Method for increasing the removal rate of a barrier film in a bulk tungsten slurry

Abstract

The present invention relates to a chemical-mechanical polishing composition comprising: (a) a first abrasive comprising cationically modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or greater; (c) a cationic polymer; (d) an iron-containing activator; (e) an oxidizing agent; and (f) water. The present invention also relates to a method of chemical-mechanical polishing a substrate, particularly a substrate comprising tungsten and a barrier layer (e.g., nitride), with the polishing composition.

Description

Background Art

[0001] Chemical mechanical polishing (CMP) compositions and methods for polishing (or planarizing) the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries, CMP slurries, and CMP compositions) for polishing a metal layer (e.g., tungsten) on a semiconductor substrate may include abrasive particles suspended in an aqueous solution and chemical accelerators such as oxidizing agents, chelating agents, catalysts, etc.

[0002] In a conventional CMP operation, the substrate (wafer) to be polished is mounted on a carrier (polishing head), and then the carrier is mounted on a carrier assembly and placed in contact with a polishing pad of a CMP apparatus (polishing tool). The carrier assembly provides a controllable pressure to the substrate and presses the substrate against the polishing pad. The substrate and the pad move relative to each other by an externally applied driving force. Due to the relative movement of the substrate and the pad, a portion of the material is abraded and removed from the surface of the substrate, thereby polishing the substrate. The polishing of the substrate by the relative movement of the pad and the substrate can be further promoted by the chemical activity of the polishing composition (e.g., by oxidizing agents and other compounds present in the CMP composition) and / or by the mechanical activity of the abrasive suspended in the polishing composition.

[0003] In a typical tungsten plugging and interconnection process, tungsten is deposited on and within openings formed in the dielectric. Excess tungsten on the dielectric layer is then removed during the CMP operation, forming tungsten plugs and interconnects within the dielectric. Following the removal of bulk tungsten, the substrate surface is subjected to a buffing process to remove debris and provide a more uniform topography to the surface. Erosion within substrate features such as tungsten plugs and interconnects is excessive metal removal from within the features and leads to non-flatness, so the requirements for buffing are stringent, as it must be minimized or, more preferably, even reversed. The buffing process involves polishing two or more different materials, such as tungsten, dielectric, and barrier materials such as silicon nitride, and therefore, a proper balance of removal rates for the various materials is required to achieve a suitable surface topography.

[0004] In conventional polishing systems, adding polymer additives to improve topography typically results in a significant decrease in the barrier film removal rate. This decrease in removal rate is greater for the barrier film than for the tungsten film. This difference in removal rate presents a challenge in determining the polishing endpoint.

[0005] Therefore, there is an ongoing need to develop new polishing methods and compositions for tungsten bulk polishing applications that provide good removal rates, as well as good surface topography and flatness, while minimizing or eliminating erosion. [Overview of the Initiative]

[0006] The present invention provides a chemical mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or higher, (c) a cationic polymer, (d) an iron-containing activator, (e) an oxidizing agent, and (f) water.

[0007] The present invention also provides a method for chemically mechanically polishing a substrate, comprising: (i) preparing a substrate; (ii) preparing a polishing pad; (iii) preparing a chemically mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or more; (c) a cationic polymer; (d) an iron-containing activator; (e) an oxidizing agent; and (f) water; (iv) bringing the substrate into contact with the polishing pad and the chemically mechanical polishing composition; and (v) moving the polishing pad and the chemically mechanical polishing composition against the substrate to grind at least a portion of the substrate and polish the substrate. [Modes for carrying out the invention]

[0008] The present invention provides a chemical mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or higher, (c) a cationic polymer, (d) an iron-containing activator, (e) an oxidizing agent, and (f) water.

[0009] The polishing composition of the present invention comprises a first abrasive comprising, essentially, or consisting of, cationically modified colloidal silica, i.e., colloidal silica modified to have a permanent positive charge. The colloidal silica before cationic modification can be any suitable colloidal silica. Examples of colloidal silica particles include, for example, the PL series of colloidal silica particles commercially available from FUSO Chemical Co. (Tokyo, Japan) (e.g., PL-1, PL-3D and PL-2, PL-7, and PL-10 colloidal silica products).

[0010] Permanent positive charge means that the positive charge on silica particles cannot be easily removed, for example, by flushing, dilution, or filtration. Permanent positive charge can result from, for example, the covalent bonding of cationic compounds to colloidal silica. While the cationic compound may undergo charge reversal at pH levels higher than those used during the polishing process, the cationic compound remains bonded to the colloidal silica. Permanent positive charge is in contrast to non-permanent positive charge, which can result from, for example, electrostatic interactions between cationic compounds and colloidal silica.

[0011] The charge on dispersed particles, such as colloidal silica particles, is commonly referred to in the art as the zeta potential (or interfacial potential). The zeta potential of a particle refers to the potential difference between the charge of the ions surrounding the particle and the charge of the bulk solution of the abrasive composition (e.g., a liquid carrier and any other components dissolved therein). The zeta potential is typically pH-dependent of the aqueous medium. For a given abrasive composition, the isoelectric point of the particle is defined as the pH at which the zeta potential is zero. As the pH increases or decreases away from the isoelectric point, the surface charge (and therefore the zeta potential) decreases or increases accordingly (to negative or positive zeta potential values). The zeta potential of dispersions such as abrasive compositions can be obtained using commercially available instruments such as the ZETASIZER® available from Malvern Instruments, the ZETAPLUS® Zeta Potential Analyzer available from Brookhaven Instruments, and electroacoustic spectrometers available from Dispersion Technologies, Inc.

[0012] Cationically modified colloidal silica particles have a positive charge of at least about 20 mV or more in the polishing composition. More specifically, cationically modified colloidal silica particles in the polishing composition can have a permanent positive charge (i.e., zeta potential) of about 20 mV or more, for example, about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, about 50 mV or more, about 55 mV or more, about 60 mV or more, about 65 mV or more, about 70 mV or more, or about 75 mV or more. Alternatively, or in addition, colloidal silica particles in the polishing composition can have a permanent positive charge (i.e., zeta potential) of about 100 mV or less, for example, about 95 mV or less, about 90 mV or less, about 85 mV or less, or about 80 mV or less. Thus, colloidal silica particles can have a permanent positive charge (i.e., zeta potential) within the range bounded by any two of the aforementioned endpoints. Preferably, the colloidal silica particles have a permanent positive charge (i.e., zeta potential) of about 20 mV to about 100 mV (e.g., about 20 mV to about 75 mV, about 25 mV to about 100 mV, about 25 mV to about 75 mV, or about 25 mV to about 50 mV) over a suitable pH range (e.g., pH of about 4 or less).

[0013] The permanent positive charge of colloidal silica particles can be measured using any suitable method, and is not particularly limited. For example, the charge characteristics of colloidal silica particles can be determined using dialysis techniques. In addition, ultrafiltration can also be used. An exemplary three-step ultrafiltration method is described herein. Those skilled in the art will recognize that the parameters of the conditions for the ultrafiltration method described herein are exemplary and should not be construed as limiting in any way.

[0014] A certain volume of polishing composition (e.g., 200 mL) is passed through a Millipore ULTRACELL® regenerated cellulose ultrafiltration disc (e.g., having a molecular weight cutoff of 100,000 Daltons and a pore size of 6.3 nm). The remaining dispersion (the dispersion held by the ultrafiltration disc) is collected and replenished with pH-adjusted deionized water to the original volume. The polishing composition is pH-adjusted to the original pH using deionized water with a suitable inorganic acid such as nitric acid. This procedure is repeated for a total of three ultrafiltration cycles (each cycle including an ultrafiltration step and a replenishment step). The zeta potential of the triple-ultrafiltered and replenished polishing composition is then measured and compared to the zeta potential of the original polishing composition.

[0015] While we do not wish to be bound by any particular theory, it is assumed that the dispersion held by the ultrafiltration disk (held dispersion) contains colloidal dull silica particles and any chemical compounds (e.g., cationic compounds) that can associate with the surface of the colloidal dull silica particles (e.g., they can bind to or adhere to the particle surface, or interact electrostatically with the particle surface). At least a portion of the liquid carrier (e.g., water) and the chemical compounds dissolved therein pass through the ultrafiltration disk. When the held dispersion is replenished to its original volume, the equilibrium in the original abrasive composition is disrupted, and it is thought that the chemical compounds associated with the particle surface may tend to move toward a new equilibrium. Compounds that are strongly associated with the particle surface (e.g., covalently bonded) tend to remain on the surface, so as to be, there is little change in the positive zeta potential of the particles. In contrast, some compounds that are weakly associated with the particle surface (e.g., electrostatic interaction) may return to the solution when the system tends toward a new equilibrium, thereby decreasing the positive zeta potential. It is thought that repeating this process a total of three ultrafiltration and replenishment cycles amplifies the above effect.

[0016] After correcting for differences in ionic strength, it is observed that there is little (or no) difference between the zeta potential of colloidal silica particles in the original polishing composition and the zeta potential of particles in the triple-ultrafiltered and replenished polishing composition obtained from the three-step ultrafiltration test described above. Before correcting for differences in ionic strength, it will be understood that the measured zeta potential may be observed to increase due to the decrease in ionic strength (due to dilution) of the triple-ultrafiltered and replenished polishing composition. After correcting for differences in ionic strength, any decrease in positive charge on the particles resulting from the aforementioned three-step ultrafiltration test (i.e., decrease in zeta potential) is less than 10 mV (e.g., less than about 7 mV, less than about 5 mV, or less than about 2 mV).

[0017] In one embodiment, the cation-modified colloidal silica particles have a zeta potential greater than about 20 mV at a pH of about 2.5, for example, greater than about 25 mV at a pH of about 2.5, greater than about 30 mV at a pH of about 2.5, greater than about 35 mV at a pH of about 2.5, greater than about 40 mV at a pH of about 2.5, greater than about 45 mV at a pH of about 2.5, or greater than about 50 mV at a pH of about 2.5.

[0018] Furthermore, as described herein, the polishing compositions of the present invention have an acidic pH, i.e., a pH of less than 7 (for example, a pH of about 2 to about 5), and therefore the cation-modified colloidal silica particles can have any preferred zeta potential described herein at the pH of the polishing composition. In preferred embodiments, the polishing composition has a pH of about 2 to about 4. For example, in embodiments where the pH of the polishing composition is about 2.5, the cation-modified colloidal silica particles can have a zeta potential of about 100 mV or less (for example, about 95 mV or less, about 90 mV or less, about 85 mV, about 80 mV or less, about 75 mV or less, about 70 mV or less, about 65 mV or less, about 60 mV or less, or about 55 mV or less). Alternatively, or in addition, cation-modified colloidal silica particles can have a zeta potential of about 20 mV or more (e.g., about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, or about 50 mV or more). Thus, cation-modified colloidal silica particles can have a zeta potential in a range bounded by any of the aforementioned endpoints. In a preferred embodiment, the pH of the polishing composition is about 2.5, and the colloidal silica particles have a zeta potential of about 30 mV to about 40 mV (e.g., about 35 mV).

[0019] In other embodiments where the pH of the polishing composition is about 3, the cation-modified colloidal silica particles may have a zeta potential of about 100 mV or less (e.g., about 95 mV or less, about 90 mV or less, about 85 mV or less, about 80 mV or less, about 75 mV or less, about 70 mV or less, about 65 mV or less, about 60 mV or less, or about 55 mV or less). Alternatively, or in addition, the cation-modified colloidal silica particles may have a zeta potential of about 20 mV or more (e.g., about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, or about 50 mV or more). Thus, the cation-modified colloidal silica particles may have a zeta potential in a range bounded by any of the aforementioned endpoints. In a preferred embodiment, the pH of the polishing composition is about 3, and the colloidal silica particles have a zeta potential of about 40 mV to about 50 mV (e.g., about 45 mV).

[0020] In other embodiments where the pH of the polishing composition is about 3.5, the cation-modified colloidal silica particles may have a zeta potential of about 100 mV or less (e.g., about 95 mV or less, about 90 mV or less, about 85 mV or less, about 80 mV or less, about 75 mV or less, about 70 mV or less, about 65 mV or less, about 60 mV or less, or about 55 mV or less). Alternatively, or in addition, the cation-modified colloidal silica particles may have a zeta potential of about 20 mV or more (e.g., about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, or about 50 mV or more). Thus, the cation-modified colloidal silica particles may have a zeta potential in a range bounded by any of the aforementioned endpoints. In a preferred embodiment, the pH of the polishing composition is about 3.5, and the colloidal silica particles have a zeta potential of about 45 mV to about 50 mV (e.g., about 47 mV).

[0021] In other embodiments where the pH of the polishing composition is about 4, the cation-modified colloidal silica particles may have a zeta potential of about 100 mV or less (e.g., about 95 mV or less, about 90 mV or less, about 85 mV or less, about 80 mV or less, about 75 mV or less, about 70 mV or less, about 65 mV or less, about 60 mV or less, or about 55 mV or less). Alternatively, or in addition, the cation-modified colloidal silica particles may have a zeta potential of about 20 mV or more (e.g., about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, or about 50 mV or more). Thus, the cation-modified colloidal silica particles may have a zeta potential in a range bounded by any of the aforementioned endpoints. In a preferred embodiment, the pH of the polishing composition is about 4, and the colloidal silica particles have a zeta potential of about 40 mV to about 50 mV (e.g., about 45 mV).

[0022] In other embodiments where the pH of the polishing composition is about 4.5, the cation-modified colloidal silica particles may have a zeta potential of about 100 mV or less (e.g., about 95 mV or less, about 90 mV or less, about 85 mV or less, about 80 mV or less, about 75 mV or less, about 70 mV or less, about 65 mV or less, about 60 mV or less, or about 55 mV or less). Alternatively, or in addition, the cation-modified colloidal silica particles may have a zeta potential of about 20 mV or more (e.g., about 25 mV or more, about 30 mV or more, about 35 mV or more, about 40 mV or more, about 45 mV or more, or about 50 mV or more). Thus, the cation-modified colloidal silica particles may have a zeta potential in a range bounded by any of the aforementioned endpoints. In a preferred embodiment, the pH of the polishing composition is about 4.5, and the colloidal silica particles have a zeta potential of about 40 mV to about 45 mV (e.g., about 42 mV).

[0023] The cationically modified colloidal silica particles of the first abrasive can be prepared using any suitable method. An exemplary method involves treating the colloidal silica particles with at least one cationic compound, such as an aminosilane compound. Suitable aminosilane compounds include primary aminosilanes, secondary aminosilanes, tertiary aminosilanes, quaternary aminosilanes, and multipodal (e.g., dipodal) aminosilanes. The aminosilane compound can be any suitable aminosilane, such as bis(2-hydroxyethyl)-3-aminopropyltrialkoxysilane, diethylaminomethyltrialkoxysilane, (N,N-diethyl-3-aminopropyl)trialkoxysilane, 3-(N-styrylmethyl-2-aminoethylaminopropyltrialkoxysilane, aminopropyltrialkoxysilane, (2-N-benzylaminoethyl)-3-aminopropyltrialkoxysilane), trialkoxysilylpropyl-N,N,N-trimethylammonium chloride, N-(trialkoxysilylethyl)benzyl-N,N,N-trimethylammonium chloride, bis(methyldialkoxysilylpropyl)-N-methylamine, bis(trialkoxysilylpropyl)urea, bis(3-(trialkoxysilyl)propyl)-ethylenediamine, bis(trialkoxysilylpropyl)amine, bis(trialkoxysilylpropyl)amine, and mixtures thereof.

[0024] Any suitable method for treating colloidal silica particles can be used. For example, the colloidal silica particles may be treated with an aminosilane compound before being mixed with the other components of the polishing composition, or the aminosilane and colloidal silica particles may be added simultaneously to the other components of the polishing composition.

[0025] In embodiments where aminosilane is added simultaneously to other components of the abrasive composition, the aminosilane compound may be present in the abrasive composition in any suitable amount. The amount of aminosilane used may depend on several factors, including, for example, particle size, particle surface area, the specific aminosilane compound used, and the desired charge on the particles. As is generally understood, the amount of aminosilane used increases with decreasing particle size (and thus increasing surface area) and increasing charge on the particles. For example, to achieve a permanent positive charge greater than about 20 mV, 20 ppm or more of aminosilane by weight may be used in a dispersion with a particle size of 110 nm, 70 ppm or more of aminosilane may be used in a dispersion with a particle diameter of 75 nm, and 130 ppm or more of aminosilane may be used in a dispersion with a particle diameter of 55 nm. Therefore, the polishing composition may contain aminosilane in amounts of about 5 ppm or more, for example, about 10 ppm or more, about 15 ppm or more, about 20 ppm or more, about 25 ppm or more, about 30 ppm or more, about 50 ppm or more, about 70 ppm or more, about 85 ppm or more, about 100 ppm or more, about 115 ppm or more, or about 130 ppm or more. The polishing composition preferably contains an amount of aminosilane sufficient to provide the desired permanent positive charge without using excess. Therefore, the polishing composition may contain an aminosilane compound in amounts of about 500 ppm or less, for example, an aminosilane compound in amounts of about 400 ppm or less, about 300 ppm or less, about 200 ppm or less, about 150 ppm or less, about 130 ppm or less, about 100 ppm or less, about 75 ppm or less, or about 60 ppm or less. Therefore, the polishing composition may contain an amount of aminosilane within the range bounded by any two of the aforementioned endpoints. Preferably, the abrasive composition contains about 5 ppm to about 500 ppm of an aminosilane compound, for example, about 10 ppm to about 300 ppm, about 15 ppm to about 200 ppm, or about 20 ppm to about 150 ppm of an aminosilane compound.

[0026] The abrasive composition of the present invention comprises, consists essentially of, or consists of a second abrasive agent comprising an abrasive having a Mohs hardness of about 5.5 or greater. As used herein, "Mohs hardness" refers to a qualitative ordinal scale that characterizes the scratch resistance of various minerals by the ability of a harder material to scratch a softer material. For the purposes of the present invention, the Mohs hardness represented for abrasive particles refers to the Mohs hardness of the bulk material from which the abrasive particles are generated. Without wishing to be bound by any particular theory, Applicants have discovered that abrasive compositions comprising a "mixed particle abrasive", i.e., an abrasive agent comprising a first abrasive agent comprising cation-modified colloidal silica particles and a second abrasive agent having a Mohs hardness of about 5.5 or greater, are particularly suitable for polishing substrates comprising tungsten, titanium, titanium nitride, or combinations thereof. In accordance with one aspect of the present invention, the second abrasive particles are harder than the first abrasive agent comprising cation-modified colloidal silica particles, as measured by the Mohs hardness of the bulk material.

[0027] The second abrasive agent can have a Mohs hardness of about 5.5 or greater, such as, for example, about 6 or greater, about 6.5 or greater, about 7 or greater, about 7.5 or greater, about 8 or greater, about 8.5 or greater, about 9 or greater, about 9.5 or greater, or about 10. Alternatively, or in addition, the second abrasive agent can have a Mohs hardness of about 10 or less, such as, for example, about 9.5 or less, about 9 or less, about 8.5 or less, or about 8 or less. Thus, the second abrasive agent can have a Mohs hardness within a range bounded by any two of the foregoing endpoints. For example, the second abrasive agent can have a Mohs hardness of about 5.5 to about 10, such as, for example, about 6 to about 9.5, about 6.5 to about 9, about 7 to about 8.5, or about 7.5 to about 8. In one embodiment, the second abrasive agent has a Mohs hardness of about 9.

[0028] The second abrasive agent can comprise two or more types of particles having a Mohs hardness of about 5.5 or greater. In one embodiment, the second abrasive agent is selected from α-alumina particles, zirconia particles, diamond particles, and combinations thereof.

[0029] In a preferred embodiment, the second abrasive comprises α-alumina particles. In another preferred embodiment, the second abrasive consists of α-alumina particles.

[0030] A suitable alumina is the α-alumina commercially available from Saint-Gobain (Worcester, MA).

[0031] In one embodiment, the polishing composition contains cation-modified colloidal silica particles as the first abrasive and α-alumina particles as the second abrasive.

[0032] The abrasive particles (i.e., the first abrasive containing cation-modified colloidal silica particles and the second abrasive having a Mohs hardness of about 5.5 or greater) can have any suitable size (e.g., primary particle size, average particle diameter, etc.). As used herein, as understood by those skilled in the art, the average particle size is the weight-average particle size (D wThis refers to the average particle size of the abrasive particles. The average particle size of the abrasive particles can be measured using any suitable technique, for example, using laser diffraction technique. Suitable particle size measuring instruments are available, for example, from Malvern Instruments (Malvern, UK). If the average particle size of the abrasive particles is too small, the polishing composition may not exhibit sufficient removal rate. Conversely, if the average particle size of the abrasive particles is too large, the polishing composition may exhibit undesirable polishing performance, such as severe substrate defects. Therefore, the abrasive particles can have an average particle size of about 10 nm or more, for example, about 15 nm or more, about 20 nm or more, about 30 nm or more, about 40 nm or more, about 50 nm or more, about 60 nm or more, about 70 nm or more, about 80 nm or more, about 90 nm or more, or about 100 nm or more. Alternatively, or additionally, the abrasive particles may have an average particle size of approximately 1,000 nm or less, for example, approximately 750 nm or less, approximately 500 nm or less, approximately 400 nm or less, approximately 300 nm or less, or approximately 200 nm or less. Thus, the abrasive particles may have an average particle size within the range bounded by any two of the aforementioned endpoints. For example, the abrasive particles may have an average particle size of approximately 10 nm to approximately 1,000 nm, approximately 20 nm to approximately 750 nm, approximately 30 nm to approximately 500 nm, approximately 40 nm to approximately 400 nm, approximately 50 nm to approximately 300 nm, approximately 60 nm to approximately 300 nm, approximately 70 nm to approximately 300 nm, approximately 80 nm to approximately 300 nm, approximately 90 nm to approximately 300 nm, or approximately 100 nm to approximately 200 nm.

[0033] In a preferred embodiment, the first abrasive containing cation-modified colloidal silica particles has an average particle size of about 110 nm.

[0034] In another preferred embodiment, the second abrasive particles having a Mohs hardness of about 5.5 or higher have an average particle size of about 70 nm to about 110 nm.

[0035] In one embodiment, the cation-modified colloidal silica particles have an average particle size of about 50 nm to about 200 nm, for example, about 55 nm, about 60 nm, about 65 nm, about 70 nm, about 75 nm, about 80 nm, about 85 nm, about 90 nm, about 95 nm, about 100 nm, about 105 nm, about 110 nm, about 115 nm, about 120 nm, about 125 nm, about 130 nm, about 135 nm, about 140 nm, about 145 nm, about 150 nm, about 155 nm, about 160 nm, about 165 nm, about 170 nm, about 175 nm, about 180 nm, about 185 nm, about 190 nm, or about 195 nm.

[0036] In another embodiment, the cation-modified colloidal silica particles have an average particle size of about 100 nm to about 140 nm.

[0037] The abrasive composition may contain any suitable amount of abrasive (i.e., a first abrasive containing cation-modified colloidal silica particles and a second abrasive having a Mohs hardness of about 5.5 or higher). If the abrasive composition of the present invention contains little to no abrasive, the composition may not exhibit sufficient removal rate. In contrast, if the abrasive composition contains an excessive amount of abrasive, the composition may exhibit undesirable polishing performance, lead to surface defects such as scratches, be cost-ineffective, and / or lack stability. The abrasive composition may contain about 10% by weight or less, for example, about 9% by weight or less, about 8% by weight or less, about 7% by weight or less, about 6% by weight or less, or about 5% by weight or less of abrasive. Alternatively, or in addition, the abrasive composition may contain about 0.01% by weight or more of abrasive, for example, about 0.05% by weight or more, about 0.1% by weight or more, about 0.2% by weight or more, about 0.3% by weight or more, about 0.4% by weight or more, about 0.5% by weight or more, or about 1% by weight or more of abrasive. Therefore, the abrasive composition may contain abrasives in amounts within the range bounded by any two of the aforementioned endpoints. For example, the abrasive composition may contain about 0.01% to about 10% by weight of abrasives, for example, about 0.05% to about 9.5% by weight of abrasives, about 0.1% to about 9% by weight of abrasives, about 0.1% to about 8% by weight of abrasives, about 0.1% to about 7% by weight of abrasives, about 0.1% to about 6% by weight of abrasives, about 0.1% to about 5% by weight of abrasives, about 0.2% to about 5% by weight of abrasives It may contain abrasives in amounts of approximately 0.3% to 5% by weight, approximately 0.4% to 5% by weight, approximately 0.5% to 5% by weight, approximately 0.6% to 5% by weight, approximately 0.7% to 5% by weight, approximately 0.8% to 5% by weight, approximately 0.9% to 5% by weight, or approximately 1% to 5% by weight.

[0038] In one embodiment, the abrasive composition contains about 0.05% to about 5% by weight of abrasive. In another embodiment, the abrasive composition contains about 0.15% to about 2% by weight of abrasive.

[0039] The first abrasive can be present in the polishing composition in any suitable amount. In one embodiment, cation-modified colloidal silica particles are present in the polishing composition in an amount of about 0.05% to about 5% by weight.

[0040] In one embodiment, cation-modified colloidal silica particles are present in the polishing composition in an amount of about 1% by weight.

[0041] The second abrasive can be present in the polishing composition in any suitable amount. While we do not wish to be bound by any particular theory, if too little of the second abrasive is present, the polishing composition may not exhibit a suitable barrier layer removal rate. If too much of the second abrasive is present, no additional increase in barrier layer removal rate may be observed, and the polishing composition may not be cost-effective. Typically, the second abrasive is present in the polishing composition in a smaller amount than the first abrasive. For example, in one embodiment, the second abrasive is present in the abrasive composition in an amount of about 25 ppm (i.e., about 0.0025% by weight) or more, based on weight, for example, about 30 ppm, about 35 ppm, about 40 ppm, about 45 ppm, about 50 ppm, about 55 ppm, about 60 ppm, about 65 ppm, about 70 ppm, about 75 ppm, about 80 ppm, about 85 ppm, about 90 ppm, about 95 ppm, about 100 ppm, about 125 ppm, about 150 ppm, about 175 ppm, about 200 ppm, about 225 ppm, about 250 ppm, about 275 ppm, about 300 ppm, about 325 ppm, It is present in the abrasive composition in amounts of approximately 350 ppm, 375 ppm, 400 ppm, 425 ppm, 450 ppm, 475 ppm, 500 ppm, 525 ppm, 550 ppm, 575 ppm, 600 ppm, 625 ppm, 650 ppm, 675 ppm, 700 ppm, 725 ppm, 750 ppm, 775 ppm, 800 ppm, 825 ppm, 850 ppm, 875 ppm, 900 ppm, 925 ppm, 950 ppm, 975 ppm, or approximately 1,000 ppm (i.e., approximately 0.1% by weight). Therefore, for example, the second abrasive can be present in the abrasive composition in an amount of about 0.0025% to about 0.1% by weight, for example, about 0.005% to about 0.75% by weight, about 0.0075% to about 0.6% by weight, or about 0.01% to about 0.5% by weight, or about 0.02% to about 0.25% by weight.

[0042] In one embodiment, the second abrasive is present in the polishing composition in an amount of about 50 ppm to about 500 ppm. In another embodiment, the second abrasive is present in the polishing composition in an amount of about 150 ppm.

[0043] In a preferred embodiment, the second abrasive is α-alumina, present in the abrasive composition in an amount of 150 ppm (0.015 wt%).

[0044] When abrasive particles are suspended in an abrasive composition, the particles are preferably colloidally stable. As used herein, the term “colloidal stability” refers to the suspension of abrasive particles in a liquid carrier (e.g., water) and the maintenance of that suspension over time. In the context of the present invention, when abrasive particles are placed in a 100 mL graduated cylinder and left undisturbed for 2 hours, the abrasive is considered colloidally stable if the difference between the particle concentration in the bottom 50 mL of the graduated cylinder ([B], in g / mL) and the particle concentration in the top 50 mL of the graduated cylinder ([T], in g / mL) is divided by the initial particle concentration in the abrasive composition ([C], in g / mL) to be 0.5 or less (i.e., {[B]-[T]} / [C] ≤ 0.5). The value of [B]-[T] / [C] is preferably 0.3 or less, and more preferably 0.1 or less.

[0045] The polishing compositions of the present invention comprise a cationic polymer. As used herein, a cationic polymer refers to a polymer that has a net positive charge under the conditions of interest (e.g., polishing conditions). While we do not wish to be bound by any particular theory, the applicants have surprisingly found that the polishing compositions described herein, comprising a cationic polymer, provide a suitable barrier layer (i.e., film) removal rate in bulktungsten polishing.

[0046] Cationic polymers include, are essentially, or may include any suitable cationic polymer. Exemplary cationic polymers include polymers containing quaternary ammonium groups, e.g., copolymers of quaternary ammonium-containing monomers / polymers with acrylamide monomers / polymers (e.g., aminoacrylate polymers). Exemplary cationic polymers also include homopolymers of cationic monomers, e.g., poly(diallyldimethylammonium) halide, e.g., poly(diallyldimethylammonium) chloride (polyDADMAC), poly(methacryloyloxyethyltrimethylammonium) halide, e.g., poly(methacryloyloxyethyltrimethylammonium) chloride (polyMADQUAT), and the like. In addition, the cationic polymer can be a copolymer of cationic and nonionic monomers (e.g., alkyl acrylates, alkyl methacrylates, acrylamides, styrenes, etc.), for example, poly(acrylamide-co-diallyldimethylammonium) chloride (polyAAm-DADMAC) and poly(dimethylamine-co-epichlorohydrin-co-ethylenediamine) (polyDEE). Some other non-limiting examples of preferred cationic polymers include polyethyleneimine, ethoxylated polyethyleneimine, poly(diallyldimethylammonium) halide, poly(amideamine), poly(methacryloyloxyethyldimethylammonium) chloride, poly(vinylpyrrolidone), poly(vinylimidazole), poly(vinylpyridine), and poly(vinylamine). In a preferred embodiment, the cationic polymer is polyDADMAC. In another preferred embodiment, the cationic polymer is polyMADQUAT. In yet another preferred embodiment, the cationic polymer is polylysine.

[0047] Alternatively, or in addition, the cationic polymer may include a nitrogen-heteroaryl group or a quaternary nitrogen-heteroaryl group, i.e., a heteroaromatic compound having at least one nitrogen atom in the aromatic ring and optionally having at least one nitrogen atom in the alkylated ring to affix a formal positive charge to the heteroaryl ring (e.g., on the nitrogen in the ring). Preferably, the heteroaryl group is bonded to the polymer's main chain either directly to the aromatic ring or via an alkylene spacer group (e.g., a methylene (CH2) group or an ethylene (CH2CH2) group) by a carbon-carbon bond (e.g., as in a quaternary poly(vinylpyridine) polymer) or a carbon-nitrogen bond (e.g., as in a quaternary poly(vinylimidazole) polymer). The positive charge on the quaternary nitrogen is offset by a counteranion, which can be, for example, a halide (e.g., a chloride), a nitrate, a methyl sulfate, or a combination of anions. In some embodiments, the cationic polymer includes, essentially, or consists of, poly(vinyl-N-alkylpyridinium) polymers, such as poly(2-vinyl-N-alkylpyridinium) polymer, poly(4-vinyl-N-alkylpyridinium) polymer, vinyl-N-alkyliridinium copolymer, poly(N1-vinyl-N3-alkylimidazolium) polymer, and the like.

[0048] Cationic polymers may also contain, be essentially, or consist of polycationic amines. As used herein, a polycationic amine is an amine compound having more than one (e.g., two or more) amine groups, each of which is cationic (i.e., positively charged). Thus, a polycationic amine may include a polyquaternary amine. As used herein, a polyquaternary amine refers to an amine compound having two to four quaternary ammonium groups, for example, a polyquaternary amine is a diquaternary amine, triquaternary amine, or tetraquaternary amine compound. Suitable quaternary amine compounds include, for example, N,N'-methylenebis(dimethyltetradecylammonium bromide), 1,1,4,4-tetrabutylpiperazine dibromide, N,N,N',N',N'-pentamethyl-N-talou-1,3-propane-diammonium dichloride, N,N'-hexamethylenebis(tributylammonium hydroxide), decametonium bromide, didodecyl-tetramethyl-1,4-butanediaminium diiodide, and 1,5-dimethyl-1,5-diazoniabicyclo(3.2.2)nonanedibromide. Suitable tertiary amine compounds include, for example, N(1),N(6)-didoecyl-N(1),N(1),N(6),N(6)-tetramethyl-1,6-hexanediminium diiodide. Suitable tetraquaternary amine compounds include, for example, methanetetrayltetrakis (tetramethylammonium bromide). Polyquaternary amine compounds may further contain long-chain alkyl groups (for example, having 10 or more carbon atoms). For example, suitable polyquaternary amine compounds having long-chain alkyl groups include N,N'-methylenebis(dimethyltetradecylammonium bromide), N,N,N',N',N'-pentamethyl-N-talou-1,3-propane-diammonium dichloride, didodecyl-tetramethyl-1,4-butanediaminium diiodide, and N(1),N(6)-didodecyl-N(1),N(1),N(6),N(6)-tetramethyl-1,6-hexanediaminium diiodide.

[0049] Polycationic amines can also be polycationic in that each of their amine groups is protonated (and therefore positively charged). For example, dicationic amines such as tetramethyl-p-phenylenediamine contain two tertiary amine groups that can be protonated (and therefore positively charged) at a polishing composition pH value lower than the pKa of the amine compound.

[0050] In one embodiment, the cationic polymer is selected from polycationic amines, polylysine, and combinations thereof. In one embodiment, the cationic polymer comprises a polycationic amine. In another embodiment, the cationic polymer comprises polylysine.

[0051] Cationic polymers (e.g., copolymers) can have any preferred molecular weight. Cationic polymers typically have an average molecular weight of about 100,000 g / mol or less, for example, about 95 kDa or less, about 90 kDa or less, about 85 kDa or less, about 80 kDa or less, about 75 kDa, about 70 kDa or less, about 65 kDa or less, about 60 kDa or less, about 55 kDa or less, about 50 kDa or less, about 45 kDa or less, about 40 kDa or less, about 35 kDa or less, about 30 kDa or less, about 25 kDa or less, or about 20 kDa or less.

[0052] Therefore, cationic polymers can have an average molecular weight of about 500 g / mol or more, for example, about 1,000 g / mol or more, about 1,500 g / mol or more, about 2,000 g / mol or more, about 2,500 g / mol or more, about 3,000 g / mol or more, about 3,500 g / mol or more, about 4,000 g / mol or more, about 4,500 g / mol or more, about 5,000 g / mol or more, about 5,500 g / mol or more, about 6,000 g / mol or more, about 6,500 g / mol or more, about 7,000 g / mol or more, about 7,500 g / mol or more, about 8,000 g / mol or more, about 8,500 g / mol or more, about 9,000 g / mol or more, about 9,500 g / mol or more, or about 10,000 g / mol or more. Alternatively, or in addition, the cationic polymer may have an average molecular weight of about 15,000 g / mol or less, for example, about 14,500 g / mol or less, about 14,000 g / mol or less, about 13,500 g / mol or less, for example, about 13,000 g / mol or less, about 12,500 g / mol or less, about 12,000 g / mol or less, about 11,500 g / mol or less, about 11,000 g / mol or less, or about 10,500 g / mol or less. Thus, the cationic polymer may have an average molecular weight within the range bounded by any two of the aforementioned endpoints. For example, cationic polymers have a molecular weight of approximately 500 g / mol to 15,000 g / mol, approximately 1,000 g / mol to 14,500 g / mol, approximately 1,500 g / mol to 14,000 g / mol, approximately 2,000 g / mol to 13,500 g / mol, approximately 2,500 g / mol to 13,000 g / mol, approximately 3,000 g / mol to 12,500 g / mol, approximately 3,500 g / mol to 12,000 g / mol, and approximately 4,000 g / mol to 14,500 g / mol. It can have an average molecular weight of 11,500 g / mol, approximately 4,500 g / mol to approximately 11,000 g / mol, approximately 5,000 g / mol to approximately 10,500 g / mol, approximately 5,500 g / mol to approximately 10,000 g / mol, approximately 6,000 g / mol to approximately 9,500 g / mol, approximately 6,500 g / mol to approximately 9,000 g / mol, approximately 7,000 g / mol to approximately 8,500 g / mol, or approximately 7,500 g / mol to approximately 8,000 g / mol.

[0053] In preferred embodiments, the cationic polymer has a molecular weight of approximately 2,000 g / mol to approximately 15,000 g / mol.

[0054] In another preferred embodiment, the cationic polymer has a molecular weight of about 8,500 g / mol.

[0055] The abrasive composition may contain any suitable amount of cationic polymer. While we do not wish to be bound by any particular theory, it is typically assumed that there is an inverse relationship between the average molecular weight of the cationic polymer and the barrier layer removal rate. That is, as the molecular weight of the cationic polymer increases, the barrier layer removal rate may decrease. In such a state, the amount of cationic polymer and / or the hardness of the second abrasive may be adjusted accordingly.

[0056] Cationic polymers can be present in the abrasive composition at any preferred concentration. Typically, cationic polymers are present in the abrasive composition in amounts of about 1 ppm or more (based on weight), for example, about 5 ppm or more, about 10 ppm or more, about 15 ppm or more, about 20 ppm or more, about 25 ppm or more, about 30 ppm or more, about 35 ppm or more, about 40 ppm or more, about 45 ppm or more, or about 50 ppm or more. Alternatively, or in addition, cationic polymers can be present in the abrasive composition in amounts of about 100 ppm or less, about 95 ppm or less, about 90 ppm or less, about 85 ppm or less, about 80 ppm or less, about 75 ppm or less, about 70 ppm or less, about 65 ppm or less, about 60 ppm or less, or about 55 ppm or less. Thus, cationic polymers can be present in the abrasive composition in amounts limited by any of the aforementioned values. For example, cationic polymers can be present in the polishing composition in amounts ranging from approximately 1 ppm to approximately 100 ppm.

[0057] In a preferred embodiment, the cationic polymer is present in an amount of about 5 ppm to about 100 ppm. In another preferred embodiment, the cationic polymer is present in an amount of about 10 ppm to about 50 ppm. In yet another embodiment, the cationic polymer is present in an amount of about 15 ppm to about 30 ppm.

[0058] The polishing composition contains an iron-containing activator. The iron-containing activator is an iron-containing compound that promotes the removal rate of tungsten during tungsten CMP operation. For example, the iron-containing activator may include iron-containing catalysts such as those disclosed in U.S. Patent Nos. 5,958,288 and 5,980,775. The iron-containing activator may include, for example, a soluble iron salt soluble in an aqueous carrier, which is essentially or can be derived from such a salt, and may include, for example, ferric (iron III) compounds or ferrous (iron II) compounds, such as iron nitrate, iron sulfate, and iron halides, such as fluorides, chlorides, bromides, and iodides, as well as perchlorates, perbromids, periodates, and iron-containing organic compounds, such as iron acetate, iron acetylacetonate, iron citrate, iron gluconate, iron malonate, iron oxalate, iron phthalate, and iron succinate, and combinations thereof. In one embodiment, the iron-containing activator is ferric nitrate.

[0059] The abrasive composition may contain any suitable amount of iron-containing activator. If the amount of iron-containing activator in the abrasive composition is too small, the tungsten removal rate may not be satisfactory. Conversely, if the abrasive composition contains an excess of iron-containing activator, the abrasive composition may be unstable or not cost-effective. The iron-containing activator may be present in the abrasive composition in amounts of about 10 ppm or more (based on weight), for example, about 25 ppm or more, about 50 ppm or more, about 75 ppm or more, about 100 ppm or more, about 125 ppm or more, about 150 ppm or more, about 175 ppm or more, about 200 ppm or more, about 225 ppm or more, about 250 ppm or more, about 275 ppm or more, about 300 ppm or more, about 325 ppm or more, or about 350 ppm or more. Alternatively, or in addition, ion-containing surfactants may be present in the abrasive composition in amounts of about 1,000 ppm or less, for example, about 975 ppm or less, about 950 ppm or less, about 925 ppm or less, about 900 ppm or less, about 875 ppm or less, about 850 ppm or less, about 825 ppm or less, about 800 ppm or less, about 775 ppm or less, about 750 ppm or less, about 725 ppm or less, about 700 ppm or less, about 675 ppm or less, about 650 ppm or less, about 625 ppm or less, about 600 ppm or less, about 575 ppm or less, about 550 ppm or less, about 525 ppm or less, about 500 ppm or less, about 475 ppm or less, about 450 ppm or less, about 425 ppm or less, about 400 ppm or less, or about 375 ppm or less. Therefore, the iron-containing activator can be present in the abrasive composition in amounts within the range bounded by any two of the aforementioned endpoints. For example, the iron-containing activator can be present in the abrasive composition in amounts of about 10 ppm to about 1,000 ppm, for example, about 25 ppm to about 975 ppm, about 50 ppm to about 950 ppm, about 75 ppm to about 925 ppm, or about 100 ppm to about 900 ppm.

[0060] In one embodiment, iron derived from the iron-containing surfactant is present in the polishing composition in an amount of about 1 ppm to about 100 ppm (based on weight). In another embodiment, iron derived from the iron-containing surfactant is present in the polishing composition in an amount of about 50 ppm. In yet another embodiment, iron derived from the iron-containing surfactant is present in the polishing composition in an amount of about 60 ppm.

[0061] In some embodiments, abrasive compositions containing an iron-containing activator may further contain a stabilizer. While we do not wish to be bound by any particular theory, it is thought that the stabilizer prevents the iron-containing activator from decomposing the oxidizing agent over time. The addition of a stabilizer may reduce the effectiveness of the iron-containing activator, and consequently, the choice of type and amount of stabilizer may affect CMP performance. More specifically, it is thought that the addition of a stabilizer forms a stabilizer / activator complex (e.g., the stabilizer binds to a soluble iron salt) that suppresses the activator's reaction with the oxidizing agent while simultaneously allowing the activator to maintain sufficient activity, thereby increasing (e.g., accelerating) the tungsten polishing rate. In one embodiment, the stabilizer is selected from 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 combinations thereof.

[0062] In a preferred embodiment, the stabilizer includes malonic acid.

[0063] The abrasive composition may contain any suitable amount of stabilizer. If the abrasive composition contains too little stabilizer, the iron-containing activator may decompose rapidly, and the abrasive performance of the abrasive composition may become unsatisfactory. Conversely, if the abrasive composition contains too much stabilizer, the abrasive composition may become unstable and not cost-effective. Typically, the stabilizer is present in the abrasive composition in an amount of about 20 ppm or more (based on weight), for example, about 50 ppm or more, about 100 ppm or more, about 150 ppm or more, about 200 ppm or more, about 250 ppm or more, about 300 ppm or more, about 350 ppm or more, about 400 ppm or more, about 450 ppm or more, about 500 ppm or more, about 550 ppm or more, about 600 ppm or more, about 650 ppm or more, about 700 ppm or more, about 750 ppm or more, about 800 ppm or more, about 850 ppm or more, about 900 ppm or more, about 950 ppm or more, or about 1,000 ppm or more. Alternatively, or in addition, the stabilizer may be present in the abrasive composition in amounts of approximately 2,000 ppm or less, approximately 1,950 ppm or less, approximately 1,900 ppm or less, approximately 1,850 ppm or less, approximately 1,800 ppm or less, approximately 1,750 ppm or less, approximately 1,700 ppm or less, approximately 1,650 ppm or less, approximately 1,600 ppm or less, approximately 1,550 ppm or less, approximately 1,500 ppm or less, approximately 1,450 ppm or less, approximately 1,400 ppm or less, approximately 1,350 ppm or less, approximately 1,300 ppm or less, approximately 1,250 ppm or less, approximately 1,200 ppm or less, approximately 1,150 ppm or less, approximately 1,100 ppm or less, or approximately 1,050 ppm or less. Thus, the stabilizer may be present in the abrasive composition in amounts within the range bounded by any two of the aforementioned endpoints.For example, stabilizers are present in concentrations of approximately 50 ppm to 2000 ppm, 100 ppm to 1950 ppm, 150 ppm to 1900 ppm, 200 ppm to 1850 ppm, 250 ppm to 1800 ppm, 300 ppm to 1750 ppm, 350 ppm to 1700 ppm, 400 ppm to 1650 ppm, 450 ppm to 1600 ppm, and 500 ppm to 1550 ppm. It can be present in the abrasive composition in amounts of approximately 550 ppm to 1,500 ppm, approximately 600 ppm to 1,450 ppm, approximately 650 ppm to 1,400 ppm, approximately 700 ppm to 1,350 ppm, approximately 750 ppm to 1,300 ppm, approximately 800 ppm to 1,250 ppm, approximately 850 ppm to 1,100 ppm, approximately 900 ppm to 1,050 ppm, or approximately 950 ppm to 1,000 ppm.

[0064] The polishing composition contains an oxidizing agent. The oxidizing agent oxidizes the metal layer to its corresponding oxide or hydroxide, for example, aluminum to aluminum oxide, titanium to titanium oxide, tungsten to tungsten oxide, and copper to copper oxide. The polishing composition may contain any suitable oxidizing agent, as long as it is water-soluble and compatible with the other components of the composition. For example, the inclusion of an oxidizing agent in the polishing composition should not result in an unstable polishing composition or inadequate polishing performance. Furthermore, those skilled in the art will understand that the selection of the oxidizing agent must be suitable for the specific polishing application. For example, in some polishing applications, contamination of the substrate with alkali metals, alkaline earth metals, or halides may be undesirable. The oxidizing agent may be added to the polishing composition during the slurry manufacturing process or immediately before the CMP operation (for example, in a tank located in a semiconductor manufacturing facility).

[0065] Suitable oxidizing agents are known in the art and include, for example, peroxides (e.g., hydrogen peroxide and its adducts, e.g., urea hydrogen peroxide; percarbonates; organic peroxides, e.g., benzoyl peroxide, peracetic acid, and di-t-butyl peroxide; organic peroxides; monopersulfates (SO5 -2 ), dispersulfate (SO2O8 -2Examples of suitable oxidizing agents include potassium nitrate and potassium iodate, as well as sodium peroxide. Other suitable oxidizing agents include compounds having elements in the best oxidation state (e.g., periodic acid, periodates, perbromic acid, perbromates, perchloric acid, perchlorates, perboric acid, perborates, and permanganates). Further suitable oxidizing agents include non-per compounds (e.g., bromates, chlorates, iodates, iodic acid, and cerium(IV) compounds, e.g., cerium ammonium nitrate). In some embodiments, the polishing composition comprises two or more oxidizing agents.

[0066] In a preferred embodiment, the oxidizing agent is hydrogen peroxide.

[0067] The polishing composition may contain any suitable amount of oxidizing agent. If the concentration of oxidizing agent in the polishing composition is too low, the metal substrate will not be oxidized to metal oxide at a suitable rate, thereby impairing the polishing performance (reduced removal rate and / or deterioration of defect performance). Conversely, if the concentration of oxidizing agent in the polishing composition is too high, the polishing composition may exhibit undesirable polishing performance, be cost-ineffective, and / or lack stability. Therefore, the oxidizing agent can be present in the polishing composition in amounts of about 0.1% to 10% by weight, for example, about 0.1% to 6% by weight, about 0.2% to 5% by weight, about 0.3% to 4% by weight, about 0.5% to 3% by weight, or about 0.25% to 2% by weight. For example, the oxidizing agent can be present in the polishing composition in amounts of about 1% by weight.

[0068] The abrasive composition may optionally further include additional components (i.e., additives) as needed. For example, depending on the desired abrasive application, the abrasive composition of the present invention may include one or more additives to improve or enhance abrasive performance. The additives are preferably compatible with the other components of the abrasive composition. In one embodiment, the abrasive composition further includes additives selected from amino acids, buffers, cationic surfactants, nonionic surfactants, catalysts, stabilizers, corrosion inhibitors, biocides, and combinations thereof.

[0069] In preferred embodiments, the abrasive composition contains a biocide. Suitable biocides include, for example, isothiazolinone biocides. The amount of biocide in the abrasive composition is typically about 1 to about 50 ppm, preferably about 10 to about 20 ppm. An exemplary biocide is the KATHON® series of biocides, commercially available from Dow Chemical.

[0070] The abrasive composition contains an aqueous carrier. The aqueous carrier contains, essentially consists of, or comprises water (e.g., deionized water) and may contain one or more water-miscible organic solvents. Examples of usable organic solvents include alcohols such as propenyl alcohol, isopropyl alcohol, ethanol, 1-propanol, methanol, and 1-hexanol; aldehydes such as acetylaldehyde; ketones such as acetone, diacetone alcohol, and methyl ethyl ketone; esters such as ethyl formate, propyl formate, ethyl acetate, methyl acetate, methyl lactate, butyl lactate, and ethyl lactate; ethers containing sulfoxides such as dimethyl sulfoxide (DMSO), tetrahydrofuran, dioxane, and diglyme; amides such as N,N-dimethylformamide, dimethylimidazolidinone, and N-methylpyrrolidone; polyhydric alcohols and their derivatives such as ethylene glycol, glycerol, diethylene glycol, and diethylene glycol monomethyl ether; and nitrogen-containing organic compounds such as acetonitrile, amylamine, isopropylamine, imidazole, and dimethylamine. Preferably, the aqueous carrier is water only, i.e., no organic solvent is present.

[0071] As described herein, the abrasive compositions of the present invention have an acidic pH, i.e., a pH of less than 7. More specifically, the abrasive compositions preferably have a pH of about 2 to about 5. Thus, the abrasive compositions may have a pH of about 2 or more, for example, about 2.1 or more, about 2.2 or more, about 2.3 or more, about 2.4 or more, about 2.5 or more, about 2.6 or more, about 2.7 or more, about 2.8 or more, about 2.9 or more, about 3.0 or more, about 3.1 or more, about 3.2 or more, about 3.3 or more, or about 3.4 or more. Alternatively, or in addition, the abrasive compositions may have a pH of about 5 or less, for example, about 4.9 or less, about 4.8 or less, about 4.7 or less, about 4.6 or less, about 4.5 or less, about 4.4 or less, about 4.3 or less, about 4.2 or less, about 4.1 or less, about 4 or less, about 3.9 or less, about 3.8 or less, about 3.7 or less, about 3.6 or less, or about 3.5 or less. Therefore, the abrasive composition may have a pH within the range bounded by any two of the aforementioned endpoints. For example, the abrasive composition may have a pH of about 2 to about 5, for example, about 2.1 to about 5, about 2.2 to about 4.9, about 2.3 to about 4.8, about 2.4 to about 4.7, about 2.5 to about 4.6, about 2.6 to about 4.5, about 2.7 to about 4.4, about 2.8 to about 4.3, about 2.9 to about 4.2, about 3.0 to about 4.1, about 3.1 to about 4.0, or about 3.2 to about 3.9.

[0072] The pH of the abrasive composition can be adjusted as needed using any suitable acid or base. Non-limiting examples of suitable acids include nitric acid, sulfuric acid, and organic acids, such as formic acid and acetic acid. Non-limiting examples of suitable bases include sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

[0073] In one embodiment, the abrasive composition has a pH of about 2 to about 4. In another embodiment, the abrasive composition has a pH of about 2.

[0074] It will be understood that when dissolved in an aqueous carrier of the abrasive composition, any component of the abrasive composition (e.g., a cationic polymer, an oxidizing agent, a catalyst, etc.), which is an acid, a base, or a salt, may exist in dissociated forms as cations and anions. The amount of such compounds present in the abrasive compositions described herein will be understood to refer to the weight of the undissociated compounds used in the preparation of the abrasive compositions.

[0075] Abrasive compositions can be produced by any suitable technique, much of which is known to those skilled in the art. Abrasive compositions can be prepared in batch or continuous processes. Typically, abrasive compositions are prepared by combining the components of the abrasive composition. As used herein, the term “components” includes individual compounding components (e.g., a first abrasive containing cationically modified colloidal silica particles, a second abrasive having a Mohs hardness of about 5.5 or higher, a cationic polymer, etc.) as well as any combination of compounding components (e.g., a first abrasive containing cationically modified colloidal silica particles, a second abrasive having a Mohs hardness of about 5.5 or higher, a cationic polymer, an iron-containing surfactant, or one or more additives, etc.).

[0076] For example, abrasive particles can be added to an aqueous carrier (e.g., water) at a desired concentration(s). The pH can then be adjusted (if necessary), and cationic polymers and other components can be added to the mixture at desired concentrations to form an abrasive composition. The abrasive composition can be prepared in advance of use by adding one or more components to the abrasive composition immediately before use (e.g., within about 1 minute before use, or within about 1 hour before use, or within about 7 days before use). The abrasive composition can also be prepared by mixing the components on the surface of the substrate during the abrasive work.

[0077] The abrasive composition may also be provided as a concentrate intended to be diluted with an appropriate amount of aqueous carrier, particularly with water, before use. In such embodiments, the abrasive composition concentrate may contain a first abrasive, a second abrasive, a cationic polymer, an iron-containing surfactant, an oxidizing agent, an additive (if present), and an aqueous carrier, in amounts such that when the concentrate is diluted with an appropriate amount of water, each component of the abrasive composition is present in the abrasive composition in amounts within the appropriate range listed above for each component. Furthermore, as will be understood by those skilled in the art, the concentrate may contain water present in the final abrasive composition in a suitable proportion to ensure that the other components dissolve at least partially or completely in the concentrate.

[0078] Polishing compositions can be prepared well in advance of use or shortly before use, but polishing compositions can also be prepared by mixing the components of the polishing composition at or near the time of use. As used herein, the term “time of use” refers to the time when the polishing composition is applied to the substrate surface (e.g., the polishing pad or the substrate surface itself). When preparing a polishing composition by utilizing mixing at the time of use, the components of the polishing composition are stored separately in two or more storage devices.

[0079] To mix the components contained in the storage device to produce an abrasive composition at or near the point of use, the storage device is typically provided with one or more flow lines connecting each storage device to the point of use of the abrasive composition (e.g., platen, abrasive pad, or substrate surface). The term "flow line" refers to the flow path from the individual storage container to the point of use of the components stored therein. Each of the one or more flow lines may connect directly to the point of use, or, in situations where multiple flow lines are used, two or more flow lines may be combined at any point into a single flow line leading to the point of use. Furthermore, one or more flow lines (e.g., individual flow lines or combined flow lines) may first connect to one or more other devices (e.g., pumping devices, measuring devices, mixing devices, etc.) before reaching the point of use of the components.

[0080] The components of the polishing composition can be delivered independently to the point of use (for example, the components are delivered to the substrate surface where they are mixed during the polishing process), or the components can be mixed immediately before being delivered to the point of use. Components are mixed "immediately before being delivered to the point of use" if they are mixed less than 10 seconds, preferably less than 5 seconds, more preferably less than 1 second, before reaching the point of use, or simultaneously upon arrival at the point of use (for example, the components are mixed in a dispenser). Components are also mixed "immediately before being delivered to the point of use" if they are mixed within 5 m of the point of use, for example within 1 m of the point of use, or even within 10 cm of the point of use (for example within 1 cm of the point of use).

[0081] If two or more components of the abrasive composition are mixed before reaching the point of use, the components can be mixed in a flow line and delivered to the point of use without using a mixing device. Alternatively, one or more flow lines can be connected to a mixing device to facilitate the mixing of the two or more components. Any suitable mixing device can be used. For example, the mixing device may be a nozzle or jet (e.g., a high-pressure nozzle or high-pressure jet) through which two or more components flow. Alternatively, the mixing device may be a container-type mixing device comprising one or more inlets into which two or more components of the abrasive composition are introduced into a mixer, and at least one outlet through which the mixed components exit the mixer and are delivered to the outlet of the mixer, either directly or via other elements of the device (e.g., through one or more flow lines). Furthermore, the mixing device may comprise one or more chambers, each having at least one inlet and at least one outlet, in which two or more components are mixed in each chamber. When using a container-type mixing device, it is preferable that the mixing device comprises a mixing mechanism to further facilitate the mixing of the components. Mixing mechanisms are commonly known in the art and include stirrers, blenders, agitators, baffles with paddles, gas sparger systems, vibrators, and the like.

[0082] The present invention also provides a method for chemically mechanically polishing a substrate, comprising: (i) preparing a substrate; (ii) preparing a polishing pad; (iii) preparing a chemically mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or more; (c) a cationic polymer; (d) an iron-containing activator; (e) an oxidizing agent; and (f) water; (iv) bringing the substrate into contact with the polishing pad and the chemically mechanical polishing composition; and (v) moving the polishing pad and the chemically mechanical polishing composition against the substrate to grind at least a portion of the substrate and polish the substrate.

[0083] The applicant has surprisingly discovered that an abrasive composition comprising (a) a first abrasive containing cation-modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or higher, (c) a cationic polymer, (d) an iron-containing activator, (e) an oxidizing agent, and (f) water provides an improved barrier film removal rate. For example, in some embodiments, the removal rate of barrier films, such as titanium nitride (TiN) and / or titanium (Ti), is increased by about two times or more, for example, about three times or more, or about four times or more, compared to conventional abrasive compositions. Thus, in one embodiment, the substrate has a layer of titanium nitride (TiN) and / or a layer of titanium (Ti) on the surface of the substrate, and at least a portion of the TiN layer and / or Ti layer is ground and polished.

[0084] In some embodiments, the substrate further comprises an oxide, such as tetraethyl orthosilicate (TEOS). Thus, the substrate may have a layer of oxide, or in particular a layer of TEOS, on its surface, and the substrate is polished by grinding at least a portion of the oxide layer, or in particular at least a portion of the TEOS layer.

[0085] In the method of the present invention, no significant decrease in the removal rate of tungsten or TEOS is observed compared to conventional polishing compositions. In addition, no significant deterioration of topography is observed. Furthermore, no significant increase in the defect rate is observed.

[0086] The polishing composition of the present invention can be used to polish any substrate, but the polishing composition is particularly useful for polishing substrates comprising at least one metal, including tungsten, and at least one dielectric material. The tungsten layer may be deposited on one or more barrier layers, for example, titanium (Ti) and / or titanium nitride (TiN). The dielectric layer may be a silicon oxide layer derived from a metal oxide, e.g., tetraethyl orthosilicate (TEOS), porous metal oxide, porous or non-porous carbon-doped silicon oxide, fluorine-doped silicon oxide, glass, organic polymer, fluorinated organic polymer, or other suitable high-k or low-k dielectric insulating layer.

[0087] Therefore, in a preferred embodiment, the substrate includes a tungsten layer on its surface, and at least a portion of the tungsten layer is ground and the substrate is polished.

[0088] In another preferred embodiment, the substrate includes a nitride layer on its surface, and the substrate is polished by grinding at least a portion of the nitride layer.

[0089] In a preferred embodiment, the nitride layer is selected from titanium nitride, silicon nitride, and combinations thereof.

[0090] In another preferred embodiment, the substrate includes a silicon oxide layer on its surface, and the substrate is polished by grinding at least a portion of the silicon oxide layer.

[0091] In a preferred embodiment, the silicon oxide layer contains TEOS.

[0092] In another preferred embodiment, the substrate includes a tungsten layer on its surface, and the substrate is polished by grinding off at least a portion of the tungsten layer.

[0093] In another preferred embodiment, the substrate includes both a tungsten layer and a titanium nitride layer on the surface of the substrate, and both the tungsten layer and the titanium nitride layer are ground and the substrate is polished.

[0094] The chemical mechanical polishing composition and method of the present invention are particularly suitable for use with a chemical mechanical polishing apparatus. Generally, the apparatus includes, in use, a platen having a velocity resulting from orbital, linear, or circular motion during movement; a polishing pad that contacts the platen and moves with the platen during operation; and a carrier that holds the substrate so as to be polished by moving in contact with the surface of the polishing pad. Polishing of the substrate is performed by positioning the substrate in contact with the polishing pad and the polishing composition of the present invention, and then moving the polishing pad relative to the substrate to grind at least a portion of the substrate and polish the substrate.

[0095] The substrate can be polished with a 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 may contain any suitable polymer with varying densities, hardness, thickness, compressibility, ability to rebound upon compression, and compressive modulus. Suitable polymers include, for example, polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester, polyacrylate, polyether, polyethylene, polyamide, polyurethane, polystyrene, polypropylene, their co-formations, and mixtures thereof. Soft polyurethane polishing pads are particularly useful in combination with the polishing method of the present invention. Typical pads include, but are not limited to, SURFIN® 000, SURFIN® SSW1, SPM3100 (Eminess Technologies), POLITEX® from Dow Chemical Company (Newark, DE), POLYPAS® 27 from Fujibo (Osaka, JP), and EPIC® D100 pads or NEXPLANAR® E6088 from Cabot Microelectronics (Aurora, IL). Particularly preferred polishing pads are the hard microporous polyurethane pads (IC1010®) from Dow Chemical.

[0096] Preferably, the chemical mechanical polishing apparatus further comprises a system for detecting the polishing endpoint in situ, many of which are known in the art. Techniques for inspecting and monitoring the polishing process by analyzing light or other radiation reflected from the surface of the substrate being polished are known in the art. Such methods are disclosed, for example, in U.S. Patents 5,196,353, 5,433,651, 5,609,511, 5,643,046, 5,658,183, 5,730,642, 5,838,447, 5,872,633, 5,893,796, 5,949,927, and 5,964,643. Preferably, inspection or monitoring of the progress of the polishing process with respect to the substrate being polished makes it possible to determine the polishing endpoint, i.e., when to terminate the polishing process with respect to a particular substrate.

[0097] Embodiment (1) Embodiment (1) presents a chemical mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or higher, (c) a cationic polymer, (d) an iron-containing activator, (e) an oxidizing agent, and (f) water. (2) Embodiment (2) presents the polishing composition of Embodiment (1), wherein the cation-modified colloidal silica particles have a zeta potential of more than 20 mV at a pH of about 2.5. (3) Embodiment (3) presents the polishing composition of Embodiment (1) or Embodiment (2), wherein the cation-modified colloidal silica particles have an average particle size of about 50 nm to about 200 nm. (4) Embodiment (4) presents one of the polishing compositions of Embodiments (1) to (3), wherein cation-modified colloidal silica particles are present in the polishing composition in an amount of about 0.05% to about 5% by weight. (5) Embodiment (5) presents one of the polishing compositions of Embodiments (1) to (4), wherein the second abrasive is selected from α-alumina particles, zirconia particles, diamond particles, and combinations thereof. (6) Embodiment (6) presents one of the polishing compositions of Embodiments (1) to (5), wherein the second abrasive contains α-alumina particles. (7) Embodiment (7) presents one of the polishing compositions of Embodiments (1) to (6), wherein the second abrasive is present in the polishing composition in an amount of about 25 ppm or more. (8) Embodiment (8) presents the polishing composition of Embodiment (7), wherein the second abrasive is present in the polishing composition in an amount of about 50 ppm to about 500 ppm. (9) Embodiment (9) presents one of the polishing compositions of Embodiments (1) to (8), wherein the cationic polymer has a molecular weight of about 100,000 g / mol or less. (10) Embodiment (10) presents the polishing composition of Embodiment (9), wherein the cationic polymer has a molecular weight of about 2,000 g / mol to about 15,000 g / mol. (11) Embodiment (11) presents one of the polishing compositions of Embodiments (1) to (10), wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC). (12) Embodiment (12) presents one of the polishing compositions of Embodiments (1) to (11), wherein a cationic polymer is present in the polishing composition in an amount of about 1 to about 100 ppm. (13) Embodiment (13) presents one of the polishing compositions of Embodiments (1) to (12), wherein the iron-containing activator contains a soluble iron salt. (14) Embodiment (14) presents the polishing composition of Embodiment (13), wherein the soluble iron salt is ferric nitrate. (15) Embodiment (15) presents one of the polishing compositions of Embodiments (1) to (14), wherein an iron-containing activator is present in the polishing composition in an amount of about 10 ppm to about 700 ppm. (16) Embodiment (16) presents an abrasive composition of Embodiment (13) or Embodiment (14) further comprising a stabilizer bound to a soluble iron salt, wherein the stabilizer is selected from phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimlic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and combinations thereof. (17) Embodiment (17) presents the polishing composition of Embodiment (16) in which a stabilizer is present in the polishing composition in an amount of about 20 ppm to about 2,000 ppm. (18) Embodiment (18) presents one of the polishing compositions of Embodiments (1) to (17), wherein the oxidizing agent is hydrogen peroxide. (19) Embodiment (19) presents any one of the polishing compositions of Embodiments (1) to (18), further comprising an amino acid, a buffer, a biocide, a cationic surfactant, a corrosion inhibitor, and an additive selected from combinations thereof. (20) Embodiment (20) presents the polishing composition of Embodiment (19), wherein the additive is a biocide. (21) Embodiment (21) presents one of the polishing compositions from Embodiments (1) to (20), wherein the polishing composition has a pH of about 2 to about 4. (22) Embodiment (22) also presents a method comprising: (i) preparing a substrate; (ii) preparing a polishing pad; (iii) preparing a chemical mechanical polishing composition comprising (a) a first abrasive containing cation-modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or more; (c) a cationic polymer; (d) an iron-containing activator; (e) an oxidizing agent; and (f) water; (iv) bringing the substrate into contact with the polishing pad and the chemical mechanical polishing composition; and (v) moving the polishing pad and the chemical mechanical polishing composition against the substrate to grind at least a portion of the substrate and polish the substrate. (23) Embodiment (23) presents the method of Embodiment (22) in which the cation-modified colloidal silica particles have a zeta potential of more than 20 mV at a pH of about 2.5. (24) Embodiment (24) presents the method of Embodiment (22) or (23) in which the cation-modified colloidal silica particles have an average particle size of about 50 nm to about 200 nm. (25) Embodiment (25) presents one of the methods of Embodiments (22) to (24) in which cation-modified colloidal silica particles are present in the polishing composition in an amount of about 0.05% to about 5% by weight. (26) Embodiment (26) presents one of the methods of Embodiments (22) to (25), wherein the second abrasive is selected from α-alumina particles, zirconium particles, diamond particles, and combinations thereof. (27) Embodiment (27) presents one of the methods of Embodiments (22) to (26), wherein the second abrasive contains α-alumina particles. (28) Embodiment (28) presents one of the methods of Embodiments (22) to (27) in which the second abrasive is present in the polishing composition in an amount of about 25 ppm or more. (29) Embodiment (29) presents the method of Embodiment (28) in which the second abrasive is present in the polishing composition in an amount of about 50 ppm to about 500 ppm. (30) Embodiment (30) presents one of the methods of Embodiments (22) to (29) in which the cationic polymer has a molecular weight of about 100,000 g / mol or less. (31) Embodiment (31) presents the method of Embodiment (30) in which the cationic polymer has a molecular weight of about 2,000 g / mol to about 15,000 g / mol. (32) Embodiment (32) presents one of the methods of Embodiments (22) to (31), wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC). (33) Embodiment (33) presents one of the methods of Embodiments (22) to (32) in which a cationic polymer is present in the polishing composition in an amount of about 1 to about 100 ppm. (34) Embodiment (34) presents one of the methods of Embodiments (22) to (33), wherein the iron-containing activator includes a soluble iron salt. (35) Embodiment (35) presents the method of Embodiment (34) in which the soluble iron salt is ferric nitrate. (36) Embodiment (36) presents one of the methods of Embodiments (22) to (35) in which the iron-containing activator is present in the abrasive composition in an amount of about 100 ppm to about 700 ppm. (37) Embodiment (37) presents an abrasive composition of Embodiment (34) or Embodiment (35) further comprising a stabilizer bound to a soluble iron salt, wherein the stabilizer is selected from phosphoric acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, aspartic acid, succinic acid, glutaric acid, pimlic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, glutaconic acid, muconic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, and combinations thereof. (38) Embodiment (38) presents the method of Embodiment (37) in which the stabilizer is present in the polishing composition in an amount of about 20 ppm to about 2,000 ppm. (39) Embodiment (39) presents one of the methods from Embodiments (22) to (38), wherein the oxidizing agent is hydrogen peroxide. (40) Embodiment (40) presents one of the methods of Embodiments (22) to (39), further comprising an additive selected from amino acids, buffers, biocides, cationic surfactants, corrosion inhibitors, and combinations thereof. (41) Embodiment (41) presents the method of Embodiment (40) in which the additive is a biocide. (42) Embodiment (42) presents one of the methods of Embodiments (22) to (41), wherein the abrasive composition has a pH of about 2 to about 4. (43) Embodiment (43) presents one of the embodiments (22) to (42) in which the substrate includes a titanium layer on the surface of the substrate, and the substrate is polished by grinding at least a portion of the titanium layer. (44) Embodiment (44) presents one of the embodiments (22) to (43) in which the substrate includes a nitride layer on the surface of the substrate, and the substrate is polished by grinding at least a portion of the nitride layer. (45) Embodiment (45) presents the method of Embodiment (44) in which the nitride layer is selected from titanium nitride, silicon nitride, and combinations thereof. (46) Embodiment (46) presents one of the embodiments (22) to (45) in which the substrate includes a silicon oxide layer on the surface of the substrate, and the substrate is polished by grinding at least a portion of the silicon oxide layer. (47) Embodiment (47) presents the method of Embodiment (46) in which the silicon oxide layer is TEOS. (48) Embodiment (48) presents one of the embodiments (22) to (47) in which the substrate includes a tungsten layer on the surface of the substrate, and the substrate is polished by grinding at least a portion of the tungsten layer. (49) Embodiment (49) presents one of the methods of Embodiments (22) to (48) in which the substrate includes both a tungsten layer and a titanium nitride layer on the surface of the substrate, and the substrate is polished by grinding both the tungsten layer and the titanium nitride layer. [Examples]

[0098] The following embodiments further illustrate the present invention, but should of course not be construed as limiting its scope.

[0099] In this specification, the following abbreviations are used: W for tungsten, Ti for titanium, TiN for titanium nitride, TEOS for tetraethyl orthosilicate, MW for molecular weight, and RR for removal rate.

[0100] Example 1 This embodiment demonstrates the effectiveness of a second abrasive having a Mohs hardness of approximately 5.5 or higher in terms of the removal speed and polishing performance of the polishing composition according to the present invention.

[0101] A substrate containing a blanket of TiN, Ti, W, and TEOS was polished with two polishing compositions (i.e., polishing compositions 1A and 1B). The polishing compositions contained the following components (3-fold concentrate): 1.0 wt% cation-modified colloidal silica as the first abrasive, 1,335 ppm malonic acid as a stabilizer, 618 ppm ferric nitrate as an iron-containing activator, 75-150 ppm polyDADMAC (MW 8,500 g / mol) as a cationic polymer, 2 wt% hydrogen peroxide as an oxidizing agent, and 15 ppm KATHON® LX as a biocide. The pH of the polishing compositions was adjusted to 2.15.

[0102] Polishing compositions 1A and 1B were identical except that polishing composition 1B further contained 150 ppm of α-alumina as a second abrasive.

[0103] The substrates were polished using a MIRRA® polisher (Applied Materials, Santa Clara, CA) and a NEXPLANAR® E6088 polishing pad (Cabot Microelectronics, Aurora, IL) with a downforce of 2 psi.

[0104] The polishing results are shown in Table 1. [Table 1]

[0105] As is clear from the results shown in Table 1, the polishing composition 1B of the present invention showed an increased removal rate of TiN and Ti barrier film while maintaining equivalent tungsten and TEOS removal rates compared to the control polishing composition 1A. Furthermore, the tungsten and TEOS removal rates of the control polishing composition 1A and the polishing composition 1B of the present invention were similar and there was no significant difference. Therefore, these results demonstrate the beneficial effect of a second abrasive particle having a Mohs hardness of about 5.5 or higher in the polishing composition according to the present invention.

Claims

1. 1. A chemical-mechanical polishing composition comprising: (a) a first abrasive comprising cationically modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or greater; (c) a cationic polymer; and (d) an iron-containing activator; and (e) an oxidizing agent; and (f) water.

2. 2. The polishing composition of claim 1, wherein the cationically modified colloidal silica particles have a zeta potential of greater than about 20 mV at a pH of about 2.

5.

3. 2. The polishing composition of claim 1, wherein the cationically modified colloidal silica particles have an average particle size of about 50 nm to about 200 nm.

4. 10. The polishing composition of claim 1, wherein the cationically modified colloidal silica particles are present in the polishing composition in an amount of about 0.01 wt. % to about 5 wt. %.

5. 10. The polishing composition of claim 1, wherein the second abrasive is selected from α-alumina particles, zirconia particles, diamond particles, and combinations thereof.

6. 6. The polishing composition of claim 5, wherein the second abrasive comprises α-alumina particles.

7. 10. The polishing composition of claim 1, wherein the second abrasive is present in the polishing composition in an amount of about 25 ppm or greater.

8. 8. The polishing composition of claim 7, wherein the second abrasive is present in the polishing composition in an amount of about 50 ppm to about 500 ppm.

9. 10. The polishing composition of claim 1, wherein the cationic polymer has a molecular weight of about 100,000 g / mol or less.

10. 10. The polishing composition of claim 9, wherein the cationic polymer has a molecular weight of about 2,000 g / mol to about 15,000 g / mol.

11. 2. The polishing composition of claim 1, wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC).

12. 10. The polishing composition of claim 1, wherein the cationic polymer is present in the polishing composition in an amount of about 1 to about 100 ppm.

13. The polishing composition of claim 1 , wherein the iron-containing activator comprises a soluble iron salt.

14. 14. The polishing composition of claim 13, wherein the soluble iron salt is ferric nitrate.

15. 10. The polishing composition of claim 1, wherein the iron from the iron-containing activator is present in the polishing composition in an amount of about 1 ppm to about 100 ppm.

16. 14. The polishing composition of claim 13, further comprising a stabilizer bound to the soluble iron salt, wherein the stabilizer is selected from 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 combinations thereof.

17. 17. The polishing composition of claim 16, wherein the stabilizer is present in the polishing composition in an amount from about 20 ppm to about 2,000 ppm.

18. The polishing composition of claim 1 , wherein the oxidizing agent is hydrogen peroxide.

19. 10. The polishing composition of claim 1, wherein the polishing composition has a pH of about 2 to about 4.

20. 1. A method of chemical mechanical polishing a substrate, comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) (a) a first abrasive comprising cationically modified colloidal silica particles; (b) a second abrasive having a Mohs hardness of about 5.5 or greater; (c) a cationic polymer; and (d) an iron-containing activator; and (e) an oxidizing agent; and (f) providing a chemical-mechanical polishing composition comprising: (iv) contacting the substrate with the polishing pad and the chemical-mechanical polishing composition; (v) moving the polishing pad and the chemical-mechanical polishing composition relative to the substrate to grind at least a portion of the substrate and polish the substrate.

21. 21. The method of claim 20, wherein the cationically modified colloidal silica particles have a zeta potential of greater than about 20 mV at a pH of about 2.

5.

22. 21. The method of claim 20, wherein the cationically modified colloidal silica particles are present in the polishing composition in an amount of about 0.05 wt. % to about 5 wt. %.

23. 21. The method of claim 20, wherein the second abrasive is selected from alpha alumina particles, zirconium particles, diamond particles, and combinations thereof.

24. The method of claim 20, wherein the second abrasive comprises alpha-alumina particles.

25. 21. The method of claim 20, wherein the second abrasive is present in the polishing composition in an amount of about 25 ppm or greater.

26. 21. The method of claim 20, wherein the cationic polymer has a molecular weight of about 100,000 g / mol or less.

27. 27. The method of claim 26, wherein the cationic polymer is polydiallyldimethylammonium chloride (pDADMAC).

28. 21. The method of claim 20, wherein the iron from the iron-containing activator is present in the polishing composition in an amount from about 1 ppm to about 100 ppm.

29. 21. The method of claim 20, wherein the polishing composition has a pH of about 2 to about 4.

30. 21. The method of claim 20, wherein the substrate includes both a tungsten layer and a titanium nitride layer on a surface of the substrate, and the method comprises grinding away both the tungsten layer and the titanium nitride layer to polish the substrate.