KR20160067490A

KR20160067490A - Refurbishing method of tungsten spent target and reuse tungsten target for forming wiring and electrode prepared thereby

Info

Publication number: KR20160067490A
Application number: KR1020140172969A
Authority: KR
Inventors: 이효원; 홍길수; 양승호; 윤원규
Original assignee: 희성금속 주식회사
Priority date: 2014-12-04
Filing date: 2014-12-04
Publication date: 2016-06-14

Abstract

The present invention relates to a method of manufacturing a high-density and high-purity tungsten target by recycling a spent tungsten target. More specifically, the present invention relates to a method of manufacturing a recycled tungsten target, comprising: (a) a step of removing backing plate from the spent tungsten target; (b) a step of removing impurities on a surface of the spent tungsten target; (c) a step of obtaining high-purity tungsten powder having the same components with the spent target; (d) a step of sintering firstly the spent target and the high-purity tungsten powder using a hot pressing (HP) method; (e) a step of performing a thermal treatment on the sintered body under a reduced-pressure or vacuum conditions; and (f) a step of manufacturing a high-density sintering body by sintering the sintered body secondarily using a hot-isostatic pressing method, and the recycled tungsten target regenerated thereof. The present invention is able to provide the recycled tungsten target having similar properties with a novel target even though the spent target is reused since the grain of the tungsten target is refined; and the tungsten target has high-purity, high-density, and a gas content thereof also controlled.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of regenerating a tungsten waste target and a reclaimed tungsten target for forming a wiring and an electrode produced therefrom. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reclaimed tungsten target,

TECHNICAL FIELD The present invention relates to a recycling method of a tungsten (W) waste target which is used as a wiring material and an electrode material such as IC, LSI and the like to exhibit low resistance, heat resistance and chemical resistance. More specifically, To a method for recycling a target and to a high purity and high density recycled tungsten target produced by the method.

Tungsten targets are widely used as gate electrodes and wiring materials for ICs and LSIs. Tungsten targets used in such applications are required to have low resistance, grain refinement, inhibition of particle generation, high purity which is thermally and chemically stable, and high density.

As a conventional method of producing a tungsten target, there are a method of producing an ingot through an electron beam melting method and hot rolling, a method of pressing a tungsten powder followed by a hot isostatic pressing method, a method of hot rolling a tungsten powder after sintering HP .

However, even when the tungsten target is manufactured using the above-described three methods, it is known that particle defects, which are problems of the previously produced tungsten target, unevenness of the film due to deformation of the structure after rolling, and crystal grain coarsening occur. Therefore, in order to solve the problems occurring in the semiconductor film formation process, it is required to develop a tungsten target having fine grain refinement, high density and high purity, and a manufacturing method thereof.

Particularly, the tungsten target currently in use is in an unstable state at the time of film formation for a long time, resulting in contamination due to generation of a large number of particles. In view of this, in order to reduce the manufacturing cost and shorten the process L / T, the reuse of the used tungsten sputtering target has been widely studied in the semiconductor industry.

Disclosure of Invention Technical Problem [8] The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a method for producing a high-purity fine tungsten (W) The recycled tungsten target can be newly manufactured.

Accordingly, it is an object of the present invention to provide a novel regeneration method for producing a recycled tungsten target by sintering a tungsten waste target from which contaminated surface impurities have been removed and a high purity tungsten powder, followed by a vacuum heat treatment and a hot isostatic pressing.

It is still another object of the present invention to provide a recycled tungsten target which can be produced by the above-described method and which can exhibit physical properties (grain refinement, high density, and high purity) equal to or higher than that of a new target.

In order to accomplish the above object, the present invention provides a method of manufacturing a high density and high purity tungsten target by recycling a tungsten waste target using a sintering method, comprising the steps of: (a) removing a backing plate of a tungsten waste target; (b) removing surface impurities of the waste target; (c) securing a high purity tungsten powder having the same composition as the waste target; (d) subjecting the waste target and the high purity tungsten powder to primary sintering using HP; (e) heat treating the sintered body in a reducing or vacuum atmosphere; And (f) subjecting the sintered body to second sintering through hot isostatic pressing to produce a high density sintered body.

According to a preferred embodiment of the present invention, the high-purity tungsten powder in the step (c) may be 4N5 or higher. Preferably, the purity of the tungsten powder is 99.995 wt% or more, the oxygen content in the powder is 500 ppm or less, the carbon content is 100 ppm or less, the content of nitrogen, hydrogen, and sulfur is each less than 50 ppm and the average particle size is controlled to 5 탆 or less.

According to another preferred embodiment of the present invention, the step (d) is preferably performed by maintaining the heat treatment at a pressure of 15 to 20 MPa and a temperature of 1500 to 2000 ° C. for 3 to 5 hours.

According to another preferred embodiment of the present invention, the step (e) preferably maintains the heat treatment at 1700 to 2000 ° C for 3 to 8 hours in a vacuum atmosphere.

According to another preferred embodiment of the present invention, the step (f) is carried out at a sintering temperature of 1520 to 1720 ° C., a pressure of 100 to 200 MPa, a holding time of 2 to 5 hours, a working vacuum degree of 10 ^-4 to 10 ^-5 Torr. &Lt; / RTI >

The present invention also provides a recycled tungsten (W) target made by the method described above.

Here, the density in the final target is 99.5% or more, the purity is 5N or more, and the oxygen and carbon content in the final target are preferably 50 ppm or less, respectively. The grain size of the final target is preferably 30 mu m or less.

In addition, the recycled tungsten target produced in the present invention can be used for wiring formation for an electrode, electrode formation, or both.

As described above, according to the present invention, sintering is performed using a previously used tungsten waste target and a high purity tungsten powder, followed by vacuum heat treatment and hot isostatic pressing to obtain fine grain size, It is possible to provide a high-density recycled tungsten target having a controlled range.

In addition, since the above-described regeneration method uses less raw material powder than a new sputtering target, the manufacturing cost of the sputtering target can be reduced and the manufacturing time can be shortened.

In addition, the present invention is environmentally friendly and economical since it is possible to recycle the sputtering waste target that is generally discarded and to reduce the amount of carbon dioxide emission due to the shortening of the manufacturing time of the sputtering target.

FIG. 1 is an operation flow chart for manufacturing a recycled tungsten target according to an embodiment of the present invention.
2 is a crystal grain image of the tungsten target produced in Example 1 (crystal grain: 30 탆 or less).

Hereinafter, the present invention will be described in detail.

Disclosure of Invention Technical Problem [8] The present invention has been made in view of the above problems, and an object of the present invention is to provide a recycle tungsten To provide a method of manufacturing a target.

To this end, in the present invention, impurities such as surface foreign substances and oxide layers are removed through surface cleaning of the previously used tungsten waste target, and then the surface-cleaned waste target and the obtained high-purity tungsten powder (5N grade) are mixed A pressing step through HP, a vacuum heat treatment step, and a sintering step using a hot isostatic pressing method are sequentially performed.

More specifically, in the present invention, after the surface impurities of the tungsten waste target are removed, the waste target and the high purity tungsten powder are sintered through a hot press (HP) process, thereby securing the cornerstone of the recycle target. Further, the gas content in the sintered body can be controlled through a vacuum heat treatment of the sintered body, and then a high density and high purity recycled tungsten target can be obtained through hot isostatic pressing for high density.

Further, in the case of recycling using a conventionally used target, it is possible to control the above-described purity and crystal grains by adjusting process conditions. However, it is also possible to control the purity and the grain size of the raw material powder portion newly filled in the sputtering waste target (Filling part) is different from each other, it is difficult to control the crystal grains in the interface part between the recycling part and the filling part.

However, according to the present invention, by performing the new regeneration method using the sintering method, the grain growth of the interface portion between the sputtering waste target portion and the newly filled powder portion is easily controlled and the uniformity is increased, and the sputtering target Can be obtained. Accordingly, the uniformity and the low sheet resistance of the thin film can be secured without a significant difference according to the position between the recycled portion (used portion) of the existing waste target and the filled portion (the newly filled high purity tungsten powder) Reference).

In addition, economical efficiency and mass productivity can be enhanced through the simplicity of the manufacturing process, and the sputtering target can be regenerated easily with a new sputtering target having uniform microcrystalline particles by using the existing sputtering waste target.

&Lt; Manufacturing method of recycled tungsten target >

Hereinafter, a method for manufacturing a recycled tungsten target for forming a wiring and an electrode according to the present invention will be described. However, the present invention is not limited to the following production methods, and the steps of each process may be modified or optionally mixed as required.

A method of manufacturing a recycled tungsten (W) target for forming a wiring and an electrode according to the present invention is characterized in that a high-purity tungsten powder and a tungsten waste target are first sintered by a hot press (HP) method, Can be produced through a hot hydrostatic pressure process.

According to a preferred embodiment of the manufacturing method, (a) a step (S10) of removing a backing plate of a tungsten waste target; (b) removing (S20) surface impurities of the waste target; (c) securing high-purity tungsten powder having the same composition as the waste target (S30); (d) sintering the waste target and the high purity tungsten powder using HP (S40); (e) heat-treating the sintered body in a reducing or vacuum atmosphere (S50); And (f) subjecting the sintered body to second sintering through hot isostatic pressing to produce a high-density sintered body (S60).

Meanwhile, FIG. 1 is a flow chart of a process for manufacturing a recycled tungsten target using a waste target. Hereinafter, the manufacturing method will be described separately for each step with reference to FIG.

(1) First, the backing plate is removed to reuse the tungsten waste target (S10).

The waste target is not particularly limited as long as it is a previously used target. For example, the waste target may be 20% or more, preferably 30 to 35% or more.

The backing plate material is made of a copper base alloy and removed by a lathe and a machining M / C to obtain a pure tungsten target. Therefore, the tungsten target can be reused. have. The rpm of the processing equipment may range from 100 to 200. At this time, if the infeed amount is 0.1 or more, the backing plate can be removed without cracking the target.

(2) removing surface impurities attached to the debonded waste target (S20).

Impurities such as oxides and carbides are present on the surface of the waste target. Since the present invention aims at reusing a tungsten waste target, it is preferable to maintain a surface state free from foreign substances. Accordingly, in the second step, a process of removing surface contaminants attached to the waste target is performed at least once through a conventional impurity removal method known in the art.

For example, impurities such as oxides and carbides can be removed through a cleaning method such as a cleaning method using an acid, an alcohol and / or distilled water, an ultrasonic cleaning method, a plasma surface cleaning method, or the like. In addition, impurities can be removed by processing the surface of the waste target within about 1 mm (preferably, from 0. 1 mm) through a method such as CNC, MCT, or a grinder, by cutting the surface with a machine.

As a preferred example of the second step, the waste target is put into nitric acid or aqua regia, and then maintained at about 100 DEG C for about 1 hour. Whether or not the impurities adhering to the surface is removed during the holding process can be visually confirmed, and then the substrate can be finally washed with an organic solvent. The impurities can be removed at room temperature, but the removal time can be reduced by adding a temperature, so that the temperature can be changed appropriately. If the surface impurities are not completely removed through the above-described procedure, the nitric acid treatment and the water treatment treatment should be repeated at least once for about 30 minutes.

In the present invention, in order to confirm whether or not the impurities adhering to the surface are removed during the holding process, the ICP analysis may be performed by collecting the test piece with time. It is preferable that the purity of the waste target from which the impurities are removed is adjusted to 99.995 wt% or more. At this time, if the analyzed value is 99.995 wt% or more, the process proceeds to the next step 3. If the analyzed value is less than 99.995 wt%, the impurity removal process is repeated one or more times.

(3) A high purity tungsten powder to be mixed with the waste target is secured (S30).

In the third step, a powder having the same composition as that of the waste target is secured as a high-purity powder to be sintered together with a cleaned waste target.

In the present invention, a high-purity tungsten powder having a purity of 99.995 wt% or more can be used. Here, the purity of the powder can be analyzed using GDMS (Glow Discharge Mass Spectrometry). At this time, if the purity of the tungsten powder is less than 99.995 wt%, it is difficult to satisfy the specifications or needs of the customer, and the result is that the particles generated from the surface of the target at the time of film formation lower the film forming characteristics. Therefore, in order to ensure the uniformity of the film deposition, it is considered that the control of the gas content such as high density, high purity, grain refinement, and C and O is the most important.

Also, it is preferable that the high purity powder is controlled in a specific range of the gas content contained in the powder. For example, the oxygen content is preferably not more than 500 ppm, the carbon content is not more than 100 ppm, and nitrogen, hydrogen, and sulfur are each controlled to be less than 50 ppm. At this time, it is possible to verify the gas content contained in the powder through O, N, H, C, S analysis.

Also, the particle size of the tungsten powder is measured through particle size analysis, and it is preferable to use a powder having an average particle size of 5 μm or less.

(4) HP sintering is performed using a waste target and high purity tungsten powder (S40).

In the fourth step, a high-purity powder of the same composition as the surface-cleaned waste target is put into a mold and sintered through a hot press method.

Prior to charging the mold with the waste target and the tungsten powder, the mold release material can be applied to the outer periphery of the mold, wherein the mold release material can be a conventional mold release material known in the art. After applying the releasing material, remove it with a wiper blade. If the application amount of the releasing material is large, the powder may react with the powder upon entering the powder and act as a contaminant. If the releasing material is small, there is a possibility of cracking when the sintering material is separated after sintering. Then, the waste target is put into the mold in which the application of the releasing material is completed, and the high purity tungsten powder is charged on the waste target.

In a preferred example of the fourth step, a carbon mold is placed on a platen, and then a waste target is charged. High purity tungsten powder is charged on the powder target, and then charged into a hot press (HP) chamber. Thereafter, the decompression is performed using a vacuum pump.

At this time, the vacuum atmosphere is exhausted to 5.0 × 0 ^-5 torr or less, and then sintering is performed. The sintering temperature is in the range of 1500 to 2000 ° C, the time is maintained for 3 to 5 hours, and the pressure is preferably applied in the range of 15 to 20 MPa.

After the sintering process is completed, the sintered body is taken out when the chamber temperature is lower than 100 캜. If the relative density of the sintered body is 98.0% or more, the process proceeds to the next five steps. If the relative density of the sintered body is less than 98.0%, the probability of particles occurring at the time of film formation increases, so that the sintered body is sintered again to secure a relative density.

(5) The sintered body is subjected to heat treatment in a reducing atmosphere or a vacuum atmosphere (S50).

The fifth step is to conduct a heat treatment in a vacuum heat treatment furnace or a reducing atmosphere for gas content control. At this time, in order to prevent the carbon from being mixed in the sintering, it is put on a ceramic plate or a tungsten plate (W plate) of the same kind, and heat treatment is performed.

In the fifth step, the sintering condition is preferably maintained at 1700 to 2000 ° C. for about 3 to 8 hours. When the sintering temperature is lower than 1700 ° C, the density is lowered and the gas reducing effect is lowered. When the heat treatment temperature exceeds 2000 ° C, the relative density and the oxygen content decrease, while the carbon content increases due to the carbon heater.

The relative density of the sintered body manufactured through the fifth step should be 98.8% or more, because the final relative density can be ensured by 99.5% or more through the final hot isostatic pressing. Therefore, the relative density of the sintered body produced in the above step is controlled to be 98.8% or more. The content of oxygen and carbon in the sintered body is preferably 50 ppm or less.

(6) High-density sintered body is manufactured through hot isostatic pressing (S60).

As a preferred example of the sixth step, the sintered body subjected to the vacuum heat treatment in the previous step is wrapped with a canning material, and then a high temperature and a high pressure are simultaneously applied using an inert gas such as nitrogen and argon as a medium. In the case of performing such a process as described above, since the pressure of the gas as the pressure medium is generated, the shape of the sintered body does not change and the pores in the target are densified in the heat and pressure state to improve the physical properties such as the relative density of the sintered body.

In the sixth step, the sintering temperature of the hot isostatic pressing method is not particularly limited, but is preferably in the range of 1520 ° C to 1720 ° C. When the sintering temperature is less than 1520 占 폚, it is difficult to secure a high-density target, and the effect of reducing the gas content is also low. When the sintering temperature exceeds 1720 占 폚, the crystal grains become coarse, and the carbon content becomes high, and it is difficult to improve the quality.

Under the preferable conditions of the sixth step, the pressure is 100 to 200 MPa, the holding time is 2 to 5 hours, and the working vacuum degree is in the range of 10 ^-4 to 10 ^-5 Torr. In the case of the sintered body sintered by the hot isostatic pressing under the above-mentioned conditions, it is possible to secure a characteristic of a relative density of 99.5% or more, a crystal grain of 30 μm or less, oxygen and carbon contents of 50 ppm or less and purity of 99.995 wt% or more.

The density of the sintered body after the above step is 99.5% or more, and the purity has a high purity of 5N class. Also, the content of the gas in the final target is reduced, for example, the content of oxygen and carbon is controlled to 50 ppm or less, respectively.

In addition, the final recycled target produced as described above has a fine grain size, for example, the grain size is adjusted to 30 μm or less.

Thereafter, the produced target is subjected to bonding and final processing according to a conventional process known in the art.

For example, the bonding of the backing plate and the recycled tungsten sintered body proceeds. The bonding rate after bonding is controlled to be 99% or more. The bonded target is processed to the final target thickness using the processing equipment. If the surface roughness is maintained at a level of 0.5 탆 through post-processing, the film forming property at the time of film formation can be improved. After the bead and arc spray treatment are performed on the backing plate surface of the processed target as described above, and the semiconductor cleaning is completed, the final product is manufactured and the packaging is proceeded.

The present invention also provides a reuse tungsten target produced by the above-described method.

At this time, the recycled tungsten target has a high density and a low gas content while having a high purity fine grain. For example, the density of the final target may be greater than 99.5%, and the purity may be higher than 5N. In addition, the oxygen and carbon content of the final target may be 50 ppm or less, respectively, and the final target crystal grain size may be 30 탆 or less.

Further, in the case of the recycled sputtering target, the crystal particles of the newly filled portion are fine, while the crystal particles of the recycled portion are coarse than the crystal particles of the filled portion. On the other hand, in the present invention, in the regeneration through the above-mentioned regeneration method, the crystal grain growth of the interfacial portion between the filled portion and the recycled portion is adjusted to 20% or less of the crystal grain of the pulverized target layer, The separation phenomenon due to the difference in particle size can be prevented, and thus, the recycling sputtering target can be stably used in the sputtering process.

According to a preferred embodiment of the present invention, the target is a recycler of a tungsten waste target; A filling part filled in a consumed part of the recycling part and composed of raw material powder having the same composition as the recycling part; And an interfacial portion existing therebetween, and the sheet resistances of the recycled portion, the interface portion and the filled portion are 2.5 to 3.0? /? Spec. And the uniformity is 1.0 to 1.35%.

In this case, the uniformity means the uniformity of the thin film resistance according to the position in the target (for example, the recycled portion, the interface portion and the filled portion). Currently, it is adjusted to 5% or less in the semiconductor process.

The recycled tungsten (W) target is preferably applied to a gate electrode or wiring material of an IC or an LSI. It can also be used to produce compounds or to produce curing materials, electrical contact materials, resistance materials, catalyst materials, photosensitizing materials or anticancer materials, and other techniques in which the W target can be usefully applied .

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples and Comparative Examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following Examples and Comparative Examples.

[Example 1]

In order to observe the effect of the present invention, a backing plate was removed using a processing machine after obtaining a tungsten waste target, and then the contamination source of the target surface at 100 DEG C for about 1 hour using nitric acid or aqua regia Respectively. Then, sintering was performed using HP with high purity tungsten powder. At this time, the tungsten powder used is tungsten powder having an oxygen (O) content of 450 ppm, a carbon (C) content of 60 ppm, a particle size of 3 to 4 μm and a purity of 5 N. After sintering, HP sintered body was prepared through heat treatment and hot isostatic pressing to improve gas content and density.

More specifically, the waste target was reused while the sintering process of the waste target and the high purity tungsten powder was carried out under the condition of 18 MPa. HP was processed at a temperature of 1800 ° C for about 3 hours to produce 98% of sintered bodies. In order to control the density and gas content of the sintered body, the vacuum heat treatment was performed under a vacuum atmosphere. At this time, the vacuum heat treatment condition was 1850 ° C. for 5 hours and the density was 98.7%. Finally, a high-density recycled tungsten sintered body of 99.5% or more could be obtained through hot hydrostatic pressure. At this time, the sintering temperature and the holding time of the hot hydrostatic pressure process were 1680 ° C., 4 hours, the pressure was 150 MPa, and the working vacuum degree was 10 ^-5 Torr. The crystal grain image of the finally produced recycled tungsten target is shown in FIG. 2, wherein the crystal grains were found to be 30 μm or less.

[Comparative Example 1]

Instead of carrying out the process of Example 1 using a recycled target, a new sintered body was prepared by using a hot press (HP) of tungsten powder, and then physical properties of the sintered body were compared with a recycled target.

In the case of Comparative Example 1, the same tungsten powder as in Example 1 was hot-pressed and sintered under the conditions of 2030 ° C and 20 MPa for 5 hours to prepare a new sintered body.

[Comparative Example 2]

Instead of performing the process of Example 1 using the recycled target, tungsten powder was molded, CIP, vacuum heat treatment, and hot isostatic pressing to produce a new sintered body.

More specifically, in the case of Comparative Example 2, the HIP process was carried out using the same tungsten powder as in Example 1, and the HIP process was carried out under the conditions of 1850 ° C. and 150 MPa for 5 hours to obtain a new sintered body.

[Evaluation Example 1: Evaluation of physical properties of tungsten target]

In order to examine the effects of the present invention, the physical properties of the tungsten target prepared in Examples and Comparative Examples 1 and 2 were respectively compared.

(1) Relative density: The three types of tungsten targets prepared were measured by using Archimedes' principle. When a theoretical density of 19.3 was applied to obtain a relative density of 99% or more, it was judged to have a high density.

(2) Gas content: Gas analysis was carried out through an OHN analyzer and a CS analyzer. At this time, when the O content was 50 ppm or less and the C content was 50 ppm or less, it was judged to have a low gas content.

(3) Crystal grains: When the crystal grains of the sintered body were analyzed and found to be 50 탆 or less, it was determined that the crystal grains were fine.

division Relative density (%) Gas Content (ppm) Grain size (탆) O C Example 99.6 25 18 26 Comparative Example 1 98.4 105 144 84 Comparative Example 2 99.5 22 36 15

From Table 1, it can be seen that Example 1 of the present invention is superior to Comparative Example 1 in terms of relative density, gas content, and grain size. And the same level of results as in Comparative Example 2 were obtained. Therefore, the present invention proves that the waste target can be recycled in an equivalent manner to the prior art.

[Evaluation example 2. Evaluation of physical properties of thin film]

The sputtering target of Example 1 in which the waste target was recycled and Comparative Examples 1 and 2 in which the new sintered body was produced was indium-bonded to a backing plate for 4 inches, and then a tungsten thin film was formed using a DC magnetron sputtering apparatus (Model: SME-200E) Respectively.

The substrate used for the tungsten thin film was a bare wafer, and the temperature of the substrate was room temperature. The power of the film was set to 2,200W. Then, the amount of Ar gas was fixed to 75 sccm, and tungsten was deposited on the wafer to a thickness of about 500 Å, and the sheet resistance was measured.

Here, the sheet resistance of the tungsten thin film was determined to have excellent sheet resistance when the film thickness was 2.5 to 3.0 Ω / ㅁ, and it was concluded that the tungsten thin film was excellent when the uniformity was less than 2%.

division Sheet resistance (Ω / ㅁ) Uniformity (%) Example Filling part 2.6 1.07 Interface 2.7 1.25 The recycling section of the waste target 2.7 1.32 Comparative Example 1 3.3 2.34 Comparative Example 2 2.9 1.24

From Table 2, it can be seen that the sheet resistance is lower and the uniformity is better than that of Comparative Example 1 in the case of the embodiment of the present invention. Particularly, the sheet resistance of the examples satisfied 2.5 to 3.0? /? Spec.

On the other hand, the comparative example 2 obtained the best sheet resistance of the comparative example, but the most similar result to the embodiment was obtained. It was found that even if the waste target is reused, the characteristics of the thin film are similar in each position, and it has been proved that even when the waste target is reused, the same level of characteristics as the new target can be secured.

Claims

In recycling waste targets to produce high density and high purity tungsten targets,
(a) removing a backing plate of a tungsten waste target;
(b) removing surface impurities of the waste target;
(c) securing a high purity tungsten powder having the same composition as the waste target;
(d) subjecting the waste target and the high purity tungsten powder to primary sintering using HP;
(e) heat treating the sintered body in a reducing or vacuum atmosphere; And
(f) Secondarily sintering the sintered body through hot isostatic pressing to produce a high-density sintered body
Wherein the remainder of the tungsten target is in contact with the tungsten target.

The method according to claim 1,
Wherein the high purity tungsten powder is 4N5 or higher in the step (c).

The method according to claim 1,
The purity of the tungsten powder in the step (c) is not less than 99.995 wt%
The content of oxygen in the powder is 500 ppm or less, the content of carbon is 100 ppm or less, the content of nitrogen, hydrogen and sulfur is each less than 50 ppm,
Wherein the average particle size is controlled to be 5 占 퐉 or less.

The method according to claim 1,
Wherein the step (d) is carried out by sintering at a pressure of 15 to 20 MPa and a temperature of 1500 to 2000 ° C for 3 to 5 hours while maintaining the heat treatment.

The method according to claim 1,
Wherein the step (e) is performed in a vacuum atmosphere for 3 to 8 hours at a temperature range of 1700 to 2000 占 폚.

The method according to claim 1,
Wherein the step (f) is hot-pressing under reduced pressure for 2 to 5 hours at a temperature of 1520 to 1720 캜, a pressure of 100 to 200 MPa, and a working vacuum degree of 10 ^-4 to 10 ^-5 Torr. A method of manufacturing a target.

The method according to claim 1,
Wherein the density of the final tungsten target is 99.5% or more, and the purity is a high purity of 5N or more.

8. A process for producing a polyurethane foam, which is produced by the process according to any one of claims 1 to 7,
The density of the final target is at least 99.5%
The purity is high purity of 5N or more,
Wherein the oxygen and the carbon content in the final target are each 50 ppm or less.

9. The method of claim 8,
And the average size of the crystal grains in the final target is 30 占 퐉 or less.

9. The method of claim 8,
A recycling portion of a tungsten waste target;
A filling part filled in a consumed part of the recycling part and composed of raw material powder having the same composition as the recycling part; And
Wherein the surface area of the recycled portion, the interface portion, and the filled portion is in the range of 2.5 to 3.0? /? Spec., And the uniformity is in the range of 1.0 to 1.35%.

9. The method of claim 8,
Wherein the recycled tungsten target is used for forming a wiring, forming an electrode, or both.