Chemical mechanical polishing composition for heavily doped boron silicon films

Abstract

The present invention provides a chemical-mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent; and (c) water, the chemical-mechanical polishing composition having a pH of about 2 or less. The present invention also provides a method for using the composition to chemically mechanically polish a substrate, particularly a substrate comprising a boron-doped polysilicon layer on a surface of the substrate.

Description

[Background technology]

[0001] Compositions and methods for planarizing or polishing the surface of a substrate are well known in the art. Polishing compositions (also known as polishing slurries) typically contain an abrasive material in a liquid carrier and are applied to a surface by contacting the surface with a polishing pad saturated with the polishing composition. Typical abrasive materials include silicon dioxide, cerium oxide, aluminum oxide, zirconium oxide, and tin oxide. Polishing compositions are typically used in conjunction with a polishing pad (e.g., a polishing cloth or disk). The abrasive material 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 utilized as patterning hard masks during the fabrication of advanced node memory devices, such as dynamic random access memory (DRAM). Due to the high levels of boron in polysilicon materials, achieving high removal rates for this material by chemical mechanical planarization (CMP) can be challenging. In addition to requiring high removal rates for boron-polysilicon films, some memory device schemes also require very low removal rates for silicon nitride and / or silicon oxide, which can function as stop layers in the device film stack. This presents a selectivity requirement during CMP. Furthermore, titanium nitride is also used in the fabrication of some memory devices. The ability to tailor the relative removal rate of titanium nitride would be a desirable feature for polishing compositions and methods useful in device fabrication.

[0003] Therefore, there remains a need in the art for polishing compositions and methods for polishing boron-polysilicon layers with high removal rates and selectivity to boron-polysilicon. Summary of the Invention

[0004] The present invention provides a chemical-mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent; and (c) water, wherein the chemical-mechanical polishing composition has a pH of about 2 or less.

[0005] The present invention further 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) a silica abrasive; (b) an oxidizing agent; and (c) water, the chemical-mechanical polishing composition having a pH of about 2 or less; (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 polish at least a portion of the substrate. [Brief explanation of the drawings]

[0006] [Figure 1] 1 shows boron-polysilicon (BSi) removal rate (Å / min) versus polishing composition as described in Example 1. [Figure 2] 1 shows tetraethyl orthosilicate (TEOS) removal rate (Å / min) versus polishing composition as described in Example 1. [Figure 3] 1 shows the boron-polysilicon (BSi) removal rate (Å / min) versus particle size exhibited by a polishing composition containing ceric ammonium nitrate (CAN), as described in Example 2. [Figure 4] 1 shows the tetraethyl orthosilicate (TEOS) removal rate (Å / min) versus particle size exhibited by a polishing composition containing ceric ammonium nitrate (CAN), as described in Example 2. [Figure 5] 1 shows the boron-polysilicon (BSi) removal rate (Å / min) versus particle type exhibited by polishing compositions containing ceric ammonium nitrate (CAN), as described in Example 3. [Figure 6]1 shows the tetraethyl orthosilicate (TEOS) removal rate (Å / min) versus particle type exhibited by a polishing composition containing ceric ammonium nitrate (CAN), as described in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present invention provides a chemical-mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent; and (c) water, wherein the chemical-mechanical polishing composition has a pH of about 2 or less.

[0008] The polishing composition includes an abrasive. As used herein, the terms "abrasive" and "abrasive particles" can be used interchangeably and can refer to any dispersion of abrasive particles. In other words, the terms "abrasive" and "abrasive particles" can be used interchangeably and can refer to (i) a plurality of a single type of abrasive or abrasive particles and / or (ii) a plurality of more than one type of abrasive or abrasive particles.

[0009] The polishing composition comprises a silica abrasive. As used herein, the terms "silica abrasive," "silica abrasive particles," "silica particles," and "abrasive particles" can be used interchangeably and refer to any silica particles (e.g., colloidal silica particles). The silica particles (e.g., colloidal silica particles) can be modified (e.g., surface-modified) or unmodified and have a negative zeta potential, a neutral zeta potential, or a positive zeta potential.

[0010] The charge on dispersed particles (e.g., colloidal silica particles), such as silica abrasives, is commonly referred to as the zeta potential (or electrokinetic 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 composition (e.g., the liquid carrier and any other components dissolved therein) in which it is measured. Zeta potential typically depends on the pH of the aqueous medium. For a given polishing 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 from the isoelectric point, the surface charge (and therefore the zeta potential) correspondingly decreases or increases (resulting in negative or positive zeta potential values, respectively). As used herein, the phrase "negative zeta potential" refers to a silica abrasive that exhibits a negative surface charge when measured in a polishing composition. As used herein, the phrase "neutral zeta potential" refers to a silica abrasive that exhibits a net zero surface charge when measured in a polishing composition. As used herein, the phrase "positive zeta potential" refers to a silica abrasive that exhibits a positive surface charge when measured in a polishing composition.

[0011] Silica particles (e.g., colloidal silica particles) can have a negative natural zeta potential, a neutral natural zeta potential, or a positive natural zeta potential. As used herein, the phrase "natural zeta potential" refers to the zeta potential of the silica abrasive before it is added to the polishing composition. For example, the natural zeta potential can refer to the zeta potential of the silica abrasive measured in a stock solution or aqueous solution before it is added to the polishing composition. Those skilled in the art will be able to determine whether the silica abrasive has a negative natural zeta potential, a neutral natural zeta potential, or a positive natural zeta potential before it is added to the polishing composition.

[0012] The native zeta potential and zeta potential of the polishing composition can be obtained using a Model DT-1202 acoustic and electroacoustic spectrometer available from Dispersion Technologies, Inc. (Bedford Hills, NY).

[0013] Silica abrasives (e.g., colloidal silica particles) may be modified (e.g., surface-modified) or unmodified and have a negative, neutral, or positive natural zeta potential. Thus, silica abrasives (e.g., colloidal silica particles) can have a positive, neutral, or negative zeta potential before being added to the chemical-mechanical polishing composition. For example, silica particles (e.g., colloidal silica particles) can have a natural zeta potential of less than 0 mV (e.g., -5 mV or less), i.e., a negative natural zeta potential, before being added to the chemical-mechanical polishing composition. Alternatively, silica particles (e.g., colloidal silica particles) can have a natural zeta potential of 0 mV or greater (e.g., 5 mV or greater), i.e., a positive natural zeta potential, before being added to the chemical-mechanical polishing composition. In other embodiments, silica particles (e.g., colloidal silica particles) have a natural zeta potential of about 0 mV, i.e., a neutral natural zeta potential.

[0014] Silica particles (e.g., colloidal silica particles) and charged silica particles (e.g., colloidal silica particles) can be prepared by a variety of methods, some examples of which are commercially used and known. Useful silica particles include precipitated or condensation-polymerized silica, which can be prepared using known methods such as the so-called "sol-gel" method or silicate ion exchange. Condensation-polymerized silica particles are often prepared by condensing Si(OH) to form substantially spherical (e.g., spherical, ovoid, or ellipsoidal) particles. The precursor Si(OH) may be obtained, for example, by hydrolysis of high-purity alkoxysilanes or by acidification of aqueous silicate solutions. U.S. Pat. No. 5,230,833 describes a method for preparing colloidal silica particles in solution.

[0015] In some embodiments, the silica abrasive is colloidal silica. As known to those skilled in the art, colloidal silica is a suspension of fine, amorphous, non-porous, and typically spherical particles in a liquid phase. Colloidal silica can be in the form of condensation-polymerized or precipitated silica particles. In some embodiments, the silica is in the form of wet-process silica particles. The particles, such as colloidal silica, can have any suitable average size (i.e., average particle diameter). If the average particle size of the abrasive particles is too small, the polishing composition may not exhibit a sufficient removal rate. In contrast, if the average particle size of the abrasive particles is too large, the polishing composition may exhibit undesirable polishing performance, such as a poor substrate defect rate.

[0016] Thus, the silica abrasive (e.g., silica particles or colloidal silica particles) can have an average particle size of about 10 nm or more, e.g., about 15 nm or more, about 20 nm or more, about 25 nm or more, about 30 nm or more, about 35 nm or more, about 40 nm or more, about 45 nm or more, or about 50 nm or more. Alternatively or additionally, the silica abrasive can have an average particle size of about 200 nm or less, e.g., about 175 nm or less, about 150 nm or less, about 125 nm or less, about 100 nm or less, about 75 nm or less, about 50 nm or less, or about 40 nm or less. Thus, the silica abrasive can have an average particle size bounded by any two of the foregoing endpoints.

[0017] For example, silica abrasives (e.g., silica particles or colloidal silica particles) can have an average particle size of about 10 nm to about 200 nm, about 20 nm to about 200 nm, about 20 nm to about 175 nm, about 20 nm to about 150 nm, about 25 nm to about 125 nm, about 25 nm to about 100 nm, about 30 nm to about 100 nm, about 30 nm to about 75 nm, about 30 nm to about 40 nm, or about 50 nm to about 100 nm. For non-spherical silica abrasive particles, the particle size is the diameter of the smallest sphere that encompasses the particle. In some embodiments, the silica abrasive has an average particle size of about 25 nm to about 100 nm. In certain embodiments, the silica abrasive has an average particle size of about 30 nm to about 75 nm. Without wishing to be bound by any particular theory, it is believed that smaller abrasive particles (e.g., less than about 100 nm) provide a lower silicon oxide (e.g., TEOS) removal rate and therefore better selectivity to boron-polysilicon. The particle size of the abrasive can be measured using any suitable technique, for example, using laser diffraction techniques. Suitable particle size measuring instruments are available, for example, from Malvern Instruments (Malvern, UK).

[0018] Silica abrasives (e.g., silica particles or colloidal silica particles) are preferably colloidally stable in the polishing composition. The term colloid refers to a suspension of particles in a liquid carrier (e.g., water). Colloidal stability refers to the maintenance of that suspension over time. In the context of the present invention, an abrasive is considered colloidally stable if, when the abrasive is placed in a 100 mL graduated cylinder and left unstirred for two hours, the difference between the particle concentration ([B] (in g / mL)) in the bottom 50 mL of the graduated cylinder and the particle concentration ([T] (in g / mL)) in the top 50 mL of the graduated cylinder, divided by the initial particle concentration in the abrasive composition, is 0.5 or less (i.e., {[B]-[T]} / [C]≦0.5). More preferably, the value of [B]-[T] / [C] is 0.3 or less, and most preferably 0.1 or less.

[0019] The silica abrasive can be present in the polishing composition in any suitable amount. If the polishing composition of the present invention contains too little abrasive, the composition may not exhibit a sufficient removal rate. In contrast, if the polishing composition contains too much abrasive, the polishing composition may exhibit undesirable polishing performance, may not be cost-effective, and / or may lack stability. The polishing composition may contain about 10 wt% or less of silica abrasive, for example, about 9 wt% or less, about 8 wt% or less, about 7 wt% or less, about 6 wt% or less, about 5 wt% or less, about 4 wt% or less, about 3 wt% or less, about 2 wt% or less, about 1 wt% or less, about 0.9 wt% or less, about 0.8 wt% or less, about 0.7 wt% or less, about 0.6 wt% or less, or about 0.5 wt% or less of silica abrasive. Alternatively or additionally, the polishing composition can comprise about 0.001 wt.% or more of silica abrasive, e.g., about 0.005 wt.% or more, about 0.01 wt.% or more, 0.05 wt.% or more, about 0.1 wt.% or more, about 0.2 wt.% or more, about 0.3 wt.% or more, about 0.4 wt.% or more, about 0.5 wt.% or more, or about 1 wt.% or more of silica abrasive. Thus, the polishing composition can optionally comprise any amount of silica abrasive bounded by any two of the foregoing endpoints.

[0020] For example, in some embodiments, the silica abrasive is present in the polishing composition in an amount of about 0.001% to about 10% by weight of the polishing composition, e.g., about 0.001% to about 8% by weight, about 0.001% to about 6% by weight, about 0.001% to about 5% by weight, about 0.001% to about 4% by weight, about 0.001% to about 2% by weight, about 0.001% to about 1% by weight, about 0.001% to about 10% by weight, or about 0.001% to about 10% by weight. ~0.05% by weight, approximately 0.01% by weight ~ approximately 10% by weight, approximately 0.01% by weight ~ approximately 8% by weight, approximately 0.01% by weight ~ approximately 6% by weight, approximately 0.01% by weight ~ approximately 5% by weight, approximately 0.01% by weight ~ approximately 4 weight% Amount%, about 0.01% to about 2% by weight, about 0.01% to about 1% by weight, about 0.025% to about 10% by weight, about 0.025% to about 8% by weight, about 0.025% to about 6% by weight, about 0 .025% to about 5% by weight, about 0.025% to about 4% by weight, about 0.025% to about 2% by weight, about 0.025% to about 1% by weight, about 0.1% to about 10% by weight, about 0.1% by weight % to about 8% by weight, about 0.1% to about 6% by weight, about 0.1% to about 5% by weight, about 0.1% to about 4% by weight, about 0.1% to about 2% by weight, about 0.1% to about 1% by weight, about 0.5% by weight The silica abrasive may be present in an amount of about 0.001 wt% to about 10 wt%, about 0.5 wt% to about 8 wt%, about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 4 wt%, about 0.5 wt% to about 2 wt%, about 0.5 wt% to about 1 wt%, about 1 wt% to about 10 wt%, about 1 wt% to about 8 wt%, about 1 wt% to about 6 wt%, about 1 wt% to about 5 wt%, about 1 wt% to about 4 wt%, or 1 wt% to about 2 wt%. In some embodiments, the polishing composition comprises about 0.001 wt% to about 10 wt% silica abrasive. In certain embodiments, the polishing composition comprises about 0.05 wt% to about 5 wt% silica abrasive. In other embodiments, the polishing composition comprises about 0.001 wt% to about 0.05 wt% silica abrasive.

[0021] The chemical-mechanical polishing composition includes an oxidizing agent, which can be any suitable compound capable of oxidizing a substrate (e.g., boron-doped polysilicon, silicon nitride, silicon oxide, or titanium nitride). For example, the oxidizing agent can be selected from oxone, ceric ammonium nitrate, peroxides (e.g., hydrogen peroxide), periodates (e.g., sodium periodate or potassium periodate), iodates (e.g., sodium iodate, potassium iodate, or ammonium iodate), persulfates (e.g., sodium persulfate, potassium persulfate, or ammonium persulfate), chlorates (e.g., sodium chlorate or potassium chlorate), chromates (e.g., sodium chromate or potassium chromate), permanganates (e.g., sodium permanganate, potassium permanganate, or ammonium permanganate), bromates (e.g., sodium bromate or potassium bromate), perbromates (e.g., sodium perbromate or potassium perbromate), ferrates (e.g., potassium ferrate), perrhenates (e.g., ammonium perrhenate), perruthenates (e.g., tetrapropylammonium perruthenate), and combinations thereof. The oxidizing agent can be in acid form (e.g., persulfuric acid), salt form (e.g., ammonium persulfate), or mixtures thereof. In some embodiments, the oxidizing agent comprises an alkali metal (e.g., sodium or potassium) salt of peroxide, periodate, iodate, persulfate, chlorate, chromate, permanganate, bromate, perbromate, ferrate, perrhenate, perruthenate, or combinations thereof.

[0022] In certain embodiments, the oxidizing agent is selected from a permanganate (e.g., sodium permanganate, potassium permanganate, or ammonium permanganate), cerium ammonium nitrate, and combinations thereof. In some embodiments, the oxidizing agent is cerium ammonium nitrate. In other embodiments, the oxidizing agent is a permanganate (e.g., sodium permanganate, potassium permanganate, or ammonium permanganate), such as potassium permanganate.

[0023] The polishing composition can include any suitable amount of oxidizing agent. The polishing composition can include about 20 wt% or less of oxidizing agent, for example, about 15 wt% or less, about 10 wt% or less, about 9 wt% or less, about 8 wt% or less, about 7 wt% or less, about 6 wt% or less, about 5 wt% or less, about 4 wt% or less, about 3 wt% or less, or about 2 wt% or less of oxidizing agent. Alternatively or additionally, the polishing composition can include about 0.1 wt% or more of oxidizing agent, for example, about 0.5 wt% or more, about 1 wt% or more, about 2 wt% or more, about 3 wt% or more, about 4 wt% or more, or about 5 wt% or more of oxidizing agent. Thus, the polishing composition can optionally include an oxidizing agent in any amount bounded by any two of the foregoing endpoints.

[0024] For example, in some embodiments, the oxidizing agent is present in the polishing composition in an amount of about 0.1 wt % to about 20 wt %, about 0.1 wt % to about 15 wt %, about 0.1 wt % to about 10 wt %, about 0.1 wt % to about 9 wt %, about 0.1 wt % to about 8 wt %, about 0.1 wt % to about 7 wt %, about 0.1 wt % to about 6 wt %, about 0.1 wt % to about 5 wt %, about 0.1 wt % to about 4 wt %, about 0.1 wt % to about 3 wt %, or about 0.1 wt % to about 2% by weight, about 0.5% to about 20% by weight, about 0.5% to about 15% by weight, about 0.5% to about 10% by weight, about 0.5% to about 9% by weight, about 0.5% to about 8% by weight, about 0.5% to about 7% by weight , about 0.5% to about 6% by weight, about 0.5% to about 5% by weight, about 0.5% to about 4% by weight, about 0.5% to about 3% by weight, about 0.5% to about 2% by weight, about 1% to about 20% by weight, about 1% to about 1% by weight 15% by weight, about 1% to about 10% by weight, about 1% to about 9% by weight, about 1% to about 8% by weight, about 1% to about 7% by weight, about 1% to about 6% by weight, about 1% to about 5% by weight, about 1% to about 4% by weight, About 1% to about 3% by weight, about 1% to about 2% by weight, about 2% to about 20% by weight, about 2% to about 15% by weight, about 2% to about 10% by weight, about 2% to about 9% by weight, about 2% to about 8% by weight, about 2% by weight The oxidizing agent can be present in an amount of about 1 wt.% to about 7 wt.%, about 2 wt.% to about 6 wt.%, about 2 wt.% to about 5 wt.%, about 2 wt.% to about 4 wt.%, about 2 wt.% to about 3 wt.%, about 3 wt.% to about 20 wt.%, about 3 wt.% to about 15 wt.%, about 3 wt.% to about 10 wt.%, about 3 wt.% to about 9 wt.%, about 3 wt.% to about 8 wt.%, about 3 wt.% to about 7 wt.%, about 3 wt.% to about 6 wt.%, about 3 wt.% to about 5 wt.%, or about 3 wt.% to about 4 wt.%. In some embodiments, the polishing composition comprises at least 1 wt.% oxidizing agent, at least 2 wt.% oxidizing agent, or at least 3 wt.% oxidizing agent.

[0025] The polishing composition can contain ferric ions, cobalt ions, manganese ions, an organic acid, or a combination thereof.

[0026] The ferric ions can be provided in the form of any suitable ferric salt. A non-limiting example of a suitable ferric salt is ferric nitrate. The polishing composition can contain any suitable amount of ferric ions. For example, the polishing composition can contain about 0.005 wt % to about 1 wt % of ferric ions, such as about 0.01 wt % to about 0.9 wt %, about 0.02 wt % to about 0.8 wt %, about 0.03 wt % to about 0.6 wt %, about 0.03 wt % to about 0.4 wt %, about 0.03 wt % to about 0.2 wt %, or about 0.03 wt % to about 0.1 wt % of ferric ions.

[0027] In some embodiments, 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 about 0.01 wt. % or less, e.g., 0.005 wt. % or less, about 0.001 wt. % or less, or about 0.0001 wt. % or less, of ferric ions, or no ferric ions can be detected in the polishing composition.

[0028] The cobalt ions can be provided in the form of any suitable cobalt salt. A non-limiting example of a suitable cobalt salt is cobalt acetate. The polishing composition can contain any suitable amount of cobalt ions. For example, the polishing composition can contain about 0.005 wt % to about 1 wt % cobalt ions, such as about 0.01 wt % to about 0.9 wt %, about 0.02 wt % to about 0.8 wt %, about 0.03 wt % to about 0.6 wt %, about 0.03 wt % to about 0.4 wt %, about 0.03 wt % to about 0.2 wt %, or about 0.03 wt % to about 0.1 wt % cobalt ions.

[0029] In some embodiments, the polishing composition is substantially free of cobalt ions. In the context of the present invention, "substantially free of cobalt ions" means that the polishing composition contains about 0.01 wt. % or less, e.g., 0.005 wt. % or less, about 0.001 wt. % or less, or about 0.0001 wt. % or less, of cobalt ions, or no cobalt ions can be detected in the polishing composition.

[0030] The manganese ions can be provided in the form of any suitable manganese salt. A non-limiting example of a suitable manganese salt is manganese acetate. The polishing composition can contain any suitable amount of manganese ions. For example, the polishing composition can contain about 0.005 wt % to about 1 wt % manganese ions, such as about 0.01 wt % to about 0.9 wt %, about 0.02 wt % to about 0.8 wt %, about 0.03 wt % to about 0.6 wt %, about 0.03 wt % to about 0.4 wt %, about 0.03 wt % to about 0.2 wt %, or about 0.03 wt % to about 0.1 wt % manganese ions.

[0031] In some embodiments, the polishing composition is substantially free of manganese ions. In the context of the present invention, "substantially free of manganese ions" means that the polishing composition contains about 0.01 wt. % or less, e.g., 0.005 wt. % or less, about 0.001 wt. % or less, or about 0.0001 wt. % or less, of manganese ions, or no manganese ions can be detected in the polishing composition.

[0032] The polishing composition can include an organic acid. The organic acid can 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. In some embodiments, the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0033] The polishing composition can contain an organic acid at any suitable concentration. For example, the polishing composition can contain about 1 mM or more of the organic acid, e.g., about 2 mM or more, about 3 mM or more, about 4 mM or more, or about 5 mM or more. Alternatively or additionally, the polishing composition can contain about 100 mM or less of the organic acid, e.g., 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 of the organic acid. Thus, the polishing composition can contain any amount of the organic acid bounded by any two of the aforementioned endpoints. For example, the polishing composition can contain about 1 mM to about 20 mM of the organic acid, e.g., about 1 mM to about 15 mM, about 2 mM to about 15 mM, about 3 mM to about 15 mM, about 3 mM to about 12 mM, about 1 mM to about 12 mM, or about 1 mM to about 10 mM. In some embodiments, the polishing composition comprises about 1 mM to about 100 mM of an organic acid.

[0034] In some embodiments, the polishing composition is substantially free of organic acids. In the context of the present invention, "substantially free of organic acids" means that the polishing composition contains about 1 mM or less, e.g., about 0.5 mM or less, about 1 μM or less, or about 0.5 μM or less, of ferric ions, or no organic acids can be detected in the polishing composition. In certain embodiments, the polishing composition is substantially free of ferric ions, substantially free of cobalt ions, substantially free of manganese ions, and / or substantially free of organic acids.

[0035] The polishing composition includes water. The water may be any suitable water, such as deionized water or distilled water. In some embodiments, the polishing composition may further include one or more organic solvents in combination with water. For example, the polishing composition may further include a hydroxyl solvent, such as methanol or ethanol, a ketone solvent, an amide solvent, or a sulfoxide solvent.

[0036] The polishing composition can have any suitable pH. Typically, the polishing composition has a pH of about 2 or less, for example, about 1.8 or less, about 1.6 or less, about 1.5 or less, about 1.4 or less, about 1.2 or less, about 1 or less, about 0.8 or less, about 0.6 or less, or about 0.5 or less. Alternatively or additionally, the polishing composition can have a pH of about -2 or more, for example, about -1.5 or more, about -1 or more, about 0.5 or more, about 0 or more, about 0.2 or more, about 0.4 or more, or about 0.5 or more. Thus, the polishing composition can have a pH limited by any two of the aforementioned endpoints. For example, the polishing composition may have a pH of from about −2 to about 2, e.g., from about −1.5 to about 2, from about −1 to about 2, from about −0.5 to about 2, from about 0 to about 2, from about 0.2 to about 2, from about 0.4 to about 2, from about 0.5 to about 2, from about −2 to about 1.8, from about −1.5 to about 1.8, from about −1 to about 1.8, from about −0.5 to about 1.8, from about 0 to about 1.8, from about 0.2 to about 1.8, from about 0.4 to about 1.8, from about 0.5 to about 1.8, The polishing composition can have a pH of about -2 to about 1.5, about -1.5 to about 1.5, about -1 to about 1.5, about -0.5 to about 1.5, about 0 to about 1.5, about 0.2 to about 1.5, about 0.4 to about 1.5, about 0.5 to about 1.5, about -2 to about 1, about -1.5 to about 1, about -1 to about 1, about -0.5 to about 1, about 0 to about 1, about 0.2 to about 1, about 0.4 to about 1, or about 0.5 to about 1. In some embodiments, the chemical-mechanical polishing composition has a pH of about 2 or less. In specific embodiments, the polishing composition has a pH of about 1.5 or less, or a pH of about 1 or less. In other embodiments, the polishing composition has a pH of about 0 to about 2, or a pH of about 0 to about 1.5.

[0037] The pH of the polishing composition can 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.

[0038] In some embodiments, the polishing composition further comprises a buffering agent. The buffering agent can be any suitable compound capable of buffering (e.g., maintaining) the polishing composition at a specific pH range. For example, the buffering agent can be selected from ammonium salts, alkali metal salts, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, borates, amino acids, and combinations thereof.

[0039] The chemical-mechanical polishing composition optionally further comprises one or more additives, such as conditioners, acids (e.g., sulfonic acids), complexing agents, chelating agents, biocides, scale inhibitors, and dispersants.

[0040] In some embodiments, the polishing composition further comprises a biocide. Non-limiting examples of suitable biocides include isothiazolinone biocides such as Kordek MLX™ (DuPont, Wilmington, DE). The polishing composition can comprise any suitable amount of biocide. For example, the polishing composition can comprise about 0.001 wt % to about 0.2 wt % of the biocide.

[0041] In some embodiments, the present invention provides a chemical-mechanical polishing composition comprising, consisting essentially of, or consisting of: (a) a silica abrasive; (b) at least 1 wt. % permanganate (e.g., potassium permanganate); and (c) water, wherein the chemical-mechanical polishing composition has a pH of about 2 or less.

[0042] In another embodiment, the present invention provides a chemical-mechanical polishing composition comprising, consisting essentially of, or consisting of: (a) a silica abrasive; (b) at least 1 wt. % cerium ammonium nitrate; and (c) water, wherein the chemical-mechanical polishing composition has a pH of about 2 or less.

[0043] The polishing composition can be manufactured by any suitable technique, many of which are known to those skilled in the art. The polishing composition can be prepared by a batch process or a continuous process. Generally, the polishing composition is prepared by combining the components of the polishing composition. As used herein, the term "component" includes individual components (e.g., silica abrasive, oxidizing agent, optional pH adjuster, and / or any optional additives) and any combination of components (e.g., silica abrasive, oxidizing agent, optional pH adjuster, and / or any optional additives, etc.).

[0044] For example, the polishing composition can be prepared by (i) providing all or part of a liquid carrier; (ii) dispersing a silica abrasive, an oxidizing agent, an optional pH adjuster, and / or any optional additives using any suitable means for preparing such a dispersion; (iii) adjusting the pH of the dispersion as needed; and (iv) optionally adding appropriate amounts of other optional components and / or additives to the mixture.

[0045] Alternatively, the polishing composition can be prepared by (i) providing one or more components (e.g., an oxidizer, an optional pH adjuster, and / or any optional additives) in a silica abrasive slurry, (ii) providing one or more components (e.g., a liquid carrier, an oxidizer, an optional pH adjuster, and / or any optional additives) in an additive solution, (iii) combining the silica abrasive slurry and the additive solution to form a mixture, (iv) optionally adding appropriate amounts of any other optional additives to the mixture, and (v) adjusting the pH of the mixture as needed.

[0046] The polishing composition can be supplied as a one-package system containing a silica abrasive, an oxidizing agent, an optional pH adjuster, and / or optional additives, and water. Alternatively, the polishing composition of the present invention can be supplied as a two-package system containing a silica abrasive slurry in a first package and an additive solution in a second package, where the silica abrasive slurry consists essentially of or consists of a silica abrasive and water, and the additive solution consists essentially of or consists of an oxidizing agent, an optional pH adjuster, and / or any optional additives. The two-package system allows the properties of the polishing composition to be adjusted by changing the mixing ratio of the two packages, i.e., the silica abrasive slurry and the additive solution.

[0047] Various methods can be employed to utilize such a two-package polishing system. For example, the silica abrasive slurry and the additive solution can be delivered to the polishing table through separate pipes that are joined and connected at the outlet of the supply pipe. The silica abrasive slurry and the additive solution can be mixed immediately before polishing or immediately before polishing, or can be supplied simultaneously onto the polishing table. Furthermore, when the two packages are mixed, deionized water can be added as needed to adjust the polishing composition and the resulting substrate polishing characteristics.

[0048] Similarly, in connection with the present invention, three, four, or more packaging systems can be utilized, with each of the multiple containers containing a different component of the chemical mechanical polishing composition of the present invention, one or more optional components, and / or different concentrations of one or more of the same components.

[0049] To mix components contained in two or more storage devices to produce a polishing composition at or near the point of use, the storage devices typically include one or more flow lines leading from each storage device to the point of use of the polishing composition (e.g., a platen, a polishing pad, or a substrate surface). As used herein, the term "point of use" refers to the point at which the polishing composition is applied to the substrate surface (e.g., a polishing pad or the substrate surface itself). The term "flow line" refers to the flow path from an individual storage container to the point of use of the components stored therein. Each flow line can lead directly to the point of use, or two or more flow lines can be combined at any point into a single flow line leading to the point of use. Furthermore, any of the flow lines (e.g., individual flow lines or combined flow lines) can first be connected to one or more other devices (e.g., pumping devices, metering devices, mixing devices, etc.) before reaching the point of use of the component.

[0050] The components of the polishing composition can be delivered independently to the point of use (e.g., delivered to the substrate surface where they are mixed during the polishing process), or one or more of the components can be combined prior to delivery to the point of use, e.g., immediately before or immediately before delivery to the point of use. Components are combined "immediately before delivery to the point of use" if they are combined about 5 minutes or more before being added in mixed form to the platen, e.g., about 4 minutes or more before being added in mixed form to the platen, about 3 minutes or more before being added, about 2 minutes or more before being added, about 1 minute or more before being added, about 45 seconds or more before being added, about 30 seconds or more before being added, about 10 seconds or more before being added, or simultaneously with delivery of the components at the point of use (e.g., the components are combined in a dispenser). Components are also combined "immediately before delivery to the point of use" if they are combined within 5 m of the point of use, e.g., within 1 m of the point of use, or within 10 cm of the point of use (e.g., within 1 cm of the point of use).

[0051] When two or more components of the polishing composition are combined before reaching the point of use, the components can be combined in a flow line and delivered to the point of use without using a mixing device. Alternatively, one or more flow lines can lead to the mixing device to facilitate the combination of the two or more components. Any suitable mixing device can be used. For example, the mixing device can be a nozzle or jet (e.g., a high-pressure nozzle or jet) through which two or more components flow. Alternatively, the mixing device can be a container-type mixing device that includes one or more inlets through which two or more components of the polishing slurry are introduced into the mixer and at least one outlet through which the mixed components exit the mixer to be delivered to the point of use directly or via other elements of the apparatus (e.g., via one or more flow lines). Furthermore, the mixing device can include two or more chambers, each chamber having at least one inlet and at least one outlet, and two or more components are combined in each chamber. When a container-type mixing device is used, the mixing device preferably includes a mixing mechanism to further facilitate the mixing of the components. Mixing mechanisms are commonly known in the art and include stirrers, blenders, agitators, paddle baffles, gas sparger systems, vibrators, and the like.

[0052] The polishing composition can 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 contains the components of the polishing composition in amounts such that, upon dilution of 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, the silica abrasive, oxidizer, optional pH adjuster, and / or any optional additives can each be present in the concentrate in an amount about two times (e.g., about three times, about four times, or about five times) higher than the concentrations described above for each component, and upon dilution of the concentrate with an equal volume of water (e.g., two, three, or four equal volumes of water, respectively), each component will be present in the polishing composition in an amount within the range described above for each component. Furthermore, as will be understood by those skilled in the art, the concentrate can contain an appropriate proportion of the water present in the final polishing composition to ensure that the silica abrasive, oxidizer, optional pH adjuster, and / or any optional additives are at least partially or completely dissolved in the concentrate.

[0053] The present invention further 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) a silica abrasive; (b) an oxidizing agent; and (c) water, the chemical-mechanical polishing composition having a pH of about 2 or less; (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 polish at least a portion of the substrate.

[0054] The substrate can be any suitable substrate. In certain embodiments, the substrate comprises boron-doped polysilicon, such as a boron-polysilicon alloy. Thus, the method may include a substrate comprising a boron-doped polysilicon layer on a surface of the substrate, wherein at least a portion of the boron-doped polysilicon layer on the surface of the substrate is polished to polish the substrate. Alternatively or additionally, the substrate may comprise a silicon nitride layer on a surface of the substrate, a silicon oxide layer on a surface of the substrate, a titanium nitride layer on a surface of the substrate, or a combination thereof. For example, the method may include a substrate comprising: (i) a silicon nitride layer on a surface of the substrate, wherein at least a portion of the silicon nitride layer on the surface of the substrate is polished to polish the substrate; (ii) a silicon oxide layer on a surface of the substrate, wherein at least a portion of the silicon oxide layer on the surface of the substrate is polished to polish the substrate; and / or (iii) a titanium nitride layer on a surface of the substrate, wherein at least a portion of the titanium nitride layer on the surface of the substrate is polished to polish the substrate. In certain embodiments, the substrate comprises a boron-doped polysilicon layer on the surface of the substrate in combination with a silicon oxide layer, a silicon nitride layer, and / or a titanium nitride layer on the surface of the substrate.

[0055] 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. Generally, the boron-doped polysilicon layer comprises at least 75% by weight boron, at least 80% by weight boron, at least 85% by weight boron, or at least 90% by weight boron. For example, the boron-doped polysilicon layer may contain about 75% to about 99.9% by weight of boron, e.g., 75% to about 99% by weight, about 75% to about 95% by weight, about 75% to about 90% by weight, about 80% to about 99.9% by weight, about 80% to about 99% by weight, about 80% to about 99% by weight, about 80% to about 95% by weight, about 80% to about 90% by weight, about 85% to about 99.9% by weight, about 85% to about 99% by weight, about 85% to about 95% by weight, about 85% to about 90% by weight, about 90% to about 99.9% by weight, about 90% to about 99% by weight, about 90% to about 95% by weight, about 95% to about 99.9% by weight, or about 95% to about 99% by weight. Without wishing to be bound by any particular theory, it is believed that the compositions and methods provided herein are particularly suitable for polishing boron-doped polysilicon having high levels of boron doping (e.g., about 75% by weight or more, about 80% by weight or more, about 85% by weight or more, or about 90% by weight or more).

[0056] The polishing composition of the present invention desirably exhibits a high removal rate when polishing a substrate comprising boron-doped polysilicon according to the method of the present invention.For example, when polishing a silicon wafer comprising a boron-doped polysilicon layer according to one embodiment of the present invention, the polishing composition desirably exhibits a removal rate of about 500 Å / min or more, for example, 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, The boron doped polysilicon removal rates are about 1400 Å / min or greater, about 1500 Å / min or greater, about 1600 Å / min or greater, about 1700 Å / min or greater, about 1800 Å / min or greater, about 1900 Å / min or greater, about 2000 Å / min or greater, about 2100 Å / min or greater, about 2200 Å / min or greater, about 2300 Å / min or greater, about 2400 Å / min or greater, about 2500 Å / min or greater, about 2600 Å / min or greater, about 2700 Å / min or greater, about 2800 Å / min or greater, about 2900 Å / min or greater, or about 3000 Å / min or greater.

[0057] In some embodiments where the substrate further comprises silicon oxide, the silicon oxide can be any suitable silicon oxide, many of which are known in the art. Suitable types of silicon oxide include, but are not limited to, borophosphosilicate glass (BPSG), tetraethyl orthosilicate (TEOS), plasma-enhanced tetraethyl orthosilicate (PETEOS), thermal oxide, undoped silicate glass, and high-density plasma (HDP) oxide. When polishing a substrate comprising silicon oxide according to the method of the present invention, the chemical mechanical polishing composition of the present invention desirably exhibits a low silicon oxide removal rate. For example, when polishing a substrate comprising silicon oxide according to one embodiment of the present invention, the polishing composition desirably exhibits a silicon oxide removal rate of about 500 Å / min or less, for example, about 250 Å / min or less, about 200 Å / min or less, about 150 Å / min or less, about 100 Å / min or less, about 50 Å / min or less, about 25 Å / min or less, about 10 Å / min or less, or about 5 Å / min or less. In some embodiments, the polishing composition exhibits a silicon oxide removal rate that is too low to be detected.

[0058] In some embodiments, the substrate further comprises silicon nitride, and the silicon nitride can be any suitable silicon nitride, many of which are known in the art. The chemical-mechanical polishing composition of the present invention desirably exhibits a low silicon nitride removal rate when polishing a substrate comprising silicon nitride according to the method of the present invention. For example, when polishing a substrate comprising silicon nitride according to one embodiment of the present invention, the polishing composition desirably exhibits a silicon nitride removal rate of about 500 Å / min or less, e.g., about 250 Å / min or less, about 200 Å / min or less, about 150 Å / min or less, about 100 Å / min or less, about 50 Å / min or less, about 25 Å / min or less, about 10 Å / min or less, or about 5 Å / min or less. In some embodiments, the polishing composition exhibits a silicon nitride removal rate that is too low to be detected.

[0059] In some embodiments, the substrate may be a carbon film. These carbon film examples can be grown using a variety of methods known in the art, including PECVD, spin-on, and the like. The resulting films can have a wide range of properties (hardness, zeta potential, hydrophobicity, and the like). These carbon film substrates can be polished with formulations of the present invention, such as the same formulation described in Inventive Example 3, and exhibit high removal rates. Slurries containing cerium ammonium nitrate and less than 0.1% solids can polish these films with high carbon removal rates and high selectivity to the underlying silicon oxide or silicon nitride films.

[0060] In some embodiments, the substrate further comprises titanium nitride, and the titanium nitride can be any suitable titanium nitride, many of which are known in the art. The chemical-mechanical polishing composition of the present invention desirably exhibits a low titanium nitride removal rate when polishing a substrate comprising titanium nitride according to the method of the present invention. For example, when polishing a substrate comprising titanium nitride according to one embodiment of the present invention, the polishing composition desirably exhibits a titanium nitride removal rate of about 500 Å / min or less, e.g., about 250 Å / min or less, about 200 Å / min or less, about 150 Å / min or less, about 100 Å / min or less, about 50 Å / min or less, about 25 Å / min or less, about 10 Å / min or less, or about 5 Å / min or less. In some embodiments, the polishing composition exhibits a titanium nitride removal rate that is too low to be detected.

[0061] The chemical mechanical polishing composition of the present invention can be tailored to provide effective polishing in a desired polishing range that is selective to a specific thin layer material while minimizing surface imperfections, defects, corrosion, erosion, and removal of the stop layer. Selectivity can be controlled to some extent by varying the relative concentrations of the components of the polishing composition. If desired, the chemical mechanical polishing composition of the present invention can be used to polish a substrate comprising boron-doped polysilicon and silicon oxide on a surface layer, and the chemical mechanical polishing composition provides a boron-doped polysilicon to silicon oxide polishing selectivity of about 5:1 or greater (e.g., about 10:1 or greater, about 15:1 or greater, about 25:1 or greater, about 50:1 or greater, about 100:1 or greater, or about 150:1 or greater). The chemical mechanical polishing composition of the present invention can also be used to polish a substrate comprising boron-doped polysilicon and silicon nitride on a surface layer, where the chemical mechanical polishing composition provides a boron-doped polysilicon to silicon nitride polishing selectivity of about 5:1 or greater (e.g., about 10:1 or greater, about 15:1 or greater, about 25:1 or greater, about 50:1 or greater, about 100:1 or greater, or about 150:1 or greater). The chemical mechanical polishing composition of the present invention can also be used to polish a substrate comprising boron-doped polysilicon and titanium nitride on a surface layer, where the chemical mechanical polishing composition provides a boron-doped polysilicon to titanium nitride polishing selectivity of about 5:1 or greater (e.g., about 10:1 or greater, about 15:1 or greater, about 25:1 or greater, about 50:1 or greater, about 100:1 or greater, or about 150:1 or greater). Thus, in embodiments, when used to polish a substrate comprising at least one layer of boron-doped polysilicon and at least one layer of silicon oxide, at least one layer of silicon nitride, and / or at least one layer of titanium nitride, the polishing composition and polishing method enable preferential removal of the boron-doped polysilicon relative to the removal of the silicon oxide, silicon nitride, and / or titanium nitride. As used herein, the phrase "polishing selectivity" refers to the ratio of the removal rates of two different thin-layer materials.

[0062] The polishing composition of the present invention preferably exhibits low particle defects when polishing a substrate, as determined by a suitable technique. The particle defects on a substrate polished with the polishing composition of the present invention can be determined by any suitable technique. For example, laser light scattering techniques such as dark field normal beam composite (DCN) and dark field oblique beam composite (DCO) can be used to determine the particle defects on the polished substrate. Suitable instruments for evaluating particle defect rates are available, for example, from KLA-Tencor (for example, a SURFSCAN™ SPI instrument operating at a threshold of 120 nm or 160 nm).

[0063] The chemical mechanical polishing composition and method of the present invention are particularly suitable for use in conjunction with a chemical mechanical polishing device. Typically, the device comprises a platen that moves during use and has a speed resulting from orbital, linear, or circular motion, a polishing pad that contacts the platen and moves with the platen during movement, and a carrier that holds the substrate to be polished by contacting and moving the substrate against the surface of the polishing pad. The substrate is polished by contacting the substrate with the polishing pad and the polishing composition of the present invention, and then moving the polishing pad relative to the substrate to polish at least a portion of the substrate.

[0064] The substrate can be polished with the chemical mechanical polishing composition using any suitable polishing pad (e.g., polishing surface). Suitable polishing pads include, for example, woven and nonwoven polishing pads. Furthermore, suitable polishing pads can include any suitable polymer with various densities, hardnesses, thicknesses, compressibility, rebound capacity upon compression, and compression moduli. Suitable polymers include, for example, polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbon, polycarbonate, polyester, polyacrylate, polyether, polyethylene, polyamide, polyurethane, polystyrene, polypropylene, co-molded products thereof, and mixtures thereof. Soft polyurethane polishing pads are particularly useful in conjunction with the polishing method of the present invention. Exemplary pads include, but are not limited to, SURFIN™ 000, SURFIN™ SSW1, SPM3100 (e.g., commercially available from Eminess Technologies), POLITEX™, EPIC™ D100 pad (commercially available from CMC Materials), IC1010 pad (commercially available from Dow, Inc.), and Fujibo POLYPAS™ 27.

[0065] Preferably, the chemical mechanical polishing apparatus further includes 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 illumination reflected from the surface of the substrate being polished are known in the art. Such methods are described, for example, in U.S. Pat. Nos. 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. Desirably, inspecting or monitoring the progress of the polishing process relative to the substrate being polished allows for the determination of the polishing endpoint, i.e., when to terminate the polishing process for a particular substrate.

[0066] The substrate can be polished with any suitable downforce. For example, the substrate can be polished with a downforce of about 1 psi or more, about 2 psi or more, about 3 psi or more, about 4 psi or more, or about 5 psi or more. Alternatively or additionally, the substrate can be polished with a downforce of about 10 psi or less, about 8 psi or less, about 6 psi or less, about 4 psi or less, or about 2 psi or less. Thus, the substrate can be polished with a downforce bounded by any two of the aforementioned endpoints. For example, the substrate can be polished with a downforce of about 1 psi to about 10 psi, about 2 psi to about 10 psi, about 1 psi to about 8 psi, about 2 psi to about 8 psi, about 1 psi to about 6 psi, about 2 psi to about 6 psi, about 1 psi to about 4 psi, or about 2 psi to about 4 psi.

[0067] In some embodiments, 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) a silica abrasive; (b) at least 1 wt. % permanganate (e.g., potassium permanganate); and (c) water, the chemical-mechanical polishing composition having a pH of about 2 or less; (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 polish at least a portion of the substrate, wherein the substrate comprises a boron-doped polysilicon layer on a surface of the substrate, and at least a portion of the boron-doped polysilicon layer on the surface of the substrate is polished to polish the substrate.

[0068] In some embodiments, 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) a silica abrasive; (b) at least 1 wt. % cerium ammonium nitrate; and (c) water, the chemical mechanical polishing composition having a pH of about 2 or less; (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 polish at least a portion of the substrate, wherein the substrate comprises a boron-doped polysilicon layer on a surface of the substrate, and at least a portion of the boron-doped polysilicon layer on the surface of the substrate is polished to polish the substrate.

[0069] Aspects (including embodiments) of the invention described herein may be useful alone or in combination with one or more other aspects or embodiments. Without limiting the above description, specific, non-limiting embodiments of the present disclosure, numbered 1 through 55, are provided below. As will be apparent to one of skill in the art upon reading this disclosure, each individually numbered embodiment may be used or combined with any preceding or succeeding individually numbered embodiment. This is intended to support all such combinations of embodiments, and is not limited to the combinations of embodiments explicitly provided below.

[0070] Embodiment (1) In embodiment (1), (a) Silica abrasive; (b) an oxidizing agent; and (c) a chemical-mechanical polishing composition comprising water, A chemical-mechanical polishing composition is presented having a pH of about 2 or less.

[0071] (2) In embodiment (2), there is provided the polishing composition of embodiment (1), wherein the polishing composition has a pH of about 1.5 or less.

[0072] (3) In embodiment (3), there is provided the polishing composition of embodiment (1) or embodiment (2), wherein the polishing composition has a pH of about 1 or less.

[0073] (4) In embodiment (4), the polishing composition of any one of embodiments (1) to (3) is provided, wherein the polishing composition comprises about 0.001 wt % to about 10 wt % of a silica abrasive.

[0074] (5) In embodiment (5), the polishing composition of any one of embodiments (1) to (4) is provided, wherein the polishing composition comprises about 0.05 wt % to about 5 wt % of a silica abrasive.

[0075] (6) In embodiment (6), there is provided the polishing composition of any one of embodiments (1) to (5), wherein the silica abrasive is colloidal silica.

[0076] (7) In embodiment (7), there is provided the polishing composition of any one of embodiments (1) to (6), wherein the silica abrasive has an average particle size of about 25 nm to about 100 nm.

[0077] (8) In embodiment (8), there is provided the polishing composition of any one of embodiments (1) to (7), wherein the silica abrasive has an average particle size of about 30 nm to about 75 nm.

[0078] (9) In embodiment (9), there is provided the polishing composition according to any one of embodiments (1) to (8), wherein the oxidizing agent is selected from oxone, cerium ammonium nitrate, peroxide, periodate, iodate, persulfate, chlorate, chromate, permanganate, bromate, perbromate, ferrate, perrhenate, perruthenate, and combinations thereof.

[0079] (10) In embodiment (10), there is provided the polishing composition according to any one of embodiments (1) to (9), wherein the oxidizing agent is selected from permanganate, cerium ammonium nitrate, and combinations thereof.

[0080] (11) In embodiment (11), there is provided the polishing composition of any one of embodiments (1) to (10), wherein the oxidizing agent is cerium ammonium nitrate.

[0081] (12) In embodiment (12), there is provided the polishing composition of any one of embodiments (1) to (10), wherein the oxidizing agent is potassium permanganate.

[0082] (13) In embodiment (13), there is provided the polishing composition of any one of embodiments (1) to (12), wherein the polishing composition comprises at least 1 wt. % of an oxidizing agent.

[0083] (14) In embodiment (14), there is provided the polishing composition of any one of embodiments (1) to (13), wherein the polishing composition comprises at least 2 wt. % of an oxidizing agent.

[0084] (15) In embodiment (15), there is provided the polishing composition of any one of embodiments (1) to (14), wherein the polishing composition comprises at least 3 wt. % of an oxidizing agent.

[0085] (16) In embodiment (16), there is provided the polishing composition of any one of embodiments (1) to (15), wherein the polishing composition further comprises ferric ions.

[0086] (17) In embodiment (17), the polishing composition of embodiment (16) is provided, wherein the polishing composition comprises about 0.01 wt % to about 1 wt % of ferric ions.

[0087] (18) In embodiment (18), there is provided the polishing composition of any one of embodiments (1) to (15), wherein the polishing composition is substantially free of ferric ions.

[0088] (19) In embodiment (19), there is provided the polishing composition according to any one of embodiments (1) to (18), wherein the polishing composition further comprises an organic acid.

[0089] (20) In embodiment (20), there is provided the polishing composition according to embodiment (19), wherein the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0090] (21) In embodiment (21), there is provided the polishing composition according to embodiment (19) or embodiment (20), wherein the polishing composition comprises about 1 mM to about 100 mM of an organic acid.

[0091] (22) In embodiment (22), there is provided the polishing composition of any one of embodiments (1) to (18), wherein the polishing composition is substantially free of organic acids.

[0092] (23) In embodiment (23), there is provided the polishing composition of any one of embodiments (1) to (22), wherein the polishing composition further comprises a buffering agent.

[0093] (24) In embodiment (24), there is provided the polishing composition of embodiment (23), wherein the buffering agent is selected from ammonium salts, alkali metal salts, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, borates, amino acids, and combinations thereof.

[0094] (25) In embodiment (25), there is provided a method for chemically mechanically polishing a substrate, the method comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) A chemical-mechanical polishing composition comprising: (a) Silica abrasive; (b) an oxidizing agent; and (c) water, providing a chemical-mechanical polishing composition having a pH of about 2 or less; (iv) contacting the substrate with a polishing pad and a chemical-mechanical polishing composition; (v) polishing at least a portion of the substrate and moving the polishing pad and chemical-mechanical polishing composition relative to the substrate to polish the substrate.

[0095] (26) In embodiment (26), the method of embodiment (25) is provided, wherein the polishing composition has a pH of about 1.5 or less.

[0096] (27) In embodiment (27), the method of embodiment (25) or embodiment (26) is provided, wherein the polishing composition has a pH of about 1 or less.

[0097] (28) In embodiment (28), the method of any one of embodiments (25) through (27) is provided, wherein the polishing composition comprises about 0.001 wt % to about 10 wt % silica abrasive.

[0098] (29) In embodiment (29), the method of any one of embodiments (25) through (28) is provided, wherein the polishing composition comprises about 0.05 wt % to about 5 wt % of a silica abrasive.

[0099] (30) In embodiment (30), the method of any one of embodiments (25) through (29) is provided, wherein the silica abrasive is colloidal silica.

[0100] (31) In embodiment (31), the method of any one of embodiments (25) through (30) is provided, wherein the silica abrasive has an average particle size of about 25 nm to about 100 nm.

[0101] (32) In embodiment (32), the method of any one of embodiments (25) through (31) is provided, wherein the silica abrasive has an average particle size of about 30 nm to about 75 nm.

[0102] (33) In embodiment (33), the method of any one of embodiments (25) to (32) is provided, wherein the oxidizing agent is selected from oxone, ceric ammonium nitrate, peroxide, periodate, iodate, persulfate, chlorate, chromate, permanganate, bromate, perbromate, ferrate, perrhenate, perruthenate, and combinations thereof.

[0103] (34) In embodiment (34), the method of any one of embodiments (25) to (33) is provided, wherein the oxidizing agent is selected from permanganate, ceric ammonium nitrate, and combinations thereof.

[0104] (35) In embodiment (35), the method of any one of embodiments (25) to (34) is provided, wherein the oxidizing agent is cerium ammonium nitrate.

[0105] (36) In embodiment (36), the method of any one of embodiments (25) to (34) is provided, wherein the oxidizing agent is potassium permanganate.

[0106] (37) In embodiment (37), the method of any one of embodiments (25) to (36) is provided, wherein the polishing composition comprises at least 1 wt. % of an oxidizing agent.

[0107] (38) In embodiment (38), the method of any one of embodiments (25) through (37) is provided, wherein the polishing composition comprises at least 2 wt. % of an oxidizing agent.

[0108] (39) In embodiment (39), the method of any one of embodiments (25) through (38) is provided, wherein the polishing composition comprises at least 3 wt. % of an oxidizing agent.

[0109] (40) In embodiment (40), the method of any one of embodiments (25) through (39) is provided, wherein the polishing composition further comprises ferric ions.

[0110] (41) In embodiment (41), the method of embodiment (40) is provided, wherein the polishing composition comprises about 0.01 wt % to about 1 wt % ferric ions.

[0111] (42) In embodiment (42), the method of any one of embodiments (25) through (39) is provided, wherein the polishing composition is substantially free of ferric ions.

[0112] (43) In embodiment (43), the method of any one of embodiments (25) to (42) is provided, wherein the polishing composition further comprises an organic acid.

[0113] (44) In embodiment (44), the method of embodiment (43) is provided, wherein the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0114] (45) In embodiment (45), the method of embodiment (43) or embodiment (44) is provided, wherein the polishing composition comprises about 1 mM to about 100 mM of an organic acid.

[0115] (46) In embodiment (46), the method of any one of embodiments (25) through (42) is provided, wherein the polishing composition is substantially free of organic acids.

[0116] (47) In embodiment (47), the method of any one of embodiments (25) to (46) is provided, wherein the polishing composition further comprises a buffering agent.

[0117] (48) In embodiment (48), the method of embodiment (47) is provided, wherein the buffering agent is selected from ammonium salts, alkali metal salts, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, borates, amino acids, and combinations thereof.

[0118] (49) In embodiment (49), the method of any one of embodiments (25) to (48) is provided, wherein the substrate includes a boron-doped polysilicon layer on a surface of the substrate, and at least a portion of the boron-doped polysilicon layer on the surface of the substrate is polished to polish the substrate.

[0119] (50) In embodiment (50), the method of embodiment (49) is provided, wherein the boron-doped polysilicon layer comprises at least 80 wt. % boron.

[0120] (51) In embodiment (51), the method of embodiment (49) is provided, wherein the boron-doped polysilicon layer comprises at least 85% by weight of boron.

[0121] (52) In embodiment (52), the method of embodiment (49) is provided, wherein the boron-doped polysilicon layer comprises at least 90% by weight of boron.

[0122] (53) In embodiment (53), the method of any one of embodiments (49) to (52) is provided, wherein the substrate further comprises a silicon nitride layer on the surface of the substrate, and at least a portion of the silicon nitride layer on the surface of the substrate is polished to polish the substrate.

[0123] (54) In embodiment (54), the method of embodiment (53) is provided, wherein the chemical-mechanical polishing composition provides a boron-doped polysilicon to silicon nitride polishing selectivity of about 5:1 or greater.

[0124] (55) In embodiment (55), the method of any one of embodiments (49) to (54) is provided, wherein the substrate further comprises a silicon oxide layer on the surface of the substrate, and at least a portion of the silicon oxide layer on the surface of the substrate is polished to polish the substrate.

[0125] (56) In embodiment (56), the method of embodiment (55) is provided, wherein the chemical-mechanical polishing composition provides a boron-doped polysilicon to silicon oxide polishing selectivity of about 5:1 or greater.

[0126] (57) In embodiment (57), a method according to any one of embodiments (49) to (56) is provided, wherein the substrate further comprises a titanium nitride layer on the surface of the substrate, and at least a portion of the titanium nitride layer on the surface of the substrate is polished to polish the substrate.

[0127] (58) In embodiment (58), the method of embodiment (57) is provided, wherein the chemical-mechanical polishing composition provides a boron-doped polysilicon to titanium nitride polishing selectivity of about 5:1 or greater. [Example]

[0128] These following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

[0129] The following abbreviations are used throughout the examples: removal rate (RR); boron-doped polysilicon (BSi); tetraethylorthosilicate (TEOS); percentage (wt %), and pounds per square inch (psi).

[0130] Example 1 This example demonstrates the effect of a polishing promoter (eg, an oxidizing agent) on the polishing performance of a polishing composition prepared according to the present invention.

[0131] Polishing Compositions 1A-1L contained 2 wt. % cationic silica particles having an average particle size of approximately 45 nm, 43.77 mM of each polishing promoter (i.e., oxidizer and / or additive), and a biocide (PROXEL™ AQ), each having a pH of approximately 1.5. The oxidizers and additives are listed in Table 1.

[0132] Patterned substrates containing TEOS or boron-doped polysilicon (BSi) layers containing approximately 95% boron by weight coated on wafers were polished with polishing compositions 1A-1L defined in Table 1 using a REFLEXION™ (Applied Materials, Inc.) polishing tool at a downforce of 3 PSI (20.55 kPa) using a NexPlanar U5890 pad (CMC Materials Inc.) conditioned with a product commercially identified as SAESOL™ DS8051 (SAESOL Diamond Ind. Co. Ltd.). REFLEXION™ polishing parameters were as follows: head speed = 87 rpm, platen speed = 98 rpm, total flow rate = 50 mL / min. TEOS-patterned substrates were polished for 30 seconds, and BSi-patterned substrates were polished for 15 seconds. Removal rates were calculated by measuring film thickness using spectroscopic ellipsometry and subtracting the final thickness from the initial thickness. The results are shown in Table 1 and plotted in Figures 1 and 2. The selectivity (Å / min) in Table 1 indicates the polishing rate of BSi relative to the polishing rate of TEOS. TIFF2025533967000002.tif109170

[0133] As is evident from the results shown in Table 1 and Figures 1 and 2, polishing compositions 1C, 1H, and 1J, which contained periodate, cerium ammonium nitrate (CAN), and potassium permanganate, respectively, provided the highest BSi removal rates. Furthermore, Table 1 shows that polishing compositions 1H and 1J, which contained cerium ammonium nitrate (CAN) and potassium permanganate, respectively, exhibited the best BSi to TEOS selectivity at approximately 16:1. Therefore, Table 1 and Figures 1 and 2 show that the addition of oxidizing agents such as periodate, cerium ammonium nitrate (CAN), and potassium permanganate increases the BSi removal rate while maintaining a low TEOS removal rate.

[0134] Example 2 This example demonstrates the effect of abrasive particle type and size on the polishing performance of polishing compositions prepared according to the present invention.

[0135] Polishing compositions containing 2 wt. % anionic, cationic, or neutral silica particles with different average particle sizes were prepared as shown in Table 2. The polishing compositions further contained 43.77 mM cerium ammonium nitrate, a biocide (PROXEL™ AQ), and each had a pH of approximately 1.5.

[0136] Patterned substrates containing TEOS or boron-doped polysilicon (BSi) layers containing approximately 95% boron by weight coated on wafers were polished with the polishing compositions containing the particles listed in Table 2 using a REFLEXION™ (Applied Materials, Inc.) polishing tool at a downforce of 3 PSI (20.55 kPa) using a NexPlanar U5890 pad conditioned with a product commercially identified as SAESOL™ DS8051. REFLEXION™ polishing parameters were as follows: head speed = 87 rpm, platen speed = 93 rpm, total flow rate = 50 mL / min. TEOS-patterned substrates were polished for 30 seconds, and BSi-patterned substrates were polished for 15 seconds. Removal rates were calculated by measuring film thickness using spectroscopic ellipsometry and subtracting the final thickness from the initial thickness. The results are shown in Table 2 and plotted in Figures 3 and 4. The selectivity (Å / min) in Table 2 indicates the polishing rate for BSi relative to the polishing rate for TEOS. TIFF2025533967000003.tif122170

[0137] As is evident from the results shown in Table 2 and Figures 3 and 4, the anionic, cationic, and neutral particles all provide high BSi removal rates while maintaining low TEOS removal rates. Furthermore, Table 2 shows that as the particle size of each particle type (i.e., anionic, cationic, and neutral) decreases, the removal selectivity of BSi relative to TEOS increases. Therefore, Table 2 and Figures 3 and 4 demonstrate that the anionic, cationic, and neutral particles are suitable for high BSi removal rates, and that smaller particle sizes can help improve BSi selectivity relative to TEOS.

[0138] Example 3 This example demonstrates the effect of the type and amount of abrasive particles and down force on the polishing performance of polishing compositions prepared according to the present invention.

[0139] Polishing compositions containing 2 wt. % cationic or neutral silica particles having an average particle size of approximately 45 nm were prepared in the amounts shown in Table 3. The polishing compositions further contained 43.77 mM cerium ammonium nitrate, a biocide (PROXEL™ AQ), and each had a pH of approximately 1.5.

[0140] Patterned substrates containing TEOS or a boron-doped polysilicon (BSi) layer containing approximately 95% boron by weight coated on the wafer were polished with the polishing compositions containing the particles listed in Table 3 using a REFLEXION™ (Applied Materials, Inc.) polishing tool with a NexPlanar U5890 pad conditioned with a product commercially identified as SAESOL™ DS8051 at the downforce provided in Table 3. REFLEXION™ polishing parameters were as follows: head speed = 87 rpm, platen speed = 98 rpm, total flow rate = 50 mL / min. TEOS-patterned substrates were polished for 30 seconds, and BSi-patterned substrates were polished for 15 seconds. Removal rates were calculated by measuring film thickness using spectroscopic ellipsometry and subtracting the final thickness from the initial thickness. The results are shown in Table 3 and plotted in Figures 5 and 6. The selectivity (Å / min) in Table 2 indicates the polishing rate of BSi relative to the polishing rate of TEOS. TIFF2025533967000004.tif82170

[0141] As is evident from the results shown in Table 3 and Figures 5 and 6, reducing the polishing down force to as low as 1.5 psi and the particle loading to as low as 0.025 wt% provides high BSi removal rates (e.g., greater than 6000 Å / min) and reduces TEOS removal rates to less than 30 Å / min (including as low as 1 Å / min). In other words, reducing the polishing down force and reducing particle loading can significantly increase the selectivity of BSi removal relative to TEOS. Thus, Table 3 and Figures 5 and 6 demonstrate that polishing compositions containing a silica abrasive, an oxidizer (e.g., ceric ammonium nitrate), and a pH of about 2 or less provide high BSi removal rates and high BSi selectivity relative to TEOS across a variety of polishing parameters.

[0142] All references, including publications, patent applications, and patents, cited in this specification are herein incorporated by reference to the same extent as if each individual reference was individually and specifically indicated to be incorporated by reference and was set forth in its entirety herein.

[0143] The use of "a" and "an," as well as "the," "at least one," and similar referents in the context of describing the invention (particularly in the context of the claims below) should be construed to encompass both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. When the term "at least one" is followed by a list of one or more items (e.g., "at least one of A and B"), it should be construed to mean one item selected from the listed items (A or B), or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" should be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise indicated. The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within that range, unless otherwise indicated herein, and each separate value is incorporated herein as if it were individually set forth herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. Any examples provided herein, or the use of exemplary language (e.g., "etc."), are solely for the purpose of better understanding the invention and do not impose limitations on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0144] Preferred embodiments of the present invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventors expect that skilled artisans will adopt such variations as necessary, and the inventors intend the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, all combinations of the above-described elements in all possible variations thereof are encompassed by the present invention unless otherwise indicated herein or clearly contradicted by context.

Claims

1. 1. A chemical-mechanical polishing composition comprising: (a) about 0.001% to about 10% by weight of a silica abrasive; (b) an oxidizing agent selected from oxone, ceric ammonium nitrate, peroxide, periodate, iodate, persulfate, chlorate, chromate, permanganate, bromate, perbromate, ferrate, perrhenate, perruthenate, and combinations thereof; and (c) water, The chemical-mechanical polishing composition has a pH of about 2 or less.

2. The polishing composition of claim 1 , wherein the polishing composition has a pH of about 1.5 or less.

3. The polishing composition of claim 1 , wherein the polishing composition has a pH of about 1 or less.

4. 10. The polishing composition of claim 1, wherein the polishing composition comprises about 0.025% to about 5% by weight of the silica abrasive.

5. 10. The polishing composition of claim 1, wherein the silica abrasive has an average particle size of about 25 nm to about 100 nm.

6. 10. The polishing composition of claim 1, wherein the silica abrasive has an average particle size of about 30 nm to about 75 nm.

7. 10. The polishing composition of claim 1, wherein the oxidizing agent is selected from permanganate, ceric ammonium nitrate, and combinations thereof.

8. 8. The polishing composition of claim 7, wherein the oxidizing agent is cerium ammonium nitrate.

9. The polishing composition of claim 1 , wherein the polishing composition comprises at least 1 wt % of an oxidizing agent.

10. 10. The polishing composition of claim 1, wherein the polishing composition further comprises about 0.01% to about 1% by weight of ferric ions.

11. The polishing composition of claim 1 , wherein the polishing composition further comprises an organic acid.

12. 12. The polishing composition of claim 11, wherein the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

13. 13. The polishing composition of claim 12, wherein the polishing composition comprises about 1 mM to about 100 mM of the organic acid.

14. The polishing composition of claim 1 , wherein the polishing composition further comprises a buffering agent.

15. 1. A method for chemically mechanically polishing a substrate, comprising: (i) providing a substrate; (ii) providing a polishing pad; (iii) providing a chemical-mechanical polishing composition, comprising: (a) about 0.001% to about 10% by weight of a silica abrasive; (b) an oxidizing agent selected from oxone, ceric ammonium nitrate, peroxide, periodate, iodate, persulfate, chlorate, chromate, permanganate, bromate, perbromate, ferrate, perrhenate, perruthenate, and combinations thereof; and (c) water, providing a chemical-mechanical polishing composition having a pH of about 2 or less; (iv) contacting the substrate with a polishing pad and a chemical-mechanical polishing composition; (v) polishing at least a portion of the substrate, and moving the polishing pad and the chemical-mechanical polishing composition relative to the substrate to polish the substrate; A method comprising:

16. 16. The method of claim 15, wherein the substrate comprises a boron-doped polysilicon layer on a surface of the substrate, and at least a portion of the boron-doped polysilicon layer on the surface of the substrate is polished to polish the substrate.

17. 17. The method of claim 16, wherein the boron-doped polysilicon layer comprises at least 80% by weight boron.

18. 18. The method of claim 17, wherein the boron-doped polysilicon layer comprises at least 90% by weight boron.

19. 16. The method of claim 15, wherein the substrate further comprises a silicon nitride layer on the surface of the substrate, and at least a portion of the silicon nitride layer on the surface of the substrate is polished to polish the substrate.

20. 16. The method of claim 15, wherein the substrate further comprises a silicon oxide layer on the surface of the substrate, and at least a portion of the silicon oxide layer on the surface of the substrate is polished to polish the substrate.

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