JP2002192538A - Method for manufacturing polyurethane polishing pad for polishing semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that when a polishing pad of polyurethane is manufactured by mixing an isocyanate-terminated prepolymer, a microbody and an active hydrogen compound and curing the mixture, voids are generated by a gas such as air contained in various kinds of materials and a gas entrained during mixing and also the voids are non-uniformly distributed and appear in varying size and that therefore, when a silicon wafer or the like is polished, scratches are generated in the surface to be polished, and provide a method for manufacturing the polishing pad showing superiority in terms of scratch resistance, polishing characteristics and flatness by inhibiting the generation of the voids in the pad as a solution of the problems. SOLUTION: In the method for manufacturing a polyurethane foam for polishing a semiconductor by mixing and stirring the isocyanate-terminated prepolymer, the active hydrogen compound and the microbody and curing the mixture, a stirred and mixed stock solution is injected into a mold while being maintained at a height at most twice as much as the thickness of moldings during the movement of the stock solution through a space from the mold, when the stock solution is injected into the mold. Thus it is possible to inhibit the generation of the voids by evacuating the gas such as air present under reduced pressure, in every step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyurethane polishing pad having fine particles in which fine particles are uniformly dispersed. The polyurethane polishing pad of the present invention can be suitably used as a polishing material suitable for polishing resin, silicon for production of glass, lenses, quartz, semiconductors, etc., electronic substrates, optical substrates, and the like.

[0002]

2. Description of the Related Art Conventionally, as a technique for producing such a polyurethane polishing pad, there is known a method of dispersing a fine hollow foam in a raw material composition for forming a polyurethane resin.

A number of patents have been filed for dispersing the microparticles in a raw material composition for forming a polyurethane resin, mainly in Japanese Patent Application Laid-Open No. 08-500622. According to the gazette, the microfoamed polyurethane resin is made of a polymer impregnated with a polymer microelement having a plurality of flexible void spaces, and the polymer microelement is made of a water-soluble polymer or polyurethane. Has become.

According to this publication, a polyurethane-based polishing pad is obtained by mixing and curing a urethane-based prepolymer and an active hydrogen compound. At this time, the polymer microelements are mixed, uniformly dispersed and cured while the mixed liquid is still low in viscosity, but in such a method, it is necessary to vigorously agitate the polymer elements because the dispersion time of the polymer elements is short. Therefore, it is easy for air to mix and generate uneven foam, and the gas dissolved in the mixture evaporates and expands due to the generation of heat and reaction heat due to vigorous stirring, and as a result, voids are generated. When a polishing pad is obtained by slicing from a manufactured urethane cured product (block), voids appear in the pad surface with uneven distribution and size. Therefore, when polishing a silicon or the like for manufacturing a semiconductor or the like using a polishing slurry, the polishing slurry is not uniformly distributed over the entire surface of the pad, but tends to be unevenly distributed and aggregated in the void portion. There has been a problem that scratches are likely to occur on the surface.

[0005]

DISCLOSURE OF THE INVENTION The present invention suppresses the generation of voids in a pad, thereby improving scratching, polishing and polishing properties.
It is an object of the present invention to provide a method for manufacturing a polishing pad having excellent flatness.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve these objects, and as a result, have found a method of manufacturing a urethane pad for semiconductor polishing with less generation of voids, and have completed the present invention. Was.

That is, in a method of producing a polyurethane foam for semiconductor polishing by mixing, stirring, and hardening an isocyanate-terminated prepolymer, an active hydrogen compound, and fine particles, a stock solution mixed and stirred is poured into a mold. In addition, the injection is performed while maintaining the height at which the stock solution from the mold moves in the space within twice the thickness of the molded product.

Another method is to mix, stir, and cure an isocyanate-terminated prepolymer, an active hydrogen compound, and fine particles to produce a polyurethane foam for semiconductor polishing. Injecting the undiluted solution weighed, stirred and mixed into a mold while tilting the reaction vessel, rubbing the opening edge of the reaction vessel into the mold or injecting along with other substances It is.

In any method, by minimizing the impact when the injected mixed liquid collides with the mold, air entrapment can be suppressed, and the generation of voids in the polishing pad can be reduced. .

[0010]

DETAILED DESCRIPTION OF THE INVENTION The isocyanate-terminated prepolymer used in the present invention is a compound having an isocyanate group at the end obtained by reacting an isocyanate compound known in the field of polyurethane with a polyol. As the isocyanate compound, a diisocyanate compound is preferable.

As the diisocyanate compound, 2,4
-Tolylene diisocyanate is mainly used, but other diisocyanates can be used in combination as long as the effects of the present invention are not impaired.
Compounds such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like. But it is not limited to this.

As the polyol, for example, polyether polyols such as poly (oxytetramethylene) glycol and poly (oxypropylene) glycol, polycarbonate polyols, polyester polyols and the like can be used.

In order to improve the physical properties, short-chain glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl −
1,3-propanediol, 1,4-butanediol,
Neopentyl glycol, 1,5-pentanediol,
Chain extenders such as 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol and dipropylene glycol can be appropriately added.

As the active hydrogen-containing compound, for example,
3'-dichloro-4,4'-diaminodiphenylmethane, chloroaniline-modified dichlorodiaminodiphenylmethane, 3,5-bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluene At least one of diamines such as diamine is mainly used. These diamines act as crosslinking agents for the isocyanate-terminated prepolymer. These diamines can be used alone, but if necessary, can be used in combination with polyether polyols such as poly (oxytetramethylene) glycol and poly (oxypropylene) glycol, polycarbonate polyols, polyester polyols and the like. is there. The polyol used in combination with the amine preferably has a low molecular weight, particularly
Poly (oxytetramethylene) glycols in the range from 00 to 1000 are preferred.

The microparticles used in the present invention contain a low-boiling hydrocarbon in the hollow part, and the shell is made of a thermoplastic resin whose softening temperature is higher than the boiling point of the low-boiling hydrocarbon contained therein. When a temperature equal to or higher than the softening temperature of the thermoplastic resin is applied, the softening of the thermoplastic resin and the volume expansion of the low-boiling hydrocarbon occur simultaneously, and the hollow microspheres have the property of expanding. Its softening temperature is preferably in the range from 90 to 120C.

The particle diameter of the unfoamed, heat-expandable hollow microspheres is preferably 5 to 30 μm. The hollow microspheres foam during the two-component reaction curing, and after foaming, are preferably present as microbubbles in a molded product having a particle size of preferably from 10 to 100 μm.

The true specific gravity of the non-foamed heat-expandable micro hollow spheres is preferably 1.0 to 1.3, and since it is close to the specific gravity of the isocyanate-terminated prepolymer, it is preferable to take this range. Separation hardly occurs and a good dispersion state can be maintained.

As the thermoplastic resin constituting the shell of the non-foamed heat-expandable micro hollow sphere, an acrylonitrile-vinylidene chloride copolymer or an acrylonitrile-methyl methacrylate copolymer can be used. Further, as the low boiling hydrocarbon present in the hollow portion of the hollow body, for example,
Isobutane, pentane, isopentane, petroleum ether and the like. The unfoamed heat-expandable micro hollow spheres are mainly foamed by the reaction heat released when the isocyanate-terminated prepolymer and the active hydrogen-containing compound are mixed and stirred, and the reaction is cured.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a manufacturing method according to claim 1.
That is, the mixed liquid of the urethane prepolymer and the fine particles is measured and mixed and stirred in a reaction vessel 22 provided with an injection port 21 at the bottom. The active hydrogen compound is further mixed and injected into the mold 10. At this time, the height of the injection port 21 from the mold surface 11 is set to be within twice the height of the molded product 31, preferably 0.5 to 1.5 times. If the height is set to be twice or more, when the liquid 30 collides with the mold surface 11, it cannot be escaped by entraining air and remains as a void as it is.

The reaction vessel 22 is preferably a tank made of stainless steel or the like, and preferably has an inlet with a valve 20 at the bottom of the tank. The shape and the like are generally cylindrical on the side used, and it is better that the bottom is slightly inclined toward the inlet so as to flow smoothly to the outlet. The volume can be appropriately determined depending on the amount used. If the raw material is defoamed under reduced pressure before the measurement, voids can be more effectively prevented.

Instead of using a reaction vessel, a stock solution mixed by a mixing head may be directly injected into a mold from a filling port by using a two-component foaming machine. In this case, the height of the injection port from the mold is also the same as the height of the molded product.
It is good to set the height within twice, preferably 0.5 to 1.5 times.

Another embodiment will be described with reference to FIG. The prepolymer is weighed into the reaction vessel 22, and the fine particles are mixed and stirred. In this case, defoaming may be performed separately in a reduced pressure container (not shown). Further, the active hydrogen compound is measured and mixed. After the stirring, the reaction vessel 22 is inclined and poured into the mold 10. The opening end 23 is brought close to the mold surface 11 so that the opening end 23 does not come out of the liquid surface, and the opening end 23 is rubbed and poured into the mold surface. At this time, when the reaction container 22 is tilted, the liquid is prevented from dripping and discontinuously dropping by the dripping prevention plate 24 to prevent air from being trapped due to the discontinuous drop. It is effective for The drip prevention plate 24 may be anything as long as it does not deform when dripped.

It is also effective to inject the material along another material, for example, a bar, a plate, a gutter or the like without directly rubbing the end of the opening with the mold surface.

As the reaction vessel 22, a stainless steel bucket or the like is practical. The drip prevention plate 24 may be a thin iron plate, aluminum, or the like. As a stirrer (not shown) for mixing the prepolymer and the fine particles, there is an ordinary dissolver, for example, a mixer for mixing powder or a primary mixer.

[0025]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.

(Example 1) Isocyanate-terminated prepolymer L-325 (N manufactured by Uniroyal Co.)
200 kg parts by weight of CO (9.45%) is weighed in a reduced pressure tank, and while maintaining the temperature at 70 ° C., the gas dissolved in the prepolymer is degassed by reducing the pressure to about 10 Torr. At this time, monitoring is performed visually through a glass monitoring window, and when the pressure rises to a predetermined line, the pressure is returned to normal pressure, pressure reduction is repeated again, and the process is repeated until the liquid no longer rises. Thereafter, 6.4 kg of Expancel 551DE (produced by Nippon Philite Co., Ltd.) was mixed with a primary mixer, and the mixture was defoamed under reduced pressure by the same method. 30 kg of the liquid in which the microparticles were mixed was weighed into a reaction vessel equipped with an injection valve at the bottom, whose height of the injection port was set to 1.5 times the height of the molded product from the mold surface, and further, at 120 ° C. Melted 3,
7.6 kg of 3'-dichloro-4,4'-diaminodiphenylmethane was charged, stirred and mixed by a primary mixer for 70 seconds, and poured into a mold to obtain a molded body.

(Comparative Example 1) A molded article was prepared in the same manner as in Example 1, except that a reaction vessel equipped with an injection valve whose injection port height was set to be three times as large as the molded product from the mold surface was used. Obtained.

The cut surfaces of 15 sheets obtained by slicing each of the obtained molded bodies into 1.3 mm were visually observed. In Example 1, each of the sheets had a diameter of 0.5 mmφ or more. 20 voids or less / 600mm
In comparison with the φ molded body, in Comparative Example 1, 50 or more pieces / 60
It was 0 mmφ.

Using them, an 8-inch silicon wafer was subjected to a polishing test (wafer load: 300 g / cm ² , platen rotation speed: 60 rpm, polishing time: 120 seconds).
The surface to be polished of the obtained silicon wafer was subjected to detection of a foreign substance having a size of 0.2 μm or more with a surface defect device manufactured by Topcon Corporation, WM2500, and a linearly detected object was evaluated as a scratch. Had less than 10 scratches. The polishing characteristics and flatness were all good. On the other hand, in the comparative examples, the scratchability was 100 or more, which was problematic in practical use.

[0030]

When the mixture of the isocyanate-terminated prepolymer, the microparticles and the active hydrogen-containing compound is poured into a mold, the method of introducing the mixture from the stirring tank is devised.
It was possible to suppress the entrapment of air generated when the mixed solution collides with the mold surface, suppress the generation of voids, and obtain a polishing pad having excellent scratching properties, polishing characteristics, and flatness.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining a method of injecting a mold from the bottom of a reaction vessel of the present invention.

FIG. 2 is a schematic diagram for explaining a method of injecting the present method container into a mold by tilting the method container.

[Explanation of symbols]

 10 type 11 type surface 20 valve 21 inlet 22 reaction vessel 23 open end of reaction vessel 24 liquid dripping prevention plate 30 mixed liquid 31 final height of molded product

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29K 105: 04 B29K 105: 04 (72) Inventor Koichi Ono 2-1-1 Katada, Otsu-shi, Shiga Toyobo Co., Ltd. Inside the Research Institute (72) Inventor Tetsuo Shimomura 2-1-1 Katata, Otsu-shi, Shiga Toyobo Co., Ltd. (72) Inventor Masahiko Nakamori 2-1-1 Katata, Otsu-shi, Shiga Toyobo Co., Ltd. F-term in the Research Institute (reference) 3C058 AA09 4F204 AA42 AG20 EA01 EB01 EF27 EF46 EF49

Claims (2)

[Claims] 1. A method for producing a polyurethane foam for semiconductor polishing by mixing, stirring, and curing an isocyanate-terminated prepolymer, an active hydrogen compound, and fine particles,
A polyurethane foam for semiconductor polishing, characterized in that, when pouring a stock solution mixed and stirred into a mold, the stock solution from the mold is poured while keeping the height at which the stock solution moves in the space within twice the thickness of the molded product. How to make 2. A method for producing a polyurethane foam for semiconductor polishing by mixing, stirring and curing an isocyanate-terminated prepolymer, an active hydrogen compound, and fine particles,
Each raw material was measured in a reaction vessel, and the undiluted solution mixed and stirred was
A method for producing a polyurethane foam for semiconductor polishing, characterized in that when pouring a reaction vessel into a mold while tilting the reaction vessel, the opening edge of the reaction vessel is rubbed against the mold or poured along with another substance.