JP2007207909A - Polishing solution for metal, and chemical mechanical polishing method employing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing solution for metal which can pursue both a high polishing speed and low erosion in polishing a workpiece (wafer) to be polished, and a chemical mechanical polishing method employing the same. <P>SOLUTION: The polishing solution for metal contains at least one kind of heterocyclic compound containing one or two nitrogen atoms as hetero atoms in a molecule, and a coloidal silica in which one part of its surface is covered with aluminum. In the chemical mechanical polishing method, a polishing pad on a polishing pad is brought into relative movement while allowing the pad to contact the face to be polished of the workpiece to be polished by rotating a polishing plate while supplying the polishing solution for metal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a metal polishing liquid used when performing chemical mechanical planarization in a semiconductor device manufacturing process, and a polishing method using the same.

In the development of a semiconductor device represented by a semiconductor integrated circuit (hereinafter referred to as LSI), in recent years, in order to reduce the size and increase the speed, there has been a demand for higher density and higher integration by miniaturizing and stacking wiring. For this purpose, various techniques such as chemical mechanical polishing (hereinafter referred to as CMP) have been used.
This CMP is an indispensable technique for performing surface flattening of a film to be processed such as an interlayer insulating film, plug formation, formation of embedded metal wiring, etc., and this technique is used to smooth a substrate or form a wiring. The excess metal thin film is removed (for example, refer to Patent Document 1).

A general method of CMP is to apply a polishing pad on a circular polishing platen (platen), immerse the surface of the polishing pad with a polishing liquid, press the surface of the substrate (wafer) against the pad, and apply a predetermined pressure from the back surface. In a state where (polishing pressure) is applied, both the polishing base plate and the substrate are rotated, and the surface of the substrate is flattened by the generated mechanical friction.
The metal polishing solution used for CMP generally contains abrasive grains (eg, alumina, silica) and an oxidizing agent (eg, hydrogen peroxide, persulfuric acid). It is considered that the basic mechanism is that the metal surface is oxidized by an oxidizing agent and the oxide film is polished by abrasive grains, and the method is described in Non-Patent Document 1, for example. Yes.

  Conventionally, tungsten and aluminum have been widely used in interconnect structures as wiring metals. However, LSIs using copper, which has lower wiring resistance than these metals, have been developed with the aim of achieving higher performance. As a method for wiring this copper, for example, a damascene method described in Patent Document 2 is known. Further, a dual damascene method in which a contact hole and a wiring trench are simultaneously formed in an interlayer insulating film and a metal is embedded in both has been widely used. In the polishing of copper metal, since it is a particularly soft metal, a highly accurate polishing technique is increasingly required. At the same time, a high-speed metal polishing means capable of exhibiting high productivity is demanded.

  In particular, in recent years, in order to reduce the size and speed of semiconductor devices, there has been a demand for higher density and higher integration by miniaturization and stacking of wiring. There is an increasing demand to reduce the dishing phenomenon, and to reduce the erosion phenomenon in which the insulator between the metal wirings is polished more than necessary and a plurality of metal surfaces are recessed on the plate.

When the present inventor conducted research on the erosion phenomenon, it was found that the erosion increases when a large size abrasive grain is used. The cause is considered to be mainly agglomeration of abrasive grains. In order to solve this problem, a technique for reducing scratches (polishing scratches) is known by using a polishing liquid containing abrasive grains in which the surface of colloidal silica is coated with aluminum to reduce particle aggregation (for example, patents). Reference 3).
However, when the inventor attempted to achieve both high-speed polishing and erosion reduction using the technique described in Patent Document 3, it was still insufficient.
US Pat. No. 4,944,836 JP-A-2-278822 JP 2003-197573 A Journal of Electrochemical Society, 1991, 138, 11, 3460-3464

This invention is made | formed in view of the said problem, and makes it a subject to achieve the following objectives.
That is, an object of the present invention is to provide a metal polishing liquid capable of achieving both high polishing speed and low erosion when polishing an object (wafer), and a chemical mechanical polishing method using the same. It is to provide.

  As a result of intensive studies, the present inventor has found that the problem can be solved by using a metal polishing liquid having the following composition, and has achieved the above object.

(1) For metal, characterized in that it contains at least one heterocyclic compound containing one or two nitrogen atoms as heteroatoms in the molecule and colloidal silica partially covered with aluminum. Polishing fluid.

(2) The metal polishing slurry according to (1), wherein the heterocyclic compound has at least one carboxy group.

(3) The polishing liquid for metal according to (1) or (2) is supplied to the polishing pad on the polishing surface plate, and the polishing surface plate is rotated so that the polishing pad is polished on the surface to be polished. A chemical mechanical polishing method characterized by polishing with relative movement while being in contact with the substrate.

  According to the present invention, when polishing an object to be polished (wafer), a metal polishing liquid capable of achieving both high polishing speed and low erosion, and a chemical mechanical polishing method using the same are provided. be able to.

<Metal polishing liquid>
The metal polishing liquid of the present invention comprises, as essential components, at least one heterocyclic compound containing one or two nitrogen atoms as heteroatoms in the molecule, and colloidal silica partially covered with aluminum. In addition, it is preferable to contain an organic acid, an oxidizing agent, or the like. Usually, it takes the form of a slurry in which the colloidal silica (abrasive grains) is dispersed in an aqueous solution in which each component is dissolved. .
In a preferred embodiment, the heterocyclic compound contained in the metal polishing slurry has at least one carboxy group.
Moreover, as another preferable aspect of the metal polishing slurry of the present invention, the pH is 2 to 9, and more preferably the pH is 5 to 8.
Although each component which comprises the said metal polishing liquid is explained in full detail below, each component may use only 1 type and may use 2 or more types together.

  In the present invention, the “metal polishing liquid” means not only a polishing liquid having a composition (concentration) used for polishing, but also a polishing concentrated liquid used by diluting if necessary when used unless otherwise specified in the present invention. This is called polishing liquid. When the concentrated liquid is used for polishing, it is diluted with water or an aqueous solution and used for polishing, and the dilution ratio is generally 1 to 20 times by volume.

[Heterocyclic compounds containing one or two nitrogen atoms as heteroatoms in the molecule]
The metal polishing liquid of the present invention is a compound that forms a passive film on the metal surface of an object to be polished, and is at least one heterocyclic compound containing 1 or 2 nitrogen atoms as heteroatoms in the molecule (hereinafter referred to as Simply referred to as a heterocyclic compound).
Here, the “heterocyclic compound” is a compound having a heterocyclic ring containing one or more heteroatoms. A heteroatom means an atom other than a carbon atom or a hydrogen atom, and a heterocycle means a cyclic compound having at least one heteroatom.
Note that a nitrogen atom or other heteroatom means only an atom that forms a component of a heterocyclic ring system, and is located outside the ring system or has at least one non-conjugated single bond to form a ring system. It does not mean an atom that is separated from or is part of a further substituent of the ring system.

The heterocyclic compound in the present invention only needs to contain one or two nitrogen atoms as the atoms forming the ring system component, and the hetero atoms other than the nitrogen atom as the atoms forming the ring system component. May further be included.
Preferable hetero atoms other than the nitrogen atom constituting the heterocyclic compound in the present invention include a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom.

First, the heterocyclic ring that is the mother nucleus is described.
The number of members of the heterocyclic ring of the heterocyclic compound used in the present invention is not particularly limited, and may be a monocyclic compound or a polycyclic compound having a condensed ring. The number of members in the case of a single ring is preferably 3 to 8, more preferably 5 to 7, and particularly preferably 5 and 6. In the case of a condensed ring, the number of rings is preferably 2 to 4, more preferably 2 or 3.

Specific examples of the heterocyclic ring include the following. However, it is not limited to these.
Pyrrole ring, imidazole ring, pyrazole ring, thiazole ring, oxazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, indazole ring, quinoline ring, phthalazine ring, quinoxaline ring, quinazoline ring, cinnoline ring, pteridine ring, Examples include acridine ring, perimidine ring, phenanthroline ring, thiadiazole ring, oxadiazole ring, benzimidazole ring, benzoxazole ring, benzthiazole ring, benzthiadiazole ring, and naphthimidazole ring. Among them, pyridine ring, quinoline are preferable. Ring, imidazole ring, benzimidazole ring, pyrazole ring, indazole ring and the like.

Next, substituents that the heterocyclic ring may have will be described.
In the present invention, when a specific moiety is referred to as a “group”, the moiety may be unsubstituted or substituted with one or more (up to the maximum possible) substituents. Means good. For example, “alkyl group” means a substituted or unsubstituted alkyl group.

Examples of the substituent that the heterocyclic ring may have include the following.
That is, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group (a linear, branched, or cyclic alkyl group, even if a polycyclic alkyl group such as a bicycloalkyl group is active) A methine group), an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group (regardless of the position of substitution), an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a heterocyclic oxycarbonyl group, a carbamoyl group ( Examples of the carbamoyl group having a substituent include 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 carbazoyl group. Carboxy group or a salt thereof, oxalyl group, oxamo Group, cyano group, carbonimidoyl group, formyl group, hydroxy group, alkoxy group (including groups containing ethyleneoxy group or propyleneoxy group unit repeatedly), aryloxy group, heterocyclic oxy group, acyloxy group, (alkoxy group) Or aryloxy) carbonyloxy group, carbamoyloxy group, sulfonyloxy group, amino group, (alkyl, aryl, or heterocyclic) amino group, acylamino group, sulfonamido group, ureido group, thioureido group, N-hydroxyureido group, Imido group, (alkoxy or aryloxy) carbonylamino group, sulfamoylamino group, semicarbazide group, thiosemicarbazide group, hydrazino group, ammonio group, oxamoylamino group, N- (alkyl or aryl) sulfoni Ureido group, N-acylureido group, N-acylsulfamoylamino group, hydroxyamino group, nitro group, quaternized heterocyclic group containing nitrogen atom (eg, pyridinio group, imidazolio group, quinolinio group, isoquinolinio group ), Isocyano group, imino group, mercapto group, (alkyl, aryl, or heterocyclic) thio group, (alkyl, aryl, or heterocyclic) dithio group, (alkyl or aryl) sulfonyl group, (alkyl or aryl) sulfinyl group , A sulfo group or a salt thereof, a sulfamoyl group (the sulfamoyl group having a substituent is, for example, an N-acylsulfamoyl group or an N-sulfonylsulfamoyl group) or a salt thereof, a phosphino group, a phosphinyl group, a phosphinyl group Examples include oxy group, phosphinylamino group, silyl group, etc. The However, it is not limited to these.

The active methine group means a methine group substituted with two electron-withdrawing groups. Examples of the electron-withdrawing group include an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, and an alkyl group. A sulfonyl group, an arylsulfonyl group, a sulfamoyl group, a trifluoromethyl group, a cyano group, a nitro group, and a carbonimidoyl group are meant. Two electron withdrawing groups may be bonded to each other to form a cyclic structure.
The salt means a cation such as alkali metal, alkaline earth metal or heavy metal, or an organic cation such as ammonium ion or phosphonium ion.

The heterocyclic compound used in the present invention preferably has at least one carboxy group, and more preferably has two or more carboxy groups.
Specifically, quinaldic acid, pyridine-3,4-dicarboxylic acid, quinoline-2-carboxylic acid, imidazole-4-carboxylic acid, benzimidazole-4-carboxylic acid, pyrazole-4-carboxylic acid, indazole-3- A carboxylic acid etc. are mentioned.

The heterocyclic compounds used in the present invention may be used alone or in combination of two or more.
Moreover, the heterocyclic compound used by this invention can be synthesize | combined according to a conventional method, and may use a commercial item.

  The total amount of the heterocyclic compound used in the present invention is the metal polishing liquid used for polishing (that is, the diluted metal polishing liquid when diluted with water or an aqueous solution. "The metal polishing liquid when doing this" is also in agreement.) In 1 L, 0.0001 to 1.0 mol is preferable, more preferably 0.0002 to 0.1 mol, and still more preferably 0.0002 to 0.01 mol. . That is, the addition amount of the heterocyclic compound is preferably 0.0001 mol or more from the viewpoint of reducing dishing and 1.0 mol or less from the viewpoint of maintaining a high polishing rate.

[Colloidal silica with a part of the surface covered with aluminum]
The metal-polishing liquid of the present invention contains colloidal silica whose surface is partially covered with aluminum as at least a part of the abrasive grains. Hereinafter, it is referred to as specific colloidal silica as appropriate.
In the present invention, “a colloidal silica whose surface is partially covered with aluminum” means a state in which aluminum is present on the surface of the colloidal silica having a site containing a silicon atom having a coordination number of 4. In addition, an aluminum atom coordinated with four oxygen atoms may be bonded to the surface of colloidal silica to form a new surface in which the aluminum atom is fixed in a four-coordinate state. It may be in a state in which silicon atoms present on the silica surface are once extracted, and a new surface replacing aluminum atoms is generated.

The colloidal silica used for the preparation of the specific colloidal silica is more preferably a colloidal silica obtained by hydrolysis of alkoxysilane that does not contain impurities such as alkali metals inside the particles. On the other hand, although colloidal silica produced by a method of removing alkali from an alkali silicate aqueous solution can also be used, in this case, there is a concern that the alkali metal remaining in the particles gradually elutes and affects the polishing performance. . From such a viewpoint, a material obtained by hydrolysis of the alkoxysilane is more preferable as a raw material.
The particle size of the colloidal silica used as a raw material is appropriately selected according to the purpose of use of the abrasive grains, but is generally about 10 to 200 nm.

As a method for obtaining such specific colloidal silica, for example, a method of adding an aluminate compound such as sodium aluminate to a dispersion of colloidal silica can be suitably used. This method is described in detail in Japanese Patent No. 3463328 and Japanese Patent Application Laid-Open No. 63-123807, and this description can be applied to the present invention.
As another method, a method of adding aluminum alkoxide to a dispersion of colloidal silica can be mentioned.
The aluminum alkoxide used here may be any, but is preferably aluminum isopropoxide, aluminum butoxide, aluminum methoxide, or aluminum ethoxide, and particularly preferably aluminum isopropoxide or aluminum butoxide.

The specific colloidal silica obtained by the above method has an aluminosilicate site generated by the reaction of tetracoordinate aluminate ions and silanol groups on the surface of the colloidal silica, which fixes a negative charge and makes the particles negative. Gives a large zeta potential. Thereby, the specific colloidal silica has a feature that it is excellent in dispersibility even in an acidic state.
Therefore, it is important that the specific colloidal silica produced by the method as described above exists in a state where an aluminum atom is coordinated to four oxygen atoms.

  In addition, the aluminum atom which four oxygen atoms coordinated in the specific colloidal silica surface in this invention can be confirmed easily by measuring a zeta potential, for example.

In the specific colloidal silica in the present invention, the amount covered with aluminum is represented by the surface atom substitution rate of the colloidal silica (number of introduced aluminum atoms / number of surface silicon atom sites). This surface atom substitution rate is preferably 0.001% to 20%, more preferably 0.01% to 10%, and particularly preferably 0.1% to 5%.
This surface atomic substitution rate can be appropriately controlled by controlling the amount (concentration) of an aluminate compound, aluminum alkoxide, etc. added to the raw material colloidal silica dispersion.

Here, the surface atom substitution rate (number of introduced aluminum atoms / number of surface silicon atom sites) of the specific colloidal silica can be determined as follows.
First, of the aluminum compound added to the dispersion, the amount of aluminum compound consumed from the unreacted aluminum compound remaining after the reaction is calculated. Assuming that the consumed aluminum-based compound has reacted 100%, from the surface area converted from the colloidal silica diameter, the specific gravity of colloidal silica 2.2, and the number of silanol groups per unit surface area (5 to 8 / nm ² ) The surface atom substitution rate can be estimated. The actual measurement is performed by elemental analysis of the obtained specific colloidal silica itself, assuming that aluminum does not exist inside the particles and spreads uniformly and thinly on the surface, and the surface area / specific gravity of the colloidal silica and the unit surface area per unit surface area. Obtained using the number of silanol groups.

A specific method for producing the specific colloidal silica in the present invention is shown below.
First, colloidal silica is dispersed in water in the range of 1 to 50% by mass, the pH of the dispersion is adjusted to 7 to 11, and then an aqueous sodium aluminate solution is added while stirring near room temperature, Stir for 0.5-10 hours.
Impurities are removed from the sol thus obtained by ion exchange, ultrafiltration, or the like to obtain specific colloidal silica.

The size (volume equivalent diameter) of the specific colloidal silica obtained is preferably 3 m to 200 nm, more preferably 5 nm to 100 nm, and particularly preferably 10 nm to 60 nm.
In addition, the value measured by the dynamic light scattering method is employ | adopted for the particle size (volume equivalent diameter) of specific colloidal silica.

  Further, the content of the specific colloidal silica in the metal polishing liquid of the present invention is preferably 0.001% by mass with respect to the mass of the metal polishing liquid used for polishing in order to exhibit the effect. The content is 5% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, and particularly preferably 0.05% by mass or more and 0.2% by mass or less.

  Among the abrasive grains contained in the metal polishing slurry of the present invention, the content of the specific colloidal silica is preferably 50% by mass or more, and particularly preferably 80% by mass or more. All of the contained abrasive grains may be a specific colloidal silica.

  For the metal polishing slurry of the present invention, fumed silica, colloidal silica, ceria, alumina, titania, etc. are preferred as abrasive grains other than specific colloidal silica, and colloidal silica is particularly preferred. These sizes are preferably equal to or more than that of the specific colloidal silica, and are preferably twice or less.

〔Oxidant〕
The metal polishing liquid of the present invention preferably contains a compound (oxidant) capable of oxidizing the metal to be polished.
Specifically, hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chlorate, perchlorate, persulfate, dichromium Acid salts, permanganates, ozone water, silver (II) salts, and iron (III) salts are mentioned, among which hydrogen peroxide is more preferably used.

  The addition amount of the oxidizing agent is preferably 0.003 mol to 8 mol, more preferably 0.03 mol to 6 mol, and more preferably 0.1 mol to 4 mol in 1 liter of the metal polishing liquid used for polishing. It is particularly preferable to do this. That is, the addition amount of the oxidizing agent is preferably 0.003 mol or more from the viewpoint of sufficient metal oxidation and ensuring a high CMP rate, and is preferably 8 mol or less from the viewpoint of preventing roughening of the polished surface.

[Organic acid]
The metal polishing slurry according to the present invention preferably further contains at least one organic acid. The organic acid here is not a metal oxidizing agent, but has an action of promoting oxidation, adjusting pH, and buffering agent.
Examples of organic acids include organic acids and amino acids.

The organic acid is preferably water-soluble. Those selected from the following group are more suitable.
That is, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methyl Hexanoic 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, apple Acid, tartaric acid, citric acid, lactic acid, hydroxyethyliminodiacetic acid, iminodiacetic acid, dihydroxyethylglycine, and salts thereof such as ammonium salt and alkali metal salt, sulfuric acid, nitric acid, ammonia, ammonium salts, or a mixture thereof Is mentioned. Among these, oxalic acid, formic acid, malonic acid, malic acid, tartaric acid, citric acid, hydroxyethyliminodiacetic acid, iminodiacetic acid, dihydroxyethylglycine and the like are preferable.

Moreover, as an amino acid, a water-soluble thing is preferable. Those selected from the following group are more suitable.
That is, glycine, L-alanine, β-alanine, L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine, L-isoleucine, L-alloisoleucine, L-phenylalanine, L- Proline, sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothreonine, L-homoserine, L-tyrosine, 3,5-diiodo-L-tyrosine, β- (3 4-Dihydroxyphenyl) -L-alanine, L-thyroxine, 4-hydroxy-L-proline, L-cystine, L-methionine, L-ethionine, L-lanthionine, L-cystathionine, L-cystine, L-cysteic acid , L-aspartic acid, L-glutamic acid, S- (carboxymethyl) -L-cysteine, 4-aminobutyric acid Acid, L-asparagine, L-glutamine, azaserine, L-arginine, L-canavanine, L-citrulline, δ-hydroxy-L-lysine, creatine, L-kynurenine, L-histidine, 1-methyl-L-histidine, Examples include 3-methyl-L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II, and antipine.
Especially for malic acid, tartaric acid, citric acid, glycine, glycolic acid, β-alanine, hydroxyethyliminodiacetic acid, iminodiacetic acid, dihydroxyethylglycine, while maintaining a practical CMP rate, the etching rate is effectively increased. This is preferable in that it can be suppressed.

  The addition amount of the organic acid is preferably 0.005 to 0.5 mol, more preferably 0.01 to 0.3 mol, in 1 L of the metal polishing liquid used for polishing. It is especially preferable to set it as 05-0.3 mol. That is, the addition amount of the organic acid is preferably 0.01 mol or more from the viewpoint of improving the polishing rate, and 0.3 mol or less is preferable from the viewpoint of not deteriorating dishing.

In the metal polishing slurry of the present invention, the organic acids may be used alone or in combination of two or more.
These organic acids can be synthesized according to a conventional method, or commercially available products may be used.

  The metal polishing slurry of the present invention may further contain other components, and examples thereof include a surfactant, a hydrophilic polymer, and other additives.

(Surfactant / Hydrophilic polymer)
The polishing liquid of the present invention preferably contains a surfactant and a hydrophilic polymer.
Both the surfactant and the hydrophilic polymer have the action of reducing the contact angle of the surface to be polished and the action of promoting uniform polishing. As the surfactant and the hydrophilic polymer used, those selected from the following groups are suitable.

Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt, and phosphate ester salt.
Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts.
Examples of amphoteric surfactants include carboxybetaine type, aminocarboxylate, imidazolinium betaine, lecithin, and alkylamine oxide.
Nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type.
Moreover, a fluorochemical surfactant can also be used.

  Examples of the hydrophilic polymer include polyglycols such as polyethylene glycol, polysaccharides such as polyvinyl alcohol, polovinyl pyrrolidone, and alginic acid, and carboxylic acid-containing polymers such as polymethacrylic acid.

  Of the above, the acid or its ammonium salt is preferably free from contamination by alkali metals, alkaline earth metals, halides and the like. Among the above exemplified compounds, cyclohexanol, polyacrylic acid ammonium salt, polyvinyl alcohol, succinic acid amide, polo vinyl pyrrolidone, polyethylene glycol, and polyoxyethylene polyoxypropylene block polymer are more preferable.

  The weight average molecular weight of these surfactants and hydrophilic polymers is preferably from 500 to 100,000, particularly preferably from 2,000 to 50,000.

  The total amount of the surfactant and / or hydrophilic polymer added is preferably 0.001 to 10 g and preferably 0.01 to 5 g in 1 liter of the metal polishing slurry used for polishing. Is more preferably 0.1 to 3 g.

[PH adjuster]
It is preferable that an acid agent, an alkali agent, or a buffering agent is added to the metal polishing slurry of the present invention so as to have a predetermined pH.
As the acid agent, an inorganic acid is used, and examples of the inorganic acid include sulfuric acid, nitric acid, boric acid, phosphoric acid and the like. Of these, sulfuric acid is preferred.
Alkaline agents and buffering agents include organic ammonium hydroxides such as ammonia, ammonium hydroxide and tetramethylammonium hydroxide, non-metallic alkaline agents such as alkanolamines such as diethanolamine, triethanolamine, triisopropanolamine, Alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, carbonates such as sodium carbonate, phosphates such as trisodium phosphate, borate, tetraborate, hydroxybenzoate, etc. Can be mentioned.
Particularly preferred alkali agents are ammonium hydroxide, potassium hydroxide, lithium hydroxide and tetramethylammonium hydroxide.

The addition amount of the pH adjuster may be an amount that allows the pH to be maintained in a preferable range, and is preferably 0.0001 mol to 1.0 mol in 1 L of the metal polishing liquid used for polishing. More preferably, the amount is 0.003 mol to 0.5 mol.
3-12 are preferable, as for pH of the metal polishing liquid at the time of using for grinding | polishing, More preferably, it is 4-9, and 5-8 are especially preferable. Within this range, the metal polishing machine of the present invention exhibits particularly excellent effects.
By using the acid agent, alkali agent and buffer, the pH of the metal polishing slurry of the present invention is adjusted to the above preferred range.

[Chelating agent]
The metal-polishing liquid according to the present invention may contain a chelating agent (that is, a hard water softening agent) as necessary in order to reduce adverse effects such as mixed polyvalent metal ions.
As a chelating agent, a general-purpose hard water softening agent that is a precipitation inhibitor of calcium or magnesium or an analogous compound thereof can be used, and two or more of these may be used in combination as necessary.
The addition amount of the chelating agent may be an amount sufficient to sequester metal ions such as mixed polyvalent metal ions. For example, 0.0003 mol to 0 in 1 L of a metal polishing liquid used for polishing. It is preferable to add it to 0.07 mol.

<Chemical mechanical polishing method>
In the chemical mechanical polishing method of the present invention, the metal polishing liquid of the present invention is supplied to the polishing pad on the polishing surface plate, and the polishing surface plate is rotated, whereby the polishing pad is polished on the object to be polished. It is characterized by polishing with relative movement while being in contact with a surface.
Hereinafter, this chemical mechanical polishing method will be described in detail.

(Polishing equipment)
First, an apparatus capable of carrying out the polishing method of the present invention will be described.
As a polishing apparatus applicable to the present invention, a holder for holding an object to be polished (semiconductor substrate or the like) having a surface to be polished and a polishing pad are attached (a motor or the like whose rotation speed can be changed is attached). A general polishing apparatus provided with a polishing surface plate can be used. For example, FREX300 (Ebara Seisakusho) can be used.

(Polishing pressure)
In the polishing method of the present invention, polishing is preferably performed at a polishing pressure, that is, a contact pressure between the surface to be polished and the polishing pad of 3000 to 250,000 Pa, and more preferably 6500 to 14000 Pa.

(Number of rotations of polishing surface plate)
In the polishing method of the present invention, the polishing is preferably performed at a rotation speed of the polishing platen of 50 to 200 rpm, more preferably 60 to 150 rpm.

(Polishing liquid supply method)
In the present invention, the metal polishing liquid is continuously supplied to the polishing pad on the polishing surface plate by a pump or the like while the target metal is polished. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

  In the polishing method of the present invention, water or an aqueous solution can be added to a concentrated polishing liquid for dilution. As a dilution method, for example, a method of supplying a concentrated polishing liquid to a polishing pad by joining and mixing a pipe for supplying a concentrated polishing liquid and a pipe for supplying water or an aqueous solution together in the middle. Can be mentioned. In this case, mixing is a method in which liquids collide with each other through a narrow passage with pressure applied, a method in which a filling such as a glass tube is filled in the piping, a flow of liquid is separated and separated, and piping is repeated. Conventional methods such as a method of providing blades that rotate with power can be used.

Further, as another dilution method, a pipe for supplying a polishing liquid and a pipe for supplying water or an aqueous solution are provided independently, and a predetermined amount of liquid is supplied from each to the polishing pad, and the polishing pad and the surface to be polished are provided. A method of mixing by relative motion can also be used in the present invention.
Further, a method in which a predetermined amount of concentrated polishing liquid and water or an aqueous solution are mixed in one container, mixed and diluted to a predetermined concentration, and then the mixed liquid is supplied to the polishing pad is also applicable to the present invention. be able to.

  In addition to these methods, a method in which the component to be contained in the polishing liquid is divided into at least two components, and when these are used, water or an aqueous solution is added and diluted to be supplied to the polishing pad is also used in the present invention. be able to. In this case, it is preferable to divide and supply the component containing an oxidizing agent and the component containing an organic acid.

  Specifically, the oxidizing agent is preferably one component (A), and the organic acid, additive, surfactant, heterocyclic compound, abrasive grains, and water are preferably one component (B). When using them, the component (A) and the component (B) are diluted with water or an aqueous solution. In this case, three pipes for supplying the component (A), the component (B), and water or an aqueous solution are necessary, and the three pipes are connected to one pipe for supplying the polishing pad, The two pipes may be combined and then another one pipe may be combined and mixed. For example, a constituent component containing an additive that is difficult to dissolve is mixed with another constituent component, a mixing path is lengthened to ensure a dissolution time, and then a polishing liquid is supplied by combining a pipe of water or an aqueous solution. It is also possible.

  Further, the above three pipes may be led to the polishing pad and mixed and supplied by the relative movement of the polishing pad and the surface to be polished. After mixing the three components in one container, the mixed solution is supplied. You may supply to a polishing pad. Further, the metal polishing liquid may be a concentrated liquid, and the diluted water may be separately supplied to the polishing surface.

(Abrasive supply amount)
In the polishing method of the present invention, the supply amount of the polishing liquid onto the polishing surface plate is preferably 50 to 500 ml / min, and more preferably 100 to 300 ml / min.

(Polishing pad)
The polishing pad used in the polishing method of the present invention is not particularly limited, and may be a non-foamed structure pad or a foamed structure pad. The former uses a hard synthetic resin bulk material like a plastic plate for a pad. Further, the latter further includes three types of a closed foam (dry foam system), a continuous foam (wet foam system), and a two-layer composite (laminated system), and a two-layer composite (laminated system) is particularly preferable. Foaming may be uniform or non-uniform.

  The polishing pad in the present invention may further contain abrasive grains (for example, ceria, silica, alumina, resin, etc.) used for polishing. In addition, the hardness may be either soft or hard, and either may be used. In the laminated system, it is preferable to use a different hardness for each layer. The material is preferably non-woven fabric, artificial leather, polyamide, polyurethane, polyester, polycarbonate or the like. In addition, the surface contacting the polishing surface may be subjected to processing such as lattice grooves / holes / concentric grooves / helical grooves.

  Next, an object to be polished (substrate, wafer) to be polished in the polishing method of the present invention will be described.

(Wiring metal material)
The object to be polished in the present invention is preferably a substrate (wafer) having wiring made of copper or a copper alloy. As the wiring metal material, a copper alloy containing silver is suitable among the copper alloys. The silver content contained in the copper alloy exhibits an excellent effect at 10% by mass or less, further 1% by mass or less, and the most excellent effect in the copper alloy in the range of 0.00001 to 0.1% by mass. Demonstrate.

(Wiring thickness)
In the DRAM device system, for example, the object to be polished in the present invention preferably has a wiring with a half pitch, preferably 0.15 μm or less, more preferably 0.10 μm or less, and further preferably 0.08 μm or less.
On the other hand, the MPU device system preferably has a wiring of preferably 0.12 μm or less, more preferably 0.09 μm or less, and still more preferably 0.07 μm or less.
The polishing liquid used in the present invention exhibits a particularly excellent effect on the object to be polished having such wiring.

(Barrier metal material)
In the object to be polished in the present invention, a barrier layer for preventing copper diffusion is provided between the copper wiring and the insulating film (including the interlayer insulating film). As the barrier metal material constituting the barrier layer, a low-resistance metal material such as TiN, TiW, Ta, TaN, W, or WN is preferable, and Ta or TaN is particularly preferable.

  Hereinafter, the present invention will be described by way of examples. The present invention is not limited to these examples.

[Examples 1 to 10, Comparative Examples 1 to 7]
Polishing liquids 101 to 110 and 201 to 207 shown in Table 1 below were prepared, and polishing tests and evaluations were performed.
(Preparation of metal polishing liquid)
The following compositions were mixed to prepare each metal polishing liquid.
-Heterocyclic compound: Compound shown in Table 1 ... 0.5 mmol / L (or no addition)
Abrasive grains: colloidal silica listed in Table 1 2 g / L
Organic acid: dihydroxyethyl glycine ... 0.18 mol / L
Oxidizing agent: hydrogen peroxide 9g / L
Pure water was added to bring the total volume to 1000 mL, and the pH was adjusted to 6.5 with ammonia water and sulfuric acid.

(Colloidal silica used in this example)
The specific colloidal silica was colloidal silica produced as follows and having a part of the surface covered with aluminum, and the number of introduced aluminum atoms / the number of surface silicon atom sites = 1%. Moreover, the size (volume equivalent diameter) of the specific colloidal silica was 45 nm as measured by the method described above.
Further, as other colloidal silica, colloidal silica that is not specific colloidal silica, that is, silicon atoms on the surface are not substituted with aluminum atoms (PL3: manufactured by Fuso Chemical Industries, Ltd., volume average particle diameter is 40 nm) was used. In Table 1, this colloidal silica is expressed as non-specific colloidal silica.

(Production of specific colloidal silica)
To 1000 g of a 20% by mass aqueous colloidal silica dispersion having a size (volume equivalent diameter) of 40 nm, aqueous ammonia is added to adjust the pH to 9.0, and the mixture is then stirred at room temperature with an Al ₂ O ₃ concentration of 3. 15.9 g of an aqueous sodium aluminate solution having a 6 mass% Na ₂ O / Al ₂ O ₃ molar ratio of 1.50 was slowly added within a few minutes and stirred for 0.5 hours. The obtained sol was placed in a SUS autoclave apparatus, heated at 130 ° C. for 4 hours, and then filled with a hydrogen-type strongly acidic cation exchange resin (Amberlite IR-120B), and a hydroxyl-type strongly basic anion exchange resin. A column packed with (Amberlite IRA-410) was passed through the column at a space velocity of 1 h ⁻¹ at room temperature, and the initial distillation was cut.
The surface atom substitution rate (number of introduced aluminum atoms / number of surface silicon atom sites) of the specific colloidal silica thus obtained was determined as follows.
First, of the sodium aluminate added to the dispersion, the amount of sodium aluminate consumed from the unreacted sodium aluminate remaining after the reaction was calculated. Assuming that 100% of the consumed sodium aluminate has reacted, from the surface area converted from the colloidal silica diameter, the specific gravity of the colloidal silica of 2.2, and the number of silanol groups per unit surface area (5 to 8 / nm ² ) The surface atom substitution rate was estimated.

(Polishing test)
Polishing was performed under the following conditions, and the polishing rate and erosion were evaluated.
・ Polishing equipment: FREX300 (Ebara Works)
-Object to be polished (wafer):
(1) For polishing rate calculation; a Cu film having a thickness of 1 μm was formed on a silicon substrate
300 mm diameter blanket wafer (2) For erosion evaluation; 300 mm diameter copper wiring wafer (pattern wafer)
(Mask pattern 754CMP (ATDF))
Polishing pad: IC1400XY-K Groove (made by Rodel)
・ Polishing conditions;
Polishing pressure (contact pressure between the surface to be polished and the polishing pad): 10324 Pa
Polishing liquid supply rate: 200 ml / min
Polishing platen rotation speed: 100rpm
Polishing head rotation speed: 50 rpm

(Evaluation methods)
Polishing speed calculation: The blanket wafer of (1) above is polished for 60 seconds, and the metal film thickness before and after polishing is calculated from the electrical resistance value at 49 equally spaced locations on the wafer surface and polished. The average value obtained by dividing by time was defined as the polishing rate.
Evaluation of erosion: In addition to the time until the copper in the non-wiring portion is completely polished on the pattern wafer of (2), an extra polishing is performed for 20% of the time, and the line and space portion ( The level difference of the line 100 μm and the space 100 μm was measured with a contact-type level gauge Dektak V3201 (manufactured by Veeco).
Table 1 shows the evaluation results.

  As is apparent from Table 1, according to the chemical mechanical polishing method using the metal polishing liquid of the present invention (the polishing method of the present invention), a high polishing rate of 700 nm / min or more and low erosion are obtained. It turns out that it is compatible. In particular, it can be seen that triazoles have little erosion when the heterocyclic compound has at least one carboxy group, and the remarkable effects of the present invention can be obtained.

Claims (3)

  A metal-polishing liquid comprising at least one heterocyclic compound containing one or two nitrogen atoms as heteroatoms in a molecule and colloidal silica partially covered with aluminum.   The metal polishing slurry according to claim 1, wherein the heterocyclic compound has at least one carboxy group.   The metal polishing liquid according to claim 1 or 2 is supplied to a polishing pad on a polishing surface plate, and the polishing surface plate is rotated to bring the polishing pad into contact with the surface to be polished of the object to be polished. A chemical mechanical polishing method, wherein polishing is carried out while relatively moving.