JP2020023408A - Ceria-based fine particle dispersion, method for producing the same and abrasive particle dispersion for polishing comprising ceria-based fine particle dispersion - Google Patents

Abstract

To provide a ceria-based composite particle dispersion liquid capable of polishing even a silica film, an Si wafer or a difficult-to-process material at high speed and attaining high surface accuracy at the same time.SOLUTION: A ceria-based fine particle dispersion is provided which comprises ceria-based fine particles having the following characteristics and an average particle diameter of 5 to 500 nm. The ceria fine particles have raw material ceria fine particles and a layer containing easily soluble silica on the surface of the raw material ceria fine particles, and the raw material ceria fine particles mainly contain crystalline ceria. The ratio of a mass D1 of the easily soluble silica contained in the layer containing the easily soluble silica to a mass D2 of the ceria-based fine particles is from 0.005 to 10%. When the ceria-based fine particles are subjected to X-ray diffraction, only a crystalline phase of ceria is detected. The ceria fine particles have an average crystallite diameter of 3 to 300 nm of the crystalline ceria measured by X-ray diffraction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ceria-based fine particle dispersion suitable as an abrasive used in semiconductor device manufacturing and the like, and in particular, planarizes a film to be polished formed on a substrate by chemical mechanical polishing (Chemical Mechanical Polishing: CMP). The present invention relates to a ceria-based fine particle dispersion, a method for producing the same, and a polishing abrasive dispersion containing the ceria-based fine particle dispersion.

  2. Description of the Related Art Semiconductor devices such as semiconductor substrates and wiring substrates achieve high performance by increasing the density and miniaturization. In the manufacturing process of this semiconductor, so-called chemical mechanical polishing (CMP) is applied, and specifically, a technique indispensable for shallow trench element isolation, flattening of an interlayer insulating film, formation of contact plugs and Cu damascene wiring, and the like. It has become.

Generally, the CMP polishing slurry is composed of abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding a target film. On the other hand, abrasive grains have a role of polishing by mechanical action, and colloidal silica, fumed silica, and ceria particles are used as abrasive grains. In particular, since ceria particles exhibit a specifically high polishing rate for a silicon oxide film, they are applied to polishing in a shallow trench element isolation step.
In the shallow trench element isolation step, not only polishing of a silicon oxide film but also polishing of a silicon nitride film is performed. In order to facilitate element isolation, it is desirable that the polishing rate of the silicon oxide film is high and the polishing rate of the silicon nitride film is low. The polishing rate ratio (selectivity) is also important.

Conventionally, as a method of polishing such a member, a relatively rough primary polishing process is performed, and then a precise secondary polishing process is performed, whereby a smooth surface or an extremely high-precision surface with few scratches or the like is obtained. The way to get is done.
Conventionally, for example, the following methods have been proposed for the polishing agent used for the secondary polishing as the finish polishing.

  For example, Patent Literature 1 discloses that an aqueous solution of cerous nitrate and a base are mixed under stirring at an amount ratio of pH 5 to 10, followed by rapid heating to 70 to 100 ° C and aging at that temperature. A method for producing ultrafine cerium oxide fine particles (average particle diameter: 10 to 80 nm) comprising a cerium oxide single crystal characterized by the following characteristics is further described. According to this production method, the particle diameter is high and the particle shape is high. It is described that cerium oxide ultrafine particles having high uniformity can be provided.

  Non-Patent Document 1 discloses a method for producing ceria-coated silica including a production step similar to the method for producing cerium oxide ultrafine particles described in Patent Document 1. This method for producing ceria-coated silica does not include a firing-dispersion step as included in the production method described in Patent Document 1.

Further, Patent Document 2 discloses an abrasive containing a slurry in which cerium oxide particles are dispersed in a medium. The cerium oxide particles are obtained by calcining and pulverizing a cerium compound. The cerium oxide particles effective for generating the plane are polycrystals composed of crystallites and having crystal grain boundaries, and the cerium oxide particles having the crystal grain boundaries are 5 to 5 of all cerium oxide particles contained in the slurry. An abrasive is described, which is 100% by volume and has a median particle diameter of 100 to 1500 nm of the cerium oxide particles having the crystal grain boundaries. It is described that by using such an abrasive, a surface to be polished such as an SiO ₂ insulating film can be polished at high speed without any damage.

Patent No. 2,746,861 Patent No. 4,776,519

See Seung-Ho Lee, Zhenyu Lu, S.M. V. Bab and Egon Matejevich, "Chemical mechanical polishing of thermal oxide films using silicone particles coated with cereal, 27th edition of the museum, 27th edition of the journal."

However, when the present inventor actually manufactured and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing rate was low, and the surface of the polishing substrate had defects (deterioration of surface accuracy, increase of scratches, (Residual polishing material on the surface of the polishing base material).
This is because the method for producing ultrafine cerium oxide particles described in Patent Document 1 does not include the sintering step, and is different from the method for producing ceria particles including the sintering step (the degree of crystallinity of the ceria particles is increased by sintering). Since only cerium oxide particles are crystallized from (aqueous solution containing cerous nitrate), the crystallinity of cerium oxide particles to be generated is relatively low, and the density of abrasive grains is low because no calcination treatment is performed. The present inventors presume that the main factors are that the polishing rate is low, cerium oxide does not adhere to the base particles, and cerium oxide remains on the surface of the polishing substrate.

  In addition, when the present inventor actually manufactured and examined the cerium oxide particles described in Patent Literature 2, when compared with the cerium oxide ultrafine particles described in Patent Literature 1 in which firing was not performed, the polishing rate was higher. It was not sufficient, and it was found that defects were likely to occur on the substrate surface after polishing. In Patent Document 2, for example, cerium carbonate is manufactured by a process of calcining at 700 ° C. and dry-pulverizing by a jet mill. However, coarse aggregates generated in the calcining step remain without being pulverized and remain. It is estimated to be. Further, since an organic material such as ammonium polyacrylate is used as the dispersant, there is a concern that the organic material is contaminated on the substrate surface.

  An object of the present invention is to solve the above problems. That is, the present invention is capable of polishing at high speed even with a silica film, a Si wafer, or a difficult-to-process material, and at the same time, achieves high surface accuracy (low scratches, little abrasive grains remaining on the substrate, improvement of the substrate Ra value). And the like, and further containing no impurities, a ceria-based fine particle dispersion that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate, a method for producing the same, and polishing containing the ceria-based fine particle dispersion. It is an object of the present invention to provide an abrasive dispersion liquid for use.

The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and have completed the present invention.
The present invention includes the following (1) to (10).
(1) A ceria-based fine particle dispersion comprising ceria-based fine particles having the following features [1] to [4] and having an average particle diameter of 5 to 500 nm.
[1] The ceria-based fine particles include raw ceria fine particles and a layer containing easily soluble silica on the surface of the raw ceria fine particles, and the raw ceria fine particles mainly include crystalline ceria. .
[2] The ratio D (D = D1 / D2 × 100) of the mass D1 of the easily soluble silica contained in the layer containing the easily soluble silica to the mass D2 of the ceria-based fine particles is 0.005 to 10%. thing.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[4] The ceria-based fine particles have an average crystallite diameter of the crystalline ceria of 3 to 300 nm, as measured by X-ray diffraction.
(2) The dispersion liquid of ceria-based fine particles according to (1), wherein the streaming potential becomes negative when the pH value is 3 to 8.
(3) When the cationic colloid titration is performed, the flow potential change amount (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titrant when the differential value of the flow potential is maximized The ceria-based fine particle dispersion according to the above (1) or (2), wherein a streaming potential curve having a ratio (ΔPCD / V) of −3000 to −100 is obtained.
ΔPCD / V = (IC) / V Equation (1)
C: streaming potential (mV) when the differential value of the streaming potential is maximized
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Addition amount (ml) of the cationic colloid titrant when the differential value of the streaming potential is maximized
(4) The dispersion of ceria-based fine particles according to any one of (1) to (3) above, wherein the number of the ceria-based fine particles in the form of coarse particles of 0.51 μm or more is 3000 million / cc or less. liquid.
(5) The ceria-based material according to any one of (1) to (4), wherein the content ratio of impurities contained in the ceria-based fine particles is as shown in the following (a) and (b). Fine particle dispersion.
(A) The content of each of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.
(6) A polishing abrasive dispersion containing the ceria-based fine particle dispersion according to any one of the above (1) to (5).
(7) The abrasive dispersion according to (6), wherein the abrasive dispersion is for planarizing a semiconductor substrate on which a silica film is formed.
(8) A method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2a.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2a: a step of adding an additive containing silica to the fired body, heating and aging at 10 to 98 ° C., and then crushing or pulverizing to obtain a ceria-based fine particle dispersion.
(9) A method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2b.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2b: a step of crushing or pulverizing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and heating and aging at 10 to 98 ° C. to obtain a ceria based fine particle dispersion.
(10) A method for producing a ceria-based fine particle dispersion, comprising the following steps A and B:
Step A: a step of continuously or intermittently adding a cerium solution having a cerium compound dissolved therein to a solvent maintained at a temperature of 3 to 98 ° C. and a pH of 5.0 to 10.0 to obtain colloidal ceria.
Step B: a step of adding an additive containing silica to the colloidal ceria and heating and aging at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.

When the ceria-based fine particle dispersion of the present invention is used for polishing purposes as, for example, a polishing abrasive dispersion, even if the target is a difficult-to-process material including a silica film, a Si wafer, etc., it can be polished at a high speed. At the same time, high surface accuracy (low scratch, low surface roughness (Ra) of the substrate to be polished, etc.) can be achieved. The method for producing a ceria-based fine particle dispersion of the present invention provides a method for efficiently producing a ceria-based fine particle dispersion exhibiting such excellent performance.
In a preferred embodiment of the method for producing a ceria-based fine particle dispersion liquid of the present invention, impurities contained in the ceria-based fine particles can be significantly reduced and the ceria-based fine particles can be highly purified. The highly purified ceria-based fine particle dispersion obtained by the preferred embodiment of the method for producing a ceria-based fine particle dispersion of the present invention contains no impurities, and thus is used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate. It can be preferably used.
Further, the ceria-based fine particle dispersion of the present invention, when used as an abrasive dispersion for polishing, is effective for flattening the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. .

6 shows an SEM image and a TEM image of the ceria-based fine particles of Example 2. 6 is an X-ray diffraction pattern of the ceria-based fine particles of Example 2. 5 shows an SEM image and a TEM image of the raw ceria fine particles of Comparative Example 1. 9 is an SEM image of raw ceria fine particles of Comparative Example 3. 9 is a graph showing streaming potential measurement results of Example 3, Example 5, and Comparative Example 2. 6 is a graph of a change rate (differential value) of a streaming potential calculated from the streaming potential measurement data shown in FIG. 5.

The present invention will be described.
The present invention is a ceria-based fine particle dispersion containing ceria-based fine particles having the following features [1] to [4] and having an average particle size of 5 to 500 nm.
[1] The ceria-based fine particles include raw ceria fine particles and a layer containing easily soluble silica on the surface of the raw ceria fine particles, and the raw ceria fine particles mainly include crystalline ceria. .
[2] The ratio D (D = D1 / D2 × 100) of the mass D1 of the easily soluble silica contained in the layer containing the easily soluble silica to the mass D2 of the ceria-based fine particles is 0.005 to 10%. thing.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[4] The ceria-based fine particles have an average crystallite diameter of the crystalline ceria of 3 to 300 nm, as measured by X-ray diffraction.
The ceria-based fine particles having the above features [1] to [4] are hereinafter also referred to as “composite fine particles of the present invention”.
Further, such a ceria-based fine particle dispersion is hereinafter also referred to as “dispersion of the present invention”.

  In addition, Non-Patent Document 1 describes a device having a configuration in which ceria particles are attached to the surface of silica particles, which is different from the present invention.

Further, the present invention is a method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2a.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2a: a step of adding an additive containing silica to the fired body, heating and aging at 10 to 98 ° C., and then crushing or pulverizing to obtain a ceria-based fine particle dispersion.
Hereinafter, such a production method is also referred to as “the production method of the present invention [α]”.

Further, the present invention is a method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2b.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2b: a step of crushing or pulverizing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and heating and aging at 10 to 98 ° C. to obtain a ceria based fine particle dispersion.
Hereinafter, such a production method is also referred to as “the production method of the present invention [β]”.

Further, the present invention is a method for producing a ceria-based fine particle dispersion, comprising the following steps A and B.
Step A: a step of continuously or intermittently adding a cerium solution having a cerium compound dissolved therein to a solvent maintained at a temperature of 3 to 98 ° C. and a pH of 5.0 to 10.0 to obtain colloidal ceria.
Step B: a step of adding an additive containing silica to the colloidal ceria and heating and aging at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.
Hereinafter, such a manufacturing method is also referred to as “the manufacturing method [X] of the present invention”.

  In the following, when simply referred to as “the production method of the present invention”, any of “the production method of the present invention [α]”, “the production method of the present invention [β]”, and “the production method of the present invention [X]” is used. Is also meant.

  In the following, when simply described as "the present invention", it means any of the dispersion of the present invention, the composite fine particles of the present invention, and the production method of the present invention.

  The dispersion of the present invention is preferably produced by the production method of the present invention.

<Dispersion of the present invention>
The dispersion of the present invention will be described.

<Raw material ceria particles>
The raw ceria particles will be described.
Since the average particle diameter of the composite fine particles of the present invention is in the range of 5 to 500 nm, the upper limit of the average particle diameter of the raw ceria fine particles is necessarily equal to or smaller than 500 nm. In the present application, the average particle diameter of the raw ceria fine particles is considered to be substantially the same as the average particle diameter of the raw ceria fine particles contained in the raw ceria fine particle dispersion used in Step 1 included in the production method of the present invention described below.
Raw material ceria fine particles having an average crystallite size in the range of 3 to 300 nm and an average particle size in the range of 5 to 500 nm are preferably used.
When the dispersion of the present invention obtained by using raw ceria fine particles having an average particle diameter in the range of 5 to 500 nm as a raw material is used as an abrasive, scratches due to polishing are reduced.
When the average particle diameter of the raw material ceria fine particles is less than 5 nm, when a dispersion obtained using such raw material ceria fine particles is used as an abrasive, the polishing rate tends not to reach a practical level.
Also, when the average particle diameter of the raw material ceria fine particles exceeds 500 nm, the polishing rate also tends to not reach a practical level, and the surface precision of the substrate to be polished tends to be reduced. It is more preferable that the raw ceria fine particles have monodispersity.

The average particle size of the raw ceria fine particles is measured as follows.
Observe at 800,000 times by STEM-EDS analysis, and measure ₂ % by mass of CeO at each measurement point. Then, the material ceria fine particles are specified by specifying a region where CeO ₂ mass% exceeds 90%. Next, the maximum diameter of the raw material ceria fine particles is taken as the long axis, the length is measured, and the value is taken as the long diameter (DL). Further, a point on the long axis that bisects the long axis is determined, two points where a straight line perpendicular to the long axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the short diameter (DS). Then, a geometric mean value of the major axis (DL) and the minor axis (DS) is determined, and this is defined as the particle diameter of the raw material ceria fine particles.
In this way, the geometric mean particle diameter of the 50 raw material ceria fine particles is measured, and a value obtained by simply averaging the measured values is defined as the mean particle diameter. The same measurement can be performed even when the layer containing easily soluble silica is a particle film (particles formed by stacking particles).
If the region of the raw material ceria fine particles can be clearly identified from the lattice fringes and contrast of crystalline ceria by STEM analysis or the like, these methods may be used instead.

  The raw material ceria fine particles are not particularly limited as long as they are crystalline ceria. Even if they are single crystals or single crystal aggregates, polycrystals (polycrystals are particles having crystal grain boundaries). Or a mixture thereof.

In the present invention, the raw material ceria fine particles contain crystalline ceria as a main component.
That the raw material ceria fine particles are mainly composed of crystalline ceria, for example, after drying the dispersion of the present invention, pulverize the obtained solid using a mortar, for example, a conventionally known X-ray diffractometer X-ray analysis is performed using (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.), and it can be confirmed that only the ceria crystal phase is detected in the obtained X-ray diffraction pattern. In such a case, the raw material ceria fine particles are mainly composed of crystalline ceria. Note that the ceria crystal phase is not particularly limited, and examples thereof include Cerianite.

The term “raw material ceria fine particles” in the present application means particles of crystalline ceria (crystalline Ce oxide), that is, ceria fine particles.
The raw ceria fine particles may contain crystalline ceria (crystalline Ce oxide) as a main component, and may contain other components, for example, components other than cerium oxide as long as the content is 10% by mass or less. Further, it is desirable that Si, La, Zr, Al and the like are dissolved in crystalline ceria. Further, a hydrated cerium compound may be included as a polishing promoter.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, only the ceria crystal phase is detected. That is, even if a crystal phase other than ceria is included, its content is small, or the solid phase is dissolved in the ceria crystal, so that it is out of the detection range by X-ray diffraction.

  The average crystallite diameter of the raw material ceria fine particles is calculated using the full width at half maximum of the maximum peak appearing in a chart obtained by subjecting the composite fine particles of the present invention to X-ray diffraction. For example, the average crystallite diameter of the (111) plane is 3 to 300 nm (full width at half maximum is 2.850 to 0.02856 °) and 10 to 250 nm (full width at half maximum is 0.860 to 0.03427 °). It is more preferably 30 to 200 nm (the full width at half maximum is 0.290 to 0.04284). In many cases, the peak intensity of the (111) plane is maximum, but the peak intensity of another crystal plane, for example, the (100) plane may be maximum. In such a case, the calculation can be performed in the same manner. In this case, the size of the average crystallite diameter may be the same as the above-mentioned average crystallite diameter of the (111) plane.

The method of measuring the average crystallite diameter of the raw material ceria fine particles will be described below, taking the case of the (111) plane (around 2θ = 28 degrees) as an example.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (for example, RINT1400, manufactured by Rigaku Denki KK). Then, the full width at half maximum of the peak of the (111) plane near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcosθ
D: average crystallite diameter (angstrom)
K: Scherrer constant (K = 0.94 in the present invention)
λ: X-ray wavelength (1.5419 angstroms, Cu lamp)
β: full width at half maximum (rad)
θ: reflection angle

  The shape of the raw material ceria fine particles is not particularly limited, and may be, for example, spherical, bale, short fiber, cocoon, tetrahedral (triangular pyramid), hexahedral, octahedral, plate-like, amorphous, or porous. , Squamous, confetti-like, raspberry-like (state in which projections or granular parts are scattered on the surface of spherical particles or substantially spherical particles).

As described above, the raw material ceria fine particles mainly include crystalline ceria, but may include an impurity element.
For example, in the raw material ceria fine particles, the content of each element of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, and Zn (hereinafter, may be referred to as “specific impurity group 1”) Is preferably 100 ppm or less, more preferably 50 ppm or less, more preferably 25 ppm or less, more preferably 5 ppm or less, and even more preferably 1 ppm or less.
Further, the content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter sometimes referred to as “specific impurity group 2”) in the raw material ceria fine particles may be 5 ppm or less, respectively. preferable.

Here, the content of the specific impurity group 1 or the specific impurity group 2 in the raw ceria fine particles and the composite fine particles of the present invention described later means the content relative to the dry amount.
The content ratio with respect to the dry amount refers to the value of the ratio of the weight of the measurement target (specific impurity group 1 or specific impurity group 2) to the mass of the solid content contained in the target object (raw ceria fine particles or composite fine particles of the present invention). Shall mean.
The mass of the solid content is determined by subjecting an object (raw material ceria fine particles or composite fine particles of the present invention) to a burning loss at 1000 ° C.

Generally, raw material ceria fine particles prepared using a cerium compound such as a cerium salt as a raw material contain the specific impurity group 1 and the specific impurity group 2 derived from the raw material in a total of about several tens to several hundreds ppm.
In the case of such a raw material ceria fine particle dispersion in which the raw material ceria fine particles are dispersed in a solvent, it is possible to reduce the content of the specific impurity group 1 and the specific impurity group 2 by performing ion exchange treatment, Even in that case, the specific impurity group 1 and the specific impurity group 2 remain in a few ppm to a few hundred ppm in total. Therefore, the cerium salt is repeatedly dissolved and recrystallized once to improve the purity, and after the dissolution, impurities are removed with a chelate type ion exchange resin or the like, and then recrystallization is performed.

In the present invention, each content of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and F in the raw material ceria fine particles. Is a value obtained by measurement using the following method.
-Na and K: Atomic absorption spectroscopy-Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th: ICP-MS (inductively coupled plasma emission spectroscopy mass spectrometry)
· Cl: potentiometric titration · NO _3, SO ₄ and F: ion chromatograph

<Layer containing easily soluble silica>
The layer containing silica which is easily soluble in the composite fine particles of the present invention (hereinafter also referred to as “easily soluble layer”) may be obtained, for example, after obtaining a fired body in the production method of the present invention, or further crushing or pulverizing the fired body. Thereafter, an additive containing silica (for example, an acidic silicic acid solution) is added, and the mixture is heated and aged while maintaining the temperature at 10 to 98 ° C., whereby it can be formed on the surface of the raw material ceria fine particles.

The layer containing easily soluble silica only needs to contain 10% by mass or more of silica, and may contain other components such as Ce, La, Zr, and Al.
The silica content in the layer containing easily soluble silica is preferably from 10 to 100% by mass, more preferably from 12 to 95% by mass, and still more preferably from 15 to 90% by mass.

The mass of silica contained in the layer containing easily soluble silica is determined by the following method.
First, the composite fine particles of the present invention are diluted to 3.0% by mass with ion-exchanged water, the pH is adjusted to 9.0 with a dilute aqueous sodium hydroxide solution or nitric acid, and the mixture is stirred for 15 minutes. Thereafter, the mixture is put into a centrifuge tube with an ultramembrane (fraction molecular weight: 5000), and treated at 1820 G for 30 minutes. After the treatment, the separated liquid that has passed through the ultramembrane is collected, and the SiO ₂ concentration is measured.
Composite particles at this time the present invention having a layer containing an easily soluble silica, if the mass of the composite particles of the present invention and D _2, and the mass D ₁ of the dissolved silica, the ratio of D ₁ with respect to D ₂ D (D = D ₁ / D ₂ × 100) is 0.005 to 10%.

Since the layer containing easily soluble silica which is formed as described above and which is dissolved by performing a process such as adjusting the pH to 9.0 or the like and stirring as described above is a soluble silica, the density is low. Think of it as a low soft silica layer. Further, since the film thickness is also very thin (approximately about 0.1 nm to 10 nm), the average particle diameter of the composite fine particles of the present invention hardly changes from the measurement, so that the particle size distribution of the composite fine particles of the present invention also changes. I don't think they did. Therefore, when a substrate is polished using the composite fine particles of the present invention as abrasive grains, the layer containing easily soluble silica has a chemical polishing effect on the substrate and an effect of increasing the depth of the abrasive grains pressed into the substrate. However, it is considered that the indentation depth is rather reduced.
However, since it is a layer containing low-density soft silica, it has the effect of increasing the contact area between the composite fine particles of the present invention as abrasive grains and the substrate, and at the same time, because of the softness, the adhesion between the substrate and the abrasive grains. It is considered that there is an effect of increasing the adhesion (adhesion action) or an effect of suppressing the rolling of the abrasive grains by adhesion to the substrate. As a result, it is considered that the frictional force between the substrate and the abrasive grains increases, and there is an effect of increasing the polishing rate. Further, since the layer containing easily soluble silica formed on the surface of the abrasive grains is soft, it has an effect of alleviating local stress concentration on the substrate due to the rectangular portion of the raw material ceria fine particles, thereby suppressing scratches. Therefore, when the dispersion of the present invention is used as an abrasive, it is considered that the polishing rate is high, and the deterioration of surface accuracy and the occurrence of scratches are small.
In addition, the layer containing the easily soluble silica may cover the whole of the particles, may not be partially covered, and may have some of the raw material ceria fine particles exposed. The ratio D (D = D1 / D2 × 100) of the mass D1 of the soluble silica contained in the layer containing the soluble silica to the mass D2 of the ceria-based fine particles is in the range of 0.005 to 10% by mass. If, for example, the cohesive action between the substrate and the particles is developed, the polishing rate becomes higher.
Here, the raw material ceria fine particles may be base particles, and the surfaces of the ceria child particles bonded to the surface of the particles may be coated with a layer containing easily soluble silica.

Further, since the surface of the layer containing easily soluble silica has a negative potential, it is considered that the layer has an effect of improving the stability of the dispersion of the present invention. Further, the layer containing easily soluble silica is easily peeled off by the pressure at the time of polishing, and adheres to the surface of the raw material ceria fine particles having a positive potential generated by breaking or collapsing the raw ceria particles during polishing, It is thought to cover ceria. Therefore, the raw material ceria fine particles generated by collapsing have a negative potential, and also have a role of suppressing remaining abrasive grains on the substrate. Further, the aggregation of the composite fine particles caused by the raw material ceria particles generated by the collapse is suppressed, and the change in the particle size distribution before and after polishing is small, so that the polishing performance is also stabilized.
The composite fine particles of the present invention have a layer containing easily soluble silica on the raw ceria fine particles, but if a layer containing easily soluble silica is formed on the raw ceria fine particles, a particle film may be formed. It may be a film, a film, a film formed on a particle film, or a particle film formed on a film. However, a silica sol produced by a known method, for example, a silica sol made of water glass or a silica sol made of alkoxysilane as a raw material, is merely deposited on ceria fine particles of the raw material to form a soft, low-density, easily soluble silica. Does not result in a layer containing In the case of a particle film, it is effective for improving the stability of the particles, but does not contribute to the improvement of the polishing rate because it is not easily soluble silica, but rather lowers the polishing rate. Therefore, in the case of a particle film, a treatment for converting the particle surface into a low-density easily soluble silica layer by an alkali treatment or the like is required.

  In the composite fine particles of the present invention, at least a part of the surface of the raw ceria fine particles is coated with a layer containing easily soluble silica, and the zeta potential of the composite fine particles of the present invention has a negative potential. Therefore, -OH groups of silica exist on the outermost surface (outermost shell) of the composite fine particles of the present invention. For this reason, when used as an abrasive, the composite fine particles of the present invention are repelled by the electric charge due to the -OH group on the surface of the polishing substrate, and as a result, it is considered that adhesion to the surface of the polishing substrate having a negative potential is reduced.

  In general, ceria has a different potential from silica, a polishing substrate, and a polishing pad. The negative zeta potential decreases as the pH moves from alkaline to near neutral, and the opposite positive potential decreases in a weakly acidic region. have. Therefore, at acidic pH during polishing, ceria adheres to the polishing substrate or polishing pad and tends to remain on the polishing substrate or polishing pad due to a difference in the magnitude of the potential or a difference in polarity at the time of polishing. On the other hand, in the composite fine particles of the present invention, since the layer containing silica is present in the outermost shell as described above, the potential becomes a negative charge due to silica. As a result, abrasive grains are less likely to remain on the polishing substrate and the polishing pad. For example, when crushing while adding an additive containing silica while maintaining pH> 9 during the crushing treatment in the production method [β] step 2b of the present invention, the surface of the ceria dispersed by the crushing becomes easily soluble silica. Covered. On the other hand, when the pH is> 9, a part of the layer containing the silica which is easily soluble is dissolved in the solvent. When such a dispersion of the present invention is adjusted to pH <7 when applied to a polishing application, dissolved silica is deposited on the composite fine particles (abrasive grains) of the present invention, and a layer containing easily soluble silica is further formed. As a result, the surface of the composite fine particles of the present invention has a negative potential. When the electric potential is low, the electric potential can be adjusted by a high molecular organic substance such as polyacrylic acid, but there is a concern that the organic substance remains on the substrate. In the present invention, since the silica softly adhering to the surface adjusts the potential, the use of organic substances is reduced, and defects due to organic substances (such as residual organic substances) on the substrate are less likely to occur.

  In addition, in the dispersion of the present invention, the existence mode of silica is various, and some do not constitute the composite fine particles of the present invention. In some cases, it may be present in a state of being adhered to. Silica dispersed or dissolved in a solvent does not have a clear particle morphology, and is measured as a soluble silica by a molybdenum silicate method or the like in a solution subjected to solid-liquid separation.

As described above, when observed with 800,000-fold by STEM-EDS analysis of the composite fine particles of the present invention, the element concentration of Si in the cross section of the composite fine particles of the present invention was measured and converted into SiO ₂ concentration, easily soluble The layer containing silica is a portion where SiO ₂ mass% is 10% or more.

In an image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, an image of the raw ceria fine particles appears dark, but around and outside the raw ceria fine particles, that is, the composite fine particles of the present invention. A part of the layer containing easily soluble silica appears as a relatively thin image on the surface side of the fine particles. STEM-EDS analysis is performed on this portion, and when the SiO ₂ mass% of the portion is determined, it can be confirmed that it is 10 mass% or more.

The ratio D (D = D1 / D2 × 100) of the mass D1 of the easily soluble silica contained in the layer containing the easily soluble silica to the mass D2 of the composite fine particles of the present invention is preferably 0.005 to 10%. , 0.01 to 8%. Most preferably, it is 0.05 to 6%.
When the proportion D is less than 0.005%, the layer containing the easily soluble silica on the surface of the composite fine particles of the present invention covers only a very small part of the layer, so that the polishing rate is not improved and the dispersion stability is not improved. Is also not improved. On the other hand, if it exceeds 10%, the dispersion stability is not further improved even if more coating is applied, but the thickness of the layer containing easily soluble silica is too large, so that the raw material ceria fine particles may be removed during polishing. This is because there is a tendency for the polishing rate to decrease due to the loss of contact.

<Composite fine particles of the present invention>
The composite fine particles of the present invention will be described.
The composite fine particles of the present invention have the aforementioned features [1] to [4].

  When the dispersion of the present invention containing the composite fine particles of the present invention having an average particle diameter in the range of 5 to 500 nm is used as an abrasive, scratches associated with polishing are reduced. When the average particle diameter is less than 5 nm, when used as an abrasive, the polishing rate tends not to reach a practical level. Also, when the average particle diameter exceeds 500 nm, the polishing rate also tends to not reach a practical level, and the surface accuracy of the substrate to be polished tends to be reduced. The method for calculating the average particle diameter of the composite fine particles of the present invention is the same as the average particle diameter (geometric average particle diameter) of the raw material ceria fine particles.

The layer containing easily soluble silica contains silica, and the fine particles of the present invention are stirred and held in an aqueous alkaline solution, and the concentration of dissolved Si in the solution is measured to confirm the layer containing easily soluble silica. can do.
That is, nitric acid or an aqueous solution of sodium hydroxide is added to a dispersion obtained by dispersing the composite fine particles of the present invention in water to adjust the pH to 9, and ion-exchanged water is added to adjust to 3.0% by mass, and then 15 minutes. The portion that is dissolved by stirring is a layer containing easily soluble silica. After that, when the solution is put into a centrifuge tube with an ultramembrane (fraction molecular weight: 5000) and treated at 1820 G for 30 minutes, it is thought that the one that constituted the easily soluble silica layer permeates through the ultramembrane. Then, the separated solution that has passed through the ultramembrane is recovered, the Si concentration is measured, and the mass of the silica dissolved in the supernatant is D1, and the mass of the ceria-based fine particles is D2. In the case of fine particles, since the ratio D of D1 to D2 (D = D1 / D2 × 100) is 0.005 to 10%, it is distinguished from raw ceria fine particles or ceria-based fine particles having no easily-dissolved silica layer. be able to.

As another method for confirming the layer containing silica which is easily soluble, EDS analysis in which an electron beam is selectively irradiated to a location specified by a scanning transmission electron microscope (STEM) is performed, and the cross section of the composite fine particles of the present invention is obtained. When the element concentrations of Ce and Si at the measurement points are measured and converted into oxides, the portion where the SiO ₂ mass% is 10% or more is the layer containing easily soluble silica.
Further, when the elemental concentration of Ce at the measurement point on the cross section of the composite fine particles of the present invention is measured and converted into oxides, the portion where the CeO ₂ mass% exceeds 90% is the raw material ceria fine particles.
In addition, when a TEM image of the composite fine particles of the present invention is observed, when a low-contrast film is confirmed in the outer layer of the composite fine particles, this film is a layer containing silica which is easily soluble.

When the ceria-based fine particles of the present invention are subjected to X-ray diffraction, only the ceria crystal phase is detected. The fact that the composite fine particles of the present invention contain crystalline ceria as a main component can be confirmed, for example, by the following method.
After the dispersion of the present invention is dried, the dispersion is pulverized using a mortar and, for example, an X-ray diffraction pattern is obtained by a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). This can be confirmed by detecting only the phase. In such a case, the composite fine particles of the present invention have crystalline ceria as a main component. Note that the ceria crystal phase is not particularly limited, and examples thereof include Cerianite.

Further, the dispersion of the present invention is dried, embedded in a resin, and then subjected to sputter coating with Pt, and a cross-sectional sample is prepared using a conventionally known focused ion beam (FIB) apparatus. For example, when an FFT pattern is obtained from a prepared cross-sectional sample by using a fast known Fourier transform (FFT) analysis with a conventionally known TEM device, a diffraction diagram of crystalline ceria such as Cerianite appears. This confirms that the composite fine particles of the present invention contain crystalline ceria as a main component. In such a case, crystalline ceria is a main component.
As another method, a method of observing the presence or absence of lattice fringes due to the atomic arrangement of the raw material ceria fine particles using a conventionally known TEM analysis on a cross-sectional sample prepared in the same manner may be mentioned. If it is crystalline, lattice fringes according to the crystal structure are observed, and if it is amorphous, lattice fringes are not observed. This confirms that the composite fine particles of the present invention contain crystalline ceria as a main component. In such a case, crystalline ceria is a main component.

In the composite fine particles of the present invention, the mass ratio of ceria (CeO ₂ ) to silica (SiO ₂ ) is from 100: 0.0005 to 11.1, preferably from 100: 0.005 to 8.7. It is considered that the mass ratio of silica to ceria is approximately the same as the mass ratio of the raw material ceria fine particles and the layer containing the easily soluble silica. If the amount of easily soluble silica in the raw material ceria particles is too small, a large amount of ceria will be exposed on the surface of the composite particles, so that the stability of the composite particles will not be maintained, and huge aggregates will be generated during storage and polishing, resulting in polishing. Defects may occur on the surface of the substrate. Further, even if the amount of silica relative to ceria is too large, the ceria is thickly covered, so that the layer containing easily soluble silica does not peel off during polishing, and the polishing effect of ceria does not appear, so that the polishing rate is reduced.
The silica and ceria to be used in calculating the mass ratio between ceria (CeO ₂ ) and silica (SiO ₂ ) are all silica (SiO ₂ ) and ceria contained in the composite fine particles of the present invention. (CeO ₂ ). Therefore, the total amount of silica and ceria components contained in the ceria contained in the raw material ceria fine particles and the silica component contained as a solid solution in ceria, and the silica and ceria components contained in the layer containing easily soluble silica disposed on the surface of the raw material ceria fine particles are determined. means.

The content (% by mass) of ceria (CeO ₂ ) and silica (SiO ₂ ) in the composite fine particles of the present invention is determined by first weighing the solid content of the dispersion of the present invention by performing a burning loss at 1000 ° C.
Next, the content (% by mass) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is determined by ICP plasma emission spectrometry, and is converted into an oxide% by mass (such as ₂ % by mass of CeO). Also, when an element other than cerium is contained, the content is determined in the same manner and converted to oxide mass%. Then, assuming that the components other than CeO ₂ and other oxides constituting the composite fine particles of the present invention are SiO ₂ , the SiO ₂ mass% can be calculated.
In the production method of the present invention, the mass ratio of silica to ceria can also be calculated from the amounts of the silica source substance and the ceria source substance used when preparing the dispersion of the present invention. This can be applied when the process is not such that ceria or silica is dissolved and removed, and in such a case, the used amount of ceria and silica and the analysis value show good agreement.

In the composite fine particles of the present invention, the single crystal raw ceria fine particles may be either “particle connected type” or “monodispersed type”, but the contact area with the substrate can be kept high, and the polishing rate can be reduced. Therefore, a particle-coupled type is desirable. The particle connection type is one in which two or more raw ceria particles are partially bonded to each other, and the connection is preferably 3 or less. The bonding between the raw material ceria fine particles may be a single crystal connected body (aggregate) via a heterophase, or a polycrystalline type connected type having a crystal grain boundary, and further an aggregate where the polycrystal is via a different phase. Or a mixture thereof.
The connection type allows a large contact area with the substrate, so that the polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing rate is high.

In the composite fine particles of the present invention, the number ratio of particles whose particle diameter is less than 0.80 (preferably 0.67 or less), which is of a particle-coupled type and whose minor axis / major axis ratio is measured by an image analysis method, is 45%. It is preferable that it is above.
Here, particles having a minor axis / major axis ratio of less than 0.80 measured by an image analysis method are considered to be of a particle-bound type.
The shape of the composite fine particles of the present invention is not particularly limited, and may be particle-connected particles or single particles (unconnected particles), and usually a mixture of both.

  Here, when the dispersion of the present invention is used for polishing, and when the improvement of the polishing rate for the substrate to be polished is emphasized, the ratio of the minor axis to the major axis measured by the image analysis method of the composite fine particles of the present invention is used. Is less than 0.80 (preferably 0.67 or less), and the number ratio of particles is preferably 45% or more (more preferably 51% or more).

  When it is also important to emphasize that the surface roughness on the substrate to be polished is at a low level, the ratio of the minor axis / major axis measured by the image analysis method of the composite fine particles of the present invention is 0.80 or more (preferably 0%). (0.9 or more) is preferably 40% or more, more preferably 51% or more.

The following aspect 1 can be cited as an example of the composite fine particle dispersion of the present invention in the case where the improvement of the polishing rate for the substrate to be polished is emphasized.
[Aspect 1] The present invention is characterized in that the composite fine particles of the present invention are characterized in that the ratio of the number of particles whose minor axis / major axis ratio measured by an image analysis method is less than 0.8 is 45% or more. Dispersion.

In the case where importance is attached to the fact that the surface roughness on the substrate to be polished is at a low level, the composite fine particle dispersion of the present invention may include the following aspect 2.
[Aspect 2] The present invention is characterized in that the composite fine particles of the present invention are characterized in that the ratio of the number of particles having a minor axis / major axis ratio of 0.8 or more measured by an image analysis method is 40% or more. Dispersion.

A method of measuring the ratio of minor axis / major axis by image analysis will be described. In a photographic projection obtained by photographing the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is taken as the major axis, and the length is measured. , And its value is defined as the major axis (DL). Further, a point on the long axis that bisects the long axis is determined, two points where a straight line perpendicular to the long axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the short diameter (DS). From this, the ratio of minor axis / major axis (DS / DL) is determined. Then, the number ratio (%) of particles having a minor axis / major axis ratio of less than 0.80 and 0.80 or less among arbitrary 50 particles observed in the photograph projection view is obtained.
In the composite fine particles of the present invention, the number ratio of particles having a minor axis / major axis ratio of less than 0.80 (preferably 0.67 or less) is preferably 45% or more, and more preferably 51% or more. . The composite fine particles of the present invention in this range have a high polishing rate when used as an abrasive, and are therefore preferable.

  The number of coarse particles of 0.51 μm or more that can be contained in the dispersion of the present invention is preferably 3000 million / cc or less. The number of coarse particles is preferably 3000 million / cc or less, more preferably 2000 million / cc or less. Coarse particles of 0.51 μm or more may cause polishing scratches and may further deteriorate the surface roughness of the polished substrate. Usually, when the polishing rate is high, the polishing rate is high, but polishing scratches occur frequently and the surface roughness of the substrate tends to deteriorate. However, when the composite fine particles of the present invention are of the particle-coupled type, a high polishing rate can be obtained. On the other hand, when the number of coarse particles of 0.51 μm or more is 3000 million / cc or less, polishing scratches are small, and The roughness can be kept low.

The method for measuring the number of coarse particles that can be contained in the dispersion of the present invention is as follows.
After diluting the sample to 0.1% by mass with pure water, 5 ml of the sample is collected and injected into a conventionally known coarse particle counting apparatus. Then, the number of coarse particles of 0.51 μm or more is determined. This measurement is performed three times, a simple average value is obtained, and the value is multiplied by 1000 to obtain a value of the number of coarse particles of 0.51 μm or more.

The composite fine particles of the present invention preferably have a specific surface area of 3 to 100 m ² / g, more preferably 6 to 80 m ² / g.

Here, a method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) is put into a measurement cell, degassed at 250 ° C. for 40 minutes in a nitrogen gas stream, and then the sample is mixed with 30% by volume of nitrogen and 70% by volume of helium. The liquid nitrogen temperature is maintained in an air stream, and nitrogen is equilibrium-adsorbed to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the above-mentioned mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured by a previously prepared calibration curve.
Such a BET specific surface area measurement method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measurement device.
In the present invention, the specific surface area means a value measured by such a method unless otherwise specified.

The average particle size of the composite fine particles of the present invention is preferably from 5 to 500 nm, more preferably from 30 to 300 nm. When the average particle diameter of the composite fine particles of the present invention is in the range of 5 to 500 nm, the polishing rate is high when applied as an abrasive, which is preferable.
The average particle diameter of the composite fine particles of the present invention means the number average value of the average particle diameter measured by the image analysis method.
A method for measuring the average particle size by the image analysis method will be described. In a photographic projection obtained by photographing the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is taken as the major axis, and the length is measured. , And its value is defined as the major axis (DL). Further, a point on the long axis that bisects the long axis is determined, two points where a straight line perpendicular to the long axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the short diameter (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is determined, and this is defined as the average particle diameter of the composite fine particles.
In this way, the geometric average particle diameter of 50 or more composite particles is measured, and their number average value is calculated.

In the composite fine particles of the present invention, the content of each element of the specific impurity group 1 is preferably 100 ppm or less, more preferably 50 ppm or less, more preferably 25 ppm or less, and more preferably 5 ppm or less. More preferably, it is still more preferably 1 ppm or less.
The content of each element of the specific impurity group 2 in the composite fine particles of the present invention is preferably 5 ppm or less. The method of reducing the content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention is as described above.
The content rates of the respective elements of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention are determined by measuring the specific impurity group 1 and the specific impurity group 2 contained in the raw material ceria fine particles described above. It can be measured by the same method as in the case.

<Dispersion of the present invention>
The dispersion of the present invention will be described.
The dispersion of the present invention is one in which the composite fine particles of the present invention as described above are dispersed in a dispersion solvent.

  The dispersion of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, for example, water such as pure water, ultrapure water, or ion-exchanged water is preferably used. Further, the dispersion of the present invention is polished by adding at least one selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling polishing performance. It is suitably used as a slurry.

  Examples of the dispersion solvent including the dispersion of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoki Glycol ether acetates such as ethyl acetate; methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, esters such as ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; hexane, heptane, isooctane; Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl- Organic solvents such as pyrrolidones such as 2-pyrrolidone can be used. These may be used by mixing with water.

  The solid concentration contained in the dispersion of the present invention is preferably in the range of 0.3 to 50% by mass.

When the cationic colloid titration is carried out, the dispersion of the present invention has a streaming potential change amount (ΔPCD) represented by the following formula (1) and a cationic colloid titration solution when the differential value of the streaming potential is maximized. It is preferable that a streaming potential curve with a ratio (ΔPCD / V) to the addition amount (V) of −3000 to −100 is obtained.
ΔPCD / V = (IC) / V Equation (1)
C: streaming potential (mV) when the differential value of the streaming potential is maximized
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Addition amount (ml) of the cationic colloid titrant when the differential value of the streaming potential is maximized

  Here, the cationic colloid titration is performed by adding the cationic colloid titrant to 80 g of the dispersion of the present invention in which the solid content concentration is adjusted to 1% by mass. A 0.001N polydiallyldimethylammonium chloride solution is used as a cationic colloid titrant.

The streaming potential curve obtained by the cationic colloid titration is, as shown in FIG. 5 shown in Examples described later, the addition amount (ml) of the cation titrant on the X axis and the streaming potential (mV) of the dispersion of the present invention on the X axis. It is a graph taken on the Y axis.
Then, the streaming potential curve of this graph is differentiated by the titer (X), and a graph is obtained in which the obtained differential value is newly set on the Y axis and the titer is set on the X axis. This graph is, for example, a graph as shown in FIG. The streaming potential at the point where the differential value (the differential value of the streaming potential on the Y-axis) in this graph is maximum is C (mV), and the addition amount of the cationic colloid titrant at that point (X-axis) is V (ml). I do.
The starting point of the streaming potential curve is the streaming potential of the dispersion of the present invention before titration. Specifically, the point at which the amount of the cationic colloid titrant added is 0 is defined as the starting point. The streaming potential at this start point is defined as I (mV).

When the value of ΔPCD / V is −3000 to −100, the polishing rate of the abrasive is further improved when the dispersion of the present invention is used as the abrasive. This ΔPCD / V is considered to reflect the degree of coating of the raw ceria fine particles with the layer containing easily soluble silica on the surface of the composite fine particles of the present invention and / or the degree of exposure of the raw ceria fine particles on the surface of the composite fine particles. . The inventor estimates that when the value of ΔPCD / V is within the above range, the polishing rate is high, and the dispersion stability of the composite fine particles is improved, so that stable polishing is performed.
Conversely, when the value of ΔPCD / V is larger than −100, the raw material ceria fine particles are not sufficiently exposed at the time of polishing because the surface of the composite fine particles is thickly covered with a layer containing easily soluble silica. The polishing rate is reduced. On the other hand, if it is smaller than -3000, the layer containing the easily soluble silica is insufficiently coated, so that the effect of improving the frictional force due to adhesion to the substrate is reduced, so that the polishing rate is reduced and the dispersion stability is maintained. The present inventors presume that aggregation occurs and causes defects and the like. ΔPCD / V is more preferably −2800 to −150, and still more preferably −2500 to −200.

  When the pH value of the dispersion of the present invention is in the range of 3 to 8, before the start of cationic colloid titration, that is, when the titer is zero, the streaming potential becomes a negative potential. Is preferred. This is because when the streaming potential is maintained at a negative potential, abrasive grains (ceria-based fine particles) are unlikely to remain on the polishing substrate, which also exhibits a negative surface potential. Further, in the measurement of the zeta potential, when the pH value is in the range of 3 to 8, it is preferable that the potential becomes a negative potential.

In the present invention, the production method is not limited as long as the raw ceria fine particles are crystalline, as long as the outermost layer of the raw ceria fine particles has easily soluble silica.
Examples of the raw ceria fine particles in the production method of the present invention include fired ceria (including ceria synthesized in a liquid phase and fired colloidal ceria) and ceria synthesized in a liquid phase (including colloidal ceria). . Specifically, Steps 1 and 2 in the production method [α] of the present invention and the production method [β] of the present invention are production processes using calcined ceria as raw material ceria fine particles. Steps A and B in the production method [X] of the present invention are production processes using colloidal ceria as raw material ceria fine particles.
In addition, easily soluble silica can be formed after crystal growth of crystalline ceria in the range of 3 to 300 nm, and specifically, is formed before or after the crushing step. be able to. The production method for forming easily soluble silica in ceria synthesized in the liquid phase is the production method [X] of the present invention, and the production method for forming readily soluble silica in calcined ceria is the production method of the present invention [X]. α] and the production method [β] of the present invention.
The details of the production will be described below.

<Production method [α], [β] of the present invention>
The production method [α] of the present invention and the production method [β] of the present invention will be described. The production methods [α] and [β] of the present invention use calcined ceria as raw material ceria fine particles. These all have a step 1 and a step 2a or a step 2b as the next step.
For convenience of explanation, step 2 corresponding to a higher concept of step 2a and step 2b will be described below.
This will be described in detail below.

<Step 1>
In step 1, a cerium compound is first prepared.
When the dispersion of the present invention applied to polishing of a semiconductor device or the like is to be prepared by the manufacturing method of the present invention, Na, Ag, Ca, Cr, Cu, Fe, K, Mg , Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and a metal salt of cerium having a low content of F are preferred. Specifically, the content of each of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, and Zn in terms of dry is 100 ppm or less, and further, U, Th, Cl, NO ₃ , SO ₃ It is desirable that the contents of ₄ and F are each 5 ppm or less. In order to improve the purity of the cerium metal salt, it is preferable to dissolve the cerium metal salt for recrystallization or to perform a treatment such as chelate ion exchange.
The kind of the metal salt of cerium is not limited, but chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide and the like of cerium can be used. Specific examples include cerous nitrate, cerium carbonate, cerous sulfate, cerous chloride and the like.
Among these, cerium carbonate is preferred. When nitrate, sulfate, or hydrochloride is applied to step 1, highly toxic and harmful gases such as SO _X , NO _{X, and} corrosive gas are generated, whereas carbonates are harmful. This is because only low-emission CO ₂ is generated.

  It is desirable that the cerium metal salt be removed in advance by using a sieve or the like to remove coarse agglomerates, and that the particle size distribution of the cerium metal salt be made uniform by performing wet or dry classification. If the particle size distribution of the cerium metal salt is not uniform, coarse or extremely small cerium crystals are generated during firing. This is because coarse cerium crystals are difficult to crush or crush, and if they remain without being crushed or crushed completely, they may cause scratches during polishing. In addition, extremely small cerium crystals are likely to remain on the polishing substrate, and abrasive grains are likely to remain.

In step 1, such a cerium compound is fired at 300 to 1200 ° C. to obtain a fired body.
A method for firing a cerium compound such as a cerium metal salt is not particularly limited, and examples thereof include a rotary kiln, a batch furnace, a fluidized-bed firing furnace, and a roller hearth kiln.The rotary kiln can be fired uniformly without uneven firing, and equipment cleaning. It is desirable to bake in a rotary kiln from the viewpoint of properties.
The firing temperature is 300 to 1200 ° C., preferably 400 to 950 ° C., and more preferably 500 to 900 ° C. This is because sintering in such a temperature range sufficiently promotes crystallization of ceria. If the firing is performed at a temperature higher than 1200 ° C., the ceria crystal grows abnormally or the particles are fused to each other to form a coarse agglomerate, and scratches occur frequently. If the firing is performed at a temperature lower than 300 ° C., the crystallization of ceria does not proceed sufficiently, so that the polishing rate becomes extremely low. It is desirable to bake in such a temperature range for 30 minutes to 10 hours, preferably 30 minutes to 5 hours, more preferably 30 minutes to 3 hours.
The rate of temperature rise during firing is preferably 10 to 300 ° C / min, more preferably 30 to 200 ° C / min.

<Step 2>
In step 2, the fired body is crushed or pulverized to obtain a raw material ceria fine particle dispersion.
Here, the crushing or pulverization of the fired body is performed by a wet method or a dry method.
In the present invention, “crushing” refers to an operation of disintegrating and dispersing an aggregated structure into a single crystal when the fired body is a single crystal aggregate, or an aggregate structure when the fired body is a polycrystal. Refers to an operation in which a crystal is disintegrated to be broken into a polycrystal smaller than the original polycrystal while maintaining the grain boundary, or the grain boundary is broken and a part is broken into a single crystal. “Pulverization” refers to an operation of turning a single crystal contained in a fired body into a smaller single crystal.
In step 2, the fired body is subjected to crushing, pulverization, or both operations.

  A conventionally known device can be used as a device for crushing or pulverizing in a wet system. For example, a batch type bead mill such as a basket mill, a horizontal / vertical type / annular type continuous bead mill, a sand grinder mill, a ball mill, etc., a rotor / stator type homogenizer, an ultrasonic dispersion type homogenizer, and crushing particles in a dispersion liquid. Examples include a wet medium stirring type mill (wet pulverizer) such as an impact pulverizer. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, an organic resin, or the like.

Water and / or an organic solvent is used as a solvent in the case of performing the crushing treatment or the crushing treatment in a wet system. For example, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water.
In addition, the solid content concentration when wet crushing is not particularly limited, but is preferably, for example, in the range of 0.3 to 50% by mass.

  In the case of performing wet disintegration, it is preferable to perform wet disintegration while maintaining the pH of the solvent at 5 to 11. This is because if the pH is maintained in this range, crushing proceeds while maintaining monodispersion of ceria. This is because crushing efficiency is hardly improved even if crushing is performed under conditions where the pH value exceeds 11, and reaggregation proceeds during crushing. If the pH is less than 5, ceria may be dissolved. The pH during crushing is preferably 5 to 11, more preferably 6 to 10.5. In addition, the impurities mixed from the media at the time of crushing can be removed by centrifugation, ion exchange, washing with an ultramembrane, or the like, if necessary.

  As a device for pulverizing or pulverizing the fired body obtained by firing in a dry manner, a conventionally known device can be used. Examples thereof include an attritor, a ball mill, a vibration mill, a vibration ball mill, a jet mill, and the like. Can be.

  Further, after the fired body obtained by firing is subjected to dry crushing treatment, a solvent may be added and wet crushing treatment may be performed at pH 5 to 11 in a range of pH 5 to 11.

<Step 2a, Step 2b>
As described above, Step 2 is a step of crushing or pulverizing the fired body to obtain a raw material ceria fine particle dispersion, and in Step 2a, adding an additive containing silica to the fired body, Heat aging at 98 ° C., and then pulverize or pulverize in the same manner as in step 2. Then, the resultant is used as a ceria-based fine particle dispersion.

  As described above, Step 2 is a step of crushing or pulverizing the fired body to obtain a raw material ceria fine particle dispersion, but in Step 2b, the fired body is crushed in the same manner as in Step 2. Crushed or crushed, an additive containing silica is added to the obtained raw material ceria fine particle dispersion, and the mixture is heated and aged at 10 to 98 ° C. Then, the resultant is used as a ceria-based fine particle dispersion.

<Additives containing silica>
The additive containing silica used in Step 2a and Step 2b will be described.

  The additive containing silica contains 10% by mass or more of silica on a dry basis, and may further contain, for example, Ce, Zr, La, or Al.

The amount of the additive containing silica is preferably 50 ppm to 43% in terms of a ratio (mass of the additive containing silica / mass of the fired body) to the mass (dry base) of the fired body, and more preferably 100 ppm to 25%. More preferably, it is more preferably 500 ppm to 11%.
If the amount is less than this range, a layer containing easily soluble silica may not be formed sufficiently. If the amount is more than this range, the layer containing the easily soluble silica may be excessively thick, or a component which does not deposit on the composite fine particles of the present invention may be generated.

  As described above, an additive containing silica is added to the fired body, and the mixture is aged by heating at 10 to 98 ° C., and then is crushed or pulverized. Deposition is promoted. The temperature for heat aging is 10 to 98 ° C, preferably 20 to 80 ° C. If it is lower than this range, it may not be deposited on the surface of the particles. If it is higher than this range, the composite fine particles of the present invention may aggregate. Through such a process, a layer containing easily soluble silica is relatively uniformly formed on the surface of the raw material ceria fine particles.

  The silica-containing additive thus treated may be entirely deposited on the surface of the raw material ceria fine particles, but may be partially present in the solvent. This is because when the pH is adjusted to 3 to 8 during polishing, the particles deposit on the surface of the composite fine particles of the present invention. Also, even if some non-deposited components remain in the solvent, the additive containing silica removes the polishing debris generated during polishing and the raw ceria fine particles generated by the collapse of the composite fine particles. This is because coating is performed to prevent scratching.

<Step 3>
The raw ceria fine particle dispersion obtained in the step 2 or the ceria based fine particle dispersion obtained in the step 2a or 2b is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently, sedimentation components are removed. Is preferred.
In such a step, that is, the raw ceria fine particle dispersion obtained in the step 2 or the ceria-based fine particle dispersion obtained in the step 2a or the step 2b is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more. The step of removing the sedimentation component is referred to as step 3.
When the relative centrifugal acceleration is 300 G or more, since coarse particles are unlikely to remain in the ceria-based fine particle dispersion, scratches are less likely to occur when the ceria-based fine particle dispersion is used for polishing such as an abrasive. .
Here, the upper limit of the relative centrifugal acceleration is not particularly limited, but is practically used at 10,000 G or less.

<Step 3a>
As described above, the step 3 is a step of subjecting the ceria-based fine particle dispersion to centrifugal treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing the sedimentation component, and the step 3a is a step following the step 2. The raw material ceria fine particle dispersion obtained in the step 2 is subjected to a centrifugal treatment at a relative centrifugal acceleration of 300 G or more, and subsequently, a sediment component is removed, and then an additive containing silica is added. Heat aging to obtain a ceria-based fine particle dispersion.
Here, the operation of adding the additive containing silica and heating and aging at 10 to 98 ° C. may be the same as in the case of the above-mentioned Step 2a and Step 2b.

  An operation of adding an additive containing silica as in Step 2a or Step 2b and performing heat aging at 10 to 98 ° C., and then performing centrifugal treatment to remove settled components, is further performed as in Step 3a. Then, an operation of adding an additive containing silica to the mixture and heating and aging at 10 to 98 ° C. may be performed to obtain a ceria-based fine particle dispersion. Such a case corresponds to the manufacturing method including step 1, step 2 and step 3a, and also corresponds to the manufacturing method [α] of the present invention or the manufacturing method [β] of the present invention.

<Production method [X] of the present invention>
The production method [X] of the present invention will be described. The production method [X] of the present invention uses ceria synthesized in a liquid phase as raw ceria fine particles. The manufacturing method [X] of the present invention includes a step A, and includes a step B as a next step.
This will be described in detail below.

<Step A>
In step A, the cerium compound described in step 1 is added to a solvent and dissolved to obtain a cerium solution. At this time, an acid may be added for the purpose of dissolving the cerium compound. The type of acid is not particularly limited, but inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid are preferable.

Next, the cerium solution is continuously or intermittently added thereto while stirring the alkaline aqueous solution or ion-exchanged water while maintaining the temperature at 3 to 98 ° C. and the pH range at 5.0 to 9.0. Neutralizing the solution produces crystalline ceria.
Here, while stirring the alkaline aqueous solution or the ion-exchanged water, maintaining the temperature at 3 to 98 ° C., the pH range at 5.0 to 9.0, and the oxidation-reduction potential at 10 to 500 mV, the cerium solution was added thereto. Is preferably added continuously or intermittently.
After adding the cerium solution, it is desirable to ripen for the purpose of completing the reaction.
By such a process, colloidal ceria is obtained.

Solids concentration when adding cerium solution to solvent is preferably from 1 to 40% by mass in terms of CeO ₂ reference. If this solid content is too low, the concentration of ceria in the production process will be low, and the productivity may be poor.

  By neutralizing the cerium solution with an alkali, crystalline ceria having an average crystallite diameter of 3 to 300 nm can be obtained. The crystalline ceria may be a single crystal, a single crystal aggregate, a polycrystal, or a mixture thereof. In addition, during the neutralization reaction, the acid used when dissolving the cerium compound or the acid introduced from the cerium compound reacts with the alkali to form a salt. Since the ionic strength is increased by the generated salt, it tends to form a single crystal aggregate.

  The temperature of the reaction solution when adding the cerium solution while stirring the alkaline aqueous solution or ion-exchanged water is from 3 to 98 ° C, preferably from 10 to 90 ° C. If the temperature is too low, the reactivity between the cerium solution and the alkali decreases, and as a result, ceria crystal growth is hindered, and cerium hydroxide and the like may be generated. Even if the crystal grows, a small ceria crystal having a crystallite diameter of less than 5 nm may be generated. Conversely, if the temperature is too high, ceria grows abnormally or single crystals agglomerate, coarse aggregates are formed, and there is a tendency that crushing or crushing becomes difficult.

  The time of the reaction solution when adding the cerium solution is preferably 0.5 to 24 hours, and more preferably 0.5 to 18 hours. If the time is too short, the crystalline cerium oxide tends to aggregate and be difficult to be crushed, which is not preferable. Conversely, if this time is too long, the formation of crystalline cerium oxide will not proceed further and will be uneconomical. After the addition of the cerium metal salt, aging may be performed at a temperature of 3 to 98 ° C. if desired. This is because aging has the effect of promoting the reaction of crystallization of ceria.

  Further, the pH range of the reaction solution when adding the cerium solution is set to 7 to 10, preferably 6 to 10. At this time, it is preferable to adjust the pH by adding an alkali or the like. As an example of such an alkali, a known alkali can be used. Specific examples include, but are not limited to, aqueous ammonia solutions, aqueous alkali hydroxides, alkaline earth metals, and aqueous solutions of amines.

  The oxidation-reduction potential of the reaction solution to which the cerium solution is added is preferably adjusted to 10 to 500 mV. The oxidation-reduction potential is more preferably set to 100 to 300 mV. When the oxidation-reduction potential becomes negative, a composite cerium compound such as a plate-like or rod-like compound may be generated without the cerium compound becoming crystalline ceria. Examples of a method for keeping the oxidation-reduction potential within the above range include a method of adding an oxidizing agent such as hydrogen peroxide and a method of blowing air and ozone.

  Cation exchange resin, anion exchange resin, ion exchange with chelate type ion exchange resin, or ultrafiltration washing, filtration washing, etc. for the purpose of removing salts remaining in the aged reaction solution by adding a cerium solution A deionization treatment can be performed if necessary. Ceria-based fine particles can be highly purified by the deionization treatment, and when used as an abrasive, equipment corrosion can be prevented. The deionization treatment is not limited to these.

  Before the colloidal ceria obtained in the step A is subjected to the next step, the colloidal ceria may be further diluted or concentrated using pure water or ion-exchanged water.

  The solid content concentration in colloidal ceria is preferably 1 to 30% by mass.

<Step B>
In step B, an additive containing silica is added to the colloidal ceria, and the mixture is heated and aged at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.
Here, the operation of adding an additive containing silica to the colloidal ceria and heating and aging at 10 to 98 ° C. may be the same as in the above-described steps 2a and 2b.

In the step B, it is preferable to obtain the ceria-based fine particle dispersion by crushing or pulverizing the colloidal ceria, adding the additive, and heat-aging at 10 to 98 ° C.
In the step B, it is preferable that the additive is added to the colloidal ceria, the mixture is aged by heating at 10 to 98 ° C., and then crushed or pulverized to obtain the ceria-based fine particle dispersion.
Here, the method of pulverizing or pulverizing may be the same as the method of pulverizing or pulverizing the fired body in step 2 described above.

  It is preferable that the ceria-based fine particle dispersion obtained in the above step B is subjected to centrifugal treatment at a relative centrifugal acceleration of 300 G or more, and subsequently, sediment components are removed. Such a process may be similar to the above-described step 3.

  In addition, the colloidal ceria obtained by the above-mentioned step A is preferably crushed or crushed, and then subjected to centrifugal treatment at a relative centrifugal acceleration of 300 G or more to remove sedimentation components. Thereafter, an additive containing silica is added. At 10 to 98 ° C to obtain a ceria-based fine particle dispersion.

  In addition, the additive containing silica is added as in the step B, and an operation of heating and aging at 10 to 98 ° C. is performed. After that, the precipitated component is removed by centrifugation, and then the additive containing silica is further added. Then, an operation of heating and aging at 10 to 98 ° C. may be performed to obtain a ceria-based fine particle dispersion. Such a case corresponds to the manufacturing method [X] of the present invention.

  In the present invention, the ceria-based fine particle dispersion obtained by the above production method can be further dried to obtain ceria-based fine particles. The drying method is not particularly limited, and for example, drying can be performed using a conventionally known dryer.

  The dispersion of the present invention can be obtained by such a production method of the present invention.

<Abrasive dispersion liquid for polishing>
The liquid containing the dispersion of the present invention can be preferably used as a polishing abrasive dispersion (hereinafter also referred to as “polishing abrasive dispersion of the present invention”). In particular, it can be suitably used as a polishing abrasive dispersion for polishing a semiconductor substrate on which an SiO ₂ insulating film is formed. In addition, a chemical component can be added to control the polishing performance, and can be suitably used as a polishing slurry. Further, the abrasive grain dispersion for polishing can be suitably used as it is as a polishing slurry.

  The abrasive dispersion liquid for polishing according to the present invention has excellent effects such as a high polishing rate when polishing a semiconductor substrate and the like, little scratches (scratch) on the polished surface during polishing, and little residual abrasive grains on the substrate. ing.

  The abrasive dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, for example, water such as pure water, ultrapure water, or ion-exchanged water is preferably used. Further, an acid, an alkali or a buffer solution may be added as a pH adjuster. Further, as an additive for controlling the polishing performance, the polishing abrasive dispersion of the present invention may further include, as an additive for controlling the polishing performance, a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, and a pH buffer. By adding more than one kind, it is suitably used as a polishing slurry.

<Polishing accelerator>
The polishing slurry dispersion of the present invention varies depending on the type of the material to be polished, but can be used as a polishing slurry by adding a conventionally known polishing accelerator as needed. Such examples include hydrogen peroxide, peracetic acid, urea peroxide, and the like, and mixtures thereof. When a polishing composition containing such a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is a metal.

  Other examples of the polishing accelerator include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, organic acids such as acetic acid, and sodium, potassium, ammonium, and amine salts of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished made of a composite component, the polishing rate for a specific component of the material to be polished is promoted so that a flat polishing is finally achieved. You can get a surface.

  When the abrasive dispersion for polishing of the present invention contains a polishing accelerator, the content is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. .

<Surfactant and / or hydrophilic compound>
A cationic, anionic, nonionic, amphoteric surfactant or a hydrophilic compound can be added to improve the dispersibility and stability of the abrasive dispersion liquid for polishing of the present invention. Both the surfactant and the hydrophilic compound have a function of reducing the contact angle to the surface to be polished, and a function of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following group can be used.

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate, and phosphate. As the carboxylate, soap, N-acyl amino acid salt, polyoxyethylene or polyoxypropylene alkyl ether carboxylate Acid sulfonate, acylated peptide; alkyl sulfonate, alkylbenzene and alkyl naphthalene sulfonate, naphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate; sulfate Salts include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, alkyl amide sulfates; and phosphate salts such as alkyl phosphates, polyoxyethylene or polyoxyphosphates. Can pyrene alkyl allyl ether phosphates.

  As cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts; carboxybetaine type, sulfobetaine type as amphoteric surfactants, Amino carboxylate, imidazolinium betaine, lecithin, alkylamine oxide can be mentioned.

  Examples of the nonionic surfactant include an ether type, an ether ester type, an ester type, and a nitrogen-containing type. Examples of the ether type include polyoxyethylene alkyl and alkyl phenyl ether, alkyl allyl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene poly. Oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ethers, and as the ether ester type, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, as an ester type Polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester , Sucrose esters, nitrogen-containing type, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amide, and the like. Other examples include a fluorine-based surfactant.

  As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and as the salt, an ammonium salt, a potassium salt, a sodium salt and the like can be mentioned, and an ammonium salt and a potassium salt are particularly preferable.

  Further, as other surfactants and hydrophilic compounds, esters such as glycerin ester, sorbitan ester and alanine ethyl ester; polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ether, polyethylene glycol alkenyl ether, alkyl Polyethylene glycol, alkyl polyethylene glycol alkyl ether, alkyl polyethylene glycol alkenyl ether, alkenyl polyethylene glycol, alkenyl polyethylene glycol alkyl ether, alkenyl polyethylene glycol alkenyl ether, polypropylene glycol alkyl ether, polypropylene glycol alkenyl ether, alkyl polypropylene Ethers such as recall, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether and alkenyl polypropylene glycol; polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, curdlan and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; Polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), poly Acrylic acid, polyacrylamide, amino polyacrylamide, ammonium polyacrylate, sodium polyacrylate, Polycarboxylic acids and salts thereof such as rimidic acid, ammonium polyamic acid salt, polyamic acid sodium salt and polyglyoxylic acid; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; ammonium methyltaurate and sodium methyltaurate Sodium methyl sulfate, ethyl ammonium sulfate, butyl ammonium sulfate, sodium vinyl sulfonate, sodium 1-allyl sulfonate, sodium 2-allyl sulfonate, sodium methoxymethyl sulfonate, ammonium ethoxymethyl sulfonate Salts, sulfonic acids such as 3-ethoxypropylsulfonic acid sodium salt, and salts thereof; propionamide, acrylamide, methylurea, nicotinamide, succinamide, and sulf And amides such as phenylamide.

  When the substrate to be polished is a glass substrate or the like, any of the surfactants can be suitably used. However, in the case of a silicon substrate for a semiconductor integrated circuit or the like, an alkali metal or an alkaline earth is used. In the case where the influence of contamination by a class of metal or halide is disliked, it is desirable to use an acid or its ammonium salt-based surfactant.

  When the abrasive dispersion for polishing according to the present invention contains a surfactant and / or a hydrophilic compound, the content thereof is 0.001 to 10 g in 1 L of the abrasive dispersion for polishing as a total amount. It is more preferably 0.01 to 5 g, particularly preferably 0.1 to 3 g.

  In order to obtain a sufficient effect, the content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the polishing slurry dispersion liquid, and is preferably 10 g or less from the viewpoint of preventing a reduction in polishing rate. .

  One or more surfactants or hydrophilic compounds may be used, or two or more surfactants or hydrophilic compounds may be used in combination.

<Heterocyclic compound>
For the polishing abrasive dispersion of the present invention, when a metal to be polished contains a metal, by forming a passivation layer or a dissolution inhibiting layer on the metal, for the purpose of suppressing the erosion of the substrate to be polished, A heterocyclic compound may be contained. Here, the “heterocyclic compound” is a compound having a heterocyclic ring containing one or more hetero atoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. Heterocycle means a cyclic compound having at least one heteroatom. Heteroatom means only those atoms that form a part of a heterocyclic ring system, which is located external to the ring system, separated from the ring system by at least one non-conjugated single bond, An atom which is part of a further substituent of is not meant. Preferred examples of the hetero atom include, but are not limited to, a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom. As examples of the heterocyclic compound, imidazole, benzotriazole, benzothiazole, tetrazole, and the like can be used. More specifically, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3- Triazole, 4-amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino1,2,4-triazole, 3,5 -Diamino-1,2,4-triazole and the like, but are not limited thereto.

  The content of the heterocyclic compound in the abrasive dispersion liquid for polishing according to the present invention is preferably 0.001 to 1.0% by mass, and more preferably 0.001 to 0.7% by mass. More preferably, it is still more preferably 0.002 to 0.4% by mass.

<PH adjuster>
The pH of the polishing composition can be adjusted by adding an acid or a base and a salt compound thereof as necessary, for example, to enhance the effect of each of the above additives.

  When adjusting the abrasive grain dispersion to a pH of 7 or more, an alkaline one is used as a pH adjuster. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, and tetramethylamine are used.

  When adjusting the abrasive grain dispersion to a pH of less than 7, an acidic pH adjuster is used. For example, mineral acids such as hydrochloric acid and nitric acid such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid are used.

<PH buffer>
A pH buffer may be used in order to keep the pH value of the polishing slurry dispersion constant. As the pH buffer, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, borate, or organic acid salts can be used.

  Further, as a dispersion solvent of the abrasive grain dispersion of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol; Ketones such as isophorone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran Ethers; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butane Glycol ether acetates such as xyl ethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene; hexane, heptane, isooctane Hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone; N-octyl Organic solvents such as pyrrolidones such as -2-pyrrolidone can be used. These may be used by mixing with water.

  It is preferable that the solid content concentration contained in the abrasive grain dispersion liquid of the present invention is in the range of 0.3 to 50% by mass. If the solid content is too low, the polishing rate may decrease. Conversely, even if the solid content concentration is too high, the polishing rate is rarely further improved, which may be uneconomical.

  Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples.

<Experiment 1>
First, details of each measurement method and test method in Examples and Comparative Examples will be described. Tables 1 and 2 show the following measurement results and test results for each example and comparative example.

[Analysis of components]
[Measurement of CeO ₂ content and SiO ₂ content]
A method for measuring the CeO ₂ content and the SiO ₂ content in the ceria-based fine particles in Examples and Comparative Examples will be described.
First, the ceria-based fine particle dispersion is subjected to a 1000 ° C. ignition loss, and the mass of the solid content is determined. Then, as in the case of Ag to Th described below, an ICP plasma emission spectrometer (for example, SII, SPS5520) is used. Was used to measure the contents of Si, La, Zr, and Al by the standard addition method, and SiO ₂ , La ₂ O ₃ , ZrO ₂ , and Al ₂ O ₃ mass% were calculated, respectively. All of SiO ₂ , La ₂ O ₃ , ZrO ₂ , and Al ₂ O _{3 form an} easily soluble layer (a layer containing easily soluble silica).
The content of CeO ₂ was determined assuming that the solid component other than SiO ₂ , La ₂ O ₃ , ZrO ₂ , and Al ₂ O ₃ was CeO ₂ .
Here, the solid content concentration of the ceria-based fine particle dispersion can also be determined.
In the measurement of the content of the specific impurity group 1 and the specific impurity group 2 described below, the content of each component with respect to the dry amount was obtained based on the mass of the solid content thus obtained.

[Component analysis of ceria-based fine particles]
The content of each element shall be measured by the following method.
First, about 1 g of a sample composed of ceria-based fine particles or a ceria-based fine particle dispersion (adjusted to a solid content of 20% by mass) is collected in a platinum dish. 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid are added and heated on a sand bath. After drying, a small amount of water and 50 ml of nitric acid are added and dissolved, put in a 100 ml measuring flask, and water is added to make 100 ml. In this solution, Na and K are measured with an atomic absorption spectrometer (for example, Z-2310 manufactured by Hitachi, Ltd.). Next, the operation of collecting 10 ml of the separated liquid from the solution contained in 100 ml into a 20 ml measuring flask is repeated five times to obtain five 10 ml of separated liquid. Using this, Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th are measured by a standard addition method using an ICP plasma emission spectrometer (for example, SII, SPS5520). I do. Here, a blank is also measured by the same method, and the blank is subtracted for adjustment, to obtain a measured value for each element.
Then, based on the mass of the solid content obtained by the above-described method, the content of each component with respect to the dry amount was obtained.

The content of each anion shall be measured by the following method.
<Cl>
Acetone was added to 20 g of a sample composed of ceria-based fine particles or a dispersion of ceria-based fine particles (adjusted to a solid content of 20% by mass) to adjust to 100 ml. To this solution, 5 ml of acetic acid and 4 ml of a 0.001 mol sodium chloride solution were added. The analysis is performed by a potentiometric titration method (manufactured by Kyoto Electronics Co., Ltd., potentiometric titrator AT-610) with a 0.002 mol silver nitrate solution.
Separately, as a blank measurement, a titer was determined by adding 5 ml of acetic acid and 4 ml of a 0.001 mol sodium chloride solution to 100 ml of acetone and titrating with a 0.002 mol silver nitrate solution, and then titrating with a sample. To obtain the titer of the sample.
Then, based on the mass of the solid content obtained by the above-described method, the content of each component with respect to the dry amount was obtained.

<NO ₃ , SO ₄ , F>
5 g of a sample composed of ceria-based particles or a dispersion of ceria-based particles (adjusted to a solid content of 20% by mass) was diluted with water to 100 ml, and centrifuged at 4000 rpm for 20 minutes in a centrifuge (HIMAC CT06E manufactured by Hitachi). The solution obtained by separating and removing the precipitated component was analyzed by ion chromatography (ICS-1100 manufactured by DIONEX).
Then, based on the mass of the solid content obtained by the above-described method, the content of each component with respect to the dry amount was obtained.

[X-ray diffraction method, measurement of average crystallite diameter]
The ceria-based fine particle dispersions obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the obtained powder was pulverized in a mortar for 10 minutes, and an X-ray diffractometer (Rigaku Denki Co., Ltd.) , RINT1400) to obtain an X-ray diffraction pattern to identify the crystal type.
Further, the full width at half maximum of the peak of the (111) plane near 2θ = 28 degrees (near 2θ = 28 degrees) in the obtained X-ray diffraction pattern was measured by the above-described method, and the average was calculated by the above-mentioned Scherrer equation. The crystallite diameter was determined.

<Average particle size>
With respect to the ceria-based fine particle dispersions obtained in Examples and Comparative Examples, the average particle diameter of the particles contained therein was measured by the above-described image analysis method.

<Number of coarse particles>
The number of coarse particles of the ceria-based fine particles contained in the polishing slurry or the abrasive dispersion for polishing was measured using Accusizer 780APS manufactured by Particle sizing system Inc. Also, after adjusting the measurement sample to 0.1% by mass with pure water, 5 mL was injected into the measurement device, measured under the following conditions, and measured three times. The value obtained by calculating the average value of the number of coarse particles of 51 μm or more was defined as the number of coarse particles of the ceria-based fine particles. The measurement conditions are as follows.
<System Setup>
・ Stir Speed Control / Low Speed Factor 1500 / High Speed Factor 2500
<System Menu>
・ Data Collection Time 60 Sec.
・ Syringe Volume 2.5ml
・ Sample Line Number ： Sum Mode
· Initial 2 ^nd -Stage Dilution Factor 350
・ Vessel Fast Flush Time 35 Sec.
・ System Flush Time / Before Measurement 60 Sec. / After Measurement 60 Sec.
・ Sample Equilibration Time 30 Sec./ Sample Flow Time 30 Sec.

[Polishing test method]
<Polishing of SiO ₂ film>
Polishing abrasive particle dispersions containing the ceria-based fine particle dispersions obtained in each of the examples and comparative examples were prepared. For some examples or comparative examples, additives (ammonium nitrate, ammonium acetate, etc.) were added to the polishing slurry dispersion to prepare a polishing slurry. Here, in each case of the polishing abrasive dispersion liquid and the polishing slurry, the solid content concentration was set to 0.6% by mass, and the pH was adjusted to 5.0 by adding nitric acid.
Next, as a substrate to be polished, an SiO ₂ insulating film (thickness: 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, the substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad ("IC-1000 / SUBA400 concentric type", manufactured by Nitta Haas) is used. Polishing was performed by supplying a polishing slurry dispersion liquid or a polishing slurry at a rotation speed of 90 rpm at a rate of 50 ml / min for 1 minute.
Then, the change in weight of the substrate to be polished before and after polishing was obtained, and the polishing rate was calculated.
The surface smoothness (surface roughness Ra) of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Corporation). Since the smoothness and the surface roughness are generally in a proportional relationship, Table 2 shows the surface roughness.
Note that the polishing scratches were observed by observing the insulating film surface using an optical microscope.

<Polishing of aluminum hard disk>
Polishing abrasive particle dispersions containing the ceria-based fine particle dispersions obtained in each of the examples and comparative examples were prepared. For some examples or comparative examples, additives (ammonium nitrate, ammonium acetate, etc.) were added to the polishing slurry dispersion to prepare a polishing slurry. Here, in each case of the polishing slurry dispersion liquid and the polishing slurry, the solid content concentration was 9% by mass, and the pH was adjusted to 2.0 by adding nitric acid.
The substrate for the aluminum hard disk was set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad was used at a substrate load of 0.05 MPa and a table rotation speed of 30 rpm using a polishing pad (“Polytex φ12” manufactured by Nitta Haas). Polishing is performed by supplying a particle dispersion or a polishing slurry at a rate of 20 ml / min for 5 minutes, and using an ultra-fine defect / visualization macro device (manufactured by Vision PSYTEC, product name: Macro-Max), and zooming over at Zoom 15 The number of scratches (linear marks) existing on the polished substrate surface corresponding to 65.97 cm ² was observed and counted, and the total was evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 "Very little"
50 to less than 80 "less"
80 or more "many"
At least 80 or more such that the total number cannot be counted.

  Examples will be described below. The term “solid content concentration” simply refers to the concentration of fine particles dispersed in a solvent regardless of chemical species.

[Preparation process 1]
Cerium carbonate was fired in a muffle furnace at 710 ° C. for 2 hours to obtain a powdered fired body. Next, 100 g of the powdery fired body was put into a 1 L beaker with a handle together with 300 g of ion-exchanged water, and irradiated with ultrasonic waves for 10 minutes in an ultrasonic bath with stirring.
Next, wet disintegration (batch type desktop sand mill manufactured by Campe Co., Ltd.) was performed for 30 minutes using quartz beads of φ0.25 mm (manufactured by Daiken Chemical Industry Co., Ltd.).
After crushing, the beads are separated through a 44 mesh wire mesh while being pressed with ion-exchanged water, and further centrifuged at a relative centrifugal acceleration of 1700 G for 102 seconds using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number “CR21G”). The precipitate was removed by centrifugation, and the solution after removal was concentrated to 1.6% by mass with a rotary evaporator to obtain a raw material ceria fine particle dispersion.

[Preparation process 2]
<Preparation of high purity silica solution>
Pure water was added to an aqueous sodium silicate solution (silica concentration: 24.06% by mass, Na ₂ O concentration: 7.97% by mass) to obtain an aqueous sodium silicate solution (silica concentration: 5% by mass).
18 kg of the obtained sodium silicate aqueous solution was passed through a 6 L strongly acidic cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain 18 kg of an acidic silicate solution (silica concentration of 4.6 mass). %, PH 2.7). Next, 18 kg of the obtained acidic silicate solution was passed through a 6 L chelate-type ion exchange resin (CR-11 manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain 18 kg of a high-purity silicate solution (silica concentration of 4. 5% by mass, pH 2.7).

<Example 1>
A 29% by mass aqueous ammonia (Kanato Chemical Co., Ltd., deer grade 1) was diluted with ion-exchanged water to prepare 1% by mass aqueous ammonia. Further, the high-purity silicate liquid obtained in the preparation step 2 was diluted with ion-exchanged water to obtain a diluted high-purity silicate liquid of 0.2% by mass.
Next, ion-exchanged water was added to the raw material ceria fine particle dispersion having a solid content concentration of 1.6% by mass obtained in the preparation step 1 to obtain a 0.5% by mass diluent (hereinafter also referred to as solution A). . While stirring 10,000 g (dry 50 g) of the solution A at room temperature, 2.5 g (0.005 g) of the above-mentioned 0.2 mass% diluted high-purity silicate solution was added, and stirring was continued for 10 minutes after the addition was completed. . Thereafter, the pH was adjusted to 9.5 by adding 1% by mass of aqueous ammonia, and the temperature was raised to 50 ° C., and the temperature was maintained for 24 hours while stirring was continued. Then, it cooled to room temperature and concentrated to 3.0 mass% with a rotary evaporator.
Next, the obtained fine particle dispersion liquid was subjected to centrifugal separation at a relative centrifugal acceleration of 675 G for 1 minute using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to remove sedimentation components and to disperse ceria-based fine particles. A liquid was obtained.

<Example 2>
In Example 1, 2.5 g of a 0.2 mass% diluted high-purity silicate liquid was added to 10,000 g of the liquid A, but in Example 2, a 0.2 mass% of a diluted high-purity silicate liquid of 10,000 g of the A liquid was added. Was added in an amount of 25 g (dry 0.05 g). Other than that, it carried out similarly to Example 1.
FIG. 1 shows an SEM image and a TEM image of the ceria-based fine particles obtained in Example 2. From the TEM image of FIG. 1, it was observed that a thin layer containing easily soluble silica was formed in the outermost layer of the ceria-based fine particles.
FIG. 2 shows an X-ray diffraction pattern of the ceria-based fine particles.

<Example 3>
In Example 1, 2.5 g of a 0.2 mass% diluted high-purity silicate liquid was added to 10,000 g of the liquid A, but in Example 2, a 0.2 mass% of a diluted high-purity silicate liquid of 10,000 g of the A liquid was added. Was added in an amount of 250 g (dry 0.5 g). Other than that, it carried out similarly to Example 1.

<Example 4>
Ion-exchanged water was added to cerous nitrate hexahydrate (manufactured by Chikamochi Junyaku Co., Ltd.) to prepare a 70 g solution having a CeO ₂ concentration of 0.2% by mass, and then 30 g of a 0.2% by mass high-purity silicate solution. Was added to obtain 100 g of a liquid mixture (solution B) of CeO ₂ and SiO ₂ .
Then, 100 g (dry 0.2 g) of a 0.2 mass% solution B was added while stirring 10,000 g (dry 50 g) of the solution A at room temperature, and stirring was continued for 10 minutes after the addition was completed. Thereafter, 1% by mass of aqueous ammonia was added to adjust the pH to 9.5, the temperature was raised to 50 ° C., and the temperature was maintained for 24 hours while stirring was continued. Thereafter, the mixture was cooled to room temperature, and concentrated to 3.0% by mass with a rotary evaporator to obtain a ceria-based fine particle dispersion.

<Example 5>
Ion-exchanged water was added to lanthanum chloride heptahydrate (97%) for a reagent manufactured by Wako Pure Chemical Industries to prepare 70 g of a 0.2% by mass La ₂ O ₃ solution, and then a high purity of 0.2% by mass was obtained. By adding 30 g of a silicic acid solution, 100 g of a mixed solution (solution C) of La ₂ O ₃ and SiO ₂ was obtained.
Then, while stirring 10,000 g (dry 50 g) of the liquid A at room temperature, 100 g (0.2 g dry) of a 0.2 mass% liquid C was added, and stirring was continued for 10 minutes after the addition was completed. Thereafter, 1% by mass of aqueous ammonia was added to adjust the pH to 9.5, the temperature was raised to 50 ° C., and the temperature was maintained for 24 hours while stirring was continued. Thereafter, the mixture was cooled to room temperature, and concentrated to 3.0% by mass with a rotary evaporator to obtain a ceria-based fine particle dispersion.

<Example 6>
Ion-exchange water was added to zirconium oxychloride octahydrate (36% industrial ZrO ₂ manufactured by Taiyo Mining Co., Ltd.) to prepare 70 g of a 0.2% by mass diluted ZrO ₂ solution, and then 0.2% by mass. % Of a high-purity silicate solution was added to obtain 100 g of a mixed solution (solution D) of ZrO ₂ and SiO ₂ .
Then, while stirring 10,000 g (dry 50 g) of the solution A at room temperature, 100 g (0.2 g of dry) of 0.2 mass% solution D was added, and stirring was continued for 10 minutes after the addition was completed. Thereafter, 1% by mass of aqueous ammonia was added to adjust the pH to 9.5, the temperature was raised to 50 ° C., and the temperature was maintained for 24 hours while stirring was continued. Thereafter, the mixture was cooled to room temperature, and concentrated to 3.0% by mass with a rotary evaporator to obtain a ceria-based fine particle dispersion.

<Example 7>
Ammonium nitrate and ion-exchanged water were added to the ceria-based fine particles (solid content: 3.0% by mass) obtained in Example 2 to prepare a polishing slurry having a solid content concentration of 1.0% by mass and an ammonium nitrate concentration of 1,000 ppm. Otherwise, the procedure was the same as in Example 2.

<Example 8>
In Example 7, ammonium nitrate was used, but in Example 8, ammonium acetate was used. Otherwise, the procedure was the same as in Example 7.

<Comparative Example 1>
The raw material ceria fine particle dispersion obtained in the preparation step 1 was evaluated in the same manner as in the example.
FIG. 3 shows an SEM image and a TEM image of the fine particles contained in the raw material ceria fine particle dispersion. In the TEM image of FIG. 3, the layer containing readily soluble silica as observed in FIG. 1 was not observed in the outermost layer of the raw material ceria fine particles.

<Comparative Example 2>
A polyacrylic acid polymer (Alon SD-10 manufactured by Toagosei Co., Ltd.) and ion-exchanged water are added to the dispersion of the raw material ceria fine particles obtained in the preparation step 1, and polyacrylic acid is added at a solid concentration of 1.0% by mass. The acid concentration was adjusted to 800 ppm, and the mixture was dispersed by ultrasonic waves after the addition. The same procedure as in Example 1 was performed using the obtained polishing slurry.

<Comparative Example 3>
837.58 g of ion-exchanged water was added to 156.25 g of the dispersion of raw ceria particles obtained in the preparation step 1 while stirring. Further added silica sol (JGC Catalysts and Chemicals Ltd. Cataloid SI-40 SiO ₂ concentration of 40.5 wt%) of 18nm slowly 6.17 g, after completion of the addition by continuing stirring for 30 minutes, the solid concentration 0. A 5% by mass ceria-based fine particle dispersion was obtained.
FIG. 4 shows an SEM image of the fine particles contained in the ceria-based fine particle dispersion.

<Experiment 2>
[Quantitative determination of a layer containing easily soluble silica]
81.8 g (dry 2.7 g) of a solution prepared by adding ion-exchanged water to 3.3% by mass to the ceria-based fine particles obtained in each of Examples and Comparative Examples was prepared, and 0.1% by mass was stirred. The pH was adjusted to 9.0 using a diluted aqueous sodium hydroxide solution or 6% nitric acid, and ion-exchanged water was added to a total of 90 g (dry 2.7 g).
After stirring was continued for 15 minutes, 20 g of the solution was put into a centrifuge tube with an ultramembrane, model number VIVASPIN20 (fraction molecular weight: 5000) manufactured by Sartorius, and the mixture was centrifuged at 1820 G by a centrifugal separator (K-KANAN H-38F). Minutes. After the treatment, the separated liquid that passed through the ultramembrane was collected, and the SiO ₂ concentration in the separated liquid was measured. The calculation of the easy dissolving layer ratio (dissolving ratio per composite fine particle dry) was obtained by the following formula.
Easily soluble layer ratio (%) = SiO ₂ concentration (ppm) ÷ 1,000,000 × 87.3 g ÷ 2.7 g × 100
The results are shown in Table 2.

<Experiment 3>
For each of the ceria-based fine particle dispersions obtained in Example 3, Example 5, Comparative Example 1 and Comparative Example 2, the flow potential was measured and the cationic colloid titration was performed. As the titrator, an automatic titrator AT-510 (manufactured by Kyoto Electronics Industry) equipped with a streaming potential titrator (PCD-500) was used.
First, a 0.05% aqueous nitric acid solution was added to the ceria-based fine particle dispersion having a solid content adjusted to 0.005% by mass to adjust the pH to 6. Next, an amount equivalent to 0.01 g as a solid content of the liquid was put into a 200 ml tall beaker, and a cationic colloid titration solution (0.001N polydiallyldimethylammonium chloride solution) was added once while stirring with a magnetic stirrer. The titration was performed with an injection volume of 0.005 ml, an injection speed of 0.005 mL / sec, and a post-injection time (intermittent time) of 5 seconds. Note that the piston speed was set at a scale 7 and the rotation scale 3 of a magnetic stirrer. Then, the addition amount (ml) of the cationic colloid titrant is plotted on the X axis, and the differential value of the cationic colloid addition amount of the streaming potential is plotted on the Y axis (mV / ml), and the streaming potential C (mV) at the maximum differential value is plotted. And the addition amount V (ml) of the cationic colloid titrant was determined, and ΔPCD / V = (IC) / V was calculated. The results are shown in Table 3.
The streaming potential curve obtained here is shown in FIG. 5, and its differential curve is shown in FIG.

  Since the ceria-based fine particles contained in the dispersion of the present invention do not contain coarse particles, they have a low scratch and a high polishing rate. Therefore, the abrasive grain dispersion containing the dispersion of the present invention can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate. Specifically, it can be preferably used for flattening a semiconductor substrate on which a silica film is formed.

Claims (10)

A ceria-based fine particle dispersion comprising ceria-based fine particles having an average particle diameter of 5 to 500 nm and having the following features [1] to [4].
[1] The ceria-based fine particles include raw ceria fine particles and a layer containing easily soluble silica on the surface of the raw ceria fine particles, and the raw ceria fine particles mainly include crystalline ceria. .
[2] The ratio D (D = D1 / D2 × 100) of the mass D1 of the easily soluble silica contained in the layer containing the easily soluble silica to the mass D2 of the ceria-based fine particles is 0.005 to 10%. thing.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[4] The ceria-based fine particles have an average crystallite diameter of the crystalline ceria of 3 to 300 nm, as measured by X-ray diffraction.   The ceria-based fine particle dispersion according to claim 1, wherein the streaming potential becomes negative when the pH value is 3 to 8. When the cationic colloid titration is performed, the flow potential change amount (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titrant at the time when the differential value of the streaming potential is maximized. The ceria-based fine particle dispersion according to claim 1, wherein a streaming potential curve having a ratio (ΔPCD / V) of −3000 to −100 is obtained.
ΔPCD / V = (IC) / V Equation (1)
C: streaming potential (mV) when the differential value of the streaming potential is maximized
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Addition amount (ml) of the cationic colloid titrant when the differential value of the streaming potential is maximized   The ceria-based fine particle dispersion according to any one of claims 1 to 3, wherein the number of the ceria-based fine particles having a coarse particle size of 0.51 µm or more is 3000 million / cc or less. The ceria-based fine particle dispersion according to any one of claims 1 to 4, wherein the content ratio of impurities contained in the ceria-based fine particles is as follows (a) and (b).
(A) The content of each of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.   A polishing abrasive dispersion containing the ceria-based fine particle dispersion according to claim 1.   The abrasive grain dispersion according to claim 6, wherein the abrasive grain dispersion is for flattening a semiconductor substrate on which a silica film is formed. A method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2a.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2a: a step of adding an additive containing silica to the fired body, heating and aging at 10 to 98 ° C., and then crushing or pulverizing to obtain a ceria-based fine particle dispersion. A method for producing a ceria-based fine particle dispersion, comprising the following step 1 and step 2b.
Step 1: a step of firing a cerium compound at 300 to 1200 ° C. to obtain a fired body.
Step 2b: a step of crushing or pulverizing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and heating and aging at 10 to 98 ° C. to obtain a ceria based fine particle dispersion. A method for producing a ceria-based fine particle dispersion, comprising the following steps A and B:
Step A: a step of continuously or intermittently adding a cerium solution having a cerium compound dissolved therein to a solvent maintained at a temperature of 3 to 98 ° C. and a pH of 5.0 to 10.0 to obtain colloidal ceria.
Step B: a step of adding an additive containing silica to the colloidal ceria and heating and aging at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.