Grinding slurry and grinding method

Abstract

A polishing slurry containing abrasive grains, a liquid medium, and a salt of a compound represented by formula (1), the abrasive grains containing first particles and second particles in contact with the first particles, the first particles containing a cerium oxide, and the second particles containing a hydroxide of a tetravalent metal element. [In formula (1), R represents a hydroxyl group or a monovalent organic group. ]

Description

This application is a divisional application of the following application. Parent Application Date: August 30, 2018 Parent Application No.: 201880055358.0 (PCT / JP2018 / 032133) Parent Application Title: Slurry for polishing and polishing method TECHNICAL FIELD

[0001] The present application relates to a slurry for polishing and a polishing method. BACKGROUND

[0002] In the manufacturing process of semiconductor elements in recent years, the importance of processing techniques for high-density and miniaturization is increasing. The CMP (chemical mechanical polishing) technique, which is one of the processing techniques, is a necessary technique in the manufacturing process of semiconductor elements for the formation of a shallow trench isolation (hereinafter referred to as "STI"), the planarization of an insulating portion formed of a pre-metal insulating material or an interlayer insulating material, the formation of a plug or a buried metal wiring, and the like.

[0003] As the most used polishing liquid, for example, a silica-based polishing liquid containing silica (silicon oxide) particles such as fumed silica, colloidal silica, or the like as abrasive grains can be cited. The silica-based polishing liquid is characterized by high versatility, and by appropriately selecting the abrasive grain content, pH, additives, and the like, a wide variety of materials can be polished regardless of insulating materials and conductive materials.

[0004] On the other hand, as a polishing liquid mainly targeting insulating materials such as silicon oxide, the demand for a polishing liquid containing cerium compound particles as abrasive grains is also expanding. For example, a ceria-based polishing liquid containing ceria (ceria) particles as abrasive grains can polish silicon oxide at high speed even with a lower abrasive grain content than the silica-based polishing liquid (for example, refer to Patent Documents 1 and 2 described below).

[0005] However, in recent years, in the manufacturing process of semiconductor elements, further miniaturization of wiring is required, and polishing damage generated at the time of polishing becomes a problem. That is, even if a slight polishing damage is generated when polishing is performed using a conventional ceria-based polishing liquid, as long as the size of the polishing damage is smaller than the width of the conventional wiring, it does not become a problem, but in the case where further miniaturization of wiring is desired, even a slight polishing damage becomes a problem.

[0006] In order to solve this problem, a slurry using particles of hydroxide of a tetravalent metal element is being studied (for example, refer to Patent Documents 3 to 5 below). In addition, a method for producing particles of hydroxide of a tetravalent metal element is also being studied (for example, refer to Patent Documents 6 and 7 below). These technologies minimize mechanical action while exerting the chemical action of the particles of hydroxide of a tetravalent metal element, thereby reducing the polishing damage caused by the particles. [Related Art Documents] [Patent Document 1]

[0007] [Patent Document 1] JP Laid-Open Patent Publication No. 10-106994 [Patent Document 2] JP Laid-Open Patent Publication No. 08-022970 [Patent Document 3] WO 2002 / 067309 [Patent Document 4] WO 2012 / 070541 [Patent Document 5] WO 2012 / 070542 [Patent Document 6] JP Laid-Open Patent Publication No. 2006-249129 [Patent Document 7] WO 2012 / 070544 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in recent years, 3D-NAND devices in which unit portions of a device are stacked in the longitudinal direction are on the rise. In this technology, the step difference of the insulating portion at the time of unit formation is several times higher than the step difference of the conventional planar type. Along with this, in order to maintain the productivity of device manufacturing, techniques for quickly eliminating the above-mentioned high step difference in the CMP process and the like are being sought.

[0009] The present inventors have found that, by using a polishing slurry containing first particles containing cerium oxide and second particles containing hydroxide of a tetravalent metal element, the polishing speed of the insulating material constituting the insulating portion can be improved, and on the other hand, in this polishing slurry, agglomeration of abrasive grains can occur, which can cause a decrease in polishing characteristics.

[0010] The present invention was made in order to solve the above-mentioned problems, and aims to provide a polishing slurry in which an increase in abrasive grain size caused by agglomeration is less likely to occur, and a polishing method using the same. MEANS FOR SOLVING THE PROBLEMS

[0011] One aspect of the present application relates to a slurry for polishing, the slurry for polishing including a polishing grain, a liquid medium, and a salt of a compound represented by the following formula (1), the polishing grain including a first particle and a second particle in contact with the first particle, the first particle including cerium oxide, and the second particle including a hydroxide of a tetravalent metal element. [Chemical Formula 1] [In formula (1), R represents a hydroxyl group or a monovalent organic group.]

[0012] In the slurry for polishing, aggregation of the polishing grain, and increase in the particle diameter of the polishing grain accompanying the aggregation, are less likely to occur. That is, the slurry for polishing is excellent in storage stability. The slurry for polishing has less change in polishing properties (e.g., polishing rate) even after long-term storage, and thus, according to the slurry for polishing, polishing can be stably performed. In addition, according to the slurry for polishing, there is a tendency that the polishing rate of an insulating material can be increased, and the insulating material can be polished at a high polishing rate. In addition, according to the slurry for polishing, in CMP technology for planarizing insulating portions formed of an STI insulating material, a pre-metal insulating material, an interlayer insulating material, or the like, there is a tendency that the insulating portions can be highly planarized.

[0013] However, generally, as the content of the polishing grain increases, there is a tendency that polishing damage is easily generated. On the other hand, according to the slurry for polishing of the present embodiment, even if the polishing grain is in a small amount, a sufficient polishing rate is easily obtained. Therefore, by using a small amount of the polishing grain, there is a tendency that an insulating material can be polished at low polishing damage while achieving a sufficient polishing rate.

[0014] The hydroxide of the tetravalent metal element can contain at least one selected from a hydroxide of a rare earth metal element and a hydroxide of zirconium.

[0015] The content of the polishing grain can be 0.01 to 10% by mass, based on the total mass of the slurry for polishing.

[0016] The salt of the compound represented by formula (1) can contain an ammonium salt. The salt of the compound represented by formula (1) can contain a salt of a compound in which R described above is a hydroxyl group. The salt of the compound represented by formula (1) can contain a salt of a compound represented by the following formula (1a). [Chemical Formula 2] [In formula (1a), R 1 represents a divalent organic group.]

[0017] The content of the salt of the compound represented by formula (1) can be 0.001 to 0.1% by mass, based on the total mass of the slurry for polishing.

[0018] Another aspect of the present application relates to use of the above-described polishing slurry in polishing of a polishing object containing silicon oxide. The above-described polishing slurry is particularly capable of increasing the polishing rate of silicon oxide, and is therefore suitable for polishing a polishing surface containing silicon oxide.

[0019] Another aspect of the present application relates to a polishing method including a step of polishing a polishing object using the above-described polishing slurry. According to this polishing method, an insulating material can be polished at a high polishing rate, and a high polishing rate can be obtained even after long-term storage of the polishing slurry. In addition, according to this polishing method, in CMP technology for planarizing insulating portions formed of STI insulating materials, pre-metal insulating materials, interlayer insulating materials, and the like, these insulating portions can be highly planarized. Effects of the Invention

[0020] According to the present application, a polishing slurry in which an increase in the particle diameter of abrasive grains caused by aggregation is less likely to occur, and a polishing method using the same can be provided. According to the present application, use of a polishing slurry in a planarization step of a substrate surface as a manufacturing technology for semiconductor elements can be provided. In addition, according to the present application, use of a polishing slurry in a planarization step of an insulating portion formed of an STI insulating material, a pre-metal insulating material, or an interlayer insulating material can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0021] [ Figure 1 ] Figure 1 is a schematic cross-sectional view showing a substrate used in a polishing method according to an embodiment. [SYMBOL EXPLANATION] 1... substrate (polishing object); 2... substrate; 3... insulating portion. DETAILED DESCRIPTION

[0022] Hereinafter, a polishing slurry according to an embodiment of the present application and a polishing method using the same will be described in detail.

[0023] <DEFINITIONS> In the present specification, a numerical range represented by "~" indicates a range including the numerical values recited before and after "~" as the minimum value and the maximum value, respectively. In a numerical range recited in stages in the present specification, the upper limit value or the lower limit value of the numerical range of a certain stage can be replaced with the upper limit value or the lower limit value of the numerical range of another stage. In addition, the upper limit value and the lower limit value can be arbitrarily combined. In the numerical range recited in the present specification, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the examples. Unless otherwise specified, the materials exemplified in the present specification can be used singly or can be used in combination of two or more. In the present specification, the content of each component in a composition, when a plurality of substances corresponding to each component is present in the composition, means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the present specification, the "polishing rate of a material A" means the rate at which a substance formed from the material A is removed by polishing. The term "process" is not only an independent process, but also included in the term as long as the intended effect of the process can be achieved even if it cannot be clearly distinguished from other processes.

[0024] <Slurry for polishing> The slurry for polishing of the present embodiment contains abrasive grains, a liquid medium, and a salt of a compound represented by the following formula (1). The slurry for polishing of the present embodiment can be used as a polishing liquid (for example, a polishing liquid for CMP (hereinafter, referred to as "CMP polishing liquid".)). Specifically, the slurry for polishing (polishing liquid) of the present embodiment can be suitably used for polishing of a polished object containing an insulating material, and particularly, can be suitably used for polishing of a polished object containing silicon oxide (silicon dioxide (SiO2), silicon oxide containing carbon (SiOC), or the like). In the present specification, the "polishing liquid" (abrasive) is defined as a composition that comes into contact with a polished surface at the time of polishing. The term "polishing liquid" itself does not have any limitation on the components contained in the polishing liquid. Hereinafter, the essential components and optional components will be described. [Chemical 3] [In formula (1), R represents a hydroxyl group or a monovalent organic group.]

[0025] (Abrasive grains) The abrasive grain includes: a first particle containing cerium oxide, and a second particle containing hydroxide of a tetravalent metal element. In the slurry for polishing, at least a part of the first particle and the second particle exist as a composite particle (for example, a composite particle formed of the first particle and the second particle) including the first particle and the second particle in contact with the first particle. In addition, in the present specification, "abrasive grain" means a particle or a collection thereof contained in the slurry for polishing, and is also referred to as "abrasive particle". The abrasive grain is generally a solid particle. It is considered that in polishing using the abrasive grain, the object to be removed is removed by the mechanical action possessed by the abrasive grain and the chemical action of the abrasive grain (mainly the surface of the abrasive grain), but the polishing mechanism based on the abrasive grain is not limited thereto.

[0026] The slurry for polishing according to the present embodiment has a tendency that the polishing rate of the insulating material can be improved. It is presumed that this is at least due to the use of the above-described abrasive grain. That is, the first particle (the particle containing cerium oxide) has strong physical action (mechanical, mechanical action) to the insulating material. On the other hand, the second particle (the particle containing hydroxide of a tetravalent metal element) has high reactivity to the insulating material based on chemical action (chemical property). For example, the hydroxyl group functions, and high reactivity of the second particle to the insulating material is obtained. In addition, in a case where the force of electrostatic attraction to the insulating material (for example, silicon oxide) is strong, high reactivity of the second particle to the insulating material is easily obtained. In this way, it is presumed that the polishing rate of the insulating material is improved by the synergistic effect obtained by combining the first particle having strong physical action and the second particle having strong chemical action.

[0027] As the cerium oxide, CeO2, Ce2O3, etc. can be exemplified. x (x = 1.5 to 2.0), and specifically, CeO2 (ceria), Ce2O3, etc. can be exemplified.

[0028] The hydroxide of a tetravalent metal element refers to a compound containing a tetravalent metal (M 4+ ) and at least one hydroxyl ion (OH － ). The hydroxide of a tetravalent metal element can contain anions other than the hydroxyl ion (for example, nitrate ion NO3 － and sulfate ion SO4 2－ ). For example, the hydroxide of a tetravalent metal element can contain anions (for example, nitrate ion NO3 － and sulfate ion SO4 2－ ) that bind to the tetravalent metal element.

[0029] Compared to an abrasive grain formed of silicon dioxide, ceria, etc., the abrasive grain containing the hydroxide of a tetravalent metal element has high reactivity to the insulating material (for example, silicon oxide), and contributes to the improvement of the polishing rate of the insulating material.

[0030] From the viewpoint of further improving the polishing rate of the insulating material, the hydroxide of the tetravalent metal element preferably includes at least one selected from the group consisting of a hydroxide of a rare earth metal element and a hydroxide of zirconium. From the viewpoint of further improving the polishing rate of the insulating material, the hydroxide of the tetravalent metal element is more preferably a hydroxide of a rare earth metal element. As a rare earth metal element capable of obtaining a tetravalent state, lanthanoid elements such as cerium, praseodymium, terbium, and the like can be given, and among them, a lanthanoid element is preferable from the viewpoint of more excellent polishing rate of the insulating material, and cerium is more preferable. The hydroxide of a rare earth metal element and the hydroxide of zirconium can be used in combination, and two or more kinds of hydroxides of rare earth metal elements can be selected and used.

[0031] The abrasive grains can be used alone or in combination of two or more kinds. The polishing slurry of the present embodiment can contain other particles than the composite particles containing the first particles and the second particles. As such other particles, for example, the first particles not in contact with the second particles (the second particles not in contact with the first particles), and particles not containing cerium oxide and the hydroxide of the tetravalent metal element (for example, particles formed of silica, alumina, zirconia, yttria, and the like) can be given.

[0032] From the viewpoint of further improving the polishing rate of the insulating material, the particle diameter of the first particles in the polishing slurry is preferably 15 nm or more, more preferably 25 nm or more, further preferably 35 nm or more, and particularly preferably 40 nm or more. From the viewpoint of improving the dispersibility of the abrasive grains and further suppressing damage to the surface to be polished, the particle diameter of the first particles is preferably 1000 nm or less, more preferably 800 nm or less, further preferably 600 nm or less, and particularly preferably 500 nm or less. From these viewpoints, the particle diameter of the first particles is preferably 15 to 1000 nm, more preferably 25 to 800 nm, further preferably 35 to 600 nm, and particularly preferably 40 to 500 nm. The average particle diameter (average secondary particle diameter) of the first particles is preferably in the above range.

[0033] From the viewpoint of further improving the polishing rate of the insulating material, the particle diameter of the second particles in the polishing slurry is preferably 1 nm or more, more preferably 2 nm or more, and further preferably 3 nm or more. From the viewpoint of improving the dispersibility of the abrasive grains and further suppressing damage to the surface to be polished, the particle diameter of the second particles is preferably 25 nm or less, more preferably 20 nm or less, and further preferably 15 nm or less. From these viewpoints, the particle diameter of the second particles is preferably 1 to 25 nm, more preferably 2 to 20 nm, and further preferably 3 to 15 nm. The average particle diameter (average secondary particle diameter) of the second particles is preferably in the above range.

[0034] From the viewpoint of further improving the polishing rate of the insulating material, the particle diameter (e.g., average particle diameter) of the second particles is preferably smaller than the particle diameter (e.g., average particle diameter) of the first particles. In general, a particle having a small particle diameter has a large surface area per unit mass and thus has high reactivity, as compared with a particle having a large particle diameter. On the other hand, a particle having a small particle diameter has a small mechanical action (mechanical polishing force), as compared with a particle having a large particle diameter. Therefore, it is presumed that, in the case where the particle diameter of the second particles is smaller than the particle diameter of the first particles, the reactivity of the second particles to the insulating material is further improved, the chemical action is further enhanced, and on the other hand, the mechanical polishing action of the first particles is further enhanced. As a result, it is presumed that the polishing rate of the insulating material can be further improved because the synergistic effect brought about by the combination of the first particles and the second particles can be further improved.

[0035] From the viewpoint of further improving the polishing rate of the insulating material, the average particle diameter (average secondary particle diameter) of the abrasive grains (all of the abrasive grains including the composite particles) in the polishing slurry is preferably 20 nm or greater, more preferably 30 nm or greater, further preferably 40 nm or greater, particularly preferably 50 nm or greater, extremely preferably 100 nm or greater, very preferably 120 nm or greater, more further preferably 150 nm or greater, particularly preferably 200 nm or greater, and most preferably 300 nm or greater. From the viewpoint of improving the dispersibility of the abrasive grains and further suppressing damage to the surface to be polished, the average particle diameter of the abrasive grains is preferably 1000 nm or less, more preferably 800 nm or less, further preferably 600 nm or less, particularly preferably 500 nm or less, extremely preferably 400 nm or less. From these viewpoints, the average particle diameter of the abrasive grains is preferably in the range of 20 to 1000 nm, more preferably in the range of 30 to 800 nm, further preferably in the range of 40 to 600 nm, particularly preferably in the range of 50 to 500 nm, extremely preferably in the range of 100 to 400 nm, very preferably in the range of 120 to 400 nm, more further preferably in the range of 150 to 400 nm, particularly preferably in the range of 200 to 400 nm, and most preferably in the range of 300 to 400 nm.

[0036] The average particle diameter (average secondary particle diameter) was measured using a light diffraction scattering type particle size distribution meter (e.g., manufactured by Beckman Coulter, Inc., trade name: N5, or manufactured by Microtrac BEL Corp., trade name: Microtrac MT3300EXII).

[0037] The D99 particle diameter of the abrasive grains in the slurry for polishing is preferably 150 nm or more, more preferably 200 nm or more, and further preferably 250 nm or more from the viewpoint of further improving the polishing rate of the insulating material. The D99 particle diameter of the abrasive grains in the slurry for polishing is preferably 2000 nm or less, more preferably 1500 nm or less, and further preferably 1200 nm or less from the viewpoint of improving the dispersibility of the abrasive grains and further suppressing damage to the surface to be polished. The D99 particle diameter of the abrasive grains in the slurry for polishing is preferably 150 to 2000 nm, more preferably 200 to 1500 nm, and further preferably 250 to 1200 nm from these viewpoints. The D99 particle diameter is measured using a light diffraction scattering particle size distribution meter (manufactured by Microtrac BEL Corporation, trade name: Microtrac MT 3300EXII).

[0038] The first particles in the slurry for polishing preferably have a negative zeta potential from the viewpoint of allowing the first particles and the second particles to act appropriately and further improving the polishing rate of the insulating material. The zeta potential of the first particles in the slurry for polishing is preferably -20 mV or less, more preferably -25 mV or less, further preferably -30 mV or less, and particularly preferably -35 mV or less from the viewpoint of further improving the polishing rate of the insulating material. The lower limit of the zeta potential of the first particles is not particularly limited. The zeta potential of the first particles can be, for example, -200 mV or more. That is, the zeta potential of the first particles can be -200 to -20 mV, -200 to -25 mV, -200 to -30 mV, or -200 to -35 mV.

[0039] The second particles in the slurry for polishing preferably have a positive zeta potential from the viewpoint of allowing the second particles and the first particles to act appropriately and further improving the polishing rate of the insulating material. The zeta potential of the second particles in the slurry for polishing is preferably +10 mV or more, more preferably +15 mV or more, further preferably +20 mV or more, and particularly preferably +25 mV or more from the viewpoint of further improving the polishing rate of the insulating material. The upper limit of the zeta potential of the second particles is not particularly limited. The zeta potential of the second particles can be, for example, +200 mV or less. That is, the zeta potential of the second particles can be +10 to +200 mV, +15 to +200 mV, +20 to +200 mV, or +25 to +200 mV.

[0040] From the viewpoint of further improving the polishing rate of the insulating material, the zeta potential of the abrasive grains (zeta potential of the entire abrasive grains) in the slurry for polishing, which contain the composite particles, is preferably +10 mV or more, more preferably +20 mV or more, further preferably +25 mV or more, particularly preferably +30 mV or more, extremely preferably +40 mV or more, and very preferably +50 mV or more. The upper limit of the zeta potential of the abrasive grains is not particularly limited. The zeta potential of the abrasive grains can be, for example, +200 mV or less. That is, the zeta potential of the abrasive grains can be +10 to +200 mV, +20 to +200 mV, +25 to +200 mV, +30 to +200 mV, +40 to +200 mV, or +50 to +200 mV.

[0041] The zeta potential refers to the surface potential of a particle. The zeta potential can be measured, for example, using a dynamic light scattering type zeta potential measuring device (for example, manufactured by Beckman Coulter, Inc., trade name: Delsa Nano C). The zeta potential of a particle can be adjusted using an additive. For example, by bringing a monovalent carboxylic acid (for example, acetic acid) into contact with a particle containing cerium oxide, a particle having a positive zeta potential can be obtained. In addition, by bringing a material having a carboxyl group (polyacrylic acid or the like) into contact with a particle containing cerium oxide, a particle having a negative zeta potential can be obtained.

[0042] The composite particles containing the first particles and the second particles can be obtained by bringing the first particles and the second particles into contact using a homogenizer, a high-pressure homogenizer (nanomizer), a ball mill, a bead mill, an ultrasonic processor, or the like, bringing the first particles and the second particles having charges opposite to each other into contact, bringing the first particles and the second particles into contact in a state in which the content of the particles is small, or the like.

[0043] From the viewpoint of further improving the polishing rate of the insulating material, the content of cerium oxide (for example, ceria) in the abrasive grains, based on the entire abrasive grains (the entire abrasive grains contained in the slurry for polishing. The same applies hereinafter), is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and particularly preferably 80% by mass or more. From the viewpoint of further improving the polishing rate of the insulating material, the content of cerium oxide (for example, ceria) in the abrasive grains, based on the entire abrasive grains, is preferably 95% by mass or less, more preferably 92% by mass or less, further preferably 90% by mass or less, particularly preferably 88% by mass or less, and extremely preferably 85% by mass or less. From these viewpoints, the content of cerium oxide in the abrasive grains, based on the entire abrasive grains, is preferably 50 to 95% by mass, more preferably 60 to 92% by mass, further preferably 70 to 90% by mass, particularly preferably 80 to 88% by mass, and extremely preferably 80 to 85% by mass.

[0044] From the viewpoint of further improving the polishing rate of the insulating material, the content of cerium oxide (e.g., ceria) in the first particles is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total first particles (the same applies hereinafter). The first particles can be substantially composed of cerium oxide (e.g., ceria) (the first particles are substantially 100% by mass of cerium oxide). That is, the content of cerium oxide in the first particles can be 100% by mass or less, based on the total first particles.

[0045] From the viewpoint of further improving the polishing rate of the insulating material, the content of the first particles is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, extremely preferably 0.4% by mass or more, and very preferably 0.5% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of further improving the storage stability of the polishing slurry, the content of the first particles is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less, based on the total mass of the polishing slurry. From these viewpoints, the content of the first particles is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, further preferably 0.1 to 1% by mass, particularly preferably 0.3 to 1% by mass, extremely preferably 0.4 to 1% by mass, and very preferably 0.5 to 1% by mass, based on the total mass of the polishing slurry.

[0046] From the viewpoint of further improving the polishing rate of the insulating material, the content of the hydroxide of the tetravalent metal element in the abrasive particles is preferably 5% by mass or more, more preferably 8% by mass or more, further preferably 10% by mass or more, particularly preferably 12% by mass or more, and extremely preferably 15% by mass or more, based on the total abrasive particles (the same applies hereinafter). From the viewpoint of further improving the polishing rate of the insulating material while making it easy to prepare the polishing slurry, the content of the hydroxide of the tetravalent metal element in the abrasive particles is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total abrasive particles. From these viewpoints, the content of the hydroxide of the tetravalent metal element in the abrasive particles is preferably 5 to 50% by mass, more preferably 8 to 40% by mass, further preferably 10 to 30% by mass, particularly preferably 12 to 20% by mass, and extremely preferably 15 to 20% by mass, based on the total abrasive particles.

[0047] From the viewpoint of further improving the polishing rate of the insulating material, the content of the hydroxide of the tetravalent metal element in the second particles is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the total second particles (the same applies hereinafter). The second particles can be in a manner that substantially consists of the hydroxide of the tetravalent metal element (a manner that 100% by mass of the second particles is the hydroxide of the tetravalent metal element). That is, the content of the hydroxide of the tetravalent metal element in the second particles can be 100% by mass or less, based on the total second particles.

[0048] From the viewpoint of improving the chemical interaction between the abrasive grains and the polished surface, and further improving the polishing rate of the insulating material, the content of the hydroxide of the tetravalent metal element in the polishing slurry is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, further preferably 0.03% by mass or more, particularly preferably 0.05% by mass or more, and extremely preferably 0.1% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of easily avoiding the aggregation of the abrasive grains, and the chemical interaction between the abrasive grains and the polished surface being good, and effectively utilizing the characteristics of the abrasive grains, the content of the hydroxide of the tetravalent metal element in the polishing slurry is preferably 5% by mass or less, more preferably 4% by mass or less, further preferably 3% by mass or less, particularly preferably 2% by mass or less, extremely preferably 1% by mass or less, and very preferably 0.5% by mass or less, based on the total mass of the polishing slurry. From these viewpoints, the content of the hydroxide of the tetravalent metal element is preferably 0.005 to 5% by mass, more preferably 0.01 to 4% by mass, further preferably 0.03 to 3% by mass, particularly preferably 0.05 to 2% by mass, extremely preferably 0.1 to 1% by mass, and very preferably 0.1 to 0.5% by mass, based on the total mass of the polishing slurry.

[0049] From the viewpoint of further improving the polishing rate of the insulating material, the content of the second particles is preferably 5% by mass or more, more preferably 8% by mass or more, further preferably 10% by mass or more, particularly preferably 12% by mass or more, and most preferably 15% by mass or more, based on the total amount of the first particles and the second particles. From the viewpoint of easy preparation of the polishing slurry and further improving the polishing rate of the insulating material, the content of the second particles is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total amount of the first particles and the second particles. From these viewpoints, the content of the second particles is preferably 5 to 50% by mass, more preferably 8 to 40% by mass, further preferably 10 to 30% by mass, particularly preferably 12 to 20% by mass, and most preferably 15 to 20% by mass, based on the total amount of the first particles and the second particles.

[0050] From the viewpoint of improving the chemical interaction between the abrasive particles and the surface to be polished and further improving the polishing rate of the insulating material, the content of the second particles is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, further preferably 0.03% by mass or more, particularly preferably 0.05% by mass or more, and most preferably 0.1% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of easily avoiding aggregation of the abrasive particles and good chemical interaction between the abrasive particles and the surface to be polished, and effectively utilizing the characteristics of the abrasive particles, the content of the second particles is preferably 5% by mass or less, more preferably 4% by mass or less, further preferably 3% by mass or less, particularly preferably 2% by mass or less, most preferably 1% by mass or less, and very preferably 0.5% by mass or less, based on the total mass of the polishing slurry. From these viewpoints, the content of the second particles is preferably 0.005 to 5% by mass, more preferably 0.01 to 4% by mass, further preferably 0.03 to 3% by mass, particularly preferably 0.05 to 2% by mass, most preferably 0.1 to 1% by mass, and very preferably 0.1 to 0.5% by mass, based on the total mass of the polishing slurry.

[0051] From the viewpoint of further improving the polishing rate of the insulating material, the content of the abrasive grains is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, further preferably 0.05% by mass or more, particularly preferably 0.07% by mass or more, extremely preferably 0.1% by mass or more, very preferably 0.15% by mass or more, more further preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of further improving the storage stability of the polishing slurry, the content of the abrasive grains is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less, based on the total mass of the polishing slurry. From these viewpoints, the content of the abrasive grains is preferably 0.01 to 10% by mass, more preferably 0.03 to 8% by mass, further preferably 0.05 to 6% by mass, particularly preferably 0.07 to 6% by mass, extremely preferably 0.1 to 6% by mass, very preferably 0.15 to 6% by mass, more further preferably 0.3 to 6% by mass, and particularly preferably 0.5 to 6% by mass, based on the total mass of the polishing slurry.

[0052] In addition, by further reducing the content of the abrasive grains, it is possible to further reduce the cost and the polishing damage, and this is preferable in this respect. Generally, when the content of the abrasive grains is reduced, there is a tendency that the polishing rate of the insulating material or the like is also reduced. On the other hand, the abrasive grains containing the particles of the hydroxide containing the tetravalent metal element can achieve the prescribed polishing rate even in a small amount, and thus it is possible to achieve a balance between the polishing rate and the advantages brought by the reduction of the content of the abrasive grains, and further reduce the content of the abrasive grains. From this viewpoint, the content of the abrasive grains can be 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less, based on the total mass of the polishing slurry. That is, the content of the abrasive grains can be, for example, 0.01 to 5% by mass, 0.03 to 4% by mass, 0.05 to 3% by mass, 0.07 to 2% by mass, 0.1 to 1% by mass, 0.15 to 1% by mass, 0.3 to 1% by mass, or 0.5 to 1% by mass, based on the total mass of the polishing slurry.

[0053] [absorbance] Preferably, the second particles contain the hydroxide of the tetravalent metal element, and satisfy at least one of the following conditions (a) and (b). In addition, the "aqueous dispersion" in which the content of the second particles is adjusted to a prescribed amount means a liquid containing the second particles and water in the prescribed amounts. (a) The second particles provide an absorbance of 1.00 or more for light having a wavelength of 400 nm in an aqueous dispersion in which the content of the second particles is adjusted to 1.0% by mass. (b) The second particle, in an aqueous dispersion in which the content of the second particle is adjusted to 0.0065% by mass, provides an absorbance of more than 1.000 for light at a wavelength of 290 nm.

[0054] Regarding condition (a) above, the grinding speed can be further improved by using particles that have an absorbance of 1.00 or higher for light at a wavelength of 400 nm in an aqueous dispersion in which the content of the second particle is adjusted to 1.0% by mass. The reason for this may not be clear, but the inventors believe it to be as follows: That is, based on the manufacturing conditions of hydroxides of tetravalent metal elements, etc., it is believed that particles containing tetravalent metals (M... 4+ ), 1 to 3 hydroxide ions (OH-) － ) and 1 to 3 anions (X c－ M(OH) is composed of ) a X b (In the formula, a + b × c = 4) particles (also, such particles are "particles containing hydroxides of tetravalent metal elements"). It is assumed that in M(OH) a X b In the middle, electron-withdrawing anions (X c－ This process increases the reactivity of hydroxide ions, as M(OH) plays a role. a X b The increased presence of M(OH) leads to a higher grinding speed. Furthermore, it is believed that the presence of M(OH) increases this rate. a X b The particles absorb light at a wavelength of 400 nm, therefore, as M(OH)... a X b The increased presence of this increases the absorbance of light at a wavelength of 400nm, thus increasing the grinding speed.

[0055] It is believed that particles containing hydroxides of tetravalent metals may contain not only M(OH) a X b It may also contain M(OH)4, MO2, etc. As an anion (X... c－ Examples include NO3. － and SO4 2－ .

[0056] In addition, particles containing hydroxides of tetravalent metals contain M(OH). a X b It can be confirmed by the following method: After thoroughly washing the particles with pure water, the particles are detected by FT-IR ATR (Fourier transform infrared spectrometer attenuated total reflection) method, which measures the total reflectance of the particles with anions (X).c－ ) corresponding peaks. The presence of anions (X c－ ) can also be confirmed by XPS (X-ray Photoelectron Spectroscopy) method.

[0057] Here, it was confirmed that M(OH) a X b The absorption peak at a wavelength of 400 nm of the particle (e.g., M(OH)3X) is much smaller than the absorption peak at a wavelength of 290 nm described later. In this regard, the present inventors studied the magnitude of the absorbance using a water dispersion liquid having a content of the particles of 1.0 mass% which is relatively large and in which a large absorbance can be easily detected, and as a result, it was found that when the particles which provide an absorbance of light at a wavelength of 400 nm of 1.00 or more in the water dispersion liquid are used, the effect of increasing the polishing rate is excellent.

[0058] From the viewpoint of easily polishing an insulating material at a more excellent polishing rate, the absorbance of light at a wavelength of 400 nm is preferably 1.50 or more, more preferably 1.55 or more, and still more preferably 1.60 or more.

[0059] Regarding the above condition (b), by using the second particles which provide an absorbance of light at a wavelength of 290 nm of 1.000 or more in a water dispersion liquid in which the content of the second particles is adjusted to 0.0065 mass%, the polishing rate can be further increased. The reason is not necessarily clear, but the present inventors consider the following. That is, the particles containing M(OH) a X b (e.g., M(OH)3X) generated depending on the manufacturing conditions of the hydroxide of the tetravalent metal element, etc. have an absorption peak near a wavelength of 290 nm, for example, by Ce 4+ (OH － )3NO3 － form an absorption peak at a wavelength of 290 nm. Therefore, it is considered that as the amount of the presence of M(OH) a X b increases, the absorbance of light at a wavelength of 290 nm increases, and the polishing rate increases.

[0060] Here, the absorbance of light near a wavelength of 290 nm has a tendency to be detected to be larger as it exceeds the measurement limit. In this regard, the present inventors studied the magnitude of the absorbance using a water dispersion liquid having a content of the particles of 0.0065 mass% which is relatively small and in which a small absorbance can be easily detected, and as a result, it was found that when the particles which provide an absorbance of light at a wavelength of 290 nm of 1.000 or more in the water dispersion liquid are used, the effect of increasing the polishing rate is excellent.

[0061] From the viewpoint of polishing the insulating material at a more excellent polishing rate, the absorbance of light having a wavelength of 290 nm is preferably 1.050 or more, more preferably 1.100 or more, particularly preferably 1.130 or more, and extremely preferably 1.150 or more. The upper limit of the absorbance of light having a wavelength of 290 nm is not particularly limited, but is preferably 10.00 or less. That is, the absorbance of light having a wavelength of 290 nm is preferably 1.000 to 10.00, more preferably 1.050 to 10.00, more preferably 1.100 to 10.00, particularly preferably 1.130 to 10.00, and extremely preferably 1.150 to 10.00.

[0062] When the second particles having an absorbance of 1.00 or more for light having a wavelength of 400 nm provide an absorbance of 1.000 or more for light having a wavelength of 290 nm in a water dispersion liquid in which the content of the second particles is adjusted to 0.0065% by mass, the insulating material can be polished at a more excellent polishing rate.

[0063] In addition, the hydroxide of the tetravalent metal element (for example, M(OH) a X b ) has a tendency not to absorb light having a wavelength of 450 nm or more (particularly, a wavelength of 450 to 600 nm). Therefore, from the viewpoint of suppressing adverse effects on polishing due to the presence of impurities and polishing the insulating material at a more excellent polishing rate, the preferable second particles are particles that provide an absorbance of 0.010 or less for light having a wavelength of 450 to 600 nm in a water dispersion liquid in which the content of the second particles is adjusted to 0.0065% by mass (65 ppm). That is, the absorbance for all light in the range of a wavelength of 450 to 600 nm in a water dispersion liquid in which the content of the second particles is adjusted to 0.0065% by mass is preferably 0.010 or less. The absorbance for light having a wavelength of 450 to 600 nm is more preferably less than 0.010. The lower limit of the absorbance for light having a wavelength of 450 to 600 nm is preferably 0.

[0064] The absorbance in the water dispersion liquid can be measured, for example, using a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Specifically, for example, a water dispersion liquid in which the content of the second particles is adjusted to 1.0% by mass or 0.0065% by mass is prepared as a measurement sample. About 4 mL of the measurement sample is put in a 1 cm square cell, and the cell is set in the device. Then, absorbance measurement is performed in the range of a wavelength of 200 to 600 nm, and the absorbance is determined from the resulting graph.

[0065] [Transmittance] The second particles contained in the slurry for polishing of the present embodiment are preferably particles that provide a light transmittance of 50% / cm or more for light having a wavelength of 500 nm in a water dispersion liquid in which the content of the second particles is adjusted to 1.0 mass%. By this, the decrease in the polishing rate caused by the addition of the additive can be further suppressed, and thus it is easy to obtain other characteristics while maintaining the polishing rate. From this perspective, the light transmittance is more preferably 60% / cm or more, further preferably 70% / cm or more, particularly preferably 80% / cm or more, extremely preferably 90% / cm or more, and very preferably 92% / cm or more. The upper limit of the light transmittance is 100% / cm.

[0066] The reason why the decrease in the polishing rate can be suppressed by adjusting the light transmittance of the particles is not clear, but the present inventors believe the following. It is believed that in the particles containing a hydroxide of a tetravalent metal element (cerium or the like), chemical action is more dominant than mechanical action. Therefore, it is believed that the number of particles contributes more to the polishing rate than the size of the particles.

[0067] It is believed that in the case where the light transmittance is low in a water dispersion liquid in which the content of the particles is 1.0 mass%, relatively many large-diameter particles (hereinafter referred to as "coarse particles") exist among the particles present in the water dispersion liquid. When an additive (for example, polyvinyl alcohol (PVA)) is added to a slurry for polishing containing such particles, other particles aggregate around the coarse particles as nuclei. As a result, it is believed that the number of particles (effective particle number) per unit area that act on the surface to be polished decreases, and the specific surface area of the particles that come into contact with the surface to be polished decreases, and thus the decrease in the polishing rate occurs.

[0068] On the other hand, it is believed that in the case where the light transmittance is high in a water dispersion liquid in which the content of the particles is 1.0 mass%, the particles present in the water dispersion liquid are in a state in which "coarse particles" are less. In the case where the amount of such coarse particles is small, even if an additive (for example, polyvinyl alcohol) is added to a slurry for polishing, the aggregation of the particles is suppressed because the coarse particles that become the nuclei of the aggregation are small, or the size of the aggregated particles becomes smaller than that of the aggregated particles generated in the conventional slurry for polishing. As a result, it is believed that the number of particles (effective particle number) per unit area that act on the surface to be polished is maintained, and the specific surface area of the particles that come into contact with the surface to be polished is maintained, and thus it is difficult to cause the decrease in the polishing rate.

[0069] According to the research by the present inventors, even in a slurry for polishing in which the particle diameter is the same as that measured in a general particle diameter measuring device, there can be a slurry for polishing that is transparent (high light transmittance) to the naked eye and a slurry for polishing that is turbid (low light transmittance) to the naked eye. It is believed that the coarse particles that can have the above-described effects, even in an extremely small amount that cannot be detected by a general particle diameter measuring device, contribute to the decrease in the polishing rate.

[0070] In addition, it was found that even if the filtration is repeated several times in order to reduce the coarse particles, the phenomenon of the decrease in the polishing rate due to the additive is not substantially improved, and the above-mentioned effect of the increase in the polishing rate due to the absorbance cannot be sufficiently exerted. Therefore, the present inventors have intensively studied the method of producing the particles, and found that the above-mentioned problems can be solved by using the particles having a high light transmittance in the aqueous dispersion.

[0071] The above-mentioned light transmittance is the transmittance of light having a wavelength of 500 nm. The above-mentioned light transmittance can be measured by a spectrophotometer. Specifically, for example, it can be measured by a spectrophotometer U3310 (device name) manufactured by Hitachi, Ltd.

[0072] As a more specific measurement method, an aqueous dispersion in which the content of the second particles is adjusted to 1.0 mass% is prepared as a measurement sample. About 4 mL of the measurement sample is put in a 1 cm square cuvette, and after the cuvette is set in the device, the measurement is performed.

[0073] The absorbance and the light transmittance provided by the second particles contained in the polishing slurry in the aqueous dispersion can be measured by preparing an aqueous dispersion having a predetermined content after removing the solid components other than the second particles and the liquid components other than water, and using the aqueous dispersion for the measurement. Although it differs depending on the components contained in the polishing slurry, the removal of the solid components and the liquid components can be performed by, for example, a centrifugal separation method using a centrifuge (separator) to which a gravitational acceleration of several G or less is applied, an ultra-centrifugal separation method using an ultra-centrifuge (separator) to which a gravitational acceleration of several tens of thousands of G or more is applied, a chromatography method such as a distribution chromatography, an adsorption chromatography, a gel permeation chromatography, an ion exchange chromatography, a filtration method such as a natural filtration, a reduced pressure filtration, a pressure filtration, an ultrafiltration, a distillation method such as a reduced pressure distillation, an ordinary pressure distillation, and they can be appropriately combined.

[0074] For example, when the compound having a weight average molecular weight of several ten thousands or more (e.g., 50 thousands or more) is contained, as the separation method of the second particles, a chromatography method, a filtration method, or the like can be mentioned, and at least one selected from a gel permeation chromatography method and an ultrafiltration method is preferred. In the case of using the filtration method, the particles contained in the slurry for grinding can be passed through a filter by setting appropriate conditions. When the compound having a weight average molecular weight of several ten thousands or less (e.g., less than 50 thousands) is contained, as the separation method of the second particles, a chromatography method, a filtration method, a distillation method, or the like can be mentioned, and at least one selected from a gel permeation chromatography method, an ultrafiltration method, and a reduced pressure distillation method is preferred. When a plurality of particles is contained, as the separation method of the second particles, a filtration method, a centrifugal separation method, or the like can be mentioned, and in the case of filtration, the particles containing the hydroxide of the tetravalent metal element are more contained in the filtrate, and in the case of centrifugal separation, the particles containing the hydroxide of the tetravalent metal element are more contained in the liquid phase. In addition, the weight average molecular weight in the present specification is measured by a gel permeation chromatography (GPC) using a calibration curve of a standard polystyrene under the following conditions.

[0075] Apparatus used: Hitachi L-6000 [manufactured by Hitachi, Ltd.] Column: Gel pack GL-R420 + Gel pack GL-R430 + Gel pack GL-R440 [manufactured by Hitachi Chemical Co., Ltd., trade name, total of 3] Eluent: Tetrahydrofuran Measurement temperature: 40°C Flow rate: 1.75 mL / min Detector: L-3300 RI [manufactured by Hitachi, Ltd.]

[0076] As the method for separating the solid component other than the second particles, for example, separation can be performed according to the following centrifugal separation conditions. Centrifugal separator: Optima MAX-TL (manufactured by Beckman Coulter, Inc.) Centrifugal acceleration: 40,000 G Treatment time: 5 minutes Treatment temperature: 25°C

[0077] As the method for separating the second particles by a chromatography method, for example, a method for fractionating the second particles according to the following conditions, a method for fractionating other components, or a combination of these methods, or the like can be mentioned. Sample solution: 100 μL of the slurry for grinding Detector: UV-VIS detector, trade name "L-4200", manufactured by Hitachi, Ltd. Wavelength: 400 nm Integrator: Manufactured by Hitachi, Ltd., GPC Integrator, product name "D-2500" Pump: Manufactured by Hitachi, Ltd., product name "L-7100" Column: Manufactured by Hitachi Chemical Co., Ltd., aqueous HPLC packed column, trade name "GL-W550S" Eluent: Deionized water Measurement temperature: 23℃ Flow rate: 1 mL / min (pressure 40–50 kg / cm²) 2 about) Measurement time: 60 minutes

[0078] Depending on the composition of the grinding slurry, even under the above conditions, there is a possibility that the second particle may not be separated. However, in such cases, separation can be achieved by optimizing the sample solution volume, column type, eluent type, measurement temperature, and flow rate. Furthermore, by adjusting the pH of the grinding slurry, it is possible to adjust the distillation time of the components contained in the slurry and separate them from the second particle. When insoluble components are present in the grinding slurry, it is preferable to remove the insoluble components as needed through filtration, centrifugation, or other methods.

[0079] [How to create the second particle] Hydroxides of tetravalent metal elements can be prepared by reacting a salt of a tetravalent metal element (metal salt) with an alkali source (alkali). Preferably, the tetravalent metal hydroxide is prepared by mixing a salt of a tetravalent metal element with an alkali solution (e.g., an alkaline aqueous solution). This yields particles with extremely fine particle sizes and a grinding slurry with superior reduction in grinding damage. This method is disclosed, for example, in Patent Documents 6 and 7. Hydroxides of tetravalent metal elements can be obtained by mixing a metal salt solution (e.g., an aqueous solution of a metal salt) of a tetravalent metal element with an alkali solution. Conventionally known salts can be used without particular limitation as the tetravalent metal salt, such as M(NO3)4, M(SO4)2, M(NH4)2(NO3)6, M(NH4)4(SO4)4 (where M represents a rare earth metal element), Zr(SO4)2·4H2O, etc. As M, chemically active cerium (Ce) is preferred.

[0080] (Salts of the compounds shown in formula (1)) The slurry for polishing of the present embodiment contains a salt of the compound represented by the above formula (1). In the present embodiment, the slurry for polishing containing the first particles and the second particles as abrasive grains also contains a salt of the compound represented by formula (1), and thus, an increase in particle diameter due to aggregation of the abrasive grains is less likely to occur, and a decrease in polishing properties can be suppressed. That is, by causing the slurry for polishing to contain a salt of the compound represented by formula (1), the storage stability of the slurry for polishing is improved, and the polishing properties (for example, the polishing rate of an insulating material) after long-term storage are improved. Therefore, according to the slurry for polishing of the present embodiment, polishing can be stably performed. This effect is particularly significant when the zeta potential of the first particles is negative and the zeta potential of the second particles is positive. In the past, in order to suppress aggregation of abrasive grains, a material having a carboxyl group has sometimes been used, but in such a conventional slurry, there has been a tendency that a sufficient polishing rate of an insulating material cannot be obtained. On the other hand, in the present embodiment, since a salt of the compound represented by formula (1) is used, a sufficient polishing rate is easily obtained compared to the conventional slurry.

[0081] When a compound represented by formula (1) (for example, phosphoric acid) is used instead of a salt of the compound represented by formula (1), the effect of improving the storage stability of the slurry for polishing cannot be obtained. One of the reasons for this is as follows. When a salt of the compound represented by formula (1) is used, the salt is adsorbed to the abrasive grains in a state in which the hydroxyl group of the salt of the compound represented by formula (1) is dissociated, and thus, the surface of the abrasive grains is charged (negatively charged) due to the dissociated hydroxyl group, and thus, aggregation of the abrasive grains is suppressed by electrorepulsion between the abrasive grains. On the other hand, when a compound represented by formula (1) (for example, phosphoric acid) is used, the compound is difficult to be adsorbed to the abrasive grains in a state in which the hydroxyl group of the compound represented by formula (1) is dissociated, and thus, the surface of the abrasive grains is difficult to be charged, and aggregation of the abrasive grains cannot be suppressed.

[0082] As the monovalent organic group possessed by the salt of the compound represented by formula (1), an alkyl group, an aryl group, a vinyl group, or the like can be given. At least one of the hydrogen atoms possessed by these organic groups can be substituted with another functional group (substituent). As the functional group (substituent), a hydroxyl group, a phosphoric acid group, a phosphoric acid salt group, a phosphorous acid group, a phosphorous acid salt group, or the like can be given. As the salt of the phosphoric acid salt group or the phosphorous acid salt group, an alkali metal salt, an alkaline earth metal salt, an ammonium salt (a group in which the hydrogen atom of a hydroxyl group is substituted with an alkali metal, an alkaline earth metal, an ammonium ion, or the like), or the like can be given. For example, the monovalent organic group can be an alkyl group in which at least one of the hydrogen atoms is substituted with a phosphoric acid salt group or a phosphorous acid salt group. Among the monovalent organic groups, from the viewpoint of further improving the storage stability of the slurry for polishing, an alkyl group is preferable. The alkyl group can be any one of a saturated or an unsaturated group, and can be any one of a linear, a branched, or a cyclic group. The number of carbon atoms of the alkyl group can be, for example, 1 to 4.

[0083] The salt of the compound represented by formula (1) is represented by, for example, the following formula (2) or the following formula (3). From the viewpoint of further improving the storage stability of the polishing slurry, the salt of the compound represented by formula (1) can contain at least one selected from the compound (salt) represented by the following formula (2) and the compound (salt) represented by the following formula (3). [Chemical Formula 4] [In formula (2), R represents a hydroxyl group or a monovalent organic group, X + represents a counter ion.] [Chemical Formula 5] [In formula (3), R represents a hydroxyl group or a monovalent organic group, X + represents a counter ion.]

[0084] As the counter ion, an alkali metal cation, an alkaline earth metal cation, an ammonium ion, and the like can be given. Among them, from the viewpoint of further improving the stability of the polishing slurry and the viewpoint of preventing the contamination of the metal of the surface to be polished, an ammonium ion is preferred. That is, the salt of the compound represented by formula (1) preferably contains an ammonium salt. The hydrogen atom of the ammonium ion can be substituted with an alkyl group or the like.

[0085] From the viewpoint of further improving the storage stability of the polishing slurry, the salt of the compound represented by formula (1) preferably contains a salt of a compound in which R is a hydroxyl group or an alkyl group, and more preferably contains a salt of a compound in which R is a hydroxyl group. From the viewpoint of further improving the storage stability of the polishing slurry, at least one selected from the salt of the compound represented by formula (2) and the salt of the compound represented by formula (3) preferably contains a salt of a compound in which R is a hydroxyl group or an alkyl group, and more preferably contains a salt of a compound in which R is a hydroxyl group.

[0086] The salt of the compound represented by formula (1) can contain at least one selected from a salt of a monophosphonic acid and a salt of a polyphosphonic acid. As the salt of the compound represented by formula (1), one kind can be used alone, or a plurality of kinds can be used in combination.

[0087] As specific examples of the monophosphonic acid, phosphoric acid, vinylphosphonic acid, ethylphosphonic acid, methylphosphonic acid, and the like can be given. As the salt of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and the like can be given.

[0088] From the viewpoint of further improving the storage stability of the polishing slurry, the salt of the polyphosphonic acid preferably contains a salt of a diphosphonic acid. From the viewpoint of further improving the storage stability of the polishing slurry, the salt of the compound represented by formula (1) preferably contains a salt of a compound represented by the following formula (1a).

[0089] [Chemical Formula 6] [In formula (1a), R 1 represents a divalent organic group.

[0090] As the divalent organic group of the salt of the compound represented by formula (1a), an alkylene group or the like can be given. At least one of the hydrogen atoms of the organic group can be substituted with another functional group (substituent). As the functional group (substituent), a hydroxyl group, a phosphoric acid group, a phosphoric acid salt group, a phosphorous acid group, a phosphorous acid salt group, or the like can be given. As the salt of the phosphoric acid salt group or the phosphorous acid salt group, an alkali metal salt, an alkaline earth metal salt, an ammonium salt (a group in which the hydrogen atom of a hydroxyl group is substituted with an alkali metal ion, an alkaline earth metal ion, an ammonium ion, or the like), or the like can be given. For example, the divalent organic group can be an alkylene group in which at least one of the hydrogen atoms is substituted with a hydroxyl group.

[0091] At least one of the hydrogen atoms of the hydroxyl group in the salt of the compound represented by formula (1a) can be substituted with a counter ion. As the counter ion, for example, an alkali metal ion, an alkaline earth metal ion, an ammonium ion, or the like can be used as X + Among the exemplified counter ions described above, an ammonium ion is preferred from the viewpoint of further improving the storage stability of the polishing slurry.

[0092] From the viewpoint of further improving the storage stability of the polishing slurry, the salt of the compound represented by formula (1a) preferably contains a hydroxyalkane diphosphonic acid salt. From the viewpoint of further improving the storage stability of the polishing slurry, the hydroxyalkane diphosphonic acid salt preferably includes an ammonium salt. From the viewpoint of further improving the storage stability of the polishing slurry, the hydroxyalkane diphosphonic acid salt preferably includes a hydroxyethane diphosphonic acid salt. From these viewpoints, the hydroxyalkane diphosphonic acid salt preferably includes an ammonium salt of 1-hydroxyethane-1,1-bis(phosphonic acid).

[0093] As the salt of the compound represented by formula (1), from the viewpoint of further improving the storage stability and the polishing rate of the polishing slurry, at least one selected from the group consisting of diammonium hydrogen phosphate, monobasic ammonium phosphate, and a hydroxyalkane diphosphonic acid salt is preferably used, and at least one selected from the group consisting of diammonium hydrogen phosphate and monobasic ammonium phosphate is more preferably used.

[0094] From the viewpoint of further improving the storage stability of the polishing slurry, the content of the salt of the compound represented by formula (1) is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, and further preferably 0.005% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of further improving the storage stability of the polishing slurry and further suppressing the reduction in the polishing rate (for example, the polishing rate of an insulating material), the content of the salt of the compound represented by formula (1) is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.03% by mass or less, based on the total mass of the polishing slurry. From these viewpoints, the content of the salt of the compound represented by formula (1) is preferably 0.001 to 0.1% by mass, more preferably 0.003 to 0.05% by mass, and further preferably 0.005 to 0.03% by mass, based on the total mass of the polishing slurry.

[0095] From the viewpoint of further suppressing the reduction in the polishing rate (for example, the polishing rate of an insulating material), the content of the salt of the compound represented by formula (1) is preferably 0.007% by mass or more, and more preferably 0.01% by mass or more, based on the total mass of the polishing slurry. From the viewpoint of further suppressing the reduction in the polishing rate (for example, the polishing rate of an insulating material), the content of the salt of the compound represented by formula (1) is preferably 0.025% by mass or less, more preferably 0.02% by mass or less, and further preferably 0.015% by mass or less, based on the total mass of the polishing slurry.

[0096] From the viewpoint of further improving the storage stability of the polishing slurry, the content of the salt of the compound represented by formula (1) is preferably 0.05 parts by mass or more, more preferably 0.25 parts by mass or more, further preferably 0.5 parts by mass or more, and particularly preferably 0.7 parts by mass or more, relative to 100 parts by mass of the abrasive grains in the polishing slurry. From the viewpoint of further improving the storage stability of the polishing slurry and further suppressing the reduction in the polishing rate (for example, the polishing rate of an insulating material), the content of the salt of the compound represented by formula (1) is preferably 5.0 parts by mass or less, more preferably 3.5 parts by mass or less, further preferably 3.0 parts by mass or less, and particularly preferably 2.0 parts by mass or less, relative to 100 parts by mass of the abrasive grains in the polishing slurry. From these viewpoints, the content of the salt of the compound represented by formula (1) is preferably 0.05 to 5.0 parts by mass, more preferably 0.25 to 3.0 parts by mass, and more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the abrasive grains in the polishing slurry. From the viewpoint of further suppressing the reduction in the polishing rate (for example, the polishing rate of an insulating material), the content of the salt of the compound represented by formula (1) is preferably 0.8 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.5 parts by mass or more, and particularly preferably 1.6 parts by mass or more, relative to 100 parts by mass of the abrasive grains in the polishing slurry, based on the total mass of the polishing slurry.

[0097] (Optical component) The polishing slurry of the present embodiment can further contain an arbitrary additive (excluding the salt of the compound represented by formula (1)) for the purpose of adjusting the polishing properties and the like. As the arbitrary additive, a material having a carboxyl group (excluding a compound equivalent to a polyoxyalkylene compound or a water-soluble polymer), a polyoxyalkylene compound, a water-soluble polymer, an oxidizing agent (for example, hydrogen peroxide), and the like can be given. Each additive can be used alone or two or more can be used in combination.

[0098] The arbitrary additive (water-soluble polymer or the like) has an effect of improving the dispersion stability of the abrasive grains in the polishing slurry and enabling the insulating material (for example, silicon oxide) to be polished at a higher speed. In addition, by enabling the insulating material (for example, silicon oxide) to be polished at a high speed, the step difference elimination property is improved, and a high planarity can also be obtained. This is considered to be because the polishing rate of the convex portion is greatly improved compared to the concave portion.

[0099] As the material having a carboxyl group, a monobasic carboxylic acid such as acetic acid, propionic acid, butyric acid, valeric acid, and the like; a hydroxy acid such as lactic acid, malic acid, citric acid, and the like; a dibasic carboxylic acid such as malonic acid, succinic acid, fumaric acid, maleic acid, and the like; a polybasic carboxylic acid such as polyacrylic acid, polymaleic acid, and the like; an amino acid such as arginine, histidine, lysine, and the like; and the like can be given.

[0100] From the viewpoint of easily exhibiting a high polishing rate of the insulating material, the weight average molecular weight of the material having a carboxyl group is preferably 100,000 or less, more preferably 80,000 or less, further preferably 60,000 or less, particularly preferably 50,000 or less, and extremely preferably 10,000 or less. From the viewpoint of being able to maintain appropriate dispersibility, the weight average molecular weight of the material having a carboxyl group is preferably 1,000 or more, more preferably 1,500 or more, further preferably 2,000 or more, and particularly preferably 5,000 or more.

[0101] The content of the material having a carboxyl group is preferably 0.01 to 10% by mass, based on the total mass of the slurry for polishing. Thereby, the aggregation of the abrasive particles with each other is suppressed while the insulating material is easily polished at a high polishing rate.

[0102] As the polyalkylene oxide compound, polyalkylene glycol, polyalkylene oxide derivatives, and the like can be given.

[0103] As the polyalkylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like can be given. As the polyalkylene glycol, at least one selected from the group consisting of polyethylene glycol and polypropylene glycol is preferable, and polyethylene glycol is more preferable.

[0104] The polyalkylene oxide derivative is, for example, a compound in which a functional group or a substituent is introduced into polyalkylene glycol, or a compound in which polyalkylene oxide is added to an organic compound. As the functional group or the substituent, for example, an alkyl ether group, an alkyl phenyl ether group, a phenyl ether group, a styrenated phenyl ether group, a glyceryl ether group, an alkyl amine group, a fatty acid ester group, and a diol ester group can be given. As the polyalkylene oxide derivative, for example, polyoxyethylene alkyl ether, polyoxyethylene bisphenol ether (for example, manufactured by Nikko Emulsion Co., Ltd., BA diol series), polyoxyethylene styrenated phenyl ether (for example, manufactured by Kao Corporation, EMULGEN series), polyoxyethylene alkyl phenyl ether (for example, manufactured by the First Industrial Co., Ltd., NOIGEN EA series), polyalkylene oxide polyglyceryl ether (for example, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., SC-E series and SC-P series), polyoxyethylene sorbitan fatty acid ester (for example, manufactured by the First Industrial Co., Ltd., SORGEN TW series), polyoxyethylene fatty acid ester (for example, manufactured by Kao Corporation, EMANON series), polyoxyethylene alkyl amine (for example, manufactured by the First Industrial Co., Ltd., AMIRADINE D), and other compounds to which polyalkylene oxide is added (for example, manufactured by Nisshin Chemical Co., Ltd., Surfynol 465, and manufactured by Nikko Emulsion Co., Ltd., TMP series) can be given.

[0105] The weight average molecular weight of the polyoxyalkylene compound is not particularly limited, and from the viewpoint of easily obtaining appropriate workability and foaming properties, it is preferably 100,000 or less, more preferably 50,000 or less, further preferably 20,000 or less, particularly preferably 10,000 or less, and extremely preferably 5,000 or less. From the viewpoint of further improving planarity, the weight average molecular weight of the polyoxyalkylene compound is preferably 200 or more, more preferably 400 or more, and further preferably 500 or more.

[0106] From the viewpoint of further improving planarity, the content of the polyoxyalkylene compound is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more, based on the total mass of the slurry for polishing. From the viewpoint of easily obtaining a moderate polishing rate, the content of the polyoxyalkylene compound is preferably 5% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less, based on the total mass of the slurry for polishing.

[0107] The water-soluble polymer has the effect of adjusting the dispersion stability of the abrasive grains, planarity, in-plane uniformity, polishing selectivity of silicon oxide with respect to silicon nitride (polishing rate of silicon oxide / polishing rate of silicon nitride), polishing selectivity of silicon oxide with respect to polysilicon (polishing rate of silicon oxide / polishing rate of polysilicon), and the like. Here, the "water-soluble polymer" is defined as a polymer that dissolves 0.1 g or more in 100 g of water. In addition, polymers equivalent to the above-described polyoxyalkylene compound are excluded from the "water-soluble polymer".

[0108] As the water-soluble polymer, there is no particular limitation, and examples include acrylic polymers such as polyacrylamide and polydimethylacrylamide; polysaccharides such as carboxymethyl cellulose, agar, curdlan, dextrin, cyclodextrin, and pullulan; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrolein; glycerin polymers such as polyglycerol and polyglycerol derivatives; and polyethylene glycol. The water-soluble polymer can be used alone or in combination of two or more.

[0109] In the case of using a water-soluble polymer, the content of the water-soluble polymer is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, and extremely preferably 0.5% by mass or more, based on the total mass of the slurry for polishing, from the viewpoint of suppressing the settlement of abrasive grains while obtaining the effect of the addition of the water-soluble polymer. The content of the water-soluble polymer is preferably 10% by mass or less, more preferably 8% by mass or less, further preferably 6% by mass or less, particularly preferably 5% by mass or less, extremely preferably 3% by mass or less, and very preferably 1% by mass or less, based on the total mass of the slurry for polishing, from the viewpoint of suppressing the settlement of abrasive grains while obtaining the effect of the addition of the water-soluble polymer. In the case of using a plurality of compounds as the water-soluble polymer, the total content of the compounds is preferably within the above range.

[0110] In the case of using an oxidizing agent, the content of the oxidizing agent is preferably 0.0001 to 10% by mass, based on the total mass of the slurry for polishing, from the viewpoint of suppressing the settlement of abrasive grains while obtaining the effect of the addition of the additive.

[0111] (Liquid medium) The liquid medium in the slurry for polishing of the present embodiment is not particularly limited, and water such as deionized water, ultrapure water, or the like is preferred. The content of the liquid medium can be the remaining portion of the slurry for polishing excluding the contents of other constituent components, and is not particularly limited.

[0112] (Properties of the slurry for polishing) The pH of the slurry for polishing of the present embodiment is preferably 2.0 or more, more preferably 2.5 or more, more preferably 2.8 or more, particularly preferably 3.0 or more, extremely preferably 3.2 or more, and very preferably 3.5 or more, from the viewpoint of further improving the polishing rate of the insulating material. The pH of the slurry for polishing is preferably 7.0 or less, more preferably 6.5 or less, more preferably 6.0 or less, particularly preferably 5.0 or less, and extremely preferably 4.0 or less, from the viewpoint of further improving the storage stability of the slurry for polishing. From these viewpoints, the pH is preferably 2.0 to 7.0, more preferably 2.5 to 6.5, more preferably 2.8 to 6.0, particularly preferably 3.0 to 5.0, extremely preferably 3.2 to 4.0, and very preferably 3.5 to 4.0. The pH of the slurry for polishing is defined as the pH at a liquid temperature of 25°C.

[0113] The pH of the polishing slurry can be adjusted by an acid component such as an inorganic acid, an organic acid, or the like; an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, an alkanolamine, or the like; and the like. In addition, a buffer can be added in order to stabilize the pH. In addition, the buffer can be added as a buffer solution (a liquid containing a buffer). As such a buffer solution, an acetate buffer solution, a phthalate buffer solution, and the like can be given.

[0114] The pH of the polishing slurry of the present embodiment can be measured with a pH meter (for example, Model PHL-40 manufactured by Toa DKK Corporation). Specifically, for example, after performing 2-point calibration of the pH meter using a phthalate pH buffer (pH: 4.01) and a neutral phosphate pH buffer (pH: 6.86) as standard buffers, the electrode of the pH meter is immersed in the polishing slurry, and the value after stabilization for 2 minutes or more is measured. The liquid temperature of the standard buffer and the polishing slurry is set to 25°C.

[0115] The polishing slurry of the present embodiment is difficult to cause aggregation of particles even in the case of long-term storage. For example, the increase rate of the D99 particle diameter ( {[D99 particle diameter after storage / D99 particle diameter before storage] - 1} x 100) of the polishing slurry of the present embodiment when stored at 60°C for 5 days is, for example, 10% or less, 5% or less, or 3% or less. The D99 particle diameter is an index that more significantly shows the good or bad of storage stability, and if the D99 particle diameter increases by 10% or more, there is a concern of generation of polishing damage and reduction of polishing rate due to an increase in coarse particles. The increase rate of the D99 particle diameter can be calculated, for example, by leaving the polishing slurry in a constant-temperature bath at 60°C for 5 days, and measuring the D99 particle diameter in the polishing slurry before and after leaving.

[0116] The polishing slurry of the present embodiment can be prepared, for example, by mixing a polishing slurry (for example, an aqueous dispersion) containing the first particles and a polishing slurry (for example, an aqueous dispersion) containing the second particles. At this time, at least one of the polishing slurry containing the first particles and the polishing slurry containing the second particles contains a salt of the compound represented by formula (1).

[0117] When the polishing slurry of the present embodiment is used as a polishing liquid (for example, a CMP polishing liquid), the components of the polishing liquid can be stored as a one-liquid polishing liquid, or can be stored as a multi-liquid (for example, two-liquid) polishing liquid kit in which the components of the polishing liquid are divided into a polishing slurry containing abrasive grains, a liquid medium, and a salt of the compound represented by formula (1) (a first liquid) and an additive liquid containing an additive and a liquid medium (a second liquid) so as to become a target polishing liquid by mixing the first liquid and the second liquid. The additive liquid can contain, for example, an oxidizing agent. The components of the polishing liquid can be stored as a polishing liquid kit in which the components are divided into three or more liquids.

[0118] In the polishing liquid set, the polishing slurry (1st liquid) and the additive liquid (2nd liquid) are mixed immediately before or during polishing to produce the polishing liquid. In addition, the one-liquid type polishing liquid can be stored as a polishing liquid storage liquid in which the content of the liquid medium is reduced, and can be used after being diluted with the liquid medium at the time of polishing. The multi-liquid type polishing liquid set can be stored as a polishing slurry storage liquid and an additive liquid storage liquid in which the content of the liquid medium is reduced, and can be used after being diluted with the liquid medium at the time of polishing.

[0119] In the case of the one-liquid type polishing liquid, as a method of supplying the polishing liquid to the polishing table, a method of directly supplying the polishing liquid by transporting it with a pipe; a method of supplying it by transporting the polishing liquid storage liquid and the liquid medium with respective pipes, and mixing them; a method of supplying it by previously mixing the polishing liquid storage liquid and the liquid medium; and the like can be used.

[0120] At the time of storage as the multi-liquid type polishing liquid set in which the polishing slurry and the additive liquid are separated, the polishing rate can be adjusted by arbitrarily changing the composition of these liquids. At the time of use of the polishing liquid set, as a method of supplying the polishing liquid to the polishing table, the following methods can be used. For example, the following methods can be used: a method of supplying it by transporting the polishing slurry and the additive liquid with respective pipes, and mixing them; a method of supplying it by transporting the polishing slurry storage liquid, the additive liquid storage liquid, and the liquid medium with respective pipes, and mixing them; a method of supplying it by previously mixing the polishing slurry and the additive liquid; a method of supplying it by previously mixing the polishing slurry storage liquid, the additive liquid storage liquid, and the liquid medium; and the like. In addition, a method of separately supplying the polishing slurry and the additive liquid in the above-described polishing liquid set to the polishing table can also be used. In this case, the polishing liquid obtained by mixing the polishing slurry and the additive liquid on the polishing table is used to polish the polished surface.

[0121] <Polishing method> The polishing method (polishing method of a base, etc.) of the present embodiment includes a polishing step of polishing a polished body (for example, a base) using the above-described polishing slurry. The polishing slurry in the polishing step can be the polishing liquid obtained by mixing the polishing slurry and the additive liquid in the above-described polishing liquid set. In the polishing step, the polished surface of the polished body can be polished. The polished surface can contain an insulating material, and can contain silicon oxide.

[0122] Figure 1 is a schematic cross-sectional view showing a base used in the polishing method of an embodiment. The base 1 includes a substrate 2 and an insulating portion 3. The insulating portion 3 is provided on one surface of the substrate 2 so as to fill a recess formed in the one surface of the substrate 2. In the base 1, the surface of the insulating portion 3 opposite to the substrate 2 is exposed, and the exposed surface becomes a polished surface.

[0123] As the substrate 2, for example, a substrate used in the production of a semiconductor element (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, and the like are formed) can be given. The insulating portion 3 is formed of an insulating material such as an STI insulating material, a pre-metal insulating material, an interlayer insulating material, and the like. As the insulating material, silicon oxide, phosphorus-silicate glass, boron-phosphorus-silicate glass, silicon oxyfluoride, fluorinated amorphous carbon, and the like can be given. The insulating portion 3 can be composed of a single material or a plurality of materials. The insulating portion 3 can be in the form of a film, for example, a silicon oxide film.

[0124] By polishing the insulating portion 3 formed on such a substrate 2 with the above-mentioned polishing slurry, the excess portion is removed, and the unevenness of the surface of the insulating portion 3 can be eliminated, and a smooth surface can be obtained on the entire surface of the insulating portion 3. The polishing slurry of the present embodiment is preferably used for polishing the surface of an insulating portion containing silicon oxide (for example, a surface having a region formed of silicon oxide in at least a part thereof).

[0125] As a method for producing the insulating portion to be polished by the polishing slurry of the present embodiment, a CVD method such as a low-pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, and the like; a spin coating method in which a liquid raw material is applied to a rotating substrate; and the like can be given.

[0126] In the polishing step, as the polishing device, a general polishing device having a holder capable of holding a base body having a surface to be polished and a polishing stage capable of attaching a polishing pad can be used. Specifically, for example, in a state in which the surface of the base body 1 (the exposed surface of the insulating portion 3) is pressed against the polishing pad (polishing cloth) of the polishing stage, the above-mentioned polishing slurry is supplied between the insulating portion 3 and the polishing pad, and the base body 1 and the polishing stage are relatively moved, and the surface to be polished of the insulating portion 3 is polished. In the polishing step, for example, a part of the insulating portion 3 is removed by polishing.

[0127] A motor or the like whose rotational speed can be changed is attached to each of the holder and the polishing stage of the polishing device. As the polishing device, for example, a polishing device manufactured by Yamanaka Mfg. Co., Ltd.: F-REX300, or a polishing device manufactured by APPLIED MATERIALS, Inc.: Reflexion can be used.

[0128] As the polishing pad, a general nonwoven fabric, a foam, a non-foam, or the like can be used. As the material of the polishing pad, a resin such as polyurethane, an acrylic resin, polyester, an acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly 4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trademark) and polyaramide), polyimide, polyimide amide, polysiloxane copolymer, an oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin, or the like 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 preferable from the viewpoint of more excellent polishing speed and planarity. It is preferable that the polishing pad be subjected to groove processing of the kind that stores the polishing slurry.

[0129] The polishing conditions are not limited, and in order not to cause the substrate to fly out, the rotation speed of the polishing stage is preferably 200 min -1 (min -1 = rpm) or less. From the viewpoint of sufficiently suppressing the occurrence of polishing damage, the polishing pressure (processing load) applied to the substrate is preferably 100 kPa or less. In the polishing process, it is preferable that the polishing slurry be continuously supplied to the polishing pad with a pump or the like during polishing. The amount of supply is not limited, but it is preferable that the surface of the polishing pad be always covered with the polishing slurry.

[0130] The substrate after polishing is preferably sufficiently washed in running water to remove the particles adhering to the substrate. In the washing, dilute hydrofluoric acid or ammonia water can be used in addition to pure water, and a brush can be used in order to improve the washing efficiency. After washing, it is preferable to shake off the water droplets adhering to the substrate and then dry the substrate using a spin dryer or the like.

[0131] As described above, the polishing slurry and the polishing method of the present embodiment can be used in the planarization process of the surface of a substrate which is a manufacturing technique of a semiconductor element, and in particular, can be appropriately used in the planarization process of an insulating portion formed of an STI insulating material, a front metal insulating material, or an interlayer insulating material. In other words, according to the polishing slurry of the present embodiment, the formation of an STI, and high-speed polishing of a front metal insulating film and an interlayer insulating film can be performed.

[0132] In addition, the polishing slurry and the polishing method of the present embodiment can also be applied to 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 (indium tin oxide); and polymer resin materials such as polyimide-based, polybenzoxazole-based, acrylic-based, epoxy-based, and phenol-based materials.

[0133] Furthermore, the polishing slurry and polishing method of this embodiment are not only applicable to film-shaped polishing objects, but also applicable to various substrates made of glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, plastics, etc.

[0134] Furthermore, the polishing slurry and polishing method of this embodiment can be used not only for the manufacture of semiconductor devices, but also for the manufacture of image display devices such as TFTs (thin-film transistors) and organic ELs (electroluminescent diodes); optical components such as photomasks, lenses, prisms, optical fibers, and single-crystal scintillators; optical components such as optical switching elements and optical waveguides; light-emitting elements such as solid-state lasers and blue lasers, and LEDs (light-emitting diodes); and magnetic storage devices such as disks and magnetic heads. Example

[0135] The present invention will now be described in detail based on specific embodiments, but the present invention is not limited to these embodiments.

[0136] <Example 1> (Preparation of slurry for grinding cerium oxide) [Preparation of slurry for cerium oxide grinding] A cerium oxide grinding slurry (pH: 5.0) containing cerium oxide particles (the first particle, hereinafter referred to as "cerium oxide particles") was prepared by mixing an aqueous solution of ammonium dihydrogen phosphate manufactured by Wako Pure Chemical Industries, Ltd. The mixing amount of ammonium dihydrogen phosphate was adjusted so that the content of ammonium dihydrogen phosphate in the CMP grinding slurry described later was as shown in Table 1.

[0137] [Determination of average particle size] A suitable amount of cerium oxide polishing slurry was added to Microtrac MT3300EXII (manufactured by Microtrac BEL Co., Ltd.), and the average particle size (average secondary particle size) of the cerium oxide particles was measured. The displayed average particle size value was taken as the average particle size (average secondary particle size). The average particle size of the cerium oxide polishing slurry was 350 nm.

[0138] [Measurement of ζ potential] An appropriate amount of cerium oxide grinding slurry was added to a product manufactured by Beckman Coulter Co., Ltd., under the trade name DelsaNano C, and the zeta potential was measured twice at 25°C. The average value of the displayed zeta potential was taken as the zeta potential. The zeta potential of the cerium oxide particles in the cerium oxide grinding slurry was -55 mV.

[0139] (Preparation of slurry for grinding cerium hydroxide) Synthesis of cerium hydroxide A 350 g of Ce(NH4)2(NO3)6 50 mass% aqueous solution (manufactured by Nippon Chemical Industrial Co., Ltd., trade name: CAN50 liquid) was mixed with 7825 g of pure water to obtain a solution. Next, while stirring the solution, 750 g of an aqueous imidazole solution (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 performed at a temperature of 25°C, a stirring rate of 400 min -1 Stirring was performed using three vane pitch paddles each having a vane portion 5 cm in length.

[0140] [Preparation of slurry for cerium oxide polishing] The obtained precipitate (precipitate containing cerium hydroxide) was subjected to centrifugal separation (4000 min -1 , 5 min) and then the liquid phase was removed by decantation, thereby performing solid-liquid separation. After mixing 10 g of the particles obtained by the solid-liquid separation with 990 g of water, the particles were dispersed in the water using an ultrasonic cleaner to prepare a slurry for cerium hydroxide polishing (content of particles: 1.0 mass%) of the particles containing cerium hydroxide (second particles. Hereinafter referred to as "cerium hydroxide particles").

[0141] [Measurement of average particle diameter] The average particle diameter (average secondary particle diameter) of the cerium hydroxide particles in the slurry for cerium hydroxide polishing was measured using N5 manufactured by Beckman Coulter, Inc. The result was 25 nm. The measurement method is described below. First, about 1 mL of a measurement sample (slurry for cerium hydroxide polishing, aqueous dispersion) containing 1.0 mass% of cerium hydroxide particles was placed in a 1 cm square cuvette, and the cuvette was set in N5. The refractive index of the measurement sample information of the N5 software was set to 1.333 and the viscosity was set to 0.887 mPa s, and the measurement was performed at 25°C, and the value displayed was read as the Unimodal Size Mean.

[0142] [Measurement of zeta potential] An appropriate amount of the slurry for cerium hydroxide polishing was placed in Delsa Nano C manufactured by Beckman Coulter, Inc., and the measurement was performed twice at 25°C. The average value of the zeta potential displayed was obtained as the zeta potential. The zeta potential of the cerium hydroxide particles in the slurry for cerium hydroxide polishing was +50 mV.

[0143] [Structural analysis of cerium hydroxide particles] A slurry for cerium hydroxide polishing was taken in an appropriate amount, vacuum-dried, and cerium hydroxide particles were separated. The obtained sample was washed with pure water, and subjected to measurement by FT-IR ATR method. As a result, a peak based on nitrate ion (NO3 － ) was observed in addition to a peak based on hydroxide ion (OH － ). Further, for the same sample, XPS (N-XPS) measurement for nitrogen was performed, and as a result, a peak based on NH4 + was not observed, and a peak based on nitrate ion was observed. From these results, it was confirmed that the cerium hydroxide particles contained at least a part of particles having nitrate ion bound to cerium element. Further, since the cerium hydroxide particles contained at least a part of particles having hydroxide ion bound to cerium element, it was confirmed that the cerium hydroxide particles contained cerium hydroxide. From these results, it was confirmed that the cerium hydroxide contained hydroxide ion bound to cerium element.

[0144] [Measurement of absorbance and transmittance] A slurry for cerium hydroxide polishing was taken in an appropriate amount, and diluted with water so that the content of particles became 0.0065 mass% (65 ppm) to obtain a measurement sample (aqueous dispersion). About 4 mL of the measurement sample was put in a 1 cm square cuvette, and the cuvette was set in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance measurement was performed in the range of wavelengths from 200 to 600 nm, and absorbance for light of wavelength 290 nm and absorbance for light of wavelengths from 450 to 600 nm were measured. The absorbance for light of wavelength 290 nm was 1.192, and the absorbance for light of wavelengths from 450 to 600 nm was less than 0.010.

[0145] About 4 mL of a slurry for cerium hydroxide polishing (content of particles: 1.0 mass%) was put in a 1 cm square cuvette, and the cuvette was set in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance measurement was performed in the range of wavelengths from 200 to 600 nm, and absorbance for light of wavelength 400 nm and transmittance for light of wavelength 500 nm were measured. The absorbance for light of wavelength 400 nm was 2.25, and the transmittance for light of wavelength 500 nm was 92% / cm.

[0146] [Preparation of CMP polishing liquid] A CMP polishing liquid was prepared by mixing 100 g of the cerium oxide polishing slurry described above, 100 g of the cerium hydroxide polishing slurry described above, 5.5 g of PGL #750 (trade name, polyglycerol (water-soluble high molecule), weight average molecular weight: 750) manufactured by Sakamoto Pharmaceutical Industry Co., Ltd., and 794.5 g of ion exchange water while stirring at 300 rpm using two pieces of a stirring blade, for 30 minutes. The CMP polishing liquid was prepared by mixing the components while irradiating ultrasonic waves using an ultrasonic cleaner (device name: US-105) manufactured by SND Co., Ltd. The pH of the polishing liquid was 4.0. The pH was measured using a pH meter model PHL-40 manufactured by Toa DKK Co., Ltd. It was confirmed by a scanning electron microscope S-4800 manufactured by Hitachi High-Technologies Corporation that the cerium oxide particles (first particles) and the cerium hydroxide particles (second particles) were in contact with each other and formed composite particles.

[0147] <Examples 2 and 3> A CMP polishing liquid was prepared in the same manner as in Example 1, except that the mixing amounts of the components were changed so that the content of ammonium dihydrogen phosphate was the value shown in Table 1.

[0148] <Examples 4 and 5 and Comparative Examples 1 to 5> Instead of ammonium dihydrogen phosphate, diammonium hydrogen phosphate (manufactured by Wako Pure Chemical Industries, Ltd.), 1-hydroxyethane-1,1-bis(phosphonic acid) ammonium (prepared by adding 25% ammonia water manufactured by Wako Pure Chemical Industries, Ltd. to 1-hydroxyethane-1,1-bis(phosphonic acid) manufactured by Wako Pure Chemical Industries, Ltd.), phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.), 1-hydroxyethane-1,1-bis(phosphonic acid) (manufactured by Wako Pure Chemical Industries, Ltd., trade name: 60% 1-hydroxyethane-1,1-bis(phosphonic acid) solution), polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., trade name: Polyacrylic Acid 5000 (weight average molecular weight: 5000)), acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.), or nitric acid (manufactured by Wako Pure Chemical Industries, Ltd.) (see Table 1 or Table 2), and adjusting the mixing amounts of the components so that the contents of the components in the polishing liquid were the values shown in Table 1 or Table 2, were used, and a CMP polishing liquid was prepared in the same manner as in Example 1, except for this.

[0149] <Average particle diameter of abrasive particles> An appropriate amount of the CMP polishing slurry was put into a product MICROTRAC MT3300EXII manufactured by MICROTRAC BEL Co., Ltd. to measure the average particle diameter of the abrasive grains. The average particle diameter value shown was taken as the average particle diameter (average secondary particle diameter). The average particle diameters of Examples 1 to 5 and Comparative Examples 1 to 5 were 350 nm.

[0150] [CMP Evaluation] The CMP polishing slurry described above was used to polish a polished substrate under the following polishing conditions. Each of the CMP polishing slurries was a polishing slurry containing 0.5 mass% of cerium oxide particles (1st particles), 0.1 mass% of cerium hydroxide particles (2nd particles), 0.5 mass% of PGL #750, and the additive shown in Table 1 or Table 2, with the remainder being ion exchange water, based on the total mass of the polishing slurry. The pH of each of the CMP polishing slurries was 4.0.

[0151] [CMP Polishing Conditions] Polishing device: Reflexion LK (manufactured by APPLIED MATERIALS, INC.) Flow rate of the CMP polishing slurry: 250 mL / minute Polished substrate: As a blanket wafer on which no pattern was formed, a polished substrate having a silicon oxide (SiO2, p-TEOS) film with a thickness of 2 μm formed by a plasma CVD method on a silicon substrate was used. Polishing pad: Foamed polyurethane resin having independent air bubbles (manufactured by Rohm and Haas Japan Co., Ltd., type IC1010) Polishing pressure: 21 kPa (3.0 psi) Rotational speed of the polished substrate and the polishing stage: Polished substrate / polishing stage = 93 / 87 rpm Polishing time: 0.5 minute (30 seconds) Cleaning of the wafer: After the CMP treatment, the wafer was cleaned with water while ultrasonic waves were applied, and then dried with a spin dryer.

[0152] The removal rate (RR) of the silicon oxide film after polishing and cleaning under the above conditions was calculated by the following equation. In addition, the difference in film thickness of the silicon oxide film before and after polishing was calculated using an optical interference film thickness measuring device (manufactured by Filmetrics Co., Ltd., trade name: F80). The measurement results are shown in Table 1 and Table 2. Removal rate (RR) = (difference in film thickness of the silicon oxide film before and after polishing [nm]) / (polishing time: 0.5 [minute])

[0153] [Storage Stability Evaluation] The increase rate of the D99 particle diameter was calculated, and the storage stability was evaluated. Specifically, the D99 particle diameter of the polishing liquid immediately after preparation and the polishing liquid that had been left to stand in a constant-temperature bath at 60°C for 5 days was measured using a Microtrac MT3300EXII manufactured by Microtrac BEL Co., Ltd., and the D99 particle diameter increase rate was calculated according to the following formula. The measurement results are shown in Tables 1 and 2. D99 particle diameter increase rate (%) = [(D99 particle diameter of the polishing liquid stored in a constant-temperature bath at 60°C for 5 days) / (D99 particle diameter of the polishing liquid immediately after preparation)] - 1] x 100

[0154] [Table 1]

[0155] [Table 2]

Claims

1. A grinding slurry comprising abrasive particles, a liquid medium, and a salt of a compound represented by formula (1) below. The average secondary particle size of the abrasive grains is 200–600 nm. The abrasive grains comprise a first particle and a second particle in contact with the first particle. The first particle contains cerium oxide. The second particle contains a hydroxide of a tetravalent metal element. The salt of the compound represented by formula (1) contains at least one selected from diammonium hydrogen phosphate and diammonium dihydrogen phosphate. Relative to 100 parts by weight of the abrasive particles, the salt content of the compound represented by formula (1) is 0.25 to 3.0 parts by weight. In formula (1), R represents a hydroxyl group or a monovalent organic group.

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