JP6960341B2 - Polishing composition - Google Patents

Description

The present disclosure relates to a polishing composition.

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

In order to prevent glazing, there is a method of adding an alkali to raise the pH to 11 or more. However, in the high pH region, the dispersion stability of the polishing particles is lowered, and as a result, a new problem arises that the polishing particles are aggregated and dissolved.

Japanese Patent Application Laid-Open No. 2004-335723 (Patent Document 1) states that the content of silica-based polishing particles is 0.05 to 0.05 to the total amount of the composition in order to prevent the occurrence of glazing without impairing the dispersion stability of the polishing particles. Disclosed is a composition for semiconductor polishing having a weight ratio of 3.0% by weight and a weight ratio of silica-based polishing particles to polishing accelerator (polishing accelerator / silica-based polishing particles) of 0.8 to 20.

Japanese Unexamined Patent Publication No. 2004-335723

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 size of 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 size of silica abrasive grains is 35 nm or more.

The silica abrasive grains are, for example, colloidal silica, fumed silica, colloidal alumina, fumed alumina, cerium oxide, silicon carbide, silicon nitride and the like. 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 alkaline compound, an amine compound, or the like.

Inorganic alkaline compounds include, for example, alkali metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, and alkaline earth metal carbonates. Examples include hydrogen salts. Inorganic alkali compounds, specifically, potassium hydroxide (KOH), sodium hydroxide, potassium hydrogen carbonate, potassium carbonate _(K 2 _CO 3), sodium hydrogen carbonate, sodium carbonate, and the like.

The amine compound is, for example, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium and a salt thereof, a heterocyclic amine and the like. 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-methylpiperazin, piperazine hydrochloride, guanidine carbonate and the like.

The above-mentioned basic compounds may be used alone or in combination of two or more. The total content of the basic compounds is not particularly limited, but is, for example, 0.1 to 7% by mass of the total polishing composition. The lower limit of the content of the basic compound is preferably 1.5% by mass. The upper limit of the content of the basic compound is preferably 6% by mass.

The pH is 9.0 to 12.0. The pH of the polishing composition can be adjusted by blending the above 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) x mass of silica abrasive grains contained in 4 L of diluted slurry (g) / amount of slurry used (L) ) ... (1)

In the formula (1), the specific surface area of the silica abrasive grains is the surface area (m ² / g) per unit mass of the silica abrasive grains measured by the pulse NMR method. The specific surface area of the silica abrasive grains can be measured, for example, by using a pulse NMR evaluation device "Acron area" manufactured by Xigo nanotools of the United States.

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, but 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 where a plurality of silica abrasive grains are aggregated to form secondary particles. The average secondary particle size of the silica abrasive grains is the average of the secondary particle size of the silica abrasive grains measured by the dynamic light scattering method. The average secondary particle size can be measured using, for example, a dynamic light scattering device "ELS-Z2" manufactured by Otsuka Electronics.

The lower limit of the average secondary particle size 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 grains do not easily settle. However, the upper limit of the average secondary particle size may be, for example, 100 nm, 90 nm, 85 nm, or 82 nm.

The average secondary particle size measured by the dynamic light scattering method can be adjusted by adjusting the size of the primary particle size and the secondary particle size of the silica abrasive grains to be 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 by the dynamic light scattering method.

The average secondary particle size measured by the dynamic light scattering method also changes due to the influence of the compound blended in the polishing composition. The average secondary particle size measured by the dynamic light scattering method generally tends to decrease as the pH increases.

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

The polishing composition according to this embodiment is prepared by appropriately mixing the above-mentioned compounding agent and water.

The polishing composition described above is diluted with water to an appropriate concentration and then used for polishing the wafer.

The embodiments of the present invention have been described above. The above-described embodiment is merely an example for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

In order to confirm the effect of the above embodiment, nine kinds 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 obtained by diluting the slurry of the undiluted solution with water. Example 4 is a polishing composition comprising an undiluted slurry (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 grains was measured using a pulse NMR evaluation device "Acron area" manufactured by Xigo nanotools of the United States. The measurement conditions are magnetic field: 0.3T, measurement frequency: 13MHz, measurement nucleus: ¹ H NMR, measurement method: CPMG pulse sequence method, sample volume: 500 μL or more, temperature: 25 ° C., Specific Surface Relaxivity (Ka): 0. It was set to 0206 g / m ² / ms.

In Comparative Examples 1 to 5 and Examples 1 to 3, the silica abrasive grains so that the total surface area of the silica abrasive grains contained in the 4 L polishing composition (slurry after dilution) diluted with water had the above value. The concentration of silica was adjusted.

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

As the basic compound, potassium hydroxide (KOH) 0.5%, tetramethylammonium hydroxide (TMAH) 1.8%, and 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 was 22 g, for Comparative Example 5, the amount of abrasive grains contained in the slurry 4L was 36 g, and for Example 1, the amount of abrasive grains contained in the slurry 4L was contained. The amount of abrasive grains to be used is 48 g, the amount of abrasive grains contained in the slurry 4L for Example 3 is 64 g, and the amount of abrasive grains contained in the slurry 4L for Example 4 is diluted with water to 1488 g and 4L. The polishing composition of the above was prepared.

The content of silica abrasive grains in the polishing composition before dilution was 0.50 to 31.0% by mass.

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

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

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

As shown in the photograph of FIG. 1, the coloring 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.). Color difference ΔE ^* ab of less than 1.6 was regarded as “uncolored”, and color difference of 1.6 or more was regarded as “colored”. In Table 1, "no coloring" is indicated by "◯" as "no glazing", and "with coloring" is indicated by "x" as "occurring glazing". Although the degree of coloring is quantified using a color difference meter, it is clearly visible that there is an inflection point in the vicinity of 1.6 of Comparative Example 4 in which the degree of coloring changes significantly. When the color difference ΔE ^* ab is less than 1.6, the value does not directly indicate the degree of coloring.

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

It is considered that the cause of glazing is that silicon reacts with alkali during polishing, silicate ions are generated, the saturation concentration is exceeded, the glazing cannot be dissolved in an aqueous solution, and the glazing is 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 stay on the surface of the silica abrasive grains by adsorption or particle growth. In the surface area measuring method using the known BET method, the surface area is measured by adsorbing nitrogen to dry silica, which is different from the surface area of silica abrasive grains in an aqueous solution. From the results of this test, it was found that the total surface area of silica abrasive grains in the aqueous solution is related to the occurrence of glazing.

Claims (1)

With silica abrasive grains
Polishing accelerators containing basic compounds and
Including water
The total surface area of the silica abrasive grains is 150 m ² / L or more.
A polishing composition having an average secondary particle size of 35 to 46 nm of the silica abrasive grains.

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