JP2021145090A - Polishing liquid and polishing method - Google Patents

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

The present invention relates to a polishing liquid and a polishing method.

In recent years, new microfabrication techniques have been developed along with the high integration or high performance of semiconductor integrated circuits (hereinafter referred to as "LSI"). The chemical mechanical polishing (hereinafter referred to as "CMP") method is also one of them, and is frequently used in the LSI manufacturing process, particularly in the flattening of the interlayer insulating film, the metal plug formation, the embedded wiring formation, etc. in the multilayer wiring formation process. This is the technology used.

The damascene method is known as an embedded wiring formation using CMP. In the damascene method, for example, first, a groove is formed in advance on the surface of an insulating material such as silicon oxide, then a barrier material (for example, a barrier membrane) having a shape that follows the surface of the insulating material is formed, and then the groove is embedded. The wiring metal is deposited on the entire barrier material. Next, after removing unnecessary wiring metal other than the wiring metal embedded in the groove, a part of the barrier material under the wiring metal is removed by CMP to form the embedded wiring.

In recent years, a tungsten material has been used as a wiring metal or a barrier material in LSI, and a polishing liquid for removing the tungsten material is required. For example, Patent Document 1 below discloses a technique for polishing a tungsten material using a polishing liquid containing abrasive grains, hydrogen peroxide, an iron compound, and the like. As described above, hydrogen peroxide may be used in the polishing liquid for polishing the tungsten material.

FIG. 1 shows an example of a method (damaching process) of forming wiring of a tungsten material by polishing. As shown in FIG. 1A, the object to be polished (substrate) 10 includes an insulating material (silicon oxide or the like) 1 having a groove on the surface and a barrier material (titanium nitride or the like) having a shape that follows the surface of the insulating material. It has 2 and a tungsten material (wiring metal) 3 that covers the entire barrier material 2 so as to embed a groove. The polishing method of the object to be polished 10 occurred in a rough polishing step (FIGS. 1 (a) to 1 (b)) in which the tungsten material 3 was polished at a high polishing rate until the barrier material 2 was exposed, and a rough polishing step. As a finish polishing step (FIGS. 1 (b) to 1 (c)) for eliminating the step, a medium polishing step of polishing the barrier material 2 and the tungsten material 3 until the insulating material 1 is exposed, and an insulating material 1, The barrier material 2 and the tungsten material 3 are polished at a sufficient polishing rate to finish the surface to be polished flat, and then a polishing step is provided in this order.

Patent No. 3822339

By the way, in the above-mentioned polishing method, from the viewpoint of reducing the number of required polishing machines and the time spent in the process, it is conceivable to perform the rough polishing step and the finish polishing step using the same polishing machine and polishing cloth. Here, in the rough polishing liquid used in the rough polishing step, metal ions are often added as a polishing accelerator for increasing the polishing speed of the tungsten material. On the other hand, although hydrogen peroxide may be used as the polishing liquid for finish polishing used in the finish polishing step, metal ions are often not contained 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 is mixed with the finish polishing polishing liquid, and the metal ions in the rough polishing polishing liquid are used for finish polishing. It may be mixed in the polishing liquid. In this case, the mixed metal ions accelerate the decomposition of hydrogen peroxide in the polishing liquid for finish polishing, so that the content of hydrogen peroxide is reduced, and the polishing speed in the finish polishing step is easily affected.

Since metal ions can act as a decomposition catalyst for hydrogen peroxide, a polishing solution for rough polishing containing a relatively large amount of metal ions in addition to hydrogen peroxide is excessive as described in Patent Document 1 above. Phosphoric acid, organic acid and the like may be used as stabilizers for the purpose of suppressing the decomposition of hydrogen peroxide. However, according to the findings of the present inventor, these are in a state where a trace amount of metal ions are contained in addition to hydrogen peroxide, as in the case where metal ions are mixed in a polishing liquid for finish polishing containing almost no metal ions. Stabilizers cannot sufficiently suppress the decomposition of hydrogen peroxide. Further, according to the findings of the present inventor, a substance that suppresses the decomposition of hydrogen peroxide may reduce the polishing rate of the tungsten material.

One aspect of the present invention is to provide a polishing liquid capable of suppressing the decomposition of hydrogen peroxide when metal ions are mixed in, while obtaining an excellent polishing rate of the tungsten material. Another aspect of the present invention is to provide a polishing method using the polishing liquid.

The present inventor has conceived of using a component capable of suppressing the decomposition of hydrogen peroxide due to the mixing of metal ions while suppressing the decrease in the polishing rate of the tungsten material, and when a compound having a specific functional group is used. We have found that the above tasks can be achieved.

One aspect of the present invention contains abrasive grains, hydrogen peroxide, compound A, and water, and the compound A is at least one selected from the group consisting of a phosphono group, a carboxy group, and a carboxylic acid base. A polishing liquid, which is a compound having the above, is provided.

According to the polishing liquid according to one aspect of the present invention, it is possible to suppress the decomposition of hydrogen peroxide when metal ions are mixed while obtaining an excellent polishing rate of the tungsten material. According to the polishing liquid according to one aspect of the present invention, although a component capable of suppressing the decomposition of hydrogen peroxide due to the mixing of metal ions is used, a sufficient polishing rate of the tungsten material can be maintained.

Another aspect of the present invention provides a polishing method comprising a step of polishing a surface to be polished containing a tungsten material using the above-mentioned polishing liquid.

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

FIG. 1 is a schematic cross-sectional view for explaining a method of forming wiring of a tungsten material by polishing.

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

<Definition>
In the present specification, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in the present specification may be used alone or in combination of two or more. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means. The term "membrane" includes a structure having a shape formed on the entire surface and a structure having a shape formed on a part of the structure when observed as a plan view. The term "process" is included in this term not only in an independent process but also in the case where the desired action of the process is achieved even if it cannot be clearly distinguished from other processes.

In the present specification, the “polishing rate” is the rate at which the substance to be polished is removed by polishing (for example, the amount of thickness reduction per unit time in the direction perpendicular to the surface to be polished. Removal Rate). Means.

<Abrasive liquid>
The polishing liquid according to the present embodiment contains abrasive grains, hydrogen peroxide, compound A, and water, and the compound A is selected from the group consisting of a phosphono group, a carboxy group, and a carboxylic acid base. It is a compound having at least one kind. The polishing liquid according to this 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 containing a tungsten material.

According to the polishing liquid according to the present embodiment, it is possible to suppress the decomposition of hydrogen peroxide when metal ions (for example, Fe ions) are mixed while obtaining an excellent polishing rate of the tungsten material. According to the polishing liquid according to the present embodiment, although a component capable of suppressing the decomposition of hydrogen peroxide due to the mixing of metal ions is used, a sufficient polishing rate of the tungsten material can be maintained. According to this embodiment, it is possible to provide an application of a polishing liquid for polishing a surface to be polished containing a tungsten material. The polishing liquid according to this embodiment can be used for polishing in a wiring forming step of a semiconductor device or the like.

The polishing liquid according to this embodiment can be suitably used for polishing a tungsten material in the finish polishing step (medium polishing step and post-polishing step) of the damascene process. The polishing liquid according to the present embodiment has an insulating material having a groove on the surface, a barrier material having a shape that follows the surface of the insulating material, and a wiring metal that covers the entire barrier material so as to embed the groove. A method for polishing a body (a body to be polished whose barrier material or wiring metal is a tungsten material), in which a first polishing step (coarse polishing step) of polishing the wiring metal until the barrier material is exposed and an insulating material are exposed. Second polishing in a polishing method including a second polishing step (medium polishing step) for polishing the barrier material and the wiring metal, and a third polishing step (post-polishing step) for polishing the insulating material, the barrier material and the wiring metal. It can be used in the process and / or the third polishing process. The above-mentioned object to be polished 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 according to the present embodiment, when the rough polishing step and the finish polishing step are performed using the same polishing machine and polishing cloth, the polishing liquid used in the rough polishing step (the polishing liquid according to the present embodiment). Metal ions of different polishing liquids) can suppress the decomposition of hydrogen peroxide even when they are mixed in the polishing liquid according to the present embodiment in the finish polishing step.

The content of metal ions in the polishing liquid according to the present 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 in the polishing liquid for finish polishing is less than that. It is considered to be about several ppm. The polishing liquid according to this embodiment does not have to contain metal ions.

(Abrasive grain)
The polishing liquid according to the present embodiment contains abrasive grains from the viewpoint of easily obtaining a sufficient polishing rate of the tungsten material and the insulating material. The abrasive grains include at least one selected from the group consisting of silica, alumina, ceria, titania, zirconia, germania, and modified products thereof from the viewpoint of further obtaining a sufficient polishing rate of the tungsten material and the insulating material. Is preferable. Colloidal silica may be used as the abrasive grains containing silica. Colloidal alumina may be used as the abrasive grains containing alumina.

Examples of the modified product include those obtained by modifying the surface of particles containing silica, alumina, ceria, titania, zirconia, germania and the like with an alkyl group. The method for modifying the surface of the particles with an alkyl group is not particularly limited, and examples thereof include a method of reacting a hydroxyl group existing on the surface of the particles with an alkoxysilane having an alkyl group. The alkoxysilane having an alkyl group is not particularly limited, but is monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, monoethyltrimethoxysilane, diethyldimethoxysilane, triethylmonomethoxysilane, monomethyltriethoxysilane, dimethyl. Examples thereof include diethoxysilane and trimethylmonoethoxysilane. The reaction method is not particularly limited, and for example, the reaction may be carried out in a polishing liquid containing particles and an alkoxysilane (such as a polishing liquid at room temperature), or heating may be performed in order to accelerate the reaction.

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 "average particle size" here means 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 meter. Specifically, for example, using COOLTER N4SD manufactured by COOLTER Electronics, measurement temperature: 20 ° C., solvent refraction rate: 1.333 (water), particle refraction rate: Unknown (setting), solvent viscosity: 1.005 cp ( Water), Run Time: 200 seconds, Laser incident angle: 90 °, Integrity (corresponding to scattering intensity and turbidity): Measure so that it falls within the range of 5E + 04 to 4E + 05, and if it is higher than 4E + 05, dilute it with water. Can be measured. Since the colloidal particles are usually obtained in a state of being dispersed in water, they can be appropriately diluted and measured so as to fall within the above scattering intensity range. As a guide, it may be adjusted so that the particles are contained in an amount of 0.5 to 2.0% by mass.

Abrasive grains have good dispersion stability in the polishing liquid, and from the viewpoint that the number of scratches (polishing scratches) generated by polishing (CMP, etc.) is small, colloidal silica having an average particle size of 200 nm or less and average grains. It is preferable to contain at least one selected from the group consisting of colloidal alumina having a diameter of 200 nm or less, and at least one 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. It is more preferable to include.

The content of abrasive grains is preferably 0.01 to 50% by mass, more preferably 0.02 to 30% by mass, still more preferably 0.05 to 20% by mass, and particularly preferably, based on the total mass of the polishing liquid. Is 0.1 to 20% by mass, extremely preferably 0.5 to 10% by mass, very preferably 1 to 5% by mass, even more preferably 1 to 3% by mass, still more preferably 1 to 2% by mass. .. When the content of the abrasive grains is 0.01% by mass or more, it is easy to obtain a sufficient polishing rate of the tungsten material and the insulating material, and when it is 50% by mass or less, it is easy to suppress the occurrence of scratches.

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

The content of hydrogen peroxide (hydrogen peroxide concentration) is preferably 0.01 to 50% by mass, more preferably 0.02 to 30% by mass, and further preferably 0.05, based on the total mass of the polishing liquid. ~ 15% by mass, particularly preferably 0.1 to 10% by mass, extremely preferably 0.3 to 5% by mass, very preferably 0.5 to 3% by mass, and even more preferably 0.7 to 2% by mass. , More preferably 0.9 to 1% by mass. When the content of hydrogen peroxide is 0.01% by mass or more, an excellent polishing rate of the tungsten material can be easily obtained. When the content of hydrogen peroxide is 50% by mass or less, it is easy to reduce the roughness of the surface to be polished. The content of hydrogen peroxide may be the residual amount of hydrogen peroxide after decomposition. The content of hydrogen peroxide in the polishing liquid can be measured by the iodine titration method, and specifically, it can be measured by the method described in Examples described later.

The content of hydrogen peroxide is preferably in the following range based on the total mass of the oxidizing agent (total mass of the oxidizing agent contained in the polishing liquid). The content of hydrogen peroxide is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, and 65% by mass or more, from the viewpoint that an excellent polishing rate of the tungsten material can be easily obtained. Particularly preferably, 80% by mass or more is extremely preferable, 90% by mass or more is very preferable, 95% by mass or more is further preferable, 98% by mass or more is further preferable, and 99% by mass or more is particularly preferable. The oxidizing agent in the polishing liquid may be in an embodiment substantially composed of hydrogen peroxide (100% by mass of the oxidizing agent is substantially hydrogen peroxide). The content of hydrogen peroxide may be the residual amount of hydrogen peroxide after decomposition.

(Oxidant)
The polishing liquid according to this embodiment may contain an oxidizing agent other than hydrogen peroxide. Examples of the oxidizing agent include nitric acid, potassium periodate, hypochlorous acid, ozone water and the like. When the object to be polished is a silicon substrate containing an element for an integrated circuit, contamination with an alkali metal, an alkaline earth metal, a halide or the like is not desirable, and therefore an oxidizing agent containing no non-volatile component is preferable.

(Compound A)
The polishing liquid according to the present embodiment contains a compound A having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylic acid base. Compound A has one or more phosphono groups and one or more carboxy groups or carboxylic acid bases. The phosphono group is a functional group represented by " _{-PO 3} H _2". Compound A, as a functional group including a phosphono group, may have a phosphate group "-O-PO ₃ H ₂ '(phosphonooxy group). Examples of the carboxylic acid base include a functional group in which the hydrogen atom of the carboxy group is replaced with a metal atom (sodium atom, potassium atom, etc.). Compound A may have a phosphono group, a carboxy group, and a carboxylic acid base.

Compound A can be used as a hydrogen peroxide decomposition inhibitor. Since the polishing liquid contains the compound A, the decomposition of hydrogen peroxide due to the mixing of metal ions in the polishing liquid can be suppressed. When the polishing liquid contains hydrogen peroxide and compound A, it is possible to suppress the decomposition of hydrogen peroxide due to the mixing of metal ions and maintain a sufficient polishing rate of the tungsten material.

The reason why compound A has an effect of suppressing hydrogen peroxide decomposition is not clear, but the chelate compound formed when the metal ion and compound A interact with each other affects the decomposition of hydrogen peroxide as compared with the metal ion itself. It is thought that this is because it is difficult to give.

Phosphoric acids that have a phosphono group but do not have a carboxy group and a carboxylic acid base, and organic acids that have a carboxy group or a carboxylic acid base but do not have a phosphono group (citrate, glycine, etc.) and salts thereof are excessive. It does not have the effect of suppressing hydrogen oxide decomposition. There are compounds other than compound A that are used as chelating agents. For example, nitrilotris (methylenephosphonic acid) suppresses hydrogen peroxide decomposition as a compound having a phosphono group but no carboxy group and carboxylic acid base. The effect is low, and 1-hydroxyethane-1,1-diphosphonic acid exhibits an effect of suppressing hydrogen peroxide decomposition, but the polishing rate of the tungsten material tends to decrease.

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

Compound A preferably satisfies at least one of the following from the viewpoint of easily obtaining an excellent polishing rate of the tungsten material and easily suppressing the decomposition of hydrogen peroxide when metal ions are mixed.
-Compound A preferably has a phosphono group and a carboxy group.
-Compound A preferably contains an aliphatic compound having a phosphono group and at least one selected from the group consisting of a carboxy group and a carboxylic acid base.
-The number of phosphono groups in compound A is preferably 5 or less, more preferably 4 or less, further preferably 3 or less, and particularly preferably 2 or less.
-The total number of carboxy groups and carboxylic acid bases in compound A is preferably 2 or more, and more preferably 3 or more.
-The total number of carboxy groups and carboxylic acid bases 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 selected from the group consisting of a carboxy group and a carboxylic acid base are bonded.
-The carbon number of compound A (including the carbon atom of the carboxy group and the carboxylic acid base) is preferably 2 or more, more preferably 3 or more, further preferably 5 or more, particularly preferably 6 or more, and extremely preferably 7 or more.
-The carbon number of compound A (including the carbon atom of the carboxy group and the carboxylic acid base) is preferably 10 or less, more preferably 9 or less, further 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 atom of the carboxy group and the carboxylic acid base) is 1 or more, preferably 2 or more, more preferably 3 or more, and further 4 or more. preferable.
When the compound A has an alkylene group, the carbon chain of the alkylene group (excluding the carbon atom of the carboxy group and the carboxylic acid base) is preferably 6 or less, more preferably 5 or less, still more preferably 4 or less.

As the compound A, a water-soluble compound can be used. Compound A includes 3-phosphonobenzoic acid, 4-phosphonobenzoic acid, 4-phosphonobutyl acid, 2- (phosphonooxy) benzoic acid, 4-phosphonopropionic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid. Examples thereof include alkali metal salts such as sodium salt and potassium salt. Compound A contains 2-phosphonobutane-1,2 from the viewpoint of easily obtaining an excellent polishing rate of the tungsten material, easily suppressing the decomposition of hydrogen peroxide when metal ions are mixed, and easily obtaining the compound A. , 4-Tricarboxylic acid and salts thereof preferably contain at least one selected from the group.

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

(Metal oxide solubilizer)
The polishing liquid according to the present embodiment contains a metal oxide dissolving agent (excluding compounds corresponding to the oxidizing agent) from the viewpoint of promoting the dissolution of the tungsten material oxidized by the oxidizing agent and easily improving the polishing speed of the tungsten material. It may be contained. The metal oxide dissolving agent is not particularly limited as long as it can dissolve the oxidized tungsten material in water, but 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, pimeric acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, p-toluenesulfonic acid and other organic acids (however, compound A , And amino acids having a first dissociation constant of 2.0-4.0); organic acid ester of the organic acid; ammonium salt of the organic acid; inorganic acid such as hydrochloric acid, sulfuric acid; ammonium of the inorganic acid Examples thereof include salts (ammonium persulfate, ammonium nitrate, ammonium chloride, chromium acid, etc.). The metal oxide dissolving agent preferably contains an organic acid from the viewpoint of easily obtaining an excellent polishing rate of the tungsten material and easily suppressing etching while maintaining a practical polishing rate, and formic acid is preferable. , Malic acid, malic acid, tartaric acid, citric acid, salicylic acid, and at least one selected from the group consisting of adipic acid. One type of metal oxide dissolving agent may be used alone, or two or more types may be used in combination.

The content of the metal oxide dissolving agent is preferably 0.001 to 20% by mass, more preferably 0.002 to 10% by mass, still more preferably 0.005 to 5% by mass, based on the total mass of the polishing liquid. It is particularly preferably 0.01 to 1% by mass, extremely preferably 0.05 to 0.5% by mass, very preferably 0.1 to 0.3% by mass, and even more preferably 0.1 to 0.2% by mass. .. When the content of the metal oxide dissolving agent is 0.001% by mass or more, excellent polishing speed of the wiring metal (for example, tungsten material) and the barrier material (for example, barrier metal) can be easily obtained. When the content of the metal oxide dissolving agent is 20% by mass or less, it is easy to suppress the etching of the tungsten material and reduce the roughness of the surface to be polished.

(Metal corrosion inhibitor)
The polishing liquid according to the present embodiment may contain a metal anticorrosive agent (metal anticorrosive agent). The metal corrosion inhibitor can be used to protect the surface of the tungsten material and the surface of the metal other than the tungsten material (for example, copper) when polishing at the same time. As a metal anticorrosive agent, 2-mercaptobenzothiazol; 1,2,3-triazol, 1,2,4-triazol, 3-amino-1H-1,2,4-triazol, Bentotriazol, 1-hydroxybenzotriazol, 1-hydroxypropylbenzotriazol, 2,3-dicarboxypropylbenzotriazol, 4-hydroxybenzotriazol, 4-carboxyl (-) 1H-) benzotriazol, 4-carboxyl (-1H-) benzotriazol methyl ester, 4-carboxyl (-1H-) benzotriazol butyl ester, 4-carboxyl (-1H-) benzotriazol octyl ester, 5 -Hexyl benzotriazol, [1,2,3-benzotriazolyl-1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazol, naphthotriazo- Triazole anticorrosive agents (compounds having a triazole skeleton) such as le, bis [(1-benzotriazolyl) methyl] phosphonic acid; pyrimidin, 1,2,4-triazolo [1,5-a] pyrimidin, 1, 3,4,6,7,8-Hexahydro-2H-pyrimidin [1,2-a] pyrimidine, 1,3-diphenyl-pyrimidine-2,4,6-trione, 1,4,5,6-tetra Hydropyrimidine, 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-methyl-5, 7-Diphenyl- (1,2,4) triazolo (1,5-a) pyrimidine, 2-methylsulfanyl-5,7-diphenyl- (1,2,4) triazolo (1,5-a) pyrimidine, Pyrimidines such as 2-methylsulfanyl-5,7-diphenyl-4,7-dihydro- (1,2,4) triazolo (1,5-a) pyrimidine, 4-aminopyrazolo [3,4-d] pyrimidine Anticorrosive agents (compounds having a pyrimidine skeleton); polymers such as polyacrylic acid, copolymers of acrylic acid, polymethacrylic acid, copolymers of methacrylic acid and the like can be mentioned. When the wiring metal contains copper, the metal anticorrosive agent is composed of polyacrylic acid, a copolymer of acrylic acid, a copolymer of polymethacrylic acid and methacrylic acid, and a triazole-based anticorrosive agent from the viewpoint of excellent anticorrosion action. It is preferable to include at least one selected from the group. One type of metal corrosion inhibitor may be used alone, or two or more types may be used in combination.

The content of the metal corrosion inhibitor is preferably 0.001 to 10% by mass, more preferably 0.005 to 5% by mass, still more preferably 0.01 to 2% by mass, based on the total mass of the polishing liquid. .. When the content of the metal anticorrosive agent is 0.001% by mass or more, it is easy to suppress the etching of the wiring metal and reduce the roughness of the surface to be polished. When the content of the metal anticorrosive agent is 10% by mass or less, the polishing rate of the wiring metal and the barrier material (for example, the barrier metal) tends to be good.

(water)
The polishing liquid according to this embodiment contains water. The water content in the polishing liquid may be the balance of the polishing liquid excluding the contents of other contained components.

(PH of polishing liquid)
The pH of the polishing liquid according to this embodiment is preferably in the following range. The pH of the polishing liquid is preferably 4.0 or less, more preferably 3.7 or less, further preferably 3.5 or less, particularly preferably 3.3 or less, from the viewpoint of easily suppressing the etching rate of the tungsten material. 0.0 or less is extremely preferable, 2.8 or less is very preferable, and 2.7 or less is even more preferable. The pH of the polishing liquid is preferably 2.0 or more, more preferably 2.1 or more, further preferably 2.2 or more, and particularly preferably 2.5 or more, from the viewpoint of easily suppressing corrosion of the polishing apparatus. 6 or more is extremely preferable, and 2.7 or more is very preferable. 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.

The pH of the polishing liquid according to this embodiment can be measured with a pH meter (for example, trade name: 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. After calibrating the pH meter at three points, put the electrode of the pH meter in the polishing solution and measure the value after it stabilizes after 2 minutes or more. At this time, the liquid temperatures of the calibration liquid and the polishing liquid are set to 25 ° C.

(PH buffer)
The polishing liquid according to the present embodiment may contain a pH buffer, if necessary, in order to adjust and stabilize the pH of the polishing liquid. The pH buffer is not particularly limited as long as the pH of the polishing liquid can be adjusted and stabilized. The polishing liquid according to the present embodiment is first dissociated from the viewpoint that it is easy to adjust the pH range to a preferable pH range of 2.0 to 4.0, that it can be arbitrarily mixed with water, and that it does not adversely affect the characteristics of the polishing liquid. It preferably contains an amino acid having a constant of 2.0 to 4.0. 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, Examples thereof include β-alanine, and glycine is preferable from the viewpoint of easy availability.

<Polishing method>
The polishing method according to the present embodiment includes a polishing step of polishing a surface to be polished containing a tungsten material using the polishing liquid according to the present embodiment. The polishing liquid may be a polishing liquid obtained by diluting the storage liquid for the polishing liquid with water. The surface to be polished may have a layer containing at least a tungsten material. Examples of the tungsten material include tungsten and a tungsten compound. Examples of the tungsten compound include a tungsten alloy and the like.

In the polishing step, for example, the surface to be polished of the object to be polished (for example, the substrate) is pressed against the polishing cloth of the platen (polishing platen), and the surface of the object to be polished opposite to the surface to be polished (of the object to be polished). With a predetermined pressure applied to the object to be polished from the back surface), the polishing liquid according to this embodiment is supplied between the surface to be polished and the polishing cloth to make the object to be polished relatively relative to the platen. The surface to be polished can be polished by moving it. In the polishing step, the material to be polished including the tungsten material can be polished. The material to be polished may be in the form of a film (film to be polished) or may be a film containing a tungsten material. Examples of the film forming method include known sputtering methods and plating methods.

The polishing step is a step of polishing a surface to be polished containing a tungsten material and at least one selected from the group consisting of a barrier material (for example, a barrier metal) and an insulating material using the polishing liquid according to the present embodiment. You may. The polishing step may be, for example, a step of polishing an object to be polished (for example, a substrate) having at least a layer containing a tungsten material and at least one selected from the group consisting of a barrier layer and an insulating layer.

Examples of the barrier material include tantalum, tantalum alloy, tantalum compound (tantalum oxide, tantalum nitride, etc.), titanium, titanium alloy, titanium compound (titanium oxide, titanium nitride, etc.) and the like. A tungsten material may be used as the barrier material. Examples of the insulating material include silicon oxide and silicon nitride.

In the polishing step, the object to be polished (substrate) 10 shown in FIG. 1 can be polished. For example, the polishing steps include a first polishing step (coarse polishing step) in which the tungsten material 3 is polished until the barrier material 2 is exposed, and a second polishing step in which the barrier material 2 and the tungsten material 3 are polished until the insulating material 1 is exposed. It may have a step (medium polishing step) and a third polishing step (post-polishing step) for polishing the insulating material 1, the barrier material 2 and the tungsten material 3 in this order.

In the above-mentioned second polishing step and third polishing step, the polishing rate of the tungsten material does not need to be the polishing rate (> 100 nm / min) required for rough polishing, but 40 nm from the viewpoint of shortening the polishing time. / Min or more is preferable.

As the polishing device, for example, when polishing with a polishing cloth, a holder capable of holding the object to be polished and a surface plate connected to a motor or the like whose rotation speed can be changed and to which the polishing pad can be attached are provided. You can use a general polishing device that you have. As the polishing pad, general non-woven fabric, polyurethane foam, porous fluororesin and the like can be used, and there is no particular limitation.

The polishing conditions are not limited, but the rotation speed of the surface plate is preferably as low as 200 rpm or less so that the object to be polished does not pop out. The pressing pressure of the object to be polished (for example, a substrate such as a semiconductor substrate) having a surface to be polished is preferably 1 to 100 kPa, and the uniformity in the surface to be polished and the flatness of the pattern can be improved. From the viewpoint of satisfaction, it is more preferably 5 to 50 kPa. During polishing, a polishing liquid can be continuously supplied to the polishing cloth by a pump or the like. There is no limit to the amount of this supply, but it is preferable that the surface of the polishing pad is always covered with the polishing liquid.

In order to perform polishing (CMP or the like) so that the surface condition of the polishing pad is always the same, it is preferable to carry out a conditioning step of the polishing pad before polishing. For example, a dresser with diamond particles is used to condition the polishing pad with a liquid containing at least water. Subsequently, it is preferable to further carry out the cleaning step of the object to be polished after carrying out the polishing method according to the present embodiment. It is preferable that the object to be polished after polishing is thoroughly washed in running water, and then the water droplets adhering to the object to be polished are wiped off by using spin dry or the like and then dried. Further, a known cleaning method (for example, while flowing a commercially available cleaning liquid onto the surface to be polished of the object to be polished, the brush is pressed against the object to be polished with a constant pressure while rotating a brush made of polyurethane, and the brush is pressed onto the object to be polished. It is more preferable to dry after carrying out the method for removing the deposits of the above.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the technical idea of the present invention is not deviated.

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

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

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

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

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

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

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

(Comparative Example 4)
A polishing solution 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 the 50 mass% 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution.

(Comparative Example 5)
Example 1 except that 0.2 g of a 50 mass% 1-hydroxyethane-1,1-diphosphonic acid aqueous solution was used instead of 0.04 g of a 50 mass% 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution. The same procedure as above was carried out to prepare a polishing liquid.

(Comparative Example 6)
Example 1 except that 0.4 g of a 50 mass% 1-hydroxyethane-1,1-diphosphonic acid aqueous solution was used instead of 0.04 g of a 50 mass% 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution. The same procedure as above was carried out to prepare a polishing liquid.

(Comparative Example 7)
The same procedure as in Example 1 was carried out except that 0.2 g of a 50 mass% nitrilotris (methylenephosphonic acid) aqueous solution was used instead of 0.04 g of the 50 mass% 2-phosphonobutane-1,2,4-tricarboxylic acid aqueous solution. , A polishing solution was prepared.

<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 solution: 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 ° C
Measurement procedure: After calibrating at three points using a calibration solution, the electrodes were placed in the measurement target and then left at 25 ° C. for 2 minutes or longer, and the pH when stable was taken as the measured value.

<Measurement of hydrogen peroxide decomposition rate>
When 100 g of the polishing liquid immediately after production was weighed and the hydrogen peroxide concentration of the polishing liquid was measured by the method described later, the hydrogen peroxide concentration was 1.0% by mass.

A test solution A was prepared by separately weighing 100 g of the polishing solution immediately after the preparation and adding 0.02 g (corresponding to 2.8 ppm of Fe ions) of a 10 mass% iron nitrate hexahydrate aqueous solution. Immediately after the preparation of the test solution A, the hydrogen peroxide concentration (initial hydrogen peroxide concentration) was measured by the method described later. Then, the test solution 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 carried out under the condition that the aqueous solution of iron nitrate nineahydrate was not added, the hydrogen peroxide decomposition rate of the polishing solution of Comparative Example 1 was 0.2%, and the hydrogen peroxide decomposition rate was small.
Hydrogen peroxide decomposition rate [%] = 100 × (initial hydrogen peroxide concentration [ppm] -decomposed hydrogen peroxide concentration [ppm]) / initial hydrogen peroxide concentration [ppm]

(Measurement of hydrogen peroxide concentration)
The hydrogen peroxide concentration of the above-mentioned polishing solution and test solution A was measured by an existing iodine titration method. First, 1.0 g of the polishing solution or the test solution A was weighed, and then 5.0 g of a sulfuric acid aqueous solution containing 0.05% by mass of hexaammonium heptamolybdate / tetrahydrate and 10% by mass of sulfuric acid was added. Further, 5.0 g of a 0.1 mol / L potassium iodide (KI) aqueous solution and 30 g of pure water were added to prepare a test solution B. A 0.1 mol / L sodium thiosulfate (Na ₂ S ₂ O ₃ ) aqueous solution was used as the titrator, and a titrator (potentiometric titrator COM-2500 manufactured by Hiranuma Sangyo Co., Ltd.) was used to prepare the above-mentioned test solution B. Titration was performed. The hydrogen peroxide concentration was calculated by the following formula.
Hydrogen peroxide concentration [ppm] = D × K × M × 1000000 / S
D: _{Volume of added Na 2} S ₂ O ₃ aqueous solution (titration solution) [L]
K: Mass equivalent of hydrogen peroxide to 1 mol of Na ₂ S ₂ O ₃ = 17 [g / mol]
M: _{Concentration of Na 2} S ₂ O ₃ aqueous solution (titration solution) [mol / L]

<Measurement of polishing speed>
(Evaluation test wafer)
A tungsten wafer in which a tungsten film having a film thickness of 600 nm was formed on a silicon wafer having a diameter of 30 cm by a CVD method was used.

(Polishing method)
Using a CMP polishing device (Reflexion LK manufactured by AMAT Co., Ltd.), while dropping each polishing liquid (excluding the polishing liquids of Comparative Examples 2 to 4) on the surface plate, the tungsten film is polished under the following conditions to polish the tungsten. The speed was measured.
Abrasive cloth: IC-1010
Polishing load: 3psi (20.6kPa)
Rotation speed: 93 rpm (head), 87 rpm (surface plate)
Abrasive droplet speed: 300 mL / min
Polishing time: 1 min

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

<Evaluation result>
From Table 1, in Comparative Example 1 in which Compound A was not used, the hydrogen peroxide decomposition rate was 2.1%, which was not good. The tungsten polishing rate was 42.0 nm / min.

In Examples 1 to 4 using Compound A, the hydrogen peroxide decomposition rate was 1.2% or less, and a sufficient effect of suppressing hydrogen peroxide decomposition was exhibited. It can be seen that as the amount of compound A used increases, the hydrogen peroxide decomposition rate decreases and the hydrogen peroxide decomposition suppressing effect improves. Further, the tungsten polishing rate of Examples 1 to 4 was not decreased as compared with Comparative Example 1, and was good at 40 nm / min or more. From this, it can be seen that Compound A does not inhibit the polishing of the tungsten material.

In Comparative Example 2 using citric acid having a carboxy group but no phosphono group, the hydrogen peroxide decomposition rate was 3.8%, and the effect of suppressing hydrogen peroxide decomposition was not confirmed. In Comparative Example 3 using phosphoric acid having a phosphono group but not a carboxy group and a carboxylic acid base, the hydrogen peroxide decomposition rate was 5.7%, and the effect of suppressing hydrogen peroxide decomposition was not confirmed. In Comparative Example 4 using glycine, which has a carboxy group and is known to interact with a metal, the hydrogen peroxide decomposition rate was 1.9%, and the effect of suppressing hydrogen peroxide decomposition was not confirmed. From the results of Comparative Examples 2 to 4, the compound having a phosphono group but not having a carboxy group and a carboxylic acid base, and the compound having a carboxy group or a carboxylic acid base but not having a phosphono group were decomposed by hydrogen peroxide. It can be seen that the inhibitory effect cannot be obtained.

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. Although the effect of suppressing hydrogen peroxide decomposition could be confirmed, the tungsten polishing rates were 38.6 nm / min and 34.4 nm / min, and excellent tungsten polishing rates could not be obtained. Although the cause of the decrease in the tungsten polishing rate is not clear, it is considered that the polishing rate is reduced by adsorbing and protecting 1-hydroxyethane-1,1-diphosphonic acid on the surface of the tungsten material.

In Comparative Example 7 using nitrilotris (methylenephosphonic acid), which is a phosphoric acid compound having a metal chelating effect, the hydrogen peroxide decomposition rate was 1.3%, and a sufficient effect of suppressing hydrogen peroxide decomposition was not exhibited. The effect of suppressing hydrogen peroxide decomposition was lower than that of Example 2 in which 2-phosphonobutane-1,2,4-tricarboxylic acid having the same concentration was used.

1 ... Insulation material, 2 ... Barrier material, 3 ... Tungsten material, 10 ... Body to be polished.

Claims (11)

Containing abrasive grains, hydrogen peroxide, compound A, and water,
A polishing solution, wherein 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 carboxylic acid base. The polishing liquid according to claim 1, wherein the compound A is a compound having a phosphono group and a carboxy group. The polishing solution according to claim 1 or 2, wherein the compound A contains 2-phosphonobutane-1,2,4-tricarboxylic acid. The polishing liquid according to any one of claims 1 to 3, wherein the content of the compound A is 0.001 to 10% by mass based on the total mass of the polishing liquid. The polishing solution according to any one of claims 1 to 4, wherein the abrasive grains contain at least one selected from the group consisting of silica, alumina, ceria, titania, zirconia, germania, and modified products thereof. The polishing liquid according to any one of claims 1 to 5, further containing a metal oxide dissolving agent. The polishing solution according to claim 6, wherein the metal oxide solubilizer contains an organic acid (excluding the compound A and an amino acid having a first dissociation constant of 2.0 to 4.0). The polishing solution according to claim 7, wherein the metal oxide dissolving agent 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. The polishing liquid according to any one of claims 1 to 8, which has a pH of 2.0 to 4.0. The polishing liquid according to any one of claims 1 to 9, further containing an amino acid having a first dissociation constant of 2.0 to 4.0. A polishing method for polishing a surface to be polished containing a tungsten material using the polishing liquid according to any one of claims 1 to 10.

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