JP7576396B2 - Polishing Pad - Google Patents

Description

The present invention relates to a polishing pad.

Polishing pads made of polyurethane resin foam are known as polishing pads for polishing objects (such as glass plates) (see, for example, Patent Document 1, etc.).

As a method for polishing an object to be polished using the polishing pad, for example, the following method is available.
First, a disk-shaped object to be polished is attached to the lower surface of an upper platen of a polishing machine, and a disk-shaped polishing pad is attached to the upper surface of the lower platen of the polishing machine. The object to be polished is then pressed against the polishing pad by the upper platen and the lower platen. Next, with the object to be polished pressed against the polishing pad, the upper platen and the lower platen are rotated while supplying a polishing slurry onto the polishing pad, thereby polishing the object to be polished.
As the polishing slurry, a polishing slurry containing water and abrasive grains is used.

JP 2007-250166 A

In recent years, there has been a greater demand than ever before for increasing the polishing speed of the workpiece.

Therefore, in consideration of the above-mentioned needs, the present invention aims to provide a polishing pad that can increase the polishing speed of the workpiece.

The polishing pad according to the present invention is a polishing pad including a polyurethane resin foam,
having a polished surface,
the polishing surface is formed of a surface of the polyurethane resin foam,
The polyurethane resin foam has a first peak and a second peak in a volumetric cell diameter distribution curve plotted with the cell diameter on the horizontal axis and the cell volume on the vertical axis,
The bubble diameter at the peak top of the first peak is 20 to 80 μm,
The bubble diameter at the peak top of the second peak is 100 to 200 μm.

In the polyurethane resin foam of this polishing pad, a volumetric cell diameter distribution curve plotted with the horizontal axis representing cell diameter and the vertical axis representing cell volume has a first peak and a second peak, the cell diameter at the peak top of the first peak being 20 to 80 μm, and the cell diameter at the peak top of the second peak being 100 to 200 μm. This allows the polishing pad to have an appropriate ratio of small-diameter cells and large-diameter cells.
And, because such a polishing pad has an appropriate ratio of large-diameter bubbles, it becomes easier to hold the polishing slurry in the bubbles during polishing, and it becomes easier to secure space for holding the polishing slurry even if polishing debris accumulates in the bubbles, and as a result, the polishing speed can be increased.
In addition, such a polishing pad has a suitable ratio of small-diameter bubbles as well as large-diameter bubbles, which makes it easier to increase the volume ratio of bubbles in the polishing pad. This makes it easier to increase the area of the bubble portion on the polishing surface, and makes it possible to reduce the contact area between the polishing pad and the workpiece during polishing. As a result, it becomes easier to increase the pressure applied by the polishing pad to the workpiece during polishing, and the polishing speed can be increased.
Therefore, such a polishing pad can increase the polishing rate of the workpiece.

The present invention can increase the polishing speed of the workpiece.

FIG. 4 is a diagram showing measurement points on a polishing pad when measuring cutting speed. FIG. 4 is a graph showing the distribution curves of bubble diameters based on the number of bubbles in polishing pads of Examples and Comparative Examples. FIG. 13 is a graph showing frequency distribution curves of bubble diameters based on the number of bubbles in polishing pads of Examples and Comparative Examples. FIG. 13 is a graph showing cumulative frequency distribution curves of bubble diameters based on the number of bubbles in polishing pads of Examples and Comparative Examples. FIG. 4 is a graph showing the volumetric bubble diameter distribution curves of polishing pads of Examples and Comparative Examples. FIG. 4 is a graph showing frequency distribution curves of volumetric bubble diameters of polishing pads of Examples and Comparative Examples. FIG. 4 is a graph showing cumulative frequency distribution curves of volumetric bubble diameters of polishing pads of Examples and Comparative Examples.

One embodiment of the present invention is described below.

The polishing pad according to this embodiment is a polishing pad including a polyurethane resin foam having a polyurethane resin.
Moreover, the polishing pad according to this embodiment has a polishing surface, which is constituted by the surface of the polyurethane resin foam.
The polishing pad of this embodiment polishes the surface to be polished by interposing a polishing slurry containing abrasive grains between the polishing surface and the surface of the object to be polished (surface to be polished) and bringing the polishing surface and the surface to be polished into sliding contact with each other.

The polyurethane resin foam has a first peak and a second peak in a volumetric cell diameter distribution curve plotted with cell diameter on the horizontal axis and cell volume on the vertical axis.
The bubble diameter at the peak top of the first peak is from 20 to 80 μm, preferably from 30 to 70 μm, and more preferably from 50 to 70 μm.
The bubble diameter at the peak top of the second peak is from 100 to 200 μm, preferably from 120 to 200 μm, and more preferably from 140 to 180 μm.

The full width at half maximum of the first peak is preferably 80 μm or less, and more preferably 10 to 40 μm.
The polishing pad according to this embodiment has an advantage that the workpiece can be polished relatively uniformly because the full width at half maximum of the first peak is 80 μm or less.

The polyurethane resin foam has a valley between the first peak and the second peak in the volumetric cell diameter distribution curve, and the cell diameter at the bottom of the valley is preferably 40 to 120 μm, and more preferably 60 to 100 μm.

The polyurethane resin foam also has a cell diameter (D80) at which the cumulative number of cells is 80% in a cumulative frequency distribution curve of cell diameters based on number, with the horizontal axis representing cell diameter and the vertical axis representing cell count, of preferably 20 to 80 μm, and more preferably 20 to 60 μm.

The polyurethane resin foam has a number-based cell diameter distribution curve plotted with cell diameter on the horizontal axis and cell count on the vertical axis, and the peak top of the highest peak on the number-based cell diameter distribution curve is determined as the maximum value. When the area (S) between the number-based cell diameter distribution curve and the horizontal axis is divided into a first area (S1) that is equal to or less than the maximum value and a second area (S2) that is equal to or greater than the maximum value, the ratio (S1/S2) of the first area (S1) to the second area (S2) is preferably 1 to 20, and more preferably 3 to 15.

The polyurethane resin foam preferably has an average bubble diameter of 20 to 120 μm, more preferably 20 to 80 μm.

The volume-based bubble diameter distribution curve, the number-based bubble diameter cumulative frequency distribution curve, and the number-based bubble diameter distribution curve can be obtained as follows using an X-ray CT scanning device (e.g., TDM1000H-I manufactured by Yamato Scientific Co., Ltd.).
That is, the volume of each bubble contained in a measurement area (e.g., 0.7 mm x 1.6 mm x 1.6 mm) of the polyurethane resin foam is measured, and the diameter of each bubble is determined as the diameter of a true sphere having the same volume as this volume.
The "average bubble diameter" refers to the arithmetic mean value of the bubble diameters calculated from the volume of each bubble [= (total value of "each bubble diameter")/(number of bubbles)].
The distribution curve of the number-based bubble diameter was created by determining the number of bubbles for each interval of bubble diameter from 0 μm to 20 μm or less, and defining the "number of bubbles in each interval" as the "number of bubbles with the upper limit bubble diameter in each interval."
Furthermore, the volumetric bubble diameter distribution curve is a curve created by calculating the sum of the bubble volumes for each interval of bubble diameters from 0 μm to 20 μm or less, and defining the "sum of bubble volumes" as the "volume at the upper limit bubble diameter for each interval."
The cumulative frequency distribution curve of the number-based bubble diameter is a curve created using data of the number-based bubble diameter distribution curve.

The cell diameter at the peak top of the first peak is the cell diameter at the point where the differential value obtained by differentiating the cell count in the volumetric cell diameter distribution curve with respect to the cell diameter three times becomes 0.
The bubble diameter at the peak top of the second peak is the bubble diameter at the point where the differential value obtained by differentiating the number of bubbles in the volumetric bubble diameter distribution curve with respect to the bubble diameter three times becomes 0.
Furthermore, the bubble diameter at the bottom of the valley is the bubble diameter at a point where the differential value obtained by differentiating the number of bubbles in the volumetric bubble diameter distribution curve with respect to the bubble diameter three times becomes zero.

Furthermore, the polyurethane resin foam preferably has an apparent density of 0.35 to 0.55 g/cm ³ .
The apparent density can be measured based on JIS K7222:2005.

The compressibility of the polyurethane resin foam is preferably 2 to 15%, and more preferably 3 to 15%.
The compression ratio can be calculated by the following method.
That is, using a compression elasticity tester (pressure probe area: 50 ^mm2 ) described in JIS L1096:2010, a polyurethane resin foam is pressed in the thickness direction with the pressurizer at a pressure of 641 gf/ ^cm2 and held for 60 seconds, after which a thickness T1 of the polyurethane resin foam is measured, and then a polyurethane resin foam is pressed in the thickness direction with the pressurizer at a pressure of 5161 gf/ ^cm2 and held for 60 seconds, after which a thickness T2 of the polyurethane resin foam is measured, and the compressibility can be calculated using the following formula.
Compression ratio = (T1-T2) x 100/T1

Furthermore, the polyurethane resin foam preferably has a hardness A of 55-60.
The A hardness is a hardness measured based on a Type A hardness test according to JIS K6253-3:2012, and is a hardness measured by pressing a pusher into the polished surface.

The polyurethane resin comprises a first constituent unit of a compound containing active hydrogen (hereinafter also referred to as an "active hydrogen compound") and a second constituent unit of a compound containing an isocyanate group (hereinafter also referred to as an "isocyanate compound").
The polyurethane resin has a structure in which an active hydrogen compound and an isocyanate compound are bonded to each other through urethane bonds, and a first constituent unit of an active hydrogen compound and a second constituent unit of an isocyanate compound are alternately repeated.

The active hydrogen compound is an organic compound having an active hydrogen group in the molecule that can react with an isocyanate group. Specific examples of the active hydrogen group include functional groups such as a hydroxyl group, a primary amino group, a secondary amino group, and a thiol group. The active hydrogen compound may have only one type of functional group in the molecule, or may have multiple types of functional groups in the molecule.

Examples of the active hydrogen compound that can be used include polyol compounds having multiple hydroxyl groups in the molecule, and polyamine compounds having multiple primary amino groups or secondary amino groups in the molecule.

The polyol compounds include polyol monomers and polyol polymers.

Examples of the polyol monomer include linear aliphatic glycols such as 1,4-benzenedimethanol, 1,4-bis(2-hydroxyethoxy)benzene, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol, and neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol. Examples of branched aliphatic glycols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and bisphenol A; and polyfunctional polyols such as glycerin, trimethylolpropane, tributyrolpropane, pentaerythritol, and sorbitol.

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

Examples of the polyol polymer include polyester polyol, polyester polycarbonate polyol, polyether polyol, and polycarbonate polyol.
The polyol polymer may also be a multifunctional polyol polymer having three or more hydroxy groups in the molecule.

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

The polyester polycarbonate polyols include, for example, reaction products of polyester glycols such as polycaprolactone polyols with alkylene carbonates, and reaction products obtained by reacting ethylene carbonate with polyhydric alcohols and then reacting the resulting reaction mixture with organic dicarboxylic acids.

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 reaction products of diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol with phosgene, diallyl carbonate (e.g., diphenyl carbonate), or cyclic carbonate (e.g., propylene carbonate).

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

The polyamine compounds include 4,4'-methylenebis(2-chloroaniline) (MOCA), 4,4'-methylenedianiline, trimethylene Bis(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, etc.

The polyisocyanate may be a polyisocyanate monomer or a polyisocyanate polymer.

Examples of the polyisocyanate monomer include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

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

Examples of modified diphenylmethane diisocyanate (MDI) include carbodiimide modified, urethane modified, allophanate modified, urea modified, biuret modified, isocyanurate modified, and oxazolidone modified. 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.

The polyisocyanate polymer may be a polymer formed by combining a polyol with at least one of an aromatic diisocyanate, an aliphatic diisocyanate, and an alicyclic diisocyanate.

The polyurethane resin contains polypropylene glycol (PPG) as a constituent unit, and thus has a relatively brittle structure, which has the advantage of increasing the cutting speed when dressing the polishing pad.
Furthermore, the polishing pad according to this embodiment contains, when the polyurethane resin is taken as 100% by mass, polypropylene glycol (PPG) contained in the structural units of the polyurethane resin is preferably 30% by mass or more, more preferably 40 to 70% by mass, and even more preferably 50 to 65% by mass.

The content of polypropylene glycol (PPG) contained in the structural units of the polyurethane resin when the polyurethane resin is taken as 100% by mass can be determined as follows.
First, a polyurethane resin foam is dissolved in a polar solvent (d-DMF, de-DMSO, etc.) to obtain a solution. Next, the solution is analyzed by 1H-NMR to quantify polypropylene glycol (PPG) and determine the content ratio of the polypropylene glycol (PPG).
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, which is then fractionated and collected by gel permeation chromatography (GPC) or the like, and each fraction is analyzed by 1H-NMR or GC-MS to quantify polypropylene glycol (PPG) and determine the content ratio of the polypropylene glycol (PPG).

The polishing pad according to this embodiment is configured as described above. Next, we will explain the manufacturing method of the polishing pad according to this embodiment.

In the method for manufacturing a polishing pad according to this embodiment, a polishing pad having a polyurethane resin foam is manufactured.
In addition, in the manufacturing method of the polishing pad according to this embodiment, a urethane prepolymer having an isocyanate group as a terminal group, microcapsules, and a foam stabilizer are mixed to obtain a dispersion liquid in which microcapsules and air are dispersed as bubbles.
The dispersion liquid is mixed with a curing agent, which is an active hydrogen organic compound containing a plurality of active hydrogen atoms in its molecule, and polymerized to obtain a polishing pad having a polyurethane resin foam.

As the microcapsules, thermally expandable microcapsules may be used, or already-expanded microcapsules obtained by thermally expanding a thermally expandable microcapsule may be used.
The microcapsules are also called "microspheres" or "microspheres".
The thermally expandable microcapsule comprises a hollow body formed of a thermoplastic resin and a liquid hydrocarbon provided in the hollow portion of the hollow body.
The thermally expandable microcapsules are made of liquid hydrocarbon that vaporizes and expands when exposed to heat.

Examples of the thermoplastic resin include acrylonitrile resin and polyvinylidene chloride resin.
The thermoplastic resin preferably has a glass transition temperature of 70 to 130° C., from the viewpoint that the heat of polymerization reaction can sufficiently expand the thermally expandable microcapsules.
The glass transition temperature is measured by the method described in JIS K7121:1987 "Method for measuring glass transition temperature of plastics."
However, the sampling method and temperature conditions are as follows.
Using a differential scanning calorimeter DSC6220 (manufactured by SII NanoTechnology Inc.), about 6 mg of sample is packed into the bottom of an aluminum measurement container so that there are no gaps, and the temperature is raised from 30°C to 300°C at a rate of 20°C/min under a nitrogen gas flow rate of 20 mL/min. From the obtained DSC curve, the midpoint glass transition temperature is calculated using analysis software attached to the device.
In this case, alumina is used as the reference material.
This midpoint glass transition temperature is determined by the method described in JIS K7121:1987 "Method of measuring transition temperature of plastics", 9.3 "Determination of glass transition temperature".

Examples of the liquid hydrocarbon include butane (isobutane, normal butane, etc.), and pentane (isopentane, neopentane, normal pentane), etc.
As the liquid hydrocarbon, from the viewpoint that the heat of polymerization reaction can sufficiently expand the thermally expandable microcapsules, butane, pentane, etc. are preferable. Moreover, hydrocarbons having a boiling point of -20°C to 30°C are preferable.

Examples of the foam stabilizer include silicone surfactants, fluorine surfactants, and ionic surfactants.

Workpieces that can be polished with the polishing pad of this embodiment include optical materials, semiconductor devices, hard disks, glass plates, silicon wafers, etc.

The polishing pad according to this embodiment is configured as described above and 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 first peak and a second peak in a volumetric bubble diameter distribution curve plotted with the horizontal axis representing the bubble diameter and the vertical axis representing the bubble volume. The bubble diameter at the peak top of the first peak is 20 to 80 μm. The bubble diameter at the peak top of the second peak is 100 to 200 μm.
Such a polishing pad can increase the polishing rate of the workpiece.

The polishing pad according to the present invention is not limited to the above embodiment. The polishing pad according to the present invention is not limited by the above-mentioned effects. Furthermore, the polishing pad according to the present invention can be modified in various ways without departing from the gist of the present invention.

Next, the present invention will be explained in more detail with reference to examples and comparative examples.

Example 1
The prepolymer, microcapsules, and foam stabilizer shown in Table 1 below were mixed at 70° C. in the blending ratio shown in Table 1 below to obtain a dispersion in which air was dispersed as bubbles.
Next, the dispersion and a curing agent were mixed in the compounding ratio shown in Table 1 below and polymerized to obtain a polishing pad as a polyurethane resin foam.

The materials in Table 1 below are specifically as follows.
Prepolymer 1: a urethane prepolymer (urethane prepolymer having an isocyanate group as a terminal group) obtained by reacting polypropylene glycol (PPG) with tolylene diisocyanate (TDI) (NCO mass %: 5.80) (Takenate L1150, manufactured by Mitsui Chemicals, Inc.)
Hardener: MOCA (4,4'-methylenebis(2-chloroaniline))
Foam stabilizer: Silicone surfactant (Decostarb B8465, manufactured by Evonik)
Microcapsules: Unexpanded hollow microparticles (F36D)

(Examples 2 and 3, Comparative Examples 1 and 2)
A polishing pad made of a polyurethane resin foam was obtained in the same manner as in Example 1, except that the materials and compositions shown in Table 1 below were used.

(A hardness, apparent density, and compressibility)
The A hardness, apparent density, and compressibility were measured by the methods described above.
The measured values are shown in Table 1 below.

(Cutting speed)
The polishing pad was processed into a donut shape as shown in FIG. 1 (outer diameter: 240 mm, inner diameter: 90 mm, thickness: approximately 2.0 mm), and the positions shown in FIG. 1 were used as measurement points (12 locations). Through holes with a diameter of approximately 3 mm were formed at these measurement points to obtain test specimens.
Next, the test specimen was attached to the platen of a polishing machine (Ecomet 2000) via double-sided tape, and the thickness of the test 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 (Kinik DiaGrid φ4 inch)
Condition Weight: 35g/ ^cm2
Platen speed: 50 rpm
Head speed: 60 rpm
Dressing time: 30 min
Water flow rate: 100 mL/min
After the cutting, the thickness of the test specimen was measured at the through hole using a depth gauge.
The cutting speed (μm/hr) at each point was calculated from the difference in thickness of the test piece before and after cutting at each point, and the arithmetic average value of the cutting speeds at each point was calculated and used as the cutting speed (μm/hr) of the polishing pad.
The measured values are shown in Table 1 below.

(Characteristics of bubbles)
The cell size distribution curve based on number (FIG. 2) was obtained by the method described above.
Based on the data of the distribution curve of the number-based bubble diameter, the frequency distribution curve of the number-based bubble diameter ( FIG. 3 ), the cumulative frequency distribution curve of the number-based bubble diameter ( FIG. 4 ), the distribution curve of the volume-based bubble diameter ( FIG. 5 ), the frequency distribution curve of the volume-based bubble diameter ( FIG. 6 ), and the cumulative frequency distribution curve of the volume-based bubble diameter ( FIG. 7 ) were also obtained.
From these curves, the bubble characteristics shown in Table 1 below were obtained using the method described above.

(Evaluation test (measurement of polishing speed))
The polishing pad was used to polish an object under the following conditions, and the removal rate was determined.
Workpiece: Silicon bare wafer (thickness: approx. 760 μm)
Polishing machine: Polishing machine PNX332B, manufactured by Okamoto Machine Tool Works, Ltd. Head type: Ceramics Flow rate of polishing slurry: 600 mL/min
Polishing slurry type: RDS8-A13x31
Polishing time: 2 min
Wafer pressure: 80 g/ ^cm2
Head speed: 29 rpm
Platen speed: 30 rpm
The polishing rate was calculated by dividing the thickness reduced by polishing by the polishing time.
The thickness was measured using a Nanospec AFT5100 manufactured by Nano-metrics.
The results of the evaluation test are shown in Table 1 below.

As shown in Table 1, when the polishing pads of Examples 1 to 3 were used, the polishing rate was higher than when the polishing pads of Comparative Examples 1 and 2 were used.

Claims (4)

A polishing pad comprising a polyurethane resin foam,
having a polished surface,
the polishing surface is formed of a surface of the polyurethane resin foam,
The polyurethane resin foam has a first peak and a second peak in a volumetric cell diameter distribution curve plotted with the cell diameter on the horizontal axis and the cell volume on the vertical axis,
The bubble diameter at the peak top of the first peak is 50 to 70 μm;
A polishing pad, wherein the bubble diameter at the peak top of the second peak is 140 to 180 μm. The polishing pad of claim 1, wherein the full width at half maximum of the first peak is 80 μm or less. the polyurethane resin foam has a valley between the first peak and the second peak in a volume-based cell diameter distribution curve,
3. The polishing pad according to claim 1, wherein the bubble diameter at the bottom of the valley is 60 to 100 μm. The polishing pad according to any one of claims 1 to 3, wherein the polyurethane resin foam has a cell diameter (D80) of 20 to 80 μm at which the cumulative number of cells is 80% in a cumulative frequency distribution curve of cell diameters based on the number of cells plotted with the cell diameter on the horizontal axis and the number of cells on the vertical axis.