JP7292215B2 - polishing pad - Google Patents

Description

Cross-reference to related applications

This application claims priority from Japanese Patent Application No. 2017-252429 and is incorporated herein by reference.

The present invention relates to polishing pads.

As a polishing pad for polishing an object to be polished (glass plate, etc.), a polishing pad made of a polyurethane resin foam is known (for example, Patent Document 1, etc.).

Japanese Patent Application Laid-Open No. 2007-250166

In recent years, it has been more demanded than ever to suppress the adhesion of foreign matter to an object to be polished and to improve the flatness of the object to be polished.

Therefore, in view of the above-mentioned requirements, it is an object of the present invention to provide a polishing pad that can improve the flatness of the object to be polished while suppressing the adhesion of foreign matter to the object to be polished.

A polishing pad according to the present invention is a polishing pad containing a polyurethane resin foam,
having a polished surface,
The polishing surface is composed of the surface of the polyurethane resin foam,
The polyurethane resin foam has a tan δ of 0.10 to 0.50 at 30° C. and an average cell diameter of 50 to 120 μm.

The figure which shows the measurement point in the polishing pad in the measurement of cutting speed. FIG. 4 is a diagram showing the number of defects on an object to be polished when the object to be polished is polished using the polishing pads of Examples and Comparative Examples. FIG. 4 is a diagram showing the haze level of an object to be polished when the object to be polished is polished using the polishing pads of Examples and Comparative Examples;

An embodiment of the present invention will be described below.

The polishing pad according to this embodiment is a polishing pad containing polyurethane resin foam having polyurethane resin.
Moreover, the polishing pad according to the present embodiment has a polishing surface, and the polishing surface is composed of the surface of the polyurethane resin foam.

It is important that the polyurethane resin foam has a tan δ at 30° C. of 0.10 to 0.50, preferably 0.15 to 0.40, and more preferably 0.20 to 0.40. It is more preferable to have
Note that tan δ at 30°C means the ratio of the loss elastic modulus E'' at 30°C to the storage elastic modulus E' at 30°C.

In addition, the polyurethane resin foam has a storage modulus E′ at 45° C. of preferably 0.5×10 ⁷ to 5.0×10 ⁷ Pa, more preferably 1.0×10 ⁷ to 4.0×. 10 ⁷ Pa.

Furthermore, the polyurethane resin foam has a storage modulus E′ at 65° C. of preferably 0.5×10 ⁷ to 5.0×10 ⁷ Pa, more preferably 1.0×10 ⁷ to 4.0×. 10 ⁷ Pa.

The storage modulus E' and the loss modulus E'' were measured according to JIS K7244-4: 1999 "Plastics-Testing methods for dynamic mechanical properties-Part 4: Tensile vibration-Non-resonance method" under the following conditions. can be measured in
Measurement temperature range: 0°C to 100°C
Heating rate: 5°C/min
Frequency: 1Hz
Strain: 0.5%

Further, the polyurethane resin foam has an average cell diameter of 50 to 120 μm.

Further, the polyurethane resin foam preferably has a standard deviation of cell diameters of 10 to 55 μm.

The average value of bubble diameters and the standard deviation of bubble diameters can be obtained as follows using an X-ray CT scanner (eg, TDM1000H-I manufactured by Yamato Scientific Co., Ltd.).
That is, the volume of each cell included in the measurement target range (for example, 0.7 mm × 1.6 mm × 1.6 mm) of the polyurethane resin foam is measured, and the diameter of a true sphere having the same volume as this volume is measured. Let it be the diameter of each bubble.
Then, the arithmetic average value of the diameters is obtained from the diameters of the individual bubbles, and this value is used as the average value of the bubble diameters. Also, the standard deviation of the diameter is obtained from the diameter of each bubble, and this is used as the standard deviation of the bubble diameter.

In the polyurethane resin foam, cells have a circular shape in a cross section perpendicular to the polishing surface.
It should be noted that "in the polyurethane resin foam, the cells have a circular shape in a cross section perpendicular to the polishing surface" means that "the polyurethane resin foam has a length of cells represented by the following formula (1). The average value of the aspect ratio of is 3/5 to 5/3.”
Average aspect ratio of length of bubbles = Length of bubbles in the direction perpendicular to the polishing surface/Length of bubbles in the direction parallel to the polishing surface (1)

The average value of the aspect ratios of the bubble lengths can be obtained as follows using an X-ray CT scanner (for example, TDM1000H-I manufactured by Yamato Scientific Co., Ltd.).
That is, first, a cross-sectional image of the polyurethane resin foam in the direction perpendicular to the polishing surface is photographed, 100 bubbles observed in this image are randomly selected, and each bubble is classified as "direction perpendicular to the polishing surface. "Length of bubble" and "Length of bubble in the direction parallel to the polishing surface" are obtained, and the aspect ratio of the length of the bubble is obtained.
Then, the arithmetic average of the aspect ratios of the lengths of these bubbles is taken, and this arithmetic average value is defined as the "average value of the aspect ratios of the lengths of the bubbles".
On the outer contour line of the bubble in the cross-sectional image, two points with the maximum mutual distance in the direction perpendicular to the polishing surface are selected, and the distance between these two points is defined as the length of the bubble in the direction perpendicular to the polishing surface. ”. In addition, on the outer contour line of the bubble in the cross-sectional image, two points with the maximum mutual distance in the direction parallel to the polishing surface are selected, and the distance between these two points is defined as the length of the bubble in the direction parallel to the polishing surface. ”.

Furthermore, the polyurethane resin foam preferably has an apparent density of 0.4 to 0.6 g/cm ³ .
In addition, the apparent density can be measured based on JIS K7222:2005.

The polyurethane resin comprises a first structural unit of a compound containing active hydrogen (hereinafter also referred to as an "active hydrogen compound") and a second structural unit of a compound containing an isocyanate group (hereinafter also referred to as an "isocyanate compound"). A constituent unit.
The polyurethane resin has a structure in which an active hydrogen compound and an isocyanate compound are urethane-bonded to alternately repeat the first structural unit of the active hydrogen compound and the second structural unit of the isocyanate compound.

The active hydrogen compound is an organic compound having an active hydrogen group capable of reacting with an isocyanate group in its molecule. Specific examples of the active hydrogen group include functional groups such as a hydroxy group, a primary amino group, a secondary amino group, and a thiol group. It may have only one type, or may have a plurality of types of the functional group in the molecule.

As the active hydrogen compound, for example, a polyol compound having a plurality of hydroxy groups in the molecule, a polyamine compound having a plurality of primary amino groups or secondary amino groups in the molecule, and the like can be used.

Examples of the polyol compound include polyol monomers and polyol polymers.

Examples of the polyol monomer include 1,4-benzenedimethanol, 1,4-bis(2-hydroxyethoxy)benzene, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1 linear aliphatic glycols such as ,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol; glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,8-octanediol, etc. and alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, glycerin, trimethylolpropane, tributyropropane, penta Examples include polyfunctional polyols such as erythritol and sorbitol.

As the polyol monomer, ethylene glycol and diethylene glycol are preferable because they tend to increase the strength during reaction, tend to increase the rigidity of the polishing pad containing the produced polyurethane foam, and are relatively inexpensive.

Examples of the polyol polymer include polyester polyols, polyester polycarbonate polyols, polyether polyols, and polycarbonate polyols.
The polyol polymer may also include a polyfunctional polyol polymer having 3 or more hydroxyl groups in the molecule.

Examples of the polyester polyol include polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone polyol, and polyhexamethylene adipate glycol.

Examples of the polyester polycarbonate polyol include a reaction product of a polyester glycol such as polycaprolactone polyol and an alkylene carbonate, and a reaction mixture obtained by reacting ethylene carbonate with a polyhydric alcohol and adding an organic dicarboxylic acid. Reaction products reacted with are also included.

Examples of the polyether polyol include polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and ethylene oxide-added polypropylene polyol.

The polycarbonate polyols include diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol, phosgene, and diallyl carbonate. (eg diphenyl carbonate) or reaction products with cyclic carbonates (eg propylene carbonate).

Other examples of the polyol compound include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and polyethylene glycol having a molecular weight of 400 or less.

Examples of the polyamine compounds include 4,4′-methylenebis(2-chloroaniline) (MOCA), 4,4′-methylenedianiline, trimethylenebis(4-aminobenzoate), 2-methyl 4,6-bis( methylthio)benzene-1,3-diamine, 2-methyl 4,6-bis(methylthio)-1,5-benzenediamine, 2,6-dichloro-p-phenylenediamine, 4,4'-methylenebis(2,3 -dichloroaniline), 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4'-diamino-3,3'- diethyl-5,5'-dimethyldiphenylmethane and the like.

Examples of the polyisocyanate include polyisocyanate and polyisocyanate polymer.

Examples of the polyisocyanate include aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate.

Examples of the aromatic diisocyanate include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. Examples of the aromatic diisocyanate include diphenylmethane diisocyanate (MDI) and modified diphenylmethane diisocyanate (MDI).

Modified products of diphenylmethane diisocyanate (MDI) include, for example, carbodiimide modified products, urethane modified products, allophanate modified products, urea modified products, biuret modified products, isocyanurate modified products, oxazolidone modified products and the like. Specific examples of such modified products include carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

Examples of the aliphatic diisocyanate include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and hexamethylene diisocyanate (HDI).

Examples of the alicyclic diisocyanate include 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, and methylenebis(4,1-cyclohexylene)=diisocyanate.

Examples of the polyisocyanate polymer include polymers in which a polyol is combined with at least one diisocyanate selected from aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate.

From the viewpoint of increasing the tan δ at 30° C. of the polyurethane resin foam, the polyurethane resin preferably contains polypropylene glycol (PPG) as a structural unit.
Moreover, since the polyurethane resin contains polypropylene glycol (PPG) as a structural unit, it has a relatively brittle structure, and as a result, it has the advantage of increasing the cutting speed during dressing of the polishing pad.
Furthermore, the polishing pad according to the present embodiment preferably contains 30% by mass or more, more preferably 40% by mass, of polypropylene glycol (PPG) contained in the constituent units of the polyurethane resin when the polyurethane resin is 100% by mass. It contains up to 70% by mass, more preferably 50 to 65% by mass.

The content ratio of polypropylene glycol (PPG) contained in the constituent units of the polyurethane resin can be obtained as follows when the polyurethane resin is 100% by mass.
First, a polyurethane resin foam is dissolved in a polar solvent (heavy DMF, heavy DMSO, etc.) to obtain a melt. Next, by analyzing the dissolved matter by 1H-NMR, polypropylene glycol (PPG) is quantified, and the content ratio of the polypropylene glycol (PPG) is determined.
Another method for determining the content of polypropylene glycol (PPG) is as follows.
First, a polyurethane resin foam is chemically decomposed with methanol to obtain a decomposition product. Next, the decomposition product is fractionated by gel permeation chromatography (GPC) or the like, and each fraction is analyzed by 1H-NMR or GC-MS to quantify polypropylene glycol (PPG). , the content ratio of the polypropylene glycol (PPG) is obtained.

The polishing pad according to this embodiment is configured as described above. Next, a method for manufacturing the polishing pad according to this embodiment will be described.

In the method for manufacturing a polishing pad according to this embodiment, a polishing pad having a polyurethane resin foam is manufactured.
Further, in the method for manufacturing a polishing pad according to the present embodiment, a dispersion liquid in which air is dispersed as bubbles is obtained by mixing a urethane prepolymer having an isocyanate group as a terminal group and a foam stabilizer.
A polishing pad having a polyurethane resin foam can be obtained by mixing and polymerizing the dispersion liquid and a curing agent which is an active hydrogen organic compound containing a plurality of active hydrogens in the molecule.
Examples of the foam stabilizer include silicone-based surfactants, fluorine-based surfactants, and ionic surfactants.

Objects to be polished with the polishing pad according to this embodiment include optical materials, semiconductor devices, hard disks, glass plates, silicon wafers, and the like.
Also, the polishing pad according to the present embodiment is suitably used for finish polishing, precision polishing, and the like.

Since the polishing pad according to this embodiment is configured as described above, it has the following advantages.
That is, the polishing pad according to this embodiment is a polishing pad containing a polyurethane resin foam. The polishing pad according to this embodiment has a polishing surface, and the polishing surface is composed of the surface of the polyurethane resin foam. The polyurethane resin foam has a tan δ of 0.10 to 0.50 at 30° C. and an average cell diameter of 50 to 120 μm.
With such a polishing pad, since the tan δ is large (0.10 or more), it is possible to suppress microvibration of the object to be polished during polishing, and to suppress damping of the object to be polished during polishing. As a result, during polishing, the polishing pad and the object to be polished are likely to come into close contact with each other.
As a result, such a polishing pad can have improved flatness.
In addition, in such a polishing pad, since the average bubble diameter is 120 μm or less, the bubbles present on the polishing surface are less likely to be clogged with foreign matter (polishing dust, etc.). The amount of adhering foreign matter is suppressed.
Therefore, according to the polishing pad of the present embodiment, it is possible to improve the flatness of the object to be polished while suppressing adhesion of foreign matter to the object to be polished.

In addition, the polishing pad according to the present invention is not limited to the above embodiment. Moreover, the polishing pad according to the present invention is not limited to the effects described above. Furthermore, the polishing pad according to the present invention can be modified in various ways without departing from the gist of the present invention.

EXAMPLES Next, the present invention will be described more specifically with reference to examples and comparative examples.

(Example 1)
By mixing the prepolymer and the foam stabilizer shown in Table 1 below at the mixing ratio shown in Table 1 below at 70° C., a dispersion liquid in which air was dispersed as bubbles was obtained.
Next, the dispersion and a curing agent were mixed and polymerized to obtain a polishing pad as a polyurethane resin foam.

The materials in Table 1 below are specifically as follows.
- Prepolymer 1: urethane prepolymer obtained by reacting polypropylene glycol (PPG) with tolylene diisocyanate (TDI) (urethane prepolymer having an isocyanate group as a terminal group) (NCOwt%: 5.80) ( Takenate L1150, manufactured by Mitsui Chemicals, Inc.)
Prepolymer 2: Urethane prepolymer obtained by reacting polytetramethylene ether glycol (PTMG) with tolylene diisocyanate (TDI) (urethane prepolymer having an isocyanate group as a terminal group) (NCOwt%: 6. 00) (Takenate L2695, manufactured by Mitsui Chemicals)
Prepolymer 3: Urethane prepolymer obtained by reacting polytetramethylene ether glycol (PTMG) with tolylene diisocyanate (TDI) (urethane prepolymer having an isocyanate group as a terminal group) (NCOwt%: 4. 31) (Takenate L2690, manufactured by Mitsui Chemicals)
・ Curing agent: MOCA (4,4′-methylenebis(2-chloroaniline))
・Foam stabilizer: Silicone surfactant (Decostarve B8465, manufactured by Evonik)
・ Catalyst: tertiary amine catalyst (Toyocat L33, manufactured by Tosoh Corporation)
The concentration of PPG in Table 1 below means the concentration of polypropylene glycol (PPG) contained in the constituent units of the polyurethane resin when the polyurethane resin is 100% by mass.

(Examples 2 to 4, Comparative Example 1)
A polishing pad as a polyurethane resin foam was obtained in the same manner as in Example 1, except that the materials and formulations shown in Table 1 below were used.

(Comparative example 2)
By mixing the prepolymer, water, and catalyst shown in Table 1 below at the mixing ratio shown in Table 1 below at 70 ° C., the isocyanate group, which is the terminal group of the prepolymer, and water are reacted to produce CO ₂ was generated to obtain a dispersion in which CO ₂ was dispersed as bubbles.
Next, the dispersion and a curing agent were mixed and polymerized to obtain a polishing pad as a polyurethane resin foam.

(D hardness)
D hardness was measured according to JIS K6253-1997.
Specifically, a polyurethane foam cut into a size of 2 cm x 2 cm (thickness: arbitrary) was used as a hardness measurement sample. was allowed to stand for 16 hours under the environment of
Here, when the thickness of the hardness measurement sample was 6 mm or more, the hardness of the hardness measurement sample was measured with a hardness tester (Asker D type hardness tester manufactured by Kobunshi Keiki Co., Ltd.).
On the other hand, when the thickness of the hardness measurement sample is less than 6 mm, a plurality of hardness measurement samples are superimposed in the thickness direction so that the total thickness of the superimposed hardness measurement samples is 6 mm or more. The hardness of the sample for hardness measurement was measured with a hardness meter (Asker D type hardness meter manufactured by Kobunshi Keiki Co., Ltd.).

(Apparent density, tan δ, and E')
Also, the apparent density, tan δ, and E' were measured by the methods described above.

(cutting speed)
The polishing pads of Examples and Comparative Examples were processed into donut shapes as shown in FIG. (12 points), and a through hole having a diameter of about 3 mm was formed at each of these measurement points to obtain a specimen.
Next, the specimen was attached to the platen of a polishing apparatus (Ecomet 2000) via a double-sided tape, and the thickness of the specimen was measured at the through-hole using a depth gauge.
Then, the surface of the pad was cut under the following cutting conditions.
Pad conditioner: AD3BI-100530-3 (DiaGrid φ4 inch manufactured by kinik)
Condition Weight: 35g/ ^cm2
Platen speed: 50rpm
Head speed: 60rpm
Dressing time: 30min
Water flow rate: 100 mL/min
After the cutting, the thickness of the specimen was measured at the through-hole using a depth gauge.
Then, the cutting speed (μm/hr) at each point is obtained from the difference in the thickness of the specimen before and after cutting at each point, and the arithmetic mean value of the cutting speed is obtained from the cutting speed at each point, which is the cutting speed of the polishing pad. (μm/hr).

(Polishing test)
Using the polishing pads of Examples and Comparative Examples, the object to be polished was polished under the following conditions. Then, it was dried by spin drying.
After drying, the number of defects on the surface of the object to be polished and the haze level were determined.
Defects mean surface defects such as foreign matter, and the smaller the number of defects, the less foreign matter adhering to the object to be polished. Haze means surface cloudiness, and the smaller the haze level, the higher the flatness of the surface of the object to be polished.
Also, the number of defects and the haze level were obtained by the following methods.
Also, 10 objects to be polished were polished for each polishing pad, and the number of defects and the haze level for each object to be polished were measured.
Results are shown in FIGS.

<Polishing conditions>
Object to be polished: Silicon bare wafer (thickness: about 760 μm)
Polishing machine: Polishing machine PNX332B, manufactured by Okamoto Machine Tool Works Head type: Ceramics Slurry flow rate: 600 mL/min
Slurry type: RDS8-A13x31
Polishing time: 2min
Wafer pressure: 80 g/cm ²
Head speed: 29rpm
Platen speed: 30rpm

<Measurement of number of defects>
The number of defects (“MAGICS Defect” in FIG. 2) was measured using a wafer defect inspection/review device (MGICS M5640, manufactured by Lasertec).
Only defects with a length of 190 μm or more were detected.

<Measurement of haze level>
The haze level (“Haze” in FIG. 3) was measured using a wafer surface inspection device (LS6600, manufactured by Hitachi Electronics Engineering Co., Ltd.).

As shown in FIG. 2, when the polishing pad of Example was used, the number of defects was smaller than when the polishing pad of Comparative Example 2 having an average cell diameter of 129 μm was used.
Further, as shown in FIG. 3, when the polishing pad of Example was used, the haze level was smaller than when using the polishing pad of Comparative Example 1, which had a tan δ of 0.079 at 30°C.

Claims (7)

A polishing pad comprising a polyurethane resin foam,
having a polished surface,
The polishing surface is composed of the surface of the polyurethane resin foam,
A polishing pad, wherein the polyurethane resin foam has a tan δ of 0.20 to 0.50 at 30° C. and an average cell diameter of 50 to 120 μm. 2. The polishing pad according to claim 1, wherein the polyurethane resin foam has a standard deviation of cell diameters of 10 to 55 μm. 3. The polishing pad according to claim 1, wherein in said polyurethane resin foam, cells have a circular shape in a cross section perpendicular to said polishing surface. The polishing pad according to any one of claims 1 to 3, wherein the polyurethane resin foam has an apparent density of 0.4 to 0.6 g/ ^cm3 . The polishing pad according to any one of claims 1 to 4, wherein the polyurethane resin foam has a storage elastic modulus E' of 0.5 x ¹⁰⁷ to 5.0 x ¹⁰⁷ Pa at 45°C. The polishing pad according to any one of claims 1 to 5, wherein the polyurethane resin foam has a storage elastic modulus E' of 0.5 x ¹⁰⁷ to 5.0 x ¹⁰⁷ Pa at 65°C. The polyurethane resin foam contains a polyurethane resin,
The polishing pad according to any one of claims 1 to 6, wherein the polyurethane resin contains polypropylene glycol as a structural unit.

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