Composition and method for polishing boron-doped polysilicon

Abstract

To provide a method of chemically mechanically polishing a substrate, especially a substrate comprising boron-doped polysilicon.SOLUTION: The method comprises bringing the substrate into contact with a chemical-mechanical polishing composition comprising: an abrasive selected from among α-alumina, silica, and a combination thereof; ferric ion, an organic acid, or a combination thereof; and water. The invention also provides a chemical-mechanical polishing composition comprising: α-alumina; a nitrogen-containing compound selected from among a zwitterionic homopolymer, a monomeric ammonium salt, and a combination thereof; an organic acid; and water. The invention further provides a chemical-mechanical polishing composition comprising silica, an organic acid, ferric ion, and water.SELECTED DRAWING: None

Description

Background Art

[0001] Compositions and methods for planarizing or polishing the surface of a substrate are known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive in a liquid base and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasives include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. Polishing compositions are typically used in combination with a polishing pad (e.g., a polishing cloth or a polishing disk). The abrasive may be incorporated into the polishing pad instead of or in addition to being suspended in the polishing composition.

[0002] Boron-doped polysilicon or boron-polysilicon alloys are increasingly being used as patterning hard masks during the manufacture of advanced node memory devices such as dynamic random access memories (DRAMs). Due to the high level of boron in the polysilicon material, it can be difficult to achieve a high removal rate of this material by chemical mechanical polishing (CMP). In addition to requiring a high removal rate of the boron-polysilicon film, some memory device schemes also require a very low removal rate for silicon nitride and / or silicon oxide that may be used as a stop layer in the device film stack. This indicates that selectivity is required during CMP. In addition, titanium nitride is also used in the manufacture of some memory devices. The ability to adjust the relative removal rate of titanium nitride would be a desirable feature in polishing compositions and methods useful for device manufacture.

[0003] Accordingly, there is still a need in the art for polishing compositions and methods for polishing boron-polysilicon layers having a high removal rate and selectivity for boron-polysilicon.

Summary of the Invention

[0004] The present invention provides a method for chemically mechanically polishing a substrate, the method comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) providing a chemical mechanical polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and combinations thereof; (b) ferric ions, an organic acid, or a combination thereof; and (c) water, and having a pH of from about 2 to about 4; (iv) contacting the substrate with the polishing pad and the chemical mechanical polishing composition; and (v) moving the polishing pad and the chemical mechanical polishing composition relative to the substrate to abrade at least a portion of the surface of the substrate to polish the substrate.

[0005] The present invention also provides a chemical mechanical polishing composition comprising: (a) from about 0.01 wt% to about 1 wt% α-alumina; (b) a zwitterionic homopolymer at a concentration of from about 5 ppm to about 25 ppm, a monomer ammonium salt at a concentration of from about 1 mM to about 10 mM, and a nitrogen-containing compound selected from combinations thereof; (c) an organic acid; and (d) water, and having a pH of from about 2 to about 4.

[0006] The present invention further provides a chemical mechanical polishing composition comprising: (a) from about 1 wt% to about 5 wt% silica; (b) an organic acid; (c) ferric ions; and (d) water, and having a pH of from about 2 to about 4.

DETAILED DESCRIPTION OF THE INVENTION

[0007] In one embodiment, the present invention provides a chemical mechanical polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and combinations thereof; (b) ferric ions, an organic acid, or a combination thereof; and (c) water, and having a pH of from about 2 to about 4.

[0008] The chemical mechanical polishing composition comprises an abrasive selected from α-alumina, silica, and combinations thereof. The α-alumina can be any suitable form of α-alumina.

[0009] The polishing composition may contain any suitable amount of α-alumina. Typically, the polishing composition contains about 0.01 wt% or more of α-alumina, exemplified by about 0.025 wt% or more, about 0.05 wt% or more, about 0.075 wt% or more, about 0.1 wt% or more, about 0.125 wt% or more, about 0.15 wt% or more, about 0.175 wt% or more, or about 0.2 wt% or more. As another option or in addition, the polishing composition contains about 1 wt% or less of α-alumina, exemplified by about 0.95 wt% or less, about 0.9 wt% or less, about 0.85 wt% or less, about 0.8 wt% or less, about 0.75 wt% or less, about 0.7 wt% or less, about 0.65 wt% or less, about 0.6 wt% or less, about 0.55 wt% or less, about 0.5 wt% or less, about 0.45 wt% or less, about 0.4 wt% or less, about 0.35 wt% or less, or about 0.3 wt% or less. Thus, the polishing composition may contain α-alumina in an amount bounded by any two of the above endpoints. For example, the polishing composition may contain about 0.01 wt% to about 1 wt% of α-alumina, such as about 0.01 wt% to about 0.9 wt%, about 0.01 wt% to about 0.8 wt%, about 0.01 wt% to about 0.7 wt%, about 0.01 wt% to about 0.6 wt%, about 0.01 wt% to about 0.5 wt%, about 0.05 wt% to about 0.5 wt%, about 0.05 wt% to about 0.4 wt%, about 0.1 wt% to about 0.4 wt%, about 0.1 wt% to about 0.4 wt%, or about 0.15 wt% to about 0.3 wt%.

[0010] α-alumina includes particles that may have any suitable average particle size (i.e., average grain size). For example, the α-alumina particles can have an average particle size of about 90 nm or more, such as about 100 nm or more, about 110 nm or more, about 120 nm or more, about 130 nm or more, about 140 nm or more, or about 150 nm or more. As another option or in addition, the α-alumina particles can have an average particle size of about 300 nm or less, such as about 290 nm or less, about 280 nm or less, about 270 nm or less, about 260 nm or less, about 250 nm or less, about 240 nm or less, about 230 nm or less, about 220 nm or less, about 210 nm or less, or about 200 nm or less. Thus, the α-alumina particles can have an average particle size with any two of the above endpoints as boundary values. For example, the α-alumina particles can have an average particle size of about 90 nm to about 300 nm, such as about 100 nm to about 280 nm, about 100 nm to about 260 nm, about 100 nm to about 240 nm, about 120 nm to about 240 nm, about 120 nm to about 220 nm, or about 120 nm to about 200 nm.

[0011] Silica can be silica in any suitable form. For example, colloidal silica can be wet-process silica such as polycondensed silica. Polycondensed silica is typically produced by condensing Si(OH)4 to form colloidal particles, and colloidal is defined as having an average particle size of about 1 nm to about 1000 nm. Si(OH)4 is typically obtained from silicates (e.g., sodium silicate and / or potassium silicate), and the silica thus obtained can be referred to as silicate-derived silica. Such abrasive particles can be manufactured according to U.S. Patent No. 5,230,833, or can be obtained as any of various commercial products such as Akzo-Nobel Bindzil (trademark) 50 / 80, 30 / 360, 159 / 500, 40 / 220, 40 / 130, and CJ2-2 products, as well as Nalco 1050, 1060, 2327, and 2329 products, and other similar products available from DuPont, Bayer, Applied Research, Nissan Chemical, Fuso Chemical Industry, and Clariant.

[0012] Colloidal silica can also be derived by the polycondensation of silicate esters such as tetramethyl orthosilicate (TMOS) and / or tetraethyl orthosilicate (TEOS). The silica derived from silicate esters is typically substantially free of alkali metals.

[0013] The polishing composition may contain any suitable amount of silica. Typically, the polishing composition contains at least about 1 wt% of silica, such as at least about 1.2 wt%, at least about 1.4 wt%, at least about 1.6 wt%, at least about 1.8 wt%, at least about 2 wt%, at least about 2.2 wt%, or at least about 2.4 wt%. As another option or in addition, the polishing composition contains up to about 5 wt% of silica, such as up to about 4.8 wt%, up to about 4.6 wt%, up to about 4.4 wt%, up to about 4.2 wt%, up to about 4 wt%, up to about 3.8 wt%, up to about 3.6 wt%, up to about 3.4 wt%, up to about 3.2 wt%, or up to about 3 wt%. Thus, the polishing composition can contain silica in an amount bounded by any two of the above endpoints. For example, the polishing composition can contain from about 1 wt% to about 5 wt% of silica, such as from about 1 wt% to about 4 wt%, from about 1 wt% to about 3 wt%, from about 2 wt% to about 5 wt%, from about 2 wt% to about 4 wt%, or from about 2 wt% to about 3 wt%.

[0014] Silica contains particles that may have any suitable average size (i.e., average particle diameter). For example, the silica particles can have an average particle size of about 40 nm or more, such as 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. As another option or in addition, the silica particles can have an average particle size of about 200 nm or less, such as about 180 nm or less, about 160 nm or less, about 140 nm or less, or about 120 nm or less. Accordingly, the silica particles can have an average particle size with any two of the above endpoints as boundary values. For example, the silica particles can have an average particle size of about 40 nm to about 180 nm, about 40 nm to about 160 nm, about 40 nm to about 140 nm, about 40 nm to about 120 nm, about 60 nm to about 200 nm, about 60 nm to about 180 nm, about 60 nm to about 160 nm, about 60 nm to about 140 nm, about 80 nm to about 200 nm, about 80 nm to about 180 nm, about 80 nm to about 160 nm, about 80 nm to about 140 nm, or about 100 nm to about 200 nm, such as about 40 nm to about 200 nm.

[0015] The abrasive (i.e., α-alumina, silica, or a combination thereof) is preferably stable as a colloid. The term colloid means a suspension of abrasive particles in a liquid base. Colloid stability means that the suspension is maintained over time. In the context of the present invention, when the abrasive is placed in a 100 ml graduated cylinder and allowed to stand for 2 hours without stirring, the difference between the concentration of particles ([B], in g / ml) in the lower 50 ml of the graduated cylinder and the concentration of particles ([T], in g / ml) in the upper 50 ml of the graduated cylinder, divided by the initial concentration of particles ([C], in g / ml) in the abrasive composition, is 0.5 or less (i.e., {[B] - [T]} / [C] ≦ 0.5), the abrasive is stable as a colloid. More preferably, the value of [B] - [T] / [C] is 0.3 or less, and most preferably 0.1 or less.

[0016] The polishing composition may contain ferric ions, organic acids, or combinations thereof. The ferric ions may be provided in the form of any suitable ferric salt. Non-limiting examples of suitable ferric salts are ferric nitrate. The polishing composition may contain any suitable amount of ferric ions. The polishing composition may contain from about 0.005 wt% to about 1 wt% of ferric ions, such as from about 0.01 wt% to about 0.9 wt%, from about 0.02 wt% to about 0.8 wt%, from about 0.03 wt% to about 0.6 wt%, from about 0.03 wt% to about 0.4 wt%, from about 0.03 wt% to about 0.2 wt%, or from about 0.03 wt% to about 0.1 wt%.

[0017] In one embodiment, the polishing composition is substantially free of ferric ions. In the context of the present invention, "substantially free of ferric ions" means that the polishing composition contains 0.01 wt% or less of ferric ions, such as 0.005 wt% or less, 0.001 wt% or less, or 0.0001 wt% or less, or that ferric ions cannot be detected in the polishing composition.

[0018] The polishing composition may contain an organic acid. The organic acid may be any suitable organic acid. Non-limiting examples of suitable organic acids include tartaric acid, lactic acid, formic acid, acetic acid, maleic acid, L-ascorbic acid, picolinic acid, and malonic acid. When the abrasive is α-alumina, in certain embodiments, the organic acid may be selected from tartaric acid, lactic acid, formic acid, acetic acid, and combinations thereof. When the abrasive is silica, in certain embodiments, the organic acid may be selected from tartaric acid, lactic acid, formic acid, acetic acid, maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0019] The polishing composition may contain an organic acid at any suitable concentration. For example, the polishing composition may contain an organic acid at about 1 mM or more, such as about 2 mM or more, or about 3 mM or more, or about 4 mM or more, or about 5 mM or more. As another option or in addition, the polishing composition may contain an organic acid at about 100 mM or less, such as about 50 mM or less, about 25 mM or less, about 20 mM or less, about 19 mM or less, about 18 mM or less, about 17 mM or less, about 16 mM or less, or about 15 mM or less. Accordingly, the polishing composition may contain an organic acid in an amount bounded by any two of the above endpoints. For example, the polishing composition may contain an organic acid from about 1 mM to about 20 mM, such as from about 1 mM to about 15 mM, from about 2 mM to about 15 mM, from about 3 mM to about 15 mM, from about 3 mM to about 12 mM, from about 1 mM to about 12 mM, or from about 1 mM to about 10 mM.

[0020] The polishing composition contains water. The water can be any suitable water, for example, deionized water or distilled water. In some embodiments, the polishing composition may further contain one or more organic solvents in combination with water. For example, the polishing composition may further contain a hydroxyl solvent such as methanol or ethanol, a ketone solvent, an amide solvent, a sulfoxide solvent, and the like.

[0021] The polishing composition may have any suitable pH. Typically, the polishing composition has a pH of about 2 or more, such as about 2.2 or more, about 2.4 or more, about 2.6 or more, about 2.8 or more, about 3 or more, about 3.4 or more, about 3.8 or more, or about 4 or more. As another option or in addition, the polishing composition may have a pH of about 5 or less, such as about 4.8 or less, about 4.6 or less, about 4.4 or less, about 4.2 or less, about 4 or less, about 3.8 or less, about 3.6 or less, about 3.4 or less, or about 3.2 or less. Accordingly, the polishing composition may have a pH bounded by any two of the above endpoints. For example, the polishing composition may have a pH from about 2 to about 5, such as from about 2 to about 4.8, from about 2 to about 4.6, from about 2 to about 4.4, from about 2 to about 4.2, from about 2 to about 4, from about 3 to about 5, or from about 3 to about 4.

[0022] The pH of the polishing composition may be adjusted using any suitable acid or base. Non-limiting examples of suitable acids include nitric acid, sulfuric acid, phosphoric 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.

[0023] The polishing composition may further comprise a nitrogen-containing compound selected from zwitterionic homopolymers, monomeric ammonium salts, and combinations thereof, as desired. In one embodiment, the nitrogen-containing compound is a zwitterionic homopolymer. In another embodiment, the zwitterionic homopolymer is ε-polylysine. ε-Polylysine may have any suitable molecular weight. For example, ε-polylysine may have a molecular weight of from about 5000 daltons to about 20000 daltons. In another embodiment, the nitrogen-containing compound is a monomeric ammonium salt. The monomeric ammonium salt may be any suitable monomeric ammonium salt. Non-limiting examples of suitable monomeric ammonium salts include diallyldimethylammonium chloride, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDMAPS), ammonium hydroxide, and the like.

[0024] The polishing composition may contain the zwitterionic homopolymer at any suitable concentration. For example, the polishing composition may contain a zwitterionic homopolymer of about 5 ppm or more, such as about 6 ppm or more, about 7 ppm or more, about 8 ppm or more, about 9 ppm or more, or about 10 ppm or more. As another option or in addition, the polishing composition may contain a zwitterionic homopolymer of about 25 ppm or less, such as about 24 ppm or less, about 23 ppm or less, about 22 ppm or less, about 21 ppm or less, or about 20 ppm or less. Accordingly, the polishing composition may contain the zwitterionic homopolymer in an amount bounded by any two of the above endpoints. For example, the polishing composition may contain a zwitterionic homopolymer of about 5 ppm to about 25 ppm, such as about 5 ppm to about 24 ppm, about 5 ppm to about 23 ppm, about 5 ppm to about 22 ppm, about 5 ppm to about 21 ppm, or about 5 ppm to about 20 ppm.

[0025] The polishing composition may contain the monomer ammonium salt at any suitable concentration. For example, the polishing composition may contain a monomer ammonium salt of about 1 mM or more, such as about 2 mM or more, about 3 mM or more, about 4 mM or more, or about 5 mM or more. As another option or in addition, the polishing composition may contain a monomer ammonium salt of about 10 mM or less, such as about 9 mM or less, about 8 mM or less, about 7 mM or less, about 6 mM or less, or about 5 mM or less. Accordingly, the polishing composition may contain the monomer ammonium salt in an amount bounded by any two of the above endpoints. For example, the polishing composition may contain a monomer ammonium salt of about 1 mM to about 10 mM, such as about 1 mM to about 9 mM, about 1 mM to about 8 mM, about 1 mM to about 7 mM, about 1 mM to about 6 mM, or about 1 mM to about 5 mM.

[0026] The polishing composition may further contain a nonionic surfactant, if desired. The nonionic surfactant may be any suitable nonionic surfactant. In some embodiments, the nonionic surfactant is selected from alkyl ethoxylates, polyethylene glycols, and combinations thereof. The alkyl ethoxylate has the formula: R(OC2H4) n OH, where R is a C1-C 30 alkyl group and n is an integer from 1 to about 1000. The polyethylene glycol has the structure: H-(O-CH2CH2) n -OH, and in the structure, n is an integer from 2 to about 5000.

[0027] The polishing composition may contain any suitable amount of nonionic surfactant. For example, the polishing composition may contain a nonionic surfactant in an amount of about 1 ppm or more, such as about 5 ppm or more, about 10 ppm or more, about 20 ppm or more, about 30 ppm or more, about 40 ppm or more, or about 50 ppm or more. As another option or in addition, the polishing composition may contain a nonionic surfactant in an amount of about 1000 ppm or less, such as about 900 ppm or less, about 800 ppm or less, about 700 ppm or less, about 600 ppm or less, or about 500 ppm or less. Thus, the polishing composition may contain a nonionic surfactant in an amount bounded by any two of the above endpoints. For example, the polishing composition may contain a nonionic surfactant in an amount of about 1 ppm to about 1000 ppm, such as about 5 ppm to about 900 ppm, about 5 ppm to about 800 ppm, about 5 ppm to about 700 ppm, about 5 ppm to about 600 ppm, or about 5 ppm to about 500 ppm.

[0028] The polishing composition may further contain a biocide, if desired. Non-limiting examples of suitable biocides are methylisothiazolinone-based biocides such as Kordek MLX™ (DuPont, Wilmington, DE). The polishing composition may contain any suitable amount of biocide. For example, the polishing composition may contain a biocide in an amount of about 0.001 wt% to about 0.2 wt%.

[0029] The polishing composition may further contain a buffer, if desired. The buffer may be any suitable buffer capable of maintaining the polishing composition at the pH described herein. Non-limiting examples of suitable buffers include formic acid, malonic acid, acetic acid, oxalic acid, citric acid, phosphoric acid, and salts thereof.

[0030] The polishing composition further comprises hydrogen peroxide, if desired. When hydrogen peroxide is present, the removal rate of titanium nitride can be increased when the polishing composition is used to polish a substrate having at least one layer of titanium nitride. The polishing composition may contain any suitable amount of hydrogen peroxide. For example, the polishing composition may contain from about 0.1 wt% to about 5 wt% (e.g., from about 0.1 wt% to about 1 wt%) of hydrogen peroxide.

[0031] In one embodiment, the present invention provides a chemical mechanical polishing composition comprising (a) from about 0.01 wt% to about 1 wt% of α-alumina, (b) an amphoteric ionomeric homopolymer at a concentration of from about 5 ppm to about 25 ppm, a monomeric ammonium salt at a concentration of from about 1 mM to about 10 mM, and a nitrogen-containing compound selected from combinations thereof, (c) an organic acid, and (d) water, and having a pH of from about 2 to about 4.

[0032] In another embodiment, the present invention provides a chemical mechanical polishing composition comprising (a) from about 1 wt% to about 5 wt% of silica, (b) an organic acid, (c) ferrous ions, and (d) water, and having a pH of from about 2 to about 4.

[0033] The polishing composition may be manufactured by any suitable technique, many of which are known to those skilled in the art. The polishing composition may be manufactured by a batch process or a continuous process. Generally, the polishing composition may be manufactured by combining its components in any order. The term "component" as used herein includes individual raw materials (e.g., α-alumina, silica, ferrous ions, organic acids, nitrogen-containing compounds that may optionally be included, hydrogen peroxide that may optionally be included, and nonionic surfactants that may optionally be included, etc.), and further any combination of raw materials (e.g., α-alumina, silica, ferrous ions, organic acids, nitrogen-containing compounds that may optionally be included, hydrogen peroxide that may optionally be included, and nonionic surfactants that may optionally be included, etc.).

[0034] For example, α-alumina or silica can be dispersed in water. Ferrous ions, an organic acid, a nitrogen-containing compound that may optionally be included, hydrogen peroxide that may optionally be included, and a nonionic surfactant that may optionally be included can then be added and mixed by any method capable of incorporating these components into the polishing composition. The polishing composition can also be produced by mixing the components at the surface of the substrate during the polishing operation.

[0035] The polishing composition can be supplied as a one-package system containing α-alumina and / or silica, ferrous ions, an organic acid, a nitrogen-containing compound that may optionally be included, hydrogen peroxide that may optionally be included, and a nonionic surfactant that may optionally be included. As another option, α-alumina and / or silica can be supplied as a dispersion in water in a first container, and ferrous ions, an organic acid, a nitrogen-containing compound that may optionally be included, hydrogen peroxide that may optionally be included, and a nonionic surfactant that may optionally be included can be supplied in a second container, in dry form, or as a solution or dispersion in water. The components in the first or second container can be in dry form, while the components in the other container can be in the form of an aqueous dispersion. Further, it is appropriate for the components in the first and second containers to have different pH values, or as another option, it is appropriate for them to have substantially similar or even equal pH values. Combinations of components of the polishing composition by other two-container or three-or-more-container arrangements are within the knowledge of those skilled in the art.

[0036] The polishing composition of the present invention may also be provided as a concentrate intended to be diluted with an appropriate amount of water before use. In such embodiments, the polishing composition concentrate comprises α-alumina and / or silica, ferric ions, an organic acid, a nitrogen-containing compound that may optionally be included, hydrogen peroxide that may optionally be included, and a nonionic surfactant that may optionally be included, and water, in an amount such that after diluting the concentrate with an appropriate amount of water, each component of the polishing composition is present in the polishing composition in an amount within the appropriate range described above for each component. For example, α-alumina and / or silica, ferric ions, an organic acid, a nitrogen-containing compound that may optionally be included, hydrogen peroxide that may optionally be included, and a nonionic surfactant that may optionally be included may each be present at a concentration of about 2 times (e.g., about 3 times, about 4 times, or about 5 times) higher than the concentration described above for each component, such that when the concentrate is diluted with an equal volume of water (e.g., 2 volumes of equal volume of water, 3 volumes of equal volume of water, or 4 volumes of equal volume of water), each component is present in the polishing composition in an amount within the range described above for each component. Hydrogen peroxide that may optionally be included may be added to the concentrate as a mixture with the water used to dilute the concentrate before use. Further, as will be understood by those skilled in the art, the concentrate may contain an appropriate proportion of the water present in the final polishing composition for the purpose of ensuring that other components are at least partially or completely dissolved in the concentrate.

[0037] The present invention also provides a method for chemically mechanical polishing a substrate, the method comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) providing a chemically mechanical polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and combinations thereof, (b) ferric ions, an organic acid, or combinations thereof, and (c) water, and having a pH of about 2 to about 4; (iv) contacting the substrate with the polishing pad and the chemically mechanical polishing composition; and (v) moving the polishing pad and the chemically mechanical polishing composition relative to the substrate to abrade at least a portion of the surface of the substrate, thereby polishing the substrate.

[0038] The substrate can be any suitable substrate. In certain embodiments, the substrate comprises boron-doped polysilicon or a boron-polysilicon alloy. In certain embodiments, the substrate comprises boron-doped polysilicon or a boron-polysilicon alloy in combination with silicon oxide and / or silicon nitride. In certain embodiments, the substrate further comprises titanium nitride. The boron-doped polysilicon can be any suitable boron-doped polysilicon, many of which are known in the art. The polysilicon can have any suitable phase and can be amorphous, crystalline, or a combination thereof. The level of boron doping can be any suitable level. For example, the level of boron doping can be from about 1 wt% to about 90 wt%, such as from about 5 wt% to about 90 wt%, from about 10 wt% to about 90 wt%, from about 20 wt% to about 90 wt%, from about 30 wt% to about 90 wt%, from about 40 wt% to about 90 wt%, from about 50 wt% to about 90 wt%, from about 60 wt% to about 90 wt%, from about 70 wt% to about 90 wt%, or from about 80 wt% to about 90 wt%. In certain embodiments, the substrate comprises one or more layers of boron-doped polysilicon. In certain embodiments, the substrate further comprises one or more layers selected from silicon nitride, silicon oxide, titanium nitride, and combinations thereof.

[0039] The polishing compositions and methods of the present invention are particularly suitable for use in conjunction with a chemical mechanical polishing apparatus. Typically, the apparatus includes a platen that operates during use and has a speed resulting from orbital, linear, or circular motion, a polishing pad in contact with the platen and moving with the platen during operation, and a carrier for holding the substrate that is to be polished by contacting the surface of the polishing pad and moving relative thereto. Polishing of the substrate is performed by disposing 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 so as to abrade at least a portion of the substrate to polish the substrate.

[0040] The substrate may be polished with any suitable polishing pad (e.g., polishing surface) using a polishing composition. Suitable polishing pads include, for example, woven and non-woven polishing pads. Further, suitable polishing pads may include any suitable polymer having various densities, hardnesses, thicknesses, compressibilities, abilities to rebound upon compression, and compression coefficients. Suitable polymers include, for example, polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester, polyacrylate, polyether, polyethylene, polyamide, polyurethane, polystyrene, polypropylene, coformed products thereof, and mixtures thereof. Soft polyurethane polishing pads are particularly useful when combined with the polishing method of the present invention. Typical pads include, but are not limited to, SURFIN™ 000, SURFIN™ SSW 1, SPM3100 (e.g., commercially available from Eminess Technologies), POLITEX™, NEXPLANAR® E6088 (Cabot Microelectronics, Aurora, IL), and Fujibo POLYPAS™ 27. A preferred polishing pad is the EPIC™ D100 pad commercially available from Cabot Microelectronics.

[0041] Desirably, the chemical mechanical polishing apparatus further comprises an in situ polishing endpoint detection system, 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 described, for example, in U.S. Patent No. 5,196,353, U.S. Patent No. 5,433,651, U.S. Patent No. 5,609,511, U.S. Patent No. 5,643,046, U.S. Patent No. 5,658,183, U.S. Patent No. 5,730,642, U.S. Patent No. 5,838,447, U.S. Patent No. 5,872,633, U.S. Patent No. 5,893,796, U.S. Patent No. 5,949,927, and U.S. Patent No. 5,964,643. Desirably, by inspecting or monitoring the progress of the polishing process with respect to the substrate being polished, it is possible to determine the polishing endpoint, i.e., to determine at what point the polishing process should be terminated with respect to a particular substrate.

[0042] The polishing composition of the present invention preferably exhibits a high removal rate when polishing a substrate containing boron-doped polysilicon or a boron-polysilicon alloy according to the method of the present invention. For example, when polishing a silicon wafer having a layer of boron-doped polysilicon or a boron-polysilicon alloy according to an embodiment of the present invention, the polishing composition preferably has a removal rate of boron-doped polysilicon or a boron-polysilicon alloy of about 500 Å / min or more, exemplified by about 550 Å / min or more, about 600 Å / min or more, about 650 Å / min or more, about 700 Å / min or more, about 750 Å / min or more, about 800 Å / min or more, about 850 Å / min or more, about 900 Å / min or more, about 950 Å / min or more, about 1000 Å / min or more, about 1100 Å / min or more, about 1200 Å / min or more, about 1300 Å / min or more, about 1400 Å / min or more, about 1500 Å / min or more, about 1600 Å / min or more, about 1700 Å / min or more, about 1800 Å / min or more, about 1900 Å / min or more, about 2000 Å / min or more, about 2100 Å / min or more, about 2200 Å / min or more, about 2300 Å / min or more, about 2400 Å / min or more, about 2500 Å / min or more, about 2600 Å / min or more, about 2700 Å / min or more, about 2800 Å / min or more, about 2900 Å / min or more, or about 3000 Å / min or more.

[0043] The polishing composition of the present invention preferably exhibits a low removal rate when polishing a substrate containing silicon oxide and / or silicon nitride according to the method of the present invention. For example, when polishing a silicon wafer containing silicon nitride or silicon oxide according to an embodiment of the present invention, the polishing composition preferably has a removal rate of silicon nitride or silicon nitride of about 100 Å / min or less, exemplified by 95 Å / min or less, about 90 Å / min or less, about 85 Å / min or less, about 80 Å / min or less, about 75 Å / min or less, about 70 Å / min or less, about 65 Å / min or less, about 60 Å / min or less, about 55 Å / min or less, about 50 Å / min or less, about 45 Å / min or less, about 40 Å / min or less, about 35 Å / min or less, about 30 Å / min or less, about 25 Å / min or less, about 20 Å / min or less, about 15 Å / min or less, about 10 Å / min or less, about 5 Å / min or less, or about 1 Å / min or less. In some embodiments, the polishing composition exhibits a removal rate of silicon nitride or silicon oxide that is too low to be detected.

[0044] The polishing composition of the present invention can exhibit a variable titanium nitride removal rate. For example, when ferrous ions and / or hydrogen peroxide are present in the polishing composition, the titanium nitride removal rate can increase when used to polish a substrate having at least one layer of titanium nitride. The titanium nitride removal rate typically increases with an increase in the concentration of ferrous ions and / or hydrogen peroxide.

[0045] Embodiment (1) In Embodiment (1), a method for chemically mechanical polishing a substrate is presented, the method comprising: (i) providing a substrate, (ii) providing a polishing pad, (iii) providing a chemically mechanical polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and combinations thereof, (b) ferrous ions, an organic acid, or a combination thereof, and (c) water, and having a pH of about 2 to about 4, (iv) contacting the substrate with the polishing pad and the chemically mechanical polishing composition, and (v) moving the polishing pad and the chemically mechanical polishing composition relative to the substrate to abrade at least a portion of the surface of the substrate to polish the substrate. Including.

[0046] (2) In Embodiment (2), the method according to Embodiment (1) is presented, wherein the abrasive is α-alumina and the polishing composition comprises about 0.01 wt% to about 1 wt% of α-alumina.

[0047] (3) In Embodiment (3), the method according to Embodiment (2) is presented, wherein the α-alumina comprises particles having an average particle size of about 90 nm to about 300 nm.

[0048] (4) In Embodiment (4), the method according to Embodiment (2) or Embodiment (3) is presented, wherein the polishing composition comprises an organic acid at a concentration of about 1 mM to about 10 mM.

[0049] (5) In Embodiment (5), the method described in Embodiment (4) is presented, and the organic acid is selected from tartaric acid, lactic acid, formic acid, acetic acid, and combinations thereof.

[0050] (6) In Embodiment (6), the method described in any one of Embodiments (2) to (5) is presented, and the polishing composition further includes a nitrogen-containing compound selected from zwitterionic homopolymers, monomer ammonium salts, and combinations thereof.

[0051] (7) In Embodiment (7), the method described in Embodiment (6) is presented, the zwitterionic homopolymer is present at a concentration of about 5 ppm to about 25 ppm, and the monomer ammonium salt is present at a concentration of about 1 mM to about 10 mM.

[0052] (8) In Embodiment (8), the method described in Embodiment (6) or Embodiment (7) is presented, the nitrogen-containing compound is a zwitterionic homopolymer, and the zwitterionic homopolymer is ε-polylysine.

[0053] (9) In Embodiment (9), the method described in Embodiment (6) or Embodiment (7) is presented, and the nitrogen-containing compound is a monomer ammonium salt.

[0054] (10) In Embodiment (10), the method described in Embodiment (9) is presented, and the monomer ammonium salt is dimethyldiallylammonium salt or ammonium hydroxide.

[0055] (11) In Embodiment (11), the method described in any one of Embodiments (1) to (10) is presented, and the polishing composition further includes a nonionic surfactant selected from alkyl ethoxylates, polyethylene glycols, and combinations thereof.

[0056] (12) In Embodiment (12), the method described in any one of Embodiments (1) to (11) is presented, and the polishing composition is substantially free of ferric ions.

[0057] (13) In Embodiment (13), the method described in Embodiment (1) is presented, the abrasive is silica, and the polishing composition contains about 1 wt% to about 5 wt% of silica.

[0058] (14) In Embodiment (14), the method described in Embodiment (13) is presented, and the silica contains particles having an average particle size of about 40 nm to about 200 nm.

[0059] (15) In Embodiment (15), the method described in Embodiment (13) or Embodiment (14) is presented, and the polishing composition contains about 0.01 wt% to about 1 wt% of ferrous ions.

[0060] (16) In Embodiment (16), the method described in any one of Embodiments (13) to (15) is presented, and the polishing composition further contains an organic acid selected from maleic acid, L - ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0061] (17) In Embodiment (17), the method described in Embodiment (16) is presented, the organic acid is maleic acid, and the polishing composition contains about 1 mM to about 100 mM of maleic acid.

[0062] (18) In Embodiment (18), the method described in any one of Embodiments (1) to (17) is presented, the substrate includes at least one layer of boron - doped polysilicon on the surface of the substrate, and at least a portion of the boron - doped polysilicon on the surface of the substrate is abraded so that the substrate is polished.

[0063] (19) In Embodiment (19), the method described in Embodiment (18) is presented, the substrate further includes at least one layer of silicon oxide on the surface of the substrate, and at least a portion of the silicon oxide on the surface of the substrate is abraded so that the substrate is polished.

[0064] (20) In embodiment (20), the method described in embodiment (18) or embodiment (19) is presented, and the substrate further comprises at least one layer of silicon nitride on the surface of the substrate, and at least a part of the silicon nitride on the surface of the substrate is abraded so that the substrate is polished.

[0065] (21) In embodiment (21), the method described in embodiment (18) or embodiment (19) is presented, and the substrate further comprises at least one layer of titanium nitride on the surface of the substrate, and at least a part of the titanium nitride on the surface of the substrate is abraded so that the substrate is polished.

[0066] (22) In embodiment (22), (a) about 0.01 wt% to about 1 wt% of α-alumina, (b) a nitrogen-containing compound selected from zwitterionic homopolymers, monomeric ammonium salts, and combinations thereof, (c) an organic acid, and (d) water, are included, and a chemical mechanical polishing composition having a pH of about 2 to about 4 is presented.

[0067] (23) In embodiment (23), the polishing composition described in embodiment (22) is presented, and the α-alumina comprises particles having an average particle size of about 90 nm to about 300 nm.

[0068] (24) In embodiment (24), the polishing composition described in embodiment (22) or embodiment (23) is presented, the nitrogen-containing compound is a zwitterionic homopolymer, the zwitterionic homopolymer is ε-polylysine, and ε-polylysine is present at a concentration of about 5 ppm to about 25 ppm.

[0069] (25) In embodiment (25), the polishing composition described in embodiment (22) or embodiment (23) is presented, and the nitrogen-containing compound is a monomeric ammonium salt.

[0070] (26) In embodiment (26), the polishing composition described in embodiment (25) is presented, the monomer ammonium salt is a dimethyldiallylammonium salt or ammonium hydroxide, and the monomer ammonium salt is present at a concentration of about 1 mM to about 10 mM.

[0071] (27) In embodiment (27), the polishing composition described in any one of embodiments (22) to (26) is presented, and the polishing composition further includes a nonionic surfactant selected from alkyl ethoxylates, polyethylene glycols, and combinations thereof.

[0072] (28) In embodiment (28), the polishing composition described in any one of embodiments (22) to (27) is presented, and the polishing composition further includes an organic acid at a concentration of about 1 mM to about 10 mM.

[0073] (29) In embodiment (29), the polishing composition described in embodiment (28) is presented, and the organic acid is selected from tartaric acid, lactic acid, formic acid, acetic acid, and combinations thereof.

[0074] (30) In embodiment (30), the polishing composition described in any one of embodiments (22) to (29) is presented, and the polishing composition is substantially free of ferric ions.

[0075] (31) In embodiment (31), (a) about 1 wt% to about 5 wt% silica, (b) an organic acid, (c) ferric ions, and (d) water, are included, and a chemical mechanical polishing composition having a pH of about 2 to about 4 is presented.

[0076] (32) In embodiment (32), the polishing composition described in embodiment (31) is presented, and the silica includes particles having an average particle size of about 40 nm to about 200 nm.

[0077] (33) In Embodiment (33), the polishing composition described in Embodiment (31) or Embodiment (32) is presented, and the organic acid is selected from maleic acid, L - ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0078] (34) In Embodiment (34), the polishing composition described in Embodiment (33) is presented, the organic acid is maleic acid, and the polishing composition contains about 1 mM to about 20 mM of maleic acid.

[0079] The following examples further illustrate the present invention, but of course, should not be construed as limiting the scope of the present invention in any way.

Example

[0080] Example 1 This example demonstrates the effect of the amounts of α - alumina and lactic acid on the removal rates of boron - doped polysilicon ("B - Si"), silicon nitride ("SiN"), and titanium nitride ("TiN").

[0081] Separate substrates with layers of B - Si, SiN, or TiN were polished with five different polishing compositions, namely, polishing compositions 1A - 1E. Polishing compositions 1A - 1E contained α - alumina and lactic acid in the amounts shown in Table 1, and the pH of each polishing composition was 3.5. The substrates were polished on a Logitech polishing tool using an E6088 polishing pad under the following conditions: platen speed = 93 rpm; polishing head speed = 87 rpm; slurry flow rate = 50 mL / min; and downward force = 27.5 kPa.

[0082] After polishing, the removal rates of B - Si, SiN, and TiN were determined. The results are shown in Table 1.

Table 1

[0083] As is clear from the results shown in Table 1, the highest B-Si removal rate was observed when the polishing composition contained 0.5 wt% α-alumina, and the lowest removal rate was observed when the polishing composition contained 0.1 wt% α-alumina. Thus, this example shows that the B-Si removal rate increases as the concentration of α-alumina increases. In addition, lactic acid resulted in an increase in the B-Si removal rate at a rate of approximately 0.4 - 0.5% per 1 mM of added lactic acid. Similarly, the TiN removal rate was also highest when the amount of α-alumina was increased. Desirably, all formulations showed a low SiN removal rate (<50 Å / min).

[0084] Example 2 This example demonstrates the effect of nitrogen-containing compounds on the removal rates of boron-doped polysilicon ("B-Si") and silicon oxide ("TEOS") shown by a polishing composition containing α-alumina.

[0085] Separate substrates with layers of B-Si or TEOS were polished with 13 different polishing compositions, namely polishing compositions 2A - 2M. Polishing compositions 2A - 2M had a pH value shown in Table 2 and contained 0.05 wt% α-alumina in water. Polishing compositions 2A and 2B (comparative examples) did not contain a nitrogen-containing compound. Polishing compositions 2C - 2M further contained diallyldimethylammonium chloride (DADMAC) (polishing compositions 2C - 2G), DDMAPS (N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) (polishing compositions 2J and 2K), ammonium hydroxide (polishing compositions 2H and 2I), or ε-polylysine (ε-PLL) (polishing compositions 2L and 2M) at the concentrations shown in Table 2. The substrates were polished on a Reflexion polishing tool using an E6088 polishing pad under the following conditions: platen speed = 123 rpm; polishing head speed = 117 rpm; slurry flow rate = 350 mL / min; and downward force = 24.1 kPa.

[0086] After polishing, the removal rates of B-Si and TEOS were determined. The removal rates and B-Si:TEOS selectivity are shown in Table 2. The B-Si:TEOS selectivity is the ratio of the B-Si removal rate to the TEOS removal rate.

Table 2

[0087] As is clear from the results shown in Table 2, when ε-polylysine (i.e., zwitterionic homopolymer) is present at a concentration of about 5 ppm to about 25 ppm, or when DADMAC or DDMAPS (i.e., monomer ammonium salts) is present at a concentration of about 1 mM to about 10 mM, the B-Si:TEOS selectivity of polishing compositions 2C to 2M was greatly improved by suppressing the TEOS removal rate. At the optimal low level of the nitrogen-containing compound, the decrease in the removal rate of B-Si is minimal, but as the amount of the nitrogen-containing compound increases, the removal rate of B-Si further decreases. In the case of a polishing composition containing α-alumina abrasive, the addition of ε-polylysine slightly decreased the removal rate of B-Si from 1800 to 1500 Å / min, but desirably, the B-Si:TEOS selectivity increased dramatically from 14 to 54.

[0088] Example 3 This example demonstrates the effect of the amount of α-alumina on the removal rates of B-Si and TEOS, as shown by a polishing composition containing α-alumina and DADMAC.

[0089] Separate substrates with a layer of B-Si or TEOS were polished with three different polishing compositions, namely, polishing compositions 3A to 3C. Polishing compositions 3A to 3C contained 0.01 wt% α-alumina and 3 mM DADMAC (polishing composition 3A), 0.05 wt% α-alumina and 3 mM DADMAC (polishing composition 3B), or 0.05 wt% α-alumina and no DADMAC (polishing composition 3C). The pH of each polishing composition was 2.9.

[0090] After polishing, the removal rates of B-Si and TEOS were determined. The removal rates and B-Si:TEOS selectivity are shown in Table 3.

Table 3

[0091] As is clear from the results shown in Table 3, when the amount of α-alumina was increased from 0.01 wt% to 0.05 wt% (polishing compositions 3A and 3B, respectively), the B-Si removal rate increased by approximately 58%, and due to the increase in the TEOS removal rate, the B-Si:TEOS selectivity decreased by approximately 58%. The polishing composition 3C that did not contain DADMAC (or contained no other nitrogen-containing compounds and was thus a comparative example) had a B-Si removal rate that was approximately 35% higher than that exhibited by the polishing composition 3B containing 3 mM DADMAC, and exhibited a B-Si:TEOS selectivity of approximately 35% of the B-Si:TEOS selectivity exhibited by the polishing composition 3B. Therefore, when DADMAC is present in the polishing compositions 3A and 3B of the present invention, compared with the polishing composition 3C, the B-Si removal rate decreases, but due to the decrease in the TEOS removal rate provided by the polishing compositions 3A and 3B, the B-Si:TEOS selectivity significantly increases as a result.

[0092] Example 4 This example demonstrates the effect of pH on the B-Si removal rate and B-Si:TEOS selectivity, as shown by a polishing composition containing α-alumina and ε-polylysine.

[0093] Separate substrates with layers of B-Si or TEOS were polished with two different polishing compositions, namely, polishing compositions 4A and 4B. The polishing compositions 4A and 4B contained 0.05 wt% α-alumina and 15 ppm ε-polylysine in water. The pH values of the polishing compositions 4A and 4B were 3.2 and 2.6, respectively.

[0094] After polishing, the removal rates of B-Si and TEOS were determined. The removal rates and B-Si:TEOS selectivity are shown in Table 4.

Table 4

[0095] As is clear from the results shown in Table 4, the polishing composition 4B with a pH of 2.6 exhibited an approximately two-fold increase in B-Si:TEOS selectivity compared to the polishing composition 4A with a pH of 3.2. The B-Si removal rate did not essentially change between the polishing compositions 4A and 4B, but the TEOS removal rate decreased by more than two-fold at the lower pH of the polishing composition 4B, and as a result, the B-Si:TEOS selectivity increased.

[0096] Example 5 This example demonstrates the effect of maleic acid and the combination of maleic acid and ferric ions on the B-Si removal rate, as shown by a polishing composition containing colloidal silica.

[0097] Separate substrates with a B-Si layer were polished with seven polishing compositions, namely, polishing compositions 5A to 5J. The polishing compositions 5A to 5J contained colloidal silica and 0.01 wt% of Kordek™ MLX (a methylisothiazolinone-based biocide), and further contained a component selected from maleic acid, catechol, L-ascorbic acid, picolinic acid, ferric nitrate, and aluminum nitrate. The substrates were polished on a Logitech polishing tool using an E6088 polishing pad under the following conditions: platen speed = 93 rpm; polishing head speed = 87 rpm; slurry flow rate = 50 mL / min; and downward force = 27.6 kPa.

[0098] After polishing, the B-Si removal rate was determined and the results are shown in Table 5.

Table 5

[0099] As is clear from the results shown in Table 5, polishing composition 5E, which contained colloidal silica, 0.058 wt% maleic acid (i.e., an organic acid), and 0.01 wt% ferric nitrate, exhibited the highest B-Si removal rate of 1536 Å / min. Polishing composition 5D, which contained the same components as polishing composition 5E but with half the amount of ferric nitrate, exhibited a B-Si removal rate that was approximately 64% of the B-Si removal rate shown by polishing composition 5E. From these results, it is demonstrated that the amount of ferric nitrate has a very strong effect on the B-Si removal rate.

[0100] Polishing compositions 5B and 5C, which contained 5 mM and 10 mM maleic acid, respectively, showed B-Si removal rates that were approximately 22% and 13% higher, respectively, than the B-Si removal rate obtained with polishing composition 5A, which did not contain maleic acid. These results demonstrate that maleic acid significantly increases the B-Si removal rate.

[0101] Polishing composition 5I, which contained the same amount of maleic acid and Kordek MLX (trademark) as polishing composition 5B but had a pH of 10, exhibited a marked increase in the B-Si removal rate compared to polishing composition 5B, which had a pH of 2.0.

[0102] Polishing composition 5B, which contained a trivalent metal salt (aluminum nitrate) instead of ferric nitrate, exhibited a significantly decreased B-Si removal rate compared to polishing compositions 5D and 5E, which contained ferric nitrate. From these results, the strong effect of ferric ions on the B-Si removal rate is further demonstrated.

[0103] Example 6 This example demonstrates the effect of the downward force on the SiN removal rate shown by a polishing composition containing colloidal silica, maleic acid, and ferric nitrate.

[0104] Separate substrates with a layer of B-Si or SiN were polished with two different polishing compositions, polishing compositions 6A and 6B. Both polishing compositions 6A and 6B contained colloidal silica and maleic acid. Polishing compositions 6A and 6B further contained 0.05 wt% or 0.1 wt% of ferric nitrate, respectively. The substrates were polished on a Reflexion polishing tool using an E6088 polishing pad under the following conditions: platen speed = 93 rpm; polishing head speed = 87 rpm; and slurry flow rate = 250 mL / min. The B-Si substrate was polished with a single downward force of 20.7 kPa. The SiN substrate was polished with a downward force of 20.7 kPa, 13.8 kPa, or 6.9 kPa as reported in Table 6.

[0105] After polishing, the removal rates of B-Si and SiN were determined. The results are shown in Table 6.

Table 6

[0106] As is apparent from the results shown in Table 6, at a downward force of 20.7 kPa, polishing composition 6B, which contained 0.1 wt% of ferric nitrate, exhibited a B-Si removal rate that was approximately 111% of the B-Si removal rate shown by polishing composition 6A, which contained 0.05 wt% of ferric nitrate. From these results, a strong effect of ferric nitrate concentration on the B-Si removal rate is demonstrated. At each of the three downward forces tested, polishing composition 6A exhibited a SiN removal rate similar to that shown by polishing composition 6B at the same downward force. As an example, at a downward force of 20.7 kPa, polishing composition 6A provided a SiN removal rate of 70 Å / min, while polishing composition 6B provided a SiN removal rate of 70.2 Å / min.

[0107] The SiN removal rates exhibited by both polishing compositions 6A and 6B were shown to decrease linearly as the downward force decreased. Desirably, by adjusting the downward force, it is possible to adjust by increasing the SiN removal rate at higher downward forces, but increasing the B-Si:SiN selectivity at lower downward forces.

[0108] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0109] The use of the terms "a", "an", "the", "at least one", and similar referents in the context of describing the present invention (especially in the context of the following claims) is to be construed to include both the singular and the plural unless otherwise indicated herein or clearly contradicted by the context. The use of the term "at least one" prior to a list of one or more items (e.g., "at least one of A and B") is to be construed to mean one item (A or B) selected from the listed items or any combination of two or more of the listed items (A and B) unless otherwise indicated herein or clearly contradicted by the context. The terms "comprising", "having", "including", and "containing" are to be construed as non-limiting terms (i.e., meaning "including, but not limited to") unless otherwise specified. The recitation of a range of values herein is merely intended to be a concise way of referring individually to each separate value within the range, and each separate value is hereby incorporated by reference herein as if it were individually recited herein unless otherwise indicated. All methods described herein may be performed in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any example or exemplary language provided herein (e.g., "such as") is merely intended to clarify the present invention and does not impose a limitation on the scope of the present invention unless otherwise claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0110] Preferred embodiments of the present invention are described herein, including the best mode known to the inventors for carrying out the present invention. Variations of these preferred embodiments will be apparent to those skilled in the art upon reading the above description. The inventors contemplate that those skilled in the art will appropriately utilize such variations, and the inventors intend that the present invention be practiced in ways other than those specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Further, any combination of the above-described elements is included in the present invention for all possible variations thereof, unless otherwise indicated herein or clearly contradicted by context.

Claims

1. A method for chemically-mechanically polishing a substrate, comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) providing a chemically-mechanically polishing composition comprising: (a) an abrasive selected from α-alumina, silica, and combinations thereof; (b) ferric ions, an organic acid, or a combination thereof; and (c) water; wherein the chemically-mechanically polishing composition has a pH of from about 2 to about 4; (iv) contacting the substrate with the polishing pad and the chemically-mechanically polishing composition; and (v) moving the polishing pad and the chemically-mechanically polishing composition relative to the substrate to abrade at least a portion of a surface of the substrate to polish the substrate. A method as described above.

2. The method of claim 1, wherein the abrasive is α-alumina and the polishing composition comprises from about 0.01 wt% to about 1 wt% α-alumina.

3. The method of claim 2, wherein the α-alumina comprises particles having an average particle size of from about 90 nm to about 300 nm.

4. The method of claim 2, wherein the polishing composition comprises an organic acid at a concentration of from about 1 mM to about 10 mM.

5. The method of claim 4, wherein the organic acid is selected from tartaric acid, lactic acid, formic acid, acetic acid, and combinations thereof.

6. The method of claim 2, wherein the polishing composition further comprises a nitrogen-containing compound selected from zwitterionic homopolymers, monomeric ammonium salts, and combinations thereof.

7. The method of claim 6, wherein the zwitterionic homopolymer is present at a concentration of from about 5 ppm to about 25 ppm and the monomeric ammonium salt is present at a concentration of from about 1 mM to about 10 mM.

8. The method of claim 6, wherein the nitrogen-containing compound is a zwitterionic homopolymer and the zwitterionic homopolymer is ε-polylysine.

9. The method of claim 6, wherein the nitrogen-containing compound is a monomeric ammonium salt.

10. The method of claim 9, wherein the monomeric ammonium salt is dimethyldiallylammonium salt or ammonium hydroxide.

11. The method of claim 1, wherein the polishing composition further comprises a nonionic surfactant selected from alkyl ethoxylates, polyethylene glycols, and combinations thereof.

12. The method according to claim 1, wherein the polishing composition substantially does not contain ferric ions.

13. The method according to claim 1, wherein the abrasive is silica and the polishing composition contains about 1 wt% to about 5 wt% silica.

14. The method according to claim 13, wherein the silica contains particles having an average particle size of about 40 nm to about 200 nm.

15. The method according to claim 13, wherein the polishing composition contains about 0.01 wt% to about 1 wt% ferric ions.

16. The method according to claim 13, wherein the polishing composition further contains an organic acid selected from maleic acid, L - ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

17. The method according to claim 16, wherein the organic acid is maleic acid and the polishing composition contains about 1 mM to about 100 mM maleic acid.

18. The method according to claim 1, wherein the substrate comprises at least one layer of boron - doped polysilicon on the surface of the substrate, and at least a part of the boron - doped polysilicon on the surface of the substrate is abraded so that the substrate is polished.

19. The method according to claim 18, wherein the substrate further comprises at least one layer of silicon oxide on the surface of the substrate, and at least a part of the silicon oxide on the surface of the substrate is abraded so that the substrate is polished.

20. (a) about 0.01 wt% to about 1 wt% of α - alumina, (b) a nitrogen - containing compound selected from zwitterionic homopolymers, monomeric ammonium salts, and combinations thereof, (c) an organic acid, and (d) water, A chemical - mechanical polishing composition, comprising and having a pH of about 2 to about 4.

21. The polishing composition according to claim 20, wherein the α - alumina contains particles having an average particle size of about 90 nm to about 300 nm.

22. The polishing composition according to claim 20, wherein the nitrogen - containing compound is a zwitterionic homopolymer, the zwitterionic homopolymer is ε - polylysine, and the ε - polylysine is present at a concentration of about 5 ppm to about 25 ppm.

23. The polishing composition according to claim 20, wherein the nitrogen - containing compound is a monomeric ammonium salt.

24. The polishing composition according to claim 23, wherein the monomeric ammonium salt is dimethyldiallylammonium salt or ammonium hydroxide, and the monomeric ammonium salt is present at a concentration of about 1 mM to about 10 mM.

25. The polishing composition according to claim 20, further comprising a nonionic surfactant selected from alkyl ethoxylates, polyethylene glycols, and combinations thereof.

26. The polishing composition according to claim 20, further comprising an organic acid at a concentration of about 1 mM to about 10 mM.

27. The polishing composition according to claim 26, wherein the organic acid is selected from tartaric acid, lactic acid, formic acid, acetic acid, and combinations thereof.

28. (a) about 1 wt% to about 5 wt% silica, (b) an organic acid, (c) ferrous ions, and (d) water, comprising a chemical mechanical polishing composition having a pH of about 2 to about 4.

29. The polishing composition according to claim 28, wherein the silica comprises particles having an average particle size of about 40 nm to about 200 nm.

30. The polishing composition according to claim 28, wherein the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

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