WO2014150804A1

WO2014150804A1 - Cmp compositions with low solids content and methods related thereto

Info

Publication number: WO2014150804A1
Application number: PCT/US2014/024274
Authority: WO
Inventors: Lin Fu; Steven Grumbine
Original assignee: Cabot Microelectronics Corporation
Priority date: 2013-03-15
Filing date: 2014-03-12
Publication date: 2014-09-25
Also published as: EP2970732A4; TWI504736B; KR102319058B1; US20140263184A1; KR20150133761A; CN105209567A; TW201500530A; JP6382932B2; US8961807B2; CN105209567B; EP2970732B1; EP2970732A1; JP2016517461A

Abstract

Disclosed are a polishing composition and method of polishing a substrate. The composition has low-load (e.g., up to 0.1 wt.%) of abrasive particles. The polishing composition also contains water and at least one anionic surfactant. In some embodiments, the abrasive particles are alpha alumina particles (e.g., coated with organic polymer). The polishing composition can be used, e.g., to polish a substrate of weak strength such as an organic polymer. An agent for oxidizing at least one of silicon and organic polymer is included in the composition in some embodiments.

Description

CMP COMPOSITIONS WITH LOW SOLIDS CONTENT

AND METHODS RELATED THERETO

BACKGROUND OF THE INVENTION

[00011 Compositions and methods for planarizing or polishing the surface of a substrate are well known in the art. Chemical-mechanical planarization, or chemical-mechanical polishing (CMP), is a common technique used to planarize substrates. CMP utilizes a chemical composition, known as a CMP composi tion or more simpl as a polishing composition (also referred to as a polishing slurry ), for removal of material from the substraie. Polishing compositions typically are applied to a substrate by contacting the surface of the substraie wi th a polishing pad (e.g., polishing cloth or polishing disk ) saturated with the polishing composition. The polishing of the substrate typically is aided by the chemical activity of the polishing composition and/or the mechanical activity of an abrasive suspended hi the polishing composition or incorporated into the polishing pad (e.g., fixed abrasive polishing pad).

|0002] Conventional CMP compositions and methods typically are not entirely satisfactory at planarizing substrates. In particular, CMP polishing compositions and methods can result in less than desirable polishing rates and high surface defectiviiy when applied to a substrate. Because the performance of many substrates is direc tly associated with the pSanarity of their surfaces, it is crucial to use a CMP composition and method that results in a high polishing efficiency, selectivity, uniformity, and removal rate for a particular substraie and leaves the substrate with a high quality polish with minimal surface defects.

[0003] The difficulty in creating an effective polishing composition for semiconductor wafers stems from the complexity of the semiconductor wafer. Semiconductor wafers are typically composed of a substrate, on which a plurality of transistors has bee formed.

Integrated circuits are chemically and physically connected into a substrate by patterning regions in the substrate and layers on the substrate. To produce an operable semiconductor wafer and to maximize the yield, performance, and reliability of the wafer, it is desirable to polish select surfaces of the wafer without adversely affecting underlying structures or topography. In fact, various problems in semiconductor fabrication can occur if the process steps are not performed on wafer surfaces tha are adequately planarized.

[000 j CMP compositions often contain oxidizing agents, which can react, with the surface of the substraie and render the surface more susceptible to removal by mechanical abrasion. Oxidizing agents containing hydrogen peroxide have been used for this purpose. hut may not provide a satisfactory removal rate for certain substrates, including those which are not highly reactive to peroxide,

[0005J Organic polymer materials are increasingly of interest for rise in substrates. Some organic films exhibit a low dielectric constant (k), such as between. 1 and 2,2, and thereby have desired insulation property. Other organic films have higher dielectric constants.

Organic polymer .materials also are relatively inexpensive. Despite these advantages associated with the use of organic polymer films in substrates, there are tradeoffs with using organic polymers, in particular, organic polymers present Significant challenges with respect to plaiiarizaiion because they can. be mechanically soft and easy to scratch. Moreover, in contrast to their mechanical sensitivity, organic polymers are often chemically inert. The combination of these chemical and mechanical characteristics makes organic polymer dielectric .materials difficult to polish using a traditional aqueous based CMP composition. Organic polymer materials used in semiconductor fabrication, typically include (a) polymers with a relatively high organic content, (b) polymers with a low and high organic content with a high level of porosi y; (c) polymers with relatively low organic content based upon silicon- oxygen type materials and inorganic materials, and (d) polymers with a combination of these properties.

[Θ006{ A need remains for a polishing composition and polishing methods that will exhibit desirable removal rates and uniformit during the polishing and planarization of substrates containing organic polymer materials, while minimizing deiectivity, such as surface imperfections and damage to underlying structures and topography during polishing and planarization. The invention provides such a polishing composition and method. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the in ven tion provided herein.

BRIEF SUMMARY OF THE INVENTIO

[0007J In one aspect, the invention provides a polishing composition comprising (a) 0.01 wt.% to 0.001 wt.,% of abrasive particles, (b) at least one anionic surfactant, and (c) water. The abrasive particles are desirably coated with a polymer, and the composition has a pH of 1.5 to 5.

[Θ008] In another aspect, the invention provides a polishing composition comprising (a) abrasive particles in an amount of up to 0.1 wt.%, (b) at least one anionic surfactant, (e) an oxidizing agent that oxidizes an organic polymer, and (d) water, wherein the composition has a ρϊϊ of 1.5 to S. [0009] In another aspect, the invention provides a method of polishing a substrate. The method comprises contacting a substrate with a polishing pad and a polishing composition comprising (a) 0,001 wt.% to 0.1 wt.% of abrasive particles, (b) at least one anionic surfactant, and (c) water. The abrasive particles are desirably coated with a polymer, and the composition has a pH of 1 .5 to 5. The method further comprises moving the polishing pad and the polishing composition rela tive to the substrate to abrade at least a portion of the substrate to polish the substrate.

[0010] In another aspect, the present invention provides a method of polishing a substrate comprising contacting a substrate with a polishing pad and a polishing composition comprising (a) abrasive particles in an amount of up to 0.1 wt.%, (b) at least one anionic surfactant, (c) an oxidizing agent that oxidizes an organic polymer, and (d) water, wherein the composition has a pH of 1 .5 to 5. The method further comprises moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWiNG(S)

[Θ011] FIG. I is a graph plotting the removal amount in 30 seconds (Y -axis) vs. the measurement points from edge to edge of a wafer (X-axts) when polishing a substrate with three different polishing compositions, in accordance with embodiments of the invention.

[Θ0Ι.2) FIG. 2 is a bar graph illustrating the number of de ects on a substrate resulting from the use of three separate polishing composi tions containing various amounts of abrasi ve particles.

[0013] FIG, 3 is an opticai microscopy image at 10X magnification of a spin-on-carbon substrate, which was polished using a polishing composition that includes a conventional load of abrasive particles, for comparative purposes.

[0O14| FIG. 4 is a bar graph illustratin the removal rate of polysilicon and spin-on- carbon from a substrate using polishing compositions comprising various surfactants or no surfactant.

DETAILED DESCRIPTIO OF THE INVENTION

}t)015| Embodiments of the invention provide a polishing composition with low abrasive particle solids content. The polishing composition in accordance with embodiments of the invention comprises abrasive particles generally in an amount of 0.1 wt.% or less (e.g., 0.0 J wt.% to 0.1 wt.%), one or more anionic surfactants, and water. Such a polishing composition is in the farm of slurry and can be used to polish surfaces, such as mechanically weak surfaces with a suitable chemical-mechanical polishing (CMP) apparatus including a polishing pad, such as described herein, in some embodiments, the polishing composition achieves high removal rates for organic film, while selectively achieving low removal rates for polysilicon material underlying the organic .film material on a substrate. Furthermore, some embodiments of the polishing composition allow for good uniformity in removal across a substrate surface,

[0016] Advantageously, the polishing composition in accordance with embodiments of the invention surprisingly and unexpectedly results in desired removal rates previously known for polishing compositions having much higher abrasive particle concentrations. Furthermore, the polishing composition achieves such desired removal rates while also surprisingly and unexpectedly achieving low defectively ( e.g., scratches and the like) on the substrate being polished.

[Oul?! In some embodiments, the abrasive particles are selected to comprise metal oxides, particularly alumina, {e.g., alpha alumina), zirconia, colloidal silica, fumed silica, ceria, or combinations thereof. The aforementioned abrasive particles are desirably coated with polymer which is selected to provide a cushion when the abrasive particles in the polishing composition interact with a substrate being polished (e.g., polymeric film). For example, the abrasive particles can be coated with polymer effective t achieve a coefficient of .friction (Cof) of 0.1 to 0.5 (e.g., 0.2 to 0.3), as determined according to a torque

measurement method, as defined herein, when the abrasive particles contact the substrate to be polished (such as mechanically weak organic film) as applied with a CMP apparatus. In the torque measurement method defined herein, an ARG2 rheometer (using cone piate geometry) from TA Instruments (New Castle, Delaware) is used to determine torque in N^»m. A polishing pad ting is attached to the piate and slurries are added in between. The torque is measured when the cone is rotated at a fixed rpm of 1.00 relative to the bottom plate. The torque is then converted to Cof according to the following calculation;

wherein t ^~ Torque, R? is the outside diameter, j is the inside diameter, and N is the normal force.

[0018] The polymer coating in some embodiments is a water soluble anionic polymer such as a hydrophilic, sulfonic acid acrylic polymer (including copolymers), acrylic acid polymer (including copolymers), .raaleic acid polymer (including copolymers, aspartic acid copolymer (including copolymer) or combinations thereof. For example, the coating can he in the form of a copolymer of acrylic acid poiy(2-acryiamido-2-methyi~1 -propane sulfonic acid), polyaerylic acid or any combination thereof. The polymer can be present in any suitable amount by weight of the abrasive particle, such as, for example, from 5 wt.% to 50 wt.%, e.g., from 10 wt.% to 30 wt.% (wt.% of polymers per weight basis of particles), !n one illustrative embodiment, the abrasive particles are alpha alumina particles, which are coated with a copolymer of acrylic acid poly(2 -aery lamido-2-meihyl-l -propane sulfonic acid).

[0019] In some embodiments, the polishing composition is substantially free of colloidal silica particles, zirconia, and/or fumed silica particles as they are withoot any polymeric coating and because mechanically weak organic films at times can be susceptible to detectivity when such particles are used in the polishing composition. As used herein,

"substantially free'⁵ of such other particles means that the polishing composition contains 0 wt. % based on the weight of the composition, or no such other partic les, or an ineffective or immaterial amount of such particles. An example of an ineffective amount is an amount below the threshold amount to achieve the intended purpose of using such particles, as one of ordinary skill in the art will appreciate. An immaterial amount may be, e.g., below 0.01 wt.%, as one of ordinary skill in die art will appreciate.

[Θ02Θ] The abrasive particles can be present in the polishing composition in any suitable concentration of 0.1. wt.% or less. For example, in various embodiments, the abrasive particles ca be included in the polishing composition in an amount from 0.001 wt.% to 0. i wt.%, such as, for example., from 0.0025 wt.% to 0J wt.%, 0.01 wt.% to 0.1 wt.%, from 0.03 wt.% to 0.1 wt.%, from 0.05 wt.% to 0.1 wt.%, from 0.0! wt.% to 0.08 wt.%, fr m 0.02 wt.% to 0.08 wt.%, from 0.03 wt.% to 0.08 wt.%, from 0.01. wt.% to 0.06 wt.%, from 0.02 wt.% to 0,06 wt.%, f om 0.01 wt.% to 0.05 wt.%, or from 0.02 wt.% to 0.05 wi.%.

[00211 The abrasive particles, such as coated alpha alumina particles, can have any suitable particle size. The size of a particle is the diameter of the smallest sphere that encompasses the particle. The coated abrasive particles can have an average particle size of 10 nm or more, e.g., 25 itra or more, 50 nm or more, 75 nm or more, or 1.00 nm or more. Alternatively, or in addition, the coated abrasive particles can have an average particle size of 250 nm or less, e.g., 225 nm or less, 200 nm or less, 175 nm or less, 160 nm or less, or 150 ran or less. Thus, the coated abrasive particles can have a particle size bounded by any of the foregoing endpoints. For example, coated abrasive particles can have an average particle size of 25 ran to 250 xm\, e.g.. 35 lira to 200 tun, 45 am to 150 am, 50 nra to 125 nm, 55 nm to

120 ran, or 60 run to 1 1 .nm.

[Θ022] The abrasive particles desirably are suspended in the polishing composition, more specifically in the aqueous carrier of the polishing composition. When the abrasive particles are suspended in the polishing composition, the abrasive particles preferably are coUoidall y stable. The term colloid refers to the suspension of abrasive particles in the aqueous carrier Colloidal stability refers to the maintenance of that suspension over time. In the context of this invention, abrasive particles are considered eollo.klai.ly stable if, when the abrasive- particles are placed into a 1.00 ml graduated cylinder and allowed to stand unagitated for a time of 2 hours, the difference between the concentration of particles in the bottom 50 ml. of the graduated cylinder (| B | in terms of g/ml) and the concentration of particles in the top 50 ml of the graduated cylinder (| | in terms of g/ml) divided by the initial concentration of particles in the abrasive composition ([CJ in terms of g/ml.) is less than or equal to 0.5 {i.e., {fB]-[T]}/[C| < 0.5). The value of [B]-[T]/[C] desirably is less than or equal to 0.3, and preferably is less than or equal to 0.1.

[6023] One or more anionic surfactants are included in embodiments of the inventive polishing composition. The anionic surfactant is included as a promoter for enhancing the ^■removal rate of the substrate surface being polished. Anionic surfactants are preferred over nonionic surfactants (e.g., difunctional block copolymers and the like) and cationic surfactants inasmuch as anionic surfactants are believed to wet. and lubricate the substrate surface being p lished to enhance the hydrophilkiiy of the substrate surface (e.g., organic film). Desirably, the polishing pad used in the CMP apparatus is also hydrophilic to further facilitate the removal rate of the substrate surface being polished.

[0024 j Particularly, in accordance with some embodiments of the invention, the anionic surfactant is effecti ve to decrease the contact angle of the substrate surface to 60° or less (e.g., down from an angle of 70° or greater) when a water droplet is applied to the substrate surface, in some embodiments, the anionic surfactant is effective to reduce the contact angle of the substrate surface to 50'^· or less, e.g., 40° ox less, 30^ft or less, 20° or less, or 5ⁿ or less. The contact angle can be measured by any suitable technique, such as drop shape method understood in the art. In some embodiments, the anionic surfactant comprises carboxylates, sulfonates, sulfates, phosphates, phosphonates, and combinations thereof. For example, the anionic surfactant can comprise a sulfonate group, such as diphenyl oxide disulfonaie. [0025] The anionic surfactant can be present in the poi.ish.rog composition in any suitable concentration. For example, in various embodiments, the anionic surfactant can be inel ded in the polishing composition in an amount from 0.0002 wt.% to 2 wt.%, such as, for example, from 0,002 wt.% to 0.2 wt.%, from 0.01 wt.% to 0.02 wt.%.

[0026] Optionally, in some embodiments, the polishing composition can include one or more oxidizing agents. The oxidizing agent is selected to oxidize the substrate to be polished, including, e.g., organic films. For example, in some embodiments, the oxidizing agent includes at least one perox {.-0—0--_.) group. Such peroxy-type oxidizers can be an organic peroxide, inorganic peroxide, or combination thereof. Examples of compounds containing at least one peroxy group include, but are not limited to, hydrogen peroxide and its adducts such as urea hydrogen peroxide and percarbonates (e.g., sodium percarbonate), organic peroxides such as benzoyl peroxide, peracetic acid, perbork acid, and di-tert-butyJ peroxide, monopersulfiuesfSOs^2"), dipersulfates (S^ , and sodium peroxide.. In one embodiment, the oxidizer is hydrogen peroxide.

I O027| If included, the one or more oxidizers can be present in the polishing composition in any suitable concentration. For example, in various embodiments, the oxidizer can be included in the polishing composition in an amount from 0. 1 wt.% to 10 wt.%, such as, for example, from 0.1 wt.% to 5wt%, from 1 wt.% to 3 wt.%, or from 1 wt.% to 2 wt.%.

jOOZSf The polishing compositio includes an aqueous carrier. The aqueous carrier contains water (e.g., deiomzed water), and may contain one or more water-miscible organic solvents. Examples of organic solvents that can be used include alcohols such as propeoyl alcohol, isopropyl alcohol, ethanol.. ί -propanoi, methanol, i -hexano!, and the like; aldehydes such as acetylaldehyde and the like: ketones such as acetone, diacetone alcohol, methyl ethyl ketone, and the like; esters such as ethyl formate, propyl formate, ethyl acetate, methyl acetate, methyl lactate, butyl lactate, ethyl lactate, and the like; ethers including sulfoxides such as dimethyl sulfoxide fDMSO), tetrahydrofuran, dioxane, digiyrae, and the like; amides such as N, N-dimethylformaniide, dimethyl imidazolidinone, N-methy!pyrrolidone, and the like; po^'Iyhydric alcohols and derivatives of the same such as ethylene glycol, glycerol, diethylene glycol, diethylene glycol monomethyl ether, and the like; and nitrogen-containing organic compounds such as acetonitrile, amylamine, isopropylamine, imidazole,

dimethyiamine, and the like. Preferably, the aqueous carrier is (i.e., consists of) water.

[Θ02 { The polishing composition can have any suitable pH. Typically, the polishing composition has a pH of 1 or greater. The pH of the polishing composition typically is 5 or less. For example, the polishing composition can have a pH in the range of 1 to 5 (e.g., a pH of .1.5, a pH of 2, a pH of 2.5, a pH of 3, a pH of 3.5, a H of 4, H of 5, or a pH in a range defined by any two of these pH values). Preferably, the pH is in the range of 1 to 3,5, or 2 to 3,5, such as 2 to 2.5.

[0030] The pti of the polishing composition can be achieved and/or maintained by any suitable means. More specifically, the polishing composition can further comprise a pH adjuster, a pH bufferin agent, or a combination thereof. The pH adjusiot can be any suitable pH-adjusting compound. For example, the pH adjustor can be an acid. The acid can be any suitable acid. Typically, the acid is acetic acid, nitric acid, phosphoric acid, oxalic acid, and combinations thereof. Preferably, the acid is nitric acid. The pH adjustor alternatively ca be a base. The base can be any suitabie base. Typically, the base is potassium hydroxide, ammonium hydroxide, and combinations thereof. Preferably, the base is ammonium

hydroxide. The pH buffering agent, can be any suitable buffering agent. For example, the pH buffering agent can be a phosphate, sulfate, acetate, borate, ammonium salt, and the like. The polishing composition can comprise any suitable amount ofa H adjustor and/or a pH buffering agent, provided that a suitable amount is used to achieve and/or maintain the p.H of the polishing composition within the pH ranges set forth herein.

[Θ031 { In some embodiments, the polishing composition is substantially free of metal cornpl.ex.ing agents, corrosion inhibitors, and/or rheology or viscosity agents. Examples of such materials are set. forth i co-pending, commonly-assigned U.S. Patent Application 13/754,413, entitled Chemical-Mechanical Polishing Composition Containing Zirconsa and Metal Oxidizer. As used herein, "'substantially free" of such metal complexing agents, corrosion inhibitors, and or theology or viscosity agents means that the polishing composition contains 0 wt. % based on the weight of the composition., or no such metal complexing agents, corrosion inhibitors, and or rheology or viscosity agents, or an ineffective or

immaterial amount of such metal complexing agents, corrosion inhibitors, and/or rheolog or viscosity agents. An example of an ineffective amount is an amount below the threshold amount to achieve the intended purpose of using such metal complexing agents, corrosion inhibi tors, and/or rheology or viscosity agents, as one of ordinary skill in the art will appreciate. An immaterial amount may be, e.g., below 0,05 wt.%, such as below 0.01 wt.%, as one of ordinary skill in the art will appreciate. However, if desired in alternative embodiments, such ingredients can be included in the polishing composition. [0032] The polishing composition can be prepared b any suitable technique, mans of which are known to those skilled in the art.. The polishing composition can. be prepared in a batch or continuous process. Generally, the polishing composition can be prepared by combining the components herein in ny order.

[0033] Embodiments of the invention also provide a method of polishing a substrate with the polishing composition described herein . The method of pol ishing a substrate comprises (t) providing a substrate, (ii) providing a polishing pad, (iii) providing the aforementioned chemical-mechanical polishing composition,, fiv) contacting the substrate with the polishing pad and the chemical-mechanical polishing composition, an.d. (v) moving the polishing pad and the chemical-mechanical polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate. In another aspect, the present Invention provides method of polishing a substrate.

[0034] In particular, some embodiments of the method comprises contacting a substrate with a polishing pad and a polishing composition comprising (a) 0.001 wt.% to 0.1 wi.% of abrasive particles, (b) at least one anionic surfactant, and (c) water. The abrasive particles are desirably coated with a polymer, and the polishing composition has a pH of 1 .5 to 5. The method further comprises moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate.

[0035] In addition, some embodiments of the invention provide a method of polishing a substrate comprising contacting a substrate with a polishing pad. and a polishing composition, comprising (a) abrasive particles in an. amo unt of up to 0.1 wt.%, (b) at least one anionic surfactant, (c) an oxidizing agent that oxidizes an organic polymer, and (d) water, wherein ihe composition, has a pH of 1 ,5 to 5. The method further comprises moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion, of the substrate to polish the substrate.

[0036] The inventive polishing composition can be useful for polishing any suitable substrate. The substrate to be polished can be the other surface of any multi-layer workpiece. Suitable substrates include the layers of semiconductors, MEMS (raicroelectroraechanica! systems), and optica! waveplates, as well as anti-reflective coatings (ARC). The polishing composition is particularly useful in the polishing of a substrate that is mechanically weak, particularly a substrate comprising an organic polymer film. In this respect, while the polishing composition can be used for polishing organic polymer films with any suitable carbon content, in some embodiments, the polishing composition is well suited for polishing substrates containing a high level of carbon, e.g., at least 50%, such as at least 60%, at least 70%, at least 80% or higher, e.g., from 50% to 85%, such as from 60% to 85%, or 70% to 85%, as measured by carbon analysis.

[0037| For example, in some embodiments, the mechanically weak organic film substrate exhibits an elastic modulus (Young's modulus) of 2.5 GPa or less, as determined according to ASTM E 1 1 1 , e.g., 2 GPa or less, such as .1.5 GPa or less, I. GPa or ess, 0.5 GPa or less, etc. In some embodiments, the substrate is a hydrophobic organic film, e.g., exhibiting a contact angle of 70* or more where a water droplet is applied to the film.

[0038J An organic polymer film to be polished with the inventive polishing composition can have any suitable dielectric constant, such as a dielectric constant of 3.5 or less (e.g., 3 or less, 2.5 or less, 2 or less, 1.5 or less, or 1 or less). Alternatively, or in addition, the organic polymer film can have a dielectric constant of 1 or more (e.g., 1.5 or more., 2 or more, 2.5 or more, 3 or more, or 3.5 or more). Thus, the organic polymer film can have a dielectric constant bounded by any two of the foregoing endpoints. For example, the organic polymer film can have a dielectric constant between i and 3.5 (e.g., between 2 and 3, between 2 and 3.5, between 2.5 and 3, between 2.5 and 3.5).

[0039] Suitable organic polymer films can comprise spin-on-carbon materials, many of which are known the art. Such spin-on -carbon materials generally have high carbon content as described herein and are generally formed by a spin-coating method. See. e.g., U.S. Patent 7,615,497 and U.S. Patent Publications 2009/0035590; 2010/01 70868; 2012/0270395; and 2013/001 .1 30. One commercially available s in-on-carbon material is OptiStack<l>

SOC1 10D from Brewer Science, Rolla, MO.

[0040] Other suitable organic films include, for example, polyimide, flxtorinated

poiyimide, polyarylenes and polyarylene ethers (such as SILK™ from Dow Chemical, FLARE™ from Allied Signal, and VELOX™ from Schumacher), polybenzocyclobutene, divinyl. siloxane bisbenzocyclobutene (DVS-BCB), polytetrafluoroethylene (PTFE), polysiloxane, polvnaphthylene ether, polyquinoiines, paralynes (such as Parylene AF4, an aliphatic tetrafluorinated poly-p-xylylene), copolymers thereof and combinations thereo Desirably, the organic polymer film comprises a ring-containing organic polymer, such as a heterocyclic organic polymer (e.g., polybenzosazole). The substrate optionally can be free of one or more silica or metal layers, especially metal layers comprising copper, tantalum, tungsten, titanium, platinum, ruthenium, iridium, aluminum, nickel, and or combinations thereof. In some embodiments, during substrate fabrication, gap sealing techniques can be employed. In this respect, a layer of organic film can be oxidized at elevated temperature to form carbon dioxide and bum off the organic polymer to form an air gap as space filling material between oxidizing layers in a sandwich structure. This arrangement allows the substrate to use air's low dielectric constant of I .

[0041 f In accordance with the invention, a substrate can be planari ed or polished with the polishing composition described herein by any suitable technique. The polishing methods of the invention are particularly suited for use in conjunction with a CMP apparatus.

Typically, the CMP apparatus comprises a platen, which, when in use, is in motion and has a velocity that results from, orbital, linear, or circula motion, a polishing pad in contact with the platen and moving with the platen when in motion, and a carrier that holds a substrate to be polished by contacting and moving relative io ihe surface of the polishing pad.

Embodiments of polishing compositions of the invention allow for increased platen speeds (e.g., 50 or greater, such as 1 0 or greater.) The polishing of the substrate takes place b the substrate being placed in contact with the polishing composition of the invention and then abrading at least a portion of the surface of the substrate, e.g., the organic polymer film, or one or more of the substrate materials described herein, with the polishing composition to polish the substrate.

[0042] Desirably, the CMP apparatus further comprises an in situ polishing endpoint detection system, many of which are known in the art. Techniques for inspecting and monitoring the polishing process by analyzing light or other radiatio reflected from a surface of the workpiece are known in the art. Such methods are described, for example, i U.S. Patent 5,196,353, U.S. Patent 5,433,651 , U.S. Patent 5,609,511, U.S. Patent 5,643,046, U.S. Patent 5,658,183, U.S. Patent 5,730,642, U.S. Patent 5,838,447, U.S. Patent 5,872,633, U.S. Patent 5,893,796, U.S. Patent 5,949,927, and U.S. Patent 5,964,643. Desirably, th inspection or monitoring of the progress of the polishing process with respect to a workpiece being polished enables the determination of the polishing end-point, i.e., the determination of when to terminate the polishing process with respect to a particular workpiece.

(0043 The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

EXAMPLE 1.

[0044 j This example compares the effect of three different polishing compositions (1A- 1C) on the removal rate of spin-on-carbon (SoC) organic film substrates (wafers). [0045] In particular, the SoC substrates were polished with polishing compositions 1 A- 1C with conventional CMP apparatus. The polishing compositions included coated alpha alumina particles in varying amounts. Particularly, the alpha alumina panicles were treated with acrylic acid poiy(2-acryIamido-2-me hyl-l-propane sulfonic acid). Each polishing composition also included I wt.% of the oxidizing agent hydrogen peroxide (HjQj . All three polishing compositions were adjusted as necessary to a pH of 2.3.

J 0046 Two of the polishing compositions also included a surfactant as a removal rate promoter, in accordance with embodiments of the invention. The surfactant was a diphenvi oxide disiilfonate anionic surfactant, commercially available under the DOWFAX brand. For comparison purposes, the third polishing composition did not include a surfactant but included a significantly higher concentration of coated abrasive particles. ^'The amounts of coated alpha alumina particles, surfactant, and hydrogen peroxide are set forth in Table 1 below:

Table 1

[0047 j The substrates were polished on a REFLEXION™ CMP apparatus (Applied Materials, nc., Santa Clara, California). The polishing pad used for polishing compositions 1 A and I B was a D200 42D XY grooved pad (Caboi Microelectronics, Aurora, Illinois), while the polishing pad used for polishing composition iC was a POLYTEX™ pad (Rodel, Inc, Phoenix, Arizona). The polishing parameters were as follows; 6.89 kPa ( I psi) clown force, 50 rpm platen speed, and 47 rprn head speed.

[00481 Following polishing, the removal rate of SoC was determined in A , The results are illustrated i FIG. I , which is a plot of removal rate amount in 30 seconds (Y-axis) at measurement points (X-axis), which indicates the location of measurements spanning the entire distance of the wafer.

[0049] These results demonstrate that the coated alpha alumina particles in combination with a surfactant are particularly effective for polishing substrates comprising organic film, even at low concentration of the abrasive particles. In particular, polishing composition 1 A had a considerably higher rate of removal than polishing composition IB, even though polishing composition lA had almost an order of magnitude less of the abrasive particles. Furthermore, polishin composition i had comparable removal rates as polishing composition I B, even though polishing composition I B had 40 times the amount of abrasive particles as polishing composition IC. In addition, the polishing compositions exhibited good uniformity, with a .non-uniformity rate less than 15% for polishing composition 1A, less than 13% for polishing composition I B, and less than 10% for polishing composition I C.

EXAMPLE 2

[0050] This example compares the effect of three different polishing compositions (2A-

2C) on the number of defects whe pol ishing SoC organic film substrates.

[0051} In particular, the SoC substrates were polished with polishing compositions 2A-

2C with a conventional CMP apparatus. Each polishing composition included coated alpha alumina particles in varying amounts and hydrogen peroxide oxidizin agent a described in

Example 1 , All three polishing compositions similarly were adjusted as necessary to a pH of

2.3.

[0052] Polishing compositions 28 and 2C included surfactant as a removal rate promoter, In accordance with embodiments of the invention. Both polishing compositions 2B and 2C included the diphenyl oxide disulfonate anionic surfactant described in Example 1. Polishing composition 2C further included a noniomc surfactant, namely, a difunctional block copolymer terminating in primary hydroxy! groups, commercially available as Piuronic 31™ (BASF, Inc., Florham Park, New Jersey). For comparison purposes, polishing composition 2A did not include surfactant The amounts of coated alpha alumina particles, surfactant, and hydrogen peroxide are set forth in Table 2 below:

Table 2

(0053] The substrates were polished an a REFLEXION™ CMP apparatus (Applied Materials, Inc., Santa Clara, California). The polishing pad was a D20 42D XY grooved pad (Cabot Microelectronics, Aurora, Illinois). The polishing parameters were as described, in Example 1.

[0054] Following polishing, the number of substrate defects was determined, with a threshold size of 0,05 microns to qualify as a defect. The results are illustrated in FIG. 2, which is a bar graph that indicates the number of substrate deiects caused by each polishing composition.

[0055] These results demonstrate that the coated alpha alumina particles in combination with surfactant is particularly effective for polishing substrates comprising an organic film with low defect count, particularly at lower abrasive concentration. In particular, polishing composition 28 provided had the lowest substrate defect, count while having the lowest, abrasive concentration and also including surfactant. Furthermore, polishing composition 2A provided a considerably higher substrate defect count than polishing composition 2C at the same abrasive concentration, but polishing composition 2C included surfactant while polishing composition 2A did not include surfactant.

EXAMPLE 3 - COMPARATIVE

[Θ056] This example illustrates the propensity of SoC organic film substrates to exhibit detectivity when subjected to polishing in conventional systems.

[0057] A polishing composition including 0.5 wt.% of colloidal silica and i% hydrogen peroxide, and having a ^'H of 2.3, was used to polish a SoC organic film substrate with con ventional CMP apparatus. The substrates were polished on a REFLEXION™ CMP apparatus (Applied Materials, Inc., Santa Clara, California). The pad wa a D200 42D XY grooved pad (Cabot Microelectronics, Aurora, Illinois). The polishing parameters were as described in Example 1.

[0058] After polishing, an optical microscopy image of the polished spin-on-carbon substrate was taken at tOX magnification, as depicted in FIG. 3. As is apparent from FIG. 3, the polished substrate exhibited considerable scratching when subjected to the conventional polishing composition which contained conventional abrasive particles in a conventional concen iration range. EXAMPLE 4

0 59J This example compares the effect of including various surfactants in different polishing compositions relative to the removai rate of (a) spin-on-carbon (SoC) organic films and (b) polysilicon underlying the organic films.

Θ06Θ] Five polishing compositions were tested (4A-4E). All of the polishing compositions included 0.15 wt.% of abrasive particles and 1 % hydrogen peroxide as described in Example 1 , and all the polishing compositions were adjusted as necessary to achieve a pH of 2.3.

(0061 J Each polishing composition varied with respect io the surfactant More particularly, polishing composition 4A included no surfactant. Polishing compositions 4.B included 0.03 wt.% of noiiionic surfactant commercially available as Surfynol 104PG™, from Air Products, Allentown, Pennsylvania. Polishing composition 4C included 0.01 t% of nonionic surfactant characterized as difunciional. block copolymer terminating in primary hydroxyl groups, commercially available as Pluronic 31™ (BASF, Inc., Florhara Park, New Jersey), Polishing composition 4D included 0,0 i wt.% ofdiphenyl oxide disulfonate anionic surfactant, commercially available as DOWFAX™, from Dow (Midland, Michigan).

Polishing composition 4E included 2 wt.% of dimethyl sulfoxide (DMSO).

(0062) The substrates were polished on a Mirra™ CMP apparatus (Applied Materials, Inc., Santa Clara, California). The polishing pad was a D200 42D XY grooved pad (Cabot Microelectronics, Aurora., Illinois). The polishing parameters were as described in Example 1.

[0063] Following polishing, the removal rale of SoC was determined in A/rain. The results are illustrated in f i^'G.4, which is a bar graph illustrating the removai rate affected b each polishing composition on. the SoC film and on the underlying polysilicon. As is apparent from FIG, 4, the removal rate of the SoC was highest, and the removal rate of the polysilicon was the lowest, with the diphenyl oxide disulfonate anionic surfactant

(0064] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those o f ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by contest.

Claims

CLAIMS):

1. A polishing composition comprising:

(a) 0.001 wt.% to 0.1 wt.% of abrasive particles coated with a polymer,

(b) at least one anionic surfactant, and

(c) water,

wherein the composition has a pH of 1.5 to 5,

2. The polishing composition of claim 1 , wherein the abrasive particles comprise alumina, fumed silica, silica, and/or zirconia,

3. The polishing composition of claim 1, wherein the abrasive particles comprise alpha alumina.

4. The polishing composition of claim 1. wherein the polymer is effecti ve to achieve a coefficient of friction of 0.1 to 0.5, as determined according to the torque measurement method, when the particles contact an organic film subsiraie having an elastic modulus of 2,5 GPa or less as determined according to ASTM E 1 1 1.

5. The polishing composition of claim 1 , wherein the polymer is a water soi.ub.le anionic polymer.

6. The polishing composition of claim L wherein the polymer is an acrylic acid poly(2-aciylam?do-2-methyl - 1 -propane sulfonic acid) .

7. The polishing composition of claim 1 , wherein the composition is effective for polishing an organic film, the compositio further comprising an oxidizing agent that oxidizes an organic polymer.

8. The polishing composition of claim 1 , wherein the composition is effective for polishing an organic film having a contact angle of 70° or greater when a water droplet is applied to the organic film, and wherein the anionic surfactant is effective to reduce the contact angle of the organic film to 60° or less when a water droplet is applied to the organic film.

9. The polishing composition of claim 1 , wherein the anionic surfactant is selected from the group consisting of carboxy!ates, sulfonates, sulfates, phosphates, phosphonates, and combinations thereof.

10. The polishing composition of claim 9, wherein the anionic surfactant comprises a sulfonate group.

1 1. The polishing composition of claim 9, wherein the anionic surfactant comprises ctiphenyl oxide disulfonate.

12. A polishing composition comprising:

(a) abrasive particles in an amount of up to 0.1 wt.%,

(b) at least one anionic surfactant,

(c) an oxidizing agent that oxidizes an organic polymer with carbon content of at !east 60%, and

(d) water,

wherein the composition has a pH of 1.5 to 5.

13. The polishing composition of claim 12, wherein the abrasive particles comprise alpha alumina particles coated with a polymer.

14. The polishing composition of claim 13, wherei the polymer is an acrylic acid po!y(2-acrylamido-2-methyl-l -propane sulfonic acid),

15. A method of polishing a substrate, which method comprises:

(i) contacting a substrate with a polishing pad and the polishing composition of claim 1 ; and

(it) moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate.

1 . The method of claim J 5, wherein the substrate comprises an organic polymer and the organic polymer is abraded to polish the substrate.

17. The metliod of claim 1 , wherein the organic polymer comprises a spin-on- carbon material.

18. The method of claim 16, wherein the organic polymer has an elastic modulus of 2.5 GPa or less, as measured according to ASTM E i l l.

] 9. The method of claim 1 , wherein the contacting results in a coefficient of friction of 0.1 to 0.5, as determined according to the torque measurement method when the particles contact the organic film substrate.

20. A method of polishing a substrate, which method comprises: (i) contacting a substrate with a polishing pad and the polishing composition of claim 12; and

(ii) moving the polishing pad and the polishing composition relative to the substrate to abrade at least a portion of the substrate to polish the substrate.

21. The meiliod of claim 20, wherein the substrate comprises an organic polymer and the organic polymer is abraded to polish the substrate.

22. The method of claim 21 , wherein the organic polymer comprises a spin-on- carbon material.

23. The method of claim 21, wherein the organic polymer has an elastic modu! as of 2.5 GPa or less, as measured according t ASTM E 11.1.

24. The method of claim 21, wherei the contacting results in a coefficient of friction of 0.1 to 0,5, as determined according to the torque measurement method when the particles contact the organic film substrate.