JPH1150243A - Titanium silicide target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the generation of particles on a titanium silicide target for forming a thin film and to reduce the generation of particles at the time of sputtering by specifying the compsn. and W content of the target and making the target free from a deposit of a W compd. SOLUTION: The titanium silicide target for forming a thin film has a compsn. represented by the formula TiSix (where 2.0<=x<=2.7), has <50 ppm W content and does not contain a deposit of a W compd. It is preferable that the amts. of Na, K, U, Th, Fe, Cr and Ni as impurities in the target are <=0.1 ppm, <=0.1 ppm, <=1 ppb, <=1 ppb, <=5 ppm, <=5 ppm and <=5 ppm, respectively. It is also preferable that the Mo content of the target is 1-500 ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a titanium silicide sputtering target for forming a thin film used as an electrode and a contact material in a semiconductor device such as an LSI and a VLSI. In particular, the present invention relates to a titanium silicide target capable of greatly reducing particle generation.

[0002]

2. Description of the Related Art Conventionally, polysilicon has been used as an electrode or wiring of an LSI semiconductor device. However, as the integration of LSI semiconductor devices has increased, signal propagation delay due to resistance has become a problem. For this reason, refractory metal silicides have come to be used as an alternative material. Such a refractory metal silicide film is formed by sputtering a silicide target. As the silicide target for sputtering, when the molar ratio x of silicon and the high melting point metal is less than 2, the film stress at the time of film formation is high and the molar ratio of silicon / high melting point metal is usually 2 because it is easy to peel off. Over silicide targets have been used. Among such refractory metal silicides, titanium silicide is particularly attracting attention as a material useful for highly integrated VLSI applications.

[0003] Various methods have heretofore been taken for the purpose of increasing the purity of titanium silicide targets. For example, JP-A-63-227771 discloses that
Metal impurities contaminated by pulverization are removed by a subsequent pickling treatment, and metal impurities are 10 ppm or less, carbon 50 ppm or less, and oxygen 500 p.
99.99% purity at pm or less, hydrogen 10 ppm or less, nitrogen 50 ppm or less
The above titanium silicide target is shown. Japanese Patent Application Laid-Open No. 61-108132 discloses a method for reducing oxygen in a silicide target material containing titanium silicide. However, the above two patents do not describe the necessity of reducing particles during sputtering.

Heretofore, the purpose of reducing the generation of particles during sputtering with respect to a titanium silicide target has been to “fine structure”, “removal of agglomerated Si phase”, “reduction of coarse Si phase”, “reduction of area ratio of free Si phase”. Attempts have been made to improve the surface. For example, JP-A-63-2
No. 19580 discloses a silicide target containing titanium silicide having a maximum particle size of TiSi ₂ phase of 20 μm or less and a maximum size of free Si phase of 50 μm or less, and shows that the refinement of the structure is effective for particle generation. I have. JP-A-64-39374 discloses a method of mixing -100 mesh synthetic silicide powder based on the finding that coagulated Si is deeply involved in particle generation. Further silicide target abundance of 10μm or more coarse Si phase which appears on the sputter surface by JP-A-5-1370 is 10 Quai / mm ² or less (TiSi
). In JP-A-6-272032, in addition to JP-A-5-1370, the area ratio of the Si phase appearing on the sputtered surface is 23% or less and the surface roughness is 1 μm.
The following titanium silicide target is disclosed. However, despite these efforts,
The problem of the generation of particles in the titanium silicide target has not been solved yet, and is a major obstacle to practical application.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of the generation of particles in a conventional titanium silicide target and to reduce the generation of particles during sputtering.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and by observing the erosion surface of the titanium silicide target after sputtering in detail, the impurity W as a particle source has been obtained.
They have found that atoms play a major role. That is, a large number of nodules (projections having a size of 10 to 200 μm) presumed to be a particle source were observed on the erosion surface of the titanium silicide target having a W content exceeding 50 ppm, and the nodules were qualitatively analyzed by EPMA. However, a W compound was detected from the top of the nodule. This is sufficient evidence to presume that nodules were generated with the foreign compound W as a nucleus. Further, after polishing the target to obtain a smooth surface,
Observation of the target structure with PMA revealed a clear W compound. This compound coexists with Si,
It is clear that it is a WSi ₂ phase. This is a WSi ₂ phase formed by combining W atoms mixed as impurities into titanium silicide with a free Si phase, and is caused by impurities W.

It is disclosed in Japanese Patent Application Laid-Open No. 5-33129 that particles are easily generated once nodules are generated.
This is shown in the case of an i-alloy target, and it is considered that the particle generation mechanism from nodules is the same regardless of whether it is a W-Ti alloy or titanium silicide. Therefore, in order to reduce particles, the W content must be 50 pp.
It turns out that it needs to be less than m.

[0008] Further, like the case of W, the contamination of Mo is liable to occur. However, according to the results of a detailed investigation by the present inventors, Mo is different from W even if it is present as an impurity up to about 500 ppm. It was confirmed that no _two phases were precipitated. Rather, the results showed that particles were less generated in the laboratory than the target in which the Mo content was suppressed to 1 ppm or less. Although the effect of Mo has not been explained mechanically, at least there is no adverse effect and the result is rather good. Therefore, a target which is positively added to some extent is also useful. Such a finding was first found in this patent.

The present invention is based on the above findings. In a titanium silicide target for forming a thin film,
The target composition is represented by TiSi _x (where x = 2.0 to 2.7), the W content in the target is less than 50 ppm,
And a titanium silicide target containing no W compound precipitate

[0010] 2. The impurity content in the target is Na
≦ 0.1ppm, K ≦ 0.1ppm, U ≦ 1ppb, Th ≦ 1ppb, Fe ≦
5. The titanium silicide target as described in 1 above, wherein 5 ppm, Cr ≦ 5 ppm, and Ni ≦ 5 ppm.

3. Mo content in target is 1 ~ 500pp
m. The titanium silicide target according to the above 1 or 2, wherein m is m.

According to the present invention, it is possible to take appropriate measures for reducing the nodules of titanium silicide and, consequently, particles.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The titanium silicide target for forming a thin film according to the present invention has a target composition of TiSi _x
Where x = 2.0 to 2.7. When x is 2 or less, the film stress at the time of film formation is high, and the film is apt to peel off, which is not preferable. On the other hand, x
Exceeds 2.7, the electrical resistance increases and the Si
It is not preferable because particles increase due to an increase in the area ratio of the phase becomes remarkable.

The W content in the titanium silicide target needs to be less than 50 ppm. In the case of a titanium silicide target having a W content of 50 ppm or more, a WSi ₂ phase formed by combining W atoms mixed as impurities in the titanium silicide with a free Si phase is formed, and nodules are generated using the WSi ₂ phase as a nucleus. However, once nodules occur on the erosion surface, it is presumed that this causes particles. Therefore, it is necessary that the W content, which is a factor for generating nodules, be less than 50 ppm, and that no W compound precipitate be contained. Further, it goes without saying that the impurity content in the target needs to be reduced as much as possible.

Alkali metal elements such as Na and K are particularly easily diffused, easily move in the insulating film, and cause deterioration of MOS-LSI interface characteristics.
Should be below 5 ppm. Radioactive elements such as U and Th emit α-rays and cause soft errors in semiconductor devices.
It should preferably be less than 0.5 ppb. Fe, Ni,
Transition metal elements such as Cr cause troubles at the interface junction. Therefore, it should be 5 ppm or less, preferably 1 ppm or less. Therefore, Na ≦ 0.1 ppm, K ≦ 0.1 pp
m, U ≦ 1ppb, Th ≦ 1ppb, Fe ≦ 5ppm, Cr ≦ 5ppm,
It is preferable that Ni ≦ 5 ppm.

Further, the content of Mo in the target of the present invention is preferably 1 to 500 ppm. Mo is up to 500ppm
Even if it exists as an impurity up to before and after, unlike Mo, MoS
No i ₂ phase precipitates. Rather, the Mo content is 1 ppm
Particle generation is less than that of a target that is suppressed below. For this reason, the mechanism has not yet been explained, but at least there is no other adverse effect, so it is useful to add it to a certain extent if it is at most 500 ppm. If it exceeds 500 ppm, it is not preferable because it may combine with a free Si phase to form a MoSi ₂ phase and become a core of nodules. There is a great possibility that the contamination of W atoms is caused by, for example, contamination in the production process of titanium silicide powder, in addition to that contained in the raw material.

When tungsten silicide is produced in addition to titanium silicide, W contamination in the raw material Si powder does not pose a particular problem for the purpose of producing tungsten silicide. Therefore, Si powder contaminated with W is used. . However, when the same Si powder is used for the production of titanium silicide, W contamination occurs, causing a problem of particle generation from the precipitate. W contamination to Si powder is caused by grinding tools. That is, a crushing device such as a ball mill is lined with the same material as silicide. WSi
Si powder for use is ground with a grinding tool lined with WSi. Therefore, the W content in Si is usually as high as 1000 to 2000 ppm.

In order to prevent this, the problem can be solved by using a pulverizing device lined with Ti or titanium silicide. Until now, this has not been possible, in part, for economic reasons. That is, since the demand for titanium silicide was not so large, there was no cost merit of manufacturing a pulverization tool dedicated to titanium silicide. In addition, since high-purity Ti is soft, when it is used as a lining, it is greatly consumed, and usually, Ti is not used as a lining. In addition, Ti is inferior in performance as a grinding medium because of its light weight.
This is the reason why no pulverizing medium was used. But,
From the problem of quality, a lining tool with Ti lining was prepared and used to crush Si and synthetic lump. As a result, the W content in the final product could be suppressed to 50 ppm or less. No precipitation of the compound was observed.

[0019]

Embodiments will be described below with reference to embodiments. (Example 1) Ti balls were put into a high-purity Ti ball mill pot, and a poly-Si lump was pulverized.
A powder was obtained. To obtain a TiH ₂ powder of -350 mesh and milling of high purity TiH ₂ Put Ti sphere Similarly ball mill pot made of high purity Ti. By mixing these two powders and heating them in a vacuum, a dehydrogenation reaction and a silicide synthesis reaction were performed at once, and a synthetic lump of TiSi _x (x = 2.40) was obtained. This silicide lump was pulverized to a high purity by a Ti ball mill to obtain -200 mesh silicide powder. W content in the raw material Si powder, the W content in the TiSi _x after synthesis were all 1ppm or less. The content of impurity elements other than W in the silicide powder was as follows. Na: 0.02ppm, K: 0.02ppm, U <0.1ppb, Th <0.1
ppb, Fe: 4ppm, Ni: 2ppm, Cr: 0.5ppm, M
o: 3ppm A sintered body was prepared from this TiSix powder by a hot press method, a target of φ300 mm × 6.35 mmt was prepared by machining, and sputtering was performed to measure particles on the wafer (6 inch diameter). There were a total of 15 particles having the above dimensions. The impurity content of the target was exactly the same as the value of the powder before hot pressing. No precipitate of W compound such as WSi ₂ was observed at all.

Example 2 Mo balls were put into a high-purity Mo ball mill pot, and the poly-Si mass was pulverized to obtain -350 mesh Si powder. To obtain a TiH ₂ powder of -350 mesh and milling of high purity TiH ₂ put Mo balls Similarly ball mill pot made of high purity Mo. By mixing these two powders and heating them in a vacuum, a dehydrogenation reaction and a silicide synthesis reaction are performed at once, and TiSi _x (x = 2.4
A composite mass of 0) was obtained. This silicide lump is Mo
The resulting mixture was pulverized with a ball mill to obtain -200 mesh silicide powder. W content in raw material Si powder, Ti after synthesis
W content in the Si _x were 1ppm or less both. -2
00 impurity element content other than W of TiSi _x powder mesh were as follows. Na: 0.02ppm, K: 0.02ppm, U <0.1ppb, Th <0.1
ppb, Fe: 4ppm, Ni 2ppm, Cr: 0.5ppm, M
o: 450 ppm A sintered body was prepared from this TiSix powder by a hot press method, a target of φ300 mm × 6.35 mmt was prepared by machining, and sputtering was performed to measure particles on the wafer (6 inch diameter). There were a total of 13 particles with the above dimensions. The impurity content of the target was exactly the same as the value of the powder before hot pressing. No precipitate of W compound such as WSi ₂ was observed at all.

Comparative Example 1 A W ball was placed in a high-purity Ti ball mill pot, and the poly-Si mass was pulverized to obtain a -350 mesh Si powder. Similarly, a W ball is put into a high-purity Ti ball mill pot, and high-purity TiH ₂ is crushed.
A 350 mesh TiH ₂ powder was obtained. By mixing these two powders and heating in a vacuum, the dehydrogenation reaction and the silicide synthesis reaction are performed at once, and TiSi _x (x = 2.40)
Was obtained. This silicide lump was pulverized to a high purity with a W ball in a Ti ball mill to obtain a -200 mesh silicide powder. W content in raw material Si powder is 250p
pm, W content in TiSi _x after synthesis was 130 ppm. The content of impurity elements other than W in the silicide powder was as follows. Na: 0.02ppm, K: 0.02ppm, U <0.1ppb, Th <0.1
ppb, Fe: 4ppm, Ni: 2ppm, Cr: 0.5ppm, M
o: 3ppm A sintered body was manufactured from this TiSix powder by hot pressing, a target of φ300mm × 6.35mmt was manufactured by machining, and when sputtering was performed, a phenomenon in which particles increased periodically occurred. Particles having a size of 0.2 μm or more on a 6-inch diameter) averaged 180 particles. It was observed that a number of nodules were generated on the erosion surface of the target, and when the structure of the target was observed, precipitates of the WSi ₂ phase were observed as shown in FIG. 4, and particles were generated from the nodules caused by the WSi ₂ phase. It was speculated to have occurred.

[0022]

The W content of the present invention is 50 ppm or less,
A TiSi _x film with less generation of particles can be obtained by sputtering using a TiSi _x target containing no W compound precipitate.

Claims (3)

[Claims] In a titanium silicide target for forming a thin film, the target composition is TiSi _x (where x = 2.0
To 2.7), wherein the target has a W content of less than 50 ppm and does not contain a precipitate of a W compound. 2. The method according to claim 1, wherein the content of impurities in the target is Na ≦
0.1ppm, K ≦ 0.1ppm, U ≦ 1ppb, Th ≦ 1ppb, Fe ≦ 5p
2. The titanium silicide target according to claim 1, wherein pm, Cr ≦ 5 ppm, and Ni ≦ 5 ppm. 3. The Mo content in the target is 1 to 500 ppm.
The titanium silicide target according to claim 1, wherein: