Surface treatment method, method for manufacturing a semiconductor substrate including the surface treatment method, surface treatment composition, and semiconductor substrate manufacturing system including the surface treatment composition.

Abstract

To provide means enabling sufficient removal of residue which is present on a surface of a polished polishing target object including silicon nitride and includes inorganic oxide abrasive grains.SOLUTION: A surface treatment method is provided, in which residues including inorganic oxide abrasive grains which is present on a surface of a polished polishing target object including silicon nitride and includes inorganic oxide abrasive grains, is reduced using a surface treatment composition. The surface treatment composition includes: a zeta potential adjusting agent which has a negatively charged functional group and whose water solution with a concentration of 20 mass% at 25°C is equal to or more than 10 mPa s; and a dispersion media. The surface treatment method includes controlling a zeta potential of the silicon nitride and a zeta potential of the inorganic oxide abrasive grains to be equal to or less than -30 mV by using the surface treatment composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a surface treatment method, a method for manufacturing a semiconductor substrate including the surface treatment method, a surface treatment composition, and a semiconductor substrate manufacturing system including the surface treatment composition.

Background Art

[0002] In recent years, with the multi-layer wiring of the semiconductor substrate surface, when manufacturing devices, a so-called Chemical Mechanical Polishing (CMP) technique for polishing and planarizing the semiconductor substrate is used. CMP is, for example, a method of planarizing the surface of an object to be polished (workpiece), such as a semiconductor substrate, using a polishing composition (slurry) containing abrasive grains selected from silica, alumina, ceria, etc., additives selected from corrosion inhibitors and surfactants, etc. Examples of the object to be polished (workpiece) include films made of silicon, polysilicon, silicon oxide, silicon nitride, etc., substrates made of these, wirings made of metal, and members such as plugs.

[0003] A large amount of impurities (also referred to as foreign substances or residues) remain on the surface of the semiconductor substrate after the CMP process. Examples of impurities include abrasive grains derived from the polishing composition used in CMP, corrosion inhibitors derived from the polishing composition used in CMP, organic substances such as surfactants, silicon-containing materials generated by polishing silicon-containing materials that are the objects to be polished, metals generated by polishing metal wirings and plugs that are the objects to be polished, and organic substances such as pad debris generated from various pads.

[0004] When the surface of the semiconductor substrate is contaminated by these impurities, the electrical characteristics of the semiconductor are adversely affected, and the reliability of the device may decrease. Therefore, it is desirable to introduce a surface treatment process after the CMP process to remove these impurities from the surface of the semiconductor substrate.

[0005] As a composition used in such a cleaning process, Patent Document 1 discloses a semiconductor device substrate cleaning solution containing a polycarboxylic acid or hydroxycarboxylic acid, a sulfonic acid-type anionic surfactant, a carboxylic acid-type anionic surfactant, and water. This cleaning solution is said to be able to remove impurities without corroding the substrate surface. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-74678 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, the technology described in Patent Document 1 had the problem that it could not adequately remove residue when cleaning the polished object.

[0008] Here, the inventors investigated the relationship between the type of polished object and the type of residue. As a result, the inventors found that inorganic oxide abrasive particles contained in the polishing composition used during polishing tend to adhere as residue to the surface of polished objects containing silicon nitride, which is particularly preferred as a semiconductor substrate. Such residue containing inorganic oxide abrasive particles can cause a decrease in the performance of semiconductor devices.

[0009] The present invention has been made in view of the above problems, and relates to polished objects containing silicon nitride. The objective is to provide a means that can sufficiently remove residue containing inorganic oxide abrasive particles present on the surface. [Means for solving the problem]

[0010] In view of the above problems, the inventors diligently conducted research. As a result, the inventors discovered that a surface treatment composition comprising a compound having a specific functional group and an aqueous solution viscosity above a specific value, and a dispersion medium, can control the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive particles to below a specific value, and that in this case, the effect of removing residue containing inorganic oxide abrasive particles from the surface of a polished object containing silicon nitride is improved, thus completing the present invention.

[0011] One embodiment of the present invention for solving the above problems is: A surface treatment method for reducing residue containing inorganic oxide abrasive particles on the surface of a polished object containing silicon nitride, using a surface treatment composition, The surface treatment composition comprises a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. The present invention relates to a surface treatment method that includes controlling the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30mV or less, respectively, using the surface treatment composition.

[0012] Another aspect of the present invention for solving the above problems is: A surface treatment composition used to reduce residue containing inorganic oxide abrasive particles on the surface of a polished object containing silicon nitride, The material comprises a zeta potential adjusting agent having a negatively charged functional group and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. This invention relates to a surface treatment composition having the function of controlling the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30mV or less. [Effects of the Invention]

[0013] The present invention provides a means for thoroughly removing residue containing inorganic oxide abrasive particles present on the surface of a polished object containing silicon nitride. [Modes for carrying out the invention]

[0014] The embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Unless otherwise specified in this specification, operations and measurements of physical properties, etc., will be performed under conditions of room temperature (20°C to 25°C) and relative humidity of 40%RH to 50%RH. In this specification, "inorganic oxide abrasive grains" contained in the polishing composition may also be simply referred to as "abrasive grains". Furthermore, the object to be polished after polishing may also be simply referred to as the "polished object".

[0015] <Surface treatment method and surface treatment composition> One aspect of the present invention relates to a surface treatment method for reducing residue containing inorganic oxide abrasive particles on the surface of a polished object containing silicon nitride using a surface treatment composition, wherein the surface treatment composition comprises a zeta potential adjusting agent having negatively charged functional groups and a viscosity of 10 mPa·s or more when an aqueous solution of 20% by mass at 25°C is used, and a dispersion medium, and the surface treatment method comprises controlling the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive particles to -30 mV or less, respectively, using the surface treatment composition.

[0016] The method for controlling the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains to -30mV or less using a surface treatment composition is not particularly limited, but it is preferable to bring a surface treatment composition containing a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10mPa·s or more in an aqueous solution of 20% by mass at 25°C, and a dispersion medium into contact with the surface of a polished object containing silicon nitride.

[0017] From these facts, another aspect of the present invention is a surface treatment composition used for reducing residues containing inorganic oxide abrasive grains on the surface of a polished object containing silicon nitride, the surface treatment composition having a negatively charged functional group and a zeta potential adjuster having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium, and having a function of controlling the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains to -30 mV or less, respectively.

[0018] According to the present invention, there is provided a means capable of sufficiently removing residues containing inorganic oxide abrasive grains present on the surface of a polished object containing silicon nitride.

[0019] The above surface treatment method is characterized by the relationship between the surface treatment composition and the polished object to be surface-treated (i.e., the object to be surface-treated) using the surface treatment composition. Specifically, the above surface treatment method has found that the relationship between the surface treatment composition, the components of the polished object, and the components of the polishing composition used to polish the polished object (more specifically, the components of the polishing composition adhering to the surface of the polished object as residues: abrasive grains) affects the reduction of residues on the surface of the polished object. As will be described later, this is because the above surface treatment method is based on the charge (zeta potential) on the surface of the polished object and the charge (zeta potential) of the components (abrasive grains) of the polishing composition present as residues on the surface of the polished object, and it is considered that the effects of the present invention are manifested.

[0020] Some components of the polishing composition tend to adhere to the surface of the polished object to be polished and remain on the surface of the polished object after the polishing process. In particular, the inorganic oxide abrasive grains contained in the polishing composition tend to remain on the surface of the polished object to be polished. In this case, the inorganic oxide abrasive grains remaining on the surface of the polished object to be polished may cause residues. The above surface treatment method and the above surface treatment composition can remove residues (i.e., inorganic oxide abrasive grains) derived from the polishing composition remaining on the surface of such a polished object to be polished.

[0021] The inventors of the present invention presume the mechanism for solving the above problems as follows.

[0022] The zeta potential modifier contained in the surface treatment composition has negatively charged functional groups, and the viscosity of a 20% by mass aqueous solution at 25°C is 10 mPa·s or higher. The zeta potential modifier contained in the surface treatment composition has negatively charged functional groups. The zeta potential modifier electrostatically adheres to the surface of the residue (residue containing inorganic oxide abrasive grains) present on the surface of the polished workpiece, and to the surface of the polished workpiece containing silicon nitride, causing these surfaces to become negatively charged. Then, electrical repulsion occurs between the negatively charged residue and the negatively charged surface of the polished workpiece containing silicon nitride. As a result, the negatively charged residue is removed from the surface of the polished workpiece containing negatively charged silicon nitride. In addition, the negatively charged residue becomes less likely to reattach to the surface of the polished workpiece containing negatively charged silicon nitride. Furthermore, the zeta potential modifier contained in the surface treatment composition has a viscosity of 10 mPa·s or higher when used as an aqueous solution at 20% by mass at 25°C. Within this range, when the zeta potential adjusting agent electrostatically adheres to the surface of the residue (residue containing inorganic oxide abrasive particles) present on the surface of the polished workpiece, and to the surface of the polished workpiece containing silicon nitride, the protective film effect of the zeta potential adjusting agent is further enhanced. As a result, the negative charge on the surface of the residue and the polished workpiece containing silicon nitride is maintained for a longer period, making it easier to remove the residue. In addition, the hydrophilization of the surface of the residue and the polished workpiece containing silicon nitride is further promoted, making it easier for the residue to disperse in the surface treatment composition, and thus making it easier to remove the residue. In this way, the chemical interaction between each component contained in the surface treatment composition and the surface of the polished workpiece and the residue on the surface of the polished workpiece makes it easier to remove the residue from the surface of the polished workpiece, and the residue on the surface of the polished workpiece is removed more effectively.

[0023] It should be noted that the above mechanism is based on speculation, and its accuracy does not affect the technical scope of the present invention.

[0024] [Residue] In this specification, "residue" refers to foreign matter adhering to the surface of a polished object. While not particularly limited, examples of residue include particulate abrasive residue derived from abrasive particles contained in the polishing composition, organic residue (described later), and other foreign matter.

[0025] In this specification, organic residue refers to components consisting of organic substances such as low-molecular-weight organic compounds and high-molecular-weight organic compounds, or organic salts, among the foreign matter adhering to the surface of a polished object. Organic residue adhering to a polished object is not particularly limited, but examples include pad debris (e.g., polyurethane) generated from pads used in the polishing or surface treatment described later, components derived from additives contained in the polishing composition used in the polishing treatment, and components derived from additives contained in the surface treatment composition used in the surface treatment.

[0026] The total residue count refers to the total number of all residues, regardless of type. The total residue count is used in wafer defect detection. The measurement can be performed using an inspection device (for example, the Surfscan® SP5 optical inspection machine manufactured by KLA-Tencor Co., Ltd.). Details of the method for measuring the total residue count will be described in the examples below.

[0027] Furthermore, since abrasive residues, organic residues (e.g., polyurethane residues), and other foreign matter differ significantly in color and shape, it is possible to determine whether a foreign matter is abrasive residue, organic residue (e.g., polyurethane residue), or other foreign matter by SEM observation. Similarly, since polyurethane residues and other organic residues differ significantly in color and shape, it is possible to determine whether an organic residue is polyurethane residue or other organic residue by SEM observation. In addition, the determination of whether a foreign matter is abrasive residue, organic residue, or other foreign matter, the type of abrasive residue, and the type of organic residue may be determined by elemental analysis using an energy-dispersive X-ray analyzer (EDX), as needed. Details of the measurement methods for the number of abrasive residues and polyurethane residues are described in the examples below.

[0028] In the surface treatment method according to the above embodiment, the zeta potential of the residue on the surface of the polished workpiece can be controlled by the surface treatment composition. Specifically, the zeta potential of the inorganic oxide abrasive grains contained in the residue is controlled to -30mV or less. The surface treatment composition according to the above embodiment has the function of controlling the zeta potential of the residue on the surface of the polished workpiece. Specifically, the surface treatment composition according to the above embodiment has the function of controlling the zeta potential of the inorganic oxide abrasive grains contained in the residue to -30mV or less. In this specification, inorganic oxide abrasive grains mean inorganic oxides used as abrasive grains in the polishing composition. Therefore, if the residue contains inorganic oxide abrasive grains, the inorganic oxide abrasive grains become abrasive residue. Preferred examples of inorganic oxide abrasive grains contained in the residue are not particularly limited, but include cerium oxide abrasive grains, anion-modified silicon oxide abrasive grains, etc., which are preferred abrasive grains in the polishing composition described later. According to a surface treatment method of a preferred embodiment of the present invention, the inorganic oxide abrasive grains include at least one of cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains, and the surface treatment composition controls the zeta potential of at least one of the cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains to -30mV or less. According to a surface treatment method of a more preferred embodiment of the present invention, the inorganic oxide abrasive grains include cerium oxide abrasive grains, and the surface treatment composition controls the zeta potential of the cerium oxide abrasive grains to -30mV or less. In its application, the surface treatment composition of a preferred embodiment of the present invention includes at least one of cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains, and the surface treatment composition has the function of controlling the zeta potential of at least one of the cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains to -30mV or less. In its application, the surface treatment composition of a more preferred embodiment of the present invention includes cerium oxide abrasive grains, and the surface treatment composition has the function of controlling the zeta potential of the cerium oxide abrasive grains to -30mV or less.

[0029] When the residue contains polyurethane, it is preferable that the zeta potential of the polyurethane contained in the residue be controlled to -10mV or less. In a surface treatment method according to a preferred embodiment of the present invention, the residue further contains polyurethane, and the surface treatment method further includes controlling the zeta potential of the polyurethane to -10mV or less by the surface treatment composition. In a surface treatment composition according to a preferred embodiment of the present invention, in its application, the residue further contains polyurethane, and the surface treatment composition further has the function of controlling the zeta potential of the polyurethane to -10mV or less.

[0030] The zeta potential of the inorganic oxide abrasive grains contained in the residue (preferably at least one of cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains, more preferably cerium oxide abrasive grains) is preferably -65mV or higher, more preferably -60mV or higher, even more preferably -55mV or higher, and particularly preferably -50mV or higher. The zeta potential of the inorganic oxide abrasive grains contained in the residue (preferably at least one of cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains, more preferably cerium oxide abrasive grains) is preferably -31mV or lower, more preferably -33mV or lower, even more preferably -35mV or lower, particularly preferably -37mV or lower, and most preferably -39mV or lower. By controlling the zeta potential of the inorganic oxide abrasive grains to a value within the above range, the effect of removing residue containing inorganic oxide abrasive grains present on the surface of the polished object containing silicon nitride is further enhanced. The surface treatment composition has the function of controlling the zeta potential of inorganic oxide abrasive grains to a value within the above range, thereby exhibiting a greater effect in removing residues containing inorganic oxide abrasive grains present on the surface of polished objects containing silicon nitride.

[0031] The zeta potential of polyurethane contained in the residue is preferably -65mV or higher, more preferably -55mV or higher, even more preferably -50mV or higher, and particularly preferably -45mV or higher. The zeta potential of polyurethane contained in the residue is preferably -30mV or lower, more preferably -35mV or lower, even more preferably -40mV or lower, and particularly preferably -43mV or lower. By controlling the zeta potential of polyurethane to a value within the above range, the effect of removing polyurethane-containing residue present on the surface of polished objects containing silicon nitride is further enhanced. The surface treatment composition has the function of controlling the zeta potential of polyurethane to a value within the above range, thereby further enhancing the effect of removing polyurethane-containing residue present on the surface of polished objects containing silicon nitride.

[0032] The zeta potential of inorganic oxide abrasive grains contained in the residue can be measured using the Zetasizer Nano ZSP manufactured by Spectris Corporation (Malvern Division). The zeta potential of polyurethane contained in the residue can be measured using the solid zeta potential measuring instrument SurPASS3 manufactured by Anton Paar Japan Co., Ltd. Details of the measurement methods are described in the examples.

[0033] The zeta potentials of inorganic oxide abrasive particles and polyurethane contained in the residue can be controlled, for example, by the type and amount of zeta potential modifier and the pH of the surface treatment composition, respectively. By increasing the negative charge of the zeta potential modifier in its presence in the surface treatment composition, the zeta potentials of the inorganic oxide residue and polyurethane can be lowered, respectively. For example, by selecting a compound having an anionic group as the zeta potential modifier, or by selecting an acid (salt) group as the anionic group, or by selecting a specific acid (salt) group as described later, the zeta potentials of the inorganic oxide residue and polyurethane can be lowered further, respectively. By moderately lowering the pH to a range that is not too low, the zeta potentials of the inorganic oxide residue and polyurethane can be lowered further, respectively. By increasing the amount of zeta potential modifier in the surface treatment composition, the zeta potential lowering effect of the zeta potential modifier can be further enhanced.

[0034] [Polished objects] In this specification, "polished object" refers to an object that has been polished in a polishing process. The polishing process is not particularly limited, but a CMP process is preferred.

[0035] The surface treatment composition used in the surface treatment method according to the above embodiment, and the surface treatment composition according to the above embodiment, are each used to reduce residue remaining on the surface of a polished object containing silicon nitride.

[0036] The polished object to be polished is preferably a polished semiconductor substrate, and more preferably a semiconductor substrate after CMP (Chemical Polishing). This is because residue can cause damage to semiconductor devices. Therefore, when the polished object to be polished is a polished semiconductor substrate, the cleaning process for the semiconductor substrate must be such that it can remove as much residue as possible.

[0037] There are no particular limitations on polished objects containing silicon nitride, but examples include polished objects consisting solely of silicon nitride, and polished objects in which silicon nitride and materials other than silicon nitride are exposed on the surface. A specific example of the former is a polished silicon nitride substrate, which is a semiconductor substrate. Regarding the latter, examples of materials other than silicon nitride include silicon-containing materials other than silicon nitride such as silicon oxide and polysilicon, metals such as tungsten, alloys, and metal nitrides. A specific example of the latter is a polished semiconductor substrate having a structure in which a silicon nitride portion and a portion consisting of at least one selected from the group consisting of silicon nitride, polysilicon, and tungsten are exposed.

[0038] The surface treatment method according to the above embodiment can control the zeta potential of silicon nitride contained in the polished object using the surface treatment composition. Specifically, the zeta potential of silicon nitride is controlled to -30mV or less. The surface treatment composition according to the above embodiment has the function of controlling the zeta potential of silicon nitride contained in the polished object. Specifically, the surface treatment composition according to the above embodiment has the function of controlling the zeta potential of silicon nitride to -30mV or less.

[0039] The zeta potential of silicon nitride is preferably -65mV or higher, more preferably -60mV or higher, even more preferably -55mV or higher, and particularly preferably -50mV or higher. The zeta potential of silicon nitride is preferably -35mV or lower, more preferably -40mV or lower, even more preferably -45mV or lower, and particularly preferably -46mV or lower. When the zeta potential of silicon nitride is within the above range, the effect of removing residues containing inorganic oxide abrasive grains present on the surface of polished objects containing silicon nitride is more effectively achieved.

[0040] The zeta potential of silicon nitride can be measured using the SurPASS3 solid-state zeta potential meter manufactured by Anton Paar Japan Co., Ltd. Details of the measurement method are described in the examples.

[0041] The zeta potential of silicon nitride can be controlled, for example, by the type and amount of zeta potential modifier and the pH of the surface treatment composition. The zeta potential of silicon nitride can be lowered by increasing the negative charge of the zeta potential modifier in its presence within the surface treatment composition. For example, the zeta potential of silicon nitride can be further lowered by selecting a compound having an anionic group as the zeta potential modifier, or by selecting an acid (salt) group as the anionic group, or by selecting a specific acid (salt) group as described later. Furthermore, the zeta potential of silicon nitride can be further lowered by moderately lowering the pH to a range that is not too low. Finally, the zeta potential lowering effect of the zeta potential modifier can be further enhanced by increasing the amount of zeta potential modifier in the surface treatment composition.

[0042] [Surface treatment composition] The surface treatment composition used in the surface treatment method according to the above embodiment comprises a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more when an aqueous solution with a concentration of 20% by mass is used at 25°C, and a dispersion medium, and the surface treatment method according to the above embodiment includes controlling the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains to -30 mV or less, respectively, using the surface treatment composition.

[0043] The surface treatment composition according to the above embodiment includes a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more for an aqueous solution with a concentration of 20% by mass at 25°C, and It contains a dispersion medium and has the function of controlling the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains to -30mV or less.

[0044] The surface treatment composition used in the surface treatment method according to the above embodiment, and the surface treatment composition according to the above embodiment, can control the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains to -30mV or less, respectively. The preferred ranges for the zeta potential of silicon nitride and the zeta potential of inorganic oxides are as described above. The reason why such control is possible is thought to be that the zeta potential adjusting agent contained in the surface treatment composition has a high affinity for silicon nitride and inorganic oxide abrasive grains contained in the polished workpiece, and is likely to adhere to the surface of silicon nitride and inorganic oxide abrasive grains. The zeta potential adjusting agent is thought to lead to the zeta potential of silicon nitride and the zeta potential of inorganic oxide abrasive grains being -30mV or less, respectively.

[0045] Furthermore, the surface treatment composition used in the surface treatment method according to one embodiment of the present invention, and the surface treatment composition according to one embodiment of the present invention, can also efficiently remove pad debris (e.g., polyurethane) generated from pads used in polishing or surface treatment. This pad debris may also be present as residue on the surface of the polished object. When the pad debris is polyurethane, the surface treatment composition used in the surface treatment method according to one embodiment of the present invention, and the surface treatment composition according to one embodiment of the present invention, can be efficiently removed by controlling the zeta potential of the polyurethane on the surface of the polished object. Here, it is preferable that the surface treatment composition controls the zeta potential of the polyurethane to -10mV or less. The preferred range for the zeta potential of the polyurethane is as described above.

[0046] The following describes each component included in the surface treatment composition.

[0047] [Zeta potential regulator] The surface treatment composition contains a zeta potential modifier having negatively charged functional groups and whose viscosity as a 20% by mass aqueous solution at 25°C is 10 mPa·s or higher.

[0048] The zeta potential adjusting agent is preferably a polymer. In this specification, "polymer" refers to a compound having a weight-average molecular weight of 1,000 or more. Therefore, the weight-average molecular weight of the zeta potential adjusting agent is not particularly limited, but is preferably 1,000 or more. Furthermore, the weight-average molecular weight of the zeta potential adjusting agent is more preferably 5,000 or more, even more preferably 8,000 or more, and particularly preferably 10,000 or more. Within these ranges, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. The reason for this is presumed to be as follows: Within the above ranges, the adsorption force to the substrate or residue becomes greater. Therefore, the possibility of the zeta potential adjusting agent detaching from the surface of the residue (residue containing inorganic oxide abrasive particles) present on the surface of the polished object, and from the surface of the polished object containing silicon nitride, is further reduced. This makes it possible to control the zeta potential more reliably. The weight-average molecular weight of the zeta potential adjusting agent is preferably 1,000,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, and particularly preferably 35,000 or less. Within these ranges, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. The reason for this is presumed to be as follows: Within the above ranges, the molecular weight of the zeta potential adjusting agent is of an appropriate value, so the amount of zeta potential adjusting agent adsorbed onto the substrate or residue becomes more appropriate, and the possibility of the zeta potential adjusting agent itself becoming residue is further reduced.

[0049] The weight-average molecular weight of the zeta potential modifier is determined by gel permeation chromatography ( It can be measured as a value equivalent to polyethylene glycol using GPC (Gross Procurement).

[0050] The negatively charged functional group of the zeta potential adjusting agent is not particularly limited, but it is preferably an anionic group. Examples of anionic groups include functional groups in which a counterion dissociates to become an anion. Acid (salt) groups are preferred as anionic groups, and sulfonic acid (salt) groups, sulfuric acid (salt) groups, phosphonic acid (salt) groups, phosphoric acid (salt) groups, carboxylic acid (salt) groups, etc., are more preferred. When the negatively charged functional group is one of these groups, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of a polished object containing silicon nitride is further improved. The reason for this is presumed to be as follows: In the acidic region, the zeta potential of silicon nitride is positive, and the zeta potential of polymers having anionic groups is negative. Therefore, silicon nitride on the surface of a polished object and polymers having anionic groups are electrically attracted to each other, and adsorption is further promoted.

[0051] In this specification, a sulfonic acid group is a sulfo group, a sulfate group is a group represented by -OSO3H, a phosphonic acid group is a phospho group, a phosphate group is a group represented by -OPO3H2, and a carboxylic acid group is a carboxyl group. Note that the phosphonic acid base and phosphate base may be acidic bases with one H remaining.

[0052] Based on these considerations, the zeta potential modifier is preferably a polymer having an anionic group and a weight-average molecular weight of 1,000 or more. More preferably, the zeta potential modifier is a polymer having an acid (salt) group and a weight-average molecular weight of 1,000 or more. Even more preferably, the zeta potential modifier is a polymer having at least one functional group selected from the group consisting of a sulfonic acid (salt) group, a sulfuric acid (salt) group, a phosphonic acid (salt) group, a phosphoric acid (salt) group, and a carboxylic acid (salt) group, and a weight-average molecular weight of 1,000 or more. The preferred weight-average molecular weights for these polymers are as described above.

[0053] Among these, the zeta potential modifier is more preferably a polymer having at least one of a sulfonic acid (salt) group and a phosphonic acid (salt) group, and even more preferably a polymer having a sulfonic acid (salt) group. Furthermore, the zeta potential modifier is particularly preferably a polymer having at least one of a hydroxyl group and a carboxylic acid (salt) group and a sulfonic acid (salt) group, and most preferably a polymer having a carboxylic acid (salt) group and a sulfonic acid (salt) group.

[0054] In this specification, "acid (salt)" means that the compound of interest may be in the form of an acid or a salt. In this specification, "acid (salt) group" means that the group of interest may be in the form of an acid or a salt. When the acid is in the form of a salt, and when the acid group is in the form of a salt, the salt is not particularly limited, but examples include alkali metal salts such as lithium salts, sodium salts, and potassium salts, salts of group 2 elements such as calcium salts, amine salts, and ammonium salts. Among these, alkali metal salts are preferred, and sodium salts are more preferred. The type of salt may be a single type or a combination of two or more types.

[0055] (Polymers containing sulfonic acid (salt) groups) Polymers having anionic groups, such as polymers having sulfonic acid (salt) groups, are not particularly limited.

[0056] Examples of polymers having sulfonic acid (salt) groups include polymers obtained by sulfonating a base polymer compound, salts thereof, and polymers obtained by (co)polymerizing one or more monomers containing sulfonic acid (salt) group monomers.

[0057] Examples of monomers containing sulfonic acid (salt) groups are not particularly limited, but include styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, 3-alyloxy-2-hydroxypropanesulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)acrylate, 2-hydroxysulfopropyl (meth)acrylate, sulfoethylmaleimide, and their salts. These can be used individually or in combination of two or more. Examples of salt types are as described above.

[0058] A polymer obtained by (co)polymerizing one or more monomers containing a sulfonic acid (salt) group may contain other constituent units. These other constituent units may be introduced by copolymerizing monomers other than the sulfonic acid (salt) group monomer (sulfonic acid (salt) group-containing monomer), or they may be introduced by retaining functional groups that were not converted to sulfonic acid (salt) groups during the introduction of the sulfonic acid (salt) group.

[0059] Other examples of constituent units include vinyl alcohol units (structural parts represented by -CH2-CH(OH)-; hereinafter also referred to as "VA units"). Another example of a constituent unit is a non-vinyl alcohol unit (structural units derived from monomers other than vinyl alcohol; hereinafter also referred to as "non-VA units"). Furthermore, the monomer copolymerizable with the sulfonic acid (salt) group-containing monomer constituting the non-VA unit is not particularly limited, but is preferably an ethylenically unsaturated monomer. Ethylene-unsaturated monomers are not particularly limited, but examples include unsaturated carboxylic acid esters, unsaturated amides, unsaturated amines, aromatic mono- or divinyl compounds, etc. Unsaturated carboxylic acid esters are not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, ethylhexyl (meth)acrylate, etc. The unsaturated amide is not particularly limited, but examples include (meth)acrylamide, N-methylol(meth)acrylamide, and diacetone(meth)acrylamide. The unsaturated amine is not particularly limited, but examples include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, and N,N,N-trimethylaminoethyl(meth)acrylate. The aromatic mono- or divinyl compound is not particularly limited, but examples include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. These can be used individually or in combination of two or more.

[0060] Furthermore, examples of monomers copolymerizable with sulfonic acid (salt) group-containing monomers include monomers having other acid (salt) groups, such as those exemplified herein as monomers having other acid (salt) groups, which can be used individually or in combination of two or more.

[0061] The polymer having a sulfonic acid (salt) group is not particularly limited, but examples include sulfonic acid (salt) group-containing polyvinyl alcohol (sulfonic acid (salt) modified polyvinyl alcohol), sulfonic acid (salt) group-containing polystyrene, sulfonic acid (salt) group-containing polyvinyl acetate (sulfonic acid (salt) modified polyvinyl acetate), sulfonic acid (salt) group-containing polyester, a (co)polymer of a sulfonic acid (salt) group-containing (meth)acrylic acid derivative, a copolymer of a (meth)acryloyl group-containing monomer and a sulfonic acid (salt) group-containing monomer, sulfonic acid (salt) group-containing polyisoprene, and sulfonic acid (salt) group-containing allyl polymer. Among these, copolymers of sulfonic acid (salt) group-containing polyvinyl alcohol, sulfonic acid (salt) group-containing polystyrene, and (meth)acryloyl group-containing monomers with sulfonic acid (salt) group-containing monomers are preferred; (co)polymers of sulfonic acid (salt) group-containing polyvinyl alcohol, polystyrene sulfonic acid (salt), and sulfonic acid (salt) group-containing monomers with (meth)acrylic acid (salt) are more preferred; (co)polymers of sulfonic acid (salt) group-containing polyvinyl alcohol, sulfonic acid (salt) group-containing monomers with (meth)acrylic acid (salt) are even more preferred; and copolymers of sulfonic acid (salt) group-containing monomers with acrylic acid (salt) are particularly preferred.

[0062] In the description of polymers containing sulfonic acid (salt) groups, examples of salt types are as explained above.

[0063] In this specification, "(meth)acrylic" comprehensively refers to acrylic and methacrylic. Similarly, "(meth)acryloyl" comprehensively refers to acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to acrylate and methacrylate.

[0064] Furthermore, in this specification, "(co)polymerization" comprehensively refers to both homopolymerization and copolymerization. Similarly, "(co)polymer" comprehensively refers to both homopolymer and copolymer.

[0065] (Polymers containing sulfate(salt) groups) Polymers having sulfate (salt) groups as polymers having anionic groups are not particularly limited. Examples of polymers having sulfate (salt) groups include polymers having sulfate (salt) groups obtained by modifying a base polymer compound, and polymers obtained by (co)polymerizing one or more monomers including sulfate (salt) group-containing monomers.

[0066] Examples of sulfate(salt) group-containing monomers are not particularly limited, but include (meth)acrylic sulfate esters, sulfate(salt) group-containing vinyl alcohols (sulfate(salt) modified vinyl alcohols), etc. These can be used individually or in combination of two or more.

[0067] Polymers obtained by (co)polymerizing one or more monomers containing sulfate (salt) group monomers may contain other constituent units. The description of other constituent units is the same as the description of polymers having sulfonic acid (salt) groups. The monomers constituting the other constituent units are also the same as the description of polymers having sulfonic acid (salt) groups.

[0068] Examples of monomers copolymerizable with sulfate (salt) group-containing monomers include other monomers having acid (salt) groups, such as those exemplified herein, which can be used individually or in combination of two or more.

[0069] Examples of polymers having sulfate (salt) groups are not particularly limited, but include polyacrylic sulfate esters, polymethacrylic sulfate esters, and sulfate (salt) group-containing polyvinyl alcohol (sulfate (salt) modified polyvinyl alcohol).

[0070] In the description of polymers containing sulfate (salt) groups, examples of salt types are as explained above.

[0071] (Polymers containing phosphonic acid (salt) groups) Polymers having phosphonic acid (salt) groups as polymers having anionic groups are not particularly limited. Examples of polymers having phosphonic acid (salt) groups include polymers having phosphonic acid (salt) groups obtained by modifying a base polymer compound, and polymers obtained by (co)polymerizing one or more monomers containing phosphonic acid (salt) group monomers.

[0072] Examples of monomers containing a phosphone (salt) group are not particularly limited, but include vinylphosphonic acid, monovinyl phosphate, allylphosphonic acid, monoallyl phosphate, and 3-b Examples include tenylphosphonic acid, mono-3-butenyl phosphate, 4-vinyloxybutyl phosphate, phosphonoxyethyl acrylate, phosphonoxyethyl methacrylate, mono(2-hydroxy-3-vinyloxypropyl) phosphate, (1-phosphonoxymethyl-2-vinyloxyethyl) phosphate, mono(3-allyloxy-2-hydroxypropyl) phosphate, mono-2-(allyloxy-1-phosphonoxymethylethyl) phosphate, 2-hydroxy-4-vinyloxymethyl-1,3,2-dioxaphosphole, 2-hydroxy-4-allyloxymethyl-1,3,2-dioxaphosphole, and salts thereof. These can be used individually or in combination of two or more.

[0073] Polymers obtained by (co)polymerizing one or more monomers containing a phosphonic acid (salt) group may contain other constituent units. The description of other constituent units is the same as the description of polymers containing a sulfonic acid (salt) group. The monomers constituting the other constituent units are also the same as the description of polymers containing a sulfonic acid (salt) group.

[0074] Examples of monomers copolymerizable with phosphonic acid (salt) group-containing monomers include monomers having other acid (salt) groups, such as those exemplified herein as monomers having other acid (salt) groups, which can be used individually or in combination of two or more.

[0075] Examples of polymers having a phosphone (salt) group are not particularly limited, but include, for example, polyvinylphosphonic acid, polyallylphosphonic acid, phosphonoxyethyl polyacrylate, phosphonoxyethyl polymethacrylate, and salts thereof. Among these, polyvinylphosphonic acid and its salts are preferred, and polyvinylphosphonic acid is more preferred.

[0076] In the description of polymers containing a phosphonic acid (salt) group, examples of salt types are as explained above.

[0077] (Polymers containing phosphate groups) Polymers having a phosphate (salt) group as anionic polymers are not particularly limited. Examples of polymers having a phosphate (salt) group include polymers obtained by phosphorylating a base polymer compound, salts thereof, and polymers obtained by (co)polymerizing one or more monomers including a phosphate (salt) group-containing monomer.

[0078] Examples of phosphorus (salt) group-containing monomers are not particularly limited, but include (meth)acryloyloxymethyl phosphate, (meth)acryloyloxyethyl phosphate, (meth)acryloyloxypropyl phosphate, (meth)acryloyloxybutyl phosphate, (meth)acryloyloxypentyl phosphate, (meth)acryloyloxyhexyl phosphate, (meth)acryloyloxyoctyl phosphate, (meth)acryloyloxydecyl phosphate, (meth)acryloyloxylauryl phosphate, (meth)acryloyloxystearyl phosphate, (meth)acryloyloxy-1,4-dimethylcyclohexyl phosphate, and their salts. These can be used individually or in combination of two or more.

[0079] Polymers obtained by (co)polymerizing one or more monomers containing a phosphate (salt) group may contain other constituent units. The description of other constituent units is the same as the description of polymers having a sulfonic acid (salt) group. The monomers constituting the other constituent units are also the same as the description of polymers having a sulfonic acid (salt) group.

[0080] Examples of monomers copolymerizable with phosphate (salt) group-containing monomers include other monomers having acid (salt) groups, such as those exemplified herein as other monomers having acid (salt) groups, which can be used individually or in combination of two or more.

[0081] Specific examples of polymers having a phosphate (salt) group are not particularly limited, but include, for example, polyacryloyloxyalkyl phosphate, polymethacryloyloxyalkyl phosphate, polyacryloyloxy-1,4-dimethylcyclohexyl phosphate, polymethacryloyloxy-1,4-dimethylcyclohexyl phosphate, and salts thereof.

[0082] In the description of polymers containing phosphate (salt) groups, examples of salt types are as explained above.

[0083] (Polymers containing carboxylic acid (salt) groups) Polymers having carboxylic acid (salt) groups as polymers having anionic groups are not particularly limited. Examples of polymers having carboxylic acid (salt) groups include polymers obtained by carboxylating a base polymer compound, salts thereof, and polymers obtained by (co)polymerizing one or more monomers including a monomer containing a carboxylic acid (salt) group.

[0084] Examples of monomers containing carboxylic acid (salt) groups are not particularly limited, but include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and their salts. These can be used individually or in combination of two or more.

[0085] Polymers obtained by (co)polymerizing one or more monomers containing carboxylic acid (salt) group monomers may contain other constituent units. The description of other constituent units is the same as the description of polymers containing sulfonic acid (salt) group monomers. The monomers constituting other constituent units are also the same as the description of polymers containing sulfonic acid (salt) group monomers.

[0086] Examples of monomers copolymerizable with carboxylic acid (salt) group-containing monomers include monomers having other acid (salt) groups, such as those exemplified herein as monomers having other acid (salt) groups, which can be used individually or in combination of two or more.

[0087] Examples of polymers having a carboxylic acid (salt) group are not particularly limited, but include polyacrylic acid, polymethacrylic acid, copolymers of acrylic acid and methacrylic acid, and salts thereof.

[0088] In the description of polymers containing a carboxylic acid (salt) group, examples of salt types are as explained above.

[0089] Furthermore, when a polymer having the above-mentioned acid (salt) group, or a polymer having at least one functional group selected from the group consisting of the above-mentioned sulfonic acid (salt) group, sulfuric acid (salt) group, phosphonic acid (salt) group, phosphoric acid (salt) group, and carboxylic acid (salt) group, is in the form of a salt, the zeta potential adjuster may form a salt only with some of the acid groups in the molecule, or all of the acid groups in the molecule may form a salt.

[0090] Based on these considerations, preferred examples of zeta potential modifiers include copolymers of sulfonic acid (salt) group-containing monomers and acrylic acid (salt), polyvinylphosphonic acid (salt), and sulfonic acid (salt) group-containing polyvinyl alcohol. Among these, copolymers of sulfonic acid group-containing monomers and acrylic acid, sodium salts of copolymers of sulfonic acid group-containing monomers and acrylic acid, sulfonic acid group-containing polyvinyl alcohol, and sodium salts of sulfonic acid group-containing polyvinyl alcohol are preferred, copolymers of sulfonic acid group-containing monomers and acrylic acid, and their sodium salts are more preferred, and sodium salts of copolymers of sulfonic acid group-containing monomers and acrylic acid are even more preferred.

[0091] If the viscosity of a 20% by mass aqueous solution of the zeta potential adjusting agent at 25°C is less than 10 mPa·s, the removal effect of residues containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is not sufficiently obtained. This is presumed to be because, within the above range, when the zeta potential adjusting agent electrostatically adheres to the surface of the residue (residues containing inorganic oxide abrasive particles) present on the surface of the polished object, and to the surface of the polished object containing silicon nitride, the protective film function of the zeta potential adjusting agent is not sufficiently obtained. The viscosity of a 20% by mass aqueous solution at 25°C is not particularly limited as long as it is 10 mPa·s or higher, but it is preferably 15 mPa·s or lower, more preferably 12 mPa·s or lower, and even more preferably 10.5 mPa·s or lower. Within these ranges, the removal effect of residues containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. The reason for this is presumed to be as follows. Within the above range, the removal of residue (residue containing inorganic oxide abrasive grains) present on the surface of the polished workpiece, and the removal of zeta potential adjusting agent electrostatically attached to the surface of the polished workpiece containing silicon nitride, becomes easier. As a result, the possibility of the zeta potential adjusting agent itself becoming residue is reduced.

[0092] Here, the viscosity of a 20% by mass aqueous solution of the zeta potential adjusting agent at 25°C refers to the value obtained by measuring the viscosity (mPa·s) at a water temperature of 25°C using a kinematic viscometer for an aqueous solution in which the zeta potential adjusting agent is concentrated at 20% by mass relative to the total mass of the aqueous solution, obtained by mixing the zeta potential adjusting agent with water (deionized water). Details of the measurement method are described in the examples.

[0093] The zeta potential adjusting agent may be a commercially available product or a synthetic product. The manufacturing method for synthesis is not particularly limited and can be obtained by known synthesis methods. Commercial products are not particularly limited, but examples include: Toagosei Co., Ltd.'s product numbers: Aron (registered trademark) A-12SL, A-6012, A-6016A, A-6017, A-6020, A-6031; Nippon Shokubai Co., Ltd.'s product numbers: Aqualic (registered trademark) L series GL-246, GL-366, GL-386, GH-234; Fujifilm Wako Pure Chemical Industries, Ltd.'s product number: PVphos acid, 30%; and Mitsubishi Chemical Corporation's product numbers: Gosenex (registered trademark) L-3266, CKS-50, etc.

[0094] Zeta potential modifiers can be used alone or in combination of two or more types.

[0095] The content (concentration) of the zeta potential adjusting agent (total amount if there are two or more types) is not particularly limited, but is preferably 0.01 g / kg or more, more preferably 0.1 g / kg or more, even more preferably 0.5 g / kg or more, even more preferably 0.8 g / kg or more, and particularly preferably 1 g / kg or more, relative to the total mass of the surface treatment composition. Within these ranges, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. This is presumed to be because the amount of zeta potential adjusting agent is moderately high, and a higher effect can be obtained from the zeta potential adjusting agent. The content (concentration) of the zeta potential adjusting agent (total amount if there are two or more types) is not particularly limited, but is preferably 100 g / kg or less, more preferably 10 g / kg or less, even more preferably 5 g / kg or less, even more preferably 3 g / kg or less, and particularly preferably 2 g / kg or less, relative to the total mass of the surface treatment composition. Within these ranges, the removal effect of residues containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. This is presumed to be because the zeta potential adjusting agent content is moderately low, making it easier to remove the zeta potential adjusting agent itself after surface treatment.

[0096] [Dispersion medium] The surface treatment composition contains a dispersion medium (solvent) for dissolving and dispersing each component. The dispersion medium preferably contains water, and more preferably contains only water. Alternatively, the dispersion medium may be a mixed solvent of water and an organic solvent for the dispersion or dissolution of each component. Examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and glycerin; ketones such as acetone; and acetonitrile. The dispersion medium is not particularly limited, but examples include water; alcohols such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and glycerin; ketones such as acetone; acetonitrile; and mixtures thereof. Of these, water is preferred as the dispersion medium. 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. When a dispersion medium other than water is included, the water content relative to the total mass of the dispersion medium is preferably 90% by mass or more and 100% by mass or less, and more preferably 99% by mass or more and 100% by mass or less. However, it is most preferable that the dispersion medium be water only.

[0097] From the viewpoint of not inhibiting the action of the components contained in the surface treatment composition, water containing as few impurities as possible is preferred as the dispersion medium. Specifically, pure water, ultrapure water, or distilled water, which is deionized water obtained by removing impurity ions with an ion exchange resin and then removing foreign matter by passing it through a filter, is more preferred.

[0098] [pH and pH adjusters] The pH of the surface treatment composition is not particularly limited, but is preferably 1 or more and less than 7. More preferably the pH of the surface treatment composition is 1.5 or more, even more preferably 2 or more, and particularly preferably 2.5 or more. More preferably the pH of the surface treatment composition is less than 5, even more preferably 4 or less, and particularly preferably 3.5 or less. Within this range, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is further improved. The reason for this is presumed to be as follows: Within the above range, the zeta potential of silicon nitride is positive when a zeta potential adjusting agent is not used, and its absolute value becomes larger (for example, the absolute value of the zeta potential (mV) may be 40 or more and 50 or less). As a result, when a zeta potential adjusting agent is used, the zeta potential adjusting agent is more strongly adsorbed to silicon nitride on the surface of the polished object, and the surface of the polished object containing silicon nitride becomes more easily negatively charged. Therefore, a preferred example of the pH range of the surface treatment composition is 2 or more and less than 5.

[0099] The pH of the surface treatment composition can be measured, for example, using a pH meter (e.g., LAQUA, manufactured by Horiba, Ltd.).

[0100] The surface treatment composition used in the surface treatment method according to the above embodiment, and the surface treatment composition according to the above embodiment, each have a zeta potential adjusting agent and a dispersion medium as essential components. However, if it is difficult to obtain the desired pH with these alone, a pH adjusting agent (a pH adjusting agent which is a different compound from the zeta potential adjusting agent) may be added to adjust the pH, within a range that does not impede the effects of the present invention. In one embodiment of the present invention, the surface treatment composition further includes a pH adjusting agent.

[0101] A known acid, base, or salt thereof can be used as the pH adjuster.

[0102] Acids that can be used as pH adjusters are not particularly limited, but examples include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, 2-methylbutyric acid, hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, heptanoic acid, 2-methylhexanoic acid, octanoic acid, 2-ethylhexanoic acid, benzoic acid, hydroxyacetic 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, 2-hydroxyisobutyric acid, and phenoxyacetic acid. There are no particular limitations on the bases that can be used as pH adjusters, but examples include amines such as aliphatic amines and aromatic amines, ammonium solutions, organic bases such as quaternary ammonium hydroxide, alkali metal hydroxides such as potassium hydroxide, hydroxides of group 2 elements, amino acids such as histidine, and ammonia.

[0103] The surface treatment composition preferably contains an acid, more preferably an inorganic acid, and may contain at least one selected from the group consisting of sulfuric acid, nitric acid, phosphorous acid, and phosphoric acid. It is even more preferable, and particularly preferable, to contain nitric acid.

[0104] pH adjusters may be commercially available or synthetic. pH adjusters may be used alone or in combination of two or more.

[0105] The amount of pH adjusting agent added is not particularly limited and can be adjusted as appropriate so that the surface treatment composition reaches the desired pH.

[0106] [Other additives] In one embodiment of the present invention, the surface treatment composition may contain other additives in any proportion as needed, as long as they do not hinder the effects of the present invention. Other additives are not particularly limited, but examples include abrasive grains, surfactants, antifungal agents (preservatives), dissolved gases, reducing agents, oxidizing agents, alkanolamines, etc. However, in one embodiment of the present invention, components other than the essential components of the surface treatment composition may cause residue, and therefore it is desirable to avoid adding them as much as possible. Therefore, it is preferable that the amount of components other than the essential components added is as small as possible, and more preferably that they are not included at all. In particular, to further improve the foreign matter removal effect, it is preferable that the surface treatment composition substantially does not contain abrasive grains. Here, "substantially does not contain abrasive grains" means that the content (concentration) of abrasive grains (total amount if there are two or more types) relative to the entire surface treatment composition (relative to the total mass of the surface treatment composition) is 0.01% by mass or less (lower limit 0% by mass), preferably 0.005% by mass or less (lower limit 0% by mass), and more preferably 0.001% by mass or less (lower limit 0% by mass).

[0107] [Surfactants] The surface treatment composition may contain a surfactant. The surfactant that can be used when the surface treatment composition contains a surfactant is not particularly limited and may be an ionic surfactant or a nonionic surfactant.

[0108] The surfactant is not particularly limited, but may have a negatively charged functional group. When the surfactant has a negatively charged functional group, the surfactant having a negatively charged functional group refers to a compound different from the zeta potential modifier described above.

[0109] When a surface treatment composition contains a surfactant, anionic surfactants are preferred as the surfactant. Examples of anionic surfactants include compounds containing at least one functional group selected from the group consisting of sulfonic acid bases, sulfate bases, phosphonic acid bases, and phosphate bases. More specifically, examples of anionic surfactants include compounds having a sulfonic acid base, compounds having a sulfate base, compounds having a phosphonic acid base, and compounds having a phosphate base.

[0110] The surfactant is preferably a low molecular weight surfactant. A low molecular weight surfactant is a compound with a molecular weight of less than 1000. The molecular weight of the low molecular weight surfactant is more preferably 200 or more and less than 1000, even more preferably 500 or more and 980 or less, and still more preferably 800 or more and 959 or less. The molecular weight of the low molecular weight surfactant can be determined, for example, using known mass spectrometry methods such as TOF-MS or LC-MS. The weight-average molecular weight of the surfactant is preferably less than 1000, more preferably 200 or more and less than 1000, even more preferably 500 or more and 980 or less, and still more preferably 800 or more and 959 or less. The weight-average molecular weight can be measured as a value converted to polyethylene glycol using gel permeation chromatography (GPC).

[0111] Surfactants can be used alone or in combination of two or more types.

[0112] The lower limit of the surfactant content (concentration) is not particularly limited, but is preferably 0.001 g / kg or more, more preferably 0.01 g / kg or more, even more preferably 0.03 g / kg or more, particularly preferably 0.05 g / kg or more, and most preferably 0.08 g / kg or more, relative to the total mass of the surface treatment composition. The upper limit of the surfactant content (concentration) is not particularly limited, but is preferably 10 g / kg or less, more preferably 5 g / kg or less, even more preferably 1 g / kg or less, particularly preferably 0.5 g / kg or less, and most preferably 0.3 g / kg or less, relative to the total mass of the surface treatment composition. If the surface treatment composition contains two or more surfactants, the above content refers to the total amount of these surfactants.

[0113] [Anti-mold agent] The surface treatment composition may contain an antifungal agent (preservative). The antifungal agent (preservative) that can be used when the surface treatment composition contains an antifungal agent (preservative) is not particularly limited. Specific examples of antifungal agents (preservatives) include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and phenoxyethanol.

[0114] Antifungal agents (preservatives) may be used alone or in combination of two or more types.

[0115] When a surface treatment composition contains an antifungal agent (preservative), the lower limit of the antifungal agent (preservative) content (concentration) is not particularly limited, but it is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, even more preferably 0.005% by mass or more, and particularly preferably 0.01% by mass or more, based on the total mass of the surface treatment composition. Similarly, the upper limit of the antifungal agent (preservative) content (concentration) is not particularly limited, but it is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on the total mass of the surface treatment composition. In other words, the content (concentration) of the antifungal agent (preservative) in the surface treatment composition is preferably 0.0001% to 5% by mass, more preferably 0.001% to 1% by mass, even more preferably 0.005% to 0.5% by mass, and particularly preferably 0.01% to 0.1% by mass, relative to the total mass of the surface treatment composition. Within this range, a sufficient effect for inactivating or destroying microorganisms can be obtained. If the surface treatment composition contains two or more antifungal agents (preservatives), the above content refers to the total amount of these agents.

[0116] In other words, in one embodiment of the present invention, the surface treatment composition is substantially composed of a zeta potential adjusting agent, a pH adjusting agent, a dispersion medium, and at least one selected from the group consisting of a surfactant and an antifungal agent. In one embodiment of the present invention, the surface treatment composition is substantially composed of a zeta potential adjusting agent, a pH adjusting agent, water, and at least one selected from the group consisting of a surfactant, an antifungal agent, and an organic solvent. In one embodiment of the present invention, the surface treatment composition is substantially composed of a zeta potential adjusting agent, a pH adjusting agent, water, and at least one selected from the group consisting of an antifungal agent and an organic solvent. In one embodiment of the present invention, the surface treatment composition is substantially composed of a zeta potential adjusting agent, a pH adjusting agent, and water. In these embodiments, "the surface treatment composition is substantially composed of X" means that the total content (total concentration) of X is greater than 99% by mass (upper limit: 100% by mass) when the total mass of the surface treatment composition is taken as 100% by mass (relative to the total mass of the surface treatment composition). Preferably, the surface treatment composition is composed of X (total content = 100% by mass). For example, "The surface treatment composition is substantially composed of a zeta potential adjusting agent, a pH adjusting agent, water, and at least one selected from the group consisting of surfactants, antifungal agents, and organic solvents" means that the total content (total concentration) of the zeta potential adjusting agent, the pH adjusting agent, water, and at least one selected from the group consisting of surfactants, antifungal agents, and organic solvents exceeds 99% by mass (upper limit: 100% by mass) of the total mass of the surface treatment composition, with 100% by mass being the total mass of the surface treatment composition. In this case, it is preferable that the surface treatment composition is composed of a zeta potential adjusting agent, a pH adjusting agent, water, and at least one selected from the group consisting of surfactants, antifungal agents, and organic solvents (total content = 100% by mass).

[0117] [Method for manufacturing surface treatment composition] The method for producing the surface treatment composition is not particularly limited. For example, it can be produced by mixing a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C with a dispersion medium (e.g., water). That is, according to another aspect of the present invention, a method for producing the above surface treatment composition is also provided, which includes mixing a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C with a dispersion medium. The type and amount of the zeta potential adjusting agent are as described above. In the method for producing the surface treatment composition according to one embodiment of the present invention, other components other than the zeta potential adjusting agent and dispersion medium may be further mixed as needed. The types and amounts of these components are as described above.

[0118] The order and method of adding each component contained in the surface treatment composition are not particularly limited. Similarly, the mixing method is not particularly limited, and known methods can be used. The method for producing the surface treatment composition described above may further include measuring and adjusting the pH of the surface treatment composition to achieve a desired pH.

[0119] [Surface treatment] A surface treatment method according to one embodiment of the present invention is performed by directly contacting a polished object containing silicon nitride with a surface treatment composition. The surface treatment method is not particularly limited, but examples include a rinse polishing method and a washing method. Thus, a surface treatment method according to one embodiment of the present invention is a rinse polishing method or a washing method. Furthermore, a surface treatment composition according to one embodiment of the present invention is a rinse polishing composition or a washing composition. Rinse polishing and washing are performed to remove foreign matter (inorganic oxide abrasive particles, residue such as pad debris, metal contamination, etc.) from the surface of a polished object and to obtain a clean surface.

[0120] The surface treatment composition is particularly suitable for use in rinse polishing. Rinse polishing is a polishing process performed on a polishing platen with a polishing pad attached. This refers to a process of removing residue from the surface of a polished object by friction (physical action) and the action of a surface treatment composition. Specific examples of rinse polishing are not particularly limited, but include a process in which, after polishing the object (e.g., final polishing, finish polishing, etc.), the polished object is placed on the polishing platen of the polishing apparatus, and the polished object is brought into contact with a polishing pad, while the surface treatment composition is supplied to the contact area, and the polished object and the polishing pad are slid relative to each other. The rinse polishing process may be performed on the same polishing platen used for polishing the object (e.g., final polishing, finish polishing, etc.), or on a different polishing platen. Among these, it is preferable that the rinse polishing process be performed on a different polishing platen than the one used for polishing the object (e.g., final polishing, finish polishing, etc.).

[0121] Rinse polishing is performed by directly contacting a polished object containing silicon nitride with a surface treatment composition. It is believed that the silicon nitride, inorganic oxide abrasive particles, and possibly polyurethane, become negatively charged due to the adhesion of the zeta potential adjusting agent by the action of the surface treatment composition. Then, the frictional force (physical action) from the polishing pad and the action of the surface treatment composition remove the inorganic oxide abrasive particles, and possibly polyurethane, from the surface of the polished object containing silicon nitride, and prevent their re-adhesion. At this time, by utilizing friction with the polishing pad on the polishing platen (friction between the polishing pad and the residue), residues such as inorganic oxide abrasive particles and pad debris are removed more effectively. After the rinse polishing, processes such as washing with water (post-washing treatment described later) are performed, which easily removes the zeta potential adjusting agent from the surface of the silicon nitride. As a result, a polished object containing silicon nitride can be obtained with significantly reduced residues including inorganic oxide abrasive particles.

[0122] The rinse polishing process is not particularly limited, but it is preferable to use a general polishing apparatus that has a holder for holding the workpiece to be polished, a motor with adjustable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached. Either a single-sided polishing apparatus or a double-sided polishing apparatus may be used. As the polishing pad, general nonwoven fabrics, polyurethanes, and porous fluororesins can be used without particular limitation, but polyurethane is preferred from the viewpoint of further reducing residue. It is preferable that the polishing pad has grooves that allow the polishing liquid to accumulate. Furthermore, when chemical mechanical polishing and rinse polishing are performed using the same polishing apparatus, it is preferable that the polishing apparatus is equipped with a nozzle for discharging a surface treatment composition in addition to a nozzle for discharging a polishing composition.

[0123] There are no particular restrictions on the processing conditions, but for example, the pressure between the polished workpiece and the polishing pad is preferably between 0.5 psi (3.5 kPa) and 10 psi (69 kPa). The head rotation speed is 10 rpm (0.17 s). -1 ) or more 100rpm(1.7s -1 ) or less is preferable. Also, the rotation speed of the polishing platen should be 10 rpm (0.17 s). -1 ) or more 100rpm(1.7s -1 The following is preferable. There is no limit to the amount of flow supply, but it is preferable that the surface of the polished workpiece is covered with the surface treatment composition, for example, 10 mL / min to 5000 mL / min. The surface treatment time is also not particularly limited, but it is preferable to be 5 seconds to 180 seconds. Within this range, it is possible to remove foreign matter (especially residues such as inorganic oxide abrasive grains and pad debris) more effectively. The temperature of the surface treatment composition during the rinse polishing process is not particularly limited and is usually room temperature (25°C), but it may be heated to about 40°C to 70°C as long as it does not impair performance.

[0124] Surface treatment compositions are also suitably used in cleaning treatments. In this specification, cleaning treatment refers to a treatment performed when the polished object has been removed from the polishing platen, and which removes residue from the surface of the polished object mainly by the action of the surface treatment composition. Specific examples of cleaning treatment include cleaning the polished object after polishing (e.g., final polishing, finish polishing, etc.) or after a rinse polishing treatment following polishing. One method involves removing the object from the polishing platen and bringing the polished object into contact with the surface treatment composition. In the contact state between the surface treatment composition and the polished object, means of applying frictional force (physical action) to the surface of the polished object may be used.

[0125] The cleaning method is not particularly limited, but examples include immersing a polished object in a surface treatment composition and performing ultrasonic treatment as needed, or holding a polished object and bringing a cleaning brush into contact with it, while supplying the surface treatment composition to the contact area and rubbing the surface of the polished object with the brush.

[0126] The cleaning apparatus is not particularly limited, but examples include a batch-type cleaning apparatus that simultaneously surfaces multiple polished workpieces contained in a cassette, a single-wafer cleaning apparatus that surfaces a single polished workpiece mounted in a holder, and a polishing apparatus equipped with a cleaning facility that allows polished workpieces to be rubbed with a cleaning brush after being removed from the polishing platen. Here, as the polishing apparatus, a general polishing apparatus having a holder for holding polished workpieces, a motor with adjustable rotation speed, a cleaning brush, etc., can be used. The cleaning brush is not particularly limited, but examples include resin brushes such as PVA (polyvinyl alcohol) brushes.

[0127] There are no particular restrictions on the cleaning conditions; they can be set appropriately depending on the type of polished object and the type and amount of impurities to be removed.

[0128] [Post-cleaning process] In a surface treatment method according to one embodiment of the present invention, the polished workpiece may be further cleaned after the surface treatment. In this specification, this cleaning treatment is referred to as post-cleaning. Specific examples of post-cleaning are not particularly limited, but include, for example, a method of pouring water over the polished workpiece after surface treatment, a method of immersing the polished workpiece after surface treatment in water, or a method of rubbing the polished workpiece after surface treatment with a cleaning brush while pouring water over it. The method, apparatus, and conditions of the post-cleaning treatment are not particularly limited, but refer to, for example, the description of the cleaning treatment. The water used for the post-cleaning treatment is not particularly limited, but it is particularly preferable to use deionized water.

[0129] In one embodiment of the present invention, surface treatment with a surface treatment composition makes the residue extremely easy to remove. Therefore, after surface treatment with the surface treatment composition, further washing with water results in extremely effective removal of the residue.

[0130] After post-cleaning, it is preferable to dry the polished object by removing any water droplets adhering to its surface using a spin dryer or similar device. Alternatively, the surface of the polished object may be dried by air blow drying.

[0131] According to the surface treatment method and surface treatment composition according to the above embodiments, residue remaining on the surface of a polished object containing silicon nitride can be sufficiently removed. In other words, according to another embodiment of the present invention, a method for reducing residue on the surface of a polished object containing silicon nitride is provided, which involves surface treating the polished object containing silicon nitride using the above surface treatment composition.

[0132] The residue on the surface of a polished object removed by the surface treatment composition includes residues that adhere to the object during the polishing process. Specifically, inorganic oxide abrasive particles are residues originating from the polishing composition, and pad debris (e.g., polyurethane) is residues originating from the polishing pad used in the polishing process. Therefore, the polishing composition and polishing process from which these residues originate will be described. In other words, the polished object that is the target of surface treatment... This explains how it is obtained.

[0133] [Polishing composition] The polishing composition used to obtain a polished workpiece, which is the target of surface treatment, comprises inorganic oxide abrasive particles and a dispersion medium. The polishing composition may further contain additives as needed. The composition of the polishing composition is not particularly limited, except that inorganic oxide abrasive particles and a dispersion medium are essential, but a preferred composition of a polishing composition is described below.

[0134] [Abrasive grains] The inorganic oxide abrasive grains included in the polishing composition are not particularly limited, but examples include particles made of inorganic oxides (metal oxides) such as silicon dioxide (silica), aluminum oxide (alumina), cerium oxide (ceria), zirconium oxide (zirconia), and titanium oxide (titania). These inorganic oxide particles may be surface-modified. For example, they may be anion-modified inorganic oxides to which organic acids such as carboxylic acids and sulfonic acids are immobilized. As such anion-modified inorganic oxides, anion-modified silicon dioxide to which organic acids such as carboxylic acids and sulfonic acids are immobilized is preferred, and anion-modified colloidal silica to which organic acids such as carboxylic acids and sulfonic acids are immobilized is more preferred. The immobilization of organic acids to the surface of such inorganic oxides is carried out, for example, by chemically bonding the functional groups of the organic acids to the surface of the inorganic oxide. Simply having inorganic oxides and organic acids coexist does not achieve the immobilization of organic acids to inorganic oxides. For example, if you want to immobilize a sulfonic acid, a type of organic acid, on colloidal silica, you can do so by the method described in, for example, “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003). Specifically, by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide, you can obtain anion-modified colloidal silica on which the sulfonic acid is immobilized on the surface. Alternatively, if you want to immobilize a carboxylic acid on colloidal silica, you can do so by the method described in, for example, “Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel”, Chemistry Letters, 3, 228-229 (2000).Specifically, anionically modified colloidal silica with a carboxylic acid immobilized on its surface can be obtained by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating it with light. Among these, anionically modified silicon oxide (hereinafter also referred to as sulfonic acid-modified silicon oxide) with a sulfonic acid immobilized on its surface is preferred, and anionically modified colloidal silica (hereinafter also referred to as sulfonic acid-modified colloidal silica) with a sulfonic acid immobilized on its surface is more preferred. The organic acid immobilized on the surface of the inorganic oxide may be in the form of an acid or a salt.

[0135] As for the inorganic oxide abrasive grains, at least one of anionically modified silicon oxide abrasive grains and cerium oxide abrasive grains is more preferred from the viewpoint of removal effect by the surface treatment composition, at least one of anionically modified silicon oxide abrasive grains and cerium oxide abrasive grains is even more preferred, and cerium oxide abrasive grains are particularly preferred. Anionically modified silicon oxide abrasive grains and cerium oxide abrasive grains tend to become negatively charged when in contact with the surface treatment composition and are easily removed from the surface of the polished object by cleaning treatment after surface treatment.

[0136] The lower limit of the average primary particle diameter of inorganic oxide abrasive grains is not particularly limited, but is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more. Within these ranges, the desired polishing speed is more easily obtained. The upper limit of the average primary particle diameter of inorganic oxide abrasive grains is not particularly limited, but is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. Within these ranges, the effect of removing residue containing inorganic oxide abrasive particles present on the surface of polished objects containing silicon nitride is more pronounced. The average primary particle diameter of the inorganic oxide abrasive particles can be calculated based on the specific surface area of ​​the inorganic oxide abrasive particles measured by the BET method, assuming that the particle shape of the inorganic oxide abrasive particles is perfectly spherical.

[0137] The lower limit of the average secondary particle diameter of inorganic oxide abrasive grains is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Within these ranges, the desired polishing speed is more easily obtained. The upper limit of the average secondary particle diameter of inorganic oxide abrasive grains is not particularly limited, but is preferably 100 nm or less, more preferably 90 nm or less, and even more preferably 80 nm or less. Within these ranges, the effect of removing residue containing inorganic oxide abrasive grains present on the surface of polished workpieces containing silicon nitride is more effectively achieved. The value of the average secondary particle diameter of inorganic oxide abrasive grains can be calculated based on measurement using a light scattering method with laser light.

[0138] Inorganic oxide abrasive grains may be synthetic or commercially available. Furthermore, inorganic oxide abrasive grains may be used alone or in combination of two or more types.

[0139] The content (concentration) of inorganic oxide abrasive grains in the polishing composition (total amount if there are two or more types) is not particularly limited, but it is preferably more than 0.01% by mass, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, relative to the total mass of the polishing composition. Within these ranges, it is easier to obtain the desired polishing speed. The content (concentration) of inorganic oxide abrasive grains (total amount if there are two or more types) is not particularly limited, but it is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total mass of the polishing composition. Within these ranges, the effect of removing residue containing inorganic oxide abrasive grains present on the surface of the polished object containing silicon nitride is more effectively achieved.

[0140] [Other ingredients] The polishing composition may contain other components (additives) besides inorganic oxide abrasive grains and dispersion media. These other components are not particularly limited, but examples include dispersants (additives that improve the redispersibility of abrasive grains that have settled), conductivity modifiers (additives that adjust the electrical conductivity of the polishing composition), abrasive grains other than inorganic oxide abrasive grains, pH adjusters, surfactants, wetting agents, chelating agents, preservatives, fungicides, dissolved gases, oxidizing agents, reducing agents, and other components used in known polishing compositions. The pH adjuster is not particularly limited, but for example, the pH adjusters mentioned in the description of the surface treatment composition above can be used.

[0141] [Polishing process] Polishing using an abrasive composition is a process of polishing an object to be polished to form a polished object.

[0142] The polishing process is not particularly limited as long as it polishes the object to be polished, but chemical mechanical polishing (CMP) is preferred. The polishing process may consist of a single step or multiple steps. Examples of multiple-step polishing processes include a preliminary polishing step (rough polishing step) followed by a finish polishing step, or a primary polishing step followed by one or more secondary polishing steps and then a finish polishing step. Surface treatment steps including the surface treatment method according to the above embodiment, and surface treatment steps using the surface treatment composition according to the above embodiment, are preferably performed after the finish polishing step.

[0143] As the polishing apparatus, a general polishing apparatus can be used that has a holder for holding the object to be polished, a motor with adjustable rotation speed, and a polishing platen to which a polishing pad (abrasive cloth) can be attached. Either a single-sided polishing apparatus or a double-sided polishing apparatus may be used.

[0144] As the polishing pad used in the polishing process, general nonwoven fabrics, polyurethanes, and porous fluororesins can be used without particular limitation. However, in the surface treatment process including the surface treatment method according to the above embodiment, and the surface treatment process using the surface treatment composition according to the above embodiment, it is preferable that the polishing pad is made of polyurethane from the viewpoint of further reducing residue. Components derived from the polishing pad may adhere to the surface of the polished object. When the polishing pad is made of polyurethane, the residue will further contain polyurethane. In the surface treatment method according to one preferred embodiment of the present invention, it is preferable to further include controlling the zeta potential of the polyurethane to -10mV or less with the surface treatment composition. The surface treatment composition according to one preferred embodiment of the present invention preferably further has the function of controlling the zeta potential of the polyurethane to -10mV or less. As a result, the residue (polyurethane) can be efficiently removed.

[0145] The Shore A hardness of the polishing pad used in the polishing process is preferably 40° or higher, more preferably 60° or higher, even more preferably 70° or higher, even more preferably 75° or higher, particularly preferably 80° or higher, and most preferably 85° or higher. The Shore A hardness of the polishing pad used in the polishing process is preferably 100° or lower, more preferably 99° or lower, even more preferably 97° or lower, even more preferably 95° or lower, and particularly preferably 93° or lower. When the Shore A hardness of the polishing pad used in the polishing process is within the above range, the polishing pad and the object to be polished come into contact with each other at an appropriate pressure, which not only allows for efficient polishing but also has the effect of preventing residue from remaining on the surface of the polished object. Examples of Shore A hardness of the polishing pad include 40° or higher and 100° or lower.

[0146] The Shore A hardness of the polishing pad is measured according to JIS K 6253-3:2012 and based on a Type A durometer.

[0147] It is preferable that the polishing pad has grooves that allow the polishing fluid to accumulate.

[0148] There are no particular restrictions on the polishing conditions. For example, the rotation speed of the polishing platen and the head (carrier) can be 10 rpm (0.17 s). -1 ) or more 100rpm(1.7s -1 The polishing pressure is preferably 0.5 psi (3.5 kPa) or more and 10 psi (69 kPa) or less. The method of supplying the polishing composition to the polishing pad is not particularly limited, and for example, a method of continuous supply using a pump or the like (flow-through) is employed. There is no limit to the amount supplied, but it is preferable that the surface of the polishing pad is always covered with the polishing composition, and it is preferably 10 mL / min or more and 5000 mL / min or less. The polishing time is also not particularly limited, but it is preferably 5 seconds or more and 180 seconds or less. The temperature of the polishing composition during the polishing process is not particularly limited, and is usually room temperature (25°C), but it may be heated to about 40°C or more and 70°C or less, as long as it does not impair performance.

[0149] [Manufacturing method for semiconductor substrates] The surface treatment method and surface treatment composition according to the above embodiments are suitably applicable when the polished object to be polished is a polished semiconductor substrate. According to another embodiment of the present invention, a method for manufacturing a semiconductor substrate is also provided, in which the polished object to be polished is a polished semiconductor substrate, and the polished semiconductor substrate is treated by the surface treatment method described above.

[0150] A method for manufacturing a semiconductor substrate preferably includes a polishing step of obtaining a polished semiconductor substrate by polishing a pre-polished semiconductor substrate containing silicon nitride using a polishing composition containing inorganic oxide abrasive particles, where the polished object to be polished is a polished semiconductor substrate, and a surface treatment step of reducing the residue containing inorganic oxide abrasive particles on the surface of the polished semiconductor substrate by the above surface treatment method.

[0151] In a method for manufacturing a semiconductor substrate, it is preferable that the inorganic oxide abrasive grains include at least one of cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains, and that the surface treatment composition used in the above surface treatment step controls the zeta potential of at least one of the cerium oxide abrasive grains and anion-modified silicon oxide abrasive grains to -30mV or less. More preferably, in a method for manufacturing a semiconductor substrate, the inorganic oxide abrasive grains include cerium oxide abrasive grains, and that the surface treatment composition used in the above surface treatment step controls the zeta potential of the cerium oxide abrasive grains to -30mV or less.

[0152] In a method for manufacturing a semiconductor substrate, the polishing step preferably includes using a polyurethane polishing pad, the residue further includes polyurethane, and the surface treatment composition used in the surface treatment step preferably further includes controlling the zeta potential of the polyurethane to -10mV or less.

[0153] Details of the semiconductor substrate to which this manufacturing method is applied are as described in the description of the polished object to be surface-treated with the surface treatment composition described above.

[0154] Furthermore, the method for manufacturing a semiconductor substrate is not particularly limited as long as it includes a step (surface treatment step) of surface-treating the surface of a polished semiconductor substrate using the above-mentioned surface treatment composition or surface-treating it using the above-mentioned surface treatment method.

[0155] [Semiconductor substrate manufacturing system] The above surface treatment composition also relates to a semiconductor substrate manufacturing system, further comprising a workpiece containing silicon nitride, a polishing pad, and a polishing composition comprising inorganic oxide abrasive particles. Another aspect of the present invention also provides a semiconductor substrate manufacturing system comprising a workpiece containing silicon nitride, a polishing pad, a polishing composition comprising inorganic oxide abrasive particles, and the above surface treatment composition, wherein the surface of the workpiece, after being polished using the polishing composition and the polishing pad, is brought into contact with the above surface treatment composition.

[0156] Preferred embodiments of the abrasive object containing silicon nitride, abrasive pad, a polishing composition containing inorganic oxide abrasive grains, and a surface treatment composition applied to semiconductor substrate manufacturing systems are the same as described above and will therefore not be described.

[0157] In one embodiment of the present invention, the semiconductor substrate manufacturing system may simultaneously surface-treat both sides of a polished object by bringing them into contact with a polishing pad and a surface treatment composition, or it may surface-treat only one side of a polished object by bringing it into contact with a polishing pad and a surface treatment composition. The preferred embodiments of the surface treatment are the same as described above and are therefore omitted from this description.

[0158] [Residue removal effect] The surface treatment composition described above is preferable if it is highly effective in removing residue from the surface of the polished object. In other words, it is preferable if the amount of residue remaining on the surface of the polished object is small when the surface treatment composition is used to treat the surface of the polished object.

[0159] Specifically, when a polished object is surface-treated with the surface treatment composition, the total number of residue particles is preferably less than 200,000, more preferably 2,000 or less, even more preferably 1,000 or less, particularly preferably 500 or less, and particularly preferably 300 or less (lower limit 0). On the other hand, since a lower total number of residue particles is preferable, there is no particular lower limit, but it may be, for example, 100 or more.

[0160] Furthermore, when a polished object is surface-treated using the surface treatment composition, the number of abrasive particles is preferably less than 200,000, more preferably 1,000 or less, even more preferably 500 or less, even more preferably 250 or less, and particularly preferably 150 or less (lower limit 0). On the other hand, since a smaller number of abrasive particles is preferable, there is no particular lower limit, but it may be, for example, 50 or more.

[0161] Furthermore, when a polished object is surface-treated with the surface treatment composition, the number of polyurethane residues is preferably 1,000 or less, more preferably 500 or less, even more preferably 250 or less, and particularly preferably 150 or less (lower limit 0). On the other hand, since a smaller number of polyurethane residues is preferable, there is no particular lower limit, but it may be, for example, 50 or more.

[0162] The above-mentioned residue counts are based on values ​​measured according to the method described in the examples, after surface treatment has been performed according to the method described in the examples.

[0163] 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.

[0164] The present invention encompasses the following embodiments and forms.

[0165] [1] A surface treatment method for reducing residue containing inorganic oxide abrasive particles on the surface of a polished object containing silicon nitride, using a surface treatment composition, The surface treatment composition comprises a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. A surface treatment method comprising controlling the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30 mV or less, respectively, using the surface treatment composition; [2] The surface treatment method according to [1], wherein the inorganic oxide abrasive grains include cerium oxide abrasive grains, and the surface treatment composition controls the zeta potential of the cerium oxide abrasive grains to -30 mV or less; [3] The surface treatment method according to [1] or [2], wherein the residue further comprises polyurethane, and the surface treatment composition further controls the zeta potential of the polyurethane to -10 mV or less; [4] The zeta potential adjusting agent is a polymer having an anionic group and having a weight-average molecular weight of 1,000 or more, according to any one of [1] to [3]; [5] The polymer having the anionic group has at least one functional group selected from the group consisting of a sulfonic acid (salt) group, a sulfate (salt) group, a phosphonic acid (salt) group, a phosphoric acid (salt) group, and a carboxylic acid (salt) group; the surface treatment method according to [4]; [6] A surface treatment method according to any one of [1] to [5], further comprising the surface treatment composition, a pH adjuster; [7] The surface treatment method according to any one of [1] to [6], wherein the pH value of the surface treatment composition is 2 or more and less than 5; [8] A surface treatment method according to any one of [1] to [7], which is a rinse polishing method or a washing method; [9] The polished object to be polished is a polished semiconductor substrate, A polishing step to obtain a polished semiconductor substrate by polishing a pre-polishing semiconductor substrate containing silicon nitride using a polishing composition containing inorganic oxide abrasive particles, A surface treatment step to reduce the residue containing the inorganic oxide abrasive particles on the surface of the polished semiconductor substrate by any of the surface treatment methods described in [1] to [8], A method for manufacturing a semiconductor substrate, including;

[10] The inorganic oxide abrasive grains include cerium oxide abrasive grains, A method for manufacturing a semiconductor substrate according to [9], comprising controlling the zeta potential of the cerium oxide abrasive grains to -30 mV or less using the surface treatment composition used in the surface treatment step;

[11] The polishing step includes using a polishing pad made of polyurethane, and the residue further comprises polyurethane. A method for manufacturing a semiconductor substrate according to [9] or

[10] , further comprising controlling the zeta potential of the polyurethane to -10 mV or less using the surface treatment composition used in the surface treatment step;

[12] The method for manufacturing a semiconductor substrate according to

[11] , wherein the Shore A hardness of the polishing pad is 40° or more and 100° or less;

[13] A surface treatment composition used to reduce residue containing inorganic oxide abrasive particles on the surface of a polished object containing silicon nitride, The material comprises a zeta potential adjusting agent having a negatively charged functional group and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. A surface treatment composition having the function of controlling the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30mV or less;

[14] The inorganic oxide abrasive grains include cerium oxide abrasive grains, The surface treatment composition described in

[13] has the function of controlling the zeta potential of the cerium oxide abrasive grains to -30 mV or less;

[15] The residue further comprises polyurethane, The surface treatment composition according to

[13] or

[14] further having the function of controlling the zeta potential of the polyurethane to -10 mV or less;

[16] A surface treatment composition according to any one of

[13] to

[15] , which is a rinse polishing composition or a cleaning composition;

[17] A semiconductor substrate manufacturing system comprising a workpiece containing silicon nitride, a polishing pad, a polishing composition containing inorganic oxide abrasive grains, and a surface treatment composition according to any one of

[13] to

[16] , A semiconductor substrate manufacturing system comprising bringing the surface of an object to be polished, after being polished using the polishing composition and the polishing pad, into contact with the surface treatment composition. [Examples]

[0166] 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%" and "parts by mass," respectively. In addition, in the following examples, unless otherwise specified, the operations were carried out under room temperature (20-25°C) / relative humidity of 40-50%RH.

[0167] [Preparation of surface treatment composition] [Preparation of surface treatment composition A1] Surface treatment composition A1 was prepared by mixing a zeta potential adjusting agent, a sulfonic acid (salt) group-containing monomer, with acrylic acid copolymer 1 (sodium salt, weight-average molecular weight 10,000, manufactured by Toagosei Co., Ltd., product number: Aron® A-6012), a pH adjusting agent, nitric acid, and a dispersion medium, water (deionized water). The amount of zeta potential adjusting agent added (content, concentration) was 1.0 g / kg relative to the total mass of surface treatment composition A1, and the amount of pH adjusting agent added (content, concentration) was set to a pH of 3 (liquid temperature: 25°C) for surface treatment composition A1. pH was measured using a pH meter (manufactured by Horiba, Ltd., product name: LAQUA®).

[0168] [Preparation of surface treatment compositions A2-A5 and B1-B6] As shown in Table 1 below, surface treatment compositions A2 to A5 and B1 to B6 were prepared in the same manner as surface treatment composition A1, except that the necessity, type, and amount (content, concentration) of a zeta potential adjuster or comparative compound (a compound used in place of the zeta potential adjuster is referred to as a comparative compound) were selected, and the amount of pH adjuster was selected so that the pH of the resulting surface treatment composition would be the pH shown in Table 1 below.

[0169] Surface treatment compositions A1 to A5 are the surface treatment compositions used in the examples, and surface treatment compositions B1 to B6 are the surface treatment compositions used in the comparative examples.

[0170] Details of the zeta potential modifier and comparative compounds are shown below.

[0171] • Copolymer 1 of a sulfonic acid (salt) group-containing monomer and acrylic acid (salt) (sodium salt, weight-average molecular weight 10,000, manufactured by Toagosei Co., Ltd., product number: Aron (registered trademark) A-6012), • Copolymer 2 (sodium salt, weight-average molecular weight 3,000, manufactured by Nippon Shokubai Co., Ltd., product number: Aquaric® L) containing a monomer containing a sulfonic acid (salt) group. GL-246), • Polyvinylphosphonic acid (30% by mass aqueous solution, weight-average molecular weight 40,000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., catalog number: PVphos acid, 30%) • Sulfonic acid group-containing polyvinyl alcohol (weight-average molecular weight 30,000, manufactured by Mitsubishi Chemical Corporation, product number: Gosenex® CKS-50), • Polyacrylic acid (weight-average molecular weight 3,000, manufactured by Toagosei Co., Ltd., product number: Aron (registered trademark) AC10SL), • Polyvinyl alcohol (weight-average molecular weight 10,000, manufactured by Nippon Vivaceuil Co., Ltd., product number: JMR-10HH) • Polyvinylpyrrolidone (weight-average molecular weight 40,000, manufactured by Tokyo Chemical Industry Co., Ltd., product number: PVP K30).

[0172] The weight-average molecular weights of the zeta potential modifier and the comparative compound were measured using gel permeation chromatography (GPC) with polyethylene glycol as the standard substance.

[0173] The composition of the obtained surface treatment composition is shown in Table 1 below.

[0174] [Viscosity of 20% by mass aqueous solutions of zeta potential modifier and comparative compound] A zeta potential adjusting agent or a comparative compound was mixed with water (deionized water) to obtain an aqueous solution in which the concentration of the zeta potential adjusting agent or comparative compound was 20% by mass relative to the total mass of the aqueous solution. The viscosity (mPa·s) of the obtained aqueous solution was measured at a water temperature of 25°C using a kinematic viscometer (manufactured by Suzuki Rika Co., Ltd., part number: manual viscosity tube No. 50). These results are shown in Table 1.

[0175] [Examples 1-20, Comparative Examples 1-24] To evaluate the performance of the obtained surface treatment compositions A1-A5 and B1-B6, a CMP (Chemical Polishing) process was performed on the workpiece to be polished, followed by a rinse polishing process on the polished workpiece obtained after the CMP process. The rinse polishing process was performed using the above-mentioned surface treatment compositions A1-A5 and B1-B6.

[0176] [CMP process] First, a CMP (Chemical Polishing) process was performed on the object to be polished. The object to be polished was a SiN substrate, as described later, and the following two types of polishing compositions were prepared.

[0177] "Polishing composition" • Polishing composition C1 (a polishing composition using CeO2 abrasive grains as abrasive grains) Colloidal ceria (Solvay HC30) (average primary particle size: 30 nm, average secondary particle size: 60 nm, 30% by mass aqueous dispersion): 1% by mass Ammonium polyacrylate (manufactured by Toagosei Co., Ltd., Aron® A-30SL, Mw: 6,000, 40% by mass aqueous solution): 0.6% by mass 30% by mass maleic acid aqueous solution (manufactured by Kanto Chemical Co., Ltd.): 0.2% by mass Water: Residual (Adjust to pH 4).

[0178] • Polishing composition C2 (a polishing composition using anionically modified SiO2 abrasive grains as abrasive grains) Anion-modified colloidal silica (sulfonic acid-functionalized silica prepared by the method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003), average primary particle size: 35 nm, average secondary particle size: 70 nm): 2% by mass 30% by mass maleic acid aqueous solution (manufactured by Kanto Chemical Co., Ltd.): 0.002% by mass Ammonium sulfate (manufactured by Kanto Chemical Co., Ltd.): 0.25% by mass Water: Residual (Adjust pH to 3).

[0179] "CMP process" For the object to be polished, a SiN substrate, which is a semiconductor substrate, was polished using either the above-mentioned polishing composition C1 or C2 under the conditions described below. The Shore A hardness of each polishing pad described below was measured according to JIS K 6253-3:2012 and based on a Type A durometer. A 300mm wafer (manufactured by Advantech Co., Ltd., part number: (CVD-)LP-SiN 2500A) was used for the SiN substrate. - Polishing equipment and polishing conditions - Polishing equipment: FREX300E manufactured by Ebara Corporation Polishing pad: Use one of the following: • Foamed polyurethane pad H800-Type1 (Shore A hardness: 89.4°) manufactured by Fuji Spinning Holdings Co., Ltd. • Foamed polyurethane pad H800-CZM (Shore A hardness: 78.9°) manufactured by Fuji Spinning Holdings Co., Ltd. • Foamed polyurethane pad X400-CZM (Shore A hardness: 76.3°) manufactured by Fuji Spinning Holdings Co., Ltd. Conditioner (dresser): Nylon brush (made by 3M) Polishing pressure: 2.0 psi (1 psi = 6894.76 Pa) Polishing plate rotation speed: 80 rpm Head rotation speed: 80 rpm Supply of polishing composition: flow-through Polishing composition supply amount: 200mL / min Polishing time: 30 seconds.

[0180] [Rinse polishing process] After polishing the SiN substrate surface in the above CMP process, the polished SiN substrate was removed from the polishing platen as the polished workpiece. Next, within the same polishing apparatus, the polished SiN substrate was mounted on a separate polishing platen, and rinse polishing was performed on the surface of the polished SiN substrate using the surface treatment compositions A1-A5 and B1-B6 prepared above, respectively, under the following conditions; -Rinse polishing apparatus and rinse polishing conditions- Polishing pressure: 1.0 psi Plate rotation speed: 60 rpm Head rotation speed: 60 rpm Supply of surface treatment composition: flow-through method Surface treatment composition supply rate: 300 mL / min Polishing time: 60 seconds.

[0181] After the rinse polishing process, the substrate surface was brush-cleaned with deionized water for 60 seconds to obtain a rinse-polished SiN substrate.

[0182] <Rating> Each polished SiN substrate after the rinse polishing process described above was measured and evaluated for the following items. The evaluation results are shown in Tables 2 to 5 below.

[0183] Table 2 below shows the "evaluation results of each surface treatment composition A1 to A5 and B1 to B6 on polished SiN substrates (Examples 1 to 5 and Comparative Examples 1 to 6)" obtained by polishing a SiN substrate (object to be polished) using polishing composition C1 and polishing pad H800-Type1 in the polishing process.

[0184] Table 3 below shows the "evaluation results of each surface treatment composition A1-A5 and B1-B6 on polished SiN substrates (Examples 6-10 and Comparative Examples 7-12)" obtained by polishing a SiN substrate (object to be polished) using polishing composition C1 and H800-CZM as the polishing pad during the polishing process.

[0185] Table 4 below shows the "evaluation results of each surface treatment composition A1-A5 and B1-B6 on polished SiN substrates (Examples 11-15 and Comparative Examples 13-18)" obtained by polishing a SiN substrate (object to be polished) using polishing composition C1 and X400-CZM as the polishing pad during the polishing process.

[0186] Table 5 below shows the "evaluation results of each surface treatment composition A1-A5 and B1-B6 on polished SiN substrates (Examples 16-20 and Comparative Examples 19-24)" obtained by polishing a SiN substrate (object to be polished) using polishing composition C2 and polishing pad H800-Type1 in the polishing process.

[0187] [Evaluation of total residue quantity] The total number of residues was evaluated using the Surfscan® SP5 optical inspection machine manufactured by KLA-Tencor Co., Ltd., to assess the number of residues on the polished SiN substrate surface after rinse polishing. Specifically, the number of residues with a diameter of 50 μm or more was counted in the remaining portion after excluding a 5 mm wide portion from the outer edge of one side of the polished SiN substrate (the portion from 0 mm to 5 mm wide, with the outer edge set to 0 mm). A smaller number of residues is preferable. The results are shown in Tables 2 to 5 below. Note that if the total number of residues exceeds 200,000, the number of particles will not be detected. Since this is not possible, it is indicated as ">200000" in Tables 2 to 5 below.

[0188] [Evaluation of abrasive residue count and polyurethane residue count] For the polished SiN substrate after the rinse polishing treatment described above, the number of abrasive grains and polyurethane residues was measured by SEM observation using a Hitachi High-Tech Review SEM RS6000. First, 100 residues were sampled from the remaining portion of one side of the polished SiN substrate, excluding a 5 mm wide section from the outer edge, using SEM observation. Next, the type of residue (abrasive grains or polyurethane) was identified from the 100 sampled residues by visual SEM observation, and the number of abrasive grain residues (CeO2 residues or anion-modified SiO2 residues) and polyurethane residues was confirmed to calculate the percentage of abrasive grain residues (%) and polyurethane residues (%) in the total residue. Then, the product of the total number of residues (number of particles) with a diameter exceeding 50 μm, measured by the evaluation of the total residue count described above, and the percentage of abrasive grain residues (%) in the total residue calculated by SEM observation was used to calculate the number of abrasive grains (particles). Furthermore, the number of polyurethane residues was calculated by multiplying the total number of residues (pieces) with a diameter exceeding 50 μm, as measured by the above-mentioned evaluation of the total number of residues, by the percentage of polyurethane residues in the residue calculated by SEM observation.

[0189] In Tables 2 to 5, "Number of abrasive grains" refers to the number of inorganic oxide abrasive grains (CeO2 abrasive grains or anion-modified SiO2 abrasive grains), and "Number of polyurethane grains" refers to the number of abrasive grains. This represents the number of residues originating from the polishing pad. Note that if the total number of residues exceeds 200,000, it was not possible to calculate the number of abrasive residues and the percentage of polyurethane residues. Since the majority of the residue is likely to be abrasive residues, in Tables 2 to 5, if the total number of residues exceeds 200,000, the number of abrasive residues is indicated as ">200000" and the number of polyurethane residues as "-".

[0190] [Zeta potential measurement of inorganic oxide abrasive grains] The zeta potential of inorganic oxide abrasive grains was measured using a Zetasizer Nano ZSP manufactured by Spectris Corporation (Malvern Division). The zeta potential of CeO2 abrasive grains during rinse polishing with a surface treatment composition, and the zeta potential of anion-modified SiO2 abrasive grains during rinse polishing with a surface treatment composition, were measured using the following model experiments. These values ​​are shown in Table 1 below.

[0191] (CeO2 abrasive grains) A CeO2 particle dispersion (Solvay HC30, a 30% by mass aqueous dispersion of colloidal ceria with an average primary particle diameter of 30 nm and an average secondary particle diameter of 60 nm) was added to the surface treatment composition prepared above to prepare a measurement solution with a CeO2 particle concentration of 0.02% by mass (the CeO2 particle content (concentration) in the measurement solution was 0.02% by mass relative to the total mass of the measurement solution). The obtained measurement solution was filled into the measurement cell of the above-mentioned apparatus (Zetasizer Nano ZSP), and the zeta potential of the CeO2 abrasive grains was measured.

[0192] (Anionically modified SiO2 abrasive grains) An anion-modified SiO2 particle dispersion (a 19.5% by mass aqueous dispersion of anion-modified colloidal silica (sulfonic acid-functionalized silica prepared by the method described in "Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups", Chem. Commun. 246-247 (2003), with an average primary particle diameter of 35 nm and an average secondary particle diameter of 70 nm)) was added to the surface treatment composition prepared above to prepare a measurement solution with an anion-modified SiO2 particle concentration of 0.02% by mass (the content (concentration) of anion-modified SiO2 particles in the measurement solution was 0.02% by mass relative to the total mass of the measurement solution). The obtained measurement solution was filled into the measurement cell of the above-mentioned apparatus (Zetasizer Nano ZSP), and the zeta potential of the anion-modified SiO2 abrasive grains was measured.

[0193] [Zeta potential measurement of polished SiN substrates and polyurethane] The zeta potentials of the polished SiN substrate and the polyurethane were measured using the SurPASS3 solid zeta potential measuring instrument manufactured by Anton Paar Japan Co., Ltd. The zeta potentials of the polished SiN substrate surface during rinse polishing with the surface treatment composition, and the zeta potentials of the polyurethane during rinse polishing with the surface treatment composition, were measured using the following model experiments. These values ​​are shown in Table 1 below.

[0194] The zeta potential of polyurethane was measured using a polyurethane pad (Foamed Polyurethane Pad H800-Type1, manufactured by Fuji Spinning Holdings Co., Ltd.) cut into 60mm squares.

[0195] The zeta potential of the polished SiN substrate surface was measured using a SiN substrate (300mm wafer, manufactured by Advantech Co., Ltd., part number: (CVD-)LP-SiN 2500A) cut into 60mm squares.

[0196] Each of these objects was placed on a zeta potential meter. Next, the surface treatment composition prepared above was passed through the objects, and the zeta potential of each object was measured.

[0197] [Table 1]

[0198] [Table 2]

[0199] [Table 3]

[0200] [Table 4]

[0201] [Table 5]

[0202] As shown in Tables 2 to 4, in Examples 1 to 15, after polishing the SiN substrate with polishing composition C1 (i.e., a polishing composition using CeO2 abrasive grains as abrasive grains), the polished SiN substrate was rinse-polished using surface treatment compositions A1 to A5. It was found that the amount of residue (total number of residues) had decreased significantly.

[0203] Furthermore, as shown in Table 5, Examples 16 to 20 showed that even when the SiN substrate was polished with polishing composition C2 (i.e., a polishing composition using anion-modified SiO2 abrasive grains as abrasive grains), rinsing the polished SiN substrate with surface treatment compositions A1 to A5 significantly reduced the amount of residue (total number of residues) on the polished SiN substrate.

[0204] This indicates that when a polishing object containing silicon nitride is polished using a polishing composition containing cerium oxide abrasive grains or anion-modified silicon oxide abrasive grains, the residue (abrasive grains, polishing pad) adhering to the polished object can be sufficiently removed by surface treating the polished object with the surface treatment composition of the present invention.

[0205] Furthermore, when the surface treatment composition is to be stored or preserved for a long period of time, it is preferable that the surface treatment composition further contains an antifungal agent (preservative). Since the antifungal agent (preservative) is thought to have little to no effect on the above results, it is considered that a surface treatment composition containing an antifungal agent (preservative) will yield similar results.

Claims

1. A surface treatment method for reducing inorganic oxide abrasive particles and polyurethane-containing residue on the surface of a polished object containing silicon nitride, using a surface treatment composition, The surface treatment composition comprises a zeta potential adjusting agent having negatively charged functional groups and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. The surface treatment composition includes controlling the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30 mV or less, respectively. The surface treatment composition includes controlling the zeta potential of the polyurethane to -40 mV or less. A surface treatment method wherein the pH of the surface treatment composition is less than 5.

2. The surface treatment method according to claim 1, wherein the inorganic oxide abrasive grains include cerium oxide abrasive grains, and the surface treatment composition controls the zeta potential of the cerium oxide abrasive grains to -30 mV or less.

3. The surface treatment method according to claim 1, wherein the zeta potential adjusting agent is a polymer having an anionic group and having a weight-average molecular weight of 1,000 or more.

4. The surface treatment method according to claim 3, wherein the polymer having the anionic group has at least one functional group selected from the group consisting of a sulfonic acid (salt) group, a sulfuric acid (salt) group, a phosphonic acid (salt) group, a phosphoric acid (salt) group, and a carboxylic acid (salt) group.

5. The surface treatment method according to claim 1, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 100,000 or less, and having at least one functional group selected from the group consisting of a sulfonic acid (salt) group, a sulfate (salt) group, a phosphonic acid (salt) group, and a phosphoric acid (salt) group.

6. The surface treatment method according to claim 1, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 100,000 or less, and having a sulfonic acid (salt) group.

7. The surface treatment method according to claim 1, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 50,000 or less, and having a sulfonic acid (salt) group.

8. The surface treatment method according to claim 1, wherein the zeta potential adjusting agent comprises a polymer having a viscosity of 10 mPa·s or more and 12 mPa·s or less in an aqueous solution with a concentration of 20% by mass at 25°C, and having at least one functional group selected from the group consisting of sulfonic acid (salt) groups, sulfuric acid (salt) groups, phosphonic acid (salt) groups, and phosphoric acid (salt) groups.

9. The surface treatment method according to claim 1, wherein the surface treatment composition further comprises a pH adjusting agent.

10. The surface treatment method according to claim 1, wherein the pH of the surface treatment composition is 2 or more and less than 5.

11. The surface treatment method according to claim 1, wherein the pH of the surface treatment composition is 2.5 or more and less than 5.

12. The surface treatment method according to claim 1, wherein the pH of the surface treatment composition is less than 4.

13. The surface treatment method according to claim 1, wherein the method is a rinse polishing method or a cleaning method.

14. The polished object to be polished is a polished semiconductor substrate. A polishing step to obtain a polished semiconductor substrate by polishing a pre-polishing semiconductor substrate containing silicon nitride using a polishing composition containing inorganic oxide abrasive particles, A surface treatment step of reducing the residue containing inorganic oxide abrasive particles and polyurethane on the surface of the polished semiconductor substrate by a surface treatment method according to any one of claims 1 to 13, A method for manufacturing a semiconductor substrate, including the method described above.

15. The inorganic oxide abrasive grains include cerium oxide abrasive grains. A method for manufacturing a semiconductor substrate according to claim 14, comprising controlling the zeta potential of the cerium oxide abrasive grains to -30 mV or less using the surface treatment composition used in the surface treatment step.

16. The method for manufacturing a semiconductor substrate according to claim 14, wherein the polishing step includes using a polishing pad made of polyurethane.

17. The method for manufacturing a semiconductor substrate according to claim 16, wherein the Shore A hardness of the polishing pad is 40° or more and 100° or less.

18. A surface treatment composition used to reduce inorganic oxide abrasive particles and polyurethane-containing residue on the surface of a polished object containing silicon nitride, The material comprises a zeta potential adjusting agent having a negatively charged functional group and having a viscosity of 10 mPa·s or more in an aqueous solution with a concentration of 20% by mass at 25°C, and a dispersion medium. It has a function to control the zeta potential of the silicon nitride and the zeta potential of the inorganic oxide abrasive grains to -30 mV or less, It has a function to control the zeta potential of the polyurethane to -40 mV or less. The pH is less than 5. Surface treatment composition.

19. The inorganic oxide abrasive grains include cerium oxide abrasive grains. The surface treatment composition according to claim 18, wherein the surface treatment composition has the function of controlling the zeta potential of the cerium oxide abrasive grains to -30 mV or less.

20. The surface treatment composition according to claim 18, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 100,000 or less, and having at least one functional group selected from the group consisting of a sulfonic acid (salt) group, a sulfate (salt) group, a phosphonic acid (salt) group, and a phosphoric acid (salt) group.

21. The surface treatment composition according to claim 18, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 100,000 or less, and having a sulfonic acid (salt) group.

22. The surface treatment composition according to claim 18, wherein the zeta potential adjusting agent comprises a polymer having a weight-average molecular weight of 8,000 or more and 50,000 or less, and having a sulfonic acid (salt) group.

23. The surface treatment composition according to claim 18, wherein the zeta potential adjusting agent comprises a polymer having a viscosity of 10 mPa·s or more and 12 mPa·s or less in an aqueous solution with a concentration of 20% by mass at 25°C, and having at least one functional group selected from the group consisting of sulfonic acid (salt) groups, sulfuric acid (salt) groups, phosphonic acid (salt) groups, and phosphoric acid (salt) groups.

24. The surface treatment composition according to claim 18, wherein the pH is 2.5 or more and less than 5.

25. The surface treatment composition according to claim 18, wherein the pH is less than 4.

26. The surface treatment composition according to claim 18, which is a rinse polishing composition or a cleaning composition.

27. A semiconductor substrate manufacturing system comprising a workpiece to be polished containing silicon nitride, a polishing pad, a polishing composition containing inorganic oxide abrasive particles, and a surface treatment composition according to any one of claims 18 to 26, A semiconductor substrate manufacturing system comprising bringing the surface of an object to be polished, after being polished using the polishing composition and the polishing pad, into contact with the surface treatment composition.

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