WO2020100563A1

WO2020100563A1 - Polishing composition

Info

Publication number: WO2020100563A1
Application number: PCT/JP2019/042115
Authority: WO
Inventors: 恵谷口; 貴俊向井
Original assignee: 株式会社フジミインコーポレーテッド
Priority date: 2018-11-12
Filing date: 2019-10-28
Publication date: 2020-05-22
Also published as: JPWO2020100563A1; JP7440423B2; TW202024259A

Abstract

Provided is a silicon wafer pre-polishing composition that has an exceptional ability to eliminate bulging of an HLM margin and is capable of preventing or suppressing polishing vibration. The polishing composition provided by the present invention includes abrasive grains, a basic compound, a water-soluble polymer, and water, and furthermore includes an organic acid or a salt thereof.

Description

Polishing composition

The present invention relates to a polishing composition. Specifically, it relates to a composition for preliminarily polishing a silicon wafer. This application claims priority based on Japanese Patent Application No. 2018-212314 filed on November 12, 2018, the entire content of which is incorporated herein by reference.

Conventionally, precision polishing using a polishing composition has been performed on the surface of materials such as metals, semimetals, nonmetals, and their oxides. For example, the surface of a silicon substrate used as a component of a semiconductor product or the like is generally finished to a high quality mirror surface through a lapping process and a polishing process. The polishing step typically includes a preliminary polishing step (preliminary polishing step) and a final polishing step (final polishing step). The preliminary polishing step typically includes a rough polishing step (primary polishing step) and an intermediate polishing step (secondary polishing step). As a technical document relating to the above-mentioned composition for preliminary polishing, for example, Patent Document 1 can be cited.

Japanese Patent Application Publication No. 2015-233031

For example, a silicon wafer is irradiated with a laser beam on the front surface or the back surface of the silicon wafer for the purpose of identification or the like, so that a mark such as a bar code, a number or a symbol (hard laser mark; hereinafter referred to as “HLM”). Sometimes) is attached. Application of the HLM is generally performed after the lapping process of the silicon wafer is completed and before the polishing process is started. Irradiation of a laser beam for attaching the HLM usually causes an altered layer on the surface of the silicon wafer around the HLM. The HLM part itself of the silicon wafer is not used for the final product, but if the above-mentioned deteriorated layer is not properly polished in the polishing step after HLM application, it may become a bulge and the yield may be reduced more than necessary. . However, the altered layer is transformed into polysilicon or the like by the energy of the laser beam and is difficult to be polished. Therefore, the silicon wafer pre-polishing composition for flattening the protrusion (hereinafter, also simply referred to as “protrusion”) at the periphery of the HLM may have a composition suitable for eliminating the protrusion. For example, in Patent Document 1, a swelling elimination property is examined with a specific composition containing silica particles as abrasive grains, potassium carbonate as a weak acid salt, and a quaternary ammonium compound as a basic compound.

On the other hand, conventionally, it is known that the polishing device vibrates during polishing (hereinafter referred to as “polishing vibration”) depending on the polishing conditions. The polishing vibration may impose a load on the apparatus and cause deterioration of components, which may adversely affect the life of the apparatus. It would be beneficial to provide a polishing composition capable of preventing or suppressing polishing vibration while ensuring the ability to eliminate ridges on the periphery of the HLM.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composition for preliminarily polishing a silicon wafer, which is excellent in eliminating protrusions on the periphery of the HLM and which can prevent or suppress polishing vibration. ..

According to the present specification, a silicon wafer pre-polishing composition is provided. This polishing composition contains abrasive grains, a basic compound, a water-soluble polymer and water, and further contains an organic acid or a salt thereof. The polishing composition is excellent in eliminating ridges on the periphery of the HLM. Further, in the polishing using the polishing composition, polishing vibration is not generated or the vibration is suppressed.

Note that, in this specification, eliminating the ridge on the periphery of the HLM means reducing the height from the reference plane (reference plane) around the HLM of the silicon wafer to the highest point of the ridge. The height from the reference surface around the HLM of the silicon wafer to the highest point of the ridge can be measured, for example, by the method described in Examples below.

In a preferred aspect, the organic acid is a polycarboxylic acid. Also, the organic acid may be a hydroxy acid. As an organic acid, by using a polyvalent carboxylic acid, a hydroxy acid, or both of them, it is preferable to realize the effect of the technology disclosed herein, that is, the compatibility between the protrusion elimination property and the polishing vibration prevention or suppression. can do.

In a preferred aspect, the abrasive grains are silica particles. The bump elimination effect can be more effectively exhibited in polishing using silica particles as the abrasive grains.

The polishing composition according to a preferred embodiment contains quaternary ammonium hydroxide or a salt thereof as the basic compound. By using a quaternary ammonium hydroxide compound as the basic compound, the elimination of the ridge on the periphery of the HLM is preferably realized. The polishing composition having the above composition is also preferable from the viewpoint of improving the polishing rate.

In the polishing composition according to a preferred embodiment, the ratio (A _OA / A _HM ) of the content (A _OA ) of the organic acid and its salt to the content (A _HM ) of the water-soluble polymer is 1 or more 100. It is below. By setting the ratio of the content of the water-soluble polymer in the polishing composition to the content of the organic acid and its salt in the above range, elimination of the bulge at the periphery of the HLM is more preferably realized.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters particularly referred to in the present specification and matters necessary for carrying out the present invention can be understood as design matters for a person skilled in the art based on conventional technology in the field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field.
In the present specification, “X to Y” indicating a range means “X or more and Y or less”.

In this specification, the average primary particle diameter of the abrasive grains means the average primary particle diameter (nm) = 6000 / (true density (g / cm ³ ) × BET from the specific surface area (BET value) measured by the BET method. Value (m ² / g)) is the particle size calculated by the formula. For example, in the case of silica particles, the average primary particle diameter can be calculated from the average primary particle diameter (nm) = 2727 / BET value (m ² / g). The specific surface area can be measured, for example, by using a surface area measuring device manufactured by Micromeritex Co., Ltd. under the trade name “Flow Sorb II 2300”.

In this specification, the aspect ratio of each particle constituting the abrasive grain is the length of the short side of the same rectangle that is the minimum long side of the rectangle circumscribing the image of the particle by a scanning electron microscope (SEM). It can be obtained by dividing by. The average aspect ratio of the abrasive grains and the standard deviation of the aspect ratio are the average value and the standard deviation of the aspect ratio of a plurality of particles within the field of view of the scanning electron microscope. Can be asked.

In this specification, the equivalent circle diameter of a particle means the value obtained by measuring the area of the image of the particle with a scanning electron microscope and determining the diameter of the circle of the same area. The average circle equivalent diameter of particles constituting the abrasive grains and the standard deviation of the circle equivalent diameter are the average value and the standard deviation of the circle equivalent diameters of a plurality of particles within the visual field range of the scanning electron microscope, and these are also common. It can be determined using various image analysis software.

<Abrasive grains>
The polishing composition disclosed herein contains abrasive grains. The abrasive grains function to mechanically polish the surface of the object to be polished.

The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected according to the purpose of use and the mode of use. The abrasive grains may be used alone or in combination of two or more. Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silicon compound particles such as silica particles, silicon nitride particles, and silicon carbide particles, and diamond particles. Specific examples of the organic particles include polymethylmethacrylate (PMMA) particles and polyacrylonitrile particles. Of these, inorganic particles are preferable.

Silica particles are mentioned as particularly preferable abrasive grains in the technology disclosed herein. The technique disclosed herein can be preferably carried out, for example, in a mode in which the abrasive grains are substantially silica particles. Here, “substantially” means 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and even 100% by weight) of the particles constituting the abrasive grains. It is a silica particle.

Specific examples of silica particles include colloidal silica, fumed silica, and precipitated silica. The silica particles may be used alone or in combination of two or more. Colloidal silica is particularly preferable because it is unlikely to cause scratches on the surface of the object to be polished and can exhibit good polishing performance (performance to reduce surface roughness, swelling elimination property, etc.). As the colloidal silica, for example, colloidal silica prepared from water glass (Na silicate) as a raw material by an ion exchange method or alkoxide method colloidal silica can be preferably used. Here, the alkoxide method colloidal silica is colloidal silica produced by a hydrolysis condensation reaction of an alkoxysilane. Colloidal silica can be used individually by 1 type or in combination of 2 or more types.

The true specific gravity of silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and further preferably 1.7 or more. The polishing rate tends to increase due to an increase in the true specific gravity of silica. From this viewpoint, silica particles having a true specific gravity of 2.0 or more (for example, 2.1 or more) are particularly preferable. The upper limit of the true specific gravity of silica is not particularly limited, but it is typically 2.3 or less, for example 2.2 or less. As the true specific gravity of silica, a value measured by a liquid replacement method using ethanol as a replacement liquid can be adopted.

The average primary particle size of the abrasive grains is not particularly limited, and can be appropriately selected from the range of about 10 nm to 200 nm, for example. From the viewpoint of improving the swelling elimination property, the average primary particle diameter is preferably 20 nm or more, and more preferably 30 nm or more. In some embodiments, the average primary particle size can be, for example, greater than 40 nm, greater than 45 nm, and greater than 50 nm. Further, from the viewpoint of preventing the occurrence of scratches, the average primary particle size is usually advantageously 150 nm or less, preferably 120 nm or less, and more preferably 100 nm or less. In some embodiments, the average primary particle size can be 75 nm or less, or 60 nm or less.

The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of the non-spherical particles include peanut shape (that is, peanut shell shape), cocoon shape, konpeito sugar shape, rugby ball shape and the like.

The average aspect ratio of the abrasive grains is not particularly limited. The average aspect ratio of the abrasive grains is 1.0 or more in principle, and can be 1.05 or more and 1.1 or more. The increase in average aspect ratio tends to generally improve ridge relief. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, from the viewpoints of scratch reduction and polishing stability improvement. In some embodiments, the average aspect ratio of the abrasive grains can be, for example, 1.5 or less, 1.4 or less, or 1.3 or less.

In some embodiments, it is possible to employ, as the abrasive grains, grains having a circle equivalent diameter of 50 nm or more and an aspect ratio of 1.2 or more and a volume ratio of 50% or more. The volume ratio may be 60% or more. When the value of the volume ratio is 50% or more, more specifically 60% or more, since the abrasive grains contain a relatively large amount of particles having a size and aspect ratio that are particularly effective for eliminating the ridge, It is possible to further improve the swelling elimination property due to the mechanical action of the abrasive grains.

In some embodiments, the average circle conversion diameter of the abrasive grains may be, for example, 25 nm or more, 40 nm or more, 55 nm or more, and 70 nm or more. The average circle conversion diameter of the abrasive grains may be, for example, 300 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. The polishing composition disclosed herein can be preferably carried out using abrasive grains having such an average circle conversion diameter.

The content of the abrasive grains is not particularly limited and can be appropriately set according to the purpose. The content of the abrasive grains with respect to the total weight of the polishing composition may be, for example, 0.01% by weight or more, may be 0.05% by weight or more, and may be 0.1% by weight or more. Increasing the content of abrasive grains generally tends to improve the swelling elimination property. In some embodiments, the content of abrasive grains may be 0.2 wt% or more, 0.5 wt% or more, and 0.6 wt% or more. From the viewpoint of preventing scratches and saving the amount of abrasive grains used, in some embodiments, the content of abrasive grains may be, for example, 10 wt% or less, 5 wt% or less, or 3 wt% or less. It may be 2% by weight or less, 1.5% by weight or less, 1.2% by weight or less, or 1.0% by weight or less. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

In the case of a polishing composition that is diluted and used for polishing (that is, a concentrated solution), the content of the abrasive grains is usually 50% by weight or less from the viewpoint of storage stability, filterability, and the like. It is suitable and more preferably 40% by weight or less. In addition, the content of the abrasive grains is preferably 1% by weight or more, and more preferably 5% by weight or more, from the viewpoint of utilizing the advantages of the concentrated liquid.

<Basic compound>
The polishing composition disclosed herein contains a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH of the composition by being added to the polishing composition. The basic compound serves to chemically polish the surface to be polished, and can contribute to the improvement of the polishing rate.

As the basic compound, an organic or inorganic basic compound containing nitrogen, an alkali metal or alkaline earth metal hydroxide, or the like can be used. Examples thereof include alkali metal hydroxides, quaternary ammoniums such as quaternary ammonium hydroxide, ammonia, amines and the like. Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Specific examples of the quaternary ammoniums include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like. Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine. , Piperazine hexahydrate, 1- (2-aminoethyl) piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.

Quaternary ammonium hydroxides are mentioned as preferable basic compounds from the viewpoint of improving the ability to eliminate bumps. Particularly preferably used is tetramethylammonium hydroxide. The above basic compounds may be used alone or in combination of two or more.

The content of the basic compound relative to the total amount of the polishing composition is preferably 0.01% by weight or more, more preferably 0.02% by weight or more, and further preferably 0.03% by weight, from the viewpoint of the polishing rate and the swelling elimination property. % Or more. Stability can also be improved by increasing the content of the basic compound. The upper limit of the content of the basic compound is appropriately 1% by weight or less, preferably 0.5% by weight or less, and more preferably 0.1% by weight or less from the viewpoint of surface quality and the like. , And more preferably 0.06% by weight or less. When two or more kinds are used in combination, the above content refers to the total content of two or more basic compounds. These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

In the case of a polishing composition that is diluted and used for polishing (that is, a concentrated solution), the content of the basic compound is usually 10% by weight or less from the viewpoint of storage stability, filterability, and the like. It is suitable and more preferably 5% by weight or less. Further, from the viewpoint of utilizing the advantages of the concentrated liquid, the content of the basic compound is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and further preferably 0.9% by weight or more. Is.

<Water-soluble polymer>
The polishing composition disclosed herein contains a water-soluble polymer. According to the polishing composition containing the water-soluble polymer, the performance of eliminating the bulge at the periphery of the HLM is likely to be improved. In carrying out the technique disclosed herein, it is not necessary to elucidate the mechanism by which the water-soluble polymer contributes to the improvement of the bulge elimination at the periphery of the HLM, but HLM is not provided on the surface of the object to be polished. It is considered that the region is selectively protected by the water-soluble polymer as compared with the peripheral edge of the HLM, and the polishing of the region is suppressed. However, it is not limited to this mechanism.

Examples of the water-soluble polymer include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polymers containing nitrogen atoms, vinyl alcohol polymers and the like. Specific examples thereof include hydroxyethyl cellulose, pullulan, random copolymers and block copolymers of ethylene oxide and propylene oxide, polyvinyl alcohol, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid. , Polystyrene sulfonate, styrene-maleic acid copolymer, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinyl imidazole, polyvinyl carbazole, polyvinyl pyrrolidone, polyacryloyl morpholine, polyvinyl caprolactam, polyvinyl piperidine and the like. The water-soluble polymer may be used alone or in combination of two or more.

In the technique disclosed herein, the molecular weight of the water-soluble polymer is not particularly limited. For example, the weight average molecular weight (Mw) of the water-soluble polymer can be about 200 × 10 ⁴ or less, and 150 × 10 ⁴ or less is suitable. From the viewpoint of suppressing polishing vibration and surface defects, the Mw may be approximately 100 × 10 ⁴ or less, or approximately 50 × 10 ⁴ or less. Further, from the viewpoint of the protective property of the surface of the silicon wafer, the Mw is usually about 0.2 × 10 ⁴ or more, about 0.5 × 10 ⁴ or more, and about 0.8 ×. It may be 10 ⁴ or more.

Note that, as the Mw of the water-soluble polymer, a value based on water-based gel permeation chromatography (GPC) (water-based, converted to polyethylene oxide) can be adopted.

The content of the water-soluble polymer in the polishing composition disclosed herein is not particularly limited, and is about 1 × 10 ⁻⁵ % by weight or more (eg, about 1 × 10 ^-4 % by weight or more), and preferably about 5 × 10 ^-4 % by weight or more. The upper limit of the content of the water-soluble polymer in the polishing composition can be, for example, about 1% by weight or less. From the viewpoint of polishing effect, detergency, etc., the content of the water-soluble polymer is preferably about 0.1% by weight or less, more preferably about 0.05% by weight or less, further preferably about 0.01% by weight or less. (For example, about 0.005% by weight or less).

The content of the water-soluble polymer in the polishing composition disclosed herein can also be specified by the relative relationship with the abrasive grains contained in the polishing composition. Specifically, it is appropriate that the content of the water-soluble polymer in the polishing composition is about 0.001 part by weight or more based on 100 parts by weight of the abrasive grains, and the content other than the HLM peripheral edge on the surface of the silicon wafer is appropriate. From the viewpoint of protecting the region, it is preferably about 0.01 parts by weight or more, more preferably about 0.05 parts by weight or more (for example, about 0.1 parts by weight or more). From the viewpoint of polishing effect and the like, the content of the water-soluble polymer is appropriately about 10 parts by weight or less, preferably about 1 part by weight or less, and more preferably about 100 parts by weight of the abrasive grains. It is about 0.5 parts by weight or less (for example, about 0.3 parts by weight or less).

<Organic acid or its salt>
The polishing composition disclosed herein is characterized by containing an organic acid or a salt thereof. By using an organic acid or a salt thereof, it is possible to prevent or suppress polishing vibration while realizing excellent swelling elimination property. In carrying out the technology disclosed herein, it is not necessary to elucidate the mechanism by which an organic acid or a salt thereof contributes to prevention of polishing vibration, etc., but an organic acid or a salt thereof is compared with an inorganic acid or a salt thereof. Therefore, it is considered that it contributes to the improvement of the uniformity of the abrasive grains on the wafer surface, whereby the mechanical polishing action becomes smooth and polishing vibration does not occur. However, it is not limited to this mechanism.

The organic acid or its salt is not particularly limited, and typically a carboxylic acid or its salt can be used. Although not particularly limited, polyvalent acids such as polyvalent carboxylic acids are preferably used as the organic acid. The number of acid groups (number of carboxyl groups in the case of polyvalent carboxylic acid) per molecule of polyvalent acid is 2 to 5, and more preferably 2, 3 or 4 (typically 2 or 3). The organic acid may be a monovalent acid such as a monocarboxylic acid. Moreover, the organic acid according to a preferred embodiment may be a hydroxy acid (typically a hydroxycarboxylic acid) having one or more hydroxyl groups in one molecule. According to the polyvalent carboxylic acid having a hydroxyl group or a salt thereof, it is possible to preferably achieve both the bulge elimination property and the prevention of polishing vibration by the technique disclosed herein. It should be noted that the organic acids and salts thereof in the present specification are different from aminocarboxylic acid compounds and organic phosphonic acid compounds used as chelating agents and therefore have amine structures such as secondary amines and tertiary amines. It may not be.

Also, it is preferable that the organic acid or salt thereof can exhibit a buffering action in combination with a basic compound. Since the polishing composition configured to exhibit such a buffering action has little pH fluctuation of the polishing composition during polishing and can be excellent in maintaining polishing efficiency, it is possible to improve swelling elimination property. The improvement and the maintenance of the polishing rate can be more suitably made compatible with each other.

Organic acids include acetic acid, itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid, glycolic acid, malonic acid, methanesulfonic acid, formic acid, malic acid, gluconic acid, alanine, glycine, lactic acid, tartronic acid, glyceric acid. , Hydroxybutyric acid, isocitric acid, hydroxyethylidene diphosphonic acid (HEDP), nitrilotris [methylene phosphonic acid] (NTMP), phosphonobutane tricarboxylic acid (PBTC) and the like. The acid may be used in the form of a salt of the acid. The acid salt may be, for example, an alkali metal salt such as sodium salt or potassium salt, or an ammonium salt. Of these, citric acid or a salt thereof is preferable. As the salt of citric acid, an ammonium salt is preferable from the viewpoint of suppressing metal contamination, and examples thereof include diammonium hydrogen citrate and triammonium citrate. The organic acids or salts thereof can be used alone or in combination of two or more. From the standpoint of preventing polishing vibration, it is preferable to use only one type selected from organic acids and salts thereof.

The content of the organic acid and its salt is not particularly limited, and may be, for example, 0.001% by weight or more, and 0.002% by weight, based on the total weight of the polishing composition, from the viewpoint of swelling elimination property. It may be more than 0.005% by weight. From the viewpoint of dispersion stability of the polishing composition and the like, in some embodiments, the total content is, for example, 5% by weight or less, 1% by weight or less, or 0.3% by weight or less. It may be 0.1% by weight or less, or 0.05% by weight or less (for example, 0.02% by weight or less). These contents can be preferably applied to the contents in the polishing liquid (working slurry) supplied to the object to be polished, for example.

The content of the organic acid and its salt in the polishing composition disclosed herein can also be specified by the relative relationship with the abrasive grains contained in the polishing composition. Specifically, the content of the organic acid and its salt in the polishing composition is appropriately about 0.01 parts by weight or more with respect to 100 parts by weight of the abrasive grains, and from the viewpoint of swelling elimination property, It is preferably about 0.1 part by weight or more, more preferably about 0.5 part by weight or more (for example, about 1 part by weight or more). From the viewpoint of dispersion stability and the like, the content of the organic acid and its salt is appropriately about 50 parts by weight or less, and preferably about 10 parts by weight or less, based on 100 parts by weight of the abrasive grains. It is preferably about 5 parts by weight or less (for example, about 3 parts by weight or less).

The content of the organic acid and its salt in the polishing composition disclosed herein can also be specified by the relative relationship with the content of the water-soluble polymer contained in the polishing composition. Specifically, the ratio of the content (A _OA ) (unit: wt%) of the organic acid and its salt (unit: wt%) to the content (A _HM ) of the water-soluble polymer (unit: wt%) in the polishing composition. _OA / A _HM ) is appropriately about 0.1 or more, and is preferably about 1 or more, and more preferably about 5 or more from the viewpoint of preventing polishing vibration. From the viewpoint of dispersion stability and the like, the ratio ( _AOA / _AHM ) is appropriately about 500 or less, preferably about 100 or less, more preferably about 50 or less (for example, about 30 or less). Is.

In the case of a polishing composition used for polishing after dilution (that is, a concentrated solution), the content of the organic acid and its salt is usually 10% by weight or less from the viewpoint of storage stability and filterability. It is suitable to be 5% by weight or less, more preferably 3% by weight or less (for example, 1% by weight or less). Further, from the viewpoint of utilizing the advantages of the concentrated liquid, the content of the organic acid and its salt is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and further preferably 0.3% by weight. % Or more.

<Water>
The polishing composition disclosed herein comprises water. As the water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water or the like can be preferably used. The water used preferably has a total content of transition metal ions of 100 ppb or less, for example, in order to prevent the functions of other components contained in the polishing composition from being hindered. For example, the purity of water can be increased by operations such as removal of impurity ions with an ion exchange resin, removal of foreign substances with a filter, and distillation.
The polishing composition disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water, if necessary. Usually, 90% by volume or more of the solvent contained in the polishing composition is preferably water, and more preferably 95% by volume or more (typically 99 to 100% by volume) is water.

<Other ingredients>
The polishing composition disclosed herein is a polishing composition such as an inorganic acid or a salt thereof, a surfactant, a chelating agent, an antiseptic agent, an antifungal agent, etc. within the range that the effect of the present invention is not significantly impaired. Typically, a known additive that can be used in the polishing composition used in the polishing step of a silicon wafer) may be further contained, if necessary.

Examples of the inorganic acid include hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid and the like. The acid may be used in the form of a salt of the acid. The acid salt may be, for example, an alkali metal salt such as sodium salt or potassium salt, or an ammonium salt. Other examples of the inorganic acid salt include sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium orthosilicate, potassium orthosilicate, calcium carbonate, calcium hydrogen carbonate and the like. The polishing composition disclosed herein can be preferably carried out in a manner substantially free of an inorganic acid salt, that is, at least intentionally free of an inorganic acid salt.

As the above-mentioned surfactant, any kind of surfactant such as amphoteric surfactant, cationic surfactant, anionic surfactant and nonionic surfactant can be used. The molecular weight of the surfactant is typically less than 2000, preferably 1500 or less. Further, the lower limit of the molecular weight of the surfactant is not limited to a particular range and may be, for example, 200 or more. As the molecular weight of the surfactant, a value calculated from a chemical formula can be adopted. The polishing composition disclosed herein can be preferably carried out in a mode that is substantially free of a surfactant, that is, a mode that is at least intentionally free of a surfactant.

Examples of the above chelating agents include aminocarboxylic acid type chelating agents and organic phosphonic acid type chelating agents. Examples of aminocarboxylic acid type chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid. , Sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid and sodium triethylenetetraminehexaacetate. Examples of the organic phosphonic acid type chelating agent are 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid). Acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid , Ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphosphonic acid Includes nosuccinic acid. Of these, organic phosphonic acid-based chelating agents are more preferable. Of these, preferred are ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and diethylenetriaminepentaacetic acid. Particularly preferred chelating agents include ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). The chelating agents may be used alone or in combination of two or more.

Examples of the above preservatives and fungicides include isothiazoline compounds, paraoxybenzoic acid esters, phenoxyethanol and the like.

The polishing composition disclosed herein preferably contains substantially no oxidizing agent. When the polishing composition contains an oxidizing agent, the silicon wafer surface is oxidized by the supply of the composition to form an oxide film, which may reduce the polishing rate. Is. Here, that the polishing composition does not substantially contain an oxidizing agent means that at least the oxidizing agent is not intentionally blended, and a trace amount of the oxidizing agent is inevitably included due to the raw material, the manufacturing method, or the like. Can be allowed. The above-mentioned minute amount means that the molar concentration of the oxidizing agent in the polishing composition is 0.0005 mol / L or less (preferably 0.0001 mol / L or less, more preferably 0.00001 mol / L or less, particularly preferably 0. 000001 mol / L or less). The polishing composition according to a preferred embodiment does not contain an oxidizing agent. The polishing composition disclosed herein can be preferably carried out, for example, in a mode containing neither hydrogen peroxide, sodium persulfate, ammonium persulfate nor sodium dichloroisocyanurate.

<Polishing composition>
The polishing composition disclosed herein is typically supplied to a polishing object in the form of a polishing liquid (working slurry) containing the polishing composition and used for polishing the polishing object. The polishing composition disclosed herein may be, for example, one diluted (typically diluted with water) to be used as a polishing liquid, or one used as it is as a polishing liquid. Good. That is, the concept of the polishing composition in the technology disclosed herein includes both a working slurry that is supplied to a polishing object and is used for polishing the polishing object, and a concentrated solution (stock solution) of the working slurry. Is included. The concentration ratio of the concentrated liquid may be, for example, about 2 to 100 times on a volume basis, and normally about 5 to 70 times is appropriate.

The pH of the polishing composition is typically 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher, still more preferably 9.5 or higher, for example 10.0 or higher. When the pH is high, the polishing rate and the swelling elimination property tend to be improved. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing a decrease in mechanical polishing action due to the abrasive grains, the pH of the polishing liquid is usually 12.0 or less. , 11.8 or less, and more preferably 11.5 or less. These pHs can be preferably applied to both the pH of the polishing liquid (working slurry) supplied to the object to be polished and its concentrated liquid.

For the pH of the polishing composition, use a pH meter (eg, glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba Ltd.) and use a standard buffer solution (phthalate pH buffer solution pH: After three-point calibration using 4.01 (25 ° C), neutral phosphate pH buffer pH: 6.86 (25 ° C, carbonate pH buffer pH: 10.01 (25 ° C)) It can be grasped by putting the glass electrode in the polishing composition and measuring the value after the glass electrode has become stable for 2 minutes or more.

The polishing composition disclosed herein may be a one-component type or a multi-component type including a two-component type. For example, the polishing liquid may be prepared by mixing Part A containing at least abrasive grains and Part B containing the remaining components, and diluting the mixture at a suitable timing as needed.

The method for producing the polishing composition disclosed herein is not particularly limited. For example, each component contained in the polishing composition may be mixed using a known mixing device such as a blade stirrer, an ultrasonic disperser, or a homomixer. The mode of mixing these components is not particularly limited, and for example, all components may be mixed at once, or may be mixed in an appropriately set order.

<Polishing>
The polishing composition disclosed herein can be used for polishing an object to be polished in a mode including the following operations, for example.
That is, a working slurry containing any of the polishing compositions disclosed herein is prepared. Then, the polishing composition is supplied to an object to be polished and polished by a conventional method. For example, the object to be polished is set in a general polishing apparatus, and the polishing composition is supplied to the surface (surface to be polished) of the object to be polished through the polishing pad of the polishing apparatus. Typically, while continuously supplying the polishing composition, the polishing pad is pressed against the surface of the object to be polished to relatively move (for example, rotationally move) the both. The polishing of the object to be polished is completed through such a polishing process.

The polishing pad used in the above polishing process is not particularly limited. For example, any of a polyurethane foam type, a non-woven fabric type, a suede type, one containing abrasive grains, one containing no abrasive grains, etc. may be used. As the polishing device, a double-sided polishing device that simultaneously polishes both sides of an object to be polished may be used, or a single-sided polishing device that polishes only one side of the object to be polished may be used.

The above polishing composition may be used in a form of being disposable once used for polishing (so-called “flowing over”), or may be repeatedly used by circulating. As an example of a method of circulating and using the polishing composition, there is a method of collecting the used polishing composition discharged from the polishing apparatus in a tank and supplying the recovered polishing composition to the polishing apparatus again. ..

<Use>
The polishing composition disclosed herein is suitable for polishing a semiconductor substrate such as a silicon wafer. Since the above polishing composition is excellent in the ability to eliminate the protrusions on the periphery of the HLM (protrusion elimination property), it can be preferably applied to the polishing of the surface to be polished including the surface with the HLM. The polishing composition disclosed herein includes a preliminary polishing step, more specifically, a rough polishing step (primary polishing step) which is the first polishing step in the polishing step, and an intermediate polishing step (secondary polishing step) subsequent thereto. Particularly preferably used in).

Prior to the polishing step using the polishing composition disclosed herein, the silicon wafer has been subjected to general treatment that can be applied to the silicon wafer, such as lapping, etching, and application of the above-described HLM. Good.
The silicon wafer typically has a surface made of silicon. Such a silicon wafer is typically a silicon single crystal wafer, for example, a silicon single crystal wafer obtained by slicing a silicon single crystal ingot. The polishing composition disclosed herein is suitable for use in polishing a silicon single crystal wafer provided with HLM.
Further, the polishing composition disclosed herein can be suitably used for polishing an object to be polished having no HLM.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the examples.

<Preparation of polishing composition>
(Example 1)
Colloidal silica as abrasive grains, tetramethylammonium hydroxide (TMAH) as a basic compound, triammonium citrate, polyvinylpyrrolidone (PVP) as a water-soluble polymer, and ion-exchanged water at room temperature 25 A polishing composition was prepared by stirring and mixing at about C for about 30 minutes. The obtained polishing composition was diluted 50 times with ion-exchanged water to obtain a polishing liquid containing each component in the concentration shown in Table 1. The wt% in the table is% by weight. The above colloidal silica has an average primary particle diameter of 55 nm, an average circle equivalent diameter by SEM observation of 93 nm, a standard deviation of circle equivalent diameter of 38.5, an average aspect ratio of 1.3, and an aspect ratio. The standard deviation of the ratio is 0.320, the volume ratio of particles having a circle equivalent diameter of 50 nm or more and an aspect ratio of 1.2 or more is 77%, and the volume content of particles having a circle equivalent diameter of 1 to 300 nm is 100. %Met. The pH of the polishing composition according to this example was 10.2.

(Comparative Example 1)
A polishing liquid according to this example was prepared in the same manner as in Example 1 except that potassium ammonium (K ₂ CO ₃ ) was used instead of triammonium citrate and the concentrations were changed to those shown in Table 1.

(Comparative Examples 2 to 4)
Regarding the polishing liquid of Comparative Example 1, the water-soluble polymer was not used in Comparative Example 2, potassium carbonate was not used in Comparative Example 3, and the abrasive grains were not used in Comparative Example 4, and the polishing liquid according to each example was used. Prepared.

[Rise height]
(Silicon wafer polishing)
The polishing liquid according to each example was used as it was as a working slurry, and the surface of a polishing target (test piece) was polished under the following conditions. As a test piece, a commercially available silicon single crystal wafer having a diameter of 100 mm after lapping and etching (thickness: 525 μm, conductivity type: P type, crystal orientation: <100>, resistivity: 0.1 Ω · cm or more 100 Ω · cm Less than) was used. An HLM is attached to the wafer.
(Polishing conditions)
Polishing device: One-side polishing device manufactured by Nippon Engis Co., Ltd., model "EJ-380IN"
Polishing pressure: 12kPa
Plate rotation speed: 50 rpm
Head rotation speed: 40 rpm
Polishing pad: Nitta Haas, product name "SUBA800"
Polishing liquid supply rate: 100 mL / min (use overflow)
Holding temperature of polishing environment: 25 ℃
Polishing time: 20 minutes

(Evaluation)
For the silicon wafer after polishing, the surface shape of the site including the HLM was measured using a stylus type surface roughness profiler (SURFCOM 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the highest protrusion from the reference plane around the HLM. The height [μm] to the point was measured. The larger the ridge height, the poorer the bulge elimination property is. The obtained results are shown in the column of "protrusion height" in Table 1.

[Polishing vibration]
(Silicon wafer polishing)
The polishing liquid according to each example was used as it was as a working slurry, and the surface of the object to be polished (test piece) was polished under the following conditions. As the test piece, a commercially available silicon wafer having a diameter of 300 mm after lapping and etching (thickness: 775 μm, conductivity type: P type, crystal orientation: <100>, resistivity: 0.1 Ω · cm or more and less than 100 Ω · cm) was used. used.
(Polishing conditions)
Polishing machine: Double-sided polishing machine manufactured by Speedfam, model "20B"
Polishing pad: Nitta Haas, product name "SUBA800"
Polishing pressure: 15kPa
Slurry flow rate: 4.5 L / min Upper surface plate rotation speed: -13.4 rpm
Lower surface plate rotation speed: +35.0 rpm (rotational direction opposite to the upper surface plate)
Revolution speed of carrier: 11.2 rpm
Holding temperature of polishing environment: 25 ℃
Polishing time: 5 minutes

(Evaluation)
During the above-mentioned polishing, "absent" was indicated when polishing vibration was observed, and "absent" when polishing vibration was not observed. The obtained results are shown in the column of "polishing vibration" in Table 1.

As shown in Table 1, in Comparative Example 1 in which the polishing composition containing the abrasive grains, the basic compound, the water-soluble polymer and water and containing no organic acid or salt thereof was used, the swelling elimination property was excellent. However, polishing vibration occurred. On the other hand, in Example 1 using the organic acid or the salt thereof, the swelling eliminating property equivalent to that of Comparative Example 1 was exhibited, and polishing vibration did not occur. In Comparative Example 2 in which the water-soluble polymer was not used, the swelling elimination property was poor and polishing vibration was generated. Also in Comparative Example 3 in which an acid or a salt thereof was not used, good swelling eliminating property was not obtained, and polishing vibration was also generated. In Comparative Example 4 in which abrasive grains were not used, polishing vibration did not occur, but the swelling elimination property was poor. From these results, according to the polishing composition containing the abrasive grains, the basic compound, the water-soluble polymer and water, and further containing the organic acid or the salt thereof, excellent swelling eliminating property and polishing vibration preventing property are realized. You know you will get.

The specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims

Contains abrasives, basic compounds, water-soluble polymers and water,
A composition for preliminarily polishing a silicon wafer, which further contains an organic acid or a salt thereof.
The polishing composition according to claim 1, wherein the organic acid is a polycarboxylic acid.
The polishing composition according to claim 1 or 2, wherein the organic acid is a hydroxy acid.
The polishing composition according to any one of claims 1 to 3, wherein the abrasive grains are silica particles.
The polishing composition according to any one of claims 1 to 4, which contains quaternary ammonium hydroxide or a salt thereof as the basic compound.
6. The ratio (A OA / A HM ) of the content (A OA ) of the organic acid and its salt to the content (A HM ) of the water-soluble polymer is 1 or more and 100 or less. The polishing composition as described in 1 above.