TWI658132B - Polishing composition, manufacturing method of polishing composition, and silicon wafer manufacturing method - Google Patents

Abstract

The invention provides a polishing composition capable of suppressing the influence on the surface quality and improving the polishing rate while polishing a silicon wafer. According to the present invention, a polishing composition for polishing a silicon wafer is provided. The polishing composition includes, as abrasive particles, silicon dioxide particles having a plurality of protrusions on the surface. The polishing composition further contains an inorganic basic compound (A) selected from the group consisting of ammonia and ammonium salts.

Description

Polishing composition, manufacturing method of polishing composition, and silicon wafer manufacturing method

The present invention relates to a polishing composition for polishing a silicon wafer and a manufacturing method thereof. The present invention also relates to a method for manufacturing a silicon wafer using the polishing composition. This application claims priority based on Japanese Patent Application No. 2013-200641 filed on September 26, 2013, the entire contents of which are incorporated herein by reference.

The surface of a silicon wafer used as a constituent element of a semiconductor device or the like is generally modified into a high-quality mirror surface through a polishing step (rough polishing step) and a polishing step (precision polishing step). The above-mentioned polishing step typically includes a pre-polishing step (a pre-polishing step) and a final polishing step (a final polishing step). As the polishing method in the above polishing step, a chemical mechanical polishing (CMP) method using a polishing composition containing water, abrasive particles, and a polishing accelerator is known. Patent documents 1 and 2 are listed in the technical literature about the polishing composition.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2008-53415

[Patent Document 2] Japanese Patent Application Publication No. 2013-121631

In recent years, higher-quality surfaces have been required for semiconductor substrates such as silicon wafers and other substrates. In particular, based on considerations of productivity, cost, etc., it is expected that a higher-quality surface can be obtained without extending the total polishing time (total polishing time) required for the polishing step. For this reason, one of the methods is directed to any polishing step upstream of the polishing step included in the polishing step, and if it can maintain a quality equal to or higher than the surface quality achieved by the polishing step, It is advantageous to be able to increase the grinding rate in this grinding step. This is because the time that may be taken for a further downstream polishing step (for example, the final polishing step) can be lengthened, and the object to be polished is polished to a smoother surface.

However, in general, the surface quality after polishing is inversely related to the polishing rate. If the polishing rate is increased, the surface quality tends to decrease.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a polishing composition that can suppress the influence on the surface quality while increasing the polishing rate. Another object of the present invention is to provide a method for manufacturing a silicon wafer using the polishing composition.

This specification provides a polishing composition for polishing a silicon wafer. The polishing composition includes, as abrasive particles, silicon dioxide particles having a plurality of protrusions on the surface (hereinafter also referred to as "silicon dioxide particles with protrusions"). The polishing composition further contains an inorganic basic compound (A) selected from the group consisting of ammonia and ammonium salts. When polishing using such a polishing composition, a more efficient and higher-quality surface can be supplied for a downstream polishing step. Therefore, the above-mentioned polishing composition can be used, for example, in any polishing step upstream of the multiple polishing step included in the polishing step than the final polishing step, and can contribute to improving the surface quality of the finally obtained silicon wafer.

The above-mentioned protrusion-added silica particles are protrusion-containing silica particles having a larger particle diameter than the volume average particle diameter of the protrusion-containing silica particles contained in the polishing composition. The average of the values obtained by dividing the projection heights of the particles by the widths of the bases of the same projections (hereinafter also referred to as "projection degree") is preferably 0.245 or more. With the average of the protrusion degrees (hereinafter also referred to as "average protrusion degree") of 0.245 or more, the silica particles with protrusions can appropriately exert the effect of increasing the polishing rate.

The polishing composition may further include a water-soluble polymer. A higher quality surface can be provided by a polishing composition containing a water-soluble polymer. With this, it is possible to effectively suppress the decrease in surface quality while increasing the polishing rate.

In a preferred aspect of the technology disclosed herein, the amount of the water-soluble polymer contained in the polishing composition is 5 g to 50 g relative to 1 kg of the polishing particles. In this composition, the effect by combining the silica particle with a processus | protrusion, an inorganic basic compound (A), and a water-soluble polymer can be exhibited favorably.

However, in recent years, the manufacturing methods of silicon wafers in the above-mentioned polishing steps mostly include a two-side polishing step of simultaneously polishing both sides of the silicon wafer, and then a more precise single-side polishing step of polishing one side of the silicon wafer. The double-sided polishing step is sometimes referred to as a single polishing step. Generally, the silicon wafer is fixed in a double-sided polishing device. The silicon wafers polished on both sides are cleaned, dried, and edge-polished as required, and then fixed in a single-sided polishing device for a single-sided polishing step. The single-side polishing step may include two or more polishing steps. The two or more grinding steps typically include a final grinding step and two grinding steps performed before the final grinding step. The two polishing steps may be further divided into a plurality of polishing steps.

The polishing composition disclosed herein is preferably used in the first polishing step (that is, the first two polishing steps) in the single-side polishing step described above. By using the above-mentioned polishing composition in the first two polishing steps, the effect due to the combination of the polishing composition containing the silicon dioxide particles with protrusions and the inorganic basic compound (A) can be exhibited particularly well.

According to the specification, a method for manufacturing a polishing composition for polishing a silicon wafer is provided. The method is characterized by preparing a polishing composition containing the following components: abrasive particles having a plurality of protruding silica particles on the surface, and inorganic alkalinization selected from the group consisting of ammonia and ammonium salts Compound (A). According to this method, any of the polishing compositions disclosed herein can be manufactured well.

According to this manual, a method for manufacturing a silicon wafer is provided. The method includes the following steps: a two-sided polishing step of polishing both sides of a silicon wafer at the same time, and a more precise single-sided polishing step of polishing one side of the silicon wafer after the two-sided polishing step. The single-side polishing step includes two or more polishing steps. In the first polishing step among them, any one of the polishing compositions disclosed herein is used for polishing. According to this silicon wafer manufacturing method, since the above-mentioned polishing composition is used in the initial polishing step in the single-side polishing step, a high-quality surface can be more efficiently supplied for the downstream polishing step. According to this, a silicon wafer with higher surface quality can be finally manufactured.

FIG. 1 is a schematic diagram showing an outline of an outer shape of a silicon dioxide particle having a plurality of protrusions on a projection surface.

Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than the matters specifically mentioned in the present specification are necessary for the implementation of the present invention. Those skilled in the art can grasp design matters based on the conventional technology in the technical field. The present invention can be implemented based on the contents disclosed in this specification and technical knowledge in the field.

<Abrasive particles>

The polishing composition disclosed herein includes silicon dioxide particles (silicon dioxide particles with projections) on the surface as abrasive particles. The silicon dioxide particles with protrusions have a higher mechanical polishing effect on the surface of the object to be polished than the silicon dioxide particles without a plurality of protrusions on the surface. Here, the spherical silica particles or peanut-type silica particles are typical examples included in the concept of silica particles having a shape without a plurality of protrusions on the surface.

The number of protrusions in the silicon dioxide particles with protrusions is preferably an average of 2 or more, more preferably 3 or more, and even more preferably 5 or more per particle. Here, the so-called protrusions are those having a sufficiently small height and width compared to the particle diameter of the silica particles. More specifically, it refers to the outline of the silicon dioxide particles shown in FIG. 1. The length from the point A through the point C to the point B does not exceed the largest circle (the largest inscribed circle) inscribed in the outline. ) Of a quarter of the circumference.

In FIG. 1, the points A and B are the base points of the protrusions in the contour line, and the point C is the apex of the protrusions. For the silicon dioxide particles with protrusions in the technology disclosed herein, the so-called protrusion width refers to the width in the base of the protrusions, and the distance between point A and point B is shown in FIG. 1. The height of the protrusion refers to the distance between the base of the protrusion and the protrusion at the farthest distance from the base, and is shown in FIG. 1 as the length of the line segment CD orthogonal to the straight line AB.

In the technique disclosed herein, the average degree of protrusion of the silica particles with protrusions is not particularly limited. For example, silicon dioxide particles with protrusions having an average protrusion degree of 0.170 or more can be used. The average protrusion is better 0.200 or more, more preferably 0.220 or more, and still more preferably 0.245 or more (for example, 0.255 or more). When the average degree of protrusion of the silicon dioxide particles with protrusions increases, the shape of the protrusions tends to become sharp. Accordingly, the effect of increasing the polishing rate can be exhibited more favorably.

The upper limit of the average protrusion degree is not particularly limited. From the viewpoint of ease of production or strength, usually, silicon dioxide particles with protrusions having an average protrusion degree of 0.5 or less can be suitably used. From the viewpoint of obtaining higher surface quality, the average protrusion degree is preferably 0.4 or less, and more preferably 0.37 or less (for example, 0.35 or less).

The term “average degree of protrusion” as used in this specification refers to the second protrusion with a particle diameter larger than the volume average particle diameter of the silica particle with protrusions contained in the polishing composition. In silicon oxide particles, when the height of the protrusions on the surface is set to H and the width of the protrusions at the base is set to W, the average value of the values (degrees of protrusions) expressed in H / W. The height H of each protrusion of the silicon dioxide particles with protrusions and the width W in the base thereof can be obtained by analyzing a scanning electron microscope image of the silicon dioxide particles with protrusions by using general image analysis software.

The average height of the protrusions in the silica particles with protrusions whose particle diameter is larger than the volume average among the silica particles with protrusions contained in the polishing composition is preferably, for example, 3.5 nm or more, and more preferably 4.0 nm. the above. As the average height of the protrusions becomes larger, the effect of increasing the polishing rate tends to become larger. The upper limit of the average height of the protrusions is not particularly limited. From the viewpoint of obtaining higher surface quality, the average height of the protrusions is usually preferably 10 nm or less, and preferably 7.0 nm or less.

The silicon dioxide particles with protrusions can be produced, for example, by the following method. That is, first, in a mixed solution of methanol and water to which ammonia water is added as a catalyst, alkoxysilane is continuously added for hydrolysis to obtain a slurry containing colloidal silica particles. The resulting slurry was distilled to remove methanol and ammonia. Subsequently, after the organic base is added to the slurry as a catalyst, alkoxysilane is continuously added again at a temperature above 70 ° C for hydrolysis, thereby forming a plurality of protrusions on the surface of the colloidal silica particles. Specific examples of the organic base that can be used here include amine compounds such as triethanolamine, and quaternary ammonium compounds such as tetramethylammonium hydroxide. According to this method, colloidal silicon dioxide particles (silicon dioxide particles with protrusions) having a content of metal impurities of 1 weight ppm or less can be easily obtained.

In addition, a general method for producing colloidal silica by hydrolysis of alkoxysilane is described in, for example, pages 154 to 156 of "The Science of the Sol Gel Method" by Hua Zifu. Further, Japanese Patent Application Laid-Open No. 11-60232 discloses that methyl silicate or a mixture of methyl silicate and methanol is added dropwise to a mixed solvent of water, methanol, ammonia, or ammonia and an ammonium salt, so that Cocoon-type colloidal silicon dioxide produced by the reaction of methyl silicate with water. Japanese Patent Application Laid-Open No. 2001-48520 discloses an elongated colloidal silicon dioxide produced by hydrolyzing an alkyl silicate with an acid catalyst, adding an alkali catalyst, and heating and polymerizing silicic acid to grow particles. Japanese Patent Application Laid-Open No. 2007-153732 discloses that colloidal silica having a large number of small protrusions can be produced by using a hydrolyzable organosilicate as a raw material by using a specific amount of a specific type of hydrolysis catalyst. Japanese Patent Application Laid-Open No. 2002-338232 discloses adding a coagulant to a monodispersed colloidal silica. And secondary condensation into a spherical shape. Japanese Patent Application Laid-Open No. 07-118008 and International Publication No. 2007/018069 disclose that in order to obtain elongated shaped colloidal silica, calcium or magnesium salts are added to active silicic acid obtained from sodium silicate. Japanese Patent Application Publication No. 2001-11433 discloses that rosary colloidal silica is obtained by adding a calcium salt to active silicic acid obtained from sodium silicate. Japanese Patent Application Laid-Open No. 2008-169102 discloses that colloidal silica having a large number of small protrusions, such as gold flat sugar, can be produced by generating and growing fine particles on the surface of seed particles. The silica particles with protrusions in this specification can be produced by using one of the methods described in these documents alone or in combination of two or more.

The polishing composition disclosed herein may contain abrasive particles other than the silica particles with protrusions within a range that does not significantly impair the effect of the present invention. The abrasive grains (hereinafter also referred to as "arbitrary abrasive grains") other than the above-mentioned silicon dioxide particles with protrusions may be, for example, spherical, peanut-shaped, or cocoon-shaped silicon dioxide abrasive grains having no shape on the surface. The arbitrary abrasive particles may be inorganic particles, organic particles, or organic-inorganic composite particles other than silicon dioxide. Specific examples of the inorganic particles include oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconia particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide (Bengala) particles. ; Nitride particles such as silicon nitride particles, boron nitride particles; carbide particles such as silicon carbide particles, boron carbide particles; diamond particles; carbonates such as calcium carbonate or barium carbonate; Specific examples of the organic particles are polymethyl methacrylate (PMMA) particles or poly (meth) acrylic particles (here, (meth) acrylic 7 It is meant to include acrylic and methacrylic acid), polyacrylonitrile particles, and the like. The arbitrary abrasive grains may be used singly or in combination of two or more kinds.

The content of the arbitrary abrasive grains is, for example, 30% by weight or less, more preferably 20% by weight or less, and more preferably 10% by weight or less of the total weight of the abrasive particles contained in the polishing composition. The technique disclosed herein can be implemented in a manner that the content of any abrasive particles is 5% by weight or less of the total weight of the abrasive particles contained in the polishing composition. It may be a polishing composition that does not substantially contain any abrasive particles. Here, when the polishing composition does not substantially contain arbitrary abrasive grains, it means that at least arbitrary abrasive grains are not intentionally prepared.

The average primary particle diameter D _P1 of the abrasive particles in the polishing composition is not particularly limited. From the viewpoint of polishing efficiency and the like, the average primary particle diameter D _{P1 of the} abrasive particles is preferably 10 nm or more, more preferably 15 nm or more, and still more preferably 20 nm or more. In addition, from the viewpoint of easily obtaining a smoother surface, the average primary particle diameter D _{P1 of the} abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.

The average primary particle diameter D _{P1 of the} abrasive particles can be calculated from the specific surface area S (m ² / g) measured by the BET method, for example, using the formula of the average primary particle diameter D _P1 (nm) = 2727 / S. The measurement of the specific surface area of the abrasive grains can be performed using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

The average secondary particle diameter D _P2 of the abrasive particles in the polishing composition is not particularly limited, but from the viewpoint of polishing efficiency and the like, it is preferably 20 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more. In addition, from the viewpoint of the sedimentation stability (dispersion stability) of the polishing composition, the average secondary particle diameter D _{P2 of the} abrasive particles is preferably 300 nm or less, typically 200 nm or less, preferably 150 nm or less, and more preferably 100 nm or less. . From the viewpoint of surface quality, the average secondary particle diameter D _{P2 of the} abrasive particles is preferably 90 nm or less, more preferably 80 nm or less, and still more preferably 70 nm or less (for example, 65 nm or less).

The average secondary particle diameter D _{P2 of the} abrasive particles can be measured as a volume average particle diameter by a dynamic light scattering method using a model "UPA-UT151" manufactured by Nikkiso Co., Ltd., for example. The volume average particle size of the abrasive grains is equal to the cumulative volume of the abrasive grains in order from the small abrasive grains measured by the dynamic light scattering method to 50% of the cumulative volume of all the abrasive grains in the polishing composition. The last cumulative particle size of the abrasive particles.

The volume-based 95% particle diameter (D95 value) of the abrasive particles in the polishing composition is preferably 500 nm or less, and more preferably 400 nm or less. As the volume-based 95% particle size of the abrasive particles decreases, the settling stability (dispersion stability) of the polishing composition tends to be improved. In addition, there is a tendency that the surface roughness of the object to be polished after polishing with the polishing composition tends to be small. The basis volume of 95% of the abrasive particles is equal to the accumulation of the volume of the abrasive particles in order from the small abrasive particles with a particle size measured by the dynamic light scattering method until the cumulative volume of all the abrasive particles in the polishing composition reaches 95%. The final cumulative abrasive particle size.

The content of the metal particles such as sodium, potassium, calcium, boron, aluminum, titanium, zirconium, manganese, iron, cobalt, copper, zinc, silver, lead and the like contained in the abrasive composition disclosed herein is preferably 1 respectively. Weight ppm or less, The total content of these metal impurities is more preferably 1 ppm by weight or less. The content of metal impurities can be measured using, for example, an IC gravimetric analyzer.

<Inorganic basic compound (A)>

The polishing composition disclosed herein includes at least one inorganic basic compound (A) selected from the group consisting of ammonia and ammonium salts. Specific examples of the ammonium salt include ammonium bicarbonate, ammonium carbonate, ammonium chloride, and ammonium chlorate. These can be used individually by 1 type or in combination of 2 or more types. The polishing composition preferably contains at least ammonia as the inorganic basic compound (A).

Although not particularly limited, the amount of the inorganic basic compound (A) contained in the polishing composition may be, for example, 0.1 mol or more per 1 kg of the polishing composition, and usually 0.5 mol or more is appropriate. . From the viewpoint of obtaining greater effects, the amount of the inorganic basic compound (A) per 1 kg of the abrasive grains is preferably 1 mol or more, more preferably 2 mol or more, and still more preferably 3 mol or more (typically 4 mols). Molar or more, such as 5 Moore or more). The upper limit of the amount of the inorganic basic compound (A) per 1 kg of the abrasive grains is not particularly limited, and generally it is more appropriate to be 50 mol or less, preferably 30 mol or less, and more preferably 20 mol or less (for example, 10 mol the following).

When the technology disclosed herein is implemented, the reason why the above-mentioned problem can be solved by combining a polishing composition containing silicon dioxide abrasive particles with protrusions and an inorganic basic compound (A) is not necessarily clear, but it is considered as follows, for example.

That is, the silicon wafer surface of the polishing object can be oxidized by the silicon wafer. The resulting oxide film is thinly covered. For example, the surface of the silicon wafer at the beginning of the first polishing step (that is, the first 2 polishing steps) in the single-sided polishing step may be cleaned after the two-sided polishing, or there may be a silicon crystal between before the start of the single-sided polishing step. An oxide film formed by the round surface in direct contact with air and natural oxidation. Even if the silicon wafer in the surface state covered with the oxide film is a thin oxide film of, for example, about 1 nm (for example, about 0.5 nm to 2 nm), the oxide film is polished and removed until it reaches the original silicon (typically, single crystal silicon) As a result of the time required for the surface, the overall polishing rate including the time for removing the oxide film becomes low. On the other hand, although a polishing composition using an inorganic strong alkali such as KOH as a polishing accelerator can exhibit a high polishing rate for an oxide film, the polishing composition has a strong chemical polishing effect on silicon, so as described above, and Increasing the polishing rate, on the contrary, tends to reduce the surface quality after polishing.

The present inventors deviated from the technical idea of using a dedicated chemical polishing effect in order to quickly remove the oxide film, and aimed at a polishing accelerator that can achieve high surface quality in polishing using silicon on the one hand, and on the other hand, it is mainly used in the removal of the oxide film As a result of actively reviewing the mechanical polishing action of the abrasive particles, the present invention has been completed. According to the polishing composition disclosed herein, the inorganic basic compound (A) selected from the group consisting of ammonia and ammonium salt is combined with the silicon dioxide particles with protrusions, and the silicon dioxide particles with protrusions are utilized. The mechanical polishing action effectively removes the oxide film and maintains high surface quality by the effect of the inorganic basic compound (A). Silicon dioxide particles with protrusions can also effectively improve the polishing rate of silicon. Accordingly, when, for example, the first grinding step in the single-side grinding step is started, An oxide film-coated silicon wafer is considered to have the effect of maintaining the surface quality while improving the polishing rate.

<water>

The polishing composition disclosed herein preferably contains water. The water contained in the polishing composition is preferably ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like. In order to avoid as much as possible hindering the effects of other components contained in the polishing composition, the water used is preferably, for example, a total content of transition metal ions of 100 ppb or less. For example, ion exchange resin can be used to remove impurity ions, filtering can be used to remove foreign matter, and distillation can be used to improve the purity of water.

The polishing composition disclosed herein may optionally further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be mixed with water uniformly. Generally, it is preferred that 90% by volume or more of the solvent contained in the polishing composition is water, and more preferably 95% by volume or more (typically 99 to 100% by volume) is water.

The polishing composition disclosed herein (typically a slurry-like composition) may preferably have, for example, a solid content (non-volatile content; NV) of 0.01% to 50% by weight, The remaining part is implemented in the form of an aqueous solvent (water or a mixed solvent of water and the above-mentioned organic solvent), or the remaining part is in the form of an aqueous solvent and a volatile compound (such as ammonia). More preferably, the NV is in a form of 0.05% to 40% by weight. The solid content (NV) was determined from the weight ratio of the residue in the polishing composition after the polishing composition was dried at 105 ° C. for 24 hours.

<Water-soluble polymer>

The polishing composition disclosed herein preferably further comprises a water-soluble polymer. By appropriately using the water-soluble polymer, it is possible to more appropriately combine the polishing rate improvement effect and the good surface quality due to the use of the silicon dioxide abrasive particles with protrusions.

The kind of water-soluble polymer to be used is not particularly limited, and can be appropriately selected from water-soluble polymers known in the field of polishing compositions. The water-soluble polymer may be used singly or in combination of two or more kinds.

The water-soluble polymer may have at least one functional group selected from a cationic group, an anionic group, and a nonionic group in the molecule. The water-soluble polymer may be, for example, a hydroxyl group, a carboxyl group, a fluorenyloxy group, a sulfo group, a primary amidine structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure, or the like. From the viewpoints of reduction of aggregates and improvement of detergency, a nonionic polymer can be preferably used as the water-soluble polymer.

Examples of water-soluble polymers that can be suitably used in the polishing composition disclosed herein include cellulose derivatives, starch derivatives, polymers containing oxygen alkylene units, polymers containing nitrogen atoms, and polyethylene. Alcohol and so on.

Specific examples of the cellulose derivative include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, Ethylhydroxyethyl cellulose, carboxymethyl cellulose, and the like. Hydroxyethyl cellulose Better.

Specific examples of the starch derivative include alpha starch, pullulan, and cyclodextrin. Among them, pullulan polysaccharide is preferred.

An example of a polymer containing oxygen alkylene units is a block copolymer of polyethylene oxide (PEO) or ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO). Random copolymers of PO or BO, etc. Among them, a block copolymer of EO and PO or a random copolymer of EO and PO is preferred. The block copolymer of EO and PO may be a diblock body, a triblock body, etc. containing a PEO block and a polypropylene oxide (PPO) block. Examples of the triblock include a PEO-PPO-PEO type triblock and a PPO-PEO-PPO type triblock. Generally, it is more preferably a PEO-PPO-PEO type triblock.

Among block copolymers or random copolymers of EO and PO, the molar ratio of EO and PO (EO / PO) constituting the copolymer is preferably greater than the viewpoint of solubility in water or detergency. 1, more preferably 2 or more, and still more preferably 3 or more (for example, 5 or more).

As the polymer containing a nitrogen atom, any one of a polymer containing a nitrogen atom in a main chain and a polymer having a nitrogen atom in a side chain functional group (side group) can be used. Examples of polymers containing nitrogen atoms in the main chain include homopolymers and copolymers of N-fluorenylalkyleneimine-type monomers. Specific examples of the N-fluorenylalkyleneimine-type monomer include N-ethylfluorenylethylimine, N-propylfluorenylethylimine, and the like. The polymer having a nitrogen atom in the side group is exemplified by a polymer containing an N-vinyl monomer unit. For example, homopolymers and copolymers of N-vinylpyrrolidone can be suitably used. Which is better The nitrogen atom-containing polymer is exemplified by poly (N-vinylpyrrolidone).

When polyvinyl alcohol (PVA) is used as the water-soluble polymer, the degree of saponification of the polyvinyl alcohol is not particularly limited. In addition, a cationic PVA having a cationic group such as a quaternary ammonium structure may be used as the PVA. The cationized PVA may have a cationic group derived from, for example, diallyl dialkylammonium salt, N- (meth) acrylfluorenylamino alkyl-N, N, N-trialkylammonium salt, and the like. The individual.

In the polishing composition disclosed herein, the molecular weight of the water-soluble polymer is not particularly limited. Water-soluble polymers having a weight average molecular weight (Mw) of 200 × 10 ⁴ or less can be used. From the viewpoint of the filterability or detergency of the polishing composition, a water-soluble polymer having an Mw of 150 × 10 ⁴ or less is preferred. In addition, from the viewpoint of improving the surface quality after polishing, the Mw of the water-soluble polymer is preferably 1 × 10 ⁴ or more, more preferably 2 × 10 ⁴ or more.

A better Mw range may vary depending on the kind of water-soluble polymer. For example, when a cellulose derivative (for example, HEC) is used as the water-soluble polymer, Mw is preferably 10 × 10 ⁴ to 150 × 10 ⁴ , more preferably 15 × 10 ⁴ to 130 × 10 ⁴ . When PVA (which can be cationized PVA) is used as the water-soluble polymer, its Mw is preferably 1 × 10 ⁴ to 10 × 10 ⁴ , more preferably 1 × 10 ⁴ to 7 × 10 ⁴ , and even more preferably 1 × 10 ⁴ to 5 × 10 ⁴ (for example, 1 × 10 ⁴ to 3 × 10 ⁴ ). When a polymer containing a nitrogen atom is used as the water-soluble polymer, its Mw is preferably 1 × 10 ⁴ to 15 × 10 ⁴ , more preferably 1 × 10 ⁴ to 10 × 10 ⁴ , and even more preferably 2 × 10 ⁴ ~ 7 × 10 ⁴ .

The relationship between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the water-soluble polymer is not particularly limited. Prevent condensation From the viewpoint of polymers, for example, those having a molecular weight distribution (Mw / Mn) of 10.0 or less are preferred, and those of 7.0 or less are more preferred.

Moreover, the Mw and Mn of a water-soluble polymer can use the value of the water-based gel permeation chromatography (GPC) (water-based, polyethylene oxide conversion).

Although not particularly limited, the content of the water-soluble polymer may be, for example, 0.01 g or more per 1 kg of abrasive particles. In the combination with the silicon dioxide abrasive particles with protrusions, from the viewpoint of obtaining a better surface quality, the content of the water-soluble polymer per 1 kg of the abrasive particles is more than 1 g, preferably 5 g or more, and more preferably 10 g or more. , And more preferably 15g or more. In addition, from the viewpoint of obtaining a good polishing rate in the combination with the inorganic basic compound (A), the content of the water-soluble polymer for 1 kg of the abrasive particles is generally 50 g or less, preferably 40 g or less, and more preferably 35 g or less ( For example, 30g or less).

(Basic Compound (B)>

The polishing composition disclosed herein may contain a basic compound (B) other than the inorganic basic compound (A) intentionally or unintentionally, as long as the effect of the present invention is not significantly impaired. The basic compound (B) as the optional component may be an organic basic compound (B1) or an inorganic basic compound (B2). The basic compound (B) may be used alone or in combination of two or more.

Examples of the organic basic compound (B1) include a quaternary ammonium salt such as a tetraalkylammonium salt. Ammonium salts of the above anions may be, for example, ^{OH -, F -, Cl -} , Br -, I -, ClO 4 -, BH 4 - and the like. For example, quaternary ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide can be suitably used. Among them, tetramethylammonium hydroxide is preferred.

Other examples of the organic basic compound (B1) include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, and N- (β-aminoethyl) Amines such as ethanolamine, hexamethylenediamine, diethylene triamine, triethylene tetramine; anhydrous piperidine, piperidine hexahydrate, 1- (2-aminoethyl) piperidine, N -Piperidines such as methylpiperidine; azoles such as imidazole or triazole; guanidine and the like.

Examples of the inorganic basic compound (B2) include ammonia, alkali metal or alkaline earth metal hydroxides, carbonates, bicarbonates, and the like; ammonia and the like. Specific examples of the 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, and sodium carbonate.

When an organic basic compound (B1) is used in addition to the inorganic basic compound (A), the amount of the organic basic compound (B1) to be used is usually less than 4 mol per 1 kg of abrasive grains. From the viewpoint of surface quality and the like It is preferably less than 3 moles, more preferably less than 2 moles. The molar number of the organic basic compound (B1) contained in the polishing composition is preferably smaller than the molar number of the inorganic basic compound (A). Alternatively, the polishing composition disclosed herein may be a composition substantially free of an organic basic compound (B1). Here, the composition for polishing does not substantially contain an organic basic compound (B1) means that it does not contain at least the organic basic compound (B1) intentionally. Therefore, it contains unavoidable traces derived from raw materials or manufacturing methods (e.g. 0.01 mol per 1 kg of abrasive particles Hereinafter, the polishing composition of the organic basic compound (B1), which is preferably 0.005 mole or less, may be included herein as a concept of the polishing composition that does not substantially contain the organic basic compound (B1).

When an inorganic basic compound (B2) is used in addition to the inorganic basic compound (A), the amount of the inorganic basic compound (B2) used is usually less than 1 mol per 1 kg of abrasive grains. It is less than 0.5 moles, more preferably less than 0.2 moles. The molar number of the inorganic basic compound (B2) contained in the polishing composition is preferably smaller than the molar number of the inorganic basic compound (A). Alternatively, the polishing composition disclosed herein may be a composition substantially free of an inorganic basic compound (B2).

When the basic compound (B) is used in addition to the inorganic basic compound (A), the molar number of the basic compound (B) contained in the polishing composition is preferably smaller than the molar number of the inorganic basic compound (A). . Alternatively, the polishing composition disclosed herein may be a composition substantially free of a basic compound (B).

<Chelant>

The polishing composition disclosed herein may contain a chelating agent as an arbitrary component. The chelating agent forms metal ions which may be contained in the polishing composition and traps them, thereby exerting the effect of suppressing the metal impurities from contaminating the object to be polished.

Examples of the chelating agent include an aminocarboxylic acid-based chelating agent and an organic phosphonic acid-based chelating agent. Examples of the amino carboxylic acid-based chelating agent include ethylenediamine tetraacetic acid, sodium ethylenediamine tetraacetate, nitrogen triacetic acid, sodium nitrogen triacetate, ammonium nitrogen triacetate, Hydroxyethyl ethylenediamine triacetic acid, sodium hydroxyethyl ethylenediamine triacetate, diethylene triamine pentaacetic acid, sodium diethylene triamine pentaacetate, triethylene tetraamine hexaacetic acid, and triethylene glycol Sodium tetraamine hexaacetate. Examples of the organic phosphonic acid-based chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylene-1,1-diphosphonic acid, aminotris (methylenephosphonic acid), and ethylenediamine Methylphosphonic 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-dicarboxyl-1,2-diphosphonic acid, methane hydroxyphosphonic acid, 2-phosphinofluorenylbutane-1,2-dicarboxylic acid, 1-phosphinofluorenylbutane-2,3,4-tricarboxylic acid and α-methylphosphinofluorenylsuccinic acid. Among these, an organic phosphonic acid-based chelating agent is preferable, and among them, ethylenediamine (methylenephosphonic acid) and diethylene triamine pentahexaacetic acid are preferred. The most preferred chelating agent is ethylenediamine (methylenephosphonic acid).

<Surfactant>

The polishing composition disclosed herein may contain a surfactant (typically a water-soluble organic compound having a molecular weight of less than 1 × 10 ⁴ ) as an arbitrary component. By using a surfactant, the dispersion stability of the polishing composition can be improved. The surfactant can be used singly or in combination of two or more kinds.

As the surfactant, an anionic or nonionic one is preferably used. From the viewpoint of low foamability or ease of pH adjustment, a nonionic surfactant is more preferred. Examples are oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like; polyoxyethylene ethyl ether, polyoxyethyl alkyl phenyl ether, and polyoxyethylene Ethylalkylamine, polyoxyethylene fatty acid ester, polyoxyethylene ethyl glyceryl ether fatty acid ester, polyoxyethylene sorbose Polyoxyalkylene adducts of alcohol anhydride fatty acid esters, etc .; nonionic interfaces of plural types of oxyalkylene copolymers (diblock, triblock, random, interactive), etc. Active agent.

The amount of the surfactant used is preferably 5 g or less per 1 kg of abrasive particles, more preferably 2 g or less, and even more preferably 1 g or less. The polishing composition disclosed herein can be preferably implemented in a state substantially free of a surfactant.

〈Other ingredients〉

The polishing composition disclosed herein may further contain organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, and antifungal agents as long as they do not significantly impede the effects of the present invention. A conventional additive for a composition, typically a polishing composition used in the polishing step of a silicon wafer.

Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid; aromatic carboxylic acids such as benzoic acid and phthalic acid; citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic Sulfonic acid, organic phosphonic acid, etc. Examples of the organic acid salt include alkali metal salts (such as sodium salts and potassium salts) and ammonium salts of organic acids. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of the inorganic acid salt include alkali metal salts (such as sodium salts and potassium salts) or ammonium salts of inorganic acids. The organic acid and its salt, and the inorganic acid and its salt can be used singly or in combination of two or more kinds.

Examples of the antiseptic and antifungal agent are isothiazoline compounds, parabens, phenoxyethanol, and the like.

The polishing composition disclosed herein is preferably substantially free of an oxidizing agent. This is because when the polishing composition contains an oxidant, the composition is supplied to a silicon wafer, and the surface of the silicon wafer is oxidized to generate an oxide film, thereby reducing the polishing rate. Specific examples of the oxidant herein include hydrogen peroxide (H ₂ O ₂ ), sodium dichloroisocyanurate, and the like. It should be noted that the composition for polishing does not substantially contain an oxidant means that it does not contain at least an oxidant intentionally.

<Slurry>

The polishing composition disclosed herein is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition, and is used for polishing the polishing object. The polishing liquid may be prepared by diluting any of the polishing compositions disclosed herein (typically, dilution with water). Alternatively, the polishing composition may be directly used as a polishing liquid. That is, the concept of the polishing composition in the technology disclosed herein includes a polishing liquid (acting slurry) used for polishing the polishing object supplied to the polishing object, and a concentrated liquid (a polishing liquid) Stock solution) both. As another example of the polishing liquid containing the polishing composition disclosed herein, a polishing liquid obtained by adjusting the pH of the composition is mentioned.

The content of the abrasive particles in the polishing liquid disclosed herein is not particularly limited, but is typically 0.05% by weight or more, preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and more preferably 0.3% by weight or more (for example, 0.4% by weight or more). By increasing the content of abrasive particles, a higher polishing rate can be achieved. In addition, from the viewpoint of dispersion stability and the like of the polishing composition, the content is usually 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, and still more preferably 3% by weight or less. under. From the viewpoint of obtaining higher surface quality, the content of the abrasive grains may be set to 2% by weight or less, or 1% by weight or less, or 0.8% by weight or less (for example, 0.5% by weight or less).

The pH of the polishing liquid is preferably 8.0 or more, more preferably 9.0 or more, and still more preferably 9.5 or more. As the pH of the polishing liquid becomes higher, the polishing rate of the silicon wafer tends to increase. The upper limit of the pH of the polishing liquid is not particularly limited, but is preferably 12.0 or less, more preferably 11.5 or less, and even more preferably 11.0 or less. Thereby, the abrasive particles (especially the silicon dioxide particles with protrusions) contained in the polishing liquid can be prevented from being dissolved by the basic compound, and the reduction of the mechanical polishing effect of the abrasive particles can be suppressed. The above-mentioned pH may be more suitable for a polishing liquid used for polishing silicon wafers. The pH of the polishing liquid can be determined by using a pH meter (for example, a glass electrode hydrogen ion concentration indicator (model F-23) manufactured by Horiba), and using a standard buffer (phthalate pH buffer pH: 4.01). (25 ° C), neutral phosphate pH buffer pH: 6.86 (25 ° C), carbonate pH buffer pH: 10.01 (25 ° C)) After 3 points correction, the glass electrode was placed in the polishing solution and the measurement process was completed. Master the stable value for more than 2 minutes.

<Concentrate>

The polishing composition disclosed herein may be in a concentrated form (that is, a concentrated liquid form of a polishing liquid) before being supplied to the object to be polished. This concentrated polishing composition is advantageous from the viewpoints of convenience, cost reduction, and the like during production, distribution, and storage. The concentration ratio can be about 2 to 100 times in volume conversion, and usually about 5 to 50 times. right. Preferably, the concentration ratio of the polishing composition in the same state is 10 to 40 times.

The polishing composition in the form of the concentrated liquid can be diluted at a desired point to prepare a polishing liquid, and the polishing liquid can be used by supplying it to the object to be polished. The dilution is typically performed by adding the aqueous solvent to the concentrated solution and mixing them. In addition, when the water-based solvent is a mixed solvent, only a part of the constituents of the water-based solvent may be added and diluted, or a mixed solvent containing the constituents at a different ratio from the water-based solvent may be added and diluted. In addition, in a multi-dose type polishing composition described later, one part of these agents may be diluted and mixed with other agents to prepare a polishing liquid, or a plurality of agents may be mixed to dilute the mixture to prepare a polishing liquid.

The NV of the concentrated liquid may be, for example, 50% by weight or less. From the viewpoints of the stability of the polishing composition (such as the dispersion stability of the abrasive particles) or the filterability, the NV of the concentrated liquid is generally preferably 40% by weight or less, preferably 30% by weight or less, more preferably 20% by weight. Less than or equal to 15% by weight. In addition, from the standpoint of convenience, cost reduction, etc. during manufacturing, distribution, storage, etc., the NV of the concentrated liquid should preferably be 0.5% by weight or more, preferably 1% by weight or more, and more preferably 3% by weight or more. 5% by weight or more.

The content of the abrasive particles in the concentrated liquid may be, for example, 50% by weight or less. From the viewpoints of the stability of the polishing composition (for example, the dispersion stability of the abrasive particles) and the filterability, the content is usually preferably 45% by weight or less, more preferably 40% by weight or less. Better state The content of the abrasive grains may be 30% by weight or less, or 20% by weight or less (for example, 15% by weight or less). In addition, from the viewpoints of convenience, cost reduction, and the like during manufacturing, distribution, and storage, the content of the abrasive particles can be set to, for example, 0.5% by weight or more, preferably 1% by weight or more, and more preferably 3% by weight or more (for example, 4% by weight or more).

The polishing composition disclosed herein may be a one-dose form or a multi-dose form represented by a two-dose form. For example, the A liquid containing a part of the constituents (typically, components other than the water-based solvent) of the polishing composition is mixed with the B liquid containing the remaining components and is used for polishing the object to be polished.

<Preparation of polishing composition>

The manufacturing method of the polishing composition disclosed herein is not particularly limited. For example, a conventional mixing device such as a wing mixer, an ultrasonic disperser, and a homomixer can be used to mix each component contained in the polishing composition. The form of mixing these components is not particularly limited, and for example, all the components may be mixed at a time, or they may be mixed in an appropriately set order.

<Grinding>

The polishing composition disclosed herein is preferably used as a polishing composition for polishing a silicon wafer (typically a single crystal silicon wafer). Hereinafter, a preferable aspect of a method for polishing an object to be polished using the polishing composition disclosed herein will be described.

That is, preparing a polishing liquid containing any of the polishing compositions disclosed herein (Typically a slurry-like polishing liquid, sometimes referred to as a polishing slurry). When the polishing liquid is prepared, the polishing liquid may be prepared by applying operations such as concentration adjustment (for example, dilution) and pH adjustment to the polishing composition. Alternatively, the polishing composition can be directly used as a polishing liquid. In addition, in the case of a multi-dose type polishing composition, when preparing the above-mentioned polishing liquid, it may include mixing such pharmaceuticals, diluting one or more pharmaceuticals before mixing, diluting the mixture after mixing, and the like.

Next, this polishing liquid is supplied to an object to be polished, and is polished by a usual method. For example, when performing the first single-side polishing step of a silicon wafer, the silicon wafer that has undergone the rubbing step and the double-side polishing step (one polishing step) is fixed to a general single-side polishing device, and the polishing pad of the polishing device A polishing liquid is supplied to the surface (surface to be polished) of the silicon wafer. Typically, the polishing liquid is continuously supplied, and the polishing pad is pressed against the surface of the silicon wafer and the two are moved relative to each other (for example, rotational movement). Subsequently, if necessary, go through two more grinding steps to perform the final final polishing to complete the polishing of the object to be polished.

The polishing pad used in the polishing step using the polishing composition disclosed herein is not particularly limited. For example, any of a non-woven fabric type, a felt type, a polyurethane type, an abrasive particle-containing material, and an abrasive particle-free material can be used.

According to this specification, a method for manufacturing a silicon wafer including a step of polishing a silicon wafer using the polishing composition disclosed herein is provided. The manufacturing method of the silicon wafer disclosed herein may further include a step of polishing both sides of the silicon wafer before using the polishing step of the polishing composition. Step. In addition, the method may further include a step of subjecting the silicon wafer subjected to the polishing step using the polishing composition to a final polishing step. The so-called final polishing here refers to the last polishing step in the manufacturing process of the target (that is, the step in which polishing is not performed after this step). The above-mentioned two-side polishing step or final polishing step may be performed using the polishing composition disclosed herein, or may be performed using other polishing compositions.

In a preferred aspect, the polishing step of the silicon wafer using the polishing composition described above is a polishing step upstream of the final polishing. Among these, in the first single-side polishing step (the first two polishing steps) performed on the silicon wafer that has undergone the double-side polishing step, the above-mentioned polishing composition is preferably used. The polishing composition disclosed herein can be preferably used as a polishing composition for polishing a silicon wafer in the first two polishing steps.

Hereinafter, several embodiments related to the present invention will be described, but it is not intended to limit the present invention to those shown in the embodiments. In addition, "part" and "%" in the following description are based on weight unless otherwise specified.

<Preparation of polishing composition> (Example 1)

A plurality of protruding silicon dioxide particles (abrasive particles A), ammonia water (29% concentration), a water-soluble polymer, and pure water were mixed on the surface to prepare the polishing composition of this example.

The average height of the protrusions of the silicon dioxide particles having a surface diameter larger than the volume average particle diameter in the used abrasive grain A was 5.5 nm, and the average protrusion degree was 0.27. The average primary particle diameter D _P1 of this abrasive grain A was 30 nm, and the average secondary particle diameter D _P2 was 58 nm. The average particle diameter D _P1 is measured using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300". In addition, the above-mentioned secondary average particle diameter D _P2 is a volume average secondary particle diameter measured using a model "UPA-UT151" manufactured by Nikkiso Co., Ltd.

As the water-soluble polymer, hydroxyethyl cellulose (HEC) having a Mw of about 120 × 10 ⁴ was used.

The amount of abrasive grain A, ammonia water and water-soluble polymer is used so that the content of abrasive grain A in the polishing composition becomes 0.46%, the content of ammonia (NH ₃ ) becomes 0.041%, and the content of water-soluble polymer becomes 0.009%. (19.6 g with respect to 1 kg of abrasive particles). The pH of the obtained polishing composition was 10.4.

(Example 2)

In Example 1, the abrasive grains A were replaced with silica particles (abrasive grains B) having a plurality of protrusions on the surface. The average height of the protrusions of the silicon dioxide particles having a larger surface diameter than the volume average particle diameter of the abrasive grains B used was 5.5 nm, and the average protrusion degree was 0.25. The average primary particle diameter D _P1 of the abrasive particles B was 30 nm, and the average secondary particle diameter D _P2 was 58 nm. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. The polishing composition had a pH of 10.4.

(Example 3)

The abrasive grain A, ammonia water (concentration: 29%), tetramethylammonium hydroxide (TMAH), water-soluble polymer, and pure water were mixed to prepare the polishing composition of this example. As the water-soluble polymer, the same HEC as in Example 1 was used. The amount of abrasive particles A, ammonia, TMAH, and water-soluble polymer is used so that the content of abrasive particles A in the polishing composition is 0.46%, the content of ammonia (NH ₃ ) is 0.03%, and the content of TMAH is 0.06%. The content of the water-soluble polymer becomes an amount of 0.009%. The pH of the obtained polishing composition was 10.8.

(Comparative example 1)

In Example 1, peanut-shaped colloidal silicon dioxide (abrasive particles C) having an average primary particle diameter D _P1 of 35 nm and an average secondary particle diameter D _P2 of 64 nm were used instead of the abrasive particles A. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. pH is 10.4,

(Comparative example 2)

In Example 1, spherical colloidal silica (abrasive particles D) having an average primary particle diameter D _P1 of 80 nm and an average secondary particle diameter D _P2 of 97 nm were used instead of the abrasive particles A. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. pH is 10.6,

(Comparative example 3)

In Example 1, TMAH was used in place of ammonia water so that the content in the polishing composition became 1.365%. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. The pH was 11.0.

(Comparative Example 4)

In Example 1, potassium hydroxide (KOH) was used in place of ammonia water in such an amount that the content in the polishing composition became 0.84%. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. The pH was 11.0.

(Comparative example 5)

In Example 1, triethanolamine was used in place of ammonia water so that the content in the polishing composition became 2.235%. Otherwise, it was the same as Example 1, and the polishing composition of this example was prepared. The pH was 11.0.

The polishing composition of each example was directly used as a polishing liquid, and the following evaluation tests were performed. The results are shown in Table 1. The test piece was a silicon wafer with a diameter of 6 inches (approximately 150 mm) (conduction type: P type, crystal orientation: <100>, resistivity: 0.1 Ω.cm or more and less than 100 Ω.cm) using a double-sided grinding device. After adjusting to a surface roughness of 0.5 nm to 1.5 nm, wash under the following conditions (SC-1 cleaning).

[SC-1 Washing Conditions]

NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 1: 1: 15 (volume ratio) was stored in the first washing tank and the second washing Each tank was kept at 80 ° C. The washing is performed by immersing the object to be cleaned in the first washing tank for 5 minutes, and then passing through the washing tank using ultrapure water, and immersing in the second washing tank for 5 minutes.

<Evaluation of polishing rate>

The weight (W1 [g]) of the test piece was measured. It was immersed in hydrofluoric acid having a concentration of 2.5% for 10 seconds, and then washed with a flow of water at a flow rate of 7 liters / minute for 10 seconds. This test piece was ground under the following conditions.

[Polishing conditions]

Grinding device: Single-sided grinding device manufactured by Fujitsu Machinery Industry Co., Ltd., model "SPM-15"

Polishing pad: felt polishing pad "Surfin 000FM" made by FUJIMI INCORPORATED Co., Ltd.

Grinding pressure: 94g / cm ²

Platen revolutions: 30 rpm

Grinding head revolutions: 30 rpm

Grinding time: 30 minutes

Supply rate of polishing liquid: 500mL / min

Temperature of grinding liquid: 25 ℃

After the polished test piece was washed under the above SC-1 washing conditions, the weight (W2 [g]) was measured. From the results, the thickness (polishing amount) reduced by polishing was calculated from the following calculation formula.

(W1-W2) [g] / Density of silicon [g / cm ³ ] (= 2.33g / cm ³ ) / Area to be polished [cm ² ] (= 363cm ² ) = Grinding amount [cm]

This polishing amount was divided by the polishing time (= 30 minutes) to calculate the polishing rate. The polishing rate was counted in the following five steps.

5 o'clock: 23nm / min or more

4 o'clock: 21nm / min or more but less than 23nm / min

3 o'clock: 19nm / min or more but less than 21nm / min

2 o'clock: 17nm / min or more but less than 19nm / min

1 point: 1nm / min or more but less than 17nm / min

<Evaluation of Surface Quality>

The above test piece was pre-polished by using a polishing slurry (manufactured by FUJIMI INCORPORATED Co., Ltd., trade name "GLANZOX 2100"), adjusted to a surface roughness of 0.1 nm to 10 nm, and polished under the following conditions.

[Polishing conditions]

Grinding device: Single-sided grinding device manufactured by Fujitsu Machinery Industry Co., Ltd., model "SPM-15"

Polishing pad: felt polishing pad "Surfin 000FM" made by FUJIMI INCORPORATED Co., Ltd.

Grinding pressure: 94g / cm ²

Platen revolutions: 30 rpm

Grinding head revolutions: 30 rpm

Grinding time: 5 minutes

Supply rate of polishing liquid: 500mL / min

Temperature of grinding liquid: 25 ℃

[Measurement of turbidity]

After the polished test piece was cleaned under the above SC-1 cleaning conditions, the turbidity was measured using a wafer inspection apparatus manufactured by KLM Tencol Corporation under the trade name "AWIS3110". The results are counted in the following five stages.

5 points: 0.035ppm or more and less than 0.040ppm

4 points: 0.040ppm or more and less than 0.045ppm

3 points: 0.045ppm or more and less than 0.050ppm

2 points: 0.050ppm or more and less than 0.060ppm

1 point: 0.060ppm or more

[Measurement of number of defects]

A wafer inspection device made by KLM Tencol Corporation, trade name "AWIS3110" was used to calculate the number of defects (particles) above 80 nm in size on the surface of a 6-inch diameter silicon wafer after cleaning. And the result is converted into 5 points by the following points.

5 points: Count is less than 600

4 points: counting from 600 to 700

3 points: counting from 700 to 800

2 points: counting from 800 to 900

14 points: counting over 900

As shown in Table 1, according to Examples 1 and 2 in which a polishing composition containing silicon dioxide particles with protrusions and ammonia was used, compared with the use of silicon dioxide particles having a shape without a plurality of protrusions on the surface, specifically, In terms of Comparative Examples 1 and 2 in which peanut-shaped or spherical colloidal silica is used as abrasive particles, the grinding rate can be increased by 10% to 20%. In addition, according to Examples 1 and 2, both the turbidity and the number of defects can maintain the same high surface quality as that of Comparative Example 1. Compared with Examples 1 and 2 using ammonia alone, Example 3, which uses TMAH as a polishing accelerator in addition to ammonia, has a higher polishing rate improvement effect, and the number of defects is also equal, but the turbidity value tends to increase slightly. .

On the other hand, Comparative Examples 3 to 5 in which a polishing composition containing no inorganic basic compound (A) was used. Although the silicon dioxide particles with protrusions were used, the polishing rate was lower than that in Comparative Example 1. In Comparative Example 3 in which KOH was used alone as a polishing accelerator, the turbidity value increased significantly compared to Comparative Example 1, and the surface quality decreased.

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

Claims (9)

A polishing composition is a polishing composition for polishing a silicon wafer. The polishing composition includes silicon dioxide particles having a plurality of protrusions on the surface as abrasive particles, and further includes an inorganic substance selected from the group consisting of ammonia and ammonium salts. The basic compound (A) has an amount of the inorganic alkaline compound (A) of 0.1 mol to 50 mol per 1 kg of the polishing composition. The average (average degree of protrusion) of the value obtained by dividing the height of the protrusions on the surface of the silicon dioxide particles having a larger particle size than the volume average particle diameter by the width of the base portion of each of the same protrusions is 0.245 or more. The polishing composition according to claim 1, wherein the average protrusion degree is 0.5 or less. The polishing composition according to claim 1, further comprising a water-soluble polymer. The polishing composition according to claim 3, wherein the amount of the water-soluble polymer contained in the polishing composition is 5 g to 50 g with respect to 1 kg of the polishing particles. The polishing composition according to claim 2, further comprising a water-soluble polymer. The polishing composition according to claim 5, wherein the amount of the water-soluble polymer contained in the polishing composition is 5 g to 50 g with respect to 1 kg of the polishing particles. The polishing composition according to any one of claims 1 to 6, which is a one-side polishing step for more precisely grinding one side of the silicon wafer after the two-side polishing step for simultaneously grinding both sides of the aforementioned silicon wafer. The first polishing step in the single-sided polishing step. A method for manufacturing a polishing composition, which is a method for manufacturing a polishing composition for polishing a silicon wafer, and is characterized by preparing a polishing composition containing the following components: containing silicon dioxide particles having a plurality of protrusions on the surface For the abrasive grains, the inorganic basic compound (A) selected from the group consisting of ammonia and ammonium salt, the amount of the foregoing inorganic basic compound (A) per 1 kg of the foregoing polishing composition is 0.1 mol or more and 50 mol Below the ear, the average value obtained by dividing the height of the protrusions on the surface of the silicon dioxide particles having a particle diameter larger than the volume average particle diameter contained in the polishing composition by the width of the bases of the same protrusions ( The average protrusion degree) is 0.245 or more. A method for manufacturing a silicon wafer, which comprises the following steps: a two-sided polishing step of simultaneously polishing both sides of a silicon wafer, a more precise single-sided polishing step of polishing a single surface of the silicon wafer that has undergone the two-sided polishing step, and The aforementioned single-side polishing step includes two or more polishing steps. In the first polishing step among the two or more polishing steps, the polishing composition according to any one of claims 1 to 6 is used for polishing.