JP2020035895A - Aqueous dispersion for chemical mechanical polishing and method for manufacturing the same - Google Patents

Abstract

To provide an aqueous dispersion for chemical mechanical polishing, having excellent stability, capable of polishing a surface to be polished at a high speed while suppressing excessive etching of the surface to be polished including a wiring metal material and a barrier metal material.SOLUTION: One embodiment of the aqueous dispersion for chemical mechanical polishing according to the present invention, includes: (A) an abrasive; (B) an iron salt; and (C) a compound having a hydroxyl group and a carboxyl group, and at least one selected from a group composed of salts of the same and has pH of 7 or more and 14 or less.SELECTED DRAWING: None

Description

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

  2. Description of the Related Art CMP (Chemical Mechanical Polishing) has been rapidly spread by flattening technology and the like in the manufacture of semiconductor devices. In this CMP, the object to be polished is pressed against a polishing pad, and the object to be polished and the polishing pad are slid relative to each other while supplying an aqueous dispersion for chemical mechanical polishing onto the polishing pad. And it is a technique of mechanically polishing.

  2. Description of the Related Art In recent years, as semiconductor devices have become finer, wiring layers formed in the semiconductor device, such as wiring and plugs, have been miniaturized. Accordingly, a technique of flattening the wiring layer by CMP has been used. The substrate of the semiconductor device includes an insulating film material, a wiring metal material, a barrier metal material for preventing the diffusion of the wiring metal material into the inorganic material film, and the like. Here, for example, silicon dioxide is mainly used as an insulating film material, copper or tungsten is used as a wiring metal material, and tantalum nitride or titanium nitride is mainly used as a barrier metal material.

  Among the substrate materials in these semiconductor devices, tungsten, which is a wiring metal material, has relatively high hardness and is hardly affected by chemicals. Therefore, in a slurry for tungsten CMP, it is important to passivate the tungsten surface with an oxidizing agent to form an oxide layer, and furthermore, the oxide layer is formed by utilizing a mechanical polishing action such as an abrasive. Can be removed. As such a slurry for tungsten CMP, for example, a technique in which iron nitrate and hydrogen peroxide are used in combination in order to cause a strong oxidation reaction has been proposed (for example, see Patent Document 1).

JP 2012-74734 A

  In the slurry for tungsten CMP described in Patent Literature 1, it is recommended to adjust the pH to an acidic range. The reason for this is that, at the pH of the acidic region, the stability of the added component can be increased, and the abrasive grains and tungsten can be easily contacted by electrostatic interaction, so that tungsten can be polished at high speed. It is presumed. In addition, in the basic region, when an iron salt such as iron nitrate is contained in the slurry, a precipitate such as iron hydroxide is generated, the stability is likely to be impaired, and a problem that sufficient polishing characteristics cannot be obtained occurs. This is because there are times.

  However, in CMP of a substrate in a semiconductor device, it may be required to polish not only tungsten which is a wiring metal material but also a barrier metal used for the purpose of improving the reliability of wiring in one step. When polishing a polishing object containing these materials in one step, the pH of the slurry is in a basic region, and the dispersion stability of abrasive grains (especially silica) is improved. It is considered possible.

Therefore, some embodiments according to the present invention can suppress excessive etching of a surface to be polished including a wiring metal material and a barrier metal material, can polish the surface to be polished at high speed, and further improve stability. Also provides an excellent chemical mechanical polishing aqueous dispersion. Some aspects of the present invention also provide a method for producing the chemical mechanical polishing aqueous dispersion.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as any of the following aspects.

One embodiment of the chemical mechanical polishing aqueous dispersion according to the present invention,
(A) abrasive grains,
(B) an iron salt;
(C) a compound having a hydroxyl group and a carboxyl group, and at least one selected from the group consisting of salts thereof;
And the pH is 7 or more and 14 or less.

In one embodiment of the chemical mechanical polishing aqueous dispersion,
The component (C) can contain at least one selected from the group consisting of a compound having a hydroxyl group, a carboxyl group, and an amine structure, and a salt thereof.

In any aspect of the chemical mechanical polishing aqueous dispersion,
The component (C) can contain at least one selected from the group consisting of a polycarboxylic acid having a hydroxyl group and two or more amine structures, and a salt thereof.

In any aspect of the chemical mechanical polishing aqueous dispersion,
The component (C) includes N- (2-hydroxyethyl) ethylenediamine-N, N ′, N′-triacetic acid, N, N-di (2-hydroxyethyl) glycine and N, N′-ethylenebis [N -(2-hydroxybenzyl) glycine] at least one selected from the group consisting of:

In any aspect of the chemical mechanical polishing aqueous dispersion,
The (B) iron salt may contain at least one selected from the group consisting of iron nitrate and iron sulfate.

In any aspect of the chemical mechanical polishing aqueous dispersion,
Wherein (C) the content of the component _M C (mol), the (B) the content of the component when the _M B (mol), the molar ratio _M C / _{M B} is 0.3 to 3.0 Can be

In any aspect of the chemical mechanical polishing aqueous dispersion,
Further, it can contain at least one kind (excluding the component (C)) selected from the group consisting of (D) an organic acid and a salt thereof.

In any aspect of the chemical mechanical polishing aqueous dispersion,
Furthermore, (E) at least one selected from the group consisting of sodium hydroxide, potassium hydroxide and ammonium hydroxide can be contained.

Any embodiment of the chemical mechanical polishing aqueous dispersion,
It can be used for polishing a substrate containing at least one selected from the group consisting of tungsten, copper, cobalt, titanium, ruthenium, titanium nitride and tantalum nitride.

One embodiment of the method for producing an aqueous dispersion for chemical mechanical polishing according to the present invention,
A first step of dispersing or dissolving (A) abrasive grains, (B) an iron salt, and (C) a compound having a hydroxyl group and a carboxyl group in an aqueous medium to obtain an aqueous dispersion;
(E) a second step of adjusting the pH of the aqueous dispersion to 7 to 14 using at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide;
including.

  ADVANTAGE OF THE INVENTION According to the aqueous dispersion for chemical mechanical polishing which concerns on this invention, while suppressing excessive etching of a wiring metal material and a barrier metal material, these materials can be grind | polished at high speed. In addition, according to the chemical mechanical polishing aqueous dispersion according to the present invention, even at a pH in a basic region, (B) the generation of a precipitate derived from an iron salt can be suppressed, and the stability is improved. Can be improved.

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

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present invention is not limited to the embodiments described below, but also includes various modified examples implemented without departing from the gist of the present invention.

  In this specification, the numerical range described using “to” means that the numerical values described before and after “to” are included as the lower limit and the upper limit.

  In the present specification, the “acidic region” refers to a region having a pH of less than 7, and the “basic region” refers to a region having a pH of 7 or more.

  The "wiring metal material" refers to a conductive metal material such as aluminum, copper, cobalt, titanium, ruthenium, and tungsten. “Insulating film material” refers to a material such as silicon dioxide, silicon nitride, amorphous silicon, and the like. The term “barrier metal material” refers to a material such as tantalum nitride and titanium nitride which is used by being laminated with a wiring metal material for the purpose of improving the reliability of the wiring.

1. Aqueous Dispersion for Chemical Mechanical Polishing The aqueous dispersion for chemical mechanical polishing according to the present embodiment comprises (A) abrasive grains (hereinafter also referred to as “(A) component”) and (B) iron salt (hereinafter, referred to as “component (A)”). And (C) a compound having a hydroxyl group and a carboxyl group, and at least one selected from the group consisting of salts thereof (hereinafter also referred to as “component (C)”). , And the pH is 7 or more and 14 or less. Hereinafter, each component contained in the chemical mechanical polishing aqueous dispersion according to the present embodiment will be described in detail.

1.1. (A) Abrasive particles The chemical mechanical polishing aqueous dispersion according to the present embodiment contains (A) abrasive particles. (A) The abrasive has a function of mechanically polishing a wiring metal material and a barrier metal film material to be polished, and improving a polishing rate for these materials. (A) The abrasive grains are not particularly limited, but include inorganic particles such as silica, ceria, alumina, zirconia, and titania. Among these, silica, alumina and titania are preferred, and silica is more preferred. In particular, silica is likely to be negatively charged at a pH in a basic region, so that the dispersion stability is improved by electrostatic repulsion. (A) The abrasive grains may be used alone or in any combination of two or more.

  Examples of the silica include fumed silica and colloidal silica, and colloidal silica is preferable. As the colloidal silica, for example, those manufactured by a method described in JP-A-2003-109921 or the like can be used.

  (A) The average particle size of the abrasive grains is not particularly limited, but the lower limit is preferably 5 nm, more preferably 10 nm, particularly preferably 15 nm, and the upper limit is preferably 300 nm, It is more preferably 150 nm, particularly preferably 100 nm. (A) When the average particle diameter of the abrasive grains is in the above range, the occurrence of polishing scratches on the surface to be polished may be reduced while improving the polishing rate of the wiring metal material and the barrier metal material. If the average particle diameter of the abrasive grains (A) is within the upper limit of 150 nm or less, the polishing rate of the wiring metal material and the barrier metal material may be further improved. When the average particle diameter of the abrasive grains (A) is at least 10 nm, which is the lower limit, the occurrence of polishing scratches on the surface to be polished may be further reduced.

  (A) The average particle size of the abrasive grains can be determined by measuring with a particle size distribution measuring device using a dynamic light scattering method as a measurement principle. Examples of the particle size measuring device by the dynamic light scattering method include a dynamic light scattering type particle size distribution measuring device “LB-550” manufactured by Horiba Ltd., a nano particle analyzer “DelsaNanoS” manufactured by Beckman Coulter, and a product manufactured by Malvern. "Zetasizernanozs" and the like. The average particle diameter measured using the dynamic light scattering method represents the average particle diameter of secondary particles formed by aggregating a plurality of primary particles.

  (A) The lower limit of the content of the abrasive grains is preferably 0.05% by mass, more preferably 0.1% by mass, and more preferably 0.3% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. Particularly preferred. (A) When the content of the abrasive grains is not less than the lower limit, a polishing rate sufficient to polish the wiring metal material and the barrier metal material may be obtained. On the other hand, the upper limit of the content of the abrasive grains (A) is preferably 10% by mass, more preferably 5% by mass, and particularly preferably 3% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. (A) When the content of the abrasive grains is equal to or less than the upper limit, storage stability tends to be good, and good flatness on the surface to be polished and reduction of polishing scratches may be realized in some cases.

1.2. (B) Iron salt The chemical mechanical polishing aqueous dispersion according to this embodiment contains (B) an iron salt. When the chemical mechanical polishing aqueous dispersion according to the present embodiment contains (B) an iron salt, the surface of a wiring metal material or a barrier metal material can be passivated to form an oxide layer. Then, (A) the oxide layer can be removed at a high speed by utilizing the mechanical polishing action of the abrasive grains. Among wiring metal materials and barrier metal materials, tungsten, cobalt, and a polishing rate of a material containing at least one of titanium nitride are easily improved, and a polishing rate of a material containing at least one of tungsten and titanium nitride is further improved. Cheap.

  In addition, the (B) iron salt includes not only an iron salt formed in the aqueous dispersion but also an ionized ionized iron (iron ion).

  (B) Specific examples of iron salts include iron nitrate, iron sulfate, ammonium iron sulfate, iron perchlorate, iron chloride, iron citrate, ammonium iron citrate, iron oxalate, and iron ammonium oxalate. Among them, at least one selected from the group consisting of iron nitrate and iron sulfate is preferable, and iron nitrate is more preferable. In particular, iron nitrate is easily dissociated into iron ions in an aqueous dispersion, and when used in combination with hydrogen peroxide, which will be described later, a strong oxidation reaction (Fenton reaction) occurs, and high-speed polishing of a wiring metal material such as tungsten can be performed. it can. As the component (B), one type may be used alone, or two or more types may be used in combination at any ratio.

  The lower limit of the content of the component (B) is preferably 0.001% by mass, more preferably 0.01% by mass, and particularly preferably 0.03% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. preferable. On the other hand, the upper limit of the content of the component (B) is preferably 1% by mass, more preferably 0.5% by mass, and particularly preferably 0.15% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. preferable. When the content of the component (B) is in the above range, the effect of passivating the surface of the wiring metal material or the barrier metal material to form an oxide layer can be sufficiently obtained, so that the polishing rate can be improved. Further, in order to suppress excessive etching, corrosion of a wiring metal material or the like may be reduced in some cases.

1.3. (C) Compound having hydroxyl group and carboxyl group The aqueous dispersion for chemical mechanical polishing according to the present embodiment has at least one selected from the group consisting of (C) a compound having a hydroxyl group and a carboxyl group, and a salt thereof. It contains. Normally, when the iron salt (B) is used at a pH in the basic range, a precipitate of iron hydroxide is formed, and the function of the iron salt (B) as an oxidizing agent is impaired. However, since the chemical mechanical polishing aqueous dispersion according to the present embodiment contains the component (C), a precipitate of iron hydroxide derived from the iron salt (B) is generated even at a pH in a basic region. Can be suppressed. As a result, the chemical mechanical polishing aqueous dispersion according to the present embodiment has good stability, and (B) the iron salt functions as an oxidizing agent, so that the wiring metal material and the barrier metal material can be polished at high speed. it can.

  Hereinafter, the mechanism by which the component (C) suppresses the generation of the precipitate derived from the iron salt (B) will be described in detail. In general, a chelating agent having only a plurality of carboxyl groups as an acid group, such as ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid, is used as a chelating agent for improving the stability of a metal in a solution. However, since these chelating agents have only a carboxyl group, they cannot sufficiently form a chelate complex with iron ions at a pH in a basic region, and as a result, precipitates such as iron hydroxide are generated. On the other hand, the component (C) has a sufficient ability to form a chelate complex with iron ions even at a pH in a basic region. This is presumably because component (C) has a hydroxyl group and thus has high water solubility, and the formation of a chelate complex is superior to that of the above chelating agent.

  The component (C) is preferably at least one selected from the group consisting of compounds having a hydroxyl group, a carboxyl group and an amine structure, and salts thereof. Further, the component (C) is more preferably at least one selected from the group consisting of polyvalent carboxylic acids having a hydroxyl group and two or more amine structures, and salts thereof. That is, a compound having one or more hydroxyl groups, two or more carboxyl groups, and two or more amine structures is more preferable.

  The molecular weight of the component (C) is preferably from 80 to 1,000, more preferably from 100 to 700. When the molecular weight of the component (C) is within the above range, the component (C) is easily dissolved in the aqueous dispersion, so that the generation of the precipitate derived from the component (B) may be easily suppressed.

Specific examples of the component (C) include N- (2-hydroxyethyl) ethylenediamine-N, N ', N'-triacetic acid, N, N-di (2-hydroxyethyl) glycine, and N- (2-hydroxyethyl). Ethyl) iminodiacetic acid and N, N'-ethylenebis [N- (2-hydroxybenzyl) glycine]. Among these, N- (2-hydroxyethyl) ethylenediamine is required to improve the polishing rate of the wiring metal material and the like and to improve the dispersion stability of the aqueous dispersion for chemical mechanical polishing while suppressing excessive etching. -N, N ', N'-triacetic acid, N, N-di (2-hydroxyethyl) glycine, N, N'-ethylenebis [N- (2-hydroxybenzyl) glycine] are preferred. Such a component (C) may be used alone or in a combination of two or more at an arbitrary ratio.

  The lower limit of the content of the component (C) is preferably 0.005% by mass, more preferably 0.01% by mass, and particularly preferably 0.03% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. preferable. When the content of the component (C) is at least the lower limit, interaction with the component (B) is likely to occur, and the polishing rate of the surface to be polished may be further improved. On the other hand, the upper limit of the content of the component (C) is preferably 1% by mass, more preferably 0.5% by mass, and particularly preferably 0.1% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. preferable. When the content of the component (C) is equal to or less than the upper limit, excessive etching may be suppressed in some cases.

In the chemical mechanical polishing aqueous dispersion according to this embodiment, the content of the component (C) and the content of the component (B) are M _C (mol) and M, respectively, based on the total mass of the chemical mechanical polishing aqueous dispersion. _{When B} (mol), the molar ratio M _C / M _B is preferably 0.3 or more and 3.0 or less, more preferably 0.4 or more and 2.5 or less. It is particularly preferred that the ratio be from 0.5 to 2.0. When the molar ratio M _C / M _B is within the above range, almost all iron ions generated by the dissociation of the component (B) can be chelated by the component (C) at the pH of the basic region. The generation of a precipitate such as iron can be effectively suppressed. As a result, the chemical mechanical polishing aqueous dispersion according to the present embodiment has good stability, and (B) the iron salt can function as an oxidizing agent, so that the wiring metal material and the barrier metal material can be polished at high speed. it can.

1.4. (D) Organic acid and salt thereof The aqueous dispersion for chemical mechanical polishing according to the present embodiment is at least one selected from the group consisting of (D) an organic acid and a salt thereof different from the component (C) (hereinafter, referred to as “D”). , "(D) component"). Since the chemical mechanical polishing aqueous dispersion according to the present embodiment contains the component (D), the component (D) is coordinated with the surface to be polished to improve the polishing rate, and the metal salt precipitates during polishing. May be suppressed. Further, by coordinating the component (D) to the surface to be polished, damage due to etching and corrosion of the surface to be polished may be reduced.

  The component (D) is preferably an organic acid having a coordinating ability to an ion or atom composed of an element of the wiring metal material, and a salt thereof. As the component (D), an organic acid having 0 to 1 hydroxyl group and 1 to 2 carboxyl groups in one molecule is more preferable, and 0 to 1 hydroxyl group and carboxyl group in one molecule. And an organic acid having a primary acid dissociation constant pKa of 1.5 to 4.5 is particularly preferable. With such a component (D), the ability to coordinate to the surface of the wiring metal material or the like is high, so that the polishing rate for the wiring metal material or the like can be improved. In addition, such a component (D) stabilizes metal ions generated by polishing a wiring metal material or the like and can suppress precipitation of a metal salt. The flatness can be obtained, and the occurrence of polishing scratches on the wiring metal material or the like can be reduced.

  Among the (D) components, specific examples of organic acids include lactic acid, tartaric acid, fumaric acid, glycolic acid, phthalic acid, maleic acid, formic acid, acetic acid, oxalic acid, citric acid, malic acid, malonic acid, glutaric acid, Succinic acid, benzoic acid, p-hydroxybenzoic acid, quinolinic acid, quinaldic acid, amidosulfuric acid; amino acids such as glycine, alanine, aspartic acid, glutamic acid, lysine, arginine, tryptophan, aromatic amino acids, and heterocyclic amino acids Can be Among these, maleic acid, succinic acid, lactic acid, malonic acid, p-hydroxybenzoic acid and glycolic acid are preferred, and malonic acid is more preferred. As the component (D), one type may be used alone, or two or more types may be used in combination at any ratio.

  Among the components (D), specific examples of the organic acid salt may be the salts of the organic acids exemplified above, and may react with a base added separately in the chemical mechanical polishing aqueous dispersion to react with the organic acid. Salts may be formed. Examples of such a base include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, rubidium hydroxide and cesium hydroxide, organic alkali compounds such as tetramethylammonium hydroxide (TMAH) and choline, and ammonia and the like. Is mentioned.

  The lower limit of the content of the component (D) is preferably 0.001% by mass, more preferably 0.01% by mass, and particularly preferably 0.1% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. preferable. On the other hand, the upper limit of the content of the component (D) is preferably 2% by mass, more preferably 1% by mass, and particularly 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, a polishing rate sufficient for polishing the wiring metal material and the barrier metal material is obtained, and the deposition of metal salts is suppressed, so that the polishing scratch on the surface to be polished is reduced. May be reduced.

1.5. (E) Sodium hydroxide, potassium hydroxide, ammonium hydroxide The chemical mechanical polishing aqueous dispersion according to the present embodiment comprises (E) sodium hydroxide, potassium hydroxide, and ammonium hydroxide in order to adjust the pH. At least one selected from the group consisting of (hereinafter, also referred to as “component (E)”). By adding the component (E) to the chemical mechanical polishing aqueous dispersion according to the present embodiment, the pH of the chemical mechanical polishing aqueous dispersion can be easily adjusted to 7 or more and 14 or less.

  As the component (E), at least one selected from the group consisting of sodium hydroxide and potassium hydroxide is preferable, and potassium hydroxide is more preferable. As the component (E), one type may be used alone, or two or more types may be used in combination at any ratio.

1.6. Other Components The chemical mechanical polishing aqueous dispersion according to the present embodiment is, in addition to water as a main liquid medium, if necessary, a surfactant, a nitrogen-containing heterocyclic compound, an oxidizing agent, and a water-soluble polymer. And the like.

<Water>
The chemical mechanical polishing aqueous dispersion according to this embodiment contains water as a main liquid medium. The water is not particularly limited, but pure water is preferred. Water only needs to be blended as the balance of the constituent material of the aqueous dispersion for chemical mechanical polishing described above, and the content of water is not particularly limited.

<Surfactant>
The chemical mechanical polishing aqueous dispersion according to the present embodiment may contain a surfactant. By containing a surfactant, an appropriate viscosity may be imparted to the chemical mechanical polishing aqueous dispersion in some cases.

The surfactant is not particularly limited, and examples thereof include an anionic surfactant, a cationic surfactant, and a nonionic surfactant. Examples of the anionic surfactant include carboxylate such as fatty acid soap and alkyl ether carboxylate; sulfonate such as alkyl benzene sulfonate, alkyl naphthalene sulfonate and α-olefin sulfonate; higher alcohol sulfate Sulfates such as ester salts, alkyl ether sulfates and polyoxyethylene alkyl phenyl ether sulfates; and fluorinated surfactants such as perfluoroalkyl compounds. Examples of the cationic surfactant include an aliphatic amine salt and an aliphatic ammonium salt. Examples of the nonionic surfactant include nonionic surfactants having a triple bond, such as acetylene glycol, acetylene glycol ethylene oxide adduct, and acetylene alcohol; and polyethylene glycol type surfactants. These surfactants may be used alone or in combination of two or more.

  When the chemical mechanical polishing aqueous dispersion according to the present embodiment contains a surfactant, the content of the surfactant is preferably 0.001 to 5 with respect to the total mass of the chemical mechanical polishing aqueous dispersion. %, More preferably 0.001 to 3% by mass, and particularly preferably 0.01 to 1% by mass.

<Nitrogen-containing heterocyclic compound>
The chemical mechanical polishing aqueous dispersion according to the present embodiment may contain a nitrogen-containing heterocyclic compound. By containing the nitrogen-containing heterocyclic compound, excessive etching of the wiring metal material may be suppressed, and surface roughness after polishing may be prevented.

  As used herein, the term "nitrogen-containing heterocyclic compound" refers to an organic compound containing at least one heterocyclic ring selected from a five-membered heterocyclic ring and a six-membered heterocyclic ring having at least one nitrogen atom. Examples of the heterocycle include a five-membered heterocyclic ring such as a pyrrole structure, an imidazole structure, and a triazole structure; and a six-membered heterocyclic ring such as a pyridine structure, a pyrimidine structure, a pyridazine structure, and a pyrazine structure. These heterocycles may form a condensed ring. Specific examples include an indole structure, an isoindole structure, a benzimidazole structure, a benzotriazole structure, a quinoline structure, an isoquinoline structure, a quinazoline structure, a cinnoline structure, a phthalazine structure, a quinoxaline structure, and an acridine structure. Among the heterocyclic compounds having such a structure, a heterocyclic compound having a pyridine structure, a quinoline structure, a benzimidazole structure or a benzotriazole structure is preferable.

  Specific examples of the nitrogen-containing heterocyclic compound include aziridine, pyridine, pyrimidine, pyrrolidine, piperidine, pyrazine, triazine, pyrrole, imidazole, indole, quinoline, isoquinoline, benzoisoquinoline, purine, pteridine, triazole, triazolidine, benzotriazole, carboxy Examples include benzotriazole and the like, and further, derivatives having these skeletons. Among these, benzotriazole, triazole, imidazole and carboxybenzotriazole are preferred. These nitrogen-containing heterocyclic compounds may be used alone or in a combination of two or more.

  When the chemical mechanical polishing aqueous dispersion according to the present embodiment contains a nitrogen-containing heterocyclic compound, the content of the nitrogen-containing heterocyclic compound is preferably 0 based on the total mass of the chemical mechanical polishing aqueous dispersion. 0.05 to 2% by mass, more preferably 0.1 to 1% by mass, and particularly preferably 0.2 to 0.6% by mass.

<Water-soluble polymer>
The chemical mechanical polishing aqueous dispersion according to the present embodiment may contain a water-soluble polymer. By containing a water-soluble polymer, it may be possible to reduce polishing friction by adsorbing to a surface to be polished such as a wiring metal material. As the water-soluble polymer, a polycarboxylic acid is preferable, and polyacrylic acid, polymaleic acid, and a copolymer thereof are more preferable. One of these water-soluble polymers may be used alone, or two or more thereof may be used in combination.

The weight average molecular weight (Mw) of the water-soluble polymer is preferably from 1,000 to 1,000,000, more preferably from 3,000 to 800,000. When the weight-average molecular weight of the water-soluble polymer is in the above range, the water-soluble polymer tends to be adsorbed on the surface to be polished such as a wiring metal material, and the polishing friction may be further reduced. As a result, the occurrence of polishing scratches on the surface to be polished may be more effectively reduced. In addition, "weight average molecular weight (Mw)" in this specification refers to the weight average molecular weight in terms of polyethylene glycol measured by GPC (gel permeation chromatography).

  When the chemical mechanical polishing aqueous dispersion according to the present embodiment contains a water-soluble polymer, the content of the water-soluble polymer is 0.01 to 1 with respect to the total mass of the chemical mechanical polishing aqueous dispersion. % By mass is preferable, and 0.03 to 0.5% by mass is more preferable.

  The content of the water-soluble polymer also depends on the weight-average molecular weight (Mw) of the water-soluble polymer, but may be adjusted so that the viscosity of the chemical mechanical polishing aqueous dispersion is less than 10 mPa · s. preferable. When the viscosity of the chemical mechanical polishing aqueous dispersion is less than 10 mPa · s, it is easy to polish a wiring metal material at a high speed, and since the viscosity is appropriate, the chemical mechanical polishing aqueous dispersion is stably formed on a polishing cloth. Can be supplied.

<Oxidizing agent>
The chemical mechanical polishing aqueous dispersion according to the present embodiment may contain an oxidizing agent different from the component (B). By containing such an oxidizing agent, the surface to be polished can be oxidized to promote a complexing reaction with the polishing liquid component to create a fragile modified layer on the surface to be polished. May improve.

  Examples of such an oxidizing agent include ammonium persulfate, potassium persulfate, hydrogen peroxide, potassium hypochlorite, ozone, potassium periodate, and peracetic acid. Among these oxidizing agents, potassium periodate, potassium hypochlorite and hydrogen peroxide are preferred, and hydrogen peroxide is more preferred. The chemical mechanical polishing aqueous dispersion according to the present embodiment causes a strong oxidation reaction (Fenton reaction) by using (B) an iron salt and hydrogen peroxide in combination, thereby rapidly polishing tungsten or the like as a wiring metal material. May be able to. These oxidizing agents may be used alone or in a combination of two or more.

  When the chemical mechanical polishing aqueous dispersion according to the present embodiment contains an oxidizing agent different from the component (B), the lower limit of the content of the oxidizing agent is based on the total mass of the chemical mechanical polishing aqueous dispersion. Thus, 0.001% by mass is preferable, 0.005% by mass is more preferable, and 0.01% by mass is particularly preferable. On the other hand, the upper limit of the content of the oxidizing agent is preferably 5% by mass, more preferably 3% by mass, and particularly preferably 1.5% by mass, based on the total mass of the aqueous dispersion for chemical mechanical polishing. When an oxidizing agent different from the component (B) is contained in the above range, an oxide film may be formed on the surface of the surface to be polished including a metal such as a wiring metal material. Preferably, it is added immediately before performing the step.

1.7. pH
The pH value of the chemical mechanical polishing aqueous dispersion according to the present embodiment is 7 or more and 14 or less, preferably 8 or more and 12 or less, and more preferably 8.5 or more and 11.5 or less. When the pH value is in the above range, (A) the dispersion stability of the abrasive grains is improved, so that the polishing rate of the wiring metal material and the barrier metal material can be improved. In particular, silica is negatively charged in a basic region having a pH value of 7-14, so that the dispersion stability is improved.

  Furthermore, the chemical mechanical polishing aqueous dispersion according to the present embodiment contains the component (C), thereby suppressing the generation of a precipitate of iron hydroxide derived from the iron salt (B) at a pH in the basic region. can do. As a result, since the iron salt (B) functions as an oxidizing agent at the pH in the basic region, the surface of the wiring metal material or the barrier metal material can be passivated to form an oxide layer. Then, the oxide layer can be removed at a high speed by utilizing the mechanical polishing action of the abrasive grains (A) having excellent dispersion stability.

  The pH of the chemical mechanical polishing aqueous dispersion according to the present embodiment may be appropriately increased or decreased, for example, by adding amounts of the component (B), the component (C), the component (D), and the component (E). Can be adjusted.

  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 desktop pH meter manufactured by HORIBA, Ltd.) at 25 ° C. and 1 atm. , Can be measured.

1.8. Use The chemical mechanical polishing aqueous dispersion according to this embodiment has a pH of 7 or more and 14 or less, whereby (A) the dispersion stability of abrasive grains is improved, and (B) an iron salt is used as an oxidizing agent. (A) The oxide layer can be removed at a high speed by making the surface of the wiring metal material and the barrier metal material passivate to produce an oxide layer. There is one of the features. Therefore, the chemical mechanical polishing aqueous dispersion according to the present embodiment includes, among semiconductor manufacturing materials, any of wiring metal materials such as tungsten, copper, cobalt, titanium, and ruthenium; and barrier metal materials such as titanium nitride and tantalum nitride. It is suitable as a polishing material for chemically and mechanically polishing a surface to be polished having at least one material.

  For the chemical mechanical polishing described above, for example, a 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-described chemical mechanical polishing, a carrier (aqueous dispersion for chemical mechanical polishing) 44 is supplied from a slurry supply nozzle 42 and a carrier head holding a substrate 50 while rotating a turntable 48 to which a polishing cloth 46 is attached. This is carried out by bringing 52 into contact. FIG. 1 also shows a water supply nozzle 54 and a dresser 56.

  The polishing load of the carrier head 52 can be selected within the range of 0.7 to 70 psi, and is preferably 1.5 to 35 psi. The number of rotations of the turntable 48 and the carrier head 52 can be appropriately selected within a 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 a range of 10 to 1,000 mL / min, and is preferably 50 to 400 mL / min.

Examples of commercially available polishing apparatuses include, for example, models “EPO-112” and “EPO-222” manufactured by Ebara Corporation; models manufactured by Lapmaster SFT, models “LGP-510” and “LGP-552”; manufactured by Applied Materials. , Model "Mirra", "Reflexion"; G & P
TECHNOLOGY, model "POLI-400L"; AMAT, model "Reflexion LK"; FILTEC, model "FLTec-15".

2. Method for Producing Aqueous Dispersion for Chemical Mechanical Polishing The method for producing an aqueous dispersion for chemical mechanical polishing according to this embodiment comprises (A) abrasive grains, (B) an iron salt, and (C) a hydroxyl group and a carboxyl group. And a first step of dispersing or dissolving the compound in an aqueous medium to obtain an aqueous dispersion, and (E) at least one selected from the group consisting of sodium hydroxide, potassium hydroxide and ammonium hydroxide. A second step of adjusting the pH of the aqueous dispersion to a value of 7 or more and 14 or less.

In the first step, the components (A), (B) and (C) described above are added to a liquid medium such as water by adding the component (B) → the component (C) → the component (A) or the component (C). It is preferable to prepare an aqueous dispersion by dissolving or dispersing the component (B) → the component (A) in this order. The method of dissolving or dispersing is not particularly limited, and any method may be applied as long as it can be uniformly dissolved or dispersed.

  In the second step, the component (E) is added to the obtained aqueous dispersion to adjust the pH of the aqueous dispersion to a predetermined value in the range of 7 to 14. The second step may be performed after the first step, may be performed simultaneously with the first step, or may be further performed after being performed simultaneously with the first step.

  In the method for producing an aqueous dispersion for chemical mechanical polishing according to the present embodiment, as the third step, the aqueous dispersion after the first step and the second step is added with the component (B) such as hydrogen peroxide. An oxidizing agent other than the above may be further added to prepare the chemical mechanical polishing aqueous dispersion. When the oxidizing agent is hydrogen peroxide, hydrogen peroxide is unstable and easily releases oxygen, and easily generates hydroxyl radicals having strong oxidizing power. Preferably, it is performed immediately before.

  The aqueous dispersion for chemical mechanical polishing thus obtained can be prepared as a concentrated type stock solution, and can be diluted with a liquid medium such as water before use.

3. Examples Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” are based on mass unless otherwise specified.

3.1. Example 1
3.1.1. Preparation of Chemical Mechanical Polishing Aqueous Dispersion In pure water in a 1 liter polyethylene bottle, malonic acid 0.2% by mass, iron nitrate 0.05% by mass, hydroxyethylethylenediamine triacetic acid 0.057% by mass, A predetermined amount of potassium hydroxide and 0.5% by mass of silica abrasive particles each having a pH were added, and the mixture was sufficiently stirred to obtain an aqueous dispersion for chemical mechanical polishing of Example 1 having a pH of 9.2.

3.1.2. Evaluation method (1) Evaluation of polishing rate Using the aqueous dispersion for chemical mechanical polishing prepared as described above, a test piece obtained by cutting a tungsten substrate having no wiring pattern and a titanium nitride substrate into 3 cm × 3 cm on a resin substrate was covered. The polishing body was subjected to a chemical mechanical polishing test for one minute under the following polishing conditions. The evaluation criteria are as follows. The results are shown in Table 1.
<Polishing conditions>
-Polishing device: Model “FLTec-15” manufactured by FILTEC
-Polishing pad: Fujibo, "H600"
・ Chemical mechanical polishing aqueous dispersion supply speed: 100 mL / min ・ Spindle rotation speed: 100 rpm
・ Head rotation speed: 90 rpm
・ Head pressing pressure: 3.8 psi
-Tungsten and titanium nitride resistivity evaluation apparatus: Model III-5 manufactured by NPS Corporation-Polishing rate of tungsten and titanium nitride (Å / min) = (((volume resistivity unique to each substrate / substrate resistance before polishing) ) − (Volume resistivity unique to each substrate / resistance value of each substrate after polishing)) / polishing time (second)) × 60
(Criteria for polishing rate evaluation)
"X" indicates that one or more conditions of tungsten polishing rate of 40 ° / min or more and titanium nitride polishing rate of 25 ° / min or more are not satisfied.
・ "△" means that all the conditions of tungsten polishing rate 40Å / min or more and titanium nitride polishing rate 25Å / min or more are satisfied.
・ "○" indicates that all the conditions of tungsten polishing rate of 50 ° / min or more and titanium nitride polishing rate of 30 ° / min or more are satisfied.
When the evaluation result is “の”, the condition of “△” is satisfied, but “○” has priority.

(2) Evaluation of etching rate A test piece obtained by cutting a tungsten substrate and a cobalt substrate each having no wiring pattern on a resin substrate into 1 cm × 3 cm, and heating the aqueous dispersion for chemical mechanical polishing prepared above to 60 ° C. Dipped for 5 minutes. The etching rates of tungsten and cobalt were determined by the following equation.
・ Tungsten and cobalt resistivity evaluation device: Model II-5 manufactured by NPS Corporation
・ Etching rate of tungsten and cobalt (Å / min) = (((Volume resistivity unique to each substrate / each substrate resistance before immersion) − (Volume resistivity unique to each substrate / each substrate resistance after immersion)) ) × 10 ¹⁰ ) / immersion time (sec) × 60
(Etching rate evaluation criteria)
-"X" indicates that one or more conditions of tungsten etching rate less than 80 ° / min and cobalt etching rate less than 60 ° / min are not satisfied.
"△" indicates that all the conditions of tungsten etching rate less than 80Å / min and cobalt etching rate less than 60Å / min are satisfied.
・ "○" indicates that all conditions of tungsten etching rate less than 30Å / min and cobalt etching rate less than 50Å / min are satisfied.
When the evaluation result is “の”, the condition of “△” is satisfied, but “○” has priority.

(3) Evaluation of stability The aqueous dispersion for chemical mechanical polishing prepared above was allowed to stand at room temperature, and the presence or absence of sediment at the bottom of the polyethylene bottle was visually confirmed.
(Criteria for evaluating stability)
・ When no sediment is generated even after standing for 2 weeks or more, "○"
・ "△" indicates that sediment is generated within 2 weeks of standing
-"X" indicates that sediment occurs immediately after preparation.

3.2. Examples 2 to 11 and Comparative Examples 1 and 2
An aqueous dispersion for chemical mechanical polishing was prepared in the same manner as in Example 1, except that the type and content of each component were changed as described in Table 1 below, and each evaluation test was performed in the same manner as in Example 1. went.

3.3. Example 12
0.2% by weight of malonic acid, 0.05% by weight of iron nitrate, 0.057% by weight of hydroxyethylethylenediamine triacetic acid, 0.057% by weight of water in a 1 liter polyethylene bottle, After each of potassium oxide and 0.5% by mass of silica abrasive were added, the mixture was sufficiently stirred to obtain an aqueous dispersion having a pH of 9.2. Thereafter, hydrogen peroxide solution was further added as an oxidizing agent so as to be 1% by mass of hydrogen peroxide, whereby an aqueous dispersion for chemical mechanical polishing of Example 12 was obtained. The polishing rate of a tungsten substrate and the stability of the chemical mechanical polishing aqueous dispersion were evaluated in the same manner as in Example 1, except that the chemical mechanical polishing aqueous dispersion thus obtained was used.

3.4. Reference Example 1
0.2% by weight of malonic acid, a predetermined amount of potassium hydroxide having a pH below, and 0.5% by weight of silica abrasive were added to pure water in a 1-liter polyethylene bottle. To obtain an aqueous dispersion having a pH of 9.2. Thereafter, an aqueous hydrogen peroxide solution was further added as an oxidizing agent so as to be 1% by mass of hydrogen peroxide to obtain an aqueous dispersion for chemical mechanical polishing of Reference Example 1. The polishing rate of a tungsten substrate and the stability of the chemical mechanical polishing aqueous dispersion were evaluated in the same manner as in Example 1, except that the chemical mechanical polishing aqueous dispersion thus obtained was used.

3.5. Evaluation Results The following Tables 1 and 2 show the compositions of the aqueous dispersions for chemical mechanical polishing and the respective evaluation results of Examples and Comparative Examples.

The following products or reagents were used for each component in Tables 1 and 2, respectively.
<Abrasives>
-Silica: manufactured by Fuso Chemical Co., Ltd., colloidal silica, average particle diameter 75 nm
<Iron salt>
・ Iron nitrate: manufactured by Tama Chemical Industry Co., Ltd., product name “FN-376”
・ Iron sulfate: manufactured by Fujifilm Wako Pure Chemical Industries, trade name “iron (II) sulfate heptahydrate”
<Compound having a hydroxyl group and a carboxyl group>
・ Hydroxyethylethylenediamine triacetic acid: manufactured by Kyrest Co., Ltd., trade name “Chillest HA”
・ N, N-di (2-hydroxyethyl) glycine: manufactured by Kyrest Co., Ltd., trade name "Kyrest GA"
<Organic acid>
-Malonic acid: trade name "malonic acid" manufactured by Fuso Chemical Industry Co., Ltd.
<Oxidizing agent>
・ Hydrogen peroxide: Fujifilm Wako Pure Chemical Industries, Ltd., trade name “Hydrogen peroxide (30%)”

According to the chemical mechanical polishing aqueous dispersions of Examples 1 to 11, both the tungsten substrate and the titanium nitride substrate can be polished at a high speed, and the etching rates of both the tungsten substrate and the cobalt substrate can be reduced. all right. Further, the chemical mechanical polishing aqueous dispersions of Examples 1 to 11 contain the component (C), thereby suppressing the generation of a precipitate derived from the component (B) at a pH in a basic region, and stabilizing the stability. Was found to improve.

  Since the chemical mechanical polishing aqueous dispersion of Comparative Example 1 did not contain the component (B) and the component (C), neither the tungsten substrate nor the titanium nitride substrate could be polished at a high speed.

  Since the chemical mechanical polishing aqueous dispersion of Comparative Example 2 did not contain the component (C), a precipitate derived from the component (B) was generated and stability was impaired. Therefore, the evaluation of the polishing rate and the evaluation of the etching rate could not be performed.

  The chemical mechanical polishing aqueous dispersion of Example 12 caused a strong oxidation reaction (Fenton reaction) by using iron nitrate and hydrogen peroxide as an oxidizing agent, and the components (B) and (C) of Reference Example 1 were used. It was found that the tungsten substrate could be polished at a higher speed than the chemical mechanical polishing aqueous dispersion containing no component.

  From the above results, according to the chemical mechanical polishing aqueous dispersion according to the present invention, it is possible to suppress excessive etching of the surface to be polished including the wiring metal material and the barrier metal material, and to reduce the surface to be polished It was found that polishing could be performed at high speed. Moreover, according to the chemical mechanical polishing aqueous dispersion according to the present invention, it was found that the generation of the precipitate derived from the component (B) could be suppressed, and the stability was also improved.

  The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the invention includes configurations substantially the same as the configurations described in the embodiments (for example, a configuration having the same function, method, and result, or a configuration having the same object and effect). Further, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the invention includes a configuration having the same operational effects as the configuration described in the embodiment or a configuration capable of achieving the same object. The 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 (aqueous dispersion for chemical mechanical polishing), 46: polishing cloth, 48: turntable, 50: substrate, 52: carrier head, 54: water supply nozzle, 56: dresser, 100 ... Polishing equipment

Claims (10)

(A) abrasive grains,
(B) an iron salt;
(C) a compound having a hydroxyl group and a carboxyl group, and at least one selected from the group consisting of salts thereof;
And an aqueous dispersion for chemical mechanical polishing, having a pH of 7 or more and 14 or less.   The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the component (C) contains at least one selected from the group consisting of a compound having a hydroxyl group, a carboxyl group, and an amine structure, and a salt thereof.   3. The chemistry according to claim 1, wherein the component (C) contains at least one selected from the group consisting of a polyvalent carboxylic acid having a hydroxyl group and two or more amine structures, and a salt thereof. 4. Aqueous dispersion for mechanical polishing.   The component (C) includes N- (2-hydroxyethyl) ethylenediamine-N, N ′, N′-triacetic acid, N, N-di (2-hydroxyethyl) glycine and N, N′-ethylenebis [N -(2-Hydroxybenzyl) glycine]. The chemical mechanical polishing aqueous dispersion according to claim 1 or 2, comprising at least one member selected from the group consisting of:   The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 4, wherein the (B) iron salt contains at least one selected from the group consisting of iron nitrate and iron sulfate. Wherein (C) the content of the component _M C (mol), the (B) the content of the component when the _M B (mol), the molar ratio _M C / _{M B} is 0.3 to 3.0 The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 5, which is:   The chemistry according to any one of claims 1 to 6, further comprising (D) at least one selected from the group consisting of organic acids and salts thereof (excluding the component (C)). Aqueous dispersion for mechanical polishing.   The chemical mechanical polishing aqueous system according to any one of claims 1 to 7, further comprising (E) at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Dispersion.   9. The substrate according to claim 1, wherein the substrate is used for polishing a substrate containing at least one selected from the group consisting of tungsten, copper, cobalt, titanium, ruthenium, titanium nitride, and tantalum nitride. 9. Aqueous dispersion for chemical mechanical polishing. A first step of dispersing or dissolving (A) abrasive grains, (B) an iron salt, and (C) a compound having a hydroxyl group and a carboxyl group in an aqueous medium to obtain an aqueous dispersion;
(E) a second step of adjusting the pH of the aqueous dispersion to 7 to 14 using at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide;
A method for producing an aqueous dispersion for chemical mechanical polishing, comprising:

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