JP6360311B2 - Polishing composition and method for producing the same - Google Patents

Description

  The present invention relates to a polishing composition and a method for producing the same.

  The surface of a silicon wafer used as a component of a semiconductor device or the like is generally finished into a high-quality mirror surface through a lapping process (rough polishing process) and a polishing process (precision polishing process). The polishing process typically includes a preliminary polishing process (preliminary polishing process) and a final polishing process (final polishing process). Patent documents 1 and patent documents 2 are mentioned as technical literature about a constituent for polish mainly used for a use which polishes semiconductor substrates, such as a silicon wafer. Patent Document 3 is a technical document related to a metal polishing liquid.

International Publication No. 2012/102144 JP 2008-53414 A International Publication No. 00/39844

Polishing compositions for polishing semiconductor substrates such as silicon wafers and other substrates (especially polishing compositions for precision polishing) contain polymers for the purpose of protecting the surface of polishing objects and improving wettability. There are many things that I let you do. As such a polymer, a polymer containing a repeating unit having a hydroxyl group (hereinafter, also referred to as “hydroxyl group-containing polymer P _h ”) can be preferably used. However, the polishing composition containing a hydroxyl group-containing polymer P _h, the dispersion of the components contained in the polishing composition (hereinafter, sometimes simply referred to as "dispersibility of the polishing composition".) That varies was there. The dispersibility of the polishing composition can affect the surface quality after polishing. Therefore, in order to stably realize high quality on the polished surface, a polishing composition having good dispersibility and little dispersion in the dispersibility is desirable.

  The present inventor has found a factor useful for improving the dispersibility of the polishing composition and reducing variation in the dispersibility of the polishing composition containing a polymer containing a repeating unit having a hydroxyl group, and completes the present invention. It came to. That is, an object of the present invention is to provide a polishing composition having good dispersibility and less variation in dispersibility. Another object of the present invention is to provide a method for producing a polishing composition capable of stably producing a polishing composition having good dispersibility.

In order to achieve the above object, according to this specification, a polishing composition comprising abrasive grains, water, and a polymer containing a repeating unit having a hydroxyl group is provided. The polishing composition further contains a hydroxycarboxylic acid. In the polishing composition, the ratio of the hydroxycarboxylic acid content (C _A ) to the polymer content (C _P ) containing the repeating unit having a hydroxyl group is 0.5 or less on a weight basis. That is, C _A / C _P is 0.5 or less. The polishing composition is typically alkaline and preferably has a pH of 9 or more.

Such a polishing composition is treated as a polymer containing a repeating unit having a hydroxyl group (a hydroxide-containing polymer P _h ) so as to supply hydroxycarboxylic acid to the water by being dissolved in water. and the particulate hydroxyl group-containing polymer P _h can be prepared with. The thus treated particulate hydroxyl group-containing polymer P _h is likely to be uniformly dissolved in water by suppressing the occurrence of aggregate of micro aggregates and visual levels of the hydroxyl group-containing polymer P _h (the so-called lump) (dispersion) . This is advantageous from the viewpoint of improving the dispersibility and the stability of the hydroxyl group-containing polymer P _h. Also preferred in order to achieve stable and good dispersibility in the polishing composition containing a hydroxyl group-containing polymer P _h. On the other hand, if the content of the hydroxycarboxylic acid contained in the polishing composition is inappropriate, the abrasive grains in the polishing composition may be aggregated and the dispersibility of the abrasive grains may be reduced. According to the polishing composition disclosed herein, by allowing the content of the hydroxycarboxylic acid to the extent that C A _/ C _P is 0.5 or less, and the dispersibility and the stability of the hydroxyl group-containing polymer P _h In addition, the dispersibility of the abrasive grains and the stability thereof can be balanced. As a result, a polishing composition having good dispersibility and little variation in dispersibility can be realized.

  The polishing composition which concerns on one preferable aspect disclosed here contains at least 1 sort (s) selected from the group which consists of a cellulose derivative and a starch derivative as a polymer containing the repeating unit which has the said hydroxyl group. In the polishing composition having such a composition, the effect of improving the dispersibility and stability of the polishing composition can be suitably exhibited.

  The polishing composition according to a preferred embodiment disclosed herein comprises, as the hydroxycarboxylic acid, citric acid, glycolic acid, malic acid, glyceric acid, tartaric acid, lactic acid, hydroxybutyric acid, salicylic acid, gallic acid, and mandelic acid. It includes at least one selected from the group. In the polishing composition containing such a hydroxycarboxylic acid, the effect of improving the dispersibility and stability of the polishing composition can be suitably exhibited.

In the polishing composition according to a preferred embodiment disclosed herein, C _A / C _P is 0.001 or more and 0.2 or less. If C A _/ C _P is due to the polishing composition in the above range, the effect of improving the dispersibility and the stability of the polishing composition can be exhibited particularly well.

  The polishing composition disclosed herein has good dispersibility and little dispersion in the dispersibility. Therefore, according to the polishing using the polishing composition, a high-quality surface can be stably realized after polishing. Taking advantage of such features, the polishing composition disclosed herein can be preferably used for polishing silicon wafers, for example. For example, it is suitable for polishing a lapped silicon wafer. A particularly preferable application target is final polishing of a silicon wafer.

According to the present invention, there is also provided a method for producing a polishing composition comprising abrasive grains, water, a polymer containing a repeating unit having a hydroxyl group, and hydroxycarboxylic acid. The production method, C A _/ C _P is 0.5 or less, and pH is characterized by preparing the polishing composition is 9 or more. According to such a method, a polishing composition having good dispersibility can be stably produced.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Abrasive>
In the technology disclosed herein, the material and properties of the abrasive grains are not particularly limited, and can be appropriately selected according to the purpose of use or the mode of use of the polishing composition. Examples of the abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of the inorganic particles include silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, oxide particles such as bengara particles; Examples thereof include nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles and poly (meth) acrylic acid particles (here, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid). And polyacrylonitrile particles. Such an abrasive grain may be used individually by 1 type, and may be used in combination of 2 or more type.

  As said abrasive grain, an inorganic particle is preferable, and the particle | grains which consist of a metal or a metalloid oxide are especially preferable. As a suitable example of abrasive grains that can be used in the technique disclosed herein, silica particles can be mentioned. For example, when the technique disclosed herein is applied to a polishing composition that can be used for polishing a silicon wafer, it is particularly preferable to use silica particles as abrasive grains. The reason is that when the object to be polished is a silicon wafer, if silica particles composed of the same elements and oxygen atoms as the object to be polished are used as abrasive grains, a metal or metalloid residue different from silicon is generated after polishing. This is because there is no possibility of contamination of the silicon wafer surface or deterioration of electrical characteristics of the silicon wafer due to diffusion of a metal or semimetal different from silicon into the object to be polished. Furthermore, since the hardness of silicon and silica is close, there is also an advantage that polishing can be performed without excessively damaging the silicon wafer surface. A polishing composition containing only silica particles as an abrasive is exemplified as a preferred embodiment of the polishing composition from this viewpoint. Silica has a property that it can be easily obtained in high purity. This is also cited as the reason why silica particles are preferable as the abrasive grains. Specific examples of the silica particles include colloidal silica, fumed silica, precipitated silica and the like. Colloidal silica and fumed silica are preferable as silica particles from the viewpoint that scratches are hardly generated on the surface of the object to be polished and a surface having a lower haze can be realized. Of these, colloidal silica is preferred. For example, colloidal silica can be preferably employed as abrasive grains of a polishing composition used for polishing (particularly final polishing) of a silicon wafer.

  The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. By increasing the true specific gravity of silica, the polishing rate (amount of removing the surface of the object to be polished per unit time) can be improved when polishing a silicon wafer. From the viewpoint of reducing scratches generated on the surface (polishing surface) of the object to be polished, silica particles having a true specific gravity of 2.2 or less are preferable. As the true specific gravity of silica, a measured value by a liquid substitution method using ethanol as a substitution liquid can be adopted.

  In the technique disclosed herein, the abrasive grains contained in the polishing composition may be in the form of primary particles or in the form of secondary particles in which a plurality of primary particles are aggregated. Further, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least a part of the abrasive grains is contained in the polishing composition in the form of secondary particles.

There is no particular average primary particle diameter D _P1 of the abrasive grains limited, from the viewpoint of polishing efficiency, preferably 5nm or more, and more preferably 10nm or more. Higher polishing effect (e.g., reduced haze, effects such as removal of defects) from the viewpoint of obtaining an average primary particle diameter _{D P1} is preferably at least 15 nm, more 20nm (e.g. 20nm greater) are more preferred. Further, in view of smoother highly surface easily obtained, an average primary particle diameter _{D P1} of the abrasive grains is preferably 100nm or less, more preferably 50nm or less, more preferably 40nm or less. The technique disclosed herein is based on the average primary particle diameter from the viewpoint of easily obtaining a higher quality surface (for example, a surface with reduced defects such as LPD (Light Point Defect) and PID (Polishing Induced Defect)). An embodiment using abrasive grains having a DP ₁ of 35 nm or less (more preferably 32 nm or less, for example, less than 30 nm) can be preferably implemented.

In the technology disclosed herein, the average primary particle diameter D _P1 of the abrasive grains is, for example, from the specific surface area S (m ² / g) measured by the BET method, and the average primary particle diameter D _P1 (nm) = 2720 / S. It can be calculated by the following formula. The measurement of the specific surface area of the abrasive grains can be performed using, for example, a surface area measuring device manufactured by Micromeritex Co., Ltd., trade name “Flow Sorb II 2300”.

It is not particularly limited abrasive grains having an average secondary particle diameter D _P2, from the viewpoint of polishing rate and the like, preferably 10nm or more, and more preferably 20nm or more. From the viewpoint of obtaining a higher polishing effect, average secondary particle diameter _{D P2} is preferably at 30nm or more, more preferably 35nm or more, further preferably more than 40nm (e.g. 40nm greater). From the viewpoint of obtaining a higher smoothness surface, average secondary particle diameter _{D P2} of the abrasive grains is appropriately 200nm or less, preferably 150nm or less, more preferably 100nm or less. In the technique disclosed herein, the average secondary particle diameter _DP2 is less than 70 nm (more preferably, from the viewpoint of easily obtaining a higher quality surface (for example, a surface in which defects such as LPD and PID are reduced). An embodiment using abrasive grains of 60 nm or less (for example, less than 50 nm) can also be preferably implemented.
Abrasive grains having an average secondary particle diameter D _P2, for example, by NIKKISO dynamic light scattering method using steel of the type to "UPA-UT151" Ltd., volume average particle diameter (arithmetic average diameter on a volume basis; Mv) as Can be measured.

The average secondary particle diameter D _P2 of the abrasive grains is generally equal to or greater than the average primary particle diameter D _P1 of the abrasive grains (1 ≦ D _P2 / D _P1 ), and is typically larger than D _P1 (1 <D _P2 / D _P1 ). Although not particularly limited, from the viewpoint of polishing effect and surface smoothness after polishing, it is appropriate that the D _P2 / D _P1 of the abrasive grains is usually in the range of 1.2 to 3. The range of 5-2.5 is preferable, and the range of 1.7-2.3 (for example, more than 1.9 and 2.2 or less) is more preferable.

  The shape (outer shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical abrasive grains include a peanut shape (that is, a peanut shell shape), a bowl shape, a confetti shape, and a rugby ball shape. For example, abrasive grains in which most of the abrasive grains have a peanut shape can be preferably employed.

  Although not particularly limited, the average value (average aspect ratio) of the major axis / minor axis ratio of the primary particles of the abrasive grains is preferably 1.05 or more, more preferably 1.1 or more. Higher polishing rates can be achieved by increasing the average aspect ratio of the abrasive grains. The average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less, from the viewpoint of reducing scratches.

  The shape (outer shape) and average aspect ratio of the abrasive grains can be grasped by, for example, observation with an electron microscope. As a specific procedure for grasping the average aspect ratio, for example, a predetermined number (for example, 200) of abrasive particles capable of recognizing the shape of independent particles using a scanning electron microscope (SEM) is used. Draw the smallest rectangle that circumscribes the image. For the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (major axis value) by the length of the short side (minor axis value) is the major axis / minor axis ratio (aspect ratio). ). An average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the predetermined number of particles.

<Water>
As water contained in the polishing composition disclosed herein, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like can be preferably used. The water to be used preferably has, for example, a total content of transition metal ions of 100 ppb or less in order to avoid as much as possible the action of other components contained in the polishing composition. 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 matter with a filter, distillation, and the like.
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, it is preferable that 90 volume% or more of the solvent contained in polishing composition is water, and it is more preferable that 95 volume% or more (typically 99-100 volume%) is water.

  The polishing composition disclosed herein (typically a slurry-like composition) has, for example, a solid content (non-volatile content; NV) of 0.01 wt% to 50 wt%, and the balance Is preferably an aqueous solvent (water or a mixed solvent of water and the above-mentioned organic solvent) or a form in which the balance is an aqueous solvent and a volatile compound (for example, ammonia). A form in which the NV is 0.05 wt% to 40 wt% is more preferable. In addition, the said solid content (NV) refers to the ratio of the weight which the residue after drying polishing composition at 105 degreeC for 24 hours occupies for the said polishing composition.

<Hydroxyl-containing polymer>
The polishing composition disclosed here contains a polymer containing a repeating unit having a hydroxyl group (hydroxyl group-containing polymer P _h ). Here, the "repeating unit having a hydroxyl group", refers to that a repeating unit constituting a hydroxyl group-containing polymer P _h having a hydroxyl group. In other words, it refers to a repeating unit having a hydroxyl group in the hydroxyl group-containing polymer P _h. Hereinafter, such a repeating unit may be referred to as “repeating unit h”. The hydroxyl group of the repeating unit h may be derived from a monomer having a hydroxyl group, or may be a hydroxyl group introduced by modifying a polymer. Examples of the method for introducing a hydroxyl group by modifying a polymer include a method of hydrolyzing a pendant group having an ester bond.

Moles proportion of repeating units h occupying the number of moles of all repeating units contained in the molecular structure of the hydroxyl group-containing polymer P _h (molar ratio) is not particularly limited, for example, 5-100% (typically 10 to 100%). From the viewpoint of solubility of the hydroxyl group-containing polymer _Ph in water, the molar ratio of the repeating unit h is usually preferably 50% or more, more preferably 70% or more, and 80% or more. More preferably, it is 90% or more (for example, 95% or more).

The number of hydroxyl groups contained in the repeating unit h may be 1 or 2 or more. Further, the hydroxyl group-containing polymer _Ph may contain one type of repeating unit h alone or may contain two or more types of repeating units h in combination.
Specific examples of the repeating unit h include an α-glucose unit, a β-glucose unit, a vinyl alcohol unit (—CH ₂ —CH (OH) —) and the like.

Hydroxyl group-containing polymer P _h in the polishing composition disclosed herein, for example, cellulose derivatives, starch derivatives, vinyl alcohol polymers may be acrylic polymers and the like. Of these, preferred examples of the hydroxyl group-containing polymer _Ph include cellulose derivatives, starch derivatives, and vinyl alcohol polymers.

  Cellulose derivatives are polymers that contain β-glucose units as the main repeating unit. Specific examples of the cellulose derivative include hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose and the like. Of these, hydroxyethyl cellulose (HEC) is preferable.

  Starch derivatives are polymers that contain α-glucose units as the main repeating unit. Specific examples of starch derivatives include pullulan and carboxymethyl starch. Of these, pullulan is preferred.

  The vinyl alcohol polymer is a polymer containing a vinyl alcohol unit (VA unit) as the repeating unit h. The ratio of the number of moles of VA units to the number of moles of all repeating units contained in the vinyl alcohol-based polymer can be, for example, 5% or more (typically 10% or more). From the viewpoint of solubility in water and the like, the ratio of the number of moles of the VA unit is usually suitably 50% or more, preferably 70% or more, and more preferably 80% or more. 90% or more, more preferably 95% or more (for example, 98% or more). The ratio of the number of moles may be substantially 100%. In the vinyl alcohol polymer, the type of repeating unit other than the VA unit is not particularly limited, and may be, for example, a vinyl acetate unit, a vinyl propionate unit, a vinyl hexanoate unit, or the like. For example, a vinyl alcohol polymer in which the repeating unit substantially consists of a VA unit and a vinyl acetate unit can be preferably used.

The acrylic polymer is typically a polymer containing a monomer unit of a (meth) acryloyl type. Here, “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Acrylic polymer as a hydroxyl-containing polymer P _h as repeating units h, for example, be one which comprises repeating units derived from a hydroxyl group (meth) acryloyl type monomers. Specific examples of the (meth) acryloyl monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and the like. The ratio of the number of moles of repeating units h to the number of moles of all repeating units contained in the acrylic polymer is preferably 5% or more, and more preferably 10% or more (for example, 15% or more). From the viewpoint of solubility in water and the like, the acrylic polymer is preferably copolymerized with a (meth) acryloyl monomer having a carboxy group in addition to a (meth) acryloyl monomer having a hydroxyl group. Preferable examples of the (meth) acryloyl monomer having a carboxy group include acrylic acid and methacrylic acid. The copolymerization ratio of the (meth) acryloyl monomer having a carboxy group is not particularly limited, and may be, for example, 50 mol% or more.

In the polishing composition disclosed herein, the weight average molecular weight of the hydroxyl group-containing polymer P _h (Mw) is not particularly limited. For example, Mw is 200 × 10 ⁴ or less (e.g., 0.99 × 10 ⁴ or less, typically 100 × 10 ⁴ or less) may be used hydroxyl group-containing polymer _{P h} of. The surface defects due to generation or agglomerates of aggregates from the viewpoint of suppressing, Mw of the hydroxyl group-containing polymer P _h is preferably less than 100 × 10 ^4, and more preferably 80 × 10 ⁴ or less . Mw of the hydroxyl group-containing polymer _{P h} may also be 50 × 10 ⁴ or less, may also be 40 × 10 ⁴ or less, or may be 30 × 10 ⁴ or less. As Mw of the hydroxyl group-containing polymer P _h is small, filterability and washability of the polishing composition tends to be improved. Further, from the viewpoint of improving the surface smoothness after polishing, the hydroxyl group-containing polymer P having an Mw of 0.2 × 10 ⁴ or more (typically 0.5 × 10 ⁴ or more, for example, 1 × 10 ⁴ or more) is usually used. _h can be preferably employed. From the viewpoint of obtaining a higher smoothness surface, Mw is 3 × 10 ⁴ may be used or more hydroxyl groups-containing polymer _{P h,} Mw is 5 × 10 ⁴ or more (typically 10 × 10 ⁴ or more, for example 15 × a hydroxyl group-containing polymer _{P h} of 10 ⁴ or more) may be used.

Relationship of the weight average molecular weight of the hydroxyl group-containing polymer P _h (Mw) to number average molecular weight (Mn) is not particularly limited. From the viewpoint of preventing the occurrence of aggregates, for example, those having a molecular weight distribution (Mw / Mn) of 10.0 or less can be preferably used, and those having a molecular weight distribution of 5.0 or less can be more preferably used.

As the Mw and Mn of the hydroxyl group-containing polymer P _h, it is possible to adopt a value based on gel permeation chromatography (GPC) (water, polyethylene oxide standard).

Although not particularly limited, the content of the hydroxyl group-containing polymer P _h can be a relative abrasive 100 parts by weight, for example 0.01 parts by weight or more. The content of the hydroxyl group-containing polymer P _h for grains 100 parts by weight is a viewpoint from suitably above 0.05 parts by weight of the improved surface smoothness after polishing (e.g., reduction of haze), preferably 0.1 part by weight More preferably, it is 0.5 parts by weight or more (typically 1 part by weight or more, for example, 2 parts by weight or more). The content of the hydroxyl group-containing polymer P _h for grains 100 parts by weight, from the viewpoint of polishing rate and washability, such as may be a 40 parts by weight or less, usually it is suitably less than 20 parts by weight, Preferably it is 15 weight part or less, More preferably, it is 10 weight part or less.

The content of the hydroxyl group-containing polymer P _h in the polishing composition (C _P) can be calculated on the basis of the information of the composition and the weight ratio of the materials used in the preparation of the polishing composition. Alternatively, it is also possible to determine by analyzing the polishing composition content of the hydroxyl group-containing polymer P _h a (C _P). The above analysis may be performed as follows, for example. That is, the polishing composition is adjusted to an environment in which organic substances (hydroxyl group-containing polymer _Ph , hydroxycarboxylic acid, etc.) are difficult to adsorb on the abrasive grains. For example, an alkali is added to the polishing composition to adjust to a high pH (for example, pH 10.2 or more). Next, the abrasive grains are removed from the polishing composition adjusted to the above environment by a technique such as centrifugation or filtration. Using the liquid after removal of the abrasive grains as a measurement sample, the total organic carbon content (TOC) of the measurement sample is measured. By subtracting the amount of the obtained TOC from a non-hydroxy-containing polymers P _h organics (such as hydroxy carboxylic acid) can be determined the content of the hydroxyl group-containing polymer P _h in the polishing composition (C _P).

<Hydroxycarboxylic acid>
The polishing composition disclosed herein contains a hydroxycarboxylic acid. Here, the hydroxycarboxylic acid refers to a compound having at least one carboxy group and at least one hydroxyl group in one molecule. The molecular weight of the hydroxycarboxylic acid is not particularly limited, but is usually a hydroxycarboxylic acid having a molecular weight of 1000 or less (typically 500 or less) from the viewpoint of solubility in the polishing composition and detergency of the polishing composition. And a hydroxycarboxylic acid having a molecular weight of 250 or less is more preferable.

The origin of the hydroxycarboxylic acid contained in the polishing composition disclosed herein is not particularly limited. For example, it may be a hydroxycarboxylic acid used as a raw material for preparing the polishing composition, a salt thereof, or a hydroxycarboxylic acid derived from a precursor thereof. Moreover, the hydroxycarboxylic acid derived from the other raw material (for example, hydroxyl-containing polymer _Ph ) used for preparation of polishing composition may be sufficient. That is, a polishing composition containing hydroxycarboxylic acid can be prepared by using a raw material capable of supplying hydroxycarboxylic acid in the polishing composition as the other raw material. The hydroxycarboxylic acid derived from the other raw material may be, for example, a hydroxycarboxylic acid or a salt thereof or a precursor thereof contained as an additive, a treating agent, or an impurity in the other raw material. Alternatively, it may be a structural portion that can be a precursor of hydroxycarboxylic acid, introduced into the other raw materials.
Here, the precursor of hydroxycarboxylic acid means a compound or a structural part capable of generating hydroxycarboxylic acid by a chemical reaction (for example, hydrolysis reaction). Examples of the salt of hydroxycarboxylic acid include alkali metal salts (sodium salt, potassium salt, etc.), ammonium salts and the like. Of these, ammonium salts are preferred.

  Specific examples of the hydroxycarboxylic acid include, but are not limited to, citric acid, glycolic acid, malic acid, glyceric acid, tartaric acid, lactic acid, hydroxybutyric acid, salicylic acid, gallic acid, and mandelic acid. The polishing composition disclosed herein may contain one kind of such hydroxycarboxylic acid alone, or may contain two or more kinds in combination.

  From the viewpoint of preventing excessive adsorption to the substrate and reducing surface defects such as LPD, a hydroxycarboxylic acid containing no aromatic ring (non-aromatic hydroxycarboxylic acid) is preferred. Specific examples of the hydroxycarboxylic acid not containing an aromatic ring include citric acid, glycolic acid, malic acid, glyceric acid, tartaric acid, lactic acid, and hydroxybutyric acid. A hydroxycarboxylic acid that does not contain an aromatic ring and does not have an alkyl group is more preferable. Specific examples of such hydroxycarboxylic acid include citric acid, glycolic acid, malic acid, glyceric acid, tartaric acid and the like. Of these, citric acid, glycolic acid, malic acid and glyceric acid are preferred.

  The content of hydroxycarboxylic acid can be, for example, 0.0001 parts by weight or more with respect to 100 parts by weight of the abrasive grains. From the viewpoint of easy preparation of the polishing composition, the content of hydroxycarboxylic acid with respect to 100 parts by weight of the abrasive is suitably 0.001 part by weight or more, preferably 0.005 part by weight or more, more preferably 0. 0.01 parts by weight or more (for example, 0.02 parts by weight or more). Further, from the viewpoint of obtaining a stable and high-quality surface after polishing, the content of hydroxycarboxylic acid with respect to 100 parts by weight of abrasive grains is usually suitably 1 part by weight or less, and 0.4 parts by weight or less. Preferably, it is 0.1 part by weight or less, more preferably 0.08 part by weight or less (eg 0.05 part by weight or less).

The content (C _A ) of the hydroxycarboxylic acid in the polishing composition can be calculated based on information such as the composition and weight ratio of materials used for the preparation of the polishing composition. Alternatively, the polishing composition can be analyzed to determine the hydroxycarboxylic acid content (C _A ). The above analysis, for example, may use liquid after removal of the abrasive grains by the method described with respect to the measurement of the content of the hydroxyl group-containing polymer P _h as described above (C _P). Using the liquid after removal of the abrasive grains as a measurement sample, the content (C _A ) of hydroxycarboxylic acid can be determined by applying capillary electrophoresis to the measurement sample.

Polishing composition disclosed herein, the content of the hydroxyl group-containing polymer _{P h} the content of hydroxy carboxylic acid to _{(C P)} ratio _{(C A) (C A /} C P) is 0.5 or less It is preferable. Polishing composition satisfying the above-mentioned C _{A /} C _P has good dispersibility, and can be with less variation in dispersibility. As shown in Examples described later, when C _A / C _P increases, the size of particles contained in the polishing composition tends to increase. By setting C _A / C _P to be in the range of 0.5 or less, the above-described particle size variation (particularly increase) due to variation in C _A / C _P value is suitably suppressed, and good dispersibility is stabilized. Can be realized.

On the other hand, in the polishing composition containing a hydroxyl group-containing polymer P _h, is to permit the inclusion of minor amounts of hydroxycarboxylic acid, it may be industrially advantageous. This allows, for example, particulate (powder, granules, etc.) in the preparation process of the polishing composition when dissolving the hydroxy-containing polymer P _h of water, the hydroxy carboxylic acid to the water by being dissolved in water It can be used has been treated so as to provide particulate hydroxyl group-containing polymer P _h become. The thus treated particulate hydroxyl group-containing polymer P _h typically may be the interaction (interaction with a chemical bond between the hydroxyl group and the hydroxy carboxylic acid or a precursor thereof having a hydroxyl group-containing polymer P _h )), The state in which the affinity for water is temporarily suppressed before dissolution in water, that is, the dissolution rate in water is reduced. The particulate hydroxyl group-containing polymer P _h of such a state by placing the water, prior to dissolution in water, the particles of the hydroxyl group-containing polymer P _h can be well dispersed in water. Particles of the hydroxyl group-containing polymer P _h dispersed in water, while supplying a hydroxycarboxylic acid to the water and slowly dissolved in water. Therefore, the treated particulate hydroxyl group-containing polymer P _h so as to provide a hydroxy carboxylic acid in water by dissolving in water, as compared with the case of dissolving the particulate hydroxyl group-containing polymer P _h untreated water Te, poor solubility of the hydroxyl group-containing polymer P _h a (undissolved lumps occurs and the like) can be remarkably suppressed. This is advantageous from the viewpoint of improving the ease of preparation of the polishing composition (for example, improving productivity) and improving the quality stability of the polishing composition (for example, reducing variation in dispersibility of the polishing composition). It is.

Incidentally, hydroxycarboxylic acids supplied to the water by which the treated particulate hydroxyl group-containing polymer P _h so as to provide a hydroxy carboxylic acid in water is dissolved in water, derived from other raw materials described above hydroxy It is a preferred example of a carboxylic acid. Treated particulate hydroxyl group-containing polymer P _h as described above, for example, a mixture of hydroxyl group-containing polymer P _{h (e.g.} hydroxyethyl cellulose) with a hydroxy carboxylic acid or salt thereof, or a precursor thereof, the hydroxyl group of the hydroxyl group-containing polymer P _h It may be a modified product in which a precursor of hydroxycarboxylic acid is bonded to a part thereof.

According to the technology disclosed herein, particulates treated so as to be able to supply hydroxycarboxylic acid to water by allowing the hydroxycarboxylic acid to be contained within a limit of C _A / C _P of 0.5 or less. while enjoying the aforementioned advantages by the use of hydroxyl-containing polymer P _h, dispersibility was excellent good and the stability of the dispersion (i.e., the variation of dispersibility is small) can be realized polishing composition It becomes. For greater dispersibility and the stability of the polishing composition, C _{A /} C _P of the polishing composition is preferably 0.2 or less, 0.1 or less (typically 0 Less than .1), more preferably 0.05 or less, and particularly preferably 0.01 or less (typically less than 0.01, for example 0.008 or less). The lower limit of the C _A / _{C P} is not particularly limited, and may be greater than zero. From the viewpoint of better take advantage of that may contain hydroxy carboxylic acids, C _{A /} C _P of the polishing composition, for example, be a 1 × 10 ^-6 or more, typically 0.0001 or higher Usually, 0.0005 or more is appropriate, and 0.0008 or more is preferable. The polishing composition disclosed herein can also be preferably implemented in an embodiment in which C _A / C _P is 0.001 or more (for example, 0.001 or more and less than 0.01).

<Basic compound>
The polishing composition disclosed herein may typically contain a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. The basic compound serves to chemically polish the surface to be polished, and can contribute to an improvement in the polishing rate. In addition, the basic compound can be useful for improving the dispersion stability of the polishing composition.

  As the basic compound, an organic or inorganic basic compound containing nitrogen, an alkali metal or alkaline earth metal hydroxide, various carbonates, bicarbonates, or the like can be used. For example, alkali metal hydroxide, quaternary ammonium hydroxide or a salt thereof, ammonia, amine and the like can be mentioned. Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Specific examples of the carbonate or bicarbonate include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate and the like. Specific examples of the quaternary ammonium hydroxide or a salt thereof 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. Such basic compounds can be used singly or in combination of two or more.

  Preferred basic compounds from the viewpoint of improving the polishing rate include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, hydrogen carbonate. Sodium and sodium carbonate are mentioned. Of these, preferred are ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide. More preferred are ammonia and tetramethylammonium hydroxide. A particularly preferred basic compound is ammonia.

<Surfactant>
The polishing composition disclosed herein can be preferably implemented in an embodiment containing a surfactant (typically, a water-soluble organic compound having a molecular weight of less than 2 × 10 ³ ) as necessary. By using the surfactant, the dispersion stability of the polishing composition can be improved. Moreover, it can be easy to reduce the haze of the polished surface. Surfactant can be used individually by 1 type or in combination of 2 or more types. In addition, the technique disclosed here can be preferably implemented even in an embodiment that does not include a surfactant.

  As the surfactant, an anionic or nonionic surfactant can be preferably used. From the viewpoint of low foaming property and ease of pH adjustment, a nonionic surfactant is more preferable. For example, oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol; polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glyceryl ether fatty acid Nonionic surfactants such as esters, polyoxyalkylene adducts such as polyoxyethylene sorbitan fatty acid esters; copolymers of plural types of oxyalkylene (diblock type, triblock type, random type, alternating type); It is done.

The molecular weight of the surfactant is typically less than 2 × 10 ³ , and is preferably 1 × 10 ³ or less from the viewpoint of filterability of the polishing composition, cleanability of the object to be polished, and the like. The molecular weight of the surfactant is typically 200 or more, preferably 250 or more, and more preferably 300 or more (for example, 500 or more) from the viewpoint of the haze reduction effect and the like. The molecular weight of the surfactant may be a weight average molecular weight (Mw) determined by GPC (aqueous, polyethylene glycol equivalent) or a molecular weight calculated from a chemical formula.

If the polishing compositions disclosed herein contain surfactants, the weight ratio of the content of W2 content W1 and a surfactant of the hydroxyl group-containing polymer P _h (W1 / W2) is not particularly limited, for example, It can be set as the range of 0.01-500, the range of 1-300 is preferable, and the range of 5-200 is more preferable.

<Other ingredients>
The polishing composition disclosed herein is a chelating agent, an inorganic acid, an inorganic acid salt, an organic acid other than hydroxycarboxylic acid, and an organic acid salt other than hydroxycarboxylic acid salt as long as the effects of the present invention are not significantly hindered. Further, known additives that can be used for polishing compositions (typically, polishing compositions used for final polishing of silicon wafers) such as preservatives and fungicides are further contained as necessary. May be.

  Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic). 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-methylphospho Nosuccinic acid is included. Of these, organic phosphonic acid-based chelating agents are more preferable, and ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are particularly preferable. A particularly preferred chelating agent is ethylenediaminetetrakis (methylenephosphonic acid).

  Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, carbonic acid and the like. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of inorganic acids. These can be used alone or in combination of two or more.

  Examples of organic acids other than hydroxycarboxylic acids include fatty acids such as formic acid, acetic acid and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, oxalic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acid, And organic phosphonic acid. Examples of organic acid salts other than hydroxycarboxylates include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids other than hydroxycarboxylates. The polishing composition disclosed herein can also be preferably implemented in an embodiment that does not substantially contain an organic acid other than hydroxycarboxylate and a salt thereof.

  Examples of antiseptics and fungicides include isothiazoline compounds, paraoxybenzoates, phenoxyethanol and the like.

Polishing compositions disclosed herein, as an optional component, may contain a water-soluble polymer other than the hydroxyl group-containing polymer P _h. The kind of such water-soluble polymer is not particularly limited, and can be appropriately selected from water-soluble polymers known in the field of polishing compositions. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

Examples of water-soluble polymers other than the hydroxyl group-containing polymer P _h, the polymer containing oxyalkylene units, polymers containing a nitrogen atom.
Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of ethylene oxide (EO) and propylene oxide (PO), a random copolymer of EO and PO, and the like. The block copolymer may be a diblock copolymer, a triblock copolymer, or the like including a PEO block and a polypropylene oxide (PPO) block.
As the polymer containing a nitrogen atom, any of a polymer containing a nitrogen atom in the main chain and a polymer having a nitrogen atom in a side chain functional group (pendant group) can be used. Examples of the polymer containing a nitrogen atom in the main chain include homopolymers and copolymers of N-acylalkylenimine monomers. Examples of polymers having a nitrogen atom in the pendant group include homopolymers and copolymers of N-vinylpyrrolidone.

Preferred Mw and Mw / Mn of the hydroxyl group-containing polymer P _h as described above can also be preferably applied to a water soluble polymer other than the hydroxyl group-containing polymer P _h. When using such a water-soluble polymer, the content thereof is preferably less than the content of the hydroxyl group-containing polymer P _h. Polishing compositions disclosed herein may be preferably implemented in a manner that does not contain a water-soluble polymer other than the hydroxyl group-containing polymer P _h substantially.

<Application>
The polishing composition disclosed herein can be applied to polishing a polishing object having various materials and shapes. The material of the polishing object is, for example, a metal or semimetal such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, or an alloy thereof; glass such as quartz glass, aluminosilicate glass, glassy carbon, etc. A ceramic material such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; a compound semiconductor substrate material such as silicon carbide, gallium nitride, and gallium arsenide; a resin material such as polyimide resin; Of these, a polishing object composed of a plurality of materials may be used. Especially, it is suitable for grinding | polishing of the grinding | polishing target object provided with the surface which consists of silicon | silicone. The technique disclosed here is, for example, a polishing composition containing silica particles as abrasive grains (typically, a polishing composition containing only silica particles as abrasive grains), and the object to be polished is silicon. It can be particularly preferably applied to a certain polishing composition.
The shape of the object to be polished is not particularly limited. The polishing composition disclosed herein can be preferably applied to polishing a polishing object having a flat surface such as a plate shape or a polyhedron shape.

  The polishing composition disclosed herein can be preferably used for final polishing of an object to be polished. Therefore, according to this specification, a method for producing a polished article (for example, a method for producing a silicon wafer) including a final polishing step using the polishing composition is provided. Note that final polishing refers to the final polishing step in the manufacturing process of the object (that is, a step in which no further polishing is performed after that step). The polishing composition disclosed herein also refers to a polishing step upstream of final polishing (a preliminary polishing step between a rough polishing step and a final polishing step. Typically, the polishing composition includes at least a primary polishing step. Further, it may include a polishing process such as secondary, tertiary, etc.). For example, it may be used in a polishing process performed immediately before final polishing.

  The polishing composition disclosed herein can be particularly preferably used for polishing a silicon wafer. For example, it is suitable as a polishing composition used for final polishing of a silicon wafer or a polishing process upstream thereof. For example, application to polishing (typically final polishing or polishing immediately before) of a silicon wafer prepared to have a surface roughness of 0.01 nm to 100 nm by an upstream process is effective. Application to final polishing is particularly preferable.

  It is preferable that the polishing composition disclosed herein does not substantially contain an oxidizing agent such as hydrogen peroxide, nitric acid, or potassium periodate. Here, “substantially not containing an oxidizing agent” means that at least intentionally no oxidizing agent is contained, and typically means that the oxidizing agent content is 0.01% by weight or less. In the case where the polishing composition disclosed herein is applied to polishing of a silicon wafer, it is particularly meaningful to have a composition that does not substantially contain an oxidizing agent. This is because when the silicon wafer is oxidized by the oxidizing agent in the polishing composition, the polishing rate can be greatly reduced.

  According to this specification, a method for producing a silicon wafer using any of the polishing compositions disclosed herein is applied. The manufacturing method includes a double-side polishing step in which both surfaces of the silicon wafer are simultaneously polished, and a single-side polishing step in which one side of the silicon wafer that has undergone the double-side polishing step is polished more precisely. In the single-side polishing step, polishing is performed using any of the polishing compositions disclosed herein.

<Polishing liquid>
The polishing composition disclosed herein is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition, and used for polishing the polishing object. The polishing liquid may be prepared, for example, by diluting (typically diluting with water) any of the polishing compositions disclosed herein. Or you may use this polishing composition as polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein is used as a polishing liquid diluted with a polishing liquid (working slurry) that is supplied to a polishing object and used for polishing the polishing object. Both concentrated liquid (polishing liquid stock solution) are included. Another example of the polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

  The content of abrasive grains in the polishing liquid is not particularly limited, but is typically 0.01% by weight or more, preferably 0.03% by weight or more, more preferably 0.05% by weight or more. 0.08% by weight or more. Higher polishing rates can be achieved by increasing the abrasive content. From the viewpoint of realizing a surface having a lower haze, usually, the content is suitably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, still more preferably 2% by weight or less, For example, it is 1% by weight or less. The technique disclosed herein is for polishing used in an embodiment in which the content of abrasive grains in the polishing liquid is 0.7% by weight or less (more preferably 0.5% by weight or less, for example, 0.25% by weight or less). It can be preferably applied to the composition.

The content of the hydroxyl group-containing polymer _{P h} in the polishing liquid is not particularly limited and may be, for example, 0.0001% by weight or more (i.e., more than 1 ppm). From the viewpoint of haze reduction or the like, the preferable content is 0.0005% by weight or more, more preferably 0.001% by weight or more, for example, 0.005% by weight or more. Further, from the viewpoint of polishing rate and the like, the content is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and 0.05% by weight or less (eg, 0.02% by weight). % Or less) is more preferable.

  The content of hydroxycarboxylic acid in the polishing liquid is not particularly limited. From the viewpoint of suppressing aggregation of abrasive grains, the preferable content is less than 10 ppm (that is, less than 0.001% by weight), more preferably 1 ppm or less, for example, 0.7 ppm or less. The lower limit of the hydroxycarboxylic acid content in the polishing liquid can be, for example, 0.001 ppm or more (typically 0.01 ppm or more).

  The pH of the polishing liquid is usually 8.0 or more, typically 8.5 or more, preferably 9.0 or more, and more preferably 9.5 or more. As the pH of the polishing liquid increases, the polishing rate of an object to be polished (for example, a silicon wafer) tends to improve. The upper limit value of the pH of the polishing liquid is not particularly limited. From the viewpoint of suppressing dissolution of the abrasive grains, usually, the pH is preferably 12.0 or less, and more preferably 11.0 or less. The pH can be preferably applied to a polishing liquid used for polishing a silicon wafer (for example, a polishing liquid for final polishing).

  When the polishing liquid disclosed here contains a basic compound, the content of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of improving the polishing rate, the content is usually preferably 0.001% by weight or more, more preferably 0.003% by weight or more of the polishing liquid. Further, from the viewpoint of haze reduction or the like, the content is preferably less than 0.4% by weight, and more preferably less than 0.25% by weight.

When the polishing composition disclosed herein contains a surfactant, the content of the surfactant in the polishing liquid is not particularly limited, and can be, for example, 1 × 10 ⁻⁵ wt% or more. From the viewpoint of haze reduction or the like, the preferred content is 1 × 10 ⁻⁴ wt% or more, more preferably 5 × 10 ⁻⁴ wt% or more, for example 1 × 10 ⁻³ wt% or more. Further, from the viewpoint of detergency and polishing rate, the content is preferably 0.2% by weight or less, and more preferably 0.1% by weight or less (for example, 0.05% by weight or less).

<Concentrate>
The polishing composition disclosed herein may be in a concentrated form (that is, in the form of a polishing liquid concentrate) before being supplied to the object to be polished. The polishing composition in such a concentrated form is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration ratio can be, for example, about 2 to 100 times in terms of volume, and usually about 5 to 50 times is appropriate. The concentration ratio of the polishing composition according to a preferred embodiment is 10 to 40 times, for example, 15 to 25 times.

  Thus, the polishing composition in the form of a concentrated liquid can be used in such a manner that a polishing liquid is prepared by diluting at a desired timing and the polishing liquid is supplied to a polishing object. The dilution can be typically performed by adding and mixing the above-mentioned aqueous solvent to the concentrated solution. In addition, when the aqueous solvent is a mixed solvent, only a part of the components of the aqueous solvent may be added for dilution, and a mixture containing these components in a different ratio from the aqueous solvent. A solvent may be added for dilution. In addition, as will be described later, in a multi-component polishing composition, a part of them may be diluted and then mixed with another agent to prepare a polishing liquid, or a plurality of agents may be mixed. Later, the mixture may be diluted to prepare a polishing liquid.

  The NV of the concentrated liquid can be 50% by weight or less, for example. From the viewpoint of the stability of the polishing composition (for example, dispersion stability of abrasive grains) and filterability, the NV of the concentrated liquid is usually suitably 40% by weight or less, and 30% by weight or less. Preferably, it is 20% by weight or less, for example, 15% by weight or less. Further, from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage, etc., the NV of the concentrate is suitably 0.5% by weight or more, preferably 1% by weight or more, more preferably Is 3% by weight or more, for example, 5% by weight or more.

  The content of abrasive grains in the concentrated liquid can be, for example, 50% by weight or less. From the viewpoint of the stability of the polishing composition (for example, dispersion stability of abrasive grains) and filterability, the content is usually preferably 45% by weight or less, more preferably 40% by weight or less. . In a preferred embodiment, the abrasive content may be 30% by weight or less, or 20% by weight or less (eg, 15% by weight or less). In addition, from the viewpoint of convenience in manufacturing, distribution, storage, etc. and cost reduction, the content of abrasive grains can be, for example, 0.5% by weight or more, preferably 1% by weight or more, and more preferably Is 2% by weight or more (for example, 3% by weight or more).

The content of the hydroxyl group-containing polymer P _h in the concentrate is not particularly limited and may be, for example, 0.002 wt% or more. From the viewpoint of haze reduction or the like, the preferable content is 0.01% by weight or more, more preferably 0.02% by weight or more, for example, 0.1% by weight or more. Further, from the viewpoint of polishing rate and the like, the content is preferably 5% by weight or less, more preferably 2% by weight or less, and 1% by weight or less (eg 0.5% by weight or less). Is more preferable.

  The hydroxycarboxylic acid content in the concentrated liquid is not particularly limited. From the viewpoint of suppressing aggregation of abrasive grains, the preferable content is less than 200 ppm (that is, less than 0.02% by weight), more preferably 50 ppm or less, for example, 20 ppm or less. The lower limit of the hydroxycarboxylic acid content in the polishing liquid can be, for example, 0.1 ppm or more (typically 1 ppm or more, for example, 5 ppm or more).

  The polishing composition disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, the liquid A containing a part of the constituents of the polishing composition (typically, components other than the aqueous solvent) and the liquid B containing the remaining components are mixed to form a polishing object. You may be comprised so that it may be used for grinding | polishing.

<Preparation of polishing composition>
The manufacturing method of polishing composition disclosed here is not specifically limited. For example, each component contained in the polishing composition may be mixed using a well-known mixing device such as a blade-type stirrer, an ultrasonic disperser, or a homomixer. The aspect which mixes these components is not specifically limited, For example, all the components may be mixed at once and may be mixed in the order set suitably.

<Polishing>
The polishing composition disclosed herein can be used for polishing a polishing object, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method for polishing a polishing object using the polishing composition disclosed herein will be described.
That is, a polishing liquid (typically a slurry-like polishing liquid, sometimes referred to as a polishing slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include preparing the polishing liquid by adding operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition. Or you may use the said polishing composition as polishing liquid as it is. Further, in the case of a multi-drug type polishing composition, to prepare the polishing liquid, mixing those agents, diluting one or more agents before the mixing, and after the mixing Diluting the mixture, etc. can be included.

Next, the polishing liquid is supplied to the object to be polished and polished by a conventional method. For example, when final polishing of a silicon wafer is performed, the silicon wafer that has undergone the lapping process and the preliminary polishing process is set in a general polishing apparatus, and the surface of the silicon wafer (surface to be polished) is passed through the polishing pad of the polishing apparatus. A polishing liquid is supplied. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the silicon wafer to relatively move (for example, rotate) the two. The polishing of the object to be polished is completed through this polishing step.
The polishing pad used in the polishing step is not particularly limited. For example, any of non-woven fabric type, suede type, those containing abrasive grains, those not containing abrasive grains, etc. may be used.

<Washing>
Moreover, the polishing object polished using the polishing composition disclosed herein is typically washed after polishing (after rinsing if necessary). This washing can be performed using an appropriate washing solution. The cleaning liquid to be used is not particularly limited. For example, an SC-1 cleaning liquid (ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ), water (H ₂ O) and the like that are common in the field of semiconductors and the like. Hereinafter, the cleaning using the SC-1 cleaning liquid is referred to as “SC-1 cleaning”), the SC-2 cleaning liquid (mixed liquid of HCl, H ₂ O ₂ and H ₂ O) or the like. be able to. The temperature of the cleaning liquid can be, for example, about room temperature to about 90 ° C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50 ° C. to 85 ° C. can be preferably used.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “part”, “%” and “ppm” are based on weight unless otherwise specified.

<Preparation of polishing composition>
Example 1
Abrasive grains, hydroxyethyl cellulose (HEC), triammonium citrate, aqueous ammonia (concentration 29%) and deionized water were mixed to obtain a concentrated liquid of the polishing composition. This concentrated solution was diluted 20 times with deionized water to prepare a polishing composition according to Example 1.
As the abrasive grains, colloidal silica having an average primary particle diameter of 25 nm and an average secondary particle diameter of 46 nm was used. The average primary particle size is measured using a surface area measuring device manufactured by Micromerex, Inc., trade name “Flow Sorb II 2300”. Moreover, the said average secondary particle diameter is a volume average particle diameter (Mv) based on the dynamic light-scattering method measured using the model "UPA-UT151" by Nikkiso Co., Ltd.
As the HEC, one having Mw of 25 × 10 ⁴ was used.
The amount of abrasive grains, HEC, triammonium citrate and aqueous ammonia used is 0.175% for the abrasive grains in the polishing composition and 90 ppm for the HEC, which is derived from the above triammonium citrate. The content of citric acid was 0.01 ppm, and the content of ammonia (NH ₃ ) derived from the ammonia water was 0.005%. The ratio of the content (concentration) of citric acid to the content (concentration) of HEC is 0.0001. The polishing composition had a pH of 10.0.

(Examples 2 and 3, Reference Example 4)
In the same manner as in Example 1 except that the amount of triammonium citrate was changed so that the content (concentration) of citric acid in the polishing composition would be the value shown in Table 1, each of Examples 2 and 3 Each of the polishing compositions according to Reference Example 4 was prepared. The pH of these polishing compositions was 10.0, 10.0, and 9.9 in order.

(Comparative Examples 1-3)
Comparative Examples 1 to 3 were carried out in the same manner as in Example 1 except that the amount of triammonium citrate was changed so that the content (concentration) of citric acid in the polishing composition was the value shown in Table 1. Each polishing composition was prepared. The pH of these polishing compositions was 9.7, 9.6, and 9.5, respectively.

<Rate of increase in particle size>
A control polishing composition was prepared in the same manner as in Example 1 except that triammonium citrate was not used. About this polishing composition for control | contrast, the particle diameter measurement based on a dynamic light-scattering method is performed using the model "UPA-UT151" by Nikkiso Co., Ltd., The volume average particle | grains of the particle | grains contained in this polishing composition The diameter (D ₀ ) was determined.
For each of the polishing compositions of Examples 1 to 3, Reference Example 4 and Comparative Examples 1 to 3, the particle size measurement based on the dynamic light scattering method is similarly performed, and the volume of the particles contained in each polishing composition The average particle size (D ₁ ) was determined. From these values, the particle size increase rate relative to the control polishing composition was calculated for the polishing composition according to each example by the following formula. The results are shown in Table 1.
Increase rate of particle size [%] = (D ₁ −D ₀ ) / D ₀ × 100

As shown in Table 1, compared with the polishing compositions of Comparative Examples 1 to 3, the polishing compositions of Examples 1 to 3 and Reference Example 4 clearly show a particle size increase rate relative to the control polishing composition. It was small. From these results, the polishing compositions of Examples 1 to 3 and Reference Example 4 are less susceptible to the influence of hydroxycarboxylic acid concentration on the dispersibility of the components contained in the polishing composition, in other words, for polishing. It turns out that the dispersion | variation in the dispersibility of a composition is suppressed.
Here, for convenience of experiments, polishing compositions having different hydroxycarboxylic acid contents were prepared by varying the amount of ammonium citrate used in the preparation of the polishing composition. containing the same tendency can be obtained even when the polymer P _h with different content of hydroxy carboxylic acids derived from, the object of the present invention is resolved to those skilled in the.

  Specific examples of the present invention have been described in detail above, 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 (6)

Abrasive grains, water, a polymer containing a repeating unit having a hydroxyl group, and a hydroxycarboxylic acid,
The ratio of the content of the hydroxycarboxylic acid to the content of the polymer containing the repeating unit having a hydroxyl group on a weight basis is 0.01 or less ,
Polishing composition whose pH is 9 or more.   The polishing composition according to claim 1, comprising at least one selected from the group consisting of a cellulose derivative and a starch derivative as the polymer containing a repeating unit having a hydroxyl group.   The hydroxycarboxylic acid includes at least one selected from the group consisting of citric acid, glycolic acid, malic acid, glyceric acid, tartaric acid, lactic acid, hydroxybutyric acid, salicylic acid, gallic acid and mandelic acid. The polishing composition according to 1. The polishing composition according to any one of claims 1 to 3, wherein a ratio of a content of the hydroxycarboxylic acid to a content of the polymer including the repeating unit having a hydroxyl group is 0.001 or more and 0.01 or less. object.   The polishing composition according to any one of claims 1 to 4, which is used for polishing a silicon wafer. The following conditions:
An abrasive, water, a polymer containing a repeating unit having a hydroxyl group, and a hydroxycarboxylic acid;
The ratio of the content of the hydroxycarboxylic acid to the content of the polymer containing the repeating unit having a hydroxyl group on a weight basis is 0.01 or less ; and
pH is 9 or higher;
The manufacturing method of polishing composition characterized by preparing the polishing composition which satisfy | fills.