Polishing composition, polishing method, and method of manufacturing semiconductor substrate

Abstract

Provided is a means capable of polishing an organic material at a high polishing speed and reducing the number of scratches after polishing. The polishing composition of the present invention contains zirconia particles and a dispersing medium, in which the zirconia particles contain at least one of tetragonal zirconia and cubic zirconia, and an average secondary particle size of the zirconia particles is less than 80 nm.

Claims

1. A polishing composition comprising zirconia particles and a dispersing medium, wherein: the zirconia particles are composed of tetragonal zirconia and cubic zirconia; a content ratio (mass ratio) of the tetragonal zirconia to the cubic zirconia in the zirconia particles is 0.5:9.5 or more and 9.5:0.5 or less; an average secondary particle size of the zirconia particles is less than 50 nm; an average primary particle size of the zirconia particles is 20 nm or less; and a pH of the polishing composition is less than 7.

2. The polishing composition according to claim 1, wherein a pH of the polishing composition is less than 6.

3. The polishing composition according to claim 1, further comprising a pH adjusting agent.

4. The polishing composition according to claim 1, wherein the content ratio (mass ratio) of the tetragonal zirconia to the cubic zirconia in the zirconia particles is 1:9 or more and 5:5 or less.

5. The polishing composition according to claim 1, wherein the average secondary particle size of the zirconia particles is 40 nm or less.

6. The polishing composition according to claim 1, wherein a zeta potential of the zirconia particles in the polishing composition is positive.

7. The polishing composition according to claim 1, wherein the zirconia particles in the polishing composition are doped with yttrium or an oxide thereof.

8. The polishing composition according to claim 1, further comprising a sugar alcohol, wherein a content of the sugar alcohol is 0.008% by mass or more with respect to a total mass of the polishing composition.

9. The polishing composition according to claim 1, further comprising a phosphorus-containing compound, wherein a content of the phosphorus-containing compound is 0.001% by mass or more and 0.05% by mass or less with respect to a total mass of the polishing composition.

10. A polishing composition comprising zirconia particles and a dispersing medium, wherein; the zirconia particles comprise at least one of tetragonal zirconia and cubic zirconia, and the zirconia particles further comprise monoclinic zirconia; a content ratio (mass ratio) of the tetragonal zirconia and the cubic zirconia to the monoclinic zirconia in the zirconia particles is 0.5:9.5 or more and 9.5:0.5 or less; an average secondary particle size of the zirconia particles is less than 50 nm; an average primary particle size of the zirconia particles is 20 nm or less; and a pH of the polishing composition is less than 7.

11. The polishing composition according to claim 10, wherein a content ratio (mass ratio) of at least one of the tetragonal zirconia and the cubic zirconia to the monoclinic zirconia in the zirconia particles is 2:8 or more and 9:1 or less.

12. The polishing composition according to claim 10, wherein the average secondary particle size of the zirconia particles is 40 nm or less.

13. The polishing composition according to claim 10, wherein a zeta potential of the zirconia particles in the polishing composition is positive.

14. The polishing composition according to claim 10, wherein the zirconia particles in the polishing composition are doped with yttrium or an oxide thereof.

15. The polishing composition according to claim 10, wherein a pH of the polishing composition is less than 6.

16. The polishing composition according to claim 10, further comprising a pH adjusting agent.

17. The polishing composition according to claim 10, further comprising a sugar alcohol, wherein a content of the sugar alcohol is 0.008% by mass or more with respect to a total mass of the polishing composition.

18. The polishing composition according to claim 10, further comprising a phosphorus-containing compound, wherein a content of the phosphorus-containing compound is 0.001% by mass or more and 0.05% by mass or less with respect to a total mass of the polishing composition.

Description

EXAMPLES

(1) The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the technical scope of the present invention should not be limited to only the following Examples. Unless otherwise specified, % and part(s) refer to % by mass and part(s) by mass, respectively. In the following Examples, unless otherwise specified, operations were performed under conditions of room temperature (25 C.)/relative humidity of 40% RH or more and 50% RH or less.

(2) [Measurement Methods of Various Physical Properties]

(3) Various physical properties were measured by the following methods.

(4) <Measurement of Particle Size>

(5) A primary particle size of zirconia particles was determined by calculating a specific surface area (SA) (nm.sup.2) by a BET method. Assuming that the zirconia particles are a true sphere, a diameter (2R) (primary particle size) (nm) of the zirconia particles was calculated based on the specific surface area (SA) using an equation: SA=4R2 (SA=specific surface area, R=radius), and an average thereof was determined as an average primary particle size (nm) of the zirconia particles.

(6) For an average secondary particle size (D50) of zirconia particles, a value measured as a volume average particle size by a dynamic light scattering method using a particle size distribution measurement apparatus (Nanotrac UPA-UT151, manufactured by MicrotracBEL Corp.) was adopted. Specifically, a particle size of zirconia particle was measured using a dispersion in which the zirconia particles were dispersed in water at a concentration of 0.1% by mass. A diameter D50 (nm) of the particle when an integrated particle volume reached 50% of a total particle volume from the fine particle side in a particle size distribution of particle sizes of the zirconia particles was calculated, and the diameter D50 (nm) was used as an average secondary particle size (D50) (nm) of the zirconia particles.

(7) <Measurement of Zeta Potential>

(8) A zeta potential ( potential) of zirconia particles was measured using a zeta potential measurement apparatus (trade name ELS-Z) manufactured by Otsuka Electronics Co., Ltd.

(9) <Measurement of pH>

(10) A pH of a polishing composition was measured by a pH meter (model number: F-71, manufactured by Horiba, Ltd.).

(11) <Measurement of Electrical Conductivity (EC)>

(12) An electrical conductivity (EC) of a polishing composition (temperature: 25 C.) was measured by a desktop electrical conductivity meter (manufactured by Horiba, Ltd., model: DS-71).

(13) [Preparation of Polishing Composition]

Example 1

(14) Method of Producing Abrasive Grains:

(15) 100 g of a 20% diacetoxyzirconium(IV) oxide aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.) was mixed with 200 g of pure water, to prepare an aqueous solution 1. 0.1 g of yttrium acetate tetrahydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was dissolved in 100 g of pure water and mixed with the aqueous solution 1 (mixed solution 1). Ammonium acetate was added to the mixed solution 1 so as to adjust conductivity of the solution to 5 mS/cm. A hydrothermal treatment was performed in an autoclave at 180 C. for 8 hours, to obtain colloidal zirconia (average primary particle size=8 nm, average secondary particle size (D50)=40 nm, shape=diamond, rugby ball type, yttrium content=0.5 mol %, monoclinic crystal:tetragonal crystal=8:2 (mass ratio)) (zirconia particles 1). Nitric acid was provided as a pH adjusting agent.

(16) The zirconia particles 1 (abrasive grains), nitric acid (pH adjusting agent), and pure water (dispersing medium) were mixed while stirring at room temperature (25 C.) for 30 minutes, to prepare a polishing composition 1. A content of the zirconia particles 1 was set to 0.5% by mass with respect to a total amount of the polishing composition 1, and a content of the nitric acid was set so as to achieve a pH of 4.5 for the polishing composition 1. A zeta potential of the zirconia particles in the obtained polishing composition 1 was found to be 35 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the polishing composition 1 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 1.

Example 2

(17) Method of Producing Abrasive Grains:

(18) 100 g of a 20% diacetoxyzirconium(IV) oxide aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.) was mixed with 200 g of pure water, to prepare an aqueous solution 2. 2 g of yttrium acetate tetrahydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was dissolved in 100 g of pure water and mixed with the aqueous solution 2 (mixed solution 2). Ammonium acetate was added to the mixed solution 2 so as to adjust conductivity of the solution to 5 mS/cm. A hydrothermal treatment was performed in an autoclave at 180 C. for 8 hours, to obtain colloidal zirconia (average primary particle size=5 nm, average secondary particle size (D50)=29 nm, shape=diamond, rugby ball type, yttrium content=13.0 mol %, tetragonal crystal:cubic crystal=1:9 (mass ratio)) (zirconia particles 2).

(19) A polishing composition 2 was prepared in the same manner as in Example 1, except that the zirconia particles 2 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the obtained polishing composition 2 was found to be 35 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the polishing composition 2 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 2.

Example 3

(20) Method of Producing Abrasive Grains:

(21) 100 g of a 20% diacetoxyzirconium(IV) oxide aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.) was mixed with 200 g of pure water, to prepare an aqueous solution 3. 1 g of yttrium acetate tetrahydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was dissolved in 100 g of pure water and mixed with the aqueous solution 3 (mixed solution 3). Ammonium acetate was added to the mixed solution 3 so as to adjust conductivity of the solution to 5 mS/cm. A hydrothermal treatment was performed in an autoclave at 180 C. for 8 hours, to obtain colloidal zirconia (average primary particle size=11 nm, average secondary particle size (D50)=35 nm, shape=diamond, rugby ball type, yttrium content=7.0 mol %, tetragonal crystal:cubic crystal=5:5 (mass ratio)) (zirconia particles 3).

(22) A polishing composition 3 was prepared in the same manner as in Example 1, except that the zirconia particles 3 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the obtained polishing composition 3 was found to be 35 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the polishing composition 3 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 3.

Example 4

(23) Method of Producing Abrasive Grains:

(24) 100 g of a 20% diacetoxyzirconium(IV) oxide aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.) was mixed with 200 g of pure water to prepare an aqueous solution 4. 0.4 g of yttrium acetate tetrahydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was dissolved in 100 g of pure water and mixed with the aqueous solution 4 (mixed solution 4). Ammonium acetate was added to the mixed solution 4 so as to adjust the conductivity of the solution to 5 mS/cm. A hydrothermal treatment was performed in an autoclave at 180 C. for 8 hours, to obtain colloidal zirconia (average primary particle size=12 nm, average secondary particle size (D50)=35 nm, shape=diamond, rugby ball type, yttrium content=3.0 mol %, monoclinic crystal:tetragonal crystal=1:9 (mass ratio)) (zirconia particles 4).

(25) A polishing composition 4 was prepared in the same manner as in Example 1, except that the zirconia particles 4 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the obtained polishing composition 4 was found to be 35 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the polishing composition 4 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 4.

Examples 5 to 9

(26) Zirconia particles 1 (abrasive grains) were obtained in the same manner as in Example 1. Nitric acid was provided as a pH adjusting agent.

(27) The zirconia particles 1 (abrasive grains), nitric acid (pH adjusting agent), sorbitol (dispersant), and pure water (dispersing medium) were mixed while stirring at room temperature (25 C.) for 30 minutes, to prepare polishing compositions 5 to 9. Here, a content of the zirconia particles 1 was set to 0.5% by mass with respect to a total amount of the polishing compositions 5 to 9. Contents of the sorbitol were 0.001% by mass (10 ppm) (Example 5), 0.005% by mass (50 ppm) (Example 6), 0.008% by mass (80 ppm) (Example 7), 0.01% by mass (100 ppm) (Example 8), and 0.05% by mass (500 ppm) (Example 9), with respect to a total amount of the polishing compositions 5 to 9. A content of the nitric acid was set so as to achieve a pH of 4.5 for each of the polishing compositions 5 to 9. A zeta potential of the zirconia particles in each of the polishing compositions 5 to 9 was found to be 35 mV. An yttrium content and a crystal composition (phase configuration) of the zirconia particles in each of the polishing compositions 5 to 9 were the same as an yttrium content and a crystal composition (phase configuration) of the zirconia particles 1.

Example 10

(28) Zirconia particles 1 (abrasive grains) were obtained in the same manner as in Example 1. Nitric acid was provided as a pH adjusting agent.

(29) The zirconia particles 1 (abrasive grains), nitric acid (pH adjusting agent), xylitol (dispersant), and pure water (dispersing medium) were mixed while stirring at room temperature (25 C.) for 30 minutes, to prepare a polishing composition 10. Here, a content of the zirconia particles 1 was set to 0.5% by mass with respect to a total amount of the polishing composition 10, a content of the xylitol was set to 0.01% by mass with respect to the total amount of the polishing composition 10, and a content of the nitric acid was set so as to achieve a pH of 4.5 for the polishing composition 10. A zeta potential of the zirconia particles in the polishing composition 10 was found to be 35 mV. An yttrium content and a crystal composition (phase configuration) of the zirconia particles in the polishing composition 10 were the same as an yttrium content and a crystal composition (phase configuration) of the zirconia particles 1.

Comparative Example 1

(30) Colloidal zirconia (manufactured by DAIICHI KIGENSO KAGAKU-KOGYO CO., LTD., ZSL-20 N, average primary particle size=12 nm, average secondary particle size (D50)=70 nm, shape=sea urchin type, yttrium content=0 mol %, monoclinic crystal) (zirconia particles 5) was provided as abrasive grains.

(31) A comparative polishing composition 1 was prepared in the same manner as in Example 1, except that the zirconia particles 5 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the comparative polishing composition 1 was found to be 40 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the comparative polishing composition 1 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 5.

Comparative Example 2

(32) Colloidal zirconia (manufactured by DAIICHI KIGENSO KAGAKU-KOGYO CO., LTD., 9631ZR, average primary particle size=12 nm, average secondary particle size (D50)=43 nm, shape=round type, yttrium content=0 mol %, monoclinic crystal) (zirconia particles 6) was provided as abrasive grains.

(33) A comparative polishing composition 2 was prepared in the same manner as in Example 1, except that the zirconia particles 6 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the comparative polishing composition 2 was found to be 40 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the comparative polishing composition 2 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 6.

Comparative Example 3

(34) Colloidal zirconia (manufactured by TAIYO KOKO Co., Ltd., ZS3000-A, average primary particle size=100 nm, average secondary particle size (D50)=220 nm, shape=spherical type, yttrium content=0 mol %, monoclinic crystal) (zirconia particles 7) was provided as abrasive grains.

(35) A comparative polishing composition 3 was prepared in the same manner as in Example 1, except that the zirconia particles 7 were used instead of the zirconia particles 1 in Example 1. A zeta potential of the zirconia particles in the comparative polishing composition 3 was found to be 35 mV. A particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles in the comparative polishing composition 3 were the same as a particle size, an yttrium content, and a crystal composition (phase configuration) of the zirconia particles 7.

(36) The configurations of the polishing compositions of each of Examples and each of Comparative Examples are shown in Table 1.

(37) A polishing speed, the number of scratches, and storage stability of the polishing composition of each of Examples and each of Comparative Examples were evaluated according to the following methods. The results are shown in Table 1.

(38) [Measurement of Polishing Speed 1]

(39) As an object to be polished (substrate), a silicon wafer (manufactured by ADVANTEC CO., LTD., 200 mm wafer, SKA, P type) (substrate 1) having a surface on which an amorphous carbon film was formed at a thickness of 5,000 was provided.

(40) Using each of the polishing compositions, the substrate 1 was polished under the following conditions, and a polishing speed was measured.

(41) (Polishing Conditions)

(42) Polishing apparatus: EJ-380IN-CH (manufactured by ENGIS JAPAN Corporation) Polishing pad: hard polyurethane pad (IC1010, manufactured by NITTA DuPont Incorporated) Polishing pressure: 1.4 psi (1 psi=6,894.76 Pa) Platen (table) rotation speed: 80 rpm Head (carrier) rotation speed: 60 rpm Supply of polishing composition: Continuously pouring without recycle Flow rate of polishing composition: 100 mL/min Polishing time: 60 seconds
(Polishing Speed)

(43) Film thicknesses before and after the polishing were determined by a light interference type film thickness measurement apparatus (model number: Lambda Ace VM-2030, manufactured by SCREEN Holdings), and a polishing speed (/min) was calculated by dividing a difference (A) in film thickness before and after the polishing by a polishing time (min) (see the following equation). A polishing speed of the substrate 1 is preferably as high as possible. The polishing speed of the substrate 1 is acceptable when it is 50 /min or more, is preferably 100 /min or more, and more preferably 120 /min or more.

(44) $\mathrm{Polishing}\mathrm{speed}\left(/\min \right)=\frac{\left[\mathrm{Film}\mathrm{thickness}\left(\right)\mathrm{of}\mathrm{object}\mathrm{to}\mathrm{be}\mathrm{polished}\mathrm{before}\mathrm{polishing}\right]-\left[\mathrm{Film}\mathrm{thickness}\left(\right)\mathrm{of}\mathrm{object}\mathrm{to}\mathrm{be}\mathrm{polished}\mathrm{after}\mathrm{polishing}\right]}{\left[\mathrm{Polishing}\mathrm{time}\left(\min \right)\right]}$
[Measurement of Number of Scratches 1]

(45) The substrate 1 (object to be polished) was polished using each of the polishing compositions under the following polishing conditions.

(46) (Polishing Conditions for Evaluating Number of Scratches)

(47) Polishing apparatus: CMP one-side polishing apparatus for 200 mm, Mirra (manufactured by Applied Materials, Inc) Polishing pad: hard polyurethane pad (IC1010, manufactured by NITTA DuPont Incorporated) Polishing pressure: 2.0 psi Platen (table) rotation speed: 83 rpm Head (carrier) rotation speed: 77 rpm Supply of polishing composition: Continuously pouring without recycle Polishing composition supply amount: 200 ml/min Polishing time: 60 seconds

(48) The number of scratches on a surface of the object to be polished after the polishing was determined by measuring coordinates of the entire surface of both surfaces of the object to be polished (excluding the outer periphery of 2 mm) using a wafer inspection apparatus Surfscan (registered trademark) SP2 manufactured by KLA Corporation, and observing all the measured coordinates with Review-SEM (RS-6000, manufactured by Hitachi High-Technologies Corporation). Scratches on a surface of a substrate having a depth of 10 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 m or more were counted as the scratches. The number of scratches is preferably as small as possible. The number of scratches is acceptable when it is less than 15, preferably less than 10, more preferably 5 or less, and particularly preferably less than 5.

(49) [Evaluation of Storage Stability]

(50) An average secondary particle size (D50) of the zirconia particles in each of the polishing compositions was measured at room temperature (25 C.) by a dynamic light scattering method using a particle size distribution measurement apparatus (Nanotrac UPA-UT151, manufactured by MicrotracBEL Corp.). Specifically, a diameter D50 (nm) of the particle when an integrated particle volume reached 50% of a total particle volume from the fine particle side in a particle size distribution of the particle sizes of the zirconia particles was calculated, and the diameter D50 (nm) was used as an average secondary particle size (D50.sub.A) (nm) of the zirconia particles.

(51) Separately, 100 g of each of the polishing compositions was weighed in a poly bottle. Next, each poly bottle was placed in a thermostatic bath set at 80 C. and left for 2 weeks. After being left for a predetermined period of time, an average secondary particle size (D50.sub.B) (nm) of the zirconia particles in each of the polishing compositions was measured by the same method as described above.

(52) Based on the average secondary particle sizes of the zirconia particles before and after being left (D50.sub.A (nm) and D50.sub.B (nm)), an increase rate (%) of the average secondary particle size was calculated by the following equation, to be used as an index of storage stability. The smaller the absolute value of the storage stability (increased rate in the average secondary particle size) (%), the better the storage stability. The absolute value of the storage stability (increased rate of the average secondary particle size) (%) is 40% or less, which is acceptable, preferably 35% or less, more preferably 25% or less, still more preferably less than 10%, and particularly preferably less than 5%.

(53) $\mathrm{Storage}\mathrm{stability}\left(\%\right)=\frac{D{50}_B\left(\mathrm{nm}\right)-D50_A\left(\mathrm{nm}\right)}{D50_A\left(\mathrm{nm}\right)}100$

(54) The evaluation results are shown in Table 1.

(55) TABLE-US-00001 TABLE 1 Zirconia particles (abrasive grains) Average Average primary secondary particle particle Y Concentration Potential size size content [% by mass] [mV] [nm] [nm] Shape [mol %] Example 1 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 2 0.5 35 5 29 Diamond shape, 13.0 rugby ball type Example 3 0.5 35 11 35 Diamond shape, 7.0 rugby ball type Example 4 0.5 35 12 35 Diamond shape, 3.0 rugby ball type Example 5 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 6 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 7 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 8 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 9 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Example 10 0.5 35 8 40 Diamond shape, 0.5 rugby ball type Comparative 0.5 40 12 70 Sea urchin type 0.0 Example 1 Comparative 0.5 40 12 43 Round shape 0.0 Example 2 Comparative 0.5 35 100 220 Sphere 0.0 Example 3 Zirconia particles abrasive gains pH Dispersant Crystal composition Adjusting pH Concentration [mass ratio] agent [] Compound [% by mass] Example 1 Monoclinic crystal: Nitric acid 4.5 Tetragonal crystal = 8:2 Example 2 Tetragonal crystal: Nitric acid 4.5 Cubic crystal = 1:9 Example 3 Tetragonal crystal: Nitric acid 4.5 Cubic crystal = 5:5 Example 4 Monoclinic crystal: Nitric acid 4.5 Tetragonal crystal = 1:9 Example 5 Monoclinic crystal: Nitric acid 4.5 Sorbitol 0.001 Tetragonal crystal = 8:2 Example 6 Monoclinic crystal: Nitric acid 4.5 Sorbitol 0.005 Tetragonal crystal = 8:2 Example 7 Monoclinic crystal: Nitric acid 4.5 Sorbitol 0.008 Tetragonal crystal = 8:2 Example 8 Monoclinic crystal: Nitric acid 4.5 Sorbitol 0.01 Tetragonal crystal = 8:2 Example 9 Monoclinic crystal: Nitric acid 4.5 Sorbitol 0.05 Tetragonal crystal = 8:2 Example 10 Monoclinic crystal: Nitric acid 4.5 Xylitol 0.01 Tetragonal crystal = 8:2 Comparative Monoclinic crystal Nitric acid 4.5 Example 1 Comparative Monoclinic crystal Nitric acid 4.5 Example 2 Comparative Monoclinic crystal Nitric acid 4.5 Example 3 Polishing speed Scratches Storage (/min) [number] stability Example 1 141 5 +37% Example 2 106 2 +32% Example 3 126 4 +34% Example 4 138 3 +38% Example 5 144 7 +34% Example 6 139 5 +22% Example 7 143 6 +1% Example 8 145 3 +0% Example 9 142 5 +0% Example 10 142 4 +3% Comparative 16.8 6 Example 1 Comparative 30.8 3 Example 2 Comparative 230 22 Example 3

(56) As is apparent from Table 1, it is found that the polishing compositions of Examples can polish an object to be polished containing an organic material (carbon) at a high polishing speed and can reduce the number of scratches after polishing.

(57) In addition, it is found from Table 1 that when sorbitol or xylitol (dispersants) is further added, aggregation of the zirconia particles can be effectively suppressed and dispersibility after storage can be improved.

Examples 11 to 15

(58) Zirconia particles 1 (abrasive grains) were obtained in the same manner as in Example 1. 29% by mass of ammonia water was provided as a pH adjusting agent.

(59) Polishing compositions 11 to 15 were prepared by mixing while stirring zirconia particles 1 (abrasive grains), ammonia water (pH adjusting agent), hydroxyethylidene diphosphonic acid (HEDP) (Example 11), methylenediphosphonic acid (MDPNA) (Example 12), nitrilotris(methylenephosphonic acid) (NTMP) (Example 13), tripolyphosphoric acid (Example 14), or ethylenediaminetetramethylenephosphonic acid (EDTMP) (Example 15) (phosphorus-containing compound), and pure water (dispersing medium) at room temperature (25 C.) for 30 minutes. A content of the ammonia water was set so as to achieve a pH of 4.5 for each of the polishing compositions 11 to 15. A zeta potential and an electrical conductivity (EC) of the zirconia particles in each of the polishing compositions 11 to 15 were measured. The results are shown in Table 2. An yttrium content and a crystal composition (phase configuration) of the zirconia particles in each of the polishing compositions 11 to 15 were the same as an yttrium content and a crystal composition (phase configuration) of the zirconia particles 1.

(60) The configurations of the polishing composition 1 of Example 1 and the polishing compositions 11 to 15 of Examples 11 to 15 are shown in Table 2. Ammonia water (pH adjusting agent) is represented as NH.sub.3 in Table 2.

(61) A polishing speed and the number of scratches of the polishing composition 1 of Example 1 and the polishing compositions 11 to 15 of Examples 11 to 15 were evaluated according to the following methods. The results are shown in Table 2.

(62) [Measurement of Polishing Speed 2]

(63) As an object to be polished (substrate), a silicon wafer (manufactured by Advanced Materials Technologies, 300 mm, blanket wafer) (substrate 2) having a surface on which a SiOC (low-k material) film was formed at a thickness of 5,000 was provided.

(64) Using each of the polishing compositions, the prepared substrate 2 was polished under the following conditions, and a polishing speed was measured.

(65) (Polishing Conditions)

(66) Polishing apparatus: CMP one-side polishing apparatus for 300 mm, FREX300E (manufactured by Ebara Corporation) Polishing pad: hard polyurethane pad (IC1010, manufactured by NITTA DuPont Incorporated) Polishing pressure: 2.0 psi (1 psi=6,894.76 Pa) Platen (table) rotation speed: 93 rpm Head (carrier) rotation speed: 87 rpm Supply of polishing composition: Continuously pouring without recycle Flow rate of polishing composition: 200 ml/min Polishing time: 60 seconds
(Polishing Speed)

(67) Film thicknesses before and after the polishing were determined by an optical film thickness measuring instrument (ASET-f5x, manufactured by KLA Corporation), and a polishing speed (/min) was calculated by dividing a difference () in film thickness before and after the polishing by a polishing time (min) (see the following equation). A polishing speed of the substrate 2 is preferably as high as possible.

(68) $\begin{array}{cc}\mathrm{Polishing}\mathrm{speed}\left(/\min \right)=\frac{\left[\mathrm{Film}\mathrm{thickness}\left(\right)\mathrm{of}\mathrm{object}\mathrm{to}\mathrm{be}\mathrm{polished}\mathrm{before}\mathrm{polishing}\right]-\left[\mathrm{Film}\mathrm{thickness}\left(\right)\mathrm{of}\mathrm{object}\mathrm{to}\mathrm{be}\mathrm{polished}\mathrm{after}\mathrm{polishing}\right]}{\left[\mathrm{Polishing}\mathrm{time}\left(\min \right)\right]}& \left[\mathrm{Math}.3\right]\end{array}$
[Measurement of Number 2 of Scratches]

(69) The substrate 2 (object to be polished) was polished using each of the polishing compositions under the following polishing conditions.

(70) (Polishing Conditions for Evaluating Number of Scratches)

(71) Polishing apparatus: CMP one-side polishing apparatus for 200 mm, Mirra (manufactured by Applied Materials, Inc) Polishing pad: hard polyurethane pad (IC1010, manufactured by NITTA DuPont Incorporated) Polishing pressure: 2.0 psi Platen (table) rotation speed: 83 rpm Head (carrier) rotation speed: 77 rpm Supply of polishing composition: Continuously pouring without recycle Polishing composition supply amount: 200 ml/min Polishing time: 60 seconds

(72) The number of scratches on a surface of the object to be polished after the polishing was determined by measuring coordinates of the entire surface of both surfaces of the object to be polished (excluding the outer periphery of 2 mm) using a wafer inspection apparatus Surfscan (registered trademark) SP2 manufactured by KLA Corporation, and observing all the measured coordinates with Review-SEM (RS-6000, manufactured by Hitachi High-Technologies Corporation). Scratches on a surface of a substrate having a depth of 10 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 m or more were counted as the scratches. The number of scratches is preferably as small as possible. The number of scratches is acceptable when it is less than 15, preferably less than 10, and more preferably 5 or less.

(73) TABLE-US-00002 TABLE 2 Zirconia particles (abrasive grains) Average Average primary secondary Y Concentration Potential particle particle content Crystal composition [% by mass] [mV] size [nm] size [nm] Shape [mol %] [mass ratio] Example 1 0.5 35 8 40 Diamond shape, 0.5 Monoclinic crystal: rugby ball type Tetragonal crystal = 8:2 Example 0.5 30 8 40 Diamond shape, 0.5 Monoclinic crystal: 11 rugby ball type Tetragonal crystal = 8:2 Example 0.5 31 8 40 Diamond shape, 0.5 Monoclinic crystal: 12 rugby ball type Tetragonal crystal = 8:2 Example 0.5 28 8 40 Diamond shape, 0.5 Monoclinic crystal: 13 rugby ball type Tetragonal crystal = 8:2 Example 0.5 26 8 40 Diamond shape, 0.5 Monoclinic crystal: 14 rugby ball type Tetragonal crystal = 8:2 Example 0.5 25 8 40 Diamond shape, 0.5 Monoclinic crystal: 15 rugby ball type Tetragonal crystal = 8:2 Phosphorus- pH containing compound Adjusting pH EC Concentration agent [] [mS/cm] Compound [% by mass] Example 1 Nitric acid 4.5 1 Example NH.sub.3 4.5 1 HEDP 0.03 11 Example NH.sub.3 4.5 1 MDPNA 0.03 12 Example NH.sub.3 4.5 1 NTMP 0.03 13 Example NH.sub.3 4.5 1 Tripoly- 0.03 14 phosphoric acid Example NH.sub.3 4.5 1 EDTMP 0.03 15 Polishing speed Scratches (/min) [number] Example 1 2312 5 Example 11 8071 3 Example 12 7520 4 Example 13 6489 5 Example 14 5123 5 Example 15 4329 5

(74) As is apparent from Table 2 above, it is found that by adding the phosphorus-containing compound, the polishing compositions 11 to 15 of Examples 11 to 15 can polish an object to be polished containing an organic material (SiOC which is a low-k material) at a higher polishing speed while keeping the number of scratches after polishing low.