JP6792554B2 - Polishing abrasive grains, polishing slurry and hard brittle material polishing method, and hard brittle material manufacturing method - Google Patents

Description

The present invention relates to an abrasive grain used for polishing a hard and brittle material such as sapphire, a polishing slurry and a method for polishing a hard and brittle material, and a method for producing a hard and brittle material.

In recent years, as next-generation semiconductor devices, semiconductor layers such as gallium nitride (GaN), which have superior characteristics to silicon semiconductors, in high-frequency devices such as mobile phones, light emitting elements such as LEDs, and power devices such as power conversion / control devices. Is being energetically developed as a laminated semiconductor wafer laminated on a semiconductor forming substrate. In such a laminated semiconductor wafer, if the surface of the semiconductor forming substrate is uneven, the growth of the semiconductor layer becomes non-uniform, and the adhesive strength between the semiconductor forming substrate and the semiconductor layer is weakened. High surface smoothness is required for the substrate.

In polishing in the manufacture of a semiconductor-forming substrate, a highly smooth surface is usually obtained by performing rough polishing by wrapping and then removing scratches caused by wrapping by chemical mechanical polishing (CMP), which is finish polishing. CMP polishes by pressing the object to be polished against a wrap with a polishing pad and moving the object to be polished and the lap relative to each other while flowing a polishing slurry containing abrasive grains and components such as acid or alkali. The surface of the object to be polished is modified by the chemical components contained in the polishing slurry to increase the mechanical polishing action of the abrasive grains, and a highly smooth polished surface can be obtained.

Sapphire (Al ₂ O ₃ ), silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), etc. are used as the substrate used for forming the semiconductor layer such as gallium nitride (GaN) described above. ing. All of these are brittle materials having high hardness, that is, hard and brittle materials, and are not easy to process by polishing as compared with conventional metallic silicon, silicon oxide and the like. The hard and brittle material generally means a hard and brittle material, and while it is a very hard material such as glass, stone or the above ceramics, it is a general term for materials that are vulnerable to impact and easily broken. Here, it refers to a Vickers hardness having a hardness of 500 HV or more and which may crack when an impact is applied.
For example, when the object to be polished is a hard and brittle material (particularly sapphire), a polishing slurry containing colloidal silica as polishing abrasive grains is often used in CMP for finish polishing (for example, Patent Documents 1 and 2). reference). However, CMP using colloidal silica as polishing abrasive grains cannot obtain a sufficient polishing rate (removal rate), and long-time polishing is required to obtain a highly smooth surface, in order to improve productivity. There is a demand for the development of polishing abrasive grains and polishing slurries that can obtain faster polishing speeds.

On the other hand, as a polishing slurry for CMP, an example in which alumina abrasive grains are used instead of colloidal silica has been reported. Patent Document 3 discloses a polishing slurry containing alumina abrasive grains having a specific particle size and proportion and having a pH in the range of 10.0 to 14.0. It has been reported that by using alumina abrasive grains in a strongly alkaline manner, an excellent polishing rate can be obtained as compared with colloidal silica abrasive grains. Further, Patent Document 4 discloses a polishing slurry containing alumina abrasive grains having a specific specific surface area and water and having a pH of 8.5 or higher. However, even in the polishing slurries containing alumina abrasive grains disclosed in Patent Documents 3 and 4, the polishing speed of the object to be polished in CMP cannot be said to be sufficient, and further improvement is required. Further, if the slurry is strongly alkaline, there is a problem that the alumina abrasive grains themselves deteriorate.

Japanese Unexamined Patent Publication No. 2008-44078 Japanese Unexamined Patent Publication No. 2009-28814 International Publication No. 2011/136387 International Publication No. 2012/11502

In the face of the above-mentioned problems, an object of the present invention is to provide a polishing abrasive grain, a polishing slurry, and a method for polishing a hard and brittle material, which can achieve both high polishing speed and surface smoothness in polishing a hard and brittle material. It is to be. Another object of the present invention is to provide a method for efficiently producing a hard and brittle material having excellent surface smoothness.

The present invention provides the following means.
<1> Abrasive abrasive grains used for polishing hard and brittle materials, which are alumina powders containing linked particles having one or more neck portions and having a mass average particle diameter of 3 μm or less. grain.
<2> The abrasive grains according to <1>, wherein the alumina is α-alumina.
<3> The polishing abrasive grain according to <2>, wherein the α-alumina has an alkali resistance of 0.7 or more.
<4> Described in any one of <1> to <3>, wherein the number ratio of the connected particles is 20% or more in the alumina powder having a particle size of 0.5 to 2 times the mass average particle size. Abrasive particles.
<5> In the alumina powder having a particle size of 0.5 to 2 times the mass average particle size, the number ratio of particles having a surface index of 1.4 or more is 25% or more, as described in <1> to <4>. Abrasive particles according to any one.
<6> A polishing slurry containing the abrasive grains according to any one of <1> to <5> and water or a solvent mainly composed of water and having a pH of 12 or more.
<7> A method for polishing a hard and brittle material, which comprises a step of chemically polishing the surface of the hard and brittle material using the polishing slurry according to <6>.
<8> A method for producing a hard and brittle material, which comprises a step of polishing the hard and brittle material by the polishing method according to <7>.
<9> The method for producing a hard and brittle material according to <8>, wherein the hard and brittle material to be polished is sapphire.
<10> The method for producing a hard and brittle material according to <9>, wherein the sapphire is a single crystal sapphire.

According to the present invention, there is provided a polishing abrasive grain, a polishing slurry, and a method for polishing a hard and brittle material, which can achieve both high polishing speed and surface smoothness in polishing a hard and brittle material. By chemically polishing the surface of the hard and brittle material using the polishing slurry, a hard and brittle material having a highly smooth surface can be produced with high productivity.

It is an SEM image of the polishing abrasive grain of Example 2 used for image analysis. It is an SEM image of the polishing abrasive grain of Example 2 used for image analysis. 6 is an SEM image of the abrasive grains of Example 1. It is an SEM image of the polishing abrasive grain of Example 2. 6 is an SEM image of the abrasive grains of Example 3. 6 is an SEM image of the abrasive grains of Example 4. 6 is an SEM image of the abrasive grains of Example 5. 6 is an SEM image of the abrasive grains of Comparative Example 1.

Hereinafter, the present invention will be described in detail by showing examples and the like, but the present invention is not limited to the following examples and the like, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

<1. Abrasive grains>
The abrasive grains of the present invention are abrasive grains used for polishing hard and brittle materials, and are alumina powders containing connected particles having one or more neck portions and having an average particle diameter of 3 μm or less. Is. The polishing abrasive grains of the present invention can be used as they are, but are usually dispersed in a solvent (dispersion medium) and used as a polishing slurry in a polishing apparatus. The details of the polishing slurry containing the polishing abrasive grains of the present invention and the polishing method using the polishing slurry will be described later.

The reason why the polishing abrasive grains of the present invention contain connected particles having one or more neck portions, thereby improving the polishing speed and the surface smoothness of the object to be polished is detailed at this stage. Although the reason is not completely clear, the shape of alumina having a neck makes it easier to hold it on the polishing pad used in CMP, and the number of abrasive grains that actually act on polishing increases and polishing is performed. It is presumed that one of the causes is the improvement in speed.

In the present invention, the "connected particles having one or more neck portions" are recesses because a plurality of primary particles are connected by sintering or the like, or the primary particles themselves have an uneven shape. It means a particle having one or more neck portions.

Examples of the method for determining whether or not the particles are connected particles having one or more neck portions include the following [determination method 1] and [determination method 2]. Those that satisfy the judgment criteria of either [Judgment Method 1] or [Judgment Method 2] are connected particles having one or more neck portions.

[Judgment method 1]
Alumina particles are observed with a scanning electron microscope (SEM) at a magnification of 20000 times, the presence or absence of a neck portion is visually determined, and alumina particles having one or more neck portions are formed on one or more neck portions. Judged as having linked particles.

[Judgment method 2]
Alumina particles are observed by SEM at a magnification of 20000 times, the area loss rate represented by the following formula (I) is calculated, and the particles having an area loss rate of 10% or more are connected with one or more necks. Judged as a state particle.

Area loss rate = (Area A-Area B) ÷ Area A x 100 (I)

The area A surrounds the alumina particles and the recesses obtained by drawing a plurality of straight lines connecting the convex portions on the outer periphery of the alumina particles so as to surround the alumina particles in the SEM image of the alumina particles. The area of the part.
The area B is the area of the alumina particles in the SEM image.
It is considered that the larger the area loss rate, the larger the unevenness of the alumina particles, or the more unevenness existing in the alumina particles. From the viewpoint of obtaining a better polishing rate, the area defect rate is preferably 15% or more. The area loss rate is usually 40% or less.
The area loss rate may be calculated by image analysis using commercially available image analysis software, for example, "WinROOF" of Mitani Corporation.

At the time of image analysis of alumina particles, it is necessary to obtain an SEM image in which the alumina particles are dispersed so that one alumina particle can be observed. One alumina particle means, for example, those continuously surrounded by a contour line when observed by SEM. However, it is difficult to obtain an SEM image suitable for image analysis in which the alumina particles are dispersed because the alumina particles are in an aggregated state simply by drying the slurry in order to obtain the dried alumina powder. Therefore, as described in [Evaluation Method 2] described later, an SEM image in which alumina particles are dispersed can be obtained by using a sufficiently diluted alumina dispersion. FIG. 1 is an SEM image in which the alumina particles of Example 2 described later are dispersed. Note that FIG. 4 is an SEM image of the aggregated alumina particles.

1 to 4 in FIG. 1 are contacted or overlapped with two or more alumina particles, and 5 is one alumina particle. In image analysis, when two or more alumina particles are in contact with each other or overlap each other as shown in FIGS. 1 to 4, the contour and number of the lower particles are unclear, so that the contour lines are continuous. Only the uppermost particle surrounded by is determined as one alumina particle and is used as an analysis target. In FIG. 2, among the alumina particles shown in FIG. 1, particles determined to be one alumina particle are filled, and the filled particles are the analysis target.

In the abrasive grains of the present invention, the number ratio of the connected particles having one or more neck portions is preferably 20% or more, preferably 50% or more of the total number of particles constituting the alumina powder. More preferably, it is more preferably 70% or more. When the number ratio of the connected particles having one or more neck portions is large, the ratio of the particles contributing to polishing in the alumina abrasive grains is large, and the polishing speed can be further increased.

The number ratio is, for example, in an SEM image in which aggregated alumina particles are observed at a magnification of 20000, 100 alumina particles are randomly extracted, and as described above, each particle is visually linked as a connected particle. It can be determined by the following formula to determine whether or not it exists.

Percentage of connected particles with one or more necks (%)
= (Number of particles visually confirmed to have a neck) ÷ (Total number of randomly extracted particles (100)) x 100 (II)

Further, the fine particles generated by crushing and the like and the coarse particles not crushed have a small contribution to the polishing action. Therefore, it is preferable to determine whether or not the alumina particles, excluding such particles, which have a large contribution to the polishing action, are connected particles having one or more neck portions as measurement targets. Therefore, in a preferred embodiment, it is preferable to measure alumina particles having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder.
From this point of view, the abrasive grains of the present invention are the number of connected particles having one or more neck portions in the alumina powder having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder. The ratio is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. When the number ratio is large, the ratio of particles contributing to polishing in the alumina abrasive grains is large, and the polishing speed can be further increased.

The number ratio is, for example, the alumina particles 100 having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder in an SEM image obtained by observing the dispersed alumina particles as described above at a magnification of 20000 times. Randomly extract the particles, calculate the area loss rate of each particle as described above, determine whether or not the particles are connected particles having one or more necks, and obtain them by the following formula. Can be done. The particle size of the alumina powder may be the equivalent circle diameter of the SEM image of the alumina particles, and may be calculated by image analysis using commercially available image analysis software, for example, "WinROOF" of Mitani Shoji Co., Ltd.

Number ratio (%) of connected particles having one or more necks in alumina powder having a particle size 0.5 to 2 times the mass average particle size of the alumina powder.
= (Number of particles with an area defect rate of 10% or more having a particle size 0.5 to 2 times the mass average particle size of the alumina powder) ÷ (0.5 to 0.5 of the mass average particle size of the alumina powder randomly extracted) Total number of particles with twice the particle size (100)) x 100 (III)

The polishing abrasive grains of the present invention contain particles having a surface index of preferably 1.4 or more, more preferably 1.5 or more, from the viewpoint of obtaining a more excellent polishing rate. The upper limit of the surface index of the particles contained in the abrasive grains of the present invention is usually 3.5. At this stage, the detailed reason for the reason why the polishing speed is improved and the surface smoothness of the object to be polished is improved by containing the particles having a surface index of 1.4 or more is not completely clear. When the surface index of the particles is 1.4 or more, the minute irregularities on the surface of the particles are large, so that the number of minute contact points between the polishing substrate and the abrasive grains used in CMP increases and the polishing speed improves. Presumed to be one. Further, setting the surface index to 3.5 or less is effective in removing particles having a high surface index, for example, very elongated flat particles, which do not contribute to the polishing rate.

In the present invention, the surface index of the alumina particles is set to 1 when the cross section is a perfect circle (three-dimensionally a sphere), and is an index showing the degree of separation from the circle, which is lower than the peripheral length and area of the alumina particles. Calculated by equation (IV).

Surface index = (square of the peripheral length of alumina particles) ÷ (area of alumina particles) ÷ 4π (IV)

The surface index of the alumina particles may be calculated from, for example, the peripheral length and area of the SEM image of the alumina particles by observing the alumina particles at a magnification of 20000 times by SEM.
The surface index may be calculated by image analysis using commercially available image analysis software, for example, "WinROOF" of Mitani Corporation. At the time of image analysis, as described above, an SEM image in which the alumina particles are dispersed is obtained so that one alumina particle can be observed, and the particles determined to be one alumina particle are set as the analysis target.

Further, the fine particles generated by crushing and the like and the coarse particles not crushed have a small contribution to the polishing action. Therefore, it is preferable to determine the surface index of alumina particles, excluding such particles, which have a large contribution to the polishing action, as the measurement target. Therefore, in a preferred embodiment, it is preferable to measure alumina particles having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder, and the surface index of the alumina particles to be measured is 1. It is preferably 4 or more.
From this point of view, in the abrasive grains of the present invention, the number ratio of particles having a surface index of 1.4 or more in the alumina powder having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder is high. It is preferably 25% or more, more preferably 30% or more, and even more preferably 35% or more. When the number ratio is large, the ratio of particles contributing to polishing in the alumina abrasive grains is large, and the polishing speed can be further increased.

The number ratio is, for example, the alumina particles 100 having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder in an SEM image obtained by observing the dispersed alumina particles as described above at a magnification of 20000 times. Individuals can be randomly extracted, the surface index of each particle can be calculated, and it can be calculated by the following formula. The particle size of the alumina powder may be the equivalent circle diameter of the SEM image of the alumina particles, and may be calculated by image analysis using commercially available image analysis software, for example, "WinROOF" of Mitani Shoji Co., Ltd.

Percentage of particles with a surface index of 1.4 or more (%) in alumina powder having a particle size 0.5 to 2 times the mass average particle size of the alumina powder
= (Number of particles with a surface index of 1.4 or more having a particle size 0.5 to 2 times the mass average particle size of the alumina powder) ÷ (0.5 to 0.5 of the mass average particle size of the alumina powder randomly extracted) Total number of particles with twice the particle size (100)) x 100 (V)

The average particle size of the alumina powder is 3 μm or less, preferably 2 μm or less. The "average particle size" defined here means a particle size equivalent to a cumulative percentage of 50% on a mass basis obtained by a laser diffraction method. If the particle size of the alumina powder, which is the abrasive grain, exceeds 3 μm, a highly smooth surface may not be obtained. The lower limit of the average particle size of the alumina powder is not limited in terms of obtaining a highly smooth surface, but since the polishing rate decreases as the particle size decreases, it is usually 0.1 μm or more, preferably 0.2 μm or more. Is.

Alumina has a crystalline form such as α-alumina and γ-alumina, but α-alumina is preferable for high-speed polishing of hard and brittle materials. Among α-alumina, α-alumina having an alkali resistance of 0.7 or more is preferable. Here, the "alkali resistance" is an index of how much the crystal structure of α-alumina is maintained when immersed in a highly alkaline solution for a certain period of time, and specifically, it is measured by an X-ray diffraction pattern. It is defined by the peak intensity ratio before and after immersion in the alkaline solution. A specific method for defining the alkali resistance will be described later in Examples.

In the present invention, α-alumina means alumina in which the main phase of the crystal phase is the α phase. Therefore, alumina may contain a general crystal phase such as γ phase, θ phase, χ phase, δ phase, κ phase or ρ phase.

Hereinafter, a method for producing the alumina powder will be described.
The method for producing the alumina powder is not particularly limited, and for example, a method for firing aluminum hydroxide produced by the Bayer process; a method for firing aluminum hydroxide produced by the aluminum alkoxide method; a method for synthesizing using organic aluminum. A method of calcining an alumina powder that becomes transition alumina or transition alumina by heat treatment as a raw material in an atmospheric gas containing hydrogen chloride; JP-A-11-049515, JP-A-2010-150090, JP-A-2008 Examples thereof include the methods described in JP-A-100903, JP-A-2002-04009, JP-A-2001-354413 and the like.
Further, if the abrasive grains have a shape having edges (shape with sharp corners) due to a fracture surface or the like, scratches are likely to remain on the polished surface of the object to be polished, which is not preferable. By using fine particles of aluminum hydroxide, it is possible to strengthen the cohesion between particles in the particle growth process by firing, etc., the strength of the connecting part (neck part) of the connected particles is excellent, and the edge caused by the neck fracture surface etc. There is an advantage that the α-alumina particles with a small amount of particles do not leave scratches on the polished surface of the object to be polished and the finish is not impaired.

As an aluminum alkoxide method, for example, aluminum alkoxide is hydrolyzed with water to obtain slurry-like, sol-like, and gel-like aluminum hydroxide, which is dried to obtain dry powder-like aluminum hydroxide. How to get it.
The powdered aluminum hydroxide obtained by drying is a bulky powder having a light bulk density of usually about 0.1 to 0.4 g / cm ³ , preferably 0.1 to 0.2 g / cm ³ . Has a light bulk density.

The cumulative pore volume of aluminum hydroxide (range of pore radius of 0.01 μm or more and 1 μm or less) is not particularly limited, but it is preferable to have a cumulative pore volume of 0.6 mL / g or more. Since such aluminum hydroxide has small primary particles, excellent dispersibility, and few agglomerated particles, it is possible to prevent the generation of strongly bonded alumina agglomerated particles that are difficult to pulverize even when fired.

The desired α-alumina powder can be obtained by firing the dry powdered aluminum hydroxide obtained by the aluminum alkoxide method. The firing of aluminum hydroxide is usually carried out by filling a firing container with aluminum hydroxide. Examples of the firing container include a sheath and the like. Further, the material of the firing container is preferably alumina from the viewpoint of preventing contamination of the obtained α-alumina powder, and particularly preferably high-purity α-alumina. The method for filling the fired aluminum hydroxide container is not particularly limited, but it is preferable that the aluminum hydroxide is filled by its own weight and not excessively compacted.

Examples of the firing furnace used for firing aluminum hydroxide include a tunnel kiln, a batch type ventilation flow type box firing furnace, a batch type parallel flow type box firing furnace, and the like. Material transfer type firing furnace to be used.

The firing temperature of aluminum hydroxide, the rate of temperature rise to the firing temperature, and the firing time are appropriately selected so as to obtain α-alumina having desired physical properties.
The firing temperature of aluminum hydroxide is, for example, 1100 ° C. or higher and 1450 ° C. or lower, preferably 1200 ° C. or higher and 1350 ° C. or lower, and the rate of temperature rise when raising the temperature to this firing temperature is usually 30 ° C./hour or higher and 500 ° C./or. It is less than an hour, and the firing time of aluminum hydroxide is usually 0.5 hours or more and 24 hours or less, preferably 1 hour or more and 10 hours or less.

Aluminum hydroxide may be fired in an atmosphere of an inert gas such as nitrogen gas or argon gas as well as in an air atmosphere, and the partial pressure of steam is divided like a gas furnace that burns by burning propane gas or the like. May be fired in a high atmosphere.

The obtained alumina powder may be aggregated in a state where the average particle size exceeds 10 μm. In that case, it is pulverized to an average particle diameter of 3 μm or less that can be used as the abrasive grains of the present invention.
The alumina powder can be pulverized by using a known device such as a vibration mill, a ball mill, or a jet mill, and either a method of pulverizing in a dry state or a method of pulverizing in a wet state can be adopted. However, in order to achieve the above-mentioned physical properties of α-alumina powder without containing coarse agglomerated particles while maintaining the neck portion, a method of crushing without using a crushing medium such as a ball, for example, crushing with a jet mill. , Or a method of using a pulverizing medium such as a ball or a bead, but adjusting the condition so as not to contain coarse agglomerated particles while maintaining the neck portion, for example, a vibration mill is mentioned as a preferable method.
The content of coarse particles of 10 μm or more contained in the obtained alumina powder is preferably 10 ppm or less, and more preferably 3 ppm or less.

When the particle sizes corresponding to the cumulative percentage of 5% and the cumulative 100% of the alumina powder from the smaller diameter side of the particle size distribution are d5 and d100, respectively, [(d100-d5) ÷ mass average particle size] is 30 or less. Is preferable, and more preferably 10 or less.

In the pulverizer, the surface in contact with α-alumina is preferably made of a high-purity alumina material or has a resin lining in that the obtained alumina powder is less contaminated with foreign matter. When pulverizing using a medium stirring mill or the like, it is preferable that the pulverizing medium used for this is also made of a high-purity alumina material.

<2. Polishing slurry>
The polishing slurry of the present invention contains the polishing abrasive grains of the present invention and water or a solvent mainly composed of water, and has a pH of 12 or more.

Since the polishing slurry of the present invention is a strong alkali having a pH of 12 or higher, when the slurry is used, the surface of the hard and brittle material to be polished is in a modified state, and the polishing of the present invention having excellent polishability in that state. Since it is physically polished by the abrasive grains, a high polishing speed can be obtained.

The pH of the polishing slurry is important not only for modifying the surface of the object to be polished, but also for controlling the dispersibility of the abrasive grains when water or a water-based solvent is used. The suitable pH range is determined in consideration of the type of abrasive grains and their alkali resistance and dispersibility. However, in the polishing slurry of the present invention, in order to promote surface modification by alkali and increase the polishing rate, The pH is 12 or higher, preferably 13 or higher.

In particular, by using α-alumina having an alkali resistance of 0.7 or more as the polishing abrasive grains, deterioration of the polishing abrasive grains is suppressed even if the slurry is stored for a long time with a pH of 12 or more and used, and excellent polishing is performed. The action can be maintained.

The concentration of the abrasive grains in the polishing slurry may be determined within a concentration range in which the polishing abrasive grains can be stably dispersed in the polishing slurry, and is usually 0.1 to 50% by weight, preferably 5 to 20% by weight. Is.

Hereinafter, the constituent components of the polishing slurry will be described. Since the polishing abrasive grains have been described in the above-mentioned polishing abrasive grains of the present invention, they will be omitted.

(solvent)
The solvent (dispersion medium) is a medium for dispersing and dissolving abrasive grains and optional components added as needed. In the slurry of the present invention, water or a solvent mainly composed of water is used. To. The "water-based solvent" means a solvent containing at least 50% by weight or more of water and containing other solvents such as ethanol or additive components in addition to water. It is preferable that water is contained in an amount of 70% by weight or more, and more preferably 90% by weight or more, among all the solvents, from the viewpoints that the environmental load is small and the disposal treatment is easy.
The water is not particularly limited, but distilled water and ion-exchanged water are preferable in terms of the influence on the compounding components, the mixing of impurities, the influence on pH and the like.

(Alkaline component)
The alkaline component is added to the slurry for adjusting the pH, and is not particularly limited as long as the effect of the present invention is not impaired. Specifically, hydroxide of an alkali metal such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. Examples thereof include hydroxides of tetraalkylammonium, hydroxides of alkaline earth metals such as calcium hydroxide and magnesium hydroxide, and ammonium hydroxide. Among these, sodium hydroxide and potassium hydroxide are preferably used from the viewpoint of availability and cost.

(Other ingredients)
In addition to the alkaline component, the polishing slurry of the present invention may appropriately contain other components as necessary, as long as the object of the present invention is not impaired. Examples of other components include dispersants, surfactants, viscosity modifiers and the like. When these other components are used, the content ratio is usually in the range of 0.01 to 10% by mass with respect to the total mass of the abrasive grains.

Examples of the dispersant include condensed phosphate or condensed phosphate, polystyrene sulfonate, polycarboxylic acid type polymer compound, polyacrylic acid type polymer compound, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester and the like. ..
Surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.
Examples of the viscosity modifier include water-soluble cellulose ethers, polysaccharides, polyhydric alcohols and derivatives thereof, water-soluble polymer compounds, water-soluble oxides having a thickening action and salts thereof, biopolymers and the like.

The polishing slurry is prepared by mixing abrasive grains (and any component) so as to be uniformly dispersed in a dispersion medium. The mixing method is not particularly limited, and examples thereof include a stirring and mixing method using an ultrasonic disperser, a homogenizer, or the like.
The mixing method can be carried out by a conventionally known mixing method, the mixing order is arbitrary, and any two of the constituent components of the polishing slurry (abrasive abrasive grains, alkaline component, solvent, and arbitrary component) or Three or more components may be mixed in advance and then the remaining components may be mixed, or all may be mixed at once.

<3. Polishing method for hard and brittle materials>
The method for polishing a hard and brittle material of the present invention (hereinafter, referred to as "the polishing method of the present invention") uses the above-mentioned polishing slurry of the present invention to polish the surface of the hard and brittle material by chemical mechanical polishing (CMP). Has a step to do. The polishing method of the present invention is the same as the conventional polishing method by CMP except that the polishing slurry of the present invention is used as the polishing slurry. That is, while supplying the polishing slurry containing the polishing abrasive grains to the polishing pad, the surface to be polished of the object to be polished is brought into contact with the polishing pad used by sticking to the surface plate, and the object to be polished is subjected to the relative movement of both. Polishing can be performed.

Specific examples of the hard and brittle material to be polished in the polishing method of the present invention include aluminum oxide (sapphire), diamond, silicon carbide, boron carbide, zirconium carbide, tungsten carbide, silicon nitride, titanium nitride, gallium nitride, and aluminum nitride. And so on. These can be polished by any of single crystal, polycrystalline and amorphous.
Among these, sapphire (particularly single crystal sapphire) suitable as a substrate for a semiconductor element is a hard and brittle material that is difficult to process, and improvement in productivity by high-speed polishing has been required. Therefore, the polishing method of the present invention is suitable. Target. The surface of the hard and brittle material after polishing is preferably smoother, and when the hard and brittle material is single crystal sapphire, the arithmetic average surface roughness (Ra) is preferably 2 nm or less, and 1 nm. More preferably: However, this is not limited to cases where surface roughness is not so required, such as when polishing is finished by using different abrasive grains.

As the polishing apparatus, a conventionally known CMP polishing apparatus can be used. Hereinafter, a case where a general single-sided polishing type CMP polishing apparatus is used will be described as an example.

A typical configuration of a single-sided polishing CMP polishing device is a platen that rotates around a rotation axis and has a polishing pad attached to the surface, and the object to be polished fixed to the bottom of the sample holder with wax or the like. A sample holder that can be pressed against the polishing pad (hereinafter, may be referred to as a head), a pressurizing mechanism for a polishing load, and a nozzle that supplies a polishing slurry containing polishing abrasive grains on the polishing pad. Prepare as a main component. In the CMP polishing device having such a configuration, the surface plate and the sample holder are rotated around their respective axes, and the polishing slurry is supplied from the nozzle to the surface of the polishing pad attached to the surface plate, and the sample holder is used. The surface to be polished of the object to be polished is polished by pressing the object to be polished held on the lower surface against the polishing pad.

The polishing speed is the polishing slurry (type of polishing abrasive grains, particle size, concentration of abrasive grains in the polishing slurry, supply speed of the slurry), polishing device (polishing load, number of rotations of surface plate and head, type of polishing pad). Is determined by. Since the polishing slurry of the present invention having the above-mentioned properties is used, a high polishing rate can be set even for a substrate made of a hard and brittle material (particularly a single crystal sapphire substrate), and a surface with high smoothness can be set. Hard and brittle material can be produced efficiently.
For example, when a polishing slurry containing alumina is used as the polishing abrasive grains and the polishing target is single crystal sapphire (c-plane), the polishing rate capable of maintaining the surface roughness (Ra) of the substrate is 1 nm. Can be 4 μm / hr or more (preferably 5 μm / hr or more, more preferably 6 μm / hr or more).

There are various types of polishing pads used by attaching to the surface plate, such as non-woven fabric, polyurethane foam, porous resin, non-porous resin, etc., and commercially available ones can be used, and the hardness and particles of the polishing abrasive grains to be used. It may be appropriately determined in consideration of polishing conditions such as diameter, polishing speed and polishing load, and the type of hard and brittle material.

The amount of the polishing slurry supplied is appropriately determined in consideration of the constituent materials of the object to be polished, the type of abrasive grains, and the concentration of abrasive grains in the slurry.
The polishing abrasive grains do not necessarily have to be supplied to the polishing pad as a polishing slurry in which all the components are mixed in advance. For example, the abrasive grains may be supplied as they are, and the solvent may be supplied separately. On the other hand, in order to evenly disperse the abrasive grains on the polishing pad and improve the uniformity of polishing, it is preferable to use it as a polishing slurry in which the abrasive grains are dispersed in a solvent in advance.

The rotation speed of the surface plate during polishing is not particularly limited, and it may be within the range of the capacity of the polishing apparatus to be used so that it can be operated stably. In order to perform polishing in a short time, it is preferable that the rotation speed of the surface plate is high, but it is appropriately determined in consideration of the polishing abrasive grains (polishing slurry) to be used and the surface smoothness required for the object to be polished. Is preferable.

The load for polishing is not particularly limited, and it may be determined within the range of the capacity of the polishing device to be used and within the range in which stable operation is possible. In order to perform polishing in a short time, it is preferable that the load is large, but since the power load of the rotary motor is also large, the polishing abrasive grains (polishing slurry) to be used and the surface smoothness required for the object to be polished are determined. It is preferable to make an appropriate decision in consideration.

The polishing slurry used for polishing the object to be polished may be collected and reused. By circulating and using the polishing slurry in the polishing apparatus, the waste liquid is reduced, so that the environmental load can be reduced and the cost can be reduced. When the polishing slurry is circulated and used, the consumed components (polishing abrasive grains, solvent, pH adjuster, and other optional components) can be appropriately replenished.

The polishing method of the present invention has been described above in the case of using a general single-sided polishing type CMP polishing apparatus, but in particular, in the polishing apparatus disclosed this time, operating conditions, various parameters, which are not explicitly disclosed, The dimensions, weight, volume, etc. of the components do not deviate from the range normally practiced by those skilled in the art, and values that can be easily assumed by those skilled in the art are adopted. Further, the polishing apparatus used in the polishing method of the present invention is not limited to the single-sided polishing type CMP polishing apparatus. For example, a double-sided polishing device or a device in which the sample holder is linearly reciprocated instead of rotationally may be used. Further, the surface plate does not rotate, but may move in one direction by, for example, a belt type.

<4. Manufacturing method of hard and brittle material>
The method for producing a hard and brittle material of the present invention includes a step of polishing the hard and brittle material by the above-mentioned polishing method of the present invention (hereinafter, referred to as "polishing step of the present invention").
Since the production method of the present invention includes the polishing step of the present invention described above, it is possible to produce a hard and brittle material having a highly productive and highly smooth surface.

In the method for producing a hard and brittle material of the present invention, steps other than the step of polishing the hard and brittle material in the polishing step of the present invention may be performed according to a known production method of the hard and brittle material as a raw material.
Hereinafter, sapphire (particularly a single crystal sapphire substrate), which is a suitable target of the method for producing a hard and brittle material of the present invention, will be described as an example.

Sapphire (particularly single crystal sapphire) is used in various applications such as a substrate for a GaN-based semiconductor layer used for a high-frequency device, an LED light emitting element, and a polarizer holding substrate for a liquid crystal projector. There is.
The properties of sapphire crystals differ depending on the plane orientation, and the c-plane, which is a polar plane, and the r-plane, which is a semi-polar plane, serve as a semiconductor substrate for growing a semiconductor layer such as gallium nitride on the surface. The a-plane and m-plane, which are non-polar surfaces, are suitable for applications and are suitable for applications that require a high-hardness, scratch-free substrate (for example, a thin film substrate or a chamber window for a semiconductor manufacturing apparatus).

In the method for manufacturing a sapphire substrate, first, a sapphire crystal (ingod) is ground to an appropriate size and cut to obtain a cut piece having a predetermined size (grinding / cutting step). Next, a plate-shaped sapphire is obtained by flat-cutting the obtained cut piece to a predetermined thickness (planar cutting step). The obtained plate-shaped sapphire is roughly polished by wrapping or the like, and scratches generated by the wrapping are removed by CMP, which is a finish polishing, to obtain a highly smooth surface.
For the steps other than CMP corresponding to the polishing step of the present invention, a known method according to a general method for manufacturing a sapphire substrate may be adopted.

The method for producing a hard and brittle material of the present invention may be applied to a product containing a hard and brittle material, for example, a hard and brittle material that is reused by removing the semiconductor layer from a wafer on which a semiconductor layer is formed. Good. In this case, a portion other than the hard and brittle material is removed from the product containing the hard and brittle material by grinding or rough polishing, and then subjected to the polishing step of the present invention.

In addition, the method for producing a hard and brittle material of the present invention may further have an arbitrary step in a timely manner, if necessary. For example, a heat treatment step, a wet etching step, a cleaning step and the like can be mentioned.

The heat treatment method in the heat treatment step is not particularly limited, and a conventionally known method may be used as the heat treatment method for the target hard and brittle material. The purpose of the heat treatment is, for example, to remove the distortion of crystals remaining inside the hard and brittle material, or to promote the oxidation of the surface of the hard and brittle material to facilitate the surface processing. The heat treatment conditions such as the heat treatment temperature and the heat treatment atmosphere are appropriately determined according to the type or purpose of the hard and brittle material to be treated.

The wet etching method in the wet etching step is not particularly limited, and a conventionally known method may be used as a wet etching method for the target hard and brittle material. Wet etching conditions such as the type of chemical solution used for wet etching, treatment temperature and treatment time are appropriately determined depending on the material of the hard and brittle material to be treated or the object to be removed.

The cleaning method in the cleaning step is not particularly limited, and a conventionally known method may be used as a cleaning method for the target hard and brittle material. For example, the hard and brittle material to be cleaned is subjected to an organic solvent such as alcohol, an acid-based cleaning solution such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, or hydrogen peroxide, alkali hydroxide, ammonia, or organic amine. It is possible to remove a small amount of foreign matter remaining on the substrate by rinsing with a basic cleaning solution such as, or immersing in the cleaning solution.

The application of the produced hard and brittle material may be appropriately selected depending on the type of other hard and brittle material. For example, in the case of sapphire, a substrate for a GaN-based semiconductor layer used for a high-frequency device, an LED light emitting element, or a polarizer holding substrate for a liquid crystal projector can be mentioned.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. The evaluation method of each physical property is as follows.

(1) Evaluation of the Number Ratio of Connected Particles Having One or More Neckes Example 1 is evaluated by [Evaluation Method 1] described later, and Examples 2 to 5 and Comparative Example 1 are evaluated by [Evaluation] described later. Method 2] was evaluated.

[Evaluation method 1]
As for the number ratio of the connected particles having one or more necks of the alumina particles, the state where the alumina particles are aggregated is observed at a magnification of 20000 times by SEM, and a total of 100 particles are randomly selected from the SEM image. After extraction, the presence or absence of a neck portion was visually determined for each particle, and the calculation was performed using the following formula. In the evaluation method 1, even if the particles have a neck portion in the SEM image, the neck portion may not be confirmed depending on the observation angle or the arrangement state of the particles. Therefore, here, the neck portion is clearly defined. Only the particles visually confirmed to have a portion were calculated as "connected particles having a neck portion".

Percentage of connected particles with one or more necks (%)
= (Number of particles visually confirmed to have a neck) ÷ (Total number of randomly extracted particles (100)) x 100 (II)

Hereinafter, the number ratio may be referred to as “number ratio [1]”.

[Evaluation method 2]
According to JIS R 1633: 1998 7.2b) and 7.3, a very small amount of alumina was added to ethanol, the suspension was prepared using an ultrasonic cleaner, and then suspended using a dropper. The liquid was dropped onto a slide glass, spread thinly, and then the solvent was evaporated and dried to vaporize carbon to obtain a sample for SEM observation. Next, using a field emission scanning electron microscope "S4800" manufactured by Hitachi High-Technologies Corporation, the sample was observed at an acceleration voltage of 2 kV and a magnification of 20000 times, and alumina particles were dispersed to the extent shown in FIG. After confirming that, an SEM image for image analysis was obtained. When the alumina particles are not dispersed to the extent shown in FIG. 1, a diluted solution obtained by diluting the suspension with ethanol twice is prepared, and the degree of dispersion of the alumina particles is adjusted in the same manner as described above. After confirmation, the same operation was repeated until the aluminum particles were dispersed to the extent shown in FIG.
The SEM image of the obtained alumina particles was analyzed using "WinROOF" of Mitani Shoji Co., Ltd., and 100 alumina particles having a diameter equivalent to a circle 0.5 to 2 times the mass average particle diameter were randomly selected. Extracted to. When two or more alumina particles were in contact with each other or overlapped with each other, only the uppermost particle was determined to be one alumina particle and extracted.
Next, using "WinROOF" of Mitani Shoji Co., Ltd., the area loss rate of each particle is calculated to determine whether or not the particle is a connected particle having one or more necks, and the mass of the alumina powder is determined. The number ratio of the connected particles having one or more neck portions in the alumina powder having a particle size of 0.5 to 2 times the average particle size was calculated by the following formula.

Number ratio (%) of connected particles having one or more necks in alumina powder having a particle size 0.5 to 2 times the mass average particle size of the alumina powder.
= (Number of particles with an area defect rate of 10% or more having a particle size 0.5 to 2 times the mass average particle size of the alumina powder) ÷ (0.5 to 0.5 of the mass average particle size of the alumina powder randomly extracted) Total number of particles with twice the particle size (100)) x 100 (III)

Hereinafter, the number ratio may be referred to as “number ratio [2]”.

(2) Evaluation of surface index In the same manner as in (1) [Evaluation method 2] above, after obtaining an SEM image in which aluminum particles are dispersed, analysis is performed using "WinROOF" of Mitani Shoji Co., Ltd. 100 alumina particles having a diameter equivalent to a circle having a particle diameter of 0.5 to 2 times the mass average particle diameter were randomly extracted.

Next, using "WinROOF" of Mitani Shoji Co., Ltd., the surface index of each particle was calculated, and the surface index of the alumina powder having a particle size of 0.5 to 2 times the mass average particle size of the alumina powder was calculated. The number ratio of particles of 1.4 or more was calculated by the following formula.

Percentage of particles with a surface index of 1.4 or more (%) in alumina powder having a particle size 0.5 to 2 times the mass average particle size of the alumina powder
= (Number of particles with a surface index of 1.4 or more having a particle size 0.5 to 2 times the mass average particle size of the alumina powder) ÷ (0.5 to 0.5 of the mass average particle size of the alumina powder randomly extracted) Total number of particles with twice the particle size (100)) x 100 (V)

Hereinafter, the number ratio may be referred to as “number ratio [3]”.

(3) Mass average particle size The average particle size was defined as a particle size equivalent to a cumulative percentage of 50% on a mass basis by a laser diffraction method using a laser particle size distribution measuring device [“Microtrack” manufactured by Nikkiso Co., Ltd.]. Further, the particle sizes corresponding to the cumulative percentage of 5% and the cumulative 100% from the small diameter side of the particle size distribution were set to d5 and d100, respectively. In the measurement, the alumina particles were ultrasonically dispersed with a 0.2 wt% sodium hexametaphosphate aqueous solution, and the refractive index of the alumina particles was 1.76.

(4) Alkali resistance Alumina powder was added to an aqueous solution adjusted to pH 13.5 with potassium hydroxide (KOH) so that the solid content concentration was 10% by weight, and the solid components after immersion for 4 weeks were recovered. The powder X-ray diffraction pattern before and after immersion in the potassium hydroxide aqueous solution was measured with RINT-2000 manufactured by Rigaku Co., Ltd., and the alkali resistance was calculated from the peak intensity of 2θ = 43.4 ° by the following formula.

Alkali resistance = (peak intensity after immersion for 4 weeks) ÷ (peak intensity before immersion)

(5) BET Specific Surface Area As a specific surface area measuring device, "Flow Sorb II 2300" manufactured by Shimadzu Corporation is used, and is specified in JIS-Z-8830: 2013 "Method for measuring the specific surface area of powder (solid) by gas adsorption". The BET specific surface area was determined by the one-point method of nitrogen adsorption method according to the method described above.

(6) Surface Roughness As a surface roughness measuring device, a white interferometer "VertScan R5500G" manufactured by Ryoka System Co., Ltd. was used, and the arithmetic average surface roughness (Ra) was determined. Six points on the polished surface were measured, and the average was taken as the polishing characteristics.

(Example 1)
(1) Production of Abrasive Abrasive Grains Aluminum isopropoxide prepared from 99.99% pure aluminum as a raw material is hydrolyzed with water to obtain slurry aluminum hydroxide, which is dried. A dry powdered aluminum hydroxide having a light bulk density of 0.1 g / cm ³ was obtained. Further, in the gas furnace in which the dry powdery aluminum hydroxide is calcined by burning propane gas or the like, the mixture is held at 1220 ° C. for 4 hours, calcined, and pulverized by a jet mill to form α-alumina powder. Abrasive abrasive grains were obtained. With respect to the obtained abrasive grains (α-alumina powder), the number ratio [1] of the connected particles having one or more neck portions was evaluated by the above method (1) [evaluation method 1], and the above method (evaluation method 1) was performed. The mass average particle size, alkali resistance and BET specific surface area were evaluated according to 3) to (5). The evaluation results are shown below. Further, FIG. 3 shows an SEM image of the abrasive grains (α-alumina powder) of Example 1 in a state where the alumina particles are aggregated.

Particle shape: Number ratio [1] 81%
Average particle size: 0.65 μm (coarse particles of 10 μm or more and 3 ppm or less)
Alkali resistance: 0.75
BET specific surface area: 4.2 m ² / g
[(D100-d5) / average particle size] = 6.7

(2) Preparation of Polishing Slurry The polishing abrasive grains of Example 1 were added to an aqueous solution adjusted to pH 13.5 with potassium hydroxide (KOH) so that the solid content concentration was 10% by weight, and the blades were stirred. Later, the polishing slurry of Example 1 was obtained by irradiating ultrasonic waves to disperse the abrasive grains for 1 hour.

(3) Polishing test A sapphire substrate (c-plane): 2 inch Φ (dialap processed, Ra 5 nm) was used as a polishing sample. Using NANO-450-DOCAb manufactured by Hi-Technos Co., Ltd. as a polishing device, polishing was performed for 1 hour under the following conditions using the slurry of Example 1, and the average polishing speed was calculated from the weight difference of the sapphire substrate before and after polishing. After calculation, the surface of the sample after polishing was observed with an optical microscope (50 times).
(Polishing conditions)
Surface plate rotation speed: 60 rpm
Sample holder (head) rotation speed: 60 rpm
Head load: 500 g / cm ²
Head sway: 1 mm / s (sway width: ± 20 mm)
Polishing pad: SUBA800 (nonwoven fabric) manufactured by Nitta Haas Co., Ltd.
Slurry amount: 0.6 L / min (using circulation)
Polishing time: 1 hour

In Example 1, the average polishing rate was 6.5 μm / hour, the surface of the sample after polishing was extremely flat, and the scratches observed before polishing were not observed.

(Example 2)
(1) Production of Abrasive Abrasive Grains The abrasive abrasive grains of Example 2 were obtained under the same conditions as in Example 1. With respect to the obtained abrasive grains (α-alumina powder), the number ratio [2] of the connected particles having one or more neck portions was evaluated by the above method (1) [evaluation method 2], and the above method (evaluation method 2) was performed. From 2) to (5), the surface index, mass average particle size, alkali resistance and BET specific surface area were evaluated. The evaluation results are shown below. Further, FIG. 4 shows an SEM image of the abrasive grains (α-alumina powder) of Example 2 in a state where the alumina particles are aggregated.

Particle shape: Number ratio [2] 63%, Number ratio [3] 73%
Average particle size: 0.65 μm (coarse particles of 10 μm or more and 3 ppm or less)
Alkali resistance: 0.75
BET specific surface area: 4.2 m ² / g
[(D100-d5) / average particle size] = 6.7

(2) Preparation of Polishing Slurry A polishing slurry of Example 2 was obtained in the same manner as in Example 1 except that the polishing abrasive grains of Example 2 were used instead of the polishing abrasive grains of Example 1.

(3) Polishing test A sapphire substrate (c-plane): 2 inch Φ (dialap processed, Ra 5.8 nm) is used as a polishing sample, and the polishing slurry of Example 2 is used instead of the polishing slurry of Example 1. The polishing test was carried out in the same manner as in Example 1 except for the above. In Example 2, the average polishing rate was 6.5 μm / hour, the surface of the sample after polishing was extremely flat, and the scratches observed before polishing were not observed. Moreover, as a result of evaluating the surface roughness by the above method (6), the surface roughness was 1.0 nm.

(Example 3)
(1) As the abrasive grains of Example 3, dry powdered aluminum hydroxide obtained by the same method as in Example 1 is held at 1200 ° C. for 3 hours in a gas furnace that is calcined by burning propane gas or the like. Alumina powder having the following physical properties obtained by firing and pulverizing with a vibration mill was used. For the abrasive grains, the number ratio [2] of the connected particles having one or more neck portions is evaluated by the above method (1) [evaluation method 2], and the above methods (2) to (5) are used. , Surface index, mass average particle size, alkali resistance and BET specific surface area were evaluated. The evaluation results are shown below. Further, FIG. 5 shows an SEM image of the abrasive grains of Example 3 in a state where the alumina particles are aggregated.
Particle shape: Number ratio [2] 42%, Number ratio [3] 54%
Average particle size: 0.38 μm
Alkali resistance: 0.75
BET specific surface area: 6.8 m ² / g
[(D100-d5) / average particle size] = 34.0

(2) Preparation of Polishing Slurry A polishing slurry of Example 3 was obtained in the same manner as in Example 1 except that the polishing abrasive grains of Example 3 were used instead of the polishing abrasive grains of Example 1.

(3) Polishing test The polishing test was carried out in the same manner as in Example 2 except that the polishing slurry of Example 3 was used instead of the polishing slurry of Example 2. In Example 3, the average polishing rate was as high as 4.7 μm / hour. In addition, no scratches observed before polishing were confirmed on the surface of the sample after polishing. As a result of evaluating the surface roughness by the above method (6), the surface roughness was 0.9 nm.

(Example 4)
(1) As the polishing abrasive grains of Example 4, aluminum hydroxide produced by the Bayer process was used as a raw material, and alumina powder having the following physical properties obtained by pulverizing with a ball mill was used. For the abrasive grains, the number ratio [2] of the connected particles having one or more neck portions is evaluated by the above method (1) [evaluation method 2], and the above methods (2) to (5) are used. , Surface index, mass average particle size, alkali resistance and BET specific surface area were evaluated. The evaluation results are shown below. Further, FIG. 6 shows an SEM image of the abrasive grains of Example 4 in a state where the alumina particles are aggregated.
Particle shape: Number ratio [2] 46%, Number ratio [3] 63%
Average particle size: 0.91 μm
Alkali resistance: 0.82
BET specific surface area: 4.1 m ² / g
[(D100-d5) / average particle size] = 4.7

(2) Preparation of Polishing Slurry A polishing slurry of Example 4 was obtained in the same manner as in Example 1 except that the polishing abrasive grains of Example 4 were used instead of the polishing abrasive grains of Example 1.

(3) Polishing test The polishing test was carried out in the same manner as in Example 2 except that the polishing slurry of Example 4 was used instead of the polishing slurry of Example 2. In Example 4, the average polishing rate was as high as 5.3 μm / hour. In addition, no scratches observed before polishing were confirmed on the surface of the sample after polishing. The surface roughness was 1.6 nm.

(Example 5)
(1) As the abrasive grains of Example 5, aluminum hydroxide produced by the Bayer process was used as a raw material, and alumina powder having the following physical properties obtained by pulverizing with a jet mill was used. For the abrasive grains, the number ratio [2] of the connected particles having one or more neck portions is evaluated by the above method (1) [evaluation method 2], and the above methods (2) to (5) are used. , Surface index, mass average particle size, alkali resistance and BET specific surface area were evaluated. The evaluation results are shown below. Further, FIG. 7 shows an SEM image of the abrasive grains of Example 5 in a state where the alumina particles are aggregated.
Particle shape: Number ratio [2] 51%, Number ratio [3] 69%
Average particle size: 0.96 μm
Alkali resistance: 0.78
BET specific surface area: 4.2 m ² / g
[(D100-d5) / average particle size] = 4.6

(2) Preparation of Polishing Slurry A polishing slurry of Example 5 was obtained in the same manner as in Example 1 except that the polishing abrasive grains of Example 5 were used instead of the polishing abrasive grains of Example 1.

(3) Polishing test A polishing test was carried out in the same manner as in Example 2 except that the polishing slurry of Example 5 was used instead of the polishing slurry of Example 2. In Example 5, the average polishing rate was as high as 5.2 μm / hour. In addition, no scratches observed before polishing were confirmed on the surface of the sample after polishing. As a result of evaluating the surface roughness by the above method (6), the surface roughness was 1.0 nm.

(Comparative Example 1)
(1) As the abrasive grains of Comparative Example 1, α-alumina powder having the following physical properties was used. For the abrasive grains, the number ratio [1] and the number ratio [2] of the connected particles having one or more neck portions are evaluated by the above method (1) [evaluation method 1] and [evaluation method 2]. Then, the surface index, mass average particle size, alkali resistance and BET specific surface area were evaluated by the above methods (2) to (5). The evaluation results are shown below. Further, FIG. 8 shows an SEM image of the abrasive grains (α-alumina powder) of Comparative Example 1 in a state where the alumina particles are aggregated.
Particle shape: Number ratio [1] 0%, Number ratio [2] 0%, Number ratio [3] 0%
Average particle size: 0.65 μm (coarse particles of 10 μm or more and 3 ppm or less)
Alkali resistance: 0.62
BET specific surface area: 4.1 m ² / g
[(D100-d5) / average particle size] = 6.3

(2) Preparation of Polishing Slurry A polishing slurry of Comparative Example 1 was obtained in the same manner as in Example 1 except that the polishing abrasive grains of Comparative Example 1 were used instead of the polishing abrasive grains of Example 1.

(3) Polishing test A polishing test was carried out in the same manner as in Example 1 except that the polishing slurry of Comparative Example 1 was used instead of the polishing slurry of Example 1. In Comparative Example 1, the average polishing rate was as low as 3.1 μm / hour.

By using the polishing slurry containing the polishing abrasive grains of the present invention, the polishing speed can be increased even for a hard and brittle material such as sapphire, which is difficult to polish, and the hard and brittle material has excellent surface smoothness. It is possible to shorten the polishing time for obtaining the material. Therefore, it has great industrial utility value.

Claims (10)

Abrasive abrasive grains used for polishing hard and brittle materials, which contain connected particles having one or more neck portions, have a mass average particle diameter of 0.2 to 2.0 μm, and have a BET ratio. Abrasive particles that are alumina powder having a surface area of 4.1 to 6.8 m ² / g . The polishing abrasive grain according to claim 1, wherein the alumina is α-alumina. The abrasive grain according to claim 2, wherein the α-alumina has an alkali resistance of 0.7 or more. The polishing abrasive grain according to any one of claims 1 to 3, wherein the number ratio of the connected particles is 20% or more in the alumina powder having a particle size of 0.5 to 2 times the mass average particle size. The polishing according to any one of claims 1 to 4, wherein the number ratio of particles having a surface index of 1.4 or more is 25% or more in an alumina powder having a particle size of 0.5 to 2 times the mass average particle size. Abrasive particles. A polishing slurry containing the polishing abrasive grains according to any one of claims 1 to 5 and water or a solvent mainly composed of water and having a pH of 12 or more. A method for polishing a hard and brittle material, which comprises a step of chemically mechanically polishing the surface of the hard and brittle material using the polishing slurry according to claim 6. A method for producing a hard and brittle material, which comprises a step of polishing the hard and brittle material by the polishing method according to claim 7. The method for producing a hard and brittle material according to claim 8, wherein the hard and brittle material to be polished is sapphire. The method for producing a hard and brittle material according to claim 9, wherein the sapphire is a single crystal sapphire.

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