JP3275344B2 - Ti-W target material and method of manufacturing the same - Google Patents

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 increase in the degree of integration of LSIs, migration of Al wiring such as contact migration due to diffusion and deposition at the contact between Al wiring and semiconductor substrate Si has become a problem. As a countermeasure, a barrier metal layer has recently been considered. As the barrier metal layer, a Ti-W thin film (typically, having a composition of Ti: 10 wt% and a balance of W) is used in many cases, and a sputtering method of a target is adopted as a forming method thereof.

[0003] This Ti-W target material for a thin film is generally produced by mixing W powder and Ti powder and hot pressing. However, the Ti powder used as a raw material of the conventional Ti-W target has a high oxygen content, and only a target having a high oxygen content has been obtained. Such a target having a large oxygen content is not preferable because the release of oxygen during sputtering causes cracks in the target, oxidation of the formed thin film, and variations in the film quality.

Recently, as a method of reducing the oxygen content of such a Ti-W target, US Pat. No. 4,838,935 discloses that at least a part of Ti powder is replaced with hydrogenated Ti, or a binodal particle size is reduced. W powder with distribution and hydrogenated Ti powder or hydrogenated Ti
It has been disclosed that the use of a mixture of powder and Ti powder can reduce the high density and low porosity and the content of carbon and oxygen. Similarly, as a method for reducing the oxygen content of a Ti-W target, JP-A-63-303017 discloses a method in which W powder and hydrogenated Ti powder are mixed and hot pressed after dehydrogenation or while dehydrogenation. Is disclosed. The use of this hydrogenated Ti powder is effective in preventing oxidation by itself and has a better crushing property than Ti powder, so that the amount of oxygen pick-up at the time of pulverization can be reduced. 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 thinner electrode patterns for semiconductor products, even if sputtering is performed using the above-described Ti-W target having a low oxygen concentration, a thin film formed by sputtering can be obtained. There is a new problem that giant particles, so-called particles, adhere and break the electrode wiring. The generation of these particles is Ti-
The problem could not be solved only by reducing the oxygen content of the W target. The above publication does not disclose the relationship between the microstructure of the Ti-W target material and the generation of particles during sputtering at all.

As a technique for preventing particles, Japanese Patent Application Laid-Open No. Hei 1-263269 discloses a method of suppressing generation of foreign matter during sputtering by removing a work strain layer of a target material. No. indicates the surface roughness of the silicide target material.
Disclosed is a method for reducing the amount of particles that peel off from the work defect layer by defining the center line roughness to be 0.05 μm or less and the compressive residual stress existing on the surface to be 5 kg / mm ² or less. Have been. However, regarding the Ti-W target material, the relationship between the microstructure and the number of generated particles was unknown.

The inventor of the present invention has studied in detail the relationship between the target structure and the generation of particles in order to solve the above-mentioned problems, and has found that coarse Ti particles are involved in the generation of particles. That is, in the coexistence of Ti and W, Ti having a small atomic weight is selectively sputtered, and the W particles included in the coarse Ti particles or the W particles in the vicinity thereof are scattered from the target material as giant particles, which causes particle generation. I found that it was one of the causes. In recent years, a magnetron type sputtering apparatus has been widely used for film formation by a sputtering method mainly in a semiconductor process. The magnetron type sputtering apparatus has a structure in which a permanent magnet is arranged behind a target material, and plasma is confined near the surface of the target material by a magnetic field. Therefore, there is an advantage that the deposition rate is high and the use efficiency of the target material is high. Recently, the position of the permanent magnets to be arranged, etc. are changed, and erosion is designed to occur on the entire surface of the target material, and there is a direction to further increase the use efficiency of the target material, but it is difficult to achieve uniform erosion over the entire surface,
In particular, in many cases, the erosion of the outermost peripheral portion of the target material does not progress at all even after the target material has been used up. The present inventors have observed in detail the process of erosion progress on the target material surface during sputtering.As a result, erosion hardly progressed at the outer peripheral portion of the target material, and spatter particles jumping out of the target material surface reattached. As a result, it was confirmed that an adhered film was formed. And as a result of observing the generation of this adhered film and the state of the thin film formed by sputtering in more detail, as the adhered film becomes thicker, the adhered film peels off from the target material surface, and fragments at the time of peeling are scattered and formed. It has been found that the particles adhere to the thin film and become particles. The present invention has been made in view of the above problems, and an object of the present invention is to provide a Ti-W target material capable of suppressing generation of particles caused by a target material, and a method for manufacturing the same.

[0008]

Means for Solving the Problems The present inventor pays attention to the structure of a target material, and by providing a Ti-W alloy phase in addition to a single phase of Ti or W, the target material is considered to be less likely to generate particles. And that the outer peripheral portion of the sputtering surface of the target material is lower than the central portion of the sputtering surface or has a specific roughness, particularly due to the deposited film on the outer peripheral portion of the target. The inventors have found that generation of particles can be suppressed, and have reached the present invention. That is, according to the present invention, the area ratio of the microstructure in the cross section of the target material is 20% or more of T.
Ti-W having an i-W alloy phase, a structure consisting of the remaining W phase and Ti phase, wherein the thickness of the outer peripheral portion of the sputtering surface of the target material is made thinner than the central portion of the sputtering surface. It is a target material. Further, the present invention relates to a microstructure area ratio of 20% in the target material cross section.
% Or more of a Ti-W alloy phase and a balance consisting of a W phase and a Ti phase, and that the surface roughness of at least one point on the outer peripheral portion of the sputtering surface of the target material is 10 μm to 1000 μm in Rmax value. This is a characteristic Ti-W target material. It has been found that it is effective to provide a Ti-W alloy phase as a target material without scattering of W particles due to a difference in sputtering speed between Ti and W.

[0009] The target material of the present invention forms a Ti-W alloy phase in addition to the Ti phase and the W phase, thereby achieving a substantial Ti phase.
The phase amount can be reduced, and the generation of coarse Ti particles in the target material can be prevented. Also, the difference in 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 substantially required to reduce the generation of particles is 20% or more. If the amount of the Ti-W alloy is such that it is formed by diffusion at the pressure contact portion between the W powder and the Ti powder, it cannot be said that the Ti-W alloy phase has been formed. In the present invention, the area ratio is limited to 20% or more in order to more specifically show the amount of the Ti-W alloy phase that can reduce the generation of particles. For the purpose of greatly reducing the generation of particles, the area ratio of the Ti-W alloy phase is desirably 60% or more. In the present invention, the composition of the Ti-W alloy phase is not limited as long as it is an alloy of Ti and W, and does not exclude those containing fine αTi which precipitates upon cooling. In the present invention, W phase and Ti
The phases need not each consist solely of W and Ti. 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. Can spread.

[0010] Providing the above-mentioned Ti-W alloy phase,
This has the effect of suppressing the generation of particles due to the missing or scattered particles of the target material constituents in the portion where the erosion of the target material surface progresses. However,
For the portion of the outer peripheral portion of the target material where erosion does not substantially proceed, another measure is required to suppress particles. As described above, the outer peripheral portion of the target material in the present invention is defined as an outer peripheral region where erosion does not substantially proceed, or an outer peripheral region where the amount of erosion is small even if it occurs. When the thickness of the outer peripheral portion of the sputtering surface of the target material is made thinner than the central portion, for example, as the easiest way to make the outer peripheral portion tapered, the sputtered particles flying in the outer peripheral direction from the central portion of the target material Becomes less likely to re-adhere to the surface of the target material, and the deposition of a film on the outer peripheral portion of the target material can be prevented. In the present invention, the thinned region of the outer peripheral portion of the target material may be a curved surface or a flat surface such as a tapered shape. Further, the surface roughness of the outermost peripheral portion of the target material was measured at an Rmax value of 10 μm, which is a measurement value specified by JIS.
By processing from m to 1000 μm, separation of the deposited film can be suppressed. Usually, the surface of the target material is polished to obtain stable discharge characteristics. recent years,
In particular, it has been pointed out that mirror polishing is effective in suppressing the generation of particles from the surface of the target material, and the surface flatness tends to be further improved. When a film is deposited on such a surface having a small surface roughness, the compression or tensile internal stress of the film accumulates in a direction parallel to the film surface, and thus the film is easily peeled. The present inventors varied the surface roughness of the target material, deposited a film, and investigated the correlation with the separation. As a result, it was found that the film was hardly peeled when the surface roughness was changed from 10 μm to 1000 μm in the direction opposite to the conventional mirror finish, that is, in the direction of slightly roughening the surface, and the Rmax value was set to 10 μm to 1000 μm. This is considered to be because the orientation of the internal stress of the film can be dispersed by moderately roughening the surface, and the stress can be relaxed by canceling. In addition, the target material of the present invention, for example, forms a sintered body by sintering W powder and Ti powder under pressure, heats the obtained sintered body, and performs an alloying process to form a Ti-W alloy phase. And then
The surface roughness of the target material is tapered on the outer periphery, or the surface roughness is blasted to an Rmax value of 10 μm to 1000 μm.
Can be manufactured. By these methods, it is possible to prevent the sputter particles from adhering to the outer peripheral portion of the target material, and to obtain a Ti-W target material with less generation of particles.

In the present invention, the Ti—W alloy phase is
As a method for obtaining%, it is preferable to perform heating at 1300 to 1500 ° C. after obtaining a sintered body of Ti and W. 1300
The reason for heating to ~ 1500C is to form a Ti-W alloy phase by diffusion treatment while suppressing the growth of crystal grains. T
The combination of i and W can form a solid solution, but in order to form an alloy without coarsening the crystal grains, heat treatment must be performed at 1500 ° C.
The following is desirable. If the temperature is lower than 1300 ° C., almost no alloying occurs even in 50 hours. Therefore, when a Ti—W alloy phase is also formed, the temperature is preferably 1300 ° C. or higher. The W powder is preferably a high-purity W powder having a purity of preferably 99.99% or more, more preferably 99.999% or more, and Ti has a purity of 99.99%.
%.

In the present invention, the hydrogenated high-purity T
By using i powder, the oxygen content in the target material can be reduced. At this time, mixing and grinding of the powder can be performed separately, but in the present invention, a ball mill,
By using an apparatus such as an attritor that simultaneously performs mechanical pulverization and mixing, it is possible to prevent a non-uniform mixture due to a difference in specific gravity between Ti and W. The Ti and W powders are preferably ground to a mean particle size of 5 μm or less. As described above, Ti and W are obtained by pulverization.
Can be uniformly dispersed to prevent Ti grains from becoming coarse during sintering and promote the alloying of Ti and W in the heat treatment. For the pressure sintering, a hot isostatic press (hereinafter referred to as HIP) or a hot press can be used. In the thin film obtained by sputtering the Ti-W target of the present invention, particles having a maximum diameter of 0.5 μm or more on the surface of the thin film can be reduced to about 0.1 or less per square centimeter, and a semiconductor device with extremely few defects can be obtained. .

[0013]

【Example】

(Example 1) High-purity W powder (99.999%) and hydrogenated high-purity Ti (99.99%) were blended so that the composition becomes W: Ti = 90: 10 by weight percentage, and the average of the powder was obtained using a ball mill. Particle size 5
The mixture was mixed and pulverized until it became not more than μm, dehydrogenated, and sintered by a hot isostatic press at 1250 ° C. for 5 hours at 1000 kgf / cm ² . Next, an alloying heat treatment was performed in a vacuum furnace at 1400 ° C. for 24 hours, and a Ti-W alloy phase having a microstructure area ratio of 70%, a W phase and a Ti phase, and W particles were present in a dispersed state. W-particles Ti-W
A target material having a structure surrounding the alloy phase was obtained. twenty four
Figure 1 shows a micrograph of the structure 600 times that of the heat treatment for a long time.
Shown in In FIG. 1, the white portion is a W particle representing a W phase, and the gray white portion substantially surrounding the W particle is a Ti-W alloy phase. Further, a black portion dispersed and present adjacent to the Ti-W alloy phase or the W particles is the Ti phase.

As shown in FIG. 1, the W particles exist as fine particles due to the heat treatment for 24 hours, and most of them are Ti-W.
W particles covered with the alloy phase and surrounded by the Ti phase could not be confirmed. It can also be seen that the ratio of the Ti phase is very small. Then, by lathe, surface polishing, electric discharge machining, the sintered body φ300mm, thickness 6mm,
A disk processed to have a surface roughness of Rmax = 3 μm was prepared.
The width of 6 mm from the end of the sputtering surface 2 of the target material 1 is 0 (no treatment) to 45 with respect to the surface of the center of the target.
Was tapered so as to have a depression angle θ of °. Figure 2
It shows the cross-sectional shape of a target material that has been tapered at 45 °. The Ti-W target material thus manufactured was sputtered on a 6-inch silicon wafer, and the number of particles for each silicon wafer was measured. The sputtering conditions were as follows: argon pressure 5.0 × 10 −3 Torr, high-frequency input power 200 W, distance between target and silicon wafer substrate 80 mm. Table 1 shows the relationship between the depression angle provided on the outer peripheral portion of the target material and the number of generated particles. The particles were measured by a light scattering method for particles having a particle diameter of 0.5 μm or more attached on the silicon wafer.
The values in Table 1 are the average values measured for each silicon wafer. According to Table 1, in the case of the sample No. 1 having no taper processing (depression angle θ = 0), an example of the present invention in which the number of generated particles was 21 in order to make the outer peripheral portion of the target material thinner than the center portion. It can be seen that the samples No. 2 to No. 5 can reduce the number of generated particles. Cumulative sputtering time 1
Observation of the outer peripheral portion of the target material after the elapse of 5 kilowatt hours showed that the sample No.
In the case of 1, the adhered film was deposited on a portion of the outer peripheral portion having a width of 6 to 8 mm, and partial peeling was observed. On the other hand, in the tape-processed target material of the present invention, adhesion of the film was small, and peeling was not confirmed. From the above, it can be understood that tapering the outer peripheral portion of the target material is very effective in suppressing particles.

[0015]

[Table 1]

(Example 2) A sintered body having a Ti-W alloy phase having a microstructure area ratio of 70% was obtained in exactly the same manner as in Example 1. Next, the sintered body was φ300mm, thickness 6mm, surface roughness Rmax = 3μm by lathe, surface polishing and electric discharge machining.
Was processed into a disc. Next, the remaining portion is masked with an adhesive tape except for a portion having a width of 10 mm from the end of the sputtering surface 2 of the target material 1, and alumina beads are sprayed onto a non-masking portion of the outer peripheral portion of the target material using a blast machine. The surface was roughened. When the Rmax value was measured using a surface roughness meter, the polished surface was normally finished to the value shown in Table 2 with Rmax = 3 μm, and the blasted beads were irradiated. FIG. 3 shows a cross-sectional shape of a target material having a rough outer peripheral surface. This target material was formed into a film under exactly the same sputtering conditions as in Example 1, and the particle size generated on the silicon wafer
The number of generated particles of 0.5 μm or more was measured. Table 2 shows the measurement results of the number of particles.

[0017]

[Table 2]

From Table 2, it can be seen that the generation of particles can be suppressed by setting the outer peripheral portion of the sputtering surface of the target material to a rough surface having an Rmax of 10 μm or more. But,
On the other hand, when the surface is roughened to have a Rmax of 1000 μm or more, the number of generated particles is conversely large.

(Example 3) A sample having a depression angle of 30 ° with respect to the center of the sputtering surface of the target material manufactured in the same manner as the sample No. 4 of the embodiment 1 was used. A portion with a width of 10 μm from the end was finished to a surface roughness Rmax = 150 μm. A film was formed under the same sputtering conditions as in Example 1, and the particle size on a silicon wafer was 0.5 μm.
The number of generated particles was measured. The number of generated particles was 10 (pcs / φ6 ″ wafer), and Rmax = 3μ in Example 1.
The generation of particles was further suppressed as compared with the sample No. 4 which is m.

Example 4 W and Ti powders were mixed and pulverized in exactly the same manner as in Example 1, and after dehydrogenation, a sintered body was obtained using a hot isostatic press. Next, it was heated to 1400 ° C. in a vacuum furnace to perform an alloying treatment. At this time, the Ti-W alloy phase area ratio formed by changing the processing time is controlled, and six Ti-W alloy phases having a structure in which the Ti-W alloy phase accounts for 0% to 90% in area ratio are obtained.
A -W sintered body was obtained. This sintered body was processed into a disk having a diameter of 300 mm and a thickness of 6 mm, and was subjected to a taper processing with a width of 6 mm from the outermost periphery and a depression angle of 45 °. The Ti-W target material thus manufactured was sputtered on a 6-inch silicon wafer, and the number of particles for each silicon wafer was measured. Sputtering conditions were as follows: argon pressure 5.0 × 10 minus the cube of 3 Tor
r, high frequency input power 200W, distance between target and silicon wafer substrate is 80mm. FIG. 4 shows the relationship between the Ti-W alloy phase area ratio of each target material and the number of particles. In a target material having the same tapered shape, when the Ti-W alloy phase area ratio exceeds 20%, the number of particles starts to decrease, and thereafter, as the ratio of the alloy phase increases, the number of particles gradually decreases. Understand. Therefore, in order to alloy the Ti-W structure and suppress the number of particles, at least 20% or more of Ti
It is understood that the -W alloy phase area ratio is necessary.

[0021]

According to the method of the present invention, the structure is such that the W particles and the Ti phase are mainly dispersed in the Ti-W alloy phase, the coarse Ti particles are extremely small, and the outer peripheral surface of the target material to be a non-erosion portion. By lowering the surface roughness of the target material from the central part surface or by setting the surface roughness to an Rmax value of 10 μm to 1000 μm, it is possible to carry out sputtering with extremely low generation of particles. A thin film can be provided.

[Brief description of the drawings]

FIG. 1 is a photograph of an alloy metal microstructure of a target material of the present invention obtained by a heat treatment for 24 hours.

FIG. 2 shows a Ti-W of the present invention having a tapered outer peripheral portion.
FIG. 3 is a cross-sectional view of a target material.

FIG. 3 is a cross-sectional view of a Ti-W target material of the present invention in which the outer peripheral surface is roughened.

FIG. 4 is a diagram showing a relationship between a Ti—W alloy phase area ratio and the number of generated particles.

[Description of Signs] 1 Target material 2 Sputtered surface

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-211575 (JP, A) JP-A-63-303017 (JP, A) JP-A-5-33129 (JP, A) 7870 (JP, Y2) YAMAUCH M, KIBAYAS HIT, Development of W-Ti Binary Alloy Sputtering Target and Study of Japan's Spontaneous Service, Nissan, Japan 22, 55-72

Claims (4)

(57) [Claims] A microstructure occupying at least 20% of a microstructure occupying a cross section of a target material, a structure comprising a balance of a W phase and a Ti phase, and an outer peripheral portion of a sputtering surface of the target material. A Ti-W target material having a thickness smaller than that of a central portion of the sputtering surface. 2. A structure comprising a Ti—W alloy phase having a microstructure area ratio of not less than 20% in a cross section of a target material and a structure including a remaining W phase and a Ti phase, and having an outer peripheral portion of a sputtering surface of the target material. At least one surface roughness is Rmax
Ti-W characterized by a value of 10 μm to 1000 μm.
Target material. 3. A sintered body obtained by sintering W powder and Ti powder under pressure to obtain a sintered body.
-A method for producing a Ti-W target material, comprising forming a W alloy phase and then tapering the outer peripheral portion of the target material. 4. A sintered body obtained by sintering W powder and Ti powder under pressure to obtain a sintered body.
-A method for producing a Ti-W target material, comprising forming a W alloy phase, and then blasting the outer peripheral portion of the target material to have a surface roughness of 10 µm to 1000 µm in Rmax value.