US20040033771A1

US20040033771A1 - Polishing tool

Info

Publication number: US20040033771A1
Application number: US10/638,312
Authority: US
Inventors: Kazuto Hirokawa; Tomohiko Akatsuka; Akira Kodera
Original assignee: Individual
Current assignee: Ebara Corp
Priority date: 2002-08-13
Filing date: 2003-08-12
Publication date: 2004-02-19
Also published as: JP2004074330A

Abstract

A polishing tool is used for polishing a workpiece such as a semiconductor wafer to a flat mirror finish. A fixed abrasive polishing tool includes abrasive particles which are subjected to surface treatment by a coupling agent, and resin for fixing said abrasive particles. The coupling agent has an organic functional group which is not substantially bonded to said resin

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing tool for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a fixed abrasive polishing tool which comprises abrasive particles fixed by a resin as a binder.

2. Description of the Related Art:

As semiconductor devices have become more highly integrated in recent years, circuit interconnections have become finer and dimensions of devices to be integrated have become smaller. From this point of view, it may be necessary to polish and planarize a surface of a semiconductor wafer to remove a film (layer) formed on the surface of the semiconductor wafer. In order to planarize a surface of a semiconductor wafer, a polishing apparatus for performing chemical mechanical polishing (CMP) has been used. This type of chemical mechanical polishing (CMP) apparatus comprises a polishing table having a polishing pad (polishing cloth) attached thereon, and a top ring for holding a workpiece to be polished, such as a semiconductor wafer. The workpiece is disposed between the polishing pad and the top ring, and pressed against the polishing pad under a certain pressure by the top ring while the polishing table and the top ring are rotated. In this state, the workpiece is polished to a flat mirror finish while a polishing liquid (slurry) is supplied onto the polishing pad.

In a chemical mechanical polishing process which employs such polishing liquid (slurry), the workpiece is polished while the polishing liquid (slurry) containing a large amount of abrasive particles is supplied onto a relatively soft polishing pad. Therefore, a problem of pattern dependence arises. Pattern dependence means that gentle irregularities are formed on a surface of a semiconductor wafer after a polishing process due to irregularities on the surface of the semiconductor wafer that existed before the polishing process, thus making it difficult to planarize the surface of the semiconductor wafer to a completely flat surface. Specifically, a polishing rate is higher in an area where irregularities have small pitches (a density of irregularities is large) and is lower in an area where irregularities have large pitches (a density of irregularities is small). Existence of areas of the higher polishing rate and areas of the lower polishing rate causes gentle irregularities to be formed on the surface of the semiconductor wafer.

In recent years, it has been proposed to polish a semiconductor wafer or the like with use of a fixed abrasive polishing tool. In such a process, a surface of a semiconductor wafer or the like is polished with a fixed abrasive which comprises abrasive particles fixed by a resin as a binder. With the process utilizing the fixed abrasive which essentially has a large hardness, it is possible to achieve a considerably higher level of planarity. However, a polishing rate of the process utilizing the fixed abrasive is generally lower than that of a process utilizing a polishing liquid (slurry) and a polishing pad. Thus, when semiconductor wafers or the like are polished, a throughput of the semiconductor wafers or the like is practically low, and hence the productivity is low.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a polishing tool which can sufficiently disperse free abrasive particles generated from a fixed abrasive to increase the number of abrasive particles on a polishing surface for thereby obtaining a higher polishing rate and a better polishing performance (sharp polishing characteristic).

According to a first aspect of the present invention, there is provided a fixed abrasive polishing tool comprising: abrasive particles which are subjected to surface treatment by a coupling agent; and resin for fixing the abrasive particles; wherein the coupling agent has an organic functional group which is not substantially bonded to the resin.

According to the present invention, the fixed abrasive polishing tool is composed of a combination of abrasive particles which is subjected to surface treatment by a coupling agent, and resin which is hardly bonded to an organic functional group of the coupling agent. Therefore, as polishing progresses, the coupling agent which is held by the resin can be easily separated from the resin. Thus, the abrasive particles which are liberated from the fixed abrasive can be dispersed well, and the number of abrasive particles on the polishing surface can be increased, thus improving a polishing rate.

In a preferred aspect of the present invention, the coupling agent comprises a chromium coupling agent, a silane coupling agent, a titanium coupling agent, an aluminium coupling agent, a zirconium coupling agent, or organometallic compounds.

In a preferred aspect of the present invention, the resin comprises polyacrylate based resin, polymethacrylate based resin, polystyrene, polyethylene, diallyl phtalate, an ethylene propylenediene ternary copolymer, an epoxy resin, a phenol resin, an urethane resin, a melamine resin, polycarbonate, polyvinyl chloride, polyimide, a styrene-butadiene copolymer, or natural rubber.

In a preferred aspect of the present invention, the coupling agent and the resin have solubility parameters which are different from each other by three or more.

In a preferred aspect of the present invention, the coupling agent and the resin have solubility parameters which are different from each other by six or more.

According to a second aspect of the present invention, there is provided a fixed abrasive polishing tool comprising: abrasive particles; and resin for fixing the abrasive particles; wherein the resin comprises a core-shell composite polymer which is formed by polymerization to surround the abrasive particles.

According to a third aspect of the present invention, there is provided a fixed abrasive polishing tool comprising: abrasive particles; first resin for holding the abrasive particles; and second resin which is bonded to the first resin; wherein bond strength of the first resin and the second resin is small.

In a preferred aspect of the present invention, the first resin comprises a water soluble resin or elastomer; and the second resin comprises teflon, a silicone rubber, a natural rubber, polyisobutylene, polybutadiene, butadiene styrene copolymer, polystyrene, neoprene, polybutadiene-acrylonitrile, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, an epoxy resin, or an urethane resin.

In a preferred aspect of the present invention, the first resin comprises teflon, a silicone rubber, a natural rubber, polyisobutylene, polybutadiene, butadiene styrene copolymer, polystyrene, neoprene, polybutadiene-acrylonitrile, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, an epoxy resin, or an urethane resin; and the second resin comprises a water soluble resin or elastomer.

In a preferred aspect of the present invention, the first resin and the second resin have solubility parameters which are different from each other by three or more.

In a preferred aspect of the present invention, the first resin and the second resin have solubility parameters which are different from each other by six or more.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a fixed abrasive polishing tool, comprising: treating abrasive particles with a coupling agent; and fixing the abrasive particles which are subjected to surface treatment by the coupling agent; wherein the coupling agent has an organic functional group which is not substantially bonded to the resin.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a fixed abrasive polishing tool, comprising: providing a core-shell composite polymer which is formed by polymerization to surround abrasive particles; and forming the core-shell composite polymer to form a polishing tool.

In a preferred aspect of the present invention, the core-shell composite polymer comprises swelling resin.

According to the present invention, the resin is formed by polymerization to surround abrasive particles serving as cores. For example, the resin is swelled by a polishing liquid, and the abrasive particles can be easily separated from the binder resin, Thus, the number of abrasive particles on the polishing surface can be increased, and a polishing rate can be increased.

The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional view of an abrasive particle; [0025]
FIG. 1B is a schematic cross-sectional view of the abrasive particle which is coated with a coating (film); [0026]
FIG. 2A is a schematic view of abrasive particles which are aggregated; [0027]
FIG. 2B is a schematic view of abrasive particles which are treated by a coupling agent and are dispersed; [0028]
FIG. 3 is a flow chart of a method of manufacturing a polishing tool according to an embodiment of a present invention; [0029]
FIG. 4 is a schematic view of a fixed abrasive polishing tool comprising abrasive particles which have polymer coating and are bonded to each other; [0030]
FIG. 5 is a schematic view of a fixed abrasive polishing tool comprising abrasive particles, a first resin for holding the abrasive particles, and a second resin for bonding the first resin; and [0031]
FIG. 6 is a schematic view showing the state in which a substrate is polished by a fixed abrasive polishing tool comprising abrasive particles held by a resin having a swelling property.[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polishing tool according to embodiments of the present invention will be described below with reference to the drawings. [0033]
FIG. 1A schematically shows an [0034] abrasive particle 11, and FIG. 1B shows the abrasive particle 11 which is treated with a coupling agent to form a coating 12 on the surface of the abrasive particle 11. The coupling agent 12 is bonded to an inorganic material constituting the abrasive particle 11, thus coating the surface of the abrasive particle 11. The fixed abrasive polishing tool has abrasive particles which are held by a binder resin, and are composed of abrasive particles, a binder resin and pores which are combined in a certain mixed ratio. The coupling agent includes an organic functional group which will be bonded to the resin. In the fixed abrasive polishing tool of the present invention, the coupling agent has an organic functional group, and the resin which is hardly bonded to the organic functional group of the coupling agent is used. Specifically, the resin is not substantially bonded to the organic functional group of the coupling agent.
According to the present invention, a surface reforming method in which abrasive particles are coated with a coupling agent or a polymer so that the abrasive particles are not aggregated even in a dry state in a manufacturing process is employed. The abrasive particles have a particle diameter of 0.5 μm or less. Materials for abrasive particles may comprise silica based abrasive particles, alumina based abrasive particles, cerium dioxide based abrasive particles, manganese dioxide based abrasive particles, titanium oxide based abrasive particles, particulate diamond, or the like. [0035]
The coupling agent is used for the purpose of increasing bond strength of different materials, particularly bond strength of an inorganic material and an organic material. The coupling agent has a functional group which tends to be bonded to inorganic materials and a functional group which tends to be bonded to organic materials. The coupling agent includes a chromium coupling agent, a silane coupling agent, a titanium coupling agent, an aluminium coupling agent, a zirconium coupling agent, organometallic compounds, etc. [0036]
In a process of manufacturing a fixed abrasive polishing tool, as shown in FIG. 2A, abrasive particles are aggregated, and hence the abrasive particles cannot be uniformly dispersed in a polishing tool. Therefore, as shown in FIG. 2B, abrasive particles are subjected to surface treatment by the coupling agent to prevent the abrasive particles from being aggregated in the manufacturing process. [0037]
In order to prevent the abrasive particles from approaching each other and thus being aggregated, steric hindrance effect caused by steric mutual repulsion between the coupling agents adsorbed on the surfaces of the abrasive particles can be utilized. In this case, as an adsorption layer is thicker, the steric hindrance effect is stronger. The thickness of the adsorption layer depends on the length of molecular chain of the coupling agent. The length of molecular chain of the coupling agent should be about 100 Å, and the length of about 100 Åis criterion of selection of the coupling agent. When the polishing tool is used for polishing substrates after its production, it is desirable that bond strength between the abrasive particles and the binder resin is small. Making the bond strength between the abrasive particles and the binder resin low can be achieved by using the coupling agent and the binder resin whose solubility parameters are different from each other by three or more, preferably four or more and more preferably six or more. By employing a combination of the coupling agent having an organic functional group and the resin which is hardly bonded to such organic functional group, the abrasive particles are easily liberated from the polishing surface of the fixed abrasive polishing tool, thus improving a polishing rate. [0038]
In the fixed abrasive polishing tool of the present invention, the coupling agent comprises a silane coupling agent or a titanium coupling agent, and in order to weaken the bond strength between the coupling agent and the binder resin, it is necessary to select a combination of an organic functional group of the coupling agent and the binder resin. [0039]
For example, if the binder resin contains alkyl groups as a functional group, like polyacrylate based resin, polymethacrylate based resin, polystyrene, polyethylene, diallylphtalate, an ethylene propylenediene ternary copolymer, then the silane coupling agent preferably comprises 3-glycidoxy propyl trimethoxysilane, 2-(3,4-epoxy cyclohexyl)ethyl trimethoxysilane, N-2-(aminoethyl)3-amino propyltriethoxysilan, 3-chloro propyl trimethoxysilane, or 3-mercapto propyl trimethoxysilane which contains an epoxy group, an amino group, halogen groups, or a mercapto group as an organic functional group. The titanium coupling group preferably contains an amino group or a carboxyl group as an organic functional group. [0040]
Further, if the binder resin comprises an epoxy resin, a phenol resin, an urethane resin, a melamine resin, polycarbonate, polyvinyl chloride, polyimide, a styrene-butadiene copolymer, or natural rubber, then the silane coupling agent preferably comprises vinyltriethoxysilane or vinyltris(2-methoxyethoxy) silane which has a vinyl group or an alkoxy group as an organic functional group. The titanium coupling group preferably has an amino group or a carboxyl group as an organic functional group. [0041]
The titanium coupling agent has weak bond strength, because the titanium coupling agent exhibits van der Waals force interaction with resin, unlike the silane coupling agent having covalent bond with resin, and hence the abrasive particles are easily liberated from the binder resin. The coupling agent having a long molecular chain preferably comprises a coupling agent which has an alkoxy group such as (C[0042] ₁₇H₃₃COO)₃SiC₃H₆OCOC₁₇H₃₃.
A process of manufacturing a fixed abrasive polishing tool will be described below with reference to FIG. 3. [0043]
FIG. 3 is a flowchart of a method of manufacturing a fixed abrasive polishing tool according to an embodiment of the present invention. In FIG. 3, a manufacturing process of the polishing tool is illustrated in a simplified manner. As shown in FIG. 3, a material of a fixed abrasive is prepared in [0044] step 1, and then a forming material comprising a dried granulated powder is produced in step 2. The forming material is compressed or heat-pressed to produce a formed body (formed resin) in step 3, and then the formed body (formed resin) is fixed to a supporting member in step 4, thus completing a polishing tool in step 5.
Next, a manufacturing process of the fixed abrasive polishing tool will be described in a concrete manner in detail. [0045]
First, a material of a fixed abrasive is prepared. Specifically, fine abrasive particles, a resin material, and additives including a dispersing agent such as a surface active agent, a stabilizer such as a buffer, an accelerator represented by a pH adjuster such as KOH, and a mirror-finish improver such as a macromolecure agent, etc. are measured to prepare a desired amount of a material of a fixed abrasive. The measured materials are mixed with each other, and, if necessary, pure water and a solvent are added to the mixture, thus producing a mixed liquid. At this time, the measured materials are sufficiently dispersed using a stirrer, an ultrasonic dispersing device, or the like. [0046]
Then, the mixed liquid is dried by a dryer such as a spray dryer into a powder (granulated powder) in which various materials are uniformly mixed. The powder (granulated powder) has a diameter of 0.1 μm to several hundreds μm, preferably an average diameter of several um to several tens μm. Alternatively, a powder may be produced by freeze-drying and then pulverizing, coagulating, and/or precipitating. In the above powder (granulated powder) producing process, the materials may be mixed and then dried, or dried and then mixed, or repeatedly mixed and dried. Depending on the material to be mixed, a material may be directly mixed with a dried powder of other materials. [0047]
Next, if necessary, suitable additives (chemical agents) are added to the mixed powder (granulated powder) obtained by the above process, thus producing a powdery mixture. The powdery mixture is then compressed by a compression forming machine which typically comprises a hot press, thereby producing a fixed abrasive polishing tool. The size of the compression forming machine is determined by the size of the fixed abrasive polishing tool to be produced. Therefore, the size of the compression forming machine may be smaller if the fixed abrasive polishing tool is of a split type, i.e., segment type, than if the fixed abrasive polishing tool is of a non-split type. If a split-type, i.e., segment-type fixed abrasive polishing tool is produced, then associated fabrication equipment and subsequent processing equipment may also be smaller in size. Consequently, initial investments are smaller, and the manufacturing cost is lower. [0048]
In order to facilitate the protection of the fixed abrasive and the installation thereof onto a polishing apparatus, the produced fixed abrasive is fixed to a member (base) having mechanical strength, such as a member made of metal or engineering plastics, by adhesion or deposition. If the fixed abrasive is made up of a number of segments, or segment having a complex shape, then the segments are difficult to be positioned when secured to the base. If the segments are positioned inaccurately on the base, then the adhesive applied to secure the fixed abrasive to the base tends to be squeezed into gaps between the segments. If the adhesive is positioned on the polishing surface of the fixed abrasive, then the adhesive is likely to hamper the polishing action or produces scratches on the semiconductor wafer being polished. Therefore, the segments of the fixed abrasive need to be positioned accurately. [0049]
In the above manufacturing process, in the case where the abrasive particles are subjected to surface treatment by the coupling agent, the abrasive particles are dispersed in a solvent, and then the coupling agent which exhibits a surface treatment ability in the solvent is added to the solvent. Thereafter, the abrasive particles and the coupling agent are sufficiently dispersed in the solvent by the ultrasonic dispersing device or the like. In this case, the coupling agent is mixed with the abrasive particles at a weight percent of about 0.1 to about 10 to the abrasive particles. [0050]
In the case of aqueous solvent, it is desirable that the coupling agent exhibits a surface treatment ability in water. The coupling agent is sufficiently dispersed in the solvent using the ultrasonic dispersing device or the like to form a coating (film) on each of the surfaces of the abrasive particles. [0051]
As described above, the coating of the coupling agent can prevent the abrasive particles from being aggregated in the manufacturing process of the fixed abrasive polishing tool, and hence the abrasive particles can be uniformly dispersed in the completed polishing tool. [0052]
Next, a resin material is dispersed in the above solvent, and then the mixture is dried by a spray drying method, a freeze vacuum drying method or the like, thus producing a granulated powder. The granulated powder is formed in such a manner that the solvent containing the abrasive particles and the resin material is atomized into a mist, and the mist is dried into a granulated powder by a high-temperature air flow. In the resultant granulated powder, the abrasive particles are kept in a dispersed state without being aggregated. [0053]
A fixed abrasive can be manufactured by the following manufacturing processes 1) to 5), in addition to the above manufacturing process. [0054]
1) A slurry and a coupling agent are mixed with each other to coat surfaces of abrasive particles with the coupling agent, and then the mixture is dried by spray drying or freeze-drying. The dried mixture is mixed with a binder powder, and is then formed by a press (heat) forming, thus producing a fixed abrasive. [0055]
2) A slurry and a coupling agent are mixed with each other to coat surfaces of abrasive particles with the coupling agent, and then the mixture is dried by spray drying or freeze-drying. The dried mixture is mixed with a liquid binder comprising an aqueous binder or a solvent binder, and is then dried by the above drying process. Thereafter, the dried mixture is formed by a press (heat) forming, thus producing a fixed abrasive. [0056]
3) An abrasive powder and a liquid containing a coupling agent are mixed with each other to coat surfaces of abrasive particles with the coupling agent, and then the mixture is dried by spray-drying or freeze-drying. The dried mixture is mixed with a binder powder, and is then formed by a press (heat) forming, thus producing a fixed abrasive. [0057]
4) An abrasive powder and a liquid containing a coupling agent are mixed with each other to coat surfaces of abrasive particles with the coupling agent, and then the mixture is dried by spray-drying or freeze-drying. The dried mixture is mixed with a liquid binder comprising an aqueous binder or a solvent binder, and is then dried by the above drying process. Thereafter, the dried mixture is formed by a press (heat) forming, thus producing a fixed abrasive. [0058]
5) As a surface treatment process by a coupling agent, the coupling agent may be synthesized in a solution containing abrasive particles. [0059]
According to the present invention, a polishing rate of the fixed abrasive may be further increased by adding a photosensitizer to the fixed abrasive, and irradiating the polishing tool with light during polishing. In this case, the photosensitizer should be contained in the binder or a photodegradable resin should be used. [0060]
A photodegradable resin is defined as a resin whose physical bond strength is weakened by irradiation of light. The photodegradable resin which is easily decomposed by light includes vinylketone copolymer, ethylene-carbon monoxide copolymer, compounds having carbon-carbon double bond, such as polybutadiene and polybutene-1 or a ketone group. [0061]
In the photosensitizer, linkage group of resin is cut under catalytic action by irradiation of light, and hence any resin such as general binder resin or a photodegradable resin can be disintegrated by light. For example, the photosensitizer includes benzophenone, anthraquinone, 2-ethylanthraquinone, 2-methylantraquinone, 2-acetylnaphthalene, xanthone, carbazole, fluorene, triphenylamine, benzoin, dibenzodioxane, thioxanthen-9-one, 9-fluorenone, 1,2-benzanthraquinone, anthracene, pyrene, benzyl, fluorescein, etc., the transition metal compound which comprises organic acid salts containing Co (cobalt), Mn (manganese), Cu (copper), Fe(iron), V(vanadium) or the like, and dithiocarbamato complexes, etc. [0062]
Further, titanium oxide serving both as photocatalyst for disintegrating resin by light and abrasive particles may be used. Titanium oxide has Mohs' scale of hardness of 6 to 8, and hence the Mohs' scale of hardness of titanium oxide is nearly equivalent to that of cerium oxide which is 7. Titanium oxide may be added to a normal non-photodegradable resin, instead of abrasive particles. Alternatively, titanium oxide may be combined with normal abrasive particles or a photodegradable resin or a photosensitizer. In order to disperse a photodegradable resin or a photosensitizer in the binder resin constituting a fixed abrasive polishing tool, the photodegradable resin or the photosensitizer is formed into a granular shape, and is dispersed in the binder resin constituting the polishing tool. The diameter of the granular photodegradable resin or the photosensitizer can be controlled in the range of about 0.01 μm to about 50 μm by using a spray drier or the like. The photodegradable resin or the photosensitizer may be mixed together when the binder resin and the abrasive particles are mixed with each other. The photodegradable resin or the photosensitizer may be mixed in other timing, as long as mixing of the photodegradable resin or the photosensitizer is performed before forming of the polishing tool. [0063]
Two kinds or more of photodegradable resins, or two kinds or more of photosensitizers may be added. In the case of adding two kinds or more of photosensitizers, in some cases, energy transfer may be smoother than that in one kind of photosensitizers. In the case where triplet energy of a [0064] photosensitizer 1 is larger than that of a photosensitizer 2, energy is transmitted from the photosensitizer 1 to the binder resin through the photosensitizer 2, and hence photodegradation of resin can be performed smoother.
By adding chemical agent having a photosensitization effect to the coupling agent or using the coupling agent having a photosensitization effect, or performing surface treatment of the abrasive particles by a photosensitizer after surface treatment of the abrasive particles by the coupling agent or performing treatment of the abrasive particles after surface treatment of the abrasive particles by the coupling agent or simultaneously with the surface treatment of the abrasive particles by the coupling agent, binding of abrasive particles and the resin can be remarkably weakened by irradiation of light during polishing. Thus, a polishing rate can be increased, and abrasive particles can be generated without being aggregated. Consequently, a substrate such as a semiconductor wafer can be processed in high quality without producing scratches on the surface of the substrate. [0065]
Next, a fixed abrasive polishing tool which employs a core-shell composite polymer will be described below. The core-shell composite polymer comprises abrasive particles as a core, and a polymer resin polymerized so as to coat each of the abrasive particles. FIG. 4 schematically shows this fixed abrasive polishing tool. In this embodiment, each of the [0066] abrasive particles 11 is covered with a coating 13 of the polymerized resin. The core-shell composite polymer including the abrasive particles each serving as a core is bonded to each other to form a fixed abrasive polishing tool.
The core-shell composite polymer may be formed by polymerization to surround the abrasive particles with the coupling agent interposed therebetween. [0067]
The core-shell composite polymer is formed by adding monomers which are polymerized to become a binder resin such as a polyacrylate based resin, a polymethacrylate based resin, polystyrene, a styrene-butadiene rubber(SBR), a nitrile-butadiene rubber(NBR), MBR, polyvinyl acetate, or an acrylstyrene copolymer to the slurry containing the above abrasive particles, and forming a [0068] coating 13 of polymers on the surfaces of the abrasive particles by emulsion polymerization or soap-free emulsion polymerization. An emulsifying agent for emulsion polymerization may include sodium/potassium fatty acid, disproportionate sodium/poatssium rosin, sodium alkylbenzensulfonate, sodium alkyl dihenylether disulfonate, sodium sulfo succinate dialkyl ester, sodium higher alcoholate sulfuric ester, sodium/pottasium alkyl ether sulfuric ester, sodium/pottasium alkyl phenyl ether sulfuric ester, partial saponified polyvinylalcohol, ethyleneoxide-added alkylphenol, ethyleneoxide-added higher alcohol, ethyleneoxide-added polypropylen glycol, quaternary ammonium salt, etc. These agents may be adsorbed by the coupling agent, and then the monomers may be polymerized.
Further, in a method of using reactive emulsifying agents as a kind of soap-free emulsion polymerization, the emulsifying agent has a polymerizing property, and the emulsifying agent is adsorbed by the coupling agent on the surfaces of the abrasive particles and is polymerized. The reactive emulsifying agents may include allyl-propenyl derivatives, acrylic acid derivatives, itaconic acid derivatives, maleic acid derivatives, etc., and copolymer of these derivatives and other monomers may also be used. [0069]
If the above coupling agent is not used, then the reactive emulsifying agent may be directly adsorbed on the surfaces of the abrasive particles to be polymerized or copolymerized with other monomers, thereby forming a [0070] coating 13 on each of the abrasive particles. A core-shell composite polymer in which a polymer coating is formed on the surfaces of the abrasive particles may be subjected directly to a heating and compression forming to form a fixed abrasive polishing tool. Because the fixed abrasive polishing tool thus formed has the abrasive particles coated with a polymer coating, the fixed abrasive polishing tool may be formed without using other binder resin.
In general, a core-shell resin has cores composed of resin, like an ABS resin. [0071]
However, in the fixed abrasive polishing tool of the present invention, the cores are composed of abrasive particles. Thus, polymer nucleus is prevented from being produced so that a core-shell resin is not formed by resins, thereby growing a polymer only on the surfaces of the abrasive particles. Specifically, entropy of the surfaces of the abrasive particles and the produced core is adjusted, and solution concentration is adjusted to lower critical supersaturated concentration or lower, thereby suppressing the growth of the produced core. That is, the solution concentration is adjusted in the range of from supersaturated concentration to lower critical supersaturated concentration. Then, in order to prevent the abrasive particles from being aggregated, the mixed liquid of the slurry (or abrasive particles) and the resin is not equipotential point and salt level of the mixed liquid of the slurry (or abrasive particles) and the resin is kept low. Further, polymer(shell) suitable for isotropic dressing which is a kind of non-mechanical dressing may be used. [0072]
Further, other manufacturing processes of the core-shell composite polymer are as follows: [0073]
Firstly, because it is difficult to grow a polymer homogeneously around the abrasive particles, adsorption treatment of surface active agents or organic polymer (organic functional groups) is applied to the surfaces of the abrasive particles. Then, a polymer coating which becomes a shell is formed by polymerization to encapsule an adsorption layer of the organic polymer (organic functional group). It is important to improve affinity of organic material and inorganic material. [0074]
Secondly, a hetero aggregation is utilized. [0075]
Thirdly, a suspension polymerization method or an emulsion polymerization method is used. [0076]
In any process, it is necessary to control the size and the particle size distribution of composite fine particles, and orientation of the composite fine particles greatly affects characteristics of the fixed abrasive polishing tool. [0077]
FIG. 5 shows a fixed abrasive polishing tool according to another embodiment of the present invention. According to the present embodiment, a fixed abrasive polishing tool comprises [0078] abrasive particles 11, a first resin 13 for holding the abrasive particles 11, and a second resin 15 for bonding the first resin 13. Specifically, core-shell composite polymers which comprise the abrasive particles 11 as cores, and polymer 13 polymerized so as to coat the abrasive particles 11 are bonded by the second resin 15, thus producing a fixed abrasive polishing tool. The first resin 13 and the second resin 15 are characterized by low bond strength, and solubility parameters which are different from each other by three or more. The solubility parameters of the first resin 13 and the second resin 15 are preferably different from each other by four or more and more preferably different from each other by six or more. In this case, a plurality of abrasive particles 11 may be dispersed in the first resin 13, and the first resin 13 may be bonded by the second resin 15.
Specifically, in the manufacturing process of the above fixed abrasive polishing tool, when a granulated powder which is a material of the fixed abrasive is formed, the granulated powder containing the [0079] abrasive particles 11 in the first resin 13 is formed. Then, the first resin 13 including the abrasive particles is held by the second resin 15 whose solubility parameter is different from solubility parameter of the first resin 13. Because the solubility parameters of the first resin 13 and the second resin 15 are different from each other by three or more, the bond strength between the first resin 13 and the second resin 15 is small, and hence the first resin 13 which holds the abrasive particles in a dispersed state is easily liberated from the second resin 15. Thus, many abrasive particles are released onto the polishing surface, thus making it possible to polish a substrate such as a semiconductor wafer at a high polishing rate. Further, because the bond strength between the first resin 13 and the second resin 15 is small, re-attachment of the resin to the polishing tool can be prevented.
Making the bond strength between the [0080] first binder resin 13 and the second binder resin 15 low can be achieved by using the two resins whose solubility parameters are different from each other by three or more, preferably four or more and more preferably six or more. In this case, the solubility parameters of the first binder resin 13 which holds the abrasive particles in a dispersed state and the second binder resin 15 approximate solubility parameter of the polishing liquid to dissolve the first and second binder resins in the polishing liquid, thereby dispersing the abrasive particles on the polishing surface to improve a polishing performance. For example, the resin whose solubility parameter approximates solubility parameter (23.4) of water includes a water soluble resin, elastomer, etc. An example is polyvinyl alcohol (23.4). This water soluble resin or elastomer is used as the first binder resin or the second binder resin. As the second binder resin or the first binder, teflon (6.2), a silicone rubber (7.3), a natural rubber (7.9), polyisobutylene (8.0), polybutadiene (8.4-8.6), butadiene styrene copolymer (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), a thermosetting resin such as an epoxy resin or an urethane resin, etc. may be used.
Further, the abrasive particles within the first binder resin may be coated with the above coupling agent or polymer to improve dispersibility of the abrasive particles. [0081]
The [0082] first resin 13 may comprise a swelling resin having a swelling property with respect to polishing liquid. When the substrate is polished, a polishing liquid is brought in contact with the polishing surface of the fixed abrasive polishing tool, and hence the resin 13 is swelled and softened to become more elastic. For example, the swelling resin includes resin which comprises polyacrylic acid, polyvinylacetal, polyvinylpyrrolidone, polyvinylalcohol, polyethyleneimine, polyethyleneoxide, styrene-maleic anhydride copolymer, polyvinylamine, polyallylamine, a water soluble resin containing oxazoline group, a water soluble melamine resin, a water soluble urea resin, an alkyd resin or sulfonamide. The swelling resin may include resin containing a water soluble cross linking agent which comprises melamine based cross linking agent, urea based cross linking agent, amino based cross linking agent, etc.
As shown in FIG. 6, the surface of the fixed [0083] abrasive polishing tool 17 is required to have a certain rigidity when a surface of a fixed abrasive polishing tool 17 contacts convexities of the substrate to be polished and to have flexibility when the surface of the fixed abrasive polishing tool 17 contacts concavities of the substrate to be polished. For example, the swelled resin 13 a is crushed at the portions of the polishing tool which are contacted by convexities 21 a of a substrate 21 such as a semiconductor wafer, and hence a high rigidity is exhibited to make a processing pressure large, thus making it possible to process the substrate at a high rate. On the other hand, the swelled resin 13 b is not crushed at the portions of the polishing tool which are contacted by concavities 21 b of the substrate 21, and hence flexibility is exhibited to make a processing pressure small. Therefore, even if the abrasive particles 11 exist on the polishing surface of the polishing tool, the scratches are not produced on the surface of the substrate.
Therefore, the surface of the fixed [0084] abrasive polishing tool 17 has a certain rigidity when the surface of the fixed abrasive polishing tool 17 contacts the convexities of the substrate to be polished and flexibility when the surface of the fixed abrasive polishing tool 17 contacts the concavities of the substrate to be polished. Therefore, only the convexities of the substrate can be polished, and the concavities of the substrate are less liable to be polished, and hence a sharp polishing characteristic can be maintained. Specifically, the resin 13 is swelled and softened by the polishing liquid, and the polishing surface is changed to have flexibility. When the convexities of the substrate are polished, the portions of the polishing tool which contact the convexities of the substrate reach compressed limit, and elastic deformation of the polishing tool is not made any more. Thus, the substrate can be processed under a large processing pressure and polished at a high polishing rate, and a sharp polishing characteristic can be obtained.
In the above embodiment, the [0085] resin 13 absorbs a polishing liquid and is swelled. For example, the resin which is softened and becomes elastic by irradiation of light may be used. Thus, by irradiation of light as polishing of the substrate progresses, the resin 13 is swelled, whereby generation of free abrasive particles is accelerated and a sharp polishing characteristic can be obtained.
As is apparent from the above, according to the present invention, the number of abrasive particles can be increased on a polishing surface to obtain a higher polishing rate and a better polishing performance(sharp polishing charastristic). [0086]
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims. [0087]

Claims

What is claimed is:

1. A fixed abrasive polishing tool comprising:

abrasive particles which are subjected to surface treatment by a coupling agent; and

resin for fixing said abrasive particles;

wherein said coupling agent has an organic functional group which is not substantially bonded to said resin.

2. A fixed abrasive polishing tool according to claim 1, wherein said coupling agent comprises a chromium coupling agent, a silane coupling agent, a titanium coupling agent, an aluminium coupling agent, a zirconium coupling agent, or organometallic compounds.

3. A fixed abrasive polishing tool according to claim 1, wherein said resin comprises polyacrylate based resin, polymethacrylate based resin, polystyrene, polyethylene, diallyl phtalate, an ethylene propylenediene ternary copolymer, an epoxy resin, a phenol resin, an urethane resin, a melamine resin, polycarbonate, polyvinyl chloride, polyimide, a styrene-butadiene copolymer, or natural rubber.

4. A fixed abrasive polishing tool according to claim 1, wherein said coupling agent and said resin have solubility parameters which are different from each other by three or more.

5. A fixed abrasive polishing tool according to claim 1, wherein said coupling agent and said resin have solubility parameters which are different from each other by six or more.

6. A fixed abrasive polishing tool comprising:

abrasive particles; and

resin for fixing said abrasive particles;

wherein said resin comprises a core-shell composite polymer which is formed by polymerization to surround said abrasive particles.

7. A fixed abrasive polishing tool comprising:

abrasive particles;

first resin for holding said abrasive particles; and

second resin which is bonded to said first resin;

wherein bond strength of said first resin and said second resin is small.

8. A fixed abrasive polishing tool according to claim 7, wherein

said first resin comprises a water soluble resin or elastomer; and

said second resin comprises teflon, a silicone rubber, a natural rubber, polyisobutylene, polybutadiene, butadiene styrene copolymer, polystyrene, neoprene, polybutadiene-acrylonitrile, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, an epoxy resin, or an urethane resin.

9. A fixed abrasive polishing tool according to claim 7, wherein

said first resin comprises teflon, a silicone rubber, a natural rubber, polyisobutylene, polybutadiene, butadiene styrene copolymer, polystyrene, neoprene, polybutadiene-acrylonitrile, polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, polyethylene terephthalate, polyacrylonitrile, an epoxy resin, or an urethane resin; and

said second resin comprises a water soluble resin or elastomer.

10. A fixed abrasive polishing tool according to claim 7, wherein said first resin and said second resin have solubility parameters which are different from each other by three or more.

11. A fixed abrasive polishing tool according to claim 7, wherein said first resin and said second resin have solubility parameters which are different from each other by six or more.

12. A method of manufacturing a fixed abrasive polishing tool, comprising:

treating abrasive particles with a coupling agent; and

fixing said abrasive particles which are subjected to surface treatment by said coupling agent;

13. A method of manufacturing a fixed abrasive polishing tool, comprising:

providing a core-shell composite polymer which is formed by polymerization to surround abrasive particles; and

forming said core-shell composite polymer to form a polishing tool.

14. A method according to claim 13, wherein said core-shell composite polymer comprises swelling resin.