JP2002194104A - Method for preparing polyurethane polishing pad used for polishing semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing polishing pad having excellent scratching property, polishing characteristic and evenness by controlling the generation of voids in the pad. SOLUTION: In the method for preparing the polyurethane polishing pad to be used for polishing a semiconductor, in which an isocyanate-terminated prepolymer, an active hydrogen compound and micro-particulates are subjected to mixing, agitating and hardening, wherein the micro-particulates are previously wet with a silicone type surface active agent or silicone oil, and before the mixing step of the isocyanate-terminated prepolymer with the active hydrogen compound, by interposing deaeration step under reduced pressure so that the generation of voids can be controlled by removing gases such as air and the like being present in each step under reduced pressure.

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 hollow bodies in which fine hollow bodies 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 silicon for production of semiconductors or the like using the polishing slurry, the polishing slurry is not uniformly distributed over the entire surface of the pad, so that the polishing slurry tends to be unevenly distributed and aggregated in the void portion. There has been a problem that scratches are likely to occur on the polished surface.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polishing pad having excellent scratching, polishing and flatness by suppressing the generation of voids in the pad. is there.

[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.

In a method for producing a polyurethane polishing pad for semiconductor polishing by mixing, stirring, and curing an isocyanate-terminated prepolymer, an active hydrogen compound, and fine particles, the prepolymer is wetted with a silicone-based surfactant or silicone oil in advance. The present invention provides a method for producing a polyurethane polishing pad for semiconductor polishing, comprising a step of defoaming under reduced pressure before a step of mixing an isocyanate-terminated prepolymer and an active hydrogen compound by using a minute body. Things.

According to the present invention, a gas such as air contained in an isocyanate-terminated prepolymer, an activated hydrogen compound, a gas such as air adsorbed on the surface of a minute body, and a entangled gas in a mixing step of a minute body. By removing bubbles such as air under reduced pressure, voids are reduced in the manufactured block, and the polishing pad obtained by slicing the block also has a small number of voids on the surface, and thus is caused by it. Scratch on the surface of the object to be polished is also reduced. In addition, by pre-wetting the microparticles with a silicone-based surfactant or silicone oil, it is possible to remove gas such as air adsorbed on the surface, and not only to reduce the amount of gas brought into the mixture, In addition to not polluting the environment when the body is thrown, not only does it not pollute the environment, but also when mixed with either or both of the isocyanate-terminated prepolymer and the active hydrogen compound, it becomes difficult to aggregate in a dumpling form, and uniform dispersion is achieved. It has become possible. The microparticles can be mixed in advance with either or both of the isocyanate-terminated prepolymer and the active hydrogen compound, but it is more preferable to mix the microparticles with the isocyanate-terminated prepolymer in advance.

Further, the invention of claim 2 provides a method for producing a polyurethane polishing pad for semiconductor polishing, which comprises a step of defoaming under reduced pressure before mixing the fine particles.

Gases such as air contained in isocyanate-terminated prepolymers, activated hydrogen compounds and the like are often dissolved in each compound, and are more difficult to remove than air entrained during mixing. It is preferable to remove the dissolved gas by degassing under reduced pressure before mixing the microparticles.

Further, the invention according to claim 3 provides a method for producing a polyurethane polishing pad for semiconductor polishing, which comprises a step of defoaming under reduced pressure after mixing the fine particles.

At the time of mixing the fine particles, voids are likely to be generated in the block due to air and the like included in the surface of the fine particles as well as air and the like contained in the surface of the fine particles. Therefore, it is preferable to remove gas.

The defoaming under reduced pressure can be performed before mixing the microparticles with either or both of the isocyanate-terminated prepolymer and the active hydrogen compound, or can be performed after the mixing. What can be done in
It is more preferable because dissolved gas can be effectively removed.

[0014]

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,
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 hydrocarbons 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 micro hollow spheres 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 fine hollow spheres is preferably 1.0 to 1.3, and this range is close to the specific gravity of the isocyanate-terminated prepolymer. Separation hardly occurs and a good dispersion state can be maintained.

As the thermoplastic resin constituting the shell of the unexpanded 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 non-foamed 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.

As the silicone-based surfactant or silicone oil that wets the microparticles beforehand, SH-192 (manufactured by Toray Dow Silicone Co., Ltd.) that does not react with isocyanate-terminated compounds is used as the silicone-based surfactant or silicone oil. ), SH-200 (manufactured by Toray Dow Silicone), L-5340 (manufactured by Nippon Unicar) and the like.

When the microparticles are wetted with a silicone-based surfactant or silicone oil, the microparticles may be charged into a tank, and the silicone-based surfactant or silicone oil may be sprayed with stirring. As a simple method, it is a practical method to pack the microparticles and spray a silicone-based surfactant or silicone oil with a spray gun.

The amount of the silicone surfactant or silicone oil to be sprayed is suitably 1 to 5 times the weight of the fine particles. By spraying the silicone-based surfactant or silicone oil and wetting the microparticles, when mixed with the isocyanate-terminated prepolymer, the microparticles are less likely to fly up and do not pollute the environment. Furthermore, since the air adsorbed on the microparticle surface is replaced by a silicone-based surfactant or silicone oil by pre-wetting evenly, not only the air intake is reduced when mixing with the prepolymer, The fine particles are not aggregated in a dumpling shape, and uniform dispersion can be achieved. If the amount of the silicone surfactant or silicone oil is 1 part by weight or less of the weight of the microparticles, the adsorption to the microparticle surface becomes insufficient, and it is inevitable that the silicone powder aggregates in a cluster when mixed with the prepolymer. become. On the contrary, spraying 5 times or more is not preferable because the one that does not react with the isocyanate-terminated prepolymer is added more than necessary, and the physical properties of the polishing pad are reduced.

At the time of mixing, first, an isocyanate-terminated prepolymer is charged into a blend tank capable of reducing pressure, and
The mixture is heated to 0 to 80 ° C, preferably 60 to 80 ° C, and mixed and stirred with microparticles which have been wetted with a silicone surfactant or silicone oil in advance. After mixing, gas such as dissolved air, air taken in during mixing, etc. is 10 Torr.
Degas and remove by depressurizing to a degree. At this time, if the liquid rises above a predetermined height, the pressure is returned to normal pressure, the pressure is reduced again, and the process is repeated until the liquid no longer rises.

By repeating the depressurizing operation after mixing the microparticles, it is possible to sufficiently remove the gas such as air which has been caught or dissolved, but it is dissolved in the isocyanate-terminated prepolymer. Since it takes time to remove the gas, it is more preferable to remove the gas by a similar decompression operation before mixing the microscopic bodies.

It is more preferable to use a blend tank having a structure that enables stirring during the decompression operation during defoaming under reduced pressure, because the minute particles are less likely to be separated due to a difference in specific gravity.

It is also possible to use fine particles which have been foamed in advance, but in this case, since the specific gravity is light, they tend to be separated by reduced pressure. In that case, setting the temperature of the prepolymer to a low temperature of 60 to 70 ° C. to set the viscosity higher in advance, and further performing the stirring while further reducing the pressure provides a more uniform polyurethane foam. .

As a stirrer for mixing the fine particles, there is an ordinary dissolver, for example, a powder mixing mixer or a primary mixer.

As a blend tank, 10 torr
It is preferable that the pressure can be reduced to a certain degree and the structure has a structure capable of stirring under reduced pressure. Further, it is preferable that a liquid level gauge is provided so that the liquid level can be monitored by reducing the pressure. Further, a monitoring window made of glass or transparent hard plastic that can withstand reduced pressure may be provided in the charging hole of the blend tank, and the state of the liquid level may be visually monitored by this.

The mixture of the depolymerized prepolymer and the fine particles is weighed in a reaction tank, and an active hydrogen compound is mixed and stirred therein, poured into a mold, and cured by reaction to form a polyurethane polishing pad for semiconductor polishing. obtain. It is preferable to use a stirrer that does not involve large bubbles for stirring. As such a stirrer, a primary mixer is suitable. For mixing with the active hydrogen compound, a two-component foaming machine may be used.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following 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. After that, Expandel 551DE (manufactured by Nippon Philite)
6.4 kg was packed in a bag, and 10 kg of a silicone-based surfactant SH-192 (manufactured by Toray Dow Corning) was sprayed with a spray gun, and the mixture was mixed with a primary mixer at 70 ° C. And degassed under reduced pressure by the same method. 30 kg of the liquid in which the microparticles are mixed is weighed into a reaction vessel, and 7.8 kg of 3,3′-dichloro-4,4′-diaminodiphenylmethane melted at 120 ° C. is added thereto. After stirring and mixing for seconds, the mixture was poured into a mold to obtain a molded body.

Comparative Example 1 A molded product was obtained in the same manner as in Example 1, except that the step of spraying the silicone-based surfactant and the step of reducing the pressure were omitted.

The cut surface of 15 sheets obtained by slicing each obtained molded body into 1.3 mm was visually observed. In Example 1, each sheet had a void of 0.5 mmφ or more. Is less than 20 pieces / 600mmφ
30 or more / 600 in Comparative Example 1
mmφ. Further, in Comparative Example 1, when the microparticles were mixed with the prepolymer, the microparticles were formed into a dumpling, and time was required for homogenization. (In the example, the balloon cluster (diameter is about 1 mm) was 3 or less in 50 mmφ,
In Comparative Example 1, there were 10 or more. )

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.

[0038]

EFFECTS OF THE INVENTION In the production of a polyurethane polishing pad for semiconductor polishing by mixing, stirring and hardening a microparticle made into an isocyanate-terminated prepolymer and an active hydrogen-containing compound, a microparticle previously made with a silicone surfactant or silicone oil By moistening the body and adding a vacuum degassing step, the occurrence of voids can be suppressed,
It was possible to obtain a polishing pad in which the fine particles were uniformly dispersed and which was excellent in the scratch property, the polishing property, and the flatness.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 14, 2002 (2002.3.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

Examples of the silicone surfactant or silicone oil for prewetting the microparticles include SH-192 (manufactured by Toray Dow Silicone) and SH-200 (manufactured by Toray Dow Silicone) which do not react with isocyanate-terminated compounds. ), L-5340 (manufactured by Nippon Unicar).

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

[0038]

When the isocyanate-terminated prepolymer, the microparticles and the active hydrogen-containing compound are mixed, agitated, and effected to produce a polyurethane polishing pad for semiconductor polishing, the microparticles are wetted with a silicone surfactant or silicone oil in advance. In addition, by further applying a reduced pressure defoaming step, the generation of voids can be suppressed, and a polishing pad excellent in scratch property, polishing characteristics, and flatness in which fine particles are uniformly dispersed can be obtained. done.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Ono 2-1-1 Katata, Otsu-shi, Shiga Inside Toyobo Co., Ltd. Research Institute (72) Inventor Tetsuo Shimomura 2-1-1 Katata, Otsu-shi, Shiga Inside Toyobo Co., Ltd. (72) Inventor Masahiko Nakamori 2-1-1 Katata, Otsu-shi, Shiga F-term in Toyobo Co., Ltd. (Ref.) 3C058 AA09 CA01 CA04 CA05 CA06 CA07 CB01 CB02 CB03 CB06 4F071 AA53 AC16 AD04 AE10 AH19 DA20 4J002 BD102 BG062 BG092 CK021 CK031 CK041 FA092 FB092 GT00

Claims (3)

[Claims] 1. A method for producing a polyurethane polishing pad for semiconductor polishing by mixing, stirring and curing an isocyanate-terminated prepolymer, an active hydrogen compound, and a microparticle, wherein a silicone-based surfactant or silicone oil is used in advance. A method for producing a polyurethane polishing pad for semiconductor polishing, comprising a step of defoaming under reduced pressure before a step of mixing an isocyanate-terminated prepolymer and an active hydrogen compound using a wet microparticle. 2. The method for producing a polyurethane polishing pad for semiconductor polishing according to claim 1, further comprising the step of defoaming under reduced pressure before mixing said microscopic objects. 3. The method for producing a polyurethane polishing pad for semiconductor polishing according to claim 1, further comprising a step of defoaming the microparticles under reduced pressure after mixing.