Chemical planarization of nonmetallic materials

Abstract

A pad for abrasive-free chemical planarization of a substrate, comprising a polymer layer configured to contact the substrate during abrasive-free chemical planarization. The polymer layer contains cerium species.

Description

Technical Field

[0001] Cross-Reference to Related Applications This application claims priority based on U.S. Provisional Patent Application No. 63 / 583,818, entitled "Chemical Planarization of Non-Metallic Materials", filed on September 19, 2023, and the content of this U.S. provisional patent application is incorporated herein by reference as part of the present specification. Background Art

[0002] Chemical mechanical planarization (CMP) is generally used in integrated circuit manufacturing processes to planarize the surface of a semiconductor substrate or the like by removing materials using a combination of chemical and mechanical forces. A typical CMP process involves using an abrasive and a chemical slurry that is corrosive to the material to be removed, in combination with a planarization pad. The substrate and the planarization pad are pressed against each other and rotated relative to each other on non-concentric rotation shafts. The combination of force and slurry removes higher topographical areas of the substrate compared to lower topographical areas, thereby planarizing the surface.

[0003] Summary This summary is provided to introduce a simplified form of some concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to embodiments that address any or all of the disadvantages mentioned in any part of this disclosure.

[0004] Examples of a pad for performing abrasive-free chemical planarization of a substrate are disclosed. In one example, there is provided a pad including a polymer layer configured to contact a substrate during abrasive-free chemical planarization, wherein the polymer layer includes a cerium species.

[0005] Brief Description of the Drawings Figure 1 shows a block diagram of an example chemical planarization system.

[0006] Figure 2A shows a schematic diagram of a pad for performing chemical planarization as an example.

[0007] Figure 2B shows an exemplary pad from Figure 2A, illustrating the contact between the higher topology portion of the substrate and the upper layer of the pad.

[0008] Figure 3 shows a schematic diagram of a pad for performing chemical planarization in another example.

[0009] Figure 4 shows a schematic diagram of another example of a pad having a textured substrate-facing surface.

[0010] Figure 5 schematically illustrates an example of incorporating cerium species and, if necessary, functional groups into a polymer.

[0011] Figure 6 illustrates examples of monomers that can be used to form chemical planarization pads.

[0012] Figures 7A and 7B show flowcharts illustrating an example of a method for forming a chemical planarization pad.

[0013] Figure 8 shows a schematic diagram of a pad for performing chemical planarization in another example.

[0014] Figure 9 schematically illustrates an example of cerium species complex formation by a polymer.

[0015] Detailed explanation As semiconductor devices such as logic, memory, and other devices become more complex with increasing miniaturization, various integration techniques have been used to interconnect these devices. Some of these integration techniques combine metal and non-metallic films to form conductive multilayer interconnects separated by electrical insulating layers. These structures require nanoscale planarization to complete the multilayer wiring structure.

[0016] CMP can be used to planarize these interconnected structures. For example, a silicon oxide film can be polished using a dispersion of cerium oxide abrasive and / or cerium oxide particles embedded in a planarizing pad. In some examples, one or more additives can be added to the cerium oxide dispersion to control the polishing rate, rate selectivity for the polishing rate of the underlying film, and other performance characteristics.

[0017] While current CMP (Chemical Polishing) methods are used in a wide range of device manufacturing processes, they also have several drawbacks. For example, current CMP methods are relatively more contaminated than other manufacturing processes, at least in part, due to the use of conditioning chemicals and polishing slurries and pads that mechanically polish the material during planarization. Defects caused by CMP can be a major factor in reducing yields at manufacturing plants. Defects and scratches that occur during CMP can largely be attributed to mechanical elements of the process, such as the abrasives in the slurry, the force of the pads on the substrate, the conditioning of the pads, and the tribological aspects of the process. Furthermore, the slurry contains abrasives that can damage the device layer, thereby forming pits and leaving residues that can result in fatal defects. Finer technology nodes are more susceptible to such defects, which can reduce the yield of logic, memory, and other semiconductor devices.

[0018] In addition, pad fragments are generated during polishing and pad conditioning. Such pad fragments can form particles and aggregates that contaminate the substrate to be processed. For example, cerium oxide or other particles embedded in the pad may detach, causing scratches or other defects. Also, the force of the pad on the wafer can cause the pad to deform. As a result, close contact with the substrate and relative motion between the substrate and the pad can result in shear stress at the interface. Furthermore, because the CMP process can be unpredictable, a trial-and-error approach may be preferable to an analytical approach. Moreover, handling, supplying, and stabilizing the slurry can present difficulties with respect to the manufacturing equipment due to the solid content. This can increase the maintenance costs of the equipment. Abrasives in the aqueous medium, or such species that detach from the pad and are released into the aqueous medium, can cause scratches and defects, limiting planarization and reducing planarization efficiency and the relative removal rate of high-topographic areas to low-topographic areas. As with conventional CMP processes, a decrease in planarization efficiency can lead to the need for over-deposition and over-planarization, resulting in resource waste, increased costs, and reduced productivity. [Overview of the project] [Problems that the invention aims to solve]

[0019] Therefore, this specification discloses an example of a pad for chemical planarization that does not require abrasive particles during planarization and does not require the highly contaminated and defect-prone mechanical processes used in conventional CMP methods. [Means for solving the problem]

[0020] In short, the disclosed example utilizes abrasive-free planarization chemistry on a pad instead of an abrasive slurry. The term “abrasive-free” indicates a planarization chemistry that does not use mechanical abrasive solid components to remove the substrate material by abrasion. The disclosed pad comprises at least one polymer layer configured to contact the substrate during abrasive-free chemical planarization. The polymer layer contains cerium species. The cerium species enable the disclosed pad to remove nonmetallic material from the substrate surface. The term “cerium species” generally refers to cerium(III) ions and / or cerium(IV) ions contained within the pad, rather than cerium oxide particles which are abrasives. The cerium species may be freely dispersed within the pad (e.g., as a salt), or may form complexes, ionic bonds, or covalent bonds with the functional groups of the polymer in the pad.

[0021] Using the disclosed pad, it is possible to control the contact between the pad and areas of the substrate with a high topology, while preventing contact between areas with a low topology. The planarization chemistry acts on the parts of the substrate in contact with the pad, while the low-topology areas are protected, thus selectively removing material from these parts of the substrate. In this way, the topology of the substrate surface can be smoothed by applying relatively light pressure to the substrate without using abrasives. This prevents scratches and other damage to the device layer, avoids defects, and increases the likelihood of improved yield compared to conventional CMP processes. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 shows a block diagram of an example chemical planarization system. [Figure 2A] Figure 2A shows a schematic diagram of a pad for performing chemical planarization as an example. [Figure 2B] Figure 2B shows an exemplary pad from Figure 2A, illustrating the contact between the higher topology portion of the substrate and the upper layer of the pad. [Figure 3] Figure 3 shows a schematic diagram of a pad for performing chemical planarization in another example. [Figure 4] Fig. 4 is a schematic diagram of another example of a pad having a textured substrate-facing surface. [Figure 5] Fig. 5 schematically illustrates an example of incorporating cerium species and optionally functional groups into a polymer. [Figure 6] Fig. 6 illustrates an example of a monomer that can be used to form a chemical planarization pad. [Figure 7A] Fig. 7A shows a flowchart depicting an example method of forming a chemical planarization pad. [Figure 7B] Fig. 7B shows a flowchart depicting an example method of forming a chemical planarization pad. [Figure 8] Fig. 8 is a schematic diagram of a pad for performing chemical planarization according to another example. [Figure 9] Fig. 9 schematically illustrates an example of complex formation of cerium species by a polymer. EXAMPLES

[0023] Prior to describing the disclosed example of an abrasive-free planarization pad, Fig. 1 is a schematic diagram of an example chemical planarization system 100 according to the present disclosure. The system 100 includes a platen 102 that supports a pad 104. The system 100 further includes a substrate holder 106 configured to hold a substrate 108 against the surface of the pad 104, and a planarization solution introduction system 110 for introducing a planarization solution 112 onto the pad 104. The system 100 may further include a pad cleaning system 114 configured to wash possible contaminants such as composite materials removed from the surface of the substrate 108 away from the pad 104. The pad cleaning system 114 may also be used for pad cleaning between uses of various planarization solution chemistries, as described below. Other components (not shown) that can be incorporated into the system 100 include, but are not limited to, a used solution recovery system, a material recirculation system (e.g., a system for recirculating planarization solution in a closed-loop process), and a species removal system.

[0024] In conventional CMP processes, a substrate holder presses the substrate against a planarizing pad supported on a platen, causing the pad and substrate to rotate non-concentrically with respect to each other. Such conventional processes utilize relatively high rotational speeds, typically 40–100 rpm. Furthermore, the substrate is pressed against the pad with relatively high pressure, typically 1–4 pounds per square inch. In contrast, the disclosed method allows for lighter pressures, such as 0.25–0.75 pounds per square inch, but not limited to these. Lighter pressures can avoid distortion of the pad shape and reduce shear stress compared to conventional CMP processes. Similarly, since rotational motion is not used for polishing, the disclosed method allows for slower rotational speeds than conventional CMP processes. Instead, the rotation of the platen 102 distributes the planarizing fluid across the entire pad 104. Any suitable rotational speed may be used. Examples include speeds in the range of 0–100 rpm, with a more specific example being speeds of 5–60 rpm. As mentioned above, since rotational motion is not used to polish the material from the substrate in the examples herein, the rotational speed may be lower than the rotational speed of the platen in conventional CMP processes. It will be understood that a variety of configurations and designs are possible for various platform types (rotary, linear or belt, vertical, roller, hollow fiber).

[0025] The planarization solution may contain chemical components that hydrolyze the substrate material (e.g., by oxidation and dissolution). The planarization solution may be configured to remove all suitable materials. As an example, polysilicon may be removed by a planarization solution containing poly(diallyldimethylammonium chloride) (PDADMAC) in deionized water. In some such examples, the PDADMAC solution may be mixed with oxalic acid and / or hydrogen peroxide and may further contain a suitable acidic or alkaline agent (e.g., nitric acid or potassium hydroxide) to adjust the pH. Other reagents can also be used for planarization of polysilicon, including, but not limited to, poly(2-acrylamide-2-methyl-1-propanesulfonic acid) (polyAMPS), poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine), poly(allylamine), and poly(ethyleneimine) (PEI). In other examples, one or more metals such as copper, molybdenum, ruthenium, rhenium, rhodium, and cobalt may be removed using a planarizing solution containing hydrogen peroxide and guanidine carbonate, in which case a pH adjuster is used to achieve the desired solution pH. In yet another example, ammonium persulfate may be used to remove a suitable metal (e.g., cobalt), and a pH adjuster is used to achieve the desired solution pH. Other examples of suitable hydrolysants include, but are not limited to, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, ammonium hydroxide, sodium hydroxide, and potassium hydroxide. In some examples, the planarizing solution additionally or alternatively contains a cerium species (e.g., Ce(III) or Ce(IV)) configured to remove non-metallic substrate materials such as polysilicon, silicon nitride, silicon carbonitride, silicon oxide, silicon oxycarbide, and silicon oxynitride.

[0026] In some cases, the planarizing solution may contain additional components. For example, the planarizing solution may contain a complexing / chelating agent for transporting the material removed from the substrate after hydrolysis. Suitable chelating agents include, but are not limited to, ethylenediaminetetraacetic acid (EDTA), sulfosalicylic acid, naphthol (PAN), dithizone, organophosphate esters, polyethylene glycol, amines, and thioxin. Furthermore, in some cases, the planarizing solution may contain a passivating agent and / or corrosion inhibitor. Examples include, but are not limited to, benzotriazole (BTA), ammonium dodecyl sulfate (ADS), tolyltriazole (TTA), thiols (e.g., PTAT (5-(phenyl)-4H-1,2-4-triazole-3-thiol)), thiodiazoles, carboxylic acids, benzoic acid, and ammonium benzoate. Other examples of materials that may be included in the planarization solution include, but are not limited to, surfactants, surface modifiers other than passivators and / or corrosion inhibitors, catalysts, thermally activated chemicals, photoactivated chemicals, seed tracers, additives, and stabilizers.

[0027] Inhibitors such as BTA help achieve planarization, particularly in the case of metal films, by suppressing the removal rate in the low-topographic regions of the wafer. However, BTA and other corrosion inhibitors are harmful and can pose environmental problems during disposal. Furthermore, BTA can interact with other materials (e.g., nano-abrasives) in conventional CMP processes, potentially creating difficult-to-remove residues on the wafer, thus complicating the post-planarization wafer cleaning process. As described later, cerium-containing functionalized pads can selectively planarize high-topographic regions without the addition of inhibitors. This results in a cleaner process and eliminates the need for a post-planarization cleaning step.

[0028] In some examples, as described later, hydrolyzing agents and complexing agents are bonded to the functionalized polymer of the pad. The hydrolyzing agents and complexing agents may form complexes with cerium species incorporated into the pad. In some such examples, the planarization solution applied to the pad may contain deionized water, and chemical planarization may be performed with cerium species and, optionally, the functionalized polymer, depending on the material to be planarized. In other such examples, the planarization solution may contain additional components other than deionized water.

[0029] Figures 2A and 2B show schematic diagrams of an example pad 200 suitable for use as pad 104. Pad 200 comprises a first polymer layer 202 and a second polymer layer 204. The first polymer layer 202 is configured to contact the substrate 206 during abrasive-free chemical planarization. The second polymer layer 204 is positioned opposite the first polymer layer 202 as the substrate contact surface of the first polymer layer 202. Such a two-layer structure may be used to realize a multi-step material removal and separation process, the process having one or more chemical steps, such as hydrolysis (and possible dissolution) of the species to be removed, oxidation, hydroxylation, ionization, radical generation, and / or chemical complex formation of the species to be removed, based on the chemical formation of the pad and the composition of the planarization solution. Furthermore, the first polymer layer 202 and the second polymer layer 204 may be configured to have other functions. For example, the second polymer layer may be configured to be compressible. Therefore, when the first polymer layer 202 comes into contact with the substrate 206 during the chemical planarization process, the second polymer layer 204 is compressed, preventing unnecessary pressure from being applied to the substrate 206. Furthermore, as will be described later, the first polymer layer may have a textured surface in some examples.

[0030] The first and second layers may be joined in any suitable way. In some examples, the first and second layers are joined by adhesive. In other examples, one of the first or second layers is insert-molded into the other. In yet another example, one or both of the first or second layers may be additively manufactured. In yet another example, the first and second layers may be formed in the same molding or casting process, in which case the composition of the material to be molded or cast is changed during pouring or injection. In such examples, an asymmetric medium is formed by having different properties between the upper and lower layers. In some examples, such an asymmetric medium may involve a gradual and systematic change in properties, or it may change abruptly at the interface between the two layers. This makes it possible to control the compressibility and other mechanical properties of the first polymer layer 202 and / or the second polymer layer 204. In other examples, the two layers are integrated and outwardly form a composite pad. Furthermore, the pad 200 may be bonded or bonded to an additional sublayer, such as a woven matrix or a flexible polymer sheet (e.g., a sub-pad of the type currently used in conventional CMP pads).

[0031] In some examples, polymer phase transition or phase separation may be used to form such asymmetric structures. In other examples, vapor-induced phase separation (air casting) may be used. In yet another example, liquid-induced phase separation (immersion casting) may be used, by dissolving the polymer in a solvent at room temperature and inducing phase separation by immersion in a liquid non-solvent. This enables various forms such as asymmetric membranes. Methods for forming asymmetric structures (e.g., multilayer porous matrices) include manipulating phase separation conditions during single-layer casting, casting small-pore membranes on large-pore substrates, simultaneously casting multilayers of various pore sizes, stacking layers of various pore sizes together, and utilizing temperature-induced phase separation (TIPS or molten casting) (heating the polymer above its melting point, dissolving it in porogens, and inducing phase separation by cooling).

[0032] In other examples, the pad comprises a single polymer layer. Figure 3 shows a schematic diagram of another example pad 300 suitable for use as pad 104 in Figure 1. Pad 300 comprises a single polymer layer 302 configured to contact a substrate 306. In some such examples, both hydrolysis and / or complex formation of the cerium species and subsequent chemical planarization are configured to occur within the same layer. In yet another example, the pad comprises three or more layers.

[0033] Referring again to Figures 2A and 2B, in some examples, the first polymer layer 202 may be relatively thin compared to the second pad and may be configured for hydrolysis and / or complex formation of the material to be planarized. Therefore, the first polymer layer 202 may have relatively large pores, be hydrophilic, and be surface-modified to functionalize the polymer surface, thereby allowing the polymer of the first polymer layer 202 to participate in the hydrolysis reaction. The first layer also contains cerium species to facilitate the planarization of materials such as silicon dioxide. In some examples, the thickness of the first layer may range from 0.1 microns to 5 microns. In other examples, the first layer may have any other suitable thickness (e.g., less than 0.1 microns or greater than 5 microns). In yet another example, the first polymer layer 202 may be non-porous. For example, as will be discussed later, the first polymer layer may have a textured surface that provides additional surface area for abrasive-free planarization chemistry.

[0034] In some examples, the second polymer layer 204 may be relatively thicker than the first layer and have relatively smaller pores than the first layer. In some examples, the second layer may be configured to retain the material removed by the first layer. For example, the second layer may have a surface that is chemically modified with a complexing agent adsorbed or bound to the second layer within its pores in order to retain the material removed from the substrate. In some examples, the thickness of the second layer may be several microns to 3 millimeters, and in more specific examples, it may be 40 microns to 2 millimeters.

[0035] Figures 2A and 2B also depict the contact between the substrate 206 and the pad 200. As shown in Figures 2A and 2B, the high-topology regions of the substrate 206 are in contact with the pad 200, while the pad 200 is not in contact with the low-topology regions of the substrate. When combined with planarization chemistry located within the pad 200 rather than in the space between the pad and the substrate, using relatively weak pressure of the substrate 206 against the pad 200 is useful in achieving faster removal of material from the high-topology regions of the substrate 206 compared to, or even excluding, the low-topology regions, because the high-topology regions are in contact with the hydrolysis and / or complex formation environment within the pad.

[0036] In Figures 2A and 2B, pressure is applied through the substrate 206 to press it against the pad 200. In some examples, the pad 200 is compressed solely by the weight of the substrate 206. In other examples, an additional force is applied to the substrate 206 (e.g., through the substrate holder 106 in Figure 1) to press the substrate 206 against the pad 200. Such a force causes compression of the pad 200, as shown in Figure 2B. In some examples, as described above, the second polymer layer 204 is configured to provide compressibility, while the first polymer layer 202 has a porous and / or textured surface configured to remove material during an abrasive-free chemical planarization process.

[0037] Furthermore, the first and / or second layers may be designed with consideration for their mechanical properties so that they are rigid enough to withstand wafer loads and downward forces / applied pressures. In some examples, the storage modulus of the first and / or second polymer layers is 15 MPa to 1200 MPa. More specifically, the storage modulus is 400 to 800 MPa. In some examples, the loss modulus of the first and / or second polymer layers is 100 to 600 MPa. More specifically, the loss modulus is 150 to 500 MPa. In some examples, the tanδ (loss ÷ storage) of the first and / or second polymer layers is 0.2 to 0.9. More specifically, it is 0.4 to 0.8. In some examples, the compressibility of the first and / or second polymer layers is less than 5%, and / or the surface tension is less than 40 mN / m. The viscoelastic and physical properties of the first polymer layer and / or the second polymer layer can be measured, for example, by standard dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA).

[0038] In some examples, as described above, the second polymer layer 204 is more compressible than the first polymer layer 202. Before compression, the first polymer layer 202 has a thickness 208A as shown in Figure 2A. After compression, the first polymer layer 202 has a second thickness 208B that is substantially the same as the first thickness 208A. In contrast, the second polymer layer 204 has a first thickness 210A before compression. The second polymer layer 204 has a second thickness 210B as shown in Figure 2B, which is thinner than the first thickness 210A as shown in Figure 2A. In this way, the second polymer layer 204 may absorb the compressive force, while the first polymer layer 202 maintains a planar substrate-facing surface. In other examples, the first polymer layer 202 is more compressible than the second polymer layer 204. In this way, the second polymer layer 204 can function as a relatively strong "foundation" that supports the first polymer layer 202 against the substrate 206.

[0039] The first and second layers may contain any one or more suitable materials. In some examples, the first polymer layer 202 and / or the second polymer layer 204 may contain one or more of the following: polyurethane, polyanhydride, polycarbonate, polyacrylate, polysulfone, polyester, polyacrylonitrile, polyethersulfone, polyarylsulfone, polyacrylonitrile, epoxy, or polyvinylidene fluoride. Furthermore, in some examples, the first and / or second layers may have a Shore A hardness of 60 to 90 or a Shore D hardness of 30 to 60. In other examples, the first and / or second layers may have hardness values ​​outside these ranges. All ranges described herein include endpoint values.

[0040] In some examples, the first layer comprises a thermoplastic material and the second layer comprises a thermosetting material. In some such examples, the second polymer layer 204 may be formed from a thermosetting polymer with a higher degree of crosslinking than the first polymer layer 202. As will be discussed later, the thermoplastic material may be 3D printed onto the second polymer layer 204 or formed in a more controlled manner than casting or injection molding. This allows for precise control of the pad's structure and physical properties. In other examples, both the first and second layers may be formed from thermosetting materials, or both layers may be formed from thermoplastic materials.

[0041] As described above, the first and / or second layers may contain a porous polymer as needed. In some examples, pores are formed in the first and / or second layers using the TIPS method or molten casting method. Another technique for forming pores in the polymer is to introduce a blowing agent, such as vapor and / or other gases (e.g., air, carbon dioxide, or nitrogen), before the molten polymer solidifies, thereby forming bubbles within the molten polymer.

[0042] In some more specific examples, the first polymer layer 202 has a lower porosity than the second polymer layer 204. For example, the average pore size of the first layer is in the range of 1 nm to 1000 nm, preferably 30 nm to 200 nm. The average pore size of the second layer is in the range of 5 nm to 1000 nm, preferably 200 nm to 1000 nm. In such examples, the second polymer layer 204 can provide adequate compressibility to adapt to the deformation of the first polymer layer 202. In other examples, the first polymer layer 202 has a higher porosity than the second polymer layer 204. In yet another example, one or more of the first polymer layer 202 and / or the second polymer layer 204 are non-porous.

[0043] In some examples, the first layer comprises a textured substrate-facing surface. Figure 4 shows a schematic diagram of another example of a pad 400 suitable for use as pad 104 in Figure 1. The pad 400 comprises a first polymer layer 402 and a second polymer layer 404. The first polymer layer 402 comprises a textured substrate-facing surface 406 configured to contact the substrate during abrasive-free chemical planarization. The textured substrate-facing surface 406 comprises several structures 408, such as protrusions, bumps, or grooves, which can create friction between the pad 400 and the substrate, leading to material removal from the substrate. In addition, the textured surface can compensate for a lack of porosity by providing a surface area for chemical reactions and / or channels for guiding the planarization fluid during processing.

[0044] As will be discussed later with reference to Figure 5, the first polymer layer and / or the second polymer layer contain a plurality of reactive units covalently bonded within the polymer chain. Each reactive unit contains a functional group. In some examples, the functional group of the reactive unit may function as a chelating ligand and / or coordinating ligand for cerium species (Ce(III) ions and / or Ce(IV) ions). In other examples, the cerium species may be ionic or covalently bonded to the functional group, or may be freely dispersed within the first polymer layer and / or the second polymer layer. Figure 5 schematically illustrates the incorporation of the functional group into the polymer and the incorporation of the cerium species into the polymer. In some examples, the functional group contains a hydrolyzing agent and / or a complexing agent for incorporation of the cerium species into the polymer. In some examples, the functional group contains one or more of carboxylic acids, amines, sulfonic acids, alcohols, phosphonic acids, amides, sulfates, nitrates, and / or polyethylenes. In some more specific examples, the functional group may include one or more of iminodisuccinic acid, ethylenediaminedisuccinic acid, glutamic acid, methylglycinediacetic acid, dicyanamide, polyAMPS, or polydiallyldimethylammonium chloride. Such species may also be used separately as chelating agents in addition to or instead of functionalizing the pad with such species. In other examples, all other appropriate functionalizations may be carried out to impart the desired chemical function to the pad. For example, the functionalization may be optimized to form a complex (e.g., a chelate and / or coordination complex) with the cerium species, thereby incorporating the cerium species into the pad. In other examples, the cerium species may be ionic or covalently bonded to the functional group. Other examples of functional groups include, but are not limited to, -COOCH2CH2OH, -N(CH2CH2OH)2, and -CONHR. In another example, the cerium species may be freely dispersed within the polymer layer.

[0045] In some examples, the polymer layer contains a hybrid distribution of covalently bonded functional groups and freely dispersed functional groups within the polymer matrix. As described above, functional groups can bond with cerium species. Cerium species can form complexes with functional groups, bond ionically or covalently with functional groups, or be freely dispersed within the polymer layer. In this way, the dispersed functional groups and cerium species can be released upon contact with a planarizing solution, thereby facilitating planarization. For example, oxalic acid can be dissolved in the polymer blend during pad manufacturing and released into the planarizing medium during planarization. The two -COO groups of oxalic acid promote Cu complex formation, enhancing Cu removal. Similarly, free oxalic acid can also complex with cerium species, promoting the dispersion of cerium species within the pad and facilitating the planarization of silicon dioxide and other materials that can be planarized using cerium species. In this way, a functionalized pad containing cerium species may enhance the material removal rate. Furthermore, the process can be repeated without reconditioning the pad. This is because abrasives are not used as long as the dispersed species are not limited and the surface irregularities of the pad maintain their integrity even after multiple planarization cycles. When a conditioning process is used to mechanically polish the pad, the planarization process remains abrasive-free. In some such approaches to performing polishing conditioning, the pad may have surface grooves or channels to facilitate the removal of polymer debris during conditioning. The benefits of a low-defect planarization process are still retained due to the absence of abrasives. Environmental benefits are ensured during the planarization process as wastewater can be chemically treated for seed and water recovery. Polymer residues from polishing conditioning may be separated before all environmental disposal.

[0046] All appropriate methods may be used to incorporate cerium species and, if necessary, functional groups into the planarization pad. In some examples, the polymer of the planarization pad may be functionalized during polymer synthesis. Figure 5 schematically illustrates the incorporation of cerium species and, if necessary, functional groups into the polymer. In scheme (1), a monomer is bonded to a chemical agent containing cerium species and, if necessary, a bifunctional reaction molecule containing the functional group of choice. A cerium-containing chemical agent, such as a cerium salt, may be incorporated during polymerization to provide the cerium species. Polymerization distributes the cerium species and the functional group of choice throughout the polymer (including within the solid mass of the polymer). For example, in scheme (1), the cerium species of the cerium-containing chemical agent (black trapezoids) is bonded to the functional group of the bifunctional reaction molecule in the functional polymer network shown by the dashed lines. In this example, the counterions of the cerium-containing chemical agent (gray trapezoids) are freely dispersed within the functional polymer network. In this way, the cerium species and functional groups are uniformly incorporated throughout the polymer layer.

[0047] In some examples, the functional group of interest may act as a complex-forming ligand for the cerium species. In other examples, the cerium species may be ionic or covalently bonded to the functional group, or freely dispersed in the polymer. Examples of cerium salts that can be used to incorporate cerium species into the pad include cerium trichloride, cerium sulfate, cerium nitrate hexahydrate, cerium carbonate, cerium acetate, cerium ammonium nitrate, cerium(III) methanesulfonate (Ce(CH3SO3)3), cerium(III) trifluoromethanesulfonate (Ce(CF3SO3)3), and combinations thereof.

[0048] One potential advantage of this approach is that the cerium species and, if necessary, functional groups are present throughout the entire pad on the pore surface. Furthermore, mechanical wear and / or chemical degradation expose the cerium species and, if necessary, functional groups beneath the substrate-facing surface, allowing the pad to operate longer than pads lacking cerium species and, if necessary, functional groups internally. In addition, single-layer pads may be manufactured in a single process, thereby reducing manufacturing time and cost compared to pads with two or more layers.

[0049] Suitable monomers for generating crosslinked polymer networks using curing agents, cerium species, or functionalization reaction molecules as needed include monomers having at least two reaction sites. Some examples of suitable monomers, as shown in the example in Figure 6, include diisocyanates (e.g., 4,4'-methylenebis(phenylisocyanate), toluene-2,4-diisocyanate, and hexamethyldiisocyanate), dieps (e.g., 1,4-butanediol diglycidyl ether, bisphenol A propoxylate diglycidyl ether, and (2-ethyl-2(hydroxymethyl))-1,3-propanediol polymer with (chloromethyl)oxirane), and anhydrides (e.g., pyromellitic dianhydride, ethylenediaminetetraacetic acid dianhydride, and diethylenetriaminepentaacetic acid dianhydride). In some examples, such monomers react with ethylene glycol and / or substituted ethylene glycols (e.g., glyceric acid) to form polyurethanes containing unreacted carboxylic acid groups. These carboxylic acids can function as chelating ligands for the incorporation of cerium species into polymer layers.

[0050] In some examples, the polymer layer contains polyurethane. In some of these examples, the functional group is located on the isocyanate portion of the polyurethane. Reaction of a hydroxyl group or amine group with the isocyanate can form urethane bonds in the polymer backbone. Examples of suitable molecules that can react with diisocyanate monomers include polyols (e.g., glyceric acid). In some of these examples, the functional group is located on the polyol portion of the polyurethane. Other examples of suitable molecules that can react with diisocyanate monomers include 2,2'-bis(hydroxymethyl)propionic acid and 3,4-dihydroxybenzoic acid. In some of these examples, the acid portion can function as a chelating ligand or coordinating ligand, or as other ionic bonding site, for the incorporation of cerium species into the polymer layer. In other examples, cerium species can be freely dispersed within the polymer layer.

[0051] In other examples, the polymer layer contains polyanhydride. In some examples, the functional groups are located in the anhydride portion of the polyanhydride. The functional groups can form complexes with cerium species or bond to cerium species ionically or covalently. The cerium species can also be freely dispersed within the polymer layer. Polyanhydride is formed by the condensation between two carboxylic acid groups, which allows for the exclusion of water molecules. The anhydride portion makes the polyanhydride more reactive and more susceptible to hydrolysis than other polymers (e.g., polyurethane). This can result in a biodegradable polymer network that reduces the environmental impact of waste. In some examples, the polyanhydride further contains a polyol portion covalently bonded to the polyanhydride. In some of these examples, the functional groups are additionally or alternatively located in the polyol portion. As mentioned above, the functional groups can form complexes with cerium species or bond to cerium species ionically or covalently. The cerium species can also be freely dispersed within the polymer layer. Polyols can be incorporated into polyanhydride systems as additives or modifiers. For example, polyols can be used as plasticizers to increase the flexibility of polyanhydride. Polyols can also be used as components of copolymers, such as copolymers containing polyanhydride and polyester bonds. This can result in hybrid materials with properties (e.g., flexibility and compressibility) that are tuned for chemical planarization.

[0052] In other examples, functional polymer networks are additionally or alternatively formed using curing agents and / or crosslinking agents containing the desired functional groups. The functional groups can form complexes with cerium species, or they can be ionically or covalently bonded to the cerium species. In yet another example, functional polymers are crosslinked using crosslinking agents that do not contain the desired functional groups. In these examples, the cerium species can also be freely dispersed within the polymer layer. Crosslinking results in a three-dimensional polymer network with greater strength and rigidity than an uncrosslinked polymer.

[0053] In some examples, the polymer layer contains epoxy. Epoxy can be formed by treating a precursor molecule containing epoxy functional groups with a curing agent. The curing agent causes crosslinking of the precursor molecule, forming a three-dimensional network structure. In some such examples, the functional groups are located on the epoxy portion of the epoxy. In other examples, the functional groups are located on a polyol bonded to the curing agent and / or within the epoxy chain, either additionally or alternatively. As described above, polyols can be incorporated into the polymer layer to modulate one or more properties of the polymer, such as flexibility, toughness, viscosity, adhesion, and hydrophobicity. In some examples, the addition of polyols or other additives can alter the rate or degree of crosslinking, which can also be used to modulate the properties of the polymer.

[0054] Referring again to Figure 5, in some examples, the functional groups are separated by oligomeric segments of the polymer chain. For example, in scheme (2), monomers are bonded to a chain extender to form an elongated prepolymer molecule. In this example, a cerium-containing chemical agent may be mixed with the elongated prepolymer molecule. Then, as shown in Figure 5, the elongated prepolymer molecule is polymerized in the presence of a bifunctional reaction molecule containing the functional group of interest to form a functional polymer network incorporating the cerium species. In some examples, the cerium species provided by the cerium-containing chemical agent can form complexes (e.g., chelate complexes or coordination complexes) with the functional group of interest. In other examples, the cerium species can form ionic bonds with the functional group of interest. In yet another example, the cerium species may be freely dispersed within the polymer network. In the example shown in scheme (2), the cerium species (black trapezoids) and the counterions of the cerium-containing chemical agent (gray trapezoids) are freely dispersed within the functional polymer network. As a result, the cerium species and functional groups are incorporated into the polymer network at long intervals where the prepolymer molecules are bonded together. Some examples of suitable cerium-containing chemicals include cerium trichloride, cerium sulfate, cerium nitrate hexahydrate, cerium carbonate, cerium acetate, cerium ammonium nitrate, cerium(III) methanesulfonate (Ce(CH3SO3)3), and cerium(III) trifluoromethanesulfonate (Ce(CF3SO3)3).

[0055] Polymers can be functionalized additionally or alternatively after polymerization. Figure (3) shows an example of post-polymerization functionalization. For example, a bifunctional reaction molecule containing the desired functional group can be bonded to the synthetic polymer. Alternatively, cerium species can be introduced into the synthetic polymer by adding a cerium-containing chemical agent. In some such examples, the functional group is bonded to the substrate-facing surface of the polymer layer. For example, the functional group can be bonded to the substrate-facing surface of the first polymer layer 202 in Figures 2A-2B. Again, as mentioned above, the functional group can function as a complex-forming ligand to introduce cerium species into the polymer layer. In other examples, the cerium species can be ionic or covalently bonded to the functional group. In yet another example, the cerium species can be freely dispersed on the substrate-facing surface of the polymer layer. In the example shown in scheme (3), the dotted lines represent the bond between the functional group of the bifunctional reaction molecule and the cerium species (black trapezoids). The counterions (gray trapezoids) of the cerium-containing chemical agent (e.g., cerium salt) are freely dispersed within the functional polymer network in this example. As a more specific example, a porous polyvinylidene fluoride (PVDF) layer or other suitable layer may be functionalized with a chelating agent such as poly(acrylic acid) to complexate cerium species. In the examples shown in Figures 2A and 2B, the porous PVDF layer may be used as either the first or second layer.

[0056] In some examples, the first polymer layer 202 in Figures 2A-2B is functionalized, while the second polymer layer 204 is not. Similarly, in some examples, the first polymer layer 202 in Figures 2A-2B may contain cerium species, while the second polymer layer 204 may not contain cerium species. This can result in cost savings, as well as faster and / or more efficient manufacturing, compared to functionalizing the entire pad. In other examples, as described above, two or more surfaces of the pad may contain cerium species and, optionally, functional groups, which may additionally or alternatively include one or more surfaces of the first polymer layer 202 and the second polymer layer 204. It will also be understood that the first polymer layer and / or the second polymer layer may contain various cerium species and, optionally, various functional groups.

[0057] In some cases, polymers may be functionalized by coating, in which case the functional groups are adsorbed onto the polymer substrate rather than crosslinked to it. For example, polymers may be functionalized by incorporating a reaction molecule containing the functional groups using a suitable solvent system. In some cases, the solvent system causes swelling of the polymer layer, which allows the functional groups to be incorporated into at least a portion of the bulk volume of the polymer layer. Cerium species can also be incorporated in a similar manner, for example, by including a cerium-containing chemical agent along with the functional groups in the solvent system used to swell the polymer layer.

[0058] In addition, when functionalized polymers are used in pads, the functionalization may be regenerated, for example, by adding new cerium species and, if necessary, functional groups at their site (e.g., via a planarization solution distribution mechanism). Other aspects of functionalization regeneration are described in detail in U.S. Patent Application No. 17 / 729,805, filed April 26, 2022, entitled “Regeneration of Pad Surfaces and Recovery of Metals,” which is incorporated herein by reference in its entirety for any purpose. In such examples, cerium species may be included in the planarization solution to promote planarization and aid in the regeneration of the pad. Examples of cerium species that may be included in the planarization solution include cerium(III) and cerium(IV) salts and / or organometallic compounds that are soluble in the solvent system used in the planarization solution.

[0059] As described above, the methods disclosed herein may be used to additionally or alternatively incorporate cerium species (e.g., Ce(III) or Ce(IV) ions (e.g., as salts or organometallic complexes)) into a pad. Without being constrained by theory, such cerium species may be bonded to reactive units in the polymer matrix and / or polymer layers. For example, cerium species may be complexed by hydroxyl, carbonyl, sulfonyl, sulfonic acid, and / or carboxylic acid functional groups present in the polymer matrix. One or more cerium species may be additionally or alternatively dispersed freely in the polymer matrix. One or more cerium species may be additionally or alternatively ionic or covalently bonded to functional groups in the polymer matrix. In some examples, as described above, the pad comprises a single layer. If the pad comprises multiple layers, it will also be understood that the cerium species may be incorporated into one or more of the layers. Pads containing cerium species may be formed in any suitable way. In some examples, as described above for scheme (2) in Figure 5, the cerium-containing chemical is incorporated into a prepolymer, which is then polymerized to form a polymer pad. All suitable cerium-containing chemicals can be used. Some examples of suitable cerium-containing chemicals include cerium trichloride, cerium sulfate, cerium nitrate hexahydrate, cerium carbonate, cerium acetate, cerium ammonium nitrate, cerium(III) methanesulfonate (Ce(CH3SO3)3), and cerium(III) trifluoromethanesulfonate (Ce(CF3SO3)3).

[0060] Figure 9 shows an example reaction scheme for the incorporation of cerium species into a polymer matrix. The polymer matrix may include, for example, polyAMPS shown in 902. PolyAMPS is a commercially available water-soluble polymer with a hydrophobic main chain. In 904, polyAMPS is reacted with cerium carbonate in the presence of water to incorporate the cerium species. The sulfonic acid portion of polyAMPS is deprotonated to form a poly(2-acrylamido-2-methyl-1-propanesulfonic acid) complex with Ce(III) ions, as shown in 906, thereby incorporating the cerium species into the polymer matrix. The combined use of polyAMPS and cerium can also be used for the planarization of polysilicon and silicon dioxide films, as will be discussed later.

[0061] The reaction scheme shown in Figure 9 can also be applied to other sulfonic acid polymers and polymers with similar reactivity, such as polymers containing sulfonyl groups. In some examples, the polymer matrix of existing polymer pads may contain sulfonyl groups. Cerium species can be incorporated into existing polymer pads in a scheme similar to that shown in Figure 9. Cerium species can be incorporated in the final stage of pad formation, or in an intermediate prepolymer stage of pad formation, such as the prepolymer stage described above.

[0062] The concentration and density of cerium species within the pad can be adjusted at the polymer matrix level, prepolymer level, or curing / chain extension level of the polymer synthesis to obtain appropriate planarization rate or material removal rate and selectivity. This enables non-abrasive planarization of non-metallic materials and planarization of film stacks containing such materials at their location. For example, a pad containing cerium species can be used to planarize silicon oxide in the presence of an aqueous solution, which may contain one or more additives, such as additives used in cerium oxide particle-containing dispersions.

[0063] Pads containing cerium species can be used to planarize native oxide films on substrate surfaces. For example, polysilicon films form a native silicon oxide layer upon exposure to air. However, pads containing cerium species can be used to planarize the native oxide. Planarizing solutions containing other chemical species can be poured onto the substrate to chemically planarize the polysilicon film beneath the oxide layer. For example, an underlying polysilicon film can be planarized at a rate of 500-600 nm / min using an aqueous solution of PDADMAC at pH 10. It will also be understood that other planarizing agents can be used. Other examples of suitable planarizing agents include polyAMPS, poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine), poly(allylamine), poly(ethyleneimine), poly(acrylamide) (PAA), and combinations thereof. Poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine), poly(allylamine), and poly(ethyleneimine) can planarize polysilicon films at similar rates to PDADMAC. An aqueous solution containing a copolymer of PAA and PDADMAC exhibits a planarization rate lower than that of PDADMAC alone, but higher than that of PAA alone. Such a solution may not harm the cerium contained in the pad. This makes it possible to use such a solution in combination with cerium-containing pads. Additional aspects of planarization are described in detail in U.S. Patent Application No. 15 / 931,556, entitled "Chemical Planarization," filed May 13, 2020; U.S. Patent Application No. 18 / 149,005, entitled "Chemical Planarization," filed December 30, 2022; U.S. Patent Application No. 17 / 729,805, entitled "Pad Surface Regeneration and Metal Recovery," filed April 26, 2022; U.S. Patent Application No. 17 / 823,857, entitled "Tool for Chemical Planarization," filed August 31, 2022; and U.S. Provisional Patent Application No. 63 / 504,098, entitled "Tool for Chemical Planarization," filed May 24, 2023. The entire contents thereof are incorporated herein by reference for all purposes.

[0064] As a more specific example, a planarization solution containing polyAMPS can be poured onto a substrate to chemically planarize a polysilicon substrate. A pad containing cerium species can be used to chemically planarize silicon oxide from the polysilicon surface. PolyAMPS can planarize the underlying polysilicon surface. The combined action of cerium species and polyAMPS may enable the planarization of a substrate having both polysilicon and silicon oxide, for example, using a single pad.

[0065] In other examples, two or more different chemical species may be included in the planarization pad. For instance, the pad may include a cerium species configured to remove silicon oxide and another chemical species configured to planarize polysilicon. In this way, a single pad can be used to remove the native oxide layer and chemically planarize the substrate.

[0066] In some cases, planaring pads containing cerium species can be used for abrasive-free planaring of patterned structures combining metallic and nonmetallic layers. For example, cerium-containing salts of sulfonic acids, carboxylic acids, and / or diamines can be incorporated into polymer pads. Sulfonic acids, carboxylic acids, and / or diamines can function as active functional groups for the chemical planaring of metals and refractory metals (e.g., barrier layers), while the cerium species can act as an active site for removing oxide or nitride materials (e.g., silicon oxide, silicon nitride, silicon oxynitride, or silicon oxycarbide) from the substrate.

[0067] In further examples, the chemical planarization process may utilize two or more independent planarization pads. For instance, a first planarization pad may be used to remove the native oxide layer from the substrate. A second planarization pad may then be used to polish the substrate after the native oxide layer has been removed. In some such examples, the substrate may be circulated from a first processing station pad in a processing tool containing the first planarization pad to a second processing station pad in a processing tool containing the second planarization pad.

[0068] In some cases, pads containing cerium species may also be used to polish other materials, either additionally or as an alternative. Other examples of suitable materials that can be polished with cerium species pads include silicon nitride, silicon oxynitride, and silicon carbonitride. By incorporating cerium species into the planarizing pad, such materials can be planarized without the use of ceria or any other abrasive in the planarizing medium.

[0069] One or more of these materials (e.g., silicon nitride, silicon oxynitride, or silicon carbonitride) can be used as stop barriers in shallow trench isolation (STI) and other related structures. In some cases, high-temperature phosphoric acid is used to remove nitride films. However, by incorporating cerium species into the planarizing pad, such nitride films can be planarized without the use of ceria or other abrasives or acids.

[0070] Figures 7A and 7B show flowcharts illustrating an example of Method 700 for forming a pad for abrasive-free chemical planarization of a substrate. The following description of Method 700 will be made with reference to Figures 1 through 6 above. It will be understood that Method 700 can be implemented in other situations as well.

[0071] In 702, Method 700 includes the step of forming a pad for abrasive-free chemical planarization of a substrate. The pad comprises a polymer layer containing cerium species incorporated into the polymer layer and optionally functional groups, the functional groups comprising one or more complexing agents and hydrolyzing agents. The functional groups can additionally or alternatively covalently or ionically bond with the cerium species or form complexes. For example, a pad can be formed containing Ce(III) or Ce(IV) complexed by the functional groups. Figures 2A-2B show an example of a pad 200 that can be formed by Method 700 in Figures 7A-7B.

[0072] The pads may be formed in any suitable manner. In some examples, in 704, the pad-forming step involves reacting a plurality of reactive units with a plurality of monomer units in the presence of a cerium-containing chemical agent, wherein one or more of the plurality of reactive units or monomer units contain a functional group. Figure 6 shows some examples of suitable monomers. In scheme (1) of Figure 5, the monomer is polymerized with a cerium-containing chemical agent containing a cerium species and a bifunctional reactive molecule containing the functional group of the choice, thereby distributing the cerium species and the functional group of the choice throughout the polymer. Examples of cerium-containing chemical agents include cerium trichloride, cerium sulfate, cerium carbonate, cerium acetate, cerium nitrate hexahydrate, cerium ammonium nitrate, cerium(III) methanesulfonate (Ce(CH3SO3)3), and / or cerium(III) trifluoromethanesulfonate (Ce(CF3SO3)3).

[0073] In another example, in 706, the pad-forming step involves reacting a plurality of reactive units with a plurality of oligomeric segments in the presence of a cerium-containing chemical agent, wherein one or more of the plurality of reactive units or oligomeric segments contain a functional group. For example, in scheme (2) shown in Figure 5, monomers are bonded to a chain extender to form an elongated prepolymer molecule. This elongated prepolymer molecule is then polymerized in the presence of a bifunctional reactive molecule containing the desired functional group to form a functionalized polymer. In such examples, the cerium-containing chemical agent may be mixed in either the prepolymer formation step or the functionalized polymer synthesis step. Examples of cerium-containing chemicals include cerium trichloride, cerium sulfate, cerium carbonate, cerium acetate, cerium nitrate hexahydrate, cerium ammonium nitrate, cerium(III) methanesulfonate (Ce(CH3SO3)3), and / or cerium(III) trifluoromethanesulfonate (Ce(CF3SO3)3), which can be combined with prepolymers such as the prepolymer shown in Figure 5, which contain cerium species. In this way, cerium species can be incorporated into the pad by polymerization of the prepolymer.

[0074] In some examples, in 708, the pad formation step includes casting a polymer layer using a prepolymer containing a cerium-containing chemical agent and curing the prepolymer. For example, the prepolymer containing the cerium-containing chemical agent may be formed as described above with reference to Figure 5. The prepolymer containing the cerium-containing chemical agent may have a higher viscosity than the monomer unit solution, making it easier to handle and pour into the mold. This enables a simple and efficient casting process, especially for complex and intricate shapes. The prepolymer can be formulated with specific compositions and properties to control elements such as hardness, flexibility, elongation, and curing time. The prepolymer can be designed to cure at ambient temperature or with minimal heat input, thus simplifying the casting process. This allows the polymer to cure at lower temperatures, reducing energy consumption and enabling casting in heat-sensitive molds. Furthermore, since the prepolymer can be manufactured under controlled conditions, using a prepolymer results in more homogeneous batch-to-batch production than polymerization from scratch. Casting with a prepolymer also allows for precise metering and control of material usage. This minimizes material waste and contributes to cost-effectiveness in manufacturing.

[0075] In some examples of 710, the pad formation step includes forming a polymer layer. For example, a prepolymer can be formed as described above to form a polymer layer.

[0076] In some examples, in 712, the pad-forming step includes reacting the surface of the polymer layer with a cerium-containing chemical agent, and optionally with a reactive unit containing a functional group, depending on whether, for example, the cerium species provided by the cerium-containing chemical agent can bind to or adsorb onto the pad surface. If the cerium adsorption affinity of the pad surface is low, the functional group may react with the pad surface. This functional group is selected to form a complex with or bind to cerium III and / or IV. Examples of functional groups are those described above. Alternatively or additionally, the functional group may be selected to perform one or more hydrolysis or complex formation of the material from the surface to be planarized.

[0077] In 714, in some examples, the pad-forming step includes swelling the polymer layer with a solvent and then incorporating cerium species and functional groups into at least a portion of the bulk volume of the polymer layer. For example, the polymer layer may be treated with a solvent system that causes swelling of the polymer layer. This makes it possible to incorporate cerium species and functional groups into at least a portion of the bulk volume of the polymer layer. Cerium species may be incorporated by adding a cerium-containing chemical agent, as described above.

[0078] In some examples, in 716, the polymer layer formation step includes forming polyurethane, where the functional groups are located on the isocyanate or polyol portion of the polyurethane. For example, as described above with reference to Figure 6, the functional groups may be located on isocyanates such as 4,4'-methylenebis(phenyl isocyanate), toluene-2,4-diisocyanate, and hexamethyl diisocyanate. Reaction of hydroxyl or amine groups with the isocyanate can form urethane bonds in the polymer main chain. In other examples, the functional groups are located on the polyol portion of the polyurethane. For example, the polyol can be reacted with the isocyanate to form polyurethane. In this way, the functional groups can be integrated into the polyurethane. Cerium species may be incorporated by complex formation with the functional groups. Cerium species may be additionally or alternatively ionic or covalently bonded to the functional groups, or freely dispersed within the polymer layer.

[0079] In some examples, in 718, the polymer layer formation step includes forming a polyanhydride, where the functional group is located on the anhydride or polyol portion of the polyanhydride. For example, as described above with reference to Figure 6, the functional group may be located on anhydrides such as pyromellitic dianhydride, ethylenediaminetetraacetic acid dianhydride, and diethylenetriaminepentaacetic acid dianhydride. In this way, the functional group can be incorporated into the polyanhydride. In another example, a polyol can be incorporated into the polyanhydride system as an additive or modifier. Cerium species may be incorporated by complex formation with functional groups. The cerium species may be additionally or alternatively ionic or covalently bonded to the functional group, or may be freely dispersed within the polymer layer.

[0080] In some examples, in 720, the polymer layer formation step includes forming an epoxy, where the functional groups are located on the epoxide portion of the epoxy. For example, as described above with reference to Figure 6, the functional groups may be located on the epoxy. Crosslinking of the epoxy forms a polymer containing the functional groups. In other examples, the functional groups are located on a polyol bonded within the epoxy chain. The polyol can function as a curing agent or additive / modifier. Polymerization incorporates the polyol and functional groups into the polymer matrix. Cerium species may be incorporated by complex formation with the functional groups. Cerium species may be additionally or alternatively ionic or covalently bonded to the functional groups, or freely dispersed within the polymer layer.

[0081] Referring here to Figure 7B, in some examples, in 722, method 700 further includes forming a second polymer layer located on the opposite side of the first polymer layer as the substrate-facing surface of the first polymer layer. In some examples, the first polymer layer 202 and the second polymer layer 204 are formed integrally as a double layer in a single process. In some such examples, the first polymer layer 202 and the second polymer layer 204 are formed by liquid casting, injection molding, extrusion, additive manufacturing, or a combination thereof.

[0082] In some examples, in 724, the process of forming the first and second polymer layers includes forming the first and second polymer layers in a single casting while varying the composition. For example, in a liquid casting process, the composition of the liquid poured into the mold may be changed during the liquid casting process. This results in a single-piece structure with two different layers produced in a single process, allowing for adjustment of the composition and other properties of the porous pad during manufacturing. Furthermore, using a single process to form both layers reduces costs and improves process efficiency compared to forming each layer individually.

[0083] In other examples, the first polymer layer 202 and the second polymer layer 204 are manufactured in separate processes. In some of these examples, the first polymer layer 202 and the second polymer layer 204 are formed by liquid casting, injection molding, extrusion, additive manufacturing, or a combination thereof.

[0084] In some examples, in 726, method 700 further includes forming the first polymer layer and then placing the first polymer layer in a mold. Method 700 further includes injection molding a polymer for the second polymer layer into the mold and incorporating the first polymer layer into the second polymer layer by insert molding. This allows for inspection of the first layer before forming the second layer and enables more precise control over the formation of the first and second layers. In some examples, manufacturing the first and second layers separately may be faster, cheaper, and / or more efficient than manufacturing them in a single step as described above.

[0085] In some examples, method 700 includes incorporating a plurality of second reactive units and / or cerium species into the polymer chain of the second polymer layer. For example, cerium species and optionally functional groups may be incorporated into the second polymer layer 204 in Figures 2A-2B in the manner described above.

[0086] In some examples, in 730, the step of forming the first polymer layer includes forming the first polymer layer using a thermoplastic material, and the step of forming the second polymer layer includes forming the second polymer layer using a thermosetting material. For example, the first polymer layer 202 in Figures 2A and 2B may contain a thermoplastic material, the second polymer layer 204 may contain a thermosetting material, or vice versa. This makes it possible for each layer to have a tunable molecular structure and physical properties (e.g., compressibility and toughness).

[0087] In some examples of 732, method 700 includes using a foaming agent to form pores in at least one of the first polymer layer or the second polymer layer. This enables the formation of a porous polymer structure, which may have a larger surface area (including the surface of the pores) and higher compressibility than a solid polymer.

[0088] In some examples, in 734, method 700 includes forming a textured surface on a first polymer layer. For example, the pad 400 in Figure 4 has a textured substrate-facing surface 406. The textured surface can facilitate the removal of material from the substrate and increase the surface area compared to a smooth substrate-facing surface.

[0089] Figure 8 shows a schematic diagram of another example of pad 800 suitable for use as pad 104 in Figure 1. Pad 800 comprises a single polymer layer 802. However, as mentioned above, in other examples, pad 800 may comprise any other suitable number of layers (e.g., two or more layers). Pad 800 comprises a plurality of microspheres 804 and / or a plurality of fillers 806. The microspheres 804 and / or fillers 806 are dispersed in the polymer layer 802 during pad manufacturing. Each microsphere 804 and filler 806 comprises a polymer, a cerium species, and a functional group optionally incorporated into the polymer (e.g., the cerium species and functional group described above with reference to Figures 5-6). However, the microspheres 804 and fillers 806 are not covalently bonded to the polymer layer 802 of pad 800. Alternatively, the microspheres 804 and fillers 806 can be retained within the polymer layer 802 by electrostatic attraction, hydrophilic / hydrophobic interactions, van der Waals forces, mechanical interlocking, etc. Furthermore, the microspheres 804 and fillers 806 can be chemically regenerated. This allows for the repeated use of cerium species and, if necessary, functional groups in multiple wafers.

[0090] This disclosure is presented as an example and with reference to relevant drawings. Components, processes, and other elements that may be substantially identical in one or more drawings are identified collaboratively and described with minimal repetition. However, it should be noted that collaboratively identified elements may differ to some extent. Also, it should be noted that some drawings are schematic and may not be drawn to scale. The various scales, aspect ratios, and number of components shown in the drawings may be intentionally distorted to make certain features or relationships more visible.

[0091] As used herein, "and / or" is defined as an inclusive OR V, as defined in the truth table below.

[0092] [Table 1]

[0093] As used herein, the term “one or more of A or B” includes A, B, or a combination of A and B. The term “one or more of A, B, or C” is synonymous with A, B, and / or C. Therefore, as used herein, “one or more of A, B, or C” includes A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0094] The configurations and / or approaches described herein are actually illustrative, and these particular embodiments or examples should not be interpreted as restrictive, and it will be understood that numerous variations are possible. A particular routine or method described herein may represent one or more of several strategies. Thus, the various operations illustrated and / or described may be performed in the order illustrated and / or described, in other orders, in parallel, or in abbreviation. Similarly, the order of the processes described above may be changed.

[0095] The subject matter of this disclosure includes all novel and non-obvious combinations and partial combinations thereof of the various processes, systems and configurations, as well as other features, functions, actions, and / or characteristics disclosed herein, and all equivalents thereof.

Claims

1. A pad for performing abrasive-free chemical planarization of a nonmetallic material, comprising a polymer layer configured to contact a substrate during the abrasive-free chemical planarization, wherein the polymer layer comprises a cerium species, and the cerium species comprises one or more of Ce(III) or Ce(IV).

2. The pad according to claim 1, wherein the cerium species is formulated as one or more of cerium trichloride, cerium sulfate, cerium carbonate, cerium nitrate hexahydrate, cerium acetate, cerium ammonium nitrate, cerium methanesulfonate (III), or cerium trifluoromethanesulfonate (III).

3. The pad according to claim 2, wherein the cerium-containing substance is formulated as one or more organometallic complexes of Ce(III) or Ce(IV).

4. The pad according to claim 1, wherein the polymer layer further comprises a functional group containing one or more complexing agents or hydrolyzing agents, which are incorporated into the polymer matrix within the polymer layer.

5. The pad according to claim 1, wherein the polymer layer comprises cerium species freely dispersed in the polymer matrix of the polymer layer.

6. The pad according to claim 4, wherein the polymer layer comprises a cerium species that is ionic or covalently bonded to the functional group.

7. The pad according to claim 4, wherein the polymer layer contains a cerium species that is complexed with the functional group.

8. The pad according to claim 4, wherein the functional group comprises one or more of a hydroxyl functional group, a carbonyl functional group, a sulfonyl functional group, or a carboxylic acid functional group.

9. The pad according to claim 1, further comprising a plurality of polymer layers, wherein the cerium species is incorporated into two or more of the plurality of polymer layers.

10. A chemical planarization tool comprising: a pad for performing abrasive-free chemical planarization of nonmetallic materials, the pad comprising a polymer layer configured to contact a substrate during the abrasive-free chemical planarization, wherein the polymer layer comprises a cerium species, and the cerium species comprises one or more of Ce(III) or Ce(IV); a platen for supporting the pad; a substrate holder configured to hold the substrate with respect to the surface of the pad; and a planarization solution introduction system for introducing a planarization solution onto the pad.

11. The tool according to claim 10, further comprising the planarizing solution introduction system, wherein the planarizing solution comprises poly(2-acrylamido-2-methyl-1-propanesulfonic acid).

12. A method comprising the step of forming a pad for abrasive-free chemical planarization of a substrate, wherein the pad comprises a polymer layer containing a cerium species, and the cerium species comprises one or more of Ce(III) or Ce(IV).

13. The method according to claim 12, wherein the pad forming step includes a step of mixing a cerium-containing chemical agent with a prepolymer and a step of polymerizing the prepolymer to form a polymer layer containing the cerium species.

14. The method according to claim 13, wherein the cerium-containing chemical agent comprises one or more of the following: cerium trichloride, cerium carbonate, cerium acetate, cerium sulfate, cerium nitrate hexahydrate, cerium nitrate ammonium, cerium methanesulfonate (III), or cerium trifluoromethanesulfonate (III).

15. The method according to claim 13, wherein the cerium-containing chemical agent comprises one or more organometallic complexes of Ce(III) or Ce(IV).

16. The method according to claim 13, wherein the pad forming step comprises a step of reacting a plurality of reactive units and a plurality of monomer units in the presence of the cerium-containing chemical agent, and one or more of the plurality of reactive units or the plurality of monomer units include a functional group.

17. The method according to claim 13, wherein the pad forming step comprises a step of reacting a plurality of reactive units and a plurality of oligomer segments in the presence of the cerium-containing chemical agent, and one or more of the plurality of reactive units or the plurality of oligomer segments contain a functional group.

18. The method according to claim 13, wherein the pad forming step comprises a step of reacting the surface of the polymer layer with the cerium-containing chemical agent and a reactive unit having a functional group.

19. The method according to claim 12, wherein the pad forming step includes a step of swelling the polymer layer with a solvent and a step of blending the cerium species and the reactive unit having a functional group into at least a portion of the bulk volume of the polymer layer.

20. The method according to claim 12, further comprising the step of forming a second polymer layer on the opposite side of the polymer layer containing the cerium species, which is disposed as the substrate contact surface of the polymer layer containing the cerium species, and further comprising the step of incorporating a second plurality of reactive units having functional groups into the polymer chain of the second polymer layer.

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