Chemical mechanical polishing composition for highly boron doped silicon films

Abstract

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. The invention also provides a method for chemical mechanical polishing of a substrate, especially a substrate comprising a boron-doped polycrystalline silicon layer on the surface of the substrate, using the composition.

Description

BACKGROUND OF THE INVENTION

[0001] Compositions and methods for planarizing or polishing a substrate surface are well known in the art. Polishing compositions (also referred to 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 impregnated with the polishing composition. Typical abrasive materials include silica, cerium oxide, alumina, zirconia, and tin oxide. Polishing compositions are typically used in combination with a polishing pad (such as a polishing cloth or a polishing disk). As an alternative or supplement to being suspended in the polishing composition, the abrasive material can also be incorporated into the polishing pad.

[0002] During the fabrication of advanced node memory devices such as dynamic random access memories (DRAMs), doped boron polysilicon or boron-polysilicon alloys are increasingly used as patterned hard masks. Due to the relatively high boron content in the polysilicon material, achieving a high removal rate of such material by chemical mechanical planarization (CMP) can be challenging. In addition to the need for a high removal rate of the boron-polysilicon film, some memory device schemes also require an extremely low removal rate of silicon nitride and / or silicon oxide, which can act as a termination layer in the device film stack. This presents selectivity requirements during CMP. Additionally, titanium nitride is also used in the fabrication of some memory devices. The ability to tune the relative removal rate of titanium nitride would be a desirable feature for polishing compositions and methods suitable for device fabrication.

[0003] Accordingly, there is still a need in the art for polishing compositions and methods for polishing boron-polysilicon layers with high removal rates and selectivity for 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, 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, wherein the chemical mechanical polishing composition has 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 abrade at least a portion of the substrate, thereby polishing the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Shows the boron-polysilicon (BSi) removal rate Comparative polishing compositions, as described in Example 1.

[0007] Figure 2 Show the removal rate of tetraethyl orthosilicate (TEOS) Compare with the polishing composition as described in Example 1.

[0008] Figure 3 Show the removal rate of boron-doped polysilicon (BSi) Compare the particle size exhibited by a polishing composition containing ammonium cerium nitrate (CAN) as described in Example 2.

[0009] Figure 4 Show the removal rate of tetraethyl orthosilicate (TEOS) Compare the particle size exhibited by a polishing composition containing ammonium cerium nitrate (CAN) as described in Example 2.

[0010] Figure 5 Show the removal rate of boron-doped polysilicon (BSi) Compare the particle type exhibited by a polishing composition containing ammonium cerium nitrate (CAN) as described in Example 3.

[0011] Figure 6 Show the removal rate of tetraethyl orthosilicate (TEOS) Compare the particle type exhibited by a polishing composition containing ammonium cerium nitrate (CAN) as described in Example 3. Detailed Description

[0012] 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.

[0013] The polishing composition contains an abrasive. As used herein, the terms "abrasive" and "abrasive particles" may be used interchangeably and may refer to any dispersion of abrasive particles. In other words, the terms "abrasive" and "abrasive particles" may be used interchangeably and may refer to (i) a plurality of single types of abrasives or abrasive particles and / or (ii) a plurality of more than one type of abrasive or abrasive particles.

[0014] The polishing composition contains a silica abrasive. As used herein, the terms "silica abrasive", "silica abrasive particles", "silica particles" and "abrasive particles" may be used interchangeably and may refer to any silica particles (such as colloidal silica particles). The silica particles (such as colloidal silica particles) may be modified (such as surface modification) or unmodified, and have a negative ζ potential, a neutral ζ potential or a positive ζ potential.

[0015] The charge on the dispersed particles (such as silica abrasives, e.g., colloidal silica particles) 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 (such as a liquid carrier and any other components dissolved therein) of the composition in which the particle is measured. The 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 thus the zeta potential) decreases or increases accordingly (decreasing or increasing to a negative zeta potential value or a positive zeta potential value, respectively). As used herein, the phrase "negative zeta potential" refers to silica abrasives that exhibit a negative surface charge when measured in a polishing composition. As used herein, the phrase "neutral zeta potential" refers to silica abrasives that exhibit a net zero surface charge when measured in a polishing composition. As used herein, the phrase "positive zeta potential" refers to silica abrasives that exhibit a positive surface charge when measured in a polishing composition.

[0016] Silica particles (e.g., colloidal silica particles) can have a negative native zeta potential, a neutral native zeta potential, or a positive native zeta potential. As used herein, the phrase "native zeta potential" refers to the zeta potential of the silica abrasive prior to adding the silica abrasive to the polishing composition. For example, the native zeta potential can refer to the zeta potential of the silica abrasive measured in a storage solution or an aqueous solution prior to adding the silica abrasive to the polishing composition. Those skilled in the art will be able to determine whether the silica abrasive has a negative native zeta potential, a neutral native zeta potential, or a positive native zeta potential prior to adding the silica abrasive to the polishing composition.

[0017] The native zeta potential and the zeta potential of the polishing composition can be obtained using a DT-1202 type acoustic and electro-acoustic spectrometer (Electro-acoustic spectrometer) purchased from Dispersion Technologies, Inc. (Bedford Hills, NY).

[0018] Silica abrasives (such as colloidal silica particles) can be modified (such as surface modification) or unmodified, and have a negative, neutral or positive zeta potential. Therefore, silica abrasives (such as 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 (such as colloidal silica particles) can have a zeta potential of less than 0 mV (such as -5 mV or lower), that is, a negative zeta potential, before being added to the chemical mechanical polishing composition. Alternatively, silica particles (such as colloidal silica particles) can have a zeta potential of 0 mV or higher (such as 5 mV or higher), that is, a positive zeta potential, before being added to the chemical mechanical polishing composition. In other embodiments, silica particles (such as colloidal silica particles) have a zeta potential of about 0 mV, that is, a neutral zeta potential.

[0019] Silica particles (such as colloidal silica particles) and charged silica particles (such as colloidal silica particles) can be prepared by various methods, some of which are commercially used and known. Suitable silica particles include precipitated or condensed silica, which can be prepared using known methods, such as by a method called the "sol-gel" method or by silicate ion exchange. Condensed silica particles are often prepared by condensing Si(OH)4 to form generally spherical (such as spherical, oval or oblong) particles. The precursor Si(OH)4 can be obtained, for example, by hydrolyzing high-purity alkoxysilane or by acidifying an aqueous silicate solution. U.S. Patent No. 5,230,833 describes a method for preparing colloidal silica particles in solution.

[0020] In some embodiments, the silica abrasive is colloidal silica. As is known to those of ordinary skill in the art, colloidal silica is a suspension of fine amorphous, non-porous and usually spherical particles in a liquid phase. Colloidal silica can be in the form of condensed or precipitated silica particles. In some embodiments, the silica is in the form of wet-type silica particles. Particles such as colloidal silica can have any suitable average size (i.e., average particle diameter). If the average size of the abrasive particles is too small, the polishing composition may not exhibit sufficient removal rate. On the contrary, if the average size of the abrasive particles is too large, the polishing composition may exhibit undesirable polishing performance, such as poor substrate defectivity.

[0021] Thus, the silica abrasive (e.g., silica particles or colloidal silica particles) can have an average particle size of about 10 nm or greater, such as about 15 nm or greater, about 20 nm or greater, about 25 nm or greater, about 30 nm or greater, about 35 nm or greater, about 40 nm or greater, about 45 nm or greater, or about 50 nm or greater. Alternatively or additionally, the silica abrasive can have an average particle size of about 200 nm or less, such as 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 defined by any two of the foregoing endpoints.

[0022] For example, the silica abrasive (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 rate of silicon oxide (e.g., TEOS) removal and thus provide a preferred selectivity to boron-doped polysilicon. Any suitable technique (e.g., using laser diffraction techniques) can be used to measure the particle size of the abrasive. Suitable particle size measuring instruments are commercially available from, for example, Malvern Instruments (Malvern, UK).

[0023] Silica abrasives (such as 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 (such as water). Colloidal stability refers to the maintenance of the suspension over time. In the context of the present invention, an abrasive is considered to be colloidally stable if, when the abrasive is placed in a 100 mL graduated cylinder and allowed to stand undisturbed for 2 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 ([C], in g / mL) in the abrasive composition, is less than or equal to 0.5 (i.e., {[B] - [T]} / [C] ≤ 0.5). More preferably, the value of [B] - [T] / [C] is less than or equal to 0.3, and most preferably less than or equal to 0.1.

[0024] The silica abrasive can be present in the polishing composition in any suitable amount. If the polishing composition of the present invention contains very little abrasive, the composition may not exhibit sufficient removal rate. Conversely, if the polishing composition contains too much abrasive, the polishing composition may exhibit undesirable polishing performance, and / or may not be cost-effective, and / or may lack stability. The polishing composition can contain about 10 wt% or less of the silica abrasive, such as 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 the silica abrasive. Alternatively or additionally, the polishing composition can contain about 0.001 wt% or more of the silica abrasive, such as 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 the silica abrasive. Thus, the polishing composition can contain any amount of the silica abrasive defined by any two of the foregoing endpoints as needed.

[0025] For example, in some embodiments, the silica abrasive may be present in the polishing composition in an amount of from about 0.001 wt% to about 10 wt%, such as from about 0.001 wt% to about 8 wt%, from about 0.001 wt% to about 6 wt%, from about 0.001 wt% to about 5 wt%, from about 0.001 wt% to about 4 wt%, from about 0.001 wt% to about 2 wt%, from about 0.001 wt% to about 1 wt%, from about 0.001 wt% to about 0.05 wt%, from about 0.01 wt% to about 10 wt%, from about 0.01 wt% to about 8 wt%, from about 0.01 wt% to about 6 wt%, from about 0.01 wt% to about 5 wt%, from about 0.01 wt% to about 4 wt%, from about 0.01 wt% to about 2 wt%, from about 0.01 wt% to about 1 wt%, from about 0.025 wt% to about 10 wt%, from about 0.025 wt% to about 8 wt%, from about 0.025 wt% to about 6 wt%, from about 0.025 wt% to about 5 wt%, from about 0.025 wt% to about 4 wt%, from about 0.025 wt% to about 2 wt%, from about 0.025 wt% to about 1 wt%, from about 0.1 wt% to about 10 wt%, from about 0.1 wt% to about 8 wt%, from about 0.1 wt% to about 6 wt%, from about 0.1 wt% to about 5 wt%, from about 0.1 wt% to about 4 wt%, from about 0.1 wt% to about 2 wt%, from about 0.1 wt% to about 1 wt%, from about 0.5 wt% to about 10 wt%, from about 0.5 wt% to about 8 wt%, from about 0.5 wt% to about 5 wt%, from about 0.5 wt% to about 4 wt%, from about 0.5 wt% to about 2 wt%, from about 0.5 wt% to about 1 wt%, from about 1 wt% to about 10 wt%, from about 1 wt% to about 8 wt%, from about 1 wt% to about 6 wt%, from about 1 wt% to about 5 wt%, from about 1 wt% to about 4 wt%, or from about 1 wt% to about 2 wt%. In some embodiments, the polishing composition comprises from about 0.001 wt% to about 10 wt% of the silica abrasive. In certain embodiments, the polishing composition comprises from about 0.05 wt% to about 5 wt% of the silica abrasive. In other embodiments, the polishing composition comprises from about 0.001 wt% to about 0.05 wt% of the silica abrasive.

[0026] The chemical mechanical polishing composition contains an oxidizing agent. The oxidizing agent can be any suitable compound capable of oxidizing the substrate (such as doped polysilicon, silicon nitride, silicon oxide, or titanium nitride). For example, the oxidizing agent can be selected from potassium peroxymonosulfate (oxone), ammonium cerium nitrate, peroxides (such as hydrogen peroxide), periodates (such as sodium periodate or potassium periodate), iodates (such as sodium iodate, potassium iodate, or ammonium iodate), persulfates (such as sodium persulfate, potassium persulfate, or ammonium persulfate), chlorates (such as sodium chlorate or potassium chlorate), chromates (such as sodium chromate or potassium chromate), permanganates (such as sodium permanganate, potassium permanganate, or ammonium permanganate), bromates (such as sodium bromate or potassium bromate), perbromates (such as sodium perbromate or potassium perbromate), ferrates (such as potassium ferrate), perrhenates (such as ammonium perrhenate), ruthenates (such as tetrapropylammonium ruthenate), and combinations thereof. The oxidizing agent can be in acid form (such as persulfuric acid), salt form (such as ammonium persulfate), or a mixture thereof. In some embodiments, the oxidizing agent contains peroxides, periodates, iodates, persulfates, chlorates, chromates, permanganates, bromates, perbromates, ferrates, perrhenates, ruthenates of an alkali metal (such as sodium or potassium), or combinations thereof.

[0027] In certain embodiments, the oxidizing agent is selected from permanganates (such as sodium permanganate, potassium permanganate, or ammonium permanganate), ammonium cerium nitrate, and combinations thereof. In some embodiments, the oxidizing agent is ammonium cerium nitrate. In other embodiments, the oxidizing agent is a permanganate (such as sodium permanganate, potassium permanganate, or ammonium permanganate), such as potassium permanganate.

[0028] The polishing composition can contain any suitable amount of the oxidizing agent. The polishing composition can contain about 20 wt% or less of the oxidizing agent, such as 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 the oxidizing agent. Alternatively or additionally, the polishing composition can contain about 0.1 wt% or more of the oxidizing agent, such as 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 the oxidizing agent. Thus, the polishing composition can contain any amount of the oxidizing agent defined by any two of the foregoing endpoints as needed.

[0029] For example, in some embodiments, the oxidizing agent may be 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%, about 0.1 wt% to about 2 wt%, about 0.5 wt% to about 20 wt%, about 0.5 wt% to about 15 wt%, about 0.5 wt% to about 10 wt%, about 0.5 wt% to about 9 wt%, about 0.5 wt% to about 8 wt%, about 0.5 wt% to about 7 wt%, about 0.5 wt% to about 6 wt%, about 0.5 wt% to about 5 wt%, about 0.5 wt% to about 4 wt%, about 0.5 wt% to about 3 wt%, about 0.5 wt% to about 2 wt%, about 1 wt% to about 20 wt%, about 1 wt% to about 15 wt%, about 1 wt% to about 10 wt%, about 1 wt% to about 9 wt%, about 1 wt% to about 8 wt%, about 1 wt% to about 7 wt%, about 1 wt% to about 6 wt%, about 1 wt% to about 5 wt%, about 1 wt% to about 4 wt%, about 1 wt% to about 3 wt%, about 1 wt% to about 2 wt%, about 2 wt% to about 20 wt%, about 2 wt% to about 15 wt%, about 2 wt% to about 10 wt%, about 2 wt% to about 9 wt%, about 2 wt% to about 8 wt%, about 2 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% of an oxidizing agent, at least 2 wt% of an oxidizing agent, or at least 3 wt% of an oxidizing agent.

[0030] The polishing composition may comprise iron ions, cobalt ions, manganese ions, organic acids, or combinations thereof.

[0031] The iron ions can be provided in any suitable form of an iron salt. Non-limiting examples of suitable iron salts are iron nitrate. The polishing composition can contain any suitable amount of iron ions. For example, the polishing composition can contain from about 0.005 wt% to about 1 wt% of iron 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% of iron ions.

[0032] In some embodiments, the polishing composition substantially does not contain iron ions. In the context of the present invention, "substantially iron-free" means that the polishing composition contains about 0.01 wt% or less of iron ions, such as about 0.005 wt% or less, about 0.001 wt% or less or about 0.0001 wt% or less of iron ions, or iron ions may not be detected in the polishing composition.

[0033] The cobalt ions can be provided in any suitable form of a cobalt salt. Non-limiting examples of suitable cobalt salts are cobalt acetate. The polishing composition can contain any suitable amount of cobalt ions. For example, the polishing composition can contain from about 0.005 wt% to about 1 wt% of cobalt 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% of cobalt ions.

[0034] In some embodiments, the polishing composition substantially does not contain cobalt ions. In the context of the present invention, "substantially cobalt-free" means that the polishing composition contains about 0.01 wt% or less of cobalt ions, such as about 0.005 wt% or less, about 0.001 wt% or less or about 0.0001 wt% or less of cobalt ions, or cobalt ions may not be detected in the polishing composition.

[0035] The manganese ions can be provided in any suitable form of a manganese salt. Non-limiting examples of suitable manganese salts are manganese acetate. The polishing composition can contain any suitable amount of manganese ions. For example, the polishing composition can contain from about 0.005 wt% to about 1 wt% of manganese 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% of manganese ions.

[0036] In some embodiments, the polishing composition substantially does not contain 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 of manganese ions, such as about 0.005 wt% or less, about 0.001 wt% or less, or about 0.0001 wt% or less of manganese ions, or manganese ions may not be detected in the polishing composition.

[0037] The polishing composition may contain 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.

[0038] The polishing composition may contain any suitable concentration of the organic acid. For example, the polishing composition may contain about 1 mM or more of the organic acid, such as about 2 mM or more, about 3 mM or more, about 4 mM or more, or about 5 mM or more of the organic acid. Alternatively or additionally, the polishing composition may contain about 100 mM or less of the organic acid, 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 of the organic acid. Thus, the polishing composition may contain any amount of the organic acid defined by any two of the foregoing endpoints. For example, the polishing composition may contain about 1 mM to about 20 mM of the organic acid, such as 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 of the organic acid. In some embodiments, the polishing composition contains about 1 mM to about 100 mM of the organic acid.

[0039] In some embodiments, the polishing composition substantially does not contain an organic acid. In the context of the present invention, "substantially free of an organic acid" means that the polishing composition contains about 1 mM or less of iron ions, such as about 0.5 mM or less, about 1 μM or less, or about 0.5 μM or less of iron ions, or an organic acid may not be detected in the polishing composition. In certain embodiments, the polishing composition substantially does not contain iron ions, substantially does not contain cobalt ions, substantially does not contain manganese ions, and / or substantially does not contain an organic acid.

[0040] The polishing composition contains water. The water can be any suitable water and can be, for example, deionized water or distilled water. In some embodiments, the polishing composition may further contain one or more organic solvents in combination with the water. For example, the polishing composition may further contain a hydroxy solvent, such as methanol or ethanol, a ketone solvent, an amide solvent, a sulfoxide solvent, and the like.

[0041] The polishing composition can have any suitable pH. Generally, the polishing composition has a pH of about 2 or lower, such as about 1.8 or lower, about 1.6 or lower, about 1.5 or lower, about 1.4 or lower, about 1.2 or lower, about 1 or lower, about 0.8 or lower, about 0.6 or lower, or about 0.5 or lower. Alternatively or additionally, the polishing composition can have a pH of about -2 or higher, such as about -1.5 or higher, about -1 or higher, about 0.5 or higher, about 0 or higher, about 0.2 or higher, about 0.4 or higher, or about 0.5 or higher. Thus, the polishing composition can have a pH defined by any two of the foregoing endpoints. For example, the polishing composition can have a pH of about -2 to about 2, such as about -1.5 to about 2, about -1 to about 2, about -0.5 to about 2, about 0 to about 2, about 0.2 to about 2, about 0.4 to about 2, about 0.5 to about 2, about -2 to about 1.8, about -1.5 to about 1.8, about -1 to about 1.8, about -0.5 to about 1.8, about 0 to about 1.8, about 0.2 to about 1.8, about 0.4 to about 1.8, about 0.5 to about 1.8, 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 lower. In certain embodiments, the polishing composition has a pH of about 1.5 or lower or about 1 or lower. In other embodiments, the polishing composition has a pH of about 0 to about 2 or about 0 to about 1.5.

[0042] Any suitable acid or base can be used to adjust the pH of the polishing composition. 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.

[0043] In some embodiments, the polishing composition further comprises a buffer. The buffer can be any suitable compound capable of buffering (e.g., maintaining) the polishing composition at a specific pH range. For example, the buffer can be selected from ammonium salts, alkali metal salts, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, borates, amino acids, and combinations thereof.

[0044] The chemical mechanical polishing composition optionally further comprises one or more additives. Illustrative additives include modifiers, acids (such as sulfonic acids), complexing agents, chelating agents, biocides, scale inhibitors, and dispersants.

[0045] In some embodiments, the polishing composition further comprises a biocide. Non-limiting examples of suitable biocides are isothiazolinone-based biocides such as Kordek MLX TM (DuPont, Wilmington, Delaware). The polishing composition can comprise any suitable amount of biocide. For example, the polishing composition can comprise from about 0.001 wt% to about 0.2 wt% of biocide.

[0046] 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% of a permanganate (such as potassium permanganate); and (c) water, wherein the chemical mechanical polishing composition has a pH of about 2 or lower.

[0047] In other 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% of ammonium cerium nitrate; and (c) water, wherein the chemical mechanical polishing composition has a pH of about 2 or lower.

[0048] The polishing composition can be produced by any suitable technique, many of which are known to those skilled in the art. The polishing composition can be prepared by batch or continuous processes. Generally, the polishing composition is prepared by combining the components of the polishing composition. As used herein, the term "component" includes individual ingredients (such as silica abrasive, oxidizing agent, optional pH adjuster, and / or any optional additives) and any combination of ingredients (such as silica abrasive, oxidizing agent, optional pH adjuster, and / or any optional additives, etc.).

[0049] For example, the polishing composition can be prepared by the steps of: (i) providing all or part of the liquid carrier; (ii) dispersing the silica abrasive, oxidizing agent, optional pH adjuster, and / or any optional additives using any suitable method for preparing such a dispersion; (iii) adjusting the pH of the dispersion as needed; and (iv) optionally adding a suitable amount of any other optional components and / or additives to the mixture.

[0050] Alternatively, the polishing composition can be prepared by the following steps: (i) providing one or more components (such as an oxidizing agent, an optional pH adjuster, and / or any optional additives) in a silica abrasive slurry; (ii) providing one or more components (such as a liquid carrier, an oxidizing agent, an optional pH adjuster, and / or any optional additives) in an additive solution; (iii) combining the silica abrasive slurry with the additive solution to form a mixture; (iv) optionally adding a suitable amount of any other optional additives to the mixture; and (v) adjusting the pH of the mixture as needed.

[0051] The polishing composition can be supplied as a single package system containing a silica abrasive, an oxidizing agent, an optional pH adjuster, and / or any optional additives and water. Alternatively, the polishing composition of the present invention can be supplied as a dual package system with a silica abrasive slurry in a first package and an additive solution in a second package, wherein the silica abrasive slurry consists essentially of or consists of a silica abrasive and water, and wherein the additive solution consists essentially of or consists of an oxidizing agent, an optional pH adjuster, and / or any optional additives. The dual package system allows the characteristics of the polishing composition to be adjusted by varying the blending ratio of the two packages, i.e., the silica abrasive slurry and the additive solution.

[0052] Various methods can be employed to utilize such a dual package polishing system. For example, the silica abrasive slurry and the additive solution can be delivered to the polishing table through different pipes joined and connected at the outlet of the supply pipe. The silica abrasive slurry and the additive solution can be mixed immediately or just prior to polishing, or can be supplied simultaneously onto the polishing table. Additionally, when mixing the two packages, deionized water can be added as needed to adjust the polishing characteristics of the polishing composition and the resulting substrate.

[0053] Similarly, triple, quadruple, or more complex package systems can be used in combination with the present invention, wherein each of the multiple containers contains different components of the chemical mechanical polishing composition of the present invention, one or more optional components, and / or one or more of the same components at different concentrations.

[0054] To mix the components contained in two or more storage devices at or near the point of use to produce a polishing composition, the storage devices are typically equipped with 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., the polishing pad or the substrate surface itself). The term "flow line" means the path from an individual storage container to the point of use of the components stored therein. The flow lines may each lead directly to the point of use, or two or more of the flow lines may merge at any point into a single flow line leading to the point of use. In addition, any of the flow lines (e.g., an individual flow line or a merged flow line) may first lead to one or more other devices (e.g., a pumping device, a measuring device, a mixing device, etc.) before reaching the point of use of one or more of the components.

[0055] The components of the polishing composition may be delivered independently to the point of use (e.g., the components are delivered to the substrate surface and thus mixed during the polishing process), or one or more of the components may be combined before being delivered to the point of use, e.g., immediately or right before being delivered to the point of use. "Immediately before being delivered to the point of use" combines the components if they are combined within about 5 minutes or less before being added to the platen in a mixed form, e.g., within about 4 minutes or less, about 3 minutes or less, about 2 minutes or less, about 1 minute or less, about 45 seconds or less, about 30 seconds or less, about 10 seconds or less before being added to the platen in a mixed form, or if the components are combined while being delivered to the point of use (e.g., combined at a dispenser). "Immediately before being delivered to the point of use" also combines the components if they are combined within 5 m of the point of use, e.g., within 1 m of the point of use or even within 10 cm of the point of use (e.g., within 1 cm of the point of use).

[0056] When two or more components of a polishing composition are combined before reaching the point of use, the components can be combined in a flow stream and delivered to the point of use without using a mixing device. Alternatively, one or more of the flow streams can lead into a mixing device to facilitate the combination of two or more components. Any suitable mixing device can be used. For example, the mixing device can be a nozzle or orifice (such as a high-pressure nozzle or orifice) through which two or more of the components flow. Alternatively, the mixing device can be a vessel-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 combined components are discharged from the mixer for delivery to the point of use directly or via other elements of the equipment (such as via one or more flow streams). Additionally, the mixing device can include more than one chamber, each chamber having at least one inlet and at least one outlet, where two or more components are combined in each chamber. If a vessel-type mixing device is used, the mixing device preferably includes a mixing mechanism to further facilitate the combination of the components. Mixing mechanisms are generally known in the art and include agitators, blenders, stirrers, paddle baffles, gas bubbler systems, vibrators, and the like.

[0057] The polishing composition can also be provided as a concentrate, and it is intended to dilute the concentrate with an appropriate amount of water before use. In such embodiments, the polishing composition concentrate contains an amount of the polishing composition components such that after diluting the concentrate with the appropriate amount of water, each component of the polishing composition will be present in the polishing composition in the appropriate ranges of amounts described above for each component. For example, the silica abrasive, the oxidizing agent, the optional pH adjuster, and / or any optional additives can each be present in the concentrate in an amount that is about 2 times (such as about 3 times, about 4 times, or about 5 times) the concentration described above for each component, so that when the concentrate is diluted with an equal volume of water (such as with 2 equal volumes of water, 3 equal volumes of water, or 4 equal volumes of water), each component will be present in the polishing composition in the ranges of amounts stated above for each component. Additionally, as will be understood by one of ordinary skill in the art, the concentrate can contain an appropriate portion of the water present in the final polishing composition to ensure that the silica abrasive, the oxidizing agent, the optional pH adjuster, and / or any optional additives are at least partially or completely dissolved in the concentrate.

[0058] The present invention further provides a method for chemically mechanical polishing a substrate, which comprises: (i) providing a substrate; (ii) providing a polishing pad; (iii) providing a chemically mechanical polishing composition comprising: (a) a silica abrasive; (b) an oxidizing agent; and (c) water, wherein the chemically mechanical polishing composition has a pH of about 2 or lower; (iv) bringing the substrate into contact with the polishing pad and the chemically mechanical polishing composition; and (v) moving the polishing pad and the chemically mechanical polishing composition relative to the substrate to abrade at least a portion of the substrate, thereby polishing the substrate.

[0059] 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 can include a substrate comprising a boron-doped polysilicon layer on a substrate surface, and wherein at least a portion of the boron-doped polysilicon layer on the substrate surface is abraded to polish the substrate. Alternatively or additionally, the substrate can comprise a silicon nitride layer on a substrate surface, a silicon oxide layer on a substrate surface, a titanium nitride layer on a substrate surface, or a combination thereof. For example, the method can include a substrate comprising (i) a silicon nitride layer on a substrate surface, and wherein at least a portion of the silicon nitride layer on the substrate surface is abraded to polish the substrate; (ii) a silicon oxide layer on a substrate surface, and wherein at least a portion of the silicon oxide layer on the substrate surface is abraded to polish the substrate; and / or (iii) a titanium nitride layer on a substrate surface, and wherein at least a portion of the titanium nitride layer on the substrate surface is abraded to polish the substrate. In certain embodiments, the substrate comprises a boron-doped polysilicon layer on a substrate surface, and a silicon oxide layer, a silicon nitride layer, and / or a titanium nitride layer on the substrate surface.

[0060] 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 contains at least 75 wt% boron, at least 80 wt% boron, at least 85 wt% boron, or at least 90 wt% boron. For example, the boron-doped polysilicon layer can contain from about 75 wt% to about 99.9 wt% boron, such as 75 wt% to about 99 wt%, about 75 wt% to about 95 wt%, about 75 wt% to about 90 wt%, about 80 wt% to about 99.9 wt%, about 80 wt% to about 99 wt%, about 80 wt% to about 95 wt%, about 80 wt% to about 90 wt%, about 85 wt% to about 99.9 wt%, about 85 wt% to about 99 wt%, about 85 wt% to about 95 wt%, about 85 wt% to about 90 wt%, about 90 wt% to about 99.9 wt%, about 90 wt% to about 99 wt%, about 90 wt% to about 95 wt%, about 95 wt% to about 99.9 wt%, or about 95 wt% to about 99 wt% boron. 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 a high level (e.g., about 75 wt% or higher, about 80 wt% or higher, about 85 wt% or higher, or about 90 wt% or higher) of boron doping.

[0061] When polishing a substrate comprising boron-doped polysilicon according to the method of the present invention, the polishing composition desirably exhibits a high removal rate. For example, when polishing a silicon wafer comprising a boron-doped polysilicon layer according to an embodiment of the present invention, the polishing composition desirably exhibits about or higher, such as about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, about or higher, or about etch rate of doped polysilicon or higher.

[0062] In some embodiments, when 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 etch rate of silicon oxide. For example, when polishing a substrate comprising silicon oxide according to an embodiment of the present invention, the polishing composition desirably exhibits about or lower, such as about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, or about etch rate of silicon oxide or lower. In some embodiments, the polishing composition exhibits an undetectably low etch rate of silicon oxide.

[0063] In some embodiments, when the substrate further comprises silicon nitride, the silicon nitride can be any suitable silicon nitride, many of which are known in the art. When polishing a substrate comprising silicon nitride according to the method of the present invention, the chemical mechanical polishing composition of the present invention desirably exhibits a low etch rate of silicon nitride. For example, when polishing a substrate comprising silicon nitride according to an embodiment of the present invention, the polishing composition desirably exhibits about or lower, such as about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, or about or a lower removal rate of silicon nitride. In some embodiments, the polishing composition exhibits a silicon nitride removal rate that is too low to be detected.

[0064] In some embodiments, the substrate can be a carbon film. Examples of these carbon films can be grown using a variety of methods known in the art, including PECVD, spin coating, and other methods. The resulting films can have a wide range of properties (hardness, ζ potential, hydrophobicity, etc.). These carbon film substrates can be polished using the formulations of the present invention, such as the same formulation as described in Example 3 of the present invention, and exhibit high removal rates. A slurry containing ammonium cerium nitrate and less than 0.1% solids is capable of polishing these films with high carbon removal rates and high selectivity for the underlying silicon oxide or silicon nitride film.

[0065] In some embodiments, when the substrate further comprises titanium nitride, the titanium nitride can be any suitable titanium nitride, many of which are known in the art. When polishing a substrate comprising titanium nitride according to the method of the present invention, the chemical mechanical polishing composition of the present invention desirably exhibits a low removal rate of titanium nitride. For example, when polishing a substrate comprising titanium nitride according to an embodiment of the present invention, the polishing composition desirably exhibits about or lower, such as about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, about or lower, or about or lower removal rate of titanium nitride. In some embodiments, the polishing composition exhibits a titanium nitride removal rate that is too low to be detected.

[0066] The chemical mechanical polishing composition of the present invention can be customized to provide effective polishing to specific thin layer materials within a desired polishing range while minimizing surface imperfections, defects, corrosion, erosion, and removal of the termination layer. Selectivity can be controlled to some extent by varying the relative concentrations of the components of the polishing composition. When desired, the chemical mechanical polishing composition of the present invention can be used to polish a substrate comprising doped boron polysilicon and silicon oxide on a surface layer, wherein the chemical mechanical polishing composition provides a polishing selectivity of doped boron polysilicon to silicon oxide of about 5:1 or higher (e.g., about 10:1 or higher, about 15:1 or higher, about 25:1 or higher, about 50:1 or higher, about 100:1 or higher, or about 150:1 or higher). Also, the chemical mechanical polishing composition of the present invention can be used to polish a substrate comprising doped boron polysilicon and silicon nitride on a surface layer, wherein the chemical mechanical polishing composition provides a polishing selectivity of doped boron polysilicon to silicon nitride of about 5:1 or higher (e.g., about 10:1 or higher, about 15:1 or higher, about 25:1 or higher, about 50:1 or higher, about 100:1 or higher, or about 150:1 or higher). Additionally, the chemical mechanical polishing composition of the present invention can be used to polish a substrate comprising doped boron polysilicon and titanium nitride on a surface layer, wherein the chemical mechanical polishing composition provides a polishing selectivity of doped boron polysilicon to titanium nitride of about 5:1 or higher (e.g., about 10:1 or higher, about 15:1 or higher, about 25:1 or higher, about 50:1 or higher, about 100:1 or higher, or about 150:1 or higher). Thus, in an embodiment, when used to polish a substrate comprising at least one doped boron polysilicon layer and at least one silicon oxide layer, at least one silicon nitride layer, and / or at least one titanium nitride layer, the polishing composition and method allow for preferential removal of doped boron polysilicon compared to the removal of 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.

[0067] When polishing a substrate, the polishing composition of the present invention desirably exhibits low particle defects as determined by a suitable technique. 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 complex (DCN) and dark field tilted beam complex (DCO)) can be used to determine particle defects on a polished substrate. Suitable instruments for evaluating particle defectivity are available from, for example, KLA-Tencor (such as SURFSCAN TM SPI instruments) operating at a 120 nm threshold or a 160 nm threshold.

[0068] The chemical mechanical polishing compositions and methods of the present invention are particularly suitable for use in combination with chemical mechanical polishing equipment. Generally, the equipment includes: a platen that is in motion during use and has a velocity generated by orbital, linear, or circular motion; a polishing pad that contacts the platen and moves with the platen when in motion; and a carrier that holds a substrate to be polished by moving the substrate in contact with and relative to the surface of the polishing pad. Polishing of the substrate is carried out by the steps of placing 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.

[0069] The substrate can be polished with a chemical mechanical polishing composition using any suitable polishing pad (e.g., a polishing surface). Suitable polishing pads include, for example, woven and non-woven polishing pads. In addition, suitable polishing pads can comprise any suitable polymer having different densities, hardnesses, thicknesses, compressibilities, ability to rebound after compression, and moduli of compression. Suitable polymers include, for example, polyvinyl chloride, polyvinyl fluoride, nylon, fluorocarbons, polycarbonates, polyesters, polyacrylates, polyethers, polyethylene, polyamides, polyurethanes, polystyrene, polypropylene, co-formations thereof, and mixtures thereof. Polyurethane soft polishing pads are particularly suitable for use in combination with the polishing method of the present invention. Typical pads include, but are not limited to, SURFIN TM 000, SURFIN TM SSW1, SPM3100 (commercially available from, for example, Eminess Technologies), POLITEX TM 、EPIC TM D100 pads (commercially available from CMC Materials), IC1010 pads (commercially available from Dow Chemical Company), and Fujibo POLYPAS TM 27.

[0070] Desirably, the chemical mechanical polishing apparatus further includes an in-situ polish 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 polished substrate 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, inspecting or monitoring the progress of the polishing process with respect to the polished substrate enables determination of the polish endpoint, i.e., determination of when to terminate the polishing process for a particular substrate.

[0071] The substrate can be polished using any suitable downforce. For example, the substrate can be polished using a downforce of about 1 psi or greater, about 2 psi or greater, about 3 psi or greater, about 4 psi or greater, or about 5 psi or greater. Alternatively or additionally, the substrate can be polished using 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 using a downforce defined by any two of the foregoing endpoints. For example, the substrate can be polished using 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.

[0072] In some embodiments, the present invention provides a method of chemically mechanically polishing a substrate, 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% of a permanganate (such as potassium permanganate); and (c) water, wherein the chemical mechanical polishing composition has 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 abrade at least a portion of the substrate, thereby polishing the substrate, wherein the substrate comprises a boron-doped polysilicon layer on the substrate surface, and wherein at least a portion of the boron-doped polysilicon layer on the substrate surface is abraded to polish the substrate.

[0073] In some embodiments, the present invention provides a method for chemical mechanical polishing of a substrate, 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% of ammonium cerium nitrate; and (c) water, wherein the chemical mechanical polishing composition has a pH of about 2 or lower; (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 substrate, thereby polishing the substrate, wherein the substrate comprises a boron-doped polysilicon layer on a substrate surface, and wherein at least a portion of the boron-doped polysilicon layer on the substrate surface is abraded to polish the substrate.

[0074] The aspects (including embodiments) of the present invention described above may be beneficial alone or in combination with one or more other aspects or embodiments. Without limiting the foregoing specification, certain non-limiting embodiments of the present invention numbered 1 to 55 are provided below. As will be apparent to those skilled in the art upon reading the present invention, each of the individually numbered embodiments may be used alone or in combination with any of the previously or subsequently individually numbered embodiments. This is intended to provide support for all such combinations of embodiments and is not limited to the combinations of embodiments explicitly provided below:

[0075] Embodiments

[0076] (1) In Embodiment (1), a chemical mechanical polishing composition is presented, comprising:

[0077] (a) a silica abrasive;

[0078] (b) an oxidizing agent; and

[0079] (c) water,

[0080] wherein the chemical mechanical polishing composition has a pH of about 2 or lower.

[0081] (2) In Embodiment (2), a polishing composition as in Embodiment (1) is presented, wherein the polishing composition has a pH of about 1.5 or lower.

[0082] (3) In Embodiment (3), a polishing composition as in Embodiment (1) or Embodiment (2) is presented, wherein the polishing composition has a pH of about 1 or lower.

[0083] (4) In Embodiment (4), a polishing composition as in any one of Embodiments (1) to (3) is presented, wherein the polishing composition comprises from about 0.001 wt% to about 10 wt% of a silica abrasive.

[0084] (5) In Example (5), a polishing composition as in any one of Examples (1) to (4) is presented, wherein the polishing composition contains from about 0.05 wt% to about 5 wt% of a silica abrasive.

[0085] (6) In Example (6), a polishing composition as in any one of Examples (1) to (5) is presented, wherein the silica abrasive is colloidal silica.

[0086] (7) In Example (7), a polishing composition as in any one of Examples (1) to (6) is presented, wherein the silica abrasive has an average particle size of from about 25 nm to about 100 nm.

[0087] (8) In Example (8), a polishing composition as in any one of Examples (1) to (7) is presented, wherein the silica abrasive has an average particle size of from about 30 nm to about 75 nm.

[0088] (9) In Example (9), a polishing composition as in any one of Examples (1) to (8) is presented, wherein the oxidizing agent is selected from potassium peroxymonosulfate, ammonium cerium nitrate, peroxides, periodates, iodates, persulfates, chlorates, chromates, permanganates, bromates, perbromates, ferrates, perrhenates, ruthenates, and combinations thereof.

[0089] (10) In Example (10), a polishing composition as in any one of Examples (1) to (9) is presented, wherein the oxidizing agent is selected from permanganates, ammonium cerium nitrate, and combinations thereof.

[0090] (11) In Example (11), a polishing composition as in any one of Examples (1) to (10) is presented, wherein the oxidizing agent is ammonium cerium nitrate.

[0091] (12) In Example (12), a polishing composition as in any one of Examples (1) to (10) is presented, wherein the oxidizing agent is potassium permanganate.

[0092] (13) In Example (13), a polishing composition as in any one of Examples (1) to (12) is presented, wherein the polishing composition contains at least 1 wt% of an oxidizing agent.

[0093] (14) In Example (14), a polishing composition as in any one of Examples (1) to (13) is presented, wherein the polishing composition contains at least 2 wt% of an oxidizing agent.

[0094] (15) In Example (15), a polishing composition as in any one of Examples (1) to (14) is presented, wherein the polishing composition contains at least 3 wt% of an oxidizing agent.

[0095] (16) A polishing composition as in any one of embodiments (1) to (15) is presented in embodiment (16), wherein the polishing composition further comprises iron ions.

[0096] (17) A polishing composition as in embodiment (16) is presented in embodiment (17), wherein the polishing composition comprises from about 0.01 wt% to about 1 wt% of iron ions.

[0097] (18) A polishing composition as in any one of embodiments (1) to (15) is presented in embodiment (18), wherein the polishing composition substantially does not contain iron ions.

[0098] (19) A polishing composition as in any one of embodiments (1) to (18) is presented in embodiment (19), wherein the polishing composition further comprises an organic acid.

[0099] (20) A polishing composition as in embodiment (19) is presented in embodiment (20), wherein the organic acid is selected from maleic acid, L-ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0100] (21) A polishing composition as in embodiment (19) or embodiment (20) is presented in embodiment (21), wherein the polishing composition comprises from about 1 mM to about 100 mM of the organic acid.

[0101] (22) A polishing composition as in any one of embodiments (1) to (18) is presented in embodiment (22), wherein the polishing composition substantially does not contain an organic acid.

[0102] (23) A polishing composition as in any one of embodiments (1) to (22) is presented in embodiment (23), wherein the polishing composition further comprises a buffer.

[0103] (24) A polishing composition as in embodiment (23) is presented in embodiment (24), wherein the buffer is selected from ammonium salts, alkali metal salts, alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates, borates, amino acids, and combinations thereof.

[0104] (25) A method for chemically mechanical polishing a substrate is presented in embodiment (25), which comprises:

[0105] (i) providing a substrate,

[0106] (ii) providing a polishing pad,

[0107] (iii) providing a chemically mechanical polishing composition, which comprises:

[0108] (a) silica abrasive;

[0109] (b) an oxidizing agent; and

[0110] (c) water,

[0111] wherein the chemical mechanical polishing composition has a pH of about 2 or lower,

[0112] (iv) contacting the substrate with the polishing pad and the chemical mechanical polishing composition, and

[0113] (v) moving the polishing pad and the chemical mechanical polishing composition relative to the substrate to abrade at least a portion of the substrate, thereby polishing the substrate.

[0114] (26) A method as presented in Example (26) is presented, where the polishing composition has a pH of about 1.5 or lower.

[0115] (27) A method as presented in Example (27) is presented, where the polishing composition has a pH of about 1 or lower.

[0116] (28) A method as presented in Example (28) is presented, where the polishing composition contains from about 0.001 wt% to about 10 wt% of a silica abrasive.

[0117] (29) A method as presented in Example (29) is presented, where the polishing composition contains from about 0.05 wt% to about 5 wt% of a silica abrasive.

[0118] (30) A method as presented in Example (30) is presented, where the silica abrasive is colloidal silica.

[0119] (31) A method as presented in Example (31) is presented, where the silica abrasive has an average particle size of from about 25 nm to about 100 nm.

[0120] (32) A method as presented in Example (32) is presented, where the silica abrasive has an average particle size of from about 30 nm to about 75 nm.

[0121] (33) A method as presented in Example (33) is presented, where the oxidizing agent is selected from potassium peroxymonosulfate, ammonium cerium nitrate, peroxides, periodates, iodates, persulfates, chlorates, chromates, permanganates, bromates, perbromates, ferrates, perrhenates, ruthenates, and combinations thereof.

[0122] (34) The method as in any one of Examples (25) to (33) is presented in Example (34), wherein the oxidizing agent is selected from permanganate, ammonium cerium nitrate, and combinations thereof.

[0123] (35) The method as in any one of Examples (25) to (34) is presented in Example (35), wherein the oxidizing agent is ammonium cerium nitrate.

[0124] (36) The method as in any one of Examples (25) to (34) is presented in Example (36), wherein the oxidizing agent is potassium permanganate.

[0125] (37) The method as in any one of Examples (25) to (36) is presented in Example (37), wherein the polishing composition contains at least 1 wt% of the oxidizing agent.

[0126] (38) The method as in any one of Examples (25) to (37) is presented in Example (38), wherein the polishing composition contains at least 2 wt% of the oxidizing agent.

[0127] (39) The method as in any one of Examples (25) to (38) is presented in Example (39), wherein the polishing composition contains at least 3 wt% of the oxidizing agent.

[0128] (40) The method as in any one of Examples (25) to (39) is presented in Example (40), wherein the polishing composition further contains iron ions.

[0129] (41) The method as in Example (40) is presented in Example (41), wherein the polishing composition contains from about 0.01 wt% to about 1 wt% of iron ions.

[0130] (42) The method as in any one of Examples (25) to (39) is presented in Example (42), wherein the polishing composition substantially does not contain iron ions.

[0131] (43) The method as in any one of Examples (25) to (42) is presented in Example (43), wherein the polishing composition further contains an organic acid.

[0132] (44) The method as in Example (43) is presented in Example (44), wherein the organic acid is selected from maleic acid, L - ascorbic acid, picolinic acid, malonic acid, and combinations thereof.

[0133] (45) The method as in Example (43) or Example (44) is presented in Example (45), wherein the polishing composition contains from about 1 mM to about 100 mM of the organic acid.

[0134] (46) A method as in any one of embodiments (25) to (42) is presented in embodiment (46), wherein the polishing composition substantially does not contain an organic acid.

[0135] (47) A method as in any one of embodiments (25) to (46) is presented in embodiment (47), wherein the polishing composition further comprises a buffering agent.

[0136] (48) A method as in embodiment (47) is presented in embodiment (48), 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.

[0137] (49) A method as in any one of embodiments (25) to (48) is presented in embodiment (49), wherein the substrate comprises a boron-doped polysilicon layer on the substrate surface, and at least a portion of the boron-doped polysilicon layer on the substrate surface is abraded to polish the substrate.

[0138] (50) A method as in embodiment (49) is presented in embodiment (50), wherein the boron-doped polysilicon layer comprises at least 80 wt% boron.

[0139] (51) A method as in embodiment (49) is presented in embodiment (51), wherein the boron-doped polysilicon layer comprises at least 85 wt% boron.

[0140] (52) A method as in embodiment (49) is presented in embodiment (52), wherein the boron-doped polysilicon layer comprises at least 90 wt% boron.

[0141] (53) A method as in any one of embodiments (49) to (52) is presented in embodiment (53), wherein the substrate further comprises a silicon nitride layer on the substrate surface, and at least a portion of the silicon nitride layer on the substrate surface is abraded to polish the substrate.

[0142] (54) A method as in embodiment (53) is presented in embodiment (54), wherein the chemical mechanical polishing composition provides a polishing selectivity of boron-doped polysilicon to silicon nitride of about 5:1 or higher.

[0143] (55) A method as in any one of embodiments (49) to (54) is presented in embodiment (55), wherein the substrate further comprises a silicon oxide layer on the substrate surface, and at least a portion of the silicon oxide layer on the substrate surface is abraded to polish the substrate.

[0144] (56) The method as in Example (55) is presented in Example (56), wherein the chemical mechanical polishing composition provides a polishing selectivity of doped boron polysilicon to silicon oxide of about 5:1 or higher.

[0145] (57) The method as in any one of Examples (49) to (56) is presented in Example (57), wherein the substrate further comprises a titanium nitride layer on the substrate surface, and at least a part of the titanium nitride layer on the polished substrate surface is polished to polish the substrate.

[0146] (58) The method as in Example (57) is presented in Example (58), wherein the chemical mechanical polishing composition provides a polishing selectivity of doped boron polysilicon to titanium nitride of about 5:1 or higher.

[0147] Examples

[0148] The following examples further illustrate the present invention, but should not be construed as limiting its scope in any way.

[0149] The following abbreviations are used throughout the examples: removal rate (RR); doped boron polysilicon (BSi); tetraethyl orthosilicate (TEOS); weight percentage (wt%) and pounds per square inch (psi).

[0150] Example 1

[0151] This example shows the effect of a polishing promoter (such as an oxidant) on the polishing performance of a polishing composition prepared according to the present invention.

[0152] The polishing compositions 1A to 1L contain 2 wt% of cationic silica particles with an average particle size of approximately 45 nm, 43.77 mM of each polishing promoter (i.e., oxidant and / or additive), except for the biocide (PROXEL TM AQ), and each has a pH of approximately 1.5. The oxidants and additives are set forth in Table 1.

[0153] A patterned substrate comprising TEOS coated on a wafer or a doped boron polysilicon (BSi) layer containing approximately 95 wt% boron is polished using the polishing compositions 1A to 1L (as defined in Table 1) at a pressure of 3 PSI (20.55 kPa) using a REFLEXION TM (Applied Materials) polishing tool, using a NexPlanar U5890 pad (CMC Materials) conditioned with a product commercially identified as SAESOL TM DS8051 (SAESOL Diamond Ind. Co., Ltd.). REFLEXION TMThe polishing parameters were as follows: head speed = 87 rpm, platen speed = 98 rpm, total flow rate = 50 mL / min. The TEOS patterned substrate was polished for 30 seconds and the BSi patterned substrate was polished for 15 seconds. The removal rate was calculated by measuring the film thickness using spectroscopic ellipsometry and subtracting the final thickness from the initial thickness. The results are set forth in Table 1 and plotted in Figure 1 and Figure 2 The selectivity in Table 1 refers to the polishing rate of BSi relative to the polishing rate of TEOS.

[0154] Table 1. Polishing Composition Removal Rates as a Function of Oxidizer

[0155]

[0156] As is evident from the results set forth in Table 1 and Figure 1 and Figure 2 the polishing compositions 1C, 1H, and 1J containing periodate, ammonium cerium nitrate (CAN), and potassium permanganate, respectively, provide the highest BSi removal rates. Additionally, Table 1 shows that the polishing compositions 1H and 1J containing ammonium cerium nitrate (CAN) and potassium permanganate, respectively, exhibit a most preferred selectivity of BSi relative to TEOS of approximately 16:1. Thus, Table 1 and Figure 1 and Figure 2 show that the addition of oxidizers such as periodate, ammonium cerium nitrate (CAN), and potassium permanganate increases the BSi removal rate while maintaining a low TEOS removal rate.

[0157] Example 2

[0158] This example demonstrates the effect of the type and size of abrasive particles on the polishing performance of the polishing compositions prepared according to the present invention.

[0159] As set forth in Table 2, polishing compositions containing 2 wt% of anionic, cationic, or neutral silica particles having different average particle sizes were prepared. The polishing compositions further contained 43.77 mM of ammonium cerium nitrate, a biocide (PROXEL TM AQ), and each had a pH of approximately 1.5.

[0160] Patterned substrates comprising TEOS coated on a wafer or a doped boron polysilicon (BSi) layer comprising approximately 95 wt% boron were polished using the polishing compositions containing the particles described in Table 2 at a pressure of 3 PSI (20.55 kPa) using a REFLEXION TM (Applied Materials) polishing tool, using a slurry commercially identified as SAESOL TMThe NexPlanar U5890 pad for product conditioning of DS8051 is used for polishing. REFLEXION TM The polishing parameters are as follows: head speed = 87 rpm, platen speed = 93 rpm, total flow rate = 50 mL / min. The TEOS patterned substrate is polished for 30 seconds and the BSi patterned substrate is polished for 15 seconds. The removal rate is calculated by measuring the film thickness using ellipsometry and subtracting the final thickness from the initial thickness. The results are presented in Table 2 and plotted in Figure 3 and Figure 4 The selectivity in Table 2 refers to the polishing rate of BSi relative to the polishing rate of TEOS.

[0161] Table 2. Removal Rates of Polishing Compositions as a Function of the Type and Size of Abrasive Particles

[0162]

[0163] As is evident from the results presented in Table 2 and Figure 3 and Figure 4 cationic particles, and neutral particles all provide high BSi removal rates while maintaining low TEOS removal rates. Additionally, Table 2 shows that as the particle size of each of the particle types (i.e., anionic, cationic, and neutral) decreases, the selectivity for removing BSi relative to TEOS increases. Thus, Table 2 and Figure 3 and Figure 4 show that anionic particles, cationic particles, and neutral particles are suitable for high BSi removal rates and smaller particle sizes can contribute to improving the selectivity of BSi relative to TEOS.

[0164] Example 3

[0165] This example demonstrates the influence of the type and amount of abrasive particles and the down pressure on the polishing performance of the polishing compositions prepared according to the present invention.

[0166] Polishing compositions containing 2 wt% of cationic or neutral silica particles having an average particle size of approximately 45 nm are prepared using the amounts set forth in Table 3. The polishing compositions further contain 43.77 mM of ammonium cerium nitrate, a biocide (PROXEL TM AQ), and each has a pH of approximately 1.5.

[0167] Patterned substrates comprising TEOS coated on a wafer or a doped boron polysilicon (BSi) layer containing approximately 95 wt% boron are polished using the polishing compositions containing the particles described in Table 3 at the down pressures provided in Table 3 using REFLEXION TM(Applied Materials) polishing tool that uses the NexPlanar U5890 pad conditioned with a product commercially identified as SAESOL TM to polish. REFLEXION TM The polishing parameters are as follows: head speed = 87 rpm, platen speed = 98 rpm, total flow rate = 50 mL / min. The TEOS patterned substrate was polished for 30 seconds and the BSi patterned substrate was polished for 15 seconds. The removal rate was calculated by measuring the film thickness using ellipsometry and subtracting the final thickness from the initial thickness. The results are presented in Table 3 and plotted in Figure 5 and Figure 6 . The selectivity in Table 2 refers to the polishing rate of BSi relative to the polishing rate of TEOS.

[0168] Table 3. Polishing Composition Removal Rates as a Function of Abrasive Particle Type and Amount and Downforce

[0169]

[0170] As is evident from the results presented in Table 3 and Figure 5 and Figure 6 reducing the polishing downforce to as low as 1.5 psi and reducing the particle amount to as low as 0.025 wt% provides a high BSi removal rate (e.g., greater than ) and reduces the TEOS removal rate to less than including reducing to as low as In other words, by reducing the polishing downforce and reducing the particle load, the selectivity for removing BSi relative to TEOS can be significantly increased. Thus, Table 3 and Figure 5 and Figure 6 show that a polishing composition containing silica abrasive, an oxidizing agent (e.g., ammonium cerium nitrate), and a pH of about 2 or lower provides a high BSi removal rate and high BSi selectivity relative to TEOS at various polishing parameters.

[0171] All references cited herein, including publications, patent applications, and patents, are hereby incorporated by reference in their entirety to the same extent as if each individual reference were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.

[0172] Unless the context clearly requires otherwise, throughout the description of the present invention, and especially in the following claims, the terms "a", "an", "the", "at least one", and similar designations shall be construed to cover both the singular and the plural. Unless the context clearly requires otherwise, the use of the term "at least one" (e.g., "at least one of A and B") following a list of one or more items shall be construed to mean one of the listed items (A or B) or any combination of two or more of the listed items (A and B). Unless otherwise noted, the terms "comprising", "having", "including", and "containing" shall be construed as open-ended terms (i.e., meaning "including, but not limited to"). Unless otherwise indicated herein, the recitation of ranges of values herein is merely intended to be a shorthand method of referring individually to each separate value falling within the range, and each separate value is incorporated into the specification as if it were individually recited herein. Unless the context clearly requires otherwise, all methods described herein may be performed in any suitable order. Unless otherwise required, the use of any and all examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illustrate the invention and does not limit the scope of the invention. The language of the specification should not be construed as indicating any non-claimed element as essential for the practice of the invention.

[0173] Preferred embodiments of the invention are described herein, including the best mode known to the inventors for practicing the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect those skilled in the art to adopt such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, if applicable law permits, the invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto. In addition, unless the context clearly requires otherwise or is otherwise clearly contrary to the context, the invention covers any combination of the above elements in all possible variations thereof.

Claims

1. A chemical mechanical polishing composition, comprising: (a) from about 0.001 wt% to about 10 wt% of a silica abrasive; (b) an oxidizing agent selected from potassium peroxymonosulfate (oxone), ammonium cerium nitrate, peroxides, periodates, iodates, persulfates, chlorates, chromates, permanganates, bromates, perbromates, ferrates, perrhenates, ruthenates, and combinations thereof; and (c) water, wherein the chemical mechanical polishing composition has a pH of about 2 or lower.

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

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

4. The polishing composition according to claim 1, wherein the polishing composition comprises from about 0.025 wt% to about 5 wt% of the silica abrasive.

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

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

7. The polishing composition according to claim 1, wherein the oxidizing agent is selected from permanganates, ammonium cerium nitrate, and combinations thereof.

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

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

10. The polishing composition according to claim 1, wherein the polishing composition further comprises from about 0.01 wt% to about 1 wt% of iron ions.

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

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

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

14. The polishing composition according to claim 1, wherein the polishing composition further comprises a buffer.

15. 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) from about 0.001 wt% to about 10 wt% of a silica abrasive; (b) an oxidizing agent selected from potassium peroxymonosulfate, ammonium cerium nitrate, peroxides, periodates, iodates, persulfates, chlorates, chromates, permanganates, bromates, perbromates, ferrates, perrhenates, ruthenates, and combinations thereof; and (c) water, wherein the chemical mechanical polishing composition has a pH of about 2 or lower, (iv) contacting the substrate with the polishing pad and the chemical mechanical polishing composition, and (v) Move the polishing pad and the chemical mechanical polishing composition relative to the substrate to abrade at least a portion of the substrate, thereby polishing the substrate.

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

17. The method according to claim 16, wherein the boron-doped polysilicon layer comprises at least 80 wt% boron.

18. The method according to claim 17, wherein the boron-doped polysilicon layer comprises at least 90 wt% boron.

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

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

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