Chemical mechanical polishing pad

Abstract

A chemical mechanical polishing pad comprising a photo-cured polymer wherein the photo-cured polymer is a photo-initiated reaction product of a photo-curable material comprising a molecule having two or more functional groups wherein the functional groups comprise a thiol group and an ethylenically unsaturated group, with the proviso that at least a portion of the molecules have the ethylenically unsaturated groups, the ethylenically unsaturated groups being (meth) acrylate groups, where the (meth) acrylate groups account for less than 70 mole percent of the total (meth) acrylate, thiol and ethylenically unsaturated functional groups, and where the (meth) acrylate groups account for less than 70 mole percent of the total (meth) acrylate, thiol and ethylenically unsaturated functional groups. And wherein photocuring comprises a reaction of the thiol group with the ethylenically unsaturated group, with the proviso that at least some of the molecules comprise three or more functional groups. The chemical mechanical polishing pad may be manufactured by additive manufacturing using stereolithography.

Description

Technical Field

[0001] The present invention relates to a method for forming a polishing pad for chemical mechanical polishing. Background Art

[0002] In the fabrication of integrated circuits and other electronic devices, multiple layers of conductive, semiconductive, and dielectric materials are deposited onto and removed from the surface of a semiconductor wafer. Many deposition techniques can be used to deposit thin layers of conductive, semiconductive, and dielectric materials. Deposition techniques commonly used in modern wafer processing include physical vapor deposition (PVD) (also known as sputtering), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electroless plating, among others. Common removal techniques include wet isotropic and anisotropic etching and dry isotropic and anisotropic etching, among others.

[0003] As the material layers are successively deposited and removed, the uppermost surface of the wafer becomes non-planar. Since subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, planarization of the wafer is needed. Planarization can be used to remove unwanted surface topography and surface defects such as rough surfaces, agglomerated materials, lattice damage, scratches, and contaminated layers or materials.

[0004] Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique for planarizing or polishing a workpiece such as a semiconductor wafer. In conventional CMP, a wafer carrier or polishing head is mounted on a carrier assembly. The polishing head holds the wafer and positions it in contact with the polishing layer of a polishing pad, which is mounted on a table or platen within a CMP apparatus. The carrier assembly provides a controllable pressure between the wafer and the polishing pad. At the same time, a polishing medium (e.g., slurry) is dispensed onto the polishing pad and drawn into the gap between the wafer and the polishing layer. For polishing, the polishing pad and the wafer typically rotate relative to each other. As the polishing pad rotates beneath the wafer, the wafer sweeps out a typically circular polishing track or polishing area where the surface of the wafer directly faces the polishing layer. The wafer surface is polished and made planar by the chemical and mechanical action of the polishing layer and the polishing medium on the surface.

[0005] Additive manufacturing of a polishing layer having porosity or a three-dimensional pattern on a polished surface has been proposed. For example, one method uses a microdroplet ejection 3D printing platform. This requires a relatively low-viscosity material that is subsequently photocured. The applied material is then photocured. Examples of photocurable systems suitable for such microdroplet ejection 3D printing can include acrylates, methacrylates, or epoxides as reactive groups for photocuring. See, for example, US2019 / 0224809, US2020 / 0157265, US2021 / 0205951, US11,612,978, and US2019 / 0337117. These chemicals typically undergo chain-growth photocuring. This can result in materials having limited toughness and elongation properties, which may lead to undesirably high wear rates.

[0006] Another method uses vat polymerization (including digital light processes and stereolithography methods for additive manufacturing). See, for example, US10,350,823. Examples of photocurable systems that can be used in this method include compositions of acrylate-capped isocyanates and acrylate monomers that can be polymerized via acrylate or methacrylate groups. See, for example, US 2022 / 0119586. Polymers cured by free-radical-initiated reactions between acrylate or methacrylate groups may have poor toughness and elongation, making them less suitable for use as a polishing layer in a chemical mechanical polishing pad.

[0007] There is a desire to have chemical mechanical polishing pads that can be produced by additive manufacturing, where these pads have good toughness, elongation, and wear rates (e.g., toughness, elongation, wear rates similar to or better than those of commonly used chemical mechanical polishing pads).

[0008] There is also a desire to have an additive manufacturing process for manufacturing a polishing layer for a chemical mechanical polishing pad that enables better toughness, better elongation, wear rates, and greater flexibility in adjusting the mechanical properties of the polishing layer. In particular, there is a desire to have a method for additive manufacturing a polishing layer for chemical mechanical polishing that provides mechanical properties similar to those of non-photocured polishing layers common in chemical polishing pads. SUMMARY OF THE INVENTION

[0009] The present disclosure relates to a chemical mechanical polishing pad comprising a photocured polymer, wherein the photocured polymer is a photoinitiated reaction product of a photocurable material comprising molecules having two or more functional groups, wherein the functional groups include thiol groups and ethylenically unsaturated groups, provided that at least a portion of these molecules have an ethylenically unsaturated group which is a (meth)acrylate group. The (meth)acrylate groups account for less than 70 mole percent of the total (meth)acrylate, thiol, and ethylenically unsaturated functional groups. Photocuring comprises the reaction of thiol groups with ethylenically unsaturated groups. At least some of these molecules contain three or more functional groups.

[0010] Also disclosed is the polishing pad described in the above paragraph, which is formed by a method comprising: providing a photocurable material in a container, selectively curing a portion of the photocurable material by irradiation to form a cured structure, selectively curing an additional portion of the photocurable material by irradiation to further build the cured structure, and repeating the selective curing by irradiation until the cured structure has the form of an element of a polishing pad. For example, the element of the polishing pad can be a polishing layer or a sublayer, or both. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic view of a top-down additive manufacturing apparatus as disclosed herein.

[0012] Figure 2 is a schematic view of a bottom-up additive manufacturing apparatus as disclosed herein. DETAILED DESCRIPTION

[0013] The chemical mechanical polishing pad disclosed herein comprises a polymer, wherein the curing of the polymer comprises the reaction of thiol groups with (meth)acrylate groups, rather than simply by a free radical initiated reaction of two (meth)acrylate groups. As used herein, "(meth)acrylate" is a term designating a class which includes acrylate, methacrylate, or a mixture comprising both acrylate and methacrylate.

[0014] The reaction mixture for forming the photocured polymer can be suitable for additive manufacturing, including in particular stereolithography or photopolymerization methods.

[0015] The photocured polymer can be formed by the reaction of a molecule having two or more functional groups, where these functional groups are ethylenically unsaturated groups and thiol groups. For example, a molecule having two or more functional groups can contain both at least one ethylenically unsaturated group and also at least one thiol group. This molecule can be considered an AB-type molecule. As another example, a molecule having two or more functional groups includes a molecule (A) having two or more ethylenically unsaturated groups and a molecule (B) having two or more thiol groups. The AB-type molecule can be used in combination with molecule (A), in combination with molecule (B), or in combination with both molecule (A) and molecule (B). To provide crosslinking, at least a portion of the molecule can have at least three reactive groups (i.e., at least three ethylenically unsaturated groups on the molecule, at least three thiol groups, at least two ethylenically unsaturated groups and one thiol group on the molecule, or at least two thiol groups and one ethylenically unsaturated group on the molecule). The relative amounts of difunctional (i.e., a molecule having two ethylenically unsaturated groups or a molecule having two thiol groups) and higher functional (e.g., a molecule having more than two ethylenically unsaturated groups or a molecule having more than two thiol groups) molecules enable control of the crosslink density. At least a portion of the ethylenically unsaturated groups are (meth)acrylate groups.

[0016] Molecule (A) can contain an oligomer (also referred to as a prepolymer), a monomer, or a mixture thereof. Molecule (B) can contain an oligomer (also referred to as a prepolymer), a monomer, or a mixture thereof. By selecting the oligomer and monomer structures and their relative amounts, the properties of the photocured polymer can be adjusted. For example, a rigid polyfunctional olefin used as molecule (A) can provide improved hardness or toughness. When using an oligomer molecule (A), mixing with a monomer molecule (A) can be used for viscosity control while avoiding the use of solvents that may need to be removed after curing.

[0017] The molecule (A) may include, for example, vinyl, vinyl ether group, allyl, allyl ether, allyl ester, maleimide, vinyl sulfone, norbornene, provided that in the reaction mixture, the molecule (A), (AB) or both (A) and (AB) include at least some (meth)acrylate groups. The monomer molecule (A) may include diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diallyl ether, trimethylolpropane diallyl ether, 1,4-butanediol divinyl ether, di(ethylene glycol) divinyl ether, tri(ethylene glycol) divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,4,6-triallyloxy-1,3,5-triazine, N,N'-methylenebis(acrylamide). Examples of the monomer (A) having (meth)acrylate groups include aliphatic or aromatic compositions having (meth)acrylate groups, and may be, for example, aliphatic polyfunctional acrylates such as 1,3-propanediol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, alkylene oxide polyfunctional acrylates such as ethylene glycol diacrylate, di(ethylene glycol) diacrylate, tri(ethylene glycol) diacrylate, tri(propylene glycol) diacrylate, alicyclic group acrylates such as 2-[5-[(acryloyloxy)methyl]-5-ethyl-1,3-dioxan-2-yl]-2-methylpropyl acrylate, tricyclodecane dimethanol diacrylate, and aromatic (meth)acrylates such as biphenyl-4,4'-diyl bis(2-methylacrylate). These monomer molecules (A) may be used in a mixture with oligomer molecules (A). The oligomer molecule (A) may be, for example, poly(ethylene glycol) diacrylate, poly(propylene glycol) diacrylate, poly(tetramethylene oxide) diacrylate, poly(dimethylsiloxane) diacrylate, polycaprolactone diacrylate, or an oligomer containing urea, urethane or thiourea.

[0018] Advantageously, the polyfunctional isocyanate can react with a molecule (i.e., a capping agent) containing ethylenic unsaturation (e.g., (meth)acrylate group) and at least one nucleophilic functional group (e.g., amine, hydroxyl, thiol, etc.) to form a urea-, carbamate- or thiourea-containing molecule A. Examples of capping agents include allylphenols (e.g., 2-allylphenol, 4-allylphenol, eugenol, isoeugenol), alkylene glycol allyl ethers (e.g., ethylene glycol allyl ether), alkylene glycol mono vinyl ethers (e.g., ethylene glycol mono vinyl ether, butanediol mono vinyl ether), allyl alcohols (e.g., 1-allylcyclohexanol, allyl alcohol, 3-buten-1-ol, 4-penten-1-ol, 2-methyl-3-buten-1-ol, 5-hexen-1-ol), allylamine, 1-allyl-2-thiourea, N-allyl-N'-(2-hydroxyethyl)thiourea, (meth)acrylic acid hydroxyalkyl esters (e.g., hydroxyethyl acrylate, hydroxyethyl methacrylate), hydroxy norbornene compounds such as 5-norbornene-2-methanol, or mixtures thereof.

[0019] The ethylenic unsaturation in molecule (A) or molecule (AB) can include, for example, vinyl, vinyl ether group, allyl, allyl ether, allyl ester, maleimide, norbornene, (meth)acrylate, provided that at least a portion of the ethylenically unsaturated groups in the reaction mixture contains (meth)acrylate groups. Allyl, allyl ether, and allyl ester can provide a good balance of storage stability and photoreactivity. As used herein, allyl means the group -CH 2 -CH=CH 2 . Monosubstituted olefins can provide a rapid reaction with thiol groups, while disubstituted olefins such as crotyl alcohol, trans-3-hexen-1-ol will react at a lower rate.

[0020] For example, to prepare molecule (A), the following reaction scheme can be used: R 1 is a linking group. For example, R 1 can include an aliphatic group or an aromatic group or both. For example, R 1 can include a divalent alkyl, cycloalkyl, divalent aryl, divalent aralkyl, or can contain carbon and heteroatoms such as nitrogen. For example, R 1 can be methylene diphenyl, isophorone, 2,4-toluene, 2,6-toluene, hexamethylene, or a uretdione backbone formed by dimerization of two isocyanate groups. Alternatively, R 1It may be an oligomeric group containing 2 or more, 3 or more, up to 150 repeating units. The repeating units may be, for example, alkylene oxides such as ethylene oxide, propylene oxide or butylene oxide, lactones such as epsilon-caprolactone, hydrocarbon and diene units in saturated and unsaturated forms such as butadiene, isoprene, ethylidene norbornene, dicyclopentadiene, vinyl norbornene, siloxanes such as dimethylsiloxane, and fluorinated units such as vinylidene fluoride and tetrafluoroethylene. R 2 is a linking group. For example, R 2 may include an aliphatic group or an aromatic group or both. For example, R 2 may be a divalent alkyl group, a divalent aryl group, a divalent arylalkyl group such as benzyl, phenyl, alkyl, an alicyclic group such as cyclohexyl. R 2 is initially provided by a terminator having the formula [Y] b -R 2 -[C═C] c Typically, the terminator may contain at least one nucleophile (e.g., OH, NH 2 , or SH) and an ethylenically unsaturated group. Examples of terminators providing (meth)acrylate include hydroxyalkyl (meth)acrylates (e.g., 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate).

[0021] For example, to form monomer (A), a polyisocyanate monomer (e.g., a diisocyanate monomer) may be reacted to form a monomer having at least two ethylenically unsaturated groups (e.g., (meth)acrylate groups). Examples of such polyisocyanate monomers include toluene diisocyanate (TDI) (e.g., 2,4-toluene diisocyanate; 2,6-toluene diisocyanate), diphenylmethane diisocyanate (MDI) (e.g., 4,4'-diphenylmethane diisocyanate); 4,4'-diisocyanatodicyclohexylmethane (H12MDI); naphthalene-1,5-diisocyanate; tolidine diisocyanate; p-phenylene diisocyanate; xylylene diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; cyclohexane diisocyanate; and mixtures thereof.

[0022] As another example, the molecule (A) may include the following oligomers: a urethane or urea prepolymer having two or more ethylenically unsaturated groups; a polysiloxane having two or more ethylenically unsaturated groups (e.g., (meth)acrylate groups), such as polydimethylsiloxane; or a polyalkylene glycol having two or more ethylenically unsaturated groups. In the case where a urethane or urea chemical composition is desired, such a molecule (A) oligomer can be derived from an isocyanate prepolymer (such as a polyalkylene glycol capped with an isocyanate group or a small molecule diisocyanate). Examples of diisocyanates for direct use or as a prepolymer capping moiety include. The isocyanate-capped urethane prepolymer may have 2 wt% to 30 wt% of unreacted isocyanate (NCO) groups. The prepolymer polyols used to form the polyfunctional isocyanate-capped urethane prepolymer may be selected from the group consisting of: diols, polyols, polyol diols, their copolymers, and mixtures thereof. For example, the prepolymer polyols may be selected from the group consisting of: polyether polyols (e.g., poly(tetramethylene oxide) glycol, poly(propylene oxide) glycol, and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of: ethylene glycol; 1,2-propanediol; 1,3-propanediol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. For example, the prepolymer polyols may be selected from the group consisting of: polytetramethylene ether glycol (PTMEG); ester-based polyols (such as ethylene glycol adipate, butanediol adipate); polypropylene ether glycol (PPG); polycaprolactone polyols; their copolymers; and mixtures thereof. For example, the prepolymer polyols may be selected from the group consisting of: PTMEG and PPG. Examples of commercially available PTMEG-based isocyanate-capped urethane prepolymers include Prepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Prepolymers (available from Lanxess, such as LF800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D and L325); Prepolymers (available from Anderson Development Company, such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). Isocyanate-capped urethane prepolymers based on non-TDI can also be used. For example, it is acceptable that the isocyanate-capped urethane prepolymers include those formed by the reaction of 4,4'-diphenylmethane diisocyanate (MDI) with polyols such as polytetramethylene glycol (PTMEG) or diols such as 1,4-butanediol (BDO). Modified MDI products such as polycarbodiimide-modified MDI (e.g., Isonate 143L) and quasi-prepolymers of MDI reacted with low molecular weight diols (e.g., Isonate 181) can be used, and these low molecular weight diols such as 1,2-propanediol; 1,3-propanediol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol or combinations thereof. Commercial examples of MDI, polymeric MDI, and MDI prepolymers include ISONATE from Dow Chemical Company TM 143L, ISONATE TM 143LP, ISONATE TM 181, ISONATE TM 240, ISONATE TM M 143, ISONATE TM M320, ISONATE TM M340, ISONATE TM 342, ISOBIND TM 1002, ISOBIND TM 1013, ISOBIND TM 1014, ISOBIND TM 1088, ISOBIND TM 1100, ISOBIND TM 1100S, ISOBIND TM 1200R, PAPI TM 135, PAPI TM 135C, PAPI TM 17, PAPI TM 20, PAPI TM 27, PAPI TM 580N, PAPI TM6146, PAPI TM 901, PAPI TM 94, POLYMERIC MDI 199, POLYMERIC MDI 253, VORANATE TM M 200, VORANATE TM M 220, VORANATE TM 229, VORANATE TM 229N, VORANATE TM M 230, VORANATE TM M 2940, VORANATE TM M 580, VORANATE TM M 595, VORANATE TM M 600, VORANATE TM M 647, VORANATE TM SD 100, VORANATE TM SD 100IF. The prepolymer may contain at least two isocyanate groups. Some commercially available products may include an undisclosed mixture of molecules having two isocyanate groups and molecules having more than two isocyanate groups. An example of a commercial prepolymer believed to have more than two isocyanates per molecule is Desmodur N-3400 from Covestro AG.

[0023] Examples of molecule (B) include but are not limited to alkyl polyfunctional thiols (e.g., 1,2-ethanedithiol, 1,3-propanedithiol, propane-1,2,3-trithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, cyclohexane-1,4-diyldimethanethiol), mercaptopropionates (e.g., ethylene glycol bis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate), thioacetates (e.g., 1,4-butanediol bis(thioacetate)), mercaptoacetates (e.g., pentaerythritol tetra(mercaptoacetate)), aromatic group dithiols, aralkyls (e.g., aryls having alkylthiol side groups) (e.g., 1,3-benzenedimethanethiol, 1,4-benzenedimethanethiol, 4,4'-bis(mercaptomethyl)biphenyl) and thiol-terminated oligomers (e.g., poly(ethanedithiol) dithiol, poly(dimethylsiloxane) dithiol or urethane or urea oligomers).

[0024] Examples of AB type molecules include allyl mercaptan and oligomers or prepolymers capped with both an ethylenically unsaturated group and a mercaptan group. Oligomers capped with both an ethylenically unsaturated group and a mercaptan group can be prepared as discussed above, but provide a capping group containing ethylenic unsaturation and a capping group having mercaptan functionality.

[0025] The photocured polymer can be formed from a reaction mixture comprising one or more molecules (A), one or more molecules (B), and a photoinitiator. The photoinitiator absorbs radiation of an activation wavelength (e.g., ultraviolet radiation having a wavelength of, for example, 200 - 500, 340 - 390 (e.g., 385 nanometers (nm))).

[0026] The reaction mixture further comprises a photoinitiator. According to the first embodiment, the photoinitiator is a radical generator. In this case, curing will involve the reaction of thiol groups with (meth)acrylate to form thioether bonds. In this case, curing may also involve the reaction of (meth)acrylate groups with other (meth)acrylate groups. Examples of radical-generating photoinitiators include phenylbis(2,4,6-trimethylbenzoyl)-phosphine oxide (PPO), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2,2-dimethoxy-2-phenylacetophenone (DMPA), 2-isopropylthioxanthone (ITX), and benzoyl peroxide. As another example, the photoinitiator can generate a base upon irradiation, which can deprotonate one of the thiol groups, leading to the reaction of the thiol with the methyl(meth)acrylate group. This method can avoid side reactions between methyl(meth)acrylate groups. Examples of photo-base generators include 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate (e.g., Fujifilm WPBG-300), (Z)-{[bis(dimethylamino)methylene]amino}-N-cyclohexyl(cyclohexylamino)methaniminium tetra(3-fluorophenyl)borate (e.g., Fujifilm WPBG-345) (e.g., 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate (e.g., Fujifilm WPBG-266), 9-anthrylmethyl N,N-diethylcarbamate (Fujifilm WPBG-018). In cases where the photo-base generator does not absorb at the applied wavelength, a photosensitizer such as a thioxanthone substance, or other photo-base generators that absorb at the target wavelength can be used. In cases where the photo-base generator generates radicals in addition to the base, a radical inhibitor substance such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) can be used to selectively inhibit radical side reactions while allowing base-catalyzed reactions. The amount of the photoinitiator in the reaction mixture can be, for example, 0.1, 0.2, 0.3, 0.4, or 0.5 to 5, to 4, to 3, to 2, or to 1.5 weight percent based on the total weight of the reaction mixture.

[0027] (For example, the) molar ratio of the ethylenically unsaturated group (at least a part of which is a (meth)acrylate group) from molecule (A) to the thiol group (for example, from molecule (B)) can be 0.5:1 to 1:0.5, 0.6:1 to 1:0.6, 0.7:1 to 1:0.7, 0.8:1 to 1:0.8, 0.9:1 to 1:0.9, 0.95:1 to 1:0.95, or can be about 1:1. Based on the total (meth)acrylate, thiol, and ethylenically unsaturated functional groups (the total number of moles of (meth)acrylate groups plus the number of moles of other ethylenically unsaturated groups plus the number of moles of thiol groups), the molar percentage of the methyl (meth)acrylate group can be less than 70%, or less than 60% or less than 55%, and is preferably at least 1%. In certain embodiments, such as when a photo-base generator is used, based on the total number of moles of (meth)acrylate groups, other ethylenically unsaturated groups, and thiol groups, the molar ratio of the methyl (meth)acrylate group is preferably at least 30%, more preferably at least 40%.

[0028] In addition to the photoinitiator, the reaction mixture can optionally contain a UV absorber. The UV absorber can be beneficial for adjusting the light penetration (i.e., the curing depth) of the reaction mixture. The UV absorber can absorb light at wavelengths (for example, 385 nm) used in additive manufacturing devices. Examples of the UV absorber include 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (DHDMBP) and avobenzone. The amount of the UV absorber can be greater than 0, at least 0.1, at least 0.2, at least 0.3, at least 0.4, or at least 0.5 to 10, to 5, or to 2 wt% based on the total weight of the reaction mixture.

[0029] The reaction mixture may optionally contain a liquid reactive diluent containing groups reactive with other components of the reaction mixture (e.g., ethylenically unsaturated groups or thiols). Such a liquid reactive diluent can reduce the viscosity of the reaction mixture to control the viscosity of the reaction mixture. Since the liquid reactive diluent reacts with other components of the reaction mixture, it does not need to be removed after the polishing layer is formed. Such removal may cause shrinkage. One type of liquid reactive diluent includes molecules containing ethylenically unsaturated groups such as (meth)acrylate, allyl, allyl ether, vinyl, and vinyl ether compounds. Examples of these molecules include, but are not limited to, alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates (where the alkyl has 1 to 4 carbon atoms), vinyltoluene, isononyl (meth)acrylate, (meth)acrylic acid, diallyl isophthalate, diallyl terephthalate, butanediol divinyl ether, N-vinylpyrrolidone, butanediol monovinyl ether, ethylene glycol vinyl ether, vinyl acetate, 1-vinylimidazole, 2-vinylpyrazine, vinyl neopentanoate, vinyl propionate, vinyl stearate, vinyl caprate, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, allyl ether, allyl hexanoate, allyl acetate, allyl butyl ether, allyl mercaptan, pentaerythritol allyl ether, allyl methyl carbonate, allyl phenyl ether, allyl heptanoate, allyl butyrate, allyl methyl sulfone, allyl sulfide, tetrahydrofurfuryl acrylate, N,N-dimethylacrylamide, N,N-dimethylacrylamide, isobornyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxyethyl methacrylate. Another type of liquid reactive diluent may include liquid thiol compounds such as 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, mercaptopropionic acid, and mercaptopropionate. The liquid reactive diluent may be present in an amount of 0% to 50%, or 1% to 40%, or 2% to 30%, or 3% to 20%, or 4% to 15%, or 5% to 10% based on the total weight of the reaction mixture.

[0030] The reaction mixture may also contain a non-reactive diluent (e.g., a solvent such as dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N-methylpyrrolidone (NMP), acetone, etc.) to reduce the viscosity. However, this may increase the step of solvent removal during the formation of the polishing layer.

[0031] The reaction mixture may also contain non-reactive components that are desired to be included in the polishing layer. The components may increase functionality such as mechanical reinforcement, porosity, or additional abrasives for polishing. Examples of these components include inorganic particles such as silica, cerium dioxide, titanium dioxide; polymer beads or particles; expandable polymer microspheres, etc.

[0032] An example of a reaction scheme for forming a composition that can be used as an element in a polishing pad as disclosed herein using a free radical generating photoinitiator is as follows: wherein a and b are integers of 2, 3, 4, 5, or 6, provided that at least some of a and b must be 3, 4, 5, or 6 in order to obtain crosslinking, R1 is a polyvalent linking group consistent with the description of molecule (A), and R2 is a polyvalent linking group consistent with the description of molecule (B).

[0033] In the case of using a photo base generator, the following is a representative reaction scheme: wherein a and b are integers of 2, 3, 4, 5, or 6, provided that at least some of a and b must be 3, 4, 5, or 6 in order to obtain crosslinking, R1 is a polyvalent linking group consistent with the description of molecule (A), and R2 is a polyvalent linking group consistent with the description of molecule (B).

[0034] The cured polymer that can be used as a polishing layer in a polishing pad as described herein can have a glass transition temperature (Tg) according to ASTM D5279-21 and selected at the temperature of maximum tanδ, such as -20 °C, or -10 °C to 120 °C, to 100 °C, to 70 °C, to 60 °C, or to 50 °C. The cured polymer that can be used as a polishing layer in a polishing pad as described herein can have a tensile modulus according to ASTM D412, such as 1, 5, or 10 to 700, to 500, or to 400 megapascals (MPa). The cured polymer that can be used as a polishing layer in a polishing pad as described herein can have an elongation at break according to ASTM D412, such as 20%, 50%, 70%, or 100% to 500%, to 450%, to 400%, or to 300%. The cured polymer that can be used as a polishing layer in a polishing pad as described herein can have a toughness according to ASTM D412, such as 1, 2, or 5 to 30, or to 20 MPa. The cured polymer that can be used as a polishing layer in a polishing pad as described herein can have a cutting rate as described herein, such as greater than 0 to 2, to 1.5, to 1 millimeter per hour (mm / h).

[0035] Also provided is a method of manufacturing a chemical mechanical polishing pad as disclosed herein. The method includes providing a photocurable material in a container, selectively curing a portion of the photocurable material by irradiation with radiation of an activation wavelength to form a cured structure, selectively curing an additional portion of the photocurable material by irradiation to further build the cured structure, repeating the selective curing by irradiation until the cured structure has the form of an element of the polishing pad, wherein the photocurable material comprises molecules having two or more functional groups, wherein the functional groups are ethylenically unsaturated groups (at least a portion of which are (meth)acrylate groups) and thiol groups, provided that at least some of these molecules contain three or more functional groups, and wherein the irradiation causes a reaction of the ethylenically unsaturated groups with the thiol groups. The photocurable material in the container can be a liquid. The photocurable material in the container can be flowable under printing conditions. The photocurable material in the container can be spreadable.

[0036] Thus, in one example, as Figure 1 shown, an additive manufacturing apparatus from bottom to top includes a container 1. The container 1 has a portion 3 that is transparent to activation radiation 7. The portion 3 can be located at the bottom of the container 1. The container 1 houses a reaction mixture 10 as described herein (i.e., the reaction mixture comprises a mixture of molecules having two or more functional groups, wherein the functional groups are ethylenically unsaturated groups (at least a portion of which are (meth)acrylate groups) and thiol groups, and the reaction is a reaction of the ethylenically unsaturated groups and the thiol groups). Such a reaction mixture can be initiated by exposure to radiation. The reaction mixture can comprise a photoinitiator that generates free radicals upon exposure to radiation of an activation wavelength. The activation radiation 7 passes through the portion 3 of the container 1 in an imaging manner to photocure a portion of the reaction mixture 10 at or immediately above the bottom of the container 1. Optionally, a layer 4 can be provided above the surface 3. The layer 4 can prevent the photocured polymer from adhering to the portion 3. The layer 4 can be, for example, a liquid immiscible with the reaction mixture or a low surface energy coating. The layer 4 is also transparent to the activation radiation 7. The first layer 11 of the photocured polymer is formed below the build platform 2. The build platform 2 and the first layer 11 are raised, thereby allowing the reaction mixture 10 to flow below the first layer 11. The radiation again passes through the surface 3 in an imaging manner to form a second layer 12 of the photocured polymer. This process is repeated to form additional layers until the desired element (e.g., the polishing layer) of the polishing pad is fully formed.

[0037] In as Figure 2In another example shown, the top-down additive manufacturing apparatus includes a container 1. The container 1 houses a reaction mixture 10 as described herein. A layer of the reaction mixture 10 is disposed above a build platform 2 and is imagewise exposed to radiation 7 to form a first layer 11 of photocured polymer on the build platform 2. The build platform 2 is then lowered, allowing an additional layer of the reaction mixture 10 to cover the first layer 11. A recoat blade 8 can be used to ensure complete coverage of the first layer 11 by the reaction mixture 10. This is particularly useful for viscous reaction mixtures. The reaction mixture is then again imagewise exposed to radiation 7 to form a second layer 12 of photocured polymer on the first layer 11. This process is repeated to form additional layers until the desired polished layer is fully formed.

[0038] The viscosity of the reaction mixture under printing conditions can be from 0.01 Pascal-seconds (Pa·s) to 20 Pa·s, or to 10 Pa·s. The printing conditions can be from room temperature to 200 °C, to 150 °C, to 100 °C, to 80 °C, to 50 °C, but should be below the boiling points and thermal degradation points of the components of the reaction mixture. Room temperature printing conditions can be advantageous for energy efficiency. The reaction mixture can be in liquid form.

[0039] The methods disclosed herein can be used to provide a polished surface having a macrotexture (e.g., grooves, ridges, protrusions, depressions), a microtexture (e.g., pores, lattice structures, network structures), or both. For example, grooves can be formed in the polished surface as long or continuous radially concentric depressions. The grooves can have a depth of, for example, 0.1, 0.2, or 0.3 mm to 1.5, to 1.2, or to 1 mm. The grooves can have a width of, for example, 0.05, 0.1, 0.2 or 0.3 to 1, to 0.8 or to 0.6 mm. Protrusions project above the top surface of the base of the polishing pad. The protrusions can be solid or open cylindrical, cubic, pyramidal, or have an irregular cross-section (e.g., leaf-shaped). The protrusions can have a height of 0.05 or 0.1 to 2, or to 1.5 mm. The protrusions can include an opening in the sidewall. The protrusions can include a polished surface that bulges above the top portion of the polishing layer on a support, wherein there is a gap between the polished surface and the top of the base of the polishing pad.

[0040] The chemical mechanical polishing pad disclosed herein can include a sub-pad on the opposite side of the polished surface of the polishing layer. The polishing layer can be adhered to the sub-pad using an adhesive material after manufacturing the sub-pad. Alternatively, the entire pad can be formed by additive printing that modulates the composition of the photosensitive reaction mixture used to form the sub-pad to provide the desired properties. The sub-pad material can be more compliant than the polishing layer. The sub-pad can include a porous layer. Alternatively, the sub-pad is an open network of interconnected structures.

[0041] Sub-instances of polymeric materials for one or more sub-layers include: polyurethanes, polycarbonates, polysulfones, nylons, epoxies, polyethers, polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates, polyvinyl chlorides, polyvinyl fluorides, polyethylenes, polypropylenes, polybutadienes, polyethyleneimines, polyethersulfones, polyamides, polyetherimides, polyketones, silicones, their copolymers (such as polyether-polyester copolymers), and combinations or blends thereof. The sub-layers can also be formed by additive manufacturing as described herein. The sub-layers can be formed from a reaction mixture as described herein using thiol-ene curing, which reaction mixture is selected to provide better compliance than that found in the polishing layer. The sub-layers can be formed from a reaction mixture having polymeric precursors (monomers, oligomers, or mixtures thereof) having ethylenically unsaturated groups and thiol groups as described herein. If the sub-layers are formed by additive manufacturing, the sub-layers and the polishing layer can be formed sequentially in reaction vessel 1, where the reaction mixture is changed when moving from one layer to another. For example, the polishing layer can be formed as described above. When forming the polishing layer, reaction mixture 10 can be removed from vessel 1 and a new reaction mixture added. The same exposure process can be carried out to form additional layers on the polishing layer. Alternatively, the sub-layers can be formed first and then the polishing layer can be formed on the sub-layers as a substrate by additive manufacturing. For example, the sub-layers can be formed by additive manufacturing and then the process of forming the polishing layer can be carried out on the sub-layers on the build platform. As another example, a preformed sub-layer can be provided on the build platform and the polishing layer can be formed on the sub-layer by additive manufacturing as described herein.

[0042] A chemical mechanical polishing pad can include a window in the polishing layer. The window is formed from a material that is transparent to the wavelengths used in endpoint detection during the use of the polishing pad. Additive manufacturing can also be used to form a chemical mechanical polishing pad that includes a window. For example, the polishing layer from the reaction mixture can be formed around window material placed on the build platform. As another example, the polishing layer can be formed with an opening and the window can be placed in the opening at a later time. As yet another alternative, the window itself can be formed by additive manufacturing. For example, the window can first be formed by additive manufacturing in vessel 1 of the apparatus and then the polishing layer can be formed around the window by additive manufacturing. As another example, the polishing layer can be formed by additive manufacturing as disclosed herein with a gap for the window and then the window can be formed by additive manufacturing in the gap. The window material can be, for example, polyurethane, acrylic polymer, cycloolefin copolymer (e.g., TOPAS 8007, etc.). In pads where the polishing layer, the sub-layer, or both are also polyurethane, it may be helpful to use polyurethane material. A specific group of examples of aliphatic polyurethanes for the window can be found, for example, in U.S. Patent 10,293,456. Examples

[0043] In a prophetic example, the reaction mixture can contain Component 1 - a small molecule (A) diallyl isophthalate (DAIP) or 2-hydroxyethyl acrylate (HEA); Component 2 - an oligomeric molecule. A2x is a low molecular weight diol-based prepolymer capped with MDI and then reacted with HEA. A2y is from a PTMEG-based prepolymer capped with TDI and then reacted with HEA; Component 3 - a molecule (B) compound having more than 2 thiol functional groups to provide crosslinking, where PTMP is pentaerythritol tetra(3-mercaptopropionate); Component 4 - a dithiol functional compound of molecule (B) to provide chain extension, where GDMP is ethylene glycol bis(3-mercaptopropionate), and HDT is 1,6-hexanedithiol; and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator at 1 wt% based on the total weight of the reaction mixture. The amounts and identities of Components 1-4 are shown in Table 1. The weight percentages are based on the total weight of the reaction mixture. All examples were prepared with a molar ratio of ethylenically unsaturated groups to thiol groups of 1:1. Table 1

[0044] The present disclosure further encompasses the following aspects.

[0045] Aspect 1: A chemical mechanical polishing pad comprising a photocured polymer, wherein the photocured polymer is a photoinitiated reaction product of a photocurable material comprising molecules having two or more functional groups, wherein the functional groups include thiol groups and ethylenically unsaturated groups, provided that at least a portion of the molecules have the ethylenically unsaturated group which is a (meth)acrylate group, wherein the (meth)acrylate groups account for less than 70 mole percent of the total (meth)acrylate, thiol, and ethylenically unsaturated functional groups, and wherein photocuring comprises the reaction of the thiol groups with the ethylenically unsaturated groups, provided that at least some of the molecules contain three or more functional groups.

[0046] Aspect 2. The chemical mechanical polishing pad according to Aspect 1, wherein the molecules having two or more functional groups comprise a first molecule having two or more ethylenically unsaturated groups and a second molecule having two or more thiol groups, provided that at least a portion of the first molecules contain at least three or more ethylenically unsaturated groups or at least a portion of the second molecules contain three or more thiol groups.

[0047] Aspect 3. The chemical mechanical polishing pad according to Aspect 1, wherein the molecules include heterotelechelic molecules having (meth)acrylate groups and thiol groups.

[0048] Aspect 4. The chemical mechanical polishing pad according to any one of the preceding aspects, wherein the reaction mixture comprises a photoinitiator that generates free radicals when exposed to radiation of an activation wavelength.

[0049] Aspect 5. The chemical mechanical polishing pad according to any one of the preceding aspects, wherein the reaction mixture comprises a photoinitiator that generates a base when exposed to radiation of an activation wavelength.

[0050] Aspect 6. The method according to aspect 2, wherein the first molecule comprises a reaction product of a polyisocyanate and a (meth)acrylate functional capping agent, and the polyisocyanate comprises an oligomer, a polyfunctional isocyanate monomer, or a mixture thereof.

[0051] Aspect 7. The chemical mechanical polishing pad according to aspect 2, wherein the first molecule comprises an oligomer comprising (meth)acrylate groups, and the second molecule comprises one or more of an alkyl polyfunctional thiol, an aromatic group polyfunctional thiol, and a thiol-capped oligomer having two or more thiol groups.

[0052] Aspect 8. The chemical mechanical polishing pad according to any one of the preceding aspects, which comprises abrasive particles in an amount less than 0.05 weight percent based on the total weight of the polishing pad.

[0053] Aspect 9. The chemical mechanical polishing pad according to any one of the preceding aspects, wherein the (meth)acrylate groups account for less than 70 mole percent of the functional groups.

[0054] Aspect 10. The polishing pad according to any one of the preceding aspects, the polishing pad being formed by a method comprising: providing a photocurable material in a container, selectively curing a portion of the photocurable material by irradiation to form a cured structure, selectively curing an additional portion of the photocurable material by irradiation to further build the cured structure, and repeating the selective curing by irradiation until the cured structure has the form of an element of the polishing pad.

[0055] Aspect 11. The polishing pad according to aspect 10, wherein the molecules having two or more functional groups comprise a first molecule having two or more (meth)acrylate groups and a second molecule having two or more thiol groups, wherein the first molecule is a monomer, an oligomer, or a mixture of two or more thereof, and the second molecule is a monomer, an oligomer, or a mixture thereof.

[0056] All ranges disclosed herein include the endpoints, and the endpoints can be combined independently of each other (e.g., a range of "up to 25 wt.%, or more specifically 5 wt.% to 20 wt.%" includes the endpoints and all intermediate values within the range of "5 wt.% to 25 wt.%", etc.). In addition, the upper and lower limits can be combined to form a range (e.g., "at least 1 or at least 2 weight percentages" and "up to 10 or 5 weight percentages" can be combined into a range of "1 to 10 weight percentages", or "1 to 5 weight percentages", or "2 to 10 weight percentages", or "2 to 5 weight percentages").

[0057] The present disclosure can alternatively include any suitable components disclosed herein, consist of any suitable components disclosed herein, or consist essentially of any suitable components disclosed herein. The present disclosure can additionally or alternatively be formulated so as to be free of, or substantially free of, any components, materials, ingredients, adjuvants or substances that are used in prior art compositions or that are otherwise not necessary to achieve the functions and / or objectives of the present disclosure.

[0058] All cited patents, patent applications and other references are incorporated herein by reference in their entirety. However, if a term in the present application conflicts or contradicts a term in the incorporated reference, then the term from the present application prevails over the conflicting term from the incorporated reference.

[0059] Unless stated to the contrary herein, all test standards are the latest standards in effect as of the filing date of the present application or, if priority is claimed, as of the filing date of the earliest priority application in which the test standard appears.

Claims

1. A chemical mechanical polishing pad comprising a photocured polymer, wherein the photocured polymer is a photoinitiated reaction product of a photocurable material comprising molecules having two or more functional groups, wherein the functional groups include thiol groups and ethylenically unsaturated groups, provided that at least a portion of the molecules have the ethylenically unsaturated groups, the ethylenically unsaturated groups are (meth)acrylate groups, wherein the (meth)acrylate groups account for less than 70 mole percent of the total (meth)acrylate, thiol and ethylenically unsaturated functional groups, and wherein the photocuring comprises a reaction of the thiol groups with the ethylenically unsaturated groups, provided that at least some of the molecules contain three or more functional groups.

2. The chemical mechanical polishing pad according to claim 1, wherein The molecules having two or more functional groups include first molecules having two or more ethylenically unsaturated groups and second molecules having two or more thiol groups, provided that at least a portion of the first molecules include at least three or more ethylenically unsaturated groups or at least a portion of the second molecules include three or more thiol groups.

3. The chemical mechanical polishing pad according to claim 1, wherein: The molecules include heterotelechelic molecules having a (meth)acrylate group and a thiol group.

4. The chemical mechanical polishing pad according to claim 1, wherein: The reaction mixture includes a photoinitiator that generates free radicals when exposed to radiation of an activating wavelength.

5. The chemical mechanical polishing pad according to claim 1, wherein: The reaction mixture comprises a photoinitiator that generates a base when exposed to radiation of an activating wavelength.

6. The method of claim 2, wherein: The first molecule comprises the reaction product of a polyisocyanate comprising an oligomer, a polyfunctional isocyanate monomer, or a mixture thereof and a (meth)acrylate functional capping agent.

7. The chemical mechanical polishing pad according to claim 2, wherein: The first molecule includes an oligomer containing a (meth)acrylate group, and the second molecule includes one or more of an alkyl multifunctional thiol, an aromatic multifunctional thiol, a multifunctional mercaptopropionate, a multifunctional thioglycolate, a multifunctional thioglycolate, a thiol-terminated oligomer having two or more thiol groups.

8. The chemical mechanical polishing pad according to claim 1, wherein: The (meth)acrylate groups account for less than 55 mole percent of the total (meth)acrylate, thiol, and ethylenically unsaturated functional groups.

9. The polishing pad of claim 1, wherein the polishing pad is formed by a method comprising: A photocurable material is provided in a container, a portion of the photocurable material is selectively cured by irradiation to form a cured structure, another portion of the photocurable material is selectively cured by irradiation to further build up the cured structure, and the selective curing by irradiation is repeated until the cured structure has the form of an element of a polishing pad.

10. The polishing pad according to claim 9, wherein: The photocurable material provided includes the following items: i) a monomer or oligomer or a mixture thereof having two or more ethylenically unsaturated groups, wherein at least a portion of the ethylenically unsaturated groups are (meth)acrylate groups, and ii) a monomer or oligomer having two or more thiol groups or a mixture thereof.

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