Silica microparticle fluid dispersion, manufacturing method thereof, and abrasive grain fluid dispersion including silica microparticle fluid dispersion

Abstract

To provide a silica microparticle fluid dispersion capable of high-speed polishing even to a silica film, a Si wafer or a material difficult to process.SOLUTION: A silica microparticle fluid dispersion includes a pseudosphere base-shaped silica microparticle having following features. [1] On an electron microscope photograph, there exists a circle inscribing an image of the pseudosphere base-shaped silica microparticle, and with regard to an arch pattern X composed of a chord and a circular arc on a circumference of the circle, the circle satisfies following relations: (I) at least partially inscribed with the chord of the arch pattern X; and (II) not inscribed at a bisector point D on the circular arc bisecting a total length of the circular arc of the arch pattern X, and at least partially inscribed with each of a circular arc curve on one side on the circular arc centering the bisector point D, and a circular arc curve on an opposite side. [2] The arch pattern X has an area of 1.1 to 4.0 times an area of the image of the pseudosphere base-shaped silica microparticle, a length of the chord is 80 nm or more and a camber is 50 nm or more. [3] The pseudosphere base-shaped silica microparticle has an average particle diameter of 50 to 350 nm, by an image analysis method.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a silica microparticle dispersion suitable as an abrasive used in the manufacture of semiconductor devices and the like, and in particular to a silica microparticle dispersion for planarizing a film to be polished formed on a substrate by chemical mechanical polishing (CMP), a method for producing the same, and a polishing abrasive dispersion containing the silica microparticle dispersion. [Background technology]

[0002] Semiconductor devices such as semiconductor substrates and wiring boards have achieved high performance through higher density and miniaturization. In the manufacturing process of semiconductors, so-called chemical mechanical polishing (CMP) is applied, and specifically, it is an essential technology for shallow trench isolation, planarization of interlayer insulating films, and formation of contact plugs and Cu damascene wiring.

[0003] Generally, CMP polishing agents consist of abrasive grains and chemical components, and the chemical components play a role in promoting polishing by oxidizing or corroding the target film. On the other hand, the abrasive grains perform polishing through mechanical action, and colloidal silica, fumed silica, and ceria particles are used as abrasive grains. Ceria particles in particular have a particularly high polishing speed for silicon oxide films, and are therefore used for polishing in the shallow trench isolation process. In the shallow trench isolation process, not only the silicon oxide film but also the silicon nitride film is polished. To facilitate isolation, it is desirable that the polishing rate of the silicon oxide film is high and that of the silicon nitride film is low, and the polishing rate ratio (selectivity) is also important.

[0004] Conventionally, the method of polishing such components involves a relatively rough primary polishing process followed by a precise secondary polishing process to obtain a smooth surface or an extremely high-precision surface with few scratches or other imperfections. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a silica microparticle dispersion capable of polishing even silica films, Si wafers, and difficult-to-process materials at high speeds, a method for producing the same, and a polishing abrasive dispersion containing the silica microparticle dispersion. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention relates to the following (1) to (8). (1) A silica microparticle dispersion liquid containing pseudo-spherical trapezoidal silica microparticles having the following characteristics [1] to [3]: [1] On the electron microscope photograph, there is a circle in which the image of the pseudo-spherical trapezoidal silica microparticles is inscribed, and further, the image of the pseudo-spherical trapezoidal silica microparticles satisfies the following relationship with respect to an arch-shaped figure X consisting of an arc and a chord on the circumference of the circle: (I) At least partially inscribed in the chord of the arcuate figure X. (II) It does not inscribe at the equal division point D on the arc that bisects the entire length of the arc of the arc-shaped figure X, and at least partially inscribes in the arc curve on one side of the arc and the arc curve on the opposite side of the arc with the equal division point D as the center. [2] The area of ​​the arched figure X is 1.1 to 4.0 times the area of ​​the image of the pseudo-spherical trapezoidal silica fine particles, the chord length is 80 nm or more, and the arrow height is 50 nm or more. [3] The pseudo-spherical trapezoidal silica fine particles have an average particle size of 50 to 350 nm as determined by image analysis. (2) The silica microparticle dispersion according to (1) above, wherein the pseudo-spherical trapezoidal silica microparticles are inscribed in at least 20% of the chord of the arcuate figure X in an electron micrograph. (3) The dispersion of the pseudo-spherical trapezoidal silica microparticles according to (1) or (2) above, further, in an electron microscope photograph, the pseudo-spherical trapezoidal silica microparticles are not inscribed in a circular arc curve extending along the arc for a length of w / 6 (w: total length of the arc) on both sides of a point D on the arc that bisects the total length of the arc, but are at least partially inscribed in two circular arc curves connecting to both ends of the circular arc curve. (4) The silica fine particle dispersion according to any one of (1) to (3) above, wherein the proportion of the pseudo-spherical trapezoidal silica fine particles to all particles in an electron micrograph is 20 to 30%. (5) A polishing abrasive dispersion comprising the silica fine particle dispersion according to any one of (1) to (4) above. (6) The polishing abrasive dispersion according to (5) above, which is used for planarizing a semiconductor substrate having a silica film formed thereon. (7) A method for producing a silica microparticle dispersion, comprising the step of subjecting a dispersion liquid containing spherical silica particles to a wet disintegration treatment while maintaining the dispersion liquid at a pH of 8.5 to 11.5, an electrical conductivity of 0.6 to 3.5 mS / cm, and a liquid temperature of 5 to 40°C, thereby obtaining the silica microparticle dispersion liquid described in (1) or (2) above. (8) The method for producing a silica fine particle dispersion according to (7) above, further comprising the steps of: (a) carrying out the disintegration treatment, subjecting the mixture to a centrifugation treatment at a relative centrifugal acceleration of 300 G or more; and (b) removing the precipitated components. Effect of the Invention

[0007] When the silica microparticle dispersion of the present invention is used, the object can be polished at high speed. When the silica microparticle dispersion of the present invention is used as a polishing abrasive dispersion for polishing difficult-to-process materials including silica films or Si wafers, the object can be polished at high speed compared to the case of using a conventional polishing abrasive dispersion (e.g., a polishing abrasive dispersion containing abrasive particles made of spherical silica microparticles). The reason for this is not clear, but the present inventor presumes that the silica microparticle of the present invention has at least one planar structure, and therefore acts as a sliding friction on the polished surface. When sliding friction acts on the polished surface in this way, it is considered that the polishing speed is improved compared to abrasive particles that act by rolling friction. The method for producing a silica fine particle dispersion of the present invention provides a method for efficiently producing a silica fine particle dispersion that exhibits such excellent performance. In a preferred embodiment of the method for producing a silica fine particle dispersion of the present invention, it is possible to significantly reduce impurities contained in the silica fine particles and achieve high purity. The highly purified silica microparticle dispersion obtained by the preferred embodiment of the method for producing a silica microparticle dispersion of the present invention does not contain impurities and can therefore be particularly preferably used for polishing the surfaces of semiconductor devices such as semiconductor substrates and wiring substrates. Furthermore, when used as an abrasive dispersion for polishing, the silica fine particle dispersion of the present invention is effective for planarizing the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. [Brief description of the drawings]

[0008] [Figure 1] Photographs and diagrams illustrating the shape of silica fine particles of the present invention. [Diagram 2] Figure 2(a) is a part of an SEM image (100,000 times magnification) of the silica fine particles obtained in Example 1, and Figure 2(b) is a part of a TEM image (100,000 times magnification). Note that A in Figure 2(a) and A' in Figure 2(b) are both images of the silica fine particles of the present invention. [Diagram 3] FIG. 3(a) is an SEM image (50,000 magnification) of the silica fine particles obtained in Comparative Example 1, and FIG. 3(b) is a TEM image (50,000 magnification). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will now be described. The present invention relates to a silica fine particle dispersion liquid containing pseudo-spherical trapezoidal silica fine particles having the following characteristics [1] to [3]. [1] On the electron microscope photograph, there is a circle in which the image of the pseudo-spherical trapezoidal silica microparticles is inscribed, and further, the image of the pseudo-spherical trapezoidal silica microparticles satisfies the following relationship with respect to an arch-shaped figure X consisting of an arc and a chord on the circumference of the circle: (I) At least partially inscribed in the chord of the arcuate figure X. (II) It does not inscribe at the equal division point D on the arc that bisects the entire length of the arc of the arc-shaped figure X, and at least partially inscribes in the arc curve on one side of the arc and the arc curve on the opposite side of the arc with the equal division point D as the center. [2] The area of ​​the arched figure X is 1.1 to 4.0 times the area of ​​the image of the pseudo-spherical trapezoidal silica fine particles, the chord length is 80 nm or more, and the arrow height is 50 nm or more. [3] The pseudo-spherical trapezoidal silica fine particles have an average particle size of 50 to 350 nm as determined by image analysis. Such a silica fine particle dispersion is hereinafter also referred to as the "dispersion of the present invention." Moreover, the pseudo-spherical trapezoidal silica fine particles having the above characteristics [1] to [3] are also referred to as "silica fine particles of the present invention" hereinafter. The dispersion of the present invention may be one in which the silica microparticles of the present invention are dispersed in a dispersion solvent, but so long as it contains the silica microparticles of the present invention, it may also contain particles that do not fall under the silica microparticles of the present invention.

[0010] The present invention also relates to a method for producing a silica microparticle dispersion, which is characterized by including a step of subjecting a dispersion liquid containing spherical silica particles to a wet disintegration treatment while maintaining the dispersion liquid at a pH of 8.5 to 11.5, an electrical conductivity of 0.6 to 3.5 mS / cm, and a liquid temperature within the ranges of 5 to 40°C, thereby obtaining the dispersion liquid of the present invention. Such a production method will be hereinafter referred to as the "production method of the present invention."

[0011] The dispersion of the present invention is preferably produced by the production method of the present invention.

[0012] Hereinafter, when the term "the present invention" is simply mentioned, it means any of the dispersion liquid of the present invention, the silica fine particles of the present invention, and the production method of the present invention.

[0013] In this specification, the expression "image of silica fine particles" means "electron microscope photograph of silica fine particles" unless otherwise specified. Electron micrographs refer to photographs (images) taken with a scanning electron microscope (SEM) or photographs (images) taken with a transmission electron microscope (TEM). Note that photographs (images) taken with a scanning electron microscope (SEM) are sometimes referred to as "SEM images," and photographs (images) taken with a transmission electron microscope (TEM) are sometimes referred to as "TEM images." Similarly, the phrase "image of silica fine particles" means "electron microscope photograph of silica fine particles." In addition, unless otherwise specified, the expression "silica fine particles are seen in an electron microscope photograph" means "in an electron microscope photograph of silica fine particles." The expression "silica fine particles are seen in an electron microscope photograph" means "in an electron microscope photograph of silica fine particles."

[0014] <Silica fine particles of the present invention> The silica fine particles of the present invention are characterized by having a pseudo-spherical trapezoidal structure, as will be described later. The shape of the silica fine particles of the present invention will be described with reference to FIG. Fig. 1(a) is an SEM image of the silica fine particles of the present invention magnified 100,000 times. Fig. 1(a) also shows a line for specifying an arched figure X inscribed in the silica fine particles of the present invention. Fig. 1(b) shows the arched figure X specified by Fig. 1(a). FIG. 1(a) 1: Silica microparticles (hereinafter also referred to as “silica microparticles 1”) 5: String 3: Circle Figure 1(b) 7: Arc 9: Arrow height D: Equal division point of arc 7 10: Bow shape X L1: Start point of arc 7 L2: End point of arc 7 S: A point on the arc 7, located on the L1 side from the equally divided point D, equivalent to 1 / 6 of the total length (w) of the arc 7 T: A point on the arc 7, located on the L2 side from the equally divided point D, equivalent to 1 / 6 of the total length (w) of the arc 7 ST: A circular curve on arc 7 that connects points S and T

[0015] In this specification, all or part of the circular arc constituting the portion of the arch-shaped figure X other than the chord 5 (from the starting point L1 to the ending point L2) may be referred to as a "circular arc curve."

[0016] A method for identifying the arcuate figure X will be described with reference to FIG. First, an electron microscope photograph (SEM image in the case of FIG. 1) of silica fine particles 1 of the present invention magnified 100,000 times as shown in FIG. 1(a) is prepared. Next, for one silica particle on the SEM image, a circle 3 is determined in which as much of the periphery of the silica particle as possible is inscribed. Next, a chord 5 that inscribes as much of the periphery of the image of the silica particle as possible in the circle 3 is determined. This identifies an arch shape consisting of chord 5 and arc 7. Here, the two intersections of chord 5 and circle 3 are defined as start point L1 and end point L2, respectively, and the curve connecting start point L1 and end point L2 on the circumference is defined as arc 7 (see Figure 1(b)). It should be noted that the arched figure identified at this stage does not necessarily correspond to the "arched figure X" of the present invention.

[0017] Next, with regard to the arch-shaped figure identified by the method of Figure 1(a), in relation to the image of the silica microparticle 1, it is confirmed whether the image of the silica microparticle 1 corresponds to an arch-shaped figure that is not inscribed in the dividing point D that divides the arc 7 equally, but is at least partially inscribed in both the arc curve (D-L1) from the dividing point D in the direction of the starting point L1 of the arc 7, and the arc curve (D-L2) from the dividing point D in the direction of the end point L2 of the arc 7. And, if applicable, the length of the chord 5 and the arrow height 9 of the arc shape consisting of the arc 7 and the chord 5, and the area of ​​the arc shape (area S X The length of the chord 5 is 80 nm or more, the length of the arrow height 9 is 50 nm or more, and the area S of the arcuate shape is X is 1.1 to 4.0 times (area S X / area S0). If both conditions are satisfied, the arc 7 and the chord 5 are defined as the arch X.

[0018] When such an arched figure X is specified, the silica fine particles for which it is specified (that is, the silica fine particles shown in FIG. 1(a)) correspond to the silica fine particles of the present invention. Such a shape of the silica fine particles of the present invention is also called a pseudo-spherical trapezoid. In geometry, a three-dimensional structure obtained by cutting a sphere between two parallel planes is sometimes called a "truss of a sphere." The silica fine particles of the present invention have such a pseudo-spherical trapezoidal structure, and when used as abrasive grains for polishing, in particular, the sliding friction effect is likely to be exerted, which is believed to contribute to an improvement in the polishing rate.

[0019] Here, the straight line portion inscribed in the chord 5 in the silica microparticle of the present invention corresponds to the planar structure of the silica microparticle of the present invention. Such a planar structure of the straight line portion inscribed in the chord 5 may be referred to as the "planar structure F". In addition, the "planar structure F" may be simply referred to as the "bottom surface of the silica microparticle". In addition, the image of the silica microparticle is not inscribed in the equal division point D of the arc of the arched figure X, and is partially inscribed in the arc curves on both sides of the equal division point D, which corresponds to the existence of a defect on the spherical surface on the opposite side (opposite side) of the planar structure F of the silica microparticle. The structure with the planar defect may be referred to as the "planar structure G". In addition, the "planar structure G" may be simply referred to as the "upper bottom surface of the silica microparticle". In addition, the defect on the spherical surface may be a structure with a defect that is approximately planar other than a planar shape.

[0020] Here, the method for measuring the area S0 of the image of the silica fine particles 1 of the present invention on the electron microscope photograph is not particularly limited. For example, it can be measured using a conventionally known image processing device.

[0021] Area S of the arc shape X X is 1.1 to 4.0 times the area S0 of the image of the pseudo-spherical trapezoidal silica microparticle 1 of the present invention, and this value (area S X / area S0) is preferably from 1.1 to 1.5, and more preferably from 1.1 to 1.3. Area S of the arc shape X X is in the range of 1.1 to 4.0 times the area S0 of the image of the pseudo-spherical trapezoidal silica microparticle 1 of the present invention, and satisfies other requirements (chord length range, arrow height length range, average particle size range of the silica microparticles, and the requirements regarding inscription of (I) and (II) above). When used as an abrasive for polishing, the silica microparticles of the present invention are likely to generate sliding friction with the substrate to be polished, and can contribute to improving the polishing rate.

[0022] The average particle size of the silica fine particles of the present invention measured by image analysis is 50 to 350 nm. When the dispersion of the present invention is used as an abrasive, the occurrence of scratches during polishing is reduced. When the average particle size is less than 50 nm, the particle size is small and the polishing rate may not reach a practical level. Furthermore, if the average particle size exceeds 350 nm, this may result in a decrease in the surface accuracy of the substrate being polished.

[0023] The average particle size of the silica fine particles of the present invention is measured by the following image analysis method. An electron microscope photograph (transmission electron microscope photograph) of the particles contained in the dispersion liquid of the present invention enlarged 100,000 times is prepared, and 50 particles corresponding to the silica fine particles of the present invention are identified on the image. Next, the maximum diameter of each particle is taken as the major axis, and the length is measured and taken as the major axis (DL). A point is also determined on the major axis that divides the major axis in half, and two points are determined where a line perpendicular to this point intersects with the outer edge of the particle, and the distance between these two points is measured and taken as the minor axis (DS). The geometric mean value of the major axis (DL) and minor axis (DS) is then calculated and taken as the particle diameter of the particle. In this manner, the particle sizes of 50 silica fine particles of the present invention are measured, and the value obtained by simple average is regarded as the average particle size of the silica fine particles of the present invention.

[0024] The arrow height 9 in the arched figure X corresponding to the silica microparticles 1 of the present invention is the distance between the chord 5 of the perpendicular line drawn from the equidistant point D to the chord 5 and the circular arc 7. Note that the arrow height value is necessarily set to one for each arched figure. Such an arrow height 9 is 50 nm or more in the arch shape X. The silica fine particles of the present invention which are inscribed in an arch shape having an arrow height of 50 nm or more in an electron microscope photograph have a sufficient thickness as an abrasive grain, are not easily broken, and are suitable for polishing by sliding friction. When silica microparticles are inscribed in an arched shape with an arrow height of less than 50 nm on an electron micrograph, the silica microparticles may not be thick enough to be used as abrasive grains. More preferably, the silica fine particles of the present invention are inscribed in an arch shape having an arrow height of 60 nm or more on an electron micrograph. The upper limit of the arrow height is about 300 nm, which corresponds to the average particle size range of the silica fine particles of the present invention (50 to 350 nm).

[0025] A chord 5 in the arched figure X corresponding to the silica fine particle 1 of the present invention is a line segment connecting a starting point L1 of the circular arc curve of the arched figure X to an end point L2. The length of the chord 5 in the arcuate shape X corresponding to the silica fine particle 1 of the present invention is 80 nm or more, and preferably 90 nm or more. Incidentally, the upper limit of the chord is about 430 nm, which corresponds to the average particle size range (50 to 350 nm) of the silica fine particles of the present invention.

[0026] In order to improve the polishing speed, the friction caused by the contact between particles and substrate is important, and there are rolling friction and sliding friction in dynamic friction, and it is generally believed that sliding friction produces a larger frictional force than rolling friction.The silica microparticle of the present invention has a pseudo-spherical trapezoidal structure with at least one planar structure, and when used as polishing abrasive grains, it is assumed that the action of sliding friction is easy to work, and contributes to improving the polishing speed more than when using spherical particles as polishing abrasive grains.

[0027] The dispersion of the present invention contains the above-mentioned pseudo-spherical silica fine particles of the present invention. An electron microscope photograph of the particles contained in the dispersion of the present invention enlarged by 100,000 times is prepared, and whether or not all particles in the image correspond to the pseudo-spherical silica microparticles of the present invention is determined in the above-mentioned manner. Then, the number ratio of the pseudo-spherical silica microparticles of the present invention is calculated. The number ratio of the silica microparticles of the present invention to the particles contained in such a dispersion of the present invention is preferably 20% or more, and more preferably 25% or more. This number ratio is preferably 20 to 30%.

[0028] The image of the silica fine particles of the present invention is at least partially inscribed in the chord of the arcuate figure X, and desirably inscribed in at least 20% of the chord of the arcuate figure X. This proportion is preferably 50% or more, more preferably 75% or more, and most preferably 100%. It is presumed that the higher the ratio of the image of the silica fine particles of the present invention to the inscribed chord, the wider the area of ​​the planar structure F, and the easier it is to exert the effect of sliding friction. The inscribed ratio of the image of the silica fine particle of the present invention to the chord of the arch-shaped figure X is measured on a TEM image or a TEM photograph, and the total value of the inscribed length of the image of the silica fine particle to the chord of the arch-shaped figure X is calculated as follows: The value divided by the length of the chord of the arc shape X is displayed in units [%].

[0029] The image of the silica fine particles of the present invention is not inscribed in the equally dividing point D on the arc that bisects the entire length of the arc 7, and is at least partially inscribed in the arc curve (D-L1) on one side of the arc and the arc curve (D-L2) on the opposite side of the arc centered on the equally dividing point D. More preferably, the image of the silica fine particles of the present invention is not inscribed in the arc curve ST that extends for a length of w / 6 (w: total length of the arc) on both sides of the equally dividing point D on the arc that bisects the entire length of the arc 7, and is at least partially inscribed in the two arc curves (S-L1, T-L1) that connect to both ends of the arc curve ST. As described above, the electron micrograph shows a pseudo-frustum of a sphere, there exists a circle inscribed in the pseudo-frustum, and furthermore, for the arch-shaped figure X consisting of an arc and a chord on the circumference of the circle, the following relationships (I) and (II) are satisfied. (I) At least partially inscribed in the chord of the arcuate figure X. (II) It does not inscribe at the equal division point D on the arc that bisects the entire length of the arc of the arc-shaped figure X, and at least partially inscribes in the arc curve on one side of the arc and the arc curve on the opposite side of the arc with the equal division point D as the center. Furthermore, the area of ​​the arched figure X was 1.3 times the area of ​​the image of the silica fine particles of the present invention shown in Figure 1 (a), the length of the chord was 314 nm, the height of the arrow was 200 nm, and the average particle diameter of the silica fine particles of the present invention was 243 nm by image analysis. It was also confirmed that the silica fine particles of the present invention shown in Figure 1 (a) were inscribed in at least 20% of the chord of the arched figure X.

[0030] The number of coarse particles of 0.51 μm or more that can be contained in the dispersion of the present invention is preferably 100 million particles / cc or less in dry conversion. The number of coarse particles is preferably 100 million particles / cc or less, more preferably 80 million particles / cc or less. Coarse particles of 0.51 μm or more can cause polishing scratches and can also cause the surface roughness of the polished substrate to deteriorate.

[0031] The method for measuring the number of coarse particles that may be contained in the dispersion of the present invention is as follows. After diluting the sample with pure water to 0.1% by mass, 5 ml of the sample is taken and injected into a conventionally known coarse particle number measuring device. The number of coarse particles of 0.51 μm or more is then calculated. This measurement is carried out three times, and the simple average value is calculated. This value is multiplied by 1000 to obtain the number of coarse particles of 0.51 μm or more.

[0032] The specific surface area of ​​the particles contained in the dispersion of the present invention is not particularly limited, but is preferably 5 to 60 m 2 / g, and 7 to 43m 2 It is more preferable that the molecular weight is / g.

[0033] 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 and degassed in a nitrogen gas flow at 250°C for 40 minutes, then the sample is kept at liquid nitrogen temperature in a mixed gas flow of 30% nitrogen by volume and 70% helium by volume to allow the nitrogen to be adsorbed in equilibrium on the sample. Next, the temperature of the sample is gradually raised to room temperature while the mixed gas is being passed through, and the amount of nitrogen desorbed during this period is detected, and the specific surface area of ​​the sample is measured using a calibration curve created in advance. Such a BET specific surface area measurement method (nitrogen adsorption method) can be carried out using, for example, a conventionally known surface area measurement device. In the present invention, the specific surface area means a value obtained by measurement in this manner, unless otherwise specified.

[0034] <Dispersion of the Present Invention> The dispersion of the present invention will now be described. The dispersion of the present invention is a dispersion in which the silica fine particles of the present invention as described above are dispersed in a dispersion solvent. The dispersion of the present invention may also contain particles other than the silica fine particles of the present invention dispersed in the dispersion solvent, in addition to the silica fine particles of the present invention as described above.

[0035] The dispersion 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. Furthermore, the dispersion of the present invention can be suitably used as a polishing slurry by adding at least one additive 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.

[0036] In addition, as the dispersion solvent provided in the dispersion liquid of the present invention, for example, alcohols such as methanol and ethanol; amides such as acetone and 2-butanone; ethers such as diethyl ether and isopropyl ether; glycol ethers such as 2-methoxyethanol and 2-ethoxyethanol; glycol ether acetates such as 2-methoxyethyl acetate and 2-ethoxyethyl acetate; esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and heptane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone and N-octyl-2-pyrrolidone, and other organic solvents can be used. These may be mixed with water and used.

[0037] The solid content concentration in the dispersion of the present invention is preferably in the range of 0.3 to 50% by mass.

[0038] <Production Method of the Present Invention> The manufacturing method of the present invention will now be described. The production method of the present invention is characterized by including a step of subjecting a dispersion liquid containing spherical silica particles to a wet crushing treatment while maintaining the dispersion liquid at a pH of 8.5 to 11.5, an electrical conductivity of 0.6 to 3.5 mS / cm, and a liquid temperature of 5 to 40°C. The dispersion of the present invention can be obtained by the production method of the present invention.

[0039] The spherical silica particles may be known ones, and are wet-disintegrated at pH 8.5 to 11.5, electrical conductivity 0.6 to 3.5 mS / cm, and liquid temperature 5 to 40°C. If either or both of the pH and electrical conductivity need to be adjusted, the pH and electrical conductivity can be adjusted using an adjuster made of an alkaline aqueous solution such as an aqueous sodium hydroxide solution. The wet disintegration is preferably carried out for, for example, 10 to 18 hours. The dispersion of the present invention can be obtained by wet disintegrating the spherical silica particles under such conditions. The pH range is preferably 9.5 to 10.5. The electrical conductivity range is preferably 0.7 to 2.8 mS / cm. The liquid temperature is preferably kept in the range of 8 to 40°C. The time required for the wet disintegration is preferably 10 to 15 hours. In the manufacturing method of the present invention, the dispersion obtained after disintegration can be passed through a wire screen of a desired mesh to separate the beads, thereby obtaining the dispersion of the present invention. After the disintegration treatment, if desired, the dispersion may be centrifuged using a centrifuge at a relative centrifugal acceleration of 300 G or more, for example, to recover the light liquid (dispersion obtained by removing the sedimentary components) or the heavy liquid, and then diluted with ion-exchanged water or the like, followed by dispersion treatment by ultrasonic irradiation to obtain the dispersion of the present invention.

[0040] <Polishing abrasive dispersion liquid> The liquid containing the dispersion of the present invention can be preferably used as a polishing abrasive dispersion (hereinafter also referred to as "polishing abrasive dispersion of the present invention"). In particular, it can be preferably used as a polishing abrasive dispersion for planarizing a semiconductor substrate on which an SiO2 insulating film is formed. In addition, it can be preferably used as a polishing slurry by adding a chemical component to control the polishing performance.

[0041] The abrasive polishing dispersion of the present invention has excellent effects such as high polishing rate when polishing semiconductor substrates and the like, less scratches on the polished surface during polishing, and less abrasive residue on the substrate.

[0042] <Polishing accelerator> The polishing abrasive dispersion of the present invention can be used as polishing slurry by adding a conventionally known polishing accelerator as necessary, depending on the type of polishing material.Examples of such accelerators include hydrogen peroxide, peracetic acid, urea peroxide, and mixtures thereof.When using the polishing agent composition containing such a polishing accelerator as hydrogen peroxide, when the polishing material is metal, the polishing speed can be effectively improved.

[0043] Other examples of the polishing accelerator include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, organic acids such as acetic acid, and the sodium salts, potassium salts, ammonium salts, and amine salts of these acids, and mixtures thereof. In the case of a polishing composition containing these polishing accelerators, when polishing a polished material consisting of a silica component, the polishing rate of a specific component of the polished material can be accelerated, and a flat polished surface can be finally obtained.

[0044] 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 mass %, and more preferably 0.5 to 5 mass %.

[0045] <Surfactant and / or hydrophilic compound> In order to improve the dispersibility and stability of the polishing abrasive dispersion 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 the effect of reducing the contact angle with the polished surface and promoting uniform polishing. As the surfactant and / or hydrophilic compound, for example, those selected from the following group can be used.

[0046] Examples of the anionic surfactant include carboxylates, sulfonates, sulfates, and phosphates. Examples of the carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylates, and acylated peptides. Examples of the sulfonates include alkyl sulfonates, alkylbenzene and alkylnaphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, and N-acylsulfonates. Examples of the sulfates include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, and alkylamide sulfates. Examples of the phosphates include alkyl phosphates, and polyoxyethylene or polyoxypropylene alkyl allyl ether phosphates.

[0047] Examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts; examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate salts, imidazolinium betaine, lecithin, and alkylamine oxide.

[0048] Examples of nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type, and examples of the ether type include polyoxyethylene alkyl and alkylphenyl ethers, alkylarylformaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block polymers, and polyoxyethylene polyoxypropylene alkyl ethers. Examples of the ether ester type include polyoxyethylene ethers of glycerin esters, polyoxyethylene ethers of sorbitan esters, and polyoxyethylene ethers of sorbitol esters. Examples of the ester type include polyethylene glycol fatty acid esters, glycerin esters, polyglycerin esters, sorbitan esters, propylene glycol esters, and sucrose esters. Examples of the nitrogen-containing type include fatty acid alkanolamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkyl amides. Other examples include fluorine-based surfactants.

[0049] The surfactant is preferably an anionic surfactant or a nonionic surfactant, and the salt includes ammonium salts, potassium salts, sodium salts, etc., with ammonium salts and potassium salts being particularly preferred.

[0050] Further, other surfactants, hydrophilic compounds, etc. include esters such as glycerin esters, sorbitan esters, and alanine ethyl esters; ethers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ethers, polyethylene glycol alkenyl ethers, alkyl polyethylene glycols, alkyl polyethylene glycol alkyl ethers, alkyl polyethylene glycol alkenyl ethers, alkenyl polyethylene glycols, alkenyl polyethylene glycol alkyl ethers, alkenyl polyethylene glycol alkenyl ethers, polypropylene glycol alkyl ethers, polypropylene glycol alkenyl ethers, alkyl polypropylene glycols, alkyl polypropylene glycol alkyl ethers, alkyl polypropylene glycol alkenyl ethers, and alkenyl polypropylene glycols; polysaccharides such as alginic acid, pectinic acid, carboxymethylcellulose, curdlan, and pullulan; glycine ammonium salts and glycine sodium salts; polycarboxylic acids and their salts, such as polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, ammonium polymethacrylic acid, sodium polymethacrylic acid, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly(p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylic acid, sodium polyacrylic acid, polyamic acid, ammonium polyamic acid, sodium polyamic acid, and polyglyoxylic acid; vinyl polymers, such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrolein; sulfonic acids and their salts, such as ammonium methyl taurate, sodium methyl taurate, sodium methyl sulfate, ethyl ammonium sulfate, butyl ammonium sulfate, sodium vinyl sulfonate, sodium 1-allyl sulfonate, sodium 2-allyl sulfonate, sodium methoxymethyl sulfonate, ammonium ethoxymethyl sulfonate, and sodium 3-ethoxypropyl sulfonate;Amides such as propionamide, acrylamide, methylurea, nicotinamide, succinamide, and sulfanilamide may be mentioned.

[0051] When the substrate to be polished is a glass substrate or the like, any surfactant can be suitably used. However, when the substrate is a silicon substrate for a semiconductor integrated circuit or the like, and the influence of contamination by alkali metals, alkaline earth metals, halides, or the like must be avoided, it is preferable to use an acid or an ammonium salt-based surfactant.

[0052] When the polishing abrasive dispersion of the present invention contains a surfactant and / or a hydrophilic compound, the total content thereof is preferably 0.001 to 10 g, more preferably 0.01 to 5 g, and particularly preferably 0.1 to 3 g, per liter of the polishing abrasive dispersion.

[0053] The content of the surfactant and / or hydrophilic compound is preferably 0.001 g or more per liter of the polishing abrasive grain dispersion in order to obtain a sufficient effect, and is preferably 10 g or less in order to prevent a decrease in the polishing rate.

[0054] The surfactant or hydrophilic compound may be used alone or in combination with two or more kinds.

[0055] <Heterocyclic compounds> Regarding the abrasive grain dispersion liquid of the present invention, when the substrate to be polished contains metal, a heterocyclic compound may be contained for the purpose of forming a passive layer or a dissolution inhibition layer on the metal to suppress the erosion of the substrate to be polished. Here, the "heterocyclic compound" is a compound having a heterocycle containing one or more heteroatoms. The heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocycle means a cyclic compound having at least one heteroatom. The heteroatom means only an atom that forms a constituent part of the ring system of the heterocycle, and does not mean an atom that is located outside the ring system, separated from the ring system by at least one non-conjugated single bond, or is a part of a further substituent of the ring system. Preferred examples of the heteroatom include, but are not limited to, a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom. As examples of the heterocyclic compound, imidazole, benzotriazole, benzothiazole, tetrazole, etc. 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-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, etc. can be mentioned, but are not limited thereto.

[0056] Regarding the content when a heterocyclic compound is blended in the abrasive grain dispersion liquid of the present invention, it is preferably 0.001 to 1.0% by mass, more preferably 0.001 to 0.7% by mass, and even more preferably 0.002 to 0.4% by mass.

[0057] <pH adjuster> In order to enhance the effects of the above additives, etc., an acid or a base and their salt compounds can be added as necessary to adjust the pH of the polishing composition.

[0058] When adjusting the pH of the abrasive grain dispersion of the present invention to 7 or higher, an alkaline substance is used as the pH adjuster. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, and tetramethylamine are used.

[0059] When adjusting the pH of the abrasive grain dispersion of the present invention to less than 7, an acidic substance is used as the pH adjuster. For example, mineral acids such as hydrochloric acid and nitric acid, and hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid, and glyceric acid are used.

[0060] <pH buffer> In order to keep the pH value of the abrasive grain dispersion of the present invention constant, a pH buffer may be used. As the pH buffer, for example, phosphates and borates or organic acid salts such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate can be used.

[0061] Examples of the dispersion solvent for the abrasive grain dispersion of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; ketones such as acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, and ethylene glycol dimethyl ether; Organic solvents that can be used include glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, and 2-butoxyethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, isooctane, and cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; and pyrrolidones such as N-methyl-2-pyrrolidone and N-octyl-2-pyrrolidone. These may be mixed with water.

[0062] The solid content of the polishing abrasive dispersion of the present invention is preferably in the range of 0.3 to 50 mass %. If the solid content is too low, the required polishing speed may not be achieved. Conversely, if the solid content is too high, the polishing speed is rarely improved. EXAMPLES

[0063] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0064] <Experiment 1> First, the details of the measurement and test methods in the examples and comparative examples will be described. The measurement and test results for each of the examples and comparative examples are shown in Table 1.

[0065] [Area of ​​the arcuate figure X for pseudo-spherical trapezoidal silica particles (S x ), area (S0), chord length, arrow height and total arc length (w)] For the particles contained in the silica fine particle dispersions obtained in the Examples and Comparative Examples, the area (S0) was calculated by the method described above with reference to FIG. x ), chord length, arrow height and total arc length (w) are calculated, and the area ratio (S x / S0) was calculated to judge whether the particles correspond to the silica fine particles of the present invention.

[0066] <Average particle size> The average particle size of the silica fine particles contained in the silica fine particle dispersions obtained in the Examples and Comparative Examples was measured based on a photographic projection image obtained by photographing the particles using a transmission electron microscope. An electron microscope photograph (transmission electron microscope photograph) of the silica microparticles of the present invention magnified 100,000 times is prepared, and for 50 particles randomly selected from the image, the maximum diameter of each particle is taken as the major axis, and the length of the particle is measured and this value is taken as the major axis (DL). A point is also determined on the major axis that divides the major axis into two equal parts, and two points where a straight line perpendicular to the major axis intersects with the outer edge of the particle are determined, and the distance between the two points is measured and taken as the minor axis (DS). The geometric mean value of the major axis (DL) and minor axis (DS) is then calculated and this is taken as the particle diameter of the particle. In this way, the particle diameters of 50 particles are measured, and the value obtained by simply averaging these values ​​is taken as the average particle diameter.

[0067] Regarding the average particle diameter of the truncated-spheroid-shaped silica fine particles contained in the silica fine particle dispersion liquids obtained in the examples and comparative examples, measurements were carried out by the above-described image analysis method based on a photographed projection image obtained by photographing using a transmission electron microscope. However, in measuring the average particle diameter of the truncated-spheroid-shaped silica fine particles, only 50 truncated-spheroid-shaped silica fine particles were selected from among the silica fine particles shown in the photographed projection image obtained by photographing using a transmission electron microscope, and measurement and calculation were carried out in the same manner as described above.

[0068] <Specific surface area> The specific surface area of the particles contained in the silica fine particle dispersion liquids obtained in the examples and comparative examples was measured by the method described above. Here, it can be carried out using a surface area measuring apparatus (manufactured by Mountech Co., Ltd., product number: Mascsorb HM-1220). In the present invention, unless otherwise specified, the specific surface area means a value obtained by measuring by such a method.

[0069] [Number ratio of truncated-spheroid-shaped silica fine particles] An electron micrograph of the particles contained in the dispersion liquid of the present invention magnified 100,000 times was prepared, and for all the particles on the image, it was judged whether or not they corresponded to truncated-spheroid-shaped silica fine particles by the method described above. Then, the number ratio of the truncated-spheroid-shaped silica fine particles was determined.

[0070] [Polishing test method] <Polishing of SiO2 film> A polishing abrasive grain dispersion liquid containing the silica fine particle dispersion liquid obtained in each of the examples and comparative examples was prepared. Here, the solid content concentration was 0.6% by mass, and nitric acid was added to adjust the pH to 5.0. Next, as a substrate to be polished, a substrate having a SiO2 insulating film (thickness 1 μm) formed by a thermal oxidation method was prepared. Next, this substrate to be polished was set in a polishing apparatus (manufactured by Nanofactor Co., Ltd., NF300), a polishing pad (manufactured by Nitta Haas Co., Ltd., "IC-1000 / SUBA400 concentric circle type") was used, and polishing was carried out by supplying the polishing abrasive grain dispersion liquid at a rate of 50 ml / min for 1 minute at a substrate load of 0.5 MPa and a table rotation speed of 90 rpm. The change in weight of the substrate to be polished before and after polishing was then determined, and the polishing rate was calculated.

[0071] [Polished substrate surface roughness] The surface smoothness (surface roughness Ra) of the substrate to be polished obtained by the above-mentioned SiO2 film polishing test was measured using an atomic force microscope (AFM, Hitachi High-Tech Science Corp.) Since smoothness and surface roughness are roughly proportional to each other, the surface roughness is listed in Table 1.

[0072] Examples are given below.

[0073] <Example 1> [Preparation of silica particle dispersion containing pseudo-spherical trapezoidal silica particles] 451 g of ion-exchanged water was added to 500 g of silica sol (manufactured by JGC Catalysts and Chemicals Co., Ltd.: Spherica Slurry SS-300, average particle size 341 nm) to obtain a diluted slurry. Next, an aqueous sodium hydroxide solution was added to this diluted slurry to adjust the pH to 9.6, and then wet-disintegration was carried out for 900 minutes in a wet disintegrator (a batch-type benchtop sand mill manufactured by Kampe Co., Ltd.) using zirconia beads of φ0.05 mm (manufactured by Nikkato Co., Ltd.). During the wet disintegration, an aqueous sodium hydroxide solution was added to maintain the pH at 9.5 to 10.5, the electrical conductivity at 0.7 to 2.8 mS / cm, and the liquid temperature at 8 to 40°C.

[0074] After crushing, the beads were separated by passing them through a 44-mesh wire screen. Figure 2(a) shows a part of an SEM image (100,000 times magnification) of the particles dispersed in the obtained silica microparticle dispersion, and Figure 2(b) shows a part of a TEM image (100,000 times magnification). As shown in FIG. 2(a), the particles contained pseudo-spherical trapezoidal silica microparticles. That is, it was confirmed that the pseudo-spherical trapezoidal silica microparticles A in FIG. 2(a) were at least partially inscribed in the chord of the arched figure X. It was also confirmed that the pseudo-spherical trapezoidal silica microparticles A were not inscribed in the equal division point D on the circular arc that bisects the total length of the circular arc of the arched figure X, and were at least partially inscribed in the circular arc curves on one side and the opposite side of the circular arc centered on the equal division point D. It was also confirmed that the area of ​​the arched figure X was 1.2 times the area of ​​the image of the pseudo-spherical trapezoidal silica microparticles, the chord length was 257 nm, and the arrow height was 150 nm. It was also confirmed that the total length (w) of the circular arc of the arched figure X was 449 nm (the value of w / 6 was 75 nm). The average particle size of the particles dispersed in the silica fine particle dispersion was 232 nm, and the average particle size of the pseudo-spherical trapezoidal silica fine particles among them was 216 nm. Furthermore, it was confirmed from FIG. 2 that the pseudo-spherical trapezoidal silica fine particles used in Example 1 were inscribed in at least 20% of the chord of the arch shape X. Furthermore, the solid content was 4.6% by mass, and the weight was 1375 g. In addition, when the number ratio of the pseudo-spherical trapezoidal silica microparticles was measured in all SEM images (100,000 times) of the silica microparticle dispersion obtained by this embodiment, including the SEM image of Figure 2(a), using the above-mentioned method for measuring the number ratio, it was 29%. Here, for all particles that correspond to the pseudo-spherical trapezoidal silica microparticles, it was confirmed that the area of ​​the arch-shaped figure X was in the range of 1.1 to 4.0 times the area of ​​the image of the pseudo-spherical trapezoidal silica microparticles, the chord length was in the range of 80 nm to 430 nm, and the arrow height was in the range of 50 nm to 300 nm.

[0075] The obtained silica fine particle dispersion was subjected to a polishing test, and the results are shown in Table 1.

[0076] <Example 2> The same operation as in Example 1 was carried out, and after crushing, the beads were separated by passing them through a 44 mesh wire mesh. The obtained silica microparticle dispersion was then processed for 102 seconds at 1700G in a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to recover the heavy liquid, which was then diluted to 59g with ion-exchanged water and then dispersed by ultrasonic irradiation to obtain a silica microparticle dispersion.

[0077] An SEM image (100,000x magnification) of the resulting particles was obtained, and it was confirmed that they contained pseudo-spherical trapezoidal silica fine particles. The average particle size of the particles contained in the obtained silica fine particle dispersion was 232 nm, and among these, the average particle size of the pseudo-spherical trapezoidal silica fine particles was 216 nm. That is, an arched figure X was present in which the area ratio when the pseudo-spherical prism-shaped silica microparticles were inscribed was 1.2 times, the chord length was 286 nm, and the arrow height was 143 nm. From the SEM image of the obtained pseudo-spherical prism-shaped silica microparticles, it was confirmed that the pseudo-spherical prism-shaped silica microparticles obtained in Example 2 were at least partially inscribed in the chord of the arched figure X. It was also confirmed that the pseudo-spherical prism-shaped silica microparticles were not inscribed in the equipartition point D on the arc that bisects the entire length of the arc of the arched figure X, and were at least partially inscribed in the arc curves on one side and the opposite side of the arc with the equipartition point D as the center. Furthermore, it was confirmed that the total length (w) of the arc of the arc shape X was 449 nm (the value of w / 6 was 75 nm). Furthermore, from the SEM image (100,000 times magnification) of the obtained particles, it was confirmed that, as in the case of Example 1, the pseudo-spherical trapezoidal silica fine particles were inscribed in at least 20% of the chord of the arch shape X. Furthermore, the solid content was 10.3% by mass, and the weight was 59 g.

[0078] For the entire SEM image (100,000 times magnification) of the silica fine particle dispersion obtained in this example, the number ratio of the pseudo-spherical trapezoidal silica fine particles was measured according to the above-mentioned method for measuring the number ratio, and was found to be 29%. Here, for all particles that correspond to the pseudo-spherical trapezoidal silica microparticles, it was confirmed that the area of ​​the arch-shaped figure X was in the range of 1.1 to 4.0 times the area of ​​the image of the pseudo-spherical trapezoidal silica microparticles, the chord length was in the range of 80 nm to 430 nm, and the arrow height was in the range of 50 nm to 300 nm.

[0079] The obtained silica fine particle dispersion was subjected to a polishing test, and the results are shown in Table 1.

[0080] <Comparative Example 1> Preparation of Silica Sol (60 nm) 12,090 g of ethanol and 6,363.9 g of ethyl orthosilicate were mixed to obtain a mixed solution a1. Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to obtain a mixed liquid b1. Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed to prepare a bed water. The water bed was adjusted to 75°C while stirring, and mixed liquid a1 and mixed liquid b1 were added simultaneously to the water bed so that the addition would be completed in 10 hours for each. After the addition was completed, the liquid temperature was kept at 75°C for 3 hours for aging, and then the solid content was adjusted to obtain 9,646.3 g of silica sol having a SiO2 solid content of 19 mass% and an average particle size of 60 nm measured by a laser diffraction / scattering method.

[0081] Preparation of silica microparticle dispersion (average particle size of silica microparticles: 108 nm) 2,733.3 g of methanol and 1,822.2 g of ethyl orthosilicate were mixed to obtain a mixed solution a2. Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to obtain a mixed liquid b2. Next, 59 g of ultrapure water and 1,208.9 g of methanol were mixed to prepare a bed of water, and 922.1 g of the silica fine particle dispersion obtained in the previous step by dispersing silica fine particles having an average particle size of 60 nm in a solvent was added thereto. The bed water containing the silica microparticle dispersion was adjusted to 65°C while stirring, and mixed liquid a2 and mixed liquid b2 were added simultaneously to the bed water so that the addition was completed within 18 hours for each. After the addition was completed, the liquid temperature was kept at 65°C for 3 hours for aging, and then the solid concentration (SiO2 solid concentration) was adjusted to 19 mass%, and 3,600 g of high-purity silica microparticle dispersion was obtained. The silica particles contained in this high-purity silica particle dispersion had an average particle diameter of 108 nm as measured by dynamic light scattering (PAR-III manufactured by Otsuka Electronics Co., Ltd.) The minor axis / major axis ratio of the silica particles was also measured based on a transmission electron microscope photograph and was found to be 1.0.

[0082] FIG. 3(a) shows an SEM image (50,000 times magnification) of the silica fine particles obtained in Comparative Example 1, and FIG. 3(b) shows a TEM image (50,000 times magnification).

[0083] [Table 1] [Industrial Applicability]

[0084] The particles contained in the dispersion of the present invention do not contain coarse particles, so they have low scratching and high polishing speed.Therefore, the polishing abrasive dispersion containing the dispersion of the present invention can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates.Specifically, it can be preferably used for planarizing semiconductor substrates on which silica film is formed.

Claims

1. A silica microparticle dispersion liquid containing 20% ​​or more pseudo-spherical trapezoidal silica microparticles having the following characteristics [1] to [3] by number ratio: [1] On the electron microscope photograph, there is a circle in which the image of the pseudo-spherical trapezoidal silica fine particles is inscribed, and further, the image of the pseudo-spherical trapezoidal silica fine particles has the following relationship with respect to an arch-shaped figure X consisting of an arc and a chord on the circumference of the circle: (I) At least partially inscribed in the chord of the arcuate figure X. (II) The pseudo-spherical trapezoidal silica microparticles are not inscribed at a point D on the arc that bisects the entire length of the arc of the arched figure X, and are at least partially inscribed in two arc curves on one side and the other side of the arc with the point D as the center, and further, in an electron microscope photograph, the pseudo-spherical trapezoidal silica microparticles are not inscribed in two arc curves that extend along the arc for a length of w / 6 (w: total length of the arc) on both sides of the point D on the arc that bisects the entire length of the arc, and are at least partially inscribed in two arc curves that connect to both ends of the arc curve. [2] The area of ​​the arched figure X is 1.1 to 1.5 times the area of ​​the image of the pseudo-spherical trapezoidal silica fine particles, the length of the chord is 80 nm or more, and the height of the arrow is 50 nm or more. [3] The pseudo-spherical trapezoidal silica fine particles have an average particle size of 50 to 350 nm as determined by an image analysis method.

2. 2. The dispersion of silica particles according to claim 1, wherein the pseudo-spherical trapezoidal silica particles are inscribed in at least 20% of the chord of an arcuate figure X in an electron micrograph.

3. 3. A polishing abrasive dispersion comprising the silica fine particle dispersion according to claim 1 or 2.

4. 4. The polishing abrasive dispersion according to claim 3, which is used for planarizing a semiconductor substrate on which a silica film is formed.

5. 3. A method for producing a silica microparticle dispersion, comprising the steps of: subjecting a dispersion liquid containing spherical silica particles to a wet disintegration treatment while maintaining the dispersion liquid at a pH of 8.5 to 11.5, an electrical conductivity of 0.6 to 3.5 mS / cm, and a liquid temperature of 5 to 40° C.; and producing the silica microparticle dispersion liquid according to claim 1 or 2.

6. The method for producing a silica fine particle dispersion according to claim 5, wherein after the disintegration treatment, a centrifugation treatment is carried out at a relative centrifugal acceleration of 300 G or more, and then the precipitated components are removed.

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