JPH04293770A - Ti-w target material and its manufacture - Google Patents

Abstract

PURPOSE:To provide the title material hardly developing particles at the time of sputtering. CONSTITUTION:This Ti-W target material is possessed with >=98% area of alloy phase composed of Ti and W at the time of observing the micro structure. Further, this manufacturing method has the feature, in which powder obtd. by executing pluverizing treatment to an ingot obtd. with melting of W and Ti subjected to solution treatment as it is or after executing the solution treatment is sintered. In this case, the melting is desirably executed by electron beam melting under reduced pressure atmosphere. Further, the other manufacturing method has the feature, in which molten metal prepared by melting W and Ti, is made to powder with atomizing method and the sintering process of the obtd. powder is added. Further, in the manufacturing method, in the case of sintering the powder, it is desirable to apply hot isostatic press or hot press.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ti--W target material used for forming barrier metal layers used in semiconductor devices and a method for manufacturing the same.

0002

2. Description of the Related Art With the recent increase in the degree of integration of LSIs, migration of Al interconnects, such as contact migration due to diffused precipitates at contact portions between Al interconnects and Si semiconductor substrates, has become a problem. As a countermeasure against this problem, barrier metal layers have been studied in recent years. As the barrier metal layer, a Ti-W thin film (typically Ti: 10 wt%,
The remainder has a composition of W. ) are often used, and the method for forming them is to sputter a target.

[0003] This Ti-W target material for thin films is generally manufactured by mixing W powder and Ti powder and hot pressing the mixture. However, conventional Ti-W
Ti powder, which is the raw material for the target, has a high oxygen content.
Only targets with high oxygen content were obtained. Such a target with a high oxygen content is undesirable because the release of oxygen during sputtering causes cracks in the target, oxidation of the formed film, variations in film quality, and the like.

Recently, US Pat. No. 4,838,9 has been proposed as a method for reducing the oxygen content of such a Ti-W target.
No. 35 discloses that Ti powder is hydrogenated at least in part.
i can be replaced with i, or binodal (bino
By using a mixture of W powder and hydrogenated Ti powder or hydrogenated Ti powder and Ti powder, which have a particle size distribution of It was disclosed that the content of can be reduced. Similarly, as a method for reducing the oxygen content of a Ti-W target, Japanese Patent Application Laid-Open No. 63-303
No. 017 discloses a method in which W powder and hydrogenated Ti powder are mixed and hot pressed after or while dehydrogenating. The use of this hydrogenated Ti powder is itself effective in preventing oxidation, and since it has better crushability than Ti powder, it is possible to reduce the amount of oxygen picked up during pulverization. In this way, a Ti-W target with a low oxygen concentration of 900 ppm or less can be obtained. As described above, research is being actively conducted to reduce the oxygen content in Ti--W target materials. However, the above-mentioned publication does not contain any information suggesting how the structure of Ti and W that constitutes the target affects sputtering, and the alloy structure, especially the presence of the Ti phase, is related to the generation of particles during sputtering. It is not disclosed at all that this is the case.

[0005]

[Problem to be Solved by the Invention] With the recent trend toward higher density and thinner electrode patterns in semiconductor products, even when sputtering is performed using the Ti-W target with a low oxygen concentration,
A new problem has arisen in that giant particles, so-called particles, adhere to thin films formed by sputtering, causing disconnections in electrode wiring. The generation of this particle is T
The problem could not be solved simply by reducing the oxygen content of the i-W target.

[0006] In order to solve the above-mentioned problems, the inventors of the present invention investigated in detail the relationship between the target structure and particle generation, and found that coarse Ti particles are related to particle generation. In other words, under the coexistence of Ti and W, Ti with a light atomic weight is selectively sputtered, and the W particles contained in coarse Ti particles or the W particles near them are scattered from the target material as giant particles, which causes particle generation. I found out that this is one of the causes. An object of the present invention is to provide a Ti-W target material with a controlled structure that generates very few particles, and a method for manufacturing the same.

[0007]

[Means for Solving the Problems] The present inventors have found that a Ti--W alloy phase is effective as a target material that does not cause scattering of W particles due to the difference in sputtering speed between Ti and W. That is, in the present invention, Ti
This is a Ti-W target material characterized in that the area of the alloy phase consisting of and W occupies 98% or more. Ti of the present invention
-W target material consists essentially only of an alloy phase consisting of Ti and W, and its composition does not matter as long as it is an alloy of Ti and W. However, since the presence of a small amount of fine αTi that precipitates during the cooling process is not a particular problem, it is necessary that the Ti-W alloy phase occupies 98% or more of the area by microstructural observation. be. In the present invention, the condition of this structure is expressed as "substantially consisting only of an alloy phase consisting of Ti and W." The target material of the present invention contains a very small amount of αTi (
Although it may contain less than 2% (area ratio), it consists essentially only of Ti-W alloy phase and does not contain free W phase or Ti phase as in the conventional case, so the sputtering rate of W and Ti can be reduced. It is possible to eliminate the generation of particles on the produced film due to the difference in .

[0008] Also, one of the manufacturing methods of the present invention is that W and T
This is a method for producing a Ti-W target, characterized in that it is obtained by solution treatment of an ingot obtained by melting i. The shape of the target can be made by cutting an ingot. In addition, another manufacturing method of the present invention is characterized in that an ingot obtained by melting W and Ti is subjected to solution treatment, then powdered, and the obtained powder is sintered to obtain Ti- This is a method for manufacturing a W target. Still another manufacturing method of the present invention is a method for manufacturing a Ti-W target, characterized in that a molten metal made by melting W and Ti is made into powder by an atomization method, and the resulting powder is obtained by sintering. be.

[0009] In the present invention, by solution-treating an ingot in which W and Ti are dissolved, it is possible to obtain a structure with little segregation and consisting essentially only of an alloy phase consisting of Ti and W. Even if αTi precipitates during a cooling process such as solution treatment, the area ratio due to the microstructure is less than 2%. Further, in the present invention, the solution treatment is preferably performed at a temperature of 1250°C to 1650°C. Ti and W are alloys that can form a complete solid solution, but 1
If it is below 250°C, it will not form a sufficient solid solution, and if it is above 1650°C, it may partially dissolve, causing segregation, which is not preferable. This solution treatment is preferably carried out in a reduced pressure atmosphere or in an inert gas in order to avoid contamination with impurities.

[0010] In the present invention, by performing solution treatment, powder treatment, and sintering, it is possible to further reduce the segregation of the structure of the target, and as a result, the generation of particles can be further reduced. Can be done. For the above-mentioned pulverization treatment, well-known methods such as a ball mill and an attritor can be used. Further, in the present invention, it is preferable to perform melting by electron beam melting under a reduced pressure atmosphere in order to avoid contamination with impurities such as oxygen. In addition, when using the atomization method in the present invention, since the liquid state is rapidly cooled to powder, there is extremely little segregation in individual powders, and there is no need for solution treatment and no pulverization process, so oxygen-containing It has the advantage of being obtained in low quantities. In the present invention, well-known methods such as gas atomization, water atomization, and rotating electrode methods can be used. Furthermore, in the present invention, sintering is performed by hot isostatic pressing (hereinafter referred to as HIP) or hot pressing, which makes it possible to obtain a high-density target, which is preferable from the viewpoint of mechanical strength.

[0011]

[Example] (Example 1) High purity W powder (purity 99.99
9% or more, average particle size 5 μm or less) and high purity Ti (purity 9%)
9.99% or more, average particle size 150 μm or less)
They were blended to have a concentration of 0 wt% and mixed using a W-lined blender. The obtained mixed powder was molded using a cold isostatic press (CIP) at 2000 kg/cm2 to form a melted raw material. This melted raw material was electron beam melted to obtain a highly pure ingot. The obtained ingot was placed in a vacuum furnace (degree of vacuum 5×
1 in a reduced pressure atmosphere (lower than 10 minus 5 torr)
A target material was obtained by solution treatment at 400° C. for 10 hours. The oxygen content of the obtained target material is 1
It was 20 ppm. The metal structure of the obtained target material was observed with a scanning electron microscope at a magnification of 600 times. A photograph of the obtained structure is shown in FIG.

As shown in FIG. 1, there is no large segregation, and there is only an alloy phase consisting essentially of Ti and W, and no independent phases of Ti or W are observed. The obtained target material is φ30
When the Ti--W target was processed into a Ti-W target and sputtered onto a 6-inch wafer, the number of particles of 0.3 μm or more generated was observed and was found to be 22, which was very small.

(Example 2) A melted raw material obtained under the same conditions as in Example 1 was subjected to electron beam melting to obtain a highly pure ingot. The obtained ingot was placed in a vacuum furnace (degree of vacuum 5×1
14 in a reduced pressure atmosphere (lower than 0 minus 5 torr)
Solution treatment was carried out under the conditions of 00℃ x 10 hours, and after coarsely pulverizing with a W boat and W rod, it was placed in a special ball mill using a W-lined pot and W balls.
After evacuating the inside of the pot, the atmosphere was replaced with Ar gas to create a non-oxidizing atmosphere, and the mixture was ground and mixed to obtain a powder of 150 μm or less. The obtained powder was filled into a HIP can with an inner diameter of 400φ, heated at 400°C for 5 hours while evacuated to 5 x 10 minus 5 torr, and sealed after removing surface adsorbed gas, and heated at 1200°C. HIP treatment was performed for 2 hours at 1000 kg/cm2 to obtain a target material. The oxygen content of this target material was 590 ppm. The metal structure of the obtained target material was the same as in Example 1, consisting only of an alloy phase consisting of Ti and W. This target material was processed to a diameter of 300 mm and used as a target, and sputtered onto a 6-inch wafer. When the number of particles of 0.3 μm or more was observed, it was found to be 8 particles, which was very small.

(Example 3) A melted raw material was prepared in the same manner as in Example 1. This melted raw material is melted and tapped using a gas atomizer to obtain an atomized powder. After classifying the obtained atomized powder to 100 mesh or less, it was filled into a HIP can with an inner diameter of 400φ, and heated at 400°C for 5 hours while evacuated to 5 × 10 minus 5 torr to remove surface adsorbed gas, etc. After removal, seal and heat at 1200°C for 2 hours.
HIP treatment was performed under the condition of kg/cm2 to obtain a target material. The oxygen content of this target material is 380 ppm
It was confirmed that the target material had a low oxygen content. The metal structure of the obtained target material was the same as in Example 1, consisting only of an alloy phase consisting of Ti and W. This target material was processed to a diameter of 300 mm and used as a target, and sputtered onto a 6-inch wafer. When the number of particles of 0.3 μm or more was observed, it was found to be 7 particles, which was very small.

(Example 4) A melted raw material obtained under the same conditions as in Example 1 was subjected to electron beam melting to obtain a highly pure ingot. The obtained ingot was placed in a vacuum furnace (degree of vacuum 5×1
14 in a reduced pressure atmosphere (lower than 0 minus 5 torr)
Solution treatment was carried out under the conditions of 00℃ x 10 hours, and after coarsely pulverizing with a W boat and W rod, it was placed in a special ball mill using a W-lined pot and W balls.
After evacuating the inside of the pot, the atmosphere was replaced with Ar gas to create a non-oxidizing atmosphere, and the mixture was ground and mixed to obtain a powder of 150 μm or less. The obtained powder was sintered and compacted using a vacuum sintering method, a hot press method, and a HIP method to obtain a target material. The conditions for each sintering method, the density of the sintered body obtained, and the results of microstructure observation show that 0.0% when sputtered onto a 6-inch wafer.
Table 1 shows the number of particles of 3 μm or more generated.

[0016]

[Table 1]

From Table 1, it can be seen that by using the hot press method and the HIP method, the density can be increased and particles generated by sputtering can be reduced. Note that when the density is low, the increase in the number of particles is considered to be due to abnormal discharge occurring during sputtering due to holes existing in the target.

(Comparative Example 1) High purity W powder (purity 99.9
99% or more, average particle size 5 μm or less) and hydrogenated high-purity Ti (purity 99.99% or more, average particle size 75 μm or less:
Hereinafter referred to as titanium hydride), titanium hydride is 10.3
The mixture was blended to 6 wt% and placed in a special ball mill using a W-lined pot and W balls. After evacuating the inside of the pot, the pot was replaced with Ar gas to create a non-oxidizing atmosphere and pulverized for 90 minutes. I mixed it while doing so. In the obtained mixed powder, no titanium hydride larger than 20 μm was observed, and the average particle size was 4 μm.

The obtained mixed powder was filled into a HIP can with an inner diameter of 400φ, and heated at 700° C. for 24 hours while evacuated to 5×10 minus 5 torr to perform dehydrogenation treatment. After dehydrogenation, the HIP can was sealed, and HIP treatment was performed at 1250° C. for 2 hours and 1000 atm. A photograph of the structure of the obtained sintered material at a magnification of 600 times is shown in FIG. Figure 2
In the figure, the white particles are W particles, and the gray areas between the W particles are the Ti phase. It can be seen that although the W in this sintered body is dispersed as fine particles, Ti agglomeration occurs partially. Further, at this stage, no Ti-W alloy phase could be confirmed. This sintered material is used as the target material, and φ
It was processed to a size of 300 and used as a target. Sputtering was performed on a 6-inch wafer using this target.
When we observed the number of particles larger than 3 μm,
The number of particles was 140, which was confirmed to be significantly larger than that of the target material of the present invention.

(Example 5) A sintered material obtained in the same manner as in Comparative Example 1 was used as a melted raw material, and this melted raw material was subjected to electron beam melting in the same manner as in Example 1 to obtain a high purity ingot. The obtained ingot was placed in a vacuum furnace (degree of vacuum: 5×10 minus 5 t
A target material was obtained by solution treatment under the conditions of 1400° C. x 10 hours in an atmosphere with a reduced pressure (at a pressure lower than that of the target material). The structure of the target material obtained was substantially the same as in Example 1.
It was confirmed that there was only an alloy phase consisting of i and W. The obtained target material was processed into a diameter of φ300 to obtain a Ti-W target, and sputtered onto a 6-inch wafer.
When the number of particles of 0.3 μm or more was observed, it was found to be 16, which was very small.

[0021]

Effects of the Invention According to the target material and the method for producing the same of the present invention, since it is possible to use only an alloy phase consisting essentially of Ti and W, sputtering can be performed with extremely low particle generation. can provide very effective targets and thin films for improving the quality of

[Brief explanation of drawings]

FIG. 1 is a photograph of the alloy metallographic structure of the target material of the present invention.

FIG. 2 is a photograph of the alloy metallographic structure of a target material of a comparative example.

Claims (7)

[Claims] 1. A Ti-W target material characterized in that the area of an alloy phase consisting of Ti and W occupies 98% or more when observed microstructurally. 2. A method for producing a Ti-W target, comprising the step of solution-treating an ingot obtained by melting W and Ti. 3. Production of a Ti-W target, comprising the steps of solution-treating an ingot obtained by melting W and Ti, then pulverizing the ingot, and sintering the obtained powder. Method 4. Claims 2 and 3, wherein the melting is performed by electron beam melting in a reduced pressure atmosphere.
The method for manufacturing a Ti-W target described in 5. A method for producing a Ti-W target, comprising the steps of: turning a molten metal made by melting W and Ti into powder by an atomizing method, and sintering the obtained powder. 6. The method for producing a Ti-W target according to claim 3, wherein the sintering is performed by hot isostatic pressing. 7. The method for manufacturing a Ti--W target according to claim 3, wherein the sintering is performed by hot pressing.