Polishing pad with window and manufacturing methods thereof

Embodiments of the present disclosure provide for polishing pads that include at least one endpoint detection (EPD) window disposed through the polishing pad material, and methods of forming thereof. In one embodiment a method of forming a polishing pad includes forming a first layer of the polishing pad by dispensing a first precursor composition and a window precursor composition, the first layer comprising at least portions of each of a first polishing pad element and a window feature, and partially curing the dispensed first precursor composition and the dispensed window precursor composition disposed within the first layer.

BACKGROUND

Field

Embodiments of the present disclosure generally relate to a polishing pad, and methods of forming a polishing pad, and more particularly, to a polishing pad used for polishing a substrate in an electronic device fabrication process.

Description of the Related Art

Chemical mechanical polishing (CMP) is commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate. Often, the material layer to be planarized is contacted to polishing pad mounted on a polishing platen. The polishing pad and/or the substrate (and thus the material layer surface on the substrate) are moved relative to one another in the presence of a polishing fluid and abrasive particles. Two common applications of CMP are planarization of a bulk film, for example pre-metal dielectric (PMD) or interlayer dielectric (ILD) polishing, where underlying features create recesses and protrusions in the layer surface, and shallow trench isolation (STI) and interlayer metal interconnect polishing. In STI and interlayer metal interconnect CMP, polishing is used to remove a via, contact or trench fill material from the exposed surface (field) of the layer having the feature extending thereinto.

Endpoint detection (EPD) methods are commonly used in CMP processes to determine when a bulk film has been polished to a desired thickness or when via, contact or trench fill material has been removed from the field (upper surface) of a layer. One EPD method includes directing a light towards the substrate, detecting light reflected therefrom, and determining a thickness of a transparent bulk film on the substrate surface using an interferometer. Another EPD method includes monitoring for changes in the reflectance of the substrate to determine the removal of a reflective material from the field of the layer surface. Typically, the light is directed through an opening in the polishing platen and the polishing pad disposed thereon. The polishing pad includes a transparent window that is positioned adjacent to the opening in the polishing platen which allows the light to pass therethrough. The window is generally formed of a polyurethane material that is adhered to the polishing pad material therearound using an adhesive or that is molded into the polishing pad during the manufacturing thereof. Typically, the material properties of the window are limited by the selection of commercially available polyurethane sheets and or molding materials that are not optimized for specific CMP processes or polishing pad materials.

Accordingly, there is a need in the art for methods of customizing and/or tuning the material properties of polishing pad EPD windows and for polishing pads formed using those methods.

SUMMARY

Embodiments herein generally relate to a polishing pad having an endpoint detection (EPD) window feature disposed therethrough, and methods of forming the polishing pad and the window feature.

In one embodiment, a method of forming a polishing pad is provided. The method includes forming a first layer of the polishing pad by dispensing a first precursor composition and a window precursor composition. The first layer herein comprises at least portions of each of a first polishing pad element and a window feature. The method further includes partially curing the dispensed first precursor composition and the dispensed window precursor composition to form an at least partially cured first layer. In some embodiments, the method further includes forming a second layer on the at least partially cured first layer by dispensing the window precursor composition and a second precursor composition. The second layer herein comprises at least portions of each the window feature, and one or more second polishing pad elements. In some embodiments, the method further includes partially curing the dispensed window precursor composition and the second precursor composition disposed within the second layer. In some embodiments, forming the first layer comprises forming a plurality of first sub-layers and forming the second layer comprises forming a plurality of second sub-layers. Forming each of the sub-layers herein includes dispensing droplets of one or more precursor compositions and at least partially curing the dispensed droplets before forming a next sub-layer thereon.

In another embodiment, another method of forming a polishing pad is provided. The method includes forming a first layer of the polishing pad by dispensing a first precursor composition, where the first layer comprises at least a portion a sub-polishing element having an opening disposed therethrough, and partially curing the dispensed first precursor composition with the first layer. The method further includes forming a second layer on the at least partially cured first layer by dispensing a second precursor composition, where the second layer comprises at least portions one or more polishing elements, and where the opening is further disposed through the second layer. The method further includes partially curing the dispensed second precursor composition within the second layer. The method further includes forming a window in the opening by dispensing a window precursor composition thereinto and curing the window precursor composition. In some embodiments, forming the first layer comprises forming a plurality of first sub-layers and forming the second layer comprises forming a plurality of second sub-layers. Forming each of the sub-layers herein includes dispensing droplets of one or more precursor compositions and at least partially curing the dispensed droplets before forming a next sub-layer thereon.

In another embodiment, a polishing article is provided. The polishing article comprises a sub-polishing element, a plurality of polishing elements extending from the sub-polishing element, and a window feature disposed through the sub polishing element and the plurality of polishing elements. In this embodiment, the sub-polishing element, the plurality of polishing elements, and the window feature are chemically bonded at the interfaces thereof.

DETAILED DESCRIPTION

Embodiments of the present disclosure provide for polishing pads that include at least one endpoint detection (EPD) window disposed through the polishing pad material, and methods of forming them. The polishing pads are formed using an additive manufacturing process, such as a two-dimensional (2D) or three-dimensional (3D) inkjet printing process. Additive manufacturing processes, such as the three-dimensional printing (“3D printing”) process described herein, enable the formation of polishing pads with discrete regions, elements, or features having unique properties and attributes. Generally, the pad material is one or more polymers, and the polymers of the regions, elements, and/or features form chemical bonds, for example covalent bonds or ionic bonds, with the polymers of adjacent regions, elements, and/or features at the interfaces thereof. The chemical bonds typically comprise the reaction product of one or more curable resin precursors used to form adjacent regions, elements, and/or features. In some embodiments, the regions, elements, and/or features form a continuous polymer phase while maintaining the distinct material properties associated with each region, element and/or feature.

FIG. 1is a schematic sectional view of an example of a polishing system100using a polishing pad200formed according to the embodiments described herein. Typically, the polishing pad200is secured to a platen102of the polishing system100using an adhesive, such as a pressure sensitive adhesive (PSA) layer (not shown), disposed between the polishing pad200and the platen102. A substrate carrier108, facing the platen102and the polishing pad200mounted thereon, includes a flexible diaphragm111configured to impose different pressures against different regions of a substrate110while urging the to be polished surface of the substrate110against the polishing surface of the polishing pad200. The substrate carrier108includes a carrier ring109surrounding the substrate110. During polishing, a downforce on the carrier ring109urges the carrier ring109against the polishing pad200to prevent the substrate110from slipping from the substrate carrier108. The substrate carrier108rotates about a carrier axis114while the flexible diaphragm111urges the to be polished surface of the substrate110against the polishing surface of the polishing pad200. The platen102rotates about a platen axis104in an opposite rotational direction from the rotation direction of the substrate carrier108while the substrate carrier108sweeps back and forth from an inner diameter of the platen102to an outer diameter of the platen102to, in part, reduce uneven wear of the polishing pad200. Herein, the platen102and the polishing pad200have a surface area that is greater than the to be polished surface area of the substrate110, however, in some polishing systems, the polishing pad200has a surface area that is less than the to be polished surface area of the substrate110. An endpoint detection (EPD) system130directs light towards the substrate110through a platen opening122and further through an optically transparent window feature208of the polishing pad200disposed over the platen opening122.

During polishing, a fluid116is introduced to the polishing pad200through a fluid dispenser118positioned over the platen102. Typically, the fluid116is a polishing fluid (including water as a polishing fluid or a part of the polishing material), a polishing slurry, a cleaning fluid, or a combination thereof. In some embodiments, the fluid116is a polishing fluid comprising a pH adjuster and/or chemically active components, such as an oxidizing agent, to enable chemical mechanical polishing of the material surface of the substrate110in conjunction with the abrasives of the polishing pad200.

FIGS. 2A and 2Care schematic top down views of polishing pads formed according to embodiments described herein.FIGS. 2B and 2Dare schematic cross sectional views of portions of the polishing pads shown inFIGS. 2A and 2Crespectively. The polishing pads200a,200bcan be used as the polishing pad200in the polishing system100ofFIG. 1. InFIGS. 2A-2B, the polishing pad200acomprises a plurality of polishing elements204a, a sub-polishing element206, and a window feature208. The plurality of polishing elements204aare disposed on and/or within the sub-polishing element206and extend from a surface thereof. The window feature208extends through the polishing pad200aand is located at a pad location between the center of the polishing pad200aand an outer edge thereof. Herein, one or more of the plurality of polishing elements204ahave a first thickness212, the sub-polishing element206extends beneath the polishing element204aat a second thickness213, and the polishing pad200ahas an overall third thickness215.

As shown inFIG. 2A, this aspect of the pad200aincludes a plurality of polishing elements204aincluding an upwardly extending post205disposed in the center of the polishing pad200aand a plurality of upwardly extending concentric rings207disposed about the post205and spaced radially outwardly therefrom. The plurality of polishing elements204aand the sub-polishing element206resultantly define a plurality of circumferential channels218adisposed in the polishing pad200abetween each of the polishing elements204aand between a plane of the polishing surface201of the polishing pad200aand a surface of the sub-polishing element206. The plurality of channels218enable the distribution of polishing fluid across the polishing pad200aand to the interface region between the polishing pad200aand the to be polished surface of a substrate110. In other embodiments, the patterns of the polishing elements204aare rectangular, spiral, fractal, random, another pattern, or combinations thereof. Herein, the width214aof the polishing element(s)204ain the radial direction of the pad200ais between about 250 microns and about 5 millimeters, such as between about 250 microns and about 2 millimeters and a pitch216of the polishing element(s)204ais between about 0.5 millimeters and about 5 millimeters. In some embodiments, the width214aand/or the pitch216in the radial direction varies across the radius of the polishing pad200a,200bto define zones of pad material properties and/or abrasive particle concentration. Additionally, the center of the series of polishing elements204amay be offset from the center of the sub-polishing element206.

InFIGS. 2C-2D, the polishing elements204bof pad200bare shown as circular cylindrical columns extending from the sub-polishing element206. In other embodiments, the polishing elements204bare of any suitable cross-sectional shape, for example individual columns with toroidal, partial toroidal (e.g., arc), oval, square, rectangular, triangular, polygonal, irregular shapes, or combinations thereof. The polishing elements204band sub-polishing element206define flow regions218bbetween the polishing elements204b. In some embodiments, the shapes and widths214of the polishing elements204b, and the distances216btherebetween, are varied across the polishing pad200bto tune the hardness, mechanical strength, fluid transport characteristics, or other desirable properties of the complete polishing pad200b. The width214bof the polishing element(s)204bis between about 250 microns and about 5 millimeters, such as between about 250 microns and about 2 millimeters, typically the polishing elements are spaced apart from each other by a distance216bbetween about 0.5 millimeters and about 5 millimeters.

As illustrated inFIGS. 2B and 2D, the polishing elements204a,204bare supported by a portion of the sub-polishing element206(e.g., portion within the first thickness212). Therefore, when a load is applied to the polishing surface201of the polishing pads200a,200b(e.g., top surface) by a substrate during processing, the load will be transmitted through the polishing elements204a,204band a portion of the sub-polishing element206located therebeneath.

In some embodiments, the materials used to form portions of the polishing pads200a,200b, such as the polishing elements204a,204band the sub-polishing element206will include the reaction product of at least one ink-jettable pre-polymer composition that is a mixture of functional polymers, functional oligomers, reactive diluents, and/or curing agents to achieve the desired properties of a polishing pad200a,200b. In some embodiments, interfaces between, and coupling between, the polishing elements204a,204band the sub-polishing element206include the reaction product of pre-polymer compositions, such as a first curable resin precursor composition, used to form the sub-polishing element206and a second curable resin precursor composition, used to form the polishing elements204a,204b. In general, the pre-polymer compositions are exposed to electromagnetic radiation, which may include ultraviolet radiation (UV), gamma radiation, X-ray radiation, visible radiation, IR radiation, and microwave radiation and also accelerated electrons and ion beams to initiate the polymerization reactions which form the continuous polymer phases of the polishing elements204a,204band the sub-polishing element206. The method(s) of polymerization (cure), or the use of additives to aid the polymerization of the polishing elements204a,204band the sub-polishing element206, such as sensitizers, initiators, and/or curing agents, such as through cure agents or oxygen inhibitors, are not restricted for the purposes hereof.

The window feature208herein comprises a continuous polymer phase formed from of at least one of oligomeric and/or polymeric segments, compounds, or materials selected from the group consisting of: polyacrylates, polymethacrylates, polyurethane acrylates, polyester acrylates, polyether acrylates, epoxy acrylates, polyacrylonitriles, block copolymers thereof, and random copolymers thereof.

Typically, the window feature208is formed of a material that includes the reaction product of at least one ink-jettable precursor composition. The ink-jettable precursor composition is a mixture of one or more of acrylate based non-yellowing monomers, acrylate based non-yellowing oligomers, photoinitiators, and/or thermal initiators, where the mixture is formulated to achieve the desired properties of the window feature208. In some embodiments, the window feature208is formed of a material that includes the reaction product of one or more of acrylates, methacrylates, epoxides, oxetanes, polyols, photoinitiators, amines, thermal initiators, and/or photosensitizers.

In one embodiment, the sub-polishing element206and the plurality of polishing elements204a,bare formed from a sequential deposition and post deposition process and comprise the reaction product of at least one radiation curable resin precursor composition, wherein the radiation curable precursor compositions contain functional polymers, functional oligomers, monomers, and/or reactive diluents that have unsaturated chemical moieties or groups, including but not restricted to: vinyl groups, acrylic groups, methacrylic groups, allyl groups, and acetylene groups.

Typical material composition properties that may be selected using the methods and material compositions described herein include storage modulus E′, loss modulus E″, hardness, tan δ, yield strength, ultimate tensile strength, elongation, thermal conductivity, zeta potential, mass density, surface tension, Poison's ratio, fracture toughness, surface roughness (Ra), glass transition temperature (Tg) and other related properties. For example, storage modulus E′ influences polishing results such as the removal rate from, and the resulting planarity of, the material layer surface of a substrate. In some embodiments, it is desirable for the window material to have a similar storage modulus as the surrounding polishing elements so that the window material wears at a similar rate and does not extend above or below the surface or the polishing pad over the lifetime thereof. Typically, polishing pad material compositions having a medium or high storage modulus E′ provide a higher removal rate for dielectric films used for PMD, ILD, and STI, and cause less undesirable dishing of the upper surface of the film material in recessed features such as trenches, contacts, and lines. Polishing pad material compositions having a low storage modulus E′ generally provide more stable removal rates over the lifetime of the polishing pad, cause less undesirable erosion of a planer surface in areas with high feature density, and cause reduced micro scratching of the material surface. Characterizations as a low, medium, or high storage modulus E′ pad material composition at temperatures of 30° C. (E′30) and 90° C. (E′90) are summarized in Table 1.

In embodiments herein, the window feature208is formed of materials having an E′30 between about 2 MPa and about 1500 MPa and an E′90 between about 2 MPa and about 500 MPa, such as between about 2 MPa, and about 100 MPa. The polishing elements204a,204band the window feature208are typically formed from materials having a medium or high (hard) storage modulus E′. Forming the window feature208from materials having the same or similar storage modulus E′ as the surrounding polishing elements204a,204bprovides for similar wear rates between the window feature208and the polishing elements204a,204bso that the window feature208remains desirably planer with the surrounding polishing pad material during the lifetime of the polishing pad. Typically, the sub-polishing element206is formed from materials different from the materials forming the polishing elements204a,204b, such as materials having a low (soft) or moderate storage modulus E′. Typically, the window feature208materials formed herein have an ultimate tensile strength of between about 2 MPa and about 100 MPA and between about 8% and about 130% of elongation to break. The window feature208materials formed herein typically have a storage modulus recovery of more than about 40%, where storage modulus recovery is a ratio of E′30 in a second cycle to E′30 in a first cycle under dynamic mechanic analysis (DMA) and a hardness under durometer of between about 60A and about 70D.

InFIGS. 2A-2Dthe window feature208has a cylindrical shape, i.e., a circular shape in top-down cross-section or plan view, with a diameter217between about 1 mm and about 100 mm. In other embodiments, the window feature208has any other top down cross-sectional shape, such as toroidal, partial toroidal (e.g., arc), oval, square, rectangular, triangular, polygonal, irregular shapes, or combinations thereof. In some embodiments, the top-down cross-sectional shape is selected to increase the bonding surface area between the polymer materials forming the polishing elements204a,204band the sub-polishing element206and a window feature formed therewith, such as shown inFIG. 2E.

FIG. 2Eis a schematic plan view of a portion of the polishing pad200adescribed inFIGS. 2A-2Bhaving a gear shaped window feature222in place of the window feature208. InFIG. 2Ethe window feature222has a top down cross-sectional shape comprising a circular cross-sectional shape with a plurality of fingers223, i.e., protuberances in the shape of gear teeth shaped, extending radially outward therefrom. Here, the plurality of fingers223form an interdigitated structure with the material of the polishing elements204aand sub-polishing element206adjacent thereto. The interdigitated structure increases the interfacial surface area between the window feature222and the polishing elements204aand sub-polishing element206, and provides structural elements tending to keep the window feature222from rotating or twisting with respect to the polishing elements204aduring installation on a polishing tool and/or during a substrate polishing process. The increased interfacial surface area, and thus the increased number of polymeric bonds between the window feature222and surrounding polishing pad material, reduces or substantially eliminates undesired process events related to pop-out of the window feature222from the polishing pad200awhich allows for more aggressive conditioning thereof and/or polishing processes.

FIG. 2Fis a schematic cross-sectional view of the polishing pad200adescribed inFIGS. 2A-2Bhaving a window feature224in place of the window feature208. Here, the window feature224features a trapezoidal cross-sectional shape in the depth direction of the polishing pad200ahaving a first width225measured proximate to the polishing surface of the polishing pad200aand coplanar therewith and a second width226measured proximate to the mounting surface (bottom surface), or at least inwardly of the polishing surface side, of the polishing pad200aand parallel to the first width225. Herein, the mounting surface of the polishing pad is opposite of, and generally parallel to, the polishing surface thereof. Here, the first width225is less than the second width226which mechanically locks the window feature224in the polishing pad200awhen the polishing pad200ais mounted on a polishing platen of a polishing system. For example, in some embodiments, the ratio of the first width225to second width226is between about 0.5:1 and about 0.9:1. In some embodiments, the window feature224of formed of and according to any of the respective material compositions or methods set forth for the window feature208described throughout the disclosure. Typically, the window feature224has any desired top down cross-sectional shape, such as circular, toroidal, partial toroidal (e.g., arc), oval, square, rectangular, triangular, polygonal, irregular shapes, or combinations thereof. In some embodiments, the top-down cross-sectional shape of the window feature224forms and interdigitated structure with the polishing pad material, such as shown for the window feature222illustrated inFIG. 2E.

FIG. 3Ais a schematic sectional view of an additive manufacturing system300used to form a polishing pad, such as polishing pads200a,200b, according to embodiments disclosed herein. The additive manufacturing system300herein includes a first dispensing head360for dispensing droplets of a first precursor composition363, a second dispensing head370for dispensing droplets of a second precursor composition373, and a third dispensing head380for dispensing droplets of a window precursor composition383. Typically, the dispensing heads360,370,380move independently of each other and independently of a manufacturing support302during the printing process to enable the placement of droplets of the precursor compositions363,373, and383at selected locations on the manufacturing support302to form a polishing pad, such as the polishing pads200a,200b. The selected locations are collectively stored as a CAD-compatible printing pattern which is readable by an electronic controller (not shown) that directs the motion of the manufacturing support302, the motion of the dispensing heads360,370,380and the delivery of the droplets of the precursor compositions363,373,383from one or more nozzles335.

Herein, the first precursor composition363is used to form the sub-polishing element206, the second precursor compositions373is used to form the polishing elements204a,204b, and the window precursor composition383is used to form the window feature208of the polishing pads200a,200bshown inFIGS. 2A-2B, 2C-2D. Typically, the first and second precursor compositions363and373each comprise a mixture of one or more of functional polymers, functional oligomers, functional monomers, and/or reactive diluents that are at least monofunctional, and undergo polymerization when exposed to free radicals, photoacids, Lewis acids, and/or electromagnetic radiation.

Examples of functional polymers used in the first and/or second precursor compositions363and373include multifunctional acrylates including di, tri, tetra, and higher functionality acrylates, such as 1,3,5-triacryloylhexahydro-1,3,5-triazine or trimethylolpropane triacrylate.

Examples of functional oligomers used in the first and/or second precursor compositions363and373include monofunctional and multifunctional oligomers, acrylate oligomers, such as aliphatic urethane acrylate oligomers, aliphatic hexafunctional urethane acrylate oligomers, diacrylate, aliphatic hexafunctional acrylate oligomers, multifunctional urethane acrylate oligomers, aliphatic urethane diacrylate oligomers, aliphatic urethane acrylate oligomers, aliphatic polyester urethane diacrylate blends with aliphatic diacrylate oligomers, or combinations thereof, for example bisphenol-A ethoxylate diacrylate or polybutadiene diacrylate. In one embodiment, the functional oligomer comprises tetrafunctional acrylated polyester oligomer available from Allnex Corp. of Alpharetta, Ga. as EB40® and the functional oligomer comprises an aliphatic polyester based urethane diacrylate oligomer available from Sartomer USA of Exton, Pa. as CN991.

Examples of photoacids used in the first and/or second precursor compositions363and373include onium salts such as Omnicat 250, Omnicat 440, and Omnicat 550, manufactured by manufactured by IGM Resins USA Inc. of Charlotte N.C. and compositional equivalents thereof, triphenylsulfonium triflate, and triarylsulfonium salt type photo acid generators such as CPI-2105 available from San-Apro Ltd. of Tokyo, Japan, and compositional equivalents thereof.

In some embodiments, the first and/or second precursor compositions363and373further comprise one or more photoinitiators. Photoinitiators used herein include polymeric photoinitiators and/or oligomer photoinitiators, such as benzoin ethers, benzyl ketals, acetyl phenones, alkyl phenones, phosphine oxides, benzophenone compounds and thioxanthone compounds that include an amine synergist, combinations thereof, and equivalents thereof. For example, in some embodiments photoinitiators include Irgacure® products manufactured by BASF of Ludwigshafen, Germany, or equivalent compositions. Herein, the first and second precursor compositions363and373are formulated to have a viscosity between about 80 cP and about 110 cP at about 25° C., between about 12 cP and about 30 cP at about 70° C., or between 10 cP and about 40 cP for temperatures between about 50° C. and about 150° C. so that the precursor compositions363,373may be effectively dispensed through the nozzles335of the dispensing heads360,370.

Examples of oligomers used in the window precursor composition383include acrylate and/or methacrylate based oligomers including multi-functional (2-6 of acrylate or methacrylate functional groups) of polyether acrylates, aliphatic polyester acrylates, aliphatic urethane acrylates, and epoxy acrylates. For example, in some embodiments, the acrylate and/or methacrylate based monomers and/or oligomers include CN991, CN964, and CN9009 available from Sartomer Americas Inc. of Exton, Pa., Ebecryl 270, Ebecryl 40 available from Allnex Group Co. in Frankfurt, Germany, Br-744BT and Br-582E8 available from Dymax Corp. of Torrington, Conn., Bac-45 available from Osaka Organic Chemical Industry LTD. of Osaka City, Japan, Exothane 10 available from ESSTECH, Inc. of Essington, Pa., and equivalent compositions thereof.

Typically, photoinitiators and/or thermal initiators used in the window precursor composition383are selected to minimize photon absorption by the material of the window feature208at wavelengths more than about 350 nm. Examples of photoinitiators used in the window precursor composition383include Omnirad 651 (2,2-dimethoxy-2-phenylacetophenone), Omnirad 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one), Omnirad 184 (1-hydroxycyclohexyl-phenyl ketone), and Esacure KIP 150 (oligomeric alpha hydroxy ketone) manufactured by IGM Resins USA Inc. of Charlotte N.C. and compositional equivalents thereof. In embodiments herein, the photoinitiator comprises less than about 5 wt % of the window precursor composition, such as less than about 1 wt %. Examples of thermal initiators include azobisisobutyronitrile 1,1′-azobis(cyclohexane-1-carbonitrile), benzoyl peroxide, equivalents thereof, and combinations thereof.

In some embodiments, the window precursor composition383further comprises a photoacid, such as an onium salt based photo acid generators, such as Omnicat 250, Omnicat 440, and Omnicat 550, manufactured by IGM Resins USA Inc. of Charlotte N.C. and compositional equivalents thereof, triphenylsulfonium triflate, and triarylsulfonium salt type photo acid generators such as CPI-210S available from San-Apro Ltd. in Tokyo, Japan, and compositional equivalents thereof.

In some embodiments, the window precursor composition383further comprises nanoparticles having a high refractive index such as titanium oxides, zirconium oxides, zirconium acrylates, and hafnium acrylates, for example TiO2, ZrO2, zirconium sulfate, zirconium acrylate, and zirconium bromonorbornanelactone carboxylate triacrylate, and combinations thereof. Generally, high refractive index nanoparticles increase the overall refractive index of the window feature208from between about 1.4 and 1.5, when not used, to between about 1.6 and about 1.9, when used. Increasing the refractive index of the window feature208reduces reflection from the surface thereof and desirably increases photon transmittance therethrough.

Herein, the window precursor composition is formulated to have a viscosity of between about 50 cP and about 500 cP at 25° C., such as between about 50 cP and about 500 cP at 25° C., so that the window precursor composition is effectively dispensed through the nozzles335of the dispensing head380.

FIG. 3Afurther illustrates a curing process using the additive manufacturing system300, according to one embodiment shows a portion of one or more previously formed layers346of a polishing pad element, such as the window feature208. During processing, the dispensing heads360,370,380deliver a plurality of droplets of one or more precursor compositions, such as the plurality of droplets343of the window precursor composition383to a surface346A of the one or more previously formed layers346. As used herein, the term “curing” includes partially curing the droplets to form a desired layer, as complete curing of the droplets may limit desirable reactions with droplets of subsequently deposited layers. The plurality of droplets343form one of a plurality of second sub-layers348which includes a cured portion348A and an uncured portion348B where the cured portion has been exposed to radiation321from the radiation source320. As shown, the cured portion348A comprises the reaction product of the window precursor composition363having a thickness between about 0.1 micron and about 1 mm, such as between about 5 microns and about 100 microns, for example between about 10 microns and about 30 microns. In some embodiments, curing of droplets of the precursor compositions363,373,383is performed in an oxygen free or oxygen limited atmosphere, such as a nitrogen or nitrogen rich atmosphere. The oxygen free or oxygen limited atmosphere increases the polymerization reaction kinetics and reactive product yield of the curing process for the acrylate based window precursor composition383.

FIG. 3Bis a close up cross-sectional view of a droplet343dispensed onto the surface346A of the one or more previously formed layers346of the window feature208. Once dispensed onto the surface346A, the droplet343spreads to a droplet diameter343A having a contact angle α. The droplet diameter343A and contact angle α are a function of at least the material properties of the precursor composition, the energy at the surface346A (surface energy) of the one or more previously formed layers346, and time. In some embodiments, the droplet diameter343A and the contact angle α will reach an equilibrium after a short amount of time, for example less than about one second, from the moment that the droplet contacts the surface346A of the one or more previously formed layers346. In some embodiments, the droplets343are cured before reaching an equilibrium droplet diameter and contact angle α. Typically, the droplets343have a diameter of between about 10 and about 200 micron, such as between about 50 micron and about 70 microns before contact with the surface346A and spread to between about 10 and about 500 micron, between about 50 and about 200 microns, after contact therewith. The surface energy of the one or more previously formed layers346and of the cured portion348B of the second layer348herein is between about 30 mJ/m2and about 45 mJ/m2.

In some embodiments, the window feature208is formed using more than one precursor composition. In those embodiments, a plurality of precursor compositions, each having distinct properties upon curing, are dispensed according to a predetermined printing pattern. Upon curing, the resulting material layer has the integrated properties of the plurality of precursor compositions. For example, in one embodiment, droplets of a first window precursor composition that would form a material having a storage modulus E′30 of 1300 MPa are dispensed adjacent to, and interspersed with, droplets of a second window precursor composition that would form a material having a storage modulus E′30 of 8 MPa. When dispensed in a 1:1 ratio the material formed from the first window precursor composition and the second window precursor composition has a E′30 of 500 MPa. Adjusting the ratio of droplets of the first and second window precursor compositions during formation of the window feature208allow customization of the material properties thereof without the need for mixing customized precursor compositions.

FIG. 4Ais a flow diagram setting forth a method400of forming a polishing article, such as the polishing pad200ashown inFIGS. 2A-2Baccording to one embodiment.FIGS. 4B-4Dillustrate elements of the method400.

At activity410the method400includes forming a first layer401of the polishing pad. Here, the first layer401includes at least a portion of a sub-polishing element206and a portion of the window feature208, as shown inFIG. 4B. In some embodiments, forming the first layer401of the polishing pad includes dispensing a first precursor composition and a window precursor composition to form the at least portions of each of the first layer401and the window feature208respectively. Here, the precursor compositions are dispensed onto a manufacturing support302, or onto a previously formed first sub-layer of the first layer401.

At activity420the method400includes partially curing the dispensed first precursor composition and the dispensed window precursor composition disposed within the first layer401. Partially curing layers herein comprises polymerization of the dispensed precursor compositions, typically by exposure of droplets of the precursor compositions to an electromagnetic radiation source, such as a UV radiation source. In some embodiments, forming the first layer401includes forming a plurality of first sub-layers where each of the first sub-layers is formed by dispensing a plurality of first droplets of the first precursor composition and a plurality of second droplets of the window precursor composition and at least partially curing the dispensed droplets before forming a next sub-layer thereon.

At activity430the method400includes forming a second layer402on the at least partially cured first layer401. In some embodiments, the second layer402includes at least portions of the first polishing pad element206, of the window feature208, and one or more second polishing pad elements204a, as shown inFIG. 4C. Here, forming the second layer402includes dispensing the first precursor composition, the window precursor composition, and a second precursor composition to form at least portions of each of the sub-polishing element206, of the window feature208, and of the one or more second polishing pad elements204arespectively.

At activity440the method400includes partially curing the second layer. In some embodiments, forming the second layer402includes forming a plurality of second sub-layers where each second sub-layer is formed by dispensing a plurality of first droplets of the first precursor composition, a plurality of second droplets of the window precursor composition, and a plurality of third droplets of the second precursor composition. In those embodiments, forming each second sub-layer includes at least partially curing the dispensed droplets before forming a next sub-layer thereon. In another embodiment, the method400does not include activities430and440.

At activity450the method400includes forming a third layer403on the at least partially cured second layer402. In some embodiments, the third layer403includes at least portions of each of the window feature208and the one or more second polishing pad elements204a, as shown inFIG. 4D. Forming the third layer403includes dispensing the second precursor composition and dispensing the window precursor composition to form the at least portions of each of the one or more second polishing pad elements204aand the window feature208respectively. In some embodiments, forming the third layer403includes forming a plurality of third sub-layers where each third sub-layer is formed by dispensing a plurality of second droplets of the window precursor composition and a plurality of third droplets of the second precursor composition and at least partially curing the dispensed droplets before forming a next sub-layer thereon. In other embodiments, the third layer403is formed directly on the first layer401.

At activity460the method400includes at least partially curing the dispensed window precursor composition and the dispensed second precursor composition disposed within the third layer.

Typically, the first, second, and third droplets form chemical bonds at the interfaces thereof during partially curing of each of the sub-layers and further form chemical bonds with the partially cured precursor compositions of a previously formed sub-layer. In some embodiments herein, the sub-polishing element206, the window feature208, and the plurality of polishing elements204aform a continuous polymer phase having discrete material properties within each element and feature.

Typically, each of the droplets used to form portions of the window feature208in the first layer401, second layer402, and the third layer403are partially cured by a curing device after, or simultaneously with, the dispensing thereof. Partially curing the droplets after, or simultaneously with, the dispensing thereof allows for the droplets to be substantially fixed in place and shape so they do not move or change their shape as subsequent droplets are deposited adjacent to, or upon, them. Partially curing the droplets also allows for control of the surface energy of each layer, and thus control of the contact angle of subsequently deposited droplets thereupon.

FIG. 5Ais a flow diagram setting forth a method500of forming a polishing pad, such as the polishing pad200ashown inFIGS. 2A-2B, according to one embodiment.FIGS. 5B-5Fillustrate elements of one embodiment of the method500.FIGS. 5G-5Killustrate elements of another embodiment of the method500.

At activity510the method500includes forming a first layer501of a polishing pad. Here, the first layer501comprises at least a portion of a sub-polishing element206having an opening220disposed therethrough, as shown inFIG. 5B. In some embodiments, forming the first layer501includes dispensing a first precursor composition to form a portion of the sub-polishing element206. Here, the opening220is formed by dispensing the first precursor composition about a desired perimeter thereof.

At activity520the method includes partially curing the dispensed first precursor composition within the first layer501. Partially curing the layers herein comprises polymerization of the dispensed precursor compositions, typically by exposure of droplets of the precursor compositions to an electromagnetic radiation from an electromagnetic radiation source, such as UV radiation from a UV source.

In some embodiments, forming the first layer501includes forming a plurality of first sub-layers where each of the first sub-layers is formed by dispensing a plurality of first droplets of the first precursor composition and at least partially curing the dispensed droplets before forming a next sub-layer thereon.

At activity530the method500includes forming one or more second layers502on the at least partially cured first layer501. Here, the one or more second layers502comprises at least a portion of the sub-polishing element206and portions of the plurality of polishing elements204a, as shown inFIG. 5C. Forming the second layer502comprises dispensing the first precursor composition and dispensing a second precursor composition to form portions of the sub-polishing element206and portions of the plurality of polishing elements204arespectively. Herein, the opening220defined in forming the first layer501is further disposed through the second layer502.

At activity540the method500includes partially curing the dispensed first precursor composition and the dispensed second precursor composition disposed within the second layer502.

In some embodiments, forming the second layer502includes forming a plurality of second sub-layers where each second sub-layer is formed by dispensing a plurality of first droplets of the first precursor composition and a plurality of second droplets a second precursor composition and at least partially curing the dispensed droplets before forming a next sub-layer thereon. In other embodiments, the method500does not include activities530and540.

At activity550the method500includes forming a third layer503on the at least partially cured second layer502, where the third layer503comprises portions of the plurality of polishing elements204a, as shown inFIG. 5C. Forming the third layer503comprises dispensing the second precursor composition to form at least portions of the one or more polishing elements204a.

At activity560the method500includes at least partially curing the dispensed second precursor composition disposed within the third layer503. Typically, the dispensed second precursor composition disposed within the third layer is at least partially cured using a curing source, such as an electromagnetic radiation source, for example a UV radiation source.

In some embodiments, forming the third layer503includes forming a plurality of third sub-layers where each of the third sub-layers is formed by dispensing a plurality of second droplets a second precursor composition and at least partially curing the dispensed droplets before forming a next sub-layer thereon. In other embodiments, the third layer503is formed directly on the first layer501.

At activity570the method500includes dispensing a window precursor composition383into the opening220. At activity580the method500further includes curing the window precursor composition383to form the window feature208.FIGS. 5D-5Fillustrate elements of activities570and580according to one embodiment of the method500.FIGS. 5G-5Jillustrate elements of activities570and580according to another embodiment of the method500.

In one embodiment, such as shown inFIGS. 5D-5F, the window precursor composition383is dispensed into the opening220and cured while the polishing pad remains on the manufacturing support302. Typically, the opening220is bounded by the at least partially cured precursor compositions used to form the plurality of polishing elements204aand the sub-polishing element206. In some embodiments, the at least partially cured precursor compositions comprise unreacted (un-polymerized) termination sites at the inner surfaces of the polishing pad material defining the opening220. For example, in some embodiments, the at least partially cured precursor composition comprise acrylate terminated surface sites at the inner walls defining the opening220, such as shown in (A) where R represents a polymerized precursor composition at the inner surface of the opening220.

As shown inFIG. 5E, the window precursor composition383is dispensed to a level planer with a polishing surface of the polishing pad. Here, curing the window precursor composition383comprises polymerization thereof by exposure to radiation321from a radiation source320, such as UV radiation from a UV lamp or UV LED lamp, as shown inFIG. 5E. In other embodiments, curing the window precursor composition383comprises polymerization thereof by thermal curing, for example by heating the window precursor composition383to a temperature between about 70° C. and about 100° C. for between about 30 minutes and about 3 hours. In some embodiments, such as shown inFIG. 5E, the method500further includes positioning a UV optically transparent polymer sheet522, such as a UV optically transparent polyolefin, polyacrylic, or polycarbonate sheet, on the dispensed window precursor composition383before the curing activity570and removing the optically transparent polymer sheet522thereafter, resulting in the structure ofFIG. 5F. Typically, curing the window precursor composition383comprises reacting the window precursor composition383with unreacted termination sites, e.g., acrylate terminated surface sties, at the inner walls defining the opening220. In those embodiments, the cured window precursor composition383forms a continuous polymer phase with the polishing pad material defining the opening220.

In another embodiment, such as shown inFIG. 5G-5J, the method500further includes removing the partially formed polishing pad from the manufacturing support302(shown inFIG. 5E-5F) and positioning an adhesive layer581thereon. Typically, the adhesive layer581is a pressure sensitive adhesive (PSA) sheet which will be used to secure the polishing pad to a polishing platen for use in a subsequent substrate polishing process. When an adhesive layer581is used, the method500further includes forming an opening therein, such as the opening582shown inFIG. 5H. Here, the opening582formed in the adhesive layer581is in registration with the opening220formed in the polishing pad. Typically, the opening582is formed using mechanical means, for example by using punch having a desired top-down cross-sectional shape.

Once the opening582is formed in the adhesive layer518a delamination insert583(shown inFIG. 5J) typically having the same top-down cross-sectional shape as the opening582. Typically, the delamination insert583has a thickness of between about 5 μm and less than the thickness of the polishing pad which may be varied to a desired thickness of a to be formed window feature. Here, the delamination insert583is positioned in the opening582and held in place relative to the mounting surface of the polishing pad by a temporary adhesive tape584. The delamination insert583and the temporary adhesive tape584seal the mounting surface of the polishing pad to prevent the window precursor composition from flowing out of the opening582during the subsequent formation of the window feature208. Herein, the delamination insert583may be formed on any one of a polymer, metal, metalloid, ceramic, glass, or a combination thereof. In some embodiments, the delamination insert583has a relatively low roughness (e.g., high gloss) hydrophobic surface with relatively low surface tension. Generally, using lower roughness, e.g., RMS roughness <300 nm, hydrophobic low tension, e.g., <20 dynes/cm, surfaces for the delamination insert583, when compared to higher roughness hydrophilic high tension surfaces, results in a lower roughness base surface of a to be formed window feature208and thus desirably increased light transmittance therethrough.

Once the delamination insert583is positioned in the opening582the window precursor composition is flowed into the opening220as described above in activity570and cured as described above in activity580and shown inFIG. 5J. The delamination insert583is then removed from the opening582to form the polishing pad (shown inFIG. 5K).

FIG. 5Killustrates a further embodiment of the methods set forth herein, such as the methods400and500. InFIG. 5Kthe cured window feature208is exposed to UV radiation588from a broadband UV radiation source587to pre-age or pre-discolor the window feature208. Pre-aging or pre-discoloring the window feature208desirably reduces changes the optical transmittance thereof across a useful lifetime of the polishing pad. Typically, changes in the optical transmittance of the window feature are due to photo-degradation of the window feature materials. The photo-degradation may be caused by exposure to ambient light in a manufacturing facility after the polishing pad is mounted on a polishing platen of a polishing system, from light transmitted through the window feature by an endpoint detection system, or both. Changes in the discoloration of the window feature material across the useful polishing pad lifetime may cause undesirable substrate processing variation due to variability in end point detection times related thereto. In some embodiments, the UV broadband radiation source587provides radiation across at least a portion of the UV spectrum including wavelengths from about 200 nm to about 450 nm, or less than about 450 nm. Typically, the UV radiation588has an intensity of between about 50 mW/cm2and about 5000 mW/cm2. In some embodiments, the window feature208is exposed to the UV radiation for between about 30 sec and about 300 sec, for example about 60 sec.

FIGS. 6A-6Cillustrate various optical properties of window features formed according to embodiments herein.FIG. 6Aillustrates the optical transparency of a window feature formed according to embodiments described herein. As shown inFIG. 6Aa window feature, such as window feature208, shows the normalized reflectance transmission (R_T) of the material of a window feature208at the beginning of the polishing pad lifetime as curve601and at the end of the polishing pad lifetime as curve602. Herein, the material of the window feature208exhibits optical transparency to light at wavelengths between about 375 nm and more than about 800 nm across the polishing pad lifetime as indicated by normalized R_T values greater than about 0.2.

FIG. 6Billustrates an R_T cutoff of the window feature shown inFIG. 6A. Herein, the R_T cutoff value is the wavelength of light in which the first derivative of the R_T curves shown inFIG. 6Areaches a maximum between no transmittance to maximum transmittance. Herein, the R_T cutoff of the window feature208at the beginning the polishing pad lifetime (curve601) and at the end of the polishing pad lifetime (curve602) is between about 350 nm and about 380 nm, such as between about 360 nm and about 370 nm, for example about 365 nm.

FIG. 6Cillustrates the discoloration of the window feature material shown inFIGS. 6A-6Bacross the useful polishing pad lifetime. Herein, the window feature material shows less than about 10% deviation in ΔR_T between about 375 nm and about 800 nm between the beginning and end of the useful polishing pad lifetime, where ΔR_T is the ratio of R_T transmission at the end of the polishing pad lifetime to the R_T transmission at the beginning of the polishing pad lifetime. In embodiments where the window feature material is pre-aged or pre-discolored by exposure to broadband UV radiation, such as described above inFIG. 5K, the window feature material has less than about 5% deviation in ΔR_T between about 350 nm and about 800 nm from the beginning to the end of the useful polishing pad lifetime.

Embodiments described herein provide for polishing pads having acrylate based window features, and methods of forming polishing pads with acrylate based window features. The acrylate based window features are compatible with optical endpoint detection systems, and desirable material properties of the window features are easily tuned during the manufacturing process thereof. Typically, the window feature is integrally formed with the material of the polishing pad so that the regions, elements, and features thereof form a continuous polymer phase with the regions, elements, or features having unique properties and attributes from each other.