JP7038022B2 - Abrasive grain dispersion for polishing containing ceria-based fine particle dispersion, its manufacturing method, and ceria-based fine particle dispersion. - Google Patents

Description

The present invention relates to a ceria-based fine particle dispersion suitable as a polishing agent used in semiconductor device manufacturing and the like, and in particular, a film to be polished formed on a substrate is flattened by 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 grain dispersion containing the ceria-based fine particle dispersion.

Semiconductor devices such as semiconductor boards and wiring boards have achieved high performance by increasing the density and miniaturization. So-called chemical mechanical polishing (CMP) is applied in the manufacturing process of this semiconductor. Specifically, it is an essential technology for separating shallow trench elements, flattening an interlayer insulating film, and forming contact plugs and Cu damascene wiring. It has become.

Generally, an abrasive for CMP is composed of abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding the target film. On the other hand, the abrasive grains have a role of polishing by mechanical action, and colloidal silica, fumed silica, and ceria particles are used as the abrasive grains. In particular, ceria particles show a specifically high polishing rate with respect to the silicon oxide film, and are therefore applied to polishing in the shallow trench element separation step.
In the shallow trench element separation step, not only the silicon oxide film is polished, but also the silicon nitride film is polished. In order to facilitate element separation, 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, and this polishing rate ratio (selection ratio) is also important.

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

For example, in Patent Document 1, an aqueous solution of first cerium nitrate and a base are stirred and mixed at an amount ratio of 5 to 10 and then rapidly heated to 70 to 100 ° C. and aged at that temperature. A method for producing ultrafine particles of cerium oxide (average particle diameter of 10 to 80 nm) made of a cerium oxide single crystal is described, and further, according to this production method, the particle size is highly uniform and the particle shape is high. It is stated that cerium oxide ultrafine particles having high uniformity can be provided.

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

Further, Patent Document 2 is a polishing agent containing a slurry in which cerium oxide particles are dispersed in a medium, and the cerium oxide particles are obtained by firing and pulverizing a cerium compound, and are new among the total cerium oxide particles. The cerium oxide particles effective for surface formation are polycrystals composed of crystallites and having a crystal grain boundary, and the cerium oxide particles having the crystal grain boundaries are 5 to 5 of the total cerium oxide particles contained in the slurry. A polishing agent having a particle size of 100% by volume and having a median particle size of cerium oxide particles having a crystal grain boundary of 100 to 1500 nm is described. It is described that by using such an abrasive, it is possible to polish the surface to be polished such as the SiO ₂ insulating film at high speed without damaging it.

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

Seung-Ho Lee, Zhenyu Lu, S.M. V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide films using silka parts coated with ceriumcoated with27 seri", Journal of

However, when the present inventor actually manufactured and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing speed was low, and further, defects on the surface of the polishing substrate (deterioration of surface accuracy, increase in scratches, It was found that the residual abrasive material on the surface of the polishing substrate) is likely to occur.
This is because the method for producing cerium oxide ultrafine particles described in Patent Document 1 does not include a firing step and is a liquid phase, as compared with a method for producing ceria particles including a firing step (the degree of crystallization of ceria particles is increased by firing). Since the cerium oxide particles are only crystallized from (an aqueous solution containing primary cerium nitrate), the degree of crystallization of the generated cerium oxide particles is relatively low, and the density of the abrasive grains is low because the firing process is not performed. The present inventor presumes that the main factors are that the polishing rate is low, cerium oxide does not adhere to the mother particles, and cerium oxide remains on the surface of the polishing substrate.

Further, when the cerium oxide particles described in Patent Document 2 were actually manufactured and examined by the present inventor, the polishing speed was higher than that of the cerium oxide ultrafine particles described in Patent Document 1 which was not fired. It was found that it was not sufficient and that defects were likely to occur on the surface of the substrate after polishing. In Patent Document 2, for example, cerium carbonate is fired at 700 ° C. and is manufactured by a process of dry crushing with a jet mill, but the cause is that coarse agglomerates generated in the firing step remain without being crushed. It is estimated to be. Further, since an organic substance such as an ammonium polyacrylic acid salt is used as a dispersant, there is a concern that the surface of the substrate may be contaminated with the organic substance.

An object of the present invention is to solve the above problems. That is, the present invention can polish a silica film, a Si wafer, or a difficult-to-process material at high speed, and at the same time, it has high surface accuracy (low scratch, less abrasive residue on the substrate, and improvement of the substrate Ra value. Etc.) can be achieved, and if it does not contain impurities, it can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates. It is an object of the present invention to provide an abrasive grain dispersion liquid.

The present inventor has diligently studied to solve the above problems and completed the present invention.
The present invention is the following (1) to (10).
(1) A ceria-based fine particle dispersion liquid containing ceria-based fine particles having an average particle diameter of 5 to 500 nm and having the following characteristics [1] to [4].
[1] The raw material ceria fine particles have a 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 contain crystalline ceria as a main component. ..
[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%. matter.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[4] The ceria-based fine particles have an average crystallinity diameter of 3 to 300 nm, which is measured by subjecting them to X-ray diffraction.
(2) The ceria-based fine particle dispersion liquid according to (1) above, wherein the flow 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 titration solution when the differential value of the flow potential becomes maximum. ) To obtain a flow potential curve having a ratio (ΔPCD / V) of -3000 to -100, the ceria-based fine particle dispersion liquid according to (1) or (2) above.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) when the differential value of the flow potential becomes maximum.
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution when the differential value of the flow potential is maximized.
(4) The ceria-based fine particle dispersion according to any one of (1) to (3) above, wherein the number of the ceria-based fine particles which are coarse particles of 0.51 μm or more is 3000 million / cc or less. liquid.
(5) The ceria system according to any one of (1) to (4) above, wherein the content ratio of impurities contained in the ceria system fine particles is as follows (a) and (b). Fine particle dispersion.
(A) The contents of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.
(6) A polishing abrasive grain dispersion liquid containing the ceria-based fine particle dispersion liquid according to any one of (1) to (5) above.
(7) The polishing abrasive grain dispersion liquid according to (6) above, wherein the polishing abrasive grain dispersion liquid is for flattening a semiconductor substrate on which a silica film is formed.
(8) A method for producing a ceria-based fine particle dispersion, which comprises the following steps 1 and 2a.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2a: A step of adding an additive containing silica to the fired body, aging it by heating at 10 to 98 ° C., and then crushing or pulverizing it to obtain a ceria-based fine particle dispersion.
(9) A method for producing a ceria-based fine particle dispersion, which comprises the following steps 1 and 2b.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2b: A step of crushing or crushing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and aging by heating at 10 to 98 ° C. to obtain a ceria fine particle dispersion.
(10) A method for producing a ceria-based fine particle dispersion, which comprises the following steps A and B.
Step A: A step of continuously or intermittently adding a cerium solution in which a cerium compound is dissolved 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 aging it by heating at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.

When the ceria-based fine particle dispersion liquid of the present invention is used for polishing as an abrasive grain dispersion liquid for polishing, for example, even if the target is a difficult-to-process material including a silica film, a Si wafer, etc., it can be polished at 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 liquid of the present invention provides a method for efficiently producing a ceria-based fine particle dispersion liquid 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 purity can be increased. Since 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 does not contain impurities, it is suitable for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates. It can be preferably used.
Further, the ceria-based fine particle dispersion liquid of the present invention is effective for flattening the surface of a semiconductor device when used as an abrasive grain dispersion liquid for polishing, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. ..

3 is an SEM image and a TEM image of the ceria-based fine particles of Example 2. It is an X-ray diffraction pattern of the ceria-based fine particle of Example 2. FIG. 3 is an SEM image and a TEM image of the raw material ceria fine particles of Comparative Example 1. It is an SEM image of the raw material ceria fine particles of Comparative Example 3. It is a graph which shows the flow potential measurement result of Example 3, Example 5 and Comparative Example 2. It is a graph of the change rate (differential value) of the flow potential calculated from the flow potential measurement data shown in FIG.

The present invention will be described.
The present invention is a ceria-based fine particle dispersion liquid containing ceria-based fine particles having an average particle diameter of 5 to 500 nm, which has the following characteristics [1] to [4].
[1] The raw material ceria fine particles have a 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 contain crystalline ceria as a main component. ..
[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%. matter.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[4] The ceria-based fine particles have an average crystallinity diameter of 3 to 300 nm, which is measured by subjecting them to X-ray diffraction.
The ceria-based fine particles having the characteristics of [1] to [4] above are also referred to as "composite fine particles of the present invention" below.
Further, such a ceria-based fine particle dispersion is also referred to as "the dispersion of the present invention" below.

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

Further, the present invention is a method for producing a ceria-based fine particle dispersion liquid, which comprises the following steps 1 and 2a.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2a: A step of adding an additive containing silica to the fired body, aging it by heating at 10 to 98 ° C., and then crushing or pulverizing it to obtain a ceria-based fine particle dispersion.
Hereinafter, such a manufacturing method is also referred to as "the manufacturing method [α] of the present invention".

Further, the present invention is a method for producing a ceria-based fine particle dispersion liquid, which comprises the following steps 1 and 2b.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2b: A step of crushing or crushing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and aging by heating at 10 to 98 ° C. to obtain a ceria fine particle dispersion.
Hereinafter, such a manufacturing method is also referred to as "the manufacturing method [β] of the present invention".

Further, the present invention is a method for producing a ceria-based fine particle dispersion, which comprises the following steps A and B.
Step A: A step of continuously or intermittently adding a cerium solution in which a cerium compound is dissolved 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 aging it by heating 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 the term "manufacturing method of the present invention" is simply referred to, any of "the manufacturing method of the present invention [α]", "the manufacturing method of the present invention [β]" and "the manufacturing method of the present invention [X]". Also means.

Further, in the following, when the term "invention" is simply referred to, it means any of the dispersion liquid of the present invention, the composite fine particles of the present invention, and the production method of the present invention.

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

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

<Raw material ceria fine particles>
The raw material ceria fine particles will be described.
Since the average particle size 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 size of the raw material ceria fine particles is inevitably the same as or smaller than 500 nm. In the present application, the average particle size of the raw material ceria fine particles is considered to be substantially the same as the average particle size of the raw material ceria fine particles contained in the raw material ceria fine particle dispersion used in step 1 included in the production method of the present invention described later.
Raw material ceria fine particles having an average crystallite diameter 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 liquid of the present invention obtained by using raw material ceria fine particles having an average particle size in the range of 5 to 500 nm as a raw material is used as an abrasive, the generation of scratches due to polishing is reduced.
When the average particle size of the raw material ceria fine particles is less than 5 nm, the polishing rate tends not to reach a practical level when a dispersion obtained by using such raw material ceria fine particles is used as an abrasive.
Further, when the average particle size of the raw material ceria fine particles exceeds 500 nm, the polishing rate also tends to not reach a practical level, which tends to reduce the surface accuracy of the substrate to be polished. The raw material ceria fine particles are more preferably those showing monodispersity.

The average particle size of the raw material ceria fine particles shall be measured as follows.
Observe at 800,000 times by STEM-EDS analysis and measure CeO ₂ % by mass at each measurement point. Then, the raw material ceria fine particles are specified by specifying the region where the CeO ₂ % by mass exceeds 90%. Next, the maximum diameter of the raw material ceria fine particles is set as the major axis, the length is measured, and the value is defined as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the raw material ceria fine particles.
In this way, the geometric mean particle diameters of 50 raw material ceria fine particles are measured, and the value obtained by simple averaging them is taken as the average particle diameter. Even when the layer containing easily soluble silica is a particle film (a film formed by stacking particles), the measurement can be performed in the same manner.
Further, if the region of the raw material ceria fine particles can be clearly identified from the lattice fringes and contrast due to 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, and whether they are single crystals or aggregates of single crystals, polycrystals (polycrystals are particles having crystal grain boundaries). It may be (pointing) or a mixture thereof.

In the present invention, the raw material ceria fine particles contain crystalline ceria as a main component.
The fact that the raw material ceria fine particles contain crystalline ceria as a main component is, for example, that the dispersion liquid of the present invention is dried and then the obtained solid substance is pulverized using a dairy pot, for example, a conventionally known X-ray diffractometer. It can be confirmed from the fact that only the crystal phase of ceria is detected in the obtained X-ray diffraction pattern by X-ray analysis using (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). In such a case, it is assumed that the raw material ceria fine particles contain crystalline ceria as a main component. The crystal phase of ceria is not particularly limited, and examples thereof include Ceriaite and the like.

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 material ceria fine particles contain crystalline ceria (crystalline Ce oxide) as a main component, and may contain other components, for example, components other than cerium oxide in an amount of 10% by mass or less. Further, it is desirable that Si, La, Zr, Al and the like are solid-solved in crystalline ceria. Further, a hydrous cerium compound may be contained as an auxiliary catalyst for polishing.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, only the crystal phase of ceria is detected. That is, even if a crystal phase other than ceria is contained, its content is low or it 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 the chart obtained by subjecting the composite fine particles of the present invention to X-ray diffraction. Then, 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 preferably 30 to 200 nm (full width at half maximum is 0.290 to 0.04284). In many cases, the intensity of the peak of the (111) plane is the maximum, but the intensity of the peak of another crystal plane, for example, the (100) plane may be the maximum. In that case, the calculation can be performed in the same manner, and the size of the average crystallite diameter in that case may be the same as the average crystallite diameter of the (111) plane described above.

The method for measuring the average crystallite diameter of the raw material ceria fine particles is shown below by taking the case of the (111) plane (near 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, for example, by a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). 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 angstrom, 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 is, for example, spherical, bale-shaped, short-fiber-shaped, cocoon-shaped, tetrahedral-shaped (trigonal pyramidal-shaped), hexahedral, octahedral, plate-shaped, amorphous, and porous. , Okoshi-like, gold-flat sugar-like, raspberry-like (a state in which protrusions or granular parts are scattered on the surface of spherical particles or substantially spherical particles).

As described above, the raw material ceria fine particles contain crystalline ceria as a main component, but may also contain an impurity element.
For example, 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") in the raw material ceria fine particles. However, each is preferably 100 ppm or less, more preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably 5 ppm or less, still more preferably 1 ppm or less.
Further, the content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter, may be referred to as “specific impurity group 2”) in the raw material ceria fine particles is 5 ppm or less. preferable.

Here, the content of the specific impurity group 1 or the specific impurity group 2 in the raw material ceria fine particles and the composite fine particles of the present invention described later means the content with respect to the dry amount.
The content rate with respect to the dry amount is the value of the ratio of the weight of the object to be measured (specific impurity group 1 or the specific impurity group 2) to the mass of the solid content contained in the object (raw material ceria fine particles or the composite fine particles of the present invention). It shall mean.
The mass of the solid content is determined by subjecting the object (raw material ceria fine particles or composite fine particles of the present invention) to a burning weight reduction of 1000 ° C.

Generally, the raw material ceria fine particles prepared from a cerium compound such as a cerium salt contain the specific impurity group 1 and the specific impurity group 2 derived from the raw material in a total amount of about several tens to several hundreds of ppm.
In the case of a raw material ceria fine particle dispersion liquid in which such 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 an ion exchange treatment. Even in that case, the specific impurity group 1 and the specific impurity group 2 remain in a total of several ppm to several hundred ppm. Therefore, the purity is improved by repeatedly dissolving and recrystallizing the cerium salt once, and after the dissolution, the impure component is removed with a chelate type ion exchange resin or the like and then recrystallized.

In the present invention, the content of each 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 measuring using the following methods.
-Na and K: Atomic absorption spectroscopic analysis-Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th: ICP-MS (inductively coupled plasma emission spectroscopic mass spectrometry)
・ Cl: Potentiometric titration method ・ NO ₃ , SO ₄ and F: Ion chromatograph

<Layer containing easily soluble silica>
The layer containing easily soluble silica in the composite fine particles of the present invention (hereinafter, also referred to as “easily soluble layer”) is, for example, after obtaining a fired body in the production method of the present invention, or further crushing or crushing the fired body. After that, an additive containing silica (for example, an acidic silicic acid solution) is added and heat-aged while keeping the temperature at 10 to 98 ° C. to form the raw material ceria fine particles on the surface.

The layer containing easily soluble silica may 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 the easily soluble silica is preferably 10 to 100% by mass, more preferably 12 to 95% by mass, and even more preferably 15 to 90% by mass.

The mass of silica contained in the layer containing easily soluble silica shall be 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 diluted sodium hydroxide aqueous solution or nitric acid, and the mixture is stirred for 15 minutes. After that, it is put into a centrifuge tube with an ultrafiltration membrane (molecular weight cut off 5000) and treated at 1820 G for 30 minutes. After the treatment, the separation liquid that has permeated the adventitia is collected and the SiO ₂ concentration is measured.
At this time, in the composite fine particles of the present invention provided with the layer containing the easily soluble silica, when the mass of the composite fine particles of the present invention is D ₂ and the mass of the dissolved silica is D ₁ , the ratio of D ₁ to D ₂ is taken. 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 is dissolved by adjusting the pH to 9.0 or the like and stirring as described above, is soluble silica, the density is high. It is considered to be a low soft silica layer. Further, since the film thickness is very thin (it is considered to be about 0.1 nm to 10 nm), the average particle size of the composite fine particles of the present invention hardly changes in measurement, so that the particle size distribution of the composite fine particles of the present invention also changes. It is thought that it has not been done. Therefore, when the substrate is polished using the composite fine particles of the present invention as abrasive grains, the layer containing easily soluble silica has an effect of chemically polishing the substrate and an effect of increasing the pressing depth of the abrasive grains into the substrate. Rather, it is thought to reduce the pushing depth.
However, since the layer contains low density and 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 it is soft, it is attached between the substrate and the abrasive grains. It is considered that there is an effect of increasing the adhesive force (adhesive action) or an effect of suppressing the rolling of abrasive particles by adhering to the substrate. As a result, the frictional force between the substrate and the abrasive grains is increased, which is considered to have the effect of increasing the polishing speed. Further, since the layer containing easily soluble silica formed on the surface of the abrasive grains is soft, it also has an effect of alleviating the local stress concentration on the substrate by the rectangular portion of the raw material ceria fine particles and suppressing scratches. Therefore, when the dispersion liquid of the present invention is used as an abrasive, it is considered that the polishing speed is high, the surface accuracy is deteriorated, and scratches are less likely to occur.
Further, the layer containing easily soluble silica may cover the entire particles, or a part thereof may not be covered and some raw material ceria fine particles may be exposed. 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 should be in the range of 0.005 to 10% by mass. This is because the adhesion between the substrate and the particles is more exhibited and the polishing speed is higher.
Here, the raw material ceria fine particles may be mother particles, and the surface of the particles may be coated with a layer containing easily soluble silica on the surface of the particles to which ceria child particles are bonded.

Further, since the surface of the layer containing easily soluble silica has a negative potential, it is considered to have an effect of improving the stability of the dispersion liquid of the present invention. Furthermore, the layer containing easily soluble silica is easily peeled off by the pressure during polishing, and adheres to the surface of the raw material ceria fine particles having a positive potential generated by the destruction or disintegration of the raw material ceria fine particles during polishing. It is thought to cover ceria. Therefore, the raw material ceria fine particles generated by disintegration have a negative potential, and also have a role of suppressing the residual abrasive grains on the substrate. Further, since the aggregation of the composite fine particles caused by the disintegrated raw material ceria fine particles is suppressed, 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 material ceria fine particles, but if a layer containing easily soluble silica is formed on the raw material ceria fine particles, the particle film can be used. It may be present or a film, a film may be formed on the particle film, or a particle film may be formed on the film. However, if a silica sol produced by a known method, for example, a silica sol made from water glass or a silica sol made from an alkoxysilane, is simply adhered onto the raw material ceria fine particles, it is soft and has a low density and is easily soluble. It does not become a layer containing. In the case of a particle film, although it is effective in improving the stability of particles, it does not contribute to the improvement of the polishing rate because it is not easily soluble silica, but rather the polishing rate is lowered. Therefore, in the case of a particle film, it is necessary to treat the particle surface with a low-density, easily soluble silica layer by alkali treatment or the like.

Further, in the composite fine particles of the present invention, at least a part of the surface of the raw material ceria fine particles is covered 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, the −OH group of silica is present on the outermost surface (outermost shell) of the composite fine particles of the present invention. Therefore, when used as an abrasive, it is considered that the composite fine particles of the present invention repel each other by the electric charge due to the −OH group on the surface of the polishing substrate, and as a result, the 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, and the negative zeta potential decreases as the pH shifts from alkaline to near neutral, and the opposite positive potential in the weakly acidic region. have. Therefore, in the acidic pH at the time of polishing, ceria adheres to the polishing base material or the polishing pad due to the difference in the magnitude of the potential or the difference in the polarity, and tends to remain on the polishing base material or the polishing pad. On the other hand, since the composite fine particles of the present invention have a layer containing silica in the outermost shell as described above, the potential becomes a negative charge due to silica, so that the pH has a negative potential from alkaline to acidic. It is maintained, and as a result, abrasive particles are less likely to remain on the polishing substrate or the polishing pad. For example, when crushing while adding an additive containing silica while maintaining pH> 9 during the crushing treatment of the production method [β] step 2b of the present invention, the surface of ceria dispersed by crushing is made of easily soluble silica. Be covered. On the other hand, when pH> 9, a part of the layer containing easily soluble silica is dissolved in the solvent. If the pH of such a dispersion of the present invention is adjusted to <7 when applied to a polishing application, the dissolved silica is deposited on the composite fine particles (abrasive grains) of the present invention, and a layer containing the easily soluble silica is formed. Since it is formed, the surface of the composite fine particles of the present invention will have a negative potential. When the potential is low, it is possible to adjust the potential with a high molecular weight organic substance such as polyacrylic acid, but there is a concern that the organic substance may remain on the substrate. In the present invention, since silica softly adhered to the surface regulates the potential, the use of organic substances is reduced, and defects caused by organic substances (residue of organic substances, etc.) on the substrate are less likely to occur.

In the dispersion liquid of the present invention, the existence mode of silica is various, and some of the silica does not constitute the composite fine particles of the present invention, and may be dispersed or dissolved in a solvent or on the surface of the composite fine particles of the present invention. It may exist in a state of being attached to. Silica dispersed or dissolved in a solvent does not have a clear particle morphology, and is measured as soluble silica in a solid-liquid separated solution by a silica molybdenum method or the like.

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

In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, the image of the raw material ceria fine particles appears dark, but the periphery and the outside of the raw material ceria fine particles, that is, the composite 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. When STEM-EDS analysis is performed on this portion and the SiO ₂ % by mass of the portion is determined, it can be confirmed that the portion is 10% by mass or more.

The ratio D (D = D1 / D2 × 100) of the easily soluble silica mass D1 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%. , 0.01-8% is more preferable. Most preferably, it is 0.05 to 6%.
When the ratio D is less than 0.005%, the polishing rate is not improved because the layer containing easily soluble silica on the surface of the composite fine particles of the present invention is only partially covered, and the dispersion stability is not improved. This is because it does not improve. If it exceeds 10%, the dispersion stability will not be improved even if it is coated more than this, and on the other hand, the thickness of the layer containing easily soluble silica is too thick, and the raw material ceria fine particles are used as a substrate during polishing. This is because it does not come into contact with the particles and the polishing speed tends to decrease.

<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 above-mentioned characteristics [1] to [4].

When the dispersion liquid of the present invention containing the composite fine particles of the present invention having an average particle size in the range of 5 to 500 nm is used as a polishing agent, the generation of scratches due to polishing is reduced. When the average particle size is less than 5 nm, the polishing rate tends not to reach a practical level when used as an abrasive. Further, when the average particle size exceeds 500 nm, the polishing rate also tends to not reach a practical level, which tends to reduce the surface accuracy of the substrate to be polished. The method for calculating the average particle size of the composite fine particles of the present invention is the same as the average particle size (geometric mean particle size) 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 alkaline aqueous solution, and the dissolved Si concentration in the solution is measured to confirm the layer containing easily soluble silica. can do.
That is, the pH is adjusted to 9 by adding nitrate or an aqueous sodium hydroxide solution to the dispersion liquid in which the composite fine particles of the present invention are dispersed in water, and ion-exchanged water is added to adjust the pH to 3.0% by mass, and then 15 minutes. The portion that dissolves by stirring is a layer containing easily soluble silica. After that, when it is put into a centrifuge tube with an ultrafiltration membrane (molecular weight cut off of 5000) and treated with 1820 G for 30 minutes, it is considered that those constituting the easily soluble silica layer permeate the ultrafiltration membrane. Therefore, when the separation liquid that has permeated the outer membrane is recovered and the Si concentration is measured, and the mass of silica dissolved in the supernatant liquid is D1 and the mass of ceria-based fine particles is D2, a composite having an easily soluble silica layer is provided. In the case of fine particles, the ratio D (D = D1 / D2 × 100) of D1 to D2 is 0.005 to 10%, so that it is distinguished from raw material ceria fine particles or ceria-based fine particles that do not have an easily soluble silica layer. be able to.

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

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

Further, the dispersion liquid of the present invention is dried, embedded in a resin, and then sputter coated with Pt to prepare a cross-sectional sample using a conventionally known focused ion beam (FIB) device. For example, when an FFT pattern is obtained by using a conventionally known TEM device for a prepared cross-sectional sample and using a fast Fourier transform (FFT) analysis, a diffraction pattern of crystalline ceria such as Cerianite appears. From this, it can be confirmed that the composite fine particles of the present invention contain crystalline ceria as a main component. Further, in such a case, crystalline ceria shall be the main component.
Another method is to observe the presence or absence of lattice fringes due to the atomic arrangement of the raw material ceria fine particles by using a conventionally known TEM analysis for the cross-sectional sample similarly prepared. If it is crystalline, plaids corresponding to the crystal structure are observed, and if it is amorphous, no plaids are observed. From this, it can be confirmed that the composite fine particles of the present invention contain crystalline ceria as a main component. Further, in such a case, crystalline ceria shall be the main component.

In the composite fine particles of the present invention, the mass ratio of ceria (CeO ₂ ) and silica (SiO ₂ ) is 100: 0.0005 to 11.1 and preferably 100: 0.005 to 8.7. The mass ratio of silica and ceria is considered to be 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 for the raw material ceria fine particles is too small, a large amount of ceria will be exposed on the surface of the composite fine particles, so that the stability of the composite fine particles will not be maintained, and huge agglomerates 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 with respect to ceria is too large, the layer containing easily soluble silica does not peel off during polishing because the ceria is thickly covered, and the polishing effect of ceria is not exhibited, so that the polishing speed is slowed down.
The silica and ceria to be used when calculating the mass ratio of the above-mentioned ceria (CeO ₂ ) and silica (SiO ₂ ) are all silica (SiO ₂ ) and ceria contained in the composite fine particles of the present invention. It means (CeO ₂ ). Therefore, the total amount of the silica component contained in the raw material ceria fine particles, such as solid dissolution in the ceria, and the silica and the ceria component contained in the layer containing the easily soluble silica arranged on the surface of the raw material ceria fine particles. means.

The content (% by mass) of ceria (CeO ₂ ) and silica (SiO ₂ ) in the composite fine particles of the present invention is first determined by weighing the solid content concentration of the dispersion liquid of the present invention by burning at 1000 ° C.
Next, the content (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 converted into an oxide mass% (CeO ₂ % by mass, etc.). If an element other than cerium is contained, the content is similarly calculated and converted to the percentage of oxide mass. Then, it is possible to calculate SiO ₂ mass%, assuming that the components other than CeO ₂ and other oxides constituting the composite fine particles of the present invention are SiO ₂ .
In the production method of the present invention, the mass ratio of silica and ceria can also be calculated from the amount of the silica source substance and the ceria source substance used when preparing the dispersion liquid of the present invention. This can be applied when the process is not such that ceria or silica is dissolved and removed, in which case the amount of ceria or silica used and the analytical value show good agreement.

In the composite fine particles of the present invention, the single crystal raw material ceria fine particles may be either "particle-connected type" or "single-dispersed type", but the contact area with the substrate can be kept high and the polishing speed can be maintained. The particle connection type is desirable because it is fast. The particle connection type is a type in which two or more raw material ceria fine particles are partially bonded to each other, and the connection is preferably 3 or less. The bonds between the raw material ceria fine particles may be a single crystal conjugate (aggregate) via a heterogeneous phase, may be a polycrystalline type linked type having a crystal grain boundary, and the polycrystal may be an aggregate via the heterogeneous phase. However, it may be a mixture thereof.
If it is a connected type, a large contact area with the substrate can be taken, so that polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing speed is high.

The composite fine particles of the present invention are of a particle-connected type, and the number ratio of particles having a minor axis / major axis ratio of less than 0.80 (preferably 0.67 or less) measured by an image analysis method is 45%. The above is preferable.
Here, the particles having a minor axis / major axis ratio of less than 0.80 measured by the image analysis method are considered to be of the particle-bonded 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 (non-connected particles), and is usually a mixture of both.

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

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

The following aspect 1 can be mentioned as the composite fine particle dispersion liquid 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 further have a number ratio of particles having a minor axis / major axis ratio of less than 0.8 as measured by an image analysis method of 45% or more. Dispersion solution.

Further, as the composite fine particle dispersion liquid of the present invention in the case where it is important that the surface roughness on the substrate to be polished is at a low level, the following aspect 2 can be mentioned.
[Aspect 2] The present invention is characterized in that the composite fine particles of the present invention further have a number ratio of particles having a minor axis / major axis ratio of 0.8 or more as measured by an image analysis method of 40% or more. Dispersion solution.

The method of measuring the minor axis / major axis ratio by the image analysis method will be described. In a photographic projection drawing obtained by taking a photograph of 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 set as the major axis, and the length thereof is measured. , Let the value be the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). From this, the minor axis / major axis ratio (DS / DL) is obtained. Then, in any 50 particles observed in the photographic projection drawing, the number ratio (%) of the particles having a minor axis / major axis ratio of less than 0.80 and 0.80 or less 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 are preferable because they have a high polishing rate when used as an abrasive.

The number of coarse particles of 0.51 μm or more that can be contained in the dispersion liquid of the present invention is preferably 3000 million / cc or less. The number of coarse particles is preferably 3000 million particles / cc or less, and more preferably 2000 million particles / cc or less. Coarse particles of 0.51 μm or more may cause polishing scratches and further deteriorate the surface roughness of the polishing substrate. Normally, when the polishing speed is high, the polishing speed is high, but on the other hand, 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-connected type, a high polishing rate can be obtained, while when the number of coarse particles of 0.51 μm or more is 3000 million / cc or less, there are few polishing scratches and the surface surface. Roughness can be kept low.

The method for measuring the number of coarse particles that can be contained in the dispersion liquid of the present invention is as follows.
After diluting and adjusting the sample to 0.1% by mass with pure water, 5 ml is collected and injected into a conventionally known coarse particle number measuring device. Then, the number of coarse particles of 0.51 μm or more is obtained. This measurement is performed three times to obtain a simple average value, and the value is multiplied by 1000 to obtain a value having a coarse particle number 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 placed in 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. Keep the liquid nitrogen temperature in the air stream and allow nitrogen to equilibrate and adsorb to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured by a calibration curve prepared in advance.
Such a BET specific surface area measuring method (nitrogen adsorption method) can be performed, for example, by using a conventionally known surface area measuring device.
In the present invention, the specific surface area means a value obtained by measuring by such a method unless otherwise specified.

The average particle size of the composite fine particles of the present invention is preferably 5 to 500 nm, more preferably 30 to 300 nm. When the average particle size of the composite fine particles of the present invention is in the range of 5 to 500 nm, the polishing rate becomes high when applied as an abrasive, which is preferable.
The average particle size of the composite fine particles of the present invention means the number average value of the average particle size measured by the image analysis method.
The method of measuring the average particle size by the image analysis method will be described. In a photographic projection drawing obtained by taking a photograph of 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 set as the major axis, and the length thereof is measured. , Let the value be the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the average particle diameter of the composite fine particles.
In this way, the geometric mean particle diameter is measured for 50 or more composite particles, and the number average value thereof 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 5 ppm or less. It is more preferably present, and further preferably 1 ppm or less.
Further, 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 for reducing the element content of each 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 of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention measures the specific impurity group 1 and the specific impurity group 2 contained in the raw material ceria fine particles. It can be measured by the same method as in the case.

<Dispersion liquid of the present invention>
The dispersion liquid of the present invention will be described.
The dispersion liquid 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 liquid of the present invention contains water and / or an organic solvent as the dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the dispersion liquid of the present invention is polished by adding one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling the polishing performance. It is suitably used as a slurry.

Further, as the dispersion solvent provided with the dispersion liquid of the present invention, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol and the like; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, isophorone and cyclohexanone. Ketones such as; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran. Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate and 2-butoxyethyl acetate; acetic acid Ethers such as methyl, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, isooctane and cyclohexane; chloride Halogenated hydrocarbons such as methylene, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; organics such as pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone A solvent can be used. These may be mixed with water and used.

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

The dispersion of the present invention is a cation colloid titration solution in which the flow potential change amount (ΔPCD) represented by the following formula (1) and the differential value of the flow potential become maximum when cation colloid titration is performed. It is preferable that a flow potential curve having a ratio (ΔPCD / V) to the addition amount (V) of -3000 to −100 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) when the differential value of the flow potential becomes maximum.
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution when the differential value of the flow potential is maximized.

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

The flow potential curve obtained by this cation colloid titration is, as shown in FIG. 5 shown in Examples described later, the X-axis of the addition amount (ml) of the cation titration solution and the flow potential (mV) of the dispersion liquid of the present invention. It is a graph taken on the Y axis.
Then, the flow potential curve of this graph is differentiated by titration (X), and a graph is obtained with the obtained differential value as the Y-axis and the titration as the X-axis. This graph is, for example, a graph as shown in FIG. 6 shown in Examples described later. The flow potential at the point where the differential value (differential value of the flow potential on the Y-axis) is maximum in this graph is C (mV), and the amount of the cationic colloid titrator added at that point (X-axis) is V (ml). do.
The starting point of the flow potential curve is the flow potential in the dispersion liquid of the present invention before titration. Specifically, the starting point is the point where the addition amount of the cationic colloid titration solution is 0. Let the flow potential at this starting point be I (mV).

When the above value of ΔPCD / V is -3000 to -100, when the dispersion liquid of the present invention is used as an abrasive, the polishing speed of the abrasive is further improved. It is considered that this ΔPCD / V reflects the coating condition of the raw material ceria fine particles by the layer containing the easily soluble silica on the surface of the composite fine particles of the present invention and / or the exposure condition of the raw material ceria fine particles on the surface of the composite fine particles. .. The present 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.
On the contrary, when the value of ΔPCD / V is larger than -100, the surface of the composite fine particles is thickly covered with a layer containing easily soluble silica, and the raw material ceria fine particles are not sufficiently exposed during polishing. Polishing speed is low. On the other hand, if it is smaller than -3000, the coating of the layer containing easily soluble silica is not sufficient, so that the effect of improving the frictional force due to adhesion with the substrate is low, so that the polishing speed is low and the dispersion stability is further maintained. The present inventor presumes that agglomeration occurs without fail and causes defects and the like. ΔPCD / V is more preferably -2800 to -150, and even more preferably -2500 to -200.

When the pH value of the dispersion of the present invention is in the range of 3 to 8, the flow potential before starting the cationic colloid titration, that is, when the titration amount is zero, becomes a negative potential. Is preferable. This is because when the flow potential maintains a negative potential, it is difficult for abrasive grains (ceria-based fine particles) to remain on the polishing substrate, which also exhibits a negative surface potential. Further, in the measurement of the zeta potential, it is preferable that the pH value is in the range of 3 to 8 and the potential is negative.

In the present invention, the production method is not limited as long as the raw material ceria fine particles are crystalline, and any outermost layer of the raw material ceria fine particles may have easily soluble silica.
Examples of the raw material ceria fine particles in the production method of the present invention include calcined ceria (including calcined ceria synthesized in the liquid phase and ceria synthesized in the liquid phase) and ceria synthesized in the 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. Further, 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.
Further, the easily soluble silica can be formed after crystal growth of crystalline ceria in the range of 3 to 300 nm, but specifically, it is formed before the crushing step or after the crushing step. be able to. The production method for forming easily soluble silica in the ceria synthesized in the liquid phase is the production method [X] of the present invention, and the production method for forming the easily soluble silica in the calcined ceria is the production method of the present invention [ α] and the production method [β] of the present invention.
The details of manufacturing will be described below.

<Manufacturing 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 ceria fine particles. All of these include step 1, and step 2a or step 2b as the next step.
For convenience of explanation, the process 2 corresponding to the superordinate concept of the process 2a and the process 2b will also be described below.
This will be described in detail below.

<Step 1>
In step 1, a cerium compound is first prepared.
When the dispersion liquid of the present invention to be applied to the polishing of semiconductor devices and the like is to be prepared by the production method of the present invention, Na, Ag, Ca, Cr, Cu, Fe, K and Mg are used as cerium compounds as raw materials. , Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and a metal salt of cerium having a low content of F are preferable. Specifically, the content of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn in terms of dry is 100 ppm or less, respectively, and U, Th, Cl, NO ₃ and SO. It is desirable that the contents of ₄ and F are 5 ppm or less, respectively. In order to improve the purity of the metal salt of cerium, it is preferable to dissolve and recrystallize the metal salt of cerium, or to carry out a treatment such as chelate ion exchange.
The type 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 thereof include first cerium nitrate, cerium carbonate, first cerium sulfate, and first cerium chloride.
Among these, cerium carbonate is preferable. When nitrates, sulfates, hydrochlorides, etc. are applied to step 1, toxic and highly harmful gases such as SO _X , NO _X , and corrosive gas are generated, whereas carbonates are harmful. This is because only low-quality CO ₂ is generated.

It is desirable that the metal salt of cerium has a uniform particle size distribution of the metal salt of cerium by removing coarse agglomerates in advance with a sieve or the like and then performing wet or dry classification. This is because if the particle size distribution of the cerium metal salt is non-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, they cause scratches during polishing. Further, extremely small cerium crystals tend to remain on the polishing substrate, and abrasive grains are likely to remain.

In step 1, such a cerium compound is calcined at 300 to 1200 ° C. to obtain a calcined body.
The method of firing a cerium compound such as a metal salt of cerium is not particularly limited, and examples thereof include a rotary kiln, a batch furnace, a fluidized firing furnace, and a roller herring smelt. Due to its nature, it is desirable to bake in a rotary kiln.
The temperature at the time of firing is 300 to 1200 ° C., but is preferably 400 to 950 ° C., more preferably 500 to 900 ° C. This is because crystallization of ceria proceeds sufficiently when firing in such a temperature range. This is because when fired at a temperature higher than 1200 ° C., ceria crystals grow abnormally, particles are fused to each other to form coarse agglomerates, and scratches occur frequently. Further, when the ceria is fired at a temperature lower than 300 ° C., the crystallization of ceria does not proceed sufficiently, so that the polishing rate becomes significantly low. It is desirable to bake in such a temperature range for 30 minutes to 10 hours, preferably to maintain the temperature for 30 minutes to 5 hours, and more preferably to maintain the temperature for 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 fired body is crushed or crushed by a wet method or a dry method.
In the present invention, "crushing" means an operation of unraveling the aggregated structure when the fired body is a single crystal aggregate and dispersing it in the single crystal body, or when the fired body is a polycrystal, the aggregated structure. Is unraveled and decomposed into a polycrystal smaller than the original polycrystal while maintaining the grain boundary, or the grain boundary is broken and a part of the crystal is decomposed into a single crystal. Further, "crushing" refers to an operation of converting a single crystal contained in a fired body into a smaller single crystal.
In step 2, the fired body is crushed and / or crushed.

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

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

In the case of wet crushing, it is preferable to carry out wet crushing while maintaining the pH of the solvent at 5 to 11. This is because if the pH is maintained in this range, ceria will be crushed while maintaining a monodisperse. This is because the crushing efficiency is difficult to improve even if the crushing is performed under the condition that the pH value exceeds 11, and the reaggregation proceeds during the crushing. Also, if the pH is less than 5, ceria may dissolve. The pH during crushing is preferably 5 to 11, more preferably 6 to 10.5. If necessary, the impure component mixed from the media during crushing can be removed by centrifugation, ion exchange, washing with an adventitia, or the like.

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

Further, after the fired body obtained by firing is crushed by a dry method, a solvent may be added and the crushed body may be crushed by a wet method in the range of pH 5 to 11.

<Step 2a, Step 2b>
As described above, the step 2 is a step of crushing or crushing the fired body to obtain a raw material ceria fine particle dispersion liquid, but in step 2a, an additive containing silica is added to the fired body, and 10 to 10 to It is aged by heating at 98 ° C., and then crushed or crushed in the same manner as in step 2. Then, the obtained product is used as a ceria-based fine particle dispersion.

Further, as described above, the step 2 is a step of crushing or crushing the calcined body to obtain a raw material ceria fine particle dispersion liquid, but in the step 2b, the calcined body is disassembled in the same manner as in the case of the step 2. It is 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 obtained product is used as a ceria-based fine particle dispersion.

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

The additive containing silica contains 10% by mass or more of silica on a dry basis, and other additives such as Ce, Zr, La, and Al may be contained.

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

As described above, when an additive containing silica is added to the fired body, and the mixture is heat-aged at 10 to 98 ° C. and then crushed or pulverized, the additive containing silica is applied to the surface of the raw material ceria fine particles. Depositation is promoted. The temperature of 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 step, a layer containing easily soluble silica is relatively uniformly formed on the surface of the raw material ceria fine particles.

The total amount of the additive containing silica treated in this way may be deposited on the surface of the raw material ceria fine particles, but a part of the additive may be present in the solvent. This is because when the pH is adjusted to 3 to 8 during polishing, it is deposited on the surface of the composite fine particles of the present invention. Further, even if some non-deposited components remain in the solvent, the additive containing silica can generate polishing debris during polishing and the raw material ceria fine particles generated by the disintegration of composite fine particles. This is because it covers and prevents scratches.

<Process 3>
The raw material ceria fine particle dispersion obtained in step 2 or the ceria-based fine particle dispersion obtained in step 2a or step 2b is subjected to centrifugation at a relative centrifugal acceleration of 300 G or more, and subsequently, the sedimentation component is removed. Is preferable.
Such a step, that is, the raw material ceria fine particle dispersion obtained in step 2, or the ceria-based fine particle dispersion obtained in step 2a or step 2b, is subjected to centrifugation at a relative centrifugal acceleration of 300 G or more, followed by centrifugation. The step of removing the sedimentation component is referred to as step 3.
When the relative centrifugal acceleration is 300 G or more, coarse particles are unlikely to remain in the ceria-based fine particle dispersion, and therefore scratches are unlikely to occur when used for polishing applications such as abrasives using the ceria-based fine particle dispersion. ..
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 centrifuging the ceria-based fine particle dispersion at a relative centrifugal acceleration of 300 G or more and subsequently removing the sedimentation component, but the step 3a is a step following the step 2. The raw material ceria fine particle dispersion obtained in Step 2 is subjected to centrifugation at a relative centrifugal acceleration of 300 G or more, and subsequently, after removing the sedimentation component, an additive containing silica is added and the temperature is 10 to 98 ° C. Heat aging to obtain a ceria-based fine particle dispersion.
Here, the operation of adding an additive containing silica and aging by heating at 10 to 98 ° C. may be the same as in the above-mentioned steps 2a and 2b.

In addition, as in step 2a or step 2b, an additive containing silica is added, and the operation is performed by heating and aging at 10 to 98 ° C., and then centrifugation is performed to remove the sedimentation component, and then further as in step 3a. An additive containing silica may be added to the mixture, and the mixture may be heat-aged at 10 to 98 ° C. 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 falls under the manufacturing method [α] of the present invention or the manufacturing method [β] of the present invention.

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

<Process A>
In step A, the cerium compound described in step 1 above 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 alkaline aqueous solution or ion-exchanged water is stirred, and the cerium solution is continuously or intermittently added to the cerium 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, the alkaline aqueous solution or the ion-exchanged water is stirred, and the cerium solution is maintained here while maintaining the temperature at 3 to 98 ° C., the pH range at 5.0 to 9.0, and the redox potential at 10 to 500 mV. Is preferably added continuously or intermittently.
After adding the cerium solution, it is desirable to mature for the purpose of completing the reaction.
By such a step, colloidal ceria is obtained.

The solid content concentration when the cerium solution is added to the solvent is preferably 1 to 40% by mass based on the CeO ₂ conversion standard. If this solid content concentration is too low, the concentration of ceria in the manufacturing process may be low and the productivity may be deteriorated.

By neutralizing the cerium solution with an alkali, crystalline ceria having an average crystallinity 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. During the neutralization reaction, the acid used to dissolve the cerium compound and the acid brought in from the cerium compound react with the alkali to form a salt. Since the ionic strength is increased by the generated salt, it tends to be an agglomerate of a single crystal.

The temperature of the reaction solution when the cerium solution is added while stirring the alkaline aqueous solution or the ion-exchanged water is 3 to 98 ° C, preferably 10 to 90 ° C. If this temperature is too low, the reactivity between the cerium solution and the alkali will decrease, and as a result, the crystal growth of ceria will be hindered, and cerium hydroxide and the like may be produced. Even if the crystal grows, a small ceria crystal having a crystallite diameter of less than 5 nm may be produced. On the contrary, if this temperature is too high, ceria grows abnormally or single crystals are aggregated, and coarse agglomerates are formed, which tends to be difficult to crush or crush.

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

The pH range of the reaction solution when the cerium solution is added is 7 to 10, but preferably 6 to 10. At this time, it is preferable to add an alkali or the like to adjust the pH. As an example of such an alkali, a known alkali can be used. Specific examples thereof include, but are not limited to, an aqueous solution of ammonia, an alkali hydroxide, an alkaline earth metal, and an aqueous solution of amines.

Further, it is preferable to adjust the redox potential of the reaction solution to which the cerium solution is added to 10 to 500 mV. The redox potential is preferably 100 to 300 mV. When the redox potential becomes negative, the cerium compound may not become crystalline ceria, but a plate-shaped or rod-shaped composite cerium compound may be produced. Examples of the method of keeping the redox 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.

For the purpose of adding a cerium solution and removing the salt remaining in the aged reaction solution, ion exchange with a cation exchange resin, anion exchange resin, chelate type ion exchange resin, ultrafiltration cleaning, filtration cleaning, etc. , Deionization treatment can be performed if necessary. It is desirable to perform deionization treatment because the ceria-based fine particles can be highly purified by deionization treatment and further, when used as an abrasive, equipment corrosion can be prevented. The deionization treatment is not limited to these.

The colloidal ceria obtained in step A may be further diluted or concentrated with pure water, ion-exchanged water, or the like before being subjected to the next step.

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

<Process B>
In step B, an additive containing silica is added to the colloidal ceria 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 aging by heating at 10 to 98 ° C. may be the same as in the above-mentioned steps 2a and 2b.

In step B, it is preferable to obtain a ceria-based fine particle dispersion liquid by crushing or crushing the colloidal ceria, adding the additive, and aging by heating at 10 to 98 ° C.
In step B, it is preferable to add the additive to the colloidal ceria, heat and age at 10 to 98 ° C., and then crush or pulverize to obtain the ceria-based fine particle dispersion.
Here, the method of crushing or crushing may be the same as the method of crushing or crushing the fired body in the above-mentioned step 2.

It is preferable that the ceria-based fine particle dispersion obtained in the above step B is centrifugally treated at a relative centrifugal acceleration of 300 G or more, and then the sedimentation component is removed. Such a process may be the same as the above-mentioned step 3.

The colloidal ceria obtained by the above-mentioned step A is preferably crushed or crushed, and then centrifugally treated at a relative centrifugal acceleration of 300 G or more to remove the sedimentation component, and then an additive containing silica is added. It is also possible to obtain a ceria-based fine particle dispersion by heating and aging at 10 to 98 ° C.

As in step B, an additive containing silica is added, and the operation is performed by heating and aging at 10 to 98 ° C., and then centrifugation is performed to remove the sedimentation component, and then the additive containing silica is further added. Then, the operation of heating and aging at 10 to 98 ° C. may be carried out 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-mentioned production method can be further dried to obtain ceria-based fine particles. The drying method is not particularly limited, and for example, it can be dried using a conventionally known dryer.

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

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

The abrasive grain dispersion liquid for polishing of the present invention has excellent effects such as high polishing speed when polishing a semiconductor substrate, less scratches (scratches) on the polished surface during polishing, and less residual abrasive grains on the substrate. ing.

The abrasive grain dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, an acid, an alkali, or a buffer solution may be added as a pH adjusting material. Further, the polishing abrasive grain dispersion liquid of the present invention is selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive for controlling the polishing performance1. It is suitably used as a polishing slurry by adding seeds or more.

<Abrasive accelerator>
Although it depends on the type of the material to be polished, it can be used as a polishing slurry by adding a conventionally known polishing accelerator to the abrasive grain dispersion liquid for polishing of the present invention, if necessary. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide and the like, and mixtures thereof. When such an abrasive composition containing 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 polishing accelerators include inorganic acids such as sulfuric acid, nitrate, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or sodium salts, potassium salts, ammonium salts, amine salts and the like of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished composed of a composite component, by accelerating the polishing rate for a specific component of the material to be polished, finally flat polishing is performed. You can get a face.

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

<Surfactant and / or hydrophilic compound>
In order to improve the dispersibility and stability of the abrasive grain dispersion liquid for polishing of the present invention, a cationic, anionic, nonionic or amphoteric surfactant or hydrophilic compound can be added. Both the surfactant and the hydrophilic compound have an action of lowering the contact angle with the surface to be polished and have an action of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following groups can be used.

Examples of the anionic surfactant include carboxylates, sulfonates, sulfates and phosphates, and the carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylics. Acid salts, acylated peptides; as sulfonates, alkyl sulfonates, alkylbenzene and alkyl naphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, N-acyl sulfonates; sulfate esters. As salts, sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkylallyl ether sulfates, alkylamide sulfates; as phosphate ester salts, alkyl phosphates, polyoxyethylene or poly Oxypropylene alkyl allyl ether phosphate can be mentioned.

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

Examples of the nonionic surfactant include an ether type, an ether ester type, an ester type, and a nitrogen-containing type, and examples of the ether type are polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene poly. Examples thereof include oxypropylene block polymer and polyoxyethylene polyoxypropylene alkyl ether, and examples of the ether ester type include polyoxyethylene ether for glycerin ester, polyoxyethylene ether for sorbitan ester, polyoxyethylene ether for sorbitol ester, and ester type. Examples of polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester, sucrose ester, and nitrogen-containing type include fatty acid alkanolamide, polyoxyethylene fatty acid amide, and polyoxyethylene alkylamide. In addition, a fluorine-based surfactant and the like can be mentioned.

As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and examples of the salt include an ammonium salt, a potassium salt, a sodium salt and the like, and an ammonium salt and a potassium salt are particularly preferable.

Further, other surfactants, hydrophilic compounds and the like include 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 and 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 Glycol, Alkyl Polypropylene Glycol Alkyl Ether , Alkyl Polypropylene Glycol Alkenyl Ethers, Esteryl Polypropylene Glycols and Other Ethers; Polysaccharides such as Arginic Acid, Pectic Acid, Carboxymethyl Cellulose, Cardolan and Pluran; Amino Acid Salts such as Glycinammonium Salts and Glycin Sodium Salts; Polylysine, polyappleic acid, polymethacrylic acid, polyammonium methacrylate, sodium polymethacrylate, polyamic acid, polymaleic acid, polyitaconic acid, polyfumalic acid, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, amino Polycarboxylic acids such as polyacrylamide, ammonium polyacrylic acid salt, sodium polyacrylic acid salt, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt and polyglioxylic acid and salts thereof; Vinyl-based polyma; ammonium methyltaurate, sodium methyltaurate, methylsodium sulfate, ethylammonium sulfate, butylammonium sulfate, sodium vinylsulfonic acid, sodium 1-allylsulfonic acid, 2-allylsulfonic acid Sulfonic acids and salts thereof such as sodium salt, sodium methoxymethyl sulfonic acid salt, ammonium ethoxymethyl sulfonic acid salt, sodium 3-ethoxypropyl sulfonic acid salt; propionamide, acrylamide, methyl urea, nicotine amide, succinic acid amide and sulf Examples thereof include amides such as ananyl amides.

When the substrate to be polished is a glass substrate or the like, any surfactant can be preferably used, but in the case of a silicon substrate for a semiconductor integrated circuit or the like, alkali metal or alkaline soil can be used. When the influence of contamination by metals or halides is disliked, it is desirable to use an acid or an ammonium salt-based surfactant thereof.

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

The content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the abrasive grain dispersion for polishing, and preferably 10 g or less from the viewpoint of preventing a decrease in the polishing speed in order to obtain a sufficient effect. ..

Only one type of surfactant or hydrophilic compound may be used, two or more types may be used, or different types may be used in combination.

<Heterocyclic compound>
The abrasive grain dispersion liquid for polishing of the present invention has the purpose of suppressing the erosion of the substrate to be polished by forming a passivation layer or a dissolution suppressing layer on the metal when the substrate to be polished contains a metal. Heterocyclic compounds may be contained. Here, the "heterocyclic compound" is a compound having a heterocycle containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocycle means a cyclic compound having at least one heteroatom. Heteroatoms refer only to the atoms that form the constituents of the heterocyclic ring system, and may be located outside the ring system, separated from the ring system by at least one unconjugated single bond, or the ring system. It does not mean an atom that is part of a further substituent of. Preferred heteroatoms include, but are not limited to, nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms. As an example 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 can be mentioned, but the present invention is not limited thereto.

The content of the heterocyclic compound in the abrasive grain dispersion liquid for polishing according to the present invention is preferably 0.001 to 1.0% by mass, preferably 0.001 to 0.7% by mass. It is more preferably 0.002 to 0.4% by mass, and even 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, if necessary, in order to enhance the effect of each of the above additives.

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

When adjusting the abrasive grain dispersion for polishing to a pH of less than 7, an acidic one is used as the pH adjuster. 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 to keep the pH value of the abrasive grain dispersion for polishing constant. As the pH buffer, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammo tetrahydrate tetrahydrate, and borates or organic acid salts can be used.

Further, as the dispersion solvent of the abrasive grain dispersion liquid for polishing of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, etc. 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 and the like. Ethers; Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; Glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate Kind; Ethers such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; Fragrant hydrocarbons such as benzene, toluene, xylene; Fat group hydrocarbons such as hexane, heptane, isooctane, cyclohexane Classes; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone. And other organic solvents can be used. These may be mixed with water and used.

The solid content concentration contained in the abrasive grain dispersion liquid for polishing of the present invention is preferably in the range of 0.3 to 50% by mass. If this solid content concentration is too low, the polishing rate may decrease. On the contrary, even if the solid content concentration is too high, the polishing rate is rarely improved further, 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, the details of each measurement method and test method in Examples and Comparative Examples will be described. For each Example and Comparative Example, the following measurement results and test results are shown in Tables 1 and 2.

[Analysis of ingredients]
[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 burning weight reduction of 1000 ° C. to determine the mass of the solid content, and then an ICP plasma emission spectrometer (for example, SII, SPS5520) is used in the same manner as in the case of Ag to Th described later. The Si, La, Zr, and Al contents were measured by the standard addition method using the above to calculate SiO ₂ , La ₂ O ₃ , ZrO ₂ , and Al ₂ O ₃ mass%, respectively. Then, it was assumed that 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).
Further, the content of CeO ₂ was determined by assuming that the solid component other than SiO ₂ , La ₂ O ₃ , ZrO ₂ , and Al ₂ O ₃ is 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 determined based on the mass of the solid content thus determined.

[Analysis of components of ceria-based fine particles]
The content of each element shall be measured by the following method.
First, about 1 g of a sample consisting 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. Add 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid and heat on a sand bath. After drying, add a small amount of water and 50 ml of nitric acid to dissolve and put in a 100 ml volumetric flask, and add water to make 100 ml. In this solution, Na and K are measured by an atomic absorption spectrophotometer (for example, Z-2310 manufactured by Hitachi, Ltd.). Next, the operation of collecting 10 ml of the separated solution from the solution contained in 100 ml into a 20 ml volumetric flask is repeated 5 times to obtain 5 10 ml of the separated solution. Then, using this, Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th are measured by an ICP plasma emission spectrometer (for example, SII, SPS5520) by a standard addition method. I do. Here, the blank is also measured by the same method, and the blank is subtracted and adjusted to obtain the measured value for each element.
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

The content of each anion shall be measured by the following method.
<Cl>
Add acetone to 20 g of a sample consisting of ceria-based fine particles or a ceria-based fine particle dispersion (adjusted to a solid content of 20% by mass) to adjust the volume to 100 ml, and add 5 ml of acetic acid and 4 ml of 0.001 mol sodium chloride solution to this solution. The analysis is performed with a 0.002 mol silver nitrate solution by a potentiometric titration method (manufactured by Kyoto Electronics: Potentiometric Titration Device AT-610).
As a separate blank measurement, 5 ml of acetic acid and 4 ml of 0.001 mol sodium chloride solution are added to 100 ml of acetone, and titration is performed with 0.002 mol silver nitrate solution. Was subtracted from the sample to determine the titration amount of the sample.
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

<NO ₃ , SO ₄ , F>
Dilute 5 g of a sample consisting of ceria-based fine particles or ceria-based fine particle dispersion (adjusted to a solid content of 20% by mass) with water, put it in 100 ml, and centrifuge at 4000 rpm for 20 minutes using a centrifuge (HIMAC CT06E manufactured by Hitachi). The liquid obtained by separating and removing the sedimentation component was analyzed by an ion chromatograph (ICS-1100 manufactured by DIONEX).
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

[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, the obtained powder was pulverized in a mortar for 10 minutes, and an X-ray diffractometer (Rigaku Denki Co., Ltd.) The X-ray diffraction pattern was obtained by RINT1400), and the crystal type was specified.
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-mentioned method, and averaged 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-mentioned image analysis method.

<Number of coarse particles>
The number of coarse particles of ceria-based fine particles contained in the polishing slurry or the abrasive grain dispersion for polishing was measured using an Accusizer 780 APS manufactured by Particle sizing system Inc. After adjusting the measurement sample to 0.1% by mass with pure water, inject 5 mL into the measuring device, measure under the following conditions, measure 3 times, and then obtain 0. The value obtained by calculating the average value of the values 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 2nd ^-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>
The abrasive grain dispersion liquid for polishing containing the ceria-based fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Further, for some Examples or Comparative Examples, an additive (ammonium nitrate, ammonium acetate, etc.) was added to the abrasive grain dispersion for polishing to prepare a polishing slurry. Here, in both the abrasive grain dispersion liquid for polishing and the polishing slurry, the solid content concentration was set to 0.6% by mass, and nitric acid was added to set the pH to 5.0.
Next, as a substrate to be polished, a SiO ₂ insulating film (thickness 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, this substrate to be polished is set in a polishing device (Nanofactor Co., Ltd., NF300), and a polishing pad (“IC-1000 / SUBA400 concentric circle type” manufactured by Nitta Hearth Co., Ltd.) is used, and the substrate load is 0.5 MPa, the table. Polishing was performed by supplying an abrasive grain dispersion for polishing or a polishing slurry at a rotation speed of 90 rpm for 1 minute at a rate of 50 ml / min.
Then, the polishing rate was calculated by obtaining the weight change of the substrate to be polished before and after polishing.
Further, the smoothness (surface roughness Ra) of the surface of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Co., Ltd.). Since the smoothness and the surface roughness are generally in a proportional relationship, the surface roughness is shown in Table 2.
The polishing scratches were observed by observing the surface of the insulating film using an optical microscope.

<Aluminum hard disk polishing>
The abrasive grain dispersion liquid for polishing containing the ceria-based fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Further, for some Examples or Comparative Examples, an additive (ammonium nitrate, ammonium acetate, etc.) was added to the abrasive grain dispersion for polishing to prepare a polishing slurry. Here, in both the abrasive grain dispersion for polishing and the polishing slurry, the solid content concentration was 9% by mass, and nitric acid was added to adjust the pH to 2.0.
The substrate for aluminum hard disk is set in a polishing device (Nanofactor Co., Ltd., NF300), and a polishing pad ("Polytex φ12" manufactured by Nitta Hearth Co., Ltd.) is used, and the substrate load is 0.05 MPa and the table rotation speed is 30 rpm. Polishing is performed by supplying a grain dispersion liquid or a polishing slurry at a rate of 20 ml / min for 5 minutes, and using an ultrafine defect / visualization macro device (manufactured by VISION PSYTEC, product name: Micro-Max), the entire surface is used in Zoom15. After observing, the number of scratches (linear marks) existing on the surface of the polished substrate corresponding to 65.97 cm ² was counted and totaled, and evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 "Very few"
50 to less than 80 "less"
80 or more "many"
At least 80 or more, too many to count the total number "*"

Examples are described below. The term "solid content concentration" simply means the concentration of fine particles dispersed in a solvent regardless of the chemical species.

[Preparation step 1]
Cerium carbonate was fired for 2 hours in a muffle furnace at 710 ° C. to obtain a powdery fired body. Next, 100 g of the powdered calcined body was placed in a 1 L patterned beaker together with 300 g of ion-exchanged water, and ultrasonic waves were irradiated in an ultrasonic bath for 10 minutes while stirring.
Next, wet crushing (batch type tabletop sand mill manufactured by Kampe Co., Ltd.) was performed with quartz beads having a diameter of 0.25 mm (manufactured by Daiken Kagaku Kogyo Co., Ltd.) for 30 minutes.
After crushing, the beads are separated while being pressed with ion-exchanged water through a 44-mesh wire mesh, and further separated by a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 1700 G for 102 seconds. Centrifugation treatment was performed to remove the sedimented component, and the removed solution was concentrated to 1.6% by mass with a rotary evaporator to obtain a raw material ceria fine particle dispersion.

[Preparation step 2]
<Preparation of high-purity silicic acid solution>
Pure water was added to an aqueous sodium silicate solution (silica concentration 24.06% by mass, Na _2O 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 strong acid cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 , and 18 kg of the acidic silicate solution (silica concentration 4.6 mass) was passed. %, pH 2.7) was obtained. Next, 18 kg of the obtained acidic silicic acid 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 , and 18 kg of a high-purity silicic acid solution (silica concentration 4.) was passed. 5% by mass, pH 2.7) was obtained.

<Example 1>
Ammonia water having a concentration of 29% by mass (Kanto Chemical Co., Inc., first-class deer) was diluted with ion-exchanged water to prepare 1% by mass of ammonia water. Further, the high-purity silicic acid solution obtained in the preparation step 2 was diluted with ion-exchanged water to obtain a 0.2% by mass diluted high-purity silicic acid solution.
Next, ion-exchanged water was added to the raw material ceria fine particle dispersion liquid having a solid content concentration of 1.6% by mass obtained in the preparation step 1 to obtain a diluted liquid having a solid content concentration of 0.5% by mass (hereinafter, also referred to as liquid A). .. While stirring 10,000 g (dry 50 g) of solution A at room temperature, 2.5 g (dry 0.005 g) of the above-mentioned 0.2% by mass diluted high-purity silicic acid solution was added, and stirring was continued for 10 minutes after the addition was completed. .. Then, 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 continuing stirring. After that, it was cooled to room temperature and concentrated to 3.0% by mass with a rotary evaporator.
Next, the obtained fine particle dispersion was centrifuged 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 disperse ceria-based fine particles. Obtained liquid.

<Example 2>
In Example 1, 2.5 g of a 0.2 mass% diluted high-purity silicic acid solution was added to 10,000 g of the A solution, but in Example 2, a 0.2 mass% diluted high-purity silicic acid solution was added to 10,000 g of the A solution. 25 g (dry0.05 g) was added. Other than that, the same procedure as in Example 1 was performed.
The SEM image and the TEM image of the ceria-based fine particles obtained in Example 2 are shown in FIG. From the TEM image of FIG. 1, it was observed that a thin and easily soluble silica-containing layer was formed in the outermost layer of the ceria-based fine particles.
Further, the X-ray diffraction pattern of the ceria-based fine particles is shown in FIG.

<Example 3>
In Example 1, 2.5 g of a 0.2 mass% diluted high-purity silicic acid solution was added to 10,000 g of the A solution, but in Example 2, a 0.2 mass% diluted high-purity silicic acid solution was added to 10,000 g of the A solution. 250 g (dry 0.5 g) was added. Other than that, the same procedure as in Example 1 was performed.

<Example 4>
Ion-exchanged water was added to first cerium nitrate hexahydrate (manufactured by Chikamochi Pure Pharmaceutical Co., Ltd.) to prepare 70 g of a solution having a CeO ₂ concentration of 0.2% by mass, and then 30 g of a 0.2% by mass high-purity silicic acid solution. Was added to obtain 100 g of a mixed solution (solution B) of CeO ₂ and SiO ₂ .
Then, while stirring 10,000 g (dry 50 g) of the A solution at room temperature, 0.2 mass% of the B solution 100 g (dry 0.2 g) was added, and stirring was continued for 10 minutes even after the addition was completed. After that, 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 continuing stirring. Then, 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 is added to lanthanum oxide heptahydrate (97%) for Wako Pure Chemicals' reagents to prepare 70 g of a 0.2% by mass La ₂ O ₃ solution, followed by a high purity of 0.2% by mass. By adding 30 g of the silicic acid solution, 100 g of a mixed solution (C solution) of La ₂ O ₃ and SiO ₂ was obtained.
Then, while stirring 10,000 g (dry 50 g) of the A solution at room temperature, 0.2 mass% of the C solution 100 g (dry 0.2 g) was added, and stirring was continued for 10 minutes even after the addition was completed. After that, 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 continuing stirring. Then, 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-exchanged water was added to zirconium oxychloride octahydrate (Industrial ZrO 236% manufactured by Taiyo Mining Co., Ltd.) to _{prepare 70 g of a 0.2 mass% diluted ZrO 2 solution} , and then 0.2 mass. By adding 30 g of a high-purity silicate solution of%, 100 g of a mixed solution (solution D) of ZrO ₂ and SiO ₂ was obtained.
Then, while stirring 10,000 g (dry 50 g) of the A solution at room temperature, 0.2 mass% of the D solution 100 g (dry 0.2 g) was added, and stirring was continued for 10 minutes even after the addition was completed. After that, 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 continuing stirring. Then, 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 are added to the ceria-based fine particles (solid content concentration 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 1000 ppm. However, other than that, the same procedure as in Example 2 was performed.

<Example 8>
Ammonium nitrate was used in Example 7, but ammonium acetate was used in Example 8. Other than that, the same procedure as in Example 7 was performed.

<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 examples.
FIG. 3 shows an SEM image and a TEM image of the fine particles contained in the raw material ceria fine particle dispersion liquid. In the TEM image of FIG. 3, the layer containing easily soluble silica as observed in FIG. 1 was not observed in the outermost layer of the raw material ceria fine particles.

<Comparative Example 2>
Polyacrylic acid polymer (Aron SD-10 manufactured by Toagosei Co., Ltd.) and ion-exchanged water are added to the dispersion liquid of the raw material ceria fine particles obtained in the preparation step 1, and the polyacrylic acid has a solid content 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 carried out using the obtained polishing slurry.

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

<Experiment 2>
[Quantification of 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 of the ceria-based fine particles obtained in each Example and Comparative Example was prepared, and 0.1% by mass with stirring. The pH was adjusted to 9.0 using the diluted sodium hydroxide aqueous solution or 6% nitric acid, and ion-exchanged water was further added to make a total of 90 g (dry 2.7 g).
After continuing stirring for 15 minutes, 20 g of the solution was put into a centrifuge tube with an adventitia, Sartorius model number VIVASPIN 20 (molecular weight cut off 5000), and a centrifuge device (H-38F manufactured by KOKUSAN) was used at 1820 G for 30 minutes. Minutes processed. After the treatment, the separation liquid that had permeated the adventitia was recovered, and the SiO ₂ concentration in the separation liquid was measured. The easy-dissolving layer ratio (dissolution ratio per composite fine particle dry) was calculated by the following formula.
Percentage of easily soluble layer (%) = SiO ₂ concentration (ppm) ÷ 1,000,000 × 87.3 g ÷ 2.7 g × 100
The results are shown in Table 2.

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

The ceria-based fine particles contained in the dispersion liquid of the present invention do not contain coarse particles, so that they have low scratches and a high polishing rate. Therefore, the abrasive grain dispersion liquid for polishing containing the dispersion liquid of the present invention can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring boards. 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 liquid containing ceria-based fine particles having an average particle diameter of 5 to 500 nm and having the following characteristics [1] to [4].
[1] The raw material ceria fine particles have a 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 contain crystalline ceria as a main component. ..
[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%. matter.
[3] When the ceria-based fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[4] The ceria-based fine particles have an average crystallinity diameter of 3 to 300 nm, which is measured by subjecting them to X-ray diffraction. The ceria-based fine particle dispersion according to claim 1, wherein the flow potential becomes negative when the pH value is 3 to 8. When 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 titration solution when the differential value of the flow potential becomes maximum. The ceria-based fine particle dispersion according to claim 1 or 2, wherein a flow potential curve having a ratio (ΔPCD / V) of -3000 to -100 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) when the differential value of the flow potential becomes maximum.
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution when the differential value of the flow potential is maximized. The ceria-based fine particle dispersion liquid according to any one of claims 1 to 3, wherein the number of the ceria-based fine particles having coarse particles of 0.51 μm or more is 3000 million / cc or less. The ceria-based fine particle dispersion liquid 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 contents of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively. An abrasive grain dispersion liquid for polishing containing the ceria-based fine particle dispersion liquid according to any one of claims 1 to 5. The polishing abrasive grain dispersion liquid according to claim 6, wherein the polishing abrasive grain dispersion liquid is for flattening a semiconductor substrate on which a silica film is formed. A method for producing a ceria-based fine particle dispersion, which comprises the following steps 1 and 2a.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2a: A step of adding an additive containing silica to the fired body, aging it by heating at 10 to 98 ° C., and then crushing or pulverizing it to obtain a ceria-based fine particle dispersion. A method for producing a ceria-based fine particle dispersion, which comprises the following steps 1 and 2b.
Step 1: A step of calcining a cerium compound at 300 to 1200 ° C. to obtain a calcined body.
Step 2b: A step of crushing or crushing the fired body, adding an additive containing silica to the obtained raw material ceria fine particle dispersion, and aging by heating at 10 to 98 ° C. to obtain a ceria fine particle dispersion. A method for producing a ceria-based fine particle dispersion, which comprises the following steps A and B.
Step A: A step of continuously or intermittently adding a cerium solution in which a cerium compound is dissolved 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 aging it by heating at 10 to 98 ° C. to obtain a ceria-based fine particle dispersion.

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