CN109312213B

CN109312213B - Polishing liquid and chemical mechanical polishing method

Info

Publication number: CN109312213B
Application number: CN201780034712.7A
Authority: CN
Inventors: 上村哲也
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2016-06-06
Filing date: 2017-05-15
Publication date: 2021-11-30
Anticipated expiration: 2037-05-15
Also published as: KR20190005918A; JPWO2017212874A1; JP6808731B2; KR102340528B1; WO2017212874A1; CN109312213A; KR20210104161A; TW201742899A; TWI727052B

Abstract

The invention provides a polishing liquid and a chemical mechanical polishing method, which are not easy to generate defects on a polished object when used for CMP. The polishing liquid of the present invention is used for chemical mechanical polishing, and contains polishing particles and an organic acid, and has a Ca concentration of 100 mass ppt or less.

Description

Polishing liquid and chemical mechanical polishing method

Technical Field

The invention relates to a polishing liquid used in chemical mechanical polishing and a chemical mechanical polishing method.

Background

In the development of semiconductor devices, in order to achieve miniaturization and high speed, high density and high integration have been demanded in recent years by miniaturization and lamination of wiring. As a technique for achieving this requirement, various techniques such as Chemical Mechanical Polishing (hereinafter, referred to as "CMP") are used. This CMP is a technique necessary for planarizing the surface of a film to be processed such as an interlayer insulating film, forming plugs, forming buried metal lines, and the like, and removes an excess metal thin film or an excess barrier layer on the insulating film when smoothing an object to be polished and forming wiring.

A general method of CMP is to apply a polishing pad to a circular polishing platen (platen), immerse the surface of the polishing pad in a polishing liquid, press the surface of an object to be polished against the pad, and rotate both the polishing platen and the object to be polished while applying a predetermined pressure (polishing pressure) from the back surface thereof, thereby planarizing the surface of the object to be polished by mechanical friction generated.

As a polishing liquid, for example, patent document 1 describes "a chemical mechanical polishing composition containing: (a) silica particles; (b) selected from the group consisting of about 5X 10 relative to the total weight of the abrasive composition^-3To about 10 mmoles/kg of at least 1 alkaline earth metal of the group of calcium, strontium, barium and mixtures thereof; (c) about 0.1 to about 15 wt% of an oxidizing agent; and (d) a liquid carrier comprising water and having a pH of from about 7 to about 13. ". If it will beThe amount of the alkaline earth metal such as calcium in the polishing composition described in patent document 1 is 0.2ppm to 400ppm in terms of the amount thereof.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-159998

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have found that many defects are generated in an object to be polished after polishing as a result of performing CMP on various objects to be polished, such as a substrate on which an inorganic insulating film such as a silicon oxide film or a silicon nitride film, or a film mainly containing polycrystalline silicon, Al, Cu, Ti, TiN, W, Ta, TaN, or the like is formed, using a polishing composition as described in patent document 1. As a result of detailed examination of the defect, it was found that most of the defect was caused by adhesion of residue and scratches (polishing scratches).

Further, it has been found that, while most of the residue adhering to the polishing object after polishing contains calcium, when polishing particles made of a negatively charged metal oxide such as silica particles or cerium oxide particles are used among the polishing particles contained in the polishing liquid, the more calcium contained in the liquid, the more marked the occurrence of scratches (polishing scratches) when the polishing object is chemically and mechanically polished.

Accordingly, an object of the present invention is to provide a polishing liquid which is less likely to cause defects in an object to be polished when used in CMP.

Another object of the present invention is to provide a chemical mechanical polishing method using the polishing liquid.

As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by a polishing liquid having a specific composition and having a reduced concentration of calcium contained in the liquid, and have completed the present invention.

That is, it has been found that the above object can be achieved by the following configuration.

(1) A polishing liquid used in chemical mechanical polishing,

the polishing liquid contains abrasive grains and an organic acid, and has a Ca concentration of 100 mass ppt or less.

(2) The polishing slurry according to (1), wherein,

the content of the metal particles in the polishing liquid, which is determined by SNP-ICP-MS measurement, is 100 mass ppt or less.

(3) The polishing slurry according to (1) or (2), further comprising a charge control agent,

the content of the charge control agent is 0.6 or less by mass ratio relative to the content of the organic acid,

the Ca concentration is 0.01 to 100 mass ppt.

(4) The polishing liquid according to any one of (1) to (3), wherein,

the Ca concentration is 0.01 to 80 mass ppt.

(5) The polishing slurry according to any one of (1) to (4), wherein the organic acid contains a polybasic acid selected from the group consisting of malonic acid, succinic acid, malic acid and citric acid.

(6) The polishing liquid according to any one of (1) to (5), wherein the pH is in the range of 1.5 to 5.0 or 9.0 to 12.0.

(7) The polishing liquid according to any one of (3) to (6), wherein the charge control agent comprises an inorganic acid selected from the group consisting of nitric acid, boric acid and phosphoric acid, or an ammonium salt thereof, or an ammonium salt of an organic acid.

(8) A chemical mechanical polishing method comprises the following steps: a polishing liquid according to any one of (1) to (7) is supplied to a polishing pad mounted on a polishing platen, while a surface to be polished of a subject to be polished is brought into contact with the polishing pad, and the subject to be polished is polished by relatively moving the polishing pad and the polishing body.

Effects of the invention

According to the present invention, it is possible to provide a polishing liquid which is less likely to cause defects on a surface to be polished when used for CMP.

Further, according to the present invention, there can be provided a chemical mechanical polishing method using the polishing liquid.

[ embodiment ]

The present invention will be described in detail below.

The following description of the constituent elements may be made in accordance with typical embodiments of the present invention, but the present invention is not limited to those embodiments.

In the present specification, the numerical range represented by "to" means a range including numerical values before and after "to" as a lower limit value and an upper limit value.

In the labeling of the group (atomic group) in the present specification, a substituted or unsubstituted label is not described, and a group having no substituent and a group having a substituent are included within a range not to impair the effect of the present invention. For example, "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group). This also applies to the individual compounds.

In the present specification, the term "preparation" means preparation by synthesizing or preparing a specific material, and includes obtaining a predetermined substance by purchase or the like.

In the present specification, "ppm" means "parts per million-million (10-6)", and "ppt" means "parts per million-million (10-12)".

In the present invention, 1psi corresponds to 6894.76 Pa.

[ polishing solution ]

The polishing liquid of the present invention contains abrasive grains and an organic acid, and has a Ca concentration (calcium concentration) of 100 mass ppt or less.

The polishing liquid of the present invention has the above-described structure, and therefore, when used for CMP, defects are less likely to occur in an object to be polished.

The detailed reason for this is not clear, but can be presumed as follows.

The polishing liquid of the present invention is characterized by being purified during the production thereof until the Ca concentration becomes 100 mass ppt or less by ion exchange and/or filtration, or the like.

With the above feature, formation of particles with calcium as nuclei can be suppressed, and adhesion of calcium as a residue to the polishing object can be suppressed. Further, when a large amount of calcium (particularly, ionic calcium) is contained in the liquid, negative charges around particles such as silica particles as abrasive grains are neutralized to decrease the zeta potential, and it is considered that aggregation of the particles is likely to occur. However, the above-described structure makes it difficult for particles to aggregate, and as a result, scratches (polishing scratches) can be suppressed when the chemical mechanical polishing is performed on the object to be polished.

And, the organic acid is complexed with the free calcium ions to reduce the amount of free calcium ions. As a result, aggregation of the particles can be further suppressed.

The adjustment of the Ca concentration by ion exchange, filtration, or the like may be performed on the solvent or raw material component used in the production process of the polishing liquid, or may be performed on the polishing liquid after production.

When the polishing liquid is used for CMP, the concentration of Ca in the polishing liquid is preferably 80 mass ppt or less, more preferably 50 mass ppt or less, further preferably 45 mass ppt or less, and particularly preferably 25 mass ppt or less, from the viewpoint that defects are not easily generated in the polishing object. The lower limit is not particularly limited, and is preferably 0.01 mass ppt or more from the viewpoint of improving the defect performance.

In the present specification, the Ca concentration refers to the total concentration of ionic calcium and nonionic calcium (e.g., calcium particles) contained in the polishing liquid, in other words, the content of calcium atoms contained in the polishing liquid.

In the present specification, the term "polishing liquid" means not only a polishing liquid used for polishing (i.e., a polishing liquid diluted as necessary) but also a concentrated polishing liquid as long as the Ca concentration is satisfied. The concentrated solution or the concentrated polishing liquid is prepared so that the concentration of a dissolved substance is higher than that of the polishing liquid used for polishing, and is used for polishing by diluting with water, an aqueous solution or the like when used for polishing. The dilution ratio is usually 1 to 20 times by volume. In the present specification, "concentrated" and "concentrated liquid" are used not in accordance with the state of use but in accordance with the conventional expressions indicating "viscous" and "viscous liquid", and are used in a different manner from the meaning of the general terms accompanying physical concentration operation such as evaporation.

The liquid properties and the components of the polishing liquid of the present invention will be described in detail below.

＜pH＞

The pH of the polishing liquid is usually 1.0 to 14.0, and can be appropriately set depending on the material of the object to be polished.

For example, when the polishing target is a metal layer as described later, the pH is preferably 9.0 to 12.0. Since the pH is 9.0 or more, the surface to be polished is activated and becomes a state in which it is more easily polished, and since the pH is 12.0 or less, the possibility that the abrasive grains such as colloidal silica are chemically dissolved is reduced.

Further, for example, when the polishing target is an inorganic semiconductor layer such as an inorganic insulating layer or polycrystalline silicon described later, the pH is preferably 1.5 to 5.0. Since the pH is 1.5 or more, corrosion of various components related to the polishing apparatus is prevented, and since the pH is 5.0 or less, the surface to be polished is activated and is in a more easily polished state.

< abrasive grains >

The polishing liquid contains polishing particles.

The abrasive grains are not particularly limited, and known abrasive grains can be used.

Examples of the abrasive grains include inorganic abrasive grains such as silica, alumina, zirconia, ceria, titania, germania, and silicon carbide; organic abrasive grains such as polystyrene, polyacrylic acid and polyvinyl chloride. Among them, silica particles or cerium oxide particles are preferable as abrasive grains, and silica particles are more preferable from the viewpoint of excellent dispersion stability in a polishing liquid and the viewpoint of a small number of scratches generated by CMP.

The silica particles are not particularly limited, and examples thereof include precipitated silica, fumed silica, and colloidal silica. Among them, colloidal silica is preferable.

The average primary particle size of the abrasive particles is not particularly limited, but is preferably 1 to 100nm from the viewpoint of more excellent dispersion stability of the polishing liquid. The average primary particle size can be confirmed by a manufacturer's catalog or the like.

Examples of commercially available products of the abrasive grains include colloidal silica such as PL-1, PL-3, PL-7 and PL-10H (all trade names, manufactured by FUSO CHEMICAL CO., LTD.).

The content of the abrasive grains is not particularly limited, but is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, preferably 10 mass% or less, and more preferably 5 mass% or less, based on the total mass of the polishing liquid. When the polishing liquid is used in CMP within the above range, a more excellent polishing rate can be obtained.

The abrasive grains may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When 2 or more kinds of abrasive grains are used in combination, the total content is preferably within the above range.

< organic acid >

The polishing liquid contains an organic acid. The organic acid is different from a compound of an oxidizing agent described later, and has a function of promoting oxidation of a metal, pH adjustment of a polishing liquid, adsorption of ionic calcium contained in the liquid (a coordination bond is preferable as an adsorption form), and a function as a buffer.

As the organic acid, a water-soluble organic acid is preferable.

The organic acid is not particularly limited, and a known organic acid can be used.

Examples of the organic acid include salts such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, hydroxyethyliminodiacetic acid, iminodiacetic acid, and ammonium salts and/or alkali metal salts thereof. Among them, from the viewpoint of more excellent chelating properties of ionic calcium contained in the liquid, a polybasic acid or a salt thereof is preferable, and a polybasic acid selected from malonic acid, succinic acid, malic acid, and citric acid is more preferable.

The content of the organic acid is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, preferably 25% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less, based on the total mass of the polishing liquid.

When the content of the organic acid is 0.001 mass% or more, a more excellent polishing rate can be obtained and the occurrence of defects can be further suppressed when the polishing liquid is used for CMP. When the content of the organic acid is 25% by mass or less, dishing is less likely to occur on the surface to be polished when the polishing liquid is used for CMP.

Further, 1 kind of the organic acid may be used alone, or 2 or more kinds may be used in combination. When 2 or more organic acids are used in combination, the total content is preferably within the above range.

< Charge control agent >

The polishing liquid preferably contains a charge control agent. The charge control agent has a function of controlling the surface charge of, for example, silica particles or cerium oxide particles as abrasive grains to suppress aggregation of the particles with each other.

The charge control agent is not particularly limited, and is preferably an inorganic acid selected from the group consisting of nitric acid, boric acid, and phosphoric acid, or an ammonium salt thereof, or an ammonium salt of an organic acid, from the viewpoint of easily accumulating on the surface of each particle.

Among them, nitric acid or ammonium nitrate is preferable as the inorganic acid selected from the group consisting of nitric acid, boric acid and phosphoric acid, or an ammonium salt thereof. Further, as the ammonium salt of the organic acid, there can be mentioned ammonium salts of the above-mentioned organic acids, and among them, ammonium benzoate is preferable.

When the polishing liquid contains a charge control agent, the content thereof is not particularly limited, and when the polishing liquid is used for CMP, from the viewpoint of making defects less likely to occur in an object to be polished, the content is preferably 3% by mass or less, more preferably 1% by mass or less, further preferably 0.5% by mass or less, and particularly preferably 0.05% by mass or less, based on the total mass of the polishing liquid. The lower limit is not particularly limited, but is preferably 0.0001% by mass or more.

When the polishing liquid is used for CMP, the content of the charge control agent is preferably 0.6 or less, more preferably 0.3 or less, further preferably 0.1 or less, particularly preferably 0.03 or less, and most preferably 0.001 or less in terms of a mass ratio relative to the content of the organic acid, from the viewpoint that defects are less likely to occur in the object to be polished. The lower limit is not particularly limited, but is preferably 0.0001 or more.

The charge control agent may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When 2 or more charge control agents are used in combination, the total content is preferably within the above range.

< oxidant >

The polishing liquid preferably contains an oxidizing agent when used for CMP applications for removing an excess metal thin film and the like during wiring formation. The oxidizing agent has a function of oxidizing a metal to be polished which is present on a surface to be polished of the object to be polished.

The oxidizing agent is not particularly limited, and a known oxidizing agent can be used.

Examples of the oxidizing agent include hydrogen peroxide, peroxides, nitric acid, nitrates, iodates, periodates, hypochlorites, chlorites, chlorates, perchlorates, persulfates, dichromates, permanganates, ozone water, silver (II) salts, and iron (III) salts. Among them, hydrogen peroxide is preferred.

When the polishing liquid contains an oxidizing agent, the content thereof is not particularly limited, but is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less, based on the total mass of the polishing liquid.

When the content of the oxidizing agent is 0.005% by mass or more, a more excellent polishing rate can be obtained when the polishing liquid is used for CMP. If the content of the oxidizing agent is 10 mass% or less, dishing is less likely to occur on the surface to be polished when the polishing liquid is used for CMP.

Further, 1 kind of the oxidizing agent may be used alone, or 2 or more kinds may be used in combination. When 2 or more oxidizing agents are used in combination, the total content is preferably within the above range.

< Azole Compounds >

The polishing liquid preferably contains an azole compound when used for CMP for removing an unnecessary metal thin film or the like during wiring formation. The azole compound not only enhances the oxidizing action by the oxidizing agent as an optional component, but also adsorbs to the surface of the object to be polished to form a coating film and controls corrosion of the metal surface, and therefore, the occurrence of dishing or corrosion can be suppressed.

In the present specification, the azole compound is a compound containing a five-membered heterocyclic ring containing 1 or more nitrogen atoms, and the number of nitrogen atoms is preferably 1 to 4. The azole compound may contain an atom other than a nitrogen atom as a hetero atom.

The derivative is a compound having a substituent which the five-membered heterocyclic ring may have.

Examples of the azole compound include compounds having a pyrrole skeleton, an imidazole skeleton, a pyrazole skeleton, an isothiazole skeleton, an isoxazole skeleton, a triazole skeleton, a tetrazole skeleton, a thiazole skeleton, an oxazole skeleton, a thiadiazole skeleton, an oxadiazole skeleton, and a tetrazole skeleton.

The azole compound may be an azole compound having a polycyclic structure including a fused ring in the skeleton. Examples of the azole compound having a polycyclic structure include compounds having an indole skeleton, a purine skeleton, an indazole skeleton, a benzimidazole skeleton, a carbazole skeleton, a benzoxazole skeleton, a benzothiazole skeleton, a benzothiadiazole skeleton, and a naphthoimidazole skeleton.

Examples of the substituent that may be contained in the azole compound include, but are not particularly limited to, a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom), an alkyl group (a linear, branched or cyclic alkyl group which may be a polycycloalkyl group such as a bicycloalkyl group or may contain an activated methine group), an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group (an optional substitution position), an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heterocycloxycarbonyl group, a carbamoyl group (a substituted carbamoyl group may include, for example, an N-hydroxycarbamoyl group, an N-acylcarbamoyl group, an N-sulfonylcarbamoyl group, an N-carbamoylcarbamoyl group, a thiocarbamoyl group and an N-sulfamoylcarbamoyl group), a carbazolyl group, a carboxyl group or a salt thereof, an oxalyl group, an oxamyl group, a cyano group, a carbodiimide group, Formyl, hydroxy, alkoxy (including an ethyleneoxy group or a group including an ethyleneoxy group as a repeating unit), aryloxy, heterocyclyloxy, acyloxy, carbonyloxy, carbamoyloxy, sulfonyloxy, amino, acylamino, sulfonamido, ureido, thio, N-hydroxyureido, imido, carbonylamino, sulfonamido, semicarbazide, thiosemicarbazide, hydrazino, ammonium, oxamido, N- (alkyl or aryl) sulfonylureido, N-acylureido, N-acylsulfamoylamino, hydroxyamino, nitro, a heterocyclic group including a quaternary nitrogen atom (for example, a pyridyl group, an imidazolyl group, a quinolyl group and an isoquinolyl group), an isocyano group, an imino group, a mercapto group, (alkyl, aryl or heterocyclic) thio, (alkyl, aryl or heterocyclic) disulfide group, (alkyl, aryl or heterocyclic group, a (alkyl, aryl or heterocyclic) disulfide group, Aryl) sulfonyl, (alkyl or aryl) sulfinyl, sulfo or a salt thereof, sulfamoyl (examples of the sulfamoyl group having a substituent include N-acylsulfamoyl and N-sulfonylsulfamoyl) or a salt thereof, phosphino, phosphinyl, phosphinyloxy, phosphinylamino and silyl groups, and the like.

Among them, preferred are a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom), an alkyl group (which is a linear, branched or cyclic alkyl group, for example, a bicycloalkyl group which may be a polycycloalkyl group and may contain an active methine group), an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group (optionally substituted).

Here, the "active methine group" refers to a methine group substituted with 2 electron-withdrawing groups. "Electron withdrawing group" means, for example, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, an alkylsulfonyl group, an arylsulfonyl group, a sulfamoyl group, a trifluoromethyl group, a cyano group, a nitro group or a carbonylimino group. And, 2 electron-withdrawing groups may be bonded to each other to constitute a cyclic structure. The term "salt" refers to cations such as alkali metals, alkaline earth metals, and heavy metals; ammonium ion and organic cation such as phosphonium ion.

Specific examples of the azole compound include 5-methylbenzotriazole, 5-aminobenzotriazole, benzotriazole, 5, 6-dimethylbenzotriazole, 3-amino-1, 2, 4-triazole, 3, 5-dimethylpyrazole, pyrazole, and imidazole.

Among them, preferred are compounds containing a benzotriazole compound (a compound containing a benzotriazole skeleton) and compounds other than a benzotriazole compound (compounds not containing a benzotriazole skeleton). The compound having a benzotriazole skeleton is easily and strongly coordinated to copper oxidized by an oxidizing agent. On the other hand, even in the case of an azole compound, a compound not having a benzotriazole skeleton is likely to be weakly coordinated to oxidized copper. By using these compounds in combination, the polishing rate can be further increased and the dishing suppressing effect can be obtained.

The compound not containing the benzotriazole skeleton is not particularly limited, and from the viewpoint of further increasing the polishing rate, 3-amino-1, 2, 4-triazole, or imidazole is preferable.

The content of the azole compound is not particularly limited, but is preferably 0.001 to 2% by mass, more preferably 0.001 to 1% by mass, and still more preferably 0.001 to 0.1% by mass, based on the total mass of the polishing liquid, from the viewpoint of further increasing the polishing rate.

In the case of using 2 or more kinds of azole compounds, the total amount thereof is preferably included in the above range.

< grinding accelerator >

The polishing liquid may contain a polishing accelerator. The inclusion of the polishing accelerator makes it easier to improve the in-plane uniformity (flatness) of the polished surface (for example, inorganic insulating layer) of the object to be polished.

As a grinding acceleratorExamples thereof include sulfonic acid compounds and phosphonic acid compounds, preferably those having a sulfonic acid group (-SO)₃H) And amino (-NH)₂-NHR or-NRR'). R and R' are each independently an alkyl group, a substituted alkyl group or an aryl group. Examples of the compound having a sulfonic acid group and an amino group include sulfamic acids such as 3-aminobenzenesulfonic acid, 4-aminobenzenesulfonic acid, aminomethanesulfonic acid, 1-aminoethanesulfonic acid, 2-amino-1-ethanesulfonic acid (taurine) and 1-aminopropane-2-sulfonic acid, amidosulfuric acid (sulfamic acid) and N-methanesulfonic acid. Among them, 4-aminobenzenesulfonic acid or amidosulfuric acid is more preferable.

When the polishing slurry contains a polishing accelerator, the content thereof is not particularly limited, and is preferably 0.001 to 10.0% by mass, more preferably 0.01 to 5.0% by mass, based on the total mass of the polishing slurry, from the viewpoint of further improving the in-plane uniformity and the polishing rate.

The polishing accelerator may be used alone in 1 kind, or may be used in combination of 2 or more kinds. When 2 or more kinds of polishing accelerators are used in combination, the total content is preferably within the above range.

< water >)

The polishing liquid preferably contains water. The water contained in the polishing liquid is not particularly limited, and ion-exchanged water, pure water, or the like can be used.

The content of water is not particularly limited, but is preferably 50 to 99% by mass in the total mass of the polishing liquid.

< surfactant and/or hydrophilic Polymer >

The polishing liquid may contain a surfactant and/or a hydrophilic polymer. The surfactant and the hydrophilic polymer have an effect of reducing the contact angle between the polishing liquid and the surface to be polished, and the polishing liquid is easily wet and spread on the surface to be polished.

The surfactant is not particularly limited, and a known surfactant selected from the group consisting of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, and the like can be used. Examples of the anionic surfactant include carboxylates, sulfonates such as alkylbenzenesulfonic acid, sulfate ester salts, and phosphate ester salts.

Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

Examples of the amphoteric surfactant include carboxybetaines, aminocarboxylates, imidazolinebetaines, lecithins, and alkylamine oxides.

Examples of the nonionic surfactant include ether type, ether ester type, nitrogen-containing type, glycol type, and fluorine type surfactants.

When the polishing liquid contains a surfactant, the content thereof is not particularly limited, and is preferably 0.00001 to 1.0% by mass, more preferably 0.0001 to 0.2% by mass, and further preferably 0.0001 to 0.05% by mass, based on the total mass of the polishing liquid, from the viewpoint that defects are less likely to occur in an object to be polished when the polishing liquid is used for CMP.

Further, 1 kind of surfactant may be used alone, or 2 or more kinds may be used in combination. When 2 or more surfactants are used in combination, the total content is preferably within the above range.

Examples of the hydrophilic polymer include polyvinyl alcohols such as polyethylene glycol, alkyl ethers of polyvinyl alcohols, polysaccharides such as polyvinyl alcohol, polyvinyl pyrrolidone, and alginic acid, carboxylic acid-containing polymers such as polymethacrylic acid and polyacrylic acid, polyacrylamide, polymethacrylamide, and polyethyleneimine. Specific examples of the hydrophilic polymer include water-soluble polymers described in paragraphs 0042 to 0044 of Japanese patent application laid-open No. 2009-088243 and paragraphs 0026 of Japanese patent application laid-open No. 2007-194261.

The hydrophilic polymer is preferably a water-soluble polymer selected from the group consisting of polyacrylamide, polymethacrylamide, polyethyleneimine and polyvinylpyrrolidone. The polyacrylamide and polymethacrylamide more preferably have a hydroxyalkyl group (e.g., N- (2-hydroxyethyl) acrylamide polymer) or a substituent group containing a polyalkylene oxide chain on a nitrogen atom, and further preferably have a weight average molecular weight of 2000 to 50000. The polyethyleneimine preferably has a polyalkylene oxide chain on a nitrogen atom, more preferably has a repeating unit represented by the following general formula (a), and further preferably has a weight average molecular weight of 2000 to 50000. In the present specification, the weight average molecular weight is a value expressed as a polystyrene equivalent value by GPC (gel permeation chromatography).

General formula (A)

[ chemical formula 1]

In the general formula (A), EO represents an oxyethylene group, and PO represents an oxypropylene group.

m and n represent a number of 0 to 200 (average number in the case of a mixture), and m + n is 2 to 200.

The alkylene oxide chain formed by the oxyethylene group and the oxypropylene group may be a random chain or a block chain.

Preferably, polyethyleneimine having an HLB (hydrophilic-lipophilic Balance Hydrophile-Lipophile Balance) value of 16 to 19 is used.

When the polishing liquid contains a hydrophilic polymer, the content thereof is not particularly limited, and when the polishing liquid is used for CMP, the content is preferably 0.0001 to 2.0% by mass, more preferably 0.01 to 1.0% by mass, and further preferably 0.03 to 0.4% by mass, based on the total mass of the polishing liquid, from the viewpoint that defects are less likely to occur in an object to be polished.

The hydrophilic polymer may be used alone in 1 kind, or may be used in combination in 2 or more kinds. When 2 or more kinds of hydrophilic polymers are used in combination, the total content is preferably within the above range.

Also, a surfactant and a hydrophilic polymer may be used in combination.

< organic solvent >

The polishing liquid may contain an organic solvent. The organic solvent is not particularly limited, and a known organic solvent can be used. Among them, water-soluble organic solvents are preferable.

Examples of the organic solvent include ketone solvents, ether solvents, alcohol solvents, glycol ether solvents, and amide solvents.

More specifically, examples thereof include acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethylene glycol, propylene glycol, and ethoxyethanol.

Among them, methyl ethyl ketone, tetrahydrofuran, dioxane, N-methylpyrrolidone, methanol, ethanol, ethylene glycol, or the like is preferable.

When the organic solvent is contained, the content thereof is not particularly limited, but is preferably 0.001 to 5.0% by mass, more preferably 0.01 to 2.0% by mass, based on the total mass of the polishing liquid.

If the content of the organic solvent is in the range of 0.01 to 2.0 mass%, a polishing liquid having further improved defect performance can be obtained.

Further, 1 kind of the organic solvent may be used alone, or 2 or more kinds may be used in combination. When 2 or more organic solvents are used in combination, the total content is preferably within the above range.

< pH adjuster and/or pH buffer >

The polishing liquid may further contain a pH adjuster and/or a pH buffer to set a predetermined pH. Examples of the pH adjuster and/or the pH buffer include an acid agent and/or an alkali agent. The pH adjuster and the pH buffer are compounds different from the organic acid or the charge adjuster.

The acid agent is not particularly limited, and examples thereof include sulfuric acid.

The alkaline agent is not particularly limited, and examples thereof include ammonia; ammonium hydroxide and organic ammonium hydroxides (e.g., tetrabutylammonium hydroxide); alkanolamines such as diethanolamine, triethanolamine and triisopropanolamine; alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; carbonates such as sodium carbonate; phosphates such as trisodium phosphate; borates and tetraborates; hydroxybenzoate salts, and the like.

Further, organic ammonium hydroxide (for example, tetrabutylammonium hydroxide) has a function as a stabilizer for abrasive grains in addition to the function as the pH adjuster and/or the pH buffer.

The content of the pH adjuster and/or the pH buffer is not particularly limited as long as it is an amount necessary for maintaining the pH within a desired range, and is preferably 0.001 to 0.1% by mass in the total mass of the polishing liquid.

[ method for producing polishing slurry ]

The polishing liquid can be produced by a known method.

The method for producing the polishing liquid will be described in detail below.

< Process for purifying raw Material >

In the production of the polishing slurry, it is desirable that any 1 or more of the raw materials used for the production of the polishing slurry are purified in advance by distillation, ion exchange, filtration or the like in order to reduce the Ca concentration in the liquid. The degree of purification is, for example, preferably to a purity of 99% or more, more preferably to a purity of 99.9% or more. In order to obtain the remarkable effect based on the present invention, it is important to use these raw materials of high purity.

The purification method is not particularly limited, and may be a method of passing through an ion exchange resin or an RO Membrane (Reverse Osmosis Membrane), or a method of distillation or filtration described later. Specifically, for example, a method of purifying a liquid by passing the liquid through a reverse osmosis membrane or the like 1 time, and then purifying the liquid by passing the liquid through a purification apparatus comprising a cation exchange resin, an anion exchange resin, or a mixed bed type ion exchange resin 2 times, and the like.

The purification treatment may be carried out by combining a plurality of known purification methods.

Further, the purification treatment may be carried out plural times.

(filtration)

The filter may be used without particular limitation as long as it is conventionally used for filtration applications and the like. Examples thereof include filters based on fluororesins such as Polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyamide resins such as nylon, and polyolefin resins (including high density and ultrahigh molecular weight) such as Polyethylene and Polypropylene (PP). Among these materials, those selected from the group consisting of polyethylene, polypropylene (including high-density polypropylene), fluororesins such as PTFE and PTA, and polyamide resins such as nylon are preferred, and among these, filters of fluororesins such as PTFE and PTA are more preferred. By using a filter formed of these materials, it is possible to effectively remove highly polar foreign matter that easily causes defects, and also to effectively reduce the Ca concentration.

The critical surface tension of the filter is preferably 70mN/m or more, more preferably 95mN/m or less, and still more preferably 75mN/m or more and 85mN/m or less. In addition, the value of the critical surface tension is the nominal value of the manufacturer. By using a filter having a critical surface tension in the above range, it is possible to effectively remove highly polar foreign matter that is likely to cause defects, and also possible to effectively reduce the Ca concentration.

The pore diameter of the filter is preferably 2 to 20nm, more preferably 2 to 15 nm. By setting these ranges, it is possible to suppress clogging of filtration, reliably remove fine foreign matters such as impurities and aggregates contained in the raw material, and effectively reduce the Ca concentration.

When a filter is used, different filters may be combined. In this case, the filtration using the 1 st filter may be performed only 1 time, or may be performed 2 times or more. When filtration is performed 2 or more times by combining different filters, the pore size after 2 nd filtration is preferably the same as or smaller than that of the 1 st filtration. Further, the 1 st filters having different pore sizes within the above range may be combined. The pore size can be referred to herein as the nominal value of the filter manufacturer. As commercially available filters, it is possible to select from various filters provided by, for example, NIHON fill Ltd, a dvantec Toyo Kaisha, Ltd, NIHON Entegris K.K, (formerly Nippon squirrel co., Ltd), kit z MICROFILTER corporation, and the like. Further, a "P-nylon filter (pore diameter: 0.02 μm, critical surface tension: 77 mN/m)" made of polyamide; (NIHON PALL LTD.; "PE-Wash Filter (pore size: 0.02 μm)" made of high-density polyethylene); (NIHON PALL LTD.) "PE-Wash Filter (pore size 0.01 μm)" made of high-density polyethylene; (NIHON PALL LTD. manufacture).

The 2 nd filter may be formed of the same material as the 1 st filter. The pore diameter of the No. 2 filter is preferably about 1 to 10 nm.

In the present invention, the filtration step is preferably performed at room temperature (25 ℃ C.) or lower. More preferably 23 ℃ or lower, and still more preferably 20 ℃ or lower. And is preferably 0 ℃ or higher, more preferably 5 ℃ or higher, and further preferably 10 ℃ or higher.

In the filtering step, particulate foreign matter and impurities can be removed, but at the above temperature, the amount of the particulate foreign matter and/or impurities dissolved in the raw material is reduced, and therefore, the particulate foreign matter and/or impurities can be more effectively removed by the filtering.

Also, the filter used is preferably treated before the raw material is filtered. The liquid used in this treatment is not particularly limited, but the metal content is preferably less than 0.001 mass ppt, and examples thereof include a liquid obtained by purifying an organic solvent other than the water so that the metal content falls within the above range. By pretreating the filter with the liquid having a reduced metal content as described above, the Ca concentration can be effectively reduced.

< method of quantitation >

The concentration of Ca contained in the raw material, the polishing liquid, or the like can be analyzed by an ICP-MS method (inductively coupled plasma mass spectrometry, and as a measuring apparatus, for example, Yokogawa Analytical Systems, manufactured by inc., Agilent 7500cs type) or the like.

The Ca concentration measured by the ICP-MS method is the total concentration of ionic calcium and nonionic calcium (e.g., calcium particles), in other words, corresponds to the content of calcium atoms contained in the polishing liquid.

Further, the amount of metal atoms present in a solution can be measured by a Single Nano Particle Inductively Coupled Plasma Mass Spectrometry (SNP-ICP-MS), which has been recently developed, in a manner of dividing into an ionic metal and a nonionic metal (metal Particle). Here, the nonionic metal (metal particles) is a component that is not dissolved in a liquid but exists as a solid.

In the polishing liquid of the present invention, the content of the nonionic metal (metal particles) as measured by the SNP-ICP-MS method is preferably 100 mass ppt or less, more preferably 50 mass ppt or less, with respect to the total mass of the polishing liquid, from the viewpoint of improving defect performance. The lower limit is not particularly limited, but is usually 0.1 mass ppt or more.

In the present specification, the nonionic metal (metal particle) refers to all metal elements contained in the liquid without limiting the metal elements.

When the amount of the nonionic metal (metal particles) contained in the polishing liquid is measured, ultra-high-purity hydrofluoric acid may be added to the polishing liquid to dissolve solid components such as polishing particles contained in the polishing liquid, and then the measurement by the SNP-ICP-MS method may be performed.

The preparation, treatment analysis and measurement of the polishing slurry of the present invention are all preferably carried out in a clean room. The cleanroom preferably meets 14644-1 cleanroom standards. Preferably, any one of ISO (international organization for standardization) class 1, ISO class 2, ISO class 3, or ISO class 4 is satisfied, more preferably, ISO class 1 or ISO class 2 is satisfied, and further preferably, ISO class 1 is satisfied.

< liquid preparation Process >

The polishing liquid of the present invention can be produced by mixing the above components, for example, without any particular limitation. The order and/or timing of mixing the above components is not particularly limited, and examples thereof include a method of dispersing abrasive grains in water having an adjusted pH in advance and sequentially mixing predetermined components.

If necessary, the polishing liquid of the liquid to be adjusted may be subjected to purification treatment such as filtration as described above to adjust the Ca concentration.

< grinding device >

The polishing apparatus is not particularly limited, and a known chemical mechanical polishing apparatus (hereinafter, also referred to as "CMP apparatus") to which the CMP method according to the above embodiment can be applied can be used.

As the CMP apparatus, for example, a general CMP apparatus including a holder holding an object to be polished (for example, a semiconductor substrate or the like) having a surface to be polished and a polishing platen (to which a motor or the like having a variable rotation speed is attached) to which a polishing pad is attached can be used. As a commercially available product, for example, Reflexion (manufactured by Applied Materials, inc.).

[ chemical mechanical polishing method ]

The chemical mechanical polishing method using the polishing liquid of the present invention is not particularly limited, and a known chemical mechanical polishing method can be applied.

As a chemical mechanical polishing method according to an embodiment in which the polishing liquid of the present invention can be used, there can be mentioned a chemical mechanical polishing method (hereinafter, also referred to as "CMP method") including the following steps: the polishing liquid is supplied to a polishing pad attached to a polishing platen, and the surface to be polished of the object to be polished is brought into contact with the polishing pad, and the object to be polished is polished by relatively moving the polishing pad and the object to be polished, thereby obtaining a polished object.

< body to be ground >

The polishing target to which the CMP method according to the above embodiment can be applied is not particularly limited. An example of the object to be polished is a substrate having at least 1 selected from the group consisting of a metal layer, an inorganic insulating layer, and an inorganic semiconductor layer on the surface thereof. That is, the metal layer, the inorganic insulating layer, or the inorganic semiconductor layer is polished by the CMP method according to the above embodiment. In addition, these layers may be laminated.

The substrate is not particularly limited, and includes, for example, a semiconductor substrate formed of a single layer and a semiconductor substrate formed of a plurality of layers.

The material constituting the semiconductor substrate composed of a single layer is not particularly limited, and is generally preferably composed of a III-V group compound such as silicon, silicon germanium, GaAs, or any combination thereof.

In the case of a semiconductor substrate composed of a plurality of layers, the structure is not particularly limited, and for example, an integrated circuit structure may be provided in which interconnection structures (in-connection features) such as metal lines and dielectric materials are exposed on the semiconductor substrate such as silicon.

The metal layer is not particularly limited, and examples thereof include a wiring layer and a barrier metal layer which can form wiring. Examples of the metal component contained in the wiring layer capable of forming the wiring include copper-based metals (copper, copper alloys, and the like). The metal material constituting the barrier metal layer is not particularly limited, and a known low-resistance metal material can be used. As the low-resistance metal material, for example, TiN, TiW, Ta, TaN, W, or WN is preferable, and among them, Ta or TaN is more preferable.

The material constituting the inorganic insulating layer is not particularly limited, and examples thereof include silicon oxide, silicon nitride, silicon carbide, silicon carbonitride, silicon oxycarbide, and silicon oxynitride. Among them, silicon oxide or silicon nitride is preferable.

The material constituting the inorganic semiconductor layer is not particularly limited, and examples thereof include polysilicon and modified silicon in which impurity elements such as B and P are doped in polysilicon.

< grinding pressure >

In the CMP method according to the above embodiment, the polishing is preferably performed at a polishing pressure, that is, at a pressure 3000 to 25000Pa, more preferably 6500 to 14000Pa, which is generated at a contact surface between a surface to be polished and a polishing pad.

< rotational speed of polishing platen >

In the CMP method according to the above embodiment, the polishing is preferably performed at a rotation speed of 50 to 200rpm, more preferably 60 to 150rpm, of the polishing platen.

Further, the polishing platen may be rotated in a planetary manner or the belt-shaped polishing pad may be linearly moved in one direction of the longitudinal direction in order to relatively move the polishing body and the polishing pad and to rotate and/or oscillate the carrier. In addition, the holder may be in any state of being fixed, rotated, or swung. These polishing methods can be appropriately selected depending on the surface to be polished and/or the polishing apparatus as long as the polishing body and the polishing pad are moved relative to each other.

< method for supplying polishing slurry >

In the CMP method according to the above embodiment, the polishing liquid is continuously supplied to the polishing pad on the polishing platen by a pump or the like while the surface to be polished is polished. The supply amount is not limited, but the surface of the polishing pad is preferably coated with the polishing liquid all the time. The form of the polishing liquid is as described above.

Examples

The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, contents of treatment, steps of treatment, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Accordingly, the scope of the present invention is not to be construed as being limited by the embodiments shown below. Unless otherwise specified, "%" means "% by mass".

[ purification of starting materials etc. ]

The raw materials and catalysts used in the examples shown below were purified in advance by distillation, ion exchange, filtration, or the like using a high-purity grade having a purity of 99% or more. In particular, in the state of a solution before adding abrasive particles, a highly accurate chemical liquid can be obtained by performing ion exchange, filtration, or the like.

In the present example, the filtration was performed by the following method. Specifically, as the filter, 15nm IEX PTFE manufactured by Entegris, inc. was used in the first stage, and 12nm ALL PTFE manufactured by Entegris, inc. was used in the second stage, and filtration was continuously performed (the number of cycles was 10). Each filter was used after being immersed in IPA (isopropyl alcohol) for hydrophilization before use.

Ultrapure water used in the examples was purified by the method described in jp 2007-254168 a, and the content of Ca atoms was set to less than 10 mass ppt by the measurement based on the normal ICP-MS method described later.

1. Preparation and evaluation of polishing solutions of examples 1 to 4 and comparative example 1

[ example 1]

Each component shown below was mixed to prepare a polishing liquid. Further, dilute sulfuric acid or sodium hydroxide was added as appropriate so that the pH of the polishing liquid became the value shown in table 1.

[ various measurements and evaluations ]

The polishing liquid of example 1 thus obtained was evaluated as follows.

< determination of Ca concentration >

In the ICP-MS analysis (normal ICP-MS analysis, not the SNP-ICP-MS analysis described later), the Ca concentration was measured in the same manner as in the SNP-ICP-MS analysis described later except that the analysis software was replaced with analysis software (Syngistix for ICP-MS software) as an ICP-MS analysis apparatus described later. Here, the "Ca concentration" measured is the total concentration of ionic calcium and nonionic calcium (e.g., calcium particles), in other words, corresponds to the content of calcium atoms contained in the polishing liquid.

< SNP-ICP-MS (Single Nano Particle-Inductively Coupled Plasma-Ma ss Spectrometry) >

The content of the metal particles was measured using "Nexion 350S" manufactured by Perkinelmer co. Here, the metal particles are nonionic metals, and are components that are not dissolved in a liquid but exist as a solid.

1) Preparation of Standard substances

As the standard substance, ultrapure water was metered into a clean glass container, and metal particles to be measured having a median particle diameter of 50nm were added so as to have a concentration of 10000 particles/ml, and then a dispersion liquid treated for 30 minutes by an ultrasonic cleaning machine was used as the standard substance for measuring the transport efficiency.

2) Measurement conditions

The liquid to be measured was aspirated at about 0.2mL/min using a PFA coaxial type nebulizer (the "PFA" is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), a quartz cyclone type atomizing chamber, and a quartz Torch having an inner diameter of 1mm (Torch Inje sector). The cleaning was performed based on 0.1L/min oxygen addition, 1600W plasma output, and ammonia gas. The analysis was performed at a time analysis degree of 50 us.

3) The content of the metal particles was measured using the following analysis software attached to the manufacturer.

Content of metal particles: syngistix nano application module special for nanoparticle analysis SNP-ICP-MS

< evaluation of polishing Rate >

Polishing was performed while supplying a polishing liquid to the polishing pad under the following conditions, and the polishing rate was evaluated.

A polishing apparatus: reflexion (Applied Materials, manufactured by inc.)

Polished body (wafer):

calculating the grinding speed;

a300 mm diameter blank wafer having a Cu film of 0.5 μm thickness formed on a silicon substrate

A300 mm diameter blank wafer having a Ta film of 0.15 μm thickness formed on a silicon substrate

SiO with a thickness of 1.0 μm is formed on a silicon substrate₂Blank wafer with film diameter of 300mm

Polishing pad: IC1010 (manufactured by Rodel Inc.)

Milling conditions:

polishing pressure (contact pressure between the surface to be polished and the polishing pad): 1.5psi

Polishing liquid supply rate: 200ml/min

The rotating speed of the grinding platform is as follows: 110rpm

Grinding head rotation speed: 100rpm

Calculation of the grinding speed:

a blank wafer for polishing rate calculation was polished for 60 seconds, 49 portions on the wafer surface at regular intervals were converted from resistance values to determine the metal film thickness before and after polishing, and the average value of the values obtained by dividing (film thickness before polishing-film thickness after polishing) by the polishing time was defined as the polishing rate (unit: nm/min).

The results are shown in table 1.

< Defect Performance >

For the wafers whose polishing rates were evaluated, defects caused by the residue and scratches of 0.30 μm or more over the entire surface of the wafer were measured using an apparatus "SP-1" manufactured by KLA-Tencor Japan Ltd.

The obtained evaluation results were subjected to defect classification, and the number of residues and the number of scratches were evaluated according to the following criteria.

(evaluation of amount of residue)

"A": the number of residues is less than 10

"B": the number of residues is more than 10 and less than 50

"C": the number of residues is more than 50 and less than 100

"D": the amount of the residue exceeds 100

(evaluation of number of scratches)

"A": the number of scratches is 10 or less

"B": the number of scratches is more than 10 and less than 50

"C": the number of scratches is more than 50 and less than 100

"D": the number of scratches exceeds 100

[ examples 2 to 4, comparative example 1]

The polishing liquids of examples 2 to 4 and comparative example 1 were prepared in the same manner as in example 1, except that the amounts of the respective components to be blended or the Ca concentration was changed, and the same evaluations were performed. The results are shown in table 1. The Ca concentration was adjusted by changing the conditions for purification of the raw material.

The results in table 1 clearly show that the generation of defects is suppressed when the polishing liquid of the present invention is used. In particular, it was confirmed that when the content of the charge control agent in the liquid is 0.3 or less (preferably 0.03 or less) in terms of the mass ratio to the content of the organic acid, the occurrence of defects can be further suppressed (comparison of examples 1 to 3). Further, it was confirmed that the generation of defects can be further suppressed by setting the Ca concentration in the liquid to 80 mass ppt or less (comparison of examples 1 and 4).

2. Preparation of polishing slurries of examples 5 to 9 and comparative example 2 and evaluation thereof

[ example 5 ]

Each component shown below was mixed to prepare a polishing liquid. Further, dilute sulfuric acid or calcium hydroxide was added as appropriate so that the pH of the polishing liquid became the value shown in table 2.

[ various measurements and evaluations ]

The polishing liquid of example 5 thus obtained was subjected to Ca concentration measurement (measurement of Ca atomic weight), SNP-ICP-MS measurement (measurement of metal particle amount), polishing rate evaluation, and defect performance evaluation in the same manner as in example 1. For the polishing rate evaluation, the polished object was set as a blank wafer for polishing rate calculation as described below.

(body to be ground)

Calculating the grinding speed;

a300 mm diameter blank wafer having a SiN film formed on a silicon substrate to a thickness of 1.0 μm

A300 mm diameter blank wafer with a 1.0 μm thick poly-Si film formed on a silicon substrate

The results are shown in table 2.

[ examples 6 to 9, comparative example 2 ]

The polishing liquids of examples 6 to 9 and comparative example 2 were prepared in the same manner as in example 5, except that the amounts of the respective components to be blended or the Ca concentration was changed, and the same evaluations were performed. The results are shown in table 2. The Ca concentration was adjusted by changing the conditions for purification of the raw material.

The results in table 2 clearly show that the generation of defects is suppressed when the polishing liquid of the present invention is used. In particular, it was confirmed that the generation of defects can be further suppressed when the content of the charge control agent in the liquid is 0.6 or less (preferably 0.3 or less) in terms of the mass ratio to the content of the organic acid (comparison of examples 5 to 8). Further, it was confirmed that the generation of defects can be further suppressed by setting the Ca concentration in the liquid to 45 mass ppt or less (comparison of examples 5, 8, and 9).

3. Preparation of polishing slurries of examples 10 to 14 and comparative example 3 and evaluation thereof

[ example 10 ]

Each component shown below was mixed to prepare a polishing liquid. Further, dilute sulfuric acid or calcium hydroxide was added as appropriate so that the pH of the polishing liquid became the value shown in table 3.

[ various measurements and evaluations ]

The polishing liquid of example 10 thus obtained was subjected to Ca concentration measurement (measurement of Ca atomic weight), SNP-ICP-MS measurement (measurement of metal particle amount), polishing rate evaluation, and defect performance evaluation in the same manner as in example 5. The results are shown in table 3.

[ examples 11 to 14, comparative example 3 ]

Polishing liquids of examples 11 to 14 and comparative example 3 were prepared in the same manner as in example 10 above, except that the amounts of the respective components to be blended or the Ca concentration was changed, and the same evaluations were performed. The results are shown in table 3. The Ca concentration was adjusted by changing the conditions for purification of the raw material.

The results in table 3 clearly show that the generation of defects is suppressed when the polishing liquid of the present invention is used. In particular, it was confirmed that the generation of defects can be further suppressed when the content of the charge control agent in the liquid is 0.01 or less in terms of a mass ratio with respect to the content of the organic acid (comparison of examples 10 to 12). Further, it was confirmed that the generation of defects can be further suppressed by setting the Ca concentration in the liquid to 80 mass ppt or less (preferably 45 mass ppt or less, more preferably 25 mass ppt or less) (comparison of examples 10, 13, and 14).

4. Preparation and evaluation of polishing solutions of examples 15 to 22 and comparative example 4

[ example 15 ]

Each component shown below was mixed to prepare a polishing liquid. Further, dilute sulfuric acid or calcium hydroxide was added as appropriate so that the pH of the polishing liquid became the value shown in table 4.

[ various measurements and evaluations ]

The polishing liquid of example 15 thus obtained was subjected to Ca concentration measurement (measurement of Ca atomic weight), SNP-ICP-MS measurement (measurement of metal particle amount), polishing rate evaluation, and defect performance evaluation in the same manner as in example 1. For the polishing rate evaluation, the polished object (wafer) was set as a blank wafer for polishing rate calculation as described below.

Calculating the grinding speed;

The results are shown in table 4.

[ examples 16 to 22, comparative example 4 ]

Polishing liquids of examples 16 to 22 and comparative example 4 were prepared in the same manner as in example 15 above, except that the amounts of the respective components to be blended or the Ca concentration was changed, and the same evaluations were performed. The results are shown in table 4. The Ca concentration was adjusted by changing the conditions for purification of the raw material.

The following describes the components used as other additives in table 4.

Alkylene polyethylene polyamine (weight average molecular weight (Mw)46000, EO: PO ═ 8: 1, equivalent to hydrophilic polymer.)

Polyglycerin (weight average molecular weight (Mw)1500, equivalent to hydrophilic polymer.)

Polyallylamine (weight average molecular weight (Mw)5000, equivalent to hydrophilic polymer.)

Polyethylene glycol (weight average molecular weight (Mw)4000, equivalent to hydrophilic polymer.)

Diallyldimethylammonium-acrylamide copolymer (weight average molecular weight (Mw)20000, corresponding to a hydrophilic polymer.)

The results in table 4 clearly show that the generation of defects is suppressed when the polishing liquid of the present invention is used. In particular, it was confirmed that the generation of defects can be further suppressed when the content of the charge control agent in the liquid is 0.1 or less in terms of a mass ratio with respect to the content of the organic acid (comparison of examples 15 to 17). Further, it was confirmed that the generation of defects can be further suppressed by setting the Ca concentration in the liquid to 80 mass ppt or less (preferably 25 mass ppt or less) (comparison of examples 15, 18, and 19).

Claims

1. A polishing liquid for chemical mechanical polishing,

the polishing liquid contains polishing particles, an organic acid, and a charge control agent, wherein the content of the charge control agent is 0.6 or less by mass relative to the content of the organic acid, and the Ca concentration is 100 mass ppt or less,

the pH of the grinding fluid is in the range of 1.5-5.0,

2. The polishing slurry according to claim 1, wherein,

the Ca concentration is 0.01-100 mass ppt.

3. The polishing slurry according to claim 1 or 2,

the Ca concentration is 0.01-80 mass ppt.

4. The polishing slurry according to claim 1 or 2,

the organic acid contains a polybasic acid selected from the group consisting of malonic acid, succinic acid, malic acid, and citric acid.

5. The polishing slurry according to claim 1,

the charge control agent contains an inorganic acid selected from the group consisting of nitric acid, boric acid and phosphoric acid, or an ammonium salt thereof, or an ammonium salt of an organic acid.

6. A chemical mechanical polishing method comprises the following steps:

a polished object obtained by polishing a surface to be polished of an object to be polished by bringing the surface to be polished of the object to be polished into contact with a polishing pad attached to a polishing platen while supplying the polishing liquid according to any one of claims 1 to 5 to the polishing pad, and relatively moving the polishing object and the polishing pad.