JP2020174083A - Aqueous dispersion for chemical mechanical polishing and chemical mechanical polishing method - Google Patents

Abstract

To provide an aqueous dispersion for chemical mechanical polishing capable of efficiently polishing a substrate including tungsten and suppressing corrosion of the tungsten surface after polishing, and a chemical mechanical polishing method using the same.SOLUTION: An aqueous dispersion for chemical mechanical polishing according to the present invention used for a substrate including tungsten includes (A) abrasive grains, (B) at least one selected from the group consisting of aluminum ions and barium ions, and (C) an oxidizer.SELECTED DRAWING: None

Description

The present invention relates to an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method using the same.

CMP (Chemical Mechanical Polishing) has rapidly become widespread in flattening technology in the manufacture of semiconductor devices. In this CMP, the object to be polished is crimped to the polishing pad, and the object to be polished and the polishing pad are slid with each other while supplying an aqueous dispersion for chemical mechanical polishing on the polishing pad to chemically make the object to be polished. Moreover, it is a technique for mechanically polishing.

In recent years, with the increase in definition of semiconductor devices, the miniaturization of wiring boards made of wiring, plugs, etc. formed in the semiconductor devices has been progressing. Along with this, a method of flattening the wiring board by CMP is used. The wiring board in the semiconductor device includes an insulating film material, a wiring material, a barrier metal material for preventing the wiring material from diffusing into the inorganic material film, and the like. As the wiring material, for example, copper or tungsten is mainly used, and as the barrier metal material, for example, a compound containing titanium, tantalum, or cobalt is mainly used.

Among them, tungsten is used as a wiring material embedded in a via hole in a semiconductor manufacturing process and as a gate electrode in a transistor, and is one of the wiring materials attracting attention. Therefore, an aqueous dispersion for chemical mechanical polishing has been studied for efficiently polishing a substrate containing tungsten. In order to efficiently polish a substrate containing tungsten, it is necessary to make the tungsten surface an oxide that can be easily removed mechanically. Therefore, commercially available aqueous dispersions for chemical mechanical polishing for tungsten are usually oxidized. The agent has been added. However, it is known that when an oxidizing agent is added, excessive tungsten etching (corrosion) occurs in the CMP process.

Therefore, in order to achieve both efficient polishing of the substrate containing tungsten and suppression of corrosion of the tungsten surface after polishing, chemical mechanical polishing containing abrasive grains having a permanent positive charge, an amine compound, and an iron-containing accelerator is used. Compositions have been proposed (see, for example, Patent Document 1).

Special Table 2017-514295

However, while the amine compound added to the chemical mechanical polishing composition described in Patent Document 1 can reduce tungsten etching (corrosion) by protecting the tungsten surface, it can protect tungsten by an excessive protective action. It has also been pointed out that the polishing rate of the including substrate may decrease. That is, it has been difficult to achieve both efficient polishing of a substrate containing tungsten and suppression of corrosion of the surface of tungsten after polishing only by combining abrasive grains having a permanent positive charge and an amine compound.

Therefore, in some aspects of the present invention, an aqueous dispersion for chemical mechanical polishing capable of efficiently polishing a substrate containing tungsten and suppressing corrosion of the tungsten surface after polishing, and chemistry using the same. Provide a mechanical polishing method.

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

One aspect of the aqueous dispersion for chemical mechanical polishing according to the present invention is
An aqueous dispersion for chemical mechanical polishing used for substrates containing tungsten.
(A) Abrasive grains and
(B) At least one selected from the group consisting of aluminum ions and barium ions, and
(C) Oxidizing agent and
Contains.

In one aspect of the aqueous dispersion for chemical mechanical polishing,
The content of the component (B) in the aqueous dispersion for chemical mechanical polishing can be 0.0005 to 0.2% by mass.

In any aspect of the aqueous dispersion for chemical mechanical polishing.
Furthermore, it can contain at least one selected from the group consisting of (D) phosphoric acid, phosphonic acid, and salts thereof.

In any aspect of the aqueous dispersion for chemical mechanical polishing.
The abrasive grains (A) can be abrasive grains having a positive charge.

In any aspect of the aqueous dispersion for chemical mechanical polishing.
The pH can be 4 or less.

In any aspect of the aqueous dispersion for chemical mechanical polishing.
Further, it can contain at least one selected from the group consisting of (E) organic acids and salts thereof.

In any aspect of the aqueous dispersion for chemical mechanical polishing.
Further, (F) a water-soluble polymer can be contained.

One aspect of the chemical mechanical polishing method according to the present invention is
The step of polishing a substrate containing tungsten by using the aqueous dispersion for chemical mechanical polishing according to any one of the above is included.

According to the aqueous dispersion for chemical mechanical polishing according to the present invention, a substrate containing tungsten can be efficiently polished, and corrosion of the tungsten surface after polishing can be suppressed. Further, according to the chemical mechanical polishing method according to the present invention, the surface to be polished with excellent flatness can be obtained by protecting the tungsten surface while efficiently polishing the substrate containing tungsten.

It is a perspective view which shows typically the chemical mechanical polishing apparatus.

Hereinafter, preferred embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and includes various modifications that are carried out without changing the gist of the present invention.

In the present specification, the numerical range described by using "~" means that the numerical values described before and after "~" are included as the lower limit value and the upper limit value.

The "wiring material" refers to a conductive metal material such as copper or tungsten. The "insulating film material" refers to a material such as silicon dioxide, silicon nitride, or amorphous silicon. The "barrier metal material" refers to a material such as titanium, tantalum, and cobalt that is used by being laminated with a wiring material for the purpose of improving the reliability of the wiring.

1. 1. Aqueous dispersion for chemical mechanical polishing The aqueous dispersion for chemical mechanical polishing according to an embodiment of the present invention includes (A) abrasive grains (hereinafter, also referred to as “component (A)”), (B) aluminum ions and It contains at least one selected from the group consisting of barium ions (hereinafter, also referred to as "(B) component") and (C) oxidizing agent (hereinafter, also referred to as "(C) component"). Hereinafter, each component contained in the aqueous dispersion for chemical mechanical polishing according to the present embodiment will be described in detail.

1.1. (A) Abrasive grains The aqueous dispersion for chemical mechanical polishing according to the present embodiment contains (A) abrasive grains. The component (A) has a function of mechanically polishing a substrate containing tungsten to improve the polishing speed of the substrate.

The component (A) is not particularly limited, and examples thereof include oxide particles such as silica particles, ceria particles, alumina particles, zirconia particles, and titania particles. Of these, silica particles are preferable.

The silica particles are not particularly limited, and examples thereof include colloidal silica and fumed silica. Of these, colloidal silica is preferable. Colloidal silica is preferably used from the viewpoint of reducing polishing defects such as scratches.

Further, the component (A) is preferably abrasive grains having a positive charge in the aqueous dispersion for chemical mechanical polishing. Tungsten contained in the substrate to be polished has a negative charge in a wide pH range. Therefore, if the component (A) is an abrasive grain having a positive charge, the component (A) tends to come into close contact with the surface of tungsten due to the electrostatic interaction between the component (A) and the surface of tungsten, and the substrate containing tungsten is formed. It may be possible to polish more efficiently.

The abrasive grains having a positive charge are not particularly limited, and examples thereof include silica particles produced by the method described in JP-A-2018-48042. Specifically, silica particles having a positive charge can be produced by hydrolyzing a solution of alkoxysilane and alkoxysilane having an alkylamino group in a solvent under predetermined conditions. The positively charged silica particles thus obtained can retain the positive charge by setting the pH of the aqueous dispersion for chemical mechanical polishing to 4 or less. Therefore, when the component (A) is the silica particles having the above-mentioned positive charge, the pH of the aqueous dispersion for chemical mechanical polishing is preferably 4 or less.

When the component (A) is an abrasive grain having a positive charge, the zeta potential of the abrasive grain in the aqueous dispersion for chemical mechanical polishing is preferably +5 mV or more, more preferably +20 mV or more, and more preferably +25 mV. The above is particularly preferable. If the component (A) has a zeta potential in the above range, the electrostatic interaction between the component (A) and the surface of tungsten becomes strong, and the substrate having tungsten may be polished more efficiently.

The average particle size of the component (A) is not particularly limited, but the lower limit thereof is preferably 5 nm, more preferably 10 nm, particularly preferably 15 nm, and the upper limit thereof is preferably 300 nm. It is preferably 150 nm, and particularly preferably 100 nm. When the average particle size of the component (A) is within the above range, it may be possible to reduce the occurrence of scratches on the surface to be polished while improving the polishing rate of the substrate containing tungsten. Within the above range, when the average particle size of the component (A) is 10 nm or more, the polishing rate of the substrate containing tungsten may be further improved. Further, when the average particle size of the component (A) is 100 nm or less, the occurrence of scratches on the surface to be polished may be further reduced.

The average particle size of the component (A) can be determined by measuring with a particle size distribution measuring device based on a dynamic light scattering method. As the particle size distribution measuring device by the dynamic light scattering method, the dynamic light scattering type particle size distribution measuring device "LB-550" manufactured by HORIBA, Ltd., the nanoparticle analyzer "DelsaNanoS" manufactured by Beckman Coulter, and Malvern "Zetasizer nanozzs" and the like can be mentioned. The average particle size measured by the dynamic light scattering method represents the average particle size of the secondary particles formed by aggregating a plurality of primary particles.

The lower limit of the content of the component (A) is preferably 0.05% by mass, more preferably 0.1% by mass, and particularly preferably 0.1% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. It is 0.3% by mass. When the content of the component (A) is at least the above lower limit value, a polishing rate sufficient for polishing a substrate containing tungsten may be obtained. On the other hand, the upper limit of the content of the component (A) is preferably 10.0% by mass, more preferably 7.0% by mass, and particularly, with respect to the total mass of the aqueous dispersion for chemical mechanical polishing. It is preferably 5.0% by mass. When the content of the component (A) is not more than the upper limit value, the storage stability tends to be good, and good flatness on the surface to be polished and scratch reduction may be realized.

1.2. (B) Aluminum Ion and / or Barium Ion The aqueous dispersion for chemical mechanical polishing according to this embodiment contains at least one selected from the group consisting of (B) aluminum ion and barium ion. The component (B) has a function of protecting the surface of the substrate containing tungsten and suppressing excessive etching and corrosion. The component (B) is substantially dissolved in an aqueous dispersion for chemical mechanical polishing. Here, the above-mentioned "substantially dissolved in an aqueous dispersion for chemical mechanical polishing" means that the component (B), which is a solute, is uniformly contained in the aqueous dispersion for chemical mechanical polishing in a state of one molecule or one ion. It refers to a state in which it exists as a mixture of various phases, and refers to a state in which fine particles such as colloidal solutions and suspensions are uniformly suspended and dispersed in an aqueous dispersion for chemical mechanical polishing. Not.

The mechanism by which the component (B) protects the surface of the substrate containing tungsten and suppresses excessive etching and corrosion is not bound by theory, but is presumed as follows.

That is, when a substrate containing tungsten is polished using the aqueous dispersion for chemical mechanical polishing according to the present embodiment, an oxide is formed on the surface of tungsten by the oxidizing agent (C) described later, and tungsten etching is performed. WO ₄ ^2-occurs soluble in the chemical mechanical polishing aqueous dispersion. Formed at this time, substantially chemical mechanical polishing aqueous dissolved in the dispersion (B) component and _WO ^{4 2-and} react the water-insoluble _Al 2 _{(WO 4) 3} and / or BaWO ₄ However, it is considered that excessive etching and corrosion can be suppressed by protecting the tungsten surface on which damage is accumulated by tungsten etching or the like. Further, since a thin film of Al ₂ (WO ₄ ) ₃ and / or BaWO ₄ is formed on the surface of tungsten at the atomic layer level, there is concern in the chemical mechanical polishing composition described in Patent Document 1. It is considered that such a decrease in polishing speed is unlikely to occur.

The method for incorporating the component (B) in the aqueous dispersion for chemical mechanical polishing according to the present embodiment is not particularly limited, but for example, the aluminum compound and / or the aluminum compound and / or the barium ion so as to have a desired content. / Or a method of adding a barium compound can be mentioned. Specific examples of the aluminum compound are not particularly limited as long as it is a compound capable of generating aluminum ions in an aqueous dispersion for chemical mechanical polishing, and examples thereof include aluminum nitrate, aluminum sulfate, and aluminum chloride. Specific examples of the barium compound are not particularly limited as long as it is a compound capable of generating barium ions in an aqueous dispersion for chemical mechanical polishing, and examples thereof include barium nitrate, barium sulfate, and barium chloride. These compounds may be used alone or in combination of two or more.

The lower limit of the content of the component (B) is preferably 0.0005% by mass, more preferably 0.0007% by mass, and particularly preferably 0.0007% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. It is 0.0010% by mass. On the other hand, the upper limit of the content of the component (B) is preferably 0.20% by mass, more preferably 0.15% by mass, and particularly preferably 0.10% by mass. When the content of the component (B) in the aqueous dispersion for chemical mechanical polishing is within the above range, the tungsten surface can be protected more effectively, and excessive etching and corrosion may be suppressed.

The content of component (B) in the aqueous dispersion for chemical mechanical polishing according to this embodiment can be determined by quantifying it using ICP mass spectrometry (ICP-MS). More specifically, after removing abrasive grains by centrifuging the aqueous dispersion for chemical mechanical polishing according to the present embodiment, the content of the component (B) contained in the supernatant is determined by using the above ICP-MS. Can be sought. As the ICP mass spectrometer, for example, "ICPM-8500" manufactured by Shimadzu Corporation, "ELAN DRC PLUS" manufactured by PerkinElmer, or the like can be used.

1.3. (C) Oxidizing agent The aqueous dispersion for chemical mechanical polishing according to the present embodiment contains (C) an oxidizing agent. The component (C) has a function of producing an oxide that is easily removed mechanically on the surface of tungsten and making it easy to polish.

Examples of the component (C) include potassium persulfate, hydrogen peroxide, iron nitrate, iron sulfate, hypochlorous acid, ozone, potassium periodate, peracetic acid and the like. Of these, hydrogen peroxide is preferable because it can effectively oxidize the surface of tungsten. These components (C) may be used alone or in combination of two or more.

The lower limit of the content of the component (C) is preferably 0.01% by mass, more preferably 0.05% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. On the other hand, the upper limit of the content of the component (C) is preferably 5.0% by mass, more preferably 1.0% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. When the content of the component (C) is within the above range, oxides can be efficiently formed on the surface of tungsten, so that the polishing rate may be improved.

1.4. (D) Phosphoric acid, phosphonic acid, and salts thereof The aqueous dispersion for chemical mechanical polishing according to this embodiment is at least one selected from the group consisting of (D) phosphoric acid, phosphonic acid, and salts thereof. (Also referred to as "component (D)" in the present specification) may be contained. When the component (D) coexists with each of the above components, the function of protecting the surface of the substrate containing tungsten is remarkably improved, and excessive etching and corrosion may be suppressed.

The component (D) is at least one selected from the group consisting of phosphoric acid, phosphonic acid, and salts thereof, but is preferably at least one selected from the group consisting of phosphoric acid and salts thereof. .. By containing at least one selected from the group consisting of phosphoric acid and salts thereof, even when an aqueous dispersion for chemical mechanical polishing containing the components (E) and (F) described later is used. In some cases, the function of protecting the substrate surface containing tungsten is improved, and excessive etching and corrosion can be suppressed.

The lower limit of the content of the component (D) is preferably 0.01% by mass, more preferably 0.05% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. On the other hand, the upper limit of the content of the component (D) is preferably 1.0% by mass, more preferably 0.5% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. When the content of the component (D) is within the above range, the function of protecting the surface of the substrate may be improved while efficiently polishing the surface of the substrate containing tungsten, and excessive etching and corrosion may be suppressed.

1.5. (E) Organic Acids and Salts thereof The aqueous dispersion for chemical mechanical polishing according to the present embodiment may contain at least one selected from the group consisting of (E) organic acids and salts thereof. By containing the component (E), the polishing rate for a substrate containing tungsten may be improved.

The component (E) is preferably an organic acid containing no nitrogen atom and a salt thereof. For example, citric acid, malonic acid, maleic acid, tartaric acid, malic acid, succinic acid, phthalic acid, and salts thereof. And so on. Of these, malic acid, malonic acid, citric acid, and salts thereof are more preferable because the surface of the substrate containing tungsten can be efficiently polished. The component (E) may be used alone or in combination of two or more.

The lower limit of the content of the component (E) is preferably 0.01% by mass, more preferably 0.06% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. On the other hand, the upper limit of the content of the component (E) is preferably 1.0% by mass, more preferably 0.5% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. When the content of the component (E) is within the above range, the polishing rate for the substrate containing tungsten may be further improved.

1.6. (F) Water-soluble polymer and salts thereof The aqueous dispersion for chemical mechanical polishing according to the present embodiment contains at least one selected from the group consisting of (F) water-soluble polymer and salts thereof. May be good. By containing the component (F), it may be possible to control the surface of the substrate containing tungsten so that it can be selectively polished.

Examples of the component (F) include polycarboxylic acids, polystyrene sulfonic acids, poly (meth) acrylic acids, polyvinyl alcohols, polyethers, nitrogen atom-free water-soluble polymers such as salts thereof, and salts thereof. Can be mentioned. Among them, poly (meth) acrylic acid, polyether and salts thereof are preferable because the surface of the substrate containing tungsten can be efficiently polished. Such a component (F) may be used alone or in combination of two or more.

The weight average molecular weight (Mw) of the component (F) is preferably 1,000 or more and 1,000,000 or less, and more preferably 3,000 or more and 800,000 or less. When the weight average molecular weight of the component (F) is within the above range, it becomes easy to selectively protect the insulating film material and the like without suppressing the polishing rate for the substrate containing tungsten, and the substrate containing tungsten and the insulating film material It may be easier to adjust the polishing speed of. The "weight average molecular weight (Mw)" in the present specification refers to a polyethylene glycol-equivalent weight average molecular weight measured by GPC (gel permeation chromatography).

The lower limit of the content of the component (F) is preferably 0.01% by mass, more preferably 0.06% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. On the other hand, the upper limit of the content of the component (F) is preferably 1.0% by mass, more preferably 0.5% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. When the content of the component (F) is within the above range, it may be possible to suppress an excessive polishing rate of the insulating film material or the like while efficiently polishing the surface of the substrate containing tungsten.

1.7. Other Components The aqueous dispersion for chemical mechanical polishing according to the present embodiment may contain a pH adjuster or the like, if necessary, in addition to water, which is a main liquid medium.

<Water>
The aqueous dispersion for chemical mechanical polishing according to the present embodiment contains water as a main liquid medium. The water is not particularly limited, but pure water is preferable. Water may be blended as the remainder of the constituent material of the above-mentioned aqueous dispersion for chemical mechanical polishing, and the content of water is not particularly limited.

<pH adjuster>
The pH of the aqueous dispersion for chemical mechanical polishing according to the present embodiment is preferably 4 or less, more preferably 1 or more and 3.5 or less, and particularly preferably 2 or more and 3 or less. When the pH of the aqueous dispersion for chemical mechanical polishing according to the present embodiment is in the above range, the effect of the above-mentioned component (B) may be easily exhibited. Further, when the pH of the aqueous dispersion for chemical mechanical polishing is in the above range, the dispersion stability of the above-mentioned component (A) in the aqueous dispersion for chemical mechanical polishing may be improved. By adjusting the pH so that the absolute value of the zeta potential of the component (A) in the aqueous dispersion for chemical mechanical polishing according to the present embodiment is 10 or less, not only the surface of the substrate containing tungsten but also the insulation can be obtained. In some cases, the film material and the like can be efficiently polished.

The aqueous dispersion for chemical mechanical polishing according to the present embodiment may contain a pH adjuster for the purpose of adjusting the pH to the above range. Examples of the pH adjuster include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid; and hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, rubidium hydroxide and cesium hydroxide. These pH adjusters may be used alone or in combination of two or more.

In the present invention, pH refers to a hydrogen ion index, and the value is measured using a commercially available pH meter (for example, a tabletop pH meter manufactured by HORIBA, Ltd.) under the condition of 25 ° C. and 1 atm. be able to.

1.8. Applications The aqueous dispersion for chemical mechanical polishing according to this embodiment is suitably used for polishing substrates containing tungsten, among the metals used for semiconductor substrates. By polishing the substrate containing tungsten using the aqueous dispersion for chemical mechanical polishing according to the present embodiment, the substrate containing tungsten is efficiently polished, the surface of the substrate is protected, and excessive etching and corrosion are prevented. It can be suppressed.

2. Chemical Mechanical Polishing Method The chemical mechanical polishing method according to an embodiment of the present invention comprises a step of polishing a substrate containing tungsten using the above-mentioned aqueous dispersion for chemical mechanical polishing (hereinafter, also referred to as “polishing step”). Including. According to the chemical mechanical polishing method according to the present embodiment, by using the above-mentioned aqueous dispersion for chemical mechanical polishing, the substrate surface containing tungsten is efficiently polished, the substrate surface is protected, and excessive etching is performed. And corrosion can be suppressed.

For the above-mentioned polishing step, for example, the polishing apparatus 100 as shown in FIG. 1 can be used. FIG. 1 is a perspective view schematically showing the polishing apparatus 100. In the above-mentioned polishing step, a carrier head that holds the substrate 50 while supplying the slurry (aqueous dispersion for chemical mechanical polishing) 44 from the slurry supply nozzle 42 and rotating the turntable 48 to which the polishing pad 46 is attached. This is done by bringing the 52 into contact. Note that FIG. 1 also shows the water supply nozzle 54 and the dresser 56.

The polishing load of the carrier head 52 can be selected in the range of 0.7 to 70 psi, preferably 1.5 to 35 psi. The rotation speed of the turntable 48 and the carrier head 52 can be appropriately selected within the range of 10 to 400 rpm, and is preferably 30 to 150 rpm. The flow rate of the slurry (aqueous dispersion for chemical mechanical polishing) 44 supplied from the slurry supply nozzle 42 can be selected within the range of 10 to 1,000 mL / min, and is preferably 50 to 400 mL / min.

Examples of commercially available polishing equipment include, for example, Ebara Corporation, model "EPO-112", "EPO-222"; Lapmaster SFT, model "LGP-510", "LGP-552"; Applied Materials. , Model "Mirra", "Reflexion"; G & P
TECHNOLOGY, model "POLI-400L"; AMAT, model "Reflexion LK"; FILTEC, model "FLTek-15"; Tokyo Seimitsu, model "ChaMP" and the like.

After the above-mentioned polishing step, a cleaning step of cleaning the surface of the substrate may be further carried out.

The cleaning method is not particularly limited, but is performed by a method in which the cleaning agent is brought into direct contact with the substrate. As a method of bringing the cleaning agent into direct contact with the substrate, a dip type in which the cleaning tank is filled with the cleaning agent and the wiring board is immersed; a spin type in which the substrate is rotated at high speed while flowing the cleaning agent from a nozzle onto the substrate; Examples thereof include a spray type method in which a cleaning agent is sprayed for cleaning. Further, as a device for performing such a method, a batch type cleaning device for simultaneously cleaning a plurality of wiring boards housed in a cassette, and a single-wafer type cleaning in which one wiring board is attached to a holder for cleaning. Devices and the like can be mentioned.

As the above-mentioned cleaning agent, for example, the cleaning compositions described in JP-A-2018-92960, JP-A-2017-112200, JP-A-2016-171294 and the like can be used.

In the above cleaning method, the temperature of the cleaning agent is usually room temperature, but it may be heated within a range that does not impair the performance, and can be heated to, for example, about 40 to 70 ° C.

Further, in addition to the method of bringing the above-mentioned cleaning agent into direct contact with the substrate, it is also preferable to use a cleaning method by physical force in combination. As a result, the removability of contamination by the particles adhering to the substrate is improved, and the cleaning time can be shortened. Examples of the cleaning method using physical force include scrub cleaning using a cleaning brush and ultrasonic cleaning.

Further, cleaning with ultrapure water or pure water may be performed before and / or after cleaning by the above cleaning method.

3. 3. Examples The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. In addition, "part" and "%" in this Example are based on mass unless otherwise specified.

3.1. Preparation of Silica-based Particle 1 Under normal temperature and pressure, 7897 parts by mass of tetramethyl orthosilicate (TMS), 80 parts by mass of 3-aminopropyltriethoxysilane (APTES), and 2073 parts by mass of methanol (Methanol) were mixed. A monomer solution was prepared. 4831 parts by mass of a 28 mass% aqueous ammonia solution, 7785 parts by mass of water, and 62499 parts by mass of methanol were charged into a reaction vessel, and the monomer solution prepared above was gradually added over 30 minutes while stirring at 35 ° C. and 200 rpm. Added. After that, it is heated to 90 ° C. and held for 6 hours, 50 parts by mass of water is added 8 times while volatilizing ammonia and methanol, and the mixture is naturally cooled to 60 ° C. to obtain an aqueous dispersion containing silica-based particles 1. Was produced.

The average particle size of the silica-based particles 1 was measured with respect to the obtained aqueous dispersion containing the silica-based particles 1 using a dynamic light scattering type particle size distribution measuring device "LB-550" manufactured by HORIBA, Ltd. , 39 nm.

3.2. Preparation of Aqueous Dispersion for Chemical Mechanical Polishing Ion-exchanged water and components other than the components (A) and (C) shown in Tables 1 and 2 were charged into a polyethylene container. Then, the component (A) shown in Tables 1 and 2 was charged into a polyethylene container, and the component (C) was further charged and stirred for 15 minutes. Then, the pH adjusters shown in Tables 1 and 2 are added so that the pH becomes the values shown in Tables 1 and 2, and the mixture is further stirred for 15 minutes to carry out Examples 1 to 14 and Comparative Examples 1 to 1. An aqueous dispersion for chemical mechanical polishing of No. 7 was obtained.

3.3. Evaluation test 33.1. Evaluation of Zeta Potential The zeta potential of component (A) contained in the aqueous dispersion for chemical mechanical polishing of Examples 1 to 14, Comparative Examples 1 to 7 and Reference Examples 1 and 2 prepared above is measured by a zeta potential measuring device. The measurement was performed using (Nihon Rufuto Co., Ltd., ultrasonic particle size distribution / zeta potential measuring device, model number "DT1200"). The results are shown in Tables 1 to 3.

3.3.2. Calculation of Etching Rate (ER) An 8-inch silicon wafer (a silicon substrate with an 8-inch thermal oxide film on which a tungsten film with a thickness of 2,000 Å is laminated) on which tungsten (W) is deposited on the surface by a sputtering method is 1 cm x It was cut into 3 cm pieces to obtain metal wafer test pieces. The film thickness of this test piece was measured in advance using a metal film thickness meter "Σ-5" manufactured by NPS Co., Ltd. Next, 100 mL of the aqueous dispersion for chemical mechanical polishing according to any one of Examples 1 to 14 and Comparative Examples 1 to 7 was placed in a polyethylene container, kept at 40 ° C., and tungsten was added to the aqueous dispersion for chemical mechanical polishing. The formed metal wafer test piece was immersed for 60 minutes. Then, it was washed with running water for 10 seconds and dried. The film thickness of the metal wafer test piece after the dipping treatment was measured again, and the etching rate (ER, unit: Å / min.) Was calculated by dividing the reduced film thickness amount by the dipping time of 60 minutes. The results are shown in Tables 1 and 2.

Further, using the aqueous dispersion for chemical mechanical polishing of Example 4 as Reference Example 1 and the aqueous dispersion for chemical mechanical polishing of Comparative Example 2 as Reference Example 2, the etching rates of the cobalt film and the copper film other than the tungsten film are used. (ER, unit: Å / min.) Was evaluated. The cobalt film is a wafer having a diameter of 8 inches on which a cobalt film of 2,000 Å is laminated, and the copper film is a wafer having a diameter of 8 inches on which a copper film of 2,000 Å is laminated and cut into 1 cm × 3 cm. Each was a metal wafer test piece. The film thickness of this test piece was measured in advance in the same manner as in the above method. 100 mL of the aqueous dispersion for chemical mechanical polishing of Example 4 or Comparative Example 2 was added and kept at 40 ° C., and the metal wafer test piece was immersed in the aqueous dispersion for chemical mechanical polishing for 10 minutes. Then, it was washed with running water for 10 seconds and dried. The film thickness of the metal wafer test piece after the immersion treatment was measured again, and the etching rate (ER, unit: Å / min.) Was calculated by dividing the reduced film thickness amount by the immersion time of 10 minutes. The results are shown in Table 3.

3.3.3. Evaluation of Corrosion Observation An 8-inch silicon wafer (a silicon substrate with an 8-inch thermal oxide film on which a tungsten film with a thickness of 2,000 Å is laminated) on which tungsten (W) is deposited on the surface by a sputtering method is cut into 1 cm x 1 cm. It was used as a silicon wafer test piece. The surfaces of these test pieces were observed in advance with a scanning electron microscope at a magnification of 50,000 times. 50 mL of the aqueous dispersion for chemical mechanical polishing according to any one of Examples 1 to 14 and Comparative Examples 1 to 7 was placed in a polyethylene container and kept at 25 ° C., the test piece (1 cm × 1 cm) was immersed for 60 minutes, and 60 under running water. The surface is washed with a commercially available urethane sponge while washing for a second, particles on the surface are removed and dried, and then surface corrosion is observed again with a scanning electron microscope at a magnification of 50,000 times, and the surface corrosion is observed according to the following criteria. evaluated. The results are shown in Tables 1 and 2.
(Evaluation criteria)
A: No change in surface shape due to corrosion was observed as compared with before immersion.
B: Corroded parts and non-corroded parts were mixed as compared with those before immersion.
C: The entire surface was corroded as compared with before immersion.

3.3.4. Evaluation of Polishing Rate Using the aqueous dispersion for chemical mechanical polishing according to any one of Examples 1 to 14 and Comparative Examples 1 to 7, a 12-inch silicon substrate or a film thickness of 20 on which a tungsten film having a thickness of 5,000 Å is laminated. A 12-inch silicon substrate on which a 000 Å silicon oxide film was laminated was cut into 4 cm × 4 cm, and a chemical mechanical polishing test was conducted for 1 minute under the following polishing conditions using a test piece to be polished. The polishing conditions for evaluating the polishing rate are as follows. The results obtained are shown in Tables 1 and 2.
(Polishing conditions)
-Polishing equipment: G & P TECHNOLOGY, model "POLI-400L"
-Abrasive pad: Fujibo, Inc., "Multi-hard polyurethane pad; H800-type1 (3-1S) 775"
・ Supply speed of aqueous dispersion for chemical mechanical polishing: 100 mL / min ・ Surface plate rotation speed: 100 rpm
・ Head rotation speed: 90 rpm
・ Head pressing pressure: 2psi
・ Polishing speed (Å / min) = (Thickness of each film before polishing-Thickness of each film after polishing) / Polishing time The thickness of the tungsten film is determined by the resistivity measuring machine (manufactured by NPS, model). The resistance was measured by the DC 4-probe method using "Σ-5"), and was calculated from the sheet resistance value and the volume resistivity of cobalt by the following formula.
Film thickness (Å) = [Cobalt film volume resistivity (Ω ・ m) ÷ Sheet resistance value (Ω))] × 1010
The thickness of the silicon oxide film was measured using a photobuffer type film thickness meter "F20 film thickness measurement system" manufactured by Filmometrics Co., Ltd.

3.4. Evaluation Results Tables 1 to 2 below show the compositions of the aqueous dispersions for chemical mechanical polishing of each example and each comparative example, and the evaluation results. Table 3 below shows the composition of the aqueous dispersion for chemical mechanical polishing of Reference Examples 1 and 2 and the evaluation results of the etching rates of the cobalt film and the copper film.

In Tables 1 to 3 above, the numerical value of each component represents mass%. However, the content of the component (A) in Tables 1 to 3 above represents the solid content concentration. The content of the component (C) in Tables 1 to 3 above represents the content of hydrogen peroxide, not the content of "35 wt% hydrogen peroxide" (that is, hydrogen peroxide solution). Further, in each Example and each Comparative Example, the total amount of each component is 100% by mass, and the balance is ion-exchanged water.

The following products or reagents were used for each component in Tables 1 to 3 above.
<Ingredient (A)>
-Silica-based particles 1: Silica-based particles 1 prepared above
-PL-3: Made by Fuso Chemical Industry Co., Ltd., trade name "PL-3", colloidal silica, average particle size 70 nm
<Ingredient (B)>
・ Aluminum nitrate ・ Nine hydrate: Wako Pure Chemical Industries, Ltd., trade name “Aluminum nitrate nine hydrate”
・ Aluminum sulfate ・ 14-18 hydrate: Wako Pure Chemical Industries, Ltd., trade name “Aluminum sulfate 14-18 water”
-Barium chloride / dihydrate: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "barium chloride"<(C)component>
-Hydrogen peroxide: Made by Mitsubishi Gas Chemical Company, Inc., trade name "35 wt% hydrogen peroxide"
<Ingredient (D)>
-Phosphoric acid: Made by Rasa Industries, Ltd., trade name "Phosphoric acid"
-Phosphonate: Made by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "Phosphonate"
<Ingredient (E)>
-Malic acid: Made by Showa Kako Co., Ltd., product name "DL-malic acid"
・ Malonic acid: Made by Juzen Co., Ltd., trade name "malonic acid"
・ Citric acid: Made by Hayashi Junyaku Kogyo Co., Ltd., trade name "citric acid (crystal)"
<(F) component>
-Polyacrylic acid: manufactured by Toa Synthetic Co., Ltd., product name "AC-10L", Mw = 50,000-Polyethylene glycol: manufactured by Junsei Chemical Co., Ltd., product name "polyethylene glycol 20000", Mw = 15,500-25, 000
<Other ingredients>
・ Sodium chloride: Made by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "sodium chloride"
・ Calcium chloride: Made by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "Calcium chloride dihydrate"
-Polyethyleneimine: Product name "Polyethyleneimine 70000 solution (30%)", Mw = about 70,000

As is clear from the above tables 1 and 2, when the aqueous dispersion for chemical mechanical polishing according to Examples 1 to 14 is used, the tungsten film can be efficiently polished and after polishing. It was possible to suppress the corrosion of the tungsten film. On the other hand, when the aqueous dispersions for chemical mechanical polishing according to Comparative Examples 1 and 3 to 7 were used, the suppression of corrosion of the tungsten film could not be realized because the component (B) was not contained. When the aqueous dispersion for chemical mechanical polishing according to Comparative Example 2 was used, the polishing rate of the tungsten film tended to decrease because polyethyleneimine was added instead of the component (B).

Further, according to Table 3 above, in the ER evaluation results of the cobalt film and the copper film by the aqueous dispersion for chemical mechanical polishing of Reference Example 1 and Reference Example 2, no clear improvement such as corrosion suppression was observed. This suggests that the aqueous dispersion for chemical mechanical polishing according to the present embodiment is particularly useful for substrates containing tungsten.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes substantially the same configurations as those described in the embodiments (eg, configurations with the same function, method and result, or configurations with the same purpose and effect). The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. The present invention also includes a configuration that exhibits the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. The present invention also includes a configuration in which a known technique is added to the configuration described in the embodiment.

42 ... Slurry supply nozzle, 44 ... Slurry (water-based dispersion for chemical mechanical polishing), 46 ... Abrasive cloth, 48 ... Turntable, 50 ... Substrate, 52 ... Carrier head, 54 ... Water supply nozzle, 56 ... Dresser, 100 ... Polishing equipment

Claims (8)

An aqueous dispersion for chemical mechanical polishing used for substrates containing tungsten.
(A) Abrasive grains and
(B) At least one selected from the group consisting of aluminum ions and barium ions, and
(C) Oxidizing agent and
A water-based dispersion for chemical mechanical polishing containing. The aqueous dispersion for chemical mechanical polishing according to claim 1, wherein the content of the component (B) in the aqueous dispersion for chemical mechanical polishing is 0.0005 to 0.2% by mass. The aqueous dispersion for chemical mechanical polishing according to claim 1 or 2, further comprising (D) at least one selected from the group consisting of phosphoric acid, phosphonic acid, and salts thereof. The aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 3, wherein the abrasive grains (A) are abrasive grains having a positive charge. The aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 4, wherein the pH is 4 or less. The aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 5, further comprising (E) at least one selected from the group consisting of organic acids and salts thereof. The aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 6, further comprising (F) a water-soluble polymer. A chemical mechanical polishing method comprising a step of polishing a substrate containing tungsten using the aqueous dispersion for chemical mechanical polishing according to any one of claims 1 to 7.

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