Polishing composition, concentrated liquid of polishing composition, and polishing method

Abstract

The purpose of the present invention is to provide a polishing composition capable of improving flatness of an outer peripheral part of a silicon wafer in preliminary polishing of the silicon wafer. Provided is a polishing composition used for preliminary polishing of a silicon wafer, the polishing composition containing abrasive grains, a basic compound, and a water-soluble polymer, wherein: the basic compound has a pKa of 10 or less; and the water-soluble polymer has a radius of gyration of 60 nm or less.

Description

Polishing Composition, Concentrate of Polishing Composition, and Polishing Method

[0001] The present invention relates to a polishing composition, a concentrate of a polishing composition, and a polishing method.

[0002] Conventionally, precision polishing using a polishing composition has been performed on the surface of materials such as metals, metalloids, non-metals, and oxides thereof. For example, the surface of a silicon wafer used as a component or the like of semiconductor products is generally finished into a high-quality mirror surface through a lapping step and a polishing step (polishing step). The polishing step typically includes a preliminary polishing step (preliminary polishing step) and a final polishing step (final polishing step).

[0003] For example, as a polishing composition for use in a preliminary polishing step of a silicon wafer, International Publication No. WO 2018 / 025655 and International Publication No. WO 2018 / 025656 disclose a polishing composition containing abrasive grains, a basic compound, and a water-soluble polymer.

[0004] In the preliminary polishing step of a silicon wafer, a problem is that excessive polishing occurs at the outer peripheral portion, causing edge sag (edge roll-off) and reducing the flatness of the outer peripheral portion. For example, although the techniques described in International Publication No. WO 2018 / 025655 and International Publication No. WO 2018 / 025656 reduce the edge roll-off of silicon wafers after preliminary polishing, in recent years, development of a polishing composition that achieves higher outer peripheral flatness over a wider area has been desired.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide means capable of improving the outer peripheral flatness of a silicon wafer after preliminary polishing.

[0006] In order to solve the above problems, the present inventors have conducted extensive research. As a result, the present inventors have found that the above problems can be solved by a polishing composition containing a specific basic compound and a water-soluble polymer, and have completed the present invention.

[0007] That is, the above problems of the present invention can be solved by the following means.

[0008] One embodiment of the present invention that can solve the above problems is a polishing composition used for pre-polishing silicon wafers, comprising abrasive grains, a basic compound, and a water-soluble polymer, wherein the pKa of the basic compound is 10 or less, and the radius of inertia of the water-soluble polymer is 60 nm or less.

[0009] The embodiments for carrying out the present invention will be described in detail below. The embodiments shown herein are illustrative examples for embodying the technical idea of ​​the present invention and do not limit the present invention. Therefore, all other implementable forms, methods of use, and operating techniques that can be conceived by those skilled in the art without departing from the gist of the present invention are included in the scope and gist of the present invention, as well as in the claims and their equivalents. The embodiments described herein can be combined in any way to form other embodiments. In this specification, "X to Y" is used to mean "X or more and Y or less," including the numerical values ​​(X and Y) described before and after it as the lower and upper limits. Also, "A and / or B" means including A, B, and combinations thereof. In addition, unless otherwise specified herein, operations and measurements of physical properties, etc., are performed under conditions of room temperature (20°C or more and 25°C or less) / relative humidity 30% RH or more and 50% RH or less.

[0010] One embodiment of the present invention is a polishing composition used for pre-polishing silicon wafers, comprising abrasive particles, a basic compound, and a water-soluble polymer, wherein the pKa of the basic compound is 10 or less, and the radius of inertia of the water-soluble polymer is 60 nm or less. A polishing composition with this configuration is provided that can improve the flatness of the outer periphery of a silicon wafer during pre-polishing.

[0011] The polishing composition according to this embodiment can improve the flatness of the outer periphery of a silicon wafer after pre-polishing. Improving the flatness of the outer periphery means increasing the flatness of the outer periphery, which means that the value of ESFQR (Edge site front least squares range) in the examples described later becomes lower. The inventors believe that by applying a combination of a basic compound with a pKa of 10 or less and a water-soluble polymer with a radius of inertia of 60 nm or less, it is possible to protect the outer periphery of the silicon wafer from over-polishing. The polishing composition according to this embodiment enables substrate protection at a fine level and allows for precise control of the outer periphery shape. The mechanism by which the polishing composition according to this embodiment achieves the above effect is merely speculation, and this does not limit the scope of the present invention.

[0012] [(A) Abrasive particles] The polishing composition according to this embodiment contains abrasive particles. The abrasive particles have the effect of mechanically polishing the object to be polished and improve the polishing speed of the object to be polished by the polishing composition. The abrasive particles contained in the polishing composition according to this embodiment are not particularly limited and include, for example, inorganic particles, organic particles, organic-inorganic composite particles, etc. Among these, inorganic particles are preferred. In a polishing composition according to a preferred embodiment of this embodiment, the abrasive particles include inorganic particles. The inorganic particles are not particularly limited but include, for example, oxide particles such as 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, and red iron oxide particles; 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, etc. Among these, silica particles are more preferred, colloidal silica and fumed silica are even more preferred, and colloidal silica is particularly preferred.

[0013] Methods for producing colloidal silica include the sodium silicate method and the sol-gel method, and colloidal silica produced by either method can be suitably used as colloidal silica according to this embodiment. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities that have the property of diffusing in semiconductors and corrosive ions such as chloride ions. Colloidal silica can be produced by the sol-gel method using conventionally known methods, and specifically, colloidal silica can be obtained by performing a hydrolysis-condensation reaction using a hydrolyzable silicon compound (for example, alkoxysilane or its derivatives) as a raw material. In addition, commercially available colloidal silica may be used.

[0014] The shape of the abrasive grains is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular or square prisms, cylindrical shapes, cylindrical shapes with a bulge in the center, donut shapes with a hole in the center, plate shapes, so-called cocoon shapes with a constriction in the center, so-called aggregate spherical shapes where multiple particles are integrated, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and many other shapes, and are not particularly limited.

[0015] While not particularly limited, the average aspect ratio of the major axis to minor axis of the abrasive grains (average aspect ratio) is, in principle, 1.0 or higher, preferably 1.05 or higher, and more preferably 1.1 or higher. A higher polishing rate can be achieved by increasing the average aspect ratio. Furthermore, from the viewpoint of reducing scratches, the average aspect ratio of the abrasive grains is preferably 3.0 or lower, more preferably 2.0 or lower, and even more preferably 1.5 or lower.

[0016] The shape (outer shape) and average aspect ratio of abrasive grains can be determined, for example, by electron microscopy observation. A specific procedure for determining the average aspect ratio is to use a scanning electron microscope (SEM) to draw the smallest rectangle circumscribing each particle image for a predetermined number of silica particles (e.g., 200 particles) whose individual particle shapes can be recognized. Then, for the rectangle drawn for each particle image, the ratio of the major axis to the minor axis (aspect ratio) is calculated by dividing the length of the major side (major axis) by the length of the minor side (minor axis). The average aspect ratio can be obtained by taking the arithmetic mean of the aspect ratios of the predetermined number of particles.

[0017] The abrasive particles contained in the polishing composition may be in the form of primary particles or secondary particles formed by the association of multiple primary particles. Furthermore, a mixture of primary and secondary abrasive particles may be present. In one preferred embodiment, at least some of the abrasive particles are contained in the polishing composition in the form of secondary particles.

[0018] The average primary particle diameter of the abrasive grains contained in the polishing composition according to this embodiment is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, and most preferably 30 nm or more. Alternatively, the average primary particle diameter of the abrasive grains contained in the polishing composition according to this embodiment may be, for example, 120 nm or less, may be 100 nm or less, preferably 90 nm or less, more preferably 80 nm or less, even more preferably 75 nm or less, particularly preferably 70 nm or less, and most preferably 60 nm or less. According to one embodiment, the average primary particle diameter of the abrasive grains contained in the polishing composition is 5 nm or more and 120 nm or less, 10 nm or more and 120 nm or less, 10 nm or more and 100 nm or less, 15 nm or more and 100 nm or less, 10 nm or more and 80 nm or less, 10 nm or more and 70 nm or less, 10 nm or more and 60 nm or less, 20 nm or more and 60 nm or less, or 20 nm or more and 50 nm or less. By keeping the average primary particle size of the abrasive grains within the above range, it is possible to improve the polishing speed while further improving the flatness of the outer periphery of the silicon wafer.

[0019] The average secondary particle diameter of the abrasive grains contained in the polishing composition according to this embodiment is preferably 15 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, particularly preferably 30 nm or more, and most preferably 35 nm or more. Furthermore, the average secondary particle diameter of the abrasive grains contained in the polishing composition according to this embodiment is preferably, for example, 200 nm or less, more preferably 150 nm or less, even more preferably 120 nm or less, particularly preferably 100 nm or less, and most preferably 80 nm or less. According to one embodiment, the average secondary particle diameter of the abrasive grains contained in the polishing composition is 15 nm or more and 200 nm or less, 15 nm or more and 150 nm or less, 20 nm or more and 120 nm or less, 15 nm or more and 100 nm or less, 20 nm or more and 100 nm or less, 15 nm or more and 80 nm or less, or 20 nm or more and 80 nm or less. By having the average secondary particle diameter of the abrasive grains within the above range, it is possible to improve the polishing speed while further improving the flatness of the outer periphery of the silicon wafer.

[0020] Furthermore, the preferred range for the average primary particle diameter and average secondary particle diameter of the abrasive grains mentioned above is also the preferred range for the average primary particle diameter and average secondary particle diameter of the abrasive grains contained in the raw material dispersion used in its preparation.

[0021] The aggregation ratio (average aggregation ratio) of abrasive grains in this embodiment is preferably 1.1 or higher, more preferably 1.2 or higher, even more preferably 1.3 or higher, and particularly preferably 1.4 or higher. Furthermore, there is no particular upper limit to the aggregation ratio of abrasive grains, but it is preferably 3.0 or lower, more preferably 2.8 or lower, even more preferably 2.6 or lower, and particularly preferably 2.4 or lower. According to one embodiment, the aggregation ratio (average aggregation ratio) of abrasive grains in this embodiment is 1.1 or higher and 2.2 or lower, 1.1 or higher and 2.0 or lower, 1.1 or higher and 1.8 or lower, 1.1 or higher and 1.6 or lower, 1.2 or higher and 2.0 or lower, 1.2 or higher and 1.8 or lower, 1.2 or higher and 1.6 or lower, or 1.2 or higher and 1.5 or lower. By having the aggregation ratio within the above range, it is possible to improve the polishing speed while further improving the flatness of the outer periphery of the silicon wafer.

[0022] The association ratio of abrasive grains is obtained by dividing the average secondary particle diameter of the abrasive grains by the average primary particle diameter.

[0023] In this specification, the average primary particle diameter is defined as the average primary particle diameter (nm) = 6000 / (true density (g / cm³)) calculated from the specific surface area (BET value) measured by the BET method. ３ ) × BET value (m ２ This refers to the particle diameter (BET particle diameter) calculated by the formula ( / g). The specific surface area can be measured, for example, using the "Flow Sorb II 2300" manufactured by Micromerities. The average secondary particle diameter of the abrasive grains refers to the particle diameter (volume-average particle diameter) measured by dynamic light scattering. The secondary particle diameter of the abrasive grains can be measured, for example, using the "FPAR-1000" manufactured by Otsuka Electronics Co., Ltd.

[0024] In a volume-based particle size distribution of abrasive grains, when D10 is defined as the particle size at which the cumulative frequency from the small particle size side accounts for 10%, and D90 is defined as the particle size at which the cumulative frequency from the small particle size side accounts for 90%, the lower limit of the ratio of D90 to D10 (D90 / D10) is preferably 1.1 or higher, more preferably 1.2 or higher, even more preferably 1.3 or higher, particularly preferably 1.4 or higher, and most preferably 1.5 or higher. Furthermore, there is no particular upper limit to D90 / D10, but it is preferably 5.0 or lower, more preferably 3.0 or lower, even more preferably 2.5 or lower, even more preferably 2.3 or lower, particularly preferably 2.2 or lower, and most preferably 2.1 or lower. Within this range, the polishing speed can be improved while further improving the flatness of the outer periphery of the silicon wafer. When D90 / D10 is small (close to 1.0), it indicates a narrow particle size distribution width, and as this value increases, it indicates a wide particle size distribution width. The smaller the D90 / D10 value, the more the stress applied to each particle (point of application) is distributed (the force is applied uniformly to each point of application). Therefore, the smaller the D90 / D10 value, the higher the flatness of the outer edge of the silicon wafer. On the other hand, if the D90 / D10 value is large (wide particle size distribution), the difference in particle size between large and small particles becomes large, and the force concentrated on the large particles increases the strain on the outer edge of the silicon wafer, which may reduce the flatness of the outer edge of the silicon wafer.

[0025] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for polishing, the content of abrasive particles in the concentrated liquid is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, even more preferably 2% by mass or more, and most preferably 3% by mass or more. In this case, although the content of abrasive particles in the concentrated liquid of the polishing composition is not particularly limited, it is preferably 50% by mass or less from the viewpoint of storage stability and filterability.

[0026] In the polishing composition used during polishing, the abrasive content in the polishing composition is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.025% by mass or more, particularly preferably 0.1% by mass or more, and most preferably 0.2% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the abrasive content in the polishing composition used during polishing is not particularly limited, but is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, particularly preferably 5% by mass or less, even more preferably 3% by mass or less, even more preferably 2% by mass or less, and most preferably 1.5% by mass or less. According to one embodiment, the abrasive content in the polishing composition is 0.001% to 3% by mass, 0.01% to 3% by mass, 0.01% to 2% by mass, 0.025% to 2% by mass, 0.1% to 3% by mass, or 0.1% to 2% by mass, based on the total mass of the polishing composition.

[0027] If the abrasive content is within the range described above, the polishing speed can be improved while further enhancing the flatness of the outer periphery of the silicon wafer. When the polishing composition contains two or more types of abrasives, the abrasive content refers to the total amount of these abrasives.

[0028] When obtaining an abrasive composition used during polishing by diluting it (i.e., when the abrasive composition is in a concentrated state and the concentrated solution is diluted), it is preferable to adjust the preferred abrasive content by diluting the concentrated solution of the abrasive composition with a dispersion medium such as water, or a solution or dispersion containing any abrasive aid therein.

[0029] Here, the abrasive grains, in correlation with the water-soluble polymer described later, affect the flatness of the outer periphery of the silicon wafer. That is, by having the abrasive grain content in the polishing composition be within a specific range relative to the water-soluble polymer content, the flatness of the outer periphery of the silicon wafer can be further improved. The mass ratio of the abrasive grain content to the water-soluble polymer content is preferably 500 or less, more preferably 300 or less, even more preferably 200 or less, particularly preferably 100 or less, and most preferably 80 or less. The mass ratio of the abrasive grain content to the water-soluble polymer content is preferably 0.5 or more, more preferably 1 or more, even more preferably 2 or more, particularly preferably 10 or more, and most preferably 15 or more. According to one embodiment, the mass ratio of the abrasive content to the water-soluble polymer content is 0.5 to 500, 0.5 to 300, 1 to 200, 1 to 100, 5 to 100, 1 to 80, 10 to 80, 15 to 80, 20 to 80, 1 to 60, 5 to 60, 10 to 60, 15 to 60, 20 to 60, 10 to 50, or 20 to 50. By having the mass ratio of the abrasive content to the water-soluble polymer content within the above range, the flatness of the outer periphery of the silicon wafer can be further improved.

[0030] According to one embodiment, the polishing composition according to this embodiment may contain silica particles and other abrasive particles other than silica particles as abrasive particles. When the polishing composition according to this embodiment is used during polishing, the content of the other abrasive particles is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less, based on the total mass of the silica particles and the other abrasive particles (total mass of abrasive particles). The most preferred embodiment is one in which the content of other abrasive particles is 0% by mass, that is, an embodiment that does not contain any abrasive particles other than silica particles.

[0031] [Basic compound] The polishing composition according to the present embodiment contains a basic compound having a pKa of 10 or less. The basic compound plays a role in chemically polishing the silicon wafer, which is the object to be polished, and contributes to improving the polishing ability of the polishing composition. Examples of the basic compound include organic basic compounds and / or inorganic basic compounds. Preferably, the polishing composition according to the present embodiment contains one or more basic compounds selected from the group consisting of organic basic compounds and inorganic basic compounds.

[0032] In the present specification, pKa refers to the acid dissociation constant in water at 25°C. The acid dissociation constant (pKa) is pKa = -log １０ represented by Ka. When dissociation in two or more steps is conceivable, the first dissociation is considered. (That is, it is sufficient as long as pKa1 is 10 or less.) Specifically, one hydrogen ion H from an electrically neutral molecule (HA) ＋ dissociates to form a monovalent anion (A － ), this step is the acid dissociation constant (pKa), or an electrically neutral molecule (B) accepts one hydrogen ion H ＋ to form a monovalent cation (BH ＋ ), this step is the acid dissociation constant (pKa). More specifically, the acid dissociation constant (pKa) of a basic compound refers to the acid dissociation constant (pKa) when the conjugate acid of the basic compound (BH ＋ ) dissociates as an acid (BH ＋ → B + H ＋ ).

[0033] In addition, in the present specification, pKa (acid dissociation constant) is a value at 25°C, which is a value described in the 6th revised edition of the Basic Section of the Chemical Handbook (edited by The Chemical Society of Japan, published by Maruzen). For compounds not described in the above Chemical Handbook, the value shall be obtained by the method of taking the pH at the half-equivalence point of the titration curve obtained when titrating with hydrochloric acid as pKa. Note that the values of the acid dissociation constants listed together with the acids exemplified in the present specification are values in accordance with the above definition.

[0034] More specific examples of basic compounds with a pKa of 10 or less include monoethanolamine (pKa = 9.5), diethanolamine (pKa = 8.9), triethanolamine (pKa = 7.8), diethylaminoethanol (pKa = 9.4), piperazine (pKa = 5.6), 1,4-diazabicyclo[2,2,2]octane (DABCO) (pKa = 8.8), imidazole (pKa = 7.0), morpholine (pKa = 8.3), N-methylmorpholine (pKa = 7.7), benzylamine (pKa = 9.6), N,N-dimethylbenzylamine (pKa = 8.9), aniline (pKa = 4.6), N,N-diethylaniline (pKa = 6.6), and ammonia (pKa = 9.2). Among these, ammonia is more preferred.

[0035] In the polishing composition according to this embodiment, the basic compound may be used alone or in a mixture of two or more. When two or more basic compounds are included, the content of the basic compounds described below refers to their total amount.

[0036] In the polishing composition according to this embodiment, the mass ratio of the content of the basic compound to the content of the water-soluble polymer is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, particularly preferably 20 or less, and most preferably 10 or less. In the polishing composition according to this embodiment, the mass ratio of the content of the basic compound to the content of the water-soluble polymer is preferably 0.1 or more, more preferably 0.5 or more, even more preferably 1 or more, particularly preferably 1.5 or more, and most preferably 2 or more. According to one embodiment, the mass ratio of the content of the basic compound to the content of the water-soluble polymer is 0.1 to 50, 0.5 to 50, 0.1 to 40, 0.5 to 40, 0.5 to 30, 1 to 20, 0.1 to 10, 0.5 to 10, 1 to 10, 1 to 8, or 1 to 5. By keeping the mass ratio of the basic compound content to the water-soluble polymer content within the above range, the flatness of the outer periphery of the silicon wafer can be further improved.

[0037] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for use in polishing, the content of the basic compound in the concentrated liquid is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, particularly preferably 0.4% by mass or more, and most preferably 0.5% by mass or more. In this case, from the viewpoint of storage stability and filterability, the content of the basic compound in the concentrated liquid of the polishing composition is preferably 50% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 3% by mass or less.

[0038] In polishing compositions used during polishing, the content of basic compounds in the polishing composition is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.003% by mass or more, particularly preferably 0.005% by mass or more, and most preferably 0.01% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the content of basic compounds in the polishing composition is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less. According to one embodiment, the content of the basic compound in the polishing composition is 0.001% by mass or more and 5% by mass or less, 0.001% by mass or more and 3% by mass or less, 0.005% by mass or more and 2% by mass or less, 0.001% by mass or more and 1% by mass or less, 0.01% by mass or more and 1% by mass or less, or 0.001% by mass or more and 0.5% by mass or less, 0.001% by mass or more and 0.1% by mass or less, or 0.01% by mass or more and 0.1% by mass or less.

[0039] If the content of basic compounds is within the above range, the flatness of the outer edge of the silicon wafer can be further improved.

[0040] [Water-soluble polymer] The polishing composition according to this embodiment contains a water-soluble polymer with a radius of inertia of 60 nm or less. The water-soluble polymer with a radius of inertia of 60 nm or less is adsorbed onto the surface of the abrasive grains and buffers the mechanical action of the abrasive grains. This reduces the impact that the abrasive grains exert on the outer periphery of the wafer. Therefore, by containing a water-soluble polymer in the polishing composition according to this embodiment, over-polishing of the outer periphery is suppressed and the flatness of the outer periphery is improved. Water-soluble polymers with a radius of inertia exceeding 60 nm have reduced adsorption efficiency to the surface of the abrasive grains due to their bulkiness, and as a result, the effect of improving the flatness of the outer periphery cannot be obtained. The radius of inertia of the water-soluble polymer is measured by the method described later.

[0041] The radius of inertia of the water-soluble polymer is preferably less than 60 nm, more preferably 55 nm or less, even more preferably 50 nm or less, particularly preferably 45 nm or less, and most preferably 40 nm or less. According to one embodiment, the radius of inertia of the water-soluble polymer is 35 nm or less, 30 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, or 5 nm or less. The lower limit of the radius of inertia of the water-soluble polymer is not particularly limited, but for example, it is 0.1 nm or more, 0.5 nm or more, or 1 nm or more. Therefore, the radius of inertia of the water-soluble polymer is preferably 0.1 nm or more and less than 60 nm, more preferably 0.1 nm or more and 55 nm or less, even more preferably 0.5 nm or more and 50 nm or less, particularly preferably 0.5 nm or more and 45 nm or less, and most preferably 1 nm or more and 40 nm or less. If the radius of inertia of the water-soluble polymer is within the above range, the flatness of the outer periphery of the silicon wafer can be further improved. According to one embodiment, the radius of inertia of the water-soluble polymer is 0.5 nm or more and less than 30 nm, 0.5 nm or more and less than 20 nm, 0.5 nm or more and less than 10 nm, 1 nm or more and less than 55 nm, 5 nm or more and less than 60 nm, 10 nm or more and less than 60 nm, 10 nm or more and less than 58 nm, 20 nm or more and less than 60 nm, 20 nm or more and less than 58 nm, 30 nm or more and less than 60 nm, 30 nm or more and less than 58 nm, 40 nm or more and less than 60 nm, or 40 nm or more and less than 58 nm.

[0042] Here, a water-soluble polymer refers to a water-soluble polymer having the same repeating structural units (homopolymer) or a water-soluble polymer having different repeating structural units (copolymer). For example, any compound having a degree of polymerization of 3 or more may be used as a water-soluble polymer. A water-soluble polymer is typically a compound with a weight-average molecular weight (Mw) of 200 or more. There are no particular restrictions on the type of polymer used as a water-soluble polymer; anionic, cationic, nonionic, and amphoteric polymers are all acceptable. Furthermore, when the water-soluble polymer is a copolymer, the copolymer may take the form of a block copolymer, random copolymer, graft copolymer, alternating copolymer, or periodic copolymer. Water-soluble polymers can be used individually or in combination of two or more types.

[0043] For water-soluble polymers, the weight-average molecular weight (Mw) can be calculated from values ​​obtained from aqueous gel permeation chromatography (GPC) (aqueous system, polyethylene oxide equivalent). A suitable GPC measuring device is the "HLC-8320GPC" model manufactured by Tosoh Corporation. Measurements can be performed, for example, under the following conditions.

[0044] [GPC Measurement Conditions] Sample concentration: 0.1% by weight Column: TSKgel GMPW ＸＬ Detector: Differential refractometer; Eluent: 100 mM sodium nitrate aqueous solution; Flow rate: 1 mL / min; Measurement temperature: 40°C; Sample injection volume: 200 μL.

[0045] Examples of anionic water-soluble polymers include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, and polymethacrylic acid. Furthermore, anionic water-soluble polymers may also be polyoxyalkylene adducts having anionic groups. Examples of polyoxyalkylene adducts having anionic groups include polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl sulfate ester, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl phosphate ester, and polyoxyethylene sulfosuccinic acid.

[0046] Examples of cationic water-soluble polymers include polyethyleneimine (PEI), polyvinylamine, polyallylamine, polyvinylpyridine, and polymers of cationic acrylamide. A specific example of polyallylamine is polydiallyldimethylammonium chloride.

[0047] Examples of nonionic water-soluble polymers include, for example, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinylpyrrolidone, polyacrylamide, poly-N-vinylacetamide, polyamines, polyvinyl ethers (polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl isobutyl ether, etc.), polyglycerin, polyalkylene glycol (oxyalkylene polymer), polyoxyalkylene adducts, water-soluble cellulose (e.g., hydroxyethylcellulose (HEC), hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose) and other polysaccharides, alginic acid polyhydric alcohol esters, water-soluble urea resins, dextrin derivatives, and casein. Furthermore, not only those having such a main chain structure, but also graft copolymers having a nonionic polymer structure in the side chain can be suitably used.

[0048] Examples of polyalkylene glycols include homopolymers of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and others, as well as copolymers of multiple types of polyalkylene glycols (e.g., diblock copolymers, triblock copolymers, random copolymers, alternating copolymers).

[0049] Examples of polyoxyalkylene adducts include polyoxyalkylene alkyl ethers, polyoxyalkylene aryl ethers (e.g., polyoxyethylene alkylphenyl ethers), polyoxyalkylene alkylamines, polyoxyalkylene fatty acid esters, polyoxyalkylene glycerol ether fatty acid esters, and polyoxyalkylene sorbitan fatty acid esters.

[0050] Examples of amphoteric water-soluble polymers include copolymers of vinyl monomers having anionic groups and vinyl monomers having cationic groups, and vinyl-based amphoteric polymers having carboxybetaine groups or sulfobetaine groups. Specifically, examples include acrylic acid / dimethylaminoethyl methacrylic acid copolymers and acrylic acid / diethylaminoethyl methacrylic acid copolymers.

[0051] Furthermore, copolymers of water-soluble polymers as exemplified above can also be used.

[0052] Water-soluble polymers can be used individually or in combination of two or more types. Furthermore, commercially available or synthetic water-soluble polymers may be used.

[0053] Among these water-soluble polymers, nonionic water-soluble polymers are preferred from the viewpoint of easily detaching them from the substrate after rinsing and polishing. More preferably, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylpyrrolidone, poly-N-vinylacetamide, polyoxyalkylene adducts (e.g., polyoxyalkylene alkyl ethers), hydroxyethylcellulose (HEC), hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, methylcellulose, and ethylcellulose are preferred, and even more preferably, polyvinyl alcohol or its derivatives (modified polyvinyl alcohol), polyvinylpyrrolidone or its derivatives (modified polyvinylpyrrolidone), polyoxyalkylene alkyl ethers, and hydroxyethylcellulose (HEC) are preferred.

[0054] The lower limit of the weight-average molecular weight (Mw) of the water-soluble polymer is preferably 200 or more, more preferably 500 or more, even more preferably 800 or more, particularly preferably 1,000 or more, and most preferably 1,200 or more. The upper limit of the weight-average molecular weight (Mw) of the water-soluble polymer is preferably 1,500,000 or less, more preferably 800,000 or less, even more preferably 500,000 or less, particularly more preferably 300,000 or less, and most preferably 100,000 or less. According to one embodiment, the weight-average molecular weight of the water-soluble polymer is 400,000 or less, 380,000 or less, 350,000 or less, 330,000 or less, or 300,000 or less, 200,000 or less, 50,000 or less, 30,000 or less, or 20,000 or less. According to one embodiment, the weight-average molecular weight (Mw) of hydroxyethylcellulose (HEC) is 10,000 to 600,000, 15,000 to 600,000, 18,000 to 500,000, 20,000 to 500,000, 25,000 to 400,000, 30,000 to 350,000, or 50,000 to 300,000.

[0055] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for use in polishing, the content of water-soluble polymers in the concentrated liquid is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and most preferably 0.2% by mass or more. In this case, from the viewpoint of storage stability and filterability, the content of water-soluble polymers in the concentrated liquid of the polishing composition is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0056] In the polishing composition used during polishing, the content of water-soluble polymers in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, particularly preferably 0.0005% by mass or more, and most preferably 0.001% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the content of water-soluble polymers in the polishing composition used during polishing is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0.05% by mass or less. According to one embodiment, the content of water-soluble polymer in the polishing composition used during polishing is 0.0001% by mass or more and 0.5% by mass or less, 0.0005% by mass or more and 0.3% by mass or less, 0.0001% by mass or more and 0.2% by mass or less, 0.0005% by mass or more and 0.2% by mass or less, 0.0001% by mass or more and 0.1% by mass or less, 0.0005% by mass or more and 0.1% by mass or less, 0.001% by mass or more and 0.1% by mass or less, or 0.001% by mass or more and 0.05% by mass or less.

[0057] Furthermore, if the polishing composition contains two or more water-soluble polymers, the content of the water-soluble polymers shall be the total amount of these polymers.

[0058] The following describes polyvinyl alcohol, polyvinylpyrrolidone, and polyoxyalkylene alkyl ether, which are preferably used as water-soluble polymers in the polishing composition according to this embodiment.

[0059] Polyvinyl alcohol may be polyvinyl alcohol, a derivative of polyvinyl alcohol, modified polyvinyl alcohol, or a derivative of modified polyvinyl alcohol.

[0060] In this specification, polyvinyl alcohol refers to a polymer containing vinyl alcohol units (hereinafter also referred to as "VA units") as repeating units. VA units are, for example, repeating units of the vinyl polymerized structure of vinyl acetate in a polymer obtained by vinyl polymerization of vinyl acetate (which may be a homopolymer of vinyl acetate or a copolymer of vinyl acetate with one or more other monomers) (i.e., -CH ２ CH(-OC(=O)-CH ３ It can be produced by hydrolysis (also called saponification) of the structural unit represented by ) (hereinafter also referred to as "VAc unit"). Unmodified polyvinyl alcohol (hereinafter also referred to as "unmodified PVA") refers to PVA that substantially does not contain repeating units other than VA units and VAc units.

[0061] A derivative of polyvinyl alcohol is a compound that contains polyvinyl alcohol within its molecule. Modified polyvinyl alcohol (hereinafter also referred to as "modified PVA") refers to a polymer that contains VA units and VAc units as repeating units, as well as other repeating units (hereinafter also referred to as "non-VA units"). A derivative of modified polyvinyl alcohol is a compound that contains modified polyvinyl alcohol within its molecule.

[0062] Modified PVA, as a non-VA unit, has the chemical formula: -CH ２ It may have a structural part represented by -CH(X)- or the chemical formula: -CH(X)-CH(X)- (hereinafter also referred to as "modified VA unit").

[0063] Here, X is a hydroxyl group (-OH) and an acetoxy group (-O-C(=O)-CH ３Any group other than )) is acceptable. For example, X is an alkyl ether group (-O-R １ ;R １ (A C1-C10 alkyl group), alkylcarbonyl ether group (-O-C(=O)-R １ ;R １ (A C2-C10 alkyl group), sulfonic acid group (-S (=O) ２ -OH), carboxylic acid group (-C(=O)-OH), carboxylic acid ester group (-C(=O)OR;R １ (A C1-C10 alkyl group), polyalkylene oxyether group (-O-(R ２ O) ｎ -H;R ２ (where n is an alkylene group having 2 to 5 carbon atoms, n is the number of moles of alkylene oxide added), amino ether group (-O-NR ３ ;R ３ Each is independently a hydrogen atom, a C1-C5 alkyl group or a C6-C20 aryl group, and an alkyl ether alkylene group (-R ４ -O-R １ ;R １ R is an alkyl group having 1 to 10 carbon atoms. ４ (A is an alkylene group having 1 to 10 carbon atoms), an alkylcarbonylalkylene group (-R ４ -C(=O)-R １ ;R １ R is an alkyl group having 1 to 10 carbon atoms. ４ (A C1-C10 alkylene group), amino group (-NR ３ ;R ３ Preferably, each of these is independently a hydrogen atom, a C1-C5 alkyl group or a C6-C20 aryl group), an aromatic group (e.g., a phenyl group, a benzyl group), or a heterocyclic group (e.g., a pyrrolidone ring (pyrrolidonyl group, etc.), a piperidine ring (piperidinyl group), a pyridine ring (pyridinyl group, etc.)).

[0064] Of these, X is preferably an alkyl ether group, and more preferably a methyl ether group (-O-CH ３), ethyl ether groups, propyl ether groups, butyl ether groups, etc. are more preferred. When such modified PVA is used, the substrate is suitably protected, and the effects of the present invention are further exhibited. Here, the alkyl group may be linear, branched, or alicyclic, and a linear alkyl group is preferred.

[0065] Examples of non-VA units that may be included in modified PVA include, but are not limited to, repeating units derived from N-vinyl type monomers or N-(meth)acryloyl type monomers, repeating units derived from ethylene, repeating units derived from alkyl vinyl ethers, and repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms, as described later. One preferred example of the above N-vinyl type monomer is N-vinylpyrrolidone. One preferred example of the above N-(meth)acryloyl type monomer is N-(meth)acryloylmorpholine. The above alkyl vinyl ether may be, for example, a vinyl ether having an alkyl group with 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, or 2-ethylhexyl vinyl ether. The above vinyl ester of monocarboxylic acid having 3 or more carbon atoms may be, for example, a vinyl ester of monocarboxylic acid having 3 to 7 carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, or vinyl hexanoate.

[0066] The modified PVA may be a modified PVA in which some of the VA units are acetalized with an aldehyde. As the aldehyde, for example, alkyl aldehydes can be preferably used, and alkyl aldehydes having an alkyl group with 1 to 7 carbon atoms are preferred, with acetaldehyde, n-propyl aldehyde, n-butyraldehyde, and n-pentyl aldehyde being particularly preferred. Using such a modified PVA provides suitable protection for the substrate, thereby further enhancing the effects of the present invention.

[0067] As the modified PVA, a cation-modified polyvinyl alcohol in which a cationic group such as a quaternary ammonium structure has been introduced may be used. Examples of the above-mentioned cation-modified polyvinyl alcohol include those into which a cationic group derived from a monomer having a cationic group, such as diallyldialkylammonium salt or N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt has been introduced. As the modified PVA, the non-VA unit has the chemical formula: -CH ２ -CH(CR ５ (OR ８ )-CR ６ (OR ９ )-R ７ ) - which may have a structural part represented by R. ５ ~R ７ Each of these independently represents a hydrogen atom or an organic group, R ８ and R ９ Each is independently a hydrogen atom or R １０ -CO- (wherein, R １０ ) indicates an alkyl group. Examples of such modified PVA include modified PVA having a 1,2-diol structure in the side chain.

[0068] The modified PVA may also be a modified PVA comprising a VA unit and a non-VA unit having at least one structure selected from an oxyalkylene group, a carboxyl group, a (di)carboxylic acid group, a (di)carboxylic acid ester, a phenyl group, a naphthyl group, a sulfo group, an amino group, a hydroxyl group, an amide group, an imide group, a nitrile group, an ether group, an ester group, and salts thereof.

[0069] Modified PVA may be a random copolymer, block copolymer, alternating copolymer, or graft copolymer containing non-VA units and VA units. Modified PVA may contain only one type of non-VA unit, or it may contain two or more types of non-VA units.

[0070] The upper limit of the degree of saponification of modified PVA is not particularly limited, but can be 100 mol% or less, 98 mol% or less, 95 mol% or less, 90 mol% or less, or 85 mol% or less. The lower limit of the degree of saponification of modified PVA is preferably 70 mol% or more, more preferably 75 mol% or more, even more preferably 80 mol% or more, and particularly preferably 85 mol% or more. The degree of saponification of modified PVA can be determined by titrating the remaining acetate groups with alkali, as well as by near-infrared spectroscopy (IR) or nuclear magnetic resonance (NMR). The effects of the present invention are further enhanced when the degree of saponification of modified PVA is within the above range. In this specification, the degree of saponification is a value obtained by measurement in accordance with JIS-K6726 (1994).

[0071] In one embodiment, the modified PVA has a structural portion represented by the following general formula (1) as a non-VA unit. In this case, the degree of saponification is preferably 60 to 99.9 mol%, and more preferably 85 to 99 mol%. The degree of acetalization is preferably 5 to 40%, and more preferably 15 to 25%. The degree of acetalization is determined by the number of VA units before acetalization of a portion of the VA units with an aldehyde. ０ The number of VA units after acetalization is N. １ When that happens, (N ０ -N １ ) / N ０ It is calculated by multiplying by 100.

[0072]

[0073] (In formula (1), R is a hydrogen atom, an alkyl group, an alkylene group, or an oxyalkylene group, and the alkyl group is a linear or branched alkyl group, and the alkyl group or alkylene group may be substituted with a functional group.)

[0074] In the above formula (1), R is preferably a methyl group, for example.

[0075] In one embodiment, modified PVA is expressed as a non-VA unit with the chemical formula: -CH ２It has a structural moiety represented by -CH(-OR)- (where R is a butyl group). In this case, the degree of saponification is 97-99 mol%, and the butyl ether group is 5-15 mol%.

[0076] The ratio of moles of non-VA units to the total number of moles of repeating units constituting the modified PVA may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. Although not particularly limited, in some embodiments, the ratio of moles of non-VA units may be 50% or more, 65% or more, 75% or more, 80% or more, or 90% or more (for example, 95% or more, or 98% or more). Furthermore, the ratio of moles of non-VA units to the total number of moles of repeating units constituting the modified PVA may be, for example, 99% or less, 98% or less, 95% or less, 90% or less, or 80% or less.

[0077] The content of non-VA units in modified PVA (content on a mass basis) may be, for example, 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more. Although not particularly limited, in some embodiments, the content of modified VA units may be 50% by mass or more (for example, more than 50% by mass), 70% by mass or more, or 80% by mass or more (for example, 90% by mass or more, or 95% by mass or more, or 98% by mass or more). Furthermore, the content of non-VA units in modified PVA (content on a mass basis) may be, for example, 99% by mass or less, 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0078] Modified PVA may contain multiple polymer chains with different non-VA unit content within the same molecule. Here, a polymer chain refers to a part (segment) that constitutes a part of a polymer molecule. For example, modified PVA may contain polymer chain A, which has a non-VA unit content of more than 50% by mass, and polymer chain B, which has a non-VA unit content of less than 50% by mass (i.e., a VA unit content of more than 50% by mass), within the same molecule.

[0079] Polymer chain A may contain only non-VA units as repeating units, or it may contain VA units in addition to non-VA units. The content of non-VA units in polymer chain A may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. In some embodiments, the content of non-VA units in polymer chain A may be 95% by mass or more, or 98% by mass or more. Substantially 100% by mass of the repeating units constituting polymer chain A may be non-VA units.

[0080] Polymer chain B may contain only VA units as repeating units, or it may contain non-VA units in addition to VA units. The VA unit content in polymer chain B may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. In some embodiments, the VA unit content in polymer chain B may be 95% by mass or more, or 98% by mass or more. Substantially 100% by mass of the repeating units constituting polymer chain B may be VA units.

[0081] Examples of modified PVA containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The above graft copolymer may be a graft copolymer in which polymer chain B (side chain) is grafted onto polymer chain A (main chain), or a graft copolymer in which polymer chain A (side chain) is grafted onto polymer chain B (main chain). In one embodiment, a modified PVA in which polymer chain B is grafted onto polymer chain A can be used.

[0082] Examples of polymer chain A include polymer chains whose main repeating units are derived from N-vinyl monomers, polymer chains whose main repeating units are derived from N-(meth)acryloyl monomers, polymer chains whose main repeating units are derived from vinyl dicarboxylates such as fumaric acid, maleic acid, and maleic anhydride, polymer chains whose main repeating units are derived from aromatic vinyl monomers such as styrene and naphthalene vinyl, and polymer chains whose main repeating units are oxyalkylene units. In this specification, unless otherwise specified, the main repeating unit refers to a repeating unit present in an amount exceeding 50% by mass.

[0083] One preferred example of polymer chain A is a polymer chain whose main repeating unit is an N-vinyl type monomer, i.e., an N-vinyl polymer chain. The content of repeating units derived from N-vinyl type monomers in the N-vinyl polymer chain is typically more than 50% by mass, may be 70% by mass or more, 85% by mass or more, or 95% by mass or more. Substantially all of polymer chain A may consist of repeating units derived from N-vinyl type monomers.

[0084] In this specification, examples of N-vinyl type monomers include monomers having a nitrogen-containing heterocyclic ring (e.g., a lactam ring) and N-vinyl chain amides. Specific examples of N-vinyl lactam type monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholindione. Specific examples of N-vinyl chain amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide. Polymer chain A may be an N-vinyl polymer chain in which more than 50% by mass (e.g., 70% by mass or more, or 85% by mass or more, or 95% by mass or more) of its repeating units are N-vinylpyrrolidone units. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

[0085] Another example of polymer chain A is a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acryloyl type monomer, i.e., an N-(meth)acryloyl polymer chain. The content of repeating units derived from an N-(meth)acryloyl type monomer in an N-(meth)acryloyl polymer chain is typically more than 50% by mass, may be 70% by mass or more, 85% by mass or more, or 95% by mass or more. It is also possible that substantially all of polymer chain A consists of repeating units derived from an N-(meth)acryloyl type monomer.

[0086] In this specification, examples of N-(meth)acryloyl type monomers include chain amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Examples of chain amides having an N-(meth)acryloyl group include (meth)acrylamides; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide. Examples of cyclic amides having an N-(meth)acryloyl group include N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

[0087] Another example of polymer chain A is a polymer chain containing oxyalkylene units as the main repeating units, i.e., an oxyalkylene polymer chain. The content of oxyalkylene units in an oxyalkylene polymer chain is typically more than 50% by mass, may be 70% or more by mass, 85% or more by mass, or 95% or more by mass. Substantially all of the repeating units contained in polymer chain A may be oxyalkylene units.

[0088] Examples of oxyalkylene units include oxyethylene units, oxypropylene units, and oxybutylene units. Each of these oxyalkylene units may be repeating units derived from the corresponding alkylene oxide. The oxyalkylene polymer chain may contain one type of oxyalkylene unit or two or more types. For example, it may be an oxyalkylene polymer chain containing a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, these oxyalkylene units may be random copolymers of the corresponding alkylene oxides, block copolymers, alternating copolymers, or graft copolymers.

[0089] Other examples of polymer chain A include polymer chains that primarily contain alkyl vinyl ether units, structural units obtained by acetalizing polyvinyl alcohol and aldehydes, etc. Among these, it is preferable to select from the group consisting of vinyl ether units having an alkyl group with 1 to 10 carbon atoms (alkyl vinyl ether units), vinyl ester units derived from monocarboxylic acids having 1 to 7 carbon atoms (monocarboxylic acid vinyl ester units), and structural units obtained by acetalizing polyvinyl alcohol and aldehydes having an alkyl group with 1 to 7 carbon atoms.

[0090] Examples of vinyl ether units having an alkyl group with 1 to 10 carbon atoms include propyl vinyl ether units, butyl vinyl ether units, and 2-ethylhexyl vinyl ether units. Examples of vinyl ester units derived from monocarboxylic acids with 1 to 7 carbon atoms include vinyl propanoate units, vinyl butanoate units, vinyl pentanoate units, and vinyl hexanoate units.

[0091] The lower limit of the weight-average molecular weight (Mw) of polyvinyl alcohol is preferably 1,000 or more, more preferably 1,500 or more, even more preferably 2,000 or more, particularly preferably 5,000 or more, and most preferably 10,000 or more. The upper limit of the weight-average molecular weight (Mw) of polyvinyl alcohol is preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, particularly preferably 50,000 or less, and most preferably 30,000 or less. According to one embodiment, the weight-average molecular weight (Mw) of polyvinyl alcohol is 1,000 to 30,000, 1,500 to 25,000, 1,800 to 22,000, 2,000 to 20,000, 2,200 to 20,000, 2,500 to 20,000, 3,000 to 20,000, or 3,000 to 15,000.

[0092] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for use in polishing, the content of polyvinyl alcohol in the concentrated liquid is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and most preferably 0.2% by mass or more. In this case, from the viewpoint of storage stability and filterability, the content of polyvinyl alcohol in the concentrated liquid of the polishing composition is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0093] In the polishing composition used during polishing, the polyvinyl alcohol content in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, particularly preferably 0.0005% by mass or more, and most preferably 0.001% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the polyvinyl alcohol content in the polishing composition used during polishing is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0.05% by mass or less.

[0094] Polyvinylpyrrolidone: Polyvinylpyrrolidone may be polyvinylpyrrolidone, a derivative of polyvinylpyrrolidone, or a copolymer of polyvinylpyrrolidone and other polymers.

[0095] In this specification, polyvinylpyrrolidone (hereinafter referred to as PVP) refers to a polymer containing vinylpyrrolidone units (hereinafter also referred to as "VP units") as repeating units. A derivative of polyvinylpyrrolidone is a compound having polyvinylpyrrolidone in its molecule. A copolymer of polyvinylpyrrolidone and another polymer refers to a polymer that contains VP units as repeating units, as well as repeating units other than VP units (hereinafter also referred to as "non-VP units").

[0096] PVP is a repeating unit with the chemical formula: -CH ２ It contains a structural part represented by -CH(2-pyrrolidonyl)-, i.e., a VP unit. PVP is produced by polymerizing N-vinyl-2-pyrrolidone. PVP is a repeating unit of the structure formed by polymerizing N-vinyl-2-pyrrolidone (-CH ２ This refers to PVP that substantially does not contain repeating units other than -CH(2-pyrrolidonyl)-) (VP unit). The notation "2-pyrrolidonyl" indicates that the structure has a 2-pyrrolidonyl group attached as a side chain.

[0097] Copolymers of polyvinylpyrrolidone and other polymers have the chemical formula -CH as non-VP units. ２ It may have a structural part represented by -CH(Y)- or the chemical formula: -CH(Y)-CH(Y)- (hereinafter also referred to as the "modified VP unit").

[0098] Here, Y can be any group other than a 2-pyrrolidonyl group. For example, Y can be a hydroxyl group (-OH group), an alkyl ether group (-O-R １ ;R １ (A C1-C10 alkyl group), alkylcarbonyl ether group (-O-C(=O)-R １ ;R １ (A C1-C10 alkyl group), sulfonic acid group (-S (=O) ２ -OH), carboxylic acid group (-C(=O)-OH), carboxylic acid ester group (-C(=O)OR;R １ (A C1-C10 alkyl group), polyalkylene oxyether group (-O-(R ２ O) ｎ -H;R ２ (where n is an alkylene group having 2 to 5 carbon atoms, n is the number of moles of alkylene oxide added), amino ether group (-O-NR ３ ;R ３ Each is independently a hydrogen atom, a C1-C5 alkyl group or a C6-C20 aryl group, and an alkyl ether alkylene group (-R ４ -O-R １ ;R １ R is an alkyl group having 1 to 10 carbon atoms. ４ (A is an alkylene group having 1 to 10 carbon atoms), an alkylcarbonylalkylene group (-R ４ -C(=O)-R １ ;R １ R is an alkyl group having 1 to 10 carbon atoms. ４ (A C1-C10 alkylene group), amino group (-NR ３ ;R ３Preferably, each of these is independently a hydrogen atom, a C1-C5 alkyl group or a C6-C20 aryl group, an aromatic group (e.g., a phenyl group, a benzyl group), or a heterocyclic group (except for the pyrrolidonyl group) (e.g., a pyridine ring (pyridinyl group, etc.)).

[0099] The non-VP units that may be included in copolymers of polyvinylpyrrolidone and other polymers are the same as those described above as non-VA units. Non-VP units may also be VA units, or modified PVA (non-VA units) in which a portion of the VA units are acetalized with an aldehyde.

[0100] The lower limit of the weight-average molecular weight (Mw) of polyvinylpyrrolidone is preferably 1,000 or more, more preferably 1,500 or more, even more preferably 2,000 or more, particularly preferably 5,000 or more, and most preferably 10,000 or more. The upper limit of the weight-average molecular weight (Mw) of polyvinylpyrrolidone is preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, particularly preferably 50,000 or less, and most preferably 30,000 or less. According to one embodiment, the weight-average molecular weight (Mw) of polyvinylpyrrolidone is 1,000 to 30,000, 1,500 to 25,000, 1,800 to 22,000, 2,000 to 20,000, 2,500 to 20,000, 3,000 to 20,000, or 5,000 to 20,000.

[0101] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for use in polishing, the content of polyvinylpyrrolidone in the concentrated liquid is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and most preferably 0.2% by mass or more. In this case, from the viewpoint of storage stability and filterability, the content of polyvinylpyrrolidone in the concentrated liquid of the polishing composition is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0102] In polishing compositions used during polishing, the polyvinylpyrrolidone content in the polishing composition is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, particularly preferably 0.0005% by mass or more, and most preferably 0.001% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the polyvinylpyrrolidone content in the polishing composition is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0.05% by mass or less.

[0103] Polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers and polyoxypropylene alkyl ethers. The alkyl group of the polyoxyalkylene alkyl ether is preferably a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, more preferably a linear, branched, or cyclic alkyl group having 3 to 18 carbon atoms, and even more preferably a linear, branched, or cyclic alkyl group having 5 to 15 carbon atoms. The polyoxyalkylene alkyl ether is preferably a polyoxyethylene alkyl ether having a linear or branched alkyl group having 1 to 20 carbon atoms. This allows for appropriate buffering of the mechanical action of the abrasive grains and improves the flatness of the outer periphery of the silicon wafer against the abrasive grains.

[0104] The average number of moles of oxyalkylene groups added to the polyoxyalkylene alkyl ether is preferably 5 moles to 3000 moles, more preferably 10 moles to 2000 moles, even more preferably 12 moles to 1000 moles, particularly preferably 15 moles to 800 moles, and most preferably 20 moles to 500 moles. This allows for appropriate buffering of the mechanical action of the abrasive grains and improves the flatness of the outer periphery of the silicon wafer against the abrasive grains.

[0105] The lower limit of the weight-average molecular weight (Mw) of the polyoxyalkylene alkyl ether is preferably 200 or more, more preferably 300 or more, even more preferably 350 or more, particularly preferably 400 or more, and most preferably 500 or more. The upper limit of the weight-average molecular weight (Mw) of the polyoxyalkylene alkyl ether is preferably 50,000 or less, more preferably 20,000 or less, even more preferably 10,000 or less, particularly preferably 5,000 or less, and most preferably 3,000 or less.

[0106] When the polishing composition is diluted with a dispersion medium or the like to form a concentrated liquid for use in polishing, the content of polyoxyalkylene alkyl ether in the concentrated liquid is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, even more preferably 0.005% by mass or more, particularly preferably 0.01% by mass or more, and most preferably 0.015% by mass or more. In this case, from the viewpoint of storage stability and filterability, the content of polyoxyalkylene alkyl ether in the concentrated liquid of the polishing composition is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and most preferably 0.1% by mass or less.

[0107] In the polishing composition used during polishing, the content of polyoxyalkylene alkyl ether in the polishing composition is preferably 0.00001% by mass or more, more preferably 0.00002% by mass or more, even more preferably 0.00003% by mass or more, particularly preferably 0.00005% by mass or more, and most preferably 0.0001% by mass or more, based on the total mass of the polishing composition, from the viewpoint of further improving the polishing speed. In this case, the content of polyoxyalkylene alkyl ether in the polishing composition used during polishing is preferably 0.05% by mass or less, more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, particularly preferably 0.01% by mass or less, and most preferably 0.005% by mass or less.

[0108] [Dispersion Medium] The polishing composition according to this embodiment preferably contains a dispersion medium for dispersing each component. The dispersion medium (especially water) has the function of dissolving or dispersing the components contained in the polishing composition.

[0109] The dispersion medium may be a mixed solvent of water and an organic solvent for the dispersion or dissolution of each component. In this case, examples of organic solvents that can be used are acetone, acetonitrile, ethanol, methanol, 2-propanol, glycerin, ethylene glycol, propylene glycol, etc., which are organic solvents that are miscible with water. Alternatively, these organic solvents may be used without mixing with water to disperse or dissolve each component, and then mixed with water. These organic solvents can be used individually or in combination of two or more. In a preferred embodiment of this model, the dispersion medium contains water. In a more preferred embodiment of this model, the dispersion medium consists substantially of water. The term "substantially" above means that a dispersion medium other than water may be included, insofar as the effects of the present invention can be achieved. More specifically, the dispersion medium preferably consists of 90% to 100% by mass of water and 0% to 10% by mass of a dispersion medium other than water, and more preferably consists of 99% to 100% by mass of water and 0% to 1% by mass of a dispersion medium other than water. In the most preferred embodiment of this model, the dispersion medium is water only.

[0110] From the viewpoint of preventing contamination of the object to be polished or interference with the action of other components, it is preferable that the water contains as few impurities as possible. For example, water with a total transition metal ion content of 100 ppb or less is preferred. Here, the purity of the water can be increased by operations such as removing impurity ions using ion exchange resin, removing foreign matter using a filter, or distillation. Specifically, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, or distilled water.

[0111] [pH] The pH of the polishing composition according to this embodiment is preferably 7.0 or higher, more preferably 7.5 or higher, even more preferably 8.0 or higher, particularly preferably 8.5 or higher, and most preferably 9.0 or higher. The pH of the polishing composition is preferably 12.5 or lower, more preferably 12.0 or lower, even more preferably 11.8 or lower, particularly preferably 11.6 or lower, and most preferably 11.5 or lower. That is, the pH of the polishing composition is preferably 7.0 or higher and 12.5 or lower, more preferably 7.5 or higher and 12.0 or lower, even more preferably 8.0 or higher and 11.8 or lower, particularly preferably 8.5 or higher and 11.6 or lower, and most preferably 9.0 or higher and 11.5 or lower. If the pH of the polishing composition is within this range, the flatness of the outer periphery of the silicon wafer can be further improved.

[0112] The pH of the polishing composition can be measured using, for example, a pH meter (e.g., a pH meter manufactured by Horiba, Ltd. (model number: LAQUA F-72)). Specific types of pH adjusting agents are described in detail below.

[0113] [Other Components] The polishing composition according to this embodiment may further contain known additives that can be used in polishing compositions, such as pH adjusters, fungicides (preservatives), surfactants, and chelating agents, to the extent that they do not impair the effects of the present invention. pH adjusters, fungicides (preservatives), and surfactants will be described below. Oxidizing agents will also be described.

[0114] [pH Adjuster] In the polishing composition according to this embodiment, the pH can be adjusted by the components described above, but the pH may be further adjusted to a desired level using a pH adjuster. Therefore, the polishing composition according to this embodiment may further contain a pH adjuster. Examples of pH adjusters include compounds other than the basic compounds described above, such as inorganic acids and organic acids. These pH adjusters may be used individually or in combination of two or more. The content of the pH adjuster can be selected by appropriately adjusting it within the range that achieves the effects of the present invention.

[0115] Specific examples of inorganic acids that can be used as pH adjusters include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Of these, hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid are preferred, with nitric acid being more preferred.

[0116] Specific examples of organic acids that can be used as pH adjusters include, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, diglycolic acid, 2-furanic acid, 2,5-franic acid, 3-furanic acid, 2-tetrahydrofuranic acid, methoxyacetic acid, methoxyphenylacetic acid, phenoxyacetic acid, methanesulfonic acid, ethanesulfonic acid, 10-camphorsulfonic acid, and isethionic acid.

[0117] As a pH adjuster, a salt of an inorganic acid or organic acid, such as a basic compound metal salt of an inorganic acid or organic acid, may be used instead of or in combination with an inorganic acid or organic acid. In the case of a combination of a weak acid and a strong base, a strong acid and a weak base, or a weak acid and a weak base, a pH buffering effect can be expected.

[0118] [Antifungal agents] Antifungal agents (preservatives) are not particularly limited and can be appropriately selected according to the desired use and purpose. Specifically, examples include isothiazoline preservatives such as 1,2-benzoisothiazole-3(2H)-one (BIT), 2-methyl-4-isothiazolin-3-one, and 5-chloro-2-methyl-4-isothiazolin-3-one, as well as phenoxyethanol.

[0119] [Surfactants] Surfactants may be used individually or in combination of two or more types. Examples of the above surfactants are not particularly limited and include surfactants that do not have repeating structural units. For example, any surfactant other than the above water-soluble polymers may be used, and examples include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Note that surfactants exclude the above water-soluble polymers.

[0120] Examples of anionic surfactants include alkyl sulfate esters, alkyl sulfates, alkylbenzene sulfonic acids, alkyl phosphate esters, alkyl sulfosuccinic acids, alkylnaphthalene sulfonic acids, alkyl diphenyl ether disulfonic acids, and salts thereof.

[0121] Examples of nonionic surfactants include alkanolamides, glycerin fatty acid esters, and sorbitan fatty acid esters. Nonionic surfactants can be used individually or in combination of two or more.

[0122] Examples of cationic surfactants include quaternary ammonium salts such as alkyltrimethylammonium salts, alkyldimethylammonium salts, and alkylbenzyldimethylammonium salts; alkylamine salts such as laurylamine hydrochloride; and pyridium salts such as laurylpyridinium chloride.

[0123] Examples of amphoteric surfactants include alkyl betaines and alkylamine oxides.

[0124] [Chelating agent] The polishing composition according to this embodiment may contain a chelating agent. Examples of chelating agents include aminocarboxylic acid-based chelating agents and organic phosphonic acid-based chelating agents.

[0125] Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate.

[0126] Organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO), 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-methylphosphonosuccinic acid.

[0127] Chelating agents can be used individually or in combination of two or more types.

[0128] [Oxidizing Agent] In some embodiments of this model, it is preferable that the polishing composition substantially does not contain an oxidizing agent. This is because if an oxidizing agent is included in the polishing composition, the surface of the object to be polished (particularly silicon wafers) will be oxidized and an oxide film will be formed, which will increase the required polishing time. A specific example of an oxidizing agent is hydrogen peroxide (H ２ O ２Examples include sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. It should be noted that "substantially free of oxidizing agents" in an abrasive composition means that it does not intentionally contain oxidizing agents. Therefore, an abrasive composition that inevitably contains trace amounts of oxidizing agents (for example, a molar concentration of oxidizing agents in the abrasive composition of 0.001 mol / L or less, preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less) due to raw materials or manufacturing methods may be included in the concept of abrasive compositions that substantially do not contain oxidizing agents as defined herein.

[0129] [Method for Manufacturing the Polishing Composition] The method for manufacturing the polishing composition according to some embodiments of this model is not particularly limited. For example, it can be manufactured by adding abrasive grains, a basic compound, a water-soluble polymer, and other components to a dispersion medium all at once or sequentially, and stirring in the dispersion medium.

[0130] [Form of Polishing Composition, etc.] The polishing compositions according to some embodiments of this embodiment may be one-component or multi-component, consisting of two or more components. Furthermore, the polishing compositions described above may be used for polishing as is, or the concentrated polishing composition may be diluted by adding water, or, in the case of a multi-component polishing composition, by diluting it with an aqueous solution containing water and some of the components before use. For example, the concentrated polishing composition can be stored or transported, and then diluted to prepare the polishing composition at the time of use. Therefore, according to the present invention, a concentrated polishing composition according to this embodiment is also provided (the polishing composition according to this embodiment may be in the form of a concentrated liquid).

[0131] A concentrated form of abrasive composition is advantageous in terms of convenience and cost reduction during manufacturing, distribution, and storage. The concentration ratio can be, for example, between 2 and 100 times in terms of volume, and is usually between 5 and 60 times. The concentration ratio (concentration ratio when the abrasive composition is in the form of a concentrated liquid) of an abrasive composition (concentrated liquid) according to a preferred embodiment is between 8 and 50 times, for example between 10 and 40 times.

[0132] [Object to be polished] The polishing composition according to this embodiment is applied to the polishing of silicon wafers (substrates having a surface made of silicon single crystals). In other words, the object to be polished by the polishing composition according to this embodiment is a silicon wafer. The polishing composition according to this embodiment is applied to the preliminary polishing of silicon wafers.

[0133] The silicon wafer polished using the polishing composition according to this embodiment may be p-type or n-type. Furthermore, there are no particular restrictions on the crystal orientation of the silicon wafer, and it may be any of <100>, <110>, or <111>.

[0134] The shape of the object to be polished is not particularly limited. Polishing compositions according to some embodiments of the present invention can be preferably applied to polishing objects having flat surfaces, such as plate-shaped or polyhedral objects.

[0135] [Polishing Method] In other embodiments of the present invention, a polishing method is provided which includes polishing a silicon wafer using the above-mentioned polishing composition. For example, according to one embodiment, a polishing method is provided which includes the step of polishing a silicon wafer using the above-mentioned polishing composition.

[0136] The surface of a silicon wafer is generally finished to a high-quality mirror finish through a lapping process and a polishing process. The polishing process usually consists of multiple polishing steps, including a preliminary polishing step (a polishing step before the final polishing step) and a final polishing step. For example, a polishing composition with high processing power (polishing power) is used in the stage where the silicon wafer is roughly polished (e.g., the preliminary polishing step), while a polishing composition with low polishing power is used in the stage where the silicon wafer is polished more delicately (e.g., the final polishing step). The polishing composition according to this embodiment is preferably used in the preliminary polishing step. The polishing composition according to this embodiment is used for preliminary polishing of a silicon wafer. Therefore, according to the present invention, a polishing method is also provided which includes a step of polishing a silicon wafer using the above-mentioned polishing composition (preferably a preliminary polishing step).

[0137] In this case, the pre-polishing process may also be carried out in multiple stages, such as performing a first pre-polishing process at high pressure, followed by a second pre-polishing process at a lower pressure than the first pre-polishing process. In other words, it is preferable that the pre-polishing process includes a first pre-polishing process and a second pre-polishing process in that order. The polishing composition according to this embodiment is preferably used in the second pre-polishing process.

[0138] In the preliminary polishing step, either a double-sided polishing device or a single-sided polishing device may be used, but it is preferable to use a double-sided polishing device. Therefore, according to the present invention, a polishing composition is also provided for use in a second polishing step performed after the first polishing step in a preliminary polishing step carried out by double-sided polishing. That is, the polishing composition according to this embodiment is preferably used in a second preliminary polishing step carried out by double-sided polishing, after the first polishing step carried out by double-sided polishing.

[0139] The polishing composition according to this embodiment can suitably polish silicon wafers with a surface roughness of 0.01 nm to 300 nm.

[0140] As a polishing apparatus, a general polishing apparatus can be used that has a holder for holding a substrate or the like with the object to be polished, a motor with a changeable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached.

[0141] The polishing pads mentioned above can be of any type, including general nonwoven fabric, polyurethane, and suede types, without any particular restrictions. The polishing pads may also be grooved to allow the polishing composition to accumulate.

[0142] The polishing conditions are set appropriately depending on the stage of the polishing process in which the polishing composition is used.

[0143] For example, in the preliminary polishing process, the rotation speed of the polishing plate is usually around 5 rpm to 100 rpm, preferably around 7 rpm to 50 rpm. When using a double-sided polishing apparatus, the rotation speeds of the upper and lower rotating polishing plates may be the same or different.

[0144] The object to be polished is usually pressed down by a surface plate. The pressure at this time can be selected as appropriate, but in the preliminary polishing process, it is usually preferably between 3 kPa and 60 kPa, and more preferably between 5 kPa and 50 kPa.

[0145] The supply speed of the polishing composition can be appropriately selected according to the size of the polishing plate, but considering economics, in the case of the pre-polishing process, it is usually preferable to have a supply speed of 0.03 L / min to 10 L / min, and more preferably 0.05 L / min to 5 L / min.

[0146] There are no particular restrictions on the holding temperature of the polishing composition in the polishing apparatus, but from the viewpoint of stability of the polishing speed and reduction of defects, it is generally preferable that the temperature be between 15°C and 40°C, and more preferably between 18°C ​​and 30°C.

[0147] The above polishing conditions (settings for the polishing device) are merely examples, and the settings may be changed outside of the above range as appropriate. Such conditions can be set appropriately by those skilled in the art.

[0148] While embodiments of the present invention have been described in detail, these are descriptive and illustrative, and not limiting, and it is clear that the scope of the present invention should be interpreted by the appended claims.

[0149] The present invention encompasses the following embodiments and forms.

[0150] [1] A polishing composition used for pre-polishing silicon wafers, comprising abrasive particles, a basic compound, and a water-soluble polymer, wherein the pKa of the basic compound is 10 or less, and the radius of inertia of the water-soluble polymer is 60 nm or less.

[0151] [2] The polishing composition according to [1] above, wherein the abrasive grains are colloidal silica.

[0152] [3] The polishing composition according to [1] or [2] above, wherein the weight-average molecular weight of the water-soluble polymer is 400,000 or less.

[0153] [4] The polishing composition according to any one of [1] to [3] above, wherein the mass ratio of the content of the basic compound to the content of the water-soluble polymer is 50 or less.

[0154] [5] The polishing composition according to any one of [1] to [4] above, wherein the mass ratio of the abrasive grain content to the water-soluble polymer content is 500 or less.

[0155] [6] The polishing composition according to any one of [1] to [5] above, wherein the association ratio of the abrasive grains is 1.5 or less.

[0156] [7] The pre-polishing includes a first pre-polishing step performed by double-sided polishing, and a second pre-polishing step performed by double-sided polishing after the first pre-polishing step, and the polishing composition is the polishing composition according to any one of [1] to [6] above used in the second pre-polishing step.

[0157] [8] A concentrated solution of any of the polishing compositions described in [1] to [7] above.

[0158] [9] A polishing method comprising the step of polishing a silicon wafer using the polishing composition described in any of [1] to [7] above.

[0159] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" mean "mass percent" and "parts by mass," respectively. In addition, in the following examples, unless otherwise specified, the operations were carried out under conditions of room temperature (20°C to 25°C) and relative humidity of 30% RH to 50% RH.

[0160] 《Average Primary Particle Diameter of Abrasive Grains》 The average primary particle diameter of abrasive grains was calculated from the specific surface area of ​​the abrasive grains and the density of the abrasive grains using the BET method. The specific surface area of ​​the abrasive grains using the BET method was measured using a "Flow Sorb II 2300" manufactured by Micromerities.

[0161] 《Average Secondary Particle Diameter of Abrasive Grains》 The particle diameter (volume-average particle diameter) measured by dynamic light scattering using the "FPAR-1000" manufactured by Otsuka Electronics Co., Ltd. was defined as the average secondary particle diameter of the abrasive grains.

[0162] 《pH of the Polishing Composition》 The pH of the polishing composition was measured using a glass electrode type hydrogen ion concentration indicator (model number: F-72, manufactured by Horiba, Ltd.). Three-point calibration was performed using standard buffer solutions: phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), and carbonate pH buffer pH: 10.01 (25°C). After that, the glass electrode was immersed in the polishing composition for at least two minutes. After the pH of the polishing composition stabilized, the pH of the polishing composition was measured.

[0163] 《Method for Measuring Radius of Inertia》 To measure the radius of inertia rg of water-soluble polymers, first, aqueous solutions were prepared so that the concentration of the water-soluble polymer was in the range of 0.1 to 1 mg / mL. For each prepared sample, a light scattering photometer "DLS-8000" (manufactured by Otsuka Electronics Co., Ltd.) was used to take measurements at 10-degree intervals within a measurement angle range of 20 to 150 degrees, and the radius of inertia rg [nm] was calculated by single-concentration plot analysis. If the polishing composition contained multiple types of water-soluble polymers, the ratio of the content of the multiple types of water-soluble polymers was matched to the ratio of their content in the polishing composition, and the total amount was prepared to achieve the above concentration before measurement.

[0164] 《Raw Materials for Polishing Compositions》 The polishing compositions shown in Table 1 below were prepared using the following raw materials.

[0165] • Abrasive grain a: Colloidal silica… Primary particle size 35 nm, secondary particle size 50 nm, association ratio: 1.43 • Abrasive grain b: Colloidal silica… Primary particle size 55 nm, secondary particle size 103 nm, association ratio: 1.87 • Basic compound a: Ammonia (pKa = 9.2 (25°C); value listed in the Basic Edition of the Chemical Handbook (6th revised edition, edited by the Chemical Society of Japan, 2021)) • Basic compound b: Tetramethylammonium hydroxide (TMAH) (pKa = 14.0 (25°C); value measured by neutralization titration) • Water-soluble polymer a: Polyvinylpyrrolidone (PVP)… Weight-average molecular weight: 17,000 • Water-soluble polymer b: Acetalized polyvinyl alcohol (AcPVA)… Weight-average molecular weight: 13,000 • Water-soluble polymer c: Hydroxyethylcellulose (HEC1)… Weight-average molecular weight: 280,000 • Water-soluble polymer d: Hydroxyethylcellulose (HEC2)... Weight-average molecular weight: 850,000 • Water-soluble polymer e: Polyoxyethylene alkyl ether (REO)... Weight-average molecular weight: <1000 • Dispersion medium: Pure water.

[0166] [Preparation of Polishing Compositions] (Examples 1-3 and Comparative Examples 1 and 2) Polishing compositions for Examples 1-3 and Comparative Examples 1 and 2 were prepared by adding abrasive grains, basic compounds, and water-soluble polymers to pure water (a dispersion medium) at room temperature (25°C) in the types and quantities shown in Table 1, and stirring and mixing at room temperature (25°C) for 30 minutes. The pH of the obtained polishing compositions for Examples 1-3 and Comparative Examples 1 and 2 was 10.8. The radius of inertia rg of the water-soluble polymers used in each polishing composition is shown in Table 1. The particle size of the abrasive grains in each polishing composition is also shown in Table 1. In Table 1, "Basic Compound / Water-Soluble Polymer" represents the mass ratio of the basic compound to the water-soluble polymer, and "Abrasive Grain / Water-Soluble Polymer" represents the mass ratio of the abrasive grain to the water-soluble polymer.

[0167] 《Evaluation of Peripheral Flatness》 The ESFQR (Edge Site Front least sQuares Range) of the wafer's peripheral edge was measured using an LSW-3022FE (manufactured by Kobelco Research Institute Co., Ltd.). The ESFQR measurement was performed for each site, which was divided into 72 equal parts in the circumferential direction within an annular region (an annular region with a width of 34 mm, excluding the outermost 1 mm of the edge) between a position 1 mm inward from the outermost edge toward the wafer center and a position 35 mm inward. The average value of the ESFQR obtained for each site was then calculated and used as the wafer's ESFQR (average value for n=72).

[0168] The ESFQR values ​​of wafers polished using the polishing compositions of Examples 1-3 and Comparative Example 2 are shown in Table 1 as relative values ​​to the ESFQR of wafers polished using the polishing composition of Comparative Example 1. A smaller value compared to Comparative Example 1 indicates an improvement in the flatness of the outer edge.

[0169] 《Roughness Evaluation》 The arithmetic mean roughness Ra of the entire wafer surface was measured using a laser scanning surface roughness meter TMS-3000WRC (manufactured by Schmitt Measurement System Inc.) in Full Band mode.

[0170] The roughness of wafers polished using the polishing compositions of Examples 1-3 and Comparative Example 2 is shown in Table 1 as a relative value to the roughness of a wafer polished using the polishing composition of Comparative Example 1. A smaller value compared to Comparative Example 1 indicates improved wafer roughness (smootherness).

[0171] The evaluation of the outer edge flatness and roughness described above was performed on silicon wafers after preliminary polishing, specifically the first and second pre-polishing processes. The first and second pre-polishing processes were carried out under the following conditions.

[0172] [Object to be polished] Silicon wafer: bare-Si p-type crystal orientation <100>, size: diameter 300 mm x thickness 785-795 μm.

[0173] [Preliminary Polishing: First Preliminary Polishing] ・Polishing machine: 20B-5P-4D (SpeedFam double-sided polishing machine) ・Polishing pads: SUBA800, grooveless on both sides (Nitta DuPont Co., Ltd.) ・Processing carrier: Stainless steel DLC coated (thickness 773 μm) ・Lower platen rotation speed: -35 rpm (clockwise rotation is considered forward when viewed from above the polishing machine) ・Upper platen rotation speed: +21 rpm (clockwise rotation is considered forward when viewed from above the polishing machine) ・Internal: -4.5 rpm ・Sun gear: -16.2 rpm ・Number of wafers polished simultaneously: 5 ・Polishing load: 5287 N (Polishing pressure: 15 kPa) ・Polishing time: Adjusted as needed so that the wafer thickness becomes 772 μm ・Flow rate: 4.5 L / min (recirculated use) ・Maintaining polishing environment: 25℃ - Polishing composition for the first preliminary polishing (composition): Abrasive grains (average primary particle size 35 nm): 0.5 mass%, tetramethylammonium hydroxide: 0.08 mass%, potassium carbonate: 0.05 mass%, polyvinylpyrrolidone (weight-average molecular weight 76,000): 0.0003 mass%, water: remainder [Preliminary polishing: Second preliminary polishing] - Polishing machine: 20B-5P-4D (double-sided polishing machine manufactured by SpeedFam) - Polishing pads: SUBA800 on both sides, grooveless (manufactured by Nitta DuPont Co., Ltd.) - Processing carrier: Stainless steel DLC coated (thickness 773 μm) - Lower platen rotation speed: -15 rpm (clockwise rotation is considered forward when viewed from above the polishing machine) - Upper platen rotation speed: +7 rpm (clockwise rotation is considered forward when viewed from above the polishing machine) - Internal: -1.5 rpm - Sun gear: -12.0 rpm - Number of blades polished simultaneously: 5 - Polishing load: 2467 N (polishing pressure: 7.0 kPa) - Polishing time: 5 minutes - Flow rate: 4.5 L / min (*flowing) - Polishing environment maintenance: 25°C - Polishing composition for the second preliminary polishing (composition)... Polishing composition of the example and comparative example.

[0174]

[0175] As is clear from Table 1 above, the polishing composition of the example can improve the flatness of the outer periphery. On the other hand, the polishing composition of the comparative example shows inferior flatness of the outer periphery. Furthermore, the polishing composition of the example can produce a silicon wafer with good surface quality in addition to improved flatness of the outer periphery.

[0176] Therefore, it can be seen that the polishing composition according to this embodiment can improve the flatness of the outer periphery.

[0177] This application is based on Japanese Patent Application No. 2025-044424, filed on 19 March 2025, the disclosures thereof being incorporated herein by reference in their entirety.

Claims

1. A polishing composition used for pre-polishing silicon wafers, comprising abrasive grains, a basic compound, and a water-soluble polymer, wherein the pKa of the basic compound is 10 or less, and the radius of inertia of the water-soluble polymer is 60 nm or less.

2. The polishing composition according to claim 1, wherein the abrasive grains are colloidal silica.

3. The polishing composition according to claim 1 or 2, wherein the weight-average molecular weight of the water-soluble polymer is 400,000 or less.

4. The polishing composition according to claim 1 or 2, wherein the mass ratio of the content of the basic compound to the content of the water-soluble polymer is 50 or less.

5. The polishing composition according to claim 1 or 2, wherein the mass ratio of the abrasive grain content to the water-soluble polymer content is 500 or less.

6. The polishing composition according to claim 1 or 2, wherein the aggregation ratio of the abrasive grains is 2.4 or less.

7. The polishing composition according to claim 1 or 2, wherein the pre-polishing comprises a first pre-polishing step performed by double-sided polishing, and a second pre-polishing step performed by double-sided polishing after the first pre-polishing step, and the polishing composition is used in the second pre-polishing step.

8. A concentrated solution of the polishing composition according to claim 1 or 2.

9. A polishing method comprising the step of polishing a silicon wafer using the polishing composition described in claim 1 or 2.

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