JP6891107B2 - Polishing composition - Google Patents

Description

The present invention relates to a polishing composition.

Ultra-precision machining is an extremely important technology in the manufacture of semiconductor products. In recent years, the miniaturization of LSI devices has progressed, and along with this, the demand for surface roughness and flatness of semiconductor wafers after precision polishing tends to become stricter.

Until now, in primary polishing, the emphasis has been mainly on the amount of grinding. However, it is known that the surface quality of the semiconductor wafer after the primary polishing affects the surface quality after the secondary polishing and the final polishing. Therefore, in the future, it will be required to achieve a higher level of wafer surface quality while maintaining the current grinding amount even in primary polishing.

Japanese Patent Application Laid-Open No. 2016-124943 describes a polishing composition containing a water-soluble polymer of polyvinyl alcohols and a piperazine compound as a polishing composition capable of reducing the surface roughness of a wafer without lowering the polishing rate. The thing is disclosed.

Japanese Unexamined Patent Publication No. 2016-124943

In the primary polishing of a 300 mm silicon wafer, double-sided polishing is generally performed. In double-sided polishing, a wafer held by a dedicated carrier is sandwiched between upper and lower surface plates to which pads are attached, and polishing is performed.

Also in the primary polishing, in order to reduce the roughness of the silicon wafer, the polishing composition may contain a water-soluble polymer. When double-sided polishing is performed using a polishing composition containing a water-soluble polymer, vibration may occur in the apparatus due to friction between the carrier and the polishing pad. If the load or rotation speed is increased in order to increase the processing efficiency, the vibration of the device increases, which causes deterioration of the quality of the silicon wafer and device failure.

An object of the present invention is to provide a polishing composition capable of reducing vibration of an apparatus.

The polishing composition according to one embodiment of the present invention is a polymer having colloidal silica, a water-soluble polymer, a basic compound, water, a weight average molecular weight of 1500 to 30000, and an ethylene oxide group. The molar concentration of the vibration suppressant is 6.9 × 10 ^-10 mol / g or more, and the weight average molecular weight of the ethylene oxide group portion per molecule of the vibration suppressant and the vibration suppression are included. The product with the mass concentration of the agent is 8.0 × ^10-2 or more, and the vibration inhibitor has a ratio of the weight average molecular weight of the ethylene oxide group to the alkylene oxide group of 80% or more.

According to the present invention, a polishing composition capable of reducing vibration of the apparatus can be obtained.

FIG. 1 is a scatter plot in which the horizontal axis represents the molar concentration of the vibration inhibitor and the vertical axis represents the _{WEO / concentration.}

The present inventor has conducted various studies in order to solve the above problems. As a result, it was found that the device vibration can be suppressed by containing a polymer having an ethylene oxide group having a weight average molecular weight of 1500 to 30000 in a predetermined concentration or more in the polishing composition. Although the principle is not clear, it is considered that the ethylene oxide group is adsorbed on the pad or carrier to improve the contact state between the pad or carrier and the water-soluble polymer.

The polymer having an ethylene oxide group may contain a copolymer with a propylene oxide group, which is a hydrophobic group, as a surfactant in the polishing composition. However, when a polymer containing a large amount of alkylene oxide groups other than ethylene oxide groups is used for double-sided polishing of a semiconductor wafer, the shape of the laser mark (unevenness added to indicate the crystal orientation of the semiconductor wafer) is remarkably deteriorated. In order to suppress the deterioration of the shape of the laser mark, it is necessary to make the ratio of the weight average molecular weight of the ethylene oxide group to the alkylene oxide group in the polymer used as the vibration inhibitor 80% or more.

The present invention has been completed based on these findings. Hereinafter, the polishing composition according to one embodiment of the present invention will be described in detail.

The polishing composition according to one embodiment of the present invention contains colloidal silica, a water-soluble polymer, a basic compound, water, and a vibration inhibitor.

As colloidal silica, those commonly used in this field can be used. The particle size of colloidal silica is not particularly limited, but for example, a colloidal silica having a secondary average particle size of 20 to 130 nm can be used.

The content of colloidal silica is not particularly limited, but is, for example, 0.15 to 20% by mass of the entire polishing composition (stock solution). The polishing composition is diluted 10 to 80 times during polishing before use. The polishing composition according to this embodiment is preferably diluted so that the silica concentration is 100 to 5000 ppm (mass ppm; the same applies hereinafter).

The water-soluble polymer is adsorbed on the surface of the semiconductor wafer to modify the surface of the semiconductor wafer. As a result, the uniformity of polishing can be improved and the surface roughness can be reduced. The water-soluble polymer is not limited to this, but is limited to hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, cellulose acetate, methyl cellulose and other celluloses, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and the like. Vinyl polymer, glycoside (glycoside), polyhydric alcohol and the like can be used.

The water-soluble polymer is preferably a polymer having no alkyleneoxyside group. Among the above-mentioned water-soluble polymers, those having a high molecular weight and a structure that easily takes in water molecules are preferable, and HEC is particularly preferable.

The content of the water-soluble polymer is not limited to this, but is, for example, 0.01 to 1.2% by mass of the entire polishing composition (stock solution).

The basic compound is chemically polished by etching the surface of the semiconductor wafer. The basic compound is, for example, an amine compound, an inorganic alkaline compound, or the like.

The amine compound is, for example, a primary amine, a secondary amine, a tertiary amine, a quaternary ammonium and its hydroxide, 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.

Examples of the inorganic alkali compound include alkali metal hydroxides, alkali metal salts, alkaline earth metal hydroxides, alkaline earth metal salts and the like. Specifically, the inorganic alkaline compound is potassium hydroxide, sodium hydroxide, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate and the like.

The above-mentioned basic compounds may be used alone or in combination of two or more. Among the above-mentioned basic compounds, ammonia, amines, alkali metal hydroxides, and alkali metal carbonates are particularly preferable.

The content of the basic compound (when two or more kinds are contained, the total amount thereof) is not particularly limited, but is, for example, 0.01 to 1.2% by mass of the entire polishing composition.

The polishing composition according to the present embodiment further contains a polymer having a weight average molecular weight of 1500 to 30000 and having an ethylene oxide group as a vibration inhibitor. That is, the polishing composition according to the present embodiment contains at least one polymer that acts as a vibration inhibitor in addition to the above-mentioned water-soluble polymer.

Polymers that can be used as vibration inhibitors include, for example, polyethylene glycol (PEG), glycerin derivatives, poroxamines, ethylene glycol diglycidyl ethers, polyhydric alcohol derivatives, fatty acid hydrocarbon esters, alkylamine derivatives, and organols. Polysiloxanes and the like.

The vibration suppressant suppresses vibration by changing the contact state of these by adsorbing to the surface of the carrier or pad to form a layer. If the weight average molecular weight is less than 1500, the thickness of the adsorption layer is small and the effect as a vibration inhibitor cannot be obtained. The lower limit of the weight average molecular weight of the polymer used as the vibration inhibitor is preferably 2000, more preferably 3000. On the other hand, when the weight average molecular weight is higher than 30,000, the number of molecules decreases, the adsorption layer becomes coarse and dense, and the effect as a vibration inhibitor cannot be obtained. The upper limit of the weight average molecular weight of the polymer used as the vibration inhibitor is preferably 25,000, and more preferably 20,000.

The polishing composition according to this embodiment has a molar concentration (at the time of use) of the vibration inhibitor of 6.9 × ^10-10 mol / g or more. If the molar concentration of the vibration inhibitor is ^{less than 6.9 × 10 -10} mol / g, the effect as a polishing inhibitor cannot be obtained. The lower limit of the molar concentration of the vibration inhibitor is preferably 1.0 × ^10-9 mol / g, and more preferably 2.0 × ^10-9 mol / g. On the other hand, if the molar concentration of the vibration inhibitor is too high, agglomeration of abrasive grains is likely to occur, and it becomes difficult to adjust the composition as a polishing composition. The upper limit of the molar concentration of the vibration inhibitor is preferably 5.0 × ^10-6 m, more preferably 5.0 × ^10-8 mol / g.

The content of the vibration inhibitor in the polishing composition (stock solution) is not particularly limited, but is, for example, 0.005 to 0.5% by mass.

The polishing composition according to the present embodiment is the product of the weight average molecular weight of the ethylene oxide group portion per molecule of the vibration inhibitor and the mass concentration of the vibration inhibitor in the polishing composition (hereinafter referred to as " _WEO / concentration"). Is written as 8.0 × ^10-2 or more. Here, the mass concentration of the vibration inhibitor is a value obtained by dividing the mass of the vibration inhibitor in the polishing composition by the mass of the entire polishing composition (after dilution).

When W _EO · concentration is less than 8.0 × ^{10 -2,} even molarity of vibration inhibitor 6.9 × ¹⁰ -10 mol / g or more, the vibration suppressing effect can not be obtained. _{The lower limit of WEO} / concentration is preferably 1.0 × 10 ^-1 , and more preferably 2.0 × 10 ^-1 . On the other hand, if the _WEO / concentration is too large, agglutination of abrasive grains is likely to occur, and it becomes difficult to adjust the composition as a polishing composition. _{The upper limit of WEO} / concentration is preferably 2.0, more preferably 1.5.

The vibration inhibitor has a ratio of the weight average molecular weight of the ethylene oxide group to the alkylene oxide group (hereinafter _{referred to as “WEO} / _WAO ”) of 80% or more. When _WEO / _WAO is less than 80%, the shape of the laser mark of the semiconductor wafer after polishing is remarkably deteriorated. _WEO / _WAO is preferably 90% or more.

The polishing composition according to this embodiment may further contain a pH adjuster. The pH of the polishing composition according to this embodiment is preferably 8.0 to 12.0.

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.

The polishing composition according to the present embodiment is prepared by appropriately mixing colloidal silica, a water-soluble polymer, a basic compound, a vibration inhibitor and other compounding materials, and adding water. The polishing composition according to the present embodiment is also prepared by sequentially mixing colloidal silica, a water-soluble polymer, a basic compound, a vibration inhibitor and other compounding materials with water. As a means for mixing these components, means commonly used in the technical field of polishing compositions such as a homogenizer and ultrasonic waves are used.

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

The polishing composition according to this embodiment can be suitably used for double-sided polishing of a silicon wafer. The polishing composition according to the present embodiment is particularly suitable for double-sided polishing of a silicon wafer using a carrier of a glass epoxy resin.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.

The polishing compositions of Examples 1 to 7 and Comparative Examples 1 to 15 shown in Table 1 were prepared.

The blending amounts in Table 1 are all before dilution (stock solution), and the rest is water. The polishing composition of Comparative Example 1 does not contain a polymer corresponding to a vibration inhibitor. The colloidal silica used had a secondary average particle size of 70 nm. The HEC used had a weight average molecular weight of 500,000. As the polyhydric alcohol, polyoxyethylene methylglucoside having a weight average molecular weight of 634 was used.

[Vibration measurement test 1]
The polishing composition shown in Table 1 was diluted 41-fold, and double-sided polishing of a 12-inch silicon wafer was performed using DSM20B-5P-4D manufactured by Speedfam. As the polishing pad, EXTERION (registered trademark) SL-31 manufactured by Nitta Haas Co., Ltd. was used. Polishing was carried out for 3 minutes, and the presence or absence of device squeal and vibration was investigated.

[Vibration measurement test 2]
The polishing composition shown in Table 1 was diluted 41-fold, and a friction analysis was carried out using POLI762 manufactured by G & P Co., Ltd. using a 12-inch glass epoxy resin as an abrasive. Here, the reason why the glass epoxy resin is used as the material to be polished is to simulate the frictional state of double-sided polishing using a carrier made of glass epoxy resin. As the polishing pad, EXTERION (registered trademark) SL-31 manufactured by Nitta Haas Co., Ltd. was used. The supply rate of the polishing composition was 300 mL / min, the surface pressure was 150 g / cm ² , and the guide pressure was 220 g / cm ² .

[Laser mark measurement test]
Nitta Haas Co., Ltd. polishing slurry Nanopure (registered trademark) NP6610 diluted 31 times, 0.5 ppm of the vibration inhibitor shown in Table 1 was added to obtain DSM20B-5P-4D manufactured by Speedfam Co., Ltd. A 12-inch silicon wafer was used for double-sided polishing. After polishing for 30 minutes, the height of the swelling of the laser mark was evaluated. Specifically, the end of the laser mark T7 cord was measured using a Wyko NT9300 (non-contact type interference microscope) manufactured by Veeco, and the height of the swelling was measured from the cross-sectional profile of the portion around the specific dot.

Table 2, the molar concentration of the vibration suppressing agent in the polishing composition after 41-fold _{dilution, W EO} · concentration, and _W EO _{/ W AO,} and vibration measurement test 1, vibration measurement test 2, and laser marking of the measurement test The result is shown.

The results of the vibration measurement test 1 are described in the “Vibration” column of Table 2.

The results of the vibration measurement test 2 are described in the “Head load” column of Table 2. The numerical values in the same column are the amount of reduction in the load of the polishing head in the direction perpendicular to the load direction based on Comparative Example 1, and the larger the value, the higher the vibration suppression effect.

The results of the laser mark test are described in the "Laser mark" column of Table 2. If the value in the same column is positive, it indicates that the edge of the laser mark after polishing has a protruding shape. The numerical value in the same column is a value standardized with the case of Comparative Example 2 as 100.

When the polishing compositions of Examples 1 to 7 were used, vibration of the apparatus did not occur, and deterioration of the shape of the laser mark was within an acceptable range.

The polishing composition of Comparative Example 1 did not contain a vibration inhibitor. Therefore, vibration of the device occurred.

The polishing compositions of Comparative Examples 2 to 4 had a low _{WEO / concentration.} Therefore, vibration of the device occurred. Moreover, since the _WEO / _WAO was low, the shape of the laser mark also deteriorated.

The polishing compositions of Comparative Examples 5 and 6 had a low _WEO / _WAO. Therefore, the shape of the laser mark deteriorated.

The polishing compositions of Comparative Examples 7 to 9 had a low molar concentration of the vibration inhibitor. Therefore, vibration of the device occurred.

The polishing compositions of Comparative Examples 10 to 12 had a low _{WEO / concentration.} Therefore, vibration of the device occurred.

In the polishing compositions of Comparative Examples 13 to 15, the weight average molecular weight of the polymer blended as the vibration inhibitor was too large. Therefore, vibration of the device occurred.

FIG. 1 is a scatter plot in which the horizontal axis represents the molar concentration of the vibration inhibitor and the vertical axis represents the _{WEO / concentration.} In FIG. 1, a white mark indicates that vibration did not occur, and a solid mark indicates that vibration occurred. As shown in FIG. 1, when the molar concentration is 6.9 × ^10-10 mol / g or more and the _WEO / concentration is 8.0 × ^10-2 or more, it can be seen that the vibration of the device can be suppressed.

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.

Claims (2)

Colloidal silica and
With water-soluble polymers
Basic compounds and
water and,
It has a weight average molecular weight of 1500 to 30000 and contains a vibration inhibitor which is a polymer having an ethylene oxide group.
The molar concentration of the vibration inhibitor is 6.9 × ^10-10 mol / g or more, and
The product of the weight average molecular weight of the ethylene oxide group portion per molecule of the vibration inhibitor and the mass concentration of the vibration inhibitor is 8.0 × ^10-2 or more.
The vibration inhibitor is a polishing composition in which the ratio of the weight average molecular weight of the ethylene oxide group to the alkylene oxide group is 80% or more. The polishing composition according to claim 1.
The composition for polishing, wherein the water-soluble polymer is hydroxyethyl cellulose.

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