Polishing liquid and polishing method

Abstract

To provide a polishing liquid in which decomposition of hydrogen peroxide can be suppressed in a case where metal ions are mixed in, while obtaining an excellent polishing speed of tungsten material, and a polishing method using the same.SOLUTION: A polishing liquid contains abrasive grains, a hydrogen peroxide, a compound A, and water. The compound A has a phosphono group and at least one type selected from the group consisting of a carboxy group and a carboxylic acid base. The polishing method uses the polishing agent to polish a surface to be polished that includes a tungsten material 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polishing liquid and a polishing method. [Background technology]

[0002] In recent years, new microfabrication techniques have been developed in response to the increasing integration and performance of semiconductor integrated circuits (hereinafter referred to as "LSI"). Chemical mechanical polishing (hereinafter referred to as "CMP") is one of these techniques, and is frequently used in the LSI manufacturing process, particularly in the planarization of interlayer insulating films in the multilayer wiring formation process, metal plug formation, buried wiring formation, and the like.

[0003] The damascene method is known as a method for forming buried wiring using CMP. In the damascene method, for example, a groove is first formed in advance on the surface of an insulating material such as silicon oxide, a barrier material (e.g., a barrier film) is formed in a shape that conforms to the surface of the insulating material, and a wiring metal is deposited on the entire barrier material so as to fill the groove. Next, unnecessary wiring metal other than the wiring metal filled in the groove is removed, and then a part of the barrier material under the wiring metal is removed by CMP to form a buried wiring.

[0004] In recent years, tungsten materials are used as wiring metals or barrier materials in LSIs, and polishing liquids for removing tungsten materials are required. For example, the following Patent Document 1 discloses a technique for polishing tungsten materials using a polishing liquid containing abrasive grains, hydrogen peroxide, iron compounds, etc. Thus, hydrogen peroxide may be used in the polishing liquid for polishing tungsten materials.

[0005] An example of a method (damascene process) for forming wiring of a tungsten material by polishing is shown in FIG. 1. As shown in FIG. 1(a), the object to be polished (substrate) 10 has an insulating material (silicon oxide, etc.) 1 having a groove on its surface, a barrier material (titanium nitride, etc.) 2 having a shape conforming to the surface of the insulating material, and a tungsten material (wiring metal) 3 covering the entire barrier material 2 so as to fill the groove. The method for polishing the object to be polished 10 includes, in this order, a rough polishing step (FIG. 1(a) to FIG. 1(b)) in which the tungsten material 3 is polished at a high polishing rate until the barrier material 2 is exposed, a middle polishing step in which the barrier material 2 and the tungsten material 3 are polished until the insulating material 1 is exposed as a finish polishing step (FIG. 1(b) to FIG. 1(c)) for eliminating steps generated in the rough polishing step, and a post-polishing step in which the insulating material 1, the barrier material 2, and the tungsten material 3 are polished at a sufficient polishing rate to finish the polished surface to be flat. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3822339 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0007] In the above-mentioned polishing method, it is possible to use the same polishing machine and polishing cloth to perform the rough polishing step and the finish polishing step, from the viewpoint of reducing the number of polishing machines required and the time spent on the steps. Here, metal ions are often added to the rough polishing polishing liquid used in the rough polishing step as a polishing accelerator to increase the polishing speed of the tungsten material. On the other hand, although hydrogen peroxide may be used in the finish polishing polishing liquid used in the finish polishing step, metal ions are often not included because the polishing speed of the tungsten material is not required to be as high as in the rough polishing step. However, when the rough polishing step and the finish polishing step are performed using the same polishing machine and polishing cloth, the rough polishing polishing liquid may be mixed into the finish polishing polishing liquid, and the metal ions in the rough polishing polishing liquid may be mixed into the finish polishing polishing liquid. In this case, the mixed metal ions promote the decomposition of hydrogen peroxide in the finish polishing polishing liquid, thereby reducing the content of hydrogen peroxide, and the polishing speed in the finish polishing step is likely to be affected.

[0008] Since metal ions can act as decomposition catalysts for hydrogen peroxide, in a rough polishing liquid containing a relatively large amount of metal ions in addition to hydrogen peroxide, phosphoric acid, organic acid, etc. may be used as a stabilizer for the purpose of suppressing the decomposition of hydrogen peroxide, as described in the above Patent Document 1. However, according to the knowledge of the present inventor, in a state in which a trace amount of metal ions is contained in addition to hydrogen peroxide, such as when metal ions are mixed into a finish polishing liquid containing almost no metal ions, these stabilizers cannot sufficiently suppress the decomposition of hydrogen peroxide. In addition, according to the knowledge of the present inventor, a substance that suppresses the decomposition of hydrogen peroxide may reduce the polishing speed of tungsten materials.

[0009] An object of one aspect of the present invention is to provide a polishing liquid capable of suppressing decomposition of hydrogen peroxide when metal ions are mixed in while obtaining an excellent polishing rate for tungsten materials. Another object of the present invention is to provide a polishing method using the polishing liquid. [Means for solving the problem]

[0010] The present inventors came up with the idea of ​​using a component that can suppress the decomposition of hydrogen peroxide due to the inclusion of metal ions while suppressing the decrease in the removal rate of tungsten materials, and found that the above-mentioned object can be achieved when a compound having a specific functional group is used.

[0011] One aspect of the present invention provides a polishing liquid comprising an abrasive grain, hydrogen peroxide, compound A, and water, wherein compound A is a compound having at least one group selected from the group consisting of a phosphono group, a carboxy group, and a carboxylate group.

[0012] According to the polishing liquid of one aspect of the present invention, it is possible to obtain an excellent polishing rate for tungsten materials while suppressing decomposition of hydrogen peroxide when metal ions are mixed in. According to the polishing liquid of one aspect of the present invention, a component capable of suppressing decomposition of hydrogen peroxide due to contamination by metal ions is used, but a sufficient polishing rate for tungsten materials can be maintained.

[0013] Another aspect of the present invention provides a polishing method comprising the step of polishing a surface to be polished that includes a tungsten material using the above-mentioned polishing liquid. Effect of the Invention

[0014] According to one aspect of the present invention, it is possible to provide a polishing liquid capable of suppressing decomposition of hydrogen peroxide when metal ions are mixed in while obtaining an excellent polishing rate for a tungsten material. According to another aspect of the present invention, it is possible to provide a polishing method using the polishing liquid. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a method for forming wiring made of a tungsten material by polishing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. However, the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the present invention.

[0017] <Definition> In this specification, a numerical range indicated using "~" indicates a range including the numerical values ​​described before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit of a numerical range of a certain stage may be replaced with the upper or lower limit of a numerical range of another stage. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types. In this specification, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. The term "film" includes a structure having a shape formed on the entire surface when observed in a plan view, as well as a structure having a shape formed on a part of the surface. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended action of the process is achieved.

[0018] In this specification, the term "polishing rate" refers to the rate at which a material being polished is removed by polishing (for example, the amount of thickness reduction per unit time in the direction perpendicular to the surface being polished; removal rate).

[0019] <Polishing liquid> The polishing liquid according to the present embodiment contains abrasive grains, hydrogen peroxide, compound A, and water, and the compound A is a compound having at least one selected from the group consisting of a phosphono group, a carboxy group, and a carboxylate group. The polishing liquid according to the present embodiment can be used as a CMP polishing liquid. The polishing liquid according to the present embodiment may be a polishing liquid for polishing a surface to be polished that includes a tungsten material.

[0020] The polishing liquid according to this embodiment can suppress the decomposition of hydrogen peroxide when metal ions (e.g. Fe ions) are mixed in while obtaining an excellent polishing rate for tungsten materials. The polishing liquid according to this embodiment uses a component capable of suppressing the decomposition of hydrogen peroxide due to the mixing of metal ions, but can maintain a sufficient polishing rate for tungsten materials. This embodiment can provide an application of the polishing liquid to polishing a surface to be polished that includes a tungsten material. The polishing liquid according to this embodiment can be used for polishing in a wiring formation process for semiconductor devices, etc.

[0021] The polishing liquid according to the present embodiment can be suitably used for polishing tungsten materials in the finishing polishing process (medium polishing process and post-polishing process) of the damascene process. The polishing liquid according to the present embodiment can be used in the second polishing process and / or the third polishing process in a polishing method for a polished object (a polished object in which the barrier material or the wiring metal is a tungsten material) having an insulating material with a groove on the surface, a barrier material with a shape that conforms to the surface of the insulating material, and a wiring metal that covers the entire barrier material so as to fill the groove, the polishing method including a first polishing process (rough polishing process) for polishing the wiring metal until the barrier material is exposed, a second polishing process (medium polishing process) for polishing the barrier material and the wiring metal until the insulating material is exposed, and a third polishing process (post-polishing process) for polishing the insulating material, the barrier material, and the wiring metal. The above-mentioned polished object may have a wiring metal containing a tungsten material. The insulating material may be silicon oxide. The barrier material may be titanium nitride. According to the polishing liquid of this embodiment, when the rough polishing process and the finish polishing process are performed using the same polishing machine and polishing cloth, decomposition of hydrogen peroxide can be suppressed even if metal ions from the polishing liquid used in the rough polishing process (a polishing liquid different from the polishing liquid of this embodiment) are mixed into the polishing liquid of this embodiment in the finish polishing process.

[0022] The content of metal ions in the polishing liquid according to this embodiment may be about several ppm (for example, 5 ppm or less, 4 ppm or less, or 3 ppm or less) based on the total mass of the polishing liquid. Since the amount of metal ions contained in the polishing liquid for rough polishing is often several ppm to several tens of ppm, the amount of metal ions that may be mixed into the polishing liquid for finish polishing is considered to be less than that, about several ppm. The polishing liquid according to this embodiment does not need to contain metal ions.

[0023] (Abrasive grain) The polishing liquid according to the present embodiment contains abrasive grains from the viewpoint of easily obtaining a sufficient polishing rate for the tungsten material and the insulating material. From the viewpoint of more easily obtaining a sufficient polishing rate for the tungsten material and the insulating material, the abrasive grains preferably contain at least one selected from the group consisting of silica, alumina, ceria, titania, zirconia, germania, and modified products thereof. As the abrasive grains containing silica, colloidal silica may be used. As the abrasive grains containing alumina, colloidal alumina may be used.

[0024] The modified material may be a particle containing silica, alumina, ceria, titania, zirconia, germania, etc., whose surface is modified with an alkyl group. The method of modifying the surface of a particle with an alkyl group is not particularly limited, and may be, for example, a method of reacting a hydroxyl group present on the surface of a particle with an alkoxysilane having an alkyl group. The alkoxysilane having an alkyl group is not particularly limited, and may be, for example, monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, monoethyltrimethoxysilane, diethyldimethoxysilane, triethylmonomethoxysilane, monomethyltriethoxysilane, dimethyldiethoxysilane, trimethylmonoethoxysilane, etc. The reaction method is not particularly limited, and may be, for example, reacted in a polishing liquid (such as a polishing liquid at room temperature) containing particles and an alkoxysilane, or may be heated to accelerate the reaction.

[0025] The average particle size of the abrasive grains is preferably 10 to 200 nm, more preferably 20 to 100 nm, and even more preferably 50 to 80 nm. The term "average particle size" as used herein refers to the average secondary particle size of the abrasive grains. The average particle size (average secondary particle size) can be measured, for example, by preparing a sample in which the abrasive grains are dispersed in water and using a light diffraction scattering type particle size distribution analyzer. Specifically, for example, using COULTER N4SD manufactured by COULTER Electronics, the measurement is performed so that the measurement temperature is 20°C, the solvent refractive index is 1.333 (water), the particle refractive index is Unknown (setting), the solvent viscosity is 1.005 cp (water), the run time is 200 seconds, the laser incidence angle is 90°, and the intensity (corresponding to scattering intensity, turbidity) is within the range of 5E+04 to 4E+05, and if it is higher than 4E+05, it can be diluted with water and measured. Colloidal particles are usually obtained in a state of being dispersed in water, so that it can also be appropriately diluted and measured so that it falls within the above scattering intensity range. As a guideline, the particles may be adjusted to be contained at 0.5 to 2.0 mass %.

[0026] From the viewpoints of having good dispersion stability in the polishing liquid and reducing the number of scratches (polishing marks) caused by polishing (CMP, etc.), the abrasive grains preferably contain at least one type selected from the group consisting of colloidal silica having an average particle size of 200 nm or less and colloidal alumina having an average particle size of 200 nm or less, and more preferably contain at least one type selected from the group consisting of colloidal silica having an average particle size of 100 nm or less and colloidal alumina having an average particle size of 100 nm or less.

[0027] The content of the abrasive grains is preferably 0.01 to 50 mass%, more preferably 0.02 to 30 mass%, even more preferably 0.05 to 20 mass%, particularly preferably 0.1 to 20 mass%, extremely preferably 0.5 to 10 mass%, very preferably 1 to 5 mass%, even more preferably 1 to 3 mass%, and even more preferably 1 to 2 mass%, based on the total mass of the polishing liquid. By having the content of the abrasive grains be 0.01 mass% or more, it is easier to obtain a sufficient polishing rate for the tungsten material and the insulating material, and by having the content be 50 mass% or less, it is easier to suppress the occurrence of scratches.

[0028] (hydrogen peroxide) The polishing liquid according to the present embodiment contains hydrogen peroxide. Hydrogen peroxide can be used as an oxidizing agent. Hydrogen peroxide can oxidize the surface of a tungsten material and improve the polishing rate of the tungsten material.

[0029] The content of hydrogen peroxide (hydrogen peroxide concentration) is preferably 0.01 to 50 mass%, more preferably 0.02 to 30 mass%, even more preferably 0.05 to 15 mass%, particularly preferably 0.1 to 10 mass%, extremely preferably 0.3 to 5 mass%, very preferably 0.5 to 3 mass%, even more preferably 0.7 to 2 mass%, and even more preferably 0.9 to 1 mass%, based on the total mass of the polishing liquid. When the content of hydrogen peroxide is 0.01 mass% or more, an excellent polishing rate for tungsten material is easily obtained. When the content of hydrogen peroxide is 50 mass% or less, roughness of the polished surface is easily reduced. The content of hydrogen peroxide may be the remaining amount of hydrogen peroxide after decomposition. The content of hydrogen peroxide in the polishing liquid can be measured by iodometric titration, and specifically, it can be measured by the method described in the examples below.

[0030] The content of hydrogen peroxide is preferably in the following range based on the total mass of the oxidizing agent (the total mass of the oxidizing agent contained in the polishing liquid). From the viewpoint of easily obtaining an excellent polishing rate of a tungsten material, the content of hydrogen peroxide is preferably 50 mass% or more, more preferably 55 mass% or more, even more preferably 60 mass% or more, particularly preferably 65 mass% or more, extremely preferably 80 mass% or more, very preferably 90 mass% or more, even more preferably 95 mass% or more, even more preferably 98 mass% or more, and particularly preferably 99 mass% or more. The oxidizing agent in the polishing liquid may be substantially composed of hydrogen peroxide (100 mass% of the oxidizing agent is substantially hydrogen peroxide). The content of hydrogen peroxide may be the amount of hydrogen peroxide remaining after decomposition.

[0031] (Oxidizing agent) The polishing liquid according to the present embodiment may contain an oxidizing agent other than hydrogen peroxide. Examples of the oxidizing agent include nitric acid, potassium periodate, hypochlorous acid, ozone water, etc. When the object to be polished is a silicon substrate including an integrated circuit element, contamination by alkali metals, alkaline earth metals, halides, etc. is undesirable, so an oxidizing agent that does not contain non-volatile components is preferred.

[0032] (Compound A) The polishing liquid according to this embodiment contains a compound A having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylate group. The compound A has one or more phosphono groups and one or more carboxy groups or carboxylate groups. The phosphono group is a functional group represented by "-PO3H2". The compound A may have a phosphoric acid group "-O-PO3H2" (phosphonooxy group) as a functional group including the phosphono group. The carboxylate group may be a functional group in which the hydrogen atom of the carboxy group is substituted with a metal atom (sodium atom, potassium atom, etc.). The compound A may have a phosphono group, a carboxy group, and a carboxylate group.

[0033] Compound A can be used as a hydrogen peroxide decomposition inhibitor. By containing compound A in the polishing liquid, it is possible to suppress the decomposition of hydrogen peroxide caused by the inclusion of metal ions in the polishing liquid. By containing hydrogen peroxide and compound A in the polishing liquid, it is possible to suppress the decomposition of hydrogen peroxide caused by the inclusion of metal ions and to maintain a sufficient polishing rate for tungsten materials.

[0034] The reason why compound A has an inhibitory effect on the decomposition of hydrogen peroxide is not clear, but it is thought that this is because the chelate compound formed when metal ions interact with compound A has less effect on the decomposition of hydrogen peroxide than the metal ions themselves.

[0035] Phosphoric acid, which has a phosphono group but no carboxy group or carboxylate group, and organic acids (citric acid, glycine, etc.) and their salts, which have a carboxy group or carboxylate group but no phosphono group, do not have the effect of inhibiting the decomposition of hydrogen peroxide. There are compounds other than Compound A that are used as chelating agents, but for example, nitrilotris(methylenephosphonic acid), which has a phosphono group but no carboxy group or carboxylate group, has a low effect of inhibiting the decomposition of hydrogen peroxide, and 1-hydroxyethane-1,1-diphosphonic acid exhibits the effect of inhibiting the decomposition of hydrogen peroxide, but tends to reduce the polishing speed of tungsten materials.

[0036] Compound A may include an aliphatic compound or aromatic compound having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylate group. Each of the phosphono group, carboxy group and carboxylate group in compound A may be bonded to the main chain (the longest carbon chain) or to a side chain. Compound A may have a functional group (hydroxyl group, ester group, etc.) other than the phosphono group, carboxy group and carboxylate group.

[0037] From the viewpoint of easily obtaining an excellent removal rate for a tungsten material and easily suppressing decomposition of hydrogen peroxide when metal ions are mixed in, it is preferable that compound A satisfy at least one of the following: Compound A preferably has a phosphono group and a carboxy group. Compound A preferably includes an aliphatic compound having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylate group. The number of phosphono groups in compound A is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and particularly preferably 2 or less. The total number of carboxy groups and carboxylate salt groups in compound A is preferably 2 or more, and more preferably 3 or more. The total number of carboxy groups and carboxylate salt groups in compound A is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. Compound A preferably has a carbon atom to which a phosphono group and at least one group selected from the group consisting of a carboxy group and a carboxylate group are bonded. The number of carbon atoms in compound A (including the carbon atoms of the carboxy group and the carboxylate group) is preferably 2 or more, more preferably 3 or more, even more preferably 5 or more, particularly preferably 6 or more, and extremely preferably 7 or more. The number of carbon atoms in compound A (including the carbon atoms in the carboxy group and the carboxylate group) is preferably 10 or less, more preferably 9 or less, even more preferably 8 or less, and particularly preferably 7 or less. When compound A has an alkylene group, the carbon chain of the alkylene group (excluding the carbon atoms of the carboxy group and the carboxylate group) is 1 or more, preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. When compound A has an alkylene group, the carbon chain of the alkylene group (excluding the carbon atoms of the carboxy group and the carboxylate group) is preferably 6 or less, more preferably 5 or less, and even more preferably 4 or less.

[0038] A water-soluble compound can be used as the compound A. Examples of the compound A include 3-phosphonobenzoic acid, 4-phosphonobenzoic acid, 4-phosphonobutyric acid, 2-(phosphonooxy)benzoic acid, 4-phosphonopropionic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and salts thereof (for example, alkali metal salts such as sodium salts and potassium salts). From the viewpoint of easily obtaining an excellent polishing rate for tungsten materials, easily suppressing the decomposition of hydrogen peroxide when metal ions are mixed in, and being easily available, it is preferable that the compound A contains at least one selected from the group consisting of 2-phosphonobutane-1,2,4-tricarboxylic acid and its salts.

[0039] The content of compound A is preferably 0.001 to 10 mass%, more preferably 0.002 to 10 mass%, further preferably 0.005 to 5 mass%, particularly preferably 0.01 to 2 mass%, extremely preferably 0.015 to 1 mass%, very preferably 0.02 to 0.5 mass%, even more preferably 0.025 to 0.3 mass%, further preferably 0.03 to 0.1 mass%, particularly preferably 0.03 to 0.08 mass%, and extremely preferably 0.03 to 0.05 mass%, based on the total mass of the polishing liquid. When the content of compound A is 0.001 mass% or more, it is easy to suppress the decomposition of hydrogen peroxide when metal ions are mixed in. When the content of compound A is 10 mass% or less, it is easy to prevent the settling of abrasive grains, etc., and it is easy to obtain excellent stability of the polishing liquid.

[0040] (Metal oxide dissolving agent) The polishing liquid according to this embodiment may contain an oxidized metal dissolving agent (excluding compounds that fall under the category of oxidizing agents) from the viewpoint of promoting dissolution of the tungsten material oxidized by the oxidizing agent and making it easier to improve the polishing rate of the tungsten material. The oxidized metal dissolving agent is not particularly limited as long as it can dissolve the oxidized tungsten material in water, and examples of the oxidized metal dissolving agent include organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and p-toluenesulfonic acid (excluding compound A and amino acids having a first dissociation constant of 2.0 to 4.0); organic acid esters of the organic acids; ammonium salts of the organic acids; inorganic acids such as hydrochloric acid and sulfuric acid; and ammonium salts of the inorganic acids (ammonium persulfate, ammonium nitrate, ammonium chloride, chromic acid, etc.). From the viewpoint of easily obtaining an excellent polishing rate for tungsten material and easily suppressing etching while maintaining a practical polishing rate, the metal oxide dissolving agent preferably contains an organic acid, and more preferably contains at least one selected from the group consisting of formic acid, malonic acid, malic acid, tartaric acid, citric acid, salicylic acid, and adipic acid. One type of metal oxide dissolving agent may be used alone, or two or more types may be used in combination.

[0041] The content of the metal oxide dissolving agent is preferably 0.001 to 20 mass%, more preferably 0.002 to 10 mass%, further preferably 0.005 to 5 mass%, particularly preferably 0.01 to 1 mass%, extremely preferably 0.05 to 0.5 mass%, very preferably 0.1 to 0.3 mass%, and even more preferably 0.1 to 0.2 mass%, based on the total mass of the polishing liquid. When the content of the metal oxide dissolving agent is 0.001 mass% or more, it is easy to obtain an excellent polishing rate of the wiring metal (e.g., tungsten material) and the barrier material (e.g., barrier metal). When the content of the metal oxide dissolving agent is 20 mass% or less, it is easy to suppress etching of the tungsten material and reduce roughness of the polished surface.

[0042] (Metal corrosion inhibitor) The polishing liquid according to the present embodiment may contain a metal corrosion inhibitor (metal corrosion inhibitor). The metal corrosion inhibitor can be used to protect the surface of a metal (e.g., copper) when simultaneously polishing a tungsten material and a metal other than the tungsten material.Metal corrosion inhibitors: 2-mercaptobenzothiazole; 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole, benzotriazole, 1-hydroxybenzotriazole, 1-hydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxyl(-1H-)benzotriazole, 4-carboxyl(-1H-)benzotriazole methyl ester, 4-carboxyl(-1H-)benzotriazole butyl triazole-based corrosion inhibitors (compounds having a triazole skeleton) such as 1,2,4-triazolo[1,5-a]pyrimidine, 1,3,4,6,7,8-hexahydro-2H-pyrimidine, ... do[1,2-a]pyrimidine, 1,3-diphenyl-pyrimidine-2,4,6-trione, 1,4,5,6-tetrahydropyrimidine, 2,4,5,6-tetraaminopyrimidine sulfate, 2,4,5-trihydroxypyrimidine, 2,4,6-triaminopyrimidine, 2,4,6-trichloropyrimidine, 2,4,6-trimethoxypyrimidine, 2,4,6-triphenylpyrimidine, 2,4-diamino-6-hydroxylpyrimidine, 2,4-diaminopyrimidine, 2-acetamidopyrimidine, 2-aminopyrimidine, 2-methylpyrimidine pyrimidine-based corrosion inhibitors (compounds having a pyrimidine skeleton) such as 2-methylsulfanyl-5,7-diphenyl-(1,2,4)triazolo(1,5-a)pyrimidine, 2-methylsulfanyl-5,7-diphenyl-4,7-dihydro-(1,2,4)triazolo(1,5-a)pyrimidine, 4-aminopyrazolo[3,4-d]pyrimidine; and polymers such as polyacrylic acid, acrylic acid copolymers, polymethacrylic acid, and methacrylic acid copolymers.When the wiring metal contains copper, the metal corrosion inhibitor preferably contains at least one selected from the group consisting of polyacrylic acid, acrylic acid copolymer, polymethacrylic acid, methacrylic acid copolymer, and triazole-based corrosion inhibitors, from the viewpoint of excellent corrosion prevention action. One type of metal corrosion inhibitor may be used alone, or two or more types may be used in combination.

[0043] The content of the metal corrosion inhibitor is preferably 0.001 to 10 mass%, more preferably 0.005 to 5 mass%, and even more preferably 0.01 to 2 mass%, based on the total mass of the polishing liquid. When the content of the metal corrosion inhibitor is 0.001 mass% or more, etching of the wiring metal is suppressed and roughness of the polished surface is easily reduced. When the content of the metal corrosion inhibitor is 10 mass% or less, the polishing speed of the wiring metal and the barrier material (e.g., barrier metal) tends to be improved.

[0044] (water) The polishing liquid according to the present embodiment contains water. The content of water in the polishing liquid may be the remainder of the polishing liquid excluding the contents of other components.

[0045] (pH of polishing solution) The pH of the polishing liquid according to this embodiment is preferably in the following range. From the viewpoint of easily suppressing the etching rate of the tungsten material, the pH of the polishing liquid is preferably 4.0 or less, more preferably 3.7 or less, even more preferably 3.5 or less, particularly preferably 3.3 or less, extremely preferably 3.0 or less, very preferably 2.8 or less, and even more preferably 2.7 or less. From the viewpoint of easily suppressing corrosion of the polishing device, the pH of the polishing liquid is preferably 2.0 or more, more preferably 2.1 or more, even more preferably 2.2 or more, particularly preferably 2.5 or more, extremely preferably 2.6 or more, and extremely preferably 2.7 or more. From these viewpoints, the pH is preferably 2.0 to 4.0. The pH of the polishing liquid is defined as the pH at a liquid temperature of 25°C.

[0046] The pH of the polishing liquid according to this embodiment can be measured with a pH meter (e.g., Model (F-51), manufactured by Horiba, Ltd.). For example, a phthalate pH standard solution (pH: 4.01), a neutral phosphate pH standard solution (pH: 6.86), and a borate pH standard solution (pH: 9.18) are used as calibration solutions to perform three-point calibration of the pH meter, and then the electrodes of the pH meter are placed in the polishing liquid and the value is measured after stabilization for at least two minutes. At this time, the liquid temperatures of the calibration solutions and the polishing liquid are set to 25°C.

[0047] (pH buffer) The polishing liquid according to this embodiment may contain a pH buffer as necessary to adjust and stabilize the pH of the polishing liquid. There is no particular limitation on the pH buffer as long as it can adjust and stabilize the pH of the polishing liquid. The polishing liquid according to this embodiment preferably contains an amino acid having a first dissociation constant of 2.0 to 4.0 from the viewpoint of easy adjustment to a preferred pH range of 2.0 to 4.0, from the viewpoint of being able to be mixed with water arbitrarily, and from the viewpoint of not adversely affecting the properties of the polishing liquid. Examples of amino acids having a first dissociation constant of 2.0 to 4.0 include glycine, asparagine, alanine, glutamic acid, glutamine, valine, glutamine, leucine, isoleucine, lysine, serine, threonine, phenylalanine, tyrosine, methionine, tryptophan, β-alanine, etc., and glycine is preferred from the viewpoint of easy availability.

[0048] <Polishing method> The polishing method according to the present embodiment includes a polishing step of polishing a surface to be polished that includes a tungsten material using the polishing liquid according to the present embodiment. The polishing liquid may be a polishing liquid obtained by diluting a stock solution for polishing liquid with water. The surface to be polished may have a layer that contains at least a tungsten material. Examples of tungsten materials include tungsten and tungsten compounds. Examples of tungsten compounds include tungsten alloys and the like.

[0049] In the polishing process, for example, the surface to be polished of the object to be polished (e.g., a substrate) is pressed against the polishing cloth of a platen (polishing platen), and a predetermined pressure is applied to the object to be polished from the surface opposite to the surface to be polished (the back surface of the object to be polished), and the polishing liquid according to the present embodiment is supplied between the surface to be polished and the polishing cloth, and the object to be polished is moved relatively to the platen, thereby polishing the surface to be polished. In the polishing process, a material to be polished containing a tungsten material can be polished. The material to be polished may be in the form of a film (polishing film), or may be a film containing a tungsten material. Examples of the film formation method include known sputtering and plating methods.

[0050] The polishing step may be a step of polishing a surface to be polished, which includes a tungsten material and at least one selected from the group consisting of a barrier material (e.g., a barrier metal) and an insulating material, using the polishing liquid according to this embodiment. The polishing step may be, for example, a step of polishing a polished object (e.g., a substrate) having at least a layer including a tungsten material and at least one selected from the group consisting of a barrier layer and an insulating layer.

[0051] Examples of the barrier material include tantalum, tantalum alloys, tantalum compounds (tantalum oxide, tantalum nitride, etc.), titanium, titanium alloys, titanium compounds (titanium oxide, titanium nitride, etc.), etc. A tungsten material may be used as the barrier material. Examples of the insulating material include silicon oxide, silicon nitride, etc.

[0052] In the polishing step, the object to be polished (substrate) 10 shown in Fig. 1 can be polished. For example, the polishing step may include, in this order, a first polishing step (rough polishing step) in which the tungsten material 3 is polished until the barrier material 2 is exposed, a second polishing step (medium polishing step) in which the barrier material 2 and the tungsten material 3 are polished until the insulating material 1 is exposed, and a third polishing step (post-polishing step) in which the insulating material 1, the barrier material 2, and the tungsten material 3 are polished.

[0053] In the second and third polishing steps described above, the polishing rate of the tungsten material does not need to be as high as that required for rough polishing (>100 nm / min), but from the viewpoint of shortening the polishing time, a polishing rate of 40 nm / min or more is preferable.

[0054] As the polishing device, for example, when polishing with an abrasive cloth, a general polishing device having a holder capable of holding the object to be polished and a platen connected to a motor or the like capable of changing the rotation speed and onto which the abrasive cloth can be attached can be used. As the abrasive cloth, general nonwoven fabric, polyurethane foam, porous fluororesin, etc. can be used, and there is no particular limitation.

[0055] There are no limitations on the polishing conditions, but the rotation speed of the platen is preferably low, 200 rpm or less, so that the object to be polished does not fly out. The pressure of the object to be polished (e.g., a substrate such as a semiconductor substrate) having a polishing surface against the polishing cloth is preferably 1 to 100 kPa, and more preferably 5 to 50 kPa from the viewpoint of satisfying the uniformity of the polishing speed on the polishing surface and the flatness of the pattern. During polishing, a polishing liquid can be continuously supplied to the polishing cloth by a pump or the like. There is no limitation on the amount of supply, but it is preferable that the surface of the polishing cloth is always covered with the polishing liquid.

[0056] In order to perform polishing (CMP, etc.) while keeping the surface condition of the polishing cloth constant, it is preferable to perform a conditioning process of the polishing cloth before polishing. For example, the polishing cloth is conditioned with a liquid containing at least water using a dresser with diamond particles. Then, after performing the polishing method according to this embodiment, it is preferable to further perform a cleaning process of the polished object. After the polishing is completed, it is preferable to thoroughly wash the polished object in running water, and then use a spin dryer or the like to remove water droplets attached to the polished object, and then dry it. In addition, it is more preferable to perform a known cleaning method (for example, a method in which a commercially available cleaning liquid is poured on the polished surface of the polished object, and the brush made of polyurethane is rotated and pressed against the polished object with a constant pressure to remove deposits on the polished object) and then dry it. EXAMPLES

[0057] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples as long as the technical idea of the present invention is not deviated from.

[0058] <Preparation of CMP Polishing Liquid> (Example 1) After dissolving 1.5 g of malic acid in 700 g of deionized water, 0.017 g of glycine was dissolved, and further, 0.04 g of a 50 mass% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid was added to obtain a mixed solution. 70 g of colloidal silica (an aqueous dispersion having a silicon dioxide content of 20 mass%, pH: 8.1, specific gravity: 1.1, viscosity: 3.5 mPa·s, average secondary particle size: 60 nm) was added to this mixed solution, and then 33 g of 30 mass% hydrogen peroxide water was added. Further, the remaining deionized water was added to prepare a polishing liquid having a total amount of 1000 g.

[0059] (Example 2) A polishing liquid was prepared in the same manner as in Example 1 except that the amount of the 50 mass% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid used was changed to 0.2 g.

[0060] (Example 3) A polishing liquid was prepared in the same manner as in Example 1 except that the amount of the 50 mass% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid used was changed to 0.4 g.

[0061] (Example 4) A polishing liquid was prepared in the same manner as in Example 1 except that the amount of the 50 mass% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid used was changed to 0.6 g.

[0062] (Comparative Example 1) A polishing liquid was prepared in the same manner as in Example 1 except that the 50 mass% aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid was not used.

[0063] (Comparative Example 2) A polishing liquid was prepared in the same manner as in Example 1, except that 0.8 g of a 50% by mass aqueous solution of citric acid was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0064] (Comparative Example 3) A polishing liquid was prepared in the same manner as in Example 1, except that 0.4 g of an 80% by mass aqueous solution of phosphoric acid was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0065] (Comparative Example 4) A polishing liquid was prepared in the same manner as in Example 1, except that 0.4 g of glycine was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0066] (Comparative Example 5) A polishing liquid was prepared in the same manner as in Example 1, except that 0.2 g of a 50% by mass aqueous solution of 1-hydroxyethane-1,1-diphosphonic acid was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0067] (Comparative Example 6) A polishing liquid was prepared in the same manner as in Example 1, except that 0.4 g of a 50% by mass aqueous solution of 1-hydroxyethane-1,1-diphosphonic acid was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0068] (Comparative Example 7) A polishing liquid was prepared in the same manner as in Example 1, except that 0.2 g of a 50% by mass aqueous solution of nitrilotris(methylenephosphonic acid) was used instead of 0.04 g of a 50% by mass aqueous solution of 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0069] <pH Measurement> The pH of the polishing liquid was measured under the following measurement conditions. The measurement results are shown in Table 1. Measuring instrument: Horiba, Ltd., product name: Model (F-51) Calibration solutions: Phthalate pH standard solution (pH: 4.01), neutral phosphate pH standard solution (pH: 6.86) and borate pH standard solution (pH: 9.18) Measurement temperature: 25℃ Measurement procedure: After three-point calibration using the calibration solution, the electrode was placed in the object to be measured and left at 25°C for at least 2 minutes. The pH value when it stabilized was recorded as the measured value.

[0070] <Measurement of hydrogen peroxide decomposition rate> Immediately after preparation, 100 g of the polishing liquid was weighed out, and the hydrogen peroxide concentration in the polishing liquid was measured by the method described below, and was found to be 1.0 mass %.

[0071] 100 g of the polishing liquid immediately after preparation was weighed out separately, and 0.02 g (corresponding to 2.8 ppm Fe ions) of a 10% by mass aqueous solution of iron nitrate nonahydrate was added to prepare test liquid A. Immediately after preparation of test liquid A, the hydrogen peroxide concentration (initial hydrogen peroxide concentration) was measured by the method described below. Thereafter, test liquid A was immersed in a water bath at 65°C for 1 hour, and then the hydrogen peroxide concentration (hydrogen peroxide concentration after decomposition) was measured by the method described below. The hydrogen peroxide decomposition rate was calculated from the following formula. The measurement results are shown in Table 1. When the above test was performed under conditions in which no aqueous solution of iron nitrate nonahydrate was added, the hydrogen peroxide decomposition rate of the polishing liquid of Comparative Example 1 was 0.2%, which was a small hydrogen peroxide decomposition rate. Hydrogen peroxide decomposition rate [%] = 100 × (initial hydrogen peroxide concentration [ppm] - hydrogen peroxide concentration after decomposition [ppm]) / initial hydrogen peroxide concentration [ppm]

[0072] (Measurement of hydrogen peroxide concentration) The hydrogen peroxide concentration of the above-mentioned polishing solution and test solution A was measured by the existing iodometric titration method. First, 1.0 g of the polishing solution or test solution A was weighed out, and then 5.0 g of an aqueous sulfuric acid solution containing 0.05 mass% hexaammonium heptamolybdate tetrahydrate and 10 mass% sulfuric acid was added. Furthermore, 5.0 g of an aqueous 0.1 mol / L potassium iodide (KI) solution and 30 g of pure water were added to prepare test solution B. The above-mentioned test solution B was titrated using a titration device (potentiometric titration device COM-2500 manufactured by Hiranuma Sangyo Co., Ltd.) with an aqueous 0.1 mol / L sodium thiosulfate (Na2S2O3) solution as the titrant. The hydrogen peroxide concentration was calculated using the following formula. Hydrogen peroxide concentration [ppm] = D x K x M x 1000000 / S D: Volume of added Na2S2O3 aqueous solution (titrant) [L] K: mass equivalent of hydrogen peroxide to 1 mol of Na2S2O3 = 17 [g / mol] M: Concentration of Na2S2O3 aqueous solution (titrant) [mol / L]

[0073] <Measurement of polishing speed> (Test wafer for evaluation) A tungsten wafer was used, which was a silicon wafer with a diameter of 30 cm on which a tungsten film with a thickness of 600 nm was formed by CVD.

[0074] (polishing method) Using a CMP polishing device (Reflexion LK, manufactured by AMAT Corporation), tungsten film was polished under the following conditions while dropping each polishing liquid (except for the polishing liquids of Comparative Examples 2 to 4) onto a platen, and the tungsten removal rate was measured. Polishing cloth: IC-1010 Polishing load: 3 psi (20.6 kPa) Rotation speed: 93 rpm (head), 87 rpm (platen) Polishing liquid dropping speed: 300mL / min Polishing time: 1 min

[0075] (Calculation of tungsten polishing rate) The thickness of the tungsten film before and after polishing was measured using a sheet resistance measuring device (VR-120 / 08S, manufactured by Hitachi Kokusai Electric Inc.), and the polishing rate was calculated from the difference in film thickness. The measurement results are shown in Table 1.

[0076] [Table 1]

[0077] <Evaluation Results> As can be seen from Table 1, the hydrogen peroxide decomposition rate was 2.1%, which was not good, in Comparative Example 1, which did not use Compound A. In addition, the tungsten polishing rate was 42.0 nm / min.

[0078] In Examples 1 to 4 using Compound A, the hydrogen peroxide decomposition rate was 1.2% or less, showing a sufficient hydrogen peroxide decomposition suppression effect. It can be seen that as the amount of Compound A used increases, the hydrogen peroxide decomposition rate decreases and the hydrogen peroxide decomposition suppression effect improves. Furthermore, the tungsten polishing speed in Examples 1 to 4 was not decreased compared to Comparative Example 1, and was good at 40 nm / min or more. This shows that Compound A does not inhibit the polishing of tungsten materials.

[0079] In Comparative Example 2, in which citric acid having a carboxy group but no phosphono group was used, the hydrogen peroxide decomposition rate was 3.8%, and no hydrogen peroxide decomposition inhibitory effect was confirmed. In Comparative Example 3, in which phosphoric acid having a phosphono group but no carboxy group or carboxylate group was used, the hydrogen peroxide decomposition rate was 5.7%, and no hydrogen peroxide decomposition inhibitory effect was confirmed. In Comparative Example 4, in which glycine, which has a carboxy group and is known to interact with metals, was used, the hydrogen peroxide decomposition rate was 1.9%, and no hydrogen peroxide decomposition inhibitory effect was confirmed. From the results of Comparative Examples 2 to 4, it can be seen that the hydrogen peroxide decomposition inhibitory effect cannot be obtained with a compound having a phosphono group but no carboxy group or carboxylate group, and a compound having a carboxy group or carboxylate group but no phosphono group.

[0080] In Comparative Examples 5 and 6, in which 1-hydroxyethane-1,1-diphosphonic acid was used as the phosphoric acid compound having a metal chelating effect, the hydrogen peroxide decomposition rates were 0.7% and 0.2%, respectively, and the hydrogen peroxide decomposition suppression effect was confirmed, but the tungsten polishing speed was 38.6 nm / min and 34.4 nm / min, and an excellent tungsten polishing speed was not obtained. The reason for the decrease in the tungsten polishing speed is not clear, but it is thought that the polishing speed decreases because 1-hydroxyethane-1,1-diphosphonic acid adsorbs and protects the surface of the tungsten material.

[0081] In Comparative Example 7, which used nitrilotris(methylenephosphonic acid), a phosphate compound having a metal chelating effect, the hydrogen peroxide decomposition rate was 1.3%, which was not a sufficient effect of inhibiting the decomposition of hydrogen peroxide and was lower than that of Example 2, which used 2-phosphonobutane-1,2,4-tricarboxylic acid at the same concentration. [Explanation of symbols]

[0082] 1...insulating material, 2...barrier material, 3...tungsten material, 10...object to be polished.

Claims

1. The method comprises the steps of: the compound A is a compound having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylate group, A polishing liquid in which the content of the compound A is 0.001 to 0.08 mass % based on the total mass of the polishing liquid (excluding a polishing composition containing an abrasive grain, an oxidizing agent, an acid, an anticorrosive agent containing a compound represented by the following formula (1) or a salt thereof, and a dispersion medium. 【Chemistry 1】 (In formula (1), R 1 is a linear or branched alkyl group having 6 to 30 carbon atoms or a linear or branched alkenyl group having 6 to 30 carbon atoms, R 2 is a single bond or an alkylene group having 1 to 4 carbon atoms, and R 3 is a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms.)

2. The polishing liquid according to claim 1 , wherein the compound A is a compound having a phosphono group and a carboxy group.

3. The polishing liquid according to claim 1 or 2, wherein the compound A contains 2-phosphonobutane-1,2,4-tricarboxylic acid.

4. 4. The polishing liquid according to claim 1, wherein the abrasive grains contain at least one selected from the group consisting of silica, alumina, ceria, titania, zirconia, germania, and modified products thereof.

5. The polishing liquid according to any one of claims 1 to 4, further comprising a metal oxide dissolving agent.

6. 6. The polishing liquid according to claim 5, wherein the oxidized metal dissolving agent contains an organic acid (excluding the compound A and an amino acid having a first dissociation constant of 2.0 to 4.0).

7. 7. The polishing liquid according to claim 6, wherein the metal oxide dissolving agent comprises at least one selected from the group consisting of formic acid, malonic acid, malic acid, tartaric acid, citric acid, salicylic acid, and adipic acid.

8. The polishing liquid according to any one of claims 1 to 7, having a pH of 2.0 to 4.

0.

9. The polishing liquid according to any one of claims 1 to 8, further comprising an amino acid having a first dissociation constant of 2.0 to 4.

0.

10. A polishing method, comprising polishing a surface to be polished that contains a tungsten material using the polishing liquid according to any one of claims 1 to 9.

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