Polishing composition and polishing method

Abstract

To provide a polishing composition that can efficiently polish a barrier layer by suppressing polishing of silicon oxide as much as possible when polishing a polishing object having a barrier layer and a layer containing silicon oxide.SOLUTION: A polishing composition includes: abrasive grains whose surfaces are cationically modified; a hydrophobic compound; and water. Therein, a water-octanol partition coefficient logD value of the hydrophobic compound at pH of the polishing composition is 1.45 or more and 3.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, with the increasing integration and performance of LSIs, the formation of buried metal wiring (damascene wiring) has been promoted. In a damascene wiring structure, a barrier layer is formed under a conductive material such as copper or copper alloy to prevent the conductive material from diffusing into the interlayer insulating film. Materials that have traditionally been used to form the barrier layer include tantalum, tantalum alloys, tantalum compounds, titanium, and titanium compounds.

[0003] In such a multilayer wiring formation process, chemical mechanical polishing (hereinafter sometimes referred to as "CMP") is used to smooth the substrate, remove excess metal thin film formed during wiring formation, and remove excess barrier layer on the insulating film.

[0004] For example, Patent Document 1 proposes that when polishing an object to be polished that includes a copper-containing layer as a wiring layer and a cobalt layer as a barrier metal layer, a method is proposed in which a high polishing rate is achieved for the copper-containing layer while suppressing polishing of the cobalt-containing layer.

[0005] Furthermore, Patent Document 2 proposes a polishing composition that achieves a high polishing rate when polishing a barrier layer and also suppresses scratches.

[0006] When CMP is performed to remove the barrier layer on such an insulating film, the insulating film made of silicon oxide is polished away along with the barrier layer, which can impair the function of the insulating film.

[0007] Therefore, when performing CMP to remove a barrier layer on an insulating film (silicon oxide), it is necessary to suppress polishing of the silicon oxide layer as much as possible. In other words, it is necessary to perform polishing by increasing the ratio of the polishing rate of the barrier layer to the polishing rate of the silicon oxide layer.

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-56254 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-62434 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a polishing composition that can efficiently polish the barrier layer while minimizing polishing of silicon oxide when polishing an object having a barrier layer and a layer containing silicon oxide, i.e., to provide a polishing composition that can increase the ratio of the polishing rate of the barrier layer to the polishing rate of silicon oxide. [Means for solving the problem]

[0010] As a result of extensive investigations, the present inventors have found that the above problems can be solved by using the following polishing composition: a polishing composition containing abrasive grains whose surfaces are cationically modified, a hydrophobic compound, and water, wherein the water-octanol partition coefficient logD of the hydrophobic compound at the pH of the polishing composition is 1.45 or more and 3.0 or less.

[0011] To measure and calculate the water-octanol partition coefficient (water-octanol partition coefficient (logD)), direct measurement methods, indirect measurement methods, calculation methods using computational chemistry, etc., as described in, for example, "Partition Coefficient" Structure Determination and Measurement / Analysis of Physical Properties and Establishment of Standard Test Methods, Technical Information Association, Technical Information Association, pp. 130-142 (2001), etc., can be used. However, taking into consideration the characteristics of each method, an appropriate method can be selected depending on the purpose and circumstances.

[0012] When the water-octanol partition coefficient logD of a hydrophobic compound is determined by a direct measurement method, logD is defined by the following equation (1). logD=log((C i oct +C u oct ) / (C i wat +C u wat )) ...Equation (1) In the above formula (1), C i oct is the total concentration of ionized species in octanol, and C u oct is the total concentration of unionized species in octanol, and C i wat is the total concentration of ionized species in an aqueous solution at a particular pH, and C u wat is the total concentration of unionized species in an aqueous solution at a particular pH.

[0013] When predicting the behavior of drugs experimentally, the apparent partition coefficient is an important parameter, and actual measurement of the partition coefficient is necessary. Therefore, computational chemistry calculation methods are preferred as a simple measurement and calculation method that does not require actual measurement of the partition coefficient. Specifically, calculation methods using SolubilityBatch, a chemical calculation software from Advanced Chemistry Development (ACD), are one example. Information on the algorithm used in this calculation method can be found on the ACD website (www.acdlabs.com). Water-octanol partition coefficients (logD) calculated using this calculation method are already included in the CAS REGISTRY file, and these can also be used. For example, calculations can be performed using ACD / LogD, a chemical calculation software from Advanced Chemistry Development (ACD). [Effects of the Invention]

[0014] According to the present invention, by using a polishing composition containing both abrasive grains whose surfaces are cationically modified and a hydrophobic compound whose water-octanol partition coefficient logD value at the pH of the polishing composition is 1.45 or more and 3.0 or less, the ratio of the removal rate of the barrier layer to the removal rate of silicon oxide can be increased. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Abrasive grain] The polishing composition according to this embodiment contains abrasive grains whose surfaces have been cationically modified. Examples of the abrasive grains whose surfaces have been cationically modified include silica and the like. In one embodiment of the present invention, specific examples of the abrasive grains include particles made of metal oxides such as silica. The abrasive grains may be used alone or in combination of two or more types. Furthermore, the abrasive grains may be commercially available products or synthetic products. Among these abrasive grains, silica is preferred, with fumed silica and colloidal silica being more preferred, and colloidal silica being particularly preferred. Methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Regardless of the method, colloidal silica produced by either method is suitable for use as the abrasive grains of the present invention. However, colloidal silica produced by the sol-gel method, which can produce high-purity colloidal silica, is preferred.

[0016] The silica whose surface is cationically modified is preferably colloidal silica whose surface is cationically modified.Here, as the colloidal silica whose surface is cationically modified, colloidal silica whose surface is fixed with an amino group or a quaternary ammonium group is preferably mentioned.As a method for producing colloidal silica having such a cationic group, as described in JP 2005-162533 A, a method of fixing a silane coupling agent having an amino group, such as aminoethyltrimethoxysilane, aminopropyltrimethoxysilane, aminoethyltriethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane, or aminobutyltriethoxysilane, or a silane coupling agent having a quaternary ammonium group, such as N-trimethoxysilylpropyl-N,N,N-trimethylammonium, on the surface of the abrasive grain can be mentioned.This allows obtaining colloidal silica whose surface is fixed with an amino group or a quaternary ammonium group. In one embodiment of the present invention, the abrasive grains have a silane coupling agent having an amino group or a silane coupling agent having a quaternary ammonium group fixed to the surface of the abrasive grains.

[0017] In one embodiment of the present invention, the average primary particle size of the abrasive grains is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. In one embodiment of the polishing composition, the average primary particle size of the abrasive grains is preferably 60 nm or less, more preferably 55 nm or less, even more preferably 50 nm or less, and particularly preferably 40 nm or less. Within these ranges, defects such as scratches that may occur on the surface of the object to be polished after polishing with the polishing composition can be suppressed. The average primary particle size of the colloidal silica is calculated, for example, based on the specific surface area of ​​the colloidal silica measured by the BET method.

[0018] The average secondary particle diameter of the abrasive grains is preferably 20 nm or more, more preferably 30 nm or more, even more preferably 40 nm or more, and particularly preferably 45 nm or more. In one embodiment of the present invention, the average secondary particle diameter of the abrasive grains is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 120 nm or less. Within such ranges, defects such as scratches that may occur on the surface of the object to be polished after polishing with the polishing composition can be suppressed. The average secondary particle diameter of the abrasive grains can be measured, for example, by dynamic light scattering, typically laser diffraction scattering.

[0019] The content of abrasive grains in the polishing composition is not particularly limited, but is typically 0.5% by mass or more, preferably 1% by mass or more, and more preferably 1.5% by mass or more.Increasing the content of abrasive grains tends to achieve a higher polishing rate.From the viewpoint of the surface smoothness of the substrate after polishing and the dispersion stability of the abrasive grains, the content is usually 25% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, for example 5% by mass or less.

[0020] [Hydrophobic compounds] The polishing composition according to this embodiment contains a hydrophobic compound having a water-octanol partition coefficient logD of 1.45 or more and 3.0 or less. The water-octanol partition coefficient logD of the hydrophobic compound is preferably 1.50 or more, and more preferably 1.58 or more. When the water-octanol partition coefficient logD of the hydrophobic compound is within this range, the hydrophobic compound adsorbs to the silicon oxide layer to form a hydrophobic film, reducing the compatibility of the polishing composition slurry with the silicon oxide layer and suppressing the removal rate of the silicon oxide layer. When the water-octanol partition coefficient logD of the hydrophobic compound is less than 1.45, the removal rate of the silicon oxide layer tends to be excessive.

[0021] Hydrophobic compounds with a water-octanol partition coefficient logD between 1.45 and 3.0 include compounds with cyclic structures, particularly those with benzene rings. Benzene rings are capable of π-π stacking, making them advantageous for forming self-assembled films. Compounds with cyclic structures enhance hydrophobicity while lacking surfactant properties. This minimizes interactions with abrasive particles and reduces the storage stability of the slurry. Furthermore, the lack of foaming during polishing reduces the impact on equipment maintenance and post-polishing wafer defects. Furthermore, incorporating N, S, and O atoms into the cyclic structure generates charge imbalances within the molecule, increasing solubility in water. The cyclic structure also facilitates molecular interactions (stacking), which tends to result in the formation of dense films.

[0022] Examples of hydrophobic compounds that satisfy the above conditions include 1,4-benzodioxane, 1H-indole, 2,3-benzofuran, 2H-1,4-benzothiazin-3(4H)-one, 1,2-benzoirithiazol-3(2H)-one, 4-hydroxy-2H-1-benzothiopyran-2-one, benzo[d]thiazole, benzo[d]oxazole, 1,3,5-trithiane, 1,3-dithiane, furan, 2H-thietane, thiophene, tetrahydrothiophene, thiane, 2H-thiopyran, 4H-thiopyran, oxepane, thiepane, thiepin, oxocane, oxonane, 1,4,5,6-tetrahydrocyclopenta[b]pyrrole, 1,4-dihydropyrrole[3,2-b]pyrrole, 1,6-dihydro ... Examples of suitable compounds include pyrrole[2,3-b]pyrrole, 6H-furo[2,3-b]pyrrole, 4H-furo[3,2-b]pyrrole, 4H-thieno[3,2-b]pyrrole, 6H-thieno[2,3-b]pyrrole, 2H-isoindole, indolizine, 1H-indazole, benzofuran, isobenzofuran, benzo[d]isoxazole, benzo[c]isoxazole, benzo[c][1,2,5]thiadiazole, 2H-chromene, 1H-chromene, phenazine, 1-oxaspiro[4,5]decane, and 3',4',5',6',-tetrahydro-3H-spiro-[isobenzofuran-1,2'-pyran], but are not limited thereto. Any compound having a logD value of 1.45 or more and 3.0 or less may be used.

[0023] Preferred hydrophobic compounds include 1,4-benzodioxane, 1H-indole, 2H-1,4-benzothiazin-3(4H)-one, 1,2-benzoirithiazol-3(2H)-one, 4-hydroxy-2H-1-benzothiopyran-2-one, benzothiazole, 1,3,5-trithiane, thiophene, thiane, 2H-thiopyran, 4H-thiopyran, thiepane, thiepin, oxocane, and oxocane. Examples include sonane, 6H-furo[2,3-b]pyrrole, 4H-furo[3,2-b]pyrrole, 4H-thieno[3,2-b]pyrrole, 6H-thieno[2,3-b]pyrrole, 2H-isoindole, indolizine, benzo[d]isoxazole, 1-oxaspiro[4,5]decane, and 3',4',5',6'-tetrahydro-3H-spiro-[isobenzofuran-1,2'-pyran]. These compounds are preferred because they have a high logD in the range of 1.45 to 3.0 and maintain water solubility.

[0024] Even if a compound has a cyclic structure, it does not have good solubility in water if it has a simple alkyl chain. Furthermore, even if a compound has a benzene ring, it does not necessarily have a water-octanol partition coefficient logD of 1.45 or more. For example, benzotriazole (BTA), 1-(hydroxymethyl)-1H-benzotriazole, 1-methyl-1H-benzotriazole, quinoline, quinoxaline, quinazoline, pyrrolidine, 1-pyrrole, 2H-pyrrole, 2-pyrroline, 3-pyrroline, pyrazolidine, imidazolidine, 2-pyrazoline, 2-imidazoline, pyridine, pyridazine, pyrimidine, pyrazine, 1,2,4-triazine, 1,3,5-triazine, etc. It was found that compounds such as cinnamidine, benzimidazole, 7-azaindole, 4-azaindole, 5-azaindole, 6-azaindole, 7-azaindazole, 1,2,3,4-tetrahydroquinoline, 1,2-dihydroisoquinoline, isoquinoline, 4H-quinolizine, phthalazine, cinnaline, and 1,8-naphthyridine have log D values ​​defined by the above formula (1) of less than 1.45, and therefore do not have a sufficient effect of suppressing the removal rate of silicon oxide.

[0025] The lower limit of the amount of hydrophobic compound having a water-octanol partition coefficient logD of 1.45 or more and 3.0 or less is preferably 0.1 mM or more, more preferably 1 mM or more, even more preferably 3 mM or more, and particularly preferably 5 mM or more.The upper limit of the amount of hydrophobic compound having a water-octanol partition coefficient logD of 1.45 or more and 3.0 or less is preferably 100 mM or less, more preferably 50 mM or more, even more preferably 30 mM or more, and particularly preferably 10 mM or more.When the content of hydrophobic compound is within the above range, it tends to be adsorbed to the silicon oxide layer, and the compatibility of the polishing composition slurry with the silicon oxide layer tends to be reduced.

[0026] [water] The polishing composition of the present invention contains water. According to a more preferred embodiment of the present invention, the dispersion medium consists essentially of water. The term "substantially" as used above means that a dispersion medium other than water may be included as long as the intended effect of the present invention can be achieved. More specifically, the composition preferably consists of 90% by mass to 100% by mass of water and 0% by mass to 10% by mass of a dispersion medium other than water, and more preferably 99% by mass to 100% by mass of water and 0% by mass to 1% by mass of a dispersion medium other than water. Most preferably, the dispersion medium is water.

[0027] The polishing composition of the present invention may further contain other components, as necessary, such as a complexing agent, a metal corrosion inhibitor, an antiseptic, an antifungal agent, an oxidizing agent, a reducing agent, a pH adjuster, a surfactant, a water-soluble polymer, an organic solvent for dissolving poorly soluble organic substances, etc. Hereinafter, the oxidizing agent and the pH adjuster, which are preferred components, will be described.

[0028] [Oxidizing agent] The polishing composition of the present invention may contain an oxidizing agent, which has the effect of reducing the corrosion rate of a barrier metal layer, particularly a TiN layer, and thereby achieving stable polishing.

[0029] Usable oxidizing agents include, for example, peroxides. Specific examples of peroxides include hydrogen peroxide, peracetic acid, percarbonates, urea peroxide, oxoacid salts of halogen elements such as perchlorates, chlorates, chlorites, and hypochlorites, as well as persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate. Among these, persulfates and hydrogen peroxide are preferred from the viewpoint of polishing speed, and hydrogen peroxide is particularly preferred from the viewpoints of stability in an aqueous solution and environmental impact.

[0030] The lower limit of the content of the oxidizing agent in the polishing composition is preferably 0.001 mass% or more, more preferably 0.01 mass% or more, and even more preferably 0.05 mass% or more. The upper limit of the content of the oxidizing agent in the polishing composition is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 3 mass% or less. By adjusting the content of the oxidizing agent within these ranges, corrosion of the barrier metal can be suppressed.

[0031] [pH adjuster] The pH of the polishing composition of the present invention can be adjusted by adding an appropriate amount of a pH adjuster, if necessary. The pH adjuster is preferably an acid, and may be either an inorganic or organic compound. This allows for control of the polishing rate of the object to be polished and the dispersibility of the abrasive grains. The pH adjuster can be used alone or in combination of two or more types.

[0032] As the pH adjuster, known acids or their salts can be used.Specific examples of the acid include inorganic acids such as sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid; carboxylic 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 lactic acid; and organic acids such as organic sulfuric acids such as methanesulfonic acid, ethanesulfonic acid, and isethionic acid.

[0033] The amount of pH adjuster added is not particularly limited, and may be adjusted appropriately so that the polishing composition has a desired pH.

[0034] [pH] The pH range of the polishing composition of the present invention is preferably less than 7, more preferably not more than 5, and even more preferably not more than 4. By adjusting the pH within this range, the corrosion rate of the barrier metal, particularly TiN, can be suppressed, and a stable polishing rate can be obtained.

[0035] [Polished object] The polishing object of the present invention is preferably a layer containing silicon oxide, and more preferably, it is suitable for polishing a silicon oxide layer further containing a barrier metal. Here, examples of silicon oxide include a silicon oxide film formed from TEOS, HDP film, USG film, PSG film, BPSG film, and RTO film, among which a silicon oxide film formed from TEOS is preferred. Furthermore, examples of barrier metals include Ti, TiN, Ta, TaN, W, WN, TaN, Ru, and Co, among which TiN is preferred.

[0036] [Method for producing polishing composition] The method for producing the polishing composition of the present invention is not particularly limited, and it can be obtained, for example, by stirring and mixing abrasive grains, a hydrophobic compound, an oxidizing agent, a pH adjuster, and, if necessary, other components in a dispersion medium or solvent such as water.

[0037] The temperature at which the components are mixed is not particularly limited, but is preferably 10 to 40° C. Heating may be performed to increase the dissolution rate. The mixing time is also not particularly limited.

[0038] [Polishing method] As described above, the polishing composition of the present invention is suitable for polishing an object having a layer containing silicon oxide, more preferably for polishing a silicon oxide layer further containing a barrier metal. Thus, the present invention provides a polishing method for polishing an object containing silicon oxide, more preferably further containing a barrier metal, with the polishing composition of the present invention. To more efficiently obtain the effects of the present invention, it is preferable to polish the layer containing silicon oxide and the barrier metal simultaneously.

[0039] When using the polishing composition of the present invention to polish a silicon oxide layer containing a barrier metal, in order to efficiently polish the barrier metal without damaging the silicon oxide insulating film, the ratio (selectivity) of the polishing rate of the barrier metal to the polishing rate of silicon oxide should be 10 or more, preferably 13 or more, and more preferably 15 or more.

[0040] As the polishing device, a general polishing device can be used, which is equipped with a holder for holding a substrate or the like having an object to be polished, a motor whose rotation speed can be changed, and a polishing platen onto which a polishing pad (polishing cloth) can be attached.

[0041] The polishing pad can be made of any material, including, without particular limitation, a general nonwoven fabric, polyurethane, porous fluororesin, etc. The polishing pad is preferably provided with grooves for accumulating the polishing composition.

[0042] The polishing conditions are not particularly limited; for example, the rotation speed of the polishing platen is preferably 10 to 500 rpm, and the pressure (polishing pressure) applied to the object to be polished is preferably 0.1 to 10 psi. The method of supplying the polishing composition to the polishing pad is also not particularly limited; for example, a method of continuously supplying the composition using a pump or the like is used. There is no limit to the amount of the composition supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition of the present invention. The supply rate (flow rate) is preferably 50 to 500 mL / min.

[0043] After polishing, the object to be polished is washed in running water, and water droplets adhering to the object to be polished are removed using a spin dryer or the like, followed by drying, to obtain a polished object to be polished. [Example]

[0044] The present invention will be described in more detail using the following examples and comparative examples, although the technical scope of the present invention is not limited to the following examples.

[0045] [Examples 1 to 11] The abrasive grains were 1.8 wt% colloidal silica (average secondary particle diameter 50 nm) cationized by coupling 3-aminopropyltrimethoxysilane (APTES) to the surface, 27.35 mM hydrogen peroxide as an oxidizing agent, and 10.00 mM of a hydrophobic compound having a log D value of 1.45 or greater, as shown in Table 1. These components were mixed in water at the indicated concentrations (mixing temperature: approximately 25°C, mixing time: approximately 60 minutes). The pH was then adjusted to 3.0 using nitric acid as a pH adjuster, yielding a polishing composition. The pH of the resulting polishing composition was measured at 25°C using a pH meter.

[0046] [Table 1]

[0047] [Comparative Example 1] As the abrasive grains, 1.8 wt% of colloidal silica similar to those used in Examples 1 to 11, and 27.35 mM of hydrogen peroxide as an oxidizing agent were mixed in water with stirring (mixing temperature: about 25°C, mixing time: about 60 minutes) to the indicated contents. Furthermore, nitric acid was used as a pH adjuster to adjust the pH to 3.0, thereby obtaining a polishing composition. The pH of the resulting polishing composition was confirmed at 25°C using a pH meter.

[0048] [Comparative Examples 2 to 17] As abrasive grains, 1.8 wt% of colloidal silica similar to those used in Examples 1 to 11, 27.35 mM of hydrogen peroxide as an oxidizing agent, and 10.00 mM of a compound having a log D value of less than 1.45 shown in Table 1 as an additive in place of a hydrophobic compound were mixed in water with stirring (mixing temperature: about 25°C, mixing time: about 60 minutes) to the indicated contents. Furthermore, nitric acid was used as a pH adjuster to adjust the pH to 3.0, thereby obtaining a polishing composition. The pH of the resulting polishing composition was confirmed at 25°C using a pH meter.

[0049] [Comparative Examples 18, 20, and 22] The abrasive grains were 1.8 wt% unsurface-modified colloidal silica (average secondary particle diameter 50 nm in Comparative Examples 18, 20, and 22, and 70 nm in Comparative Example 24) (average secondary particle diameter 50 nm), and the oxidizing agent was 27.35 mM hydrogen peroxide. Each was stirred and mixed in water to the indicated contents (mixing temperature: approximately 25°C, mixing time: approximately 60 minutes).

[0050] [Comparative Examples 19, 21, and 23] The abrasive grains were 1.8 wt% unmodified colloidal silica (average secondary particle diameter 50 nm in Comparative Examples 19, 21, and 23, and 70 nm in Comparative Example 25), 27.35 mM hydrogen peroxide as an oxidizing agent, and 10 mM indole with a log D value of 2.59 as a hydrophobic compound. These components were mixed in water with stirring (mixing temperature: approximately 25°C, mixing time: approximately 60 minutes) to the indicated contents. The pH was then adjusted to 3.0 using nitric acid as a pH adjuster, yielding a polishing composition. The pH of the resulting polishing composition was confirmed at 25°C using a pH meter.

[0051] The surfaces of substrates to be polished were polished using the resulting polishing compositions (Examples 1 to 18, Comparative Examples 1 to 23) under the following polishing conditions. The substrates to be polished were TiN blanket wafers with a 2500 Å thick TiN film formed on the surface of a silicon substrate, and silicon oxide blanket wafers with a 10000 Å thick silicon oxide film formed on the surface of a silicon substrate. The diameter of the substrates to be polished was 200 mm.

[0052] [Polishing conditions] Polishing equipment: Applied Materials polishing machine, model Mirra Polishing pad: IC1010 (manufactured by Rohm and Haas) Polishing fluid supply rate: 113 mL / min Processing pressure: 4 psi Lower surface plate rotation speed: 113rpm Polishing time: 1 minute Feed rate (flow rate): 220mL / min

[0053] The polishing compositions were used to polish each of the above objects, and the removal rates (Å / min) of the TiN film and the silicon oxide film were measured. The removal rate of the TiN film was determined by dividing the difference in thickness (Å) of the TiN blanket wafer before and after polishing, measured using a sheet resistance meter based on the DC four-probe method, by the polishing time (min). The removal rate of the silicon oxide film was determined by dividing the difference in thickness (Å) of the silicon oxide blanket wafer before and after polishing, measured using an optical interference film thickness measurement device (KLA-Tencor Corporation, Model: ASET-f5x), by the polishing time (min). The removal rate of the TiN layer relative to the removal rate of the silicon oxide layer was calculated as the selectivity ratio, and the silicon oxide inhibition rate was calculated by dividing the removal rate of the silicon oxide film of the composition containing the hydrophobic compound by the removal rate of the silicon oxide film of the composition without the hydrophobic compound. The results are shown in Table 1.

[0054] As is clear from Table 1 above, the polishing compositions of Examples 1 to 11 contain cationized colloidal silica and a hydrophobic compound with a logD value of 1.45 or more, and the polishing rate for silicon oxide is suppressed relative to the polishing rate for TiN, resulting in a selectivity ratio of the polishing rate for TiN to the polishing rate for silicon oxide of 10 or more. In contrast, Comparative Examples 1 to 17, which contain cationized colloidal silica but do not contain a hydrophobic compound with a logD value of 1.45 or more, do not sufficiently suppress the polishing rate for silicon oxide relative to the polishing rate for TiN, resulting in a selectivity ratio of the polishing rate for TiN to the polishing rate for silicon oxide of less than 10. Furthermore, in Comparative Examples 18 to 23, which used unsurface-modified colloidal silica as the abrasive, it was difficult to sufficiently polish TiN.

Claims

1. A polishing composition comprising abrasive grains whose surfaces are cationically modified, a hydrophobic compound, and water, the polishing composition has a pH of 4 or less, the value of the water-octanol partition coefficient log D of the hydrophobic compound at the pH of the polishing composition is 1.45 or more and 3.0 or less; the hydrophobic compound is at least one selected from the group consisting of 1,4-benzodioxane, 1H-indole, 2,3-benzofuran, 2H-1,4-benzothiazin-3(4H)-one, 4-hydroxy-2H-1-benzothiopyran-2-one, 1,2-benzoirithiazol-3(2H)-one, benzo[d]thiazole, benzo[d]oxazole, 1,3,5-trithiane, 1,3-dithiane, and furan; A polishing composition used for polishing a layer containing silicon oxide and a barrier metal.

2. 2. The polishing composition according to claim 1, wherein the abrasive grains are colloidal silica whose surfaces are cationically modified.

3. The polishing composition according to claim 1 or 2, further comprising an oxidizing agent.

4. 4. The polishing composition according to claim 1, further comprising a pH adjuster.

5. A polishing method comprising polishing a layer containing silicon oxide and a barrier metal with the polishing composition according to any one of claims 1 to 4.

6. 6. The polishing method according to claim 5, wherein the ratio of the polishing rate of said barrier metal to the polishing rate of said silicon oxide is 10 or more.

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