JP2004074330A - Fixed abrasive polishing tool, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed abrasive polishing tool in which free abrasives separated from fixed abrasives are favorably dispersed to increase the number of acting abrasives to a subject surface to be polished for achieving sufficient polishing speed and sharp polishing characteristics. <P>SOLUTION: This fixed abrasive polishing tool is composed of abrasives 11 and resin 15, and surface-treated with coupling agent. A combination of the coupling agent with the resin comprises a combination of organofunctional groups in the coupling agent with the resin that is naturally hard to be coupled with them. In the fixed abrasive polishing tool, composed of the abrasives and the resin, the resin is core shell type composite high polymer 13 comprising the abrasives as nuclei, and high polymer polymerized and coated around the abrasives. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polishing tool for polishing a surface of a workpiece such as a semiconductor wafer into a mirror surface, and more particularly to a fixed abrasive polishing tool in which abrasive grains are held by a binder resin.
[0002]
[Prior art]
In a chemical mechanical polishing (CMP) apparatus using a polishing liquid (slurry), since polishing is performed while supplying a polishing liquid (slurry) containing a large amount of polishing grains to a relatively soft polishing cloth, there is a problem with pattern dependency. There is. The pattern dependency means that a gentle unevenness due to the unevenness is formed even after the polishing due to the unevenness pattern on the semiconductor wafer existing before the polishing, and it is difficult to obtain perfect flatness. That is, the polishing rate is high in the uneven portion with a fine pitch, and the polishing speed is low in the uneven portion with a large pitch, so that gentle unevenness is formed between a portion having a high polishing speed and a portion having a low polishing speed. That is the problem.
[0003]
In recent years, a polishing process using a fixed abrasive polishing tool in which abrasive grains are fixed with a binder resin has been announced. In the fixed-abrasive polishing process, very high flatness is obtained due to the high hardness, which is a fundamental feature of the polishing process. However, the polishing speed is generally lower than that of polishing using a polishing liquid (slurry) and a polishing pad. When polishing a semiconductor wafer or the like, there is a problem that the throughput is practically low and the productivity is reduced.
[0004]
[Problems to be solved by the invention]
In the present invention, the abrasive grains released from the fixed abrasive grains are dispersed well, thereby increasing the number of abrasive grains acting on the polished surface, having a sufficient polishing rate, and having a sharp polishing characteristic. The purpose is to provide tools.
[0005]
[Means for Solving the Problems]
The fixed abrasive polishing tool of the present invention is a fixed abrasive polishing tool composed of abrasive particles surface-treated with a coupling agent and a resin, wherein the combination of the coupling agent and the resin is It is characterized by being composed of a combination of an organic functional group of the coupling agent and a resin that is inherently difficult to bond.
[0006]
According to the present invention, the fixed abrasive polishing tool is composed of a combination of the organic functional group of the coupling agent having surface-treated abrasive grains and a resin that is inherently difficult to bond. The agent is easily separated from the resin holding it. Thereby, the abrasive grains released from the fixed abrasive grains are well dispersed, so that the number of abrasive grains acting on the polished surface can be increased and the polishing rate can be improved.
[0007]
Further, the fixed abrasive polishing tool of the present invention is a fixed abrasive polishing tool comprising an abrasive and a resin, wherein the resin has the abrasive as a nucleus and a polymer is polymerized around the abrasive. It is a core-shell type composite polymer coated. Further, a fixed abrasive polishing tool comprising abrasive grains, a first resin that holds the abrasive grains, and a second resin that further bonds the first resin, wherein the first resin The second resins are characterized by low adhesion to each other (eg, having a solubility parameter separated by 3 or more).
[0008]
According to the present invention described above, the resin is polymerized and coated around the abrasive grains as a nucleus. For example, the resin swells with the polishing liquid, so that the abrasive grains can be easily separated from the binder resin. As a result, the number of abrasive grains acting on the polished surface can be increased, and the polishing rate can be improved.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0010]
FIG. 1A shows the abrasive grains 11, and FIG. 1B shows that the abrasive grains 11 have been treated with a coupling agent and a film of the coupling agent 12 has been formed on the surface thereof. The coupling agent 12 binds to the inorganic substance constituting the abrasive grains 11 and covers the surface thereof. In the fixed abrasive polishing tool, the abrasive grains are held in a binder resin, and the abrasive grains, the binder resin, and the pores are combined in an appropriate ratio. The coupling agent contains an organic functional group that binds to the resin. However, in the fixed abrasive polishing tool of the present invention, the organic functional group of the coupling agent and a resin of a type that is not easily bonded to the functional group. And a combination of the above.
[0011]
As a means for preventing the abrasive grains in the fixed abrasive polishing tool from agglomerating each other even in a dry state in the manufacturing stage, a surface modification method of coating the abrasive grains with a coupling agent or a polymer is employed. Examples of the abrasive grains include silica-based, alumina-based, cerium-oxide-based, manganese dioxide-based, fine-particle diamond, and titanium-oxide-based particles having a particle size of 0.5 μm or less.
[0012]
Coupling agents are used for the purpose of improving the bonding strength between dissimilar materials, especially between inorganic and organic materials, and have both a functional group associated with the inorganic material and a functional group associated with the organic material. I have. Examples of the coupling agent include chromium-based, silane-based, titanium-based, aluminum-based, zirconium-based, and organometallic compounds.
[0013]
In the manufacturing stage of the fixed abrasive polishing tool, as shown in FIG. 2A, there is a problem that the abrasive grains are aggregated and the abrasive grains are not uniformly dispersed in the polishing tool. Therefore, as shown in FIG. 2 (b), by subjecting the abrasive grains to a surface treatment with a coupling agent, it is possible to prevent agglomeration of the abrasive grains during the manufacturing stage.
[0014]
In order to prevent agglomeration, which is the approach between abrasive grains, it is possible to use the steric hindrance effect that the coupling agent adsorbed on the abrasive grains repels three-dimensionally. Appears strongly. The thickness of the adsorption layer is determined by the length of the molecular chain of the coupling agent. It is said that the length is only required to be about 100 mm, which is a reference for selecting a coupling agent.
[0015]
It is preferable that the bonding between the abrasive grains and the binder resin is weak at the stage of use for polishing after manufacturing. By employing a combination of the organic functional group of the coupling agent and a resin that is inherently difficult to bond, the abrasive grains are easily released from the fixed abrasive polishing tool on the polishing surface during polishing, thereby improving the polishing rate. be able to.
[0016]
The coupling agent used in the fixed abrasive polishing tool of the present invention is, in particular, a silane coupling agent and a titanium coupling agent, and when weakening the binding between the coupling agent and the binder resin of the fixed abrasive, It is necessary to select a combination of the organic functional group of the coupling agent and the binder resin.
[0017]
For example, when the binder resin contains an alkyl group as a functional group such as a polyacrylic / polymethacrylic / polystyrene / polyethylene / diallylphthalate / ethylene propylene diene terpolymer, the silane coupling agent is an organic compound. 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxychlorohexyl) ethyltrimethoxysilane or N-2- (aminoethyl) 3 containing an epoxy group, an amino group, a halogen group or a mercapto group as a functional group -Aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane and the like are preferred. As the titanium-based coupling agent, those having an amino group or a carboxyl group in the organic functional group are suitable.
[0018]
When the binder resin is an epoxy resin, a phenol resin, a urethane resin, a melamine resin, a polycarbonate, a polyvinyl chloride, a polyimide, a styrene-butadiene copolymer, a natural rubber, or the like, the silane-based coupling agent is converted to an organic functional group. Vinyl triethoxysilane and vinyl tris (2-methoxyethoxy) silane having a vinyl group or an alkoxy group are preferable, and a titanium-based coupling agent having an amino group or a carboxyl group in an organic functional group is preferable as described above. is there.
[0019]
Titanium-based coupling agents, unlike silane-based coupling agents that covalently bond with resin, exhibit a van der Waals-like interaction with the resin, and therefore have a weaker bond, and are more readily abrasive than binder resin. Is released. As the coupling agent having a long molecular chain, (C ₁₇ H ₃₃ COO) ₃ SiC ₃ H ₆ OCOC ₁₇ H ₃₃ having an alkoxy group is preferable.
[0020]
Next, an outline of a method for manufacturing a fixed abrasive polishing tool will be described with reference to FIG. First, the raw material of the fixed abrasive is adjusted. That is, fine abrasive grains, resin materials and additives, ie, abrasive dispersants such as surfactants, processing stabilizers such as buffers, processing accelerators represented by pH adjusters such as KOH, and polymer agents A required amount of a fixed abrasive raw material (powder) composed of an additive containing a specularity improver or the like is weighed. These raw materials are mixed, and if necessary, pure water and a solvent are added to prepare a mixed solution. At this time, a dispersion process using a stirrer, an ultrasonic disperser or the like is performed to sufficiently disperse each raw material.
[0021]
Next, using a drying method represented by a spray dryer, dry granulation is performed, and a powder (granulated powder) of 0.1 μm to several hundred μm in which various raw materials are uniformly mixed, preferably having an average particle diameter of A powder (granulated powder) of several to several tens μm is manufactured. Alternatively, in addition to the above-described drying method, a method of producing a mixed particle by utilizing a pulverized powder after freeze-drying and an agglomeration and / or precipitation action may be employed. The above-mentioned powder (granulated powder) may be produced by mixing, if necessary, a drying step or a mixing step after drying, or these steps may be repeated as appropriate. Depending on the material to be mixed, the powder is directly mixed with a dry powder of another material. A step may be taken.
[0022]
Next, if necessary, an appropriate additive (agent) is added to the mixed powder (granulated powder) obtained in the above step, and the mixture is molded by a compression molding technique represented by a hot press. Get. At this time, the size of the compression molding machine is determined by the size to be molded. For this reason, the size of the compression molding machine can be reduced by manufacturing fixed abrasive grains having a divided structure, that is, a segment structure, as compared with fixed abrasive grains having a non-divided structure. Further, the auxiliary equipment and the equipment in the post-process also require a smaller apparatus to manufacture fixed abrasive grains having a divided structure, that is, a segment structure, so that the initial investment is small and the production cost can be reduced.
[0023]
In order to protect the fixed abrasive grains and facilitate mounting on the polishing device, the fixed abrasive grains obtained in the above process are fixed to a metal or engineering plastic support (base) such as metal or engineering plastic by bonding or welding. I do. At this time, fixed abrasive grains composed of many or complex shaped segments are difficult to position at the time of fixing, and if the positioning is incorrect, an adhesive for fixing the fixed abrasive grains and the base is used. There is a risk of protruding between segments. When the adhesive is on the fixed abrasive polishing surface, it is not preferable to hinder polishing or generate scratches on the wafer, so that accurate positioning is required.
[0024]
In the above manufacturing process, in order to surface-treat the abrasive grains with a coupling agent, the abrasive grains are dispersed in a solvent, a coupling agent capable of being treated in the solvent is charged, and the abrasive grains are ground in the solvent using an ultrasonic dispersion device or the like. Disperse the particles and coupling agent well. At this time, it is preferable that the coupling agent is mixed in an amount of about 0.1 to 10 wt% with respect to the abrasive grains. When an aqueous solvent is used as the solvent, it is preferable to use a coupling agent that can be treated in water. By sufficiently dispersing the coupling agent in the solvent using the ultrasonic dispersion device or the like, a film of the coupling agent is formed on the surface of the abrasive grains. As described above, the coating of the coupling agent can prevent the agglomeration of the abrasive grains in the manufacturing process of the fixed abrasive polishing tool, and can uniformly disperse the abrasive grains in the polishing tool.
[0025]
Thereafter, the resin raw material is dispersed in the solvent, and a granulated powder is formed by using a spray drying method, a freeze vacuum drying method, or the like. The granulated powder is formed by spraying a solvent containing abrasive grains and a resin raw material into, for example, a mist and drying by a high-temperature air stream to form a powder. Obtained in the state.
[0026]
Next, a description will be given of a fixed abrasive polishing tool using a core-shell composite polymer in which a polymer is polymer-coated around the abrasive with the abrasive as a core. FIG. 4 schematically shows the fixed abrasive polishing tool. In this embodiment, a coating 13 formed by polymerizing a resin around the abrasive grains 11 as a nucleus is formed. Then, the core-shell type composite polymer having the abrasive grains 11 as a unit as a core is bonded to each other to form a fixed abrasive polishing tool. Here, the core-shell type composite polymer may be formed by polymerizing a polymer around the abrasive grains via a coupling agent.
[0027]
The core-shell type composite polymer is formed by adding a binder resin such as a polyacrylic / polymethacrylic / polystyrene / SBR / NBR / MBR / polyvinyl acetate / acrylstyrene copolymer or the like to a slurry containing the abrasive grains. , And emulsion polymerization or soap-free emulsion polymerization is performed to form a polymer film 13 on the surface of the abrasive grains. Also, emulsifiers for emulsion polymerization, for example, sodium / potassium fatty acid, sodium / potassium disproportionated rosin, sodium alkyl benzene sulfonate, sodium alkyl diphenyl ether disulfonate, sodium dialkyl sulfosuccinate, sodium sulfate higher alcohol, alkyl (or alkyl phenyl) ) Sodium / ammonium ether sulfate, partially saponified polyvinyl alcohol, alkylphenol ethylene oxide adduct, higher alcohol ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, quaternary ammonium salt and the like can be used. After adsorbing these to the coupling agent, the polymerization of the above monomer can be carried out.
[0028]
In a method using a reactive emulsifier, which is one of the soap-free emulsion polymerization methods, the emulsifier itself has polymerizability, and can be polymerized by being adsorbed by a coupling agent on the surface of the abrasive grains. Examples of the reactive emulsifier include allyl / propenyl derivatives, acrylic acid derivatives, itaconic acid derivatives, and maleic acid derivatives. Copolymers of these with other monomers can also be used.
[0029]
When the above-mentioned coupling agent is not used, the reactive emulsifier can be directly adsorbed on the surface of the abrasive grains and polymerized or copolymerized with another monomer to form the coating 13 on the surface of the abrasive grains. A fixed abrasive polishing tool can be formed by directly heating and compression molding a core-shell composite polymer raw material having a polymer film formed on the surface of these abrasive grains. Since the fixed abrasive polishing tool formed in this way has a polymer film on the abrasive grains itself, the fixed abrasive polishing tool can be formed without using other binder resin.
[0030]
In general, the core-shell type resin has a core portion made of a resin, such as an ABS resin. However, the fixed abrasive polishing tool of the present invention is characterized in that abrasive grains are used in the core portion. For this reason, the generation of the polymer nucleus is suppressed so that the core-shell type resin is not formed between the resins, and the polymer is grown only on the surface of the abrasive grains. That is, the entropy of the abrasive grain surface and the generated nucleus is adjusted, and the solution is adjusted to be equal to or lower than the lower critical supersaturation concentration of the homogeneous solution to suppress the growth of the generated nucleus. That is, the solution concentration is adjusted to be equal to or higher than the supersaturated concentration and equal to or lower than the lower critical supersaturated concentration. Then, in order to suppress agglomeration of the abrasive grains, the equipotential point is removed, and the salt concentration is kept low. Further, a polymer (shell) suitable for an isotropic dressing method using non-mechanical dressing may be adopted.
[0031]
The following methods are available for producing the core-shell composite polymer.
First, since it is difficult to grow a polymer uniformly around the abrasive grains, the surface of the abrasive grains is subjected to an adsorption treatment of a surfactant or an organic polymer (functional group). Then, a polymer film serving as a shell is formed on the adsorption layer of the organic polymer (functional group) by capsule polymerization. The point is to improve the affinity between organic and inorganic substances.
Second, it utilizes heteroaggregation.
Third, a suspension polymerization method and an emulsion polymerization method are employed.
In either method, it is necessary to control the size and particle size distribution of the composite fine particles, and the orientation or the like greatly affects the characteristics as a fixed abrasive polishing tool.
[0032]
FIG. 5 shows a fixed abrasive polishing tool according to another embodiment of the present invention. The polishing tool according to this embodiment includes abrasive grains 11, a first resin 13 for holding the abrasive grains, and a second resin 15 for further bonding the first resin 13. That is, a core-shell type composite polymer in which the polymer 13 is polymer-coated around the abrasive grain 11 as a nucleus is combined with the second resin 15 to form a fixed abrasive grain polishing tool. Here, the first resin 13 and the second resin 15 are characterized by low bonding properties and a solubility parameter separated by 3 or more. Note that the solubility parameters are preferably separated by 6 or more. Here, the plurality of abrasive grains 11 may be dispersed only in the first resin 13, and the second binder resin 15 may bond the first binder resin 13.
[0033]
That is, in the above-described manufacturing process of the fixed abrasive polishing tool, when forming the granulated powder that is the raw material of the fixed abrasive polishing tool, the granulated powder containing the abrasive grains 11 in the binder resin 13 is formed. Then, the first resin containing abrasive grains is held by using the second resin 15 having a different solubility parameter. Since the solubility parameters of the first resin 13 and the second resin 15 are separated by 3 or more, the adhesive force between these resins is reduced, and the first binder resin 13 in which the abrasive grains are dispersed and held becomes Many working abrasive grains are easily released from the second binder resin 15 and are released to the polishing surface, thereby enabling high-speed polishing. Further, since the adhesive force between the resins 13 and 15 is low, it is possible to prevent the resin from re-adhering to the polishing tool.
[0034]
Reducing the bonding property between the first binder resin 13 and the second binder resin 15 can be realized by using, for example, resins having different solubility parameters by 3 or more, preferably 6 or more. At this time, by making the solubility parameter of the first or second binder resin 13 and 15 in which the abrasive grains are dispersed and held close to that of the polishing liquid, the abrasive grains are dissolved in the polishing liquid and the abrasive grains are dispersed on the polishing surface to polish. To promote. For example, as a resin having a water solubility parameter (23.4) which is close to the water solubility resin / elastomer, for example, polyvinyl alcohol (23.4) and the like can be used as the first or second binder resin. As the second or first binder resin, Teflon (6.2), silicone rubber (7.3), natural rubber (7.9), polyisobutylene (8.0), polybutadiene (8.4-8. 6), polybutadiene styrene (8.1-8.6), polystyrene (9.7), neoprene (8.2-9.2), polybutadiene-acrylonitrile (9.4-9.5), polyvinyl chloride ( 9.5-9.7), polyvinyl acetate (9.4), polymethyl methacrylate (9.5), polyethylene terephthalate (10.7), polyacrylonitrile (15 4), it can be used thermosetting resins such as epoxy resins and urethane resins.
Further, the abrasive grains in the first binder resin may be coated with the above-described coupling agent or polymer in order to further improve the dispersibility.
[0035]
Here, as the first resin 13, a swelling resin having a property of swelling with respect to the polishing liquid can be used. During polishing, when the polishing surface of the fixed-abrasive polishing tool comes into contact with the polishing liquid, the resin 13 swells and softens and changes to have elasticity.
[0036]
As shown in FIG. 6, the surface of the fixed abrasive polishing tool 17 needs to have a certain degree of rigidity at the time of contact with the convex portion of the workpiece and flexibility at the time of contact with the concave portion. For example, the swollen resin 13a is crushed in a portion where the convex portion 21a of the object 21 to be polished such as a semiconductor wafer comes into contact, high rigidity is exerted, processing pressure is increased, and high processing efficiency is exhibited. On the other hand, in the concave portion 21b of the object 21 to be polished, the processing pressure is reduced due to the swollen resin 13b, the material has a soft property, and no scratch occurs even when the abrasive grains 11 are interposed.
[0037]
Therefore, the surface of the fixed abrasive polishing tool 17 exhibits a certain degree of rigidity when the workpiece comes into contact with the convex portion, and exhibits flexibility when contacting the concave portion. Therefore, only the convex portions can be polished, and the concave portions can be hardly polished, and sharp polishing characteristics can be maintained. That is, the resin 13 swells and softens due to the polishing liquid and changes so as to have elasticity. When the convex portion of the workpiece is polished, it reaches the compression limit, and since it does not deform elastically, it can be processed with a large processing pressure. Polishing is possible and sharp polishing characteristics can be exhibited.
[0038]
In this embodiment, an example has been described in which the resin 13 absorbs the polishing liquid and swells. However, for example, a resin having such a property that the resin is softened and elasticized by irradiation with a light beam may be used. In this way, similarly, by irradiating light with the progress of polishing, the resin 13 is swollen, whereby it is possible to promote self-generation of free abrasive grains and obtain sharp polishing characteristics.
[0039]
It should be noted that the above-described embodiment describes one mode of the embodiment of the present invention, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.
[0040]
【The invention's effect】
According to the present invention described above, the number of abrasive grains acting on the polished surface during the polishing process can be increased, and a sufficient polishing rate can be given to the fixed abrasive polishing tool. In addition, sharp polishing characteristics can be obtained for the workpiece.
[Brief description of the drawings]
FIG. 1A is a view showing abrasive grains, and FIG. 1B is a view showing a state in which a coating of a coupling agent is formed on the abrasive grains.
FIG. 2A is a diagram showing a state where abrasive grains are aggregated, and FIG. 2B is a view showing a state where abrasive grains are dispersed by performing a surface treatment with a coupling agent.
FIG. 3 is a flowchart showing an outline of a manufacturing process of a fixed abrasive polishing tool.
FIG. 4 is a view schematically showing a fixed abrasive polishing tool formed by combining abrasive grains provided with a polymer film.
FIG. 5 is a view schematically showing a fixed abrasive polishing tool formed by combining a first resin holding abrasive grains by using a second resin.
FIG. 6 is a diagram schematically showing a state at the time of polishing when a resin holding abrasive grains has swelling properties.
[Explanation of symbols]
Reference Signs List 11 Abrasive grains 12 Surface treatment film with coupling agent 13 Core-shell type composite polymer film (first resin)
13a, 13b Swelling resin 15 Second resin 17 Fixed abrasive polishing tool 21 Workpiece (semiconductor wafer)
21a convex part 21b concave part

Claims (7)

Abrasive grains surface-treated with a coupling agent, and a fixed abrasive polishing tool composed of a resin, wherein the combination of the coupling agent and the resin is an organic functional group of the coupling agent, A fixed-abrasive polishing tool characterized by being made of a combination with a resin that is inherently difficult to bond. A method for producing a fixed abrasive polishing tool in which abrasive grains are surface-treated with a coupling agent and the abrasive grains are fixedly held by a resin, wherein the combination of the coupling agent and the resin has the coupling agent. A method for producing a fixed abrasive polishing tool, comprising a combination of an organic functional group and a resin that is inherently difficult to bond. A fixed-abrasive polishing tool composed of abrasive grains and a resin, wherein the resin is a core-shell composite polymer in which a polymer is polymer-coated around the abrasive grains with the abrasive grains as a nucleus. Characterized fixed abrasive polishing tool. A resin is polymerized around the abrasive grains as a nucleus, a core-shell type composite polymer material having the abrasive grains as a core is formed, and a polishing tool is formed by molding the core-shell type composite polymer material. Manufacturing method of a fixed abrasive polishing tool. The method according to claim 4, wherein the resin is a swelling resin. Abrasive grains,
A first resin that holds the abrasive grains;
A second resin that further binds the first resin, a fixed abrasive polishing tool comprising:
The fixed abrasive polishing tool, wherein the first resin and the second resin have a low adhesive strength to each other. 7. The fixed abrasive polishing tool according to claim 6, wherein the first resin and the second resin are separated by a solubility parameter of 3 or more, preferably 6 or more.

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