Polishing pads and polishing devices

Abstract

The present invention provides a polishing pad and polishing apparatus that enable efficient cleaning of the polishing pad after polishing, when using a weakly acidic slurry that becomes negatively charged during polishing of the workpiece, by suppressing the re-adsorption of foreign matter onto the polished surface of the polishing layer. [Solution] According to one aspect of the present invention, a polishing pad 10 is provided, comprising a polishing layer 11, wherein the polishing layer 11 contains a resin 11B, the zeta potential A at the polishing surface 11A of the polishing layer 11 measured using an electrolyte with a pH of 5.0 is 0 mV or a positive zeta potential, and the zeta potential B at the polishing surface 11A of the polishing layer 11 measured using an electrolyte with a pH of 7.0 is a negative zeta potential.

Description

[Technical Field]

[0001] This invention relates to polishing pads and polishing devices. [Background technology]

[0002] Traditionally, chemical mechanical polishing (CMP) using a slurry and polishing pad has been employed for polishing workpieces such as semiconductor wafers, as extremely precise flatness is required. CMP is a method of polishing the surface of a workpiece, such as a semiconductor wafer, by supplying slurry to the polishing surface of a rotating polishing pad while pressing and rotating the workpiece. Currently, polishing pads made from synthetic resins such as polyurethane resin are used.

[0003] In recent years, with the increasing integration of circuits formed on semiconductor substrates, polishing pads are required to have high planarization performance. Since the slurries used in CMP are compositions with electrical properties, electrostatic attraction and repulsion forces are generated between the workpiece and the polishing pad. For this reason, research is currently being conducted focusing on the affinity with the slurry. For example, polishing pads that exhibit a positive zeta potential over a pH range of 2 to 12 (see, for example, Patent Document 1), polishing pads that exhibit a positive zeta potential of +0.1mV to +30mV over a pH range of 3 to 5 (see, for example, Patent Document 2), or polishing pads that exhibit a negative zeta potential of -50mV or more and less than 0mV in the neutral region (see, for example, Patent Document 3) are known.

[0004] By the way, after polishing by CMP, foreign matter such as residual abrasive particles and polishing debris that were contained in the slurry remains on the polished surface of the polished layer. Therefore, it is necessary to remove the foreign matter from the polished surface by loosening it with a washing process using a large amount of pure water. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-75355 [Patent Document 2] Japanese Patent Publication No. 2005-294661 [Patent Document 3] Patent No. 4326587 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, during the cleaning process after polishing by CMP, foreign matter that has been lifted from the polished surface may re-adhere to the polished surface. In particular, as disclosed in Patent Document 1, if the polishing pad exhibits a positive zeta potential over the entire range including the neutral region, and a negatively charged weakly acidic slurry is used, high polishing performance is observed during polishing because an electrostatic attraction acts between the slurry and the polished surface. However, during the cleaning process after polishing, as the pH approaches the neutral region, an electrostatic attraction acts between the slurry and the polished surface, making it easy for foreign matter such as abrasive particles to re-adhere to the polished surface.

[0007] This invention was made to solve the above problems. Specifically, the objective is to provide a polishing pad and polishing apparatus that can efficiently clean a polishing pad after polishing, suppressing the re-adsorption of foreign matter onto the polished surface of the polishing layer, when using a weakly acidic slurry that becomes negatively charged during polishing of the workpiece. [Means for solving the problem]

[0008] [1] A polishing pad comprising a polishing layer, wherein the polishing layer contains a resin, and the zeta potential A at the polishing surface of the polishing layer, measured using an electrolyte with a pH of 5.0, is 0 mV or a positive zeta potential, and the zeta potential B at the polishing surface of the polishing layer, measured using an electrolyte with a pH of 7.0, is a negative zeta potential.

[0009] [2] The polishing pad according to [1], wherein the absolute value of the ratio of the zeta potential B to the zeta potential A is 2.5 or more.

[0010] [3] The polishing pad according to [1] or [2] above, wherein the resin includes a polyurethane resin.

[0011] [4] The cured product of the curable resin composition includes an isocyanate group-terminated urethane prepolymer containing structural units derived from polyisocyanate and structural units derived from polyol, and a multimeric polyamine. The structural units derived from the polyol do not contain an ester bond and have the structural units represented by the following formula (1). The polishing pad according to [3] above.

Chemical formula

[0012] [5] The polyamine contains at least one of a trimer and a tetramer. The polishing pad according to [4] above.

[0013] [6] The polishing layer further contains hollow particles. The polishing pad according to any one of [1] to [5] above.

[0014] [7] A polishing apparatus comprising the polishing pad according to any one of [1] to [6] above.

Advantages of the Invention

[0015] According to the present invention, in the cleaning of the polishing pad after polishing when using a weakly acidic slurry that is negatively charged during the polishing of the workpiece to be polished, re-adsorption of foreign substances onto the polishing surface of the polishing layer can be suppressed, and a polishing pad and a polishing apparatus that can be efficiently cleaned can be provided.

Brief Description of the Drawings

[0016] [Figure 1] Figure 1 is a schematic configuration diagram of a polishing pad according to an embodiment. [Figure 2] Figure 2 is an enlarged view of a part of Figure 1. [Figure 3] Figure 3 is a schematic configuration diagram of a zeta potential analyzer. [Figure 4]Figure 4 is a schematic diagram of a polishing apparatus equipped with a polishing pad according to an embodiment. [Figure 5] Figure 5 is a graph showing the zeta potential of the polished surface of the polishing layer in the polishing pads according to Examples 1 and 2 as a function of pH. [Figure 6] Figure 6 is a graph showing the zeta potential of the polished surface of the polishing layer in the polishing pads according to Comparative Examples 1 to 3, as a function of pH. [Modes for carrying out the invention]

[0017] The polishing pad and polishing apparatus according to the present invention will be described below. Figure 1 is a schematic diagram of the polishing pad according to this embodiment, Figure 2 is an enlarged view of a part of Figure 1, Figure 3 is a schematic diagram of the zeta potential analyzer, and Figure 4 is a schematic diagram of the polishing apparatus equipped with the polishing pad according to this embodiment.

[0018] <<<Polishing pad>>> As shown in Figure 1, the polishing pad 10 is, for example, disc-shaped and comprises a polishing layer 11, a cushion layer 12, and an adhesive layer 13 for bonding the polishing layer 11 and the cushion layer 12. The polishing pad 10 has a cushion layer 12 and an adhesive layer 13, but it is sufficient to have a polishing layer 11, and it is not necessary to have a cushion layer 12 and an adhesive layer 13. The surface 10A of the polishing pad 10 is the polishing surface 11A of the polishing layer 11. The polishing surface 11A is the surface for polishing the object to be polished.

[0019] <<Polishing layer>> As shown in Figure 2, the polishing layer 11 contains resin 11B and hollow particles 11C dispersed in the resin 11B. The polishing layer 11 does not necessarily have to contain hollow particles 11C. The thickness of the polishing layer 11 can be approximately 1 to 5 mm.

[0020] When the zeta potential A of the polished surface 11A was measured using an electrolyte with a pH of 5.0, the zeta potential A of the polished surface 11A of the polishing layer 11 was 0 mV or a positive zeta potential. When the zeta potential B of the polished surface 11A was measured using an electrolyte with a pH of 7.0, the zeta potential B of the polished surface 11A of the polishing layer 11 was a negative zeta potential. "Zeta potential" is a measure of the electrostatic attraction or repulsion force of a solid surface and is widely used as an indicator of the dispersion stability of fine particles.

[0021] The absolute value of the ratio of the zeta potential B to the zeta potential A (│zeta potential B / zeta potential A│) is preferably 2.5 or greater. If the absolute value of this ratio is 2.5 or greater, the zeta potential in the polishing process of the workpiece using a negatively charged weakly acidic slurry (for example, with a pH of about 5) and the cleaning process in the neutral region after polishing can be made to differ significantly, thereby suppressing the re-adsorption of foreign matter onto the polished surface 11A of the polishing layer 11 and enabling more efficient cleaning. The lower limit of the absolute value of this ratio is more preferably 3.0 or greater, 3.5 or greater, or 4.0 or greater, and the upper limit is more preferably 10.0 or less, 8.0 or less, or 6.0 or less.

[0022] The lower limit of the zeta potential A is preferably greater than 0mV, 0.5mV or more, or 1.0mV or more, from the viewpoint of significantly differentiating the zeta potential of the workpiece during the polishing process and the post-polishing cleaning process, and the upper limit is preferably 50.0mV or less, 40.0mV or less, or 30.0mV or less. The lower limit of the zeta potential B is preferably -100.0mV or more, -80.0mV or more, or -60.0mV or more, and the upper limit is preferably -30.0mV or less, -25.0mV or less, or -20.0mV or less, from the viewpoint of significantly differentiating the zeta potential of the workpiece during the polishing process and the post-polishing cleaning process.

[0023] When the zeta potential C of the polished surface 11A is measured using an electrolyte solution with a pH of 6.0, it is preferable that the zeta potential C is negative. A negative zeta potential C allows for a greater electrostatic repulsion force to act between the negatively charged slurry and the polished surface 11A before the pH reaches 7.0 during the cleaning process, making it more difficult for foreign matter such as abrasive particles to be re-adsorbed onto the polished surface. The lower limit of the zeta potential C is preferably -20.0mV or higher, -15.0mV or higher, or -10.0mV or higher, and the upper limit is preferably -0.1mV or lower, -0.5mV or lower, or -1.0mV or lower.

[0024] When the zeta potential D of the polished surface 11A is measured using an electrolyte with a pH of 3.0 and the zeta potential E of the polished surface 11A is measured using an electrolyte with a pH of 4.0, it is preferable that the zeta potentials D and E are 0 mV or positive. Having zeta potentials D and E that are 0 mV or positive allows for good compatibility with negatively charged weakly acidic slurries. The lower limit of the above zeta potentials D and E is preferably greater than 0 mV, 0.5 mV or more, or 1.0 mV or more, and the upper limit is preferably 50.0 mV or less, 40.0 mV or less, or 30.0 mV or less.

[0025] The zeta potentials A to E of the polished surface 11A can be measured by the flow potential method using a zeta potential analyzer. The zeta potential analyzer 20 shown in Figure 3 comprises a flow channel 21, two holders 22 positioned opposite each other on either side of the flow channel 21, an inlet electrode 23 positioned opposite each other on the inlet side of the flow channel 21, an outlet electrode 24 positioned opposite each other on the outlet side of the flow channel 21, variable gap cells 25 positioned between the inlet electrode 23 and the holder 22 and between the outlet electrode 24 and the holder 22, and gaskets 26 positioned between the variable gap cells 25 and the holder 22. To measure the zeta potential of the polished surface 11A using such a zeta potential analyzer 20, first, the polishing layers 11 are fixed to the holders 22 so that the polished surfaces 11A face each other. Then, electrolytes with pH values ​​of 3.0, 4.0, 5.0, and 6.0 are flowed between the polished surfaces 11A under pressure. As a result, an electrical double layer is formed on the polishing surface 11A of the polishing layer 11. Since a potential difference is generated between the inlet electrode 23 and the outlet electrode 24, the zeta potential ζ of the polishing surface 11A is calculated for each pH when electrolytes with pH 3.0, 4.0, 5.0, 6.0, and 7.0 are flowed through, based on the Helmholtz-Smoluchowski equation (equation (1) below). The pH of the electrolyte can be adjusted, for example, by adding hydrochloric acid aqueous solution and / or potassium hydroxide aqueous solution to potassium chloride aqueous solution.

number

[0026] The polishing layer 11 has pores formed by the opening of hollow particles 11C into the polishing surface 11A. The average pore diameter of the polishing layer 11 is preferably 5 μm or more and 20 μm or less. If the average pore diameter is 5 μm or more, a large amount of slurry can be retained near the surface of the polishing layer 11 when polishing the workpiece. If the average pore diameter is 20 μm or less, the surface roughness of the polishing surface 11A does not become too large, making it easier to adjust the zeta potential within the above range. The lower limit of the average pore diameter is more preferably 6 μm or more, 8 μm or more, or 10 μm or more, and the upper limit is more preferably 18 μm or less, 17 μm or less, or 15 μm or less. The average pore diameter can be measured using a laser microscope (product name "VK-X1000", manufactured by KEYENCE Corporation).

[0027] The porosity of the holes in the polished surface 11A of the polishing layer 11 is not particularly limited, but is preferably 10% to 50%, more preferably 10% to 45%, and most preferably 10% to 40%. When the porosity is within the above numerical range, the slurry is well retained and the workpiece can be polished stably. Here, the porosity of the holes in the polished surface of the polishing layer means the ratio (%) of the total area of ​​holes present on the surface to the surface area of ​​the polishing layer.

[0028] The content of hollow particles 11C in the entire polishing layer 11 or the entire cured product of the curable resin composition for the polishing layer described later is not particularly limited, but is preferably 0.1% by mass or more and 10.0% by mass or less. If the content of hollow particles 11C is within the above numerical range, the desired polishing characteristics can be obtained. The lower limit of the content of hollow particles 11C is more preferably 0.5% by mass or more, or 1.0% by mass or more, and the upper limit is more preferably 5.0% by mass or less, or 4.0% by mass or less.

[0029] The density of the abrasive layer 11 is not particularly limited, but is 0.60 g / cm³. 3 More than 1.25g / cm 3The following is preferable. When the density is within the above numerical range, the generation of scratches due to polishing by-products (polishing debris) can be reduced. The lower limit of the density of the polishing layer 11 is 0.65 g / cm³. 3 Above, or 0.70 g / cm³ 3 It is more preferable that the amount be greater than or equal to 1.15 g / cm³, with an upper limit of 1.15 g / cm³. 3 The following, or 1.10 g / cm³ 3 The following are preferable.

[0030] The Shore D hardness of the polishing layer 11 is not particularly limited, but is preferably 35 to 75. If the Shore D hardness is 35 or higher, minor irregularities can be flattened, and if the Shore D hardness is 75 or lower, the occurrence of scratches on the workpiece can be reduced. The lower limit of the Shore D hardness of the polishing layer 11 is more preferably 40 or higher, or 45 or higher, and the upper limit is more preferably 70 or lower, or 65 or lower.

[0031] <Resin> The resin 11B is not particularly limited, but for example, polyurethane resin is preferred. Polyurethane resin can be synthesized from polyisocyanate and polyol, and in particular, the reaction product of urethane prepolymer and curing agent is preferred. The urethane prepolymer can be synthesized from isocyanate-terminated urethane prepolymer having isocyanate groups at the ends and polyol. The urethane prepolymer contains structural units derived from polyisocyanate and structural units derived from polyol. The structural units derived from polyisocyanate, structural units derived from polyol, and curing agent will be described below.

[0032] (Constituent units derived from polyisocyanate) The constituent units derived from polyisocyanates are not particularly limited, but examples include constituent units derived from alicyclic isocyanates, aliphatic isocyanates, and aromatic isocyanates. Among these, constituent units derived from aromatic isocyanates are preferred, and constituent units derived from 2,4-tolylene diisocyanate (2,4-TDI) are more preferred.

[0033] Alicyclic isocyanates are not particularly limited, but examples include 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, and isophorone diisocyanate.

[0034] Aliphatic isocyanates are not particularly limited, but examples include hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, trimethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0035] Aromatic isocyanates are not particularly limited, but examples include phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), xylylene diisocyanate, naphthalene diisocyanate, and diphenylmethane-4,4'-diisocyanate (MDI).

[0036] (Constituent units derived from polyols) The constituent units derived from polyols are not particularly limited, but examples include low molecular weight polyols with a molecular weight of less than 300 and high molecular weight polyols with a number-average molecular weight of 300 or more. Among these, it is preferable to use both low molecular weight polyols and high molecular weight polyols in combination from the viewpoint of keeping the zeta potential and its standard deviation within the above range.

[0037] The molecular weight of the low molecular weight polyol and the number-average molecular weight of the high molecular weight polyol can be measured as the molecular weight in terms of polyethylene glycol / polyethylene oxide (PEG / PEO) based on gel permeation chromatography (GPC) under the following conditions. <Measurement conditions> Columns: Ohpak SB-802.5HQ (exclusion limit 10000) + SB-803HQ (exclusion limit 100000) Mobile phase: 5mM LiBr / DMF Flow rate: 0.3ml / min (26kg / cm 2 ) Oven: 60℃ Detector: RI 40℃ Sample volume: 20 μl

[0038] The low molecular weight polyol is not particularly limited as long as the zeta potentials A and B can be within the above range, but examples include low molecular weight polyols having two hydroxyl groups such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecanedimethanol, and 1,4-cyclohexanedimethanol; and low molecular weight polyols having three or more hydroxyl groups such as glycerin, hexanetriol, trimethylolpropane, isocyanuric acid, and erythritol. The low molecular weight polyol may be used alone or in combination of two or more. Among these, low molecular weight polyols having two hydroxyl groups are preferred, and diethylene glycol is more preferred.

[0039] The polymeric polyol is not particularly limited as long as the zeta potentials A and B are within the above ranges, but examples include polyether polyols, polyester polyols, polycarbonate polyols, polyether polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer-modified polyols. The polymeric polyol may be used alone or in combination of two or more. Among these, polyether polyols are preferred, linear polyether polyols are more preferred, and polytetramethylene ether glycol (PTMG) is even more preferred. The number average molecular weight of the polymeric polyol is preferably 300 to 3000, more preferably 500 to 2500, and most preferably 850 to 2000.

[0040] The constituent units derived from the polyol preferably do not contain ester bonds and have the constituent units shown in the following formula (1). Such constituent units are linear alkylene groups and do not contain highly polar ester bonds, so they have low polarity. For this reason, the zeta potential of the polished surface 11A tends to be positive in the pH range of 3.0 to 5.0. [ka] In the above formula (1), R represents an optionally substituted linear alkylene group having 3 to 12 carbon atoms, and m represents an integer of 4 or more. If the carbon number of the alkylene group is 3 or more, the polarity of the polishing layer 11 decreases, so that in the pH range of 3.0 to 5.0, the zeta potential of the polishing surface 11A tends to be a positive zeta potential. If the carbon number is 12 or less, the hardness of the polishing layer 11 can be maintained within a desired range. The alkylene group may be an unsubstituted alkylene group. Also, if m is 4 or more, the polarity of the polishing layer 11 decreases, so that in the pH range of 3.0 to 5.0, the zeta potential of the polishing surface 11A tends to be a positive zeta potential. The lower limit of the carbon number of the alkylene group is preferably 4 or more, 5 or more, or 6 or more, and the upper limit is preferably 11 or less, or 10 or less. The lower limit of m is preferably 5 or more, 6 or more, or 7 or more, and the upper limit is preferably 30 or less, 25 or less, or 20 or less. R can be represented by -C n R 1 2n -. Here, R 1 is a hydrogen or halogen atom, and n is the above carbon number. Such a structural unit can be obtained as a polymer polyol by using a linear polyether polyol, preferably polytetramethylene ether glycol (PTMG).

[0041] (Hardener) The hardener is not particularly limited, and examples thereof include polyamines. As the polyamine, for example, from the viewpoint of making the zeta potential of the polishing surface 11A tend to be a positive zeta potential in the pH range of 3.0 to 5.0, it preferably contains a polyamine having a trimer or higher multimer. The hardener may be used alone or in combination of two or more. For example, a polyamine and a multimer polyamine may be used in combination.

[0042] The polyamines are not particularly limited, but examples include aliphatic polyamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; alicyclic polyamines such as isophoronediamine and dicyclohexylmethane-4,4'-diamine; and aromatic polyamines such as 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, and 2,2-bis(3-amino-4-hydroxyphenyl)propane. Trifunctional triamine compounds and polyamine compounds with four or more functions can also be used. Among these, aromatic polyamines are preferred, and 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) is more preferred. MOCA is a dimer in which two molecules of chloroaniline are linked via a methylene group.

[0043] Examples of polyamine polymers include the polyamine polymers exemplified above. Examples of polyamine polymers include trimer and tetramer polyamines. As for polyamine polymers, MOCA polymers containing a trimer in which three molecules of chloroaniline are linked via methylene groups and / or a tetramer in which four molecules of chloroaniline are linked via methylene groups are preferred.

[0044] When polyamine and polymerized polyamine are used together as a curing agent, the mass ratio of polyamine to polymerized polyamine is preferably 8:2 to 5:5. Within this mass ratio range, the zeta potential of the polished surface 11A tends to be positive in the pH range of 3.0 to 5.0. A mass ratio of 8:2 to 6:4, or 7:3 to 6:4, is more preferable.

[0045] From the viewpoint of keeping the above zeta potentials A and B within the above range, it is preferable to use a combination of an isocyanate-terminated urethane prepolymer that does not contain ester bonds and has the structural unit shown in formula (1) above, and a polymerized polyamine as the structural unit derived from the polyol.

[0046] <Hollow particles> The hollow particle 11C is a particle that has an outer shell and a cavity inside. The shape of the hollow particle 11C is not particularly limited, but for example, it may be spherical or substantially spherical.

[0047] The material for the outer shell of the hollow particle 11C is not particularly limited, but examples include polyvinyl alcohol polymers, polyvinylpyrrolidone polymers, poly(meth)acrylic acid polymers, polyacrylamide polymers, polyethylene glycol polymers, polyhydroxyether acrylate polymers, polyethylene oxide polymers, polyurethane polymers, and acrylonitrile polymers. Among these, acrylonitrile polymers are preferred from the viewpoint of easily adjusting the zeta potential of the polished surface to the range described above. Furthermore, it is preferable that the material for the outer shell of the hollow particle 11C does not contain polyvinylidene chloride copolymers such as polyvinylidene chloride-acrylonitrile copolymers. By not containing polyvinylidene chloride copolymers in the material for the outer shell of the hollow particle 11C, it is easier to adjust the zeta potential of the polished surface to the range described above.

[0048] The polishing pad 10 is used to polish the workpiece. The workpiece is not particularly limited, but examples include optical materials, semiconductor wafers, and glass substrates for hard disks.

[0049] <<Manufacturing method for polishing pads>> Such abrasive pads 10 can be manufactured, for example, as follows: First, a prepolymer such as a urethane prepolymer, a curing agent, and unexpanded hollow particles are prepared.

[0050] Unexpanded hollow particles contain, for example, liquid hydrocarbons inside their outer shell. By heating the unexpanded hollow particles, the liquid hydrocarbons vaporize, causing the hollow particles to expand and increasing their particle size.

[0051] Hollow particles can be either expandable or non-expandable. Expandable hollow particles allow for control of particle size through heating, making it possible to obtain particles with smaller diameters than currently available non-expandable hollow particles. From this perspective, it is preferable to use expandable hollow particles. The average particle size (D) of expandable hollow particles 50 The average particle size (D) of the hollow particles is not particularly limited, but can be approximately 1 μm to 20 μm in its pre-expansion state. 50 This can be measured using a laser diffraction particle size distribution analyzer (for example, the "Mastersizer 2000" product manufactured by Spectris Corporation).

[0052] Next, the prepolymer and hollow particles are mixed and maintained at a temperature between 50°C and 80°C. Meanwhile, the curing agent is maintained at approximately 120°C. The reason for mixing the hollow particles with the prepolymer is that if they were mixed with the curing agent, there is a risk that the hollow particles would expand due to the heat.

[0053] Subsequently, the prepolymer and hollow particles are mixed with a curing agent to obtain a curable resin composition for the polishing layer. Then, the curable resin composition for the polishing layer is supplied to a mold and heated in a range of 75°C to 140°C to expand the expandable hollow particles and cure the curable resin composition for the polishing layer. This yields a resin block, which is a cured product of the curable resin composition for the polishing layer.

[0054] The hardened resin block is removed from the mold and sliced ​​to a predetermined thickness to obtain the polishing layer 11. After grooves are machined into the surface of the polishing layer 11, the polishing layer 11 and the cushion layer 12 are bonded together via the adhesive layer 13. Finally, it is cut into a disc shape. This yields the polishing pad 10.

[0055] According to this embodiment, the zeta potential A at the polished surface 11A of the polishing layer 11, measured using an electrolyte with a pH of 5.0, is 0 mV or a positive zeta potential, while the zeta potential B at the polished surface 11A of the polishing layer 11, measured using an electrolyte with a pH of 7.0, is a negative zeta potential. Therefore, the positive and negative zeta potentials of the polished surface 11A differ between the polishing process of the workpiece using a weakly acidic slurry (for example, with a pH of around 5) that is negatively charged and the cleaning process in the neutral region after polishing. As a result, the electrostatic repulsion force with foreign matter such as remaining abrasive grains and polishing debris is good during cleaning in the neutral region after polishing, thereby suppressing the re-adsorption of foreign matter to the polished surface 11A during cleaning after polishing and enabling efficient cleaning.

[0056] <<<Polishing equipment>>> The polishing pad 10 is used by being incorporated into a polishing device. The polishing device 30 shown in Figure 4 is a chemical mechanical polishing device. The polishing device 30 comprises the polishing pad 10, a polishing platen 31 to which the polishing pad 10 is attached by double-sided tape (not shown) or the like provided on the cushion layer 12 of the polishing pad 10, a holding platen 32 for holding the workpiece 40, and a slurry supply unit 33 for supplying slurry when polishing the workpiece 40. The polishing pad 10 rotates together with the polishing platen 31 with the workpiece 40 pressed against the surface 10A of the polishing pad 10, polishing the workpiece 40. At that time, slurry is supplied between the polishing pad 10 and the workpiece 40 from the slurry supply unit 33. The slurry is a mixture (dispersion) of water and various chemical components and hard, fine abrasive particles, and the polishing effect is increased by the relative motion with the workpiece 40 as the chemical components and abrasive particles in the slurry flow through it. The slurry is supplied to the polishing surface 11A through grooves or holes (not shown) provided in the polishing layer 11, and then discharged. [Examples]

[0057] To illustrate the present invention in detail, examples are given below, but the present invention is not limited to these. Figure 5 is a graph showing the zeta potential of the polished surface of the polishing layer in polishing pads according to Examples 1 and 2 as a function of pH, and Figure 6 is a graph showing the zeta potential of the polished surface of the polishing layer in polishing pads according to Comparative Examples 1 to 3 as a function of pH.

[0058] <Example 1> First, an isocyanate-terminated urethane prepolymer, a curing agent, and hollow particles (Expancel® 044DU20 manufactured by Nippon Philite Co., Ltd., outer shell: acrylonitrile polymer) were prepared. The isocyanate-terminated urethane prepolymer was obtained by mixing and reacting 2,4-tolylene diisocyanate (2,4-TDI), polytetramethylene ether glycol (PTMG650) with a number average molecular weight of 650, and diethylene glycol (DEG), with an NCO equivalent of 460. As the curing agent, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and the polymer MOCA (LM-52 manufactured by Kumiai Chemical Industry Co., Ltd., a mixture of trimers and tetramers) were prepared. The hollow particles, Expansel® 044DU20, had an average particle size (D 50 The diameter is 8.5 μm, the expansion start temperature is 100-108°C, and the maximum expansion temperature is 143-160°C.

[0059] Next, the urethane prepolymer and hollow particles were mixed in a mass ratio of 100:2.8, heated to 60°C, and degassed under reduced pressure. MOCA and polymerized MOCA were also mixed in a mass ratio of 7:3, dissolved at 120°C, and degassed under reduced pressure. Then, the urethane prepolymer, curing agent, and hollow particles were mixed in a mass ratio of 100:26.3:2.8. The resulting mixture was poured into a mold and primary cured at 80°C for 30 minutes. The resin block containing the formed foamed hollow particles was removed from the mold and secondary cured in an oven at 120°C for 4 hours. After the resulting resin block cooled to 25°C, it was heated again in an oven at 120°C for 5 hours. The resulting resin block was sliced ​​in a direction perpendicular to the thickness direction of the resin block to create a polishing layer with a thickness of 1.3 mm. Double-sided tape was attached to the back of this polishing layer to create a polishing pad. The density of the resulting polishing pad was 0.8 g / cm³. 3 The Shore D hardness was 61, and the average pore diameter was 13 μm. The density and Shore D hardness of the polishing pads in Examples 1 and 2 and Comparative Examples 1 to 3 were measured based on the method described later.

[0060] <Example 2> In Example 2, a polishing pad was obtained in the same manner as in Example 1, except that polypropylene glycol with a number-average molecular weight of 2000 was further added as a curing agent, and MOCA, polymerized MOCA, and polypropylene glycol were mixed in a mass ratio of 2:1:1. The density of the obtained polishing pad was 0.8 g / cm³. 3 The Shore D hardness was 50, and the average pore diameter was 13 μm.

[0061] <Comparative Example 1> First, an isocyanate-terminated urethane prepolymer, a curing agent, and hollow particles (Expancel® 461DU20 manufactured by Nippon Philite Co., Ltd., outer shell: polyvinylidene chloride-acrylonitrile copolymer) were prepared. The isocyanate-terminated urethane prepolymer was obtained by mixing and reacting 2,4-tolylene diisocyanate (2,4-TDI), polypropylene glycol (PPG1000) with a number average molecular weight of 1000, and diethylene glycol (DEG), with an NCO equivalent of 500. 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) was prepared as the curing agent. The hollow particles, Expansel® 461DU20, had an average particle size (D 50 The diameter is 8.5 μm, the expansion start temperature is 100-106°C, and the maximum expansion temperature is 143-151°C.

[0062] Next, the urethane prepolymer and hollow particles were mixed in a mass ratio of 100:2.8, heated to 60°C, and degassed under reduced pressure. MOCA was also dissolved at 120°C and degassed under reduced pressure. Then, the urethane prepolymer, curing agent, and hollow particles were mixed in a mass ratio of 100:26.3:2.8. The resulting mixture was poured into a mold and primary cured at 80°C for 30 minutes. The resin block containing the formed foamed hollow particles was removed from the mold and secondary cured in an oven at 120°C for 4 hours. After the resulting resin block cooled to 25°C, it was heated again in an oven at 120°C for 5 hours. The resulting resin block was sliced ​​perpendicular to the thickness direction of the resin block to create a polishing layer with a thickness of 1.3 mm. Double-sided tape was attached to the back of this polishing layer to create a polishing pad. The density of the resulting polishing pad was 0.67 g / cm³. 3 The Shore D hardness was 46, and the average pore diameter was 13 μm.

[0063] <Comparative Example 2> In Comparative Example 2, instead of PPG1000, a polyether polycarbonate diol (PEPCD1000) with a number-average molecular weight of 1000 was used. An isocyanate-terminated urethane prepolymer was formed by mixing 2,4-TDI, PEPCD1000, and DEG and reacting them, except that the process was the same as in Comparative Example 1. The density of the obtained polishing pad was 0.78 g / cm³. 3 The Shore D hardness was 60, and the average pore diameter was 13 μm.

[0064] <Comparative Example 3> First, two types of isocyanate-terminated urethane prepolymers, a curing agent, and hollow particles (Expancel® 461DU20 manufactured by Nippon Philite Co., Ltd., outer shell: polyvinylidene chloride-acrylonitrile copolymer) were prepared. The first isocyanate-terminated urethane prepolymer was obtained by reacting 2,4-tolylene diisocyanate (2,4-TDI) with polytetramethylene ether glycol (PTMG650) having a number average molecular weight of 650 and diethylene glycol (DEG), and its NCO equivalent was 420. The second isocyanate-terminated urethane prepolymer was obtained by mixing and reacting 2,4-tolylene diisocyanate (2,4-TDI) with a polyester diol (BG ester 2000) having a number average molecular weight of 2000 obtained by reacting adipic acid and 1,4-butanediol and diethylene glycol (DEG), and its NCO equivalent was 600. As a curing agent, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) was prepared.

[0065] Next, the first isocyanate-terminated urethane prepolymer, the second isocyanate-terminated urethane prepolymer, and hollow particles were mixed in a mass ratio of 70:30:2.8, heated to 60°C, and degassed under reduced pressure. MOCA was also dissolved at 120°C and degassed under reduced pressure. Subsequently, the urethane prepolymer (total):curing agent:hollow particles were mixed in a mass ratio of 100:26.3:2.8. The resulting mixture was poured into a mold and primary cured at 80°C for 30 minutes. The resin block containing the formed foamed hollow particles was removed from the mold and secondary cured in an oven at 120°C for 4 hours. After the resulting resin block was allowed to cool to 25°C, it was heated again in an oven at 120°C for 5 hours. The resulting resin block was sliced ​​in a direction perpendicular to the thickness direction of the resin block to create a polishing layer with a thickness of 1.3 mm, and double-sided tape was attached to the back of this polishing layer to create a polishing pad. The density of the resulting polishing pad was 0.89 g / cm³. 3 The Shore D hardness was 54, and the average pore diameter was 13 μm.

[0066] Table 1 shows the formulations of the curable resin compositions for the polishing layer used in Examples 1 and 2 and Comparative Examples 1 to 3. [Table 1]

[0067] <density> Density of the polishing layer of the polishing pads in Examples 1 and 2 and Comparative Examples 1 to 3 (g / cm³) 3 The measurements were taken in accordance with the Japanese Industrial Standard (JIS K 6505).

[0068] <Shore D hardness> The Shore D hardness of the polishing layers of the polishing pads in Examples 1 and 2 and Comparative Examples 1 to 3 was measured using a Shore D hardness tester in accordance with the Japanese Industrial Standard (JIS K 6253). Here, the measurement samples were obtained by stacking multiple polishing layers as necessary, so that the total thickness was at least 4.5 mm. <Zeta potential measurement> In the polishing layers of the polishing pads according to Examples 1 and 2 and Comparative Examples 1 to 3, the zeta potential of the polished surface of the polishing layer was measured using a zeta potential analyzer. Specifically, two 2 cm × 1 cm sample pieces were first taken from each polishing layer. Then, the two sample pieces were set in two holders of a solid surface zeta potential analyzer ("SurPASS3" manufactured by Anton Paar Japan). The two sample pieces were positioned one above the other along the flow path so as to be in contact with the flow path. Meanwhile, the pH of a 1 mM potassium chloride aqueous solution was adjusted using hydrochloric acid aqueous solution and potassium hydroxide aqueous solution in the titration unit of the above apparatus to obtain six types of aqueous solutions with pH values ​​of 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0 as electrolytes. Then, each aqueous solution was supplied to the above flow path under pressure, and the potential difference of the aqueous solution at the inlet and outlet of the flow path was measured to determine the zeta potential of the surface of each sample piece based on the above formula (1). Furthermore, using the obtained zeta potential, the absolute value (│B / A│) of the ratio of the zeta potential B of the surface of the sample piece measured using an electrolyte solution with a pH of 7.0 to the zeta potential A of the surface of the sample piece measured using an electrolyte solution with a pH of 5.0 was determined. (Measurement conditions) • Measuring cell: Variable gap ·Measurement temperature: 25℃ • Number of measurements: Each sample piece is measured three times.

[0069] <Polishing Test> Polishing tests were conducted using the polishing pads described in Examples 1 and 2 and Comparative Examples 1 to 3 under the following polishing conditions.

[0070] (polishing conditions) Polishing machine used: F-REX300X (manufactured by Ebara Corporation) Disk: A188 (manufactured by 3M) Abrasive temperature: 20℃ Polishing plate rotation speed: 85 rpm Polishing head rotation speed: 86 rpm Polishing pressure: 3.5 psi Polishing slurry: PL-6115 (Use a mixture of PL-6115 concentrate and pure water in a 1:1 weight ratio) (Manufactured by Fujimi Incorporated Co., Ltd.) Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Workpiece to be polished: TEOS film substrate (disc shape with a diameter of 300 mm) Pad Break: 32N 30 minutes Conditioning: Ex-situ, 32N, 4 scans

[0071] <Cleaning Evaluation> In the polishing pads according to Examples 1 and 2 and Comparative Examples 1 to 3, which were polished in the above-mentioned <Polishing Test>, pure water was supplied to the polishing surface while rotating the polishing platen to clean the polishing surface. The pure water was supplied from the slurry supply section of the polishing machine used in the above-mentioned <Polishing Test>. The rotation speed of the polishing platen was 85 rpm, the supply volume (flow rate) of pure water was 10,000 ml / min, and the supply time (cleaning time) of pure water was 30 seconds. The evaluation criteria for the cleaning performance were as follows: A: No foreign matter was found on the polished surface. B: Foreign matter was found on the polished surface.

[0072] The results are shown in Table 2. [Table 2]

[0073] As shown in Table 2 and Figure 6, in the polishing pads of Comparative Examples 1 to 3, the zeta potential of the polishing surface of the polishing layer at pH 5.0 and the zeta potential of the polishing surface of the polishing layer at pH 7.0 were both negative, and the sign of the zeta potential of the polishing surface of the polishing layer at pH 5.0 and the sign of the zeta potential of the polishing surface of the polishing layer at pH 7.0 were the same, so as shown in Table 2, foreign matter was found on the polishing surface during the cleaning process after polishing. In contrast, as shown in Table 2 and Figure 5, in the polishing pads of Examples 1 and 2, the zeta potential of the polishing surface of the polishing layer at pH 5.0 was positive, and the zeta potential of the polishing surface of the polishing layer at pH 7.0 was negative, and the sign of the zeta potential of the polishing surface of the polishing layer at pH 5.0 and the sign of the zeta potential of the polishing surface at pH 7.0 were different, so as shown in Table 2, no foreign matter was found on the polishing surface during the cleaning process after polishing. [Explanation of Symbols]

[0074] 10… Polishing pad 10A…Surface 11...polishing layer 11A…Polished surface 11B…Resin 11C...Hollow particle 12…Cushion layer 20... Zeta potential analyzer 30...Polishing equipment

Claims

1. A polishing pad having an abrasive layer, The polishing layer contains a resin, The zeta potential A on the polished surface of the polished layer, measured using an electrolyte solution with a pH of 5.0, is 0 mV or a positive zeta potential. A polishing pad in which the zeta potential B at the polished surface of the polishing layer, measured using an electrolyte solution with a pH of 7.0, is a negative zeta potential.

2. The polishing pad according to claim 1, wherein the absolute value of the ratio of the zeta potential B to the zeta potential A is 2.5 or more.

3. The polishing pad according to claim 1, wherein the resin comprises a polyurethane resin.

4. The polishing pad according to claim 3, wherein the resin is a cured product of a curable resin composition comprising an isocyanate-terminated urethane prepolymer containing structural units derived from polyisocyanate and structural units derived from polyol, and a polymer of polyamine, and the structural units derived from polyol do not contain ester bonds and have structural units represented by the following formula (1). 【Chemistry 1】 (In formula (1), R represents a linear alkylene group having 3 to 12 carbon atoms, which may be substituted, and m represents an integer of 4 or more.)

5. The polishing pad according to claim 4, wherein the polyamine comprises at least one of a trimer and a tetramer.

6. The polishing pad according to claim 1, wherein the polishing layer further comprises hollow particles.

7. A polishing device comprising the polishing pad described in claim 1.

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