JPH1012573A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] To stably manufacture a high-performance semiconductor device. SOLUTION: When forming Ti silicide by a salicide process, as a Ti film before silicidation, high purity low oxygen Ti having a Ti purity of not less than 99.999% and an oxygen content of not more than 200 ppm is used. Form a film.
Ti of C ₅₄ structure the Ti film by two-step annealing
Silicide. In the annealing of the second step,
A small specific resistance can be obtained with a wide annealing temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which Ti silicide is formed by a salicide process.

[0002]

2. Description of the Related Art Along with miniaturization of LSIs, a problem has arisen that not only the wiring resistance of a gate electrode but also the resistance of a diffusion layer is increased. In particular, current CMOS devices have 0.35μ
The m-rule is in the mass production stage, and the parasitic resistance which does not follow the scaling law becomes large in 0.35 μm and smaller devices, and the performance cannot be improved as in the conventional trend. Therefore, salicide (SALICID), which forms silicide on the gate electrode and the source / drain diffusion layers at the same time,
E: Self Aligned Silicide) process has become essential to reduce resistance.

[0003] As materials for refractory metal silicides in the salicide process, Ti, Co, Pt,
Each silicide of Ni has been studied, but Ti silicide is considered the most promising because of its low specific resistance and excellent compatibility with the conventional process. FIG. 1 shows a general Ti silicide forming step by a salicide process.

In general formation of Ti silicide by a salicide process, a MOS transistor 1 is first formed, and then a polysilicon 2 serving as a gate electrode is formed by hydrofluoric acid treatment.
Then, the oxide film on the diffusion layer 3 is removed to expose a clean silicon surface [FIG. 1 (a)]. Subsequently, a Ti thin film 6 is formed on the entire surface by a sputtering method (FIG. 1B). Then, the lamp is annealed in a nitrogen atmosphere to 600 to
First annealing at 50 ° C. is performed. By this annealing, S
The polysilicon 2 and the diffusion layer 3 which are i-exposed portions cause a silicidation reaction with the Ti thin film 6, and a C ₄₉
A Ti silicide 7 having a structure is formed (FIG. 1C).

After the first annealing, unreacted Ti remaining on the oxide film such as the sidewalls 4 and the element isolation film 5 is formed.
The thin film and the TiN thin film are selectively removed by etching [FIG. 1 (d)]. Then, by lamp annealing again, 8
A second annealing at about 00 ° C. is performed. Thus, Ti silicide 7 C ₄₉ structure is phase transition Ti silicide 8 of low resistance C ₅₄ structure.

In the formation of Ti silicide by the salicide process, two-step annealing in which the annealing is divided into two stages is essential. This is for the following reasons.

The Ti silicide having a C ₄₉ structure is 500 to 70
It is formed at a temperature of 0 ° C. and has a specific resistance of 70 to 100.
It is about μΩ · cm. On the other hand, Ti silicide C ₅₄ structure is formed by a temperature of above 700 ° C., its specific resistance is about 15~20μΩ · cm. As the Ti silicide on the gate electrode and the diffusion layer is required having a low resistance C ₅₄ structure, when directly forming the Ti silicide on the gate electrode and the diffusion layer, on the sidewalls and the isolation layer also formed of Ti silicide C ₅₄ structure over, due to a short circuit of transistor comrades shorting or adjacent the gate electrode and the diffusion layer which occurs. Therefore, 6
After the formation of the Ti silicide C ₄₉ structure by a first annealing of 00 to 650 ° C., to remove the Ti film and TiN film of unreacted on the sidewall and the device isolation film, then,
Procedure of causing the remaining Ti silicide by second annealing at about 800 ° C. phase transition to Ti silicide C ₅₄ structure is stepped.

[0008]

In the manufacture of a semiconductor device using the formation of Ti silicide by such a salicide process, a phenomenon called the "fine line effect" in which the wiring width of the gate electrode is 1 μm or less and the specific resistance of the wiring increases. Is a problem. This can be explained by two mechanisms of poor phase transition and aggregation of Ti silicide in the second annealing. Poor phase transition and aggregation that cause the "fine line effect" are as follows.

In the formation of Ti silicide by the salicide process, as described above, C ₄₉ is formed by the second annealing.
The structure is changed to a _C54 structure, but when the wiring width of the gate electrode is reduced, the phase change is less likely to occur, and as a result, the specific resistance increases. This is the “fine line effect” due to poor phase transition.

[0010] On the other hand, the aggregation is performed by the second annealing in the Ti silicide forming step or the heat treatment in the subsequent steps.
For example, this is a phenomenon in which a Ti silicide thin film is cut in an island shape in a reflow process of an interlayer insulating film or the like, and occurs due to insufficient heat resistance. This phenomenon also becomes apparent as the wiring width of the gate electrode decreases, resulting in a serious increase in specific resistance.

FIG. 2 is a table schematically showing the relationship between the second annealing temperature and the specific resistance of Ti silicide. By performing the second annealing, the specific resistance of Ti silicide becomes
Although the temperature is basically lowered as compared with the state after the completion of the first annealing, the specific resistance is not sufficiently lowered when the temperature of the second annealing is low. This is mainly due to poor phase transition. When the temperature of the second annealing is increased, the phase transition proceeds with this, and the specific resistance is reduced. On the other hand, the occurrence of aggregation causes the specific resistance to increase again. Therefore, the specific resistance becomes minimum in a specific temperature range. Here, the width of the annealing temperature range in which the specific resistance is minimized is called a window.

By the way, Ti by the salicide process
There have been various reports on the cause of the "fine line effect" which is a problem in silicide formation, and one of the causes is considered to be the influence of oxygen. This oxygen is knocked on when implanting ions through the oxide film and is implanted into silicon, a natural oxide film existing on the silicon surface before Ti film formation is taken into the interface, or polysilicon is formed by CVD film formation. At the time, oxygen is mixed in, causing poor phase transition or aggregation.

In order to eliminate the influence of oxygen as much as possible,
For example, ion implantation is performed through a nitride film, or a Ti film is continuously formed in a vacuum after removing a natural oxide film by Ar sputtering or the like in a high vacuum before forming a Ti film. In order to reduce the amount of oxygen mixed in by performing a sufficient nitrogen purge, measures have been taken.

However, in spite of these measures for reducing oxygen, the fact is that the "fine line effect" is not sufficiently suppressed.

That is, in order to suppress the "thin wire effect", it is basically sufficient to lower the minimum value of the specific resistance obtained by the second annealing, but conventionally, as shown by a solid line in FIG. In addition, it was difficult to reduce the minimum value of the specific resistance to 20 μΩ · cm or less. For this minimum, see C ₅₄
The specific resistance of the structure Ti silicide is 15-20μΩcm
Because of the degree, the same level is ideal, but in reality, it is difficult to reach that point. Further, since the annealing temperature range (window) where the specific resistance is minimum is narrow like a pinpoint and the process margin of the annealing temperature is narrow, it is difficult to stably obtain a low resistance in an actual semiconductor manufacturing process.

[0016] If considering the actual semiconductor manufacturing process or the like, as shown by the broken line in FIG. 2, the specific resistance is sufficiently low to the same extent as C ₅₄ structure, and, annealing temperature at which the low resistance value is obtained Ideally, the process margin is large, but in spite of various measures to reduce oxygen, the ideal has not yet been realized.

An object of the present invention is to suppress a poor phase transition and agglomeration in the second annealing in the formation of Ti silicide by a salicide process, thereby securing a small specific resistance with a wide temperature range, and thereby providing a high-performance semiconductor. An object of the present invention is to provide a method of manufacturing a semiconductor device which enables stable manufacture of a device.

[0018]

In the formation of Ti silicide by a salicide process, a Ti film before silicidation is generally formed by a sputtering method using a Ti target or a CVD method. Ti here
The specifications of the target are required to have a small amount of impurities, that is, high purity, and efforts have been made to reduce any impurities that adversely affect the semiconductor device.

More specifically, Fe, Ni, Cr, C, which increase the junction leakage current and serve as a lifetime killer,
heavy metals such as u, alkali metals such as Na and K which cause poor operation characteristics of MOS transistors, and emitting α-rays and DR.
Radioactive elements such as U and Th that cause soft errors such as AM have been reduced.

[0020] On the other hand, efforts have been made to reduce oxygen together with the above-mentioned metal impurities and the like, since Ti has a property of being easily oxidized and oxygen is easily mixed in during the manufacturing process.

As a harmful effect of oxygen impurities in the Ti target, for example, in Japanese Patent Application Laid-Open No. 4-116161,
Oxidation of the formed Ti thin film and deterioration of homogeneity are mentioned, and Japanese Patent Publication No. 4-75301 discloses an increase in electric resistance. In order to eliminate these adverse effects, Japanese Patent Laid-Open No. 4-116161 discloses that
A Ti target having an oxygen content of about 400 ppm is obtained by sintering the Ti powder produced by the rotating electrode method under pressure. In Japanese Patent Publication No. 4-75301, as a method for producing high-purity Ti for forming a thin film having an oxygen content of 250 ppm or less, crude Ti obtained by molten salt electrolysis is used.
Is used in an electron beam in a high vacuum.

As for Ti silicide, its T content is reduced by reducing the oxygen content in the Ti target.
The decrease in the electrical resistance of i-silicide is disclosed in
This is described in JP-A-358030. Here, a Ti silicide having a specific resistance of 15 μΩ · cm or less is obtained by using a Ti target having an oxygen content of 250 ppm or less.

The oxygen content in the Ti target is 2 to prevent oxidation of the Ti thin film, deterioration of homogeneity, and increase in electric resistance.
About 50 to 400 ppm was sufficient. However, regarding the "fine line effect" which is a problem in the formation of Ti silicide by the salicide process, as described above, the specific resistance after the second annealing is reduced to 20 μΩ · cm or less even in combination with various oxygen reduction measures. It is difficult. Further, no effective countermeasure for increasing the temperature width called a window (FIG. 2) in the second annealing has been proposed.

Under these circumstances, the present inventors have focused on the purity and oxygen content of the Ti film before silicidation formed by sputtering, and investigated their effects on the specific resistance in the second annealing. did. As a result, the purity is 9
9.999% (5N) or more and oxygen content is 200p
At pm or less, both phase transition failure and aggregation are effectively suppressed in the second annealing, the effective specific resistance is reduced, and the window is departed from the pinpoint state, and an effective temperature margin is secured. It turned out to be. In particular, when the Ti purity was 99.9999% (6N) and the oxygen content was 50 ppm or less, a ground-breaking finding that a specific resistance of 20 μΩ · cm or less was obtained with a wide window exceeding 100 ° C. .

The method of manufacturing a semiconductor device according to the present invention is based on such knowledge. When a semiconductor device is manufactured using Ti silicide by a salicide process, the Ti film before silicidation has a purity of 99%. .999%
This is a structural feature in that a high-purity low-oxygen Ti film having an oxygen content of 200 ppm or less is formed as described above.

[0026] In this specification, the purity of Ti means the purity excluding gas components such as oxygen and carbon components.

In the method of manufacturing a semiconductor device according to the present invention, as the Ti purity of the Ti film becomes higher and the oxygen content decreases, the specific resistance due to the second annealing tends to decrease and the window tends to expand. From this viewpoint, the Ti purity is preferably 99.9995% (5N5) or more, and more preferably 99.9999% (6N) or more. Oxygen content is less than 100 ppm, especially 50 ppm
The following is desirable, and more preferably, it is 30 ppm or less. In particular, when the Ti purity is 99.9999% (6N) or more,
When the oxygen content is 50ppm or less, 20μΩ · cm or less, which corresponds to the specific resistance of the C ₅₄ structure is obtained in a wide processing temperature range, the temperature range when the oxygen content is 30ppm exceeds 100 ° C..

The breakdown of the content of impurities other than oxygen is Fe,
Regarding heavy metals such as Ni, Cr and Cu, the total amount is 1 from the viewpoint of reduction of junction leak current, securing of life time, and the like.
0 ppm or less is desirable, and 1 ppm or less is particularly desirable. With respect to the alkali metals of Na and K, the total amount is 0.05 pp from the viewpoint of the operational stability of the MOS transistor and the like.
m or less, and particularly preferably 0.02 ppm or less.
Regarding the radioactive elements of Th and U, the total amount is preferably 2 ppb or less, particularly preferably 1 ppb or less from the viewpoint of preventing soft errors due to α-ray radiation.

The thickness of the Ti film is desirably large from the viewpoint of increasing the thickness of the Ti silicide to reduce its electrical resistance and increasing the physical strength of the Ti silicide to suppress aggregation in the second annealing. However, if the thickness is too large, a problem such as a junction leak due to intrusion of impurities into the diffusion layer becomes a problem.
0 to 50 nm is desirable, and 30 to 40 nm is particularly desirable.

As for the Ti target for forming the Ti film, a purified Ti material obtained by the iodine method which easily obtains low oxygen, in particular, by the iodide method via lower iodide which can easily obtain both high purity and low oxygen. Is preferred.

The iodide method via lower iodide is a method for purifying high-purity Ti which was previously developed by one of the present applicants (Japanese Patent No. 20221364). This refining method is a kind of iodine method (iodide pyrolysis method), but differs from the conventional general iodine method shown in chemical formula 2 in that titanium is purified by the reaction of chemical formula 1.

[0032]

## STR1 ## Iodide method via lower iodide Iodination reaction (synthesis reaction): Crude Ti + TiI ₄ → 2TiI ₂ Precipitation reaction (decomposition reaction): TiI ₂ → Ti + 2I

[0033]

## STR2 ## Conventional iodine method Iodination reaction (synthesis reaction): Crude Ti + 2I ₂ → TiI ₄ Precipitation reaction (decomposition reaction): TiI ₄ → Ti + 2I ₂

In the iodide method via lower iodide, titanium diiodide, which is a lower iodide, is thermally decomposed instead of directly thermally decomposing titanium tetraiodide, so that the thermal decomposition temperature can be reduced to that of conventional iodide. It is a major feature that the temperature can be lowered by about 200 ° C. compared with the method, whereby the amount of oxygen impurities can be significantly reduced in addition to the purification and removal of metal impurities.
A high purity and low oxygen Ti material having an oxygen content of 999% (6N) or more and an oxygen content of 50 ppm or less can be easily purified.

Incidentally, the Ti material obtained by the crawl method which is a typical production method of Ti usually has a purity of usually 9%.
It is 9.9% (3N) and the oxygen content is about 400 ppm. Further, even in the purification by the iodine method, the conventional general one has a higher thermal decomposition temperature of about 200 ° C. than that of the iodide method via lower iodide, and therefore has a large amount of impurities and a large variation. Therefore, Ti purity is usually 99.99%
(4N) and the oxygen content is about 100 ppm,
Even when the variation in the amount of impurities is considered, the Ti purity is 99.99.
It is still difficult at present to purify high-purity low-oxygen Ti such as 99% (6N) and an oxygen content of 30 ppm.

It is to be noted that the reduction of the oxygen content in the Ti target lowers the electric resistance of the Ti film and consequently lowers the electric resistance of the Ti silicide as described in JP-A-4-358030. However, there is no consideration about windows. Furthermore, Ti silicide here is a barrier metal or the like in a contact formed by one-time annealing.
It is not based on a salicide process using two-step annealing. Further, a Ti target used for forming a Ti film before silicidation is manufactured from a purified material by a conventional general iodine method.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIG.

In the method of manufacturing a semiconductor device according to the present invention, a step of forming Ti silicide by a salicide process is important. In this step, after a MOS transistor 1 is formed, polysilicon 2 serving as a gate electrode and a diffusion layer 3 are formed.
The upper oxide film is removed to expose a clean silicon surface [FIG. 1 (a)].

Subsequently, a Ti thin film 6 is formed on the entire surface by a sputtering method (FIG. 1B). In order to prevent oxygen or the like from entering the Ti thin film 6, sputtering must be performed under a high vacuum, and the degree of vacuum is 1 × 10 ⁻⁷ Torr.
The following is desirable. Further, as the sputtering target, it is desirable to use a high-purity low-oxygen Ti target manufactured from a purified Ti material by an iodide method via a lower iodide.

After the sputtering, a first annealing at 600 to 650 ° C. is performed by lamp annealing in a nitrogen atmosphere. This annealing, polysilicon 2 and the diffusion layer 3 undergoes a Ti film 6 and silicidation reaction is Si exposed portion, Ti silicide 7 C ₄₉ structure is formed on these [FIG. 1 (c)] .

After the first annealing is completed, unreacted Ti remaining on the oxide film such as the sidewall 4 and the element isolation film 5 is formed.
The thin film and the TiN thin film are selectively removed by etching [FIG. 1 (d)]. Then, by lamp annealing again, 8
A second annealing at about 00 ° C. is performed. Thus, Ti silicide 7 C ₄₉ structure is phase transition Ti silicide 8 of low resistance C ₅₄ structure.

[0042]

Next, the effects of the present invention will be clarified by showing examples of the present invention and comparing them with comparative examples.

Purified Ti material by the iodide method via lower iodide (Ti purity: 99.95%, oxygen content: 400 pp
Using m), a Ti target having a Ti purity of 99.9999% (6N) and an oxygen content of 30 ppm was produced by a process of EB melting, rolling and heat treatment. Table 1 shows the amount of impurities in the manufactured Ti target as Example 1 in Table 1.

[0044]

[Table 1]

In Example 2 in Table 1, the Ti purity was 99.99.
It is a high-purity low-oxygen Ti target with 9% (5N) and an oxygen content of 100 ppm. This is because the high-purity low-oxygen Ti purified by the iodide method via the lower iodide is used.
It is manufactured by blending a material and a commercially available high-purity Ti material manufactured by the Kroll method at an appropriate weight ratio and dissolving the EB.

The comparative example is a Ti target manufactured by a method similar to the above from a commercially available high-purity Ti material manufactured by the Kroll method, and has a Ti purity of 99.995%.
(4N5), the oxygen content is 250 ppm.

Using the three types of manufactured Ti targets, a Ti silicide formation experiment assuming a salicide process was performed by the following method.

On the silicon substrate from which the surface native oxide film has been removed, a Ti thin film is formed by a sputtering method using the Ti targets of Examples 1, 2 and Comparative Example. The method of removing the oxide film and the method of forming the film at this time are not particularly limited. For example, in this embodiment, the natural oxide film is removed using 1% hydrogen fluoride water, and the ultimate vacuum degree is continuously 5 × 10 ^{−. A} film thickness of 30 nm was obtained under the conditions of ⁸ Torr, processing pressure of ⁸ mTorr, substrate temperature of 30 ° C., and DC power of 2 kW.

Next, by performing a first annealing to form a Ti silicide having a C ₄₉ structure on the silicon substrate. Although the processing at this time is not particularly limited, for example, in this embodiment, the ultimate vacuum degree is 10 mTorr or less, the nitrogen flow rate is 3000 cc / min, the processing pressure is atmospheric pressure, the temperature raising rate is 100 ° C./sec, and the processing temperature is 625. Lamp annealing was performed at 30 ° C. for a processing time of 30 sec.

Subsequently, the unreacted Ti thin film or TiN thin film other than the Ti silicide is selectively removed using, for example, a solution obtained by mixing ammonia water and hydrogen peroxide at a ratio of 1: 2.

Finally, a second annealing is performed to cause a phase transition of the Ti silicide to form a titanium silicide having a low resistance C ₅₄ structure. The heat treatment at this time is not particularly limited. For example, in this embodiment, the ultimate vacuum degree is 10 mTorr.
Hereinafter, nitrogen flow rate: 3000 cc / min, processing pressure: atmospheric pressure, heating rate: 100 ° C./sec, processing time: 30
In seconds, lamp annealing was performed. The processing temperature is set at 70 to determine the phase transition temperature and aggregation.
Various selections were made within the range of 0 to 1100 ° C.

The sheet resistance and the film thickness of the Ti silicide obtained as described above were measured, and the specific resistance was calculated from the product of the resistance and the film thickness. The crystal structure was examined by X-ray diffraction. Table 2 shows the minimum value of the specific resistance and the film thickness together with the result of measuring the oxygen content of the Ti film before silicidation.
The thickness of the Ti film is 30 nm as described above. FIG. 3 shows the relationship between the specific resistance and the second annealing temperature.
FIG. 4 shows the relationship between the phase transition ratio and the second annealing temperature investigated from the crystal structure.

[0053]

[Table 2]

In the comparative example, the Ti purity was 99.995% (4N
5) is a case where a Ti target having an oxygen content of 250 ppm is used, and the Ti target formed by the target is used.
The oxygen content of the membrane is 260 ppm.

According to FIG. 3, the specific resistance is reduced by the second annealing, and the specific resistance is reduced as the annealing temperature is increased. However, the minimum value of the specific resistance does not become less than 20 μΩ · cm, but becomes 30 μΩ. · More than about 32 µΩ · cm. The annealing temperature range in which a specific resistance close to 30 μΩ · cm is obtained is a pinpoint region near 880 ° C., and the specific resistance rapidly increases before and after that.

On the other hand, according to FIG. 4, also in the case of the comparative example, the phase transition is completed at 880 ° C. That is, all of the Ti silicide has a C ₅₄ structure at 880 ° C. or higher. Nevertheless, the reason why a specific resistance of 20 μΩ · cm or less cannot be obtained is considered not only because there are many impurities but also because aggregation has already started in this temperature range. There is also a report that the occurrence of aggregation starts at 800 ° C.

In Example 2, the Ti purity was 99.999% (5%).
N) in which a Ti target having an oxygen content of 100 ppm was used, and the Ti target formed by the target was used.
The oxygen content of the membrane is 90 ppm.

As can be seen from FIG. 3, the minimum value of the specific resistance is about 22 μΩ · cm, which is 30 μΩ · cm or less. Moreover, the annealing temperature range at which a specific resistance of 30 μΩ · cm or less is obtained is about 100 ° C. from about 830 ° C. to about 930 ° C.
° C, and a break from the pinpoint state, which is a problem in the comparative example, is achieved. This can be seen from FIG.
It is judged that the phase transition was promoted by the reduction of the oxygen content under high purity, the temperature of the phase transition was lowered, and the occurrence of aggregation was suppressed. However, even in this example, despite the completion of the phase transition, a specific resistance of 20 μΩ · cm or less cannot be obtained. This is probably due to the direct influence of impurities and the influence of aggregation.

In Example 1, the Ti purity was 99.9999%.
(6N) using a Ti target having an oxygen content of 30 ppm, and a T target formed by the target.
The oxygen content of the i-film is 30 ppm.

As can be seen from FIG. 3, the minimum value of the specific resistance is about 19 μΩ · cm, which is 20 μΩ · cm or less. In addition, a process margin with a wide annealing temperature is secured at 20 μΩ · cm or less. The temperature range is 820
From about 110 ° C to about 930 ° C,
When viewed at μΩ · cm or less, the temperature reaches 800 ° C. to nearly 1000 ° C. The superiority of Example 1 is obvious even in comparison with Example 2 as well as Comparative Example. This is because the temperature of the phase transition was further reduced by further promoting the phase transition (FIG. 4).
And that the aggregation was effectively suppressed in a wide temperature range.

Incidentally, regarding the promotion of the phase transition, the completion temperature was 820 ° C. in Example 1, and 840 ° C. in Example 2.
FIG. 4 shows that the temperature was 880 ° C. in the comparative example. Regarding the suppression of aggregation, the second annealing temperature when the specific resistance becomes 40 μΩ · cm due to the increase in specific resistance due to the aggregation is about 990 ° C. in Example 1, and about 9 ° C. in Example 2.
FIG. 3 shows that the temperature was 60 ° C., and about 940 ° C. in the comparative example.

When sputtering is performed under high vacuum as in this embodiment, the amount of impurities in the sputtering target and the amount of impurities in the Ti film formed by the sputtering basically match. The present inventors believe that the slight inconsistency in the amount of oxygen is due to a measurement error, contamination of oxygen during the measurement, and the like.

The thickness of the Ti silicide is reduced in the order of Example 1, Example 2, and Comparative Example (Table 2). T
The present inventors consider the following as a reason why such a phenomenon has occurred even though the thickness of the i-film is the same.

In the silicidation in a nitrogen atmosphere as in the embodiment, the Ti film on Si is silicided from the Si side, and is nitrided from the surface side. After the treatment, the nitride layer is removed together with the unreacted layer (Ti layer) thereunder. The small thickness of the Ti silicide means that the thickness of the removal layer is large. The reason why the film thickness of Ti silicide increases in the order of Comparative Example, Example 2, and Example 1 is that the silicidation reaction was promoted more than the nitridation reaction of the surface as the oxygen content decreased. Conceivable. And it goes without saying that a large film thickness is basically advantageous for suppressing aggregation in the second annealing.

The present inventors have found that the Ti purity is 99.99.
The same investigation was performed on a Ti target having 9% (5N) and an oxygen content of 200 ppm, and it was confirmed that a result similar to that of Example 2 was obtained.

[0066]

As is apparent from the above description, the method of manufacturing a semiconductor device of the present invention suppresses phase transition defects and agglomeration in the second annealing in the formation of Ti silicide by the salicide process. The resistance can be effectively reduced, and the annealing temperature range at which the low resistance can be obtained can be significantly increased. Therefore, the "fine line effect", which is a problem in the salicide process, can be stably suppressed, and contributes to the stable production of high-performance semiconductor devices.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a process of forming Ti silicide by a salicide process.

FIG. 2 is a table schematically showing a relationship between a specific resistance and an annealing temperature in a second annealing.

FIG. 3 is a table showing a result of investigation on a relationship between a specific resistance and an annealing temperature in a second annealing.

FIG. 4 is a table showing a result of investigation on a relationship between a phase transition ratio and an annealing temperature in a second annealing.

[Explanation of symbols]

1 Ti silicide Ti silicide 8 C ₅₄ structure of the MOS transistor 2 serving as a gate electrode polysilicon third diffusion layer 4 side wall 5 isolation layer 6 Ti film 7 C ₄₉ structure

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Setsuo Okamoto 1 Higashihama-cho, Amagasaki City, Hyogo Prefecture Inside Sumitomo Cities Co., Ltd. (72) Inventor Katsuichi Fukui 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Sumitomo Metal Industries Inside (72) Inventor Muneo Harada 4-33, Kitahama, Chuo-ku, Osaka-shi, Osaka Inside Sumitomo Metal Industries, Ltd. (72) Takahiko Oma 4-5-33, Kitahama, Chuo-ku, Osaka, Osaka Within Sumitomo Metal Industries Co., Ltd.

Claims (2)

[Claims] When manufacturing a semiconductor device using the formation of Ti silicide by a salicide process, a Ti film before silicidation has a Ti purity of not less than 99.999% and an oxygen content of not more than 200 ppm. A method for manufacturing a semiconductor device, comprising forming a film of high-purity low-oxygen Ti. 2. A sputtering target for forming the Ti film, which has a purity of 99.999 produced from a purified Ti material by an iodide method via a lower iodide.
2. The method for manufacturing a semiconductor device according to claim 1, wherein a high-purity low-oxygen Ti target having an oxygen content of 9% or more and an oxygen content of 50 ppm or less is used.