Method for producing a polished object and polishing agent set

Abstract

A method of producing a polished object comprising: a double-sided polishing step in which an object to be polished is subjected to double-sided polishing using a double-sided polishing agent containing first abrasive grains having an average primary particle diameter of 40 nm or more and a nitrogen-containing, water-soluble polymer, so that a double-sided polished object is obtained; and a one-side polishing step in which the double-sided polished object is subjected to one-side polishing using a one-side polishing agent containing second abrasive grains having an average primary particle diameter of 40 nm or less and a water-soluble polymer, wherein a ratio of an average primary particle diameter (A) of the first abrasive grains with respect to an average primary particle diameter (B) of the second abrasive grains (A) / (B) is more than 1 and 2.5 or less, and wherein the concentration of the water-soluble polymer in the single-side polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-side polishing agent.

Description

Technical area

[0001] The present invention relates to a method for producing a polished object, a polishing agent set, a double-sided polishing agent and a single-sided polishing agent. Background of the technology

[0002] For example, a metal and a semiconductor such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or stainless steel and an alloy thereof; a glassy substance such as quartz glass, aluminosilicate glass, or glassy carbon; a ceramic material such as alumina, silicon dioxide, sapphire, silicon nitride, tantalum nitride, or titanium carbide; a compound semiconductor wafer material such as silicon carbide, gallium nitride, or gallium arsenide; and a resin material such as a polyimide resin are polished according to various requirements such as flattening and are applied in various fields.

[0003] In particular, in order to manufacture a semiconductor device such as an integrated circuit, various studies have been conducted on a technique for polishing a silicon wafer to produce a mirror wafer having a high-quality plane mirror surface without scratches or contamination.

[0004] A polishing step of a semiconductor wafer, such as a silicon wafer, can be performed in at least two stages: pre-polishing and final polishing. During pre-polishing, rough polishing is performed to flatten a surface or improve surface roughness. Final polishing is performed to improve haze or eliminate polishing defects.

[0005] In such multi-step polishing, Patent Literature 1 focuses on the following aspect. That is, when a subsequent polishing step is performed while abrasive grains in a polishing agent used in a previous polishing step remain on a wafer surface after polishing is completed, defects caused by polishing, such as scratches, are generated on the wafer surface in the subsequent polishing step due to the remaining abrasive grains.Patent Literature 1 discloses a polishing agent in which (1) the particle diameter of contained abrasive grains (polishing abrasive grains before a final step) is equal to or larger than that of abrasive grains in a polishing agent used in a polishing step two stages before the final step (polishing abrasive grains two stages before the final step), and (2) the concentration of polishing abrasive grains before the final step is equal to or smaller than that of polishing abrasive grains two stages before the final step in a polishing agent used in the polishing step two stages before the final step. Patent Literature 1 discloses a technique for obtaining a semiconductor wafer having high surface quality that can be adapted to a highly integrated device.

[0006] Haze generated on the surface of a semiconductor wafer during wafer processing not only affects the electrical properties and yield of the semiconductor device, but also reduces the detection limit when particles adhering to the wafer surface are measured by a particle counter. The haze level of the surface of a semiconductor wafer achieved by a manufacturing process involving precise surface polishing using a conventional polishing compound is becoming insufficient as the quality required for semiconductor wafers increases today due to the high performance and high integration density of semiconductor devices.Similarly, according to more detailed semiconductor device design rules, LLS (Localized Light Scatters), which are a type of defects observed on the wafer surface after polishing with a polishing compound, also require higher quality because LLS affect the performance of the semiconductor device.

[0007] From this aspect, even if polishing is performed by the polishing method disclosed in Patent Literature 1, an amount of haze cannot be reduced, and defects cannot be sufficiently removed.Patent Literature 2 discloses a method for manufacturing a magnetic disk substrate comprising the following steps: (1) using a polishing liquid composition A containing alumina particles and water to polish a surface to be polished of a substrate to be polished; (2) rinsing the substrate obtained in step 1; (3) using a polishing liquid composition B containing silica particles, a nitrogen-containing compound, and water to polish the surface to be polished of the substrate obtained in step 2; (4) washing the substrate obtained in step 3; and (5) using a polishing liquid composition C containing silica particles and water to polish the surface to be polished of the substrate obtained in step 4.Steps 1 to 3 are performed in the same polishing machine, and step 5 is performed in a different polishing machine from the first polishing machine. Patent Literature 3 discloses a water-based dispersion substance for polishing chemical machines containing (A) abrasive grains, (B) organic acid, and (C) copper ions.Patent Literature 4 discloses a chemical / mechanical polishing method for polishing an object to be polished having an irregular surface, which comprises a substrate having convexities and concavities, a stopper layer formed on the convexities of the substrate, and an embedded insulating layer formed to cover the concavities of the substrate and the stopper layer, the method being characterized by comprising a first polishing step of flattening the embedded insulating layer using a slurry (A) and a second polishing step of further polishing the embedded insulating layer. List of citationsPatent literature Patent literature 1: JP 2011 - 165 909 A Patent literature 2: JP 2013 - 140 647 A Patent literature 3: JP 2009 - 206 240 A Patent literature 4: DE 60 2004 012 793 T2 Overview of the inventionTechnical problem

[0008] The present invention has been achieved in view of such circumstances. An object thereof is to provide a method for producing a polished object that can exceptionally reduce the degree of haze on a surface of an object to be polished while significantly reducing defects, and a polishing agent kit that can be used therefor. Solution to the problem

[0009] The present inventors conducted intensive research. As a result, focusing on a composition of a double-side polishing agent used in double-side polishing and a single-side polishing agent used in single-side polishing, the present inventors made the particle diameter of abrasive grains used in double-side polishing relatively large, specified a minimum particle diameter of the abrasive grains used in double-side polishing and a maximum particle diameter of the abrasive grains used in single-side polishing, and made the particle diameter of the abrasive grains used in double-side polishing not unnecessarily larger than the particle diameter of the abrasive grains used in single-side polishing, so that it falls within a specific range.Furthermore, the present inventors have particularly found that the above-described problems can be solved by using a specific polymer in the double-side polishing, and have completed the present invention.

[0010] That is, the present invention solves the problems described above by providing a method for producing a polished object, which comprises a double-side polishing step of subjecting an object to be polished to double-side polishing using a double-side polishing agent including first abrasive grains having an average primary particle diameter of 40 nm or more and a nitrogen-containing water-soluble polymer, so that a double-side polished object is obtained;and a single-side polishing step in which the double-sided polished object is subjected to single-side polishing using a single-side polishing agent containing second abrasive grains having an average primary particle diameter of 40 nm or less and a water-soluble polymer, and wherein a ratio of an average primary particle diameter (B) of the second abrasive grains with respect to an average primary particle diameter (A) of the first abrasive grains (A) / (B) is more than 1 and 2.5 or less, and wherein the concentration of the water-soluble polymer in the single-side polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-side polishing agent.

[0011] Furthermore, the present invention solves the above-described problems by providing a polishing agent set including first abrasive grains having an average primary particle diameter of 40 nm or more used in double-sided polishing, a nitrogen-containing, water-soluble polymer used in double-sided polishing, second abrasive grains having an average primary particle diameter of 40 nm or less used in single-sided polishing, and a water-soluble polymer used in single-sided polishing, and wherein the ratio of the average primary particle diameter (B) of the second abrasive grains with respect to the average primary particle diameter (A) of the first abrasive grains (A) / (B) is more than 1 and 2.5 or less.and wherein the concentration of the water-soluble polymer in the single-sided polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-sided polishing agent. Advantageous effect of the invention

[0012] According to the present invention, it is possible to provide a method for producing a polished object that can exceptionally reduce the haze level of a surface of an object to be polished while significantly reducing defects, and a polishing agent set that can be used therefor. As other effects of the present invention, it is possible to provide a method for producing a polished object that can lower a laser mark height and improve a numerical value of an ESFQR indicating a local flatness of a wafer edge portion, and a polishing agent set that can be used therefor. Short description of the drawings Fig. 1 is a perspective view illustrating an embodiment of a single-side polishing apparatus used in polishing by a single-side polishing agent. Fig. 2 is a perspective view illustrating an embodiment of a double-side polishing apparatus used in polishing by a double-side polishing agent. Description of embodiments

[0013] Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments only. The dimensional ratio of the drawings is exaggerated for convenience of explanation and may differ from the actual ratio. The term "X to Y" indicating a range herein means "X or more and Y or less." "Weight" and "mass," "weight%" and "mass%," and "part by weight" and "part by mass" are considered synonymous. Unless otherwise specified, operations and measurements of physical properties or the like are conducted under the conditions of room temperature (20 to 25°C) / relative humidity of 40 to 50%.

[0014] A first aspect of the present invention is a method for producing a polished object, which comprises a double-sided polishing step in which an object to be polished is subjected to double-sided polishing using a double-sided polishing agent including first abrasive grains having an average primary particle diameter of 40 nm or more and a nitrogen-containing, water-soluble polymer, to obtain a double-sided polished object, and a single-sided polishing step in which the double-sided polished object is subjected to single-sided polishing using a single-sided polishing agent including second abrasive grains having an average primary particle diameter of 40 nm or less and a water-soluble polymer,and wherein a ratio of an average primary particle diameter (B) of the second abrasive grains with respect to an average primary particle diameter (A) of the first abrasive grains (A) / (B) is more than 1 and 2.5 or less.,

[0015] As described above, the present inventors, focusing on a composition between a double-side polishing agent used in double-side polishing and a single-side polishing agent used in single-side polishing, made the particle diameter of abrasive grains used in double-side polishing relatively large, set a minimum particle diameter of the abrasive grains used in double-side polishing and a maximum particle diameter of the abrasive grains used in single-side polishing, and made the particle diameter of the abrasive grains used in double-side polishing not uselessly larger than the particle diameter of the abrasive grains used in single-side polishing.Furthermore, the present inventors have found, particularly by using a specific polymer in double-side polishing, that it is possible to exceptionally reduce a degree of haze of a surface of an object to be polished, while defects can be remarkably reduced.

[0016] The object to be polished used in a manufacturing method of the first aspect of the present invention is not particularly limited. Examples include a metal and a semiconductor wafer such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or stainless steel, and an alloy thereof; a glassy substance such as quartz glass, aluminosilicate glass, or glassy carbon; a ceramic material such as alumina, silicon dioxide, sapphire, silicon nitride, tantalum nitride, or titanium carbide; a compound semiconductor wafer material such as silicon carbide, gallium nitride, or gallium arsenide; and a resin material such as a polyimide resin. The shape of the object to be polished is also not particularly limited.For example, the manufacturing method can preferably be applied to polishing an object to be polished having a flat surface such as a plate shape or a polyhedron shape. By polishing such an object to be polished, it is possible to produce a polished object that can exceptionally reduce a degree of haze while significantly reducing defects. Of these objects to be polished, the object to be polished may include a variety of materials. In particular, the object to be polished is preferably a semiconductor wafer. The manufacturing method of the first aspect of the present invention is particularly preferable for polishing an object to be polished having a surface formed of single-crystal or polycrystalline silicon.

[0017] The following primarily describes an embodiment of the first aspect of the present invention in which the object to be polished is a silicon wafer. It should be understood that the object to be polished is not limited to a silicon wafer. The examples described above can be used.

[0018] The silicon wafer used in the manufacturing method of the first aspect of the present invention may be a p-type or an n-type. The crystal orientation of the silicon wafer is not particularly limited, and it may be any of <100> , <110> and <111> The resistivity of the silicon wafer is not particularly limited. The thickness of the silicon wafer is, for example, 600 to 1,000 µm, but is not particularly limited. The manufacturing method of the first aspect of the present invention can be applied to a wafer having any diameter, such as 200 mm, 300 mm, or 450 mm.In particular, the manufacturing method of the first aspect of the present invention essentially includes a double-side polishing step and can therefore be applied to a wafer having a large diameter, such as 300 mm or 450 mm. It should be understood that a wafer having a diameter other than these diameters may be used.

[0019] The following describes a silicon wafer manufacturing process. A single-crystal silicon ingot is sliced ​​into slices, and a silicon wafer is produced (slicing step). The edges of the silicon wafer are then chamfered (chamfering step). The wafer surface is then roughly polished by lapping and shaped to a predetermined shape (lapping step). Furthermore, the surface layer of the silicon wafer whose quality has changed due to lapping is removed (removal of the wafer's processing quality layer), and the silicon wafer is etched (etching process). After etching, the edges and surface of the silicon wafer are polished (double-sided or single-sided) (polishing step), and then the wafer is cleaned (cleaning step). The silicon wafer can be rinsed between polishing steps or between the polishing step and the cleaning step (rinsing step).

[0020] The manufacturing method of the first aspect of the present invention is characterized in that a polished object is manufactured from the series of processes in the polishing step. In the polishing step of the present embodiment, the surface of the silicon wafer (double-sided or single-sided) is brought into contact with a polishing pad, and the wafer surface and the polishing pad are relatively slid while a polishing agent (a double-sided polishing agent or a single-sided polishing agent) is applied to the contact portion. Thereby, the wafer surface is polished. In a preferred embodiment of the first aspect of the present invention, the double-sided polishing step is a rough polishing step (preliminary polishing step), and the single-side polishing step is a final polishing step.In the preferred embodiment of the first aspect of the present invention, the double-side polishing step is performed once, and the single-side polishing step is performed once (first embodiment of the first aspect of the present invention, described in detail below). In the preferred embodiment of the first aspect of the present invention, the double-side polishing step is performed once, and the single-side polishing step is performed twice (second embodiment of the first aspect of the present invention, described in detail below). As a modification example of the second embodiment of the first aspect of the present invention, the double-side polishing step is performed multiple times, and the single-side polishing step is performed three or more times.In the preferred embodiment of the first aspect of the present invention, the silicon wafer is rinsed after completion of each step (that is, after the double-side polishing step, after the single-side polishing step, after each step when the single-side polishing step is performed multiple times, or after each step when the double-side polishing step is performed multiple times) to change polishing agents, to remove polishing residues, or to protect the wafer surface.

[0021] A polishing device is described below. Fig. Figure 1 is a perspective view illustrating a single-side polishing apparatus used in polishing using a single-side polishing agent. The single-side polishing apparatus can be used in the rinsing step using a rinsing agent. As shown in Fig.1, a one-side polishing device 11 includes a disk-shaped turntable 12, on the upper surface of which a polishing pad 14 is applied. The turntable 12 is provided so as to be integrally rotatable with respect to a first shaft 13 extending in a direction of an arrow 13a in Fig. 1 rotates. At least one wafer holder 15 is provided above the turntable 12. The wafer holder 15 is provided so as to be integrally rotatable with respect to a second shaft 16 extending in a direction of an arrow 16a in Fig.1 rotates. A wafer holding plate 19 having a wafer holding opening 18 is detachably attached to the lower surface of the wafer holder 15 via a ceramic plate 17 and a urethane attachment (not shown). The single-side polishing apparatus 11 may further include a polishing agent supply device 21 and a rinsing agent supply device (not shown). The polishing agent supply device 21 may discharge a polishing agent for single-side polishing through an orifice 21a. The rinsing agent supply device (not shown) may discharge a rinsing agent through an orifice (not shown). The polishing agent supply device 21 of the single-side polishing apparatus 11, which does not include a rinsing agent supply device or orifice (not shown), may discharge a rinsing agent through the orifice 21a.

[0022] When a silicon wafer is polished, the polishing agent supply device 21 is arranged above the turntable 12, as shown in Fig.1. A silicon wafer to be polished is sucked into the wafer holding opening 18 and held in the wafer holder 15. First, the wafer holder 15 and the turntable 12 begin to rotate, and a single-side polishing agent is discharged from the polishing agent supply device 21, and the single-side polishing agent is applied to the polishing pad 14. Then, the wafer holder 15 is moved toward the turntable 12 (also referred to as the lower plate 23 in a double-side polishing apparatus 22 described below) so that the silicon wafer is pressed onto the polishing pad 14. A side of the silicon wafer in contact with the polishing pad 14 is thereby polished. The polishing pad is not particularly limited, and a polyurethane type, a nonwoven fabric type, a suede type, or the like can be used.

[0023] By including another disc-shaped turntable onto which a polishing pad is applied, the Fig. 1 can be used as a double-sided polishing apparatus to polish both sides of the silicon wafer. Fig. 2 is a perspective view illustrating an embodiment of a double-side polishing apparatus used in polishing by a double-side polishing agent.

[0024] In one embodiment of a double-side polishing apparatus of the first aspect of the present invention, a disk-shaped turntable is further arranged above, on which a polishing pad is mounted, to be used as an upper turntable (upper table 24), on which a polishing pad 14 is mounted. The silicon wafer held by the wafer holding opening 18 is held by the polishing pad 14 mounted on the lower table 23 and the polishing pad 14 mounted on the upper table 24. The upper turntable includes a double-side polishing agent flow opening (polishing agent supply chute 26) for flowing a double-side polishing agent discharged from the polishing agent supply device 21 into a lower part.The upper turntable (upper plate 24) and the lower turntable (lower plate 23) rotate in opposite directions, as shown by arrows 13a and 16a. A double-side polishing agent is discharged from the double-side polishing agent supply device 21, and the two polishing pads 14 rotate while pressing against both sides of the silicon wafer. Both sides of the silicon wafer are thereby polished. As shown in FIG. Fig. 2, in the device 22 for double-sided polishing, the Fig. 1 is not required. Instead of the wafer holder 15, a wafer holding plate is required, which has a wafer holding opening 18. These are collectively referred to as wafer holder or processing carrier 25. According to the wafer holder 15 shown in Fig.In the embodiment illustrated in Figure 2, one holding plate contains one wafer, and three holding plates are arranged. However, according to another embodiment, one holding plate may contain three wafers. Any device can be used in the present invention. The number of holding plates or the number of wafers held by one holding plate is not particularly limited. A conventionally known device can be used as it is or by appropriately improving the conventionally known device.

[0025] A rotation speed can be selected appropriately. However, in double-side polishing, the rotation speed is usually about 10 to 50 rpm, and preferably about 15 to 30 rpm. In this case, the rotation speeds of the upper turntable and the lower turntable may be different from each other, but they are usually set to the same relative speed with respect to the wafer. In single-side polishing, the rotation speed is usually about 10 to 100 rpm, and preferably about 20 to 50 rpm. At such a rotation speed, it is possible to exceptionally reduce the haze level of the surface of the silicon wafer (double-sided or single-sided). Furthermore, it is possible to significantly reduce defects, lower a laser mark height, and improve a numerical value of an ESFQR. As described above, the silicon wafer is usually pressurized by the turntable.In this case, the pressure can be appropriately selected. However, for double-side polishing, the pressure is usually preferably about 5 to 25 kPa, more preferably about 10 to 15 kPa. For single-side polishing, the pressure is usually preferably about 5 to 25 kPa, more preferably about 10 to 15 kPa. At such a pressure, it is possible to remarkably reduce the haze level of the surface of the silicon wafer. Furthermore, it is possible to significantly reduce defects, lower a laser mark height, and improve a numerical value of an ESFQR.

[0026] A supply rate of a polishing agent (a double-side polishing agent or a single-side polishing agent) can be appropriately selected according to the size of the platen. However, from an economic perspective, the supply rate of a double-side polishing agent in double-side polishing is usually preferably about 1 to 10 l / min, and more preferably about 2 to 5 l / min. In single-side polishing, the supply rate of a single-side polishing agent is usually preferably about 0.1 to 5 l / min, preferably about 0.5 to 2 l / min. At such a supply rate, it is possible to efficiently polish the surface of the silicon wafer and remarkably reduce the haze level of the surface of the silicon wafer. Furthermore, it is possible to significantly reduce defects, lower a laser mark height, and improve a numerical value of an ESFQR.The holding temperature of a polishing agent (double-side polishing agent or single-side polishing agent) in a polishing apparatus is not particularly limited. However, from the perspective of maintaining the polishing speed and reducing the degree of haze, the holding temperature is usually preferably about 15 to 40°C, more preferably about 18 to 25°C. The polishing conditions described above are merely examples. The polishing conditions may be outside the above-described range, or the settings may be appropriately changed.

[0027] When rinsing a polished silicon wafer, a rinsing agent supply device is arranged above the turntable 12 in place of the polishing agent supply device 21. A polishing agent in the polishing agent supply device 21 can be discharged, and a rinsing agent can be added therein instead of the polishing agent. After the operating conditions of the single-side polishing apparatus 11 are switched from the polishing settings to the rinsing settings, a rinsing agent is discharged from the rinsing agent supply device and applied to the polishing pad 14. The surface of the silicon wafer in contact with the polishing pad 14 is thereby rinsed.In the rinsing step, a polishing agent to be used in a subsequent step can be used as it is, or an agent obtained by removing abrasive grains from the polishing agent to be used in the subsequent step can be used as the rinsing agent. When a polishing agent is used as the rinsing agent, components of the polishing agent can be increased or decreased, or they can be diluted with water as needed.

[0028] In the following, the first aspect of the present invention will be described by dividing the first aspect into several embodiments. (First Embodiment of the First Aspect of the Present Invention)

[0029] In the first embodiment of the first aspect of the present invention, a double-side polishing step in which a silicon wafer is subjected to double-side polishing using a double-side polishing agent to obtain a double-side polished silicon wafer is performed once, and a single-side polishing step in which the double-side polished silicon wafer is subjected to single-side polishing using a single-side polishing agent is performed once. From the perspectives of efficient polishing, cost reduction, and wastewater treatment, each step is preferably performed once. [abrasive grains]

[0030] Abrasive grains polish a surface of an object to be mechanically polished. Specific examples of the abrasive grains include particles made of a metal oxide such as silica, alumina, cerium oxide, zirconia, or titanium dioxide, and particles made of silicon carbide, calcium carbonate, or diamond. One type of these compounds can be used alone, or a combination of two or more types can be used. Of the abrasive grains, silica particles are preferred. Examples include colloidal silica and fumed silica. The type of the first abrasive grain and the type of the second abrasive grain can be the same or different from each other, but they are preferably the same to prevent cross-contamination (where a previous step affects a subsequent step).If the type of the first abrasive grains differs from that of the second abrasive grains, abrasive grains can be combined appropriately for use. Of the silica particles, colloidal silica is preferred. When colloidal silica or fumed silica is used, especially when colloidal silica is used, scratches generated on the surface of an object to be polished during a polishing step can be reduced.

[0031] The content of the first abrasive grains in a double-side polishing agent is preferably 0.1 mass % or more, more preferably 0.2 mass % or more. The content of the second abrasive grains in a single-side polishing agent is preferably 0.05 mass % or more, more preferably 0.1 mass % or more. Increasing the content of the abrasive grains improves surface finishing performance with respect to a surface to be polished, such as polishing speed.

[0032] The content of the first abrasive grains in a double-side polishing agent is preferably 50 mass % or less, more preferably 45 mass % or less. The content of the second abrasive grains in a single-side polishing agent is preferably 20 mass % or less, more preferably 15 mass % or less. By reducing the content of the abrasive grains, there is a tendency to improve dispersion stability of the polishing agent and reduce residue of the abrasive grains on the polished surface. Specifically, the lower limit of the content is based on an assumption of a concentration in a form of dilution described below. Specifically, the upper limit of the content is based on an assumption of a concentration in a concentrated liquid described below.

[0033] The average primary particle diameter (A) of the first abrasive grains used in the double-side polishing agent is not particularly limited as long as the diameter is 40 nm or more. The diameter may be more than 40 nm, 45 nm or more or less, 50 nm or more or less, 53 nm or more or less, 55 nm or more or less, 60 nm or more or less, 65 nm or more or less, 70 nm or more or less, 80 nm or more or less, 85 nm or more or less, 90 nm or more or less, or 92 nm or more or less. When it is necessary to achieve greater effects of the present invention, the diameter is preferably less than 90 nm, more preferably less than 70 nm.

[0034] The larger the abrasive grains, the closer the laser mark height tends to be to zero. A higher content of a nitrogen-containing, water-soluble polymer tends to bring the laser mark height closer to zero.

[0035] When the abrasive grains used are considerably large and a dispersion state is excellent such that the mechanical action of the abrasive grains is exhibited, the precision of the ESFQR tends to be high. It is possible to particularly improve the laser marking height and the ESFQR by using considerably large abrasive grains in the double-side polishing agent. In the present invention, the average primary particle diameter (A) of the first abrasive grains used in the double-side polishing agent is 40 nm or more. The dispersion of the abrasive grains is improved by adding a nitrogen-containing water-soluble polymer (compared with a case where no water-soluble polymer is added or a case where a water-soluble polymer not containing nitrogen is added).

[0036] The average primary particle diameter (B) of the second abrasive grains is not particularly limited as long as the diameter is 40 nm or less. The diameter may be 38 nm or more or less, 35 nm or more or less, 32 nm or more or less, 30 nm or more or less, 28 nm or more or less, 25 nm or more or less, or 23 nm or more or less. When it is necessary to achieve greater effects of the present invention, the diameter is preferably less than 40 nm. In particular, it is possible to improve LLS and haze by using significantly small abrasive grains in the single-side polishing agent.

[0037] A ratio of the content (concentration) of the second abrasive grains with respect to the content (concentration) of the first abrasive grains is not particularly limited, but is preferably 0.3 to 8 or 1 to 8 from the viewpoint of polishing efficiency and surface accuracy.

[0038] The average secondary particle diameter of the first abrasive grains used in the double-side polishing agent is preferably 50 nm or more, more preferably 80 nm or more, and preferably 250 nm or less, more preferably 180 nm or less, from the viewpoint of disappearance of the laser mark height and improvement of the ESFQR. The average secondary particle diameter of the second abrasive grains used in the single-side polishing agent is more preferably 10 nm or more, and preferably 100 nm or less, more preferably 70 nm or less, from the viewpoint of reducing LLS.

[0039] For example, values ​​of the average primary particle diameter and the average secondary particle diameter of the abrasive grains are calculated from a specific surface area measured by a BET method. For example, a measurement of the specific surface area of ​​the abrasive grains can be performed using a "Flow Sorbll 2300" manufactured by Micromeritics, Japan.

[0040] In a preferred embodiment of the first aspect of the present invention, the number of LLSs with a size of 37 nm or more in a silicon wafer after double-side polishing and single-side polishing is preferably 50 or less, more preferably 20 or less. The smaller the number, the better the silicon wafer. The number of LLSs in the present invention means a value calculated by a measurement method described in Examples.

[0041] In the preferred embodiment of the first aspect of the present invention, the lower the haze (relative value) of the silicon wafer after double-side polishing and single-side polishing, the better the silicon wafer. Specifically, the haze is 26 or less, 25 or less, 24 or less, 23 or less, 22 or less, 21 or less, 20 or less, or 19 or less. However, the essential lower limit is about 10. The haze (relative value) means a value calculated by a measurement method described in Examples.

[0042] In the preferred embodiment of the first aspect of the present invention, the laser marking height of the silicon wafer after double-side polishing and single-side polishing is preferably 50 nm or less, more preferably 30 nm or less. However, the essential lower limit is about 10 nm. The laser marking is for marking an ID or the like in a silicon wafer and is represented by forming recesses (dots) by irradiating an outer peripheral portion of the silicon wafer with a laser beam and arranging the dots. The laser marking is applied primarily to a portion corresponding to a back surface outer peripheral portion of the silicon wafer.In the case of polishing with a double-sided polishing machine, only the parts around the laser mark have a lower polishing amount compared to a part without a laser mark, due to changes in silicon quality, and therefore, projection is easily generated in an unfavorable manner. Here, the height of the projection is referred to as the laser mark height. The laser mark height is a value calculated using a measurement method described in the examples.

[0043] In the preferred embodiment of the first aspect of the present invention, the ESFQR of the silicon wafer after double-side polishing and single-side polishing is preferably 70 nm or less, more preferably 50 nm or less. However, the essential lower limit is about 10 nm. ESFQR (Edge flatness metric, Sector based, Front surface referenced, least squares fit reference plane, Range of the data within sector) means a value obtained by measuring the SFQR in a fan-shaped area (sector) formed in an outer peripheral portion of the entire periphery of the wafer. ESFQRmax indicates a maximum value of ESFQRs in all sectors. ESFQRmean indicates an average value of ESFQRs in all sectors. In the present invention, ESFQR means a value of ESFQRmean.The ESFQR defined in the present invention is a value obtained by measuring the SFQR at a site where an edge exclusion (a width of the outer peripheral portion where no device is formed on the wafer) is 1 mm, the entire circumference of the wafer is divided into 72 parts at 5° intervals, and the length of one side in the radial direction constituting the site is 35 mm, using a flatness measuring device (WaferSight2, manufactured by KLA-Tencor Corporation). SFQR (Site Front Least Squares Range) means a maximum deviation on the + side (that is, on the upper side when a wafer is placed horizontally with the wafer surface facing upward) and the - side (the correspondingly lower side) from a reference plane, which is a plane at the site, obtained by calculating data in the specified site by a least squares method.ESFQR also means a value calculated using a measurement method described in the examples.

[0044] In the preferred embodiment of the first aspect of the present invention, regarding a minimum polishing amount in single-side polishing, which has the number of LLS of the silicon wafer after double-side polishing and single-side polishing of 20 or less, the smaller the minimum polishing amount, the better the silicon wafer. Specifically, the minimum polishing amount is 550 nm or less, less than 550 nm, 400 nm or less, 350 nm or less, less than 350 nm, 300 nm or less, less than 300 nm, 290 nm or less, 270 nm or less, 250 nm or less, 230 nm or less, or 210 nm or less. However, the essential lower limit is about 200 nm.

[0045] As described above, in the present invention, the ratio (A) / (B) of the average primary particle diameter (B) of the second abrasive grains with respect to the average primary particle diameter (A) of the first abrasive grains is more than 1 and 2.5 or less. Within such a range, it is possible to efficiently polish the surface of the silicon wafer and exceptionally reduce the haze level of the surface of the silicon wafer. Furthermore, it is possible to significantly reduce defects, significantly reduce a laser mark height, and improve the numerical value of the ESFQR.

[0046] It is only required that (A) / (B) be more than 1 and 2.5 or less, but it is preferably 1.6 or more and less than 2.3, more preferably more than 1.8 and 2.2 or less, even more preferably 1.9 or more and 2.2 or less. In this case, the particle diameter (B) is preferably less than 40 nm, more preferably less than 35 nm. With such a value, the number of LLS is particularly reduced, the haze (relative value) is particularly reduced, the laser mark height can be particularly lowered, the ESFQR is particularly improved, the above-described minimum polishing amount is particularly small, and the polishing speed is high.

[0047] When polishing is performed in a final polishing step through a pre-polishing step, optimization of the entire series of polishing processes in both steps is not performed even if each step is optimized individually. Therefore, an inappropriate polishing slurry may be selected in some of the steps. Specifically, in the pre-polishing step, a flatness of the polished surface represented by the ESFQR or the polishing speed is important, and in the final polishing step, an occurrence of defects such as the number of LLS or the like is important. However, a mismatch occurs between the polishing slurries in the steps, and defects such as the number of LLS cannot be further reduced.Therefore, to balance the polishing effect between the pre-polishing step and the final polishing step, not only (A) > (B) but also (A) / (B) is preferably within a constant condition range.

[0048] One of the characteristics of the manufacturing method of the first aspect of the present invention is that the double-side polishing agent in double-side polishing includes a nitrogen-containing, water-soluble polymer, and the single-side polishing agent in single-side polishing includes a water-soluble polymer. Specifically, by adding a nitrogen-containing, water-soluble polymer to the double-side polishing agent in double-side polishing, it is possible to reduce the number of LLSs. Furthermore, it is possible to lower the laser marking height, and the ESFQR is improved. [Nitrogen-containing, water-soluble polymer]

[0049] A nitrogen-containing, water-soluble polymer in the double-sided polishing agent maintains flatness from the center to the edges of the object to be polished. The nitrogen-containing, water-soluble polymer is not particularly limited as long as the nitrogen-containing, water-soluble polymer has one or more nitrogen atoms in a monomer unit or one or more nitrogen atoms in a part of a side chain. Examples include an amine, an imine, an amide, an imide, a carbodiimide, a hydrazide, and a urethane compound. Any of a chain form, a cyclic form, a primary compound, a secondary compound, and a tertiary compound can be used. The nitrogen-containing, water-soluble polymer may have a structure of a salt formed using a nitrogen atom as a cation.Either a polymer containing a nitrogen atom in the main chain or a polymer containing a nitrogen atom in a side chain functional group (side group) can be used. One type of nitrogen-containing, water-soluble polymer can be used in the double-sided polishing agent, or a combination of two or more types can be used. However, from a manufacturing cost perspective, one type is preferred.

[0050] Examples of the nitrogen-containing water-soluble polymer having a salt structure include a quaternary ammonium salt. Examples of the nitrogen-containing water-soluble polymer include a polycondensation polyamide such as water-soluble nylon, a polycondensation polyester such as water-soluble polyester, a polyaddition polyamine, a polyaddition polyimine, a polyaddition (meth)acrylamide, a water-soluble polymer having a nitrogen atom in at least a part of an alkyl main chain, and a water-soluble polymer having a nitrogen atom in at least a part of a side chain. The water-soluble polymer having a nitrogen atom in a side chain includes a water-soluble polymer having a quaternary nitrogen atom in a side chain.A specific example of the polyaddition-formed nitrogen-containing water-soluble polymer is selected from the group consisting of polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, poly-N-vinylformamide, polyvinylcaprolactam, and polyvinylpiperidine. The nitrogen-containing water-soluble polymer may partially have a hydrophilic structure such as a vinyl alcohol structure, a methacrylic acid structure, a vinylsulfonic acid structure, a vinyl alcohol carboxylic acid ester structure, or an oxyalkylene structure. Furthermore, the nitrogen-containing water-soluble polymer may be a polymer having a plurality of structural types, for example, a diblock type thereof, a triblock type thereof, a random type thereof, or an alternating type thereof.The nitrogen-containing, water-soluble polymer may contain a cation, an anion, both an anion and a cation, or a non-ion in part or all of its molecule. One type of these nitrogen-containing, water-soluble polymers may be used alone, or a combination of two or more types may be used.

[0051] Examples of the polymer containing a nitrogen atom in a main chain include a homopolymer and a copolymer of an N-acylalkyleneimine monomer. Specific examples of the N-acylalkyleneimine monomer include N-acetylethyleneimine and N-propionylethyleneimine.

[0052] Examples of the polymer containing a nitrogen atom in a side group include a polymer containing an N-(meth)acryloyl monomer unit and a polymer containing an N-vinyl monomer unit. Here, "(meth)acryloyl" means acrylic and methacrylic, including. For example, a homopolymer and a copolymer of N-(meth)acryloyl morpholine and a homopolymer and a copolymer of N-vinylpyrrolidone can be used. Unless otherwise specified, the copolymer here means various copolymers, including a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

[0053] Of the nitrogen-containing water-soluble polymers, the nitrogen-containing water-soluble polymer is preferably selected from the group consisting of a copolymer containing polyvinylpiperidone, polyvinylimidazole, polyvinylcarbazole, or polyvinylpyrrolidone in a part of the structure, a copolymer containing polyvinylpyrrolidone, poly-N-vinylformamide, or polyvinylcaprolactam in a part of the structure, polyvinylcaprolactam, and polyvinylpiperidine from the viewpoint of reducing the number of LLSs, lowering the laser mark height, and improving the ESFQR. The nitrogen-containing water-soluble polymer is preferably selected from the group consisting of polyvinylpyrrolidone and poly-N-vinylformamide from the viewpoint of an ability to form a film for protecting the wafer surface.

[0054] The weight-average molecular weight of the nitrogen-containing, water-soluble polymer in the double-side polishing agent, with respect to polyethylene oxide, is preferably about 2,000 to 250,000, more preferably about 3,000 to 200,000, and even more preferably about 4,000 to 150,000. Within such a range, the intended effects of the present invention can be easily exhibited.

[0055] The content of the nitrogen-containing water-soluble polymer in the double-side polishing agent is preferably 0.001 to 0.03 mass%, more preferably 0.002 to 0.02 mass%, even more preferably 0.005 to 0.02 mass%, particularly preferably 0.005 to 0.01 mass%. Within such a range, the intended effects of the present invention can be easily exhibited.

[0056] Such a range is based in particular on an assumption of a concentration in a concentrated liquid described below. [Water-soluble polymer]

[0057] A water-soluble polymer increases the wettability of a surface to be polished. One type of water-soluble polymer can be used in the single-side polishing agent, or a combination of two or more types can be used. However, from a manufacturing cost perspective, one or two types are preferred.

[0058] A water-soluble polymer having at least one functional group selected from a cation group, an anion group, and a non-ion group in the molecule can be used. Specific examples of the water-soluble polymer include water-soluble polymers having a hydroxy group, a carboxyl group, an acyloxy group, a sulfo group, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, or a polyoxyalkylene structure in the molecule. From the viewpoint of reducing agglomerates and improving cleaning performance, a non-ionic water-soluble polymer can be preferably used.Preferred examples thereof include a polymer containing an oxyalkylene unit, a polymer containing a nitrogen atom (the nitrogen-containing water-soluble polymer described above), polyvinyl alcohol (polyvinyl alcohol having a saponification degree of 70 mol% or more), and a cellulose derivative.

[0059] Examples of the polymer containing an oxyalkylene unit include polyethylene oxide (PEO), a block copolymer of ethylene oxide (EO) and propylene oxide (PO), and a random copolymer of EO and PO. The block copolymer of EO and PO may be a diblock copolymer or a triblock copolymer containing a polyethylene oxide (PEO) block and a polypropylene oxide (PPO) block. The above triblock copolymer includes a PEO-PPO-PEO type triblock copolymer and a PPO-PEO-PPO type triblock copolymer. Usually, the PEO-PPO-PEO type triblock copolymer is more preferred. In the block copolymer or the random copolymer of EO and PO, the molar ratio of EO and PO included in the copolymer (EO / PO) is preferably more than 1, more preferably 2 or more, still more preferably 3 or more (for example, 5 or more) from the viewpoint of solubility in water, cleaning performance, and the like.

[0060] More specific examples include a cellulose derivative, an imine derivative such as poly(N-acylalkyleneimine), polyvinyl alcohol, polyvinylpyrrolidone, a copolymer containing polyvinylpyrrolidone in a part of the structure, polyvinylcaprolactam, a copolymer containing polyvinylcaprolactam in a part of the structure, polyoxyethylene, a polymer containing an oxyalkylene unit, a polymer having a plurality of types of structures such as a diblock type thereof, a triblock type thereof, a random type thereof, or an alternating type thereof, and polyether-modified silicone.

[0061] Of these compounds, a cellulose derivative, polyvinyl alcohol, polyvinylpyrrolidone, and a polymer containing an oxyalkylene unit are preferred. Specific examples of the cellulose derivative include a cellulose derivative such as hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, methylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, or carboxymethylcellulose, and pullulan. Of the cellulose derivatives, hydroxyethylcellulose is preferred from the viewpoint of high wettability to a polished surface and excellent cleaning performance. By combining polyvinylpyrrolidone with a cellulose derivative as a water-soluble polymer included in the one-side polishing agent, agglomerates in the polishing agent can be suppressed.Therefore, the number of LLS is reduced, turbidity is reduced, laser marking height is lowered, and ESFQR is improved.

[0062] The weight-average molecular weight of the water-soluble polymer in the one-side polishing agent, in terms of polyethylene oxide, is preferably about 20,000 to 400,000, more preferably about 30,000 to 350,000, and even more preferably about 40,000 to 300,000. Within such a range, the intended effects of the present invention can be easily exhibited.

[0063] The content of the water-soluble polymer in the single-side polishing agent is preferably 0.05 mass % or more, more preferably 0.08 mass % or more, even more preferably 0.1 mass % or more, and preferably 1.0 mass % or less, more preferably 0.7 mass % or less, even more preferably 0.5 mass % or less. Within such a range, the intended effects of the present invention can be easily exhibited.

[0064] Such a range is based in particular on an assumption of a concentration in a concentrated liquid described below.

[0065] The concentration of the water-soluble polymer in the single-side polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-side polishing agent from the perspective of protecting the surface of an object to be polished. The ratio in this case is not particularly limited, but is preferably 10 times or more, more preferably 20 times or more, even more preferably 50 times or more, and preferably 1,000 times or less, more preferably 200 times or less, even more preferably 100 times or less. Within such a range, it is possible to efficiently polish the surface of an object to be polished and remarkably reduce the degree of haze of the surface of the object to be polished. Furthermore, it is possible to significantly reduce defects, lower the laser mark height, and improve the numerical value of an ESFQR.

[0066] The double-side polishing agent and the single-side polishing agent used in the manufacturing method of the first aspect of the present invention each preferably contain, in addition to the above-described components, a third component such as water, a basic compound, a surfactant, or a chelating agent. [Water]

[0067] Water in the polishing agent (double-sided polishing agent or single-sided polishing agent) dissolves or disperses other components. To minimize the inhibition of other components, the total content of transition metal ions in water is preferably 100 ppb or less. For example, the purity of water can be increased by removing foreign ions using an ion exchange resin, removing foreign matter using a filter, or distilling. Specifically, ion-exchange water, pure water, ultrapure water, or distilled water are preferred.

[0068] The pH value of the polishing agent is preferably in a range of 8 to 12, more preferably in a range of 9 to 11.

[0069] For preparing the polishing agent described above, it is possible to use, for example, a known mixing device such as a paddle mixer, an ultrasonic dispersion machine, or a homomixer. The raw materials of the polishing agent can be mixed simultaneously, or the mixing sequence can be determined appropriately. [Basic compound]

[0070] A basic compound chemically polishes a surface of an object to be polished and improves a dispersion stability of the polishing agent (the double-sided polishing agent or the single-sided polishing agent).

[0071] Specific examples of basic compounds include a hydroxide or salt of an alkali metal, quaternary ammonium hydroxide or a salt thereof, ammonia, and an amine. Examples of alkali metals include potassium and sodium. Examples of salts include carbonate, bicarbonate, sulfate, and acetate. Examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, and tetrabutylammonium.

[0072] Examples of quaternary ammonium hydroxide compounds include quaternary ammonium hydroxide and a salt thereof. Specific examples include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

[0073] Specific examples of the amine include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(ß-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, and guadinine. One type of these basic compounds can be used alone, or a combination of two or more types can be used.

[0074] Of the basic compounds, at least one selected from ammonia, an ammonium salt, a hydroxide of an alkali metal, an alkali metal salt and a quaternary ammonium hydroxide compound is preferably used.

[0075] Of the basic compounds, at least one selected from ammonia, a potassium compound, sodium hydroxide, a quaternary ammonium hydroxide compound, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate and sodium carbonate is more preferably used.

[0076] The polishing agent (especially the double-sided polishing agent) preferably contains a potassium compound and a quaternary ammonium hydroxide compound as the basic compound. Examples of the potassium compound include a potassium hydroxide and a salt thereof. Specific examples include potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, and potassium chloride. The polishing agent most preferably contains potassium hydroxide, potassium carbonate, and a tetraalkylammonium hydroxide such as tetramethylammonium hydroxide or tetraethylammonium hydroxide as the basic compound.

[0077] The content of the basic compound in the double-side polishing agent is preferably 0.01 mass % or more, more preferably 0.03 mass % or more. By increasing the content of the basic compound, a higher polishing speed can be more easily achieved. The content of the basic compound in the polishing agent is preferably less than 4 mass %, more preferably less than 3 mass %. By decreasing the content of the basic compound, deterioration of the shape of the edges of an object to be polished can be more easily suppressed. Specifically, the lower limit of the content is based on an assumption of a concentration in a form of dilution described below. Specifically, the upper limit of the content is based on an assumption of a concentration in a concentrated liquid described below.

[0078] The content of the basic compound in the one-side polishing agent is preferably 0.001 mass % or more, more preferably 0.003 mass % or more. By increasing the content of the basic compound, a higher polishing speed can be more easily achieved. The content of the basic compound in the polishing agent is preferably less than 2 mass %, more preferably less than 1 mass %. By decreasing the content of the basic compound, the shape of the edges of an object to be polished can be more easily maintained. Specifically, the lower limit of the content is based on an assumption of a concentration in a form of dilution described below. Specifically, the upper limit of the content is based on an assumption of a concentration in a concentrated liquid described below. [surfactant]

[0079] The polishing agent (double-sided polishing agent or single-sided polishing agent) may contain a surfactant. A surfactant suppresses the roughness of the polishing surface of an object to be polished, making it easier to reduce the degree of turbidity of the polished surface. Especially when the polishing agent contains a basic compound, roughness of the polishing surface of an object to be polished tends to occur easily due to chemical polishing (chemical etching) by the basic compound. Therefore, using a basic compound in combination with a surfactant is particularly effective.

[0080] A surfactant with a weight-average molecular weight of less than 1,000 is preferred. Examples include an anionic surfactant and a nonionic surfactant. Of the surfactants, a nonionic surfactant is preferred. The nonionic surfactant has low foaming properties and is therefore easy to handle during preparation or use of the polishing agent. For example, adjusting the pH is easier than when using an ionic surfactant.

[0081] Examples of the nonionic surfactant include an oxyalkylene polymer such as polyethylene glycol or polypropylene glycol, a polyoxyalkylene adduct such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, polyoxyethylene glycerol ether fatty acid ester or polyoxyethylene sorbitan fatty acid ester, a copolymer of a plurality of types of oxyalkylenes (diblock type, triblock type, random type and alternating type).

[0082] Specific examples include a polyoxyethylene-polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene oleylamide, Polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,Polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil. Of these surfactants, polyoxyethylene alkyl ether, especially polyoxyethylene decyl ether, is preferred.

[0083] One type of these surfactants may be used alone, or a combination of two or more types may be used. [Chelating agent]

[0084] The polishing agent (double-sided polishing agent or single-sided polishing agent) may contain a chelating agent. A chelating agent in the polishing agent (double-sided polishing agent or single-sided polishing agent) suppresses residual metal impurities in an object to be polished by capturing the metal impurities originally contained in the polishing agent, generated from the object to be polished or a polishing device during polishing, or added from the outside, and forming a complex therewith. Particularly when the object to be polished is a semiconductor, suppressing the residual metal impurities prevents metal contamination of the semiconductor and suppresses deterioration of the semiconductor.

[0085] Examples of the chelating agent include an aminocarboxylic acid chelating agent and an organic phosphonic acid chelating agent. Specific examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate.

[0086] Specific examples of the organic phosphonic acid chelating agent include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), triethylenetetraminehexa(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. One type of these chelating agents may be used alone, or a combination of two or more types may be used.

[0087] Of the chelating agents, an organic phosphonic acid chelating agent is preferred, and ethylenediaminetetrakis(methylenephosphonic acid) is more preferred.

[0088] The content of the chelating agent in the polishing agent (the double-side polishing agent or the single-side polishing agent) is preferably 0.0001 mass % or more, more preferably 0.0005 mass % or more. Increasing the content of the chelating agent further suppresses residual metal impurities in an object to be polished. The content of the chelating agent in the polishing agent (the double-side polishing agent or the single-side polishing agent) is preferably 0.5 mass % or less, more preferably 0.1 mass % or less. Decreasing the content of the chelating agent further maintains a shelf life of a polishing agent. Specifically, the lower limit of the content is based on an assumption of a concentration in a form of dilution described below.The upper limit of the content is based in particular on an assumption of a concentration in a concentrated liquid described below. [Antiseptic and fungicide]

[0089] The polishing agent (double-sided polishing agent or single-sided polishing agent) may contain an antiseptic and a fungicide. Specific examples of the antiseptic and fungicide include an isothiazoline compound, para-oxybenzonate, and phenoxyethanol. [Ingredients other than those described above]

[0090] The polishing agent may optionally further contain a known additive generally included in a polishing agent, such as an organic acid, a salt of an organic acid, an inorganic acid, or a salt of an inorganic acid.

[0091] Examples of the organic acid include a fatty acid such as formic acid, acetic acid, propionic acid, or (meth)acrylic acid; an aromatic carboxylic acid such as benzoic acid or phthalic acid; citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acid, and organic phosphonic acid. Examples of the organic acid salt include an alkali metal salt such as a sodium salt of an organic acid or a potassium salt thereof, and an ammonium salt.

[0092] Examples of inorganic acid salts include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts such as sodium or potassium salts of inorganic acids, and ammonium salts.

[0093] One type of organic acids and their salts and inorganic acids and their salts may be used alone, or a combination of two or more types thereof may be used.

[0094] The polishing agent described above (the double-sided polishing agent or the single-sided polishing agent) can be a single-component type or a multi-component type containing two or more agents. The polishing agent described above (the double-sided polishing agent or the single-sided polishing agent) can be used for polishing as it is. Alternatively, a polishing agent can be prepared and used for polishing by diluting a concentrated liquid of the polishing agent with water, or by diluting a multi-component polishing agent with an aqueous solution containing water and some components. For example, it is possible to prepare a polishing agent by diluting a concentrated liquid of the polishing agent upon use after the concentrated liquid has been stored or transported.That is, the concept of the polishing agent in the technique disclosed herein includes both a polishing liquid (working slurry) that is supplied to an object to be polished and used to polish the object to be polished, and a concentrated liquid (stock solution of the polishing liquid) that is diluted and used as a polishing liquid.

[0095] From the perspective of convenience, cost reduction, and the like, a concentrated polishing agent is advantageous in manufacturing, distribution, storage, or the like. A concentration increase may be, for example, about 2 to 100 times in terms of volume, and is usually appropriately about 5 to 50 times. The concentration increase of a polishing agent (in particular, a single-side polishing agent) according to a preferred embodiment is 10 to 40 times, for example, 15 to 25 times, for example, 18 to 22 times. The concentration increase of a polishing agent (in particular, a double-side polishing agent) according to another preferred embodiment is 10 to 40 times, for example, 20 to 35 times, for example, 28 to 32 times. (Second Embodiment of the First Aspect of the Present Invention)

[0096] The second embodiment of the first aspect of the present invention includes a double-side polishing step in which a silicon wafer is subjected to double-side polishing using a double-side polishing agent to obtain a double-side polished silicon wafer, and a single-side polishing step in which the double-side polished silicon wafer is subjected to single-side polishing using a single-side polishing agent. The single-side polishing step is performed twice. Performing the single-side polishing step twice is preferable from a productivity perspective. Of the two single-side polishing steps, the first polishing is also called "first-stage single-side polishing," and the subsequent polishing is also called "second-stage single-side polishing."

[0097] There is a difference in the frequency of the single-side polishing step between the first embodiment of the first aspect of the present invention and the second embodiment of the first aspect of the present invention. The description of the first embodiment of the first aspect of the present invention is basically applied to other parts in the second embodiment of the first aspect of the present invention. As a modification example of the second embodiment of the first aspect of the present invention, the double-side polishing step may be performed twice or more times, and the single-side polishing step may be performed three times or more times. The upper limit of the frequency of the double-side polishing step is about three times. The upper limit of the frequency of the single-side polishing step is about six times.

[0098] In the second embodiment of the first aspect of the present invention, one-side polishing is performed in the first-stage one-side polishing step and the second-stage one-side polishing step. Therefore, the second abrasive grains are used in both steps. These second abrasive grains may have different particle diameters or the same particle diameter, as long as the second abrasive grains have an average primary particle diameter of 40 nm or less and (A) / (B) is more than 1 and 2.5 or less. However, from the viewpoint of machinability, it is preferable to use the second abrasive grains having the same particle diameter.When using second abrasive grains with different particle diameters, the second abrasive grains used in the second-stage single-side polishing are preferably smaller than those used in the first-stage single-side polishing. The ratio thereof is preferably about 0.9 to 0.5 or about 0.8 to 0.7.

[0099] In the second embodiment of the first aspect of the present invention, the one-side polishing step is performed twice, and therefore, the one-side polishing step at the second stage is the final one-side polishing step. A water-soluble polymer used in the final one-side polishing step preferably includes at least one selected from a polymer containing an oxyalkylene unit, a nitrogen-containing water-soluble polymer, polyvinyl alcohol, and a cellulose derivative, and more preferably includes a cellulose derivative. In this way, by using a cellulose derivative in the final one-side polishing step, the number of LLS is particularly reduced, the degree of haze (relative value) is particularly reduced, the above-described minimum polishing amount is particularly small, and the polishing speed is high.This applies similarly to a case where the single-side polishing step is performed three times or more. If the single-side polishing step is performed three times, a similar effect can be achieved by using a cellulose derivative in a single-side polishing step at a third stage. <Zweiter Aspekt der vorliegenden Erfindung>

[0100] A second aspect of the present invention is a polishing agent kit including first abrasive grains having an average primary particle diameter of 40 nm or more used in double-side polishing, a nitrogen-containing water-soluble polymer used in double-side polishing, second abrasive grains having an average primary particle diameter of 40 nm or less used in single-side polishing, and a water-soluble polymer used in single-side polishing, and wherein a ratio of an average primary particle diameter (B) of the second abrasive grains with respect to an average primary particle diameter (A) of the first abrasive grains (A) / (B) is more than 1 and 2.5 or less.By performing double-side polishing and single-side polishing using the polishing agent set of the second aspect of the present invention, an effect similar to the first aspect of the present invention can be achieved. The description of the first aspect of the present invention is similarly applied to the first abrasive grains, the nitrogen-containing water-soluble polymer, the second abrasive grains, the water-soluble polymer, and the ratio of the average primary particle diameter (B) of the second abrasive grains with respect to the average primary particle diameter (A) of the first abrasive grains (A) / (B). Therefore, a description thereof is omitted here.

[0101] A form of the polishing agent set is not particularly limited. A double-sided polishing agent in which first abrasive grains and a nitrogen-containing, water-soluble polymer have been mixed in advance, and a single-sided polishing agent in which second abrasive grains and a water-soluble polymer have been mixed in advance are stored in separate containers and can be packaged together or separately. The double-sided polishing agent and the single-sided polishing agent do not need to be packaged. Even if the double-sided polishing agent and the single-sided polishing agent are placed on a shelf or the like to be used in double-sided polishing and single-sided polishing, respectively, these agents are considered the polishing agent set of the present invention.Alternatively, even if first abrasive grains used in double-side polishing, a nitrogen-containing water-soluble polymer used in double-side polishing, second abrasive grains used in single-side polishing, and a water-soluble polymer used in single-side polishing are stored in separate containers without being mixed in advance, these are regarded as the polishing agent set of the present invention. As in the second embodiment of the first aspect of the present invention, similarly to the case where two types of single-side polishing agents are present, even if two double-side polishing agents are prepared in which second abrasive grains and a water-soluble polymer are mixed in advance, these agents are regarded as the polishing agent set of the present invention.Even if second abrasive grains and a water-soluble polymer are stored in separate containers, they are considered to be the polishing agent kit of the present invention.

[0102] That is, when first abrasive grains and a nitrogen-containing water-soluble polymer are prepared to be used in double-side polishing, and second abrasive grains and a water-soluble polymer are prepared to be used in single-side polishing, these are included in the concept of the polishing agent set of the second aspect of the present invention. Examples

[0103] Next, the present embodiment will be described in more detail by means of examples and comparative examples.

[0104] Double-side polishing agents obtained by mixing colloidal silica, a water-soluble polymer compound (a nitrogen-containing water-soluble polymer compound), and ion-exchange water used in Examples 1 to 26 and Comparative Examples 1 to 12 were prepared to obtain the agents shown in Table 1. Single-side polishing agents obtained by mixing colloidal silica, a water-soluble polymer compound, and ion-exchange water used in Examples 1 to 26 and Comparative Examples 1 to 12 were prepared to obtain the agents shown in Table 1.Details of the double-sided polishing agents (preliminary polishing agent in double-sided polishing processing) and the single-sided polishing agents (final polishing agent in single-sided polishing processing) in the examples and comparative examples are shown in Table 1. Preparation was carried out by stirring and mixing the components (mixing temperature: about 25 °C, mixing time: about 10 minutes).

[0105] “BET particle diameter” and “average secondary particle diameter” in Table 1 indicate an average primary particle diameter and an average secondary particle diameter, respectively, calculated from a specific surface area (BET method) measured using a “Flow Sorbll 2300” manufactured by Micromeritics Japan.

[0106] "Colloidal silicon dioxide content in mass %" in Table 1 indicates a colloidal silicon dioxide content contained in 100 mass % of a double-sided polishing agent or a single-sided polishing agent.

[0107] In the column “Type of water-soluble polymer” in Table 1, “HEC” indicates hydroxyethylcellulose, “PVP” indicates polyvinylpyrrolidone, “PNVF” indicates poly-N-vinylformamide, “PEG” indicates polyethylene glycol, and “PEO” indicates polyethylene oxide.

[0108] "Water-soluble polymer Mm" in Table 1 indicates a weight-average molecular weight of a nitrogen-containing water-soluble polymer compound included in a double-side polishing agent (in terms of polyethylene oxide) and a weight-average molecular weight of a water-soluble polymer included in a single-side polishing agent (in terms of polyethylene oxide).

[0109] "Content of water-soluble polymer in mass fraction in %" in the column "Pre-polishing agent in a double-sided polishing process" in Table 1 indicates a content of a nitrogen-containing, water-soluble polymer contained in 100 mass fractions in % of a double-sided polishing agent.

[0110] "Content of water-soluble polymer in mass fraction in %" in the column "Final polishing agent in a one-sided polishing process" in Table 1 indicates a content of a water-soluble polymer contained in 100 mass fractions in % of a one-sided polishing agent.

[0111] It should be noted that the contents of colloidal silicon dioxide in final polishing agents (one-sided polishing agents) in one-sided polishing processing were all 9 mass fractions in %.

[0112] Next, using a polishing liquid obtained by diluting a double-side polishing agent (a pre-polishing agent in double-side polishing processing) having a composition shown in Examples 1 to 25 and Comparative Examples 1 to 11, 30 times with pure water, a silicon wafer (diameter: 300 mm, conductivity type: p-type, crystal orientation: <100> , specific resistance: 1 Ω·cm or more and less than 100 Ω·cm) was subjected to double-side polishing once under polishing conditions 1 described in Table 2 to obtain a double-side polished silicon wafer. The silicon wafer was then rinsed once.The double-side polished silicon wafer was subjected to one-side polishing once under polishing conditions 3 described in Table 2 using a polishing liquid obtained by diluting 20 times with pure water a one-side polishing agent (a final polishing agent in one-side polishing processing) having a composition shown in each of Examples 1 to 25 and Comparative Examples 1 to 11.

[0113] In Example 26 and Comparative Example 12, the above-described silicon wafer was subjected to one-side polishing once using a polishing liquid obtained by diluting a double-side polishing agent (a pre-polishing agent in double-side polishing processing) 30 times with pure water under Polishing Conditions 1 described in Table 2 to obtain a double-side polished silicon wafer. The silicon wafer was then rinsed once. The double-side polished silicon wafer was subjected to one-side polishing under Polishing Conditions 3 described in Table 2 using a polishing liquid obtained by diluting a single-side polishing agent (a final polishing agent in single-side polishing processing 1) having a composition each shown in Example 26 and Comparative Example 12 20 times with pure water.Subsequently, the silicon wafer was subjected to one-side polishing under polishing conditions 3 described in Table 2 using a polishing liquid obtained by diluting a one-side polishing agent (a final polishing agent in one-side polishing processing 2) with pure water 20 times.

[0114] The rinsing agent used for rinsing contains 0.01 mass % hydroxyethylcellulose, 0.0005 mass % ammonia, and ion exchange water. Rinsing was performed under conditions where the polishing agent from polishing conditions 1 was replaced with the rinsing agent.

[0115] Components other than those described in Table 1 are described below. <Mittel zum doppelseitigen Polieren>

[0116] As a basic compound, 1.5 parts by mass of tetramethylammonium hydroxide (TMAH) and 1.0 parts by mass of potassium carbonate (K2CO3) were added (to accelerate polishing and buffer pH). As a chelating agent (to capture metal contaminants), 0.1 parts by mass of ethylenediaminetetramethylenephosphonic acid (EDTPO) was added. The remainder was water. <Mittel zum einseitigen Polieren>

[0117] 0.2 mass fractions of ammonia in % were used as the basic compound. <Die Anzahl von LLS>

[0118] The number of LLS (Localized Light Scatters) in Table 1 was measured using a Surfscan SP2 wafer inspection device manufactured by KLA-Tencor Corporation. "○" in "Number of LLS (37 nm or more)" in Table 1 indicates the number of LLS of 20 or less, "○" indicates 21 to 50, "Δ" indicates 51 to 100, and "X" indicates 101 or more. <Trübung (relativer Wert)>

[0119] The "Haze (Relative Value)" column in Table 1 presents results obtained by measuring the haze level after double-side polishing and single-side polishing on the surface of the silicon wafer. Specifically, the haze level was measured using a "Surfscan SP2" wafer inspection device manufactured by KLA-Tencor Corporation and expressed as a numerical value in DNO (Dark Narrow Oblique) mode (unit: ppb). <Laser-Markierungshöhe>

[0120] Laser mark height is a parameter that indicates a maximum section height of a roughness curve using an HRP340 manufactured by KLA-Tencor Corporation and indicates a difference in the height of a surface of a silicon wafer between the highest part and the lowest part in a fixed measurement field (1 mm x 5 mm).

[0121] "O", shown in "Laser Marking Height" in Table 1, indicates the laser marking height of 30 nm or less, O indicates the laser marking height of 31 to 50 nm, Δ indicates the laser marking height of 51 to 70 nm, and X indicates the laser marking height of 71 nm or more. <esfqr>

[0122] An average value of ESFQRs obtained by performing a measurement under the conditions of a site length of 35 mm and an edge exclusion area of ​​1 mm (a total of 72 sites) using a wafer flatness measuring device "Wafer Sight 2" manufactured by KLA-Tencor Corporation is presented.

[0123] ⊙, represented in "ESFQR" in Table 1, indicates 50 nm or less, ○ indicates 51 to 70 nm, Δ indicates 71 to 100 nm, and X indicates 101 nm or more. <Mindestpolierbetrag bei einer einseitigen Polierbearbeitung, bei der LLS als ⊙ bewertet werden>

[0124] The minimum polishing amount in a one-side polishing processing in which LLS were evaluated as ⊙ was calculated by measuring the minimum polishing amount until the number of LLS reached 20 or less in the measurement of the number of LLS described above.

[0125] The results are presented in Table 1. For Comparative Examples 3 to 5 and 11, regardless of how hard the surface was polished, it was not possible to reduce the number of LLS to 20 or less. [Table 2] Polishing condition 1 Polishing device Double-sided polishing machine (DSM20B-5P-4D; manufactured by SpeedFam Company Limited) Burden 15 kPa relative speed of the upper plate 20 / min relative speed of the lower plate 20 / min polishing pad MH-S15A (manufactured by Nitta Haas Incorporated) Feed speed of the polishing agent 4 l per minute Polishing time 30 to 50 minutes (depending on the amount of polishing) Polishing amount 15 µm Holding temperature of the polishing agent 23 °C [Table 3] Polishing condition 3 Polishing device Single-side polishing jig (PNX-332B; manufactured by Okamoto Machine Tool Works, Ltd.) Burden 15 kPa Rotational speed of the plate 30 / min Speed ​​of the object to be polished 30 / min polishing pad POLYPAS 27NX (manufactured by Fujibo Holdings, Inc.) Feed speed of the polishing agent 1 liter per minute Polishing time 8 minutes Polishing amount 0.25 µm or more Holding temperature of the polishing agent 20 °C <Erörterung>

[0126] In Examples 1 to 26, it is generally possible to exceptionally reduce the degree of haze and significantly reduce defects. Furthermore, it is possible to lower the laser marking height and improve a numerical value of the ESFQR, which indicates the local flatness of a wafer edge portion.

[0127] In contrast, in Comparative Examples 1 and 2, the double-sided polishing agent does not contain a nitrogen-containing water-soluble polymer, and therefore the number of LLS is very large. This means that it is not possible to significantly reduce the degree of haze and defects.

[0128] In Comparative Examples 3 to 5 and 11, both the haze level and the number of LLS are very poor. This is because the requirement that the average primary particle diameter of the second abrasive grains be 40 nm or less is not met.

[0129] In Comparative Example 6, no nitrogen-containing water-soluble polymer is added, but HEC is used, which has a high ability to impart wettability to a polished surface and excellent cleaning performance, and therefore the results are relatively good. However, the number of LLS is larger than that in Example 3, in which the conditions are the same except for this point. From this point of view, it can be said that it is not possible to reduce the degree of haze and significantly reduce defects. Similarly, in Comparative Examples 7 and 12, (A) / (B) is 2.6. Therefore, the number of LLS is larger than that in Examples 10 and 26, in which the conditions are the same except for the particle diameter (B). From this point of view, it can be said that it is not possible to reduce the degree of haze and significantly reduce defects.In this regard, the upper limit for a critical point of (A) / (B) can be suggested to be 2.5 or less. Comparative Example 9 is discussed similarly.

[0130] Furthermore, Comparative Example 8 does not meet the specified (A) / (B). Therefore, the number of LLS is larger than that of Example 7, where the conditions except (A) / (B) are the same. From this perspective, it can be said that it is not possible to significantly reduce the degree of haze and defects.

[0131] Comparative Example 10 also fails to meet the specified (A) / (B). Therefore, the number of LLS is larger than that in Example 1, where the conditions except for (A) / (B) are the same. From this perspective, it can be said that it is not possible to significantly reduce the haze level and defects. In this regard, a lower limit of more than 1 for a critical point of (A) / (B) can be suggested.

[0132] This patent application is based on Japanese Patent Application No. 2013-166.142, filed on August 9, 2013. List of reference symbols 11 Device for one-sided polishing 14 polishing pads 12 turntables 13a Arrow 13 first wave 15 wafer holder 16 second wave 16a Arrow 17 ceramic plate 18 Wafer holding opening 19 Wafer holding plate 21 Polishing agent feed device 21a Mouth 22 Device for double-sided polishing 23 lower plate 24 upper plate 25 processing carriers 26 Polishing agent feed chute< / esfqr>

Claims

[1] A method of producing a polished object, comprising: a double-sided polishing step in which an object to be polished is subjected to double-sided polishing using a double-sided polishing agent containing first abrasive grains having an average primary particle diameter of 40 nm or more and a nitrogen-containing, water-soluble polymer, so that a double-sided polished object is obtained; and a one-side polishing step in which the double-sided polished object is subjected to one-side polishing using a one-side polishing agent containing second abrasive grains having an average primary particle diameter of 40 nm or less and a water-soluble polymer, wherein a ratio of an average primary particle diameter (A) of the first abrasive grains with respect to an average primary particle diameter (B) of the second abrasive grains (A) / (B) is more than 1 and 2.5 or less, and wherein the concentration of the water-soluble polymer in the single-side polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-side polishing agent. [2] A method for producing a polished object according to claim 1, wherein (A) / (B) is 1.6 or more and less than 2.

3. [3] A method for producing a polished object according to claim 1 or 2, wherein the nitrogen-containing water-soluble polymer has one or more nitrogen atoms in a monomer unit or one or more nitrogen atoms in a part of a side chain. [4] A method for producing a polished object according to any one of claims 1 to 3, wherein the nitrogen-containing water-soluble polymer is selected from the group consisting of polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, poly-N-vinylformamide, polyvinylcaprolactam and polyvinylpiperidine. [5] A method for producing a polished object according to any one of claims 1 to 4, wherein the one-sided polishing step is carried out several times, and a water-soluble polymer used in the final one-side polishing step includes at least one selected from a polymer containing an oxyalkylene unit, a nitrogen-containing water-soluble polymer, polyvinyl alcohol, and a cellulose derivative. [6] A method for producing a polished object according to any one of claims 1 to 5, wherein the object to be polished is a semiconductor wafer. [7] A method of manufacturing a polished object according to claim 6, wherein the semiconductor is silicon. [8] A double-side polishing agent used in the method for producing a polished object according to any one of claims 1 to 7, wherein the double-side polishing agent includes abrasive grains having an average primary particle diameter of 40 nm or more and a nitrogen-containing water-soluble polymer. [9] A one-side polishing agent used in the method for producing a polished object according to any one of claims 1 to 7, wherein the one-side polishing agent includes abrasive grains having an average primary particle diameter of 40 nm or less and a water-soluble polymer. [10] Polishing kit including: first abrasive grains having an average primary particle diameter of 40 nm or more used in double-side polishing; a nitrogen-containing, water-soluble polymer used in double-sided polishing; second abrasive grains having an average primary particle diameter of 40 nm or less, used in single-side polishing; and a water-soluble polymer used in one-sided polishing, where a ratio of an average primary particle diameter (A) of the first abrasive grains with respect to an average primary particle diameter (B) of the second abrasive grains (A) / (B) is more than 1 and 2.5 or less, and wherein the concentration of the water-soluble polymer in the single-side polishing agent is higher than that of the nitrogen-containing water-soluble polymer in the double-side polishing agent.

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