JP2024050520A - Polishing Pad - Google Patents

Abstract

[Problem] To provide a polishing pad having excellent defect performance and excellent polishing rate. [Solution] The polishing pad has a polishing layer made of a polyurethane resin foam made from an isocyanate-terminated prepolymer and a curing agent, and the ratio (IC80/IC40) of the mesophase content weight percentage in the polishing layer measured at 80°C by pulse NMR method (IC80) to the mesophase content weight percentage in the polishing layer measured at 40°C by pulse NMR method (IC40) is 0.40 to 1.00. [Selected Figure] Figure 1

Description

The present invention relates to a polishing pad. The polishing pad of the present invention is used for polishing optical materials, semiconductor devices, glass substrates for hard disks, etc., and is particularly suitable for polishing devices in which an oxide layer, metal layer, etc. is formed on a semiconductor wafer.

2. Description of the Related Art Chemical mechanical polishing (CMP) is commonly used as a polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates.
The CMP method will be described with reference to FIG. 1. As shown in FIG. 1, a polishing apparatus 1 for carrying out the CMP method is provided with a polishing pad 3, which contacts a holding platen 16 and a polished object 8 held by a retainer ring (not shown in FIG. 1) that holds the polished object 8 so as not to shift, and includes a polishing layer 4, which is a layer for polishing, and a cushion layer 6 that supports the polishing layer 4. The polishing pad 3 is rotated while the polished object 8 is pressed against it, and polishes the polished object 8. At that time, a slurry 9 is supplied between the polishing pad 3 and the polished object 8. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard fine abrasive grains, and the chemical components and abrasive grains in the slurry are flowed and move relative to the polished object 8 to increase the polishing effect. The slurry 9 is supplied to the polishing surface through grooves or holes and discharged.

The material of the polishing layer used in polishing semiconductor devices is a hard polyurethane material obtained by reacting a prepolymer containing an isocyanate component (such as toluene diisocyanate (TDI)) and a high molecular weight polyol (such as polyoxytetramethylene glycol (PTMG)) with a diamine-based hardener (such as 4,4'-methylenebis(2-chloroaniline) (MOCA)). This hard polyurethane material is composed of a soft segment formed from a high molecular weight polyol and a hard segment formed from a urethane bond or urea bond. In recent years, with the miniaturization of wiring in semiconductor devices, conventional polishing layers or polishing pads may not have sufficient polishing rate or defect performance (such as scratches), and further investigation is being conducted.

Patent Document 1 discloses a polishing pad that uses a polishing layer with a content of more than 70% crystalline phase (S phase) measured by pulse NMR, which reduces hardness changes due to heat, resulting in sufficient polishing and less scratching, and thus enabling stable polishing.

However, after examining Patent Document 1, it was found that scratches may easily occur and the defect performance may not be desirable if the crystal phase exceeds 70% at room temperature.

Relisted 2016/158348

Generally, polishing is performed at about 40° C., but frictional heat generated during polishing can cause the polishing pad to reach localized temperatures of about 80° C. (high temperatures). Since the physical properties of the polishing pad (particularly the polishing layer) are easily changed by frictional heat, the polishing characteristics become unstable in the temperature range (40 to 80° C.) that can occur during polishing, resulting in undesirable polishing rate and defect performance.
As a result of their investigations, the inventors have found that when foreign matter is mixed into the polishing pad of Patent Document 1 during polishing, the foreign matter causes a rise in temperature, which can change the proportions of crystalline phase, intermediate phase, and amorphous phase, and thus change the characteristics of the polishing layer.
The present inventors have investigated the proportions of the crystalline phase, mesophase and amorphous phase in the polishing layer, and have found that the above-mentioned problems can be solved when the ratio (IC80/IC40) of the weight proportion of the mesophase in the polishing layer measured at 80°C by pulse NMR (IC80) to the weight proportion of the mesophase in the polishing layer measured at 40°C by pulse NMR (IC40) is 0.40 to 1.00, thereby achieving the present invention.

[1] A polishing pad having a polishing layer made of a polyurethane resin foam made from an isocyanate-terminated prepolymer and a curing agent,
A polishing pad in which the ratio (IC80/IC40) of the weight proportion (IC80) of the mesophase in the polishing layer measured at 80°C by pulse NMR to the weight proportion (IC40) of the mesophase in the polishing layer measured at 40°C by pulse NMR is 0.40 to 1.00.
[2] The polishing pad according to [1], wherein the ratio (NC80/NC40) of the weight proportion of the amorphous phase in the polishing layer measured at 80°C by pulse NMR to the weight proportion (NC40) of the amorphous phase in the polishing layer measured at 40°C by pulse NMR is 1.00 to 2.00.
[3] The polishing pad according to [1], wherein the weight percentage (IC40, IC80) of the mesophase in the polishing layer measured at 40°C and 80°C by pulse NMR method is 15.0% by weight or less.
[4] The polishing pad according to [1], wherein the weight percentages of the crystalline phase in the polishing layer (CC40, CC80) measured at 40°C and 80°C by pulse NMR are 15.0 to 30.0% by weight.
[5] The polishing pad according to [1], wherein the polishing layer comprises PPG and PEPCD.
[6] The polishing pad according to [5], wherein the ratio of PEPCD to the total of PPG and PEPCD in the polishing layer is less than 80%.

The polishing pad may reach localized temperatures of around 80°C due to frictional heat generated during polishing, but the polishing pad of the present invention has a ratio (IC80/IC40) of the weight percentage of the intermediate phase in the polishing layer measured at 80°C by pulse NMR to the weight percentage of the intermediate phase in the polishing layer measured at 40°C by pulse NMR, which is 0.40 to 1.00, so that the proportion of the intermediate phase is maintained in the temperature range during polishing (40°C to 80°C), and the pad has excellent defect performance and an excellent polishing rate.

FIG. 1 is a schematic diagram showing a state of polishing. FIG. 2A is a perspective view and FIG. 2B is a cross-sectional view of the polishing pad.

The following describes the mode for carrying out the invention, but the present invention is not limited to the mode for carrying out the invention.

<<Polishing pad>>
The structure of the polishing pad 3 will be described with reference to Fig. 2. As shown in Fig. 2, the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably disk-shaped, but is not particularly limited thereto, and the size (diameter) can also be appropriately determined depending on the size of the polishing apparatus 1 equipped with the polishing pad 3, and can be, for example, about 10 cm to 2 m in diameter.
In the polishing pad 3 of the present invention, the polishing layer 4 is preferably bonded to the cushion layer 6 via an adhesive layer 7 as shown in FIG.
The polishing pad 3 is attached to a polishing platen 10 of the polishing device 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing device 1 while being pressed against the object 8 to be polished, thereby polishing the object 8 to be polished.

<Polishing layer>
(composition)
The polishing pad 3 includes a polishing layer 4 for polishing an object to be polished 8. The material constituting the polishing layer 4 is a polyurethane resin foam. The material and manufacturing method of the polyurethane resin foam will be described later.
The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3 and can be about 10 cm to 2 mm in diameter, and the thickness of the polishing layer 4 can be about 0.8 to 5 mm.
The polishing layer 4 is rotated together with the polishing table 10 of the polishing device 1, and while a slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the object 8 to be polished, thereby polishing the object 8 to be polished.
The polishing layer 4 preferably has hollow microspheres 4A (foamed) dispersed therein. When the hollow microspheres 4A are dispersed therein, when the polishing layer 4 is worn, the hollow microspheres 4A are exposed to the polishing surface, generating minute voids on the polishing surface. These minute voids hold the slurry, allowing the polishing of the workpiece 8 to proceed more rapidly. The polishing layer 4 is also dry molded.

(Groove processing)
It is preferable to provide grooves on the surface of the polishing layer 4 of the present invention on the side of the polished object 8, as necessary. The grooves are not particularly limited, and may be either slurry discharge grooves that communicate with the periphery of the polishing layer 4 or slurry holding grooves that do not communicate with the periphery of the polishing layer 4, or may have both slurry discharge grooves and slurry holding grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, and examples of the slurry holding grooves include concentric grooves and perforations (through holes), and these may also be combined.

(Shore D hardness)
The Shore D hardness of the polishing layer 4 of the present invention is not particularly limited, but is, for example, 20 to 100, preferably 30 to 80, and more preferably 40 to 70. If the Shore D hardness is low, it becomes difficult to flatten fine irregularities by low-pressure polishing. If the Shore D hardness is too high, it may be rubbed strongly against the polished object 8, causing scratches on the processed surface of the polished object 8.

In the polishing pad 3 of the present invention, hollow microspheres 4A are used to encapsulate air bubbles inside the polyurethane resin molding. Hollow microspheres refer to microspheres with voids. The shapes of the hollow microspheres 4A include spherical, elliptical, and shapes similar to these. Examples include pre-expanded types and unexpanded thermally expandable microspheres that have been thermally expanded.

(Crystalline phase, mesophase, amorphous phase)
In the polishing layer of the polishing pad of the present invention, the ratio (IC80/IC40) of the weight percentage of the mesophase in the polishing layer measured at 80° C. by pulse NMR to the weight percentage (IC40) of the mesophase in the polishing layer measured at 40° C. by pulse NMR is 0.40 to 1.00. Note that when the term "weight percentage" is used in this specification, it is calculated on a weight basis (% by weight).
The ratio (IC80/IC40) of the weight fraction (IC80) of the mesophase in the polishing layer measured at 80° C. by pulse NMR to the weight fraction (IC40) of the mesophase in the polishing layer measured at 40° C. by pulse NMR is preferably 0.45 or more, more preferably 0.50 or more. On the other hand, the upper limit is preferably 0.95 or less, more preferably 0.90 or less.
By satisfying the above range, the weight proportion of the intermediate phase does not increase in the temperature range expected during polishing, and the weight proportions of the crystalline phase and amorphous phase increase, making it possible to achieve both excellent defect performance and polishing rate, which is preferable.

The ratio (NC80/NC40) of the weight proportion of the amorphous phase in the polishing layer measured at 80°C by pulse NMR (NC80) to the weight proportion of the amorphous phase in the polishing layer measured at 40°C by pulse NMR (NC40) is preferably 1.00 to 2.00.
The lower limit of NC80/NC40 is more preferably 1.05 or more, while the upper limit is more preferably 1.80 or less.
By satisfying the above range, both excellent defect performance and polishing rate can be achieved at the temperature expected during polishing, which is preferable.

The weight percentages of the intermediate phase in the polishing layer measured by pulse NMR at 40°C and 80°C (IC40, IC80) are preferably 15.0% by weight or less, and more preferably 12.0% by weight or less. By keeping the weight percentages of the intermediate phase in the polishing layer measured at 40°C and 80°C low, the weight percentages of the crystalline phase and amorphous phase become large, which makes it easier for the phase to be bifurcated, and the characteristics of the hard segment component and the soft segment component are more easily expressed, resulting in appropriate hardness and elasticity.

The weight percentage of the crystalline phase in the polishing layer measured by pulse NMR at 40° C. and 80° C. (CC40, CC80) is preferably 15.0% by weight or more and 30.0% by weight or less. The lower limit is more preferably 17.0% by weight. On the other hand, the upper limit is more preferably 29.0% by weight.
When the weight ratio of the crystalline phase is within a predetermined range, an excellent polishing rate tends to be maintained due to the action of the hard segment.

The ratio (CC80/CC40) of the weight proportion of the crystalline phase (CC80) measured at 80° C. to the weight proportion of the crystalline phase (CC40) measured at 40° C. by pulse NMR is preferably 0.70 to 1.50.
The lower limit of CC80/CC40 is more preferably 0.75 or more, while the upper limit is preferably 1.40 or less.
Generally, when polishing is performed, the temperature of the polishing pad rises due to friction. The polishing layer of the polishing pad of the present invention has a relatively small weight ratio of intermediate phase, and even if the temperature rises, the weight ratio of amorphous phase and crystalline phase changes little. Therefore, within the polishing temperature range, the structure of the polishing layer changes little, so that a stable high polishing rate can be obtained.

The ratio of the crystalline phase, intermediate phase, and amorphous phase of the polishing layer is measured by pulse NMR. In the pulse NMR measurement, the polyurethane resin foam is classified into a short phase (S phase), a middle phase (M phase), and a long phase (L phase) in the order of shortest spin-spin relaxation time, and the weight ratio of each phase is obtained. Regarding the weight ratio of the S phase, M phase, and L phase, for example, the crystalline phase is mainly observed as the S phase in the pulse NMR measurement, the non-crystalline phase (amorphous phase) is mainly observed as the L phase, and the intermediate phase is mainly observed as the M phase in the pulse NMR measurement. Furthermore, the hard segment portion is mainly observed as the S phase in the pulse NMR measurement, and the soft segment portion is mainly observed as the L phase.
The spin-spin relaxation time can be determined, for example, by performing measurement by the Solid Echo method using a "JNM-MU25" manufactured by JEOL.
In this specification, the weight ratio of the amorphous phase in the polishing layer measured at 40°C by pulse NMR method may be expressed as "NC40", the weight ratio of the intermediate phase in the polishing layer measured at 40°C by pulse NMR method may be expressed as "IC40", and the weight ratio of the crystalline phase in the polishing layer measured at 40°C by pulse NMR method may be expressed as "CC40". In addition, when measuring at 80°C instead of 40°C, for example, if it is the weight ratio of the crystalline phase, change the "40" of CC40 to "80" and make it "CC80".

<Cushion layer>
(composition)
The polishing pad 3 of the present invention has a cushion layer 6. It is desirable for the cushion layer 6 to make the contact of the polishing layer 4 with the workpiece 8 more uniform. Examples of materials for the cushion layer 6 include resins; impregnated materials in which the resin is impregnated into a base material; flexible materials such as synthetic resins and rubbers; and sponge materials using the resins. Examples of the resins include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber.

The cushion layer 6 may be a foam having a cellular structure. As the cellular structure, in addition to a nonwoven fabric having voids formed therein, a suede-like structure having teardrop-shaped bubbles formed by a wet film forming method, or a sponge-like structure having fine bubbles can be preferably used.
Among these, when a cushion layer is made of a nonwoven fabric impregnated with polyurethane or a sponge-like material, it has good compatibility with the polishing layer, and therefore it is possible to obtain a high polishing rate while maintaining the defect performance.

<Adhesive Layer>
The adhesive layer 7 is a layer for adhering the cushion layer 6 and the polishing layer 4, and is usually made of a double-sided tape or an adhesive. The double-sided tape or adhesive may be any known double-sided tape or adhesive in the art (e.g., an adhesive sheet).
The polishing layer 4 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be made of at least one adhesive selected from, for example, acrylic, epoxy, and urethane adhesives. For example, an acrylic adhesive is used, and the thickness can be set to 0.1 mm.

"Defect" is a general term that includes defects such as "particles," which are fine particles remaining on the surface of the object being polished, "pad debris," which are debris from the polishing layer that is attached to the surface of the object being polished, and "scratch," which are scratches on the surface of the object being polished. Defect performance refers to the ability to reduce these "defects."

And the polishing rate refers to the amount of polishing done per unit time.

<<Method of manufacturing polishing pad>>
A method for producing the polishing pad 3 of the present invention will now be described.

<Material for the polishing layer>
A polyurethane resin foam is used as the material for the polishing layer 4. A specific example of the main component material is a material obtained by reacting an isocyanate-terminated prepolymer with a curing agent. In addition, a foaming agent is added to the material to cause foaming.

The manufacturing method for the polishing layer 4 will be explained below using an example that uses an isocyanate-terminated prepolymer and a curing agent.

Examples of a method for producing the polishing layer 4 using an isocyanate-terminated prepolymer and a curing agent include a material preparation step of preparing at least an isocyanate-terminated prepolymer, an additive, and a curing agent; a mixing step of mixing at least the isocyanate-terminated prepolymer, the additive, and the curing agent to obtain a mixture for molding a molded body; a molding step of molding the polishing layer 4 from the mixture for molding a molded body; and a bonding step of bonding the polishing layer and the cushion layer.

The process is divided into the material preparation process, the mixing process, the molding process, and the joining process, and each process will be explained below.

<Material preparation process>
In order to manufacture the polishing layer 4 of the present invention, an isocyanate-terminated prepolymer and a curing agent are prepared as raw materials for the polyurethane resin foam. Here, the isocyanate-terminated prepolymer is a urethane prepolymer for forming the polyurethane resin foam.

Each ingredient is explained below.

(Isocyanate-terminated prepolymer)
The isocyanate-terminated prepolymer is a compound obtained by reacting the following polyisocyanate compound with a polyol compound under commonly used conditions, and contains a urethane bond and an isocyanate group in the molecule. In addition, other components may be contained in the isocyanate-terminated prepolymer within a range that does not impair the effects of the present invention.

The isocyanate-terminated prepolymer may be a commercially available one, or may be one synthesized by reacting a polyisocyanate compound with a polyol compound. There is no particular limitation on the reaction, and the addition polymerization reaction may be carried out using a method and conditions known in the production of polyurethane resins. For example, the prepolymer may be produced by adding a polyisocyanate compound heated to 50°C to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, and then heating the compound to 80°C after 30 minutes and reacting at 80°C for 60 minutes.
The isocyanate-terminated prepolymer preferably has an NCO equivalent of about 300 to 700. From the viewpoint that the weight ratio of the crystalline phase and the amorphous phase does not change significantly even when the temperature is increased from 40° C. to 80° C., and from the viewpoint of improving defect performance, an isocyanate-terminated prepolymer having a high NCO equivalent is preferred, for example, an isocyanate-terminated prepolymer having an NCO equivalent of 480 or more is preferred. Therefore, when the isocyanate-terminated prepolymer is a commercially available product, it is preferred that the NCO equivalent falls within the above range, and when produced by synthesis, it is preferred to adjust the NCO equivalent to the above range by using the following raw materials in an appropriate ratio.

(Polyisocyanate Compound)
In this specification, the polyisocyanate compound means a compound having two or more isocyanate groups in the molecule.
The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl- Examples of the polyisocyanate include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidine diisothiocyanate, etc. These polyisocyanate compounds may be used alone, or a plurality of polyisocyanate compounds may be used in combination.

The polyisocyanate compound preferably contains 2,4-TDI and/or 2,6-TDI.

(Polyol Compound as Raw Material for Prepolymer)
In this specification, the polyol compound means a compound having two or more hydroxyl groups (OH) in the molecule.
Examples of polyol compounds used in the synthesis of a urethane bond-containing polyisocyanate compound as a prepolymer include diol compounds, triol compounds, etc., such as ethylene glycol, diethylene glycol (DEG), butylene glycol, etc.; and polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), polypropylene glycol (PPG), polyether polycarbonate diol (PEPCD), etc. PEPCD is a compound represented by the following general formula:

In the above formula, m and n represent the number of repeating units and each independently represents a real number. PEPCD can be used alone or in combination of two or more kinds.
In the above formula, m and n represent the number of repeating units and each independently represents a real number. PEPCD can be used alone or in combination of two or more kinds.
Among the above components, a combination of PEPCD and PPG is preferred since it makes it easier to adjust the ratio (IC80/IC40) of the weight fraction of the mesophase in the polishing layer measured at 80°C (IC80) to the weight fraction of the mesophase in the polishing layer measured at 40°C (IC40) by pulse NMR method to 0.40 to 1.00.
Furthermore, the upper limit of the ratio of PEPCD to the total of PPG and PEPCD is preferably less than 80%, more preferably 70% or less. The lower limit is preferably a ratio exceeding 20%, more preferably 30% or more. By having the ratio of PPG and PEPCD within the desired range, there is a tendency that both an excellent polishing rate and excellent defect performance can be achieved.
The number average molecular weight (Mn) of the polyol such as PPG or PEPCD is not particularly limited, and is preferably 500 to 3000, more preferably 800 to 2500. By adjusting the number average molecular weight of the polyol, the weight ratio of the crystalline phase, the mesophase, and the amorphous phase can be adjusted. Here, the number average molecular weight can be measured by gel permeation chromatography (GPC). In addition, when measuring the number average molecular weight of the polyol compound from the polyurethane resin, each component is decomposed by a conventional method such as amine decomposition, and then it can be estimated by GPC.

(Additive)
As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4 as necessary.

(Hardening agent)
In the method for producing the polishing layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with the isocyanate-terminated prepolymer and the like in the mixing step. By adding the curing agent, in the subsequent molding step, the main chain end of the isocyanate-terminated prepolymer bonds with the curing agent to form a polymer chain, which then hardens.
Examples of the curing agent include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis[3-(isopropylamino)-4- polyamine compounds such as 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylene bis-4-aminobenzoate, and polytetramethylene oxide-di-p-aminobenzoate; ethylene glycol, Pyrene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3- Examples of the polyhydric alcohol compounds include methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol. The polyhydric amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. As the polyamine compound, a diamine compound is preferable, and for example, it is more preferable to use 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

When two or more types of polyols are used as raw materials for the isocyanate-terminated prepolymer, the two or more types of polyols may be mixed and reacted with a polyisocyanate compound, or two or more types of polyols may be reacted with a polyisocyanate compound, and then the mixture may be mixed and cured.

The polishing layer 4 can be formed by using hollow microspheres 4A, which have an outer shell and are hollow inside, as a material. The material of the hollow microspheres 4A may be a commercially available one, or may be one obtained by synthesis using a conventional method. The material of the outer shell of the hollow microspheres 4A is not particularly limited, and examples thereof include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride and organic silicone resins, and copolymers of two or more types of monomers constituting these resins (e.g., acrylonitrile-vinylidene chloride copolymers, etc.). In addition, examples of commercially available hollow microspheres include, but are not limited to, the Expancel series (trade name manufactured by Akzo Nobel), Matsumoto Microsphere (trade name manufactured by Matsumoto Yushi Co., Ltd.), etc.
The gas contained in the hollow microspheres 4A is not particularly limited, but may be, for example, a hydrocarbon, specifically, isobutane, pentane, isopentane, or the like.

The shape of the hollow microspheres 4A is not particularly limited, and may be, for example, spherical or nearly spherical. The average particle size of the hollow microspheres 4A is not particularly limited, but is preferably 5 to 200 μm, more preferably 5 to 80 μm, even more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The average particle size can be measured by a laser diffraction particle size distribution analyzer (for example, Mastersizer 2000, manufactured by Spectris Co., Ltd.).

The material for hollow microspheres 4A is added in an amount of preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, and even more preferably 1 to 4 parts by weight, per 100 parts by weight of isocyanate-terminated prepolymer.

In addition to the above components, conventionally used blowing agents may be used in combination with the hollow microspheres 4A within the scope of the present invention, and a gas that is non-reactive with the above components may be blown in during the mixing step described below. Examples of the blowing agent include water and blowing agents that are mainly composed of hydrocarbons with 5 or 6 carbon atoms. Examples of the hydrocarbon include linear hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

<Mixing step>
In the mixing step, the isocyanate-terminated prepolymer obtained in the preparation step, the additive, and the curing agent are fed into a mixer and stirred and mixed. The mixing step is carried out in a state where the components are heated to a temperature at which the fluidity of each component can be ensured.

<Molding process>
In the molding process, the mixture for molding prepared in the mixing process is poured into a mold preheated to 30 to 100°C for primary curing, and then heated at about 100 to 150°C for about 10 minutes to 5 hours for secondary curing to form a cured polyurethane resin (polyurethane resin foam). At this time, the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin, thereby curing the mixture.
If the viscosity of the urethane prepolymer (isocyanate-terminated prepolymer) is too high, the fluidity is deteriorated, and it becomes difficult to mix uniformly during mixing. If the temperature is increased to lower the viscosity, the pot life is shortened, and the mixing spots are generated, and the size of the hollow microspheres 4A formed in the obtained foam varies. On the other hand, if the viscosity is too low, the bubbles move in the mixed liquid, and it becomes difficult to form the hollow microspheres 4A dispersed uniformly in the obtained foam. For this reason, it is preferable to set the viscosity of the isocyanate-terminated prepolymer in the range of 500 to 10,000 mPa·s at a temperature of 50 to 80° C. This can be done, for example, by changing the molecular weight (degree of polymerization) of the isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer is heated to about 50 to 80° C. to be in a flowable state.

In the molding process, the mixture is reacted in a mold as necessary to form a foam. At this time, the isocyanate-terminated prepolymer reacts with the curing agent to crosslink and harden.

After obtaining the polyurethane resin foam, it is sliced into sheets to form multiple polishing layers 4. A general slicer can be used for slicing. When slicing, the lower part of the polishing layer 4 is held, and it is sliced to a predetermined thickness starting from the upper part. The slice thickness is set, for example, in the range of 0.8 to 2.5 mm. For a polyurethane resin foam molded in a 50 mm thick mold, for example, about 10 mm of the upper and lower parts of the polyurethane resin foam are not used due to scratches, etc., and 10 to 25 polishing layers 4 are formed from about 30 mm of the center. In the hardening and molding step, a polyurethane resin foam is obtained in which hollow microspheres 4A are formed approximately evenly inside.

The polishing surface of the obtained polishing layer 4 is grooved as necessary. By performing cutting or the like on the polishing surface using a required cutter, grooves with any pitch, width, and depth can be formed. Examples of slurry holding grooves include circular grooves formed in a concentric pattern, and examples of slurry discharge grooves include linear grooves formed in a lattice pattern and linear grooves formed radially from the center of the polishing layer.

The polishing layer 4 thus obtained is then attached with double-sided tape to the side opposite the polishing surface of the polishing layer 4. There are no particular limitations on the double-sided tape, and any double-sided tape known in the art can be selected and used.

<Method of manufacturing the cushion layer 6>
As described above, examples of the material for the cushion layer 6 include an impregnated material in which resin fibers such as polyethylene and polyester (nonwoven fabric, flexible film, etc.) are impregnated with a resin solution such as urethane, a suede material using a resin material such as urethane, and a sponge material using a material such as urethane. In the present invention, the cushion layer 6 can be made of a known material, and the manufacturing method can also be known.

<Joining process>
In the bonding process, the formed polishing layer 4 and cushion layer 6 are bonded (bonded) with an adhesive layer 7. For example, an acrylic adhesive is used for the adhesive layer 7, and the adhesive layer 7 is formed to a thickness of 0.1 mm. That is, the acrylic adhesive is applied to the surface of the polishing layer 4 opposite to the polishing surface with a substantially uniform thickness. The surface of the polishing layer 4 opposite to the polishing surface and the surface of the cushion layer 6 (the surface on which the skin layer is formed) are pressed together via the applied adhesive, and the polishing layer 4 and the cushion layer 6 are bonded with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to confirm that there is no dirt or foreign matter attached, and the polishing pad 3 is completed.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

In each example and comparative example, "parts" means "parts by mass" unless otherwise specified.

The NCO equivalent is a value indicating the molecular weight of the prepolymer (PP) per NCO group, calculated by (mass (parts) of polyisocyanate compound + mass (parts) of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound x mass (parts) of polyisocyanate compound / molecular weight of polyisocyanate compound) - (number of functional groups per molecule of polyol compound x mass (parts) of polyol compound / molecular weight of polyol compound)].

(Regarding the polishing layer)
A given 2,4-tolylene diisocyanate (2,4-TDI) as an isocyanate compound, PPG (polypropylene glycol) as a polyol compound, and PEPCD (polyether polycarbonate diol) were reacted to prepare urethane prepolymer 1, urethane prepolymer 2, urethane prepolymer 3, and urethane prepolymer 4 (see Table 1 for the components used in the preparation of the urethane prepolymers). A mixture of urethane prepolymers mixed in the ratio shown in Table 2 was mixed with non-expanded hollow microspheres whose shell portion is made of acrylonitrile-vinylidene chloride copolymer and in which isobutane gas is contained in the shell, to obtain a mixed liquid. The obtained mixed liquid was charged into a first liquid tank and kept warm at 60°C. Next, MOCA was charged into a second liquid tank as a curing agent separately from the first liquid, and heated and melted at 120°C and kept warm. The liquids in the first liquid tank and the second liquid tank were each injected into a mixer equipped with two injection ports so that the R value, which represents the equivalent ratio of the amino group and hydroxyl group present in the curing agent to the terminal isocyanate group in the prepolymer, was 0.9. The two injected liquids were mixed and stirred while being injected into a mold preheated to 80°C, and then the mold was closed and heated at 80°C for 30 minutes to perform primary curing. The primary cured molded product was demolded and then secondary cured in an oven at 120°C for 4 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25°C, and then heated again in an oven at 120°C for 5 hours, and then sliced to a thickness of 1.3 mm to obtain the polishing layers A to E shown in Tables 2 and 3. The density and D hardness of each polishing layer are shown in Table 2. The materials used for each polishing layer are also shown in Table 3. The weight ratios of the crystalline phase, intermediate phase, and amorphous phase in the polishing layer of each polishing layer, measured by pulse NMR, are shown in Table 4. The ratio of the amorphous phase to the intermediate phase (NC40/IC40, NC80/IC80) and the ratio of the crystalline phase to the intermediate phase (CC40/IC40, CC80/IC80) of each polishing layer measured at 40°C and 80°C by pulse NMR method are shown in Table 5. The weight ratio of each phase of each polishing layer changes with temperature is shown in Table 6. The measurement method and conditions of density, D hardness, and pulse NMR measurement are as follows.

(density)
The density (g/cm ³ ) of the polishing layer was measured in accordance with Japanese Industrial Standards (JIS K 6505).

(Shore D hardness)
The Shore D hardness of the polishing layer was measured using a Shore D hardness tester in accordance with the Japanese Industrial Standards (JIS-K-6253). Here, the measurement sample was obtained by stacking multiple polishing layers as necessary so that the total thickness was at least 4.5 mm.

(Pulsed NMR Measurement)
The conditions for the pulse NMR measurements carried out on the polishing layers A to E are as follows: The phases were divided into crystalline phase, intermediate phase, and amorphous phase according to the relaxation time, and the weight ratios of each phase were calculated.
Equipment: Bruker Minispec mq20 (20MHz)
Nuclide ^1H
Measurement _T2
Measurement method: Solid echo method Acquisition Scale: 0.4 msec
Scan 128 times Recycle Delay 0.5sec
Measurement temperature: 40℃, 80℃
After the temperature of the device reached the measurement temperature and the sample was set, the measurement was started after leaving it for 5 minutes. Measurement was performed once every 5 minutes from the start of the measurement, for a total of 23 measurements. The average value obtained by averaging the 12th to 23rd measurements out of the 23 measurements was used as the measurement result. The samples used were prepared by punching out the abrasive layers A to E in a dry state that had been kept in a thermo-hygrostat at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) for 40 hours to a diameter of 8 mm, and filling the sample pellets obtained by punching out the pellets in the sample tube to a height of 1 to 1.5 cm using the above device and conditions.

(About the cushion layer)
A nonwoven fabric made of polyester fibers with a density of 0.15 g/ ^cm3 was immersed in a resin solution (DMF solvent) containing a urethane resin (manufactured by DIC Corporation, product name "C1367"). After immersion, the resin solution was squeezed out of the nonwoven fabric using a mangle roller capable of applying pressure between a pair of rollers, and the nonwoven fabric was substantially uniformly impregnated with the resin solution. Next, the nonwoven fabric impregnated with the resin solution was immersed in a coagulating liquid made of water at room temperature to wet-coagulate the resin, thereby obtaining a resin-impregnated nonwoven fabric. Thereafter, the resin-impregnated nonwoven fabric was removed from the coagulating liquid and further washed with a washing liquid made of water to remove N,N-dimethylformamide (DMF) in the resin, and then dried. After drying, the skin layer on the surface of the resin-impregnated nonwoven fabric was removed by buffing, and a cushion layer of 1.3 mm in thickness made of the resin-impregnated nonwoven fabric was obtained.

Examples and Comparative Examples
The polishing layer A and the cushion layer were bonded with a 0.1 mm thick double-sided tape (a PET substrate with an adhesive made of an acrylic resin on both sides) to obtain the polishing pad of Example 1. Instead of the polishing layer A, the polishing layers B, C, D and E were bonded in the same manner to obtain the polishing pads of Example 2, Example 3, Comparative Example 1 and Comparative Example 2.

(Polishing performance evaluation)
Using the resulting polishing pads of Examples 1, 2, 3, and Comparative Examples 1 and 2, polishing tests were carried out under the following polishing conditions to evaluate the polishing performance (polishing rate and defect performance).

(Polishing conditions)
Polishing machine used: F-REX300X (manufactured by Ebara Corporation)
Disk: A188 (manufactured by 3M)
Polishing agent temperature: 20°C
Polishing platen rotation speed: 90 rpm
Polishing head rotation speed: 81 rpm
Polishing pressure: 3.5 psi
Polishing slurry (metal film): CSL-9044C (a mixture of CSL-9044C stock solution and pure water at a weight ratio of 1:9 was used) (manufactured by Fujifilm Planar Solutions Co., Ltd.)
Polishing slurry flow rate: 200 ml/min
Polishing time: 60 seconds Polished material (metal film): Cu film substrate Pad break: 32N 10 minutes Conditioning: In-situ 18N 16 scans, Ex-situ 32N 4 scans

(Polishing rate evaluation)
The polishing rates of the 15th, 25th, and 50th substrates polished were measured. In the examples and comparative examples, the polishing rate was evaluated by the polished thickness. The thickness was measured using a four-probe sheet resistance measuring device (manufactured by KLA Tencor Corporation, product name "RS-200", measurement: DBS mode). The results are shown in Table 7. The evaluation was made as ◯ when the polishing rate of all substrates was 9000 Å or more, and as × otherwise.

(Discussion of polishing test results)
The results in Table 7 show that the polishing pads of Examples 1, 2 and 3 have improved polishing rates and are superior in polishing performance compared to the polishing pad of Comparative Example 1.

(Defect performance evaluation)
The 16th, 26th, and 51st substrates that had been polished were subjected to a high sensitivity measurement mode of a surface inspection device (KLA Tencor, Surfscan SP5) to detect defects (surface defects) with a size of 110 nm or more. For each detected defect, an SEM image taken using a review SEM was analyzed to count the number of scratches. If the number of scratches was 10 or less, which is considered necessary in practice, it was indicated as ○, and if the number of scratches was more than 10, it was indicated as ×. The results are shown in Table 8. Table 8 also shows the results of the polishing rate.

The results in Table 8 show that the polishing pads of Examples 1, 2, and 3 have a slightly reduced number of scratches compared to Comparative Example 2, and are therefore able to suppress the occurrence of defects.

The present invention contributes to the manufacture and sale of polishing pads and has industrial applicability.

Reference Signs List 1 Polishing device 3 Polishing pad 4 Polishing layer 4A Hollow microspheres 6 Cushion layer 7 Adhesive layer 8 Object to be polished 9 Slurry 10 Polishing platen

Claims (6)

A polishing pad having a polishing layer made of a polyurethane resin foam made of an isocyanate-terminated prepolymer and a curing agent,
A polishing pad in which the ratio (IC80/IC40) of the weight proportion (IC80) of the mesophase in the polishing layer measured at 80°C by pulse NMR to the weight proportion (IC40) of the mesophase in the polishing layer measured at 40°C by pulse NMR is 0.40 to 1.00. The polishing pad according to claim 1, in which the ratio (NC80/NC40) of the weight percentage of the amorphous phase in the polishing layer measured at 80°C by pulse NMR method (NC80) to the weight percentage of the amorphous phase in the polishing layer measured at 40°C by pulse NMR method (NC40) is 1.00 to 2.00. The polishing pad according to claim 1, wherein the weight percentage of the intermediate phase in the polishing layer (IC40, IC80) measured at 40°C and 80°C by pulse NMR method is 15.0% by weight or less. The polishing pad according to claim 1, wherein the weight percentage of the crystalline phase in the polishing layer (CC40, CC80) measured at 40°C and 80°C by pulse NMR is 15.0 to 30.0% by weight. The polishing pad of claim 1, wherein the polishing layer comprises PPG and PEPCD. The polishing pad according to claim 5, wherein the ratio of PEPCD to the total of PPG and PEPCD in the polishing layer is less than 80%.