CMP compositions containing novel abrasives

Abstract

The chemical-mechanical polishing composition comprises a liquid carrier and colloidal silica particles dispersed in the liquid carrier. The colloidal silica particles have a positive charge of at least 10 mV in the liquid carrier and can be characterized as having (i) a number-average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42. For example, when the polishing composition is a tungsten CMP composition, the polishing composition may further optionally comprise an iron-containing accelerator and a tungsten etch inhibitor.

Description

[Technical Field]

[0001] Chemical-mechanical polishing (CMP) compositions and methods for polishing (or planarizing) the surface of a substrate are well known. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for polishing various metal (e.g., tungsten) and non-metal (e.g., silicon oxide) layers on semiconductor substrates may contain abrasive particles suspended in an aqueous solution and various chemical additives, such as oxidizers, chelating agents, catalysts, topography control agents, buffers, and the like. [Background technology]

[0002] In a conventional CMP operation, the substrate (wafer) to be polished is mounted on a carrier. The carrier is mounted on a carrier assembly and positioned in contact with a polishing pad within a CMP polishing tool. The carrier assembly provides a controlled pressure to the substrate against the polishing pad. The substrate and pad are driven into relative motion by an external driving force. The relative motion of the substrate and pad abrades and removes a portion of material from the surface of the substrate, thereby polishing the substrate. Polishing of the substrate by the relative motion of the pad and substrate is further assisted by the chemical activity of the polishing composition and / or the mechanical activity of an abrasive suspended in the polishing composition.

[0003] In many CMP operations, optimal planarization and / or planarization efficiency are critical. For example, in tungsten CMP operations, excessive oxide erosion and / or dishing can lead to electrical contact problems that can complicate subsequent lithography steps and degrade electrical performance. Despite many advances toward commercial CMP slurries, there remains a need in the industry for CMP slurries (or compositions), such as tungsten CMP slurries, to improve planarization during CMP operations.

[0004] Furthermore, the semiconductor industry is subject to constant, and sometimes extreme, downward price pressures. To maintain economically favorable CMP methods, high throughput is generally required, which in turn necessitates high removal rates and high planarization efficiencies. Downward price pressures also extend to the CMP consumables themselves (e.g., slurries and pads). Such price pressures pose a challenge to slurry formulators, as cost reduction pressures often conflict with slurry performance metrics. There is a real need in the industry for CMP slurries (e.g., tungsten CMP compositions) to improve planarity at high throughput and low cost. Summary of the Invention [Means for solving the problem]

[0005] A chemical-mechanical polishing composition is disclosed. The composition includes a liquid carrier and colloidal silica particles dispersed in the liquid carrier. The colloidal silica particles have a positive charge of at least 10 mV in the liquid carrier and can be characterized as having (i) a number-average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42. The polishing composition may further optionally include an iron-containing accelerator and, when the polishing composition is a tungsten CMP composition, a tungsten etch inhibitor (e.g., polylysine).

[0006] For a more complete understanding of the disclosed subject matter, and its advantages, reference is now made to the following description taken in conjunction with the accompanying FIG. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A is a TEM image showing partially aggregated colloidal silica. [Figure 1B] FIG. 1B is a TEM image showing another partially aggregated colloidal silica. [Figure 1C]FIG. 1C is a TEM image showing colloidal silica prepared by blending distinguishable first and second colloidal silicas. DETAILED DESCRIPTION OF THE INVENTION

[0008] A chemical-mechanical polishing composition is disclosed. In one embodiment, the composition comprises a liquid carrier and colloidal silica particles dispersed in the liquid carrier. The colloidal silica particles have a positive charge of at least 10 mV in the liquid carrier and have (i) a number-average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42. When the polishing composition is a tungsten CMP composition, the polishing composition may further optionally comprise an iron-containing accelerator and an etch inhibitor (e.g., polylysine).

[0009] In another embodiment, the composition comprises a liquid carrier and colloidal silica particles dispersed in the liquid carrier. The colloidal silica particles have a positive charge of at least 10 mV in the liquid carrier and a weight-normalized particle size span of greater than about 0.42, and at least 15% of the colloidal silica particles comprise three or more aggregated primaries. When the polishing composition is a tungsten CMP composition, the polishing composition may further optionally comprise an iron-containing accelerator and an etch inhibitor (e.g., polylysine).

[0010] In yet another embodiment, the composition comprises a liquid carrier and colloidal silica particles dispersed in the liquid carrier. The colloidal silica particles comprise a blend of first and second colloidal silica particles dispersed in the liquid carrier. The first and second colloidal silica particles have a positive charge of at least 10 mV in the liquid carrier. The first colloidal silica particles may be characterized by a number average aspect ratio greater than 1.35, while the second colloidal silica particles may be characterized by a number average aspect ratio less than 1.15. For example, when the polishing composition is a tungsten CMP composition, the polishing composition may further optionally comprise an iron-containing accelerator and an etch inhibitor (e.g., polylysine).

[0011] The polishing composition contains colloidal silica particles (abrasive particles) suspended in a liquid carrier. As used herein, the term "colloidal silica particles" refers to silica particles prepared via a wet process, rather than pyrogenic or flame hydrolysis processes, which produce structurally distinct particles. The colloidal silica may be precipitated silica or condensation-polymerized silica. Precipitated silica or condensation-polymerized silica can be prepared by any method known to those skilled in the art, such as a sol-gel process or by silicate ion exchange. Condensation-polymerized silica particles are often prepared by condensing Si(OH)4, which forms roughly spherical particles.

[0012] Colloidal silica particles can be characterized as having a favorable combination of physical properties. For example, in one embodiment, colloidal silica particles can be characterized as having a number-average aspect ratio above an aspect ratio threshold and a weight-normalized particle size span above a span threshold. In another embodiment, colloidal silica particles can be characterized as having a weight-normalized particle size span above a span threshold and a particle agglomeration distribution (e.g., percentage of agglomerated particles above a threshold).

[0013] In one embodiment, the colloidal silica particles can be characterized as having both (i) a number-average (median) aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42. For example, the number-average aspect ratio can be greater than about 1.3 (e.g., greater than about 1.35, greater than about 1.4, or greater than about 1.45), and the weight-normalized particle size span can be greater than about 4.5 (e.g., greater than about 0.5, greater than about 0.55, greater than about 0.6, greater than about 0.65, or greater than about 0.7).

[0014] The aspect ratio of a colloidal silica particle is defined herein as the maximum caliper diameter of the particle divided by the minimum caliper diameter of the particle. The number-average aspect ratio represents a statistical measure of the average (median) aspect ratio of the colloidal silica particles in the polishing composition (based on number rather than weight). The number-average aspect ratio can refer to the AR50, since statistically half (50%) of the particles have an aspect ratio below the median and half (50%) of the particles have an aspect ratio above the median.

[0015] The number-average aspect ratio of colloidal silica particles in a polishing composition can be determined by evaluating high-magnification transmission electron microscope (TEM) images of a large number of particles (e.g., at magnifications of about 10,000 to about 30,000). To obtain a statistically significant median aspect ratio, it is generally necessary to measure and calculate the aspect ratio for a large number of colloidal silica particles (e.g., at least 500 or more particles, or 1,000 or more particles) using multiple images (e.g., at least 10 or more images, 15 or more images, or 20 or more images). The maximum and minimum caliper diameters of each particle can be measured manually (particle by particle), for example, using a scale bar on the TEM image. However, due to the need to evaluate a large number of particles, a user-guided automated process is preferred. Such an automated process preferably utilizes commercially available image analysis software. One suitable user-guided automated process is detailed in Example 1 below.

[0016] The normalized particle size span, based on weight, of colloidal silica is defined herein using the following formula:

number

[0017] In the above formula, NSpan represents the weight-normalized particle size span of the colloidal silica, and D10, D50, and D90 represent the CPS particle size decile bins obtained from the weight-average particle size distribution (i.e., the distribution when particles are counted by weight). The particle size distribution, and therefore D10, D50, and D90, are obtained using a CPS Disc Centrifuge Particle Size Analyzer (e.g., Model DC24000HR) available from CPS Instruments, Prairieville, Louisiana. As will be readily apparent to those skilled in the art, the CPS Disc Centrifuge Particle Size Analyzer includes standard settings for obtaining both weight-average and number-average particle size distributions. As will be further apparent to those skilled in the art, D50 represents the median particle size. In other words, D50 represents the particle size value above which 50 percent of the particles in a sample (counted by weight) are larger and 50 percent are smaller. D10 represents the particle size value above which 90 percent of the particles in a sample (counted by weight) are larger and 10 percent are smaller, and D90 represents the particle size value above which 10 percent of the particles in a sample (counted by weight) are larger and 90 percent are smaller.

[0018] The colloidal silica particles in the disclosed embodiments may have virtually any suitable particle size. The particle size of particles suspended in a liquid carrier can be defined in the art using a variety of means. For example, particle size can be defined as the diameter of the smallest sphere that contains the particle and can be measured using a number of commercially available instruments, including, for example, a CPS Disc Centrifuge, Model DC24000HR (available from CPS Instruments, Prairieville, Louisiana) or a Zetasizer® available from Malvern Instruments®. The average particle size of the colloidal silica particles can be about 5 nm or more (e.g., about 10 nm or more, or about 20 nm or more). The average particle size of the colloidal silica particles can be 200 nm or less (e.g., about 180 nm or less, or about 160 nm or less). Thus, the average particle size of the colloidal silica particles can be from about 5 nm to about 200 nm (e.g., from about 10 nm to about 180 nm, or from about 20 nm to about 160 nm).

[0019] In a preferred embodiment, the colloidal silica particles may further have a particle size distribution (characterized using a CPS Disk Centrifuge particle size analyzer) with a weight average median particle size (D50 counted by weight) of about 50 nm to about 150 nm (e.g., about 60 nm to about 140 nm, about 70 nm to about 130 nm, about 75 nm to about 125 nm, or 80 nm to about 120 nm). Alternatively and / or additionally, the colloidal silica particles may further have a particle size distribution (characterized using a CPS Disk Centrifuge particle size analyzer) with a number average median particle size (D50 counted by number of colloidal silica particles) of about 10 nm to about 100 nm (e.g., about 20 nm to about 60 nm, about 25 nm to about 60 nm, or 30 nm to about 50 nm).

[0020] In another embodiment, the colloidal silica particles can be characterized as having a weight-normalized particle size span greater than about 0.42, with at least 12% of the colloidal silica particles comprising three or more aggregated primary particles. For example, the weight-normalized particle size span can be greater than about 0.42 (e.g., greater than about 0.45, greater than about 0.5, greater than about 0.55, greater than about 0.6, greater than about 0.65, or greater than 0.7), with at least 15 percent or more of the colloidal silica particles (e.g., greater than 18 percent, greater than 20 percent, or greater than 25 percent) comprising three or more aggregated primary particles. In certain of the foregoing embodiments, the colloidal silica can be aggregated such that less than 60 percent of the colloidal silica particles (e.g., less than 50 percent, or less than 40 percent) are primary particles.

[0021] Colloidal silica particles may be both aggregated and non-aggregated (i.e., some particles may be aggregated and the rest may be non-aggregated). Non-aggregated particles are individually discrete particles (broadly referred to in the art as primary particles or primaries). These particles are generally spherical or nearly spherical. Aggregated particles are particles in which multiple primary particles are clustered or bonded together to form aggregates having a generally irregular or non-spherical shape (e.g., elongated or branched shape). Non-aggregated (primary) particles are sometimes referred to herein as monomers. Aggregated particles are also sometimes referred to as dimers (having two primaries), trimers (having three primaries), tetramers (having four primaries), etc.

[0022] Colloidal silica particle aggregation is best assessed using high magnification scanning electron microscope (SEM) and / or transmission electron microscope (TEM) images. Example TEM images showing both aggregated and non-aggregated colloidal silica particles are shown in Figures 1A, 1B, and 1C.

[0023] 1A shows partially aggregated colloidal silica. Non-aggregated primary particles are designated 102. Aggregated particles containing two primaries (dimers) are designated 104. And aggregated particles containing three or more primaries (trimers, tetramers, etc.) are designated 106.

[0024] FIG. 1B shows partially aggregated colloidal silica. It is clear that the colloidal silica shown in FIG. 1B is significantly less aggregated than the colloidal silica shown in FIG. 1A. It is also clear that the primary particle size of the silica shown in FIG. 1B is larger than the primary particle size of the colloidal silica shown in FIG. 1A. Non-aggregated primary particles are designated 112. Aggregated particles containing two primaries (dimers) are designated 114. Colloidal silica particles containing three primaries (trimers) are designated 116.

[0025] 1C shows a blend of a first colloidal silica and a second colloidal silica. Non-aggregated primary particles are shown at 122. Aggregated particles containing two primaries (dimers) are shown at 124. And aggregated particles containing three or more primaries (trimers, tetramers, etc.) are shown at 126.

[0026] With further reference to the colloidal silicas shown in Figures 1A, 1B, and 1C, it is noted that the colloidal silica shown in Figure 1A was found to have a number average aspect ratio (AR50) of 1.44 and a weight-normalized particle size span of 0.39. The colloidal silica shown in Figure 1B was found to have a number average aspect ratio (AR50) of 1.08 and a weight-normalized particle size span of 0.22. The colloidal silica shown in Figure 1C (i.e., the blend) was found to have a number average aspect ratio (AR50) of 1.36 and a weight-normalized particle size span of 0.44.

[0027] Of course, colloidal silica having the above-mentioned properties can be prepared using virtually any suitable technique known to those skilled in the art. For example, colloidal silica can be formed using a multi-step process in which primary particles are first grown in solution, as described, for example, in U.S. Pat. No. 5,230,833. The pH of the solution can then be adjusted to an acidic value for a predetermined period of time to promote aggregation (or partial aggregation) of the primary particles, as described, for example, in U.S. Pat. No. 8,529,787. An optional final step allows the aggregates (and any remaining primary particles) to further grow, thereby obtaining colloidal silica particles having the above-mentioned aspect ratio, normalized span, and / or aggregation properties.

[0028] In another embodiment, the colloidal silica can be prepared by blending at least first and second (e.g., first and second, first, second and third, or first, second, third and fourth) colloidal silicas in a predetermined ratio. For example, in one embodiment, the colloidal silica can be prepared by blending first and second distinct colloidal silicas. In these colloidal silicas, the number-average aspect ratio of the first colloidal silica is greater than 1.30 (e.g., greater than about 1.35 or greater than about 1.4), and the number-average aspect ratio of the second colloidal silica is less than 1.2 (e.g., less than about 1.15 or less than about 1.1). In such an embodiment, each of the first and second colloidal silicas can further have a weight-normalized particle size span of less than about 0.42. For example, the weight-normalized particle size span of the first colloidal silica can be less than about 0.42, and the weight-normalized particle size span of the second colloidal silica can be less than about 0.3.

[0029] In yet other embodiments obtained by blending at least first and second distinct colloidal silicas, at least 20 percent (e.g., at least 25 percent or at least 30 percent) of the first colloidal silica particles may comprise three or more aggregate-type primary particles, and at least 50 percent (e.g., at least 60 percent, at least 70 percent, or at least 80 percent) of the second colloidal silica particles may be monomers or dimers. The colloidal silica shown in Figure 1C is an example of one such embodiment obtained by blending first and second distinct colloidal silicas (e.g., blending compositions 1C and 1E to obtain composition 1U, as detailed in Example 1 below).

[0030] Of course, the first and second (or first, second, and third, etc.) colloidal silicas can be blended in virtually any suitable ratio to achieve the desired aspect ratio, normalized span, and / or aggregation properties described above. For example, in embodiments involving a blend of first and second colloidal silicas, the first colloidal silica particles and the second colloidal silica particles can be blended in a weight ratio of about 1:15 to about 15:1 (e.g., about 1:15 to about 1:1, about 1:1 to about 15:1, about 1:10 to about 10:1, or about 1:5 to about 5:1).

[0031] In embodiments comprising a blend of first and second (or first, second, and third, etc.) colloidal silicas, the blended colloidal silica may comprise virtually any suitable commercially available colloidal silica. As will be apparent to those skilled in the art, colloidal silicas having a wide range of physical properties are commercially available from numerous sources, including, for example, Nissan Chemical Industries, Ltd., Nalco Holding Company, W.R. Grace and Company, Fuso Chemical Co., Ltd., Nouryon, Nyacol Nano Technologies, Inc., Tama Chemical Industries, Ltd., and JGC Holdings Corporation.

[0032] The polishing composition may contain substantially any suitable amount of the colloidal silica particles. For example, the polishing composition may contain about 0.01 wt. % or more (e.g., about 0.05 wt. % or more, about 0.1 wt. % or more, about 0.2 wt. % or more, about 0.3 wt. % or more, about 0.4 wt. % or more, or about 0.5 wt. % or more) of colloidal silica particles at the point of use. The amount of colloidal silica particles in the polishing composition may be about 20 wt. % or less (e.g., about 20 wt. % or less, about 5 wt. % or less, about 3 wt. % or less, about 2 wt. % or less, or about 1 wt. % or less) at the point of use. Thus, it will be appreciated that the amount of colloidal silica particles may be in a range bounded by any two of the above endpoints, for example, from about 0.01% to about 20% by weight at the point of use (e.g., from about 0.1% to about 10% by weight, from about 0.1% to about 5% by weight, from about 0.1% to about 3% by weight, or from about 0.2% to about 3% by weight).

[0033] A liquid carrier is generally used to facilitate the deposition of the abrasive (colloidal silica particles) and any chemical additives on the surface of the substrate to be polished (e.g., planarized). The liquid carrier may be any suitable carrier (e.g., solvent), including lower alcohols (e.g., methanol, ethanol, etc.), ethers (e.g., dioxane, tetrahydrofuran, etc.), water, and mixtures thereof. Preferably, the liquid carrier comprises, consists essentially of, or consists of water, more preferably deionized water.

[0034] The colloidal silica particles preferably have a positive charge in the polishing composition (e.g., in the liquid carrier). The charge on the colloidal silica particles is generally referred to in the art as zeta potential (or kinetic potential). As known to those skilled in the art, the zeta potential of a particle refers to the difference between the charge of the ions surrounding the particle and the charge of the bulk solution of the polishing composition (e.g., the liquid carrier and any other components dissolved in the liquid carrier). Zeta potential can be obtained using commercially available instruments, such as a Zetasizer available from Malvern Instruments, a ZetaPlus Zeta Potential Analyzer available from Brookhaven Instruments, and / or an electroacoustic spectrometer available from Dispersion Technologies, Inc.

[0035] The colloidal silica particles preferably have a positive charge in the polishing composition of about 10 mV or more (e.g., about 15 mV or more, about 20 mV or more, or about 25 mV or more). The positive charge of the colloidal silica particles in the polishing composition is preferably about 60 mV or less (e.g., about 55 mV or less, or about 50 mV or less). Thus, it will be appreciated that the positive charge of the colloidal silica particles in the polishing composition may be within a range bounded by any one of the above endpoints, for example, from about 10 mV to about 60 mV (e.g., from about 15 mV to about 60 mV, or from about 25 mV to about 50 mV).

[0036] Although the disclosed embodiments are not limited in this regard, it may be advantageous for the colloidal silica particles to have a permanent positive charge. A permanent positive charge means that the positive charge on the silica particles is not easily reversible, for example, through flushing, dilution, filtration, and the like. The permanent positive charge may be the result of, for example, a covalent bond between a cationic compound and the colloidal silica. This contrasts with a reversible positive charge, which may be the result of, for example, an electrostatic interaction between a cationic compound and the colloidal silica. However, as used herein, a permanent positive charge of at least 10 mV means that the zeta potential of the colloidal silica particles remains above 10 mV after the three-step ultrafiltration test detailed in commonly assigned U.S. Pat. No. 9,238,754.

[0037] Colloidal silica particles having a permanent positive charge in the polishing composition can be obtained by treating the particles with at least one aminosilane compound, as disclosed, for example, in commonly assigned U.S. Patent Nos. 7,994,057 and 9,028,572. Alternatively, colloidal silica particles having a permanent positive charge in the polishing composition can be obtained by incorporating a chemical species, such as an aminosilane compound, into the colloidal silica particles, as disclosed, for example, in commonly assigned U.S. Patent No. 9,422,456.

[0038] Alternatively, the colloidal silica particles may be imparted with a non-permanent positive charge, for example, via contact with a cation-containing component (i.e., a positively charged species) in the liquid carrier. For example, a non-permanent positive charge can be achieved by treating the particles with at least one cation-containing component selected from ammonium salts (preferably quaternary amine compounds), phosphonium salts, sulfonium salts, imidazolium salts, and pyridinium salts.

[0039] The polishing composition may have virtually any suitable pH depending on the intended use. In other words, the polishing composition may be acidic, neutral, or alkaline. In part to minimize safety and distribution concerns, the pH is generally about 2 to about 12 (e.g., about 2 to about 6, about 5 to about 9, or about 8 to about 12). In embodiments in which the polishing composition is intended for tungsten metal (W CMP compositions), the pH is preferably acidic and therefore less than about 7. In such embodiments, the pH is preferably about 1 or greater (e.g., about 1.5 or greater, or about 2 or greater) and about 6 or less (e.g., about 5 or less, or 4 or less). Accordingly, the pH of the disclosed W CMP compositions is preferably about 1 to about 6 (e.g., about 1 to about 5, about 2 to about 5, or about 2 to about 4).

[0040] The pH of the polishing composition can be achieved and / or maintained by any suitable means. The polishing composition may include virtually any suitable pH adjuster or buffer system. For example, suitable pH adjusters may include nitric acid, sulfuric acid, phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, maleic acid, ammonium hydroxide, and the like, while suitable buffers may include phosphates, sulfates, acetates, malonates, oxalates, borates, ammonium salts, and the like.

[0041] The disclosed polishing compositions may include virtually any suitable chemical additive. Polishing compositions formulated to polish metal layers may include, for example, one or more of the following components: oxidizers, chelating agents, polishing rate accelerators, catalysts, polishing rate inhibitors, topography control agents, etch inhibitors, pH buffers, dispersants, and biocides. Polishing compositions formulated to polish dielectric layers may include, for example, one or more of the following components: cationic, anionic, or nonionic polymers, secondary polishing rate accelerators or inhibitors (e.g., for nitride layers), dispersants, conditioners, scale inhibitors, chelating agents, stabilizers, pH buffers, and biocides. Such additives are purely optional. The disclosed embodiments are not so limited and do not require the use of any one or more of such additives.

[0042] Certain disclosed polishing composition embodiments can be configured to polish tungsten metal (during a tungsten CMP operation). Such tungsten CMP compositions may optionally further comprise an iron-containing accelerator, a stabilizer, and / or an oxidizer. As used herein, an iron-containing accelerator is an iron-containing compound that enhances the removal rate of tungsten during a tungsten CMP operation. For example, the iron-containing accelerator may comprise a soluble iron-containing catalyst, such as those disclosed in U.S. Patent Nos. 5,958,288 and 5,980,775. Such iron-containing catalysts may be soluble in the liquid carrier and may include, for example, ferric (iron III) or ferrous (iron II) compounds, such as iron nitrate, iron sulfate, fluorides, chlorides, bromides, and iodides, as well as iron halides including perchlorates, perbromates, and periodates, and organic iron compounds, such as iron acetates, carboxylic acids, acetylacetonates, citrates, gluconates, malonates, oxalates, phthalates, and succinates, and mixtures thereof.

[0043] The iron-containing promoter may comprise an iron-containing activator (e.g., a free radical-generating compound) or an iron-containing catalyst associated with (e.g., coated or bonded to) the surface of the colloidal silica particles, such as those disclosed in U.S. Patent Nos. 7,029,508 and 7,077,880. For example, the iron-containing promoter may be bonded to silanol groups on the surface of the colloidal silica particles.

[0044] The amount of iron-containing accelerator in the polishing composition may vary depending on the oxidizer and chemical form of the accelerator used. When the oxidizer is hydrogen peroxide (or one of its analogs) and a soluble iron-containing catalyst (e.g., ferric nitrate or ferric nitrate hydrate) is used, the catalyst may be present in the composition in an amount sufficient to provide about 0.5 to about 3000 ppm Fe at the point of use, based on the total weight of the composition. The polishing composition may contain about 1 ppm or more (e.g., about 2 ppm or more, about 5 ppm or more, or about 10 ppm or more) Fe at the point of use. The polishing composition may contain about 1000 ppm or less (e.g., about 500 ppm or less, about 200 ppm or less, or about 100 ppm or less) Fe at the point of use. Thus, the polishing composition may contain a range of Fe bounded by any one of the above endpoints. The composition may contain about 1 to about 1000 ppm (eg, about 2 to about 500 ppm, about 5 to about 200 ppm, or about 10 to about 100 ppm) Fe at the point of use.

[0045] Embodiments of the polishing composition containing an iron-containing accelerator may further include a stabilizer. Without such a stabilizer, the iron-containing accelerator and, if present, the oxidizer may react in a manner that rapidly degrades the oxidizer over time. Because the addition of a stabilizer tends to reduce the effectiveness of the iron-containing accelerator, the selection of the type and amount of stabilizer added to the polishing composition can significantly affect CMP performance. The addition of a stabilizer can cause a stabilizer / accelerator complex to form. This complex inhibits the accelerator from reacting with the oxidizer, if present, while at the same time allowing the accelerator to remain sufficiently active to promote rapid tungsten polishing rates.

[0046] Useful stabilizers include phosphoric acid, organic acids, phosphate compounds, nitriles, and other ligands that bind to metals to reduce reactivity toward hydrogen peroxide decomposition, and mixtures thereof. Acid stabilizers can be used in their conjugated form, e.g., carboxylates can be used in place of carboxylic acids. The term "acid" used herein to describe useful stabilizers also refers to the conjugate base of an acid stabilizer. The stabilizers can be used alone or in combination and can significantly reduce the rate at which an oxidizing agent, e.g., hydrogen peroxide, decomposes.

[0047] Preferred stabilizers include phosphoric acid, acetic acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid (EDTA), propylenediaminetetraacetic acid (PDTA), and mixtures thereof. Preferred stabilizers can be added to the compositions of the present invention in amounts of from about 1 equivalent to about 3.0 weight percent or more (e.g., from about 3 to about 10 equivalents) per iron-containing promoter. As used herein, the term "equivalent per iron-containing promoter" refers to one molecule of stabilizer per iron ion in the composition. For example, two equivalents per iron-containing promoter refers to two molecules of stabilizer for each catalyst ion.

[0048] The polishing composition may optionally further comprise an oxidizer. The oxidizer can be added to the polishing composition during the slurry manufacturing process or just prior to the CMP operation (e.g., in a tank located in a semiconductor manufacturing facility). Preferred oxidizers include inorganic or organic per-compounds. A per-compound, as defined herein, is a compound containing at least one peroxy group (-O--O-) or a compound containing an element in its highest oxidation state. Examples of compounds containing at least one peroxy group include hydrogen peroxide and its adducts, such as urea hydrogen peroxide, percarbonates, organic peroxides, such as benzoyl peroxide, peracetic acid, and di-t-butyl peroxide, monopersulfates (SO5 =), Dipersulfate (S2O8 = ), and sodium peroxide. Compounds containing elements in their highest oxidation states include, but are not limited to, periodic acid, periodates, perbromic acid, perbromates, perchloric acid, perchlorates, perboric acid, perborates, and permanganates. The most preferred oxidizing agent is hydrogen peroxide.

[0049] The oxidizer may be present in the polishing composition at the point of use in an amount of, for example, about 0.1 to about 20% by weight. In embodiments in which a hydrogen peroxide oxidizer and a soluble iron-containing accelerator are used, the oxidizer may be present in the polishing composition at the point of use in an amount of about 0.1% to about 10% by weight (e.g., about 1% to about 10% by weight, about 1% to about 5% by weight).

[0050] Exemplary polishing compositions designed to polish tungsten metal may optionally further contain a compound that inhibits tungsten etching. Suitable inhibitor compounds inhibit the conversion of solid tungsten to soluble tungsten compounds while simultaneously allowing the solid tungsten to be effectively removed via the CMP operation. The polishing composition may contain virtually any suitable inhibitor, such as the inhibitor compounds disclosed in commonly assigned U.S. Patent Nos. 9,238,754, 9,303,188, and 9,303,189.

[0051] Examples of classes of compounds that are useful inhibitors of tungsten etching include nitrogen-containing functional groups, such as nitrogen-containing heterocycles, alkylammonium ions, aminoalkyls, and amino acids. Useful aminoalkyl corrosion inhibitors include, for example, hexylamine, tetramethyl-p-phenylenediamine, octylamine, diethylenetriamine, dibutylbenzylamine, aminopropylsilanol, aminopropylsiloxane, dodecylamine, mixtures thereof, and synthetic and naturally occurring amino acids, including, for example, lysine, tyrosine, glutamine, glutamic acid, cystine, and glycine (aminoacetic acid).

[0052] Alternatively and / or additionally, the suppressor compound may comprise an amine compound in solution in a liquid carrier. The amine compound may comprise a primary amine, a secondary amine, a tertiary amine, or a quaternary amine. The amine compound may further comprise a monoamine, a diamine, a triamine, a tetramine, or an amine-based polymer having multiple repeating amine groups (e.g., four or more amine groups).

[0053] Suitable inhibitor compounds may further comprise cationic polymers, such as, for example, poly(vinylimidazolium), poly(methacryloyloxyethyltrimethylammonium) chloride (polyMADQUAT), poly(diallyldimethylammonium) chloride (e.g., polyDADMAC) (i.e., Polyquaternium-6), poly(dimethylamine-co-epichlorohydrin), poly[bis(2-chloroethyl)ether-alt-1,3-bis[3-(dimethylamino)propyl]urea] (i.e., Polyquaternium-2), copolymers of hydroxyethyl cellulose and diallyldimethylammonium (i.e., Polyquaternium-4), copolymers of acrylamide and diallyldimethylammonium (i.e., Polyquaternium-5), and the like. Polyquaternium-7), quaternized hydroxyethyl cellulose ethoxylate (i.e., Polyquaternium-10), copolymers of vinylpyrrolidone and quaternized dimethylaminoethyl methacrylate (i.e., Polyquaternium-11), copolymers of vinylpyrrolidone and quaternized vinylimidazole (i.e., Polyquaternium-16), i.e., Polyquaternium-24, terpolymers of vinylcaprolactam, vinylpyrrolidone, and quaternized vinylimidazole (i.e., Polyquaternium-46), 3-methyl-1-vinylimidazolium methylsulfate-N-vinylpyrrolidone copolymer (i.e., Polyquaternium-44), and copolymers of vinylpyrrolidone and diallyldimethylammonium. Additionally, suitable cationic polymers include personal care cationic polymers such as Luviquat® Supreme, Luviquat® Hold, Luviquat® UltraCare, Luviquat® FC 370, Luviquat® FC 550, Luviquat® FC 552, Luviquat® Excellence, GOHSEFIMER K210®, GOHSENX K-434, and combinations thereof.

[0054] In certain embodiments, the tungsten inhibitor compound may comprise a cationic polymer having amino acid monomers (such compounds are sometimes referred to as polyamino acid compounds). Suitable polyamino acid compounds may comprise virtually any suitable amino acid monomer group, including, for example, polyarginine, polyhistidine, polyalanine, polyglycine, polytyrosine, polyproline, and polylysine. In certain embodiments, polylysine is the preferred polyamino acid. Of course, polylysine may include ε-polylysine and / or α-polylysine, which are composed of D-lysine and / or L-lysine. Polylysine may thus include α-poly-L-lysine, α-poly-D-lysine, ε-poly-L-lysine, ε-poly-D-lysine, and mixtures thereof. In a preferred embodiment, the tungsten inhibitor comprises polylysine, and most preferably ε-poly-L-lysine. Of course, the polyamino acid compound may be used in any available form. For example, instead of (or in addition to) the polyamino acid, the conjugate acid or base and salt forms of the polyamino acid can be used.

[0055] The disclosed polishing compositions for polishing tungsten metal may contain virtually any suitable inhibitor compound concentration. Generally speaking, the concentration is desirably high enough to provide adequate etch inhibition, but low enough so that the compound is soluble and does not reduce the tungsten polishing rate below an acceptable level. By soluble, it is meant that the compound is completely dissolved in the liquid carrier, or that the compound forms or is supported in micelles in the liquid carrier. The concentration of the inhibitor compound will need to vary depending on a number of factors, including, for example, the solubility of the inhibitor compound, the number of amine groups in the inhibitor compound, the length of the alkyl groups, the relationship between etch rate inhibition and polishing rate inhibition, the oxidizer used, and the concentration of the oxidizer. In certain desirable embodiments, the concentration of the amine compound in the polishing composition is from about 0.1 μM to about 10 mM (i.e., about 10 -7 ~about 10 -2For example, in embodiments utilizing a polymeric inhibitor, such as a cationic polymer, the concentration may be toward the lower end of the range (e.g., about 10 molar at the point of use). -7 ~about 10 -4 In other embodiments utilizing non-polymeric compounds (fewer cationic groups, lower molecular weight), the concentration may be toward the higher end of the range (e.g., about 10 moles at the point of use). -5 ~about 10 -2 moles).

[0056] The polishing composition may optionally further comprise a biocide. The biocide may comprise any suitable biocide, such as an isothiazolinone biocide. The amount of biocide in the polishing composition is typically from about 1 ppm to about 50 ppm at the point of use, and preferably from about 1 ppm to about 20 ppm.

[0057] The polishing composition can be prepared using any suitable technique. Many of these techniques are known to those skilled in the art. The polishing composition can be prepared by a batch or continuous process. Generally speaking, the polishing composition can be prepared by combining its components in any order. As used herein, "component" includes individual ingredients (e.g., colloidal silica, iron-containing accelerator, amine compound, etc.).

[0058] For example, polishing composition components (e.g., iron-containing accelerators, stabilizers, etch inhibitors, and / or biocides) can be added directly to colloidal silica having the above-described physical properties (e.g., specified aspect ratio, normalized span, and positive charge). In another example, the first and second colloidal silicas can be optionally treated with, for example, an aminosilane compound to produce the corresponding colloidal silica having a positive charge. The first and second colloidal silicas can be mixed together before adding other polishing composition components. Alternatively, other components can be added to one of the colloidal silicas before mixing the first and second colloidal silicas together. The colloidal silica and other components can be blended together using any defined technique to achieve the appropriate mixture. Such blending / mixing techniques are well known to those skilled in the art. The optional oxidizer can be added at any time during the preparation of the polishing composition. For example, the polishing composition can be prepared prior to use, with one or more components, such as an oxidizer, being added immediately prior to the CMP operation (e.g., within about 1 minute, or within about 10 minutes, or within about 1 hour, or within about 1 day, or within about 1 week before the CMP operation).The polishing composition can also be prepared by mixing the components at the substrate surface (e.g., on a polishing pad) during the polishing operation.

[0059] The polishing composition is advantageously supplied as a one-package system containing colloidal silica having the above physical properties and other optional ingredients. It is desirable to supply the oxidizer separately from the other ingredients of the polishing composition, and for example, the oxidizer can be combined with the other ingredients of the polishing composition by the end user immediately prior to use (e.g., within one week, one day, one hour, ten minutes, or one minute before use). Various other two-container, three-container, or four-or-more-container combinations of ingredients of the polishing composition are within the knowledge of those skilled in the art.

[0060] The polishing composition of the present invention may be provided as a concentrate. The concentrate is intended to be diluted with an appropriate amount of water before use. In such an embodiment, the polishing composition concentrate can contain colloidal silica, water, and other optional components, such as iron-containing accelerators, stabilizers, etch inhibitors, and biocides, with or without an oxidizer, in amounts such that, upon dilution of the concentrate with an appropriate amount of water and, if not already present, with an optional oxidizer, each component of the polishing composition will be present in the polishing composition in an amount within the appropriate range described above for each component. For example, the colloidal silica and other optional components can each be present in the polishing composition in an amount that is about twice (e.g., about three, four, five, or ten times) the point-of-use concentration described above for each component, such that, upon dilution of the concentrate with an equal volume of water (e.g., 2, 3, 4, or 9 equal volumes of water, respectively) and with an appropriate amount of optional oxidizer, each component will be present in the polishing composition in an amount within the range described above for each component. Additionally, as will be apparent to those skilled in the art, the concentrate may contain an appropriate portion of the water present in the final polishing composition to ensure that the other ingredients are at least partially or completely dissolved in the concentrate.

[0061] The disclosed polishing compositions can be used to polish virtually any substrate, including silicon nitride layers, silicon oxide layers, and / or metal layers, such as tungsten, copper, aluminum, or cobalt layers, and / or barrier layers, such as titanium, titanium nitride, tantalum, and / or tantalum nitride layers. Certain advantageous embodiments may be particularly useful for polishing substrates that include at least one metal, including tungsten, and at least one dielectric material, such as silicon oxide. In such applications, the tungsten layer can be deposited on one or more barrier layers, including titanium and / or titanium nitride (TiN). The dielectric layer can be a metal oxide, such as a silicon oxide layer derived from tetraethyl orthosilicate (TEOS), a porous metal oxide, a porous or non-porous carbon-doped silicon oxide, a fluorine-doped silicon oxide, glass, an organic polymer, a fluorinated organic polymer, or any other suitable high- or low-k insulating layer.

[0062] The polishing method of the present invention is particularly suitable for use in conjunction with a chemical mechanical polishing (CMP) apparatus. Typically, the apparatus includes a platen that moves during use and has a velocity resulting from orbital, linear, or circular motion, a polishing pad that contacts the platen and moves with the platen during movement, and a carrier that holds the substrate to be polished by contacting and moving against the surface of the polishing pad. The substrate is polished by placing the substrate in contact with the polishing pad and the polishing composition of the present invention, and then moving the polishing pad against the substrate, thereby polishing the substrate by abrading at least a portion of the substrate (e.g., tungsten, titanium, titanium nitride, and / or the dielectric materials described herein).

[0063] In certain desirable embodiments, the disclosed polishing compositions enable high tungsten removal rates and high planarization efficiencies to be achieved on substrates having a tungsten metal layer and a dielectric layer. For example, in certain advantageous embodiments, tungsten removal rates of greater than 3000 Å / min (e.g., greater than 3500 Å / min, greater than 4000 Å / min, greater than 4500 Å / min, or greater than 5000 Å / min) can be achieved. In such embodiments, array erosion and / or tungsten line dishing of less than 250 Å (e.g., less than 200 Å, less than 150 Å, less than 100 Å, or less than 50 Å) can be achieved on 1×1 μm arrays.

[0064] Substrates can be planarized or polished with the chemical-mechanical polishing composition using any suitable polishing pad (e.g., polishing surface). Suitable polishing pads include, for example, woven and nonwoven polishing pads. Furthermore, suitable polishing pads can comprise any suitable polymer having a variety of densities, hardnesses, thicknesses, compressibility, rebound ability upon compression, and compression moduli. Suitable polymers include, for example, polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester, polyacrylate, polyether, polyethylene, polyamide, polyurethane, polystyrene, polypropylene, co-formed products thereof, and mixtures thereof.

[0065] Needless to say, the disclosure includes numerous embodiments, examples of which include the following:

[0066] In a first embodiment, the chemical-mechanical polishing composition may comprise, consist of, or consist essentially of a liquid carrier, colloidal silica particles dispersed in the liquid carrier, the colloidal silica particles having a positive charge of at least 10 mV in the liquid carrier, an iron-containing accelerator, and a metal etch inhibitor, wherein the colloidal silica particles have (i) a number-average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42.

[0067] A second embodiment may include the first embodiment, wherein the colloidal silica particles have a number average aspect ratio greater than about 1.35.

[0068] A third embodiment may include any one of the first to second embodiments, wherein the colloidal silica particles have a weight-normalized particle size span greater than about 0.6.

[0069] A fourth embodiment may include the first embodiment, wherein the colloidal silica particles (i) have a number average aspect ratio greater than about 1.35 and a weight normalized particle size span greater than about 0.6.

[0070] A fifth embodiment may include any one of the first to fourth embodiments, wherein the colloidal silica particles have a number particle size distribution D50 of about 20 nm to about 60 nm.

[0071] A sixth embodiment may include any one of the first to fifth embodiments, wherein the colloidal silica particles have a weight particle size distribution D50 of about 60 nm to about 140 nm.

[0072] A seventh embodiment may include any one of the first through sixth embodiments, wherein the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles, wherein the first colloidal silica particles have a number average aspect ratio greater than about 1.35 and the second colloidal silica particles have a number average aspect ratio less than about 1.15.

[0073] An eighth embodiment may include the seventh embodiment, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1.

[0074] A ninth embodiment may include any one of the seventh to eighth embodiments, wherein the first colloidal silica particles have a weight-normalized particle size span less than about 0.42, and the second colloidal silica particles have a weight-normalized particle size span less than about 0.42.

[0075] A tenth embodiment may include any one of the first to ninth embodiments, wherein the colloidal silica particles have a permanent positive charge of at least 10 mV.

[0076] An eleventh embodiment may include any one of the first through tenth embodiments, wherein the iron-containing accelerator comprises a soluble iron-containing catalyst, and the composition further comprises a stabilizer bound to the soluble iron-containing catalyst, the stabilizer being selected from the group consisting of phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and mixtures thereof.

[0077] A twelfth embodiment may include any one of the first to eleventh embodiments, and further includes a hydrogen peroxide oxidizing agent.

[0078] A thirteenth embodiment may include any one of the first through twelfth embodiments and has a pH of about 1.0 to about 5.0.

[0079] A fourteenth embodiment may include any one of the first to thirteenth embodiments, wherein the metal etching inhibitor is polylysine.

[0080] In a fifteenth embodiment, a chemical-mechanical polishing composition comprises, may consist of, or consist essentially of: a liquid carrier; colloidal silica particles dispersed in the liquid carrier, the colloidal silica particles having a positive charge of at least 10 mV in the liquid carrier; an iron-containing accelerator; and a metal etching inhibitor; and the colloidal silica particles have a normalized particle size span of greater than about 0.42, and at least 15% of the colloidal silica particles comprise three or four or more aggregated primaries.

[0081] A sixteenth embodiment may include the fifteenth embodiment, wherein the colloidal silica particles have a normalized particle size span greater than about 0.6.

[0082] A seventeenth embodiment may include any one of the fifteenth to sixteenth embodiments, wherein less than 50% of the colloidal silica particles are monomeric.

[0083] An eighteenth embodiment may include any one of the fifteenth through seventeenth embodiments, wherein the colloidal silica particles have a normalized particle size span greater than about 0.6, and less than 50% of the colloidal silica particles are monomeric.

[0084] A nineteenth embodiment may include any one of the fifteenth to eighteenth embodiments, wherein the colloidal silica particles have a number average aspect ratio greater than about 1.25.

[0085] A twentieth embodiment may include any one of the fifteenth to eighteenth embodiments, wherein the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles, at least 20% of the first colloidal silica particles comprise three or more aggregate primaries, and at least 50% of the second colloidal silica particles are monomers or dimers.

[0086] A twenty-first embodiment may include the twentieth embodiment, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1.

[0087] A twenty-second embodiment may include any one of the fifteenth to twenty-first embodiments, wherein the colloidal silica particles have a permanent positive charge of at least 10 mV.

[0088] A 23rd embodiment may include any one of the 15th through 22nd embodiments, wherein the iron-containing accelerator comprises a soluble iron-containing catalyst, and the composition further comprises a stabilizer bound to the soluble iron-containing catalyst, the stabilizer being selected from the group consisting of phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and mixtures thereof.

[0089] The twenty-fourth embodiment may include any one of the fifteenth to twenty-third embodiments, further including a hydrogen peroxide oxidizing agent.

[0090] A twenty-fifth embodiment may include any one of the fifteenth through twenty-fourth embodiments and has a pH of about 1.0 to about 5.0.

[0091] A twenty-sixth embodiment may include any one of the fifteenth to twentieth embodiments, wherein the metal etching inhibitor is polylysine.

[0092] In a twenty-seventh embodiment, the chemical-mechanical polishing composition comprises a liquid carrier and The composition may comprise, consist of, or consist essentially of: first colloidal silica particles dispersed in the liquid carrier, the first colloidal silica particles having (i) a positive charge in the liquid carrier of at least 10 mV and (ii) a number average aspect ratio greater than 1.35; second colloidal silica particles dispersed in the liquid carrier, the second colloidal silica particles having (i) a positive charge in the liquid carrier of at least 10 mV and (ii) a number average aspect ratio less than 1.15; an iron-containing accelerator; and a polyamino acid tungsten etch inhibitor.

[0093] A twenty-eighth embodiment may include the twenty-seventh embodiment, wherein the first and second colloidal silica particles each have a normalized particle size span of less than about 0.42.

[0094] A 29th embodiment may include any one of the 27th to 28th embodiments, wherein at least 20% of the first colloidal silica particles include three or more aggregated primaries, and at least 50% of the second colloidal silica particles are monomers or dimers.

[0095] A thirtieth embodiment may include any one of the twenty-seventh to twenty-ninth embodiments, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1.

[0096] A thirty-first embodiment may include any one of the twenty-seventh to thirtieth embodiments, wherein the tungsten etch inhibitor is polylysine.

[0097] In a thirty-second embodiment, a chemical-mechanical polishing composition comprises a liquid carrier; colloidal silica particles dispersed in the liquid carrier, the colloidal silica particles having a positive charge of at least 10 mV in the liquid carrier; and the colloidal silica particles have (i) a number average aspect ratio greater than about 1.25 and (ii) a weight normalized particle size span greater than about 0.42.

[0098] A thirty-third embodiment may include the thirty-second embodiment, wherein the number average aspect ratio is greater than about 1.35 and the weight-normalized particle size span is greater than about 0.6.

[0099] A thirty-fourth embodiment may include any one of the thirty-second to thirty-third embodiments, wherein at least 15% of the colloidal silica particles include three or more aggregated primaries.

[0100] A thirty-fifth embodiment may include any one of the thirty-second through thirty-fourth embodiments, wherein the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles, and wherein the first colloidal silica particles have a number average aspect ratio greater than about 1.35 and the second colloidal silica particles have a number average aspect ratio less than about 1.1.

[0101] A thirty-sixth embodiment may include the thirty-fifth embodiment, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1.

[0102] In a thirty-second embodiment, a method of chemically mechanically polishing a substrate comprises: (a) removing the substrate; (i) a liquid carrier; (ii) colloidal silica particles dispersed in said liquid carrier, said colloidal silica particles having a positive charge in said liquid carrier of at least 10 mV; and (iii) the colloidal silica particles have (i) a number average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42; contacting the polishing composition with (b) moving the polishing composition relative to the substrate; and (c) grinding the substrate to remove a portion of at least one layer from the substrate, thereby polishing the substrate. This includes:

[0103] A thirty-eighth embodiment may include the thirty-seventh embodiment, wherein the substrate includes a tungsten layer, the composition further includes an iron-containing accelerator and a tungsten etch inhibitor, and during polishing in (c), a portion of the tungsten layer is removed from the substrate.

[0104] A thirty-ninth embodiment may include the thirty-eighth embodiment, wherein the tungsten inhibitor is polylysine.

[0105] A fortieth embodiment can include any one of the thirty-seventh to thirty-ninth embodiments, wherein the number average aspect ratio is greater than about 1.35 and the weight-normalized particle size span is greater than about 0.6.

[0106] A forty-first embodiment may include any one of the thirty-seventh to fortieth embodiments, wherein at least 15% of the colloidal silica particles include three or more aggregated primaries.

[0107] The colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles, wherein the first colloidal silica particles have a number average aspect ratio greater than about 1.35 and the second colloidal silica particles have a number average aspect ratio less than about 1.15.

[0108] The following examples illustrate the invention but, of course, should not be construed as in any way limiting its scope.

[0109] Example 1 Twenty-three colloidal silica-containing compositions were prepared and evaluated. The colloidal silica in each composition contained a permanent positive charge by surface treatment with an aminosilane and / or via an internal aminosilane. Compositions 1A and 1C were treated with 3-aminopropyltrimethoxysilane (APTMS). Compositions 1B, 1E, 1F, 1G, 1H, 1I, and 1J were treated as described in Example 7 of U.S. Pat. No. 9,382,450. Composition 1D was prepared as described in Example 13 of U.S. Pat. No. 9,422,456. The remaining 13 compositions contained blends of the above colloidal silica compositions. The 23 colloidal silica compositions are detailed in Table 1A below. Additional analytical data are provided in Tables 1B and 1C. Table 1A [Table 1]

[0110] Samples of each colloidal silica composition were prepared for TEM imaging by drop-casting 30 μL of sample onto a lacey carbon-coated Cu grid, which was then spread on a filter to allow excess liquid to escape. After drying, multiple bright-field TEM images were obtained from the remaining particles (those remaining after the liquid escaped). Example TEM images are shown in Figures 1A, 1B, and 1C above. In this example, 20 images were acquired for each sample and stacked into a single file using FIJI open-source image processing software (https: / / en.wikipedia.org / wiki / Fiji_(software)). Each image was acquired at a magnification of 20,000, and contained 2048 x 2048 pixels. FIJI software was used to subtract the background (using the rolling ball method) and scale the intensity resolution by contrast-enhancing the image. Pixel size was calculated and entered into the software (using the image scale bar). Binary images of the particles and background were generated using machine learning software (using the trainable WEKA segmentation algorithm, available in FIJI) (black particles on a white background). The machine learning software was user-guided, with the user defining the selected particles. The WEKA software then evaluated the selected images within the stack. An iterative process allowed the software to accurately locate the particles. A binary image was then generated by applying the trained algorithm to the entire stack. A particle analysis routine (available from FIJI) was then applied to the images within the stack to calculate the aspect ratio of each identified particle within each image (aspect ratio is defined as the largest caliper diameter of the particle divided by the smallest caliper diameter of the particle). The median value (AR50) was calculated and is recorded in Table 1B for each of the colloidal silica compositions.

[0111] The degree of aggregation of 12 of the 23 colloidal silica compositions was evaluated by further analyzing the TEM images. The degree of aggregation was evaluated by counting the number percentage of colloidal silica particles having three or more primary particles (trimer+) and the number percentage of primary particles having one or two primary particles (dimer-). The results are also recorded in Table 1B.

[0112] The zeta potential of the colloidal silica particles in each of the polishing compositions was measured at 0.3 wt. % total silica solids and a pH of about 2.4 using a Zetasizer® available from Malvern Instruments. These zeta potential values ​​are also recorded in Table 1B. Table 1B [Table 2]

[0113] The particle size distribution of each colloidal silica composition was obtained using a CPS Disc Centrifuge Particle Size Analyzer (e.g., Model DC24000HR) available from CPS Instruments, Prairieville, Louisiana. Standard instrument settings were used to obtain the D10, D50, and D90 by weight (i.e., D10, D50, and D90 were obtained by weight rather than by number). From these values, the normalized span by weight was calculated for each colloidal silica composition using the above equation. The D10, D50, and D90 values, and the calculated normalized span, are recorded in Table 1C. Table 1C [Table 3]

[0114] Example 2 Tungsten (W) polishing rates were evaluated in this example for certain of the colloidal silica compositions described above in Example 1. Each of the polishing compositions contained 0.3 weight percent colloidal silica and had a pH of about 2.5 at the point of use. Each composition further contained 412 weight ppm iron nitrate nonahydrate, 890 weight ppm malonic acid, 15 weight ppm cationic polymer, polydiallyldimethylammonium chloride (e.g., polyDADMAC), 30 weight ppm benzisothiazolinone biocide (BIT), and 5 weight percent hydrogen peroxide at the point of use. W polishing rates were obtained by polishing a 200 mm blanket wafer with a W layer using a Mirra® CMP tool (available from Applied Materials) with a NexPlanar E6088 polishing pad at a downforce of 2.0 psi, a platen speed of 100 rpm, a head speed of 85 rpm, and a slurry flow rate of 150 ml / min. The polishing time was 60 seconds. The measured tungsten polishing rates are listed in Table 2. Table 2 [Table 4]

[0115] As is evident from the results shown in Table 2, high tungsten removal rates can be achieved for compositions having a number average rate greater than about 1.25 and a normalized particle size span greater than about 0.40.

[0116] Example 3 Tungsten polishing rate, array erosion, and line recession (dishing) were evaluated for six polishing compositions in this example. This example demonstrated the synergistic combination of colloidal silica and polylysine tungsten etch inhibitors according to the present invention to achieve both high tungsten polishing rates and extremely low array erosion and line recession. Each polishing composition contained malonic acid (3A 445 ppm by weight and 3B-3F 890 ppm by weight), iron nitrate nonahydrate (3A 206 ppm by weight and 3B-3F 412 ppm by weight), polylysine (3A-3C, 3E, 3F 10 ppm by weight and 3D 16 ppm by weight), benzisothiazolinone biocide (3A-3C 10 ppm and 3D-3F 30 ppm), and 5 weight percent hydrogen peroxide. The pH at the point of use was 2.5. Further details regarding the colloidal silica compositions are provided in Table 3A.

[0117] Tungsten polishing rates were obtained by polishing 300 mm blanket tungsten wafers, while array erosion and line dishing values ​​were obtained by polishing 300 mm 2 kÅ Silyb 754 tungsten patterned wafers (available from Silyb Wafer Services). Wafers were polished using a Reflexion® CMP polishing tool (Applied Materials) and an IC1010 polishing pad (Rohm and Haas / Dow Chemical) at a downforce of 2.0 psi, a platen speed of 100 rpm, and a head speed of 101 rpm. The slurry flow rate was 250 mL / min. Each patterned wafer was polished to the optical endpoint plus additional overpolish. The amount of overpolish is shown in Table 3B. Array erosion and line recession values ​​were obtained using atomic force microscopy (AFM) profilometry measurements over 1 x 1 and 3 x 1 micron line features. The tungsten polishing rates are shown in Table 3A, and the array erosion and line dishing values ​​are shown in Table 3B. Table 3A [Table 5] Table 3B [Table 6]

[0118] As is evident from the data sets shown in Tables 3A and 3B, only Composition 3D, which has a number-average aspect ratio greater than about 1.25 and a weight-normalized particle size span greater than about 0.40, can achieve high polishing rates (e.g., greater than 5000 Å / min) and highly planar surfaces (e.g., array erosion and line recession both less than 100 Å for 1×1 micron features). Furthermore, Composition 3D was found to achieve excellent planarity even with 30 percent overpolishing.

[0119] It should be understood that the recitation of ranges of values ​​herein, unless otherwise indicated, is merely intended to serve as a shorthand method for referring individually to each separate value falling within that range, and each separate value is incorporated herein as if it were individually set forth in the specification. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any and all examples, or language denoting examples (e.g., "such as") provided herein, are intended merely to better illustrate the invention. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0120] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors anticipate that skilled artisans will adopt such variations as necessary, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Furthermore, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. The following embodiments can be given as examples of the present invention. (Appendix 1) 1. A chemical-mechanical polishing composition comprising: A liquid carrier; colloidal silica particles dispersed in said liquid carrier, said colloidal silica particles having a positive charge in said liquid carrier of at least 10 mV; an iron-containing accelerator; Metal etching inhibitors and and the colloidal silica particles have (i) a number average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42; Chemical-mechanical polishing compositions. (Appendix 2) 2. The composition of claim 1, wherein the colloidal silica particles have a number average aspect ratio greater than about 1.35. (Appendix 3) 2. The composition of claim 1, wherein the colloidal silica particles have a weight-normalized particle size span greater than about 0.6. (Appendix 4) 2. The composition of claim 1, wherein the colloidal silica particles have (i) a number average aspect ratio greater than about 1.35 and a weight-normalized particle size span greater than about 0.6. (Appendix 5) Attachment 1: The composition according to Appendix 1, wherein the colloidal silica particles have a number particle size distribution D50 of about 20 nm to about 60 nm. (Appendix 6) Attachment 1: The composition according to Appendix 1, wherein the colloidal silica particles have a weight particle size distribution D50 of about 60 nm to about 140 nm. (Appendix 7) the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles; the number average aspect ratio of the first colloidal silica particles is greater than about 1.35; and the number average aspect ratio of the second colloidal silica particles is less than about 1.15; 10. The composition of claim 1. (Appendix 8) 8. The composition of claim 7, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1. (Appendix 9) the first colloidal silica particles have a weight-normalized particle size span of less than about 0.42; and the second colloidal silica particles have a weight-normalized particle size span of less than about 0.42; 8. The composition of claim 7. (Appendix 10) 2. The composition of claim 1, wherein the colloidal silica particles have a permanent positive charge of at least 10 mV. (Appendix 11) 10. The composition of claim 1, wherein the iron-containing accelerator comprises a soluble iron-containing catalyst, and the composition further comprises a stabilizer bound to the soluble iron-containing catalyst, the stabilizer being selected from the group consisting of phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and mixtures thereof. (Appendix 12) 10. The composition of claim 1, further comprising a hydrogen peroxide oxidizing agent. (Appendix 13) 2. The composition of claim 1, having a pH of about 1.0 to about 5.0. (Appendix 14) 2. The composition of claim 1, wherein the metal etching inhibitor is polylysine. (Appendix 15) 1. A chemical-mechanical polishing composition comprising: A liquid carrier; colloidal silica particles dispersed in said liquid carrier, said colloidal silica particles having a positive charge in said liquid carrier of at least 10 mV; an iron-containing accelerator; Metal etching inhibitors and Including, the colloidal silica particles have a normalized particle size span greater than about 0.42; and At least 15% of the colloidal silica particles contain three or more aggregated primaries; Chemical-mechanical polishing compositions. (Appendix 16) 16. The composition of claim 15, wherein the colloidal silica particles have a normalized particle size span greater than about 0.6. (Appendix 17) 16. The composition of claim 15, wherein less than 50% of the colloidal silica particles are monomeric. (Appendix 18) the colloidal silica particles have a normalized particle size span greater than about 0.6; and Less than 50% of the colloidal silica particles are monomers; 16. The composition of claim 15. (Appendix 19) 16. The composition of claim 15, wherein the colloidal silica particles have a number average aspect ratio greater than about 1.25. (Appendix 20) 16. The composition of claim 15, further comprising a hydrogen peroxide oxidizing agent. (Appendix 21) 16. The composition of claim 15, having a pH of about 1.0 to about 5.0. (Appendix 22) 16. The composition of claim 15, wherein the metal etching inhibitor is polylysine. (Appendix 23) 1. A chemical-mechanical polishing composition comprising: A liquid carrier; colloidal silica particles dispersed in said liquid carrier, said colloidal silica particles having a positive charge in said liquid carrier of at least 10 mV; and the colloidal silica particles have (i) a number average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42; Chemical-mechanical polishing compositions. (Appendix 24) 24. The composition of claim 23, wherein the number average aspect ratio is greater than 1.35 and the weight normalized particle size span is greater than about 0.6. (Appendix 25) 24. The composition of claim 23, wherein at least 15% of the colloidal silica particles comprise three or more aggregated primaries. (Appendix 26) the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles; the number average aspect ratio of the first colloidal silica particles is greater than about 1.35; and the number average aspect ratio of the second colloidal silica particles is less than about 1.1; 24. The composition of claim 23. (Appendix 27) 27. The composition of claim 26, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of about 1:15 to about 1:1. (Appendix 28) 1. A method for chemically mechanically polishing a substrate, comprising: The method comprises: (a) removing the substrate; (i) a liquid carrier; (ii) colloidal silica particles dispersed in said liquid carrier, said colloidal silica particles having a positive charge in said liquid carrier of at least 10 mV; and (iii) the colloidal silica particles have (i) a number average aspect ratio greater than about 1.25 and (ii) a weight-normalized particle size span greater than about 0.42; contacting the polishing composition with (b) moving the polishing composition relative to the substrate; and (c) grinding the substrate to remove a portion of at least one layer from the substrate, thereby polishing the substrate. Including, A method for chemically mechanically polishing a substrate. (Appendix 29) the substrate includes a tungsten layer; the composition further comprises an iron-containing accelerator and a tungsten etch inhibitor; and (c) during polishing, a portion of the tungsten layer is removed from the substrate. 29. The method described in Appendix 28. (Appendix 30) 30. The method of claim 29, wherein the tungsten inhibitor is polylysine. (Appendix 31) 29. The method of claim 28, wherein the number average aspect ratio is greater than 1.35 and the weight normalized particle size span is greater than about 0.6. (Appendix 32) 29. The method of claim 28, wherein at least 15% of the colloidal silica particles comprise three or more aggregated primaries.

Claims

1. A chemical-mechanical polishing composition for polishing tungsten, comprising: A liquid carrier; colloidal silica particles dispersed in the liquid carrier, the colloidal silica particles having a positive charge in the liquid carrier of at least 10 mV; an iron-containing accelerator; Metal etching inhibitors and and the colloidal silica particles have (i) a number average aspect ratio greater than 1.25 and (ii) a weight normalized particle size span greater than 0.42; (wherein the weight-normalized particle size span of the colloidal silica particles is calculated using the following formula: [Equation 1] where NSpan represents the weight-normalized particle size span of the colloidal silica particles, D10 represents the particle size value above which 90 percent of the particles in a sample are larger and 10 percent are smaller (counted by weight), D50 represents the particle size value above which 50 percent of the particles in a sample are larger and 50 percent are smaller (counted by weight), and D90 represents the particle size value below which 10 percent of the particles in a sample are smaller and 90 percent are smaller (counted by weight). Chemical-mechanical polishing compositions.

2. 10. The composition of claim 1, wherein the colloidal silica particles have a number average aspect ratio greater than 1.

35.

3. 10. The composition of claim 1, wherein the colloidal silica particles have a weight-normalized particle size span greater than 0.

6.

4. 10. The composition of claim 1, wherein the colloidal silica particles have (i) a number average aspect ratio greater than 1.35 and (ii) a weight normalized particle size span greater than 0.

6.

5. 2. The composition of claim 1, wherein the colloidal silica particles have a number particle size distribution with a D50 of 20 nm to 60 nm.

6. 2. The composition of claim 1, wherein the colloidal silica particles have a weight particle size distribution of D50 between 60 nm and 140 nm.

7. the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles; the number average aspect ratio of the first colloidal silica particles is greater than 1.35; and the number average aspect ratio of the second colloidal silica particles is less than 1.15; The composition of claim 1.

8. 8. The composition of claim 7, wherein the first colloidal silica particles and the second colloidal silica particles are blended in a weight ratio of 1:15 to 1:

1.

9. the first colloidal silica particles have a weight-normalized particle size span of less than 0.42; and the second colloidal silica particles have a weight-normalized particle size span of less than 0.42; The composition of claim 7.

10. 10. The composition of claim 1, wherein the colloidal silica particles have a permanent positive charge of at least 10 mV.

11. 10. The composition of claim 1, wherein the iron-containing accelerator comprises a soluble iron-containing catalyst, and the composition further comprises a stabilizer bound to the soluble iron-containing catalyst, the stabilizer being selected from the group consisting of phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and mixtures thereof.

12. The composition of claim 1 further comprising a hydrogen peroxide oxidizing agent.

13. The composition of claim 1, having a pH of 1.0 to 5.

0.

14. The composition of claim 1 wherein the metal etching inhibitor is polylysine.

15. 10. The chemical mechanical polishing composition of claim 1, wherein at least 15% of the colloidal silica particles comprise three or more aggregated primaries.

16. A chemical mechanical polishing composition for polishing tungsten, comprising: A liquid carrier; colloidal silica particles dispersed in the liquid carrier, the colloidal silica particles having a positive charge in the liquid carrier of at least 10 mV; and the colloidal silica particles have (i) a number average aspect ratio greater than 1.25 and (ii) a weight normalized particle size span greater than 0.42; (wherein the weight-normalized particle size span of the colloidal silica particles is calculated using the following formula: [Equation 2] where NSpan represents the weight-normalized particle size span of the colloidal silica particles, D10 represents the particle size value above which 90 percent of the particles in a sample are larger and 10 percent are smaller (counted by weight), D50 represents the particle size value above which 50 percent of the particles in a sample are larger and 50 percent are smaller (counted by weight), and D90 represents the particle size value below which 10 percent of the particles in a sample are smaller and 90 percent are smaller (counted by weight). Chemical-mechanical polishing compositions.

17. the colloidal silica particles comprise a blend of first colloidal silica particles and second colloidal silica particles; the number average aspect ratio of the first colloidal silica particles is greater than 1.35; and the number average aspect ratio of the second colloidal silica particles is less than 1.1; 17. The composition of claim 16.

18. 17. The composition of claim 16, wherein at least 15% of the colloidal silica particles comprise three or more aggregated primaries.

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