WO2003016585A1

WO2003016585A1 - Sintered tungsten target for sputtering and method for preparation thereof

Info

Publication number: WO2003016585A1
Application number: PCT/JP2002/005545
Authority: WO
Inventors: Ryo Suzuki; Hirohito Miyashita
Original assignee: Nikko Materials Company, Limited
Priority date: 2001-08-10
Filing date: 2002-06-05
Publication date: 2003-02-27
Also published as: JP2003055758A; TW574377B

Abstract

A sintered tungsten target for sputtering, characterized in that it exhibits a relative density of 99 % or more, an average crystal grain diameter of 100 μm or less, an oxygen content of 20 ppm or less and a deflection force of 500 MPa or more; and a method for preparing the tungsten target with stability at a low cost, which uses improved production conditions for a raw material tungsten powder and improved sintering conditions. The sintered tungsten target has a high level of density and a high degree of the fineness of a crystal structure which have never been achieved by a conventional pressure sintering method and is markedly improved in deflection force, which has resulted in the significant decrease in the occurrence of particle defects.

Description

TECHNICAL FIELD The present invention relates to a tungsten sintered compact target for sputtering and a method for producing the same.

The present invention relates to a tungsten target used for forming a gate electrode such as IC or LSI or a wiring material by a sputtering method, and a method for manufacturing the same. Background art

In recent years, the use of materials with lower electric resistance as electrode materials and wiring materials has been studied with the increasing integration of ultra-LSIs. High-purity tungsten, which is highly stable, is promising as an electrode material and a wiring material.

The electrode materials and wiring materials for this VLSI are generally manufactured by the sputtering method or the CVD method. However, the sputtering method has a relatively simple structure and operation of the apparatus, can easily form a film, and is low in cost. Therefore, it is more widely used than the CVD method.

However, when an electrode material or a wiring material for ultra-LSI is formed by a sputtering method, if a defect called a particle is present on a film-formed surface, a failure such as a wiring failure occurs and the yield is reduced. In order to reduce the generation of particles on the deposition surface, a tungsten target having a high density and fine crystal grains is required.

Conventionally, as a method of manufacturing a tungsten target, a method of producing an ingot by using an electron beam melting method and hot-rolling the ingot (Japanese Patent Application Laid-Open No. 61-107,278), pressure-sintering tungsten powder And then roll (hot rolling) (Japanese Patent Laid-Open No. 3-150356, Japanese Patent Laid-Open No. Hei 6-22065) and a tungsten layer laminated on one surface of the tundastain bottom plate by the CVD method. The so-called CVD-W method (Japanese Patent Application Laid-Open No. 6-158030) is known. However, the tungsten target manufactured by the above-described electron beam melting method or the method of rolling and then sintering tungsten powder under pressure is mechanically brittle because the crystal grains are easily coarsened, and particle defects are generated on the sputtered film. There is a problem that it is easy. For example, the target of hot rolling after sintering of tungsten powder has a flexural strength of 40 OMPa or less, which is considered to be due to embrittlement peculiar to the rolled structure of the tungsten sintered material.

Furthermore, a particularly problematic problem with tungsten rolled products is that, starting from a block-shaped sintered material and requiring a step of strong rolling, a thick target or a large target size is required. That requires a large sintered material. Such a large-sized sintered body is liable to cause non-uniform structure and density. Recently, there has been a growing demand for evening gates with a thickness of more than 1 Omm or large evening gates with a 400 mm or more evening get size. There is a problem that it cannot be handled.

On the other hand, although the CVD-W method shows good sputtering characteristics, it takes a lot of time and money to produce the target, and is inefficient, and at the same time, it has a columnar structure, so its mechanical strength is low. There is also the problem of being low. Disclosure of the invention

The present inventors focused on the powder sintering method, which has a relatively simple manufacturing process, and improved the sintering characteristics and manufacturing conditions of the tungsten powder used. We have created a tungsten target for sputtering that has a high density and a fine crystal structure that has not been achieved, and has dramatically increased bending strength, thereby suppressing the generation of particle defects during film formation due to sputtering. The aim is to obtain a method that can manufacture evening targets stably at low cost.

The present invention

1. Rust density of at least 99%, average particle diameter of at most 100 z ^ m, oxygen content of at most 2 Oppm, and transverse rupture strength of at least 50 OMPa. Get sintered body 2. The total amount of alkali metals such as Na and K is 1 ppm or less, the total amount of radioactive elements such as U and Th is 10 ppb or less, the carbon content is 10 ppm or less, Fe, Ni, Cr, 2. The tungsten sintered compact target for sputtering according to 1 above, wherein the total sum of transition metals such as Co or heavy metals is 10 ppm or less.

3. The sputtering ring as described in 1 or 2 above, wherein the density is 99.5% or more, the average particle size is 8 Oim or less, and the crystal particle size is isotropic and randomly oriented. Get tungsten sintered body

4. Tungsten sintered body for sputtering characterized by sintering using tungsten powder having a powder specific surface area of at least 0. n ^ Zg (BET method) and an oxygen content of not more than Ι Ο Ο Ορρm Manufacturing method

5. The sintering is performed using tungsten powder having a powder specific surface area of 0.6 m ² / g to 0.8πι ² ^ (BET method) and an oxygen content of 800 ppm or less. For manufacturing tungsten sintered compact for sputtering

6. Using tungsten powder with a powder specific surface area of 0.4mVg (BET method) or more, hot-press sintering in a vacuum or reducing atmosphere at a pressing start temperature of 1200 ° C or less, and then hot isostatic pressing Method for producing tungsten getter for sputtering, characterized by pressure sintering (HIP)

7. The method for producing a tungsten sintered compact target for sputtering as described in 6 above, wherein the powder specific surface area is 0.6 m ² / g to 0.8 m ² Zg (BET method) or more.

8. The method for producing a tungsten sintered compact target for sputtering as described in 4 to 7 above, wherein the relative density is made 93% or more by hot press sintering 9. Temperature of 1600 ° C. or more and pressure of 150 kgZcm ^The method for producing a tungsten sintered compact target for sputtering according to any one of the above items 4 to 8, wherein hot pressing is performed at ² or more.

10. The method for producing a tungsten sintered compact target for sputtering as described in each of 4 to 9 above, wherein hot isostatic pressing sintering (HIP) is performed without encapsulation. 1 1. Temperature 1700 ° C or higher, pressure 1000 kg, sputtering evening Ring evening tungsten sintered body according to each of the 4-10, characterized by hot isostatic pressing sintering in cm ² or more Method of manufacturing target

12. Hot-isostatic pressing at a temperature of 1850 ° C. or more and a pressing force of 1800 kg / cm ² or more. Production method

I will provide a. Embodiment of the Invention

Normally, commercially available high-purity tungsten powder having a purity of 5 N or more has a powder specific surface area of 0.3 m ² Zg or less. In order to produce a tungsten target of over 2000%, a firing temperature of 2000 ° C. or more is required. However, at a firing temperature of 2000 ° C or more, crystal grains become coarser than 100 m.

Pressure sintering at such a high temperature becomes an important problem, for example, the reaction between the die and the stainless steel in the hot press method or the reaction with the capsule material in the HIP, and the production cost increases.

In powder metallurgy, it is generally known that the finer the particle size of the powder used, that is, the larger the specific surface area, the better the sinterability.

However, as described above, commercially available high-purity tungsten powder has a specific surface area of about 0.2 m ² / g even if it is fine.

Therefore, the present inventors have used ammonium metatungstate as a starting material, and have conducted hydrogen purification of tungstate crystals having a purity of 5 N or more obtained by performing high-purity purification to remove hydrogen gas and remove reaction product gas. by accelerating the rate of specific surface area of ^{^{0. 4m 2 / g~0. 8m 2}} / g, particle size 0. 4~0. 8 zm, and oxygen content 10 OO ppm or less, preferably 800 p pm A tungsten powder was prepared and used. If the oxygen content exceeds 1000 ppm, the sinterability deteriorates. Therefore, the lower the oxygen content of the tundastene powder used, the better. Furthermore, as the material of the tungsten target of the present invention, the total amount of alkali metals such as Na and K that affect semiconductor characteristics is 1 ppm or less, the total amount of radioactive elements such as U and Th is 10 ppb or less, Use tundatin powder having a content of 10 ppm or less and a total of transition metals such as Fe, Ni, Cr, and Mo or heavy metals of 10 ppm or less.

By hot pressing tungsten powder having such a large specific surface area at 1600 ° C or more, preferably 1800 ° C or more, pressure 150 kgZcm ² or more, and pressing start temperature 1200 ° C or less, The density became 93% or more, and the pores became closed pores, so it was possible to perform HIP treatment without encapsulation.

If the pressure start temperature exceeds 1200 ° C, crystal grains grow and the sinterability deteriorates. Also, it takes 2000 to obtain a closed pore density (93% or more) that enables capsule-free HIP. A hot press temperature of at least ° C is required, and there are problems as described below. Therefore, it is desirable to set the pressurization start temperature at 1200 ° C or less.

As described above, setting the hot pressing temperature to 2000 ° C or more is effective for densification, but causes problems such as coarsening of crystal grains and reaction with dies. It is desirable to press. When hot pressing, the use of carbon sheets on the upper and lower surfaces can promote oxygen dissociation from the material.

Further, the HIP treatment is performed at a temperature of 1700 ° C. or more, preferably 1850 ° C. or more, and a pressing force of 1000 kgZcm ² or more, preferably 1800 kgZcm ² or more, so that the relative density is 99% or more and the average crystal is Tungsten targets with a grain size of 100 or less and an average grain size of 80 m or less can be obtained. In this case, the crystal grain shape is an isotropic shape without random grains unlike a rolled product, and is randomly oriented.

In this case, the HIP processing can be performed in a capsule-free manner. As the specific surface area of the tungsten powder is larger, the density of the tungsten sintered body after hot pressing is higher and the crystal structure is finer, so that the density can be easily increased by the HIP processing and the density after the HIP processing is higher. As a result, the occurrence of particle defects was significantly reduced on the film produced using the tungsten target obtained. Examples and comparative examples

Hereinafter, description will be made based on examples and comparative examples. This embodiment is merely an example, and the present invention is not limited to this example. That is, the present invention includes other aspects or modifications included in the present invention.

(Example 1, Example 2, Example 3)

800 ° using tungsten powder with a powder specific surface area of 0.42 m ² Zg, 0.62 m ² / g, 0.78 m ² Zg and an oxygen content of 360 ppm, 540 ppm and 840 ppm, respectively. Pressure was applied from C to 300 kgZcm ² , and hot press firing was performed at 1600 ° C. and 1800 ° C. for 2 hours (Example 1, Example 2, and Example 3 respectively). Table 1 shows the relative density of the obtained tungsten sintered body. The relative density, average particle size, oxygen content, and three-point bending fold of the sintered body obtained by subjecting this tungsten sintered body to HIP treatment at 1800 ° (1500 kg / cm 2 hr) Table 2 shows the number of particles on the film when sputtering was performed using this tungsten sintered body.

As shown in Table 1, the relative density of the sintered body after hot pressing was 93.7% to 98.2%. Also, as shown in Table 2, the relative density of the tungsten sintered body after the HIP treatment was 99% to 99.8%. The average crystal grain size of the sintered body obtained as described above was 55 m to 88 / m, and in each case was 100 m or less. Further, the oxygen contents were all 20 ppm or less, and the bending strength was 52 OMPa to 63 OMPa, and was 50 OMPa or more.

The number of particles on the film sputtered using this tungsten sintered body was 0.03 to 0.07 cm ² , which was 0.1 particles / cm ² or less, and a very good film was obtained. Specific surface of the powder Oxygen in the powder, Phot press Hot press Product (m ² Zg) Weight (ppm) Relative density after temperature (° C) Example 1 0.42 360 1600 93.7%

1800 96.8% Example 2 0.26 540 1600 95.2%

1800 97.8% Example 3 0.78 840 1600 95.9%

1800 98.2% Example 4 1.1 790 1600 96.4%

1800 98.8% Example 5 1.1.4 890 1600 96.2%

1800 98.5% Comparative Example 1 1600 91.1% Comparative Example 2 0.23 210 1800 93.6% Comparative Example 3 2200 95.4% Comparative Example 4 1.1 1310 1800 91.8% Pressure start temperature: 800 ° C, Pressure: 300 kg / cm ^:

Table 2

HIP conditions: 1800 ° CX 1500 kgZcm ² X 2h

(Examples 4 and 5)

Powder specific surface area saved without exposing the tungsten powder tungsten oxide powder obtained by hydrogen reduction of the atmosphere is 1. 1111 ² 8 and 1. 4m ² / g and the oxygen 790 content, each p pm 890 p pm Except for the use of the tungsten powder (Examples 4 and 5 respectively), the properties of the hot-pressed sintered body and the sintered body after the HIP treatment produced under the same conditions as in Example 1 are also shown in Tables 1 and 2. See Figure 2.

From these results, all sintered bodies had a relative density of 99.5% or more, an oxygen content of 20 ppm or less, an average crystal grain size of 60 m or less, and a bending strength of 600 MPa or more. The number of particles on the film formed by using this tungsten sintered body was 0.01, ^ πι ² 0.05, Zcm ² , and a good film was obtained. (Example 6, Example 7, Example 8)

Tungsten powder having a specific surface area of 0.78 m ² Zg and an oxygen content of 840 ppm was used, and the pressing force by hot pressing was set to 150, 200, and 300 kg / cm ² (Examples 6, 7 and 7, respectively) Table 3 shows the properties of the hot-press sintered body and the sintered body after HIP treatment, which were manufactured under the same conditions as in Example 3 except for 8).

The relative density of the obtained sintered body is 99.7% to 99.8%, the average particle size is 67 ^ m to 72 m, and the sintered body satisfying the relative density of 99% or more and the average particle size of 100 zm or less I got it. Table 3

Powder specific surface area used: 0.78m ² / g

Hot press temperature · Retention time: 1800 ° CX2hr

HIP conditions: 1800 ° CX l 500 kgZcm ² X2h r

(Example 9, Example 10)

Using tungsten powder with a specific surface area of 0.78 m ² Zg and an oxygen content of 840 ppm, a pressure of 300 kg Z cm ² was applied from 1000 ° C and 1200 ° C (Examples 9 and 10 respectively) to 1800 ° C Table 3 shows the relative density and average crystal grain size of the tungsten sintered body manufactured under the same conditions as in Example 3 except that the hot press firing was performed for 2 hours. In each case, the relative density after HIP treatment was 99% or more, and the average crystal grain size was 100 m or less.

(Comparative Example 1, Comparative Example 2, Comparative Example 3)

Sintered by hot press sintering using tungsten powder with specific surface area of 0.23 m ² Zg and oxygen content of 210 ppm at a pressure of 3 OO kgZcm ² and temperatures of 1600 ° C., 1800 ° C. and 2200 ° C. Was subjected to HIP treatment under the same conditions as in Example 1 (Comparative Example 1, Comparative Example 2, and Comparative Example 3 respectively). Table 1 similarly shows the properties of the obtained sintered body.

The sintered compact hot-pressed at a temperature of 1600 ° C. in Comparative Example 1 and a temperature of 1800 ° C. in Comparative Example 2 had a relative density of 99% or less after HIP treatment, and the number of particles on the film formed by sputtering was 0.6. The pieces were as large as Zcm ² and 1.7 pieces cm ^2, which was not practical.

The sintered body of Comparative Example 3 which had been hot-pressed at 2200 ° C had a relative density after HIP treatment of 99%, but had an average crystal grain size of 177 m and was coarse. The number of particles above was also as high as 0.3 / cm ² . (Comparative Example 4)

The specific surface area 1.1111 ² / ^/ 8, with the oxygen content 131 O ppm of tungsten powder was subjected to hot press firing at 1800 ° C and 300 k gZcm ^2.

Thereafter, HIP processing was performed under the same conditions as in Example 1. Table 1 also shows the characteristics of the obtained sintered body.

The relative density of the sintered body after the HIP treatment was 97.5%, which was 99% or less. (Comparative Example 5)

A tungsten sintered compact was produced under the same conditions as in Example 3 except that the hot press pressure was set to 120 kgZcm ² . Table 2 also shows the relative density and average particle size of the obtained sintered body. The average crystal grain size was as fine as 55 jm, but the relative density was as low as 94.7%. (Comparative Example 6)

Table 2 shows the relative density and the average crystal grain size of the tungsten sintered body manufactured under the same conditions as in Example 4 except that the pressing start temperature during hot pressing was set at 140 ° C. The average crystal grain size was 98, which was less than 100, but was larger than the average crystal grain size obtained in the other examples, and the relative density was less than 99%. It was unsuitable as a target for performing a film. The invention's effect

The tungsten target for sputtering manufactured by the method of the present invention has a feature that the density is higher and the crystal grain size is smaller than that of a tungsten target obtained by a conventional pressure sintering method. This has the effect of significantly reducing the manufacturing cost compared to the conventional CVD-W method.

Further, by performing sputtering using this tungsten target, there is an excellent feature that particle defects on the film are significantly reduced and product yield is greatly improved.

Claims

Scope of request 1. Tungsten sintering for sputtering characterized by a relative density of 99% or more, an average particle size of 100 / m or less, an oxygen content of 20 ppm or less, and a transverse rupture of 50 OMPa or more. Body target.

2. The total amount of alkali metals such as Na and K is 1 ppm or less, the total amount of radioactive elements such as U and Th is 10 ppb or less, the carbon content is 10 ppm or less, Fe, Ni, Cr and C. 2. The tundene sintered compact target for sputtering according to claim 1, wherein a total sum of transition metals such as o or heavy metals is 10 ppm or less.

3. The sputtering according to claim 1, wherein the density is 99.5% or more, the average particle size is 80 / m or less, and the crystal grains are isotropic and are randomly oriented. For tungsten sintered compact.

4. Manufacture of one-gate stainless steel for sputtering, characterized by sintering using tungsten powder having a powder specific surface area of 0.4 mVg (BET method) or more and an oxygen content of lOOOppm or less. Method.

5. powder specific surface area of 0 · 6m ² Zg~0. A 8mVg (BET method), the請Motomeko 4, wherein the sintering using the following tungsten powder oxygen containing Yuryou 800 ppm Manufacturing method of tungsten sintered body for sputtering.

6. Using a tungsten powder with a powder specific surface area of 0.4mVg (BET method) or more, hot-press sintering in a vacuum or reducing atmosphere at a pressing start temperature of 1200 ° C or less, and then hot isostatic A method for producing a tungsten sintered compact for sputtering, characterized by pressure sintering (HIP).

7. The method for producing a tungsten sintered body for sputtering according to claim 6, wherein the powder specific surface area is 0.6 m ² Zg to 0.8 mVg (BET method) or more.

8. The method for producing a tungsten sintered compact target for sputtering according to claim 4, wherein the relative density is made 93% or more by hot press sintering.

9. The method for producing a tungsten sintered body for sputtering according to claim 4, wherein hot pressing is performed at a temperature of 1600 ° C. or more and a pressure of 150 kgZcm ² or more.

10. The method for producing a tungsten sintered compact for spattering according to any one of claims 4 to 9, wherein hot isostatic pressing (HIP) is performed without encapsulation.

11. The stainless steel sintered body for sputtering according to claim 4, wherein hot isostatic sintering is performed at a temperature of 1700 ° C. or more and a pressure of 1000 kgZ cm ² or more. Manufacturing method.

12. The stainless steel sintered body for sputtering according to claim 4, wherein hot isostatic sintering is performed at a temperature of 1850 ° C. or more and a pressure of 1800 kgZcm ² or more. Method of manufacturing the gate.