JP2003282498A - Abrasive and carrier particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide abrasive exhibiting excellent polishing efficiency and carrier particles for use therein. <P>SOLUTION: The abrasive contains carrier particles and abrasive grains wherein the zeta potential of the abrasive grain has a sign not reverse to that of the carrier particle. Since a cohesive force among the carrier particles is weak when the zeta potential of the abrasive grain has a sign not reverse to that of the carrier particle in the abrasive, the carrier particles can be decomposed readily and dispersed into the abrasive during a polishing operation. Furthermore, polishing efficiency can be enhanced because the required quantity of abrasive grains are held by the carrier particles. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive containing carrier particles and abrasive grains, which is excellent in polishing efficiency because the zeta potentials of the abrasive grains and the carrier particles in the abrasive are not opposite signs, The present invention relates to carrier particles for the abrasive and a polishing method using the abrasive.

[0002]

2. Description of the Related Art Conventionally, in the process of finishing electronic components such as semiconductor substrates and magnetic disk substrates and their substrates, free abrasive grain polishing using various polishing cloths has been adopted to realize a mirror surface. Elastic polishing cloths such as woven cloth, non-woven cloth, and foam are used as tools.

Such free-abrasive grain polishing is a method in which a polishing cloth is placed on a surface plate as a polishing pad and polishing is performed while adding abrasive grains between the polishing pad and the object to be polished.
The object to be polished is rotated under pressure to achieve surface polishing with the abrasive grains. Therefore, the polishing pad is placed so that the object to be polished and the surface plate do not come into direct contact with each other to cause scratches. For example, a woven cloth has a bad influence on the roughness and waviness of the texture. In some cases, even non-woven fabrics have problems such as uneven density. In addition, since a load is applied to the polishing cloth, the polishing cloth gradually loses elasticity and becomes hard by repeated use. Also,
Since the abrasive grains are supplied in a state of being suspended in the polishing liquid, chips and abrasive grains may be deposited on the polishing cloth to reduce the polishing efficiency, or aggregate carrier particles may be generated, which may cause scratches. . For this reason, the work of reshaping the surface of the polishing cloth is required, which causes a reduction in production efficiency due to the temporary suspension of the polishing process. Further, the size of the polishing pad is inevitably increased with the increase in size of the object to be polished such as a silicon wafer in recent years, and skill is also required for mounting the polishing pad on the surface plate. For this reason, due to the recent demand for high-precision processing in precision polishing, a harder polishing cloth is required, and a two-layer polishing cloth in which a hard resin layer and a soft resin layer are laminated is also proposed. .

On the other hand, as a method for carrying out mirror surface processing without using a polishing pad, there is float polishing in which a workpiece is levitated from a surface plate by utilizing a hydroplane phenomenon and polished in a fluid-supported state. However, this fluid-supported polishing has lower polishing efficiency than the case of using a conventional polishing cloth.

As a polishing method which does not use a polishing pad, Japanese Patent Laid-Open No. 2001-300843 discloses an abrasive for polishing the surface of an object to be polished, which is held on the mother particles and the surface thereof. An abrasive containing ultrafine abrasive grains is disclosed. In the conventional polishing method, polishing was carried out by making abrasive grains present between the polishing pad placed on the surface plate and the object to be polished, but the method described in the above publication is super-sized on the surface of the mother particles. It holds fine abrasive grains and performs polishing without a polishing pad. The ultrafine abrasive grains are held by the mother particles in the polishing agent during polishing, and even if the ultrafine abrasive grains in the polishing agent peel off from a part of the surface of the mother particles during polishing The ultrafine abrasive grains adhere and are polished by the ultrafine abrasive grains.

Further, JP-A-2000-269170 is characterized in that it contains polymer particles, inorganic particles and water, and that the zeta potential of the polymer particles and the zeta potential of the inorganic particles have opposite signs. Discloses an aqueous dispersion for chemical mechanical polishing used for manufacturing a semiconductor device. In an aqueous dispersion in which the zeta potentials of polymer particles and inorganic particles have opposite signs, these particles electrostatically agglomerate into a unit and are useful as a chemical mechanical polishing aqueous dispersion useful as a polishing agent for a film to be processed of a semiconductor device. It will be.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method of using mother particles disclosed in Japanese Patent Laid-Open No. 00843 makes the conventional polishing pad unnecessary, and is cost effective because it does not require replacement or modification of the polishing pad. However, in the method of using carrier particles for holding or adhering abrasive grains instead of such a polishing pad, the carrier particles do not directly contact the platen and the object to be polished and do not damage the object to be polished. Thus, it functions to maintain the gap between the surface plate and the object to be polished, and also to rub the abrasive grains in the polishing slurry against the surface of the object to be polished. In such a polishing method, it is conceivable that the interfacial chemical properties of the carrier particles are involved in the adhesion and retention of the abrasive grains and affect the processing characteristics. Further, the surface shape such as the roughness and waviness of the surface plate may affect the mobility of the carrier particles, and it is desired to elucidate the factors that affect the processing characteristics for further improving the polishing efficiency.

The method described in JP-A-2000-269170 is a method in which the zeta potentials of the polymer particles and the inorganic particles have opposite signs, so that they are bound by electrostatic force to form composite particles. However, when such composite particles are used, the polishing efficiency may be poor.

[0009]

As a result of a detailed examination of a polishing method using two kinds of carrier particles, that is, abrasive particles and carrier particles, carrier particles dispersed and supplied in a polishing liquid are found to be on a surface plate and an object to be polished. It has been found that optimum polishing efficiency can be obtained for the object to be polished by acting as a myriad of micropads with the object and controlling the mechanical properties of the carrier particles. In particular, it has been found that when the zeta potentials of the carrier particles and the abrasive particles are not opposite in sign, the dispersibility of the carrier particles in the abrasive is excellent and the polishing efficiency is improved.

That is, the present invention provides an abrasive containing carrier particles and abrasive particles, wherein the zeta potential of the abrasive particles and the zeta potential of the carrier particles are not opposite in sign. It is a thing. Abrasive grains are efficiently retained by carrier particles even when the zeta potential is not of opposite sign,
Moreover, since the aggregation of the carrier particles can be suppressed, the dispersibility of the carrier particles in the polishing agent is excellent and the polishing efficiency is improved.

The present invention also provides the above abrasive, wherein the zeta potential of the carrier particles in the abrasive is +30 to -100 mV. Within this range, the dispersibility in the abrasive is particularly excellent and the polishing efficiency is improved.

The present invention also provides carrier particles for use in the abrasive. By using the carrier particles as an abrasive, an abrasive having excellent polishing efficiency can be prepared while suppressing scratches.

The present invention also provides a method for polishing the surface of an object to be polished, using the above-mentioned polishing agent.
By using the above polishing agent, the surface of the object to be polished can be polished with less burden on the polishing machine.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The first aspect of the present invention is an abrasive containing carrier particles and abrasive grains, wherein the zeta potential of the abrasive grains and the zeta potential of the carrier particles are not opposite in sign. The second aspect of the present invention is carrier particles for the abrasive.

The abrasive containing carrier particles and abrasive grains is an abrasive prepared by mixing and agitating carrier particles and abrasive grains in a solvent, and the abrasive grains are formed on the surface of the carrier particles in the abrasive. Are held, and the carrier particles act as a myriad of micropads between the surface plate and the object to be polished. The carrier particles that hold the abrasive grains on the surface contribute to polishing by bringing the object to be polished that rotates under pressure into contact with the abrasive grains, so that the carrier particles have excellent abrasive grain retention properties and a large amount of abrasive grains If it can be brought into contact with the object to be polished, the polishing efficiency is improved. Further, since the abrasive grains come into contact with the object to be polished through the carrier particles, the polishing efficiency is lowered when the carrier particles are not dispersed in the polishing agent. This dispersibility changes depending on various characteristics such as the hydrogen ion concentration and viscosity of the abrasive solvent, but when carrier particles aggregate, the dispersibility in the abrasive decreases. However, if the aggregating condition is relaxed, it can be easily separated into a single molecule in the abrasive and the dispersibility can be secured. Therefore, the relationship between the retention of the abrasive grains to the carrier particles due to the difference in zeta potential, and the relationship between the dispersibility of the carrier particles was examined. It was found that the carrier particles are excellent in retaining property to the carrier particles, but other carrier particles are bonded through the retained abrasive particles to form a strong aggregate of carrier particles. Therefore, even in an abrasive, it cannot be easily broken down into unit particles of carrier particles. On the contrary,
If the zeta potential of the carrier particles in the abrasive and the zeta potential of the abrasive particles are not of opposite sign, the cohesive force between the carrier particles is weak and can be easily decomposed during polishing and dispersed in the abrasive. Moreover, the carrier particles held the required amount of abrasive grains. That is, the present invention provides an abrasive characterized in that the zeta potential of the abrasive grains and the zeta potential of the carrier particles do not have opposite signs. The zeta potential is the zeta potential of carrier particles and abrasive grains in the abrasive. Hereinafter, the abrasive and the carrier particles of the present invention will be described in detail.

The carrier particles of the present invention are not limited in material as long as the zeta potential in the polishing agent does not have the opposite sign to the zeta potential of the abrasive grains in the polishing agent. The zeta potential of the carrier particles in the specific solvent may be positive or negative as long as the zeta potential of the abrasive grains in the abrasive and the zeta potential of the carrier particles do not have opposite signs. Therefore, in principle, the carrier particles may be an organic polymer compound or an inorganic compound. However, an organic polymer compound is preferable in terms of excellent transportability of abrasive grains as a micropad and polishing efficiency. At this time, the polymerization method is also not particularly limited. Therefore, addition polymerization by repeating addition, condensation polymerization by repeating condensation, ring-opening polymerization performed by a monomer having a cyclic structure opening a ring, emulsion polymerization,
Suspension polymerization, dispersion polymerization, coordination polymerization, photopolymerization, radiation polymerization,
It may be any of plasma polymerization, plasma-initiated polymerization, group transfer polymerization, etc., and the reaction mechanism may be any of radical polymerization, cationic polymerization, and anionic polymerization. Further, it may be a homopolymer, a copolymer, a block copolymer. , A graft copolymer, or the like,
Further, the polymer may have intramolecular crosslinks.

As the organic polymer compound, at least one kind of urethane, polyamide, polyimide, polyester, polyethylene, polystyrene, crosslinked polystyrene, polypropylene, polyvinyl chloride, polyvinylidene chloride, ABS is used as the organic polymer compound in view of the retention of abrasive grains and dispersibility. Resin, polystyrene / AS resin, acrylic resin, methacrylic resin, phenol resin, urea / melamine resin, silicone resin,
Epoxy resin, polyacetal resin, benzoguanamine resin, polycarbonate, polyphenylene ether, polyphenylene sulfide, polysulfone, polyarylate, polyetherimide, polyethersulfone, polyetherketone, etc., or a mixture or composition of two or more thereof. It can be formed from objects.

Further, the carrier particles may be a composite of an organic polymer compound and an inorganic compound. For example, the organic polymer compound is used as a nucleus, and the surface of the inorganic compound is chemically or physically supported, adsorbed, attached by a chemical bond, or the like, or the organic polymer compound is synthesized in the presence of the inorganic compound. The organic polymer compound contains an inorganic compound, the inorganic compound serves as a nucleus, and the surface is covered with a thin film of the organic polymer compound, or the surface is modified by forming a graft chain by chemical bonding. It may be quality. Further, the organic polymer compound itself having a hollow portion, the hollow portion filled with a gas or liquid other than air, and the like may be used. As the inorganic compound used as such a complex, at least one kind of microbeads such as carbon microbeads, glass beads, and mesocarbon beads can be used alone or in combination of two or more kinds. Micro beads such as carbon micro beads, glass beads, and meso carbon beads are commercially available from Osaka Gas Co., Ltd., Simicon Composite Co., Ltd., etc.

More specific carrier particles include the following. For example, in a hydrophilic solvent containing polyvinyl alcohol, an aromatic monomer such as styrene is used as a benzoyl peroxide as an initiator, and 4000 to 10000 is used.
After dispersing the content in the flask at a stirring speed of rpm, the reaction was carried out at a temperature of 60 to 100 ° C. for 5 to 24 hours, and the obtained solid matter was separated by filtration and washed thoroughly with water.

Further, in a hydrophilic solvent containing polyvinyl alcohol, methyl methacrylate, ethyl methacrylate, butyl methacrylate, butyl acrylate, 2-methacrylate
Using (meth) acrylic acid ester such as ethylhexyl acrylate with lauroyl peroxide as an initiator, 4
Polymerized particles obtained by dispersing the content in the flask at a stirring speed of 000 to 10000 rpm, polymerizing the mixture at a temperature of 50 to 100 ° C. for 5 to 24 hours, and filtering the solid obtained and thoroughly washing with water can be exemplified. .

As the composite of the organic polymer compound and the inorganic compound, for example, with respect to 100 parts by mass of the uncured benzoguanamine-based resin emulsion (resin solid content conversion),
1 to 15 parts by mass of silica having pores having a specific surface area by the BET method of 50 to 400 m ² / g and curing catalyst 0.01 to 5
There is an organic polymer fine particle obtained by adding a part by mass and proceeding the resin curing reaction in an emulsified state in which fine particle silica and a curing catalyst coexist, to obtain a cured product from an aqueous medium. The resin, which is hardened in the emulsified state and separated from the aqueous medium by filtration or centrifugation, is a lump, but is loosened with a slight force to form a fine powder. Further, since the polymerization is carried out in the coexistence of silica and a curing catalyst, coarse particles are not contained and the dispersibility is excellent.

Further, benzoguanamine or a mixture of 100 to 50 parts by weight of benzoguanamine and 0 to 50 parts by weight of melamine and formaldehyde are added in a proportion of 1.2 to 3.5 mol per 1 mol of benzoguanamine or the mixture. After reacting in the range of pH 5 to 10 to make a soluble fusible resin having a miscibility of methanol in the range of 0 to 150%, it is added to a protective colloid aqueous solution under stirring and the soluble fusible resin is added. After holding at a temperature in the range of 40 to 60 ° C. for at least 1 hour, 60 to 2 under normal pressure or pressure.
A cured product obtained by curing at a temperature in the range of 00 ° C can also be used. The cured product obtained by such a method is preferable in that it has a uniform fine particle diameter and is excellent in the bonding / holding property with the abrasive grains. The methanol miscibility means that 2 g of a reaction product of benzoguanamine or a mixture of benzoguanamine and melamine and formaldehyde was dissolved in 5 g of methanol, and water was added dropwise while maintaining the temperature at 25 ° C. to generate cloudiness. It is a numerical value obtained by multiplying the ratio of the mass of water and the mass of the reaction product by 100. Examples of protective colloids include polyvinyl alcohol, carboxymethyl cellulose, sodium alginate, polyacrylic acid, and water-soluble polyacrylic acid salt. Examples of soluble fusible resins include water-soluble monoazo dyes, metal-containing azo dyes, and anthraquinonic acid dyes.

The carrier particles used in the present invention function as spacers for preventing scratches due to direct contact between the surface plate and the object to be polished, and also function as carriers for holding the abrasive grains and transporting them to the processing region, and It is necessary to uniformly disperse in the processing region and to stay for a certain period of time so as to continue polishing. In order to secure such various characteristics, the average particle diameter of carrier particles is 0.1 to 0.1 when the shape is a sphere.
The thickness is 30 μm, more preferably 0.5 to 20 μm, and particularly preferably 1 to 15 μm. In order to obtain a polymer in such a range, it can be prepared by appropriately selecting the compounding amount of the polymerization initiator, the temperature and the like. When the particles are polymers, they may have fine protrusions composed of organic polymer chains on the surface. In the present invention, in order to ensure the function of the carrier particles as a spacer, the average size of carrier particles in the case of an irregular shape is calculated by averaging the shortest lengths as the average particle diameter. In addition,
The molecular weight of the polymer is not particularly limited as long as the carrier particles are in the above range. Incidentally, in order to adjust the average particle diameter, during the production of the above organic polymer compound, particularly by blending an appropriate amount of a chain regulator during polymerization, controlling the polymerization temperature, the polymerization time, or a crosslinking agent during the polymerization. It can be adjusted by a method such as addition.

The abrasive of the present invention is an abrasive containing the above carrier particles and abrasive grains. The size of the abrasive grains is 1/10000 to 1/5 of the carrier particles, preferably 1/10.
00 to 1/5, particularly preferably 1/1000 to 1/10
Is. The size of the abrasive grains depends on the average particle size of the carrier particles, but is generally 0.001 to 3 μm, more preferably 0.005 to 2 μm, and particularly preferably 0.01 to 1 μm.
m. If it exceeds 3 μm, scratches are likely to occur, while if it is less than 0.001 μm, the polishing efficiency may deteriorate.

It is sufficient that such abrasive grains can polish the surface of an object to be polished, and for example, at least one kind of colloidal silica, silica, alumina, ceria, titania, zirconia, silicon nitride, silicon carbide, manganese oxide, diamond. And mixtures of these can be used.
The abrasive grains polish the surface of the object to be polished, and need to be held on the surface of the carrier particles during the polishing process. In this case, the abrasive particles may be attached to the carrier particles again after the abrasive particles have been separated from a part of the surface of the carrier particles during polishing. In the present invention, since the carrier particles and the abrasive particles have zeta potentials having opposite signs in the abrasive, it is considered that the bonding force between them is not necessarily strong. However, the form held by the abrasive grains with respect to the carrier particles is not limited to that due to the zeta potential. Therefore, in addition to this, other chemical bonds or physical bonds may be included, and the abrasive grains may be appropriately selected from those suitable for polishing the object to be polished.

The mixing ratio of the carrier particles and the abrasive grains is such that the abrasive grains are 10 to 20 relative to 100 parts by weight of the carrier particles.
00 parts by mass, more preferably 50 to 1000 parts by mass, particularly preferably 50 to 500 parts by mass. 2000
If it exceeds the mass part, the number of abrasive grains not held by the carrier particles increases, and an excessive amount of abrasive grains is wasted in the polishing process. On the other hand, if the amount is less than 10 parts by mass, the polishing efficiency will decrease. In addition,
When the abrasive grains already contain a solvent such as colloidal silica, the compounding amount of the abrasive grains is calculated by using the amount of silica in the colloidal silica as the compounding amount of the abrasive grains.

The abrasive of the present invention contains a solvent in addition to the abrasive particles and the carrier particles in order to facilitate the bonding between the abrasive particles and the carrier particles or to improve the polishing efficiency. The solvent for such an abrasive may be a hydrophilic solvent or a hydrophobic solvent, and can be appropriately selected according to the characteristics of the object to be polished, the type of carrier particles used, the type of abrasive grains, and the like.
Examples of the hydrophilic solvent include pure water, ion-exchanged water, alcohols having 1 to 12 carbon atoms such as methanol, ethanol, butanol, propanol, and t-butanol, which may have a branch, ethylene glycol, and propylene glycol. There are glycols. In addition, examples of the hydrophobic solvent include oils such as mineral oil, vegetable oil and silicone oil. In the present invention, one kind or two or more kinds of these solvents may be used in combination. This solvent can be adjusted to have an optimum hydrogen ion concentration depending on the characteristics of both the carrier particles and the abrasive grains for facilitating the bonding, or to have an optimum viscosity for improving the dispersibility of both. it can. The amount of the solvent used is not particularly limited, but is preferably 2 to 200 times the total amount of the carrier particles and the abrasive grains, and more preferably 5 to 50 times.
It is mass times.

The abrasive in such a state is one in which the abrasive particles are held by the carrier particles in a solvent for an abrasive, and the carrier particles and the abrasive particles are mixed in the presence of the solvent, and if necessary, It can be produced by stirring accordingly. At this time, it may be produced by adding carrier particles to a solvent in which the abrasive grains are dispersed and stirring, and it is particularly preferable to use a homogenizer or an ultrasonic disperser. Further, when the carrier particles are obtained by polymerizing a polymerizable monomer in a solvent for polymerization, the carrier particles are isolated from the solvent for polymerization, and thereafter the abrasive particles are not dried. It can also be prepared by holding it in the. When the carrier particles are dried, a gas is included on the surface or inside of the polymer, or as a result of coalescence or agglomeration of particles, the affinity with the solvent and the dispersibility are decreased even if they are subsequently mixed with other solvents. There is a case. Therefore, the wettability of the carrier particles is 5% by mass or more, more preferably 10 to 1000% by mass, and particularly preferably 20 to 5% by mass.
It is preferable to maintain it at 00% by mass. When it is less than 5% by mass, a large amount of gas is present on the surface and inside of the carrier particles, and the dispersibility may be lowered. If the wettability of the carrier particles is 5% by mass or more, washing the carrier particles with another solvent after isolation from the polymerization solvent may be used. In addition, the "wetness" in the present application is a solvent-containing mass (%) contained in the carrier particles, and when the solvent is a mixed solution of two or more kinds, it is converted into the total amount. Thus, if the carrier particles are isolated from the solvent and handled without drying, high dispersibility in the solvent can be ensured and polishing efficiency can be further improved.

The polishing agent of the present invention can be produced by mixing the above-mentioned carrier particles and abrasive grains in the presence of a solvent and stirring the mixture if necessary. At this time, the carrier particles may be added to a solvent in which the abrasive particles are dispersed, and the mixture may be stirred. The abrasive may contain a pH adjusting agent, a viscosity adjusting agent, a dispersant, a coagulant, and a surfactant, as long as the effects of the present invention are not impaired.

In the present invention, the zeta potentials of the abrasive grains and the carrier particles in the polishing agent need not have opposite signs, but generally, the zeta potentials are the same when the solid and the liquid in contact with each other undergo relative motion. It refers to the potential difference that occurs at the interface. Of the electric double layer generated at the interface between the solid and the liquid, a stationary phase or an adsorption layer is provided in a portion close to the solid, and ions having an opposite charge to the surface of the solid are fixed. Since the stationary phase moves together with the solid when the solid and the liquid make a relative motion, the potential difference that actually controls the motion is the potential difference between the surface of the stationary phase and the inside of the solution. This zeta potential fluctuates as the pH of the solution changes. Therefore, in the present invention, by combining specific carrier particles and abrasive particles, by adjusting the pH of the abrasive containing these particles,
It is possible to adjust the abrasives whose zeta potentials are not opposite in sign.

The carrier particles may be those in which the polymer forming the carrier particles has a specific functional group, a surfactant,
When either the polymer dispersant or the inorganic fine particles adhere to the surface, the particles can be adjusted to have a negative or positive zeta potential in the abrasive. At least one of a carboxyl group, a sulfonic acid group, a hydroxyl group, an amino group and an imino group in the molecular chain of the above organic polymer compound
A specific functional group can be introduced into carrier particles by copolymerizing two types of monomers, and anionic or cationic surfactants, polymer dispersants, and inorganic fine particles are added to the polymerization liquid of organic polymer compounds. Or by adding an anionic or cationic surfactant, a polymer dispersant, or inorganic fine particles to the polishing agent, these can be attached to the surface of the carrier particles. The thus-prepared carrier particles have an isoelectric point, and the zeta potential becomes positive below the pH of the isoelectric point and becomes negative above the pH of the isoelectric point.

The abrasive grains in the polishing agent are those having an isoelectric point at pH 3 to 7, such as silica, ceria and zirconia, and those having an isoelectric point at pH 7 to 9 are alumina,
There is Titania. The zeta potential of these abrasive grains becomes positive below the pH of the isoelectric point and becomes negative above the pH of the isoelectric point.

In the present invention, when the zeta potential of the abrasive grains in the abrasive is 0 or negative, the zeta potential of the carrier particles is preferably 0 to -100 mV, and more preferably -0.1 mV. ~ -80 mV, particularly preferably -1 ~
-60 mV. If it exceeds -100 mV, the alkalinity of pH is high and it may be unsuitable for polishing. The difference in zeta potential between the abrasive grains and the carrier particles is preferably 5 to 80 mV, more preferably 10 to 70 mV, and particularly preferably 10 to 50 mV. If it is less than 5 mV, the bonding force between the abrasive grains and the carrier particles may be insufficient, and the carrier particles may not retain a sufficient amount of the abrasive grains. On the other hand, 80 mV
If it exceeds, it is disadvantageous in that the cohesive force is too strong.

When the zeta potential of the abrasive grains in the abrasive is 0 or positive, the zeta potential of the carrier particles is
It is preferably 0 to 50 mV, more preferably 0.1 to 40 mV, and particularly preferably 1 to 30 mV. If it exceeds 50 mV, the acidity of pH may be high and it may be unsuitable for polishing. The difference in zeta potential between the abrasive grains and the carrier particles is preferably 5 to 49 mV, more preferably 5 to 40 mV, and particularly preferably 10 to 30 mV. If it is less than 5 mV, the bonding force between the abrasive grains and the carrier particles may be insufficient, and the carrier particles may not retain a sufficient amount of the abrasive grains. On the other hand, if it exceeds 49 mV, it is disadvantageous in that the cohesive force is too strong.

Since the zeta potentials of the abrasive grains and carrier particles in the polishing agent depend on the pH of the polishing agent, the zeta potentials of the two can be made to have no opposite signs by adjusting the pH. In particular, when the carrier particles have a zeta potential based on cations and anions, the positive and negative polarities are reversed with the isoelectric point as a boundary. In such a case, the abrasive grains and pH can be adjusted in advance with reference to the isoelectric point of the carrier particles so that the zeta potentials of the carrier particles and the abrasive grains do not have opposite signs in the abrasive solvent.

In order to adjust the pH of the polishing agent or improve the dispersibility and stability of the polishing agent, a hydroxide of an alkali metal, ammonia, an inorganic acid or an organic acid can be added. As the alkali metal hydroxide, sodium hydroxide, potassium hydroxide or the like can be used. Further, nitric acid, sulfuric acid, phosphoric acid and the like can be used as the inorganic acid, and formic acid, acetic acid, oxalic acid, malonic acid, succinic acid, benzoic acid and the like can be used as the organic acid. Further, the pH can be adjusted by using a hydroxide such as rubidium hydroxide or cesium hydroxide. Also, the pH of the aqueous dispersion
By adjusting, it is possible to improve the dispersibility as well as the polishing rate, and to adjust the pH appropriately while considering the electrochemical properties of the surface to be processed, the dispersibility of the polymer particles, the stability, and the polishing rate. It is preferable to set.

The abrasive of the present invention contains carrier particles and abrasive particles, and the abrasive particles are held on the surface of the carrier particles in the polishing step. When the abrasive particles are not held on the surface of the carrier particles, the object to be polished cannot be polished because the average particle diameter of the carrier particles is larger than that of the abrasive particles. Therefore, the carrier particles and the abrasive grains in the abrasive are present as composite particles in which the abrasive grains are held on at least the surface of the carrier particles, and the binding force at this time is also electrostatic force, ionic bond, van der Waals force or physical force. It is thought to be due to mechanical or mechanical force. However, in the polishing agent of the present invention, it is not necessary that the carrier particles and the abrasive grains are always present as composite particles, and the carrier particles substantially function as a spacer in the polishing step, and It only has to function as a medium for transportation. Therefore, the carrier particles and the abrasive grains are separated during the storage of the polishing agent, but the carrier particles and the abrasive grains are brought into contact with each other by stirring or the like when being supplied to the polishing step, and the polishing is performed in the polishing step. Carrier particles and abrasive particles are brought into contact with each other by the supply force of the agent or the rotational force of the object to be polished, and the abrasive particles are held on the surface of the carrier particles, so that the surface of the object to be polished can be substantially polished. It may be possible.

A third aspect of the present invention is a method of polishing the surface of an object to be polished, using the first polishing agent.

In the polishing method, the polishing agent is supplied in a predetermined amount between a surface plate provided in the polishing machine and the object to be polished, and the abrasive grains contained in the abrasive are brought into contact with the object to be polished. When the object to be polished is rotated for this purpose, the surface of the object is polished by the relative movement of the abrasive grains and the object to be polished.

If the polishing machine has a surface plate and is provided with a polishing agent supply means and a means for rotating the object to be polished, the size of the surface plate is appropriately selected according to the size of the object to be polished. can do.

The platen is preferably made of metal such as copper or tin, glass, ceramic or plastic and has good flatness. The shape of the platen is not limited to a flat surface,
It may be a curved surface, a spherical surface or an uneven surface. By using such a surface plate, the conventional urethane-based polishing pad becomes unnecessary, and the flatness and minute undulations are improved.

The object to be polished comes into contact with the abrasive grains while rotating on the polishing agent. In the present invention, the object to be polished may be rotated at a generally known rotational speed, carrier particles, abrasive grains, or the object to be polished. It can be appropriately selected depending on the material and the like.

The object to be polished may have a suitable working pressure depending on the type and size of carrier particles or abrasive grains. In the present invention, it is preferably 5 to 100 KPa, and more preferably. It is 10 to 70 KPa.

Further, the supply amount of the polishing agent can be appropriately selected according to the size of the surface plate, and the stirring force of the polishing agent at the time of supplying it to the polishing step also depends on the kind and blending amount of carrier particles or abrasive grains to be used. It can be appropriately selected according to the above.

Specifically, the constant amount in the above-mentioned supply of the polishing agent onto the surface plate is 1 to 100 ml / min, preferably 10 to 50 ml / min. When lapping the object to be polished while rotating the platen at a predetermined rotation speed, the predetermined rotation speed is 10 to 500 rpm.
And preferably 20 to 200 rpm.

In the polishing method of the present invention, particularly when a silicon wafer, crystal, glass, sapphire or the like is the object to be polished, its surface is excellent in mirror polishing.

[0047]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Benzoquanamine resin particles (manufactured by Nippon Shokubai Co., Ltd., trade name "Eposter L15", average particle diameter of about 10 μm) were used as carrier particles, and ceria (manufactured by Seimi Chemical Co., Ltd., high-purity ceria, average) was used as abrasive particles. A particle diameter of 0.8 μm) and ion-exchanged water were used as a solvent, and abrasive particles were prepared by mixing and stirring abrasive particles at a concentration of 5% by mass and carrier particles at a concentration of 2.5% by mass. The pH was adjusted to 7.5 with an aqueous potassium hydroxide solution. pH 7.5
The zeta potentials of the carrier particles and the abrasive grains were measured with a laser zeta potentiometer (ELS-8000, Otsuka Electronics Co., Ltd.) and found to be -40 mV and -3 mV, respectively.

Comparative Example 1 Ceria (TE-508 manufactured by Seimi Chemical Co., average particle size 0.9 μm) was used as the abrasive grain of Example 1, and the pH was adjusted.
The abrasive was prepared in the same manner as in Example 1 except that the hydrochloric acid solution was adjusted so that The zeta potentials of the carrier particles and the abrasive grains at pH 6 were measured with a laser zeta potentiometer (ELS-8000, Otsuka Electronics Co., Ltd.) and found to be -20 mV and +8.9 mV, respectively.

Test Example 1 The polishing agents prepared in Example 1 and Comparative Example 1 were treated with a single-side polishing machine (Okamoto Machine Tool Co., Ltd., trade name "SPL").
-15 ") was used to perform a polishing test of a 3-inch crystal wafer.

The surface plate has a surface roughness Ra (arithmetic mean roughness).
Alumina of 1.7 μm was used. The rotation speed of the crystal wafer and surface plate was 60 rpm, and the supply amount of the polishing agent was 25 ml /
And the working pressure is 10 kPa and the swing of the workpiece is 50 m.
m, cycle 25 seconds, and polished for 20 minutes.

After the completion of polishing, the plate was washed with pure water, the polishing efficiency was calculated from the decrease in mass after polishing, and the presence or absence of scratch was visually evaluated. The results are shown in Table 1.

[0053]

[Table 1]

[0054]

When an abrasive containing carrier particles and abrasive particles is used, new carrier particles and abrasive particles are supplied as the abrasive, and deteriorated abrasive particles are discharged, so that the processing efficiency does not decrease and long-term operation is possible. A stable polishing efficiency can be maintained throughout. At this time, when the zeta potential of the carrier particles and the zeta potential of the abrasive particles in the abrasive are not opposite in sign, the cohesive force between the carrier particles is weak, so they are easily decomposed during polishing and dispersed in the abrasive. The carrier particles can hold the required amount of abrasive particles. The polishing agent of the present invention achieves polishing with excellent polishing efficiency.

Continued front page    (72) Inventor Ryuji Aizawa             12-25 Kannondai, Tsukuba City, Ibaraki Prefecture             Nippon Shokubai Co., Ltd. (72) Inventor Yasuhiro Tani             4-6-1, Komaba, Meguro-ku, Tokyo             Institute of Industrial Science and Technology (72) Inventor Kenji Kawada             4-6-1, Komaba, Meguro-ku, Tokyo             Institute of Industrial Science and Technology (72) Inventor Toshiyuki Enomoto             4-6-1, Komaba, Meguro-ku, Tokyo             Institute of Industrial Science and Technology (72) Inventor Tokio Isami             34-1 Musashino, Akishima-shi, Tokyo Japan             Within Micro Coating Co., Ltd. F term (reference) 3C058 AA07 CB02 CB03 DA02 DA17

Claims (4)

[Claims] 1. An abrasive containing carrier particles and abrasive particles, wherein the zeta potential of the abrasive particles and the zeta potential of the carrier particles are not opposite in sign. 2. The zeta potential of the carrier particles in the polishing agent is +50 to −100 mV.
The polishing agent according to claim 1. 3. Carrier particles for use according to claim 1 or 2. 4. A method for polishing the surface of an object to be polished, which uses the abrasive according to claim 1.