JPH0598435A - Ti-w target material and its manufacture - Google Patents

Abstract

PURPOSE:To provide a Ti-W target material small in the generation of particles at the time of sputtering, particularly in the initial state and its manufacturing method. CONSTITUTION:This material is a Ti-W target material having a structure constituted of a Ti-W alloy phase by >=20%, by area, of a micro structure occupied on the cross section of the target material, a W phase and a Ti phase and having <=3mum surface roughness by Rmax value. Furthermore, as for its manufacturing method, W powder and Ti powder are subjected to press sintering into a sintered compact; the obtd. sintered compact is subjected to heating and alloying treatment to form a Ti-W alloy phase; and then, by surface grinding treatment, its roughness is regulated to <=3mum by Rmax value. Preferably, heating treatment is moreover executed at <=1500 deg.C; where the surface roughness of the target material is preferably regulated to <=1mum by Rmax value.

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 a barrier metal layer used in a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent high integration of LSIs, Al wiring and Al wiring such as contact migration due to a diffusion precipitation portion in a contact portion of a semiconductor substrate Si,
Migration has become a problem. Barrier metal layers have been studied in recent years as a countermeasure. As the barrier metal layer, a Ti-W thin film (typically Ti: 10 wt
%, And the balance W. ) Is often used, and a method of sputtering a target is adopted as a method for forming the same.

This Ti-W target material for thin films is generally manufactured by mixing W powder and Ti powder and hot pressing. However, conventional Ti-W
The Ti powder that is the raw material of the target has a high oxygen content,
Only targets with a high oxygen content were obtained.
Such a target having a large oxygen content is not preferable because the release of oxygen during sputtering causes cracking of the target, oxidation of the formed film, variation in film quality, and the like.

Recently, as a method of reducing the oxygen content of such a Ti-W target, US Pat. No. 4,838,9 has been proposed.
No. 35, T containing hydrogenated at least a part of Ti powder
i, or binodal
It is disclosed that by using a mixture of W powder and hydrogenated Ti powder or hydrogenated Ti powder and Ti powder having a dal) particle size distribution, high density and low porosity and carbon and oxygen contents can be reduced. Was done. Similarly, as a method for reducing the oxygen content of the Ti-W target, Japanese Patent Laid-Open No. 63-303017 discloses that W powder and hydrogenated Ti powder are mixed and hot pressed after or while dehydrogenating. A method of doing is disclosed. Since the use of this hydrogenated Ti powder is effective in preventing oxidation itself and has better crushability than Ti powder,
It is possible to reduce the amount of oxygen picked up during grinding. Thus, a Ti-W target having a low oxygen concentration of 900 ppm or less can be obtained.

[0005]

With the recent trend toward higher density and finer electrode patterns of semiconductor products, even if sputtering is performed using the above-mentioned low oxygen concentration Ti-W target,
Huge particles, so-called particles, adhere to the thin film formed by sputtering, causing a new problem of breaking the electrode wiring. The generation of this particle is T
It could not be solved only by reducing the oxygen content of the i-W target. The above publication also does not disclose the relationship between the microstructure of the Ti-W target material and the generation of particles during sputtering.

As a technique for preventing particles, JP-A-1-263269 discloses a method of suppressing the generation of foreign matter during sputtering by removing the work strain layer of the target material, and JP-A-3-130360. No. 1 shows the surface roughness of the silicide target material as Ra.
(Center line roughness) is set to 0.05 μm or less, and the compressive residual stress existing on the surface part is also regulated to 5 kg / mm ² or less to reduce the amount of particles that fall off from the processing defect layer. It is disclosed. However, regarding the Ti-W target material,
The relationship with the number of particles generated was unknown.

The present inventor has studied in detail the relationship between the target structure and particle generation in order to solve the above-mentioned problem of particle generation, and has found that coarse Ti particles are involved in particle generation. That is, in the coexistence of Ti and W, Ti having a light atomic weight is selectively sputtered, and W particles included in coarse Ti particles or W particles in the vicinity thereof are scattered as large particles from the target material. It was found to be one of the causes. Furthermore, when the relationship between the cumulative sputtering time and the number of particles generated was investigated, it became clear that there is a tendency that the number of particles generated is large at the initial stage of sputtering. Therefore, it is necessary to suppress the generation of particles particularly in the initial stage of sputtering. An object of the present invention is to provide a Ti-W target material that suppresses particles particularly in the initial stage of sputtering and a method for manufacturing the same.

[Means for Solving the Problems]

The inventors of the present invention have found that the film deposition in the chamber of the apparatus is small at the initial stage of sputtering, and therefore the generation frequency of particles due to the peeling of the deposited film in the chamber should be low. It was estimated that the occurrence of the phenomenon was due to the target material. In addition, the inventors performed a detailed observation with an electron microscope about changes in the surface shape and texture with the progress of erosion of the target material surface by sputtering, and the target material surface by mechanical polishing before sputtering and etching by ion irradiation. It was found that the texture of the surface is very different from that of the surface after erosion has progressed. In other words, on the surface after polishing, missing parts of the sintered particles are observed over the entire surface, and the surface irregularities are large, whereas the etched surface by ion irradiation is very smooth and the irregularities are small. From the above, it was found that it is effective to make the surface roughness of the target material as smooth as possible in order to prevent the generation of particles in the initial stage of sputtering.

That is, the present invention has a Ti—W alloy phase having an area ratio of 20% or more of the microstructure in the cross section of the target material, a structure composed of the W phase and the Ti phase, and has a surface roughness of the target material. A Ti-W target material having an Rmax value of 3 μm or less. Further, the target material of the present invention is adjacent to the W particles that are dispersed and present as a specific structure, the Ti-W alloy phase that substantially surrounds the W particles, and the Ti-W alloy phase or the W particles. A Ti-W target material having a structure of dispersed Ti phase and having a surface roughness of 3 μm or less in Rmax value. Further, in the present invention, the surface roughness of the target material is preferably 1 μm or less in Rmax value.

By forming a Ti-W alloy phase, the target material of the present invention can reduce the substantial amount of Ti phase and prevent the generation of coarse Ti particles in the target material. Further, the difference in the sputtering rate between the W phase and the Ti phase can be buffered by the Ti-W alloy phase. The area ratio of the Ti-W alloy phase that is substantially necessary to reduce the generation of particles is 20% or more. W
It cannot be said that the Ti—W alloy phase is formed with the amount of the Ti—W alloy that is formed at the pressed portion of the powder and the Ti powder.
In the present invention, the area ratio is limited to 20% or more in order to more specifically indicate the amount of the Ti-W alloy phase that can reduce the generation of particles. In the present invention, the Ti-W alloy phase is not limited to any composition as long as it is an alloy of Ti and W, and does not exclude one containing fine αTi precipitated during cooling. Further, in the present invention, the W phase and the Ti phase do not have to be composed of only W and Ti, respectively. For example, when a sintered body of W powder and Ti powder is heated,
It is natural that a small amount of Ti diffuses into the W phase of the obtained structure, and similarly, a small amount of W can also diffuse into the Ti phase.

The target of the present invention is made of alloyed Ti.
By defining the surface roughness of the target material having the −W phase to be 3 μm or less in Rmax value, it is possible to suppress not only the generation of particles during the sputtering period but also the generation of particles at the initial stage of sputtering. Providing the Ti-W alloy phase described above is effective in reducing particles after the erosion progresses and the surface layer of the target material is removed. However, at the initial stage of sputtering, the surface condition after machining has a great influence on the generation of particles, and therefore the generation of particles cannot be sufficiently suppressed only by providing the Ti—W alloy phase. That is, the surface roughness when the target shape is obtained by grinding with a lathe or the like is about 6 μm in Rmax value,
This is almost the same as the particle size of the target material constituent particles made of Ti and W after sintering, and many minute cracks and defects due to the lack of target material constituent particles are present on the surface. In such a defect part, the bonding strength between particles is weak,
Fine particles are emitted from this point and become particles. In addition, the convex portion around the defective portion due to the lack of particles easily serves as a starting point of abnormal discharge during sputtering, and the impact of the discharge promotes the loss of fine constituent particles.

In order to suppress the generation of particles in the initial stage of sparring by the above mechanism, it is necessary to finish the surface to have a finer surface roughness depending on the particle diameter of the target material constituent particles, and the Rmax value is 3 μm or less. Further, when the surface roughness is 1 μm or less in terms of Rmax value, the surface becomes a mirror surface state, and the defect layer that is the starting point of the loss of fine particles is removed, which is preferable for suppressing particles. On the contrary, when the surface roughness exceeds 3 μm in Rmax value, the effect of suppressing particles by surface polishing is very small.

Further, in the method of the present invention, W powder and Ti powder are pressure-sintered into a sintered body, and the obtained sintered body is heated and alloyed to form a Ti-W alloy phase. The Rmax value is 3 μm or less by the formation and subsequent surface polishing treatment. By this method, the Ti—W alloy phase having a microstructure area ratio of 20% or more in the target material cross section and W
It is possible to obtain a Ti-W target material having a structure composed of a phase and a Ti phase, and having a surface roughness of the target material of 3 μm or less in Rmax value.

Further, the roughness of the target material surface and Rmax
It is desirable to perform heat treatment at 1500 ° C. or less after finishing the value to 3 μm or less. By performing such a heat treatment, it is possible to release the residual stress of the target material surface layer accumulated in the process of polishing to Rmax value of 3 μm or less. The residual stress on the surface of the target material promotes the above-mentioned loss and release of fine target material constituent particles that cause particles, and is preferably released in order to suppress the generation of particles. The condition that the heat treatment temperature is 1500 ° C. or lower was determined in consideration of the recrystallization temperature of tungsten. That is, in order to release the stress residual state accompanied by the distortion of the crystal lattice, it is necessary to supply heat energy to the extent that atoms can be rearranged, and the high melting point (3410 ° C.) of the main components of the target material is required.
The recrystallization temperature of Tungsten is 1500
The temperature was set to ℃ or below. If the heat treatment temperature exceeds 1500 ° C., rapid crystal grain growth occurs, so 1500 ° C. or less is desirable to release stress without coarsening the crystal grains.

Further, in the present invention, as a method for obtaining a Ti--W alloy phase of 20%, it is preferable to carry out heating at 1300 to 1500 ° C. after obtaining a sintered body of Ti and W. The heating at 1300 to 1500 ° C. is for generating a Ti—W alloy phase while suppressing the growth of crystal grains by the diffusion treatment. Although a combination of Ti and W can be solid-solubilized at all, it is desirable that this diffusion treatment is performed at 1500 ° C. or lower in order to alloy the grains without coarsening them. Also,
If it is less than 1300 ° C., almost no alloying occurs even after 50 hours.
0 ° C or higher is good. The W powder preferably has a purity of 99.
It is desirable that the high-purity W powder has a purity of 99% or more, and more preferably a purity of 99.999% or more.
It is desirable that the high purity Ti is 9.99% or more. Further, by using the hydrogenated high-purity Ti powder in the present invention, the oxygen content in the target material can be reduced.

At this time, the powders may be mixed and pulverized separately, but in the present invention, by using an apparatus such as a ball mill or an attritor that mechanically pulverizes and mixes at the same time, the difference in specific gravity between Ti and W causes unevenness. Can be prevented from becoming a mixture. Ti and W powders have an average particle size of 5μ
It is preferable to grind to a particle size of m or less. By finely pulverizing the powder, it is possible to uniformly disperse Ti and W, prevent coarsening of Ti particles during sintering, and promote alloying of Ti and W during heat treatment. Further, hot isostatic pressing (hereinafter referred to as HIP) or hot pressing can be used for pressure sintering. T of the present invention
A thin film obtained by sputtering an i-W target can have about 0.1 or less particles having a maximum diameter of 0.5 μm or more on the surface of the thin film per square centimeter, and a semiconductor device with extremely few defects can be obtained. ..

[0017]

【Example】

Example 1 High purity W powder (99.999%) and hydrogenated high purity T
i powder (99.99%) is composed of W: Ti in percentage by weight.
= 90:10, mixed and pulverized using a ball mill until the average particle size of the powder is 5 μm or less, and after dehydrogenation, hot isostatic press at 1250 ° C. for 5 hours 1000
Sintered at kgf / cm ² . Then in a vacuum furnace at 1400 ° C
Alloying heat treatment for 24 hours at 70% by area ratio of microstructure consisting of Ti-W alloy phase, W phase and Ti phase,
A target material having a structure in which W particles are dispersed and present, and the W particles are surrounded by a Ti—W alloy phase is obtained. Next, three pieces of the target material processed into φ300 were prepared. These three target materials are GC # 120, diamond #
Each of the grindstones of 1000 and Cr ₂ O ₃ # 5000 was used to finish to different surface roughness. The surface roughness has three types of Rmax values of 6 μm, 1.5 μm, and 1 μm in order of roughness. Next, these three target materials having different surface roughness were held together in a vacuum furnace at 1000 ° C. for 1 hour to perform heat treatment for stress relief. The Ti-W target material thus manufactured was sputtered on a 6-inch silicon wafer. The number of particles for each silicon wafer was measured with respect to the number of processed silicon wafers. Sputtering conditions are Argon pressure 5.0 × 10 -3 Torr
r, high-frequency input power 200 W, and the distance between the target and the silicon wafer substrate is 80 mm.

FIG. 1 shows an experimental result of particle generation. The horizontal axis represents the number of processed Si wafers, and the vertical axis represents the number of particles having a particle diameter of 0.5 μm or more generated in the vacuum chamber. The white circles, white squares, and white triangles in the figure represent the results for target materials having surface roughnesses of Rmax values of 6 μm, 1.5 μm, and 1 μm, respectively. According to FIG. 2, when Rmax = 6 μm, the number of particles generated is 60 to 190 at the initial stage of sputtering, whereas Rmax = 1.5 μm.
In the case of m and 1.0 μm, the generation of particles is small in the initial stage of sputtering and the number of particles is 20 each.
-60 and 10-40. From this, it can be seen that by setting the surface roughness of the target material to 3 μm or less, preferably 1 μm or less in terms of Rmax value, the generation of particles can be suppressed, and the effect is very remarkable.

Example 2 A Ti-W target material was prepared in exactly the same manner as in Example 1 and the surface was polished with a grindstone of Cr ₂ O ₃ # 5000 to finish it to a roughness of Rmax = 1 μm. I prepared 2 sheets. One of them was heat-treated at 1000 ° C. for 1 hour in a vacuum furnace to remove stress, and the other one was not heat-treated. The same target film formation as in Example 1 was performed using these two target materials, and the number of particles for each silicon wafer was measured with respect to the number of processed silicon wafers. FIG. 2 shows the experimental results. The horizontal axis represents the number of processed Si wafers, and the vertical axis represents the number of particles having a particle size of 0.5 μm or more generated in the vacuum chamber. In the figure, the white squares represent the results for the target material that was subjected to heat treatment for stress relief, and the black solid squares represent the results for the target material without heat treatment. The number of particles of the heat-treated target material is 10 to 40, whereas the number of particles of the target material without heat treatment is 30 to 80.
It is an individual. From this, the target material surface and Rmax
It can be seen that it is effective to suppress particles by performing a heat treatment for stress removal after flatly polishing to = 1 μm.

[0020]

EFFECTS OF THE INVENTION According to the method of the present invention, the surface of a sintered body having a structure in which W particles and Ti phase are dispersed mainly in the Ti-W alloy phase and the number of coarse Ti particles is extremely small is determined by Rmax.
By polishing to a value of 3 μm or less, it is possible to manufacture a Ti—W target material with few particles generated in the initial stage of sputtering. Further, the generation of particles can be further reduced by removing the stress by performing a heat treatment at 1500 ° C. or less after polishing. By using the target material of the present invention, it is possible to carry out sputtering in which generation of particles is extremely small, and thus it is possible to provide a target and a thin film which are very effective in improving the quality of semiconductor devices.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of particles subjected to sputtering and the number of particles for Ti—W target materials having different surface roughnesses.

FIG. 2 is a diagram showing the relationship between the number of particles subjected to sputtering and the number of particles for a Ti—W target material with and without heat treatment.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/285 S 7738-4M R 7738-4M

Claims (5)

[Claims] 1. A Ti—W alloy phase having a microstructure area ratio of 20% or more in a target material cross section, a W phase and a T phase.
Ti having a structure consisting of i-phase and having a surface roughness of the target material of 3 μm or less in Rmax value.
-W target material. 2. Dispersed W particles, a Ti-W alloy phase substantially surrounding the W particles, and a Ti phase dispersed adjacent to the Ti-W alloy phase or W particles, and A Ti-W target material, wherein the surface roughness of the target material is 3 μm or less in Rmax value. 3. The surface roughness of the target material is 1 at the Rmax value.
The Ti-W target material according to claim 1 or 2, wherein the Ti-W target material has a thickness of not more than µm. 4. W powder and Ti powder are pressure-sintered to obtain a sintered body, the obtained sintered body is heat-treated to form a Ti—W alloy phase, and then surface polishing treatment is performed to obtain Rmax. 3 by value
A method for manufacturing a Ti-W target material, which is characterized in that the thickness is at most μm. 5. W powder and Ti powder are pressure-sintered to obtain a sintered body, and the obtained sintered body is heated and alloyed to obtain Ti.
-W alloy phase is formed and then surface polishing treatment is performed to obtain Rm.
A method for manufacturing a Ti-W target material, which comprises subjecting an ax value to 3 μm or less and then performing heat treatment at 1500 ° C. or less.