Polishing liquid, polishing liquid set, and polishing method

Abstract

A polishing liquid which contains: abrasive grains containing a hydroxide of a tetravalent metal element; a polymer that comprises a structural unit represented by formula (1); and a liquid medium. (In formula (1), * represents a bonding hand.)

Description

[Technical Field]

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

[0002] In recent years, the importance of processing technologies for higher density and finer feature sizes has been increasing in the manufacturing process of semiconductor devices. One of these processing technologies, chemical mechanical polishing (CMP), is essential for forming shallow trench isolation (STI), planarizing pre-metal insulating materials or interlayer insulating materials, and forming plugs or buried metal wiring.

[0003] In recent years, semiconductor device manufacturing processes have required further miniaturization of processing dimensions, and as a result, polishing scratches that occur during CMP polishing have become a problem. To address this problem, polishing solutions using hydroxide particles of tetravalent metal elements have been investigated (see, for example, Patent Document 1 below). This technology aims to reduce polishing scratches caused by the particles by minimizing the mechanical action while utilizing the chemical action of the hydroxide particles of tetravalent metal elements.

[0004] Furthermore, in order to reduce the processing dimensions, for example, in the formation of shallow trench isolation (STI), a stopper (a polishing stopper made of a stopper material) may be used as one means for stopping polishing at a predetermined position. In one example of CMP using a stopper, a part of the polished part of an article (polished article) having a substrate with a concave-convex pattern (e.g., an element isolation structure), a stopper placed on the convex parts of the substrate, and a polished part (e.g., an insulating part made of an insulating material) placed on the substrate and the stopper so as to fill the concave parts of the substrate is polished until the stopper is exposed. This makes it easy to control the amount of polishing of the polished part. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 070544 Summary of the Invention [Problem to be solved by the invention]

[0006] In the formation of STI, the article to be polished generally has an insulating material of silicon oxide (SiO2) and a stopper material of silicon nitride (SiN). In recent years, with the miniaturization of semiconductor devices, there has been an increasing demand for such articles to further narrow the pitch of the concave-convex pattern (e.g., element isolation width). With conventional polishing solutions using hydroxide particles of tetravalent metal elements, the stopper in the narrow width portion is overpolished (eroded), making it impossible to achieve sufficient element isolation. Furthermore, with the recent miniaturization of semiconductor devices, the stopper layer has become thinner, so overpolishing of the stopper must be further suppressed.

[0007] Therefore, one object of the present invention is to provide a polishing liquid that can suppress over-polishing of the stopper while having a sufficient polishing rate for silicon oxide when polishing an article having a substrate with a concave-convex pattern with a narrow pitch width, a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate. [Means for solving the problem]

[0008] One aspect of the present invention relates to a polishing liquid containing abrasive grains containing a hydroxide of a tetravalent metal element, a polymer containing a structural unit represented by the following formula (1), and a liquid medium. [ka] [In formula (1), * represents a bond.]

[0009] The polishing liquid of the above aspect can polish a polished portion containing silicon oxide at a sufficient polishing rate while suppressing over-polishing of a stopper containing silicon nitride. In particular, when polishing an article having a substrate having a concave-convex pattern with a narrow pitch, a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate, it is possible to suppress over-polishing of the stopper while maintaining a sufficient polishing rate for silicon oxide.

[0010] In one embodiment, the polymer may further contain a structural unit derived from a (meth)acrylic acid ester. The structural unit derived from a (meth)acrylic acid ester may be a structural unit represented by the following formula (2): [ka] [In formula (2), R 1 represents a hydrogen atom or a methyl group, and R 2 ~R 4 each independently represents a hydrocarbon group having 1 to 4 carbon atoms, n represents an integer of 1 or more and 4 or less, and X - indicates a counter anion, and * indicates a bond.]

[0011] In one embodiment, the weight average molecular weight of the polymer may be 50,000 or greater.

[0012] In one embodiment, the hydroxide of a tetravalent metal element may be cerium hydroxide.

[0013] In one embodiment, the pH of the polishing liquid may be 3.0 to 5.0.

[0014] In one embodiment, the polishing fluid may be a polishing fluid used to selectively polish silicon oxide relative to silicon nitride.

[0015] Another aspect of the present invention relates to a polishing liquid set in which the components of the polishing liquid are stored separately as a first liquid and a second liquid, the first liquid containing abrasive grains and a liquid medium, and the second liquid containing a polymer and a liquid medium. With this polishing liquid set, the polishing liquid is obtained by mixing the first liquid and the second liquid.

[0016] Another aspect of the present invention relates to a polishing method including the steps of: preparing an article having a substrate having a concave-convex pattern, a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate; and polishing a part of the polished portion using the polishing liquid or a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. This method makes it possible to polish the polished portion containing silicon oxide at a sufficient polishing rate while suppressing the occurrence of polishing scratches due to over-polishing of the stopper. [Effects of the Invention]

[0017] According to the present invention, when polishing an article having a substrate having a concave-convex pattern with a narrow pitch width, a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate, it is possible to provide a polishing liquid that has a sufficient polishing rate for silicon oxide while suppressing over-polishing of the stopper. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of the polishing method of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a patterned wafer before and after erosion evaluation in the example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[0020] In this specification, a numerical range indicated with "to" indicates a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range. 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. Furthermore, in this specification, "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. In this specification, the content of each component in a 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.

[0021] <Polishing liquid> The polishing liquid of one embodiment contains abrasive grains containing a hydroxide of a tetravalent metal element, a polymer containing a structural unit represented by the following formula (1), and a liquid medium. [ka] [In formula (1), * represents a bond.]

[0022] The polishing liquid is, for example, a polishing liquid for CMP, and is suitably used for selectively polishing silicon oxide relative to silicon nitride. Specifically, the polishing liquid is suitably used for polishing a polished portion of an article (polished article) having a substrate having a concave-convex pattern (for example, an element isolation structure), a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate, thereby exposing the stopper.

[0023] The polishing liquid can polish a silicon oxide-containing polished surface at a sufficient polishing rate while suppressing over-polishing of a silicon nitride-containing stopper. This effect is particularly pronounced when the substrate constituting the article has a concavo-convex pattern with a narrow pitch (line / space (L / S) width). Therefore, the polishing liquid can produce an article in which the pitch (line / space (L / S) width) of the pattern defined by the silicon oxide-containing polished portion and the silicon nitride-containing stopper is narrow, thereby reducing over-polishing of the stopper. Furthermore, the polishing liquid can suppress the polishing rate of silicon nitride, which tends to result in high polishing selectivity (the ratio of the silicon oxide polishing rate to the silicon nitride polishing rate, or silicon oxide polishing rate / silicon nitride polishing rate).

[0024] (abrasive grain) The abrasive grains contain hydroxides of tetravalent metal elements. "Hydroxides of tetravalent metal elements" refers to tetravalent metal ions (M 4+ ) and at least one hydroxide ion (OH - The hydroxides of tetravalent metal elements are compounds containing anions other than hydroxide ions (e.g., nitrate ions, NO 3- , and sulfate ions SO4 2- For example, the hydroxide of a tetravalent metal element may contain an anion (excluding hydroxide ions, for example, nitrate ions NO ) bonded to the tetravalent metal element from the viewpoint of further improving the polishing speed of the material to be removed (for example, insulating materials such as silicon oxide). 3- , and sulfate ions SO4 2- ), and more preferably contains nitrate ions bonded to a tetravalent metal element.

[0025] The hydroxide of a tetravalent metal element can be prepared by reacting a salt of the tetravalent metal element (metal salt) with an alkali source (base). The hydroxide of a tetravalent metal element is preferably prepared by mixing a salt of the tetravalent metal element with an alkaline solution (e.g., an alkaline aqueous solution). This allows for the production of extremely fine particles, resulting in a polishing solution with even greater scratch reduction. Such a method is disclosed, for example, in Patent Document 1. The hydroxide of a tetravalent metal element can be prepared by mixing a metal salt solution (e.g., an aqueous metal salt solution) containing a salt of the tetravalent metal element with an alkaline solution. Conventional salts of tetravalent metal elements can be used. Examples include M(NO3)4, M(SO4)2, M(NH4)2(NO3)6, M(NH4)4(SO4)4 (M represents a rare earth element), and Zr(SO4)2·4H2O. Chemically active cerium (Ce) is preferred as M.

[0026] The content of the abrasive grains is preferably within the following range based on the total mass of the polishing liquid. From the viewpoint of easily fully exhibiting the function of the hydroxide of a tetravalent metal element, the content of the abrasive grains is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.02% by mass or more, particularly preferably 0.03% by mass or more, extremely preferably 0.04% by mass or more, and very preferably 0.05% by mass or more. From the viewpoint of easily avoiding agglomeration of the abrasive grains, easily achieving good chemical interaction with the polished surface, and easily utilizing the properties of the abrasive grains, the content of the abrasive grains is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, extremely preferably 1% by mass or less, extremely preferably 0.5% by mass or less, extremely preferably 0.3% by mass or less, even more preferably 0.1% by mass or less. From these viewpoints, the content of the abrasive grains is preferably 0.005 to 20% by mass.

[0027] When the average particle size (average secondary particle size) of the abrasive grains is relatively small, the specific surface area of the abrasive grains in contact with the polished surface increases, thereby further improving the polishing rate of the material to be removed (e.g., insulating material), and further reducing polishing scratches by suppressing mechanical action. Therefore, the average particle size of the abrasive grains containing hydroxides of tetravalent metal elements is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, particularly preferably 100 nm or less, extremely preferably 80 nm or less, very preferably 60 nm or less, even more preferably 40 nm or less, more preferably 20 nm or less, and even more preferably 10 nm or less, from the viewpoint of obtaining a better polishing rate of the material to be removed (e.g., insulating material) and further reducing polishing scratches. The average particle size of the abrasive grains containing hydroxides of tetravalent metal elements is preferably 1 nm or more, more preferably 2 nm or more, from the viewpoint of obtaining a better polishing rate of the material to be removed (e.g., insulating material) and further reducing polishing scratches. From these viewpoints, the average particle size of the abrasive grains containing hydroxides of tetravalent metal elements is preferably 1 to 300 nm.

[0028] The "average particle size" of abrasive grains refers to the average secondary particle size of the abrasive grains in the polishing solution. The average particle size of abrasive grains can be measured using a light diffraction / scattering particle size analyzer (e.g., DelsaMax PRO, manufactured by Beckman Coulter, Inc.). Specifically, the measurement method using the DelsaMax PRO involves pouring approximately 0.5 mL (L stands for "liters"; the same applies below) of polishing solution into a 12.5 mm x 12.5 mm x 45 mm (height) measurement cell and placing the cell inside the device. The refractive index of the measurement sample is set to 1.333, the viscosity to 0.887 mPa·s, and the measurement is performed at 25°C. The value displayed as the Unimodal Size Mean (cumulant diameter) can be used as the average particle size of the abrasive grains.

[0029] The polishing liquid preferably has high transparency to visible light (visually transparent or nearly transparent). Specifically, the abrasive grains contained in the polishing liquid preferably have a light transmittance of 50% / cm or more for light with a wavelength of 500 nm in an aqueous dispersion containing the abrasive grains at a content of 1.0% by mass. This further suppresses the decrease in the polishing rate of the material to be removed (e.g., insulating material) caused by the addition of additives, making it easy to obtain other properties while maintaining the polishing rate. From the same perspective, the light transmittance is more preferably 60% / cm or more, even more preferably 70% / cm or more, particularly preferably 80% / cm or more, extremely preferably 90% / cm or more, and extremely preferably 92% / cm or more. The upper limit of the light transmittance is 100% / cm.

[0030] Although the reason why adjusting the light transmittance of abrasive grains can suppress a decrease in the removal rate of the material to be removed (e.g., insulating material) is not fully understood, it is thought that the abrasive action of abrasive grains containing hydroxides of tetravalent metal elements (e.g., cerium) is dominated by chemical action rather than mechanical action, and therefore the number of abrasive grains is thought to contribute more to the removal rate than the size of the abrasive grains.

[0031] When the light transmittance of an aqueous dispersion containing 1.0% by mass of abrasive grains is low, it is believed that the abrasive grains present in the aqueous dispersion contain a relatively large number of particles with a large particle size (hereinafter referred to as "coarse particles"). When an additive is added to a polishing solution containing such abrasive grains, the coarse particles act as nuclei to cause other particles to aggregate. As a result, the number of abrasive grains acting on the polished surface per unit area (the number of effective abrasive grains) decreases, and the specific surface area of the abrasive grains in contact with the polished surface decreases, which is thought to result in a slower polishing rate.

[0032] On the other hand, when the light transmittance of an aqueous dispersion containing 1.0% by mass of abrasive grains is high, it is believed that the abrasive grains present in the aqueous dispersion contain few "coarse particles." When the amount of coarse particles present is small, even if an additive is added to the polishing solution, there are few coarse particles that can serve as agglomeration nuclei, so agglomeration between the abrasive grains is suppressed, or the size of the agglomerated particles is relatively small. As a result, the number of abrasive grains acting on the polished surface per unit area (the number of effective abrasive grains) is maintained, and the specific surface area of the abrasive grains in contact with the polished surface is maintained, so the polishing rate is unlikely to decrease.

[0033] Past studies have shown that even when polishing solutions have the same abrasive particle size measured with a general particle size measuring device, some may be visually transparent (high light transmittance) and others may be visually cloudy (low light transmittance). This suggests that coarse particles that can cause the above-mentioned effects can contribute to a decrease in the polishing rate, even in amounts so small that they cannot be detected with a general particle size measuring device.

[0034] The light transmittance is the transmittance for light having a wavelength of 500 nm. The light transmittance is measured with a spectrophotometer, specifically, for example, a spectrophotometer U3310 (device name) manufactured by Hitachi, Ltd.

[0035] More specifically, the measurement sample is prepared as an aqueous dispersion with an abrasive grain content of 1.0% by mass. Approximately 4 mL of this sample is placed in a 1 cm x 1 cm cell, and the cell is then set in the device for measurement.

[0036] The abrasive grains containing hydroxides of tetravalent metal elements have an absorbance of 1.00 or more for light with a wavelength of 400 nm in an aqueous dispersion containing the abrasive grains adjusted to 1.0 mass %. This makes it possible to further improve the polishing speed of the material to be removed (e.g., insulating material). The reason for this is not entirely clear, but it is thought that the amount of one tetravalent metal ion (M 4+ ) to 1 to 3 hydroxide ions (OH -) and 1 to 3 anions (X c- ) and having the formula M(OH) a X b (where a + b × c = 4) is considered to be generated as part of the abrasive grains (note that such particles are also "abrasive grains containing hydroxides of tetravalent metal elements"). M(OH) a X b So, electron-withdrawing anions (X c- ) acts to improve the reactivity of hydroxide ions, and M(OH) a X b It is believed that the polishing rate increases as the amount of M(OH) increases. a X b Since the particle represented by absorbs light with a wavelength of 400 nm, M(OH) a X b It is believed that the polishing rate increases as the amount of present increases and the absorbance of light with a wavelength of 400 nm increases.

[0037] Abrasive grains containing hydroxides of tetravalent metal elements have the formula M(OH) a X b It is believed that this may include not only particles represented by the formula M(OH)4, MO2, etc. c- ) as NO3 - , SO4 2- etc.

[0038] The abrasive grains have the composition formula M(OH) a X b The presence of anions (X) was confirmed by thoroughly washing the abrasive grains with pure water and then measuring the X-ray diffraction intensity using the FT-IR ATR (Fourier Transform Infra Red Spectrophotometer Attenuated Total Reflection) method. c- ) can be confirmed by detecting the peak corresponding to the anion (X c-) can also be confirmed. From X-ray absorption fine structure (XAFS) measurements, EXAFS analysis can be performed to identify M and anions (X c- ) can also be checked for binding.

[0039] where M(OH) a X b It has been confirmed that the absorption peak at a wavelength of 400 nm of (for example, M(OH)3X) is much smaller than the absorption peak at a wavelength of 290 nm, which will be described later. In contrast, in an aqueous dispersion containing 1.0 mass % abrasive grains, which has a relatively high abrasive grain content and is therefore easily detectable, using abrasive grains that give an absorbance of 1.00 or more for light with a wavelength of 400 nm is highly effective in improving the removal rate of the material to be removed (for example, an insulating material).

[0040] The absorbance for light with a wavelength of 400 nm is preferably 1.00 or more, more preferably 1.20 or more, even more preferably 1.40 or more, particularly preferably 1.50 or more, extremely preferably 1.80 or more, and very preferably 2.00 or more, from the viewpoint of obtaining an even better polishing rate for the material to be removed (e.g., an insulating material).

[0041] The polishing speed of the material to be removed (e.g., insulating material) can be further improved by using abrasive grains containing hydroxides of tetravalent metal elements that exhibit an absorbance of 1.000 or more for light with a wavelength of 290 nm in an aqueous dispersion containing the abrasive grains at a content of 0.0065 mass %. The reason for this is not entirely clear, but it is believed that hydroxides of tetravalent metal elements, which are produced depending on the manufacturing conditions, have a composition formula of M(OH) a X b (e.g., M(OH)3X) particles have a calculated absorption peak at a wavelength of around 290 nm, e.g., Ce 4+ (OH - )3NO3 - Particles made of M(OH) have an absorption peak at a wavelength of 290 nm. a X b It is believed that the polishing rate increases as the amount of SiO increases and the absorbance of light with a wavelength of 290 nm increases.

[0042] Here, the absorbance of light at a wavelength of around 290 nm tends to be detected so high that it exceeds the measurement limit. In contrast, when using abrasive grains that give an absorbance of 1.000 or more at a wavelength of 290 nm in an aqueous dispersion containing 0.0065 mass % abrasive grains, which has a relatively small abrasive grain content and is therefore easily detected as having a small absorbance, the polishing rate of the material to be removed (e.g., insulating material) can be improved effectively.

[0043] From the viewpoint of polishing the material to be removed at a higher polishing rate, the absorbance for light having a wavelength of 290 nm is preferably 1.000 or more, more preferably 1.050 or more, even more preferably 1.100 or more, particularly preferably 1.150 or more, and extremely preferably 1.190 or more. The absorbance for light having a wavelength of 290 nm is preferably 10,000 or less.

[0044] When the abrasive grains that provide an absorbance of 1.00 or more for light with a wavelength of 400 nm provide an absorbance of 1.000 or more for light with a wavelength of 290 nm in an aqueous dispersion in which the abrasive grain content is adjusted to 0.0065 mass %, the material to be removed can be polished at an even better polishing rate.

[0045] Hydroxides of tetravalent metal elements (e.g., M(OH)aXb) tend not to absorb light with wavelengths of 450 nm or longer, particularly light with wavelengths of 450 to 600 nm. Therefore, from the perspective of polishing the target material at an even better polishing rate while suppressing the adverse effects of impurities on polishing, it is preferable that the abrasive grains have an absorbance of 0.010 or less for light with wavelengths of 450 to 600 nm in an aqueous dispersion adjusted to a content of 0.0065% by mass (65 ppm). That is, it is preferable that the absorbance for all light in the wavelength range of 450 to 600 nm in an aqueous dispersion adjusted to a content of 0.0065% by mass does not exceed 0.010. The lower limit of the absorbance for light with wavelengths of 450 to 600 nm is preferably 0.

[0046] The absorbance of the aqueous dispersion can be measured, for example, using a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Specifically, for example, an aqueous dispersion with an abrasive grain content adjusted to 1.0 mass % or 0.0065 mass % is prepared as a measurement sample. Approximately 4 mL of this measurement sample is placed in a 1 cm square cell, and the cell is placed in the device. Next, absorbance is measured in the wavelength range of 200 to 600 nm, and the absorbance is determined from the resulting chart.

[0047] The absorbance and light transmittance provided by abrasive grains in an aqueous dispersion can be measured by preparing an aqueous dispersion with a predetermined abrasive grain content after removing solid components other than abrasive grains and liquid components other than water. Removal of solid or liquid components can be performed using various methods, depending on the components contained in the polishing solution; centrifugation methods such as centrifugation using a centrifuge capable of applying a gravitational acceleration of several thousand Gs or less, or ultracentrifugation using an ultracentrifuge capable of applying a gravitational acceleration of several tens of thousands Gs or more; chromatography methods such as partition chromatography, adsorption chromatography, gel permeation chromatography, and ion exchange chromatography; filtration methods such as gravity filtration, vacuum filtration, pressure filtration, and ultrafiltration; and distillation methods such as vacuum distillation and atmospheric distillation, or any combination of these methods.

[0048] For example, when the polishing liquid contains a compound with a weight-average molecular weight of several tens of thousands or more (e.g., 50,000 or more), methods such as chromatography and filtration are available, with gel permeation chromatography and ultrafiltration being preferred. When filtration is used, the abrasive particles contained in the polishing liquid can be passed through a filter by setting appropriate conditions. When the polishing liquid contains a compound with a weight-average molecular weight of several tens of thousands or less (e.g., less than 50,000), methods such as chromatography, filtration, and distillation are available, with gel permeation chromatography, ultrafiltration, and reduced-pressure distillation being preferred. When the polishing liquid contains abrasive particles other than abrasive particles containing hydroxides of tetravalent metal elements, methods such as filtration and centrifugation are available, with the filtrate containing more abrasive particles containing hydroxides of tetravalent metal elements being contained in the filtrate in the case of filtration, and the liquid phase containing more abrasive particles containing hydroxides of tetravalent metal elements being contained in the liquid phase in the case of centrifugation.

[0049] In the method for separating the abrasive grains by chromatography, for example, the abrasive grains and / or other components can be separated under the following conditions.

[0050] Sample solution: 100 μL of polishing solution Detector: Hitachi, Ltd., UV-VIS detector, product name: L-4200, wavelength: 400 nm Integrator: Hitachi, Ltd., GPC Integrator, Product Name: D-2500 Pump: Hitachi, Ltd., Product name: L-7100 Column: Hitachi Chemical Co., Ltd., packed column for aqueous HPLC, product name: GL-W550S Eluent: deionized water Measurement temperature: 23℃ Flow rate: 1 mL / min (Pressure: 40-50 kgf / cm 2 (approximately 3.9 to 4.9 MPa) Measurement time: 60 minutes

[0051] It is preferable to degas the eluent using a degasser before performing chromatography. If a degasser cannot be used, it is preferable to degas the eluent in advance using ultrasound or the like.

[0052] Depending on the components contained in the polishing solution, it may not be possible to separate the abrasive particles even under the above conditions. In such cases, the abrasive particles can be separated by optimizing the amount of sample solution, type of column, type of eluent, measurement temperature, flow rate, etc. By adjusting the pH of the polishing solution and adjusting the distillation time of the components contained in the polishing solution, it may be possible to separate the components from the abrasive particles. If the polishing solution contains insoluble components, it is preferable to remove them by filtration, centrifugation, etc., as necessary.

[0053] The abrasive grains may contain components other than hydroxides of tetravalent metal elements (e.g., ceria, silica, alumina, zirconia, organic resin particles, etc.), but the content of hydroxides of tetravalent metal elements is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 98% by mass or more, and extremely preferably 99% by mass or more, based on the total mass of the abrasive grains. From the viewpoints of easy preparation of the abrasive and further excellent polishing properties, the abrasive grains are preferably composed of hydroxides of tetravalent metal elements (substantially 100% by mass of the abrasive grains are hydroxides of tetravalent metal elements). Note that components other than hydroxides of tetravalent metal elements may be contained in the abrasive grains as particles composed of components other than hydroxides of tetravalent metal elements, or may be contained in the abrasive grains as particles containing hydroxides of tetravalent metal elements and components other than hydroxides of tetravalent metal elements.

[0054] (polymer) The polymer contains a structural unit represented by the above formula (1). The structural unit represented by the above formula (1) may be rephrased as a structural unit derived from vinylpyrrolidone. That is, the polymer may be a homopolymer of vinylpyrrolidone (polyvinylpyrrolidone) or a copolymer of vinylpyrrolidone and another copolymerization component.

[0055] The content of the structural unit represented by formula (1) is preferably 0.00001% by mass or more, more preferably 0.0001% by mass or more, and even more preferably 0.001% by mass or more, based on the total mass of the polymer. When the content of the structural unit represented by formula (1) is equal to or greater than the above-mentioned lower limit, over-polishing of the stopper tends to be more effectively suppressed. The content of the structural unit represented by formula (1) is preferably 10% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less, based on the total mass of the polymer. When the content of the structural unit represented by formula (1) is equal to or less than the above-mentioned upper limit, the polishing rate of silicon oxide (SiO2), which is the object to be polished, tends not to decrease.

[0056] The polymer may further contain a structural unit other than the structural unit represented by formula (1). As the structural unit other than the structural unit represented by formula (1), a structural unit derived from a (meth)acrylic acid ester is preferred from the viewpoint of further suppressing over-polishing of the stopper. Here, the (meth)acrylic acid ester means an acrylic acid ester and a methacrylic acid ester.

[0057] In order to further suppress over-polishing of the stopper, it is preferable that the structural unit other than the structural unit represented by formula (1) has a cationic group (e.g., a quaternary ammonium group). The counter anion of the cationic group is, for example, F - , Cl - , Br - , I - , CH3COO - , CF3COO - , CH3SO3 - , CH3CH2SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOSO3 - and H2PO4 - etc.

[0058] From the above viewpoint, the polymer more preferably contains a structural unit derived from a (meth)acrylic acid ester having a cationic group, and further preferably contains a structural unit represented by the following formula (2). [ka]

[0059] In formula (2), R 1 represents a hydrogen atom or a methyl group, and R 2 ~R 4 each independently represents a hydrocarbon group having 1 to 4 carbon atoms, n represents an integer of 1 or more and 4 or less, and X - represents a counter anion, and * represents a bond. The structural unit represented by formula (2) is 1 ~R 3 is a methyl group, and R 4A structural unit in which is an ethyl group and n is 2 is preferred.

[0060] The polymer further comprising a structural unit derived from a (meth)acrylic acid ester may be obtained by polymerizing vinylpyrrolidone with a (meth)acrylic acid ester, or by polymerizing vinylpyrrolidone with a (meth)acrylic acid ester and then reacting the resulting polymer with other components. For example, a polymer further comprising a structural unit derived from a (meth)acrylic acid ester may be obtained by polymerizing vinylpyrrolidone with a (meth)acrylic acid ester having a tertiary amino group, followed by alkylating the tertiary amino group in the resulting polymer. In other words, the polymer may be a quaternary ammonium salt containing a quaternary ammonium group.

[0061] From the viewpoint of further suppressing overpolishing of the stopper, the content of the structural unit derived from the (meth)acrylic acid ester is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and even more preferably 40 to 60 mass %, based on the total mass of the polymer. In this embodiment, the content of the structural unit represented by formula (2) is preferably within the above range.

[0062] From the viewpoint of further suppressing over-polishing of the stopper, the weight-average molecular weight of the polymer is preferably 50,000 or more, more preferably 100,000 or more, even more preferably 300,000 or more, particularly preferably 400,000 or more, and extremely preferably 500,000 or more. From the viewpoint of reducing the polishing rate of silicon oxide (SiO2), which is the object to be polished, the weight-average molecular weight of the polymer is preferably 5,000,000 or less, more preferably 3,000,000 or less, and even more preferably 2,000,000 or less. From these viewpoints, the weight-average molecular weight of the polymer is preferably 50,000 to 5,000,000.

[0063] The weight average molecular weight can be measured, for example, by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene under the following conditions. Equipment used: Hitachi L-6000 model [manufactured by Hitachi, Ltd.] Columns: Gel Pack GL-R420 + Gel Pack GL-R430 + Gel Pack GL-R440 [Hitachi Chemical Co., Ltd. product name, total of 3] Eluent: tetrahydrofuran Measurement temperature: 40℃ Flow rate: 1.75mL / min Detector: L-3300RI [Hitachi, Ltd.]

[0064] A specific example of a suitable polymer is polyquaternium-11.

[0065] The polymer content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, particularly preferably 2 parts by mass or more, and extremely preferably 3 parts by mass or more, per 100 parts by mass of abrasive grains, from the viewpoint of further suppressing over-polishing of the stopper. The polymer content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 7 parts by mass or less, per 100 parts by mass of abrasive grains, from the viewpoint of reducing the polishing rate of silicon oxide (SiO2) to be polished. From these viewpoints, the polymer content is preferably 0.1 to 20 parts by mass, per 100 parts by mass of abrasive grains.

[0066] (liquid medium) The liquid medium is preferably water such as deionized water, ultrapure water, etc. The content of the liquid medium may be the remainder of the polishing liquid excluding the contents of other constituents.

[0067] (Optional additives) The polishing liquid may further contain any additive (excluding compounds that fall under the category of polymers) for the purpose of adjusting the polishing characteristics.

[0068] The optional additives include, for example, polyoxyalkylene compounds and water-soluble polymers.

[0069] Examples of the polyoxyalkylene compound include polyalkylene glycols and polyoxyalkylene derivatives.

[0070] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polybutylene glycol, etc. The polyalkylene glycol is preferably at least one selected from the group consisting of polyethylene glycol and polypropylene glycol, and more preferably polyethylene glycol.

[0071] The polyoxyalkylene derivative is, for example, a compound in which a functional group or a substituent is introduced into a polyalkylene glycol, or a compound in which a polyalkylene oxide is added to an organic compound. Examples of the functional group or substituent include an alkyl ether group, an alkylphenyl ether group, a phenyl ether group, a styrenated phenyl ether group, a glyceryl ether group, an alkylamine group, a fatty acid ester group, and a glycol ester group. Examples of polyoxyalkylene derivatives include polyoxyethylene alkyl ethers, polyoxyethylene distyrenated phenyl ethers (e.g., the Emulgen series manufactured by Kao Corporation), polyoxyethylene alkylphenyl ethers (e.g., the Noigen EA series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), polyoxyalkylene polyglyceryl ethers (e.g., the SC-E series and SC-P series manufactured by Sakamoto Pharmaceutical Co., Ltd.), polyoxyethylene sorbitan fatty acid esters (e.g., the Solgen TW series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), polyoxyethylene fatty acid esters (e.g., the Emanone series manufactured by Kao Corporation), polyoxyethylene alkylamines (e.g., Amiladin D manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and other compounds to which polyalkylene oxides are added (e.g., Surfynol 465 manufactured by Nissin Chemical Industry Co., Ltd., and the TMP series and BAP4-30H manufactured by Nippon Nyukazai Co., Ltd.).

[0072] The weight-average molecular weight of the polyoxyalkylene compound is preferably 100,000 or less, more preferably 50,000 or less, even more preferably 20,000 or less, particularly preferably 10,000 or less, and extremely preferably 5,000 or less, from the viewpoint of easily obtaining suitable workability and foamability.The weight-average molecular weight of the polyoxyalkylene compound is preferably 200 or more, more preferably 400 or more, even more preferably 500 or more, particularly preferably 1,000 or more, and extremely preferably 1,500 or more, from the viewpoint of further improving polishing selectivity and flatness.The weight-average molecular weight can be measured in the same manner as the above polymer.

[0073] From the viewpoint of further improving polishing selectivity and flatness, the content of the polyoxyalkylene compound is preferably 0.01 mass% or more, more preferably 0.02 mass% or more, even more preferably 0.1 mass% or more, particularly preferably 0.3 mass% or more, extremely preferably 0.4 mass% or more, and very preferably 0.5 mass% or more, based on the total mass of the polishing liquid.From the viewpoint of easily obtaining a moderate polishing rate, the content of the polyoxyalkylene compound is preferably 5 mass% or less, more preferably 2 mass% or less, and even more preferably 1 mass% or less, based on the total mass of the polishing liquid.In addition, when multiple compounds are used as the polyoxyalkylene compound, it is preferable that the total content of each compound satisfies the above range.

[0074] Water-soluble polymers have the effect of adjusting polishing characteristics such as flatness, in-plane uniformity, polishing selectivity of silicon oxide over silicon nitride (polishing rate of silicon oxide / polishing rate of silicon nitride), and polishing selectivity of silicon oxide over polysilicon (polishing rate of silicon oxide / polishing rate of polysilicon). Here, a "water-soluble polymer" is defined as a polymer that dissolves at least 0.1 g in 100 g of water.

[0075] Examples of water-soluble polymers include acrylic polymers such as polyacrylamide and polydimethylacrylamide; polysaccharides such as alginic acid, pectinic acid, carboxymethyl cellulose, agar, curdlan, dextrin, cyclodextrin, and pullulan; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrolein; glycerin-based polymers such as polyglycerin and polyglycerin derivatives; polyethylene glycol, etc. The water-soluble polymers can be used alone or in combination of two or more.

[0076] When a water-soluble polymer is used, the content of the water-soluble polymer is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and even more preferably 0.01% by mass or more, based on the total mass of the polishing liquid, from the viewpoint of suppressing the settling of abrasive grains while obtaining the effect of adding the water-soluble polymer.The content of the water-soluble polymer is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of suppressing the settling of abrasive grains while obtaining the effect of adding the water-soluble polymer.When multiple compounds are used as the water-soluble polymer, it is preferable that the total content of each compound satisfies the above range.

[0077] In addition to the above, the polishing liquid may further contain a cationic compound, a carboxylic acid, an amino acid, an oxidizing agent (for example, hydrogen peroxide), and the like.

[0078] (Characteristics of polishing liquid) The pH of the polishing liquid is preferably 3.0 or higher, more preferably 3.2 or higher, and even more preferably 3.5 or higher, from the viewpoint of further improving the polishing rate of the material to be removed. The pH of the polishing liquid is preferably 5.0 or lower, more preferably 4.7 or lower, and even more preferably 4.5 or lower, from the viewpoint of further improving the polishing suppression effect of the stopper material. The pH of the polishing liquid is preferably 3.0 to 5.0, from the viewpoint of improving the storage stability of the polishing liquid and further improving the polishing suppression effect of the stopper material. The pH of the polishing liquid is defined as the pH at a liquid temperature of 25°C.

[0079] The pH of the polishing solution can be adjusted by adding an acid component such as an inorganic acid or an organic acid, or an alkaline component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, or alkanolamine. To stabilize the pH, a buffering agent or a buffer solution (a solution containing a buffering agent) may be used. Examples of buffer solutions include acetate buffer solutions and phthalate buffer solutions.

[0080] The pH of the polishing solution can be measured with a pH meter (e.g., Model PHL-40 manufactured by Denki Kagaku Keiki Co., Ltd.). Specifically, for example, after two-point calibration of the pH meter using a phthalate pH buffer solution (pH: 4.01) and a neutral phosphate pH buffer solution (pH: 6.86) as standard buffer solutions, the pH meter electrode is placed in the polishing solution and the value is measured after stabilization for at least two minutes. The liquid temperatures of both the standard buffer solution and the polishing solution are 25°C.

[0081] (How to save) The polishing liquid of this embodiment is a one-component polishing liquid, and may be stored as a stock liquid for polishing liquid with a reduced content of liquid medium during storage. This stock liquid may be diluted with the liquid medium during polishing.

[0082] <Polishing liquid set> One embodiment of the polishing liquid set is a multi-liquid (e.g., two-liquid) polishing liquid set in which the components of the polishing liquid are separated into a first liquid and a second liquid so that the polishing liquid of the above embodiment is obtained by mixing the first liquid (slurry) and the second liquid (additive liquid). The polishing liquid set includes, for example, a first liquid containing abrasive grains containing a hydroxide of a tetravalent metal element and a liquid medium, and a second liquid containing a polymer containing a structural unit represented by formula (1). Of the first and second liquids, the optional additive is preferably contained in the second liquid. In the polishing liquid set, the first and second liquids are mixed to prepare the polishing liquid immediately before or during polishing. The polishing rate can be adjusted by arbitrarily changing the composition of the first and second liquids. The polishing liquid set may be stored as a stock liquid for slurry and a stock liquid for additive liquid, each of which has a reduced content of the liquid medium. These stock liquids may be diluted with the liquid medium during polishing.

[0083] <Polishing method> 1 is a schematic cross-sectional view showing a polishing method according to one embodiment. The polishing method according to one embodiment includes the steps of: preparing an article 4 having a substrate 1 having a concave-convex pattern; a stopper 2 containing silicon nitride arranged on the convex portions of the substrate 1; and a polished portion 3 containing silicon oxide arranged on the substrate 1 and the stopper 2 so as to fill the concave portions of the substrate 1; and polishing a portion of the polished portion 3 (at least the portion located on the stopper 2) using the polishing liquid according to the above embodiment or a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to the above embodiment. The polished portion 3 may also be referred to as an insulating portion.

[0084] The substrate 1 may be, for example, a substrate used in semiconductor device manufacturing (e.g., a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed). The concave-convex pattern may be, for example, an L / S pattern. The L / S pitch may be, for example, 0.1 μm / 0.1 μm or less.

[0085] The stopper 2 contains silicon nitride as a stopper material. The stopper 2 is formed of, for example, a stopper material containing silicon nitride. The content of silicon nitride in the stopper 2 is, for example, 90% by mass or more, and may be 95% by mass or more, or 99% by mass or more. The stopper 2 may contain elements other than silicon and nitrogen (carbon, hydrogen, etc.) in order to adjust the material.

[0086] The polishing target portion 3 contains silicon oxide as an insulating material. The polishing target portion 3 is formed of, for example, an insulating material containing silicon oxide. The content of silicon oxide in the polishing target portion 3 is, for example, 90 mass % or more, and may be 95 mass % or more or 99 mass % or more. The polishing target portion 3 may contain trace amounts of boron (B), phosphorus (P), carbon (C), etc. to improve embeddability.

[0087] The stopper 2 and the polished portion 3 can be formed by, for example, a CVD method such as a low-pressure CVD method, a sub-atmospheric pressure CVD method, or a plasma CVD method; or a spin-coating method in which a liquid source is applied to a rotating substrate.

[0088] Specifically, the polished portion 3 containing silicon oxide can be obtained by, for example, using a low-pressure CVD method to thermally react monosilane (SiH4) with oxygen (O2), a sub-atmospheric pressure CVD method to thermally react tetraethoxysilane (Si(OC2H5)4) with ozone (O3), a plasma reaction between tetraethoxysilane and oxygen, or a spin coating method to apply a liquid raw material containing inorganic polysilazane, inorganic siloxane, etc. onto a substrate and then subject it to a thermal curing reaction in a furnace or the like.

[0089] For example, a stopper containing silicon nitride can be formed by a low-pressure CVD method in which dichlorosilane and ammonia are thermally reacted, or a plasma CVD method in which monosilane, ammonia, and nitrogen are plasma-reacted.

[0090] A polishing machine can be used in the polishing step. Specifically, a general polishing machine having a holder capable of holding the article 4 and a polishing platen to which a polishing pad can be attached can be used. Each of the holder and the polishing platen is equipped with a motor or the like capable of changing the rotation speed. For example, the polishing machine Reflexion manufactured by APPLIED MATERIALS can be used as the polishing machine.

[0091] As the polishing pad, general nonwoven fabrics, foams, non-foams, etc. can be used. As the material of the polishing pad, resins such as polyurethane, acrylic resin, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (e.g., Nylon (trade name) and aramid), polyimide, polyimideamide, polysiloxane copolymer, oxirane compound, phenolic resin, polystyrene, polycarbonate, and epoxy resin can be used. As the material of the polishing pad, at least one selected from the group consisting of foamed polyurethane and non-foamed polyurethane is preferred, particularly from the viewpoint of further improving the polishing rate and flatness. The polishing pad is preferably provided with grooves to allow the polishing liquid to accumulate.

[0092] In the polishing step, for example, while the portion to be polished 3 of the article 4 is pressed against a polishing pad (abrasive cloth) on a polishing table, a polishing liquid is supplied between the portion to be polished 3 and the polishing pad, and the article 4 and the polishing table are moved relative to each other to polish the surface (surface to be polished) of the portion to be polished 3. By polishing the portion to be polished 3 and removing excess portions, unevenness on the surface of the article 4 is eliminated, resulting in a polished article 5 having a smooth surface across its entire surface. The polished article 5 comprises a substrate 1, a stopper 2 arranged on the convex portion of the substrate 1, and a remaining portion 3' of the portion to be polished 3 arranged on the concave portion of the substrate 1. Note that part of the stopper 2 may be removed in the polishing step.

[0093] In the case of a one-component polishing liquid, methods for supplying the polishing liquid onto the polishing table include a method in which the polishing liquid is directly pumped and supplied; a method in which the polishing liquid storage liquid and the liquid medium are pumped through separate pipes and then joined and mixed before supply; and a method in which the polishing liquid storage liquid and the liquid medium are mixed in advance before supplying.

[0094] When polishing using a polishing liquid set, the polishing liquid can be supplied onto the polishing platen using the following methods. For example, a method in which the slurry and the additive liquid are sent through separate pipes and then merged and mixed before supplying; a method in which a slurry storage liquid, an additive storage liquid, and a liquid medium are sent through separate pipes and then merged and mixed before supplying; a method in which the slurry and the additive liquid are mixed in advance before supplying; a method in which the slurry storage liquid, the additive storage liquid, and a liquid medium are mixed in advance before supplying; etc. can also be used. A method in which the slurry and the additive liquid in the polishing liquid set are each supplied onto the polishing platen can also be used. In this case, the surface to be polished is polished using the polishing liquid obtained by mixing the slurry and the additive liquid on the polishing platen.

[0095] There are no restrictions on polishing conditions, but the rotation speed of the polishing platen should be set to 200 min to prevent the semiconductor substrate from popping out. -1 The polishing pressure (processing load) applied to the semiconductor substrate is preferably 100 kPa or less from the viewpoint of sufficiently suppressing the occurrence of polishing scratches. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad using a pump or the like. There is no limit to the amount of supply, but it is preferable that the surface of the polishing pad is always covered with the polishing liquid.

[0096] After polishing, the article is preferably thoroughly washed in running water to remove particles adhering to the article. Dilute hydrofluoric acid or aqueous ammonia may be used in addition to pure water for washing, and a brush may also be used to improve washing efficiency. After washing, it is preferable to use a spin dryer or the like to remove water droplets adhering to the polished article and then dry the article.

[0097] Although the polishing method of this embodiment has been described above, the present invention is not limited to the above embodiment. For example, the polishing liquid and polishing liquid set of this embodiment can be applied to materials other than silicon oxide. That is, the material to be removed may be a material other than a material containing silicon oxide. Examples of such materials include high-dielectric-constant materials such as Hf-based, Ti-based, and Ta-based oxides; semiconductor materials such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; phase-change materials such as GeSbTe; inorganic conductive materials such as ITO; and polymer resin materials such as polyimide, polybenzoxazole, acrylic, epoxy, and phenolic. The stopper may be formed of a stopper material (e.g., polysilicon) other than a material containing silicon nitride. The article to be polished may also include an article having a polished portion but no stopper. The polishing liquid and polishing liquid set of this embodiment may be applied not only to film-like objects to be polished, but also to various substrates made of glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, plastic, and the like.

[0098] The polishing liquid and polishing liquid set of this embodiment can be used not only in the manufacture of semiconductor elements, but also in the manufacture of image display devices such as TFTs and organic ELs; optical components such as photomasks, lenses, prisms, optical fibers, and single-crystal scintillators; optical elements such as optical switching elements and optical waveguides; light-emitting elements such as solid-state lasers and blue laser LEDs; and magnetic storage devices such as magnetic disks and magnetic heads. [Example]

[0099] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0100] <Synthesis of hydroxides of tetravalent metal elements> A solution was obtained by mixing 350 g of a 650 mass% aqueous solution of Ce(NH4)2(NO3) (manufactured by Nippon Chemical Industry Co., Ltd., product name: CAN50 Liquid) with 7825 g of pure water. Next, while stirring this solution, 750 g of an aqueous solution of imidazole (10 mass% aqueous solution, 1.47 mol / L) was added dropwise at a mixing rate of 5 mL / min to obtain a precipitate containing cerium hydroxide. The synthesis of cerium hydroxide was carried out at a temperature of 25°C and a stirring rate of 400 min. -1 The stirring was carried out using a three-blade pitch paddle with a blade length of 5 cm.

[0101] The resulting precipitate containing cerium hydroxide was centrifuged (4000 min -1 After stirring for 5 minutes, the liquid phase was removed by decantation, thereby carrying out solid-liquid separation. 10 g of the particles obtained by solid-liquid separation was mixed with 990 g of water, and the particles were dispersed in the water using an ultrasonic cleaner to prepare a cerium hydroxide slurry (particle content: 1.0 mass%).

[0102] <Measurement of average particle size> The average particle size of the abrasive grains (abrasive grains containing cerium hydroxide) in the cerium hydroxide slurry was measured using a Beckman Coulter DelsaMax PRO (trade name). It was found to be 6 nm. The measurement method is as follows: First, approximately 0.5 mL of the polishing liquid (cerium hydroxide slurry, aqueous dispersion) was placed in a 12.5 mm x 12.5 mm x 45 mm (height) measurement cell, and the cell was then placed in the instrument. Next, the refractive index of the measurement sample was set to 1.333 and the viscosity to 0.887 mPa·s, and the measurement was performed at 25°C.

[0103] <Structural analysis of abrasive grains> An appropriate amount of cerium hydroxide slurry was collected, vacuum dried to isolate the abrasive grains, and then thoroughly washed with pure water to obtain a sample. The obtained sample was measured using the FT-IR ATR method, and hydroxide ions (OH - In addition to the peak due to nitrate ions (NO3 - ) was observed. In addition, when the same sample was subjected to XPS (N-XPS) measurement for nitrogen, a peak due to NH4+ No peak based on [the relevant factor] was observed, but a peak based on nitrate ions was observed. From these results, it was confirmed that the abrasive grains contained in the cerium hydroxide slurry at least partially contained particles having nitrate ions bonded to cerium elements. Also, since it at least partially contained particles having hydroxide ions bonded to cerium elements, it was confirmed that the abrasive grains contained cerium hydroxide. From these results, it was confirmed that cerium hydroxide contained hydroxide ions bonded to cerium elements.

[0104] <Measurement of Absorbance and Light Transmittance> An appropriate amount of the cerium hydroxide slurry was collected and diluted with water so that the abrasive grain content became 0.0065 mass% (65 ppm) to obtain a measurement sample (aqueous dispersion). Approximately 4 mL of this measurement sample was placed in a 1 cm square cell, and the cell was placed inside a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance measurement was performed in the wavelength range of 200 to 600 nm, and the absorbance for light with a wavelength of 290 nm and the absorbance for light with a wavelength of 450 to 600 nm were measured. The absorbance for light with a wavelength of 290 nm was 1.192, and the absorbance for light with a wavelength of 450 to 600 nm was less than 0.010.

[0105] Approximately 4 mL of the cerium hydroxide slurry (particle content: 1.0 mass%) was placed in a 1 cm square cell, and the cell was placed inside a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance measurement was performed in the wavelength range of 200 to 600 nm, and the absorbance for light with a wavelength of 400 nm and the light transmittance for light with a wavelength of 500 nm were measured. The absorbance for light with a wavelength of 400 nm was 2.25, and the light transmittance for light with a wavelength of 500 nm was 92% / cm.

[0106] <Preparation of CMP Polishing Liquid> (Example 1) A CMP polishing solution with a pH of 3.8 was prepared by mixing polyglycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd., weight-average molecular weight: 750), polyoxyethylene distyrenated phenyl ether (manufactured by Kao Corporation, trade name: Emulgen A-500, average number of oxyethylene units added: 50), polyquaternium-11 ("Polymer A" in Table 1, a quaternary ammonium salt obtained from a copolymer of vinylpyrrolidone and dimethylaminoethyl methacrylate and diethyl sulfate; manufactured by Osaka Organic Chemical Industry Ltd., trade name: HC Polymer 2L, weight-average molecular weight: 800,000), and the above-mentioned cerium hydroxide slurry. The pH was adjusted with an acid and a base to prepare a CMP polishing solution. The amounts of each component were adjusted so that the content (solids content, based on the total mass of the polishing solution) of each component was as shown in Table 1.

[0107] The pH of the CMP polishing liquid was evaluated under the following conditions. Measurement temperature: 25±5℃ Measuring device: Electrochemical Instruments Co., Ltd., Model PHL-40 Measurement method: After two-point calibration using standard buffer solutions (phthalate pH buffer solution, pH: 4.01 (25°C); neutral phosphate pH buffer solution, pH: 6.86 (25°C)), the electrode was placed in a CMP polishing solution, and the pH was measured using the measuring device after stabilization for at least 2 minutes.

[0108] Example 2 A CMP polishing liquid with a pH of 3.8 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone ("Polymer B" in Table 1, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., weight-average molecular weight: 450,000) was used instead of polyquaternium-11.

[0109] (Comparative Example 1) A CMP polishing liquid with a pH of 3.8 was prepared in the same manner as in Example 1, except that polyquaternium-11 was not used.

[0110] (Comparative Example 2) A polishing liquid for CMP with a pH of 3.8 was prepared in the same manner as in Example 1, except that a polyoxyethylene polyoxypropylene block polymer of ethylenediamine (Polymer C in Table 1, manufactured by ADEKA Corporation, trade name: Pluronic TR-913R (Pluronic is a registered trademark)) was used instead of polyquaternium-11.

[0111] (Comparative Example 3) A polishing liquid for CMP with a pH of 3.8 was prepared in the same manner as in Example 1, except that polyoxyethylene polyoxypropylene glyceryl ether (Polymer D in Table 1, manufactured by Aoki Yushi Kogyo Co., Ltd., trade name: GEP-10000, ethylene oxide / propylene oxide: 50 / 50, weight average molecular weight: 10,000) was used instead of polyquaternium-11.

[0112] <Evaluation of polishing liquid physical properties> (Measurement of abrasive grain size) When the average particle size of the abrasive grains (abrasive grains containing cerium hydroxide) in the CMP polishing liquids of Examples 1 to 2 and Comparative Examples 1 to 3 was evaluated under the following conditions, it was 6 nm in all cases. Measurement temperature: 25 ± 5°C Measuring device: Manufactured by Beckman Coulter, Inc., trade name: Delsa Max PRO Measurement method: Approximately 0.5 mL of the CMP polishing liquid was placed in a measuring cell of 12.5 mm × 12.5 mm × 45 mm (height), and the cell was installed in the Delsa Max PRO. The refractive index of the measurement sample information in the Delsa Max PRO software was set to 1.333 and the viscosity was set to 0.887 mPa·s for measurement, and the value displayed as the cumulant diameter was read.

[0113] <Evaluation of CMP polishing rate> Using the CMP polishing liquids of Examples 1 to 2 and Comparative Examples 1 to 3, a blanket wafer (a wafer without a pattern formed) as the polished substrate was polished under the following polishing conditions. (CMP polishing conditions) · Polishing device: Reflexion (manufactured by APPLIED MATERIALS) ·CMP polishing liquid flow rate: 200mL / min Polishing pad: Closed-cell polyurethane foam (manufactured by ROHM AND HAAS ELECTRONIC MATERIALS CMP INC., model number IC1010 A6) Polishing pressure: 13.8kPa (2.0psi) Relative speed between substrate and polishing plate: 100.5 m / min Polishing time: 1 minute Cleaning: After CMP processing, the substrate was cleaned with water while irradiating it with ultrasonic waves, and then dried with a spin dryer.

[0114] Specifically, first, as blanket wafers, a substrate in which a 1 μm-thick silicon oxide film was formed on a silicon substrate by plasma CVD, and a substrate in which a 0.2 μm-thick silicon nitride film was formed on a silicon substrate by CVD were prepared.

[0115] The substrate was then polished under the above conditions and cleaned. The difference in film thickness of the polished film before and after polishing was measured using an optical interference film thickness measuring device (Filmetrics, product name: F80), and the polishing rates of the polished films (silicon nitride film and silicon oxide film) (polishing rate of silicon nitride film: SiNRR, and polishing rate of silicon oxide film: SiO2RR) were calculated using the following formula. The results are shown in Table 1. Polishing rate (RR) = [Difference in film thickness before and after polishing (nm)] / [Polishing time (min)]

[0116] <Erosion evaluation> Using the CMP polishing solutions of Examples 1 and 2 and Comparative Examples 1 to 3, a patterned wafer (a patterned wafer on which a simulated pattern was formed) was polished as a substrate to be polished under the following polishing conditions. (CMP polishing conditions) Polishing equipment: Reflexion (Applied Materials) ·CMP polishing liquid flow rate: 200mL / min Polishing pad: Closed-cell polyurethane foam (manufactured by ROHM AND HAAS ELECTRONIC MATERIALS CMP INC., model number IC1010 A6) Polishing pressure: 13.8kPa (2.0psi) Relative speed between substrate and polishing plate: 100.5 m / min Polishing time: Adjusted so that the silicon oxide film on the convex portions was polished and then over-polished by 100 nm. Specifically, it was calculated from the following formula using the polishing rate of the silicon oxide film (SiO2RR) calculated in the above "Evaluation of the polishing rate of CMP". Pattern wafer polishing time (min) = [thickness of silicon oxide film on convex part (nm) / polishing rate of silicon oxide film (min / nm)] + [100 (nm) / polishing rate of silicon oxide film (min / nm)] Cleaning: After CMP processing, the substrate was cleaned with water while irradiating it with ultrasonic waves, and then dried with a spin dryer.

[0117] Specifically, an AMT-STI MASK (diameter: 300 mm) manufactured by Advanced Materials Technology Corporation was first prepared as a patterned wafer. This patterned wafer was obtained by laminating a silicon nitride film as a stopper film on a silicon substrate, forming trenches in an exposure process, and laminating a silicon oxide film (SiO2 film) as an insulating film on the silicon substrate and silicon nitride film so as to fill the silicon nitride film and trenches. The silicon oxide film was formed by the HDP (High Density Plasma) method. The lines (protrusions) and spaces (recesses) had a narrow-pitch pattern with a pitch of 0.36 μm and a protrusion pattern density of 50%.

[0118] Here, the line and space is a simulated pattern in which active portions (protrusions) masked with a silicon nitride film (stopper film) and trench portions (recesses) in which grooves are formed are arranged alternately. For example, "line and space at a 0.36 μm pitch" means that the total width of the line and space portions is 0.36 μm. Also, for example, "line and space at a 0.36 μm pitch and a protrusion pattern density of 50%" means a pattern in which protrusions with a protrusion width of 0.18 μm and recesses with a recess width of 0.18 μm are arranged alternately. The size of the above pattern is 2.2 mm × 2.2 mm, and the pattern is surrounded on all four sides by 50 μm protrusion patterns (50 μm pattern portions).

[0119] In the patterned wafer, the thickness of the silicon oxide film was 420 nm on both the silicon substrate and the silicon nitride film. Specifically, the thickness of the silicon nitride film on the silicon substrate was 130 nm, the thickness of the convex portion of the silicon oxide film was 420 nm, the thickness of the concave portion of the silicon oxide film was 420 nm, and the trench depth was 180 nm.

[0120] Next, the patterned wafer was polished to a residual step of 100 nm or less using a known CMP abrasive that exhibits self-stopping properties (the property of decreasing the polishing rate as the residual step of the simulated pattern decreases). Specifically, a polishing agent consisting of HS-8005-D4 (product name) manufactured by Hitachi Chemical Co., Ltd., HS-7303GP (product name) manufactured by Hitachi Chemical Co., Ltd., and water in a ratio of 2:1.2:6.8 was used to polish the wafer until the silicon oxide film thickness of the convex portions at a 0.36 μm pitch and 50% convex pattern density was 100 nm. This resulted in a polished substrate 10 shown in FIG. 2(a). In FIG. 2, reference numeral 11 denotes a silicon substrate, reference numeral 12 denotes a silicon nitride film (stopper film), and reference numeral 13 denotes a silicon oxide film.

[0121] Next, the substrate to be polished was polished under the above conditions and washed to obtain the polished substrate 20 shown in FIG. 2(b). The two-dimensional uneven shape of the obtained substrate 20 was measured. An automatic atomic force profiler (manufactured by Bruker, product name: InSight CAP) was used to measure the two-dimensional uneven shape. From the results of measuring the two-dimensional uneven shape after polishing, the silicon nitride film in the 50 μm pattern portion was used as the reference, and the height difference D therebetween was determined to be the erosion of the narrow-pitch pattern portion. The results are shown in Table 1.

[0122] [Table 1] [Explanation of symbols]

[0123] 1... Base material, 2... Stopper, 3... Part to be polished, 4... Article (before polishing), 5... Article (after polishing).

Claims

1. abrasive grains containing a hydroxide of a tetravalent metal element; a polymer including a structural unit represented by the following formula (1) and a structural unit derived from a (meth)acrylic acid ester; a liquid medium; The polishing liquid, wherein the structural unit derived from a (meth)acrylic acid ester is a structural unit represented by the following formula (2): 【Chemical 1】 [In formula (1), * represents a bond.] 【Chemistry 2】 [In formula (2), R 1 represents a hydrogen atom or a methyl group, R 2 to R 4 each independently represent a hydrocarbon group having 1 to 4 carbon atoms, n represents an integer of 1 to 4, X − represents a counter anion, and * represents a bond.]

2. The polishing liquid described in claim 1, further containing a polyoxyalkylene compound.

3. A polishing liquid as described in claim 1 or 2, further containing polyglycerin.

4. 4. The polishing liquid according to claim 1, wherein the polymer has a weight-average molecular weight of 50,000 or more.

5. 5. The polishing liquid according to claim 1, wherein the hydroxide of the tetravalent metal element is cerium hydroxide.

6. 6. The polishing liquid according to claim 1, wherein the pH is 3.0 to 5.

0.

7. 7. The polishing liquid according to claim 1, which is used for selectively polishing silicon oxide relative to silicon nitride.

8. A polishing liquid set, wherein the components of the polishing liquid according to any one of claims 1 to 7 are stored separately as a first liquid and a second liquid, the first liquid containing the abrasive grains and a liquid medium, and the second liquid containing the polymer and a liquid medium.

9. a step of preparing an article including a substrate having a concave-convex pattern, a stopper containing silicon nitride arranged on the convex portions of the substrate, and a polished portion containing silicon oxide arranged on the substrate and the stopper so as to fill the concave portions of the substrate; and polishing a portion of the polished portion using the polishing liquid according to any one of claims 1 to 7 or a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8.

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