WO2011093195A1

WO2011093195A1 - Aqueous dispersion for chemical mechanical polishing, chemical mechanical polishing method using same, and kit for preparing aqueous dispersion for chemical mechanical polishing

Info

Publication number: WO2011093195A1
Application number: PCT/JP2011/050917
Authority: WO
Inventors: 達慶河本; 太一阿部; 和男西元; 志保　浩司
Original assignee: Jsr株式会社
Priority date: 2010-01-27
Filing date: 2011-01-20
Publication date: 2011-08-04
Also published as: TW201139633A; JPWO2011093195A1

Abstract

Disclosed is an aqueous dispersion for chemical mechanical polishing, which is characterized by containing abrasive grains, ferrate ions (FeO₄ ^2-) and a dispersion medium.

Description

Chemical mechanical polishing aqueous dispersion, chemical mechanical polishing method using the same, and chemical mechanical polishing aqueous dispersion preparation kit

The present invention relates to a chemical mechanical polishing aqueous dispersion, a chemical mechanical polishing method using the chemical mechanical polishing aqueous dispersion, and a chemical mechanical polishing aqueous dispersion preparation kit.

In recent years, with the increase in definition of semiconductor devices, the miniaturization of wirings formed in the semiconductor devices is progressing. Along with this, a technique of planarizing the wiring layer by chemical mechanical polishing (hereinafter also referred to as “CMP”) is used. For example, in Japanese Translation of PCT International Publication No. 2002-518845, a conductive metal such as aluminum, copper, or tungsten is deposited in a fine groove or hole provided in an insulating film such as silicon oxide on a semiconductor substrate by a method such as sputtering or plating. Then, a damascene process has been proposed in which the excessively laminated metal film is removed by CMP, and the metal is left only in the fine grooves and holes.

When manufacturing a semiconductor device by the Cu damascene method, the copper film on the barrier metal film is removed by polishing (first polishing process), and then the barrier metal film is removed by polishing, and the copper film and interlayer insulation are used as necessary. It is common to carry out two-stage polishing that combines a step of further polishing and planarizing the film (second polishing step).

In the first polishing process, the property of polishing the copper film at a high speed is required, but at the end of the first polishing process (when another material film such as a barrier metal film is exposed), a high polishing rate for the copper film is obtained. It is difficult to suppress dishing of the copper film while maintaining it. Furthermore, in the second polishing process, not only the copper film, but also the semiconductor substrate surface (surface to be polished) where the other material film such as the barrier metal film is exposed is maintained at a high speed, and the dishing of the copper film is suppressed. It is difficult to do.

In order to polish the surface to be polished at high speed, the applied pressure at the time of polishing may be increased to increase the frictional force applied to the surface to be polished. However, in such a case, there is a problem that smoothness such as dishing of the surface to be polished is deteriorated as the polishing rate is increased. On the contrary, in order to improve the smoothness such as dishing of the surface to be polished, the applied pressure at the time of polishing may be lowered, but there is a problem that the polishing rate of the surface to be polished is remarkably reduced. For this reason, the approach from the polishing method for improving the polishing characteristics has reached its limit.

In order to solve these problems, aqueous dispersions for chemical mechanical polishing having various compositions have been proposed. For example, International Publication No. 2007/116770 pamphlet discloses a technique for suppressing dishing of a copper film while maintaining a polishing rate by containing a water-soluble polymer in a polishing composition. However, it is insufficient at present when further miniaturization is required.

Also, as one method for improving the polishing rate and dishing, there is a method of adding a strong oxidizing agent containing a metal to the polishing composition. For example, Japanese Patent Application Laid-Open No. 11-116948 discloses a technique for adding iron nitrate or the like to a polishing composition. However, it has been difficult to solve the problem of suppressing contamination by the metal ions on the surface to be polished after the polishing process is completed.

On the other hand, tungsten having excellent embedding property is used for the via hole that electrically connects the wirings in the vertical and vertical directions. A chemical mechanical polishing aqueous dispersion for polishing a tungsten film requires a strong oxidizing action. For example, in JP 2005-518091 A, an oxidizing agent such as hydrogen peroxide, an iron catalyst such as iron nitrate, and silica are used. Techniques relating to polishing compositions containing abrasive grains such as these have been proposed. Furthermore, the chemical mechanical polishing aqueous dispersion used for polishing the tungsten film is required to have a higher polishing rate and to minimize the metal contamination remaining on the surface to be polished. In order to achieve these properties in a well-balanced manner, for example, Japanese Patent Application Laid-Open No. 2007-19093 and Japanese Translation of PCT International Publication No. 2008-503875 discuss a technique for adding a water-soluble polymer to a polishing composition.

However, the conventional chemical mechanical polishing aqueous dispersion for polishing a tungsten film as described above achieves both a high polishing rate for the tungsten film and a reduction in metal contamination remaining on the surface to be polished at the end of the polishing process. There was a limit to making it happen. That is, as described above, in order to realize a high polishing rate for the tungsten film, the surface of the tungsten film is oxidized using a chemical mechanical polishing aqueous dispersion containing a large amount of iron catalyst such as iron nitrate. The technique is taken. However, when such a chemical mechanical polishing aqueous dispersion is used, a large amount of iron ions remain on the surface to be polished at the end of the polishing step, so that iron ions are completely removed from the surface to be polished. There was a problem that it was very difficult.

Some aspects of the present invention solve the above-described problems, thereby achieving both a high polishing rate for the metal film and a high flatness on the surface to be polished, and metal contamination on the surface to be polished at the end of the polishing process. Chemical mechanical polishing aqueous dispersion, chemical mechanical polishing method using the same, and chemical mechanical polishing aqueous dispersion preparation kit are provided.

The present invention has been made to solve at least a part of the above-described problems, and can be realized as the following aspects or application examples.

[Application Example 1]
One aspect of the chemical mechanical polishing aqueous dispersion according to the present invention is:
Abrasive grains,
Ferrate ions (FeO ₄ ²⁻ ),
A dispersion medium;
It is characterized by containing.

[Application Example 2]
In the chemical mechanical polishing aqueous dispersion of Application Example 1,
The concentration of the ferrate ion (FeO ₄ ²⁻ ) may be 10 ⁻⁶ mol / L or more and 10 ⁻² mol / L or less.

[Application Example 3]
In the chemical mechanical polishing aqueous dispersion of Application Example 1 or Application Example 2,
The abrasive grains can be colloidal silica.

[Application Example 4]
In the chemical mechanical polishing aqueous dispersion according to any one of Application Examples 1 to 3,
It can further contain at least one selected from hydrogen peroxide, potassium persulfate and ammonium persulfate.

[Application Example 5]
The chemical mechanical polishing aqueous dispersion according to any one of Application Examples 1 to 4 can be used for polishing a semiconductor substrate including a copper film or a tungsten film.

[Application Example 6]
The chemical mechanical polishing aqueous dispersion according to any one of Application Examples 1 to 5 can be produced by mixing abrasive grains, an iron salt, and a dispersion medium.

[Application Example 7]
The chemical mechanical polishing aqueous dispersion preparation kit according to the present invention comprises:
A kit for preparing the chemical mechanical polishing aqueous dispersion of any one of Application Examples 1 to 6.
A first composition containing ferrate ions and water;
A second composition containing abrasive grains and a dispersion medium;
It is characterized by including.

[Application Example 8]
In the chemical mechanical polishing aqueous dispersion preparation kit of Application Example 7,
A third composition containing hydrogen peroxide, at least one selected from potassium persulfate and ammonium persulfate, and water may further be included.

[Application Example 9]
The chemical mechanical polishing method according to the present invention comprises:
A semiconductor substrate including a copper film or a tungsten film is polished using the chemical mechanical polishing aqueous dispersion according to any one of Application Examples 1 to 6.

The chemical mechanical polishing aqueous dispersion according to the present invention contains a ferric ion (FeO ₄ ²⁻ ) that exhibits higher oxidizing power than hydrogen peroxide or the like that has been generally used. It is possible to achieve both a high polishing rate with respect to and a high flatness on the surface to be polished. Moreover, conventionally, metal contamination of the surface to be polished, which is a problem with the chemical mechanical polishing aqueous dispersion containing iron ions, can be greatly reduced.

According to the chemical mechanical polishing aqueous dispersion preparation kit of the present invention, the chemically unstable ferric acid ion (FeO ₄ ²⁻ ) is separated from other components and stored, so that the ferric acid can be obtained. Decomposition of ions (FeO ₄ ²⁻ ) can be suppressed. If the chemical mechanical polishing aqueous dispersion is prepared by mixing the first composition, the second composition and the third composition immediately before use, the performance of the chemical mechanical polishing aqueous dispersion is maximized. be able to.

According to the chemical mechanical polishing method of the present invention, the polishing rate for the metal film formed on the semiconductor substrate can be significantly improved as compared with the conventional method. Moreover, metal contamination of the surface to be polished can be greatly reduced.

FIG. 1 is a cross-sectional view schematically showing an object to be processed in the chemical mechanical polishing method according to the first specific example. FIG. 2 is a cross-sectional view schematically showing an object to be processed at the end of the first polishing process of the first specific example. FIG. 3 is a cross-sectional view schematically showing an object to be processed at the end of the second polishing process of the first specific example. FIG. 4 is a cross-sectional view schematically showing an object to be processed in the chemical mechanical polishing method according to the second specific example. FIG. 5 is a cross-sectional view schematically showing an object to be processed at the end of the first polishing process of the second specific example. FIG. 6 is a cross-sectional view schematically showing an object to be processed at the end of the second polishing process of the second specific example. FIG. 7 is a perspective view schematically showing a chemical mechanical polishing apparatus.

Hereinafter, preferred embodiments according to the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, Various modifications implemented in the range which does not change the summary of this invention are also included.

1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to an embodiment of the present invention includes abrasive grains, ferrate ions (FeO ₄ ²⁻ ), and a dispersion medium. To do. Hereinafter, each component contained in the chemical mechanical polishing aqueous dispersion according to the present embodiment will be described in detail.

1.1. Abrasive Grains The chemical mechanical polishing aqueous dispersion according to the present embodiment contains abrasive grains. The abrasive is not particularly limited as long as it has an action of mechanically polishing a metal film, and examples thereof include colloidal silica, fumed silica, ceria, alumina, zirconia, and titanium oxide. Among these, colloidal silica is preferable from the viewpoint of reducing scratches (polishing scratches). As the colloidal silica, one produced by a known method as described in, for example, JP-A-2003-109921 can be used.

The average particle diameter of the abrasive grains is preferably 5 nm or more and 1000 nm or less, more preferably 10 nm or more and 700 nm or less, and particularly preferably 15 nm or more and 500 nm or less. When the average particle diameter of the abrasive grains is within the above range, a sufficient polishing rate can be obtained in polishing the metal film, and the occurrence of dishing can be reduced. In addition, from the viewpoint of the storage stability of the chemical mechanical polishing aqueous dispersion, a stable chemical mechanical polishing aqueous dispersion in which the settling and separation of abrasive grains hardly occur can be obtained. As the average particle size of the abrasive grains, an average particle size calculated using the dynamic light scattering method as a measurement principle can be applied. Examples of the measuring device include a particle size distribution measuring device (manufactured by Horiba, Ltd., model “LB550”).

When measuring the average particle size of colloidal silica, the ratio measured by using the BET method instead of the average particle size measured by the particle size distribution measuring apparatus based on the dynamic light scattering method described above. The average particle size calculated from the surface area can be applied. Examples of the measuring device include a fluid type specific surface area automatic measuring device (manufactured by Shimadzu Corporation, “micrometrics Flowsorb II 2300”) and the like.

Below, the method of calculating an average particle diameter from the specific surface area of colloidal silica is demonstrated. Assuming that the colloidal silica has a true spherical shape, the particle diameter is d (nm) and the specific gravity is ρ (g / cm ³ ), the surface area A of n particles is A = nπd ² . N particles mass N becomes N = ρnπd ^3/6. The specific surface area S is represented by the surface area of all the constituent particles per unit mass of the powder. Then, the specific surface area S of n particles is S = A / N = 6 / ρd. Substituting the specific gravity ρ = 2.2 of the silica particles into this formula and converting the unit, the following formula (1) can be derived.
Average particle diameter (nm) = 2727 / S (m ² / g) (1)
Therefore, the average particle diameter of colloidal silica can be calculated | required by substituting the value of the specific surface area measured using BET method for the said Formula (1).

The content of the abrasive grains is preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. Yes, and particularly preferably 0.1% by mass or more and 6% by mass or less.

1.2. Ferrate ion (FeO ₄ ²⁻ )
The chemical mechanical polishing aqueous dispersion according to the present embodiment contains ferrate ions (FeO ₄ ²⁻ ). In a general chemical mechanical polishing aqueous dispersion, a persulfate (peroxodisulfate) such as hydrogen peroxide or ammonium persulfate is used as an oxidizing agent. It is known that persulfate exhibits an oxidizing action equivalent to that of peroxodisulfuric acid by acidifying the pH of the chemical mechanical polishing aqueous dispersion. The redox potentials for these standard electrodes are hydrogen peroxide: 1.8 V and persulfate (peroxodisulfate): 2.0 V, respectively. On the other hand, the oxidation-reduction potential with respect to the standard hydrogen electrode of ferrate ions whose iron oxidation number is VI is as high as 2.2V. By having such a high redox potential, ferrate ions can strongly oxidize the surface of the metal film and greatly improve the polishing rate for the metal film.

The ferrate ions are generated by dissolving at least one selected from ferrates such as potassium ferrate, barium ferrate, sodium ferrate and ammonium ferrate in a dispersion medium such as water. Among these, potassium ferrate is preferably used from the viewpoint of residual contamination to the semiconductor device and solubility in water.

By using ferrate ions, residual contamination of iron ions on the surface to be polished after polishing, which has been a problem with conventional slurry containing iron ions, can be greatly reduced.

As described above, since ferrate ions have a high redox potential, the surface of the metal film can be efficiently oxidized with a small addition. More specifically, the concentration of ferrate ions in the chemical mechanical polishing aqueous dispersion is preferably 10 ⁻⁶ mol / L or more and 10 ⁻² mol / L or less, and preferably 10 ⁻⁵ mol / L or more and 10 ⁻⁴ or less. More preferably, it is at most mol / L. When the concentration of ferrate ions is within the above range, a sufficient polishing rate for the metal film can be achieved, and generation of residues derived from ferrate ions can be reduced.

Ferrate ion is chemically unstable due to its strong reactivity, and can strongly oxidize metals such as copper and tungsten under neutral to acidic conditions, but it is an aqueous dispersion for chemical mechanical polishing. As unstable. Therefore, when preparing an aqueous dispersion for chemical mechanical polishing, it is preferable to add and mix a necessary amount of ferrate just before polishing because stable polishing characteristics can be expressed. In addition, since ferric acid ions have a property of being decomposed by light, it is preferable to shield from light when storing the chemical mechanical polishing aqueous dispersion.

1.3. Dispersion medium The chemical mechanical polishing aqueous dispersion according to the present embodiment contains a dispersion medium. Examples of the dispersion medium include water, a mixed medium of water and alcohol, a mixed medium containing water and an organic solvent having compatibility with water, and the like. Among these, water, a mixed medium of water and alcohol are preferably used, and water is more preferably used.

1.4. Other Additives The chemical mechanical polishing aqueous dispersion according to the present embodiment further contains additives such as an oxidizing agent, a water-soluble polymer, a surfactant, an amino acid, a complexing agent, and a pH adjuster as necessary. It may be added. Hereinafter, each additive will be described.

1.4.1. Oxidizing agent The chemical mechanical polishing aqueous dispersion according to the present embodiment may further contain an oxidizing agent as necessary. The oxidizing agent has an effect of facilitating polishing by creating a fragile modified layer on the surface of the metal film by oxidizing the surface of the metal film and promoting a complexing reaction with the polishing liquid component. In addition, although the iron acid ion mentioned above also has a function as an oxidizing agent, in this invention, an "oxidizing agent" means components other than a ferric acid ion.

Examples of the oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, ferric nitrate, diammonium cerium nitrate, iron sulfate, hypochlorous acid, ozone, potassium periodate, and peracetic acid. These oxidizing agents may be used individually by 1 type, and may be used in combination of 2 or more type. Of these oxidizing agents, at least one selected from ammonium persulfate, potassium persulfate and hydrogen peroxide is preferable in view of oxidizing power, compatibility with the protective film, ease of handling, and the like.

In particular, in the case of an aqueous dispersion for chemical mechanical polishing for tungsten films, it is preferable to contain at least one selected from hydrogen peroxide and ammonium persulfate (hereinafter also referred to as “specific oxidizing agent”). When ammonium persulfate is added to the chemical mechanical polishing aqueous dispersion, it is considered that a part of the water in the aqueous dispersion is oxidized by ammonium persulfate to generate hydrogen peroxide. As a result, although the effect is weaker than when the equivalent amount of hydrogen peroxide is directly added, the same effect as when hydrogen peroxide is added can be expected.

In the case of a chemical mechanical polishing aqueous dispersion for a tungsten film, it is considered that a reaction represented by the following formula (2) is promoted by using ferrate ions and a specific oxidizing agent in combination.
W + K ₂ FeO ₄ + H ₂ O ₂ → FeWO ₄ + 2KOH (2)
It is considered that such a reaction oxidizes the surface of the tungsten film and creates a fragile modified layer on the surface of the tungsten film, thereby making it easy to polish the tungsten film. As described above, the polishing rate for the tungsten film can be greatly improved by the synergistic effect obtained by using the ferrate ion and the specific oxidizing agent in combination as compared with the case of using them alone.

The content of the oxidizing agent is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, particularly preferably based on the total mass of the chemical mechanical polishing aqueous dispersion. Is 0.5 mass% or more and 1.5 mass% or less. When the content of the oxidizing agent is within the above range, the reaction represented by the formula (2) can be further promoted, which is preferable.

1.4.2. Water-soluble polymer The chemical mechanical polishing aqueous dispersion according to this embodiment may further contain a water-soluble polymer as necessary. The water-soluble polymer has the effect of suppressing the occurrence of dishing and the like and further improving the flatness of the surface to be polished by adsorbing to the surface of the surface to be polished and forming a film. In particular, when the surface to be polished contains a tungsten film, there is an effect of controlling the polishing of the tungsten film by easily adsorbing to the surface of the tungsten film having irregularities to form a protective film. That is, by using an appropriate amount of the water-soluble polymer, it is possible to progress the polishing of the convex portion while protecting the concave portion of the tungsten film, thereby eliminating the initial step.

The water-soluble polymer is not particularly limited, and examples thereof include an anionic polymer, a cationic polymer, and a nonionic polymer. Examples of the anionic polymer include polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, and salts thereof. Examples of the cationic polymer include polyalkyleneimine, polyvinylpyrrolidone, polyvinylamine, polyvinylpyridine, polyallylamine, polyvinylpiperazine, polylysine, and polyvinylimidazole. Among these cationic polymers, polyalkyleneimine is preferable, and polyethyleneimine is more preferable. Examples of nonionic polymers include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylamide and the like. These water-soluble polymers may be used individually by 1 type, and may be used in combination of 2 or more type.

The number average molecular weight of the water-soluble polymer is preferably 200 or more and 1,000,000 or less, more preferably 10,000 or more and 100,000 or less. In the present invention, the “number average molecular weight” is a value in pullulan conversion, and gel permeation chromatography (column model number “Shodex Asahipak GF-710HQ + GF-510HQ + GF-310HQ” manufactured by Showa Denko KK, eluent “0.2M mono Ethanolamine aqueous solution ").

The content of the water-soluble polymer is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 1% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. is there. When the number average molecular weight and the content of the water-soluble polymer are in the above ranges, when the tungsten film is included in the surface to be polished, the polishing friction can be appropriately reduced by the protective film formed on the surface of the tungsten film. Therefore, the flatness of the tungsten film can be further improved.

1.4.3. Surfactant The chemical mechanical polishing aqueous dispersion according to the present embodiment may further contain a surfactant as necessary. The surfactant has an effect of imparting an appropriate viscosity to the chemical mechanical polishing aqueous dispersion. The viscosity of the chemical mechanical polishing aqueous dispersion is preferably adjusted to be 0.5 mPa · s or more and less than 10 mPa · s at 25 ° C. By applying an appropriate viscosity to the chemical mechanical polishing aqueous dispersion, the pressure applied to the polishing pad can be transmitted efficiently and uniformly to the surface to be polished, and in particular the flatness of the surface to be polished. Can be improved.

The surfactant is not particularly limited, and examples thereof include anionic surfactants, cationic surfactants, and nonionic surfactants. Examples of anionic surfactants include carboxylates such as fatty acid soaps and alkyl ether carboxylates; sulfonates such as alkylbenzene sulfonates, alkylnaphthalene sulfonates, and α-olefin sulfonates; higher alcohol sulfates Salts, sulfates such as alkyl ether sulfates and polyoxyethylene alkylphenyl ether sulfates; phosphate ester salts such as alkyl phosphates; and fluorine-containing surfactants such as perfluoroalkyl compounds. Examples of the cationic surfactant include aliphatic amine salts and aliphatic ammonium salts. Examples of the nonionic surfactant include a nonionic surfactant having a triple bond such as acetylene glycol, acetylene glycol ethylene oxide adduct, and acetylene alcohol; a polyethylene glycol type surfactant. Polyvinyl alcohol, cyclodextrin, polyvinyl methyl ether, hydroxyethyl cellulose and the like can also be used. Among the surfactants exemplified above, alkylbenzene sulfonate is preferable, and potassium dodecylbenzenesulfonate and ammonium dodecylbenzenesulfonate are more preferable from the viewpoint of polishing while maintaining flatness with respect to the tungsten film in the first polishing step. These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the surfactant is preferably 0.001% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. Especially preferably, it is 0.05 mass% or more and 0.2 mass% or less. When the content of the surfactant is in the above range, polishing can be performed while suppressing the occurrence of dishing on the surface to be polished, so that the flatness of the surface to be polished can be further improved.

1.4.4. Amino acid The chemical mechanical polishing aqueous dispersion according to the present embodiment may further contain an amino acid as necessary. Amino acids have the property of easily forming coordinate bonds with copper ions. Therefore, when the surface to be polished contains a copper film, amino acids form a coordinate bond on the surface of the copper film. By this action, it is possible to ensure high flatness of the surface to be polished while suppressing surface roughness of the copper film. As mentioned above, amino acids are excellent in affinity with copper film and copper ion, so it is possible to improve the polishing rate for copper film and to elute into aqueous dispersion for chemical mechanical polishing by polishing copper film By forming a coordinate bond with the copper ion, the precipitation of copper can be suppressed. By suppressing the precipitation of copper in the chemical mechanical polishing aqueous dispersion, it is possible to suppress the occurrence of polishing defects such as scratches on the copper film.

Examples of amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, parin and the like. . These amino acids can be used alone or in combination of two or more.

The chemical mechanical polishing aqueous dispersion according to the present embodiment preferably contains at least one selected from glycine, alanine and glutamine among the amino acids exemplified above. This is because glycine, alanine, and glutamine have a stronger effect of increasing the polishing rate for the copper film because the action of forming a coordination bond with copper ions is stronger among the amino acids exemplified above. Among these, it is particularly preferable to contain glycine having such a high effect.

The amino acid content is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less, and particularly preferably 2% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. % To 4% by mass.

1.4.5. Complexing agent The chemical mechanical polishing aqueous dispersion according to the present embodiment may further contain a complexing agent as required. The complexing agent forms a water-insoluble complex with tungsten and has an effect of protecting the surface of the polished surface. By this function and effect, polishing of the convex portion can be advanced while protecting the concave portion of the tungsten film, and the initial step can be eliminated. Here, “water-insoluble” means that it does not substantially dissolve in water, and poor water solubility is included if the wet etching rate in the state of coexisting with the oxidizing agent is less than 3 nm / min.

The complexing agent is preferably a compound having at least a heterocyclic ring in the structure, and includes at least one heterocyclic ring selected from a heterocyclic 5-membered ring and a heterocyclic 6-membered ring having a nitrogen atom in the structure. More preferably, it is a compound having Examples of the heterocyclic ring include a hetero five-membered ring such as a pyrrole structure, an imidazole structure, and a triazole structure; a hetero six-membered ring such as a pyridine structure, a pyrimidine structure, a pyridazine structure, and a pyrazine structure.

Such a heterocyclic ring may form a condensed ring. Examples of such a heterocyclic ring include indole structure, isoindole structure, benzimidazole structure, benzotriazole structure, quinoline structure, isoquinoline structure, quinazoline structure, cinnoline structure, phthalazine structure, quinoxaline structure, acridine structure and the like.

Among these compounds having a heterocyclic ring, a compound having a pyridine structure, a quinoline structure, a benzimidazole structure, or a benzotriazole structure is preferable. More specifically, quinolinic acid, quinaldic acid, benzimidazole, and benzotriazole are preferable, and quinolinic acid and quinaldic acid are more preferable. These complexing agents may be used alone or in combination of two or more.

The content of the complexing agent is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.02% by mass or more and 5% by mass or less, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. Especially preferably, it is 0.1 mass% or more and 2 mass% or less. When the content of the complexing agent is in the above range, polishing can be performed while eliminating the initial level difference of the tungsten film, so that the flatness of the surface to be polished can be further improved.

1.4.6. pH adjuster The chemical mechanical polishing aqueous dispersion according to the present embodiment may further contain a pH adjuster as necessary. Examples of the pH adjuster include basic salts such as potassium hydroxide, ethylenediamine and TMAH (tetramethylammonium hydroxide); organic acids such as phthalic acid, maleic acid and citric acid and salts thereof; nitric acid, hydrochloric acid, sulfuric acid and the like. Examples thereof include inorganic acids and salts thereof.

In particular, the pH adjuster having two or more carboxyl groups exemplified above has a high coordination ability not only for the wiring metal but also for the metal species that generate stable polyvalent ions used in the barrier metal film. Therefore, the polyvalent ions generated by polishing the wiring metal and the barrier metal film can be stabilized and the precipitation of the metal salt can be reduced. Thereby, the surface roughness of the surface to be polished can be suppressed and high flatness can be obtained, and the occurrence of surface defects such as scratches can be reduced.

1.5. pH
The pH of the chemical mechanical polishing aqueous dispersion according to this embodiment is not particularly limited, but is preferably 1 or more and 10 or less. When the chemical mechanical polishing aqueous dispersion according to this embodiment is used, the pH is preferably 1 or more and 6 or less. In particular, when the pH of the chemical mechanical polishing aqueous dispersion for the tungsten film is within the above range, the reactivity between the chemical mechanical polishing aqueous dispersion and the tungsten film is improved, and the ferric acid ions have an optimum oxidizing power. This is preferable because it can be shown. On the other hand, when the chemical mechanical polishing aqueous dispersion according to the present embodiment is stored, the pH is preferably 7 or more and 10 or less. It is preferable that the pH of the chemical mechanical polishing aqueous dispersion is basic within the above range because decomposition of ferrate ions can be suppressed and the storage stability of the chemical mechanical polishing aqueous dispersion can be increased.

1.6. Application One of the applications of the chemical mechanical polishing aqueous dispersion according to the present embodiment is an application as an abrasive for polishing a copper film forming a wiring of a semiconductor device. Specifically, it can be used as an abrasive when forming Cu damascene wiring. The process of forming the Cu damascene wiring by polishing mainly comprises a first polishing process for removing the copper film and a second polishing process for mainly removing the conductive barrier metal film formed under the copper film. The chemical mechanical polishing aqueous dispersion is effective when used in the first polishing step. The chemical mechanical polishing aqueous dispersion according to the present embodiment can be used in the second polishing step because it can achieve both a high polishing rate and a high flatness for the metal film.

In the first polishing step, the deposited copper film is polished at a high speed until the barrier metal film is exposed (bulk polishing process), and the copper film remaining in the bulk polishing process is exposed until the barrier metal film is exposed. There are cases where the process is divided into a polishing process (fine polishing process). The chemical mechanical polishing aqueous dispersion according to the present embodiment is effective when used in a bulk polishing step because it can polish a copper film as a wiring material at high speed while maintaining flatness.

Another application of the chemical mechanical polishing aqueous dispersion according to the present embodiment is an application as an abrasive for polishing a tungsten film forming a wiring of a semiconductor device. Specifically, it can be used in a chemical mechanical polishing step when forming a via connection tungsten plug.

Examples of the object to be processed include an object to be processed including an insulating film having a via hole and a tungsten film provided on the insulating film via a barrier metal film. The chemical mechanical polishing process of the object to be processed mainly includes a first polishing process for mainly removing the tungsten film and a second polishing process for simultaneously polishing the tungsten film, the barrier metal film, and the insulating film formed mainly under the tungsten film. However, the chemical mechanical polishing aqueous dispersion according to the present embodiment is effective when used in the first polishing step from the viewpoint of having a high polishing rate for the tungsten film. The chemical mechanical polishing aqueous dispersion according to the present embodiment has non-selective polishing properties with respect to the tungsten film and the silicon oxide film, and therefore may be used in the second polishing step.

2. Chemical mechanical polishing method The chemical mechanical polishing method according to the present embodiment polishes a semiconductor substrate (such as a wafer) containing a copper film or a tungsten film using the chemical mechanical polishing aqueous dispersion according to the present invention described above. Features. Hereinafter, a first specific example and a second specific example of the chemical mechanical polishing method according to the present embodiment will be described in detail with reference to the drawings.

2.1. First Specific Example 2.1.1. FIG. 1 is a cross-sectional view schematically showing a target object suitable for use in the chemical mechanical polishing method according to the first specific example. The target object 100 is formed through the following steps (1) to (4).

(1) First, as shown in FIG. 1, a base 10 is prepared. The base 10 may be composed of, for example, a silicon substrate and a silicon oxide film formed thereon. Furthermore, a functional device such as a transistor (not shown) may be formed on the base 10. Next, a silicon oxide film 12 that is an insulating film is formed on the substrate 10 by using a CVD method or a thermal oxidation method.

(2) Next, the silicon oxide film 12 is patterned. Using the obtained pattern as a mask, wiring trenches 14 are formed in the silicon oxide film 12 by photolithography.

(3) Next, a barrier metal film 16 is formed on the surface and inner wall surface of the silicon oxide film 12 by applying sputtering. The electrical contact between the copper film and the silicon oxide film 12 is not very good, but good electrical contact is realized by interposing the barrier metal film 16. Examples of the material of the barrier metal film 16 include tantalum, tantalum nitride, titanium, and titanium nitride.

(4) Next, the copper film 18 is formed by applying the CVD method. The copper forming the copper film 18 includes not only pure copper but also an alloy containing 95% by weight or more of copper, such as copper-silicon and copper-aluminum.

2.1.2. Polishing method 2.1.2.1. First Polishing Step FIG. 2 is a cross-sectional view schematically showing an object to be processed at the end of the first polishing step of the first specific example. As shown in FIG. 2, the first polishing step is a step of polishing the copper film 18 using the chemical mechanical polishing aqueous dispersion according to the present invention until the barrier metal film 16 is exposed. According to this step, by using the chemical mechanical polishing aqueous dispersion described above, the metal contamination of the object 100 is reduced, and the high polishing rate for the copper film 18 and the high flatness of the surface to be polished are compatible. Can be made.

2.1.2.2. Second Polishing Step FIG. 3 is a cross-sectional view schematically showing an object to be processed at the end of the second polishing step of the first specific example. As shown in FIG. 3, the second polishing step is a step of polishing the barrier metal film 16 and the copper film 18 using the chemical mechanical polishing aqueous dispersion until the silicon oxide film 12 is exposed. The chemical mechanical polishing aqueous dispersion according to the present invention described above may be used in the second polishing step because it can achieve both a high polishing rate and high flatness for the metal film.

2.2. Second specific example 2.2.1. To-be-processed object FIG. 4: is sectional drawing which showed typically the to-be-processed object suitable for use of the chemical mechanical polishing method which concerns on a 2nd example. The object 200 is formed through the following steps (1) to (4).

(1) First, as shown in FIG. 4, a base 11 is prepared. The base 11 may be composed of, for example, a silicon substrate and a silicon oxide film formed thereon. Furthermore, a functional device such as a transistor (not shown) may be formed on the base 11. Next, a silicon oxide film 13 that is an insulating film is formed on the substrate 11 by using a CVD method or a thermal oxidation method.

(2) Next, the silicon oxide film 13 is patterned. Via holes 15 are formed in the silicon oxide film 13 by photolithography using the obtained pattern as a mask.

(3) Next, a barrier metal film 17 is formed on the surface and inner wall surface of the silicon oxide film 13 by applying sputtering. The electrical contact between the tungsten film and the silicon oxide film 13 is not very good, but good electrical contact is realized by interposing the barrier metal film 17. Examples of the material of the barrier metal film 17 include tantalum, tantalum nitride, titanium, and titanium nitride.

(4) Next, the tungsten film 19 is formed by applying the CVD method.

2.2.2. Chemical mechanical polishing method 2.2.2.1. First Polishing Step FIG. 5 is a cross-sectional view schematically showing an object to be processed at the end of the first polishing step of the second specific example. As shown in FIG. 5, the first polishing step is a step of polishing the tungsten film 19 using the chemical mechanical polishing aqueous dispersion according to the present invention until the barrier metal film 17 is exposed. According to this step, by using the chemical mechanical polishing aqueous dispersion according to the present invention described above, metal contamination of the object to be processed 200 is suppressed, and a high polishing rate for the tungsten film 19 and a high flatness on the surface to be polished are provided. It is possible to balance the sex.

2.2.2.2. Second Polishing Step FIG. 6 is a cross-sectional view schematically showing an object to be processed at the end of the second polishing step of the second specific example. As shown in FIG. 6, the second polishing step is a step of polishing the barrier metal film 17 and the tungsten film 19 using the chemical mechanical polishing aqueous dispersion until the silicon oxide film 13 is exposed. Note that the chemical mechanical polishing aqueous dispersion according to the present invention described above may be used in the second polishing step because it has non-selective polishing properties with respect to the tungsten film and the silicon oxide film. By using the chemical mechanical polishing aqueous dispersion according to the present invention in the second polishing step, it is possible to obtain a finished surface with extremely excellent flatness.

2.3. Chemical Mechanical Polishing Device For the first polishing step and the second polishing step described above, for example, a polishing device 300 as shown in FIG. 7 can be used. FIG. 7 is a perspective view schematically showing the polishing apparatus 300. In each polishing step, a carrier (a chemical mechanical polishing aqueous dispersion) 44 is supplied from a slurry supply nozzle 42, and a carrier head 52 holding a semiconductor substrate 50 while rotating a turntable 48 to which a polishing cloth 46 is attached. This is done by bringing them into contact. In FIG. 7, the water supply nozzle 54 and the dresser 56 are also shown.

The polishing load of the carrier head 52 can be selected within the range of 0.7 to 70 psi, preferably 2.1 to 35 psi. Further, the rotational speeds of the turntable 48 and the carrier head 52 can be appropriately selected within the range of 10 to 400 rpm, and preferably 30 to 150 rpm. The flow rate of the slurry (polishing composition) 44 supplied from the slurry supply nozzle 42 can be selected within the range of 10 to 1,000 mL / min, and preferably 50 to 400 mL / min.

Examples of commercially available polishing apparatuses include Ebara Seisakusho, Model “EPO-112”, “EPO-222”; Lap Master SFT, Model “LGP-510”, “LGP-552”; Applied Materials, Model “Mirra”, “Reflexion” and the like can be mentioned.

3. Chemical Mechanical Polishing Aqueous Dispersion Preparation Kit The chemical mechanical polishing aqueous dispersion according to the present embodiment is directly mixed with abrasive grains, compounds that form ferrate ions, and other additives in pure water. -It can be prepared by stirring. The chemical mechanical polishing aqueous dispersion thus obtained may be used as it is, but a chemical mechanical polishing aqueous dispersion containing each component in a high concentration (concentrated) is prepared and desired at the time of use. It may be used after diluting to a concentration of.

Also, it is possible to prepare a kit in which a plurality of liquids (for example, two or three liquids) containing any of the above components are prepared and mixed at the time of use. Storage stability can be improved by dividing into a plurality of liquids containing any of the above components. In this case, after preparing a chemical mechanical polishing aqueous dispersion by mixing a plurality of liquids, this may be supplied to the chemical mechanical polishing apparatus, or a plurality of liquids may be supplied individually to the chemical mechanical polishing apparatus. A chemical mechanical polishing aqueous dispersion may be prepared on a surface plate.

Hereinafter, a most preferred embodiment will be described as a chemical mechanical polishing aqueous dispersion preparation kit according to the present invention.

A chemical mechanical polishing aqueous dispersion preparation kit according to an embodiment of the present invention is a kit for preparing the chemical mechanical polishing aqueous dispersion described above, and includes ferrate ions (FeO ₄ ²⁻ ) and It contains the 1st composition containing water, and the 2nd composition containing an abrasive grain and a dispersion medium, It is characterized by the above-mentioned.

The first composition can be prepared by dissolving in water at least one selected from ferrates such as potassium ferrate, barium ferrate, sodium ferrate and ammonium ferrate. The ferrate ion contained in the first composition is particularly unstable under neutral to acidic conditions. Therefore, the pH of the first composition is preferably 7 or more and 10 or less, and more preferably 8 or more and 10 or less. In addition, since ferrate ions have a property of being decomposed by light, when storing the first composition, it is preferable to store it in a light-shielding container or the like. In addition, it is desirable not to add other additives to the first composition from the viewpoint of preventing the reaction between ferrate ions and other components and the decomposition of the ferrate ions.

The second composition can be prepared by adding abrasive grains to the dispersion medium. Other additives may be added to the second composition as long as the dispersion stability of the abrasive grains is not impaired.

According to such a chemical mechanical polishing aqueous dispersion preparation kit, a chemically unstable ferric acid ion (FeO ₄ ²⁻ ) is stored separately from other components, so that the ferric acid ion (FeO ₄ ^2- ) Decomposition can be suppressed. If the chemical mechanical polishing aqueous dispersion is prepared by mixing the first composition and the second composition immediately before use, the performance of the chemical mechanical polishing aqueous dispersion can be maximized.

The chemical mechanical polishing aqueous dispersion preparation kit according to the present embodiment is prepared by dissolving at least one selected from hydrogen peroxide, potassium persulfate and ammonium persulfate in water. A composition may be included. In addition, it is desirable not to add another additive to a 3rd composition from a viewpoint of preventing reaction of an oxidizing agent and another component, or decomposition | disassembly of an oxidizing agent.

In addition, it is preferable that the first composition and the third composition are mixed as much as possible just before the chemical mechanical polishing is performed and used in a short time after mixing. The time from mixing to chemical mechanical polishing is preferably 1 second to 7 days later, more preferably 1 second to 1 hour later. Further, since it is not preferable in terms of quality to mix and use an old mixed solution and a new mixed solution, it is desirable to perform line mixing or batch mixing.

4). Examples Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to these examples.

4.1. Preparation of aqueous dispersion for chemical mechanical polishing 4.1.1. Preparation of Colloidal Silica Water Dispersion No. 3 water glass (silica concentration: 24% by mass) was diluted with water to obtain a diluted sodium silicate aqueous solution having a silica concentration of 3.0% by mass. This diluted sodium silicate aqueous solution was passed through a hydrogen-type cation exchange resin layer to obtain a pH 3.1 active silicic acid aqueous solution from which most of the sodium ions were removed. Thereafter, 10% by weight aqueous potassium hydroxide solution was immediately added with stirring to adjust the pH to 7.2, followed by further heating and boiling for 3 hours. To the resulting aqueous solution, 10 times the amount of the active silicic acid aqueous solution whose pH was previously adjusted to 7.2 was added little by little to grow colloidal silica.

Next, the aqueous dispersion containing the colloidal silica was concentrated under reduced pressure to obtain an aqueous colloidal silica dispersion having a silica concentration of 32.0% by mass and a pH of 9.8. This colloidal silica aqueous dispersion was passed again through the hydrogen-type cation exchange resin layer to remove most of the sodium, and then added with a 10% by mass potassium hydroxide aqueous solution to obtain a silica particle concentration of 28.0% by mass, A colloidal silica aqueous dispersion (a) having a pH of 10.0 was obtained.

The average particle size calculated from the specific surface area measured using the BET method was 45 nm. In the measurement of the surface area of the colloidal silica particles by the BET method, the value obtained by measuring the colloidal silica recovered by concentrating and drying the silica particle dispersion was used. For measurement of the specific surface area, a flow-type specific surface area automatic measuring device (manufactured by Shimadzu Corporation, “micrometrics FlowSorb II 2300”) was used.

Further, a colloidal silica aqueous dispersion having an average particle diameter of 80 nm calculated from the specific surface area measured using the BET method by the same method as described above while controlling the heat aging time, the type and amount of the basic compound, etc. (B) was obtained.

4.1.2. Preparation of aqueous dispersion for chemical mechanical polishing 50 parts by mass of ion-exchanged water, colloidal silica aqueous dispersion (a) equivalent to 3 parts by mass in terms of silica, colloidal silica water equivalent to 3 parts by mass in terms of silica Dispersion (b), 0.006 parts by mass of potassium ferrate, and 0.1 parts by mass of maleic acid were placed in a polyethylene bottle and stirred for 15 minutes. At this time, potassium ferrate was prepared using “Ferrator” which is an iron acid production machine manufactured by Ferrate Treatment Technologies. Finally, ion-exchanged water was added to a polyethylene bottle so that the total amount of all components was 100 parts by mass, and then filtered with a filter having a pore size of 1 μm to obtain a chemical mechanical polishing aqueous dispersion A. .

Further, except that potassium ferrate was changed to the components / addition amounts shown in Table 1 and the type of additive was changed to the components / addition amounts shown in Table 1, the preparation method of the chemical mechanical polishing aqueous dispersion A and Similarly, chemical mechanical polishing aqueous dispersions BX were obtained.

4.2. Evaluation test of chemical mechanical polishing aqueous dispersion 4.2.1. Evaluation test on copper film 4.2.1.1. Polishing rate evaluation of copper film A polishing pad (Applied Materials, model “Mirra”) is equipped with a porous polyurethane polishing pad (Rodel Nitta, product number “IC1000”) and polishing compositions A to A While supplying any one of L, the following polishing rate measurement substrate was polished for 30 seconds under the following polishing conditions, and the polishing rate was calculated by the following method.
(A) A polishing rate measurement substrate / a silicon substrate with an 8-inch thermal oxide film provided with a 15,000 mm thick copper film.
(B) Polishing conditions / carrier head rotation speed: 100 rpm
・ Turntable rotation speed: 100rpm
Carrier head load: 3.5 psi
Polishing composition supply rate: 200 mL / min The polishing composition supply rate in this case refers to a value obtained by assigning the total supply amount of all the supply liquids per unit time.
(C) Calculation method of polishing rate The film thickness before and after the polishing process was measured by using an electrically conductive film thickness measuring instrument (manufactured by KLA-Tencor Corporation, model “Omnimap RS75”), and the film thickness decreased by polishing. The polishing rate was calculated from the polishing time. The results are also shown in Table 1.
The polishing rate for the copper film is preferably 50 nm / min or more under the above conditions. In this case, “◯” is shown in the evaluation column in Table 1. In addition, when the polishing rate for the copper film was less than 50 nm / min, it was indicated as “x” in the column of evaluation in the table because it could not be applied to an actual device.

4.2.1.2. Evaluation of Flatness of Patterned Wafer It is known that in a chemical mechanical polishing of a patterned wafer on which a groove serving as a wiring pattern is formed, a portion that is excessively polished locally occurs. This is because the surface of the pattern wafer before chemical mechanical polishing has irregularities reflecting the grooves that form wiring patterns formed on the surface of the metal film, and when chemical mechanical polishing is performed, a locally high pressure is applied according to the pattern density. This is because the polishing speed of the portion increases. For this reason, by polishing and evaluating a patterned wafer imitating a semiconductor substrate, the polishing characteristics of the chemical mechanical polishing aqueous dispersion according to this example in the state of actual use were confirmed.

For the wafer with the following pattern, the polishing process was performed in the same manner as the polishing conditions in “4.2.1.1. Evaluation of polishing rate of copper film” except that the polishing time was 1 minute. The flatness and the presence or absence of defects were evaluated. The results are also shown in Table 1.
(1) Patterned substrate An 8-inch wafer on which a 400 nm PETEOS film is formed is processed into a “SEMATECH 854” pattern to form a groove pattern having a depth of 400 nm, and then a 25 nm Ti / TiN film is further laminated. A test substrate on which a copper film was laminated (manufactured by SEMATECH INTERNIONAL) was used.
(2) Evaluation of flatness For the surface to be polished of the patterned wafer after the polishing process, a copper wiring width (line, L) / insulating film width is used using a high resolution profiler (model “HRP240ETCH” manufactured by KLA Tencor). The dishing amount (nm) in the copper wiring part having (space, S) of 100 μm / 100 μm was measured. It can be determined that the dishing amount is preferably 0 to 100 nm, more preferably 0 to 90 nm, and particularly preferably 0 to 60 nm.
When the dishing amount was 0 to 100 nm, “◯” was written in the evaluation column in Table 1. In addition, when the dishing amount is 100 nm or more, “x” is written in the evaluation column in the table, indicating that adaptation to an actual device is impossible.

4.2.1.3. Evaluation of amount of residual iron in copper film Polishing was performed using (a) polishing rate measurement substrate and (b) polishing conditions in the same manner as described in “4.2.1.1. Evaluation of polishing rate of copper film” as follows. Thus, the residual iron content of the copper film was evaluated. The amount of residual iron was subjected to surface analysis of the surface to be polished using a total reflection X-ray fluorescence analyzer (manufactured by Rigaku Corporation, “TXRF V300”). More specifically, an area of 60 mm from the center of a polished 8-inch wafer is irradiated with 8 kiloeV X-rays, and the concentration and amount are estimated from the type and intensity of the element from the wavelength of fluorescent X-rays generated from the area. be able to. Since an iron-based compound is contained as an additive, the above-mentioned detected concentration was obtained from the intensity of the fluorescent X-ray at 0.3 nm that appears specifically when iron was present. The results are also shown in Table 1. The amount of residual iron is preferably 0.2 × 10 ¹⁰ atoms / cm ² or less in view of device performance. In this case, “○” was written in the evaluation column in the table. Further, if it exceeds 0.20 × ^{10 10} atoms / cm ^2, as the application to an actual device is impossible, it indicated as "×" in the column of evaluation in the table.

4.2.2. Evaluation test on tungsten film 4.2.2.1. Polishing rate evaluation of tungsten film A chemical mechanical polishing device (Applied Materials, Model “Mirra”) is equipped with a porous polyurethane polishing pad (Rodel Nitta, product number “IC1000”) and water for chemical mechanical polishing. While supplying any one of the system dispersions M to X, the following polishing rate measurement substrate was subjected to polishing treatment for 30 seconds under the following polishing conditions, and the polishing rate was calculated by the following method.
(A) A polishing rate measuring substrate / a silicon substrate with an 8-inch thermal oxide film provided with a 8,000 mm thick tungsten film.
(B) Polishing conditions / carrier head rotation speed: 80 rpm
・ Turntable rotation speed: 80rpm
Carrier head load: 3.5 psi
Supply rate of chemical mechanical polishing aqueous dispersion: 120 mL / min The supply rate of chemical mechanical polishing aqueous dispersion in this case refers to a value obtained by assigning the total supply amount of all supply liquids per unit time.
(C) Calculation method of polishing rate The film thickness before and after the polishing process was measured by using an electrically conductive film thickness measuring instrument (manufactured by KLA-Tencor Corporation, model “Omnimap RS75”), and the film thickness decreased by polishing. The polishing rate was calculated from the polishing time. The results are also shown in Table 2.
The polishing rate for the tungsten film is preferably 40 nm / min or more under the above conditions. In this case, “◯” is shown in the evaluation column in Table 1. Further, it is more preferably 100 nm / min or more. In this case, “◎” is shown in the evaluation column in Table 1. On the other hand, when the polishing rate for the tungsten film was less than 40 nm / min, it was indicated as “x” in the column of evaluation in the table, indicating that it could not be applied to an actual device.

4.2.2.2. Evaluation of flatness of patterned wafer The polishing treatment was performed in the same manner as the polishing conditions in “4.2.2.1. Evaluation of Polishing Rate of Tungsten Film” except that the polishing time was 1 minute for the following patterned wafer. The flatness and the presence or absence of defects were evaluated by the following method. The results are also shown in Table 2.
(1) Patterned substrate An 8-inch wafer on which a 400 nm PETEOS film is formed is processed into a “SEMATECH 854” pattern to form a groove pattern having a depth of 400 nm, and then a 25 nm Ti / TiN film is further laminated. A test substrate (manufactured by SEMATECH INTERNATIONAL) on which a tungsten film was laminated was used.
(2) Evaluation of flatness Using a high-resolution profiler (model “HRP240ETCH” manufactured by KLA Tencor) for the polished surface of the patterned wafer after the polishing process step, the tungsten wiring width (line, L) / insulating film width The dishing amount (nm) in the tungsten wiring portion having (space, S) of 100 μm / 100 μm was measured. It can be determined that the dishing amount is preferably 0 to 100 nm, more preferably 0 to 90 nm, and particularly preferably 0 to 60 nm. When the dishing amount was 0 to 100 nm, “◯” was written in the evaluation column in Table 1. In addition, when the flatness is 100 nm or more, “x” is written in the column of evaluation in the table, indicating that adaptation to an actual device is impossible.

4.2.3. Evaluation of residual iron content of tungsten film Polishing was performed using the same (a) polishing rate measurement substrate and (b) polishing conditions in “4.2.2.1. Evaluation of polishing rate of tungsten film”. The residual iron amount of the tungsten film was evaluated in the same manner as described in “2.1.3.

4.3. Evaluation results 4.3.1. Evaluation results in copper film When the chemical mechanical polishing aqueous dispersions of Examples 1 to 5 are used, a high polishing rate is achieved in polishing the copper film, and a polished surface with a sufficiently small residual iron content is obtained. I was able to. From the results of Examples 1 to 5, it was found that the polishing rate for the copper film increases as the ferrate ion concentration increases.

The chemical mechanical polishing aqueous dispersions of Examples 6 to 7 correspond to compositions obtained by further adding malonic acid and glycine to Example 1. Even when the chemical mechanical polishing aqueous dispersions of Examples 6 to 7 were used, almost the same performance as Example 1 could be obtained.

The chemical mechanical polishing aqueous dispersions of Examples 8 to 9 correspond to compositions obtained by further adding hydrogen peroxide or ammonium persulfate as the oxidizing agent to Example 1. When the chemical mechanical polishing aqueous dispersions of Examples 8 to 9 were used, the polishing rate for the copper film could be further increased as compared with Example 1.

The chemical mechanical polishing aqueous dispersions of Comparative Examples 1 and 2 correspond to compositions in which ferric nitrate is added instead of potassium ferrate. The ferric nitrate content in the chemical mechanical polishing aqueous dispersion of Comparative Example 1 was 0.006 parts by mass equivalent to the potassium ferrate content in the chemical mechanical polishing aqueous dispersion of Example 1. . However, with ferric nitrate, the polishing rate for the copper film was 20 nm / min, and a sufficient polishing rate could not be obtained. On the other hand, since the ferric nitrate content in the chemical mechanical polishing aqueous dispersion of Comparative Example 2 was 6 parts by mass, a sufficient polishing rate for the copper film was obtained, but residual contamination of iron occurred.

Since the chemical mechanical polishing aqueous dispersion of Comparative Example 3 did not contain potassium ferrate or ferric nitrate, a sufficient polishing rate for the copper film could not be obtained.

4.3.2. Evaluation Results in Tungsten Film When the chemical mechanical polishing aqueous dispersions of Examples 10 to 14 are used, a high polishing rate is achieved in polishing the tungsten film, and a polished surface with a sufficiently small residual iron content is obtained. I was able to. From the results of Examples 10 to 14, it was found that the polishing rate for the tungsten film increases as the ferrate ion concentration increases.

The chemical mechanical polishing aqueous dispersions of Examples 15 to 16 correspond to compositions obtained by further adding malonic acid and glycine to Example 10. Even when the chemical mechanical polishing aqueous dispersions of Examples 15 to 16 were used, almost the same performance as Example 10 could be obtained.

The chemical mechanical polishing aqueous dispersion of Example 17 corresponds to a composition in which ammonium persulfate is added as an oxidizing agent. From the result of Example 17, it was estimated that the improvement of the polishing rate for the tungsten film was smaller than that in the case where an equivalent amount of hydrogen peroxide was added, but it was found that application to an actual device is possible.

The chemical mechanical polishing aqueous dispersions of Comparative Examples 4 to 5 correspond to compositions in which ferric nitrate is added instead of potassium ferrate. The ferric nitrate content in the chemical mechanical polishing aqueous dispersion of Comparative Example 4 was 0.006 parts by mass equivalent to the potassium ferrate content in the chemical mechanical polishing aqueous dispersion of Example 10. . However, with ferric nitrate, the polishing rate for the tungsten film was 30 nm / min, and a sufficient polishing rate could not be obtained. On the other hand, since the ferric nitrate content in the chemical mechanical polishing aqueous dispersion of Comparative Example 5 was 6 parts by mass, a sufficient polishing rate for the tungsten film was obtained, but residual contamination of iron occurred.

Since the chemical mechanical polishing aqueous dispersion of Comparative Example 6 did not contain potassium ferrate or ferric nitrate, a sufficient polishing rate for the tungsten film could not be obtained.

The chemical mechanical polishing aqueous dispersion of Comparative Example 7 corresponds to a composition in which only hydrogen peroxide which is a general oxidizing agent is added without adding potassium ferrate. In this case, the polishing rate for the tungsten film was 30 nm / min, and a sufficient polishing rate could not be obtained.

The polishing composition according to the present invention includes Cu, Al, Ti, TiN, Ta, TaN, V, Mo, Ru, Zr, Mn, Ni, Fe, Ag, Mg, Mn, or Si, It is expected to be effective for polishing a laminated structure including a layer made of any of the above elements or compounds, or a structure having substantially no barrier metal.

10.11 ... Substrate, 12.13 ... Silicon oxide film, 14 .... Wiring groove, 15 .... Via hole, 16.17 ... Barrier metal film, 18 .... Copper film, 19 ... Tungsten film, 42 ... Slurry supply nozzle, 44 ... Slurry (polishing composition), 46 ... polishing cloth, 48 ... turntable, 50 ... semiconductor substrate, 52 ... carrier head, 54 ... water supply nozzle, 56 ... dresser, 100/200 ... target object, 300 ... chemical Mechanical polishing equipment

Claims

Abrasive grains,
Ferrate ions (FeO 4 2− ),
A dispersion medium;
An aqueous dispersion for chemical mechanical polishing, comprising
In claim 1,
An aqueous dispersion for chemical mechanical polishing, wherein the concentration of ferrate ions (FeO 4 2− ) is 10 −6 mol / L or more and 10 −2 mol / L or less.
In claim 1 or claim 2,
An aqueous dispersion for chemical mechanical polishing, wherein the abrasive grains are colloidal silica.
In any one of Claims 1 to 3,
An aqueous dispersion for chemical mechanical polishing, further comprising at least one selected from hydrogen peroxide, potassium persulfate and ammonium persulfate.
The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 4, which is used for polishing a semiconductor substrate including a copper film or a tungsten film.
The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 5, which is prepared by mixing abrasive grains, ferrate, and a dispersion medium.
A kit for preparing the chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 6,
A first composition containing ferrate ions and water;
A second composition containing abrasive grains and a dispersion medium;
A chemical mechanical polishing aqueous dispersion preparation kit.
In claim 7,
A kit for preparing an aqueous dispersion for chemical mechanical polishing, further comprising a third composition containing at least one selected from hydrogen peroxide, potassium persulfate, and ammonium persulfate, and water.
A chemical mechanical polishing method for polishing a semiconductor substrate including a copper film or a tungsten film using the chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 6.