Examples 1 and 2. FIG.

4 is a scanning electron micrograph of the sputtering target prepared in Example 3.

5 is a scanning electron micrograph of the sputtering target prepared in Comparative Example 1.

6 is a scanning electron micrograph of the sputtering target prepared in Example 6.

7 is a scanning electron micrograph of the sputtering target prepared in Comparative Example 2.

Claims (12)

delete Iii) forming a molded article by molding Mo nano powder having a particle size of 20-200 nm, Ii) The molded product is first sintered to 1000 to 1100 ° C at a heating rate of 5 to 15 ° C / min, Iii) A method for producing an ultrafine grain Mo sputtering target, which is produced through a step of secondary sintering of a first sintered sintered body at 900 to 950 ° C. delete The method of claim 2, The Mo nano powder is a method for producing an ultra-fine grain Mo sputtering target which is prepared by injecting MoO ₃ raw material powder into a ball and a ball mill, followed by ball milling in an argon atmosphere and then reducing the powder. The method of claim 4, wherein The ball milling is a method for producing an ultra-fine grain Mo sputtering target that is carried out by mixing the ball and the MoO ₃ raw material powder at a loading ratio (weight ratio) of 14: 1 to 18: 1. The method of claim 4, wherein The ball milling is a method for producing an ultra-fine grain Mo sputtering target that is performed for 1 to 24 hours at a speed of 100 to 500 rpm. The method of claim 4, wherein The reduction is a method for producing an ultrafine grain Mo sputtering target which is to perform a step of heating the powder obtained after the ball mill process to a temperature of 700 ~ 900 ℃ in a hydrogen atmosphere, as it is without holding time. The method of claim 2, The manufacturing method of the ultrafine crystal grain Mo sputtering target which is performed by isotropic uniaxial molding under a pressure of 200 to 300 MPa. The method of claim 2, The secondary sintering is performed for 3 to 20 hours, the method of manufacturing an ultrafine grain Mo sputtering target. Ultrafine grain Mo sputtering target produced by the method of claim 2. delete The method of claim 10, Said Mo sputtering target is ultra-fine grain Mo sputtering target of 84-95% of density, 2.5-3.5 GPa of Vickers hardness, and 200-500 nm of grain size.

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