JP2001031953A - Polishing agent for metallic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polishing agent used to polish a metallic film at a high polishing speed without causing scratches and dishing, which agent comprises abrasive grains, a corrosion inhibitor, a persulfate-type oxidizing agent, and water, is substantially free from an organic acid which forms a complex with a metal, and has a specified pH value. SOLUTION: This polishing agent has an adjusted pH of 3-7. The abrasive grains are desirably silica having a specific surface area of 20-350 m2/g and are desirably used in a concentration of 0.1-30 wt.% based on the polishing agent. The corrosion inhibitor is desirably benzotriazole and is desirably used in a content of 10-1,000 ppm. The persulfate-type oxidizing agent is desirably ammonium persulfate and is used in an amount of, desirably, 0.1-10 wt.%. The polishing agent is useful when used in a process comprising: forming an insulation film having a recess for metal wiring on the surface of a semiconductor substrate, forming a metallic film on it through a barrier film in such a manner that it may fill the recess, and removing part of the metallic film and the barrier film by polishing to form a leveled surface on the insulation film and that part of the metallic film which remains in the recess.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel abrasive. Specifically, the present invention provides an abrasive having excellent polishing characteristics of a metal film and low dissolution characteristics of the metal film.

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, wiring technology has been increasingly miniaturized and multilayered. The multi-layered wiring technology increases the level difference on the surface of the semiconductor substrate. As a result, there is a problem in that the processing accuracy and reliability of wiring formed thereon are reduced, and miniaturization is hindered.

In order to solve the above-mentioned problems caused by the multi-layering, a technique has been developed in which a layer on which wiring patterns, electrodes, etc. (hereinafter, referred to as wirings, etc.) are formed is flattened, and further wirings, etc. are formed thereon. ing. That is, an insulating film having a concave portion for metal wiring is formed on a surface of a semiconductor substrate, and a metal film is formed thereon so as to fill the concave portion via a barrier film. In this method, the film is removed by polishing to form a flattened surface of the insulating film and the metal film present in the concave portion. In the above technique, the barrier film has a function of preventing aluminum, copper, or tungsten used as a metal film from diffusing into the insulating film, and improving the adhesion between the metal film and the semiconductor substrate, Generally, titanium nitride or tantalum nitride is used.

In order to realize high polishing performance, the above-mentioned polishing method employs a method in which mechanical polishing is used in combination with a chemical reaction which promotes the polishing. This method is called a chemical mechanical polishing (hereinafter, abbreviated as CMP) method, and various compositions of polishing agents to be used according to a polishing target such as a metal film, an insulating film, and a barrier film have been proposed. The general composition of the above-mentioned abrasive is composed of abrasive grains and a chemical. Various types of abrasives have been proposed by adding types of abrasive grains, types of chemicals, and various additives.

[0005]

However, in the CMP method, generally, the metal to be polished is dissolved by a chemical, and the metal that fills the recesses on the surface of the insulating film which is to be left as wiring is thinned (hereinafter referred to as a phenomenon). This phenomenon is called dishing). When dishing occurs, a wiring failure easily occurs. Therefore, it is necessary to suppress the occurrence of dishing as much as possible. On the other hand, it is known that the addition of an anticorrosive such as benzotriazole is effective for suppressing corrosion of a metal film such as copper. However,
Dishing cannot be completely suppressed with conventional abrasives.
Further, if a large amount of a so-called anticorrosive agent such as the above-mentioned benzotriazole is added to suppress dishing, the polishing rate of the metal film is excessively reduced, which may cause a practical problem.

As described above, it is difficult to achieve both the problem of polishing speed and the problem of dishing, and the solution of the problem has been awaited.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems. As a result, under certain conditions, abrasives using a combination of anticorrosive and specific oxidizing agent,
The present inventors have found that a metal film can be polished at a high polishing rate and that dishing can be almost completely suppressed, and the present invention has been proposed.

That is, the present invention provides a polishing composition comprising abrasive grains, an anticorrosive, a persulfate-based oxidizing agent and water, containing substantially no organic acid capable of forming a complex with a metal and having a pH of 3 to 7. An abrasive for a metal film, which is adjusted to a range.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the abrasive according to the present invention will be described in detail.

The metal film to be polished by the metal film polishing agent of the present invention includes an aluminum film, a copper film and a tungsten film. Among them, the present invention is particularly effective for a copper film.

The abrasive grains used in the present invention are not particularly limited. Silica, alumina, ceria, zirconia, silicon nitride, silicon carbide and the like can be used. Among the above, when using silica for abrasive grains, the abrasive is stable,
In addition, it is advantageous in that it can be polished with less scratches.

As the silica, known silica can be used without any particular limitation. For example, fumed silica produced by burning silicon tetrachloride or a silane-based gas in a flame, or sol-gel silica produced by hydrolysis using alkoxysilane as a raw material (hereinafter also referred to as high-purity colloidal silica) And precipitated silica produced by using sodium silicate as a raw material and neutralized with a mineral acid, and colloidal silica produced by using the sodium silicate as a raw material by the Ostwald process.

The specific surface area of the silica is not particularly limited, but is preferably in the range of 20 to 350 m ² / g. That is, when the specific surface area is smaller than 20 m ² / g, the silica particles tend to settle easily. On the other hand, if the specific surface area is larger than 350 m ² / g, there may be a problem in the stability of the abrasive.

The concentration of the silica in the metal film polishing slurry of the present invention is preferably in the range of 0.1 to 30% by weight.
The range of 0.1 to 20% by weight is optimal. When the concentration of silica is less than 0.1% by weight, the polishing rate of the metal film is reduced. When the concentration is more than 30% by weight, the stability of the polishing agent such as gelling of the polishing agent is reduced. is there.

In the present invention, it is extremely important to use an anticorrosive. Known types of anticorrosives can be used without limitation. Representative examples include benzotriazole, imidazole, benzimidazole, benzothiazole, 2-aminothiazole and derivatives thereof. Among them, benzotriazole is preferred.

The content of the anticorrosive in the metal polishing agent is in the range of 10 to 1000 ppm, preferably 30 to 2 ppm.
50 ppm, more preferably 30 to 150 ppm
Is suitable. If it is less than 10 ppm, the anticorrosion effect may be too small to easily dissolve the metal film. Also,
If it exceeds 1000 ppm, the polishing rate may be significantly reduced.

When silica is used for the abrasive grains, ammonium persulfate is used for the persulfate oxidizing agent, and benzotriazole is used for the anticorrosive, the benzotriazole content is 50 to 1
The range of 00 ppm can be said to be an extremely favorable range while almost completely suppressing dishing and hardly lowering the polishing rate as compared with the case where no anticorrosive agent is added.

In the present invention, it is extremely important to use a persulfate oxidizing agent as the oxidizing agent. That is, even if another oxidizing agent such as hydrogen peroxide or ferric nitrate is used, the same excellent performance as the polishing agent of the present invention cannot be exhibited. For example, when hydrogen peroxide is used instead of the persulfate-based oxidizing agent, the polishing rate is extremely reduced, and the object of the present invention cannot be achieved. The structure of the persulfate is shown below.

[0019]

Embedded image Illustrating specific representative examples of the above persulfate oxidizing agent,
Examples thereof include ammonium persulfate, potassium persulfate, and sodium persulfate. Among them, the abrasive of the present invention is mainly used in the manufacturing process of a semiconductor device,
Ammonium persulfate, which does not contain alkali metals such as a and K, and which is easily available industrially, is preferably used.

In the present invention, the amount of the above-mentioned persulfate-based oxidizing agent in the abrasive is in the range of 0.1 to 10% by weight, preferably 0.5 to 6% by weight in the abrasive. It is. If it is less than 0.1% by weight, the polishing rate of the metal film may be low. If it exceeds 10% by weight, the polishing rate tends to be too high to make it difficult to control the polishing rate, and the use of a high-concentration oxidizing agent is problematic in terms of danger, and the burden of wastewater treatment is reduced. There is a concern that problems such as an increase will occur.

In the polishing agent of the present invention, the polishing rate for the metal film tends to be almost proportional to the concentration of the persulfate oxidizing agent added to the polishing agent. Also, by setting to, a desired polishing rate can be obtained.

Incidentally, in addition to the above requirements, it is extremely important that the metal film polishing agent of the present invention does not contain an organic acid capable of forming a complex with a metal. Most of the conventionally known polishing methods for metal films contain organic acids such as oxalic acid, tartaric acid, phthalic acid and succinic acid. These are those that form a protective film by forming a complex between the organic acid and the metal oxide or metal ion on the surface of the metal film, or are added to promote dissolution or facilitate polishing. I have. At this time, the oxidizing agent often uses hydrogen peroxide. On the other hand, the present inventors have found that when a persulfate-based oxidizing agent is used as an oxidizing agent, the polishing of a high metal film can be performed by substantially eliminating the presence of an organic acid capable of forming a complex with a metal. It has been found that the speed can be realized and the solubility of the metal film can be kept low.

It is important to adjust the pH of the abrasive of the present invention to a range of 3-7. That is, when the pH is less than 3 or more than 7, the abrasive becomes unstable due to gelation or the like, and dishing of the metal film easily occurs.
In particular, when silica is used for abrasive grains, benzotriazole is used as an anticorrosive, and ammonium persulfate is used as an oxidizing agent,
The pH of the abrasive is preferably in the range of 3 to 5.

In the present invention, an appropriate amount of acid or alkali may be added in order to adjust the pH of the abrasive to the above range.
It is preferable to use an acid that does not form a complex with a metal, such as an inorganic acid, as the acid. For example, when ammonium persulfate is used as a persulfate-based oxidizing agent, it is preferable to use sulfuric acid as an acid and ammonia as an alkali as a pH adjuster. In the present invention, as described above, it is effective to reduce the ionic species in the polishing slurry as much as possible in order to improve the reproducibility of polishing and the stability of the polishing slurry. When high-purity fumed silica or high-purity colloidal silica is used for the abrasive grains, the pH of the polishing agent can be adjusted to the above range only with the anticorrosive and the persulfate-based oxidizing agent. Yes, it is preferred.

In the use of the metal film abrasive of the present invention,
The order of addition of each component is not particularly limited, and it is sufficient that all components are included at the time of use, that is, at the time of polishing. However, in general, the oxidizing agent often decomposes gradually when converted to an aqueous solution or left at room temperature, and its oxidizing power often decreases. Therefore, it is desirable to add the oxidizing agent at the time of use. Therefore, it is desirable to prepare an abrasive composed of abrasive grains, an anticorrosive, and water, and to add a persulfate oxidizing agent when used.

The abrasive grains, which have been described above,
Each concentration of the anticorrosive and the persulfate oxidizer mainly describes the optimum concentration range when used as an abrasive, and the one with a higher concentration than the above is manufactured and diluted with pure water when used. There is no problem to use it. That is, an abrasive containing abrasive grains and an anticorrosive agent several times higher than the concentration at the time of actual use is prepared, diluted several times with pure water at the time of use, and an appropriate amount of a persulfate-based oxidizing agent is used. May be added for use.

The manufacture of a semiconductor device using an abrasive is performed by laminating an insulating film, a barrier film, and a metal film on a semiconductor substrate surface in a predetermined pattern and polishing the laminated film.

The above-mentioned semiconductor substrate is typically a silicon substrate used for semiconductor devices such as ICs and LSIs, but a semiconductor substrate such as germanium or a compound semiconductor is also used.

The insulating film is used for electrical isolation between wiring layers, and is not particularly limited as long as it is insulating. Generally, a silicon oxide film (plasma-TE
OS film and SOG film) and organic SO
A G film or the like is used.

Further, the barrier film is a thin film formed between the insulating film and the metal film in order to prevent the diffusion of the wiring metal into the insulating film and to improve the adhesion of the metal film to the insulating film. In addition, a tantalum film, a tantalum nitride film, a titanium film, a titanium nitride film, a tungsten nitride film, and the like can be given. Among them, a titanium nitride film and a tantalum nitride film are preferable.

Further, the metal film is a wiring material for forming a wiring pattern and an electrode, and examples thereof include an aluminum film, a copper film, and a tungsten film. The metal abrasive of the present invention exerts a remarkable effect particularly on a copper film.

In the above-mentioned polishing for producing a semiconductor device, the metal polishing slurry of the present invention can be used to change the specific surface area (average particle diameter) of the abrasive grains to be used and the concentration of the abrasive grains so that the metal abrasive for the barrier film can be formed. Two types of polishing agents having different film selectivity can be provided.

That is, according to the present invention, the specific surface area is 20 to
350m^Two/ G range abrasive grains, anticorrosive, persulfate
An abrasive for metal films, comprising an oxidizing agent (hereinafter referred to as an abrasive).
Below, referred to as abrasive A) and the above-mentioned abrasive A
The specific surface area is 60-150m ^Two/ G range polishing
Granules, anticorrosive, persulfate oxidizer
(Hereinafter, referred to as abrasive B) is provided.
You.

The polishing agent A is a polishing agent having a high selectivity of the metal film to the barrier film, and the polishing agent B is a polishing agent capable of polishing the barrier film together with the metal film at a high polishing rate.

In order to polish the metal film with a higher selectivity to the barrier film, it is desirable that the concentration of the abrasive grains in the polishing agent A is as low as possible, specifically, 10% by weight.
The following are preferred. The specific surface area is 60 to 150 m ^2.
/ G of abrasive grains, the abrasive A
It is preferable to lower the concentration of the abrasive grains in the medium, and specifically, to be 5% by weight or less.

In order to polish the barrier film together with the metal film at a high polishing rate, it is desirable that the concentration of the abrasive grains in the polishing agent B is as high as possible, specifically, 5% by weight.
More preferably, it is more preferably 10% by weight or more.

The polishing method using the metal polishing agent of the present invention is not particularly limited, but the following method can be mentioned as an example of a preferable polishing method.

That is, an insulating film having a concave portion for metal wiring is formed on the surface of a semiconductor substrate, and a metal film is formed thereon so as to fill the concave portion via a barrier film, and then the metal film and the barrier film are polished. In forming a flattened surface of the insulating film and the metal film present in the concave portions by removing the metal film, after selectively performing polishing of the metal film with the polishing agent A,
A polishing method characterized by simultaneously polishing a metal film and a barrier film (hereinafter, referred to as polishing method 1); forming an insulating film having a concave portion for metal wiring on a semiconductor substrate surface; After the metal film is formed so as to fill the concave portion by polishing, the metal film and the barrier film are removed by polishing to form a flat surface of the insulating film and the metal film present in the concave portion. A typical polishing method (hereinafter referred to as polishing method 2) is characterized in that the metal film is polished by B and the metal film and the barrier film are polished simultaneously and continuously.

The method of forming the metal wiring employing the above-described polishing method 1 is also referred to as a two-step polishing method, and the method of forming the metal wiring employing the above-described polishing method 2 is referred to as a single-step polishing method.

In the polishing method 1, the metal film is selectively polished with the polishing agent A as the first-stage polishing, and then the barrier film and the metal film are simultaneously polished. As the polishing agent used for the polishing, a known polishing agent that can polish a barrier film at a polishing rate equal to or higher than that of a metal film can be used. In addition, in the second stage polishing, in addition to the above, an abrasive made of water in which the above-mentioned abrasive B or silica is dispersed at a concentration of 10 to 200 g / l (hereinafter, referred to as abrasive C) can be used.

For finishing, the polishing method 1 and the polishing method 2 are followed by polishing, and then the polishing method for simultaneously polishing the metal film, the barrier film and the insulating film using the polishing agent C (hereinafter referred to as “polishing method”). Polishing method 3) can also be employed.

The polishing method 1 will be described in detail with reference to FIG.

The recess A provided in the insulating film formed on the surface of the semiconductor substrate is a groove or a connection hole formed on the insulating film for forming a wiring or the like.

First, (a) the insulating film 2 having the concave portion A
The metal film 4 sequentially laminated on the upper surface is formed by (b) the polishing agent A of the present invention.
Then, polishing is stopped at the position where the barrier film 3 exists (first-stage polishing).

In the first stage polishing, the polishing agent A of the present invention is used.
By using, the metal film can be selectively removed from the barrier film while suppressing the occurrence of scratching and dishing, so that a flat surface composed of the barrier film and the metal film can be formed. At this time, the selection ratio of the metal film to the barrier film (metal film / barrier film polishing rate ratio) is preferably 5 or more, and more preferably 10 or more.

Next, (c) the barrier film and the metal film are simultaneously polished (second-stage polishing).

Further, if necessary, the metal film, the barrier film and the insulating film are simultaneously polished using the polishing agent C (hereinafter referred to as finish polishing).

After the removal of the metal film with the polishing agent A in the first-stage polishing, the barrier film and the metal film buried in the concave portions are present in an exposed state on the surface to be polished.

Since the polishing agent C used in the second-stage polishing needs to remove the barrier film from the surface to be polished, it is desirable to polish the barrier film at a polishing rate equal to or higher than that of the metal film. The selectivity of the metal film to the film (metal film / barrier film polishing rate ratio) is preferably 1 or less, more preferably 0.7 or less.

If the selectivity exceeds 1, the metal film may be polished too much more than the barrier film, and the dishing characteristics may be reduced.

In the present invention, the polishing agent C is preferably a polishing agent comprising silica particles and water.
The use of silica particles in the range of 100 to 100 m ² / g is preferable because the polishing rate of the barrier film is high. More preferably, it is preferable to use silica particles synthesized in a liquid phase such as a sol-gel method and produced without passing through a drying step.

That is, the silica particles synthesized in the liquid phase are excellent in dispersibility, and have a feature that the generation of scratches to be polished during polishing is very small because the particles are spherical and soft. .

Since the thickness of the barrier film formed on the semiconductor substrate is generally in the range of 100 to 500 angstroms, the polishing rate of the polishing agent C to the barrier film is 50 to 1000 angstroms / min. Range, preferably 200-500 angstroms / m
In the range of “in”, the control is easy, and the time required for removing the barrier film is preferably 2 minutes or less, more preferably 1 minute or less.

The polishing rate is 50 angstroms / m.
If it is less than in, productivity may decrease, and if it is more than 1000 Å / min, not only barrier film but also
In some cases, the lower part of the insulating film or the metal film of the wiring may be polished, and it may be difficult to stop polishing at a desired position, and controllability may be reduced.

In order to achieve such polishing characteristics, an abrasive C
The concentration of the silica particles therein is preferably in the range of 1 to 20% by weight. Since the polishing of the barrier film is often performed by the mechanical action of silica particles, the desired polishing rate can be controlled by changing the concentration of the silica particles.

The polishing agent C has a pH in the range of 5 to 9,
When the thickness is preferably in the range of 6 to 8, the metal film and the insulating film tend to be polished at almost the same polishing rate, which is preferable. If the pH of the polishing agent is less than 5, the polishing rate of the metal film may exceed 9, and the polishing rate of the insulating film may be significantly higher than the polishing rate of the barrier film. In such a case, dishing easily occurs in the metal film or the insulating film, and the flatness of the semiconductor substrate surface may be reduced. When the pH is less than 5 or more than 9, the metal film tends to be easily corroded.

As described above, the surface of the semiconductor substrate can be highly flattened by polishing with the polishing agent C composed of silica and water.

To the polishing agent C, a very small amount of an anticorrosive or an oxidizing agent, which is a component of the polishing agent for a metal film of the present invention, or an additive such as a surfactant or a water-soluble polymer may be added. Can also. It is also a preferred embodiment to add a small amount of an amine such as triethanolamine or an amine salt in order to improve the finished state of the metal film surface.

Further, polishing of the barrier film and the metal film, that is,
Subsequent to the second-stage polishing, finish polishing is performed as necessary. The polishing agent used for such polishing is preferably capable of polishing a metal film, a barrier film, and an insulating film at substantially the same polishing rate. Particularly preferably, the selectivity (metal film / insulating film polishing rate ratio and barrier film / insulating film polishing rate ratio) between the metal film and the barrier film with respect to the insulating film is preferably from 0.3 to 0.3.
3, more preferably 0.5-2, especially 0.8-1.
2.

If it exceeds the above range, either one of the films is selectively polished, and dishing easily occurs.

As the above-mentioned abrasive, one having the above-mentioned selection ratio may be selected from known abrasives, or one having the above-mentioned selection ratio from among the abrasives C may be used. . In the latter case, the second stage polishing and the final polishing can be performed continuously, which is preferable.

Next, the polishing method 2 will be described in detail with reference to FIG.

The recess A provided in the insulating film formed on the surface of the semiconductor substrate is a groove or a connection hole formed on the insulating film for forming a wiring or the like.

(A) The barrier film 3 and the metal film 4 sequentially laminated on the insulating film 2 having the concave portion A are polished using the polishing agent B of the present invention. Then, the metal film 4 and the barrier film 3 are simultaneously polished.

In the above polishing, the use of the polishing agent B of the present invention makes it possible to simultaneously remove the metal film and the barrier film while suppressing the occurrence of scratching and dishing.
It is possible to extremely efficiently form a flat surface of the insulating film and the metal film present in the concave portion. That is, in the two-stage polishing method described above, two types of polishing agents must be prepared and polishing must be performed twice, whereas in the present method, the desired polishing can be performed by one type of polishing agent and one polishing. Is terminated.

Further, if necessary, the finish polishing described in detail in the above-described one-step polishing method can be performed. That is, by simultaneously polishing the metal film, the barrier film and the insulating film,
Further, a polished surface having an excellent surface condition can be obtained.

The above-described one-step polishing method and two-step polishing method may be properly used depending on the type and shape of the object to be polished such as a semiconductor device to be polished.

[0068]

According to the present invention, it is possible to achieve both a protective action and a dissolving action (polishing) of a metal film by using a specific oxidizing agent other than hydrogen peroxide and an anticorrosive agent substantially without an organic acid. did. It is a combination of a persulfate-based oxidizing agent represented by ammonium persulfate and an anticorrosive. Ammonium persulfate oxidizes the metal film as an oxidizing agent, but in this system, the dissolved metal ions are considered to be dissolved as sulfates. For example, when copper is used as the metal film, it is considered that copper is dissolved in the form of copper sulfate. At this time, the presence of an anticorrosive is essential, and if there is no anticorrosive, the dissolution of the metal film does not stop. However, by adding an appropriate amount of the anticorrosive, a polishing agent having a balanced polishing rate and solubility is provided. It is possible to

[0069]

As will be understood from the above description, according to the metal polishing slurry of the present invention, it is possible to polish a metal film at a practical polishing rate while suppressing the generation of scratches, and further, it is possible to dissolve the metal film in the metal film. It has the characteristic that the property is extremely low.

Further, the abrasive of the present invention forms an insulating film having a concave portion for metal wiring on the surface of a semiconductor substrate, and forms a metal film on the insulating film via a barrier film so as to fill the concave portion. The metal film and the barrier film are removed by polishing to form a flattened surface of the insulating film and the metal film present in the concave portion.

Therefore, by using the metal abrasive of the present invention, a very flat semiconductor substrate surface can be obtained.

[0072]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. (Polishing test) Copper (Cu) film or tantalum nitride (Ta)
A polishing test was performed using a 4-inch silicon wafer having an N) film or a silicon oxide (SiO ₂ ) film formed on the surface. The polishing pad is Rodel IC1000 / S
Using UBA400, processing pressure 300 g / cm ² , platen rotation speed 40 rpm, dropping rate of abrasive 80 ml / min
The polishing test was performed under the following conditions to determine the polishing rate. (Solubility test) A solubility test was performed using a silicon wafer having a Cu film formed on the surface. The test pieces were immersed in an abrasive, and the container containing them was placed in a thermostatic shaker maintained at 50 ° C. Ten minutes later, the wafer was taken out of the constant temperature shaker, and the wafer was immediately transferred from the abrasive into pure water to wash away the abrasive remaining on the surface. From the change in the thickness of the Cu film before and after the immersion, the dissolution rate of the Cu film in the abrasive was determined. In addition, the dissolution rate of the Cu film is 10 angstroms / min.
In the following cases, due to the problem of the accuracy of the film thickness measurement, it is described as 10 Å / min or less. Example 1 Various silica, benzotriazole (hereinafter abbreviated as BTA), water and ammonium persulfate were mixed in predetermined amounts, and the silica concentration was 2, 7, 14% by weight, and the BTA concentration was 100.
Several types of abrasives having a concentration of 1 ppm by weight of ammonium persulfate were adjusted. Silica includes high-purity colloidal silica having a specific surface area of 30 or 75 m ² / g and a specific surface area of 5
Several types of fumed silica ranging from 0 to ²⁰⁰ m2 / g were used.

Table 1 shows the results of the polishing test.

As can be seen from the above results, the abrasive for a metal film of the present invention has a silica having a specific surface area of 30 to 350 m ² /
g and the concentration of silica in the range of 2 to 14% by weight,
It was found that polishing was possible at a practical polishing rate of 2000 Å / min or more, and the dissolution rate of the metal film was low. Therefore, in the polishing agent for metal films of the present invention, the specific surface area of silica is preferably in the range of 20 to 350 m ² / g, and the silica concentration is preferably in the range of 0.1 to 30% by weight.

The polishing rate of the TaN film was in the range of 100 to 500 Å / min, depending on the type and concentration of silica. Therefore, the selectivity ratio of the Cu film to the TaN film under any conditions (Cu / TaN)
Was 5 or more. Furthermore, it was also found that a selection ratio of 10 or more can be easily obtained by selecting the type and concentration of silica.

On the other hand, the specific surface area of silica is 60 to 150 m
^When the concentration of silica is 5% by weight or more in the range of ² / g,
The polishing rate of the TaN film is 400 Å / min.
Because of the above, it was found that the method was suitable for the single-step polishing method for simultaneously polishing the Cu film and the TaN film.

For reference, the polishing rate of the SiO ₂ film was also examined. When silica of 80 m ² / g or more was used, S
The polishing rate of the iO ₂ film is 100 Å / min.
This was extremely low, and was found to be extremely suitable for a process using an SiO ₂ film as a stopper film.

[0078]

[Table 1] Example 2 and Comparative Example 1 No. 1 of Example 1 except that the concentration of BTA was changed in the range of 0 to 500 ppm. An abrasive was prepared and tested as in 1.

Table 2 shows the test results. In addition, No. 1
Is a comparative example.

It has been found that the polishing rate of the Cu film strongly depends on the BTA concentration, and the polishing rate of the Cu film decreases as the BTA concentration increases.

On the other hand, the dissolution rate of the Cu film strongly depends on the presence or absence of BTA. That is, in the case of no addition, the dissolution could not be suppressed at all at 500 Å / min or more, but the dissolution could be suppressed drastically by adding even a small amount of BTA, and the dissolution rate of the Cu film was increased by increasing the concentration of BTA. It showed a tendency to decrease.

Considering the polishing rate and dissolution rate of the Cu film as described above, the amount of the anticorrosive added is 10 to 100.
A range of 0 ppm has been found to be suitable.

If the dissolution rate of the metal film is 100 Å / min or more, there is a concern that dishing of the metal film after polishing becomes large and the surface of the metal film may be roughened.
Desirably less than in.

[0084]

[Table 2] Example 3 and Comparative Example 2 The procedure of Example 1 was repeated except that various oxidizing agents were added instead of ammonium persulfate. An abrasive was prepared and tested as in 1.

Table 3 shows the results of the test. In addition, No.
3 and 4 are comparative examples.

When ammonium persulfate and potassium persulfate were used as the oxidizing agents, the Cu film showed a high polishing rate of about 4000 Å / min or more, but when other oxidizing agents were used, the polishing of the Cu film was stopped. Speed is 100
It was found to be as low as 0 Å / min or less.

[0087]

[Table 3] Example 4 and Comparative Example 3 No. 1 of Example 1 except that the concentration of ammonium persulfate was changed in the range of 0 to 4% by weight. An abrasive was prepared and tested as in 1.

Table 4 shows the results of the test. In addition, No. 1
Is a comparative example.

It was found that when ammonium persulfate was not added, the Cu film could hardly be polished. It was found that a practical polishing rate of 2000 Å / min or more can be easily obtained by adding ammonium persulfate.

The polishing rate of the Cu film tends to be proportional to the concentration of ammonium persulfate, and it has been found that a desired polishing rate can be obtained by changing the concentration of ammonium persulfate. On the other hand, the polishing rate of the TaN film or SiO ₂ film is
It was found that it hardly depends on the concentration of ammonium persulfate. The dissolution rate of the Cu film hardly depended on the concentration of ammonium persulfate, and was as low as about 10 angstroms / min.

[0091]

[Table 4] Example 5 and Comparative Example 4 The effect when the metal film abrasive of the present invention contained an organic acid capable of forming a complex with a metal was examined. N of Example 1
o. About 3000 ppm of various organic acids were added to the polishing agent No. 1, and the pH of the polishing agent was adjusted to a range of 5 to 7 using ammonia and tested.

Table 5 shows the results of the test. In addition, No. 2
-5 are comparative examples.

No. 3 containing no organic acid In the first embodiment, the Cu film can be polished at a polishing rate of 4000 Å / min or more, while the Cu film such as oxalic acid can be polished.
It was found that a material containing an organic acid capable of forming a complex cannot produce a practical polishing rate.

[0094]

[Table 5] Example 6 and Comparative Example 5 Sulfuric acid or ammonia was added to adjust the pH of the abrasive to 2
8 of Example 1 except that the range was adjusted to the range of No. 8. An abrasive was prepared and tested as in 1.

The results of the test are shown in Table 6. In addition, No.
Reference numerals 1 and 6 are comparative examples.

When the pH was in the range of 3 to 7, the dissolution rate of the Cu film was sufficiently low at around 10 angstroms / min, but when the pH was less than 3 or more than 7, the dissolution rate increased to 100 angstroms / min or more. Or
It was found that the polishing rate was reduced.

Therefore, the polishing slurry for metal films of the present invention has a pH
Was found to be preferably in the range of 3 to 7.

[0098]

[Table 6] Example 7 No. 1 in Example 1. The application to the two-stage polishing method was studied using the first abrasive (first abrasive). A high-purity colloidal silica having a specific surface area of 30 m ² / g and a predetermined amount of water are mixed to prepare a neutral (pH 6.8) abrasive having a silica concentration of 7% by weight. used.

SiO ₂ formed on silicon wafer surface
Wiring grooves having a width of 100 μm are formed on the film at intervals of 100 μm, and a Ta film having a thickness of about 200 angstroms is formed thereon.
TE in which an N film and a Cu film having a thickness of about 1.2 μm are sequentially laminated
Using a G wafer, the silicon wafer surface was first polished for about 3 minutes with a first abrasive. As a result, the Cu film on the portion of the SiO ₂ film other than the wiring groove is removed, and the TaN
The film and the Cu film in the wiring groove were exposed. continue,
After polishing for about 1 minute with the second abrasive, the TaN film was removed, and the SiO ₂ film in portions other than the wiring grooves and the Cu film in the wiring grooves were exposed. When the surface of the polished silicon wafer was observed with an electron microscope, no scratch or dishing was observed, and the SiO
There is almost no step on the surface of the Cu film of the ₂ film and the wiring groove,
It was confirmed that a flat surface was formed.

For reference, the first abrasive and the second abrasive
Abrasive Cu film, TaN film, SiO _TwoEach against the membrane
The polishing rates are shown in Table 7. As you can see
In addition, the first abrasive used here efficiently polished the metal film
It turns out that it is possible. The second abrasive is a barrier
It can be seen that the film can be efficiently polished.

From the above results, the polishing agent of the present invention can selectively polish a metal film, and subsequently can polish a flat semiconductor substrate by simultaneously polishing a metal film and a barrier film using a second polishing agent. It was found that it was suitable for the two-stage polishing method to be formed.

[0102]

[Table 7] Example 8 No. 1 of Example 1. The application to the single-stage polishing method using 10 abrasives (abrasive 1) was studied. The specific surface area is 30m
^A predetermined amount of ² / g high-purity colloidal silica and water are mixed,
A neutral (pH 7.1) abrasive having a silica concentration of 3% by weight was prepared and used as a finishing abrasive.

SiO ₂ formed on silicon wafer surface
Wiring grooves having a width of 100 μm are formed on the film at intervals of 100 μm, and a Ta film having a thickness of about 200 angstroms is formed thereon.
TE in which an N film and a Cu film having a thickness of about 1.2 μm are sequentially laminated
Using the G wafer, the surface of the silicon wafer was polished with the polishing agent 1 for about 4 minutes. As a result, the Cu film and the TaN film on portions other than the SiO ₂ film wiring groove were polished and removed, and the Cu film in the wiring groove was exposed. Subsequently, polishing was performed for about 1 minute with a finishing abrasive.

[0104] When a silicon wafer surface after polishing was observed by an electron microscope, scratches and dishing was not observed at all, the SiO ₂ film and the wiring groove in the portion other than the wiring grooves Cu
There was almost no step on the surface of the film, and it was confirmed that a flat surface was formed.

For reference, Table 8 shows the respective polishing rates of the polishing agent 1 and the finishing polishing agent with respect to the Cu film, the TaN film, and the SiO ₂ film. As can be seen, the polishing agent 1 used here can efficiently polish the metal film and the barrier film, and the finish polishing agent can polish the metal film, the barrier film, and the insulating film at almost the same polishing rate. .

From the above results, it was found that the polishing slurry of the present invention is suitable for the one-step polishing method in which the metal film is polished and then the barrier film can be continuously polished.

[0107]

[Table 8]

[Brief description of the drawings]

FIG. 1 is a schematic view showing a typical embodiment of a polishing method using the polishing agent of the present invention.

FIG. 2 is a schematic view showing a typical embodiment of a polishing method using the polishing agent of the present invention.

[Explanation of Symbols] A recess 1 semiconductor substrate 2 insulating film 3 barrier film 4 metal film

Claims (1)

[Claims] 1. A polishing composition comprising abrasive grains, an anticorrosive, a persulfate-based oxidizing agent, and water, substantially free of an organic acid capable of forming a complex with a metal, and having a pH adjusted to a range of 3 to 7. An abrasive for metal films.