JPH09104972A - Titanium target for sputtering and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a Ti target material capable of making sputtered particles uniform in directional property, facilitating the formation of a film along a narrow deep contact hole and capable of suppressing the occurrence of particles. SOLUTION: This Ti target has a Vickers hardness of 110-130, preferably 115-125 and a recrystallized structure. It is obtd. by cold-working Ti at a temp. below the recrystallization temp., carrying out heating for recrystallization and regulating the hardness so as to attain a Vickers hardness of 110-130.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium target for sputtering used when forming a film containing titanium by sputtering and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, due to higher integration, higher functionality, and higher reliability of LSI, the precision required for fine wiring technology has become more and more strict. Along with this, the contact hole for electrically connecting the fine wiring is narrowed, and the P-type or N-type doped layer formed thereunder is formed in a shallower and narrower region. When the above-mentioned LSI dope layer is shallow, if aluminum or the like used as wiring is directly formed on the silicon substrate, they cause an interdiffusion reaction, and aluminum or the like easily breaks through the dope layer and destroys the semiconductor junction structure. The problem occurs.
In order to prevent such mutual diffusion reaction, molybdenum-silicon, tungsten-
A diffusion preventing layer (also referred to as a barrier metal layer) made of a high melting point material such as silicon or tungsten-titanium is formed.

In recent years, a titanium nitride compound layer is said to be particularly excellent as a diffusion preventive layer as the diffusion preventive layer, and research for lowering the contact resistance between the titanium nitride compound layer and the silicon substrate is underway for practical use. By the way. For example, as one means of reducing the contact resistance between the silicon substrate and the titanium nitride compound layer, monthly Semiconducto
r World 1992.12, p196-p205 or monthly Semiconduct
or World 1989.12, p189-p192, it has been found effective to form a titanium silicide layer having a low contact resistance between the titanium nitride compound layer and the silicon substrate.

To form the titanium silicide layer, (1) a titanium target is sputtered to form a pure titanium thin film on a silicon substrate as shown in the above-mentioned document, and then heat treatment is performed in a nitrogen or ammonia gas atmosphere. By nitriding the surface layer of the pure titanium thin film to form a titanium nitride compound layer, and reacting the pure titanium thin film with the silicon substrate to form titanium silicide, or (2) sputtering a titanium target to obtain an ultrathin film. After forming a pure titanium thin film, it is heat-treated to form a titanium silicide film, and then a titanium target is deposited on the titanium silicide film by reactive sputtering in which nitrogen is introduced into a sputtering gas to form a titanium nitride thin film having a stoichiometric composition. Has been taken.

As described above, a titanium target is often used in the process of obtaining a film of titanium nitride, titanium silicide or the like used in a highly integrated LSI. The titanium target is used for forming a film of titanium nitride, titanium silicide, or the like used in a highly integrated LSI by sputtering.
Various improvements have been proposed for titanium targets. For example, as described in Japanese Examined Patent Publication No. 4-75301, the effect of a trace amount of radioactive element is eliminated by reducing the amount of oxygen, reducing the electric resistance of a thin film, and making it highly purified.

Further, as described in JP-A-5-214521, in order to improve the film formation rate of a titanium film,
It has been proposed to orient the preferred orientation of the titanium target to (0002). In addition, JP-A-6-10107
In Japanese Patent Laid-Open No. 6-280009 or JP-A-6-280009, in order to suppress the generation of particles from a target of titanium, in order to make the film thickness distribution of the titanium film formed by sputtering uniform, cold working and subsequent There is proposed a method for preventing the adhesion of foreign matter generally called a particle by controlling the heat treatment of (1) to obtain a fine recrystallized structure.

[0007]

[Problems for Solving the Problems] L which is a semiconductor integrated circuit
With the high integration of SI, the contact hole tends to be narrower and shallower, and the contact hole is formed by sputtering.
It is becoming difficult to form a film uniformly on the bottom of the wafer. That is, in sputtering, if the sputtered particles knocked out from the target surface by Ar ions or the like are particles that are perpendicularly incident on the substrate on which the film is to be formed, they can reach the bottom surface of the contact hole. Therefore there is no problem. However, in reality, there is a distribution in the direction of sputtered particles knocked out from the target by sputtering. This means that sputtered particles may obliquely enter the contact hole, and if there are many obliquely incident particles, the contact hole is not the bottom surface of the contact hole to be formed, but the contact hole. −
Since a large amount of film is formed on the side surface of the contact hole,
The opening of the hole becomes narrow, and it becomes difficult to form a film uniformly on the bottom surface of the contact hole.

[0008] In order to solve such a problem, conventionally, Electr
As described in onic Journal (October, 1994, p. 32), (1) a partition plate called a collimator is targeted so that only sputtered particles are incident perpendicularly to the substrate. There is a method to insert it between the substrate and the substrate. However, in this method, most of the sputtered particles adhere to this collimator, the film formation rate is significantly reduced, the productivity is reduced, and the titanium film adhered to the collimator is peeled off and adhered to the substrate, Cause electrical disconnection, short circuit,
This is not a preferable method because it may reduce the production yield. (2) There is also a method in which the distance between the target and the substrate is widened so that only the sputtered particles that reach the substrate are as perpendicular to the substrate as possible, but this method also forms a film. There is a problem that the speed (film forming rate) is remarkably reduced, productivity is reduced, and the vacuum layer (chamber) for sputtering is enlarged, and the apparatus itself is large and expensive.

Further, as described above, the contact hole tends to be narrow and shallow, and the generation of foreign matter, that is, the generation of particles is a serious defect of the contact hole. In order to reduce the generation of particles, a structure having fine recrystallized grains may be used, as described in the above-mentioned Japanese Patent Laid-Open No.
As described in JP-A-10107 or JP-A-6-280009, it is still not sufficient to form a fine recrystallized structure, and further reduction of particles is required. An object of the present invention is to provide a titanium target material and a manufacturing method thereof, which can align the directions of sputtered particles, can easily form a film in a narrow and deep contact hole, and can also reduce the generation of particles. is there.

[0010]

The inventors of the present invention have made earnest studies on the relationship between the material properties of the titanium target, the directionality of sputtered particles, and the generation of particles. When the hardness of the titanium target is set within a certain range, the results are remarkable. It has been found that it is effective in increasing the straightness of sputtered particles and suppressing the generation of particles. That is, the present invention is a titanium target for sputtering, which has a Vickers hardness in the range of 110 ≦ HV ≦ 130 and has a recrystallized structure. Preferably 115 ≦ HV ≦ 125
The hardness range can further enhance the straightness of the sputtered particles.

The titanium target of the present invention described above is subjected to a heat treatment for recrystallization after being subjected to cold working at a temperature not higher than the recrystallization temperature, and the Vickers hardness is adjusted within the range of 110 ≦ HV ≦ 130. Can be obtained by Further, in order to further suppress the generation of particles, the average crystal grain size is set to 20 μm or less.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, one of the features of the present invention is that the Vickers hardness of a titanium target is 110 ≦ H.
It lies within the predetermined range of V ≦ 130. And another feature is that it has a recrystallized structure. The reason why it is possible to increase the straightness of sputtered particles and reduce the generation of particles by setting a specific hardness in this way is not clear, but it is considered as follows.

When the titanium material obtained by cold working is heat-treated, a fibrous structure having anisotropy in the working direction causes
A recrystallized structure without crystallographically uniform crystal grains is produced. When the heating is continued, the strain is further released and the titanium becomes low in hardness. Here, if the heat treatment is finished in a state where the hardness is not largely reduced after the recrystallized structure, there is no structural anisotropy, but the strain applied by the cold working remains. When such a titanium material is used as a target, there is no structural anisotropy and the generation of particles can be suppressed. Further, it is considered that the strain was released at the same time during the sputtering, and this effect increased the straightness of the sputtered particles. That is, it was concluded that if the strain released during recrystallization is not completely released but is left to some extent and kept in a high hardness state, the straightness of sputtered particles is enhanced.

In order to specifically obtain the above-mentioned target of the present invention, the cold working rate is increased, the working temperature is lowered to give more strain, and the heat treatment temperature for recrystallization is set to a low temperature. As a result, a target having a recrystallized structure and high hardness can be obtained. For the titanium target of the present invention, if the Vickers hardness is less than 110, the straightness of sputtered particles is not significantly improved, so that the Vickers hardness is preferably 110 or more. on the other hand,
When the Vickers hardness of the titanium target exceeds 130, the strain in the material is too large and particles are frequently generated, which is not preferable.

Furthermore, the present inventors can further suppress the generation of particles by making the crystal grain size of the target material finer in addition to the above-mentioned hardness regulation. In particular,
The average crystal grain size is preferably 20 μm or less, and particularly when it is 10 μm or less, the straightness of sputtered particles is remarkably enhanced and the generation of particles is significantly reduced.

[0016]

Example After hot forging a 5N (99.999% purity) grade titanium ingot, rolling and heat treatment were carried out under various conditions shown in Table 1 to produce several kinds of titanium targets. Table 1 shows the Vickers hardness and average crystal grain size of the obtained target, the number of particles when a film was formed using each target, and the bottom coverage ratio.
The number of particles is 0.3μ in a 6 inch wafer.
It is expressed by the number of m or more, and the bottom coverage rate is the hole diameter.
It was calculated from the top film thickness and the bottom film thickness when a film was formed in a contact hole with an aspect ratio of 1.5 at 0.5 μm.
A high value of the bottom coverage rate indicates that more sputtered particles have reached the bottom of the contact hole, and is an index indicating that the sputtered particles have high straightness. In addition, the above-mentioned film formation is performed at an ultimate vacuum of 5 × 10−5 Pa, an argon pressure of 0.3 Pa,
Power supply (per target unit surface) 15W / c
m ² and the substrate temperature were 200 ° C. FIG. 1 is a view showing a typical microstructure photograph of the target of the present invention.

[0017]

[Table 1]

As shown in Table 1, the Vickers hardness is 11
The titanium target for sputtering of the present invention having a recrystallized structure in the range of 0 ≦ HV ≦ 130 has a low hardness. It can be seen that there is a significant increase in the bottom coverage as compared with the targets of Nos. 2 to 4, and the straightness of the sputtered particles in sputtering can be greatly improved. In addition, the sample No. of the comparative example. No. 2 is the sample No. 2 of the present invention. Although it had almost the same crystal grains as No. 6, the hardness was low and the bottom coverage was low. This is sample No. 2 is the sample No. 2 of the present invention. Compared with No. 6, the rolling ratio is low and the temperature for recrystallization is high, so the strain applied by cold rolling is almost released, and it is considered that the bottom coverage could not be improved.

Further, the sample No. of the comparative example. No. 10 is the sample No. of the present invention. Increase the recrystallization heating temperature further than 9
Although the temperature was set to 50 ° C., the average crystal grain size increased, the hardness decreased, the number of particles increased, and the bottom coverage was also unfavorable. Moreover, the recrystallization heating temperature was set to a low temperature of 300 ° C. in Comparative Example No. No. 11 is not preferable because recrystallization is not completed, particles are remarkably generated, and bottom coverage is remarkably reduced.

[0020]

According to the target of the present invention, in forming a titanium film by sputtering, it is easy to form a film in a narrow and deep contact hole, and good bottom coverage can be obtained. Furthermore, the generation of particles during sputtering can be reduced.
Therefore, it is possible to provide an effective target for obtaining a thin film forming a part of a semiconductor component having an extremely precise structure in recent years.

[Brief description of the drawings]

FIG. 1 is a photograph showing an example of a metal microstructure of a target of the present invention.

Claims (3)

[Claims] 1. A Vickers hardness of 110 ≦ HV ≦ 130.
And a recrystallized structure in the range of 1), and a titanium target for sputtering. 2. The titanium target for sputtering according to claim 1, wherein the average crystal grain size is 20 μm or less. 3. After cold working below the recrystallization temperature,
The Vickers hardness is 110 ≦ when heat treatment for recrystallization is performed.
A method of manufacturing a titanium target for sputtering, characterized in that the hardness is adjusted so that HV ≦ 130.