KR20160109917A - Preparation method of reuse tantalum target and the reuse tantalum target prepared thereby - Google Patents

Abstract

The present invention relates to a method for producing a recycled tantalum target having controlled grain size, purity and gas content, and a recycled tantalum target made therefrom.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reclaimed tantalum target and a recycled tantalum target,

The present invention relates to a method for producing a recycled tantalum target having controlled grain size, purity and gas content, and a recycled tantalum target made therefrom.

The main wiring is made of aluminum (Al) or copper (Cu) for driving elements such as transistors, capacitors, resistors and diodes in the semiconductor chip and tantalum (Ta) or tantalum nitride TaN) or the like is used. The tantalum (Ta) and tantalum nitride (TaN) are thermodynamically stable because they have a high melting point and do not react well with copper (Cu) at high temperatures, so that they can be used as a diffusion barrier for protecting the substrate and copper (Cu). The diffusion preventing film using TaN is formed by sputtering a tantalum target in a mixed gas of argon (Ar) and nitrogen (N ₂ ). The tantalum target that is currently in commercial use has a problem that the plasma becomes unstable at the time of forming the film for a long time, and a large amount of particles are generated and cause contamination.

The problem with the tantalum targets described above is known to be caused by uneven grain size, impurities, high gas content, etc. in the tantalum target. Therefore, in order to solve the above-mentioned problems occurring in the semiconductor film forming process, it is urgently required to develop a tantalum target having a high purity and a low gas content while controlling the grain size.

In addition, as the semiconductor chip is used in various industrial fields, the amount of tantalum target used is increased, so that a tantalum waste target is also required to be recycled for economical cost reduction and process time reduction.

In order to solve the above problems, it is an object of the present invention to provide a method for manufacturing a recycled tantalum target having fine crystal grains, high purity and low gas content.

It is another object of the present invention to provide a recycled tantalum target produced by the above production method.

In order to accomplish the above object, the present invention provides a method of manufacturing a tantalum waste target, comprising the steps of: (a) removing impurities from a tantalum waste target; (b) preparing a tantalum powder to be charged into the tantalum waste target; (c) preparing a preform by injecting the tantalum powder prepared in the step (b) into the tantalum waste target from which the impurities have been removed in the step (a); (d) cold isostatic pressing the preform; (e) heat-treating the preformed article by cold isostatic pressing to produce a molded article; (f) hot isostatic pressing the formed body; And (g) subjecting the formed body subjected to hot isostatic pressing to a recrystallization heat treatment to obtain a recycled tantalum target.

In addition, the present invention provides a recycled tantalum target produced by the above production method.

The present invention can produce a recycled tantalum target having a fine grain size, a high purity and a low gas content by charging tantalum powder of the same composition as the tantalum waste target into a tantalum waste target consuming 30% or more.

Further, by recycling the waste target by the above-described manufacturing method, the present invention can economically manufacture a tantalum target by reducing manufacturing cost and manufacturing process compared to existing tantalum targets.

FIG. 1 is a flow chart of a manufacturing process of a recycled tantalum target according to the present invention.
2 is an OM image of a recycled tantalum target produced according to Example 21 of the present invention.

Hereinafter, a method of manufacturing a recycled tantalum target according to the present invention will be described. However, the recycled tantalum target of the present invention is not limited to the following production method, and the steps of each process may be modified or optionally mixed as necessary.

(a) removing impurities from the tantalum waste target

The tantalum waste target is used in a semiconductor process and is a waste target in which more than 30% of the tantalum waste target is consumed. This tantalum waste target is rinsed secondarily to remove impurities on the surface.

The primary cleaning may be an acid cleaning, and conventional acid cleaning methods known in the art may be used without limitation. At this time, the cleaning solution used may be nitric acid or hydrochloric acid. The secondary cleaning is plasma cleaning, and conventional plasma cleaning methods known in the art can be used without limitation. Through this cleaning, the tantalum waste target from which the impurities are removed can have a purity of 99.995 wt% or more.

(b) preparing tantalum powder to be charged into the tantalum waste target

The tantalum powder is used to fill the consumable portion of the tantalum waste target and is a powder having the same components as the tantalum waste target.

The purity of the tantalum powder is not particularly limited, but it is preferably 99.995 wt% or more when analyzed by GDMS (Glow Discharge Mass Spectrometry). When the purity of the tantalum powder is less than 99.995 wt%, a large amount of particles may be formed during the film formation using the recycled tantalum target.

The particle size of the tantalum powder is not particularly limited, but it is preferable that D (50) is 30 탆 or less. When the particle size of the tantalum powder is more than 30 탆, the grain size of the recycled tantalum target may become large, and the density may be lowered due to difficulty in diffusion between powders during the press molding.

The gas content of the tantalum powder is not particularly limited, but is preferably 1000 ppm or less of oxygen, 100 ppm or less of carbon, 50 ppm or less of nitrogen, 50 ppm or less of hydrogen and 50 ppm or less of sulfur. If the gas content of the tantalum powder exceeds 1000 ppm of oxygen and 100 ppm of carbon, it may be difficult to control the gas content of the formed body to 100 ppm or less and 50 ppm or less of carbon through press molding and heat treatment.

(c) preparing a preform by adding the tantalum powder prepared in the step (b) to the tantalum waste target from which the impurities have been removed in the step (a)

The preform is manufactured using a hydraulic press after charging the tantalum waste target in which the consumable portion is present in the forming mold and filling the tantalum powder. At this time, before the tantalum powder is charged, the releasing material is applied to the outer periphery of the forming mold.

As the release material, a conventional grease known in the art can be used without limitation, and the grease can be applied to the molding mold and then removed using a wiper. If the application amount of the releasing material is large, it may contaminate the preform formed by reacting with the tantalum powder when the tantalum powder is loaded. If the amount of the releasing material applied is small, cracks may be formed in the preform after the preform is manufactured. cracks can occur. Therefore, it is preferable to apply an appropriate amount of release material to the forming mold.

After the tantalum powder is charged into the molding die coated with the releasing material and then the height of the powder is made constant, the preform is manufactured by using a hydraulic press after the horizontal work. At this time, the pressure applied to the hydraulic press is not particularly limited, but is preferably 80 to 160 MPa. If the pressure applied to the hydraulic press is less than 80 MPa, the density of the preform may be lowered to cause cracking in the preform. If the pressure exceeds 160 MPa, the forming mold may be damaged or the edge of the preform edge can occur.

The relative density of the prepared preform is preferably 50% or more. If the produced preform has a relative density of less than 50%, cracks may occur in the preform when taken out and transferred from the forming mold.

Thereafter, the presence or absence of a crack in the taken-out preform is checked, and the preform is vacuum-packed.

(d) cold isostatic pressing (CIP) of the preform

The pressure for cold isostatic pressing (CIP) of the preform is not particularly limited, but is preferably 1000 to 2500 bar. When the pressure for cold isostatic pressing is less than 1000 bar, the density of the preform formed by cold isostatic pressing becomes low and may be damaged during transportation. When the pressure is more than 2500 bar, the preform formed by cold isostatic pressing is bent or cracked .

Thereafter, the preform formed by cold isostatic pressing is taken out, the vacuum packaging paper from which the remaining moisture has been removed is removed, and the relative density is calculated by measuring the dimensions. The relative density of the preform is determined by using the size of the preform, and when the hydrometer is used, the moisture penetrates into the preform and the degree of vacuum may be lowered during the pressing.

The relative density of the preform formed by cold isostatic pressing is preferably 60% or more. If the relative density is less than 60%, cracks may be generated or broken during transportation.

(e) a step of heat-treating the preformed body by cold isostatic pressing (CIP) to produce a molded article

The cold isostatic pressing preform is thermally treated to reduce the gas content in the preform to produce a molded article. The heat treatment may be carried out in a vacuum or reducing atmosphere using a hot isostatic pressing (HIP) or a hot press, although conventional heat treatment processes known in the art can be used without limitation. In order to prevent carbon contamination during the heat treatment, the heat treatment preferably proceeds on a ceramic plate or a tantalum bulk of the same component.

The conditions for the heat treatment of the preform are not particularly limited, but the heat treatment temperature is preferably 1800 to 2100 占 폚, and the heat treatment time is preferably 5 to 10 hours. If the heat treatment temperature is lower than 1800 ° C, the density of the formed body is lowered and the effect of reducing the gas content may be lowered. If the heat treatment temperature is higher than 2100 ° C, the density of the molded body is increased and the oxygen content in the gas content is decreased. It can be raised by a carbon heater.

The relative density of the molded body is preferably 85% or more. When the relative density of the molded article is less than 85%, it may be difficult to secure a molded article having a density of 99.0% or more by hot isostatic pressing, which is a subsequent step.

The gas content of the molded body is not particularly limited, but it is preferably at most 50 ppm oxygen, at most 30 ppm carbon, at most 30 ppm nitrogen, at most 30 ppm hydrogen, Sulfur is preferably 30 ppm or less. If the gas content of the molded product exceeds 50 ppm of oxygen and 30 ppm of carbon, it may be difficult to control the content of oxygen and carbon in the molded product through a post-process. Accordingly, when the content of oxygen and carbon in the molded article is higher than the above-mentioned value, the gas content is further controlled by heat treatment.

(f) hot isostatic pressing (HIP) of the molded body

The conditions for hot isostatic pressing (HIP) are not particularly limited, but the pressure for hot isostatic pressing is preferably 90 to 180 MPa, and the temperature for hot isostatic pressing is 1500 to 1800 DEG C And the time for hot isostatic pressing is preferably 1 to 4 hours. When the hot isostatic pressing temperature and time are less than 1500 ° C and less than 1 hour, it may be difficult to achieve a relative density of 99.0% of the hot isostatically formed molded body. When the temperature and time for hot isostatic pressing are more than 1800 DEG C and more than 4 hours, the grain size of the hot isostatic pressing formed body may become large.

It is preferable that the relative density of the molded body obtained by hot isostatic pressing is not less than 99.0%. The gas content of the hot isostatically formed compact is not particularly limited, but it is preferably at most 100 ppm oxygen, at most 50 ppm carbon, at most 30 ppm nitrogen, Hydrogen of 30 ppm or less, and sulfur of 30 ppm or less.

(g) Recrystallizing heat treatment of the hot isostatic pressing (HIP)

The recrystallization heat treatment of the formed body by hot isostatic pressing may be carried out in a vacuum or a reducing atmosphere using hot isostatic pressing (HIP) or hot press, although conventional heat treatment processes known in the art can be used without limitation. have. At this time, in order to prevent carbon contamination during the recrystallization heat treatment, the recrystallization heat treatment is preferably carried out on a ceramic plate or a tantalum bulk of the same component.

The conditions for recrystallizing the heat-treated compact by hot isostatic pressing are not particularly limited, but the recrystallization heat treatment temperature is preferably 1200 to 1800 ° C, and the recrystallization heat treatment time is preferably 5 to 10 hours. If the recrystallization heat treatment temperature is lower than 1200 ° C, the effect of recrystallization of the formed body may be lowered, and if it exceeds 1800 ° C, the grain size of the formed body may become larger due to abrupt grain growth.

Thereafter, the recycled tantalum target produced according to the present invention may undergo additional bonding and processing steps.

The recycled tantalum target may be bonded by any conventional bonding method known in the art, and indium bonding or diffusion bonding may be applied.

The temperature for the indium bonding is not particularly limited, but is preferably 200 to 220 ° C. When the temperature for the indium bonding is less than 200 ° C, the recycled tantalum target and the backing plate may be separated.

The diffusion bonding method may be hot isostatic pressing, and the diffusion bonding temperature is not particularly limited, but may be 500 to 800 ° C. At this time, the material of the backing plate used may be aluminum (Al) or copper (Cu) alloy.

The recycled tantalum target bonded to the backing plate may be processed by any conventional process known in the art without limitation, and may be a lathe process.

As described above, the present invention can provide a tantalum target having a high purity, a low gas content, and a fine crystal grain by a single process by manufacturing the recycled tantalum target by the above-described manufacturing method.

The tantalum target of the present invention can be used in various fields, and in particular, in a semiconductor or hard disk drive (HDD) process.

Hereinafter, the present invention will be described concretely with reference to Examples. However, the following Examples are intended to illustrate one embodiment of the present invention, but the scope of the present invention is not limited by the following Examples.

[Examples and Experimental Examples]

A tantalum waste target in which more than 30% of the consumed parts were used was debonded from the backing plate. At this time, the tantalum waste target was processed at 0.5 mm or more at the bonding interface to remove the contamination by the diffusion bonding backing plate. Then, the debonded tantalum waste target was washed with a nitric acid solution first and then washed with a plasma cleaner to obtain a waste target having a purity of 99.998%. The washed tantalum waste target was cut into a diameter of 130 mm, and the weight of the cut tantalum waste target was 850 g.

660 g of tantalum powder having a purity of 99.998% by weight and a gas content of 840 ppm of oxygen, 15 ppm of carbon, 23 ppm of nitrogen, 13 ppm of hydrogen and 1 ppm of sulfur and having a particle size of D (50) of 17 μm was prepared.

A tantalum waste target was charged into a forming mold (130 mm in diameter, 60 mm in height) coated with a release material, filled with the prepared tantalum powder, and subjected to a hydraulic press to prepare a preform. The molding conditions applied and the density of the prepared preform are shown in Table 1 below.

Example One 2 3 4 5 Molding conditions Pressure (MPa) 50 80 120 160 200 density (%) 55 61 65 71 75

As shown in Table 1, the prepared preforms (Examples 1 to 5) increased in density as the pressure applied to the hydraulic press increased. However, when the pressure was 50 MPa (Example 1), the preform was cracked in the process of separating the preform, and the corners were damaged.

The cold-isostatic pressing was performed using the pre-formed body (Example 4) which had a high density and soundness in the pre-molded article manufacturing step. Before the cold isostatic pressing, the preform was doubly packed using a vacuum packing machine. The applied molding conditions and the density of the preform formed by cold isostatic pressing are shown in Table 2 below.

Example 6 7 8 9 10 Density (%) of preform 71 71 71 71 71 Molding conditions Pressure (Bar) 500 1000 1500 2000 2500 density (%) 72 75 78 80 84

As shown in Table 2, in the preforms (Examples 6 to 10) subjected to cold isostatic pressing, the relative density increased as the molding pressure increased. However, when the pressure was 500 Bar (Example 6), the surface of the preform was damaged by cold isostatic pressing of the preform, and powder during the process of removing the vacuum package. This is because the density of the tantalum waste target is more than 99%, but the density of the portion filled with the tantalum powder is less than 50%, and the portion filled with the tantalum powder is damaged.

After the heat treatment was performed using the preform (Example 10) having the highest density in the cold isostatic pressing process, a compact was produced. The molding conditions applied, the density and the gas content of the produced molded article are shown in Table 3 below.

Example 11 12 13 14 Cold isostatic pressing
Density (%) of preform 72 72 72 72 Molding conditions
Temperature (℃) 1600 1800 2000 2200 Time (hr) 8 8 8 8 density (%) 95.0 96.0 97.5 98.5 Gas Content (ppm)
Oxygen 180 125 43 36 carbon 26 27 24 250 nitrogen 15 13 17 19 Hydrogen 3 5 4 6 sulfur 0 0 0 0

As shown in Table 3, in the formed bodies (Examples 11 to 14), the density of the molded body was increased as the heat treatment temperature was increased, and nitrogen, hydrogen, and sulfur were kept at less than 30 ppm with decreasing oxygen in the gas content. However, when the temperature was 2200 ° C (Example 14), the carbon content was high in the gas content.

The hot isostatic pressing was performed using the formed body (Example 13) having a density of 97.5% or more and a lowest gas content in the heat treatment step. The applied molding conditions and the density and the grain size of the molded body subjected to hot isostatic pressing are shown in Table 4 below.

Example 15 16 17 Density of molded body (%) 97.5 97.5 97.5 Molding conditions Pressure (MPa) 95 95 95 Temperature (℃) 1400 1600 1800 Time (hr) 4 4 4 density (%) 99.4 99.6 99.9 Grain size (탆) 62 75 135

As shown in Table 4, the compacts (Examples 15 to 17) increased in density and grain size as the molding temperature increased, and the gas content was less than 28 ppm of oxygen, less than 26 ppm of carbon, Less than 20 ppm nitrogen, less than 20 ppm hydrogen, and less than 20 ppm sulfur.

And subjected to a recrystallization heat treatment using the hot isostatically formed compact (Example 16). The molding conditions applied and the density and grain size of the recrystallized heat-treated compact are shown in Table 5 below.

Example 18 19 20 21 22 Hot isostatic pressing
Density of molded body (%) 99.6 99.6 99.6 99.6 99.6 Grain size (탆) 64 64 64 64 64 Molding conditions
Temperature (℃) 1000 1200 1500 1800 2000 Time (hr) 8 8 8 8 8 density (%) 99.6 99.6 99.6 99.6 99.7 Grain size (탆) 64 72 87 96 267

As shown in Table 5, when the recrystallization heat treatment temperature is 1000 占 폚 (Example 18), the effect of recrystallization heat treatment is low because there is no change in crystal grain size of the formed product, and when the temperature is 2000 占 폚 The crystal grain size of the crystal grains is not less than 100 占 퐉, which is not suitable for the recrystallization annealing condition. Therefore, the recrystallization heat treatment temperature is preferably 1200 to 1800 ° C.

The molded body subjected to the recrystallization heat treatment (Example 21) was bonded to a backing plate. At this time, the backing plate was copper (Cu) and the bonding was diffusion bonding. Thereafter, the bonded recycled tantalum target was processed into a final shape.

Claims (12)

(a) removing impurities from a tantalum waste target;
(b) preparing a tantalum powder to be charged into the tantalum waste target;
(c) preparing a preform by injecting the tantalum powder prepared in the step (b) into the tantalum waste target from which the impurities have been removed in the step (a);
(d) cold isostatic pressing the preform;
(e) heat-treating the preformed article by cold isostatic pressing to produce a molded article;
(f) hot isostatic pressing the formed body; And
(g) Recrystallizing heat treatment of the hot isostatic pressing
Wherein the recycled tantalum target is a tantalum target. The method according to claim 1,
Wherein the purity of the tantalum waste target from which the impurities are removed in the step (a) is 99.995 wt% or more. The method according to claim 1,
In the step (b), the purity of the tantalum powder is 99.995 wt% or more, the particle size of the tantalum powder is 30 μm, and the gas content of the tantalum powder is 1000 ppm or less, 100 ppm or less, 50 ppm or less Or less, hydrogen 50 ppm or less, and sulfur 50 ppm or less. The method according to claim 1,
Wherein the tantalum powder target of the step (a) and the tantalum powder of the step (b) are introduced into a hydraulic press and a pressure of 80 to 160 MPa is applied to the preform to produce the preform. The method according to claim 1,
Wherein the pressure for cold isostatic pressing of the preform is 1000 to 2500 bar in the step (d). The method according to claim 1,
Wherein the preform is subjected to cold isostatic pressing in the step (e) at a temperature of 1800 to 2100 캜 for heat treatment and for a time of 5 to 10 hours for heat treatment. The method according to claim 1,
Wherein the gas content of the green body in the step (e) is 50 ppm or less for oxygen, 30 ppm or less for carbon, 30 ppm or less for nitrogen, 30 ppm or less for hydrogen and 30 ppm or less for sulfur. The method according to claim 1,
Wherein a temperature for hot isostatic pressing of the molded body in the step (f) is 90 to 180 MPa, a temperature for hot isostatic pressing is 1500 to 1800 ° C, and a time for hot isostatic pressing is 1 to 4 hours Gt; The method according to claim 1,
Wherein the gas content of the molded body subjected to hot isostatic pressing in the step (f) is not more than 100 ppm oxygen, not more than 50 ppm carbon, not more than 30 ppm nitrogen, not more than 30 ppm hydrogen, and not more than 30 ppm sulfur. The method according to claim 1,
Wherein the temperature for recrystallization heat treatment of the molded body subjected to hot isostatic pressing in the step (g) is 1200 to 1800 占 폚, and the time for recrystallization heat treatment is 5 to 10 hours. A recycled tantalum target produced by the method of any one of claims 1 to 10. 12. The method of claim 11,
Recycled tantalum targets used in semiconductor or hard disk drive (HDD) processes.

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