JP2009152647A - Metal polishing solution and substrate polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal polishing solution which is capable of quickly polishing tantalum, tantalum alloys, tantalum nitrides, and other tantalum compounds used as a barrier layer of copper or a copper alloy and has a low abrasive concentration to be free of polishing flaws and is capable of forming a buried metal film pattern of less thinning and high reliability, and to provide a polishing method using the same. <P>SOLUTION: The metal polishing solution includes abrasive grains, a conductor oxidizing agent, a protective film forming agent for a metal surface, an acid, and water, wherein the concentration of the abrasive grains is 0.05 to 3.0 wt.% and the metal polishing solution has a pH of ≤3 and the concentration of the conductor oxidizing agent is 0.01 to 3 wt.%. In the polishing method of polishing a target surface to be polished by supplying the metal polishing solution to a polishing pad on a platen to bring the metal polishing solution into contact with the target surface and relatively moving the target surface and the polishing pad, the barrier layer containing tantalum, tantalum nitrides, tantalum alloys, and other tantalum compounds is polished using the metal polishing solution. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention particularly relates to a metal polishing liquid used for polishing a wiring formation process of a semiconductor device and a substrate polishing method using the same.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as LSIs). The chemical mechanical polishing (hereinafter referred to as CMP) method is one of them, and is a technique frequently used in the LSI manufacturing process, particularly in the multilayer wiring formation process, planarization of the interlayer insulating film, metal plug formation, and buried wiring formation. . This technique is disclosed in, for example, US Pat. No. 4,944,836.

  Recently, in order to improve the performance of LSIs, the use of copper or copper alloys as wiring materials has been attempted. However, it is difficult to finely process copper or a copper alloy by a dry etching method frequently used in the formation of a conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly used in which a copper or copper alloy thin film is deposited and embedded on an insulating film in which a groove is formed in advance, and the copper or copper alloy thin film other than the groove is removed by CMP to form a buried wiring. It has been adopted. This technique is disclosed, for example, in JP-A-2-278822.

  A general method of metal CMP such as copper or copper alloy is a surface on which a polishing pad is pasted on a circular polishing platen (platen), the surface of the polishing pad is immersed in a metal polishing liquid, and a metal film of a substrate is formed. Is pressed and a polishing surface plate is rotated with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, and the metal film on the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. Is. The metal polishing liquid used in CMP is generally composed of an oxidizing agent and abrasive grains, and a metal oxide dissolving agent and a protective film forming agent are further added as necessary. First, it is considered that the basic mechanism is to oxidize the surface of a metal film with an oxidizing agent and scrape the oxidized layer with abrasive grains. Since the oxide layer on the metal surface of the recess does not touch the polishing pad so much and the effect of scraping off by the abrasive grains does not reach, the metal layer of the projection is removed and the substrate surface is flattened with the progress of CMP. The details are disclosed in Journal of Electrochemical Society, Vol. 138, No. 11 (published in 1991), pages 3460 to 3464.

  As a method for increasing the polishing rate by CMP, it is effective to add a metal oxide dissolving agent. It can be interpreted that if the metal oxide particles scraped by the abrasive grains are dissolved in the polishing liquid (hereinafter referred to as etching), the effect of scraping by the abrasive grains is increased. Although the polishing rate by CMP is improved by adding a metal oxide solubilizer, on the other hand, when the oxide layer on the metal film surface in the recess is also etched (dissolved) and the metal film surface is exposed, the metal film surface is further oxidized by the oxidant. If this is repeated, etching of the metal film in the recesses proceeds. For this reason, a phenomenon occurs in which the central portion of the surface of the metal wiring embedded after polishing is depressed like a dish (hereinafter referred to as “dicing”), and the planarization effect is impaired.

  In order to prevent this, a protective film forming agent is further added. The protective film forming agent forms a protective film on the oxide layer on the surface of the metal film and prevents dissolution of the oxide layer in the polishing liquid. This protective film can be easily scraped off by abrasive grains, and it is desirable not to reduce the polishing rate by CMP. In order to suppress corrosion during dishing or polishing of copper or copper alloy, and to form a highly reliable LSI wiring, it contains BTA as a protective film forming agent and a metal oxide solubilizer composed of aminoacetic acid or amide sulfuric acid such as glycine A method using a metal polishing liquid is proposed. This technique is described in, for example, JP-A-8-83780.

  In metal embedding formation such as damascene wiring formation of copper or copper alloy or plug wiring formation of tungsten, etc., when the polishing rate of the silicon dioxide film that is an interlayer insulating film formed other than the embedded portion is high, the interlayer insulating film Thinning in which the thickness of each wiring is reduced occurs. As a result, resistance variation occurs due to an increase in wiring resistance, pattern density, and the like, so that a characteristic in which the polishing rate of the silicon dioxide film is sufficiently small with respect to the metal film to be polished is required. Accordingly, a method has been proposed in which the polishing rate of silicon dioxide is suppressed by anions generated by acid dissociation so that the polishing solution has a pH higher than pKa-0.5. This technique is described in, for example, Japanese Patent No. 2819196.

  On the other hand, tantalum, a tantalum alloy, tantalum nitride, other tantalum compounds, and the like are formed as a barrier layer to prevent copper diffusion into the interlayer insulating film in a lower layer such as copper or copper alloy of the wiring. Therefore, it is necessary to remove the exposed barrier layer by CMP except for the wiring portion in which copper or a copper alloy is embedded. However, since these barrier layer conductors have higher hardness than copper or copper alloys, a combination of polishing materials for copper or copper alloys cannot often provide a sufficient polishing rate. In view of this, a two-step polishing method comprising a first step of polishing copper or a copper alloy and a second step of polishing a barrier layer conductor has been studied.

  In the second step, CMP of the barrier layer, it is necessary to prevent the copper or copper alloy embedded wiring portion from being diced, and the pH of the polishing liquid is reduced in order to suppress the polishing rate and etching rate of copper or copper alloy. That was considered a negative effect.

  Tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds used as the barrier layer are chemically stable and difficult to etch, and have high hardness, so mechanical polishing is not as easy as copper and copper alloys. Therefore, if the hardness of the abrasive grains is increased, polishing scratches may occur in the copper or copper alloy, resulting in poor electrical characteristics, or if the abrasive grain concentration is increased, the silicon dioxide film is polished. There was a problem that the speed increased and thinning occurred. The present invention suppresses the occurrence of dishing, thinning and polishing flaws in copper or copper alloy wiring, realizes a high polishing rate of the barrier layer at a low abrasive concentration, and enables the formation of a highly reliable metal film embedded pattern And a polishing method for a substrate using the same.

  The present inventors have found that the polishing rate of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds used as the barrier layer conductor has a maximum at a low abrasive concentration, and decreases when the concentration is too high. This phenomenon is remarkable when tantalum, a tantalum alloy, tantalum nitride, and other tantalum compounds are polished in a low pH region and a low oxidizing agent concentration region. The present invention suppresses the occurrence of dishing, thinning and polishing flaws in copper or copper alloy wiring, realizes a high polishing rate of the barrier layer at a low abrasive concentration, and enables the formation of a highly reliable metal film embedded pattern (1) A polishing liquid containing abrasive grains, a conductor oxidizing agent, a protective film forming agent for metal surfaces, an acid and water, and an abrasive concentration of 0.05 to 3.0% by weight. This is a metal-polishing liquid. Further, (2) the abrasive is preferably the metal polishing liquid according to the above (1), which is at least one selected from silica, alumina, ceria, titania, zirconia, and germania. Furthermore, it is preferable that (3) the abrasive is the metal polishing slurry according to (1) or (2) above, which is colloidal silica or colloidal alumina. The colloidal silica is preferably one produced by hydrolysis of silicon alkoxide, but one produced using sodium silicate as a raw material can also be used. The average particle size is preferably 50 nm or less. (4) It is preferable that the pH of the metal polishing liquid is 3 or less and the concentration of the oxidizing agent is 0.01 to 3% by weight. (5) It is preferable that the metal polishing liquid further contains a water-soluble polymer. (6) The water-soluble polymer includes polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyacrylamide, and polyvinyl. At least one selected from the group consisting of alcohol, polyvinyl pyrrolidone, polyamic acid or a salt thereof is preferable. (7) It is preferable that the density | concentration of the oxidizing agent of the conductor in that case is 0.01 to 1.5 weight%.

(8) The acid is preferably an organic acid, and (9) more preferably at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid and citric acid. (10) As the protective film forming agent, it is preferable to use at least one kind (BTAs) selected from benzotriazole (BTA) or a derivative thereof widely used conventionally. (11) The conductor oxidizing agent is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. (12) The conductor is preferably a barrier layer of copper, a copper alloy, or an oxide thereof. (13) The barrier layer is preferably tantalum, tantalum nitride, a tantalum alloy, or other tantalum compounds.

  The polishing method of the present invention is (14) a polishing method in which a metal-polishing liquid is supplied to a polishing pad on a polishing platen and brought into contact with the surface to be polished and the surface to be polished and the polishing pad are moved relative to each other to polish. A method for polishing a substrate, comprising polishing a barrier layer made of tantalum, tantalum nitride, a tantalum alloy, and other tantalum compounds using the metal polishing liquid according to any one of (1) to (13) above. In addition, the polishing method of the present invention is a method for polishing a substrate that polishes a surface containing copper or a copper alloy and its barrier layer using the metal polishing liquid according to any one of the above (1) to (13).

  In the present invention, it contains abrasive grains having an abrasive concentration of 0.05 to 3% by weight, and the polishing liquid is made to have a low pH region and a low oxidant concentration region, whereby copper or copper alloy wiring is diced and thinned. A metal polishing liquid that suppresses generation of polishing scratches and realizes a high polishing rate of the barrier layer at a low abrasive concentration and a polishing method using the same. As a method of polishing the barrier layer, when the hardness of the abrasive grains is increased as described above, polishing scratches occur in the copper or copper alloy, resulting in poor electrical characteristics, or a high grain concentration of the abrasive grains. In such a case, there has been a problem that the polishing rate of the silicon dioxide film increases and thinning occurs. The present inventors have found that polishing of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds used as the barrier layer easily proceeds in a low pH region and a low oxidizing agent concentration region. Further, it has been found that the abrasive concentration at which the polishing rate is maximized exists in the low concentration region. When such a polishing liquid is used, since the oxidant concentration is a sufficiently low region, wiring dicing due to an increase in the etching rate of copper or copper alloy, which is generally a problem in a low pH region, does not become a problem. It was found that the erosion was small due to the low abrasive concentration.

  The metal polishing liquid of the present invention has an abrasive concentration of 0.05 to 3% by weight, so that tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds used as a barrier layer can be polished, and copper Alternatively, it is possible to suppress the occurrence of dishing, thinning and polishing flaws in the copper alloy wiring, and to form a highly reliable embedded pattern of the metal film.

  In the present invention, a metal film containing a barrier layer and copper or copper alloy is formed and filled on a substrate having a silicon dioxide recess on the surface. When this substrate is first CMPed using a polishing solution for copper and copper alloy having a sufficiently high polishing rate ratio of copper or copper alloy / barrier layer, the barrier layer on the convex portion of the substrate is exposed on the surface, and the copper or copper in the concave portion is exposed. A desired conductor pattern in which the alloy film remains is obtained. The metal-polishing liquid of the present invention is a polishing liquid containing abrasive grains, a conductor oxidizing agent, a protective film-forming agent for metal surfaces, an acid and water, and has an abrasive concentration of 0.05 to 3% by weight. Moreover, it is preferable to adjust so that pH may be 3 or less and the density | concentration of the oxidizing agent of a conductor may be 0.01-3 weight%. A water-soluble polymer may be added as necessary. In the present invention, the abrasive concentration of the metal polishing slurry is 0.05 to 3% by weight, more preferably 0.1 to 1% by weight, based on the total weight. If the blending amount is less than 0.05%, the effect of inserting abrasive grains is small, and if it exceeds 3% by weight, the polishing rate of the barrier layer tends to decrease.

  When the pH of the metal polishing liquid is greater than 3, the polishing rate of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds is low. The pH can be adjusted by the amount of acid added. It can also be adjusted by adding alkali components such as ammonia, sodium hydroxide, tetramethylammonium hydride.

  On the other hand, the polishing liquid for metal in the present invention has the maximum polishing rate of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds when the concentration of the oxidant of the conductor is around 0.15% by weight. A primary oxide layer that is easily mechanically polished is formed on the surface of the conductor film such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds by the oxidizing agent, and a high polishing rate can be obtained. In general, when the pH is less than 3, the etching rate of the copper or copper alloy film is high, and it is difficult to suppress the etching with the protective film forming agent. However, in the present invention, since the concentration of the oxidizing agent is sufficiently low, the etching suppression by the protective film forming agent is possible. If the concentration of the oxidizer exceeds 3% by weight, not only the etching rate of copper or copper alloy increases, but not only does dishing easily occur, but also conductors such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds. Since a secondary oxide layer that is harder to polish than the primary oxide layer is formed on the film surface, the polishing rate decreases. When the concentration of the oxidizing agent is less than 0.01% by weight, the oxide layer is not sufficiently formed, so that the polishing rate becomes low, and the tantalum film may be peeled off.

  In the present invention, the oxidizing agent for the conductor of the metal polishing liquid has a concentration of 0.01 to 1.5% by weight when it contains a water-soluble polymer. The water-soluble polymer is adsorbed on the surface of tantalum, tantalum alloy, tantalum nitride, other tantalum compounds, or their oxide films, so that the oxidant concentration range in which a high polishing rate can be obtained is reduced. In addition, since the water-soluble polymer is easily adsorbed on the surface of a nitride compound film such as a tantalum nitride film or titanium nitride, the polishing rate of the nitride compound film such as a tantalum nitride film or titanium nitride is reduced. On the other hand, the water-soluble polymer has the effect of forming a metal surface protective film and improves planarization characteristics such as dishing and thinning.

Examples of the conductor oxidizing agent in the present invention include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, etc. Among them, hydrogen peroxide is particularly preferable. When the substrate is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, or the like is not desirable, and thus an oxidizing agent that does not include a nonvolatile component is desirable. However, hydrogen peroxide is most suitable because ozone water has a severe compositional change over time. However, in the case where the substrate to be applied is a glass substrate that does not include a semiconductor element, an oxidizing agent that includes a nonvolatile component may be used.

  The acid used in the present invention is preferably an organic acid, formic acid, acetic acid, propionic acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid. , N-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelin Acids, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, etc., and salts such as ammonium salts of these organic acids, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride, chromic acid, etc. Or the mixture etc. are raised. Among these, malonic acid, malic acid, tartaric acid, glycolic acid, and citric acid are preferable in that a practical CMP polishing rate can be obtained.

  The protective film forming agent in the present invention is benzotriazole (BTA), a BTA derivative, for example, one obtained by substituting one hydrogen atom of the benzene ring of BTA with a methyl group, substituted with a tolyltriazole or a carboxyl group, etc. benzotriazole-4- Carboxylic acid, its methyl, ethyl, propyl, butyl and octyl esters, or naphthotriazole, naphthotriazole derivatives or mixtures containing these.

  The water-soluble polymer used in the present invention is preferably selected from the following groups. Polymers having a basic structural unit as a monomer having a carboxyl group, such as polyacrylic acid, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyacrylamide, or the like Examples thereof include polymers having a monomer having a vinyl group such as a salt, polyvinyl alcohol, and polyvinylpyrrolidone as a basic structural unit. However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, contamination with an alkali metal, an alkaline earth metal, a halide, or the like is not desirable, so an acid or an ammonium salt thereof is desirable. This is not the case when the substrate is a glass substrate or the like. By adding these water-soluble polymers, the dishing characteristics can be improved due to the effect of inhibiting etching by the protective film forming agent.

  The abrasive for the metal polishing liquid of the present invention may be any of inorganic abrasives such as silica, alumina, ceria, titania, zirconia, germania and silicon carbide, and organic abrasives such as polystyrene, polyacryl and polyvinyl chloride. However, colloidal silica and colloidal alumina having good dispersion stability in the polishing liquid, a small number of polishing scratches (scratches) generated by CMP, and an average particle diameter of 50 nm or less are preferable. The average particle size is more preferably 30 nm or less, and particularly preferably 20 nm or less, in which the polishing rate of the barrier layer becomes larger and the polishing rate of silicon dioxide becomes smaller. Colloidal silica is known for its production by hydrolysis of silicon alkoxide or ion exchange of sodium silicate, and colloidal alumina is known for its production by hydrolysis of aluminum nitrate.

  The conductor film to which the present invention is applied is a copper or copper alloy barrier layer, and is preferably made of tantalum, tantalum alloy, tantalum nitride, or other tantalum compounds. .

  The amount of the acid used in the present invention is preferably 0.0001 to 0.05 mol with respect to 100 g of the total amount of the conductor oxidizing agent, acid, protective film forming agent, water-soluble polymer and water, and is preferably 0.001 to 0.05 mol. More preferably, the content is 001 to 0.01 mol. When this compounding quantity exceeds 0.05 mol, there exists a tendency for the etching of copper or a copper alloy to increase.

  The blending amount of the protective film forming agent used in the present invention is preferably 0.0001 to 0.01 mol with respect to 100 g of the total amount of the conductor oxidizing agent, acid, protective film forming agent, water-soluble polymer and water. 0.0005 to 0.005 mol is more preferable. If the amount is less than 0.0001 mol, the etching of copper or copper alloy tends to increase, and the effect remains unchanged even if the amount exceeds 0.01 mol.

  In the present invention, a water-soluble polymer can also be added. The amount of the water-soluble polymer is 0. 0 g with respect to 100 g of the total amount of the conductor oxidizing agent, acid, protective film forming agent, water-soluble polymer and water. It is preferable to set it as 001-0.5 weight%, and it is more preferable to set it as 0.01-0.2 weight%. If the blending amount is less than 0.001% by weight, the combined effect with the protective film forming agent tends not to appear in etching suppression, and if it exceeds 0.5% by weight, the polishing rate by CMP tends to decrease.

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

(Examples 1 to 3, Comparative Example 1)
(Production method of metal polishing liquid)
Water was added to 0.4% by weight of acid and 0.2% by weight of benzotriazole (BTA) as a protective film forming agent to dissolve, and hydrogen peroxide (special grade, 30% aqueous solution) was added as an oxidizing agent for the conductor. What was obtained by adding 5% by weight was used as a metal polishing slurry. To the abrasive grains, 0.1 to 5% by weight of colloidal silica having an average particle diameter of 30 nm prepared by hydrolysis of tetraethoxysilane in an ammonia solution was added, and water was adjusted accordingly to 98.8 to 93.9% by weight. It was. The pKa of glycolic acid used is 3.7. In Examples 1 to 3 and Comparative Example 1, CMP was performed in Table 1 using the above-described metal polishing slurry having an abrasive concentration.

(Polishing conditions)
Substrate: Silicon substrate with a 200 nm thick tantalum film Silicon substrate with a 100 nm thick tantalum nitride film Silicon substrate with a 1 μm thick silicon dioxide film Silicon substrate polishing pad with a 1 μm thick copper film : Polyurethane resin with closed cells Polishing pressure: 24.5 KPa (250 gf / cm ² )
Relative speed between substrate and polishing surface plate: 18 m / min
(Abrasive product evaluation items)
Polishing rate by CMP: The film thickness difference before and after CMP of the film was calculated from the electric resistance value.

Etching rate: The copper layer thickness difference before and after immersion in a metal polishing slurry stirred at 25 ° C. and 100 rpm was calculated from the electrical resistance value.

Dishing amount: A groove having a depth of 0.5 μm is formed in silicon dioxide, a tantalum nitride film having a thickness of 50 nm is formed as a barrier layer by a known sputtering method, and a copper film is similarly formed by sputtering. Two-step polishing is performed using a silicon substrate embedded by heat treatment as a substrate, and insulation is obtained from the surface shape of the stripe pattern portion in which the wiring metal portion width of 100 μm and the insulating film portion width of 100 μm are alternately arranged by a stylus type step gauge. The amount of reduction of the wiring metal part relative to the film part was determined. As the first-stage polishing liquid for copper, polishing was performed using a polishing liquid for copper and copper alloy having a sufficiently high polishing rate ratio of copper to tantalum nitride. After one-step polishing, a substrate sample is prepared so that the amount of dishing measured with the barrier layer exposed on the insulating film portion is 50 nm, and the above metal polishing solution is used until there is no barrier layer in the insulating film portion. And then polished in two steps.

Thinning amount: Measure the surface shape of the striped pattern part with a total width of 2.5 mm in which the wiring metal part width of 45 μm and the insulating film part width of 5 μm are alternately formed on the above-mentioned substrate for evaluating the dishing amount with a stylus type step gauge Then, the amount of film reduction of the insulating film portion near the center of the pattern with respect to the insulating film field portion around the stripe pattern was obtained. After one-step polishing, a substrate sample was prepared so that the thinning amount measured with the barrier layer exposed on the insulating film portion was 20 nm, and the above metal polishing solution was used until the barrier layer disappeared in the insulating film portion. And then polished in two steps.

Table 1 shows the polishing rate by CMP in Examples 1 to 3 and Comparative Example 1. Table 2 shows the amount of dishing and the amount of thinning.

  In Examples 1 to 3, since the polishing rate of the tantalum and tantalum nitride films which are the barrier layer conductors is high and the polishing rate of the silicon dioxide film is relatively low, good dishing and thinning characteristics can be obtained. On the other hand, in Comparative Example 1, the polishing rate of the barrier layer film (special tantalum film) was low and the polishing rate of the silicon dioxide film was considerably high, so that the dishing and thinning characteristics deteriorated.

Claims (15)

  It is a polishing liquid containing abrasive grains, a conductor oxidizing agent, a protective film forming agent for metal surfaces, an acid and water, the abrasive concentration is 0.05 to 3.0 wt%, and the pH of the metal polishing liquid is 3 or less, and the density | concentration of the oxidizing agent of a conductor is 0.01 to 3 weight%, The metal polishing liquid characterized by the above-mentioned.   The metal polishing slurry according to claim 1, wherein the abrasive is at least one selected from silica, alumina, ceria, titania, zirconia, and germania.   The metal polishing slurry according to claim 1 or 2, wherein the abrasive grains are colloidal silica or colloidal alumina.   The metal polishing liquid according to any one of claims 1 to 3, wherein an average particle diameter of the abrasive grains is 50 nm or less.   The metal-polishing liquid according to any one of claims 1 to 4, further comprising a water-soluble polymer.   The metal-polishing liquid according to claim 5, wherein the water-soluble polymer is at least one selected from the group consisting of polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyacrylamide, polyvinyl alcohol, and polyvinylpyrrolidone. .   The metal polishing slurry according to claim 5 or 6, wherein the concentration of the oxidizing agent in the conductor is 0.01 to 1.5% by weight.   The metal polishing slurry according to any one of claims 1 to 7, wherein the acid is an organic acid.   The metal polishing slurry according to claim 8, wherein the acid is at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid, and citric acid.   The metal polishing liquid according to any one of claims 1 to 9, wherein the protective film forming agent is at least one selected from benzotriazole (BTA) or a derivative thereof.   The metal polishing according to any one of claims 1 to 10, wherein the conductor oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. liquid.   The metal polishing slurry according to any one of claims 1 to 11, wherein the conductor is a barrier layer of copper, a copper alloy, or an oxide thereof.   The metal polishing slurry according to claim 12, wherein the barrier layer is tantalum, tantalum nitride, a tantalum alloy, or other tantalum compounds. A polishing method for polishing a substrate having a surface to be polished on the surface,
The substrate comprises a barrier layer;
The barrier layer is selected from tantalum, tantalum nitride, tantalum alloy, and other tantalum compounds,
A polishing method comprising a step of polishing the surface to be polished with the polishing pad while supplying the metal polishing liquid according to any one of claims 1 to 13 between the film to be polished and the polishing pad. .   The substrate polishing method according to claim 14, wherein the surface to be polished includes copper or a copper alloy and a barrier layer thereof.