JP2004048033A - Metal-wiring forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal-wiring forming method inhibiting the sticking of a product of polishing to a polishing pad and forming an uniform wiring layer at high throughput even in the case of polishing a large quantity of copper-based metals in a polishing process. <P>SOLUTION: In a metal-wiring forming method having a process of forming recesses in an insulation film 1 that is formed on a substrate, a process of forming a copper-based metal film 2 on the entire surface in such a manner as to fill the recess, and a process of polishing the copper-based metal film by a chemical mechanical polishing method, the polishing process uses a chemical mechanical polishing slurry containing abrasives, an oxidizing agent, and citric acid. A polishing pad is contacted with a polishing surface at a pressure of 27kPa or above to perform polishing. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a method for forming a copper-based metal electrical connection portion using a chemical mechanical polishing method.

In recent years, in the formation of semiconductor integrated circuits such as ULSIs in which miniaturization and densification are accelerating, copper is attracting attention as a very useful electrical connection material because of its excellent electromigration resistance and low resistance.

Currently, formation of wiring using copper is performed as follows due to problems such as difficulty in patterning by dry etching. That is, a concave portion such as a groove or a connection hole is formed in an insulating film, a barrier metal film is formed, a copper film is formed on the entire surface by a plating method so as to fill the concave portion, and then a chemical mechanical polishing ( The surface is flattened by polishing until the surface of the insulating film other than the concave portion is completely exposed by a method (hereinafter referred to as “CMP”), and the electrical connection portion such as a buried copper wiring, a via plug, or a contact plug in which copper is embedded in the concave portion is formed. Has formed.

Hereinafter, a method of forming a buried copper wiring will be described with reference to FIG.

First, as shown in FIG. 1A, a silicon nitride film 3 and a second interlayer insulating film 4 are formed in this order on a first interlayer insulating film 1 on which a lower wiring 2 is formed, and then a second interlayer insulating film is formed. A groove having a wiring pattern shape and a concave portion in which a connection hole reaching the lower wiring 2 is formed in a part of the film 4 are formed by a conventional method.

Next, as shown in FIG. 1B, a barrier metal film 5 is formed by a sputtering method. Next, a copper film 6 is formed on the entire surface by plating so that the concave portions are buried. Here, the plating thickness should be equal to or greater than the sum of the groove depth, the connection hole depth, and the manufacturing variation in the plating process.

(1) Thereafter, as shown in FIG. 1C, the copper film 6 is polished by a CMP method using a polishing pad in the presence of a polishing slurry to planarize the substrate surface. Subsequently, as shown in FIG. 1D, polishing is continued until the metal on the second interlayer insulating film 4 is completely removed.

Ｃ A CMP slurry for polishing a copper film generally contains an oxidizing agent and abrasive grains as main components. The basic mechanism is to etch the copper surface by the chemical action of the oxidizing agent and to mechanically remove the oxidized surface layer with abrasive grains.

Further, as polishing abrasive grains used in a polishing slurry having a high polishing rate of a copper film, primary particles having a desired average particle diameter are easily produced, and polishing rates are high. It has been the mainstream to use primary particles of α-alumina having a diameter of about several hundred nm.
JP-A-10-116804 JP-A-8-83780 JP-A-11-238709 JP-A-10-46140 JP-A-11-21546 JP-A-10-44047 JP-A-10-163141 JBCotton, Proc. 2nd Intern. Congr. Metallic Corrosion, (1963) p.590 D. Chadwick et al., Corrosion Sci., 18, (1978) p. 39 Notoya Takeo, Rust Prevention Management, 26 (3) (1982), p.74 Okabe Heihachiro ed., "Development of Petroleum Product Additives and the Latest Technology" (1998) CMC, pp.77-82

As semiconductor integrated circuits have become increasingly finer and denser in recent years, and the device structure has become more complicated, and in order to cope with an increase in wiring resistance due to the finer wiring, multilayer wiring and the like for the purpose of shortening the wiring length have been developed. However, as the number of layers of the logic multi-layer wiring increases, the surface of the substrate becomes more and more uneven, and the level difference becomes larger. In addition, the upper wiring portion of the multilayer wiring is used for power supply wiring, signal wiring, or clock wiring, and it is necessary to deepen the wiring groove to lower these wiring resistances and improve various characteristics. is there. Therefore, the thickness of the interlayer insulating film formed on such a substrate surface also increases, and in order to form a buried conductive portion such as a buried copper wiring or a via plug in the thick interlayer insulating film, the thickness is large enough to fill a deep recess. It has become necessary to form a copper film. In order to reduce the resistance of the thinned wiring and to reduce the resistance of the signal wiring and clock wiring to increase the transmission speed, it is necessary to form a thick wiring in the depth direction. A thick copper film is formed. In addition, even when the power supply wiring is formed of a buried copper wiring, a thick copper film is formed in order to reduce the resistance of the power supply wiring and minimize a potential change. Conventionally, a thick copper film having a thickness of several thousand nm has been formed, whereas a thickness of several hundred nm has been sufficient.

When the buried conductive portion is formed by forming such a thick copper film, the polishing amount of copper to be removed in one CMP step increases, so that a large amount of polishing debris such as copper and copper oxide is removed by the CMP apparatus. Therefore, the polishing rate is reduced to such an extent that polishing becomes impossible or it is difficult to finish the polishing surface uniformly. At present, a wafer diameter is required to be increased in order to improve productivity. When the wafer diameter is increased, a copper film area is increased in addition to a copper thickness, so that a polishing amount of copper tends to increase more and more. It is in. Hereinafter, polishing scraps such as copper and copper oxide generated when the copper-based metal film is polished are referred to as “polishing products”.

On the other hand, for the surface plate of the CMP device, the in-plane uniformity of the surface plate is ensured, the uniformity of the dropped polishing slurry is uniform, the installation location of the CMP device is restricted, the workability of replacing the polishing pad, the cleanliness in the clean room, There is a limit to the size up for reasons such as securing the degree.

(4) When the polishing amount of copper increases, the throughput decreases at the same polishing rate as when the film thickness is small, so that it is necessary to increase the polishing rate of copper. However, when the polishing rate of copper is increased, a large amount of polishing products is generated in a short time, so that the adhesion of copper to the polishing pad surface becomes more remarkable.

When a large amount of the polishing product adheres to the polishing pad surface as described above, the polishing pad must be washed or replaced every time polishing is completed. Since the polishing operation needs to be performed again after the cleaning or the replacement, the throughput is significantly reduced.

Also, when the contact pressure (polishing pressure) of the polishing pad to the polishing surface is increased to increase the polishing rate and to enhance the uniformity of the polishing surface, when the polishing product adheres to the polishing pad surface, the polishing surface is removed. Not only cannot the internal uniformity be sufficiently improved, but also the adhesion of polishing products to the polishing pad surface is promoted.

Patent Literature 1 discloses a problem that copper ions generated during CMP accumulate on a polishing pad and re-attach to the wafer surface, thereby deteriorating the flatness of the wafer surface or causing an electrical short circuit. In order to solve this problem, it is described that a polishing composition containing a redeposition inhibitor such as benzotriazole is used in CMP. However, Patent Document 1 describes a problem caused by re-adhesion of copper ions to the wafer surface, but does not describe any problem caused by adhesion of the polishing product to the pad surface. In addition, benzotriazole used as an anti-redeposition agent also acts as an antioxidant (Non-Patent Documents 1 to 4), and reduces the polishing rate of copper, so that the amount of addition is limited. Furthermore, since benzotriazole is originally added to prevent dishing (Patent Documents 2 and 3), if priority is given to prevention of dishing, adjustment of the addition amount is restricted.

Patent Literature 4 describes a chemical mechanical polishing composition containing a specific carboxylic acid, an oxidizing agent, and water, wherein the pH is adjusted to 5 to 9 with an alkali. As an example, a polishing composition (Example 7) containing citric acid as a carboxylic acid and aluminum oxide as an abrasive is illustrated. However, this publication only describes the effect of adding a carboxylic acid such as citric acid on improving the polishing rate and preventing the occurrence of dishing due to corrosion marks.

Patent Document 5 discloses a polishing method using a chemical / mechanical polishing slurry containing urea, an abrasive, an oxidizing agent, a film forming agent, and a complexing agent. Hydrogen peroxide, benzotriazole as a film forming agent, and citric acid as a complexing agent are exemplified. However, the effects of the addition of the complexing agent merely disturb the passive layer formed by the film forming agent such as benzotriazole and limit the depth of the oxide layer. .

Patent Literature 6 discloses, as abrasive grains, aggregates of metal oxides having a size distribution of less than about 1.0 μm and an average aggregate diameter of less than about 0.4 μm, or individual particles having primary particles of less than 0.4 μm. Describes the use of independent metal oxide spherical particles. However, the invention described in this publication aims to suppress surface defects and contamination due to CMP, form uniform metal layers and thin films, and control selectivity between barrier films and insulating films. This publication does not describe any problem caused by the adhesion of the polishing product to the polishing pad surface. Further, as the exemplified alumina abrasive, only general precipitated alumina and fumed alumina are described, but there is no description about θ alumina. Further, copper is only exemplified as a connection material, and only Al is used in the embodiment.

Patent Document 7 describes θ-alumina as abrasive grains. However, in this publication, [theta] -alumina is only described as an example of aluminum oxide, such as [alpha] -alumina, and nothing is described about secondary particles of [theta] -alumina. Further, the invention described in this publication provides a polishing composition which prevents scratching and dishing, has a high polishing rate of a copper film, has an appropriate selectivity, and has good stability during storage. There is no description about suppressing adhesion of a polishing product to the polishing pad surface.

Therefore, an object of the present invention is to form a metal wiring capable of forming a uniform wiring layer with high throughput by suppressing the adhesion of polishing products to a polishing pad even when a large amount of copper-based metal is polished in the polishing step. It is to provide a method.

The present invention provides a step of forming a concave portion in an insulating film formed on a substrate, a step of forming a copper-based metal film over the entire surface so as to fill the concave portion, and a method of chemically and mechanically polishing the copper-based metal film. In the metal wiring forming method having a step of polishing, the polishing step uses a chemical mechanical polishing slurry containing citric acid as an abrasive, an oxidizing agent and an adhesion inhibitor to a polishing pad of a polishing product, The polishing pad is brought into contact with the polishing surface at a pressure of 27 kPa or more, and the polishing is performed so that the polishing amount per unit area of the polishing pad in one polishing operation is 2 × 10 ⁻⁴ g / cm ² or more. Metal wiring forming method.

In the present invention, “copper-based metal” refers to copper or an alloy containing copper as a main component, and “recess” refers to a groove for forming an embedded wiring, or a connection hole such as a contact hole or a through hole. . The insulating film formed on the substrate includes an interlayer insulating film formed on the lower wiring layer.

According to the present invention, even when a large amount of copper-based metal is polished in the polishing step, the citric acid in the polishing slurry suppresses the adhesion of the polishing product to the polishing pad, and provides a uniform wiring layer with high throughput. Can be formed.

Hereinafter, preferred embodiments of the present invention will be described.

In the polishing step of the metal wiring forming method of the present invention, the main component is citric acid, which is an agent for suppressing the adhesion of the polishing product to the polishing pad, or secondary particles formed by agglomeration of primary particles as an abrasive. A slurry for chemical mechanical polishing (hereinafter, also referred to as “polishing slurry”) containing (hereinafter, also referred to as “secondary particles θ alumina”) is used. According to CMP using such a polishing slurry, even when a thick or large-area copper-based metal film is polished, that is, when a large amount of copper-based metal is polished in one polishing operation. Even so, the adhesion of the polishing product to the polishing pad can be suppressed, and good polishing can be continuously performed without interrupting the polishing operation. Further, since the adhesion of the polishing product to the polishing pad can be suppressed, the polishing speed can be increased by increasing the contact pressure of the polishing pad with the polishing surface, and the in-plane uniformity of the polishing surface can be sufficiently improved. . As a result, a uniform wiring having a small variation in resistance can be formed.

Conventionally, in a slurry for chemical mechanical polishing, carboxylic acid, which is a kind of organic acid, is used as a proton donor for improving the polishing rate, and citric acid is known as one kind of such carboxylic acid. It was only. The present inventors have conducted intensive studies in order to solve the above-described problem. As a result, even when a large amount of copper-based metal is polished in one polishing operation, citric acid is present in the polishing slurry. As a result, it was found that the adhesion of the polishing product to the polishing pad was suppressed, and the present invention was completed.

Also, in a slurry for chemical mechanical polishing for polishing a copper-based metal film, conventionally, alumina generally used as an abrasive is generally α-alumina composed of primary particles. Focusing on θ-alumina, the inventors have found that the use of a specific θ-alumina containing secondary particles as a main component as an abrasive suppresses the adhesion of polishing products to a polishing pad, leading to the completion of the present invention. Was.

In the CMP in the present invention using the polishing slurry, the polishing amount per unit area of the polishing pad in one polishing operation in polishing a substrate having a copper-based metal film on the surface is 2 × 10 ⁻⁴ g / cm. ^{Even in the} case of polishing ^two or more copper-based metals, good polishing can be performed without pad contamination, and even in the case of polishing of 1 × 10 ⁻³ g / cm ² or more, 1 × 10 ⁻³ g / cm ² or more. CMP can be favorably performed even with polishing of 10 ⁻² g / cm ² or more. In such a case, for example, when forming a buried conductive portion in which the sum of the wiring height and the depth of the connection hole is about 1.5 μm in the formation of the upper wiring in the multilayer wiring structure, the film thickness of about 2.0 μm or more It is necessary to form a copper film, and a large amount of the copper film is polished per unit area of the polishing pad.

研磨 As a polishing pad used for polishing such a large amount of copper-based metal, a polishing pad using a general porous urethane resin can be used.

The polishing slurry used in the present invention contains, as a basic composition, an abrasive, an oxidizing agent, an organic acid, and water, and in this basic composition, contains citric acid, which is an adhesion inhibitor, as an organic acid, or as an abrasive. It contains θ-alumina (secondary particle-θ-alumina-containing particles) mainly composed of secondary particles formed by aggregation of primary particles. Further, the basic composition may contain citric acid and θ-alumina mainly containing secondary particles of θ-alumina as an abrasive. Further, an antioxidant may be further contained for preventing dishing and controlling the polishing rate.

The content of citric acid in the polishing slurry used in the present invention is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more based on the total amount of the slurry composition, from the viewpoint of exhibiting a sufficient adhesion suppressing effect. More preferred. In addition, from the viewpoint of the thixotropic properties of the polishing slurry, the content is preferably 5% by mass or less, more preferably 3% by mass or less.

Since the color of the polishing waste liquid discharged during the CMP using the polishing slurry containing citric acid was bluish green, the copper ions ionized and eluted by the action of the oxidizing agent and the citric acid in the polishing slurry Are considered to form a complex, and the polished copper component is discharged without the copper compound adhering to the polishing pad or the polishing surface as a polishing product.

On the other hand, the content of the secondary particles of the secondary-particle-containing θ-alumina is 60% by mass or more based on the entire secondary-particle-containing θ-alumina from the viewpoint of more sufficiently suppressing the adhesion of the polishing product to the polishing pad. Is preferably 65% by mass or more, more preferably 70% by mass or more.

The average particle size of the secondary particles is preferably 0.05 μm or more, more preferably 0.07 μm or more, and further preferably 0.08 μm or more. The upper limit is preferably 0.5 μm or less, more preferably 0.4 μm or less, and even more preferably 0.3 μm or less.

Furthermore, the proportion of the secondary particles having a particle size of 0.05 μm or more and 0.5 μm or less in the entire secondary particles of θ alumina is preferably 50% by mass or more, more preferably 55% by mass or more, and 60% by mass or more. % Is more preferable.

In addition, the secondary particle-containing θ-alumina preferably does not substantially contain primary particles and secondary particles having a particle diameter of preferably 2 μm, more preferably 1.5 μm, and still more preferably 1 μm.

平均 The average particle size of the primary particles constituting the secondary particles of the above-mentioned θ-alumina is preferably 0.005 μm or more, more preferably 0.007 μm or more, and further preferably 0.008 μm or more. The upper limit is preferably 0.1 μm or less, more preferably 0.09 μm or less, and even more preferably 0.08 μm or less.

Since the average particle diameter of the primary particles constituting the secondary particles and the θ-alumina in the present invention is much smaller than the primary particles of α-alumina generally used as conventional abrasive grains, The average particle size of the secondary particles composed of the primary particles can be adjusted to the same level as the average particle size of the conventional primary particles of α-alumina. Then, when CMP is performed using a polishing slurry containing θ-alumina having the secondary particles as a main component (secondary particles θ-alumina) as a main component of the abrasive grains, the copper polishing surface and the secondary particles are removed. Since the contact area with the constituent primary particles is small, the polishing product generated by mechanical removal is small. Further, the generated polishing product is finely pulverized due to voids and irregularities between the primary particles constituting the secondary particles, so that the polishing product becomes a finer polishing product.

In addition, the secondary particle-containing θ-alumina has a large surface area as compared with the conventional primary particles of α-alumina, and thus has good dispersibility. Is suppressed. For this reason, generation of a large-sized polishing product generated from the polished surface by being scraped off by the giant particles is suppressed. For the above reasons, in the CMP using the polishing slurry containing the secondary particles θ-alumina, since the generated polishing product is minute, the polishing product hardly causes clogging on the polishing pad surface, and Polish products are easily washed away by the continuously supplied polishing slurry. Therefore, even when a large amount of copper is polished, contamination of the polishing pad is suppressed.

Ｃ In the CMP using the polishing slurry, in addition to the effect of suppressing polishing pad contamination, generation of scratches on the polishing surface is also suppressed. Since the secondary particle-containing θ-alumina can be deformed by the polishing load from the polishing pad, stress concentration does not occur at the contact portion between the polishing surface and the primary particles constituting the secondary particles. As a result, the occurrence of scratches is suppressed without the polishing surface being scooped largely.

モ ー Further, the Mohs hardness of θ-alumina is 7, while the Mohs hardness of α-alumina is 9. That is, θ-alumina has a lower hardness than α-alumina and has an appropriate hardness for polishing a soft metal such as copper, so that scratch is less likely to occur.

Further, the secondary particles of the θ-alumina are excellent in dispersibility because the secondary particles of the alumina have a large surface area, and since the primary particles are extremely fine, the polishing slurry used in the present invention has a long-term stability. It also has the feature of being excellent.

The average particle size of the abrasive grains, the ratio of the abrasive grains having a specific range of grain size and the maximum particle size are measured by measuring the particle size distribution of the abrasive grains by a light scattering method, and statistically processing the obtained particle size distribution. It can be calculated by applying. Further, the particle size distribution of the polishing abrasive grains can be obtained by measuring the particle diameters of a large number of polishing abrasive grains using an electron microscope.

The production of θ alumina can be performed by removing water of crystallization from a colloid consisting of a hydrate or hydroxide of a salt containing Al by a heat treatment at a controlled rate of temperature rise. Aggregates formed by fusion of the contact portions of the adjacent primary particles during the heat treatment are secondary particles. In the production of θ-alumina, fine colloidal particles having a controlled particle size can be prepared, so that fine primary particles having an average particle size and a particle size distribution suitable for the present invention can be obtained. For this reason, secondary particles of θ-alumina having the same particle size as the primary particles of conventional α-alumina can be formed. Further, since the bonding force of the fusion between the primary particles formed during the heat treatment is an appropriate value, the bonding between some of the primary particles can be broken by dispersion under appropriate conditions. Thus, secondary particles having a particle size suitable for the present invention can be formed.

The secondary particle-containing θ-alumina used in the present invention can be prepared by dispersing the θ-alumina formed as described above in a dispersion medium under appropriate conditions. The θ-alumina produced by the heat treatment of the colloid is composed of a huge aggregate having an average particle diameter of about 10 μm in which a large number of primary particles are fused. This is added to the aqueous medium in a range of 10% by mass to 70% by mass. If necessary, a dispersant may be added in a range of 0.01% by mass or more and 10% by mass or less. The addition amount of the θ-alumina and the dispersant affects the particle size of the obtained secondary particles.

Dispersion can be performed using an ultrasonic disperser, a bead mill disperser, a ball mill disperser, a kneader disperser, or the like. Among these, it is preferable to use a bead mill disperser or a ball mill disperser because secondary particles having a desired particle size can be formed stably. Further, in order to remove particles having a particle size of 2 μm or more, a filter mechanism may be provided in these dispersers.

The dispersion time affects the particle size distribution of the secondary particles, and is preferably 140 minutes or more, more preferably 150 minutes or more, and still more preferably 180 minutes, in order to obtain secondary particles having a highly monodisperse particle size distribution. Disperse for more than a minute. Further, in order to suppress mixing of foreign matter, the upper limit of the dispersion time is preferably 400 minutes or less, more preferably 350 minutes or less, and even more preferably 300 minutes or less.

As the dispersant, one or more of a surfactant type and a water-soluble polymer type dispersant can be used.

Examples of the surfactant-based dispersant include anionic, cationic, amphoteric and nonionic surfactants. As the anionic surfactant, soluble salts such as sulfonic acid, sulfate ester, carboxylic acid, phosphate ester, and phosphonic acid can be used. These soluble salts include, for example, sodium alkylbenzenesulfonate (ABS), sodium dotesyl sulfate (SDS), sodium stearate, sodium hexametaphosphate and the like. Examples of the cationic surfactant include amine salts containing a tertiary amine capable of forming a salt, modified salts thereof, quaternary ammonium salts, onium compounds such as phosphonium salts and sulfonium salts, pyridinium salts, Cyclic nitrogen compounds such as quinolinium salts and imidazolinium salts, and heterocyclic compounds can be used. Examples of these cationic surfactants include cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), cetyldimethylbenzylammonium bromide, cetylpyridinium chloride, dodecylpyridinium chloride, and alkyldimethylchlorobenzyl chloride. Examples thereof include ammonium and alkylnaphthalenepyridinium chloride.

Nonionic surfactants include polyethylene glycol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and other fatty acids to which ethylene oxide is added and polymerized, ether-type nonionic surfactants, polyethylene glycol condensation Surfactants of the type can be used. Examples of these nonionic surfactants include POE (10) monostearate, POE (10) monostearate, POE (25) monostearate, POE (40) monostearate, and POE (45) monostearate. Rate, POE (55) monostearate, POE (21) lauryl ether, POE (25) lauryl ether, POE (15) cetyl ether, POE (20) cetyl ether, POE (23) cetyl ether, POE (25) cetyl Ether, POE (30) cetyl ether, POE (40) cetyl ether, POE (20) stearyl ether, POE (2) nonyl phenyl ether, POE (3) nonyl phenyl ether, POE (5) nonyl phenyl ether, POE (7) ) Nonylphenyl ether, POE ( 0) Nonyl phenyl ether, POE (15) nonyl phenyl ether, POE (18) nonyl phenyl ether, POE (20) nonyl phenyl ether, POE (10) octyl phenyl ether, POE (30) octyl phenyl ether, POE (6) Sorbitan monooleate, POE (20) sorbitan monolaurate, POE (6) sorbitan monolaurate, POE (20) sorbitan monolaurate, POE (20) sorbitan monopalmirate, POE (6) sorbitan monostearate, POE (20) sorbitan monostearate, POE (20) sorbitan tristearate, POE (20) sorbitan trioleate, POE (6) sorbitan monooleate, POE (20) sorbitan monooleate Rukoto can. Here, POE is polyoxyethylene, and the number in parentheses represents the number of repeating units —CH ₂ CH ₂ O—.

As the amphoteric surfactant, -COOH group consisting anion in the molecule, -SO ₃ H group, and at least one or more types of atomic groups from such -OSO ₃ H groups and -OPO ₃ H ₂ group, the cation As the atomic group, a compound containing a primary to tertiary amine or a quaternary ammonium can be used. For example, there are betaine, sulfobetaine, sulfate betaine type, and more specifically, betaine lauryldimethylaminoacetate, N-coconut fatty acid acyl-N-carboxymethyl-N-hydroxyethylenediamine sodium and the like.

In addition, examples of the water-soluble polymer-based dispersant include ionic polymers and nonionic polymers. Examples of the ionic polymer include alginic acid or a salt thereof, polyacrylic acid or a salt thereof, polycarboxylic acid or a salt thereof, cellulose, carboxymethyl cellulose, hydroxylethyl cellulose, and the like.As the nonionic polymer, polyvinyl alcohol, Examples include polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, and the like.

The weight average molecular weight of the water-soluble polymer-based dispersant is preferably 100 or more, more preferably 500 or more, and still more preferably 1,000 or more, and as the upper limit, 100,000 or less, more preferably 80,000 or less, and 50,000 or less. preferable. When the weight average molecular weight is within this range, the increase in viscosity of the obtained polishing slurry can be suppressed, and secondary particles having a good particle size distribution can be formed.

Secondary Particles Other abrasive grains may be used as needed, as long as the effect of the alumina is not impaired. Other polishing abrasives include alumina other than θ-alumina such as α-alumina and δ-alumina, silica such as fumed silica and colloidal silica, titania, zirconia, germania, ceria, and metal oxide polishing abrasives thereof. Or a mixture of two or more selected from the group consisting of:

The content of the secondary particles θ-alumina is preferably 1% by mass or more, more preferably 3% by mass or more, and preferably 30% by mass or less, and more preferably 10% by mass, based on the entire slurry for chemical mechanical polishing. The following% is more preferable. When the polishing slurry contains two or more types of polishing abrasive grains, the total content of each polishing abrasive grain is preferably at least 1% by mass, and more preferably at least 3% by mass, based on the entire chemical mechanical polishing slurry. More preferably, the upper limit is preferably 30% by mass or less, and more preferably 10% by mass or less.

In the present invention, when a polishing slurry containing citric acid is used, the above-mentioned secondary particles containing θ-alumina are not used as an abrasive, and generally used α-alumina, θ-alumina, δ-alumina, etc. A mixture of two or more kinds selected from the group consisting of alumina, silica such as fumed silica and colloidal silica, titania, zirconia, germania, ceria, and metal oxide abrasive grains thereof can be used. The average particle diameter of such an abrasive is preferably 5 nm or more, more preferably 50 nm or more, as an average particle diameter measured by a light scattering diffraction method, from the viewpoint of polishing rate, dispersion stability, and surface roughness of the polished surface. Further, the thickness is preferably 500 nm or less, more preferably 300 nm or less. The particle size distribution is preferably 3 μm or less as the maximum particle size (d100), more preferably 1 μm or less.

研磨 The content of the abrasive in the polishing slurry is appropriately set in the range of 0.1 to 50% by mass with respect to the total amount of the slurry composition in consideration of polishing efficiency, polishing accuracy and the like. It is preferably at least 1% by mass, more preferably at least 2% by mass, even more preferably at least 3% by mass. As a maximum, 30 mass% or less is preferred, 10 mass% or less is preferred, and 8 mass% or less is still more preferred.

The pH of the polishing slurry used in the present invention is preferably pH 4 or higher, more preferably pH 5 or higher, more preferably pH 8 or lower, and preferably pH 7 or lower, from the viewpoints of polishing rate, corrosion, slurry viscosity, and dispersion stability of the abrasive. Is more preferred. On the other hand, if the pH is too high, citric acid is dissociated, the ability to form a complex with the polishing product is reduced, and the effect of suppressing the adhesion of citric acid is reduced, so that the polishing product easily adheres to the polishing pad. Conversely, if the pH is too low, the polishing rate of copper will be too high, and the surface shape of the copper wiring will be degraded, causing depressions, which will tend to cause steps.

(4) The pH of the polishing slurry can be adjusted by a known method, for example, by directly adding an alkali to a slurry in which abrasive particles are dispersed and a carboxylic acid is dissolved. Alternatively, part or all of the alkali to be added may be added together with an alkali salt of carboxylic acid. Examples of the alkali used include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, carbonates of alkali metals such as sodium carbonate and potassium carbonate, ammonia, and amines.

The oxidizing agent can be appropriately selected from known water-soluble oxidizing agents in consideration of the type of the conductive metal film, polishing accuracy, and polishing efficiency. For example, peroxides such as H ₂ O ₂ , Na ₂ O ₂ , Ba ₂ O ₂ , (C ₆ H ₅ C) ₂ O ₂ , and hypochlorous acid (HClO) are used as materials that do not cause contamination of heavy metal ions. ), Perchloric acid, nitric acid, ozone water, and organic peroxides such as peracetic acid and nitrobenzene. Among them, hydrogen peroxide (H ₂ O ₂ ) which does not contain a metal component and does not generate harmful double products is preferable. The amount of the oxidizing agent contained in the polishing slurry used in the present invention is preferably 0.01% by mass or more, more preferably 0.05% by mass or more based on the total amount of the polishing slurry, from the viewpoint of obtaining a sufficient effect of addition. 0.1 mass% or more is more preferable. From the viewpoint of suppressing dishing and adjusting to an appropriate polishing rate, the amount is preferably 15% by mass or less, more preferably 10% by mass or less. When an oxidizing agent such as hydrogen peroxide that is relatively easily deteriorated with time is used, a predetermined concentration of the oxidizing agent-containing solution and a predetermined polishing slurry are obtained by adding the oxidizing agent-containing solution. Such a composition may be separately prepared, and the two may be mixed immediately before use.

カ ル ボ ン A known carboxylic acid or amino acid may be added as a proton donor in order to promote oxidation of the oxidizing agent and perform stable polishing. Since citric acid is a carboxylic acid, it can also function as a proton donor, but a different carboxylic acid or an organic acid such as an amino acid may be separately added.

Examples of carboxylic acids other than citric acid include, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, lactic acid, succinic acid, nicotinic acid, oxalic acid, malonic acid, tartaric acid, malic acid, glutaric acid, citric acid Acids, maleic acid, and salts thereof.

As amino acids, for example, L-glutamic acid, D-glutamic acid, L-glutamic acid monohydrochloride, L-glutamic acid sodium monohydrate, L-glutamine, glutathione, glycylglycine, DL-alanine, L-alanine, β- Alanine, D-alanine, γ-alanine, γ-aminobutyric acid, ε-aminocaproic acid, L-arginine monohydrochloride, L-aspartic acid, L-aspartic acid monohydrate, potassium L-aspartate, L-asparagine Acid calcium trihydrate, D-aspartic acid, L-titrulline, L-tryptophan, L-threonine, L-arginine, glycine, L-cystine, L-cysteine, L-cysteine hydrochloride monohydrate, L-oxy Proline, L-isoleucine, L-leucine, L-lysine monohydrochloride, DL-methionine, L-methionine, L-ortinine hydrochloride, L-phenylalanine, D-phenylglycine, L-prolyl , L-serine, L-tyrosine, L-valine and the like.

(4) The content of the organic acid is preferably 0.01% by mass or more, more preferably 0.05% by mass or more based on the total amount of the polishing slurry, from the viewpoint of obtaining a sufficient effect of adding a proton donor. From the viewpoint of suppressing dishing and adjusting to an appropriate polishing rate, the content including citric acid is preferably 5% by mass or less, more preferably 3% by mass or less.

研磨 An antioxidant may be further added to the polishing slurry of the present invention. The addition of the antioxidant makes it easy to adjust the polishing rate of the copper-based metal film, and by forming a coating on the surface of the copper-based metal film, the deterioration of the surface shape of the copper wiring due to chemical polishing, That is, dishing and recess can be suppressed.

Examples of the antioxidant include benzotriazole, 1,2,4-triazole, benzofuroxane, 2,1,3-benzothiazole, o-phenylenediamine, m-phenylenediamine, catechol, o-aminophenol, -Mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, melamine, and derivatives thereof. Among them, benzotriazole and its derivatives are preferred. As the benzotriazole derivative, the benzene ring has a hydroxyl group, an alkoxy group such as methoxy and ethoxy, an amino group, a nitro group, an alkyl group such as a methyl group and an ethyl group, and a butyl group, or a fluorine, chlorine, bromine, and iodine group. Substituted benzotriazoles having a halogen substituent are mentioned. Further, naphthalenetriazole, naphthalenebistriazole, substituted naphthalenetriazole substituted in the same manner as described above, and substituted naphthalenebistriazole can be exemplified.

か ら The content of the antioxidant is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more based on the total amount of the polishing slurry, from the viewpoint of obtaining a sufficient anticorrosion effect. From the viewpoint of adjusting the polishing rate to an appropriate value, the content is preferably 5.0% by mass or less, more preferably 2.5% by mass or less. If the content of the antioxidant is too large, the anticorrosion effect is too effective, the copper polishing rate is too low, and the CMP takes time.

The polishing slurry used in the present invention may contain various additives such as a dispersant, a buffer, and a viscosity modifier that are generally added to the polishing slurry, as long as the properties are not impaired. .

組成 The polishing slurry used in the present invention preferably has a composition ratio adjusted so that the polishing rate of the copper-based metal film is preferably 300 nm / min or more, more preferably 400 nm / min or more. The polishing slurry used in the present invention preferably has a composition ratio adjusted so that the polishing rate of the copper-based metal film is preferably 1500 nm / min or less, more preferably 1000 nm / min or less.

は As a method for producing a polishing slurry used in the present invention, a general method for producing a free abrasive polishing slurry composition can be applied. That is, an appropriate amount of abrasive particles is mixed with the dispersion medium. If necessary, mix the appropriate amount of protective agent. In this state, since the air is strongly adsorbed on the surface of the abrasive particles, the abrasive particles have poor wettability and exist in an aggregated state. Therefore, in order to make the aggregated abrasive particles into primary particles, the particles are dispersed. In the dispersing step, a general dispersing method and dispersing apparatus can be used. Specifically, it can be carried out by a known method using, for example, an ultrasonic disperser, various types of bead mill dispersers, kneaders, ball mills and the like. In addition, citric acid may cause flocculation of the abrasive grains and at the same time enhance thixotropic properties. Therefore, in order to perform good dispersion, it is preferable to add and mix after the dispersion is completed.

研磨 The polishing step in the present invention can be performed using, for example, a chemical mechanical polishing apparatus (CMP apparatus) as shown in FIG.

ウ ェ ハ The wafer 21 on which an insulating film, a copper-based metal film, or the like is formed on a substrate is set on a wafer carrier 22 of a spindle. The surface of the wafer 21 is brought into contact with a polishing pad 24 attached to a rotating plate (platen) 23, and while the polishing slurry is supplied from the polishing slurry supply port 25 to the surface of the polishing pad 24, The polishing is performed by rotating both of the polishing pads 24. If necessary, the pad conditioner 26 is brought into contact with the surface of the polishing pad 24 to condition the polishing pad surface. The polishing slurry may be supplied from the rotating plate 23 to the surface of the polishing pad 24.

に お い て In the present invention, the contact pressure of the polishing pad with respect to the polishing surface during CMP is 27 kPa or more. It is preferably at least 34 kPa. By increasing the contact pressure of the polishing pad, the deflection of the polishing pad can be suppressed, so that the in-plane uniformity of the polished surface can be increased. As a result, the variation in wiring height is reduced, and the variation in wiring resistance is reduced. Becomes smaller. In addition, since the in-plane uniformity can be increased and the polishing rate can be increased, the throughput can be improved. Furthermore, even when high-speed polishing is performed, the content of the oxidizing agent such as hydrogen peroxide in the polishing slurry can be set to a region where the handling property is good and stable polishing is possible. The upper limit of the contact pressure (polishing pressure) of the polishing pad to the polishing surface is not particularly limited, but from the viewpoint of the polishing rate and the in-plane uniformity of the polishing surface, the contact between the wafer and the polishing pad is sufficiently performed. In addition, in order for the polishing slurry to be supplied between the wafer and the polishing pad, the pressure is preferably 48.3 kPa (7 psi) or less.

As other CMP conditions, when a polishing pad slightly larger than the wafer (a polishing pad having a radius smaller than the wafer diameter) is used, for example, a retainer pressure: 25.2 kPa (3.65 psi) to 27.9 kPa (4.05 psi) is used. ), Platen rotation speed: 260-280 rpm, polishing slurry supply rate: 80-150 ml / min. When a polishing pad having a radius larger than the diameter of the wafer is used, for example, the rotation speed of the platen can be 30 to 100 rpm, and the supply rate of the polishing slurry can be 100 to 300 ml / min.

At present, the size (diameter) of the wafer is 6 inches or 8 inches, but according to the present invention, the adhesion of the polishing product to the polishing pad is suppressed even for a wafer having a diameter of 12 inches or more. Good CMP can be performed.

According to the present invention described above, a substrate in which a barrier metal film is formed on an insulating film having a concave portion such as a groove or a connection hole, and a copper-based metal film is entirely formed on the insulating film so as to fill the concave portion is formed thereon. It is preferably used in a method of performing CMP until the surface of the insulating film other than the above is almost completely exposed to form an electrical connection such as a buried wiring, a via plug, or a contact plug. Examples of the barrier metal film include Ta, TaN, Ti, TiN, W, WN, and WSiN. Examples of the insulating film include a silicon oxide film, a BPSG film, and an SOG film. Examples of the copper-based metal film include a copper alloy film including various conductive metals such as silver, gold, platinum, titanium, tungsten, and aluminum, in addition to the copper film.

According to the present invention described above, even when a large amount of copper is polished due to a thick copper film or a large area, adhesion of polishing products to a polishing pad is suppressed, and the pad surface is cleaned. Since there is no necessity, a large amount of copper-based metal can be satisfactorily CMPed by one polishing operation without interrupting the polishing operation.

In addition, the cleaning of the polishing pad surface is not required, and the conditioning time can be reduced, so that the life of the polishing pad can be extended.

Further, according to the present invention, since the adhesion of the polishing product to the polishing pad can be suppressed, the polishing speed can be increased by increasing the contact pressure of the polishing pad with the polishing surface, and the in-plane of the polishing surface can be increased. Uniformity can be sufficiently improved. As a result, the variation in the wiring height is reduced, the variation in the wiring resistance is also reduced, and a uniform embedded wiring can be formed.

Further, according to the present invention, in the polishing step, it is possible to suppress the polishing product from being attached not only to the polishing pad surface but also to the polishing surface, so that there is no problem in element characteristics such as an electrical short circuit between wirings. In addition, a polished surface having excellent in-plane uniformity can be formed, and dishing and erosion can be suppressed.

The present invention will be described in more detail with reference to the following examples.

(CMP conditions)
The CMP was performed using SH-24 type manufactured by Speed Fam Ipec. A polishing pad (IC 1400 manufactured by Rodale Nitta) with a diameter of 61 cm (24 inches) was attached to the surface plate of the polishing machine. The polishing conditions were as follows: the contact pressure of the polishing pad: 27.6 kPa (4 psi); the polishing area of the polishing pad: 1820 cm2; the rotation speed of the platen: 55 rpm; the rotation speed of the carrier: 55 rpm; and the supply amount of the slurry polishing liquid: 100 ml / min.

(Measurement of polishing rate)
The polishing rate was calculated from the surface resistivity before and after processing. Specifically, four needle-like electrodes arranged at regular intervals on a wafer are placed on a straight line, a constant current is passed between two outer probes, and a potential difference generated between the two inner probes is measured. The resistance (R ′) is obtained, and the surface resistance (ρs ′) is further obtained by multiplying the resistance (R ′) by a correction coefficient RCF (Resistivity Correction Factor). Further, the surface resistivity (ρs) of the wafer film whose thickness is known as T (nm) is obtained. Here, since the surface resistivity is inversely proportional to the thickness, if the thickness is d when the surface resistivity is ρs ′, then d (nm) = (ρs × T) / ρs ′ holds, and the thickness d is calculated from this. The polishing rate was calculated by dividing the change in film thickness before and after polishing by the polishing time. The surface resistivity was measured using a four-probe resistance meter (Loresta-GP) manufactured by Mitsubishi Chemical Corporation.

(Evaluation of in-plane uniformity of polished surface)
Before and after polishing, the surface resistivity (resistivity) at 40 points in the wafer surface was measured, and the k value of the absolute polishing amount distribution was obtained as an index of in-plane uniformity.

The thickness of copper on the wafer is determined for each point by measuring the surface resistivity at each point in the wafer surface, and the film thickness value after polishing is subtracted from the film thickness value before polishing to obtain the shaving amount P for each point. I asked. The maximum value Pmax, minimum value Pmin, and average value Pav of the shaving amount P at 40 points were obtained. From these values, the in-plane uniformity k (%) = (Pmax−Pmin) × 100 / (2 × Pav) was calculated.

(Example 1)
An embedded wiring of copper was formed using a Ta film as a barrier metal film.

On a 6-inch wafer (silicon substrate) on which semiconductor elements such as transistors are formed (not shown), as shown in FIG. 1A, a first silicon oxide film 1 having a lower wiring 2 is formed. After a silicon nitride film 3 and a second silicon oxide film 4 having a thickness of about 1.5 μm are formed thereon, wiring grooves are formed in the second silicon oxide film 4 by a conventional method such as photolithography and patterning by etching. Further, a connection hole reaching the lower wiring 2 was formed in a part thereof. Next, a Ta film having a thickness of 50 nm was formed by a sputtering method, a copper film having a thickness of about 50 nm was formed by a sputtering method, and then a copper film 6 having a thickness of about 2.0 μm was formed by a plating method.

基板 The substrate thus manufactured was subjected to CMP using various polishing slurries shown in Table 1, and the polishing of the polishing pad after polishing the copper film by about 2 μm was evaluated by visual observation and polishing rate.

(4) Citric acid, glutaric acid, glycine, and benzotriazole (BTA) used reagents manufactured by Kanto Chemical Co., Ltd. The silica used was fumed silica Qs-9 manufactured by Tokuyama Corporation, and the alumina used was θ-alumina (AKP-G008) manufactured by Sumitomo Chemical Co., Ltd.

Table 1 shows the CMP results together with the composition of the polishing slurry. In the CMP using the polishing slurry containing citric acid, almost no adhesion of the polishing product was observed on the polishing pad surface, and the polishing rate was stable and constant until the polishing was completed. On the other hand, in the CMP using the polishing slurry not containing citric acid but containing carboxylic acid (glutaric acid) or amino acid (glycine), a large amount of polishing products adhered to the polishing pad after polishing was completed.

In CMP using a polishing slurry containing citric acid, the in-plane uniformity of the polished surface was 5%. Further, when the contact pressure of the polishing pad was increased from 27.6 kPa (4 psi) to 34.5 kPa (5 psi) and the same CMP was performed, the in-plane uniformity was 3.5%. At this time, there was no adhesion of the polishing product to the polishing surface.

FIG. 4 shows the change in the in-plane uniformity (k value) with respect to the polishing pressure when CMP was performed using a polishing slurry containing citric acid and a polishing slurry not containing it. It can be seen that when the polishing slurry containing citric acid is used (○), the k value is smaller than when no polishing slurry is used (□), and polishing with excellent in-plane uniformity can be performed even at the same polishing pressure. This is because the polishing product adheres to the polishing pad in the CMP polishing using the polishing slurry not containing citric acid, whereas the polishing product of the polishing pad in the CMP using the polishing slurry containing citric acid. Is not attached.

　（含２次粒子θアルミナ分散液の調製）
　含２次粒子θアルミナの調製は、住友化学工業社製θアルミナ（ＡＫＰ−Ｇ００８）を用いて行った。この調製前のθアルミナをＳＥＭにより観察したところ、最小粒径０．０３μｍ、最大粒径０．０８μｍの多数の１次粒子（平均粒径０．０５μｍ）が融着により結合した凝集体からなることが判った。この凝集体の平均粒径は１０μｍであった。なお、この最小粒径に対して著しく小さい１次粒子やこの最大粒径に対してかなり大きい１次粒子も微量に観察される場合もあったが、最終的に得られる研磨用スラリーの特性には全く影響せず、また平均粒径の値にも全く寄与しない程度であった。

(Preparation of secondary particle θ alumina dispersion)
The preparation of the secondary particle-containing θ-alumina was carried out using θ-alumina (AKP-G008) manufactured by Sumitomo Chemical Co., Ltd. Observation of the pre-prepared θ-alumina by SEM revealed that a large number of primary particles (average particle diameter 0.05 μm) having a minimum particle diameter of 0.03 μm and a maximum particle diameter of 0.08 μm consisted of aggregates bonded by fusion. It turns out. The average particle size of the aggregate was 10 μm. In some cases, a very small amount of primary particles with respect to the minimum particle size and a large amount of primary particles with respect to the maximum particle size were observed. Had no effect at all and did not contribute to the value of the average particle size at all.

(4) Next, the dispersant Aqualic HL415 manufactured by Nippon Shokubai Co., Ltd. was mixed with ion-exchanged water so as to have a concentration of 4% by mass. The obtained mixed liquid was dispersed at a rotation speed of 1,000 times / minute by using a bead mill (Super Mill) manufactured by Inoue Seisakusho. The dispersion time was varied between 20 and 400 minutes to prepare a plurality of dispersions.

Θ For θ-alumina contained in each dispersion, the particle size distribution of the whole particles was measured by a particle size distribution analyzer LS-230 manufactured by Beckman Coulter. The maximum particle size was determined from the particle size distribution of all the obtained particles. The particle size distribution of the secondary particles was calculated by subtracting the particle size distribution of the primary particles from the particle size distribution of the whole particles. The average particle size of the secondary particles was determined by performing statistical processing on the particle size distribution of the obtained secondary particles. Furthermore, for the dispersion liquid having a dispersion time of 200 minutes, the content of the secondary particles with respect to the entirety of the secondary particles θ-alumina and the total secondary particles of the secondary particles having a particle size of 0.05 μm or more and 0.5 μm or less are used. The percentage of the total was also determined.

FIG. 3 shows the maximum particle size (●) of θ alumina and the average particle size (粒径) of secondary particles in the dispersion at each dispersion time. When the dispersion time was 120 minutes or less, large secondary particles having a particle size exceeding 3 μm were included, but when the dispersion time was 140 minutes or more, the maximum particle diameter was 1 μm or less.

When the dispersion time is 200 minutes, the average particle size of the secondary particles is 0.15 μm, the maximum particle size is 0.6 μm, the content of the secondary particles is 74% by mass based on the entirety of the secondary particles and the alumina, and the particle size is The ratio of secondary particles having a particle size of 0.05 μm or more and 0.5 μm or less to the entire secondary particles was 62% by mass. In addition, no foreign matter was particularly confirmed.

(Example 2)
Among the dispersion liquids obtained as described above, a dispersion liquid having a dispersion time of 200 minutes was used, 5.03% by mass of secondary particles θ-alumina, 0.47% by mass of citric acid, 1.9% by mass % Of H2O2 and a pH of 7 was prepared. The pH was adjusted with ammonia, and H2O2 was added immediately before CMP.

Next, a silicon oxide film, a wiring groove, a connection wiring opening, a barrier metal film, and a copper film were formed on a 6-inch silicon substrate in the same manner as in Example 1.

基板 The substrate thus manufactured was subjected to CMP using the polishing slurry 1 to polish a copper film by about 2 μm. The polishing rate was constant until the polishing was completed, and the polishing could be performed stably. Thereafter, dirt on the polishing pad was evaluated visually and by a polishing rate. As a result, it was found that the polishing product was hardly adhered to the polishing pad. Further, when the polished surface was observed with an SEM, generation of scratches was also suppressed. The in-plane uniformity of the polished surface was 5%. Further, when the contact pressure of the polishing pad was increased from 27.6 kPa (4 psi) to 34.5 kPa (5 psi) and the same CMP was performed, the in-plane uniformity was 3.5%. At this time, there was no adhesion of the polishing product to the polishing surface, and the scratch was suppressed.

(Example 3)
Polishing slurry 2 was prepared in the same manner as polishing slurry 1 except that malic acid was used instead of citric acid. Using this polishing slurry 2, CMP was performed in the same manner as described above. The polishing rate was constant until the polishing was completed, and the polishing could be performed stably. The polishing product hardly adhered to the polishing pad. Further, when the polished surface was observed with an SEM, generation of scratches was also suppressed. The in-plane uniformity of the polished surface was 5% or less. Further, when the contact pressure of the polishing pad was increased from 27.6 kPa (4 psi) to 34.5 kPa (5 psi) and the same CMP was performed, the in-plane uniformity was 3.5%. At this time, there was no adhesion of the copper polishing product to the polished surface, and the scratch was suppressed.

(Comparative Example 1)
Polishing slurry 3 was prepared in the same manner as polishing slurry 2 except that commercially available α-alumina was used instead of θ-alumina. When CMP was performed using the polishing slurry 3 in the same manner as described above, a large amount of polishing products was attached to the polishing pad. The in-plane uniformity of the polishing surface was 8% when the contact pressure of the polishing pad was 27.6 kPa (4 psi) and 6.5% when the contact pressure was 34.5 kPa (5 psi).

FIG. 4 is a process cross-sectional view for describing a method of forming a buried copper wiring. It is a schematic structure figure of a chemical mechanical polishing device. FIG. 3 is a diagram showing a change in the particle size of θ alumina with respect to a dispersion time. 5 is a graph showing a change in in-plane uniformity (k value) with respect to a polishing pressure.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 first interlayer insulating film 2 lower layer wiring 3 silicon nitride film 4 second interlayer insulating film 5 barrier metal film 6 copper film 21 wafer 22 wafer carrier 23 rotating plate (plate)
24 Polishing Pad 25 Polishing Slurry Supply Port 26 Pad Conditioner

Claims (6)

Forming a recess in the insulating film formed on the substrate, forming a copper-based metal film over the entire surface so as to fill the recess, and polishing the copper-based metal film by a chemical mechanical polishing method In the method for forming a metal wiring having
The polishing step uses a slurry for chemical mechanical polishing containing citric acid as an abrasive, an oxidizing agent and an adhesion inhibitor of a polishing product to the polishing pad, and contacts the polishing pad with a polishing surface at a pressure of 27 kPa or more. A method for forming a metal wiring, wherein the polishing is performed such that the polishing amount per unit area of the polishing pad in one polishing operation is 2 × 10 ⁻⁴ g / cm ² or more. The method of claim 1, wherein the slurry for chemical mechanical polishing further comprises an antioxidant. 3. The method according to claim 1, wherein the content of the citric acid in the slurry for chemical mechanical polishing is 0.01% by mass or more and 5% by mass or less. 4. The metal wiring forming method according to claim 3, wherein the content of the antioxidant in the slurry for chemical mechanical polishing is 0.0001% by mass or more and 5% by mass or less. 5. The method according to claim 1, wherein the abrasive is silica particles. The method according to claim 1, wherein the polishing is performed so that the polishing amount is 1 × 10 ⁻³ g / cm ² or more.

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