WO2004072203A1 - Process for producing polishing composition - Google Patents

Process for producing polishing composition Download PDF

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Publication number
WO2004072203A1
WO2004072203A1 PCT/JP2004/001413 JP2004001413W WO2004072203A1 WO 2004072203 A1 WO2004072203 A1 WO 2004072203A1 JP 2004001413 W JP2004001413 W JP 2004001413W WO 2004072203 A1 WO2004072203 A1 WO 2004072203A1
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WO
WIPO (PCT)
Prior art keywords
silica
dispersion
concentration
polishing composition
weight
Prior art date
Application number
PCT/JP2004/001413
Other languages
French (fr)
Japanese (ja)
Inventor
Yoshiharu Ohta
Yasuyuki Itai
Keiji Fukuda
Original Assignee
Nitta Haas Incorporated
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nitta Haas Incorporated filed Critical Nitta Haas Incorporated
Priority to US10/545,370 priority Critical patent/US20060240748A1/en
Publication of WO2004072203A1 publication Critical patent/WO2004072203A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1454—Abrasive powders, suspensions and pastes for polishing
    • C09K3/1463—Aqueous liquid suspensions
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09G—POLISHING COMPOSITIONS; SKI WAXES
    • C09G1/00—Polishing compositions
    • C09G1/02—Polishing compositions containing abrasives or grinding agents

Definitions

  • the present invention relates to a method for producing a polishing composition used in a polishing step of a semiconductor production step.
  • an etch-back method that removes unevenness by etching, a film formation method that forms a flat film by plasma CVD (Chemical Vapor Deposition), a fluidization method that planarizes by heat treatment, and a recess by selective CVD.
  • the selective growth method for embedding is used.
  • the above methods have problems in that they are appropriate depending on the type of film, such as an insulating film and a metal film, and that the region to be planarized is extremely narrow.
  • a planarization processing technique that can overcome such problems, there is planarization by CMP.
  • a slurry in which fine particles (abrasive grains) are suspended is supplied to the surface of the polishing pad, and the surface is polished by moving the pressed polishing pad and the silicon wafer relatively.
  • a wide range of wafer surfaces can be flattened with high precision.
  • a CMP device that performs planarization by CMP is mainly composed of a rotating platen section, a carrier section, a slurry supply section, and a dressing section.
  • a polishing pad is attached to the upper surface of the rotary platen with an adhesive tape or the like, and the lower surface is connected to a rotary drive mechanism via a rotary shaft.
  • the carrier part has a backing material and a retainer
  • the silicon wafer, which is the object to be polished, is held by polishing, and the processed surface of the silicon wafer is pressed against the polishing pad.
  • the upper surface is connected to a rotation drive mechanism via a rotation shaft.
  • the slurry supply unit supplies a slurry in which particles such as silica, ceria and alumina are suspended in a medium to the surface of the polishing pad.
  • the dressing part is equipped with a plate on which industrial diamond particles are electrodeposited, and the surface of the polishing pad with reduced polishing characteristics is reclaimed by scraping off the part to which polishing debris has adhered.
  • the CMP device rotates the rotating platen and the carrier by a rotary drive mechanism, supplies slurry to the approximate center of the polishing pad, and moves the silicon wafer and polishing pad relatively. Polish the silicon wafer processing surface.
  • Fumed silica or colloidal silica is used as a raw material for silica slurry. Although fumed silica has a higher purity than colloidal silicide, it can produce silica slurries with less impurities, but has high cohesiveness, and it is difficult to achieve high dispersion in a medium.
  • An object of the present invention is to provide a method for producing a polishing composition having excellent dispersion stability and a small amount of aggregated particles. Is to provide the law.
  • the present invention provides a first step of preparing an acidic fumed silica dispersion
  • the polishing composition obtained after the completion of the mixing with the fumed silica dispersion is added to the basic substance aqueous solution prepared so as to have a predetermined pH and a silica concentration, and the fumed silica dispersion is added. And a second step of mixing.
  • the present invention is characterized in that the basic substance aqueous solution is prepared so that the polishing composition has a pH of 8 to 12 and a silica concentration of 10 to 30% by weight.
  • the present invention is characterized in that the specific surface area of the fumed silica is 50 to 200 m 2 Zg.
  • the present invention is also characterized in that the basic substance aqueous solution contains at least one of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide.
  • an acidic fumed silica dispersion is prepared.
  • the specific surface area of the fumed silica used is preferably 50 to 200 m 2 / g.
  • an aqueous solution of a basic substance is prepared.
  • the concentration and volume of the aqueous solution of the basic substance are adjusted by mixing with the fumed silica dispersion prepared in the first step so that the pH of the intended polishing composition is 8 to 12, It is adjusted to be 10 to 30% by weight.
  • the basic substance aqueous solution contains at least one of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide.
  • an aqueous solution of a basic substance is added to the fumed silica dispersion, but in the present invention, the fumed silica dispersion is added to the prepared aqueous solution of the basic substance.
  • the aqueous solution of the basic substance is in excess, so that the mixture is strongly alkaline and pH shock occurs.
  • the very low silica concentration prevents the occurrence of agglomeration.
  • the silica concentration of the mixed solution increases, but the alkalinity of the mixed solution is weakened by adding the fumed silica dispersion. Therefore, the pH shock is weak, and the occurrence of aggregation is suppressed.
  • the first step includes:
  • Fumed silica is introduced into water whose pH is adjusted to 1.0 to 2.7 so that the initial silica concentration is 46 to 54% by weight, and a high shearing force is applied to disperse the fumed silica dispersed liquid.
  • fumed silica is first introduced into water whose pH is adjusted to 1.0 to 2.7 so that the initial silica concentration is 46 to 54% by weight, and high shearing force is applied. To prepare a fumed silica dispersion. By adjusting the pH to 1.0 to 2.7, a high shearing force can be efficiently applied, and the dispersibility can be improved.
  • silica concentration is 33 to 44% by weight.
  • the mixing of the fumed silica dispersion and the aqueous solution of the basic substance be completed in less than 5 hours.
  • the mixing of the fumed silica dispersion with the aqueous solution of the basic substance is completed in less than 5 hours.
  • the pH of the mixed solution can be rapidly reduced, and the time during which the pH conditions under which the fumed silica is likely to aggregate can be shortened to suppress the occurrence of aggregation.
  • the present invention is characterized in that the polishing composition obtained in the second step further includes a third step of performing a filtration treatment using a filter having a filtration accuracy of 1 to 4 / im. Sign.
  • the polishing composition obtained in the second step is subjected to a filtration treatment using a filter having a filtration accuracy of 1 to 4 / im.
  • the polishing composition obtained in the second step has a small amount of aggregates, it is possible to efficiently remove the aggregates by using a filter having a filtration accuracy of 1 to 4 ⁇ m. it can.
  • FIG. 1 is a flowchart according to an embodiment of the present invention.
  • FIG. 2 is a graph showing the effect of pH on the aggregate particle growth rate.
  • FIG. 3 is a graph showing the effect of the initial silica concentration of the silica dispersion on the particle size distribution of the silica slurry.
  • Figure 4 is a graph showing the effect of silica concentration on the number of coarse particles in the silica slurry.
  • FIG. 5 is a graph showing the influence of mixing conditions on the particle size distribution of silica slurry.
  • FIG. 6 is a graph showing the effect of the pouring time of the slurry dispersion on the particle size distribution of the silica slurry.
  • FIG. 7 is a graph showing the effect of the charging rate of the silica dispersion on the pH of the mixed solution.
  • FIG. 8 is a diagram showing the influence of the filtration accuracy of the filter on the performance of removing coarse particles.
  • FIG. 9 is a diagram showing the influence of the filter precision on the processing flow rate.
  • FIG. 10 is a graph showing the number of coarse particles included in Comparative Examples 1 and 2 and Example 1.
  • FIG. 11 is an external view schematically showing the CMP apparatus 100. As shown in FIG. 11
  • FIG. 12 is a cross-sectional view of the carrier section 122.
  • FIG. 13 is a diagram showing the results of the polishing process using Example 1 and Comparative Examples 1 and 2.
  • the method for producing silica slurry has two main steps.
  • the first step is a step of preparing an acidic silica dispersion
  • the second step is a step of mixing the silica dispersion and an aqueous solution of a basic substance.
  • an acid such as hydrochloric acid is added to ultrapure water to make it acidic, for example, pH2, and fumed silica is added thereto while applying a shearing force to produce a dispersion.
  • an aqueous alkaline solution such as potassium hydroxide is dropped and mixed while stirring the silica dispersion.
  • silica agglomerates are generated due to the pH shock when the pH of the silylation dispersion changes from acidic to alkaline.
  • the silica in the state of the silica dispersion, the silica is in a high concentration, so that aggregation is more likely to occur.
  • a silica slurry having excellent dispersion stability can be produced by improving the conditions for preparing the silylic dispersion and the mixing conditions of the silylic dispersion and the aqueous solution.
  • FIG. 1 is a flowchart showing an embodiment of the present invention.
  • the first step will be described in detail.
  • the first step consists of smaller steps.
  • step 1-1 the pH of ultrapure water is adjusted to 1.0 to 2.7, and a specific surface area of 50 to 20 Om 2 / g is applied while applying a shearing force with a high-shear dispersion device.
  • the fumed silica powder is charged until the initial silica concentration reaches 46 to 54% by weight, and a shearing force is applied for 1 to 5 hours with a high shear disperser.
  • step 112 a small amount of ultrapure water is added to the silica dispersion so that the silica concentration becomes 45 to 53% by weight, and a shearing force is applied for 10 to 40 minutes.
  • step 1-3 ultrapure water is added to the silica dispersion so that the silica concentration is 33 to 44% by weight, and a shearing force is applied for 0.5 to 4 hours.
  • the first step a high shear force is applied, and the viscosity of the silica dispersion liquid can be sufficiently reduced by adding ultrapure water in step 1-2.
  • the second step will be described.
  • Step 2-1 the silica dispersion is added to the basic substance aqueous solution prepared so that the pH after mixing becomes 8 to 12 and the silica concentration becomes 10 to 30% by weight.
  • the generation of aggregates during mixing can be suppressed by adding the silica dispersion to the aqueous solution of the basic substance. This is for the following reason.
  • the pH of the mixed solution is strongly alkaline, ie, 12 to 14, due to an excess of the aqueous solution of the basic substance, and a pH shock occurs.
  • the silicon concentration is very low, the occurrence of aggregation is suppressed.
  • the silica concentration of the mixture increases, but the introduction of the silica dispersion causes the mixture to have a weak alkaline pH of 8 to 12 so that the pH shock is weak and the occurrence of aggregation is suppressed. Is done. Further, it is desirable to charge all the silica dispersions within 5 hours.
  • the pH of the aqueous solution of the basic substance is 12 to 14, which is the pH range where the surface of the fumed silica elutes. Therefore, by quickly feeding the silica dispersion, it is possible to quickly shift to ⁇ 8 to 12 which is a dispersion stable region of silica particles.
  • the generation of aggregates during mixing can be suppressed by adding the silica dispersion to the aqueous solution of the basic substance.
  • the silica slurry obtained through the first and second steps has few aggregates and low viscosity, the aggregates can be effectively removed by the filter.
  • step 3-1 filtration is performed using a filter with a filtration accuracy of 1 to 4 ⁇ m.
  • processing can be performed at a flow rate of 2 to 101 / min, and coarse particles can be removed while maintaining a sufficient processing flow rate.
  • silica slurry was prepared under the conditions that H was 2, 3, and 7, respectively.
  • the conditions other than pH were all the same.
  • FIG. 2 is a graph showing the effect of pH on the aggregate particle growth rate.
  • the vertical axis shows the growth rate of the aggregated particles, and the horizontal axis shows the shaking time.
  • Shaking experiments were performed to examine the dispersion stability of the silica slurry.
  • Shaking experiment Put the prepared silica slurry in a centrifuge tube with a volume of 5 O m 1, place it in a vertical shaker, shake it at a shaking speed of 310 spm (stroke per minute) and a shaking stroke of 40 mm. After a predetermined time has elapsed, remove the centrifuge tube and use a particle size distribution analyzer (HOR
  • the median particle size of the silica slurry was measured using IB A model LA-910).
  • the growth rate of the aggregated particles was calculated by ((median particle diameter after shaking ⁇ median particle diameter before shaking)) Median particle diameter before shaking X 100 (%).
  • Line 1 1 indicates the case of pH 2
  • Line 1 2 indicates the case of pH 3
  • the growth rate was about 18%, and in the case of pH 7, the growth rate was about 88% after 10 days, indicating that aggregation occurred. This is thought to be because the isoelectric point of the fumed Siri force is near pH 2, and the particle surface becomes electrically neutral at pH 2, and high shear force is likely to be applied. -From the above, it was found that the pH of the silica dispersion is preferably in the range of 1 to 2.7.
  • silica slurries were prepared under the conditions of an initial silica concentration of 45% by weight, 50% by weight, 55% by weight, and 60% by weight, respectively.
  • the conditions other than the initial silica concentration were all the same.
  • FIG. 3 is a graph showing the effect of the initial concentration of the silicic acid dispersion on the particle size distribution of the silica slurry.
  • the vertical axis indicates frequency, and the horizontal axis indicates particle size.
  • Curve 14 shows the case where the initial silica concentration is 45% by weight
  • curve 15 shows the case where the initial silica concentration is 50% by weight
  • curve 16 shows the case where the initial silica concentration is 55% by weight.
  • the curve 17 shows the case where the silica concentration is 60% by weight.
  • the particle size distribution of the silica slurry shifts to the left as the initial silica concentration increases, indicating that the higher the initial silica concentration, the higher the dispersibility.
  • the initial silica concentration is as low as 45% by weight, it is considered that the dispersibility is low because the shear force of the high shear disperser was not sufficiently transmitted. Also 55% by weight In the case of and 60% by weight, the shearing force is sufficiently transmitted, so that the dispersibility is high. However, it is not appropriate because the viscosity of the slurry dispersion increases and the load on the dispersing machine is large.
  • the initial silicic acid concentration was 50% by weight, it was found that the load on the disperser was small and the dispersibility was high.
  • the initial silica concentration of the silica dispersion was preferably 46 to 54% by weight.
  • silica slurries were prepared under the conditions of addition and non-addition. The conditions were the same except for the addition of ultrapure water.
  • the median particle diameter of the silica slurry was larger than when the addition was not performed.
  • the shearing force is more easily transmitted when the concentration of the shearing force is higher, the dispersibility when not added is reduced, and the viscosity of the silica slurry is increased by about 4%. From the above, it was found that it is preferable to add a small amount of ultrapure water to the silica dispersion to make the silica concentration 45 to 53% by weight.
  • silica slurry was prepared under the conditions of 32% by weight, 40% by weight, 45% by weight, and 49% by weight (without addition of ultrapure water). The conditions other than the silicide concentration were all the same.
  • Figure 4 is a graph showing the effect of silicide concentration on the number of coarse particles in silica slurry. The vertical axis indicates the number of coarse particles, and the horizontal axis indicates the particle diameter.
  • Curve 18 shows the case where the silica concentration is 32% by weight
  • curve 19 shows the case where the silica concentration is 40% by weight
  • curve 20 shows the case where the silica concentration is 45% by weight
  • curve 2 1 shows the case where the silica concentration is 49% by weight.
  • Particles having a particle size larger than 0.5 ⁇ m were regarded as coarse particles, and the number of particles having each particle size was counted.
  • the silica concentration was 40% by weight
  • the number of coarse particles was the smallest compared to the case where the silica concentration was 32% by weight, 45% by weight, and 49% by weight. This is probably because the viscosity at 40% by weight is most efficiently applied with the shearing force of the disperser. According to When the silica concentration is 32% by weight, the viscosity is low, and the weight is 45%. /. , 49% by weight is considered too viscous.
  • the silica concentration of the silica dispersion liquid was preferably 33 to 44% by weight.
  • the basic substance aqueous solution is added to the silica dispersion (first mixing condition) and the silica dispersion is added to the basic substance aqueous solution
  • first mixing condition the silica dispersion
  • second mixing conditions Potassium hydroxide was used as the basic substance. All conditions other than the mixing conditions were the same.
  • FIG. 5 is a graph showing the effect of mixing conditions on the particle size distribution of silica slurry.
  • the vertical axis indicates frequency, and the horizontal axis indicates particle size.
  • Curves 22 a and 22 b show the case of the first mixing condition, and curve 23 shows the case of the second mixing condition.
  • the pH shock is large and aggregates are easily generated.
  • a peak due to aggregates was observed at around 10 ⁇ m.
  • a sharp peak was observed near the particle diameter of 0.1 ⁇ m, indicating that the dispersibility was improved.
  • the median particle size of the silica slurry was also measured.
  • the median particle diameter of the silica dispersion before mixing was 110 nm.
  • the median particle size of the silica slurry when the silicic acid dispersion and the aqueous hydroxide solution were mixed under the first mixing condition was 808 nm, and very large aggregates were present.
  • the median particle diameter of the silica slurry when mixed under the second mixing condition was found to be 110 nm and hardly aggregated. From the above, it was found that when mixing a silica dispersion and a basic substance aqueous solution, it is better to add the silica dispersion to the basic substance aqueous solution.
  • silica slurry was prepared under the respective conditions of charging all the silica dispersion in 5 hours and charging the silica dispersion in 20 minutes. .
  • the basic substance is hydroxylated Was used. The conditions other than the charging time were all the same.
  • FIG. 6 is a graph showing the effect of the charging time of the silica dispersion on the particle size distribution of the silica slurry.
  • the vertical axis indicates frequency, and the horizontal axis indicates particle size.
  • Curve 24 shows the case where the charging time is 5 hours, and curve 24 shows the case where the charging time is 20 minutes.
  • FIG. 7 is a graph showing the effect of the charging rate of the silica dispersion liquid on the pH of the mixed liquid.
  • the vertical axis indicates the pH of the mixed solution, and the horizontal axis indicates the charging time of the silica dispersion.
  • Curve 26 shows the case where the charging speed is 25 1 / min
  • curve 27 shows the case where the charging speed is 12.5 1 / min
  • curve 28 shows the case where the charging speed is 51 / min. Is shown.
  • the pH of the mixed solution can be quickly reduced to pH 12 or less, which is the stable region of silica.
  • Step 3-1 filtration was performed under the conditions of filtration accuracy of 1 ⁇ m, 3 / xm, 5 ⁇ 7 ⁇ m and 10 ⁇ m.
  • a depth-type filter with a small pressure loss and a large flow rate was used as the filter.
  • FIG. 8 is a diagram showing the influence of the filtration accuracy of the filter on the performance of removing coarse particles.
  • the vertical axis shows the number of coarse particles in the silica slurry, and the figure shows the number of coarse particles before filtration and the number of coarse particles after filtration.
  • Line 29 shows the change in the number of particles when the filtration accuracy is 1 ⁇ m
  • line 30 shows the change in the number of particles when the filtration accuracy is 3 / m
  • line 31 shows the change when the filtration accuracy is 5 ⁇ m
  • the line 32 shows the change in the number of particles when the filtration accuracy is 7 ⁇ m
  • the line 33 shows the change in the number of particles when the filtration accuracy is 10 ⁇ m. 2 shows the change in the number of particles in the case of FIG.
  • the filtration accuracy is 5 ⁇ , 7 zm N 10 ⁇ m
  • the filtration accuracy is as large as the coarse particles, so the number of coarse particles after the filtration process hardly changes, and sufficient filtration performance can be obtained. Did not.
  • the filtration accuracy was 1 ⁇ , 3 / im, the number of coarse particles after the filtration treatment was significantly reduced.
  • FIG. 9 is a diagram showing the influence of the filtration accuracy of the filter on the processing flow rate.
  • the vertical axis shows the processing flow rate of the filtration process, and the figure shows the processing flow rate at each filtration accuracy.
  • Symbol 74 indicates the flow rate when the filtration accuracy is 1 / m
  • symbol 75 indicates the flow rate when the filtration accuracy is 3 ⁇ m
  • symbol 76 indicates the flow rate when the filtration accuracy is 5 ⁇ m.
  • the symbol 77 indicates the flow velocity when the filtration accuracy is 7 ⁇ m
  • the symbol 78 indicates the flow velocity when the filtration accuracy is 10 ⁇ m.
  • the processing flow rate at this time is 2-101 Zmin.
  • Example 1 comparison results between a conventional silica slurry manufactured based on the conventional technology and a silica slurry manufactured based on the present invention (hereinafter, referred to as “Example 1”) will be described.
  • the first conventional silica slurry (hereinafter referred to as “Comparative Example 1”) was manufactured based on the manufacturing method described in Japanese Patent No. 2953125, and the second conventional silica slurry was used. (Hereinafter, referred to as “Comparative Example 2”) was prepared so that the silica concentration was lower than that of the first conventional silica slurry, and the viscosity was almost the same as that of the silica slurry prepared based on the present invention.
  • Example 1 was produced by the following procedure.
  • FIG. 10 is a graph showing the number of coarse particles included in Comparative Examples 1 and 2 and Example 1.
  • the vertical axis indicates the number of coarse particles, and the horizontal axis indicates the particle diameter.
  • Curve 39 shows Example 1
  • curve 40 shows Comparative Example 1
  • curve 41 shows Comparative Example 2.
  • Example 1 It was found that the number of coarse particles in Example 1 was significantly reduced as compared with Comparative Examples 1 and 2.
  • Table 1 shows the comparison results of the three types of silica slurries for the number of coarse particles and other physical properties.
  • Example 1 As shown in Table 1, in Example 1, the median particle diameter was small and the viscosity was low despite the high silica concentration.
  • FIG. 11 is an external view schematically showing the CMP apparatus 100.
  • the CMP apparatus 100 includes a polishing pad 101, a rotary platen section 121, a carrier section 122, a slurry supply section 123, and a dressing section 124.
  • the polishing pad 1 is pressed against the silicon wafer held by the carrier 122 of the CMP apparatus 100 and polishes the surface of the silicon wafer by relative movement with respect to the silicon wafer.
  • the rotating platen unit 121 includes a platen 102 that supports the polishing pad 101 by applying an adhesive tape or the like over substantially the front surface of the upper surface, and a rotating shaft provided on the lower surface side of the platen 102. And a rotation drive mechanism 103 connected through the support means. The rotation driving force of the rotation drive mechanism 103 is transmitted to the surface plate 102 through a rotation shaft, and the surface plate 102 rotates around the vertical axis at a predetermined rotation speed together with the polishing pad 101.
  • the number of rotations can be set freely, and an appropriate number of rotations is selected according to the type of wafer to be polished, the type of film, the type of polishing pad 1, and the like.
  • the carrier section 122 includes a carrier body 104, a backing material 105, a retainer ring 106, and a rotation drive mechanism 107.
  • This is a holding means for holding a silicon wafer 108 as a polished object and rotating in a state in which the polishing pad 1 • 1 and the silicon wafer 108 are pressed against each other.
  • the fixing of the silicon wafer 108 to the carrier body 104 is performed by moistening the knocking material 105 and adsorbing it by the surface tension of water.
  • the outer periphery of the silicon wafer 108 is held by a retainer ring 106 so that the silicon wafer 108 does not come off during the polishing process.
  • the rotation drive mechanism 107 is connected to the upper surface side of the carrier main body 104 via a rotation shaft.
  • the rotation driving force of the rotation drive mechanism 107 is transmitted to the carrier main body 104 through the rotation shaft, and the carrier main body 104 rotates around the vertical axis at a predetermined rotation speed together with the silicon wafer 108. .
  • the number of revolutions can be set freely.Similar to the rotating platen section 121, the appropriate number of revolutions depends on the type of wafer and film to be polished, the type of polishing pad 101, etc. Is selected.
  • the carrier portion 122 is pressed vertically downward in a direction approaching the rotating platen portion 121, and the polishing pad 101 and the silicon wafer 108 are pressed against each other.
  • the pressurization of the carrier section 122 may be performed by the rotation drive mechanism 107 or a separate pressurization mechanism may be used.
  • the slurry supply section 123 is a supply means including a nozzle 109, a slurry supply pipe 110, and a slurry tank 111.
  • the silica slurry stored in the slurry tank 1 1 1 by a pump or the like is flowed into the slurry supply pipe 1 10 and polished from the nozzle 1 0 9 installed at the upper part and approximately in the center of the rotary platen 12 1.
  • the pad 101 is supplied at a predetermined flow rate to the surface.
  • Example 1 and Comparative Examples 1 and 2 were used as the silica slurry to be supplied.
  • the dressing section 124 consists of a plate 112 on which industrial diamond particles, which are conditioners, are electrodeposited, and a rotary drive mechanism 113 connected to the plate 112 via a rotating shaft. Means. At the time of dressing, the rotating drive mechanism 113 rotates the plate 112 to bring the diamond particles into contact with the polishing surface of the polishing pad 101 and scrape off the clogged portion, thereby polishing the polishing pad 101. Play characteristics.
  • the carrier supply unit 122 is pressurized vertically downward and the slurry supply unit 123 is pressed while the polishing pad 101 and the silicon wafer 108 are pressed against each other.
  • Supply silica slurry The supplied silica slurry penetrates between the polishing pad 101 and the silicon wafer 108, and rotates and relatively moves the rotating platen unit 121 and the carrier unit 122, thereby forming a chemical by the medium.
  • the surface of the silicon wafer 108 is polished with high precision by the action and the mechanical action of the abrasive grains.
  • the carrier part 122 is arranged so that the center of the carrier part 122 is approximately 1/2 in the radial direction from the rotation center of the rotary platen part 121.
  • the polishing process is performed only by the rotation of the rotating platen section 122 and the carrier section 122.
  • the rotation directions of the rotating platen section 122 and the carrier section 122 may be the same or different. Further, the rotation rotation speeds of the rotating platen section 122 and the carrier section 122 may be the same or different.
  • the dressing by the dressing unit 124 may be performed after polishing one or more silicon wafers, or may be performed during the polishing process. Since the radius of the diamond plate 1 12 of the dressing section 124 is often smaller than the radius of the polishing pad 101, when dressing is performed after the polishing process, the above-described rotary platen section 121 and the carrier are used. Pattern of relative movement with part 1 22 (2) and
  • the polishing is performed during the polishing process, as shown in the figure, it is arranged on the opposite side of the carrier 122 from the center of the rotating platen 121, and the operation is performed in substantially the same manner as the relative movement pattern (2). Just do it.
  • Polishing was performed using the CMP apparatus 100 as described above.
  • a T EOS wafer was used as the object to be polished, and IC 1400 K—Groov e (manufactured by Rodel Nitta) was used as the polishing pad 101.
  • the rotation speed of the rotary platen section 121 was 60 rpm, and the silica slurry was supplied at a speed of 100 ml / min. After polishing for 1 minute, the number of scratches (size of 0.2 xm or more) on the wafer surface was counted using a wafer surface inspection device (LS6600) manufactured by Hitachi Electronics Engineering.
  • FIG. 13 is a diagram showing the results of the polishing process using Example 1 and Comparative Examples 1 and 2.
  • the vertical axis indicates the number of scratches per wafer.
  • Example 1 and Comparative Example Each of 1 and 2 was polished three times.
  • the silica slurry manufactured according to the present invention has high dispersibility and a small number of coarse agglomerated particles, so that the number of scratches on the wafer surface can be reduced in the polishing process.
  • a polishing composition excellent in dispersion stability and containing few aggregated particles can be obtained by adding a fumed sili-cide dispersion to the prepared basic substance aqueous solution.
  • the viscosity of the polishing composition can be reduced by adding a small amount of water.
  • the pH of the mixed solution is rapidly reduced, and the time during which the pH conditions under which the fumed silica easily aggregates is shortened, thereby suppressing the occurrence of aggregation. can do.
  • the polishing composition obtained in the second step since the polishing composition obtained in the second step generates few aggregates, the aggregates can be efficiently removed by filtration.

Abstract

A process for producing a polishing composition excelling in dispersion stability wherein the amount of agglomerated particles is reduced. In step 1-1 thereof, ultrapure water is adjusted so as to have a pH value of 1.0 to 2.7. Under shearing force given by a high shear disperser, fumed silica powder of 50 to 200 m2/g specific surface area is charged therein until an initial silica concentration of 46 to 54 wt.%, and the high shear disperser is operated so as to apply shearing force for 1 to 5 hr. In step 1-2, a small amount of ultrapure water is added to the silica dispersion so as to realize a silica concentration of 45 to 53 wt.% and shearing force is applied for 10 to 40 min. In step 1-3, ultrapure water is added to the silica dispersion so as to realize a silica concentration of 33 to 44 wt.% and shearing force is applied for 0.5 to 4 hr. In step 2-1, the silica dispersion is added to an aqueous solution of basic substance prepared so that the pH value after mixing is in the range of 8 to 12 and so that the silica concentration is in the range of 10 to 30 wt.%.

Description

明 細 書  Specification
研磨用組成物の製造方法  Method for producing polishing composition
【技術分野】  【Technical field】
本発明は、 半導体製造工程のうちの研磨工程に用いられる研磨用組成物の製造 方法に関する。  The present invention relates to a method for producing a polishing composition used in a polishing step of a semiconductor production step.
【背景技術】  [Background Art]
半導体製造の分野では、 半導体素子の微細化および多層化による高集積化に伴 い、 半導体層や金属層の平坦化技術が重要な要素技術となっている。 ウェハに集 積回路を形成する際、 電極配線などによる凹凸を平坦化せずに層を重ねると、 段 差が大きくなり、 平坦性が極端に悪くなる。 また段差が大きくなった場合、 フォ トリソグラフィにおいて凹部と凸部の両方に焦点を合わせることが困難になり微 細化を実現することができなくなる。 したがって、 積層中の然るべき段階でゥェ ハ表面の凹凸を除去するための平坦化処理を行う必要がある。 平坦化処理には、 エッチングにより凹凸部を除去するエッチバック法、 プラズマ C V D (Chemical Vapor Deposition) などにより平坦な膜を形成する成膜法、 熱処理によって平坦 化する流動化法、 選択 C V Dなどにより凹部の埋め込みを行う選択成長法などが め 。  In the field of semiconductor manufacturing, flattening technology for semiconductor layers and metal layers has become an important elemental technology as semiconductor devices become finer and more integrated due to their multilayer structure. When forming an integrated circuit on a wafer, if layers are stacked without flattening irregularities due to electrode wiring, etc., the steps will increase and flatness will be extremely poor. In addition, when the step becomes large, it becomes difficult to focus on both the concave portion and the convex portion in photolithography, and it becomes impossible to realize miniaturization. Therefore, it is necessary to perform a planarization process for removing irregularities on the wafer surface at an appropriate stage during lamination. For the planarization process, an etch-back method that removes unevenness by etching, a film formation method that forms a flat film by plasma CVD (Chemical Vapor Deposition), a fluidization method that planarizes by heat treatment, and a recess by selective CVD. The selective growth method for embedding is used.
以上の方法は、 絶縁膜、 金属膜など膜の種類によって適否があることや平坦化 できる領域がきわめて狭いという問題がある。 このような問題を克服することが できる平坦化処理技術として C M Pによる平坦化がある。  The above methods have problems in that they are appropriate depending on the type of film, such as an insulating film and a metal film, and that the region to be planarized is extremely narrow. As a planarization processing technique that can overcome such problems, there is planarization by CMP.
C M Pによる平坦化処理では、 微細な粒子 （砥粒） を懸濁したスラリを研磨パ ッド表面に供給しながら、 圧接した研磨パッドとシリコンウェハとを相対移動さ せて表面を研磨することにより、 広範囲にわたるウェハ表面を高精度に平坦化す ることができる。  In the planarization process by CMP, a slurry in which fine particles (abrasive grains) are suspended is supplied to the surface of the polishing pad, and the surface is polished by moving the pressed polishing pad and the silicon wafer relatively. A wide range of wafer surfaces can be flattened with high precision.
C M Pによる平坦化を行う C M P装置は、 主に回転定盤部、 キャリア部、 スラ リ供給部およびドレッシング部から構成される。 回転定盤部は、 その上面に粘着 テープなどで研磨パッ ドが貼り付けられ、 下面側は、 回転駆動機構と、 回転軸を 介して接続される。 キャリア部は、 その下面にバッキング材およびリテーナリン グによって被研磨物であるシリコンウェハを保持し、 シリコンウェハの加工面を 研磨パッドに圧接させる。 上面側は、 回転駆動機構と、 回転軸を介して接続され る。 A CMP device that performs planarization by CMP is mainly composed of a rotating platen section, a carrier section, a slurry supply section, and a dressing section. A polishing pad is attached to the upper surface of the rotary platen with an adhesive tape or the like, and the lower surface is connected to a rotary drive mechanism via a rotary shaft. The carrier part has a backing material and a retainer The silicon wafer, which is the object to be polished, is held by polishing, and the processed surface of the silicon wafer is pressed against the polishing pad. The upper surface is connected to a rotation drive mechanism via a rotation shaft.
スラリ供給部は、 シリカ、 セリアおょぴアルミナなどの粒子を媒体に懸濁させ たスラリを研磨パッドの表面に供給する。 ドレッシング部は、 産業用ダイヤモン ド粒子を電着したプレートを備え、 研磨屑などが付着した部分を削り取ることで、 研磨特性が低下した研磨パッドの表面を再生する。  The slurry supply unit supplies a slurry in which particles such as silica, ceria and alumina are suspended in a medium to the surface of the polishing pad. The dressing part is equipped with a plate on which industrial diamond particles are electrodeposited, and the surface of the polishing pad with reduced polishing characteristics is reclaimed by scraping off the part to which polishing debris has adhered.
C M P装置は、 回転駆動機構によって回転定盤部おょぴキヤリァ部を回転させ るとともに、 研磨パッ ドの略中央部にスラリを供給し、 シリコンウェハと研磨パ ッドとを相対移動させることでシリコンウェハ加工面の研磨を行う。  The CMP device rotates the rotating platen and the carrier by a rotary drive mechanism, supplies slurry to the approximate center of the polishing pad, and moves the silicon wafer and polishing pad relatively. Polish the silicon wafer processing surface.
近年、 I C (Integrated Circuit) チップのデザインルールが微細化するに伴 い、 スラリに起因してシリコンウェハの被研磨面に生じるマイクロスクラツチが 問題となっている。 マイクロスクラツチの因子としては、 媒体に懸濁させた砥粒 の凝集物または分散不良物として存在する粗大粒子が考えられる。  In recent years, with the miniaturization of design rules for IC (Integrated Circuit) chips, microscratching on the polished surface of silicon wafers due to slurry has become a problem. As a factor of the micro-scratches, coarse particles present as agglomerates or poorly dispersed abrasive grains suspended in a medium can be considered.
シリカスラリの原料には、 ヒュームドシリカまたはコロイダルシリカが用いら れる。 ヒュームドシリカは、 コロイダルシリ力に比べて純度が高いため不純物の 少ないシリカスラリを生成することができるが、 凝集性が高く媒体中への高分散 化を実現するのが困難である。  Fumed silica or colloidal silica is used as a raw material for silica slurry. Although fumed silica has a higher purity than colloidal silicide, it can produce silica slurries with less impurities, but has high cohesiveness, and it is difficult to achieve high dispersion in a medium.
ヒュームドシリカの分散安定性を向上させることを目的とした従来のシリカス ラリの製造方法には特許第 2 9 3 5 1 2 5号公報、 特許第 2 9 4 9 6 3 3号公報、 特開 2 0 0 1 - 2 6 7 7 1号公報に記載された方法がある。 いずれの方法につい ても、 剪断条件およびシリカ濃度などを規定することで、 安定した分散性を実現 しょうとしている。  Conventional methods for producing silica slurry for improving the dispersion stability of fumed silica include Patent Nos. 2,935,125, 2,964,633, and There is a method described in Japanese Patent Application Laid-Open No. 2000-016767. Regardless of the method, we are trying to achieve stable dispersibility by specifying the shearing conditions and silica concentration.
実際に、 上記の特許文献に記載された製造方法でヒュームドシリカを原料とす るシリカスラリを作製したところシリカの分散性能は不十分であり、 スラリ中に 凝集物が多く存在した。  Actually, when a silica slurry using fumed silica as a raw material was produced by the production method described in the above-mentioned patent document, the dispersing performance of silica was insufficient, and many aggregates were present in the slurry.
【発明の開示】  DISCLOSURE OF THE INVENTION
本発明の目的は、 分散安定性に優れ、 凝集粒子の少ない研磨用組成物の製造方 法を提供することである。 An object of the present invention is to provide a method for producing a polishing composition having excellent dispersion stability and a small amount of aggregated particles. Is to provide the law.
本発明は、 酸性のヒュームドシリカ分散液を調製する第 1工程と、  The present invention provides a first step of preparing an acidic fumed silica dispersion,
前記ヒュームドシリカ分散液との混合終了後に得られる研磨用組成物が、 所定 の p Hおよびシリカ濃度となるように調製した塩基性物質水溶液に対して、 前記 ヒュームドシリカ分散液を添加して混合する第 2工程とを有することを特徴とす る研磨用組成物の製造方法である。  The polishing composition obtained after the completion of the mixing with the fumed silica dispersion is added to the basic substance aqueous solution prepared so as to have a predetermined pH and a silica concentration, and the fumed silica dispersion is added. And a second step of mixing.
また本発明は、 前記研磨用組成物の p Hが 8〜 1 2、 シリカ濃度が 1 0〜3 0 重量％となるように前記塩基性物質水溶液を調製することを特徴とする。  Further, the present invention is characterized in that the basic substance aqueous solution is prepared so that the polishing composition has a pH of 8 to 12 and a silica concentration of 10 to 30% by weight.
また本発明は、 前記ヒュームドシリカの比表面積は、 5 0〜2 0 0 m2Z gであ ることを特徴とする。 Further, the present invention is characterized in that the specific surface area of the fumed silica is 50 to 200 m 2 Zg.
また本発明は、 前記塩基性物質水溶液は、 少なくとも水酸化アンモニゥム、 水 酸化ナトリウム、 水酸化力リウム、 水酸化カルシウム、 水酸化バリゥムまたは水 酸化マグネシゥムのいずれかを含むことを特徴とする。  The present invention is also characterized in that the basic substance aqueous solution contains at least one of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide.
本発明に従えば、 まず第 1工程で、 酸性のヒュームドシリカ分散液を調製する。 なお、 用いるヒュームドシリカの比表面積は、 5 0〜 2 0 0 m2/ gが好ましい。 次に第 2工程で、 塩基性物質水溶液を調製する。 塩基性物質水溶液の濃度およ び体積は、 第 1工程で調整されたヒュームドシリカ分散液との混合によって、 目 的とする研磨用組成物の p Hが 8〜 1 2、 シリ力濃度が 1 0〜3 0重量％となる ように調製する。 なお、 塩基性物質水溶液は、 少なくとも水酸化アンモニゥム、 水酸化ナトリウム、 水酸化カリ ウム、 水酸化カルシウム、 水酸化バリゥムまたは 水酸化マグネシウムのいずれかを含む。 According to the present invention, in the first step, an acidic fumed silica dispersion is prepared. The specific surface area of the fumed silica used is preferably 50 to 200 m 2 / g. Next, in a second step, an aqueous solution of a basic substance is prepared. The concentration and volume of the aqueous solution of the basic substance are adjusted by mixing with the fumed silica dispersion prepared in the first step so that the pH of the intended polishing composition is 8 to 12, It is adjusted to be 10 to 30% by weight. The basic substance aqueous solution contains at least one of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide.
従来の製造方法では、 ヒュームドシリカ分散液に対して塩基性物質水溶液を添 加するが、 本発明では、 調製された塩基性物質水溶液に対して、 ヒュームドシリ 力分散液を添加する。  In the conventional production method, an aqueous solution of a basic substance is added to the fumed silica dispersion, but in the present invention, the fumed silica dispersion is added to the prepared aqueous solution of the basic substance.
ヒュームドシリカ分散液の投入初期は、 塩基性物質水溶液が過剰であるため、 混合液は強いアルカリ性であり、 p Hショ ックが生じる。 しかし、 シリカ濃度が 非常に低いため、 凝集の発生は抑制される。 投入が進むと、 混合液のシリカ濃度 は上昇するが、 ヒュームドシリカ分散液の投入によって混合液のアルカリ性が弱 くなるため、 p Hショ ックが弱く、 凝集の発生が抑制される。 At the initial stage of the introduction of the fumed silica dispersion, the aqueous solution of the basic substance is in excess, so that the mixture is strongly alkaline and pH shock occurs. However, the very low silica concentration prevents the occurrence of agglomeration. As the injection proceeds, the silica concentration of the mixed solution increases, but the alkalinity of the mixed solution is weakened by adding the fumed silica dispersion. Therefore, the pH shock is weak, and the occurrence of aggregation is suppressed.
これにより、 分散安定性に優れ、 凝集裣子の少ない研磨用組成物が得られる。 また本発明は、 前記第 1工程は、  As a result, a polishing composition having excellent dispersion stability and a small amount of coagulated particles can be obtained. Further, in the present invention, the first step includes:
p Hを 1 . 0〜2 . 7に調製した水中に、 初期シリカ濃度が 4 6〜5 4重量％ になるようにヒュームドシリカを投入し、 高剪断力を与えてヒュームドシリ力分 散液を調製する工程と、  Fumed silica is introduced into water whose pH is adjusted to 1.0 to 2.7 so that the initial silica concentration is 46 to 54% by weight, and a high shearing force is applied to disperse the fumed silica dispersed liquid. A step of preparing;
シリカ濃度が 4 5〜5 3重量％になるように、 前記ヒュームドシリカ分散液に 水を添加する工程と、  Adding water to the fumed silica dispersion so that the silica concentration is 45 to 53% by weight;
シリカ濃度が 3 3〜4 4重量％になるように、 前記ヒュームドシリカ分散液に さらに水を添加する工程とを有することを特徴とする。  Adding water to the fumed silica dispersion so that the silica concentration is 33 to 44% by weight.
本発明に従えば、 まず p Hを 1 . 0〜2 . 7に調製した水中に、 初期シリカ濃 度が 4 6〜5 4重量％になるようにヒュームドシリカを投入し、 高剪断力を与え てヒュームドシリカ分散液を調製する。 P Hを 1 . 0〜2 . 7に調製することで、 高剪断力を効率良く与え、 分散性を向上させることができる。 According to the present invention, fumed silica is first introduced into water whose pH is adjusted to 1.0 to 2.7 so that the initial silica concentration is 46 to 54% by weight, and high shearing force is applied. To prepare a fumed silica dispersion. By adjusting the pH to 1.0 to 2.7, a high shearing force can be efficiently applied, and the dispersibility can be improved.
次にシリカ濃度が 4 5〜 5 3重量％になるように、 ヒュームドシリカ分散液に 水を添加する。 少量の水を添加することで研磨用組成畅の粘度を低下させること ができる。  Next, water is added to the fumed silica dispersion so that the silica concentration is 45 to 53% by weight. By adding a small amount of water, the viscosity of the polishing composition 畅 can be reduced.
最後にシリカ濃度が 3 3〜4 4重量％になるように、 さらに水を添加する。 シ リカ濃度を 3 3〜4 4重量％とすることで、 凝集物の発生を抑制することができ る。  Finally, water is further added so that the silica concentration is 33 to 44% by weight. By setting the silica concentration to 33 to 44% by weight, generation of aggregates can be suppressed.
また本発明は、 前記第 2工程は、 5時間未満で前記ヒュームドシリカ分散液と 前記塩基性物質水溶液との混合を終了させることを特徴とする。  Further, in the invention, it is preferable that in the second step, the mixing of the fumed silica dispersion and the aqueous solution of the basic substance be completed in less than 5 hours.
本発明に従えば、 5時間未満で前記ヒュームドシリカ分散液と前記塩基性物質 水溶液との混合を終了させる。 5時間未満で混合を終了させることで、 混合液の p Hを素早く低下させ、 ヒュームドシリカが凝集しやすい p H条件となる時間を 短く して凝集の発生を抑制することができる。  According to the present invention, the mixing of the fumed silica dispersion with the aqueous solution of the basic substance is completed in less than 5 hours. By terminating the mixing in less than 5 hours, the pH of the mixed solution can be rapidly reduced, and the time during which the pH conditions under which the fumed silica is likely to aggregate can be shortened to suppress the occurrence of aggregation.
また本発明は、 前記第 2工程で得られた研磨用組成物に対して、 濾過精度が 1〜4 /i mのフィルタを用いて濾過処理を行う第 3工程をさらに有することを特 徴とする。 Further, the present invention is characterized in that the polishing composition obtained in the second step further includes a third step of performing a filtration treatment using a filter having a filtration accuracy of 1 to 4 / im. Sign.
本発明に従えば、 第 3工程において、 第 2工程で得られた研磨用組成物に対し て、 濾過精度が 1〜4 /i mのフィルタを用いて濾過処理を行う。  According to the present invention, in the third step, the polishing composition obtained in the second step is subjected to a filtration treatment using a filter having a filtration accuracy of 1 to 4 / im.
上記のように、 第 2工程で得られた研磨用組成物は凝集物の発生が少ないため、 濾過精度が 1〜 4 μ mのフィルタを用いることで、 効率良く凝集物を除去するこ とができる。  As described above, since the polishing composition obtained in the second step has a small amount of aggregates, it is possible to efficiently remove the aggregates by using a filter having a filtration accuracy of 1 to 4 μm. it can.
【図面の簡単な説明】  [Brief description of the drawings]
本発明の目的、 特色、 および利点は、 下記の詳細な説明と図面とからより明確 になるであろう。  The objects, features and advantages of the present invention will become more apparent from the following detailed description and drawings.
図 1は、 発明の実施の一形態であるフローチヤ一トである。  FIG. 1 is a flowchart according to an embodiment of the present invention.
図 2は、 凝集粒子成長率に対する p Hの影響を示すグラフである。  FIG. 2 is a graph showing the effect of pH on the aggregate particle growth rate.
図 3は、 シリカスラリの粒度分布に対するシリカ分散液の初期シリカ濃度の影 響を示すグラフである。  FIG. 3 is a graph showing the effect of the initial silica concentration of the silica dispersion on the particle size distribution of the silica slurry.
図 4は、 シリカスラリ中の粗大粒子数に対するシリカ濃度の影響を示すグラフ C?ある。  Figure 4 is a graph showing the effect of silica concentration on the number of coarse particles in the silica slurry.
図 5は、 シリカスラリの粒度分布に対する混合条件の影饗を示すグラフである。 図 6は、 シリカスラリの粒度分布に対するシリ力分散液の投入時間の影響を示 すグラフである。  FIG. 5 is a graph showing the influence of mixing conditions on the particle size distribution of silica slurry. FIG. 6 is a graph showing the effect of the pouring time of the slurry dispersion on the particle size distribution of the silica slurry.
図 7は、 混合液の p Hに対するシリカ分散液の投入速度の影響を示すグラフで め 。  FIG. 7 is a graph showing the effect of the charging rate of the silica dispersion on the pH of the mixed solution.
図 8は、 粗大粒子の除去性能に対するフィルタの濾過精度の影響を示す図であ る。  FIG. 8 is a diagram showing the influence of the filtration accuracy of the filter on the performance of removing coarse particles.
図 9は、 処理流速に対するフィルタの滤過精度の影響を示す図である。  FIG. 9 is a diagram showing the influence of the filter precision on the processing flow rate.
図 1 0は、 比較例 1および 2と、 実施例 1に含まれる粗大粒子数を示すグラフ である。  FIG. 10 is a graph showing the number of coarse particles included in Comparative Examples 1 and 2 and Example 1.
図 1 1は、 C M P装置 1 0 0の概略を示す外観図である。  FIG. 11 is an external view schematically showing the CMP apparatus 100. As shown in FIG.
図 1 2は、 キャリア部 1 2 2の断面図である。  FIG. 12 is a cross-sectional view of the carrier section 122.
図 1 3は、 実施例 1および比較例 1， 2を用いた研磨処理結果を示す図である。 【発明を実施するための最良の形態】 FIG. 13 is a diagram showing the results of the polishing process using Example 1 and Comparative Examples 1 and 2. BEST MODE FOR CARRYING OUT THE INVENTION
以下図面を参考にして本発明の好適な実施例を詳細に説明する。  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
シリカスラリの製造方法は、 大きく分けて 2つの工程を有する。 第 1の工程は、 酸性のシリカ分散液を作製する工程であり、 第 2の工程は、 シリカ分散液と塩基 性物質の水溶液とを混合する工程である。  The method for producing silica slurry has two main steps. The first step is a step of preparing an acidic silica dispersion, and the second step is a step of mixing the silica dispersion and an aqueous solution of a basic substance.
第 1の工程では、 塩酸などの酸を超純水に添加して酸性、 たとえば p H 2とし、 これに剪断力を与えながらヒュームドシリカを投入して分散液を作製する。  In the first step, an acid such as hydrochloric acid is added to ultrapure water to make it acidic, for example, pH2, and fumed silica is added thereto while applying a shearing force to produce a dispersion.
第 2の工程では、 シリカ分散液を撹拌しながら、 水酸化カリウムなどのアル力 リ性水溶液を滴下して混合する。  In the second step, an aqueous alkaline solution such as potassium hydroxide is dropped and mixed while stirring the silica dispersion.
第 2の工程では、 シリ力分散液の p Hが酸性からアル力リ性に変化するときの p Hショ ックによって、 シリカ凝集物が発生する。 特に、 シリカ分散液の状態で はシリカが高濃度であるため、 より凝集が発生しやすくなっている。  In the second step, silica agglomerates are generated due to the pH shock when the pH of the silylation dispersion changes from acidic to alkaline. In particular, in the state of the silica dispersion, the silica is in a high concentration, so that aggregation is more likely to occur.
本発明では、 シリ力分散液の作製条件およびシリ力分散液とアル力リ水溶液と の混合条件を改良することで、 分散安定性に優れたシリカスラリを製造すること ができる。  In the present invention, a silica slurry having excellent dispersion stability can be produced by improving the conditions for preparing the silylic dispersion and the mixing conditions of the silylic dispersion and the aqueous solution.
図 1は、 本発明の実施の一形態であるフローチャートである。  FIG. 1 is a flowchart showing an embodiment of the present invention.
まず、 第 1の工程について詳細に説明する。 第 1の工程はさらに小さなステツ プからなる。  First, the first step will be described in detail. The first step consists of smaller steps.
ステップ 1— 1では、 超純水の p Hを 1 . 0〜2 . 7に調製し、 高剪断分散装 置で剪断力を与えながら、 5 0〜 2 0 O m 2 / gの比表面積を有するヒュームド シリカパウダーを、 初期シリカ濃度が 4 6〜5 4重量％になるまで投入し、 高剪 断分散装置で 1〜 5時間剪断力を与える。 In step 1-1, the pH of ultrapure water is adjusted to 1.0 to 2.7, and a specific surface area of 50 to 20 Om 2 / g is applied while applying a shearing force with a high-shear dispersion device. The fumed silica powder is charged until the initial silica concentration reaches 46 to 54% by weight, and a shearing force is applied for 1 to 5 hours with a high shear disperser.
ステップ 1一 2では、 シリカ濃度が 4 5〜5 3重量％になるように、 シリカ分 散液に少量の超純水を添加し、 1 0〜4 0分間剪断力を与える。  In step 112, a small amount of ultrapure water is added to the silica dispersion so that the silica concentration becomes 45 to 53% by weight, and a shearing force is applied for 10 to 40 minutes.
ステップ 1— 3では、 シリカ濃度が 3 3〜4 4重量％になるように、 シリカ分 散液に超純水を加え、 0 . 5〜4時間剪断力を与える。  In step 1-3, ultrapure water is added to the silica dispersion so that the silica concentration is 33 to 44% by weight, and a shearing force is applied for 0.5 to 4 hours.
以上のように、 第 1の工程では、 高剪断力を与えるとともに、 ステップ 1— 2 の超純水添加によって、 シリカ分散液の粘度を十分低くすることができる。 次に、 第 2の工程について説明する。 As described above, in the first step, a high shear force is applied, and the viscosity of the silica dispersion liquid can be sufficiently reduced by adding ultrapure water in step 1-2. Next, the second step will be described.
ステップ 2— 1では、 混合後の p Hが 8 ~ 1 2となり、 シリカ濃度が 1 0〜3 0重量％となるように調製した塩基性物質水溶液に対して、 シリカ分散液を投入 する。 従来の混合とは異なり、 塩基性物質水溶液にシリカ分散液を投入すること で混合時の凝集物発生を抑制することができる。 これは以下の理由による。 シリカ分散液の投入初期は、 塩基性物質水溶液が過剰であるため、 混合液の p Hは 1 2〜 1 4と強いアルカリ性であり、 p Hショックが生じる。 しかし、 シリ 力濃度が非常に低いため、 凝集の発生は抑制される。 投入が進むと、 混合液のシ リカ濃度は上昇するが、 シリカ分散液の投入によって混合液の p Hが 8〜1 2と 弱いアルカリ性となるため、 p Hショックが弱く、 凝集の発生が抑制される。 さらに、 5時間以内に全てのシリカ分散液を投入することが望ましい。 塩基性 物質水溶液の p Hは 1 2〜1 4であり、 ヒュームドシリカの表面が溶出する p H 領域である。 よって、 シリカ分散液を素早く投入することで、 シリカ粒子の分散 安定領域である ρ Η 8〜1 2にすばやくシフトできる。  In Step 2-1, the silica dispersion is added to the basic substance aqueous solution prepared so that the pH after mixing becomes 8 to 12 and the silica concentration becomes 10 to 30% by weight. Unlike the conventional mixing, the generation of aggregates during mixing can be suppressed by adding the silica dispersion to the aqueous solution of the basic substance. This is for the following reason. At the initial stage of the introduction of the silica dispersion, the pH of the mixed solution is strongly alkaline, ie, 12 to 14, due to an excess of the aqueous solution of the basic substance, and a pH shock occurs. However, since the silicon concentration is very low, the occurrence of aggregation is suppressed. As the introduction proceeds, the silica concentration of the mixture increases, but the introduction of the silica dispersion causes the mixture to have a weak alkaline pH of 8 to 12 so that the pH shock is weak and the occurrence of aggregation is suppressed. Is done. Further, it is desirable to charge all the silica dispersions within 5 hours. The pH of the aqueous solution of the basic substance is 12 to 14, which is the pH range where the surface of the fumed silica elutes. Therefore, by quickly feeding the silica dispersion, it is possible to quickly shift to ρΗ8 to 12 which is a dispersion stable region of silica particles.
以上のように、 第 2の工程では、 塩基性物質水溶液に、 シリカ分散液を投入す ることで、 混合時の凝集物発生を抑制することができる。  As described above, in the second step, the generation of aggregates during mixing can be suppressed by adding the silica dispersion to the aqueous solution of the basic substance.
第 1および第 2の工程を経て得られたシリカスラリは、 凝集物が少なく、 粘度 が低いので、 フィルタによつて効果的に凝集物を除去することができる。  Since the silica slurry obtained through the first and second steps has few aggregates and low viscosity, the aggregates can be effectively removed by the filter.
ステップ 3— 1では、 濾過精度が 1〜4 μ mのフィルタを用いて濾過を行う。 これにより、 流速 2〜1 0 1 /m i nで処理することが可能で、 十分な処理流量 を保持しつつ、 粗大粒子を除去することができる。  In step 3-1, filtration is performed using a filter with a filtration accuracy of 1 to 4 µm. As a result, processing can be performed at a flow rate of 2 to 101 / min, and coarse particles can be removed while maintaining a sufficient processing flow rate.
以下では、 各ステップの条件についての検討結果について説明する。  In the following, the result of studying the conditions of each step will be described.
( 1 ) シリカ分散液の p Hについて  (1) pH of silica dispersion
ステップ 1一 1における p Hについて、 Hが 2， 3， 7のそれぞれの条件で シリカスラリを作製した。 なお、 p H以外の条件は全て同じとした。  Regarding the pH in step 11-1, silica slurry was prepared under the conditions that H was 2, 3, and 7, respectively. The conditions other than pH were all the same.
図 2は、 凝集粒子成長率に対する p Hの影響を示すグラフである。 縦軸は凝集 粒子の成長率を示し、 横軸は振盪時間を示している。  FIG. 2 is a graph showing the effect of pH on the aggregate particle growth rate. The vertical axis shows the growth rate of the aggregated particles, and the horizontal axis shows the shaking time.
シリカスラリの分散安定性を調べるために振盪実験を行った。 振盪実験は、 容 量 5 O m 1 の遠沈管に作製したシリカスラリを 2 O m 1入れ、 縦型振盪機にセッ トし、 振盪速度 3 1 0 s p m (stroke per minute) 、 振盪ストローク 4 0 mm で振盪を行い、 所定時間経過後に遠沈管を取り出し、 粒度分布測定装置 （H O RShaking experiments were performed to examine the dispersion stability of the silica slurry. Shaking experiment Put the prepared silica slurry in a centrifuge tube with a volume of 5 O m 1, place it in a vertical shaker, shake it at a shaking speed of 310 spm (stroke per minute) and a shaking stroke of 40 mm. After a predetermined time has elapsed, remove the centrifuge tube and use a particle size distribution analyzer (HOR
I B A製： model LA-910) を用いてシリカスラリのメジアン粒子径を測定した。 凝集粒子の成長率は、 （振盪後のメジアン粒子径ー振盪前のメジアン粒子径） 振盪前のメジアン粒子径 X 1 0 0 (%) で算出した。 The median particle size of the silica slurry was measured using IB A model LA-910). The growth rate of the aggregated particles was calculated by ((median particle diameter after shaking−median particle diameter before shaking)) Median particle diameter before shaking X 100 (%).
折れ線 1 1は p H 2の場合を示し、 折れ線 1 2は p H 3の場合を示し、 折れ線 Line 1 1 indicates the case of pH 2, Line 1 2 indicates the case of pH 3, line
1 3は p H 7の場合を示している。 p H 2の場合は、 1 0日間振盪しても粒子径 に変化がなく、 高い分散安定性を有していることがわかった。 H 3の場合は、13 shows the case of pH 7. In the case of pH 2, the particle size did not change even after shaking for 10 days, indicating high dispersion stability. For H3,
1 0日後で成長率約 1 8 %、 p H 7の場合は、 1 0日後で成長率約 8 8 %といず れも凝集が生じていることがわかった。 これは、 ヒュームドシリ力の等電点が p H 2付近であるため、 p H 2では粒子表面が電気的に中性となり、 高剪断力が加 わりやすいためと考えられる。 - 以上より、 シリカ分散液の p Hは 1〜2 . 7とするのが好ましいことがわかつ た。 After 10 days, the growth rate was about 18%, and in the case of pH 7, the growth rate was about 88% after 10 days, indicating that aggregation occurred. This is thought to be because the isoelectric point of the fumed Siri force is near pH 2, and the particle surface becomes electrically neutral at pH 2, and high shear force is likely to be applied. -From the above, it was found that the pH of the silica dispersion is preferably in the range of 1 to 2.7.
( 2 ) シリカ分散液の初期シリカ濃度について  (2) Initial silica concentration of silica dispersion
ステップ 1一 1における初期シリカ濃度について、 初期シリカ濃度を 4 5重 量％、 5 0重量％、 5 5重量％、 6 0重量％のそれぞれの条件でシリカスラリを 作製した。 なお、 初期シリカ濃度以外の条件は全て同じとした。  Regarding the initial silica concentration in step 11-1, silica slurries were prepared under the conditions of an initial silica concentration of 45% by weight, 50% by weight, 55% by weight, and 60% by weight, respectively. The conditions other than the initial silica concentration were all the same.
図 3は、 シリカスラリの粒度分布に対するシリ力分散液の初期シリ力濃度の影 響を示すグラフである。 縦軸は頻度を示し、 横軸は粒子径を示している。 曲線 1 4は、 初期シリカ濃度が 4 5重量％の場合を示し、 曲線 1 5は、 初期シリカ濃度 が 5 0重量％の場合を示し、 曲線 1 6は、 初期シリカ濃度が 5 5重量％の場合を 示し、 曲線 1 7は、 シリカ濃度が 6 0重量％の場合を示している。  FIG. 3 is a graph showing the effect of the initial concentration of the silicic acid dispersion on the particle size distribution of the silica slurry. The vertical axis indicates frequency, and the horizontal axis indicates particle size. Curve 14 shows the case where the initial silica concentration is 45% by weight, curve 15 shows the case where the initial silica concentration is 50% by weight, and curve 16 shows the case where the initial silica concentration is 55% by weight. The curve 17 shows the case where the silica concentration is 60% by weight.
グラフからわかるように、 初期シリカ濃度が高くなるほどシリカスラリの粒度 分布が左にシフトすることから、 分散性は初期シリカ濃度が高いほうが高いこと がわかった。 初期シリカ濃度が 4 5重量％と低い場合は、 高剪断分散装置の剪断 力が十分に伝達しなかったため、 分散性が低いと考えられる。 また、 5 5重量％ および 6 0重量％の場合、 剪断力が十分に伝達されるので分散性は高いが、 シリ 力分散液の粘度が上昇し、 分散機への負担が大きいため適切ではない。 初期シリ 力濃度が 5 0重量％の場合は、 分散機への負担も小さく、 分散性も高いことがわ 力 つた。 As can be seen from the graph, the particle size distribution of the silica slurry shifts to the left as the initial silica concentration increases, indicating that the higher the initial silica concentration, the higher the dispersibility. If the initial silica concentration is as low as 45% by weight, it is considered that the dispersibility is low because the shear force of the high shear disperser was not sufficiently transmitted. Also 55% by weight In the case of and 60% by weight, the shearing force is sufficiently transmitted, so that the dispersibility is high. However, it is not appropriate because the viscosity of the slurry dispersion increases and the load on the dispersing machine is large. When the initial silicic acid concentration was 50% by weight, it was found that the load on the disperser was small and the dispersibility was high.
以上より、 シリカ分散液の初期シリカ濃度は、 4 6〜5 4重量％とするのが好 ましいことがわかった。  From the above, it was found that the initial silica concentration of the silica dispersion was preferably 46 to 54% by weight.
( 3 ) 少量の超純水添加について  (3) Addition of a small amount of ultrapure water
ステップ 1— 2における超純水の添加について、 添加する場合と添加しない場 合のそれぞれの条件でシリカスラリを作製した。 なお、 超純水の添加以外の条件 は全て同じとした。  Regarding the addition of ultrapure water in Step 1-2, silica slurries were prepared under the conditions of addition and non-addition. The conditions were the same except for the addition of ultrapure water.
少量の超純水を添加しない場合は、 シリカスラリのメジアン粒子径が添加した 場合より大きくなった。 また、 剪断カはシリ力濃度が高いほうが伝わりやすいた め、 添加しない場合の分散性は低下し、 シリカスラリの粘度が約 4 %上昇した。 以上より、 シリカ分散液に少量の超純水を添加して、 シリカ濃度を 4 5〜5 3 重量％とするのが好ましいことがわかった。  When a small amount of ultrapure water was not added, the median particle diameter of the silica slurry was larger than when the addition was not performed. In addition, since the shearing force is more easily transmitted when the concentration of the shearing force is higher, the dispersibility when not added is reduced, and the viscosity of the silica slurry is increased by about 4%. From the above, it was found that it is preferable to add a small amount of ultrapure water to the silica dispersion to make the silica concentration 45 to 53% by weight.
( 4 ) シリカ分散液のシリカ濃度について  (4) About silica concentration of silica dispersion
ステップ 1— 3におけるシリカ濃度について、 シリカ濃度を 3 2重量％、 4 0 重量％、 4 5重量％および 4 9重量％ (超純水の添加無し） のそれぞれの条件で シリカスラリを作製した。 なお、 シリ力濃度以外の条件は全て同じとした。 図 4は、 シリカスラリ中の粗大粒子数に対するシリ力濃度の影響を示すグラフ である。 縦軸は粗大粒子数を示し、 横軸は粒子径を示している。  Regarding the silica concentration in steps 1-3, silica slurry was prepared under the conditions of 32% by weight, 40% by weight, 45% by weight, and 49% by weight (without addition of ultrapure water). The conditions other than the silicide concentration were all the same. Figure 4 is a graph showing the effect of silicide concentration on the number of coarse particles in silica slurry. The vertical axis indicates the number of coarse particles, and the horizontal axis indicates the particle diameter.
曲線 1 8はシリカ濃度が 3 2重量％の場合を示し、 曲線 1 9はシリカ濃度が 4 0重量％の場合を示し、 曲線 2 0はシリカ濃度が 4 5重量％の場合を示し、 曲線 2 1はシリカ濃度が 4 9重量％の場合を示している。 粒子径が 0 . 5 μ mより大 きな粒子を粗大粒子とし、 各粒子径を有する粒子数をカウントした。  Curve 18 shows the case where the silica concentration is 32% by weight, curve 19 shows the case where the silica concentration is 40% by weight, curve 20 shows the case where the silica concentration is 45% by weight, and curve 2 1 shows the case where the silica concentration is 49% by weight. Particles having a particle size larger than 0.5 μm were regarded as coarse particles, and the number of particles having each particle size was counted.
シリカ濃度が 3 2重量％、 4 5重量％、 4 9重量％の場合に比べて、 シリカ濃 度が 4 0重量％の場合の粗大粒子数が最も少なかった。 これは、 4 0重量％のと きの粘度が、 最も効率良く分散機の剪断力が加わるためと考えられる。 したがつ て、 シリカ濃度が 3 2重量％の場合は粘度が低く、 4 5重量。/。、 4 9重量％は粘 度が高過ぎると考えられる。 When the silica concentration was 40% by weight, the number of coarse particles was the smallest compared to the case where the silica concentration was 32% by weight, 45% by weight, and 49% by weight. This is probably because the viscosity at 40% by weight is most efficiently applied with the shearing force of the disperser. According to When the silica concentration is 32% by weight, the viscosity is low, and the weight is 45%. /. , 49% by weight is considered too viscous.
以上より、 シリカ分散液のシリカ濃度は、 3 3〜4 4重量％とするのが好まし いことがわかった。  From the above, it was found that the silica concentration of the silica dispersion liquid was preferably 33 to 44% by weight.
( 5 ) シリカ分散液と塩基性物質水溶液の混合条件について  (5) Mixing conditions of silica dispersion and basic substance aqueous solution
ステップ 2— 1におけるシリカ分散液と塩基性物質水溶液の混合について、 シ リカ分散液に塩基性物質水溶液を投入する場合 （第 1混合条件） と、 塩基性物質 水溶液にシリカ分散液を投入する場合 （第 2混合条件） のそれぞれの条件でシリ カスラリを作製した。 塩基性物質としては、 水酸化カリウムを用いた。 なお、 混 合条件以外の条件は全て同じとした。  Regarding the mixing of the silica dispersion and the basic substance aqueous solution in step 2-1, the basic substance aqueous solution is added to the silica dispersion (first mixing condition) and the silica dispersion is added to the basic substance aqueous solution A silica slurry was prepared under the respective conditions (second mixing conditions). Potassium hydroxide was used as the basic substance. All conditions other than the mixing conditions were the same.
図 5は、 シリカスラリの粒度分布に対する混合条件の影響を示すグラフである。 縦軸は頻度を示し、 横軸は粒子径を示している。 曲線 2 2 a， 2 2 bは、 第 1混 合条件の場合を示し、 曲線 2 3は、 第 2混合条件の場合を示している。  FIG. 5 is a graph showing the effect of mixing conditions on the particle size distribution of silica slurry. The vertical axis indicates frequency, and the horizontal axis indicates particle size. Curves 22 a and 22 b show the case of the first mixing condition, and curve 23 shows the case of the second mixing condition.
前述のように第 1混合条件の場合は p Hショックが大きく、 凝集物が発生しゃ すい。 実際に、 粒度分布では、 1 0 μ m付近に凝集物によるピークが見られた。 これに対して、 第 2混合条件では、 粒子径が 0 . 1 μ m付近に鋭いピークが見ら れ、 分散性が向上していることがわかった。 また、 シリカスラリのメジアン粒子 径についても測定を行った。 混合前のシリカ分散液のメジアン粒子径は 1 1 0 n mであった。 第 1混合条件でシリ力分散液と水酸化力リゥム水溶液とを混合した ときのシリカスラリのメジァン粒子径は、 8 0 8 2 n mとなり非常に大きな凝集 物が存在した。 これに対して、 第 2混合条件で混合したときのシリカスラリのメ ジアン粒子径は、 1 1 0 n mと変わらずほとんど凝集していないことがわかった。 以上より、 シリカ分散液と塩基性物質水溶液とを混合する場合は、 塩基性物質 水溶液にシリカ分散液を投入するのがよいことがわかった。  As described above, in the case of the first mixing condition, the pH shock is large and aggregates are easily generated. In fact, in the particle size distribution, a peak due to aggregates was observed at around 10 μm. On the other hand, under the second mixing condition, a sharp peak was observed near the particle diameter of 0.1 μm, indicating that the dispersibility was improved. The median particle size of the silica slurry was also measured. The median particle diameter of the silica dispersion before mixing was 110 nm. The median particle size of the silica slurry when the silicic acid dispersion and the aqueous hydroxide solution were mixed under the first mixing condition was 808 nm, and very large aggregates were present. On the other hand, the median particle diameter of the silica slurry when mixed under the second mixing condition was found to be 110 nm and hardly aggregated. From the above, it was found that when mixing a silica dispersion and a basic substance aqueous solution, it is better to add the silica dispersion to the basic substance aqueous solution.
( 6 ) シリカ分散液の投入時間について  (6) Silica dispersion charging time
ステップ 2 _ 1における塩基性物質水溶液へのシリカ分散液の投入時間につい て、 全てのシリカ分散液を 5時間で投入した場合と、 2 0分間で投入した場合の それぞれの条件でシリカスラリを作製した。 塩基性物質としては、 水酸化力リウ ムを用いた。 なお、 投入時間以外の条件は全て同じとした。 Regarding the charging time of the silica dispersion into the aqueous solution of the basic substance in Step 2 -1, silica slurry was prepared under the respective conditions of charging all the silica dispersion in 5 hours and charging the silica dispersion in 20 minutes. . The basic substance is hydroxylated Was used. The conditions other than the charging time were all the same.
図 6は、 シリカスラリの粒度分布に対するシリカ分散液の投入時間の影響を示 すグラフである。 縦軸は頻度を示し、 横軸は粒子径を示す。 曲線 2 4は投入時間 が 5時間の場合を示し、 曲線 2 5は投入時間が 2 0分間の場合を示している。 シリカ分散液を長時間かけて投入すると、 水酸化カリゥム水溶液が強いアル力 リ性であるため、 p Hショックによって凝集物が発生してしまう。 投入時間を短 くすることで、 混合液の p Hをシリカの安定領域である p H l 2以下にまで素早 く低下させることができるので、 凝集物の発生を抑制することができる。  FIG. 6 is a graph showing the effect of the charging time of the silica dispersion on the particle size distribution of the silica slurry. The vertical axis indicates frequency, and the horizontal axis indicates particle size. Curve 24 shows the case where the charging time is 5 hours, and curve 24 shows the case where the charging time is 20 minutes. When the silica dispersion is introduced over a long period of time, aggregates are generated by the pH shock because the aqueous solution of potassium hydroxide has a strong alkaline property. By shortening the charging time, the pH of the mixed solution can be quickly reduced to a pH of less than or equal to pH12, which is a stable region of silica, so that generation of aggregates can be suppressed.
以上より、 塩基性物質水溶液へのシリカ分散液の投入は、 5時間未満で終了さ せるのが好ましいことがわかった。  From the above, it was found that it is preferable that the introduction of the silica dispersion into the aqueous solution of the basic substance be completed in less than 5 hours.
図 7は、 混合液の p Hに対するシリカ分散液の投入速度の影響を示すグラフで ある。 縦軸は混合液の p Hを示し、 横軸はシリカ分散液の投入時間を示す。 曲線 2 6は投入速度が 2 5 1 /m i nの場合を示し、 曲線 2 7は投入速度が 1 2 . 5 1 /m i nの場合を示し、 曲線 2 8は投入速度が 5 1 /m i nの場合を示してい る。  FIG. 7 is a graph showing the effect of the charging rate of the silica dispersion liquid on the pH of the mixed liquid. The vertical axis indicates the pH of the mixed solution, and the horizontal axis indicates the charging time of the silica dispersion. Curve 26 shows the case where the charging speed is 25 1 / min, curve 27 shows the case where the charging speed is 12.5 1 / min, and curve 28 shows the case where the charging speed is 51 / min. Is shown.
このように、 投入速度を速くすることで、 混合液の p Hをシリカの安定領域で ある p H 1 2以下にまで素早く低下させることができる。  As described above, by increasing the charging rate, the pH of the mixed solution can be quickly reduced to pH 12 or less, which is the stable region of silica.
( 7 ) フィルタの濾過精度および処理流速について  (7) Filter accuracy and flow rate
まず、 ステップ 3— 1におけるフィルタの濾過精度について、 濾過精度を 1 μ m、 3 /x m、 5 μ 7 μ mおよび 1 0 μ mのそれぞれの条件で濾過を行った。 フィルタとしては、 圧力損失が小さく大流量が得られるデプス型フィルタを用レ、 た。  First, with respect to the filtration accuracy of the filter in Step 3-1, filtration was performed under the conditions of filtration accuracy of 1 μm, 3 / xm, 5μ7μm and 10μm. As the filter, a depth-type filter with a small pressure loss and a large flow rate was used.
図 8は、 粗大粒子の除去性能に対するフィルタの濾過精度の影響を示す図であ る。 縦軸はシリカスラリ中の粗大粒子数を示しており、 図には濾過処理前の粗大 粒子数と、 濾過処理後の粗大粒子数とを示している。 直線 2 9は濾過精度が 1 μ mの場合の粒子数変化を示し、 直線 3 0は濾過精度が 3 / mの場合の粒子数変化 を示し、 直線 3 1は濾過精度が 5 μ mの場合の粒子数変化を示し、 直線 3 2は濾 過精度が 7 μ mの場合の粒子数変化を示し、 直線 3 3は濾過精度が 1 0 μ mの場 合の粒子数変化を示している。 FIG. 8 is a diagram showing the influence of the filtration accuracy of the filter on the performance of removing coarse particles. The vertical axis shows the number of coarse particles in the silica slurry, and the figure shows the number of coarse particles before filtration and the number of coarse particles after filtration. Line 29 shows the change in the number of particles when the filtration accuracy is 1 μm, line 30 shows the change in the number of particles when the filtration accuracy is 3 / m, and line 31 shows the change when the filtration accuracy is 5 μm The line 32 shows the change in the number of particles when the filtration accuracy is 7 μm, and the line 33 shows the change in the number of particles when the filtration accuracy is 10 μm. 2 shows the change in the number of particles in the case of FIG.
濾過精度が 5 μ πι、 7 z mN 1 0 μ mの場合、 濾過精度が粗大粒子の粒子径ょ り大きいので、 濾過処理後の粗大粒子数がほとんど変化せず、 十分な濾過性能は 得られなかった。 これに対して、 濾過精度が 1 μ πι、 3 /i mの場合は、 濾過処理 後の粗大粒子数が大幅に減少した。 When the filtration accuracy is 5 μπι, 7 zm N 10 μm, the filtration accuracy is as large as the coarse particles, so the number of coarse particles after the filtration process hardly changes, and sufficient filtration performance can be obtained. Did not. On the other hand, when the filtration accuracy was 1 μπι, 3 / im, the number of coarse particles after the filtration treatment was significantly reduced.
次に、 ステップ 3— 1におけるフィルタの処理流量について、 上記と同様の条 件で濾過を行った。  Next, filtration was performed under the same conditions as above for the processing flow rate of the filter in step 3-1.
図 9は、 処理流速に対するフィルタの濾過精度の影響を示す図である。 縦軸は 濾過処理の処理流速を示しており、 図には各濾過精度における処理流速を示して いる。 シンボル 7 4は濾過精度が 1 / mの場合の流速を示し、 シンボル 7 5は濾 過精度が 3 μ mの場合の流速を示し、 シンボル 7 6は濾過精度が 5 μ mの場合の 流速を示し、 シンボル 7 7は濾過精度が 7 μ mの場合の流速を示し、 シンボル 7 8は濾過精度が 1 0 μ mの場合の流速を示している。  FIG. 9 is a diagram showing the influence of the filtration accuracy of the filter on the processing flow rate. The vertical axis shows the processing flow rate of the filtration process, and the figure shows the processing flow rate at each filtration accuracy. Symbol 74 indicates the flow rate when the filtration accuracy is 1 / m, symbol 75 indicates the flow rate when the filtration accuracy is 3 μm, and symbol 76 indicates the flow rate when the filtration accuracy is 5 μm. The symbol 77 indicates the flow velocity when the filtration accuracy is 7 μm, and the symbol 78 indicates the flow velocity when the filtration accuracy is 10 μm.
図からわかるように、 濾過精度が小さくなるほど、 流速も小さくなつている。 実際の製造工程を考慮した場合、 2 1 /m i n以上の流速があれば実用に耐え得 るので、 濾過精度が 1 μ mの場合でも実用可能である。  As can be seen from the figure, the lower the filtration accuracy, the lower the flow velocity. In consideration of the actual manufacturing process, a flow rate of 2 1 / min or more can withstand practical use, so that it can be used even if the filtration accuracy is 1 μm.
粗大粒子の除去性能と、 処理流速とを考慮すると、 濾過精度が 1〜4 i mのフ ィルタを用いればよいことがわかった。 このときの処理流速は、 2 - 1 0 1 Zm i nとなる。  Considering the removal performance of coarse particles and the processing flow rate, it was found that a filter with a filtration accuracy of 1 to 4 im should be used. The processing flow rate at this time is 2-101 Zmin.
次に、 従来技術に基づいて作製した従来のシリカスラリと、 本発明に基づいて 作製したシリカスラリ （以下では 「実施例 1」 と呼ぶ。 ) との比較結果について 説明する。 第 1の従来のシリカスラリ (以下では 「比較例 1」 と呼ぶ。 ) は、 特 許第 2 9 3 5 1 2 5号公報に記載の製造方法に基づいて作製し、 第 2の従来のシ リカスラリ （以下では 「比較例 2」 と呼ぶ。 ） は、 第 1の従来のシリカスラリよ りシリカ濃度を低く し、 本発明に基づいて作製したシリカスラリと同程度の粘度 となるように作製した。  Next, comparison results between a conventional silica slurry manufactured based on the conventional technology and a silica slurry manufactured based on the present invention (hereinafter, referred to as “Example 1”) will be described. The first conventional silica slurry (hereinafter referred to as “Comparative Example 1”) was manufactured based on the manufacturing method described in Japanese Patent No. 2953125, and the second conventional silica slurry was used. (Hereinafter, referred to as “Comparative Example 2”) was prepared so that the silica concentration was lower than that of the first conventional silica slurry, and the viscosity was almost the same as that of the silica slurry prepared based on the present invention.
実施例 1は、 以下の手順で作製した。  Example 1 was produced by the following procedure.
( a ) 高剪断分散装置に超純水を入れ、 塩酸を添加し p Hを 2に調整した。 ( b ) 高剪断力を与えながら、 ヒュームドシリカを初期シリカ濃度が 5 0重 量％になるまで投入した。 (a) Ultrapure water was charged into a high-shear dispersion device, and the pH was adjusted to 2 by adding hydrochloric acid. (b) The fumed silica was introduced while applying a high shearing force until the initial silica concentration became 50% by weight.
( c ) ヒュームドシリカ投入後、 2時間 3 0分間高剪断力をシリカ分散液に与 えた。  (c) A high shearing force was applied to the silica dispersion for 2 hours and 30 minutes after the introduction of the fumed silica.
( d ) シリカ分散液の濃度が、 4 9重量％になるように少量の超純水を添加し、 引き続き高剪断力を 3 0分間与えた。  (d) A small amount of ultrapure water was added so that the concentration of the silica dispersion was 49% by weight, and then a high shearing force was applied for 30 minutes.
( e ) シリカ分散液のシリカ濃度が 4 0重量％になるように、 超純水を添加し、 1時間高剪断力を与えた。  (e) Ultrapure water was added so that the silica concentration of the silica dispersion was 40% by weight, and a high shearing force was applied for 1 hour.
( f ) 最終製品であるシリカスラリの p Hが 1 1、 シリ力濃度が 2 5重量％に なるように水酸化カリゥム濃度を調整した水酸化力リゥム水溶液に、 シリカ分散 液を投入した。  (f) The silica dispersion was put into an aqueous solution of a hydroxide slurry in which the concentration of potassium hydroxide was adjusted so that the pH of the silica slurry as the final product was 11 and the concentration of the slurry was 25% by weight.
( g ) さらに、 濾過精度 3 μ mのデプス型フィルタを用いて、 粗大粒子を除去 した。  (g) Further, coarse particles were removed using a depth filter having a filtration accuracy of 3 μm.
図 1 0は、 比較例 1および 2と、 実施例 1に含まれる粗大粒子数を示すグラフ である。 縦軸は粗大粒子数を示し、 横軸は粒子径を示す。 曲線 3 9は実施例 1を 示し、 曲線 4 0は比較例 1を示し、 曲線 4 1は比較例 2を示している。  FIG. 10 is a graph showing the number of coarse particles included in Comparative Examples 1 and 2 and Example 1. The vertical axis indicates the number of coarse particles, and the horizontal axis indicates the particle diameter. Curve 39 shows Example 1, curve 40 shows Comparative Example 1, and curve 41 shows Comparative Example 2.
実施例 1の粗大粒子数は、 比較例 1および 2に比べて大幅に減少していること がわかった。 粗大粒子数およびその他の物性値について、 3種のシリカスラリの 比較結果を表 1に示す。  It was found that the number of coarse particles in Example 1 was significantly reduced as compared with Comparative Examples 1 and 2. Table 1 shows the comparison results of the three types of silica slurries for the number of coarse particles and other physical properties.
【表 1】  【table 1】
Figure imgf000015_0001
Figure imgf000015_0001
表 1に示すように、 実施例 1は、 メジアン粒子径が小さく、 シリカ濃度が高い こもかかわらず粘度が低くなっている。  As shown in Table 1, in Example 1, the median particle diameter was small and the viscosity was low despite the high silica concentration.
さらに、 これらのシリカスラリを用いて実際にシリコンウェハの研磨を行った 図 1 1は、 C M P装置 1 0 0の概略を示す外観図である。 C M P装置 1 0 0は, 研磨パッド 1 0 1と、 回転定盤部 1 2 1、 キャリア部 1 2 2、 スラリ供給部 1 2 3およびドレッシング部 1 2 4から構成される。 研磨パッド 1は、 C M P装置 1 0 0のキヤリァ部 1 2 2に保持されたシリコンウェハと圧接され、 シリコンゥェ ハとの相対移動によって、 シリコンウェハ表面を研磨する。 In addition, silicon wafers were actually polished using these silica slurries. FIG. 11 is an external view schematically showing the CMP apparatus 100. The CMP apparatus 100 includes a polishing pad 101, a rotary platen section 121, a carrier section 122, a slurry supply section 123, and a dressing section 124. The polishing pad 1 is pressed against the silicon wafer held by the carrier 122 of the CMP apparatus 100 and polishes the surface of the silicon wafer by relative movement with respect to the silicon wafer.
回転定盤部 1 2 1は、 研磨パッド 1 0 1を上面の略前面にわたって粘着テープ などで貼り付けて支持する定盤 1 0 2と、 その定盤 1 0 2の下面側に設けられる 回転軸を介して接続される回転駆動機構 1 0 3とからなる支持手段である。 回転 駆動機構 1 0 3による回転駆動力は回転軸を通じて定盤 1 0 2に伝達され、 定盤 1 0 2は研磨パッド 1 0 1とともに所定の回転数で鉛直方向軸線まわりに回転す る。 回転数は自由に設定することが可能で、 研磨の対象となるウェハの種類や膜 の種類、 研磨パッド 1の種類などによって適切な回転数が選択される。  The rotating platen unit 121 includes a platen 102 that supports the polishing pad 101 by applying an adhesive tape or the like over substantially the front surface of the upper surface, and a rotating shaft provided on the lower surface side of the platen 102. And a rotation drive mechanism 103 connected through the support means. The rotation driving force of the rotation drive mechanism 103 is transmitted to the surface plate 102 through a rotation shaft, and the surface plate 102 rotates around the vertical axis at a predetermined rotation speed together with the polishing pad 101. The number of rotations can be set freely, and an appropriate number of rotations is selected according to the type of wafer to be polished, the type of film, the type of polishing pad 1, and the like.
キヤリァ部 1 2 2は、 図 1 2の断面図に示すとおり、 キヤリァ本体 1 0 4と、 バッキング材 1 0 5と、 リテーナリング 1 0 6と、 回転駆動機構 1 0 7とからな り、 被研磨物であるシリコンウェハ 1 0 8を保持し、 研磨パッド 1 ◦ 1とシリコ ンウェハ 1 0 8と圧接させた状態で回転する保持手段である。 シリコンウェハ 1 0 8のキャリア本体 1 0 4への固定は、 ノ ッキング材 1 0 5を湿潤させ、 水の表 面張力によつて吸着させて行う。 さらに研磨処理中にシリコンウェハ 1 0 8が外 れないように、 リテーナリング 1 0 6によってシリコンウェハ 1 0 8の外周部を 保持している。 回転駆動機構 1 0 7は、 回転軸を介してキャリア本体 1 0 4の上 面側に接続される。 回転駆動機構 1 0 7による回転駆動力は回転軸を通じてキヤ リァ本体 1 0 4に伝達され、 キヤリァ本体 1 0 4はシリコンウェハ 1 0 8ととも に所定の回転数で鉛直方向軸線まわりに回転する。 回転数は自由に設定すること が可能で、 回転定盤部 1 2 1と同様に、 研磨の対象となるウェハの種類や膜の種 類、 研磨パッド 1 0 1の種類などによって適切な回転数が選択される。 またキヤ リア部 1 2 2は、 回転定盤部 1 2 1に近接する方向、 鉛直下向きに加圧され、 研 磨パッド 1 0 1とシリコンウェハ 1 0 8とが圧接される。 キヤリァ部 1 2 2の加 圧は、 回転駆動機構 1 0 7が行ってもよいし、 別途加圧機構を用いてもよい。 スラリ供給部 1 2 3は、 ノズル 1 0 9、 スラリ供給管 1 1 0およびスラリタン ク 1 1 1からなる供給手段である。 As shown in the cross-sectional view of FIG. 12, the carrier section 122 includes a carrier body 104, a backing material 105, a retainer ring 106, and a rotation drive mechanism 107. This is a holding means for holding a silicon wafer 108 as a polished object and rotating in a state in which the polishing pad 1 • 1 and the silicon wafer 108 are pressed against each other. The fixing of the silicon wafer 108 to the carrier body 104 is performed by moistening the knocking material 105 and adsorbing it by the surface tension of water. Further, the outer periphery of the silicon wafer 108 is held by a retainer ring 106 so that the silicon wafer 108 does not come off during the polishing process. The rotation drive mechanism 107 is connected to the upper surface side of the carrier main body 104 via a rotation shaft. The rotation driving force of the rotation drive mechanism 107 is transmitted to the carrier main body 104 through the rotation shaft, and the carrier main body 104 rotates around the vertical axis at a predetermined rotation speed together with the silicon wafer 108. . The number of revolutions can be set freely.Similar to the rotating platen section 121, the appropriate number of revolutions depends on the type of wafer and film to be polished, the type of polishing pad 101, etc. Is selected. Further, the carrier portion 122 is pressed vertically downward in a direction approaching the rotating platen portion 121, and the polishing pad 101 and the silicon wafer 108 are pressed against each other. The pressurization of the carrier section 122 may be performed by the rotation drive mechanism 107 or a separate pressurization mechanism may be used. The slurry supply section 123 is a supply means including a nozzle 109, a slurry supply pipe 110, and a slurry tank 111.
ポンプなどによりスラリタンク 1 1 1に貯溜されているシリカスラリを、 スラ リ供給管 1 1 0内に流し、 回転定盤部 1 2 1の上部かつ略中央部に設置したノズ ル 1 0 9から研磨パッド 1 0 1表面に対して所定の流量で供給する。 この供給す るシリカスラリとして、 実施例 1および比較例 1， 2を用いた。  The silica slurry stored in the slurry tank 1 1 1 by a pump or the like is flowed into the slurry supply pipe 1 10 and polished from the nozzle 1 0 9 installed at the upper part and approximately in the center of the rotary platen 12 1. The pad 101 is supplied at a predetermined flow rate to the surface. Example 1 and Comparative Examples 1 and 2 were used as the silica slurry to be supplied.
研磨の進行に伴い、 研磨パッド 1 0 1の研磨面近傍の微細孔には研磨屑ゃ砥粒 などが詰まり、 研磨レートなどの研磨特性が低下する。 ドレッシング部 1 2 4は コンディショナである産業用ダイヤモンド粒子を電着したプレート 1 1 2と、 回 転軸を介してプレート 1 1 2と接続される回転駆動機構 1 1 3とから構成される 再生手段である。 ドレッシング時には、 回転駆動機構 1 1 3によりプレート 1 1 2を回転させ、 ダイヤモンド粒子と研磨パッド 1 0 1の研磨面を接触させ、 目詰 まりした部分を削り取ることで、 研磨パッド 1 0 1の研磨特性を再生する。 研磨処理時の各部位の動作については、 キャリア部 1 2 2が鉛直下向きに加圧 され、 研磨パッド 1 0 1とシリコンウェハ 1 0 8とが圧接された状態で、 スラリ 供給部 1 2 3がシリカスラリを供給する。 供給されたシリカスラリカ 研磨パッ ド 1 0 1とシリコンウェハ 1 0 8との間に浸透し、 回転定盤部 1 2 1とキャリア 部 1 2 2とを回転かつ相対移動させることで、 媒体による化学的作用と砥粒によ る機械的作用によりシリコンウェハ 1 0 8の表面を高精度で研磨する。  As the polishing proceeds, fine holes near the polishing surface of the polishing pad 101 are clogged with polishing debris and abrasive grains, and the polishing characteristics such as a polishing rate are reduced. The dressing section 124 consists of a plate 112 on which industrial diamond particles, which are conditioners, are electrodeposited, and a rotary drive mechanism 113 connected to the plate 112 via a rotating shaft. Means. At the time of dressing, the rotating drive mechanism 113 rotates the plate 112 to bring the diamond particles into contact with the polishing surface of the polishing pad 101 and scrape off the clogged portion, thereby polishing the polishing pad 101. Play characteristics. Regarding the operation of each part at the time of the polishing process, the carrier supply unit 122 is pressurized vertically downward and the slurry supply unit 123 is pressed while the polishing pad 101 and the silicon wafer 108 are pressed against each other. Supply silica slurry. The supplied silica slurry penetrates between the polishing pad 101 and the silicon wafer 108, and rotates and relatively moves the rotating platen unit 121 and the carrier unit 122, thereby forming a chemical by the medium. The surface of the silicon wafer 108 is polished with high precision by the action and the mechanical action of the abrasive grains.
回転定盤部 1 2 1とキャリア部 1 2 2との相対移動については以下のような複 数のパターンがある。  There are several patterns for the relative movement between the rotating platen section 122 and the carrier section 122 as follows.
( 1 ) 図に示すように、 キャリア部 1 2 2の中心が、 回転定盤部 1 2 1の回転 中心から半径方向に略 1 / 2の位置となるようにキャリア部 1 2 2を配置し、 回 転定盤部 1 2 1とキャリア部 1 2 2の自転のみで研磨処理を行う。  (1) As shown in the figure, the carrier part 122 is arranged so that the center of the carrier part 122 is approximately 1/2 in the radial direction from the rotation center of the rotary platen part 121. The polishing process is performed only by the rotation of the rotating platen section 122 and the carrier section 122.
( 2 ) 研磨パッド 1 0 1の半径とシリコンウェハ 1 0 8の半径との差があまり 大きくない場合は （1 ) でもよいが、 研磨パッド 1の半径がシリコンウェハ 9の 粒径より大きい場合は、 研磨パッド 1 0 1の表面のうちシリコンウェハ 1 0 8と 接触しない部分が存在するので、 研磨パッド 1 1 0 1の全面を使用できるように (1) の回転定盤部 1 2 1とキャリア部 1 2 2の自転に加えて、 キャリア部 1 2 2を回転定盤部 1 2 1の半径方向に往復移動させる。 (2) If the difference between the radius of the polishing pad 101 and the radius of the silicon wafer 108 is not so large, (1) may be used, but if the radius of the polishing pad 1 is larger than the particle size of the silicon wafer 9, Since there is a portion of the surface of the polishing pad 101 that does not contact the silicon wafer 108, the entire surface of the polishing pad 1101 can be used. (1) In addition to the rotation of the rotating platen section 121 and the carrier section 122, the carrier section 122 is reciprocated in the radial direction of the rotating platen section 121.
(3) (1) の回転定盤部 1 2 1とキャリア部 1 22の自転に加えて、 キヤリ ァ部 1 22を、 回転定盤部 1 2 1の中心回りに回転移動させる。  (3) In addition to the rotation of the rotating platen section 121 and the carrier section 122 in (1), the carrier section 122 is rotated around the center of the rotating platen section 121.
(4) (2) と同じく研磨パッド 1 0 1の半径がシリ コンウェハ 1 08の半径 より大きい場合は、 半径方向の往復移動と回転定盤部 1 2 1の中心回りの回転移 動と組み合わせる。 たとえば、 キャリア部 1 22が回転定盤部 1 2 1の中心回り に螺旋軌道を描くように移動させればよい。  (4) When the radius of the polishing pad 101 is larger than the radius of the silicon wafer 108 as in (2), reciprocation in the radial direction and rotation around the center of the rotary platen 121 are combined. For example, the carrier section 122 may be moved so as to draw a spiral trajectory around the center of the rotary platen section 121.
なお、 回転定盤部 1 2 1およびキヤリァ部 1 22の自転回転方向は同じであつ てもよいし、 異なっていてもよい。 また、 回転定盤部 1 2 1およびキャリア部 1 22の自転回転速度も同じであってもよいし、 異なっていてもよい。  The rotation directions of the rotating platen section 122 and the carrier section 122 may be the same or different. Further, the rotation rotation speeds of the rotating platen section 122 and the carrier section 122 may be the same or different.
ドレッシング部 1 24によるドレツシング時期は、 1または複数のシリコンゥ ェハを研磨処理した後に行う場合と、 研磨処理中に行う場合とがある。 ドレッシ ング部 1 24のダイヤモンドプレート 1 1 2の半径は、 研磨パッド 1 0 1の半径 よりも小さい場合が多いので、 研磨処理後にドレッシングを行う場合は、 上記の 回転定盤部 1 2 1とキャリア部 1 22との相対移動のパターン （2) および The dressing by the dressing unit 124 may be performed after polishing one or more silicon wafers, or may be performed during the polishing process. Since the radius of the diamond plate 1 12 of the dressing section 124 is often smaller than the radius of the polishing pad 101, when dressing is performed after the polishing process, the above-described rotary platen section 121 and the carrier are used. Pattern of relative movement with part 1 22 (2) and
(4) とほぼ同様にして行えばよい。 研磨処理中に行う場合は、 図に示すように、 回転定盤部 1 2 1の中心を挟んでキヤリァ部 1 22と反対側に配置し、 相対移動 のパターン （2) とほぼ同様にして行えばよい。 This can be performed in substantially the same manner as (4). When the polishing is performed during the polishing process, as shown in the figure, it is arranged on the opposite side of the carrier 122 from the center of the rotating platen 121, and the operation is performed in substantially the same manner as the relative movement pattern (2). Just do it.
以上のような CMP装置 100を用いて研磨処理を行った。  Polishing was performed using the CMP apparatus 100 as described above.
被研磨物として T E O Sウェハを用い、 研磨パッド 1 0 1として、 I C 140 0 K— G r o o v e (ロデール .ニッタ社製） を用いた。 回転定盤部 1 2 1の 回転速度は、 60 r pmとし、 シリカスラリは 1 00m l /m i nの速度で供給 した。 1分間研磨処理を行った後、 日立電子エンジニアリング社製ウェハ表面検 查装置 （L S 6 600) を用いてウェハ表面のスクラッチ数 （大きさ 0. 2 xm 以上） をカウントした。  A T EOS wafer was used as the object to be polished, and IC 1400 K—Groov e (manufactured by Rodel Nitta) was used as the polishing pad 101. The rotation speed of the rotary platen section 121 was 60 rpm, and the silica slurry was supplied at a speed of 100 ml / min. After polishing for 1 minute, the number of scratches (size of 0.2 xm or more) on the wafer surface was counted using a wafer surface inspection device (LS6600) manufactured by Hitachi Electronics Engineering.
図 1 3は、 実施例 1および比較例 1， 2を用いた研磨処理結果を示す図である。 縦軸は 1枚のウェハ当たりのスクラッチ数を示している。 実施例 1およぴ比較例 1， 2のそれぞれについて、 3回の研磨処理を行った。 FIG. 13 is a diagram showing the results of the polishing process using Example 1 and Comparative Examples 1 and 2. The vertical axis indicates the number of scratches per wafer. Example 1 and Comparative Example Each of 1 and 2 was polished three times.
比較例 1のスクラッチ数が 2 6 1〜 3 9 9 (平均 3 2 2 ) であり、 比較例 2の スクラツチ数が 1 0 3〜 1 5 4 (平均 1 2 3 ) であるのに対して、 実施例 1のス クラッチ数は 2 8〜6 3 (平均 4 0 ) と大幅に減少した。  While the number of scratches in Comparative Example 1 is 26 1 to 39 9 (average 32 2), and the number of scratches in Comparative Example 2 is 103 to 15 4 (average 12 3), The number of scratches in Example 1 was significantly reduced to 28 to 63 (average 40).
このように、 本発明に基づいて作製されたシリカスラリは、 高分散性を有し、 粗大凝集粒子数が少ないため、 研磨処理においてウェハ表面のスクラツチ数を減 少させることができる。  As described above, the silica slurry manufactured according to the present invention has high dispersibility and a small number of coarse agglomerated particles, so that the number of scratches on the wafer surface can be reduced in the polishing process.
本発明は、 その精神または主要な特徴から逸脱することなく、 他のいろいろな 形態で実施できる。 したがって、 前述の実施形態はあらゆる点で単なる例示に過 ぎず、 本発明の範囲は特許請求の範囲に示すものであって、 明細書本文には何ら 拘束されない。 さらに、 特許請求の範囲に属する変形や変更は全て本発明の範囲 内のものである。  The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiments are merely examples in all respects, and the scope of the present invention is set forth in the appended claims, and is not limited by the specification text. Further, all modifications and changes belonging to the claims are within the scope of the present invention.
【産業上の利用可能性】  [Industrial applicability]
以上のように本発明によれば、 調製された塩基性物質水溶液に対して、 ヒユー ムドシリ力分散液を添加することで、 分散安定性に優れ、 凝集粒子の少ない研磨 用組成物が得られる。  As described above, according to the present invention, a polishing composition excellent in dispersion stability and containing few aggregated particles can be obtained by adding a fumed sili-cide dispersion to the prepared basic substance aqueous solution.
また本発明によれば、 高剪断力を効率良く与え、 分散性を向上させることがで さる。  Further, according to the present invention, it is possible to efficiently apply a high shear force and improve the dispersibility.
また本発明によれば、 少量の水を添加することで研磨用組成物の粘度を低下さ せることができる。  Further, according to the present invention, the viscosity of the polishing composition can be reduced by adding a small amount of water.
また本発明によれば、 5時間未満で混合を終了させることで、 混合液の p Hを 素早く低下させ、 ヒュームドシリカが凝集しやすい p H条件となる時間を短く し て凝集の発生を抑制することができる。  Further, according to the present invention, by stopping the mixing in less than 5 hours, the pH of the mixed solution is rapidly reduced, and the time during which the pH conditions under which the fumed silica easily aggregates is shortened, thereby suppressing the occurrence of aggregation. can do.
また本発明によれば、 第 2工程で得られた研磨用組成物は凝集物の発生が少な いため、 濾過処理によって効率良く凝集物を除去することができる。  Further, according to the present invention, since the polishing composition obtained in the second step generates few aggregates, the aggregates can be efficiently removed by filtration.

Claims

請 求 の 範 囲 The scope of the claims
1. 酸性のヒュームドシリカ分散液を調製する第 1工程と、  1. a first step of preparing an acidic fumed silica dispersion;
前記ヒュームドシリカ分散液との混合終了後に得られる研磨用組成物が、 所定 の p Hおよびシリカ濃度となるように調製した塩基性物質水溶液に対して、 前記 ヒュームドシリカ分散液を添加して混合する第 2工程とを有することを特徴とす る研磨用組成物の製造方法。  The polishing composition obtained after the completion of the mixing with the fumed silica dispersion is added to the basic substance aqueous solution prepared so as to have a predetermined pH and a silica concentration, and the fumed silica dispersion is added. A method for producing a polishing composition, comprising: a second step of mixing.
2. 前記第 1工程は、  2. The first step is:
p Hを 1. 0〜2. 7に調製した水中に、 初期シリカ濃度が 4 6〜 54重量％ になるようにヒュームドシリカを投入し、 高剪断力を与えてヒュームドシリカ分 散液を調製する工程と、  Fumed silica is added to water adjusted to pH 1.0 to 2.7 so that the initial silica concentration is 46 to 54% by weight, and a high shear force is applied to disperse the fumed silica dispersion. A step of preparing;
シリ力濃度が 4 5〜 5 3重量％になるように、 前記ヒュームドシリカ分散液に 水を添加する工程と、  Adding water to the fumed silica dispersion so that the concentration of silylation is 45 to 53% by weight;
シリカ濃度が 3 3〜44重量％になるように、 前記ヒュームドシリカ分散液に さらに水を添加する工程とを有することを特徴とする請求項 1記載の研磨用組成 物の製造方法。  2. The method for producing a polishing composition according to claim 1, further comprising a step of adding water to the fumed silica dispersion so that the silica concentration is 33 to 44% by weight.
3. 前記研磨用組成物の p Hが 8〜 1 2、 シリ力濃度が 1 0〜 3 0重量％とな るように前記塩基性物質水溶液を調製することを特徴とする請求項 1または 2記 載の研磨用組成物の製造方法。  3. The aqueous solution of a basic substance is prepared such that the pH of the polishing composition is 8 to 12 and the concentration of silicic acid is 10 to 30% by weight. A method for producing the polishing composition described above.
4. 前記第 2工程は、 5時間未満で前記ヒュームドシリカ分散液と前記塩基性 物質水溶液との混合を終了させることを特徴とする請求項 1〜 3のいずれか 1つ に記載の研磨用組成物の製造方法。  4. The polishing method according to claim 1, wherein the second step terminates the mixing of the fumed silica dispersion and the basic substance aqueous solution in less than 5 hours. A method for producing the composition.
5. 前記ヒュームドシリカの比表面積は、 5 0~ 2 0 0 nf 2/gであることを 特徴とする請求項 1〜 4のいずれか 1つに記載の研磨用組成物の製造方法。  5. The method for producing a polishing composition according to claim 1, wherein the fumed silica has a specific surface area of 50 to 200 nf 2 / g.
6. 前記塩基性物質水溶液は、 少なくとも水酸化アンモニゥム、 水酸化ナトリ ゥム、 水酸化カリウム、 水酸化カルシウム、 水酸化バリウムまたは水酸化マグネ シゥムのいずれかを含むことを特徴とする請求項 1〜 5のいずれか 1つに記載の 研磨用組成物の製造方法。  6. The aqueous solution of a basic substance according to claim 1, wherein the aqueous solution contains at least one of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, and magnesium hydroxide. 6. The method for producing a polishing composition according to any one of 5.
7. 前記第 2工程で得られた研磨用組成物に対して、 濾過精度が 1〜4 μ πιの フィルタを用いて濾過処理を行う第 3工程をさらに有することを特徴とする請求 項 1〜 6のいずれか 1つに記載の研磨用組成物の製造方法。 7. With respect to the polishing composition obtained in the second step, the filtration accuracy is 1 to 4 μπι. The method for producing a polishing composition according to any one of claims 1 to 6, further comprising a third step of performing a filtration treatment using a filter.
PCT/JP2004/001413 2003-02-14 2004-02-10 Process for producing polishing composition WO2004072203A1 (en)

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GB2229432A (en) * 1989-03-21 1990-09-26 Cabot Corp Aqueous colloidal dispersion of fumed silica, acid and stabilizer
EP0773270A2 (en) * 1995-11-10 1997-05-14 Tokuyama Corporation Polishing slurries and a process for the production thereof
US6248144B1 (en) * 1999-07-15 2001-06-19 Fujimi Incorporated Process for producing polishing composition

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TWI306115B (en) 2009-02-11

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