Chemical mechanical polishing pad

Abstract

To provide a chemical mechanical polishing pad.SOLUTION: A chemical mechanical polishing pad comprises a polishing layer containing a photocured polymer. The photocured polymer is the photoinitiated reaction product of a photocurable material that is free of molecules comprising (meth)acrylate groups. The photocurable material comprises molecules having two or more functional groups. The functional groups include a thiol group and ethylenically unsaturated group other than a (meth)acrylate group. The photocure includes reaction of the thiol group with the ethylenically unsaturated group. At least some of the molecules comprise three or more functional groups. The chemical mechanical polishing pad can be made by additive manufacturing using stereolithography.SELECTED DRAWING: None

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 manufacture of integrated circuits and other electronic devices, a plurality of layers of conductive, semiconductive, and dielectric materials are deposited on and removed from the surface of a semiconductor wafer. Thin layers of conductive, semiconductive, and dielectric materials can be deposited using a number of deposition techniques. Common deposition techniques in current wafer processing include, among others, physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating. Common removal techniques include, among others, wet and dry isotropic etching and anisotropic etching.

[0003] As layers of material are sequentially deposited and removed, the top surface of the wafer becomes non-flat. Since subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, it is necessary to planarize the wafer. Planarization is useful for removing undesirable surface shapes and surface defects such as rough surfaces, agglomerated materials, damage to the crystal lattice, scratches, and contaminated layers or materials.

[0004] Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize or polish workpieces such as semiconductor wafers. In conventional CMP, a wafer carrier, or polishing head, is attached to a carrier assembly. The polishing head holds the wafer and positions the wafer to contact the polishing layer of a polishing pad attached to 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. To perform the polishing, the polishing pad and the wafer typically rotate relative to each other. When the polishing pad rotates under the wafer, the wafer typically sweeps an annular polishing track, or polishing region, where the surface of the wafer directly faces the polishing layer. The wafer surface is polished and planarized by the chemical and mechanical action of the polishing layer and polishing medium on the surface.

[0005] Additive manufacturing of a polishing layer having a porous or three-dimensional pattern on a polishing surface has been proposed. For example, one approach uses a droplet jet 3D printing platform. This requires a relatively low viscosity material that is then photocured. The applied material is then photocured. Examples of photocurable systems suitable for use in such droplet jet 3D printing may include acrylates, methacrylates, or epoxides as reactive groups for photocuring. See, for example, (Patent Document 1), (Patent Document 2), (Patent Document 3), (Patent Document 4), and (Patent Document 5). These chemical substances generally undergo chain growth photocuring. This can result in materials with limited toughness and elongation properties that may lead to an undesirably high wear rate.

[0006] Another approach uses vat polymerization, including digital light processes, scanning lasers, or stereolithography approaches to additive manufacturing. See, for example, (Patent Document 6). Examples of photocurable systems useful in this method include compositions of acrylate block isocyanate monomers and acrylate monomers that can be photopolymerized via acrylate or methacrylate groups. See, for example, (Patent Document 7).

[0007] It is desirable to obtain a chemical mechanical polishing pad that can be manufactured by additive manufacturing and has excellent toughness, elongation, and wear rate (e.g., the toughness, elongation, and wear rate are comparable to or better than those of commonly used chemical mechanical polishing pads).

[0008] Also, it is desirable to obtain an additive manufacturing process for manufacturing a polishing layer for a chemical mechanical polishing pad that enables better toughness, better elongation, wear rate, and higher flexibility in adjusting the mechanical properties of the polishing layer. In particular, it is desirable to obtain a chemical mechanical polishing pad that can be manufactured by additive manufacturing and has excellent toughness, excellent elongation, and excellent wear rate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

[0010] Disclosed herein is a chemical mechanical polishing pad comprising a photocurable polymer, wherein the photocurable polymer is a photoinitiation reaction product of a photocurable material that does not contain a molecule containing a (meth)acrylate group, the photocurable material contains a molecule having two or more functional groups, the functional groups contain a thiol group and an ethylenically unsaturated group other than a (meth)acrylate group, the photocuring includes a reaction between the thiol group and the ethylenically unsaturated group, and at least some of the molecules contain three or more functional groups.

[0011] Also disclosed is the above polishing pad formed from a method including preparing 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. For example, the element of the polishing pad may be a polishing layer or a sub-pad layer, or both. [Brief Description of the Drawings]

[0012]

Figure 1

Figure 2

[0013] The disclosed chemical mechanical polishing pad includes a photocurable polymer having excellent elongation, toughness, and wear rate. Photocuring is achieved by reacting ethylenically unsaturated groups with thiol groups to form thioether (or sulfide) bonds in the polymer. The photocurable polymer can form a polishing layer, a sub-pad layer, or both. The polishing layer or sub-pad layer formed in this way may not contain polishing particles. The polishing layer can contain less than 0.1% by volume, less than 0.09% by volume, less than 0.08% by volume, less than 0.07% by volume, less than 0.06% by volume, less than 0.05% by volume, less than 0.04% by volume, less than 0.03% by volume, less than 0.02% by volume, or less than 0.01% by volume of polishing particles based on the total volume of the polishing layer.

[0014] The reaction mixture used to form the photocurable polymer is particularly suitable for additive manufacturing, including stereolithography or vat polymerization. The reaction mixture does not contain molecules containing (meth)acrylate groups. As used herein, (meth)acrylate includes acrylate, methacrylate, or a mixture containing both acrylate and methacrylate.

[0015] The photocurable polymer can be formed by the reaction of a molecule having two or more functional groups, wherein the functional groups are ethylenically unsaturated groups and thiol groups. For example, the molecule having two or more functional groups can contain both at least one ethylenically unsaturated group and at least one thiol group. This molecule can be regarded as an AB-type molecule. As another example, examples of the molecule having two or more functional groups include 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), or in combination with molecule (B), or in combination with both molecule (A) and molecule (B). To crosslink, at least a part 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 crosslink density can be controlled by the relative amount of the bifunctional molecule (i.e., a molecule having two ethylenically unsaturated groups or a molecule having two thiol groups) with respect to the more highly functional molecule (e.g., a molecule having more than two ethylenically unsaturated groups or a molecule having more than two thiol groups).

[0016] Molecule (A) can include an oligomer (also called a prepolymer), a monomer, or a mixture thereof. Molecule (B) can include an oligomer (also called a prepolymer), a monomer, or a mixture thereof. By selecting the structures of the oligomer and monomer and their relative amounts, the properties of the photocurable polymer can be adjusted. For example, a rigid polyfunctional alkene used as molecule (A) can improve hardness or toughness. When an oligomer molecule (A) is used, it can be useful for controlling the viscosity while avoiding the use of a solvent that may need to be removed after curing when mixed with a monomer molecule (A).

[0017] The monomer molecule (A) may be, for example, 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, 2,2'-diallylbisphenol A, a polyfunctional acrylamide such as N,N'-methylenebis(acrylamide), or a mixture thereof. These monomer molecules (A) can be used in a mixture with oligomer molecules (A).

[0018] Advantageously, the polyfunctional isocyanate can react with a molecule containing ethylenic unsaturation and at least one nucleophilic functional group (such as amine, hydroxy, thiol, etc.) (i.e., an end-capping agent) to form a molecule A containing urea, urethane, or thiourea. Examples of the capping agent include allylphenol (such as 2-allylphenol, 4-allylphenol, eugenol, isoeugenol), alkylene glycol allyl ether (such as ethylene glycol allyl ether), alkylene glycol monovinyl ether (such as ethylene glycol monovinyl ether, butanediol monovinyl ether), allyl alcohol (such as 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, a hydroxynorbornene compound such as 5-norbornene-2-methanol, or a mixture thereof.

[0019] The ethylenic unsaturation in molecule (A) or molecule (AB) can include, for example, a vinyl group, a vinyl ether group, an allyl group, an allyl ether, an allyl ester, maleimide, norbornene. Allyl, allyl ether, and allyl ester can provide an excellent balance of storage stability and photoreactivity. As used herein, an allyl group is the group -CH 2 -CH=CH 2 which means. Monosubstituted alkenes react rapidly with thiol groups, while disubstituted alkenes such as crotyl alcohol and trans-3-hexen-1-ol react at a slower rate. The ethylenic unsaturation is preferably not an acrylate group or an acrylic acid group.

[0020] For example, the following reaction scheme can be used to prepare molecule (A):

Chemical formula

[0021] 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 arylalkyl, or can contain carbon and heteroatoms, such as nitrogen. For example, R 1 includes methylenediphenyl, isophorone, 2,4-toluene, 2,6-toluene, hexamethyl, or a uretdione skeleton formed from the dimerization of two isocyanate groups. Alternatively, R 1may be an oligomeric group containing two or more repeating units, three or more and up to 150 repeating units. The repeating units may be, for example, alkylene oxides such as ethylene oxide, propylene oxide, or tetramethylene oxide; lactones such as caprolactone; hydrocarbons and saturated and unsaturated forms of diene units 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 contain an aliphatic group or an aromatic group or both. For example, R 2 may be a divalent alkyl; a divalent aryl; a divalent arylalkyl such as benzyl, phenyl, alkyl; or an alicyclic group such as cyclohexyl. R 2 initially is provided by an end-capping agent of the formula [Y] b -R 2 -[C=C] c Typically, the end-capping agent may contain at least one nucleophilic group (e.g., OH, NH 2 , or SH) and an ethylenically unsaturated group.

[0022] For example, to form the monomer (A), a polyisocyanate monomer (e.g., a diisocyanate monomer) can be reacted to form a monomer having at least two ethylenically unsaturated 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; para-phenylene diisocyanate; xylylene diisocyanate; isophorone diisocyanate; hexamethylene diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; cyclohexane diisocyanate; and mixtures thereof, etc.

[0023] As another example, the molecule (A) may include an oligomer of a urethane or urea prepolymer having two or more ethylenically unsaturated groups; a polysiloxane such as a polydimethylsiloxane having two or more ethylenically unsaturated groups; or a polyalkylene glycol having two or more ethylenically unsaturated groups. When the chemistry of urethane or urea is desired, such a molecule (A) oligomer can be derived from an isocyanate prepolymer such as a polyalkylene glycol end-capped with an isocyanate group or a small molecule diisocyanate. Examples of diisocyanates used directly or as prepolymer end-caps include the following. The isocyanate-terminated urethane prepolymer can have 2 to 30% by weight of unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the polyfunctional isocyanate-terminated urethane prepolymer can be selected from the group consisting of diols, polyols, polyol diols, their copolymers, and mixtures thereof. For example, the prepolymer polyol can be a polyether polyol (e.g., poly(oxytetramethylene) glycol, poly(oxypropylene) glycol, and mixtures thereof); a polycarbonate polyol; a polyester polyol; a polycaprolactone polyol; mixtures thereof; and mixtures thereof with one or more low molecular weight polyols selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 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 polyol can be selected from the group consisting of polytetramethylene ether glycol (PTMEG), ester-based polyols (such as ethylene adipate, butylene adipate, etc.), polypropylene ether glycol (PPG), polycaprolactone polyol, their copolymers, and mixtures thereof.For example, the prepolymer polyol can be selected from the group consisting of PTMEG and PPG. Examples of commercially available PTMEG-based isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene® prepolymers (available from Lanxess, such as LF800A, LF900A, LF910A, LF930A, LF931A, LF939A, LF950A, LF952A, LF600D, LF601D, LF650D, LF667, LF700D, LF750D, LF751D, LF752D, LF753D, and L325); Andur® prepolymers (available from Anderson Development Company, such as 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF). Non-TDI-based isocyanate-terminated urethane prepolymers can also be used. For example, isocyanate-terminated urethane prepolymers include those formed by the reaction of 4,4'-diphenylmethane diisocyanate (MDI) with a polyol such as polytetramethylene glycol (PTMEG), or a diol such as 1,4-butanediol (BDO), and are acceptable. Modified MDI products such as polycarbodiimide-modified MDI (e.g., Isonate 143L), and pseudo prepolymers of MDI reacted with low molecular weight diols such as 1,2-propylene glycol, 1,3-propylene glycol, 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, tripropylene glycol, or combinations thereof (e.g., Isonate 181) may be used.Examples of commercially available MDI, polymeric MDI, and MDI prepolymers include ISONATE™ 143L, ISONATE™ 143LP, ISONATE™ 181, ISONATE™ 240, ISONATE™ M143, ISONATE™ M320, ISONATE™ M340, ISONATE™ 342, ISOBIND™ 1002, ISOBIND™ 1013, ISOBIND™ 1014, ISOBIND™ 1088, ISOBIND™ 1100, ISOBIND™ 1100S, ISOBIND™ 1200R, PAPI™ 135, PAPI™ 135C, PAPI™ 17, PAPI™ 20, PAPI™ 27, PAPI™ 580N, PAPI™ 6146, PAPI™ 901, PAPI™ 94, POLYMERIC MDI 199, POLYMERIC MDI 253, VORANATE™ M200, VORANATE™ M220, VORANATE™ 229, VORANATE™ 229N, VORANATE™ M230, VORANATE™ M2940, VORANATE™ M580, VORANATE™ M595, VORANATE™ M600, VORANATE™ M647, VORANATE™ SD100, VORANATE™ SD100 IF from The Dow Chemical Company. The prepolymer can contain at least two isocyanate groups. Some commercially available products may contain an undisclosed mixture of molecules having two isocyanate groups and molecules having more than two isocyanate groups. An example of a commercially available prepolymer that is thought to have more than two isocyanates per molecule is Desmodur N-3400 from Covestro AG.

[0024] Examples of the 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 - diyl dimethanethiol), mercaptopropionic acid esters (e.g., ethylene glycol bis(3 - mercaptopropionate), trimethylolpropane tris(3 - mercaptopropionate), pentaerythritol tetrakis(3 - mercaptopropionate), tris[2 - (3 - mercaptopropionyloxy)ethyl] isocyanurate), thioglycolate esters (e.g., 1,4 - butanediol bis(thioglycolate)), mercaptoacetate esters (e.g., pentaerythritol tetrakis(mercaptoacetate)), aromatic dithiols, arylalkyls (e.g., aryls having alkylthiol pendant groups) (e.g., 1,3 - benzenedimethanethiol, 1,4 - benzenedimethanethiol, 4,4’ - bis(mercaptomethyl)biphenyl) and thiol - terminated oligomers (e.g., poly(ethylene glycol) dithiol, poly(dimethylsiloxane) dithiol, or urethane or urea oligomers).

[0025] Examples of AB - type molecules include allyl mercaptan, and oligomers or prepolymers capped with both an ethylenically unsaturated group and a thiol group. The oligomers capped with both an ethylenically unsaturated group and a thiol group can be prepared as described above, providing one capping group containing ethylenic unsaturation and one capping group having a thiol functional group.

[0026] The photocurable polymer can be formed from a reaction mixture containing (i) one or more molecules (A) and one or more molecules (B), or (ii) AB - type molecules (optionally also containing molecule (A), molecule (B), or both). This reaction mixture does not contain molecules containing (meth)acrylate groups.

[0027] The reaction mixture preferably contains a photoinitiator. Upon exposure to activating radiation, a reaction occurs between the thiol groups and the ethylenically unsaturated groups. For example, the photoinitiator absorbs radiation of an activating wavelength (e.g., ultraviolet light with a wavelength of 200 - 500, 340 - 390 (e.g., 385 nanometers (nm))). For example, when irradiated, the photoinitiator can generate radicals that initiate the reaction between the ethylenically unsaturated groups and the thiol groups, and can form a photocurable polymer. 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. When the reactivity of the ethylenically unsaturated groups is high, the free radicals may also initiate side reactions of the ethylenically unsaturated groups with other ethylenically unsaturated groups. As another example, when irradiated, the photoinitiator can generate a base that can deprotonate the thiol groups and react the thiols with the ethylenically unsaturated groups. This approach can avoid side reactions between the ethylenically unsaturated groups, but requires the ethylenically unsaturated groups to be electron - deficient due to the adjacent chemical structure on the molecule having the ethylenically unsaturated groups. Examples of electron - deficient alkenes capable of base - catalyzed coupling reactions with thiol groups include, but are not limited to, vinylsilanes, maleimides, and acrylamides. Examples of photo - base generators include 1,2 - dicyclohexyl - 4,4,5,5 - tetramethylbiguanidium n - butyltriphenylborate (e.g., Fujifilm WPBG - 300), (Z)-{[bis(dimethylamino)methylidene]amino}-N - cyclohexyl(cyclohexylamino)methaniminium tetrakis(3 - fluorophenyl)borate (e.g., Fujifilm WPBG - 345), (e.g., 1,2 - diisopropyl - 3 - [bis(dimethylamino)methylidene]guanidium 2 - (3 - benzoylphenyl)propionate (e.g., Fujifilm WPBG - 266), 9 - anthrylmethyl N,N - diethylcarbamate (e.g., Fujifilm WPBG - 018).When the photo-base generator does not absorb at the applicable wavelength, for example, thioxanthone species or other photo-base generators that absorb at the target wavelength can be used as photosensitizers. When the photo-base generator generates radicals in addition to bases, radical inhibitors such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) can be used to selectively suppress radical side reactions while enabling base-catalyzed reactions. The amount of the photoinitiator in the reaction mixture may be from 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt% to a maximum of 5 wt%, a maximum of 4 wt%, a maximum of 3 wt%, a maximum of 2 wt%, or a maximum of 1.5 wt% based on the total weight of the reaction mixture.

[0028] (For example, the ethylenically unsaturated group of molecule (A)) to the molar ratio of the thiol group (for example, of molecule (B)) may 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 may be about 1:1.

[0029] The reaction mixture can optionally contain a UV absorber in addition to the photoinitiator. The UV absorber can facilitate the adjustment of the light transmission (i.e., the curing depth) of the reaction mixture. The UV absorber can absorb light at a wavelength (e.g., 385 nm) used in additive manufacturing devices, for example. Examples of UV absorbers include 2,2'-dihydroxy-4,4'-dimethoxybenzophenone (DHDMBP) and avobenzone. The amount of the UV absorber may be greater than 0, at least 0.1 wt%, at least 0.2 wt%, at least 0.3 wt%, at least 0.4 wt%, or at least 0.5 wt% to a maximum of 10 wt%, a maximum of 5 wt%, or a maximum of 2 wt% based on the total weight of the reaction mixture.

[0030] The reaction mixture may optionally contain a liquid reactive diluent containing a group (such as an ethylenically unsaturated group or a thiol) that reacts with other components of the reaction mixture. This 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 formation of the polishing layer. Such removal may cause shrinkage. Examples of the liquid reactive diluent include butanediol monovinyl ether, ethylene glycol vinyl ether, N-vinyl pyrrolidone, vinyl acetate, 1-vinyl imidazole, 2-vinyl pyrazine, vinyl pivalate, vinyl propionate, vinyl stearate, vinyl decanoate, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, allyl ether, allyl hexanoate, allyl acetate, allyl butyl ether, pentaerythritol allyl ether, allyl methyl carbonate, allyl phenyl ether, allyl heptanoate, allyl butyrate, allyl methyl sulfone, and allyl sulfide. Also, liquid thiol compounds such as mercaptopropionic acid and monofunctional mercaptopropionate esters can be mentioned as examples. The liquid reactive diluent can 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.

[0031] The reaction mixture may also contain a non-reactive diluent (such as a solvent like dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N-methyl pyrrolidone (NMP), acetone, etc.) to reduce the viscosity. However, this may add a solvent removal step to the process of forming the polishing layer.

[0032] The reaction mixture may also contain non-reactive components that are desired to be included in the polishing layer. This component can impart functionalities such as mechanical reinforcement and porosity. Examples of these include polymer beads or particles containing expandable polymer microspheres, etc.

[0033] An example of a reaction scheme for forming a composition useful in a polishing pad (e.g., as a polishing layer) is as follows. This reaction scheme shows the dominant reaction when ethylenically unsaturated groups that are not strongly electron-deficient (e.g., allyl, vinyl, vinyl ether) react using a photoinitiator that generates free radicals [Chemical formula] (wherein a and b are integers of 2, 3, 4, 5, or 6, but at least a part of a and b must be 3, 4, 5, or 6 in order to obtain crosslinking, R1 is a polyvalent linking group that conforms to the description of molecule (A), and R2 is a polyvalent linking group that conforms to the description of molecule (B)).

[0034] However, when the ethylenically unsaturated group is electron-deficient (e.g., maleimide or acrylamide), the reaction may include competing homopolymerization of the ethylenically unsaturated monomers as follows: [Chemical formula] (wherein a and b are integers of 2, 3, 4, 5, or 6, but at least a part of a and b must be 3, 4, 5, or 6 in order to obtain crosslinking, R1 is a polyvalent linking group that conforms to the description of molecule (A), and R2 is a polyvalent linking group that conforms to the description of molecule (B)).

[0035] When a photo-base generator is used, a representative reaction scheme is as follows: [Chemical formula] (wherein a and b are integers of 2, 3, 4, 5, or 6, but at least a part of a and b must be 3, 4, 5, or 6 in order to obtain crosslinking, R1 is a polyvalent linking group that conforms to the description of molecule (A), and R2 is a polyvalent linking group that conforms to the description of molecule (B)).

[0036] Examples of specific reaction schemes are [Chemical formula] is.

[0037] The cured polymer described herein that can be used as the polishing layer of a polishing pad has a glass transition temperature (T g ) that is selected from the temperature of the maximum tanδ from, for example, -20 °C or -10 °C to a maximum of 120 °C, a maximum of 100 °C, a maximum of 70 °C, a maximum of 60 °C, or a maximum of 50 °C, in accordance with ASTM D5279-21. The cured polymer described herein that can be used as the polishing layer of a polishing pad can have a tensile modulus of, for example, from 1 megapascal, from 5 megapascals, or from 10 megapascals to a maximum of 700 megapascals, a maximum of 500 megapascals, or a maximum of 400 megapascals (MPa) in accordance with ASTM D412-05. The cured polymer described herein that can be used as the polishing layer of a polishing pad can have an elongation in accordance with ASTM D412 of, for example, from 20%, 50%, 70%, or 100% to a maximum of 500%, a maximum of 450%, a maximum of 400%, or a maximum of 300%. The cured polymer described herein that can be used as the polishing layer of a polishing pad can have toughness in accordance with ASTM D412 of, for example, from 1 MPa, 2 MPa, or 5 MPa to a maximum of 30 MPa or a maximum of 20 MPa. The cured polymer described herein that can be used as the polishing layer of a polishing pad can have a cut rate of, for example, greater than 0 to a maximum of 2 millimeters per hour, a maximum of 1.5 millimeters per hour, a maximum of 1 millimeter per hour (mm / h).

[0038] Also provided is a method of manufacturing a chemical mechanical polishing pad disclosed herein. The method includes preparing 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, further constructing a cured structure by selectively curing an additional portion of the photocurable material by irradiation, repeating selective curing by irradiation until the cured structure has the form of an element of the polishing pad, wherein the photocurable material includes a molecule having two or more functional groups, the functional groups being ethylenically unsaturated groups and thiol groups, the photocurable material does not include (meth)acrylate groups, at least a portion of the molecule includes three or more functional groups, and the ethylenically unsaturated groups and thiol groups react upon irradiation. The photocurable material in the container can be liquid. The photocurable material in the container can have fluidity under printing conditions. The photocurable material in the container can be spreadable.

[0039] Thus, in one example, as shown in FIG. 1, a bottom-up additive manufacturing apparatus includes a container 1. The container 1 has a portion 3 that is transparent to the activating radiation 7. The portion 3 can be located at the bottom of the container 1. The container 1 contains the reaction mixture 10 described herein (i.e., the reaction mixture contains a mixture of molecules having two or more functional groups, which functional groups are ethylenically unsaturated groups and thiol groups, and the reaction is a reaction between an ethylenically unsaturated group and a thiol group). This reaction mixture can be initiated by exposure to radiation. The reaction mixture can include a photoinitiator that generates free radicals upon exposure to radiation of an activation wavelength. The activating radiation 7 passes through the portion 3 of the container 1 and cures a portion of the reaction mixture 10 that is at or just above the bottom of the container 1. Optionally, a layer 4 may be provided on the surface 3. The layer 4 can prevent the adhesion of the photocurable polymer to the layer 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 activating radiation 7. A first layer 11 of photocurable polymer is formed under the build platform 2. The build platform 2 and the first layer 11 are raised such that the reaction mixture 10 flows under the first layer 11. The radiation again passes through the surface 3 and forms a second layer 12 of photocurable polymer. This is repeated until the desired elements (e.g., a polishing layer) of the polishing pad are fully formed, forming additional layers.

[0040] In another example shown in FIG. 2, the top-down additive manufacturing apparatus includes a container 1. The container 1 contains the reaction mixture 10 described herein. A layer of the reaction mixture 10 is supplied onto the build platform 2 and is imagewise exposed to radiation 7 to form a first layer 11 of photocurable polymer on the build platform 2. Then, the build platform 2 is lowered and an additional layer of the reaction mixture 10 can cover the first layer 11. A recoating blade 8 may be used to ensure complete coverage of the first layer 11 by the reaction mixture 10. This is particularly useful for viscous reaction mixtures. Thereafter, the reaction mixture is again imagewise exposed to radiation 7 to form a second layer 12 of photocurable polymer on the first layer 11. This is repeated until the desired elements (e.g., the polishing layer) of the polishing pad are fully formed, forming additional layers.

[0041] The viscosity of the reaction mixture under printing conditions can be from 0.01 Pascal-seconds (Pa-s) up to a maximum of 20 Pa-s, or up to a maximum of 10 Pa-s. The printing conditions can be from room temperature up to a maximum of 200 °C, 150 °C, 100 °C, 80 °C, 50 °C, but need to be lower than the boiling point and thermal decomposition point of the components of the reaction mixture. For energy efficiency, printing conditions at room temperature may be advantageous. The reaction mixture can be in liquid form.

[0042] The methods disclosed herein can be used to provide a polishing surface having macrotexture (e.g., grooves, ridges, protrusions, depressions), microtexture (e.g., pores, lattice structures, network structures), or both. For example, the grooves can be formed as long or continuous radially concentric depressions from the polishing surface. The grooves can have a depth, for example, from 0.1 mm, 0.2 mm, or 0.3 mm up to a maximum of 1.5 mm, 1.2 mm, or 1 mm. The grooves can have a width, for example, from 0.05 mm, 0.1 mm, 0.2 mm, or 0.3 mm up to a maximum of 1 mm, 0.8 mm, or 0.6 mm. The protrusions project above the base upper surface of the polishing pad. They can be non-hollow or hollow cylindrical, cubic, pyramidal, or of irregular cross-section (e.g., lobe-shaped). The protrusions can have a height from 0.05 mm or 0.1 mm up to a maximum of 2 mm or 1.5 mm. The protrusions can include openings in the side walls. The protrusions can include a polished surface raised above the upper portion of a polishing layer on a support having a gap between the polished surface and the base upper surface of the polishing pad.

[0043] The chemical mechanical polishing pads disclosed herein can include a sub-pad located on the opposite side of the polishing surface of the polishing layer. The polishing layer can be adhered to the sub-pad after manufacturing the sub-pad using an adhesive material. Alternatively, the composition of the photosensitive reaction mixture used to form the sub-pad can be adjusted to obtain desired properties, and the entire pad can be formed by additional printing. 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 polymer structures.

[0044] Examples of polymer materials for the sub-pad layer include polyurethane, polycarbonate, polysulfone, nylon, epoxy resin, polyether, polyester, polystyrene, acrylic polymer, polymethyl methacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, silicone, their copolymers (such as polyether-polyester copolymers), and combinations or blends thereof. The sub-pad can be formed using thiol-ene curing from the reaction mixtures described herein that are selected to provide higher compliance than that found in the polishing layer. The sub-pad can be formed from a reaction mixture comprising a polymer precursor (monomer, oligomer, or mixture thereof) having ethylenically unsaturated groups and thiol groups as described herein. However, the polymer precursor for the sub-pad is selected to provide higher compliance than that found in the polishing layer. When the sub-pad is formed by additive manufacturing, the sub-pad and the polishing layer can be sequentially formed in reaction vessel 1 while changing the reaction mixture as it moves from one layer to another. For example, the polishing layer can be formed as described above. When the polishing layer is formed, reaction mixture 10 can be removed from vessel 1 and a new reaction mixture can be added. The same exposure process can be performed to form additional layers on the polishing layer. Alternatively, the sub-pad can be formed first, and then the polishing layer can be formed by additive manufacturing on the sub-pad as the substrate. For example, a process can be performed where the sub-pad is formed by additive manufacturing and then the polishing layer is formed on the sub-pad on the build platform. As another example, a pre-formed sub-pad on the build platform can be provided and the polishing layer can be formed on the sub-pad by the additive manufacturing described herein.

[0045] A chemical mechanical polishing pad can include a window in the polishing layer. The window is formed of a material that is transparent to the wavelength used for endpoint detection during use of the polishing pad. A chemical mechanical polishing pad including a window can also be formed using additive manufacturing. For example, the polishing layer from the reaction mixture can be formed around the window material disposed on the build platform. As another example, the polishing layer can be formed with an opening in which the window will later be disposed. As yet another alternative, the window itself can be formed by additive manufacturing. For example, the window can first be formed by additive manufacturing within the vessel 1 of the apparatus, and then the polishing layer can be formed by additive manufacturing around the window. As another example, a polishing layer with a gap for the window can be formed by the additive manufacturing disclosed herein, and then the window can be formed by additive manufacturing in the gap. The window material can be, for example, polyurethane, acrylic polymer, cyclic olefin copolymer (such as TOPAS 8007, etc.). The use of polyurethane materials may be useful in pads where the polishing layer, sub-pad layer, or both are also polyurethane. A specific set of examples of aliphatic polyurethanes for windows can be found, for example, in (Patent Document 8).

Example

[0046] Small molecule (A) which is component 1 - 1,2 - diallyl phthalate (DAP) or diallyl isophthalate (DAIP); Component 2 - oligomer molecules (A2a is derived from a prepolymer based on PTMEG terminated with TDI and then reacted with allylphenol, A2b is a prepolymer based on a low - molecular - weight diol terminated with MDI and then reacted with allylphenol, and A2c is a prepolymer based on a low - molecular - weight diol terminated with MDI and then reacted with eugenol); Component 3 - molecule (B) compound having more than two thiol functional groups that provide cross - linking (TMPMP is trimethylolpropane tris(3 - mercaptopropionate) and PTMP is pentaerythritol tetrakis(3 - mercaptopropionate)); Component 4 - molecule (B) dithiol functional compound that provides chain extension (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 weight percent based on the total weight of the reaction mixture; A reaction mixture was prepared. The amounts of components 1 - 4 and what they are are shown in Table 1. The weight percentages are based on the total weight of the reaction mixture. All examples were prepared at a molar ratio of 1:1 of ethylenically unsaturated groups to thiol groups.

[0047]

Table 1

[0048] Examples 1 - 7 and the photocurable acrylate composition were film - cast and irradiated with 50 mW / cm 2Both sides were photocured for 5 minutes using a mercury lamp. All samples were non-porous and did not contain composite material fillers such as polymer microspheres or polymer particles. The glass transition temperature (Tg) was determined in accordance with ASTM D5279-21, and the temperature at the maximum tanδ was selected. The tensile modulus was determined in accordance with ASTM D412, the elongation was determined in accordance with ASTM D412-05, and the toughness was determined in accordance with ASTM D412. The photocurable acrylate and Examples 1 to 3 were also tested for the cut rate by the following method: The sample test piece for the wear test was a ring with an outer diameter of 7 / 8 inch (2.2 cm), an inner hole cut-out diameter of 3 / 8 inch (0.95 cm), and a rim width of 1 / 2 inch (1.3 cm). The sample was either punched out from a pad / plaque sample or photocured in a PTFE mold of the same dimensions using the Dymax 2000-EC photocuring flood system described above. The sample was attached to a VEXTA gear head for a Vue-More Manufacturing sample disk rotary small polisher (SSP) and conditioned with a Saesol AK45 disk (170 μm diamond with a 315 μm interval) with a diameter of 4.25 inches (10.8 cm). The conditioning disk was rotated at 3 rpm (clockwise), and the sample was rotated at 300 rpm (counterclockwise) under a downforce of 1.78 psi (12.3 kPa) (measured while being pressed against the rotating diamond conditioning disk). The sample was pressed against the conditioning disk at a midpoint between the center and the outer periphery of the conditioning disk. The test was conducted with deionized water at room temperature without exchange or recirculation. The wear data was obtained by taking out the sample at 5- to 30-minute intervals and measuring the thickness with a Keyence CL-3000 confocal displacement sensor. The thickness measurement was performed at three points at 120° intervals around the sample ring and averaged at each time point. These wear results are shown in Table 2.

[0049]

Table 2

[0050] Fabrication of the polishing pad The reaction mixtures of Examples 4 to 6 were each poured into a separate 12-inch (30.5 cm) circular mold and cured on both sides for 5 minutes with a mercury lamp having an incident intensity of 50 milliwatts per square centimeter (mW / cm 2 ). Subsequently, the samples were milled to a thickness of 0.080 inches (0.2 cm) using a computer numerical control (CNC) mill and grooved with a circular groove pattern (width 0.03 inches × pitch 0.08 inches, i.e., 0.076 × 0.2 cm). Thereafter, the samples were laminated onto DuPont's Suba IV sub-pads and punched to a final diameter of 9 inches (22.9 cm).

[0051] Comparative non-photocurable cast polyurethane samples for polishing evaluation were drawdown cast and cured at 104 °C for 16 hours. Subsequently, the cured samples were faced, grooved, laminated, and punched in the same manner as the photocurable samples. Comparative polyurethane A is characterized by an elastic modulus of 348 MPa and an elongation of 298%. Comparative polyurethane B is characterized by an elastic modulus of 183 MPa and an elongation of 430%.

[0052] Polishing procedure: The polishing tests were carried out using a benchtop CMP tool of Bruker TriboLab. Prior to polishing, a break-in operation was performed (for 10 minutes) using a Saesol AF38 diamond conditioning disk, and each pad was conditioned with deionized water (for 10 seconds, ex-situ). The TEOS wafers were polished for 60 seconds each at a downforce of 3, 5, and 7 psi (20.7, 34.5, and 48.3 kPa) and a platen:head rotation speed of 150:151, 225:226, 300:301 (a total of 18 runs per pad). In all polishing tests, Klebosol 1730 slurry was used at a flow rate of 100 mL / min. The results are shown in Table 3.

[0053]

Table 3

[0054] The present disclosure further includes the following aspects.

[0055] Aspect 1: A chemical mechanical polishing pad comprising a photocurable polymer, wherein the photocurable polymer is a photo-initiation reaction product of a photocurable material that does not contain a molecule containing a (meth)acrylate group, the photocurable material contains a molecule having two or more functional groups, the functional groups contain a thiol group and an ethylenically unsaturated group other than a (meth)acrylate group, the photocuring includes a reaction between the thiol group and the ethylenically unsaturated group, and at least some of the molecules contain three or more functional groups.

[0056] Aspect 2: The chemical mechanical polishing pad according to Aspect 1, wherein the molecule having two or more functional groups contains a first molecule having two or more ethylenically unsaturated groups and a second molecule having two or more thiol groups, provided that at least some of the first molecule contains at least three or more ethylenically unsaturated groups, or at least some of the second molecule contains three or more thiol groups.

[0057] Aspect 3: The chemical mechanical polishing pad according to Aspect 1, wherein the molecule having two or more functional groups contains a heterotelechelic molecule having an ethylenically unsaturated group and a thiol group.

[0058] Aspect 4: The chemical mechanical polishing pad according to any one of Aspects 1 to 3, wherein the reaction mixture contains a photoinitiator that generates radicals when exposed to radiation of an activation wavelength.

[0059] Aspect 5: The chemical mechanical polishing pad according to any one of Aspects 1 to 4, wherein the ethylenically unsaturated group contains an allyl group.

[0060] Aspect 6: The chemical mechanical polishing pad according to Aspect 5, wherein the reaction mixture contains a photoinitiator that generates a base when exposed to radiation of an activation wavelength.

[0061] Aspect 7: The chemical mechanical polishing pad according to aspect 2, wherein the first molecule comprises a reaction product of a polyisocyanate comprising an oligomer, a polyfunctional isocyanate monomer, or a mixture thereof, and an ethylenically unsaturated end-capping agent.

[0062] Aspect 8: The chemical mechanical polishing pad according to aspect 2, wherein the first molecule comprises an oligomer containing two or more ethylenically unsaturated groups and a monomer containing two or more ethylenically unsaturated groups, and the second molecule comprises one or more of an alkyl polyfunctional thiol, an aromatic polyfunctional thiol, a polyfunctional mercaptopropionate ester, a polyfunctional thioglycolate ester, a polyfunctional mercaptoacetate ester, and a thiol-terminated oligomer having two or more thiol groups.

[0063] Aspect 9: The chemical mechanical polishing pad according to any one of aspects 1 to 8, comprising less than 0.05 weight percent of polishing particles based on the total weight of the polishing pad.

[0064] Aspect 10: The polishing pad according to any one of aspects 1 to 9, formed from a method comprising preparing 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 construct a cured structure, and repeating the selective curing by irradiation until the cured structure has the form of a polishing layer of the polishing pad.

[0065] Aspect 11: The photocurable material to be prepared comprises i) a monomer or oligomer having two or more ethylenically unsaturated groups or a mixture thereof, and ii) a monomer or oligomer having two or more thiol groups or a mixture thereof The polishing pad according to aspect 10.

[0066] All ranges disclosed in this specification include the endpoints, and the endpoints can be combined with each other independently (e.g., the range of "up to 25% by weight, more specifically 5% to 20% by weight" includes the endpoints and all intermediate values within the range of "5% to 25% by weight", etc.). Further, the upper and lower limits described can be combined to form a range (e.g., combining "at least 1% by weight or at least 2% by weight" with "up to 10 or 5% by weight" can result in a range of "1 to 10% by weight" or "1 to 5% by weight" or "2 to 10% by weight" or "2 to 5% by weight").

[0067] This disclosure can be any of including, consisting of, or consisting essentially of any suitable components disclosed herein. This disclosure can additionally or alternatively be formulated to not include, or substantially not include, any components, materials, raw materials, aids, or species that are used in prior art compositions or that are not necessary for achieving the functions and purposes of this disclosure.

[0068] All patents, patent applications, and other references cited are hereby incorporated by reference in their entirety. However, if there is a conflict or contradiction between the terms of the incorporated reference and the terms of this application, the terms of this application shall prevail over the conflicting terms of the incorporated reference.

[0069] Unless otherwise specified herein, all test standards are the latest valid standards as of the filing date of this application, or, if a priority is claimed, the latest valid standards as of the filing date of the earliest priority application in which the test standard appears.

Description of Symbols

[0070] 1 Container 2 Build Platform 3 Transparent Portion 4 Layer 7 Activating Radiation 8 Recoating Blade 10 Reaction Mixture 11 First Layer 12 The second layer

Claims

1. 1. A chemical mechanical polishing pad comprising a photocured polymer, the photocured polymer being a photoinitiated reaction product of a photocurable material that does not include molecules that include (meth)acrylate groups, the photocurable material including molecules having two or more functional groups, the functional groups including thiol groups and ethylenically unsaturated groups other than (meth)acrylate groups, and the photocuring including a reaction between the thiol groups and the ethylenically unsaturated groups, but at least some of the molecules including three or more functional groups.

2. 2. The chemical mechanical polishing pad of 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. 2. The chemical mechanical polishing pad of claim 1, wherein the molecule having two or more functional groups comprises a heterotelechelic molecule having an ethylenically unsaturated group and a thiol group.

4. 10. The chemical mechanical polishing pad of claim 1, wherein the reaction mixture includes a photoinitiator that generates radicals upon exposure to radiation at an activating wavelength.

5. The chemical mechanical polishing pad of claim 4 , wherein the ethylenically unsaturated groups comprise allyl groups.

6. 10. The chemical mechanical polishing pad of claim 1, wherein the reaction mixture includes a photoinitiator that generates a base upon exposure to an activating wavelength of radiation.

7. 3. The chemical mechanical polishing pad of claim 2, wherein the first molecule comprises a reaction product of a polyisocyanate, including an oligomer, a multifunctional isocyanate monomer, or a mixture thereof, and an ethylenically unsaturated endcapping agent.

8. 3. The chemical mechanical polishing pad of claim 2, wherein the first molecules include an oligomer containing two or more ethylenically unsaturated groups and a monomer containing two or more ethylenically unsaturated groups, and the second molecules include one or more of an alkyl polyfunctional thiol, an aromatic polyfunctional thiol, a polyfunctional mercaptopropionate ester, a polyfunctional thioglycolate ester, a polyfunctional mercaptoacetate ester, and a thiol-terminated oligomer having two or more thiol groups.

9. 2. The polishing pad of claim 1, formed from a method including providing the photocurable material in a container; selectively curing a portion of the photocurable material by irradiation to form a hardened structure; selectively curing additional portions of the photocurable material by irradiation to further build up the hardened structure; and repeating the selective curing by irradiation until the hardened structure has the configuration of the polishing layer of the polishing pad.

10. The photocurable material to be prepared is i) a monomer or oligomer having two or more ethylenically unsaturated groups, or a mixture thereof; and ii) Monomers or oligomers having two or more thiol groups, or mixtures thereof 10. The polishing pad of claim 9, comprising:

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