JP7565737B2 - Polishing Pad - Google Patents

Description

The present invention relates to a polishing pad. In particular, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, etc.

Chemical mechanical polishing (CMP) is a commonly used polishing method for flattening 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, the polishing apparatus 1 for carrying out the CMP method is equipped with a polishing pad 3, which is in contact with the workpiece 8 held on a holding platen 16 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 workpiece 8 is pressed against it, and polishes the workpiece 8. At that time, a slurry 9 is supplied between the polishing pad 3 and the workpiece 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 workpiece 8, thereby increasing the polishing effect. The slurry 9 is supplied to the polishing surface through grooves or holes and discharged.

In the CMP method, there is a method of optically checking whether the object 8 has been polished to the desired position. For example, the polishing apparatus 1 shown in FIG. 1 is equipped with an optical sensor 14 for checking the end point. Specifically, a translucent end point detection window 5 is provided in a part of the polishing pad 3, and a light source 13 and an optical sensor 14 are provided under the polishing platen 10.

The principle of end point detection by optical techniques will be explained with reference to Figure 2. When light 2 irradiated by a light source 13 is incident on a thin film (e.g., an insulating film) 12 formed on a substrate 11, which is the workpiece 8 to be polished, a portion of the light 2a is reflected by the surface of the thin film 12, while another portion of the light 2b passes through the thin film 12 and is reflected by the surface of the workpiece 8 to be polished. The reflected light 2a and 2b pass through an end point detection window 5 and are detected by an optical sensor 14. The phase difference and intensity of the reflected light vary depending on the thickness of the thin film 12, and by detecting the phase difference and change in reflection intensity, the polishing status of the thin film 12 can be confirmed.

Here, the end point detection window 5 may be made of the same material as the polishing layer 4, for example, polyurethane, which has optical transparency. However, polyurethane is known to deteriorate when exposed to ultraviolet light, and the end point detection window 5 deteriorates due to the light irradiated to detect the end point. Therefore, various additives have been used to suppress deterioration of the end point detection window 5.

For example, Patent Document 1 discloses a polishing pad having an end point detection window that contains at least one of an ultraviolet absorber and a hindered amine light stabilizer.

Patent Document 2 also discloses a polishing pad with an end point detection window that contains a light absorbing compound such as cyanoacrylate.

JP 2012-071416 A Special Publication No. 2015-512799

However, while the polishing pads described in Patent Documents 1 and 2 suppress deterioration of the end point detection window to some extent, there is a risk of the end point detection window turning yellow. When the end point detection window turns yellow, the light transmittance of the end point detection window changes, which may affect the detection accuracy of the polishing state (polishing end point).

The present invention was made in consideration of the above problems, and aims to provide a polishing pad with an end point detection window that enables accurate detection of the polishing state (polishing end point) by suppressing yellowing of the end point detection window.

As a result of intensive research, the present inventors have found that an end point detection window that contains a specific antioxidant suppresses yellowing, has little effect on polishing detection accuracy, and enables accurate detection of the polishing state (polishing end point).
[1] A polishing pad having a polishing layer with an end point detection window in a portion thereof, the end point detection window containing a phenol-based antioxidant and a phosphorus-based antioxidant.
[2] The polishing pad according to [1], wherein the end point detection window contains a phenol-based antioxidant and a phosphorus-based antioxidant in a weight ratio of phenol-based antioxidant:phosphorus-based antioxidant=1:0.1 to 1:10.
[3] The polishing pad according to [1] or [2], wherein the number average molecular weight of the phenol-based antioxidant is 300 to 1,000.
[4] The polishing pad according to any one of [1] to [3], wherein the number average molecular weight of the phosphorus-based antioxidant is 300 to 800.
[5] The polishing pad according to any one of [1] to [4], wherein the end point detection window contains 0.1 to 5.0 wt % of the phenol-based antioxidant.
[6] The polishing pad according to any one of [1] to [5], wherein the end point detection window contains 0.1 to 5.0 wt % of the phosphorus-based antioxidant.

The polishing pad of the present invention, which has an end point detection window that is less susceptible to oxidative deterioration due to light and less prone to yellowing, has less of a negative effect on the accuracy of detection of the polishing state (polishing end point) due to yellowing, making it possible to accurately detect the polishing state (polishing end point).

FIG. 1 is a perspective view of a polishing apparatus 1. As shown in FIG. FIG. 2 is a schematic diagram showing the paths of incident and reflected light. FIG. 3 is a perspective view of a polishing pad 3 of the present invention. FIG. 4 is a cross-sectional view (A-A' cross-sectional view) of the polishing pad 3 of the present invention. FIG. 5 is a schematic diagram showing a method for producing the polishing pad 3 of the present invention.

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. 3. The polishing pad 3 provided in the polishing apparatus 1 includes a polishing layer 4 having at least one end point detection window 5 (two end point detection windows 5 are provided in Fig. 3) penetrating the polishing pad 3, as shown in Fig. 3, and a cushion layer 6. Since the polishing pad 3 has the end point detection window 5, the polishing status of the workpiece 8 can be optically confirmed using a light source 13 and an optical sensor 14.
The shape of the polishing pad 3 is preferably disk-shaped, but is not particularly limited thereto, and the size (diameter) can 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 1 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, but it may be composed of only the polishing layer 4.
The polishing pad 3 is attached to a polishing platen 10 of a polishing device by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing device while being pressed against an object 8 to be polished, thereby polishing the object.

<Polishing layer>
The polishing pad 3 includes a polishing layer 4 for polishing an object to be polished. The material constituting the polishing layer 4 is preferably a polyurethane resin, a polyurea resin, or a polyurethane-polyurea resin, and more preferably a polyurethane resin.
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 usually be about 0.5 to 5 mm.
The polishing layer 4 is rotated together with the polishing platen 10 of the polishing device 1, and while slurry 9 is flowed onto it, the chemical components and abrasive grains contained in the slurry are moved relative to the workpiece 8, thereby polishing the workpiece 8. By providing the surface of the polishing layer 4 with grooves in a concentric, lattice, radial, or other pattern, it is possible to adjust the retention and discharge of the slurry 9 and change the polishing characteristics.
If desired, the abrasive layer 4 may also contain hollow bodies, such as hollow microspheres.

<End point detection window>
The polishing layer 4 has at least one end point detection window 5. The end point detection window 5 is for confirming the end point of polishing by optical means and therefore has light transmittance. Therefore, it is preferable that the end point detection window 5 has high light transmittance.
The number of the end point detection window 5 may usually be one or more. The diameter of the end point detection window 5 is preferably about 1 cm to 15 cm, and the thickness is the same as that of the polishing layer 4, usually about 0.5 to 5 mm. Details of the end point detection window 5 will be described in the section <<Method of manufacturing the end point detection window>>.

The end point detection window 5 generally has a cylindrical shape that penetrates the upper and lower surfaces of the polishing layer 4, but is not particularly limited as long as it penetrates the upper and lower surfaces of the polishing layer 4, and can be appropriately selected as a square prism, triangular prism, or other shape.

(Light Transmittance)
Since the end point detection window 5 allows light to pass through, it is preferable that the light transmittance is high, for example, at wavelengths of 300 to 800 nm. For example, the transmittance of light at 660 nm is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and even more preferably 80% or more. In particular, if the light transmittance at wavelengths of 400 to 700 nm is high, errors are less likely to occur and measurements can be made with high accuracy. The light transmittance can be measured using a spectrophotometer (U-3210 Spectro Photometer, manufactured by Hitachi, Ltd.), and the sample thickness in this case is, for example, 1.3 mm.

(Chromaticity (b*) and yellowing degree (Δb*))
The characteristics of the end point detection window 5 in the present invention include a low yellow chromaticity b* and a small degree of yellowing even when used. The chromaticity b* is expressed in the b* color space, and the larger the value of the chromaticity b*, the stronger the yellow color. That is, the main component of the material for the end point detection window 8 is often a polyurethane resin, a polyurea resin, or a polyurethane polyurea resin, but there is a problem that the material turns yellow over time. The end point detection window 5 has a low yellow chromaticity b* and is less prone to yellowing even when used.
The chromaticity (b*1) of yellow expressed in the L*a*b* color space using a color difference meter immediately after the manufacture of the end point detection window 5 is preferably 25 or less, more preferably 20 or less, and even more preferably , 15 or less.
The chromaticity (b*1) measured using a color difference meter before and after the light fastness test (performed using an F-type device in accordance with JIS B 7751) of the end point detection window 5 was The difference (Δb*) in chromaticity (b*2) is preferably 20 or less, more preferably 15 or less, and further preferably 13 or less.
In the L*a*b* color space, in addition to b*, which indicates the chromaticity of yellow or blue, there is L*, which indicates the brightness, and a*, which indicates the chromaticity of red or green. Brightness before and after light fastness test The color difference ΔE* can be calculated from the differences in L*, chromaticity a*, and b*.
ΔE*=[(L*2-L*1) ² + (a*2-a*1) ² + (b*2-b*1) ² ] ^1/2
Here, the lightness before the light fastness test is L*1, the chromaticity a*1, b*1, and the lightness after the light fastness test is L*2, the chromaticity a*2, b*2.
The color difference ΔE* is preferably 25 or less, more preferably 20 or less, and further preferably 17 or less.

(Tensile strength)
In addition, the characteristics of the end point detection window 5 in the present invention include suppressing deterioration due to light, and particularly a small change in tensile strength. The light irradiated from the light source during end point detection deteriorates the end point detection window 5. Since deterioration of the end point detection window 5 affects the polishing performance and scratch performance of the polishing pad 3, it is preferable that the physical properties of the end point detection window 5 are maintained even when irradiated with light. Among the physical properties, tensile strength in particular has a large effect on scratch performance, so it is preferable that the change in tensile strength is small. In the end point detection window 5 of the polishing pad 1 of the present invention, the ratio of the tensile strength after the light resistance test to the tensile strength before the light resistance test is within a specific range. The ratio of the tensile strength after the light resistance test to the tensile strength before the light resistance test of the end point detection window 5 is preferably 0.85 to 1.00, more preferably 0.87 to 1.00, and even more preferably 0.90 to 1.00.

<Cushion layer>
The cushion layer 6 is preferably made of a resin-impregnated nonwoven fabric, a flexible material such as a synthetic resin, a foam having a cellular structure, or the like, and such materials enable the polishing layer 4 to contact the workpiece 8 more uniformly. In the present invention, the polishing pad 3 may be made of only the polishing layer 4, but it is preferable that the cushion layer 6 is bonded to the polishing pad 3.
In addition, in the cushion layer 6, it is necessary to form holes in the same number as the end point detection windows 5 in the portions corresponding to the installation positions of the end point detection windows 5 so as to allow light for optical detection to pass through.

<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. Any double-sided tape or adhesive known in the art can be used.
The polishing pad 3 and the cushion layer 6 are bonded together by an adhesive layer 7. The adhesive layer 7 can be formed 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.

<Polishing equipment>
As already explained, the polishing apparatus 1 equipped with the polishing pad 3 of the present invention can confirm the polishing state by optical means. For example, as shown in Fig. 1, the polishing table 10 of the polishing apparatus 1 is equipped with a light source 13 and an optical sensor 14. Light emitted from the light source 13 passes from the bottom to the top of the polishing table 10, passes through a hole in the cushion layer 6 and further through the end point detection window 5 of the polishing pad 3, reaches the workpiece 8 to be polished, and is reflected by the workpiece 8 and returned, and is detected by the optical sensor 14. In this way, the light source 13 and the optical sensor 14 rotate together with the polishing table 10, thereby allowing the polishing state to be confirmed while polishing.

<<Method of Manufacturing End Point Detection Window>>
A method for producing the endpoint detection window of the present invention will now be described.

<End point detection window material>
The end point detection window 5 measures the film thickness by transmitting light and measuring the wavelength of the light reflected by the substrate, but since it may be required to perform the same function as the polishing layer 4, i.e., polish the workpiece 8, it is preferable that the scratching performance and polishing performance are equivalent, and the main component is preferably the same as that of the polishing layer 4. That is, the main component of the material for the end point detection window 8 is preferably a polyurethane resin, a polyurea resin, or a polyurethane polyurea resin, and more preferably a polyurethane resin. Specific examples of the main component include materials obtained by reacting a urethane bond-containing polyisocyanate compound with a curing agent.

The end point detection window 5 provided in the polishing pad 3 of the present invention contains a phenolic antioxidant and a phosphorus-based antioxidant as antioxidants. By combining a phenolic antioxidant with a phosphorus-based antioxidant, it is possible to manufacture an end point detection window 5 having a high light transmittance that could not be achieved by using a phenolic antioxidant alone or a phosphorus-based antioxidant alone, and the end point detection window 5 containing a phenolic antioxidant and a phosphorus-based antioxidant is less susceptible to deterioration and changes in physical properties (particularly a decrease in tensile strength) due to oxidation, and is less susceptible to yellowing. Specific components will be described later.

The manufacturing method for the material of the end point detection window 5 will be explained below using an end point detection window made of an isocyanate compound containing a urethane bond, a polyol compound, and a hardener as an example.

The method for manufacturing the end point detection window 5 using a urethane bond-containing polyisocyanate compound and a curing agent can include, for example, a material preparation step for preparing at least a urethane bond-containing polyisocyanate compound, an antioxidant, an additive, and a curing agent; a mixing step for mixing at least the urethane bond-containing polyisocyanate compound, the antioxidant, the additive, and the curing agent to obtain a mixture for molding a molded body; and a curing step for molding the end point detection window from the mixture for molding a molded body.

The material preparation process, mixing process, and molding process will be explained below.

<Material preparation process>
In order to manufacture the end point detection window 5 of the present invention, at least a urethane bond-containing polyisocyanate compound (urethane prepolymer), a curing agent, a phenol-based antioxidant, and a phosphorus-based antioxidant are prepared as raw materials for the polyurethane resin molded body (cured resin). Here, the urethane bond-containing polyisocyanate is a urethane prepolymer for forming the polyurethane resin molded body. When the end point detection window 5 is to be a polyurea resin molded body or a polyurethane-polyurea resin molded body, a prepolymer appropriate for the purpose is used.

Each ingredient is explained below.

(Urethane bond-containing polyisocyanate compound)
The urethane bond-containing polyisocyanate compound (urethane 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 urethane bond-containing polyisocyanate compound within the range that does not impair the effects of the present invention.

As the urethane bond-containing polyisocyanate compound, commercially available products may be used, or a product synthesized by reacting a polyisocyanate compound with a polyol compound may be used. There are no particular limitations on the reaction, and an addition polymerization reaction may be carried out using a method and conditions known in the manufacture of polyurethane resins. For example, the polyisocyanate compound may be added to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, and the temperature may be raised to 80°C after 30 minutes, and the reaction may be continued at 80°C for 60 minutes.

The NCO equivalent of the urethane bond-containing polyisocyanate compound (urethane prepolymer) obtained as described above is preferably 200 or more and 700 or less, more preferably 250 or more and 600 or less, and even more preferably 300 or more and 550 or less. By keeping the NCO equivalent within the above range, it is possible to more appropriately adjust the range of the desired physical properties.

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)].

(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, more preferably contains 2,4-TDI and 2,6-TDI. Even more preferably, it consists of only 2,4-TDI and 2,6-TDI. The mass ratio of 2,4-TDI to 2,6-TDI is preferably 100:0 to 50:50, more preferably 90:10 to 60:40, even more preferably 90:10 to 70:30, and even more preferably 80:20.

(Polyol Compound as a 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 the 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). Among these, PTMG is preferred. The number average molecular weight (Mn) of PTMG is preferably 500 to 2000, more preferably 600 to 1300, and even more preferably 650 to 1000. 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, it can also be estimated by GPC after decomposing each component by a conventional method such as amine decomposition.
The above polyol compounds may be used alone or in combination of two or more polyol compounds.

(Antioxidants)
As described above, the material of the endpoint detection window 5 contains a phenol-based antioxidant and a phosphorus-based antioxidant. The coexistence of a phenol-based antioxidant and a phosphorus-based antioxidant results in a lower degree of yellowing than when each antioxidant exists alone. The total content of the antioxidants in the endpoint detection window 5 is preferably 0.1 to 6.0 wt %, and more preferably 0.2 to 4.0 wt %, based on the weight of the entire endpoint detection window. The reason that the degree of yellowing is lower than when each antioxidant exists alone is believed to be as follows.

It is believed that polyurethane, which is a typical main component of the endpoint detection window 5, generates radicals when exposed to light, producing colored substances. The radical reaction becomes a cyclic reaction as shown in the following formula (1), and yellowing progresses (in the formula, R represents an organic group).
However, it is believed that the presence of a phenol-based antioxidant captures the peroxy radicals, and the presence of a phosphorus-based antioxidant stabilizes the compound, preventing the cycle reaction. In addition to preventing the progression of yellowing, the physical properties of the end point detection window 5 can be maintained, particularly the decrease in tensile strength. By suppressing the decrease in tensile strength of the end point detection window 5, the polishing performance and scratch performance can be maintained at the same level as the polishing layer 4.

(Mixing ratio)
The weight mixing ratio of the phenolic antioxidant and the phosphorus-based antioxidant (phenolic antioxidant:phosphorus-based antioxidant) is not particularly limited, but from the viewpoint of yellowing degree, it is preferably 1:0.1 to 1:10, and more preferably 1:0.2 to 1:8. When a polyurethane resin, a polyurea resin, or a polyurethane polyurea resin is used as the main component of the endpoint detection window 5, the above ratio is even more effective.

The method of mixing these antioxidants is not particularly limited, but if a phenol-based antioxidant is mixed into the prepolymer at an early stage, the reaction may proceed. Therefore, it is preferable to add the phenol-based antioxidant when mixing the curing agent and the prepolymer. For example, the curing can be promoted by mixing the phenol-based antioxidant into the curing agent and then mixing the mixture of the curing agent and the phenol-based antioxidant into the prepolymer.
On the other hand, unlike the phenol-based antioxidant, the phosphorus-based antioxidant may be mixed into the prepolymer before the curing reaction, or may be mixed with the curing agent together with the phenol-based antioxidant and then mixed with the prepolymer.

The molecular weight of the phenol-based antioxidant is not particularly limited, but from the viewpoint of compatibility with polyurethane and the like, the number average molecular weight is preferably 300 to 1,000, and more preferably 400 to 700.
The molecular weight of the phosphorus-based antioxidant is not particularly limited, but from the viewpoint of compatibility with polyurethane and the like, the number average molecular weight is preferably 300 to 800, and more preferably 300 to 550.

Specific examples of phenolic antioxidants include 6-di-tert-butyl-p-cresol, 2,6-diphenyl-4-octadecyloxyphenol, stearyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, distearyl (3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate, tridecyl 3,5-di-tert-butyl-4-hydroxybenzylthioacetate, bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], thiodiethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,4'-thiobis( 6-tert-butyl-m-cresol), 2-octylthio-4,6-bis(3,5-di-tert-butyl-4-hydroxyphenoxy)-s-triazine, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), bis[3,3-bis(4-hydroxy-3-tert-butylphenyl)butyric acid]glycol ester, 4,4'-butylidenebis(6-tert-butyl-3-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, bis[2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl]terephthalate, 1, 3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, 1,3,5-tris[(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanurate, tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, 2-tert-butyl-4-methyl-6-(2-acroyloxy-3-tert-butyl -5-methylbenzyl)phenol, triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,0-tetraoxaspiro[5.5]undecane, 4,4-butylidenebis(6-tert-butyl-3-methylphenol), etc.

Among the above phenol-based antioxidants, preferred examples from the viewpoint of improving the transmittance of the end point detection window 5 and being less likely to yellow include Irganox 245, Adeka STAB AO-50/Adeka STAB AO-50F (trademark), Adeka STAB AO-60/Adeka STAB AO-60G (trademark), Adeka STAB AO-80 (trademark) (all manufactured by ADEKA CORPORATION); Sumilizer BBM-S (trademark), Sumilizer GA-80 (trademark), Sumilizer BHT (trademark), Sumilizer BP-76 (trademark), Sumilizer BP-101 (trademark) (all manufactured by Sumitomo Chemical Co., Ltd.), etc.

Specific examples of phosphorus-based antioxidants include triphenyl phosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(2,5-di-tert-butylphenyl)phosphite, tris(nonylphenyl)phosphite, tris(dinonylphenyl)phosphite, tris(mono- and di-mixed nonylphenyl)phosphite, diphenyl acid phosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, diphenyl decyl phosphite, diphenyl octyl phosphite, bis(nonylphenyl ) pentaerythritol phosphite, phenyl diisodecyl phosphite, tributyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, dibutyl acid phosphite, dilauryl acid phosphite, trilauryl trithio phosphite, bis(neopentyl glycol)·1,4-dicyclohexane dimethyl diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite thritol diphosphite, bis{2,4-bis(1-methyl-1-phenylethyl)phenyl}pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tetra(C12-15 mixed alkyl)-4,4-isopropylidenediphenyl phosphite, bis[2,2'-methylenebis(4,6-diamylphenyl)].isopropylidenediphenyl phosphite, tetratridecyl.4,4'-butylidenebis(2-tert-butyl-5-methylphenol) diphosphite, hexa(tridecyl).1,1,3-tris(2- Examples include methyl-5-tert-butyl-4-hydroxyphenyl)butane triphosphite, tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite, tris(2-[(2,4,8,10-tetrakis-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]ethyl)amine, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 2-butyl-2-ethylpropanediol-2,4,6-tri-tert-butylphenol monophosphite.

Among the above phosphorus-based antioxidants, the preferred phosphite compounds from the viewpoint of resistance to yellowing are triphenyl phosphite, distearyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, and bis{2,4-bis(1-methyl-1-phenylethyl)phenyl}pentaerythritol diphosphite.

Specific examples include Adeka STAB PEP-8 (trademark), Adeka STAB PEP-24G (trademark), Adeka STAB PEP-45 (trademark), and Adeka STAB TPP (all manufactured by ADEKA CORPORATION); JPP681S (trademark, manufactured by Johoku Chemical Industry Co., Ltd.), Alkanox P-24 (trademark, manufactured by Great Lakes), Ultranox P626 (trademark, manufactured by GE Specialty Chemicals), Doverphos S-9432 (trademark), and Doverphos S-9228 (trademark) (all manufactured by Dover Chemical); and Irgaofos 126 and 126FF (trademarks, manufactured by CIBA SPECIALTY CHEMICALS).

Among the above antioxidants, phenol-based antioxidants such as bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)] and stearyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and phosphorus-based antioxidants such as triphenyl phosphite and tridecyl phosphite are particularly preferred.

(Hardening agent)
In the manufacturing method of the endpoint detection window 5 of the present invention, a curing agent (also called a chain extender) is mixed with a urethane bond-containing polyisocyanate compound, etc. in the mixing step. By adding the curing agent, in the subsequent molding step, the main chain terminal of the urethane bond-containing polyisocyanate compound 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 (methylene bis-o-chloroaniline) (hereinafter abbreviated as MOCA). The total content of the curing agent in the end point detection window 5 is preferably 10 to 50% by weight, more preferably 15 to 40% by weight, based on the weight of the entire end point detection window.

(Additives)
An additive may be optionally added to the material of the end point detection window 5 so as not to lose transparency.

<Mixing step>
In the mixing step, the urethane bond-containing polyisocyanate compound (urethane prepolymer), additives, and curing agent obtained in the preparation step 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.
In the mixing step, at least the urethane bond-containing polyisocyanate compound (urethane prepolymer), the phenol-based antioxidant, the phosphorus-based antioxidant, and the curing agent are fed into a mixer and stirred and mixed. The phenol-based antioxidant and the phosphorus-based antioxidant are added and mixed so as not to cause a reaction before mixing as described above. In this way, a mixed solution for molding a molded body is prepared. The mixing step is carried out in a state where the temperature is raised to a temperature at which the fluidity of each of the above components can be ensured. The R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent to the isocyanate groups present at the terminals of the urethane bond-containing polyisocyanate compound as the urethane prepolymer, can be used as an index. The R value is preferably 0.70 to 1.30, more preferably 0.75 to 1.20, even more preferably 0.80 to 1.10, even more preferably 0.80 to 1.00, and even more preferably 0.85 to 0.95.

<Molding process>
In the molding process, the mixture prepared in the mixing process is poured into a rod-shaped 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 molded body). At this time, the urethane prepolymer and the curing agent react to form a polyurethane resin, and the mixture hardens.
The mold may be provided with projections and recesses or a threaded structure, thereby preventing the end point detection window 5 from coming off the molded polishing layer 4.

If air bubbles are present in the end point detection window 5, the light from the light source 13 will be reflected by the air bubbles, reducing the light transmittance and affecting the accuracy of end point detection. Therefore, in order to prevent air bubbles from being present in the end point detection window 5, for example, sufficient degassing under reduced pressure can be performed at the material preparation stage.

<<Method of manufacturing the polishing layer>>
A method for producing the polishing layer 4 of the present invention will be described. The material of the polishing layer 4 is not particularly limited as long as it is a material that can be used for polishing, but for example, a polyurethane resin material obtained by reacting a urethane bond-containing polyisocyanate compound with a curing agent can be used.

The polishing layer 4 is preferably a polyurethane resin material having air bubbles. The air bubbles in the polyurethane resin material are classified into closed air bubbles, in which multiple air bubbles exist independently, and open air bubbles, in which multiple air bubbles are connected by communicating holes, depending on the form of the air bubbles. Of these, the polyurethane resin material used in the present invention preferably has closed air bubbles, and is more preferably a polyurethane resin material containing a polyurethane resin and hollow microspheres dispersed in the polyurethane resin.

The polyurethane resin material having closed cells can be molded by using hollow microspheres that have an outer shell and are hollow inside. The hollow microspheres may be commercially available or may be obtained by synthesis using a conventional method. The material of the outer shell of the hollow microspheres is not particularly limited, but 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, as well as copolymers of two or more of the monomers that constitute these resins. In addition, examples of commercially available hollow microspheres include, but are not limited to, the Expancel series (trade name manufactured by Akzo Nobel) and Matsumoto Microsphere (trade name manufactured by Matsumoto Oil Co., Ltd.).

The shape of the hollow microspheres in the polyurethane sheet is not particularly limited, and may be, for example, spherical or nearly spherical. The average particle size of the hollow microspheres 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 using a laser diffraction particle size distribution measuring device (for example, Mastersizer 2000, manufactured by Spectris Co., Ltd.).

The hollow microspheres are 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 3 parts by weight, per 100 parts by weight of the urethane prepolymer.

In addition to the above components, conventionally used blowing agents may be used in combination with the hollow microspheres as long as the effects of the present invention are not impaired, and a gas that is non-reactive with each of the 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 a hydrocarbon having 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.

The manufacturing method of the polishing layer 4 using a urethane bond-containing polyisocyanate compound and a curing agent includes, for example, a manufacturing method including at least a preparation step of preparing the materials; a mixing step of obtaining a mixture of the materials; a molding step of molding a polyurethane resin molded body from the mixture; and a polishing layer forming step of forming a polishing layer having a polishing surface for polishing an object to be polished from the polyurethane resin molded body. These steps are the same as the manufacturing method of the end point detection window, except that it is not necessary to use a phenol-based antioxidant and a phosphorus-based antioxidant, so a detailed explanation is omitted. Note that this explanation does not prevent the polishing layer 4 other than the end point detection window 5 from using both a phenol-based antioxidant and a phosphorus-based antioxidant, and if necessary, both a phenol-based antioxidant and a phosphorus-based antioxidant may be used in the polishing layer 4 as well.

<Method of manufacturing a polishing layer with an end point detection window>
The polishing layer 4 of the polishing pad 3 of the present invention has at least one end point detection window 5. The polishing layer 4 having this end point detection window 5 will be described.
5, first, a cylindrical end point detection window 5 is manufactured. This manufacturing method may involve extrusion molding of a material, or may involve shaping into a cylindrical shape by grinding or the like. Note that the side surface of the end point detection window 5 may be provided with an uneven surface or a threaded structure as necessary to facilitate fitting with the polishing layer 4.
Next, the urethane prepolymer, hardener, and hollow microspheres that are the materials for the polishing layer 4 are fed into a mixer and stirred and mixed. With the cylindrical end point detection window 5 provided, the material for the polishing layer 4 is hardened around it to form a block-shaped polishing layer 4 equipped with the cylindrical end point detection window 5.
Finally, the polishing layer 4 can be cut out to have the desired shape of the polishing pad 3, thereby forming the polishing layer 4 in the desired shape.
The polishing layer 4 having the end point detection window 5 can be formed as described above, but is not limited thereto.

The polishing layer 4 with the end point detection window 5 thus obtained has double-sided tape attached to the side opposite the polishing surface of the polishing layer 4. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used.

The polishing pad 3 of the present invention may have a single-layer structure consisting of only the polishing layer 4, or may have a multi-layer structure in which another layer (lower layer, support layer, cushion layer 6 in Figures 3 and 5) is attached to the surface of the polishing layer 4 opposite the polishing surface. When it has a multi-layer structure, the multiple layers can be bonded and fixed together using double-sided tape or adhesive, while applying pressure as necessary. There are no particular restrictions on the double-sided tape or adhesive used in this case, and any double-sided tape or adhesive known in the art can be selected and used. The cushion layer 6 has a through hole 6a pre-formed at a position corresponding to the end point detection window 5.

Furthermore, in the polishing pad 3 of the present invention, the front and/or back surface of the polishing layer 4 and the end point detection window 5 may be ground as necessary, and the surface may be grooved or embossed. There is no particular restriction on the method of grinding, and grinding can be performed by a known method. Specifically, grinding with sandpaper can be mentioned. There is no particular restriction on the shape of the grooves, and examples of such shapes include a lattice type, a concentric circle type, and a radial type.

When using the polishing pad 3 of the present invention, the polishing pad 3 is attached to the polishing table 10 of the polishing machine 1 so that the polishing surface of the polishing layer 4 faces the workpiece. Then, the polishing table is rotated while supplying slurry to polish the processed surface of the workpiece.

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.

Example 1
(Manufacture of End Point Detection Window)
100 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 490, which is obtained by reacting 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 650, and diethylene glycol (DEG), were charged into a first liquid tank and kept warm at 60°C. Next, separately from the first liquid, 23.7 parts of MOCA as a curing agent, 0.6 parts of bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)] as a phenol-based antioxidant, and 0.4 parts of triphenyl phosphite as a phosphorus-based antioxidant were added and mixed to obtain a mixed liquid. The obtained mixed liquid was kept warm at 120°C in a second liquid tank. The liquids in the first liquid tank and the second liquid tank were each injected into a mixer equipped with two injection ports through the respective injection ports. The two injected liquids were injected into a mold of a molding machine preheated to 80°C while being mixed and stirred, and then the mold was closed and heated to 80°C for 30 minutes for primary curing. The primarily cured molded product was demolded and then secondary cured in an oven at 120°C for 4 hours to obtain a urethane resin molded product to be used as an end point detection window. At this time, the R value, which represents the equivalent ratio of the amino group present in the curing agent to the isocyanate group present at the end of the isocyanate group-terminated urethane prepolymer, was adjusted to 0.90.

(Manufacture of abrasive layer)
On the other hand, 2,4-tolylene diisocyanate (2,4-TDI), poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 1000, poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 650, and diethylene glycol (DEG) were reacted to form 100 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 455. The shell portion was made of an acrylonitrile-vinylidene chloride copolymer, and 2.7 parts of unexpanded hollow microspheres having an average particle size of 8.5 μm and having isobutane gas encapsulated in the shell were added and mixed, and the mixture was charged into a first liquid tank and kept at 60° C. Next, 25.8 parts of MOCA were added and mixed as a curing agent separately from the first liquid, and the mixture was kept at 120° C. in a second liquid tank. The liquids in the first liquid tank and the second liquid tank were each injected into a mixer equipped with two injection ports through the respective injection ports. In this case, the R value, which represents the equivalent ratio of the amino group present in the curing agent to the isocyanate group present at the end of the isocyanate group-terminated urethane prepolymer, was adjusted to 0.90. The end point detection window was installed in the mold, and the two injected liquids were injected into the mold of a molding machine preheated to 80°C while mixing and stirring, and then the mold was closed and heated to 80°C for 30 minutes to perform primary curing. After the primary cured molded product was demolded, it was secondary cured in an oven at 120°C for 4 hours to obtain a urethane resin molded product. The obtained urethane resin 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 an abrasive layer.
Furthermore, a double-sided tape was attached to the surface of the polishing layer opposite to the polishing surface, and this was then attached to the cushion layer to obtain a polishing pad.

When a test sample was polished using a polishing pad consisting of the obtained end point detection window and the obtained polishing layer, stable end point detection was possible by the light passing through the end point detection window.

<Example 2, Comparative Examples 1 to 3>
End point detection window samples of Example 2 and Comparative Examples 1 to 3 were obtained in the same manner as for obtaining the end point detection window of Example 1, except that the materials were changed as follows.
In Example 2, 0.4 parts of the same phenol-based antioxidant as in Example 1 and 0.6 parts of the same phosphorus-based antioxidant as in Example 1 were added to prepare an end point detection window.
In Comparative Example 1, an end point detection window was prepared without adding a phenol-based antioxidant or a phosphorus-based antioxidant.
In Comparative Example 2, only the same phenol-based antioxidant as in Example 1 was added in an amount of 0.6 parts to prepare an end point detection window.
In Comparative Example 3, only the same phosphorus-based antioxidant as in Example 1 was added in an amount of 0.6 parts to prepare an end point detection window.

<Light transmittance>
Samples of the end point detection windows of Examples 1 and 2 and Comparative Examples 1 to 3 were processed to a length of 60 mm × width of 20 mm × thickness of 1.3 mm, and light transmittance was measured. The measurement device used was a Hitachi U-3210 Spectro Photometer. Results are shown in Table 1, with a mark of O indicating that the light transmittance was 80% or more at wavelengths of 400 nm to 700 nm, and a mark of X indicating that the light transmittance was less than 80%.

<Light resistance test>
Samples of the end point detection windows of Examples 1 and 2 and Comparative Examples 1 to 3 were processed to a length of 110 mm x width of 60 mm x thickness of 1.3 mm, and a light resistance test was carried out for 25 hours at a black panel temperature of 63°C ± 3°C using an F-type device in accordance with JIS B 7751 (2007). The tester used for the light resistance test was an ultraviolet auto fade meter U48AU manufactured by Suga Test Instruments Co., Ltd. The light transmittance of the samples after the light resistance test was evaluated as follows: O for a light transmittance of 80% or more at wavelengths of 400 nm to 700 nm, and X for a light transmittance of less than 80%, and the results are shown in Table 1.

<Color measurement>
The end point detection window samples of Examples 1 and 2 and Comparative Examples 1 to 3 before and after the light fastness test were subjected to color measurement using a color difference meter (colorimeter: CM-700d manufactured by Konica Minolta Japan Co., Ltd.) with a measurement illuminant of D65 light source, measurement conditions: (de: 8°) Sa10W10, and reflected light measurement, and the chromaticity b*, yellowing degree Δb*, and color difference ΔE* were obtained (the yellow chromaticity before the light fastness test was b*1, the chromaticity after the light fastness test was b*2, and the yellowing degree (difference in yellowness) was Δb*). The results are shown in Table 1. The color measurement was performed in accordance with the spectroscopic measurement method of JIS Z 8722 (2009). The color difference was calculated in accordance with JIS Z 8781-4 (2013). The number of measurements was three, and the average value was used as the result.

<Tensile test>
A tensile test was carried out on each of the end point detection window samples of Examples 1 and 2 and Comparative Examples 1 to 3 before and after the light resistance test, and the results of the tensile strength were obtained are shown in Table 1. The tensile test was carried out on samples punched into a dumbbell No. 3 shape in accordance with JIS K 7312 (1996) under conditions of 20°C and 60% RH. An RTC series tensile tester was used, with a full-scale load of 20 kgf and a test speed of 100 mm/min.

Description of symbols 1 Polishing device 2 Incident light 2a, 2b Reflected light 3 Polishing pads 4, 41, 42 Polishing layer 4a Surface of polishing layer 5 End point detection window 5a Surface of end point detection window 6 Cushion layer 7 Adhesive layer 8 Object to be polished 9 Slurry 10 Polishing surface plate 11 Base 12 Thin film 13 Light source 14 Optical sensor 15 Abrasive grains, polishing debris 16 Holding surface plate

Claims (6)

A polishing pad having a polishing layer with an end point detection window in a portion thereof, the end point detection window containing a phenol-based antioxidant and a phosphorus-based antioxidant, the ratio of a tensile strength after a light resistance test to a tensile strength before the light resistance test in the end point detection window being 0.85 to 1.00, and the light resistance test being carried out in accordance with JIS B 7751 (2007) using an F-type apparatus at a black panel temperature of 63°C ± 3°C for 25 hours . The polishing pad of claim 1, wherein the end point detection window contains the phenolic antioxidant and the phosphorus-based antioxidant in a weight ratio of phenolic antioxidant:phosphorus-based antioxidant = 1:0.1 to 1:10. The polishing pad according to claim 1 or 2, wherein the number average molecular weight of the phenol-based antioxidant is 300 to 1000. The polishing pad according to any one of claims 1 to 3, wherein the number average molecular weight of the phosphorus-based antioxidant is 300 to 800. The polishing pad according to any one of claims 1 to 4, wherein the end point detection window contains 0.1 to 5.0 wt% of the phenolic antioxidant. The polishing pad according to any one of claims 1 to 5, wherein the end point detection window contains 0.1 to 5.0 wt % of the phosphorus-based antioxidant.