JP3189788B2 - Method of forming copper wiring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a copper wiring formed on a semiconductor substrate, and more particularly to a method for forming a highly reliable copper wiring by a damascene process.

[0002]

2. Description of the Related Art Aluminum (Al) has conventionally been generally used as a material used for wiring of a semiconductor device. In recent years, a technique using copper (Cu) as a wiring material has attracted attention. This is because the resistivity of copper (Cu) is 1.
This is because it is 55 Ω · m, which is much smaller than 2.50 Ω · m, which is the resistivity of aluminum (Al).

[0003] However, copper (Cu) is converted to aluminum (A).
Since the etching process is difficult unlike 1), it is difficult to adopt a method of forming a film on the entire main surface of the semiconductor substrate and then patterning it into a wiring shape like aluminum (Al). For this reason, when copper (Cu) is used as a wiring material, it is necessary to adopt a damascene process in which a groove is formed in advance at a position where a wiring is to be formed and copper (Cu) serving as a wiring is embedded in the groove. Becomes

A conventional method of forming a copper (Cu) wiring by the damascene process will be described with reference to FIG. 5. First, a TiN film 34 is formed by sputtering on an insulating film 32 in which a groove is formed (FIG. 5). (A)). This is copper (C
u) easily diffuses into the insulating film, so that the insulating film and copper (C
This is because it is necessary to interpose a barrier layer for preventing diffusion between the substrate and u). The diffusion of copper (Cu) into the insulating film causes an increase in leakage current, a variation in threshold voltage, and an increase in the dielectric constant of the insulating film. Therefore, the TiN film 34 as a barrier layer is important.

Next, a Cu film 36 is formed on the TiN film 34
A copper (Cu) wiring is formed by forming the substrate by a VD method (FIG. 5B) and finally polishing the surface by a CMP method to remove an unnecessary Cu film 36 (not shown).

In this method, the Cu film 36 is replaced with the TiN film 34.
Since it is formed directly on the upper surface, the formed Cu film 36
Instead of a (111) alignment film having high electromigration resistance, a (200) alignment film having low electromigration resistance is obtained. That is, electromigration is likely to occur in the copper (Cu) wiring formed by the method shown in FIG. 5, and the reliability is reduced. The reason why the (200) orientation film has lower electromigration resistance than the (111) orientation film has not been elucidated at present. The Cu film 36 formed by the CVD method is a TiN film 3 formed by the sputtering method.
Poor adhesion with 4. For this reason, there is a possibility that the Cu film 36 may fall off from the groove in the surface polishing step by the above-described CMP method, which causes a problem that the production yield is reduced.

In order to solve such a problem, a method shown in FIG. 6 has been proposed as a method of manufacturing a copper wiring in which the problem is improved. In this method, a TiN film 40 is formed on an insulating film 38 by a sputtering method in a sputtering chamber, and a Cu film 42 is formed on the TiN film 40 by a sputtering method (FIG. 6A). To the Cu film 42 in the CVD chamber.
A Cu film 44 is formed by the method (FIG. 6).
(B)).

In this method, since the Cu film 42 formed by the sputtering method is interposed between the TiN film 40 and the Cu film 44 formed by the CVD method, the Cu film 44 has a relatively (111) orientation. The film becomes high, and the electromigration resistance is improved as compared with the method shown in FIG.
Furthermore, a Cu film 44 formed by a CVD method having poor adhesion to each other.
Since the Cu film 42 formed by the sputtering method is interposed between the TiN film 40 formed by the sputtering method and the TiN film 40 formed by the sputtering method, the adhesion of the Cu film 44 is greatly improved. It does not fall out of the groove.

[0009]

As described above, the Cu film 44 formed by the method shown in FIG. 6 is compared with the Cu film 36 formed by the method shown in FIG.
1) Although excellent in orientation and adhesion, as a result of a study by the present inventors, the variation in sheet resistance of the Cu film 44 is as large as about 5%, and the (111) orientation of the Cu film 44 is insufficient. It turned out to be.

Accordingly, an object of the present invention is to reduce the variation in sheet resistance of a Cu film and further improve the (111) orientation of the film, thereby providing a highly reliable copper (C) film.
u) To provide a method for forming wiring.

[0011]

The inventors of the present invention have conducted research to elucidate the cause of the sheet resistance variation and the insufficient (111) orientation of the film. It was clarified that this was due to the effect of the oxide slightly formed on the surface.

After the formation of the Cu film by the sputtering method, when the semiconductor substrate (wafer) is moved from the sputtering chamber to the CVD chamber in order to form the Cu film by the CVD method, the Cu film in the air It is considered to have been formed by exposure to Due to the presence of this oxide, the sheet resistance fluctuates or the (11
1) The reason why the orientation is impaired is as follows.

That is, in the process of forming a Cu film by the CVD method, there are a process of generating a Cu nucleus to be a growth nucleus and a process of growing this nucleus. It is a cause of inhibition. In other words, since this oxide is chemically stable, nuclei are unlikely to be generated thereon, while the formation positions of the oxide are random, so that the generation density of Cu nuclei also varies randomly, and thus randomly varies. The resulting nuclei begin to grow, thereby impairing the uniformity of the resulting Cu film. Further, the Cu film that has started to grow also grows non-uniformly so as to avoid chemically stable oxides. These result in variations in sheet resistance. In addition, as a result of the loss of uniformity of the film, uniform growth of the film is hindered, which causes the (111) orientation to deteriorate.

Further, the delay in the generation of the nuclei increases the incubation time, which is the time required to reach the growth process, which further promotes the nonuniformity of the Cu film.

[0015]

That is, a first step of forming a barrier layer covering an insulating film formed on a semiconductor substrate, and after the first step, a first Cu film is formed on the barrier layer by sputtering. A second step and the first step by the second step.
A third step of annealing the semiconductor substrate on which the Cu film is formed, and after the third step, a CV is formed on the first Cu film.
A fourth step of forming a second Cu film by a method D, wherein the annealing in the third step is performed at a temperature of 300 ° C. or more under a vacuum of 10 ⁻⁶ Torr or less for at least 3 minutes to form a copper wiring It is characterized by having a process.

In the method for forming a copper wiring according to the present invention, a step of forming a first Cu film by a sputtering method in a sputtering chamber on an insulating film formed on a semiconductor substrate; Moving the semiconductor substrate on which is formed to an annealing chamber, annealing the semiconductor substrate under vacuum in the annealing chamber, and exposing the semiconductor substrate annealed in the annealing chamber to the atmosphere. The method is characterized by including a step of moving to a CVD chamber and a step of forming a second Cu film on the first Cu film in the CVD chamber by a CVD method.

In the method of forming a copper wiring according to the present invention, a step of forming a first Cu film by a sputtering method in a sputtering chamber on an insulating film formed on a semiconductor substrate; CVD on semiconductor substrate with
Moving the semiconductor substrate under vacuum in the CVD chamber;
Forming a second Cu film on the first Cu film by a CVD method in the CVD chamber after annealing in the VD chamber.

The spa is formed on the insulating film formed on the semiconductor substrate.
First Cu film is formed in sputtering chamber by sputtering method
And a semiconductor substrate on which the first Cu film is formed
To the CVD chamber without exposing it to the atmosphere
And the semiconductor under vacuum in the CVD chamber.
Annealing the substrate; and annealing in the CVD chamber.
After the neal, the previous process is performed by the CVD method in the CVD chamber.
Forming a second Cu film on the first Cu film.
Copper wiring formation method.

[0020]

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming a copper wiring according to an embodiment of the present invention will be described with reference to FIG.

First, in an oxide film (SiO 2 film) 10 formed on a semiconductor substrate (not shown), a groove 1 is formed by dry etching in a region where a copper (Cu) wiring is to be formed.
2 is formed (FIG. 1A).

The oxide film 10 having the groove 12 thus formed
100n of TiN film 14 by sputtering
m (FIG. 1B). As described above, this is to prevent copper (Cu) formed thereafter from diffusing into the oxide film 10 to increase the leakage current, vary the threshold voltage, and increase the dielectric constant of the insulating film. It is a necessary barrier layer.

This step of forming the TiN film 14 by the sputtering method is performed in the sputtering chamber 22 shown in FIG.

Next, in the sputtering chamber 22, T
A Cu film 16 formed by sputtering on the iN film 14 is 100 n
m (FIG. 1C). As described above, this is used as an adhesion layer between the subsequently formed Cu film formed by the CVD method and the TiN film 14, and as a film for forming the subsequently formed Cu film formed by the CVD method into a (111) oriented film. is necessary.

Next, the semiconductor substrate on which the Cu film 16 has been formed by the sputtering method is transferred to the annealing chamber 24 by the moving device 28 shown in FIG. The anneal chamber 24 is a part of the apparatus 50 integrated with the CVD chamber 26 as shown in FIG. 2, in which the semiconductor substrate is removed without breaking the vacuum and at least exposing it to the atmosphere. Annealing chamber 24 to CVD chamber 2
6 can be moved.

Next, the semiconductor substrate introduced into the annealing chamber 24 is placed under a vacuum of 10 ⁻⁶ Torr or less under a vacuum of 400 Torr.
Anneal at 10 ° C. for 10 minutes. By such an annealing process, when the semiconductor substrate is moved from the sputtering chamber 22 to the annealing chamber 24 by the moving device 28, Cu
The oxide 18 formed on the surface of the film 16 is eliminated (FIG. 1).
(D)). Furthermore, the annealing process improves the (111) orientation of the Cu film 16 by the sputtering method and also increases the grain size.

After that, 170 in the annealing chamber 24.
Cool to ° C. Nitrogen or the like may be introduced into the annealing chamber 24 to increase the cooling rate. At this time, it is important that oxygen is not mixed in the cooling gas such as nitrogen. Further, the cooling rate may be increased by transferring the wafer to a block or wafer holder cooled to about 100 ° C. By promoting the cooling in this way, it is possible to minimize a decrease in throughput caused by performing the annealing process.

Although the annealing temperature in the annealing process is not limited to the above-mentioned 400 ° C., in order to sufficiently desorb the oxide 18 formed on the surface of the Cu film 16, the annealing temperature is set to 3 ° C.
It is necessary to anneal at a temperature of 00 ° C. or higher. Also, the annealing time is not limited to the above 10 minutes, but the oxide 18
For sufficient desorption, annealing for at least 3 minutes or more is required. The above-described annealing at 400 ° C. for 10 minutes is an example of the most preferable annealing temperature and annealing time in the present embodiment in consideration of the detachment effect of the oxide 18 and the throughput.

Then, the semiconductor substrate is transferred from the annealing chamber 24 to the CVD chamber 26 in the apparatus 50, and at a substrate temperature of 170 ° C. and a pressure of 20 Torr, hexafluoroacetylacetonato copper trimethylvinylsilane (Cu (hfsc) (tmvs 1), a Cu film 20 is formed by the CVD method (FIG. 1E). The thickness of the Cu film 20 needs to be at least such that the groove 12 is completely filled.

Thereafter, the surface is polished by the CMP method and the unnecessary Cu film 20, Cu film 16 and Ti
The copper (C) is removed by removing the N film 14 (not shown).
u) Wiring is formed.

As described above, according to the present embodiment, the copper (C
u) According to the wiring formation method, the oxide 18 formed on the Cu film 16 was desorbed in the annealing chamber 24 in the device 50 when the semiconductor substrate was moved from the sputtering chamber 22 to the device 50. Thereafter, since the Cu film 20 is formed in the CVD chamber 26 in the apparatus 50,
The uniformity of the Cu film 20 by the method becomes very high. Therefore, copper (Cu) formed by the method according to the present embodiment is used.
The variation in the sheet resistance of the wiring can be suppressed to 2% or less, the (111) orientation of the Cu film 20 by the CVD method is greatly improved, and the electromigration resistance is also improved. Further, the annealing in the annealing chamber 24 not only removes the oxide 18 but also removes the C by sputtering.
In order to improve the (111) orientation itself of the u film 16, the uniformity of the Cu film 20 formed thereon by the CVD method becomes very high.

The method for forming a copper (Cu) wiring according to the present invention can also be realized by an apparatus configuration as shown in FIG. 3, that is, a sputtering chamber 30, a CVD chamber 46, and a moving device 48. With such an apparatus configuration, in the sputtering chamber 30, C by sputtering is used.
After the formation of the u film 16, the semiconductor substrate may be moved to the CVD chamber 46 by the moving device 48, and the oxide 18 formed at this time may be annealed in the CVD chamber 46 itself. Use of such an apparatus configuration has an advantage that an annealing chamber is not required.

However, in such an apparatus configuration, since both the annealing process and the CVD process are performed in the CVD chamber 46, when the processing temperatures of both processes are largely separated,
Since it is necessary to cool or heat the semiconductor substrate in the CVD chamber 46 between both processes, the throughput is reduced. For this reason, such a device configuration is
It is particularly preferable when the processing temperatures in both processes are close to each other.

When the apparatus configuration shown in FIG. 3 is used, instead of performing an annealing process in the CVD chamber 46, the oxide 18 is removed by performing hydrogen plasma, hydrogen fluoride gas irradiation, Ar sputtering, or the like. You may. However, in this case, since the annealing treatment is omitted, the (111) orientation of the Cu film 16 itself by sputtering is not improved.

Further, in the method of forming a copper (Cu) wiring according to the present invention, an apparatus configuration as shown in FIG. 4, that is, a sputtering chamber 54 and a CVD chamber 56 are integrated,
The present invention can also be realized by the device 52 which can move the semiconductor substrate between the two chambers without exposing the semiconductor substrate to the atmosphere. With such an apparatus configuration, after the Cu film 16 is formed by the sputtering method in the sputtering chamber 54, the semiconductor substrate can be moved to the CVD chamber 56 without breaking the vacuum without exposing the semiconductor substrate to the atmosphere. The oxide 18 is not formed on the Cu film 16. For this reason, since the annealing process itself can be omitted, there is no deterioration in throughput.

However, if the annealing treatment itself is omitted, the (111) orientation of the Cu film 16 itself does not improve by the sputtering method.
An annealing process may be performed in the CVD chamber 56.

[0038]

As described above, according to the present invention,
Since a Cu film having reduced sheet resistance variation and greatly improved (111) orientation is formed, a very reliable copper (Cu) wiring is formed.

[0039]

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for forming a copper wiring according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an apparatus configuration for performing a method of forming a copper wiring according to an embodiment of the present invention.

FIG. 3 is a diagram showing another example of an apparatus configuration for performing the method for forming a copper wiring according to the embodiment of the present invention;

FIG. 4 is a diagram showing still another example of a device configuration for performing the method of forming a copper wiring according to the embodiment of the present invention;

FIG. 5 is a process chart showing a conventional method for forming a copper wiring.

FIG. 6 is a process chart showing another conventional method for forming a copper wiring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Oxide film 12 Groove 14 TiN film 16 Cu film by sputtering method 18 Oxide 20 Cu film by CVD method 22, 30, 54 Sputter chamber 24 Annealing chamber 26, 46, 56 CVD chamber 28, 48 Moving device 28 50, 52 Apparatus

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/28-21/288 H01L 21/3205-21/3213 H01L 21/768

Claims (4)

(57) [Claims] 1. A first step of forming a barrier layer covering an insulating film formed on a semiconductor substrate, and after the first step, a first Cu film is formed on the barrier layer by a sputtering method. A second step, and the first C
a third step of annealing the semiconductor substrate on which the u film is formed; and a fourth step of forming a second Cu film on the first Cu film by a CVD method after the third step. A method of forming a copper wiring, wherein the annealing in the third step is performed at a temperature of 300 ° C. or more and a vacuum of 10 ⁻⁶ Torr or less for at least 3 minutes. 2. The method according to claim 1, wherein the first step and the second step are performed in a same sputtering chamber, and the semiconductor substrate is moved to an annealing chamber by a moving device. After the process is performed in a chamber for annealing, the semiconductor substrate is subjected to CVD in the same apparatus as the chamber for annealing.
2. The method for forming a copper wiring according to claim 1, wherein the method is moved to a chamber for performing the fourth step. 3. The method according to claim 1, wherein the first step and the second step are performed in a same sputtering chamber, and the semiconductor substrate is moved to a CVD chamber by a moving device. 2. The method according to claim 1, wherein the third step and the fourth step are performed. 4. The method according to claim 1, wherein the first step and the second step are performed in a same sputtering chamber, and the semiconductor substrate is moved to a CVD chamber in the same apparatus as the sputtering chamber. In the chamber for CVD, the third
2. The method according to claim 1, wherein the steps (a) and (b) are performed.