JP2019127511A - Polishing composition - Google Patents

Abstract

To provide a polishing composition capable of suppressing generation of grazing.SOLUTION: There is provided a polishing composition comprising silica abrasive grain, a polishing promoter including a basic compound, and water. A total surface area of the silica abrasive grain is 150 m/L or greater. An average secondary particle diameter of the silica abrasive grain is 35 nm or greater.SELECTED DRAWING: None

Description

  The present disclosure relates to a polishing composition.

  In a semiconductor polishing composition containing silica-based abrasive particles such as colloidal silica and fumed silica, polishing dust generated when polishing a wafer accumulates in a polishing pad, and a phenomenon called glazing occurs. When glazing occurs, there arises a problem that the polishing performance is reduced, such as a reduction in the amount of grinding, and the polishing pad is colored depending on the polishing composition.

  In order to prevent glazing, there is a method of adding an alkali to increase the pH to 11 or more. However, in the high pH region, the dispersion stability of the abrasive particles is lowered, and as a result, the problem of aggregation and dissolution of the abrasive particles arises.

  JP-A-2004-335723 (Patent Document 1) discloses that the content of silica-based abrasive particles is 0.05 to from the total amount of the composition in order to prevent the occurrence of glazing without impairing the dispersion stability of the abrasive particles. Disclosed is a composition for semiconductor polishing, which is 3.0% by weight and has a weight ratio of silica-based abrasive particles to polishing accelerator (polishing accelerator / silica-based abrasive particles) of 0.8 to 20.

JP, 2004-335723, A

  An object of the present disclosure is to provide a polishing composition that suppresses the occurrence of glazing.

The polishing composition according to the present embodiment contains silica abrasive grains, a polishing accelerator containing a basic compound, and water. The total surface area of the silica abrasive grains is 150 m ² / L or more. The average secondary particle diameter of the silica abrasive grains is 35 nm or more.

  According to this embodiment, a polishing composition that suppresses the occurrence of glazing can be obtained.

FIG. 1 is a photograph confirming the coloring of the polishing pad.

The polishing composition according to the present embodiment contains silica abrasive grains, a polishing accelerator containing a basic compound, and water. The total surface area of the silica abrasive grains is 150 m ² / L or more. The average secondary particle diameter of the silica abrasive grains is 35 nm or more.

  Examples of the silica abrasive grains include colloidal silica, fumed silica, colloidal alumina, fumed alumina, cerium oxide, silicon carbide, and silicon nitride. Of these, colloidal silica is preferably used.

  The basic compound functions as a polishing accelerator that etches and chemically polishes the surface of the wafer. The basic compound is, for example, an inorganic alkali compound or an amine compound.

Inorganic alkali compounds include, for example, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, alkaline earth metal carbonates Hydrogen salt etc. are mentioned. Specifically, the inorganic alkali compound is potassium hydroxide (KOH), sodium hydroxide, potassium hydrogencarbonate, potassium carbonate (K ₂ CO ₃ ), sodium hydrogencarbonate, sodium carbonate or the like.

  Examples of the amine compound include a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium and a salt thereof, and a heterocyclic amine. Specifically, ammonia, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, hexylamine, Cyclohexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, monoethanolamine, diethanolamine, triethanolamine, N- (β-aminoethyl) ethanolamine, anhydrous piperazine , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methyl piperazine, piperazine hydrochloride, carbonate Blurred, and the like.

  The basic compound mentioned above may be used individually by 1 type, and 2 or more types may be mixed and used for it. The total content of the basic compounds is not particularly limited, and is, for example, 0.1 to 7% by mass of the entire polishing composition. The lower limit of the basic compound content is preferably 1.5% by mass. The upper limit of the content of the basic compound is preferably 6% by mass.

  The pH is from 9.0 to 12.0. The pH of the polishing composition can be adjusted by blending the basic compound.

The total surface area of the silica abrasive grains is calculated by the following formula (1).
Total surface area of silica abrasive grains (m ² / L) = specific surface area of silica abrasive grains (m ² / g) × mass of silica abrasive grains contained in 4 L of diluted slurry (g) ÷ use amount of slurry (L ) ... (1)

In Formula (1), the specific surface area of a silica abrasive is a surface area per unit mass (m ² / g) of a silica abrasive measured by pulse NMR method. The specific surface area of the silica abrasive can be measured, for example, using a pulse NMR evaluation apparatus “Acron area” manufactured by Xigo nanotools, US.

The lower limit of the total surface area of the silica abrasive grains is 150 m ² / L, preferably 160 m ² / L, and more preferably 178 m ² / L. The upper limit of the total surface area of the silica abrasive grains is not particularly limited, and may be, for example, 5000 m ² / L, 10000 m ² / L, or 100,000 m ² / L.

  The silica abrasive grains in the polishing composition are usually dispersed in a state in which a plurality of silica abrasive grains are aggregated to form secondary particles. The average secondary particle size of the silica abrasive is the average of the secondary particle size of the silica abrasive measured by the dynamic light scattering method. The average secondary particle diameter can be measured, for example, using a dynamic light scattering device “ELS-Z2” manufactured by Otsuka Electronics.

  The lower limit of the average secondary particle diameter is 35 nm, preferably 40 nm, more preferably 45 nm. The upper limit of the average secondary particle size is not particularly limited, but is preferably 130 nm so that the silica abrasive particles hardly settle. However, the upper limit of the average secondary particle diameter may be, for example, 100 nm, 90 nm, 85 nm, or 82 nm.

  The average secondary particle diameter measured by the dynamic light scattering method can be adjusted by the size of the primary particle diameter and the secondary particle diameter of the silica abrasive particles blended as a raw material in the polishing composition. The larger the primary particle size and the secondary particle size of the silica abrasive grains blended as a raw material in the polishing composition, the larger the average secondary particle size measured using the dynamic light scattering method.

  The average secondary particle size measured by the dynamic light scattering method also changes depending on the effect of the compound added to the polishing composition. The average secondary particle size measured by dynamic light scattering generally tends to decrease as the pH increases.

  In addition to the above, the polishing composition according to the present embodiment may optionally contain any compounding agent generally known in the field of polishing compositions, such as a chelating agent, a surfactant, and a water-soluble polymer.

  The polishing composition according to the present embodiment is produced by appropriately mixing the above compounding agent and water.

  The polishing composition described above is used for polishing a wafer after being diluted with water so as to obtain an appropriate concentration.

  The embodiment of the present invention has been described above. The above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

In order to confirm the effect of the above embodiment, nine types of polishing compositions (slurries) were prepared and tested as shown in Table 1 below.

  Comparative Examples 1 to 5 and Examples 1 to 3 are polishing compositions in which the slurry of the stock solution is diluted with water. Example 4 is a polishing composition comprising a slurry of the stock solution (not diluted with water).

  The total surface area of the silica abrasive grains was calculated by the above formula (1).

The specific surface area of the silica abrasive was measured using a pulse NMR evaluation apparatus "Acron area" manufactured by Xigo nanotools, US. Measurement conditions were: magnetic field: 0.3 T, measurement frequency: 13 MHz, measurement nucleus: ¹ H NMR, measurement method: CPMG pulse sequence method, sample amount: 500 μL or more, temperature: 25 ° C., Specific Surface Relaxivity (Ka): 0. It was set to 00002g / m < ² > / ms.

  About Comparative Examples 1-5 and Examples 1-3, a silica abrasive grain so that the total surface area of the silica abrasive grain contained in 4L polishing composition (slurry after dilution) diluted with water may become said value. Concentration was adjusted.

  The average secondary particle diameter of the silica abrasive was measured using a dynamic light scattering device "ELS-Z2" manufactured by Otsuka Electronics Co., Ltd.

  As basic compounds, potassium hydroxide (KOH) 0.5%, tetramethylammonium hydroxide (TMAH) 1.8%, diethylenetriamine (DETA) 1.5% were used, and the pH was adjusted to 10.0 or more.

  For Comparative Examples 1 to 4 and Example 2, the amount of abrasive grains contained in the slurry 4L is 22 g, for Comparative Example 5, the amount of abrasive grains contained in the slurry 4L is 36 g, and for Example 1 contained in the slurry 4L The amount of abrasives to be treated is 48 g, the amount of abrasives contained in 4 L of slurry for Example 3 is 64 g, and the amount of abrasives contained in 4 L of slurry for Example 4 is 1 488 g diluted with water to 4 L The polishing composition was prepared.

  Content of the silica abrasive grain in the polishing composition before dilution was 0.50-31.0 mass%.

  The prepared polishing composition was used to polish an 8-inch silicon wafer. Equipment and pads used for polishing, and polishing conditions are as follows.

Polishing device: Single-side polishing device Polishing pad: "SUBA ^TM 840" manufactured by Nitta Haas
Polishing conditions:
Polishing time: 40 minutes x 2 times Plate rotation speed: 115 rpm
Carrier rotation speed: 100 rpm
Polishing load: 300 g / cm ²
Slurry feed rate: 300 mL / min Plate cooling temperature: 25 ° C
Cooling temperature of slurry: 25 ° C
Slurry amount: 4L
Slurry supply: circulation

[Grazing evaluation method]
After the polishing for 40 minutes was repeated twice, the polishing pad (abrasive cloth) was visually observed to confirm the presence or absence of coloring.

As shown in the photograph of FIG. 1, the color of the polishing pad was visually recognized, and the value of ΔE ^* ab was measured using a color difference meter (color difference meter data processor “DP-400” manufactured by Konica Minolta Co., Ltd.). A color difference ΔE ^* ab of less than 1.6 was regarded as “not colored”, and a color difference Δ1.6 or more was regarded as “colored”. In Table 1, “No coloring” is indicated by “o” as “no glazing has not occurred”, and “colored” is indicated as “x” as “glazing has occurred”. Although the degree of coloring is quantified using a color difference meter, it is clearly seen that there is an inflection point where the degree of coloring changes largely in the vicinity of 1.6 of Comparative Example 4 by visual observation. When the color difference ΔE ^* ab is less than 1.6, the numerical value does not indicate the degree of coloring as it is.

[Test results]
It was confirmed that the generation of glazing can be suppressed when the total surface area of the silica abrasive grains is 150 m ² / L or more and the average secondary particle diameter is 35 nm or more.

  The cause of glazing is considered to be that silicon and alkali react during polishing, silicate ions are generated, exceed the saturation concentration, and cannot be dissolved in an aqueous solution, and are deposited and deposited on the surface of the polishing pad. When the total surface area of the silica abrasive grains is increased, it is considered that the precipitates remain on the surface of the silica abrasive grains by adsorption or particle growth. In the method for measuring the surface area using a known BET method, the surface area is measured by nitrogen adsorption on dry silica, which is different from the surface area of silica abrasive grains in an aqueous solution. The results of this test revealed that the total surface area of the silica abrasive grains in the aqueous solution was related to the occurrence of glazing.

Claims (1)

Silica abrasive grains,
A polishing accelerator comprising a basic compound;
Including water,
The total surface area of the silica abrasive grains is 150 m ² / L or more,
The polishing composition, wherein the average secondary particle diameter of the silica abrasive is 35 nm or more.