WO2005093803A1

WO2005093803A1 - Composition for polishing semiconductor

Info

Publication number: WO2005093803A1
Application number: PCT/JP2005/005767
Authority: WO
Inventors: Yoshiharu Ohta; Yasuyuki Itai
Original assignee: Nitta Haas Incorporated
Priority date: 2004-03-29
Filing date: 2005-03-28
Publication date: 2005-10-06
Also published as: TW200602471A; JP2005286046A

Abstract

Polishing scratches in the surface of a semiconductor device is reduced significantly without damaging the advantage of fumed silica, i.e. high polishing speed, even though fumed silica is contained as a polishing agent. When a wafer (3) mounted on a pad (2) stuck to a turn table (1) is polished by exerting a load on the wafer (3) by means of a pressure head (4) and rotating the pad (2) and the pressure head (4), a water dispersion liquid of fumed silica containing 15% or more by volume of fumed silica particles having a particle size of 100 nm or less based on the entire fumed silica particles is employed as a polishing composition (5) supplied onto the pad (2). Since aggregation of fumed silica due to an external load and/or long term storage scarcely takes place, polishing scratches in the surface of a polished semiconductor device, especially those having a diameter of 0.2 μm or above, are scarcely produced and a high polishing speed is attained.

Description

Specification

Semiconductor polishing composition

Technical field

The present invention relates to a semiconductor polishing composition.

Background art

[0002] The I匕学mechanical polishing (CMP, Chemical Mechanical Polishing) is to flatten the semiconductor wafer, in order to achieve high performance and high integration of semiconductor devices, the current in the required essential technique ^ ¹ It has become.

In the CMP process, the wafer is placed on the pad attached to the polishing platen so that the polished surface of the wafer is in contact with the pad, and a pressing head is pressed against the wafer to apply a certain load to the wafer and polish it. The wafer is polished by rotating the pad and the pressure head while supplying the composition for use to the pad surface.

The polishing composition is an aqueous slurry in which a polishing agent is dispersed, and an appropriate polishing agent is selected from various polishing agents depending on the material of a film formed on the surface to be polished of the wafer. Among them, silica-based abrasives such as colloidal silica and fumed silica are widely used (for example, see JP-A-52-47369).

Among these silica-based abrasives, colloidal silica has excellent dispersion stability in water. Therefore, when the concentration of the colloidal silica in the polishing composition, which is an aqueous dispersion of colloidal silica, is within an appropriate range, aggregation of the colloidal silica hardly occurs even after long-term storage. However, colloidal silica has the advantage of requiring more time to polish wafers with relatively low polishing rates. Therefore, a polishing accelerator such as an organic acid, an oxidizing agent such as hydrogen peroxide, a corrosion inhibitor such as a benzotriazole compound, a surfactant, and the like are used together with colloidal silica. Colloidal silica is industrially manufactured using sodium silicate as a raw material, and as a result, may contain impurities such as sodium and contaminate the wafer during polishing. Therefore, it is necessary to purify and highly purify colloidal silica. As described above, when colloidal silica is manufactured industrially, a purification step for high purification is indispensable, productivity is reduced, and manufacturing cost is reduced. To rise.

On the other hand, fumed silica has a higher polishing rate than colloidal silica. Since it is synthesized by combustion of silicon tetrachloride in an oxyhydrogen flame, the amount of impurities is small and it is industrially inexpensive. However, fumed silica has poor dispersibility in water. Therefore, the polishing composition, which is an aqueous dispersion of fumed silica, is subjected to a pipe load (such as a collision with the inner wall of the pipe) during supply to the CMP process, and a load of a supply pump (such as a pressure load by the supply pump). Agglomeration of fumed silica occurs due to external loads such as pressure applied to the pressure head (pressure applied by the pressure head, etc.) and environmental conditions during transportation. Also, fumed silica is likely to aggregate during long-term storage. Fumed silica, which has become large particles due to agglomeration, generates many polishing scratches on the wafer. Such a polishing flaw impairs the reliability of the electrical connection of the wafer.If there are many polishing flaws, particularly if the polishing flaw exceeds 0.2 xm in diameter per wafer, the wafer is damaged. Becomes defective, and the yield in the polishing process decreases.

In view of the high polishing rate and cost advantage of fumed silica, various techniques for improving the water dispersibility have been proposed.

For example, water and fumed silica are mixed while being subjected to high shearing force to obtain an aqueous dispersion containing a high concentration of fumed silica. There is a method of obtaining a polishing composition containing mudosilica (for example, see Japanese Patent No. 2935125).

Further, an acid and fumed silica are sequentially added and mixed with water while applying a high shearing force, and after further adding water, an alkali aqueous solution is added to obtain a polishing composition containing fumed silica. (For example, see Japanese Patent No. 2949633) Further, fumed silica is added to water having a pH of 2 to 4 while applying a high shearing force so that the concentration becomes 40 to 60% by weight, and further water is added. Adjust the viscosity to 2 ~:! OOOOcps, stir for more than 5 minutes while applying low shear force, add water to adjust the fumed silica concentration to 10-38% by weight, and then add alkali under strong stirring And adjusting the pH to 9 to 12 to obtain a polishing composition containing fumed silica. — See No. 26771).

However, the polishing compositions described in Japanese Patent No. 2935125, Japanese Patent No. 2949633, and Japanese Patent Application Laid-Open No. 2001-26771 have improved water dispersibility of fumed silica compared to conventional ones. However, it has not yet reached a satisfactory level. Therefore, fumed silica cannot be prevented from aggregating due to external load and / or long-term storage.

Disclosure of the invention

An object of the present invention is to provide a semiconductor polishing composition which is an aqueous dispersion of fumed silica and which can efficiently polish a semiconductor device such as a wafer at a high polishing rate without causing polishing scratches. It is to be.

The present invention is an aqueous dispersion of fumed silica, wherein the content of fumed silica having a particle size of 100 nm or less is 15% by volume or more of the total amount of fumed silica, and is a composition for polishing a semiconductor. .

Further, the semiconductor polishing composition of the present invention is characterized in that the content of fumed silica having a particle size of 100 nm or less is 15 to 90% by volume (15 to 90% by volume) of the total amount of fumed silica. I do.

Further, the semiconductor polishing composition of the present invention is characterized in that the maximum frequency particle size is in the range of 115 nm or less in the volume-based particle size distribution of fumed silica. Further, the semiconductor polishing composition of the present invention is characterized in that, in the volume-based particle size distribution of fumed silica, the maximum frequency particle size is in the range of 80 to 115 nm (80 nm or more and 115 nm or less). .

Furthermore, the semiconductor polishing composition of the present invention is characterized in that the content of the above-mentioned fumed silica is 10 to 30% by weight (10% to 30% by weight) of the total amount of the composition. Further, the semiconductor polishing composition of the present invention is characterized by being prepared by adding an acidic fumed silica dispersion to an aqueous alkaline solution.

Further, the semiconductor polishing composition of the present invention is characterized in that the pH of the above-mentioned aqueous solution is 12 to 14 (12 or more, 14 or less).

Brief Description of Drawings [0004] The objects, features and advantages of the present invention will become more apparent from the following detailed description and drawings.

FIG. 1 is a drawing schematically showing a CMP process.

FIG. 2 is a graph showing a volume ratio (%) of particles having a particle diameter and particles having a particle diameter smaller than the particle diameter in all the fumed silica particles in the semiconductor polishing composition.

FIG. 3 is a graph showing, as a frequency (%), a volume ratio of particles of each particle diameter to all fumed silica particles in the semiconductor polishing composition of the present invention.

FIG. 4 is a graph showing, as a frequency (%), a volume ratio of particles of each particle diameter to all fumed silica particles in a semiconductor polishing composition of a comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

The semiconductor polishing composition of the present invention (hereinafter simply referred to as “polishing composition” unless otherwise specified) is an aqueous dispersion of fumed silica having a content of fumed silica having a particle size of 100 nm or less. It is 15% by volume or more, preferably 15 to 90% by volume of the total amount of fumed silica. When the content of the particle diameter lOOnm or less fumed silica exceeds 15 volume ^_0/0, and reduced water dispersible Hyumudoshiri force, external load and Z or storage, occur agglomeration of Hiyu fumed silica in particular long-term storage, It causes many polishing scratches on the surface of semiconductor devices such as wafers.

The polishing composition of the present invention preferably has a maximum frequency particle size (that is, a particle size having the largest volume ratio to the total amount of fumed silica) of 115 nm or less in the volume-based particle size distribution of fumed silica. More preferably, it is 80 to 115 nm. When the maximum frequency is in the above range, the effects of the present invention are more remarkably exhibited.

In this specification, the volume-based particle size distribution and the particle size (including the average particle size) of the fumed silica are measured by a laser diffraction / scattering type particle size distribution analyzer (trade name: LA910, manufactured by Horiba, Ltd.) It is a value measured using.

As the fumed silica used in the present invention, those conventionally used in this field can be used.However, considering its water dispersibility and polishing rate, the average primary particle diameter is preferably 1 to 500 nm, more preferably. Is 5 to 300 nm, particularly preferably 5 to 80 nm. Although the specific surface area of the fumed silica is not particularly limited, the specific surface area measured by the BET method is preferably 400 m ² / g or less, more preferably 50 to 50 μm, in consideration of its water dispersibility and polishing rate. 200 m ² / g, particularly preferably 50 to 150 m ² / g.

As fumed silica, two or more kinds of fumed silica having different average primary particle diameters and Z or specific surface areas can be used in combination.

Fumed silica can be produced, for example, by gas phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame. Further, it can be produced by the method described in JP-A-2000-86227. According to the publication, a volatile silicon compound is supplied to a burner together with a combustible gas and a mixed gas containing oxygen, and is burned at a temperature of 1000 to 2100 ° C. to thermally decompose the volatile silicon compound. Thus, fumed silica can be produced. Here, known volatile silicon compounds can be used, for example, SiH, SiCl, CH SiCl, CH

4 4 3 3 3

SiHCl, HSiCl, (CH) SiCl, (CH) SiCl, (CH) SiH, (CH) SiH,

2 3 3 2 2 3 3 3 2 2 3 3 Coxysilanes and the like. Among these, a volatile silicon compound containing a halogen atom is preferable. The volatile silicon compounds can be used each alone or two or more of them can be used in combination. As the combustible gas, a gas that generates water by combustion in the presence of oxygen is preferable, and examples thereof include hydrogen, methane, and butane. Air can be used instead of oxygen. The usage ratio of the volatile silicon compound and the mixed gas is appropriately selected according to the type of combustible gas contained in the mixed gas. For example, when the combustible gas is hydrogen, about 2.5 to 3.5 moles of oxygen and about 1.5 to 3.5 moles of hydrogen may be used per mole of the volatile silicon compound.

In the present invention, a commercially available fumed silica can also be used. Specific examples thereof include AEROSIL 90G and AEROSIL 130 (both are trade names, manufactured by Nippon Aerosil Co., Ltd.).

The content of the fumed silica in the polishing composition of the present invention is not particularly limited and can be appropriately selected from a wide range according to the average primary particle diameter, the specific surface area, and the like. In consideration of holding and obtaining a high polishing rate, the polishing composition is preferably used in an amount of from: to 30% by weight, more preferably from 10 to 28% by weight, based on the total amount of the polishing composition. The polishing composition of the present invention may include, for example, a polishing accelerator, an oxidizing agent, an organic acid, a complexing agent, a corrosion inhibitor, a surfactant and the like within a range that does not impair the water dispersibility of the fumed silica. Common additives may be included.

Examples of the polishing accelerator include piperazines, primary amine compounds having 1 to 6 carbon atoms, and quaternary ammonium salts. Examples of the piperazine include piperazine, anhydrous piperazine, piperazine hexahydrate, N-aminoethylpiperazine, 1,4-bis (3-aminopropyl) pirazine, and the like. Examples of the primary amine compound having a carbon number of! To 6 include α-oxshetylamine (α-aminoethyl alcohol), monoethanolamine (aminoaminoethyl alcohol), and aminoethylethanol. Min, triethylenetetramine, ethylenediamine and the like. Examples of the quaternary ammonium salts include, for example, tetramethylammonium chloride, tetramethylammonium hydroxide, dimethylethylammonium chloride, Ν, Ν-dimethylmorpholinium sulfate, and tetrabutylammonium salt. And ammonium bromide. One type of polishing accelerator can be used alone, or two or more types can be used in combination. The content of the polishing accelerator in the polishing composition of the present invention is not particularly limited, but is preferably about 0.001 to 5% by weight of the total amount of the polishing composition. Examples of the oxidizing agent include potassium iodate, periodic acid, potassium iodide, iodic acid and the like. One oxidizing agent can be used alone, or two or more oxidizing agents can be used in combination. The content of the oxidizing agent in the polishing composition of the present invention is not particularly limited, but is preferably about 0.01 to 20% by weight of the total amount of the polishing composition.

Examples of organic acids include monocarboxylic acids having 2 to 6 carbon atoms such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and lactic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, malic acid, fumaric acid, and the like. Examples thereof include dicarboxylic acids having 2 to 6 carbon atoms, tricarboxylic acids having 3 to 6 carbon atoms such as citric acid and isocunic acid, aromatic carboxylic acids such as salicylic acid, and ascorbic acid. Organic acids also include the salts of the carboxylic acids and ascorbic acid. One type of organic acid can be used alone, or two or more types can be used in combination. The content of the organic acid in the polishing composition of the present invention is not particularly limited, but is preferably about 0.005 to 5% by weight of the total amount of the polishing composition.

Examples of complexing agents include ethylenediaminetetraacetic acid (EDTA), Rangenamine triacetic acid (HEDTA), diethylenetriamine pentaacetic acid (DTP A), nitrite triacetic acid (NTA), triethylenetetramine hexaacetic acid (TTHA), hydroxyethylimino diacetic acid (HIDA), dihydroxyethylglycine ( DHEG), ethylene glycol-bis (/ 3-aminoethynoleether) -N, N, 14-acetic acid (EGTA), 1,2-diaminocyclohexane-N, N, Ν,, Ν '_4 acetic acid (CDTA), etc. Is mentioned. One complexing agent can be used alone, or two or more complexing agents can be used in combination. The content of the complexing agent in the polishing composition of the present invention is not particularly limited, but is preferably about 0.005 to 5% by weight of the total amount of the polishing composition.

Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, benzotriazole-4 monocarboxylic acid and its alkyl ester, naphthotriazole and its derivative, imidazole, quinaldic acid, and invar derivative. One type of corrosion inhibitor can be used alone, or two or more types can be used in combination. The content of the corrosion inhibitor in the polishing composition of the present invention is not particularly limited, but is preferably about 0.005 to 0.5% by weight of the total amount of the polishing composition.

Examples of the surfactant include anionic surfactants such as a polyacrylate, an alkylbenzene sulfonate, an alkane sulfonate, and _a -olefin sulfonate, a fatty acid monoethanolamide, a fatty acid diethanolamide, and a fatty acid ethylene. Glycol ester, mono fatty acid glycerin ester, fatty acid sorbitan ester, fatty acid sucrose ester, alkyl polyoxyethylene ether, polybutylpyrrolidone, polybutylal cornole, hydroxyethynoresenorelose, canoleboxy methinoresenorelose, polyethylene glycol And other nonionic surfactants. One surfactant may be used alone, or two or more surfactants may be used in combination. The content of the surfactant is not particularly limited, but is preferably about 1% by weight or less of the total amount of the polishing composition, more preferably about 0.001 to:!% By weight.

Further, the polishing composition of the present invention may contain alcohols as long as the preferable properties are not impaired. By adding alcohols, for example, dissolution stability of a polishing accelerator or the like can be improved. As the alcohols, aliphatic saturated alcohols having 1 to 6 carbon atoms are preferred. Specific examples thereof include, for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol. And linear or branched aliphatic saturated alcohols having 1 to 6 carbon atoms, such as toluene, pentanol and hexanol. These alcohols may have a substituent such as a hydroxyl group in the alkyl moiety. Alcohols can be used alone or in combination of two or more. The content of the alcohol in the polishing composition of the present invention is not particularly limited, but is preferably about 0.0 :! to 5% by weight of the total amount of the polishing composition.

The polishing composition of the present invention can be produced, for example, by a method including the following steps (1) to (5).

(1) Adjustment process of acidic aqueous solution

In this step, an acidic aqueous solution is prepared. The acidic aqueous solution can be prepared by adding an acid to water. Known acids can be used as the acid, and examples thereof include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as phosphoric acid. Of these, hydrochloric acid, which is preferred by inorganic acids, is particularly preferred. The acids can be used alone or in combination of two or more if necessary. The pH of the acidic aqueous solution is preferably 1.0 to 3.0, more preferably 1.0 to 2.7, and particularly preferably 2.

(2) Mixing process of acid solution and fumed silica

In this step, an acidic aqueous solution and fumed silica are mixed to prepare an acidic fumed silica dispersion. It is preferable that the mixing is performed while high shearing force is applied. The mixing time is not particularly limited, but is preferably 1 hour or more, and more preferably 2 hours or more.

The concentration of the fumed silica in the acidic fumed silica dispersion is not particularly limited, but is preferably 40 to 60% by weight, more preferably 46 to 54% by weight of the total amount of the dispersion.

(3) Acid fumed silica dispersion dilution step

In this step, water is added to the acidic fumed silica dispersion to dilute the concentration of the fumed silicate in the dispersion to preferably 30 to 45% by weight, more preferably 33 to 44% by weight. At this time, it is preferable to carry out a plurality of water additions instead of lowering the concentration to a desired concentration by one water addition, and to dilute the water stepwise. It is particularly preferable to add water about 2 to 4 times. For example, the acidic fumed silica dispersion, the concentration of fumed silica added 1 weight ^_0/0 decreased to that amount of water and mixed for about 10 to 40 minutes. Then, further fumed silica concentration Of water to a desired concentration, and mix for about 30 minutes to 4 hours. In mixing, it is preferable to apply a shearing force.

In addition, the mixing time after adding water to the acidic fumed silica dispersion liquid is not limited to the above, and can be appropriately selected according to the degree of dilution (water addition). In general, the greater the degree of dilution, the longer the mixing time.

(4) Preparation process of alkaline aqueous solution

In this step, an aqueous alkaline solution is prepared. The alkaline aqueous solution can be prepared by adding alkali to water. Known alkalis can be used, for example, hydroxides of alkali metals such as ammonium hydroxide, sodium hydroxide and potassium hydroxide, and alkaline earth metals such as calcium hydroxide, barium hydroxide and magnesium hydroxide. Hydroxide and the like. Of these, ammonium hydroxide is more preferred, with alkali metal hydroxides and ammonium hydroxide being preferred. One alkali can be used alone, or two or more alkalis can be used in combination as needed.

One or more general additives such as a polishing accelerator, an oxidizing agent, an organic acid, a complexing agent, a corrosion inhibitor, a surfactant and the like can be added to the aqueous alkali solution.

The pH of the alkaline aqueous solution is preferably 12-14.

(5) Preparation process of polishing composition

In this step, the polishing composition of the present invention is prepared.

The polishing composition of the present invention can be prepared by calorically mixing an acidic aqueous fumed silica dispersion with an aqueous alkaline solution.

For mixing, it is necessary to add an acidic fumed silica dispersion to an aqueous alkaline solution. Conversely, when an aqueous alkali solution is added to the acidic fumed silica dispersion, the water dispersibility of the fumed silica is reduced, and a desired polishing composition cannot be obtained. Also, upon mixing, the aqueous alkaline solution is strongly alkaline and the acidic fumed silica dispersion is strongly acidic. Agglomeration of do silica tends to occur. Therefore, according to the concentration of the fumed silica in the acidic fumed silica dispersion, it is preferable to add the calories so as not to cause aggregation. More preferably, an alkaline aqueous solution of an acidic fumed silica dispersion liquid It should be carried out so that the addition to the solution is completed within 5 hours.

The mixing ratio of the acidic fumed silica dispersion and the aqueous alkali solution is not particularly limited, but the pH of the polishing composition is preferably 8 to 12 and the fumed silica concentration is preferably 10 to 30% by weight. Mixing may be performed.

The polishing composition thus obtained can be subjected to classification, if necessary. Classification can be performed according to a known method, for example, filtration with a filter. As a filter used for the filter filtration, for example, a depth type filter having a filtration accuracy of about!

In addition, the water used for preparing the polishing composition of the present invention is not particularly limited, but in consideration of use, ultrapure water, pure water, ion-exchanged water, distilled water, and the like are preferable.

When polishing a semiconductor device such as a wafer using the polishing composition of the present invention, the same as conventional polishing of a wafer except that the polishing composition of the present invention is used instead of the conventional polishing composition. Can be done. For example, as shown in FIG. 1, a wafer 3 is placed on a pad 2 affixed to a polishing platen 1 such that a surface to be polished of the wafer 3 is in contact with the pad 2, and a pressure head 4 is mounted on the wafer 3. The wafer 3 is polished by rotating the node 2 and the pressure head 4 while pressing and applying a constant load to the wafer 3 and supplying the polishing composition 5 to the surface of the pad 2. .

The polishing composition of the present invention can be used as a polishing composition in general CMP processing of wafers. Specifically, thin films formed on wafers, such as metal films such as W, Cu, Ti, and Ta, ceramic films such as TiN, TaN, and SiN, and oxide films such as SiO and p-TEOS

3 4 2

It can be suitably used for polishing a wafer on which a thin film such as a low dielectric film such as a HSQ film, a methylated HSQ film, a SiLK film, or a porous film is formed.

Further, the polishing composition of the present invention is not limited to CMP processing of a semiconductor wafer, and can be suitably used when polishing metals, ceramics, and the like for other uses.

Example

Hereinafter, the present invention will be specifically described with reference to Examples, Comparative Examples, and Test Examples.

(Example 1)

[Preparation of acidic fumed silica dispersion] 0.01N hydrochloric acid aqueous solution was added to ultrapure water to adjust the pH to 2. This aqueous solution of hydrochloric acid, fumed silica (average primary particle diameter 20 nm, specific surface area 90m ² Zg) mosquitoes卩Ete 2 hours combined 30 minutes mixing, the fumed silica concentration is 50 wt ^_0/0, the acidic fumed silica A dispersion was prepared.

[Dilution of acidic fumed silica dispersion]

Ultrapure water was added to the acidic fumed silica dispersion and mixed for 30 minutes. As a result, an acidic fumed silica dispersion having a fumed silica concentration of 49% by weight was obtained.

Further, ultrapure water was added to the acidic fumed silica dispersion having a fumed silica concentration of 49% by weight and mixed for 1 hour. Thus, the acidic Hyumudoshiri force dispersion of fumed silica concentration of 40 weight ^_0/0 was obtained. The pH of the dispersion was 2.

In addition, the above mixing was performed while applying a shearing force using a high shear dispersing apparatus (trade name: Hibis Disper, manufactured by Tokushu Kika Co., Ltd.) in each case.

[Preparation of alkaline aqueous solution]

A 0.9 wt% aqueous solution of ammonium hydroxide was added to ultrapure water to prepare a pH 13 aqueous solution of anorecali.

[Preparation of Polishing Composition of the Present Invention]

To 26.3 kg of the alkaline aqueous solution, 43.7 kg of an acidic fumed silica dispersion having a fumed silica concentration of 40% by weight was added with stirring, and after the addition was completed, the mixture was further mixed for 0.1 hour to prepare the polishing composition of the present invention. Prepared.

The obtained polishing composition was filtered with a filter having a filtration accuracy of 1 μm (trade name: Profile 2, manufactured by Pall Corporation) to remove coarse aggregated particles. The polishing composition had an average particle size of fumed silica of 90 nm, a fumed silica concentration of 25% by weight, and a pH of 10.5.

(Example 2)

In the preparation process of the acidic fumed silica dispersion, the polishing composition of the present invention (fumed silica) was prepared in the same manner as in Example 1 except that the mixing time between the aqueous hydrochloric acid solution of pH 2 and the fumed silica was changed to 2 hours. An average particle diameter of 110 nm, a fumed silica concentration of 25% by weight, and a pH of 10.5) were prepared. (Example 3)

In the preparation step of the acidic fumed silica dispersion liquid, the polishing composition of the present invention (fumed silica) was prepared in the same manner as in Example 1 except that the mixing time of the pH 2 aqueous hydrochloric acid solution and the fumed silica was changed to 4 hours. An average particle diameter of 87 nm, a fumed silica concentration of 25% by weight, and a pH of 0.5) were prepared.

(Comparative Example 1)

The fumed silica is crushed in ultrapure water to a concentration of 30% by weight, dispersed for 30 minutes, and further dispersed by applying a shearing force using a high-shear disperser (Hibis Disper) to obtain a fumed silica concentration. 30 wt ^_0/0, were prepared fumed silica dispersion.

This fumed silica dispersion was mixed with a 0.9% by weight aqueous solution of ammonium hydroxide to obtain a polishing composition of Comparative Example 1 (average particle diameter of fumed silica 150 nm, fumed silica concentration 13% by weight, pH 10 7) was prepared.

(Comparative Example 2)

A polishing composition was prepared according to Example 1 of the specification of Japanese Patent No. 2935125, filtered through a filter having a filtration accuracy of 5 μm, and then subjected to a polishing composition of Comparative Example 2 (average particle diameter of fumed silica of 120 nm). Fumed silica concentration 25% by weight, pH 11). In addition, this polishing composition was clogged with a filter having a filtration accuracy of 1 μm, and could not be sufficiently filtered.

(Comparative Example 3)

A polishing composition was prepared according to Example 1 of the specification of Japanese Patent No. 2949633, and filtered through a filter having a filtration accuracy of 10 μm. The polishing composition of Comparative Example 3 (average particle diameter of fumed silica of 120 nm) was used. , fumed silica concentration of 25 weight ^{_0/0, pHl} l) was prepared. In addition, this polishing composition was clogged with a filter having a filtration accuracy of 1 μm, and could not be sufficiently filtered.

(Comparative Example 4)

A polishing composition was prepared according to Example 1 of JP-A-2001-26771, and filtered with a filter having a filtration accuracy of 3 μm. The polishing composition of Comparative Example 4 (average particle diameter of fumed silica) was used. 131 nm, fumed silica concentration 12.5 wt ^{_0/0, ρΗΙΟ.} 5) was prepared. Note that this The polishing composition was clogged with a filter having a filtration accuracy of 1 μm, and could not be sufficiently filtered.

(Test Example 1)

For the polishing compositions of Examples:! -3 and Comparative Examples:! -4, the particle size distribution of fumed silica was determined using a laser diffraction Z-scattering particle size distribution analyzer (trade name: LA910). The results are shown in FIGS.

Fig. 2 shows the particle size (xm) on the horizontal axis and the frequency accumulation (%) on the vertical axis, and the volume ratio of particles of each particle size (μηι) or less in the polishing composition to the total fumed silica particles. Is a graph showing the frequency accumulation (%). 3 and 4, the horizontal axis represents the particle diameter m) and the vertical axis represents the frequency (%), and the frequency (%) of the particles of each particle diameter in the polishing composition relative to the total fumed silica particles is expressed as the frequency (%). %). 3A shows Example 1, FIG. 3B shows Example 2 and FIG. 3C shows Example 3. In FIG. 4, FIG. 4A shows Comparative Example 1, FIG. 4B shows Comparative Example 2, and FIG. 4C shows Comparative Example 4.

The volume ratio of particles having a particle size of lOOnm or less is as follows: Example 1: 78%, Example 2: 20%, Example 3: 89%, Comparative example 1: 3%, Comparative example 2: 6%, Comparative example 4: 9%. Note that Comparative Example 3 showed almost the same as Comparative Example 2.

In addition, the maximum frequency indicating the largest volume ratio is as follows: Example 1: 0.100 xm, ί row 2: 115 xm, ί row 3: 0.087 zm, it comparison ί row 1: 0.172 xm, i comparison ί Row 2: 0.131 μm, Comparative Example 4: 0.131 zm. Note that Comparative Example 3 showed almost the same value as Comparative Example 2.

(Test Example 2)

Using the polishing compositions of Examples:! -3 and Comparative Examples:! -4, polishing of silicon wafers was performed under the following conditions.

[Polishing conditions]

Silicon wafer: 8 "_PETE〇S, manufactured by Advantech Co., Ltd.

Polishing device: Product name SH24, SpeedFam manufactured polishing pad: Product name IC1400A2, 0 50 K-Grv.24 "P9H Polishing table rotation speed: 60rpm

Caro pressure head rotation speed: 41rpm

Polishing load surface pressure: about 4.83 X 10 ⁴ Pa (7psi)

Flow rate of polishing composition for semiconductor polishing: lOOmlZ min

Polishing time: 60 seconds

The polished semiconductor wafer surface was observed with a wafer surface inspection device, and the number of polishing scratches having a diameter of 0.2 x m or more per semiconductor wafer was examined. The polishing test was performed three times for each composition. The results are shown in Table 1.

[table 1]

When the semiconductor polishing composition of Comparative Example 3 was used, almost the same number of polishing flaws as those of Comparative Example 2 were generated.

From Table 1, it can be seen that the semiconductor polishing compositions of Examples: ~ 2 have less than 100 polishing scratches with a diameter of 0.2 / m or more, whereas the comparative examples:! ~ 3 It is evident that significantly more than 100 polishing scratches occur. At present, it is required that the number of polishing scratches having a diameter of 0.2 m or more is less than 100 for the purpose of securing the reliability of electrical connection of the semiconductor wafer. It is clear that this is an excellent semiconductor polishing composition that can satisfy the requirements.

The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in all aspects, and the scope of the present invention is defined by the claims, and is not restricted by the specification. Further, all modifications and changes belonging to the claims are within the scope of the present invention. is there.

Industrial applicability

According to the present invention, there is provided a water dispersion of fumed silica, 15 volumes of content force fumed silica the total amount of the following Hiyu fumed silica particle size lOOnm ^_0/0 or more, preferably 15 to 90 body product% A semiconductor polishing composition is provided.

The polishing composition of the present invention has very little aggregation of fumed silicon force due to external load and / or long-term storage. Therefore, when a semiconductor device is polished using the polishing composition, the reliability of the electrical connection after polishing of the semiconductor device, which hardly causes polishing scratches on the semiconductor device, can be further improved. In addition, semiconductor devices can be efficiently polished (planarized) at a high polishing rate. Therefore, the yield of the semiconductor device after polishing can be improved, and the production efficiency can be increased.

According to the present invention, the content of the fumed silica having a particle size of 100 nm or less is 15 vol% or more, preferably 15 to 90 vol%, and the maximum frequency in the volume-based particle size distribution of the fumed silica. By using a semiconductor polishing composition having a particle diameter of 115 nm or less, preferably 80 to 115 nm, the above-described effects of the present invention become more remarkable.

Further, according to the present invention, the content of fumed silica in the polishing composition of the present invention is preferably 10 to 30% by weight, more preferably 10 to 28% by weight of the total amount of the composition. When the content of fumed silica is within this range, its water dispersibility is particularly good.

Further, according to the present invention, the polishing composition of the present invention can be produced preferably by adding an acidic pseudosilica dispersion to an aqueous alkaline solution and mixing.

At that time, it is more preferable that the pH of the aqueous alkali solution is 12 to: 14. By adjusting the pH in this manner, the polishing composition of the present invention can be easily produced.

Claims

The scope of the claims

[1] An aqueous dispersion of fumed silica, wherein the content of fumed silica having a particle size of 100 nm or less is 15% by volume or more of the total amount of fumed silica.

[2] The semiconductor polishing composition according to claim 1, wherein the content of fumed silica having a particle size of 100 nm or less is 15 to 90% by volume of the total amount of fumed silica.

3. The semiconductor polishing composition according to claim 1, wherein the maximum frequency particle size is in a range of 115 nm or less in a volume-based particle size distribution of the fumed silica.

[4] The semiconductor polishing material according to any one of claims 1 to 3, wherein the maximum frequency particle size is in the range of 80 to 115 nm in the volume-based particle size distribution of the fumed silica. Composition.

[5] The composition for polishing a semiconductor according to any one of claims 1 to 4, wherein the content of the fumed silica is 10 to 30% by weight of the total amount of the composition.

[6] The semiconductor polishing composition according to any one of [1] to [5], which is prepared by adding an acidic fumed silica dispersion to an aqueous alkaline solution.

7. The composition for polishing a semiconductor according to claim 6, wherein the alkaline aqueous solution has a pH of 2 to 14.