WO2014047014A1

WO2014047014A1 - Incorporating additives into fixed abrasive webs for improved cmp performance

Info

Publication number: WO2014047014A1
Application number: PCT/US2013/060022
Authority: WO
Inventors: Julie Y. Qian; William D. Joseph; Stephen C. LOPER
Original assignee: 3M Innovative Properties Company
Priority date: 2012-09-21
Filing date: 2013-09-17
Publication date: 2014-03-27
Also published as: SG11201502225XA; JP2015532895A; KR20150058302A; EP2897767A1; US20150217424A1; CN104822495A; EP2897767A4; TW201420706A

Abstract

A structured abrasive article is provided that has a backing having first and second opposed major surfaces and a structured abrasive layer disposed on and secured to the first major surface of the backing. The structured abrasive layer includes a polymeric binder, abrasive particles dispersed in the binder and an additive dispersed in the binder. The additive provides improved chemical mechanical planarization (CMP) polish performance, including high oxide/nitride selectively, high removal rates, lower nitride loss and improved with-in- wafer non-uniformity (WIWNU).

Description

INCORPORATING ADDITIVES INTO FIXED ABRASIVE WEBS

FOR IMPROVED CMP PERFORMANCE

Cross Reference to Related Applications

This application claims the benefit of U.S. Provisional Application No. 61/703,815, filed September 21, 2012, the disclosure of which is incorporated by reference herein in its entirety.

Field

The present invention relates generally to fixed abrasive webs having improved chemical mechanical planarization (CMP) polishing performance. In particular, the present invention relates to fixed abrasive webs containing additives that improve CMP polishing performance.

Background

Abrasive articles are frequently used in microfinishing applications such as semiconductor wafer polishing, microelectromechanical (MEMS) device fabrication, finishing of substrates for hard disk drives, polishing of optical fibers and connectors, and the like. For example, during integrated circuit manufacture, semiconductor wafers typically undergo numerous processing steps including deposition of metal and dielectric layers, patterning of the layers, and etching. In each processing step, it may be necessary or desirable to modify or refine an exposed surface of the wafer to prepare it for subsequent fabrication or manufacturing steps. The surface modification process is often used to modify deposited conductors (e.g., metals, semiconductors, and/or dielectric materials). The surface modification process is also typically used to create a planar outer exposed surface on a wafer having an exposed area of a conductive material, a dielectric material, or a combination.

One method of modifying or refining exposed surfaces of structured wafers treats a wafer surface with a fixed abrasive article. In use, the fixed abrasive article is typically contacted with a semiconductor wafer surface, often in the presence of a working fluid, with a motion adapted to modify a layer of material on the wafer and provide a planar, uniform wafer surface.

Fixed abrasive articles generally have an abrasive layer of abrasive particles bonded together by a binder and secured to a backing. In one type of fixed abrasive article, the abrasive layer is composed of discrete raised structural elements (e.g., posts, ridges, pyramids, or truncated pyramids) termed "shaped abrasive composites". This type of fixed abrasive article is known in the art variously by the terms "textured, fixed abrasive article" or "structured abrasive article" (this latter term shall be used hereinafter). The abrasive articles can include abrasive particles and at least one nonionic polyether surfactant dispersed in a crosslinked polymer binder as disclosed in U.S. S.N. 12/560,797 (Woo et al).

Summary

In one embodiment, the present invention is a structured abrasive article including a backing having first and second opposed major surfaces and a structured abrasive layer disposed on and secured to the first major surface of the backing. The structured abrasive layer includes a polymeric binder, abrasive particles dispersed in the binder and a first additive dispersed in the binder. The first additive may be a multidentate acidic complexing agent, wherein the multidentate acidic complexing agent comprises an amino acid, a dipeptide formed from an amino acid and combinations thereof. The structured abrasive layer may include a second additive. The second additive comprises a nonionic surfactant, silicon surfactant, fluorosurfactant, water soluble polymer and combinations thereof.

The additives provide improved chemical mechanical planarization (CMP) polish performance, including high oxide/nitride selectively, high removal rates, lower nitride loss and improved with-in- wafer non-uniformity (WIWNU ).

In another embodiment, the present invention is a method of abrading a workpiece. The method includes contacting at least a portion of a structured abrasive article with a surface of a workpiece and moving at least one of the workpiece or the structured abrasive layer relative to the other to abrade at least a portion of the surface of the workpiece. The structured abrasive article includes a backing having first and second opposed major surfaces and a structured abrasive layer disposed on and secured to the first major surface. The structured abrasive layer includes a polymeric binder, abrasive particles dispersed in the binder and a first additive dispersed in the binder. The first additive may be a multidentate acidic complexing agent, wherein the multidentate acidic complexing agent comprises an amino acid, a dipeptide formed from an amino acid and combinations thereof. The structured abrasive layer may include a second additive. The second additive comprises a nonionic surfactant, silicon surfactant, fluorosurfactant, water soluble polymer and combinations thereof. The additives provide improved chemical mechanical planarization (CMP) polish performance, including high oxide/nitride selectively, high removal rates, lower nitride loss and improved WIWNU. Brief Description of the Drawings

Fig. 1 is a perspective view of an exemplary structured abrasive article according to one embodiment of the present invention.

Fig. 2 is a schematic side view of an exemplary method of abrading a surface of a wafer according to the present invention.

Detailed Description

In the following description, reference is made to the accompanying set of drawings that form a part of the description hereof and in which are shown by way of illustration several specific embodiments. It is to be understood that other embodiments are

contemplated and may be made without departing from the scope or spirit of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense.

Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

The structured abrasive article of the present invention includes additives within the web itself, allowing increased design control of the final product, increased consistency in downstream polishing processes and elimination of the need for waste treatment of polishing or working fluids. The additives provide improved chemical mechanical planarization (CMP) polish performance, including high oxide/nitride selectively, high removal rates, lower nitride loss and improved with-in-wafer non-uniformity (WIWNU ).

Referring now to Fig. 1, structured abrasive article 100 includes at least backing 110. Abrasive layer 120 is disposed on backing 110 and includes a plurality of shaped abrasive composites 130. Shaped abrasive composites 130 include abrasive particles (not shown) dispersed in a binder (not shown).

The backing 110 may be flexible, rigid, or in between. A variety of backing materials are suitable for this purpose, including both flexible backings and backings that are more rigid. In some embodiments, the backing may be at least a translucent film. Useful translucent film backings include backing films selected from polymer films, treated versions thereof, and combinations thereof. Exemplary translucent backing films include films made from polyester (e.g., polyethylene terephthalate or polycaprolactone), co-polyester, polycarbonate, polyimide, polyamide, polypropylene, polyurethane, polyethylene, cellulosic polymers, and blends and combinations thereof. In some embodiments, the backing can include an elastomeric urethane or a foam.

The thickness of the backing is typically in a range of from about 20 to about 1000 micrometers, particularly from about 50 micrometers to about 500 micrometers, and more particularly from about 60 micrometers to about 200 micrometers. At least one surface of the backing may be coated with the abrasive layer. In general, the backing is of substantially uniform in thickness. If the backing is not sufficiently uniform in thickness, greater variability in wafer polishing uniformity may occur during wafer planarization.

The abrasive layer includes a plurality of shaped abrasive composites. As used herein, the term "shaped abrasive composite" refers to one of a plurality of shaped bodies comprising abrasive particles dispersed in a binder, the shaped bodies collectively providing a textured, three-dimensional abrasive layer. In some embodiments, the shaped abrasive composites are "precisely- shaped". The term "precisely-shaped abrasive composite" refers to an abrasive composite having a molded shape that is substantially the inverse of a mold cavity used to make it. Typically, precisely-shaped abrasive composites are substantially free of abrasive particles protruding beyond the exposed surface of the abrasive composite before the structured abrasive article has been used.

Provided structured abrasive articles can have a high weight content of abrasive particles in the abrasive layer 120. For example, abrasive particles constitute, on a weight basis, at least about 50 percent of the abrasive layer; and may constitute at least about 60, 70, 75, about 80, or about 90 percent by weight of the abrasive layer. Typically, as the weight percentage of the abrasive particles in the shaped abrasive composites increases, higher removal rates can be achieved.

Examples of suitable abrasive particles include fused aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, silicon nitride, tungsten carbide, titanium carbide, diamond, cubic boron nitride, hexagonal boron nitride, garnet, fused alumina zirconia, alumina-based sol gel derived abrasive particles and the like. The alumina abrasive particle may contain a metal oxide modifier. Examples of alumina-based sol gel derived abrasive particles can be found in U.S. Pat. Nos. 4,314,827; 4,623,364; 4,744,802; 4,770,671; and 4,881 ,951. The diamond and cubic boron nitride abrasive particles may be mono crystalline or

po ly crystalline.

Other examples of suitable inorganic abrasive particles include silica, iron oxide, chromia, ceria, zirconia, titania, tin oxide, gamma alumina, and the like. For pianarization of dielectric containing wafer surfaces (e.g., silicon dioxide-containing surfaces), it is preferred that the abrasive particles have a Mohs hardness less than 8. Such particles, when properly incorporated into an abrasive article, provide the desired rate of cut and the desired surface finish on the wafer during pianarization. Some harder abrasive particles may impart an undesirably coarse surface finish on the oxide-containing wafer surface, so care should be exercised in selection of the appropriate abrasive material, such being within the ability of one skilled in the art. In the case of dielectric co taining wafer surfaces (e.g., silicon dioxide- containing surfaces), ceria abrasive particles are useful.

The abrasive particles can include ceria (i.e., cerium oxide) particles having an average particle size, on a volume basis, of less than about 250 nanometers, less than about 150 nanometers, less than about 100 nanometers, or even less than about 50 nanometers. In one embodiment, the abrasive particles can consist essentially of ceria particles. The phrase "consist essentially of used in this context is intended to exclude other (i.e., non-ceria) abrasive particles in amounts that materially affect abrading properties of the structured abrasive article, if used in wafer pianarization of silicon-containing wafers. It will be recognized that that the ceria particles may comprise agglomerates and/or aggregates of smaller primary ceria particles. For example, the ceria particles (whether present as primary particle, agglomerates, aggregates, or a combination thereof) may have an average particle size, on a volume basis, in a range of from about 1, about 5, about 10, about 20, about 30, or about 40 nanometers up to about 50, about 60, about 70, about 80, about 90, about 95 nanometers, or more. Other nano-scale abrasive particles, on the size scale as that described for ceria, may be employed, including silica, ziconia, titania and alumina.

The ceria particles can be supplied, for example, in the form of a powder, dispersion, or sol; typically, as a dispersion or sol. Methods and sources for obtaining ceria sols having an average particle size less than about 250 nanometers are well known in the art. Ceria dispersions and sols suitable for use in the present disclosure include, for example, ceria sols and dispersions commercially available for suppliers such as Evonik Degussa Corp. of Parsippany, NJ; Rhodia, Inc. of Cranberry, NJ; Ferro Corporation of Independence, OH; and Umicore SA, Brussels, Belgium. The abrasive particles may be homogeneously or heterogeneously dispersed in the polymeric binder. The term "dispersed" refers to the abrasive particles being distributed throughout the polymeric binder. Dispersing the ceria particles substantially homogeneously in the binder typically increases performance of the structured abrasive article. Accordingly, it is typically useful to treat the ceria particles with a surface modifying agent to facilitate their dispersion and/or reduce aggregation, and enhance subsequent coupling to the binder. Surface modifying agents for ceria are well known in the art. One type of surface modifying agent includes carboxylic (meth)acrylates. Exemplary carboxylic (meth)acrylates include (meth)acrylic acid, monoalkyl esters of maleic acid, fumaric acid, monoalkyl esters of fumaric acid, maleic acid, itaconic acid, isocrotonic acid, crotonic acid, citraconic acid, and β-carboxyethyl (meth)acrylate.

In one exemplary method for treating the ceria particles with a carboxylic

(meth)acrylate, a dispersion (e.g., a sol) of the ceria particles in an aqueous medium (e.g., water) is combined with a polyether acid and carboxylic (meth)acrylate (in amounts of each that are sufficient to surface treat and thereby stabilize the ceria particles) and a water- miscible organic solvent having a higher boiling point than water. Typically, the proportion of polyether acid to carboxylic (meth)acrylate is in a range of from about 3:5 to 5:3, although other proportions may be used. Examples of useful solvents include l-methoxy-2-propanol, dimethylformamide, and diglyme. Once combined, the water is substantially removed by evaporation under reduced pressure resulting in a ceria dispersion in which the ceria particles are stabilized against aggregation by associated carboxylic (meth)acrylate molecules. The resultant ceria dispersion can typically be readily combined with a binder precursor, and any additional carboxylic (meth)acrylate that may be included in the binder precursor.

While the carboxylic (meth)acrylate typically serves to facilitate bonding of the ceria particles to the binder, the polyether acid is included primarily to facilitate dispersion stability of the ceria particles in the binder (or its precursor components) and/or solvent. As used herein, the term "polyether acid" refers to a compound having a polyether segment covalently to an acidic group or salt thereof. Exemplary polyether segments include polyethylene glycol segments, polyethylene glycol segments, and mixed poly(ethylene glycol/propylene glycol) segments. Exemplary acidic groups include -C0₂H, -P0₂H, -PO₃H, -SO₃H, and salts thereof. In certain embodiments, the polyether acids can have up to 12 carbon atoms, inclusive, and are represented by the formula:

R^-O X-A wherein R¹ represents H, an alkyl group having from 1 to 6 carbon atoms (e.g., methyl ethyl, or propyl), or an alkoxy group having from 1 to 6 carbon atoms (e.g., methoxy, ethoxyl, or propoxy); each R² independently represents a divalent alkylene group having from 1 to 6 carbon atoms (e.g., ethylene, propylene, or butylene); n represents a positive integer (e.g., 1, 2, or 3; and X represents a divalent organic linking group or a covalent bond; and A represents an acidic group (e.g., as described hereinabove). Exemplary polyether acids include 2'-(2"-methoxyethoxy)ethyl succinate (monoester), methoxyethoxyethoxyacetic acid, and methoxyethoxyacetic acid. The binder can further include a reaction product of components comprising a carboxylic (meth)acrylate and a poly(meth)acrylate. As discussed above, at least a portion of the carboxylic (meth)acrylate is typically combined with the abrasive particles prior to combining the resultant dispersion with the remaining binder components, although this is not a requirement.

The abrasive layer includes abrasive particles dispersed in a binder. The binders for the abrasive articles of this invention are preferably formed from a binder precursor, typically an organic binder precursor. The binder precursor has a phase that is capable of flowing sufficiently so as to be coatable, and then solidifying. The solidification can be achieved by curing (e.g., polymerizing and/or crosslinking) and/or by drying (e.g., driving off a liquid), or simply upon cooling. The precursor can be an organic solvent-borne, water-borne, or 100% solids (i.e., a substantially solvent-free) composition. Both thermoplastic and thermosetting materials, as well as combinations thereof, can be used as the binder precursor.

The binder precursor is preferably a curable organic material (i.e., a material capable of polymerizing and/or crosslinking upon exposure to heat and/or other sources of energy, such as E-beam, ultraviolet, visible, etc., or with time upon the addition of a chemical catalyst, moisture, and the like). Binder precursor examples include amino resins (e.g., aminoplast resins) such as alkylated urea-formaldehyde resins, melamine-formaldehyde resins, and alkylated benzoguanamine-formaldehyde resin, acrylate resins (including acrylates and methacrylates) such as vinyl acrylates, acrylated epoxies, acrylated urethanes, acrylated polyesters, acrylated acrylics, acrylated polyethers, vinyl ethers, acrylated oils, and acrylated silicones, alkyd resins such as urethane alkyd resins, polyester resins, reactive urethane resins, phenolic resins such as resole and tiovoiac resins, phenolic/latex resins, epoxy resins such as bisphenoi epoxy resins, isocyanates, isocyanurates, poiysiioxane resins (including alkylalkoxysilane resins), reactive vinyl resins, and the like. The resins may be in the form of monomers, oligomers, polymers, or combinations thereof In some embodiments, a substantially solvent-free binder precursor is used. In this case, the abrasive layer is typically formed by mixing low molecular weight reactive materials, such as, monomers and/or oligomers, along with any other desired cure initiators, cure accelerators, cure agents, dispersants, other additives and/or fillers; and abrasive particles. The abrasive particles are dispersed in the binder precursor, followed by curing of the binder precursor/abrasive particle mixture to form the abrasive layer. The binder precursor/abrasive particle mixture is often referred to as a "slurry". Suitable binder precursors are typically in an uncured or uncrosslinked state and are flowable at or near ambient conditions. After addition of the abrasive particles, the binder precursor is then typically exposed to conditions (typically an energy source) that at least partially cure and/or crosslink (i.e., free-radical polymerization) the binder precursor, thereby converting it into a binder capable of retaining the dispersed abrasive particles. Exemplary energy sources include: e-beam, ultraviolet radiation, visible radiation, infrared radiation, gamma radiation, heat, and combinations thereof.

The binder precursor may include one or more multi-fictional (meth)acrylates. Useful multi-functional (meth)acrylates include, but are not limited to, monomers and/or oligomers that have at least two (meth)acrylate groups; for example, tri(meth)acrylates, and

tetra(methacrylates). Exemplary poly(methacrylates) include: di(meth)acrylates such as, for example, 1,3-butylene glycol di(meth)acrylate, 1 ,4-butanediol di(meth)acrylate,

1,6-hexanediol di(meth)acrylate, 1 ,6-hexanediol mono(meth)acrylate mono(meth)acrylate, ethylene glycol di(meth)acrylate, alkoxylated aliphatic di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, caprolactone modified neopentyl glycol hydroxypivalate di(meth)acrylate, caprolactone modified neopentyl glycol hydroxypivalate di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol

di(meth)acrylate, dipropylene glycol di(meth)acrylate, ethoxylated (10) bisphenol A di(meth)acrylate, ethoxylated (3) bisphenol A di(meth)acrylate, ethoxylated (30) bisphenol A di(meth)acrylate, ethoxylated (4) bisphenol A di(meth)acrylate, hydroxypivalaldehyde modified trimethylolpropane di(meth)acrylate, neopentyl glycol di(meth)acrylate,

polyethylene glycol (200) di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate; tri(meth)(meth)acrylates such as glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated tri(meth)acrylates (e.g., ethoxylated (3) trimethylolpropane tri(meth)acrylate, ethoxylated (6) trimethylolpropane tri(meth)acrylate, ethoxylated (9) trimethylolpropane tri(meth)acrylate, ethoxylated (20) trimethylolpropane tri(meth)acrylate), pentaerythritol tri(meth)acrylate, propoxylated tri(meth)acrylates (e.g., propoxylated (3) glyceryl tri(meth)acrylate, propoxylated (5.5) glyceryl tri(meth)acrylate, propoxylated (3) trimethylolpropane tri(meth)acrylate, propoxylated (6) trimethylolpropane tri(meth)acrylate), trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate; and higher functionality (meth)acryl containing compounds such as ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated (4) pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, caprolactone modified dipentaerythritol

hexa(meth)acrylate; oligomeric (meth)acryl compounds such as, for example, polyester (meth)acrylates, epoxy (meth)acrylates; and combinations thereof. Such compounds are widely available from vendors such as, for example, Sartomer Co. of Exton, PA; UCB Chemicals Corporation of Smyrna, GA; and Aldrich Chemical Company of Milwaukee, WI.

The binder precursor may include an effective amount of at least one photoinitiator; for example, in an amount of from about 0.1, about 1, or about 3 percent by weight, up to about 5, about 7, or even about 10 percent by weight, or more. Useful photoinitiators include those known as useful for free-radically photocuring (meth)acrylates. Exemplary

photoinitiators include benzoin and its derivatives such as alpha-methylbenzoin; alpha- phenylbenzoin; alpha-allylbenzoin; alpha-benzylbenzoin; benzoin ethers such as benzil dimethyl ketal (available as IRGACURE 651 from Ciba Specialty Chemicals, Tarrytown, NY), benzoin methyl ether, benzoin ethyl ether, benzoin n-butyl ether; acetophenone and its derivatives such as 2-hy droxy-2 -methyl- 1 -phenyl- 1-propanone (available as DAROCUR 1173 from Ciba Specialty Chemicals) and 1 -hydroxy cyclohexyl phenyl ketone (available as IRGACURE 184 from Ciba Specialty Chemicals); 2-methyl- 1 -[4-(methylthio)phenyl]-2-(4- morpholinyl)- 1-propanone (available as IRGACURE 907 from Ciba Specialty Chemicals); 2-benzyl-2-(dimethylamino)- 1 -[4-(4-morpholinyl)phenyl]- 1 -butanone (available as

IRGACURE 369 from Ciba Specialty Chemicals); and (phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (available as IRGACURE 819 from Ciba Specialty Chemicals, NY. Other useful photoinitiators include mono- and bis-acylphosphines (available, for example, from Ciba Specialty Chemicals as IRGACURE 1700, IRGACURE 1800, IRGACURE 1850, and DAROCUR 4265).

The binder precursor may comprise an effective amount of at least one thermal initiator; for example, in an amount of from about 0.1, about 1, or about 3 percent by weight, up to about 5, about 7, or even about 10 percent by weight, or more. Exemplary thermal free- radical initiators include: azo compounds such as, for example, 2,2-azo-bisisobutyronitrile, dimethyl 2,2'-azobis(isobutyrate), azobis(diphenyl methane), 4,4'-azobis-(4-cyanopentanoic acid), (2,2'-azobis(2,4-dimethylvaleronitrile (available as VAZO 52 from E. I. du Pont de Nemours and Co. of Wilmington, DE); peroxides such as, for example, benzoyl peroxide, cumyl peroxide, tert-butyl peroxide, cyclohexanone peroxide, glutaric acid peroxide, and dilauryl peroxide; hydrogen peroxide; hydroperoxides such as, for example, tert butyl hydroperoxide and cumene hydroperoxide; peracids such as, for example, peracetic acid and perbenzoic acid; potassium persulfate; and peresters such as, for example, diisopropyl percarbonate.

In some embodiments, it may be desirable to include one or more monoethylenically unsaturated free-radically polymerizable compounds in the binder precursor; for example, to reduce viscosity and/or or reduce crosslink density in the resultant binder. Exemplary monoethylenically unsaturated free-radically polymerizable compounds include:

mono(meth)acrylates include hexyl (meth)acrylate, 2-ethylhexyl acrylate, isononyl

(meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, dodecyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-octyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, or octadecyl (meth)acrylate; N-vinyl compounds such as, for example, N-vinylformamide, N-vinylpyrrolidinone, or N-vinylcaprolactam; and

combinations thereof.

In some embodiments, the abrasive layer may also include one or more additives. The additives result in high oxide/nitride selectively, high removal rates, lower nitride loss and improved WIWNU uniformity. Although not to bound by theory, it is thought that during the wafer polishing process, which typically includes a working liquid, the additive(s) may actively influence the polishing process by being maintained at the surface of the abrasive layer in contact with the wafer and/or by being released into the working liquid, thereby interacting with the wafer surface being polished. To facilitate dissolution of the additive(s) into the working liquid, the additive(s) typically has/have a molecular weight in a range of from 100 to 1,200 grams per mole, although higher and lower molecular weights may be used. The solubility of the additive in the working liquid is influenced by general principles of solubility of a solute in a solvent, as known in the art. As the working liquid is often an aqueous solution, the chemical structure of the additive(s) preferentially has/have at least one polar functional group or chemical feature, to facilitate solubility in the aqueous, working liquid.

Examples of suitable additives include, but are not limited to: acidic complexing agents, nonionic surfactants, silicon surfactants, fluorosurfactants and water soluble polymers. Although anyone of the above additives may be considered the first or second additive of the abrasive layer, in some embodiments, the acidic complexing agent is the first additive. In further embodiments which include the acidic complexing agent as the first additive, the second additive is selected from the group consisting of nonionic surfactant, silicon surfactant, fluorosurfactant, water soluble polymer and combinations thereof.

Typically, the additives are added to the binder precursor and are considered part of the binder precursor mixture. After addition of the abrasive particles to the binder precursor mixture, followed by curing, the additives are incorporated into the abrasive layer 120 and the correspondingly formed shaped abrasive composites 130.

In some embodiments, the abrasive layer includes one or more acidic complexing agents, as an additive. Examples of suitable acidic complexing agents include, but are not limited to, multidentate acidic complexing agents. Examples of suitable multidentate acidic complexing agents include, but are not limited to, at least one of an amino acid or a dipeptide formed from an amino acid. Examples of suitable amino acids include, but are not limited to: alanine, proline, glycine, histidine, lysine, arginine, ornithene, cysteine, tyrosine, dipeptides formed from two amino acids, acidic multidentate complexing agents and combinations thereof. Particularly suitable amino acids include, but are not limited to, L-Arginine and L-Proline. An example of a suitable commercially available L-Arginine includes, but is not limited to, L-Arginine (Sigma-Aldrich Co. LLC, St. Louis, Missouri). An example of a suitable commercially available L-Proline includes, but is not limited to, L-Proline. The acidic complexing agent is generally present in an amount between about 0.1% and about 3% by weight, particularly in an amount between about 0.25%> and about 2% by weight, and more particularly in an amount between about 0.5% and about 1.5% by weight.

In some embodiments, the abrasive layer includes one or more nonionic surfactants, as an additive. The non-ionic surfactant may be dispersed in the binder precursor. Typically, there is no covalent chemical bond between the surfactant and the binder. The binder precursor can be crosslinked as described further on to help contain the surfactant in the abrasive layer and regulate its release from the abrasive layer. The amount of non-ionic surfactant present in the abrasive layer can be in a range of from 0.75 to 2.2, from 1.0 to 2.2, from 1.3 to 2.2 percent by weight, typically from 1.5 to 2.0 percent by weight, based on a total weight of the abrasive layer. To facilitate dissolution of the surfactant into the aqueous, working liquid, the nonionic surfactant typically has a molecular weight in a range of from 300 to 1,200 grams per mole, although higher and lower molecular weights may be used.

In some embodiment, the non-ionic surfactant may be a polyether non-ionic surfactant. As used herein, the term "polyether nonionic surfactant" refers to one or more nonionic (i.e., not having a permanent charge) surfactant(s) that has/have a polyether segment, typically forming at least a portion of the backbone of the surfactant, although this is not a requirement. As is generally the case for surfactants, the polyether nonionic surfactant should not be covalently bound to the binder. To facilitate dissolution into the aqueous fluid, the polyether nonionic surfactant typically has a molecular weight in a range of from 300 to 1,200 grams per mole, although higher and lower molecular weights may be used.

Examples of polyether nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl-phenyl ethers, polyoxyethylene acyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol laurate, polyethylene glycol stearate, polyethylene glycol distearate, polyethylene glycol oleate, oxyethylene-oxypropylene block copolymer, polyoxyethylene sorbitan laurate,

polyoxyethylene sorbitan stearate, polyoxyethylene sorbitan oleate, and polyoxyethylene laurylamide.

Useful polyether nonionic surfactants also include, for example, condensation products of a higher aliphatic alcohol with about 3 equivalents to about 100 equivalents of ethylene oxide (e.g., those marketed by Dow Chemical Co. under the trade designation TERGITOL 15-S such as, for example, TERGITOL 15-S-20; and those marketed by ICI Americas of Bridgewater, NJ under the trade designation BRIJ such as, for example, BRIJ 58, BRIJ 76, and BRIJ 97). BRIJ 97 surfactant is polyoxyethylene (10) oleyl ether; BRIJ 58 surfactant is polyoxyethylene (20) cetyl ether; and BRIJ 76 surfactant is polyoxyethylene (10) stearyl ether.

Useful polyether nonionic surfactants also include, for example, polyethylene oxide condensates of an alkyl phenol with about 3 equivalents to about 100 equivalents of ethylene oxide (e.g., those marketed by Rhodia of Cranbury, NJ under the trade designations IGEPAL CO and IGEPAL CA). IGEPAL CO surfactants include nonylphenoxy

poly(ethyleneoxy)ethanols. IGEPAL CA surfactants include octylphenoxy poly(ethyleneoxy)ethanols. Useful polyether nonionic surfactants also include, for example, block copolymers of ethylene oxide and propylene oxide or butylene oxide (e.g., those marketed by BASF Corp. of Mount Olive, NJ under the trade designations PLURONIC (e.g., PLURONIC L10) and TETRONIC). PLURONIC surfactants may include propylene oxide polymers, ethylene oxide polymers, and ethylene oxide -propylene oxide block copolymers. TETRONIC surfactants include ethylene oxide-propylene oxide block copolymers.

In some embodiments, polyether nonionic surfactants can include polyoxyethylene sorbitan fatty acid esters (e.g., polyoxyethylene sorbitan monooleates), which may have differing degrees of ethoxylation such as, for example, 20 ethylene oxide units per molecule (e.g., marketed as TWEEN 60) or 20 ethylene oxide units per molecule (e.g., marketed as TWEEN 80)) and polyoxyethylene stearates (e.g., those marketed under the trade

designations TWEEN and MYRJ by Uniqema of New Castle, DE). TWEEN surfactants include poly(ethylene oxide) C₁₂-C₁₈ sorbitan monoesters. MYRJ surfactants include poly(ethylene oxide) stearates.

In some embodiments, the polyether nonionic surfactant is the only surfactant present in the shaped abrasive composites or in the aqueous fluid during abrading. In some cases, it may be desirable to add lesser quantities of anionic surfactants such as an anionic phosphate polyether ester available as TRITON H55 from Dow Chemical Co.

Generally, the nonionic surfactant exhibits a calculated hydrophile-lipophile balance (i.e. HLB), calculated as the weight percent of hydrophile in the surfactant molecule divided by 5, of at least about 4, particularly at least about 6, more particularly at least about 8, and more particularly at least about 10. The calculated HLB is generally no greater than 20. The nonionic surfactant may be advantageously selected from linear primary alcohol ethoxylate, secondary alcohol ethoxylate, branched secondary alcohol ethoxylate, octylphenol ethoxylate, acetylenic primary alcohol ethoxylate, acetylenic primary di-alcohol ethoxylate, alkane di-alcohol, hydroxyl-terminated ethylene oxide-propylene oxide random copolymer, fluoroaliphatic polymeric ester, and mixtures thereof. Examples of suitable commercially available ethylene oxide nonionic surfactants include, but are not limited to, Tergitol 15-S-7 (Sigma- Aldrich Co. LLC, St. Louis, Missouri) and Titron X-100 (Sigma- Aldrich Co. LLC, St. Louis, Missouri). The nonionic surfactant acid is generally present in an amount between about 0.1% and about 3% by weight, particularly in an amount between about 0.25% and about 2% by weight, and more particularly in an amount between about 0.5% and about 1.5% by weight. In some embodiments, the abrasive layer includes one or more silicon surfactants, as an additive. An example of a suitable commercially available silicon surfactant includes, but is not limited to, Silwet L-7200, Silwet L-7280 (Momentive Performance Material, Friendly, West Virginia). The silicon surfactant is generally present in an amount between about 0.1% and about 3% by weight, particularly in an amount between about 0.25% and about 2% by weight, and more particularly in an amount between about 0.5% and about 1.5% by weight.

In some embodiments, the abrasive layer includes one or more fluorosurfactants, as an additive. Examples of suitable commercially available fluorosurfactants include, but are not limited to, FC 9 (3M Company, St. Paul, Minnesota) and Zonyl (Dupont, Wilmington, Delaware). The fluorosurfactant is generally present in an amount between about 0.1% and about 3% by weight, particularly in an amount between about 0.25% and about 2% by weight, and more particularly in an amount between about 0.5% and about 1.5% by weight.

In some embodiments, the abrasive layer includes one or more water soluble polymers, as an additive. Examples of suitable water soluble polymers include, but are not limited to, polymeric acids, e.g. polyacrylic acids and polyphosphoric acids. The water soluble polymer is generally present in an amount between about 0.1% and about 3% by weight, particularly in an amount between about 0.25% and about 2% by weight, and more particularly in an amount between about 0.5% and about 1.5% by weight.

Combinations of one or more of the additives (acidic complexing agents, nonionic surfactants, silicon surfactants, fluorosurfactants and water soluble polymers) may be used. A preferred combination is an acidic complexing agent with a nonionic surfactant. More specifically, a multidentate acidic complexing agent, comprising an amino acid, a dipeptide formed from an amino acid and combinations thereof, is used in conjunction with a nonionic surfactant. The amino acid may be selected from the group consisting of: alanine, proline, glycine, histidine, lysine, arginine, ornithene, cysteine, tyrosine, and combinations thereof.

The nonionic surfactant may be a polyether nonionic surfactant. The nonionic surfactant may be selected from the group consisting of: linear primary alcohol ethoxylate, secondary alcohol ethoxylate, branched secondary alcohol ethoxylate, octylphenol ethoxylate, acetylenic primary alcohol ethoxylate, acetylenic primary di-alcohol ethoxylate, alkane di- alcohol, hydroxyl-terminated ethylene oxide-propylene oxide random copolymer, fluoroaliphatic polymeric ester, and mixtures thereof.

Other materials can be included in the abrasive layer, including one or more of an antioxidant, a colorant, a heat and light stabilizer, or a filler (the filler having substantially no impact on abrading performance). Provided structured abrasive articles, that include shaped abrasive composites, can be made by general methods well-known in the art. For example, in one embodied method a binder precursor and abrasive particles, in the form of a slurry, can be urged into

complementary cavities in a production tool that have the dimensions of the desired shaped abrasive composites. Then, the translucent film backing can be brought into contact with the slurry and, in some instances, the production tool. The binder precursor can be at least sufficiently cured to remove the shaped abrasive composites from the production tool.

Alternatively, the production tool, at least translucent film backing, and slurry can be simultaneously fed through a nip. Optionally, further curing (e.g., thermal post curing) can be carried out at this stage to further advance the degree of cure and thereby improve the binder properties. Further details concerning methods for forming shaped abrasive composites can be found in, for example, U. S. Pat. No. 5,152,917 (Pieper et al).

Individual shaped abrasive composites can have the form of any of a variety of geometric solids or be irregularly shaped. Typically, the shaped abrasive composites are precisely-shaped (as defined above). Typically, the shaped abrasive composite is formed such that the base of the shaped abrasive composite, the portion of the shaped abrasive composite in contact with the translucent film backing, is secured to the translucent film backing. The proximal portion of the shaped abrasive composite typically has the same or larger a larger surface area than that portion of the shaped abrasive composite distal from the base or backing.

Precisely-shaped abrasive composites may be of any three-dimensional shape that results in at least one of a raised feature or recess on the exposed surface of the abrasive layer. Useful shapes include, for example, cubic, prismatic (e.g., hexagonal prisms), pyramidal (e.g., square pyramidal or hexagonal pyramidal), truncated pyramidal, conical, frustoconical, hemispherical, cross, or post-like cross sections with a distal end. Composite pyramids may have four sides, five sides or six sides. Combinations of differently shaped and/or sized abrasive composites may also be used. The abrasive layer of the structured abrasive may be continuous or discontinuous. The shaped abrasive composites may be arranged in rows, in concentric circles, in helices, or in lattice fashion, or may be randomly placed. Further details concerning structured abrasive articles having precisely-shaped abrasive composites, and methods for their manufacture may be found, for example, in U.S. Pat. Nos. 5,435,816 (Spurgeon et al); 5,454,844 (Hibbard et al); 5,851,247 (Stoetzel et al); and 6,139,594 (Kincaid et al). The sides forming the shaped abrasive composites may be perpendicular relative to the backing, tilted relative to the backing or tapered with diminishing width toward the distal end. However, if the sides are tapered, it may be easier to remove the shaped abrasive composite from the cavities of a mold or production tool. The substantially perpendicular angles are preferred because this results in a consistent nominal contact area as the composite wears.

The height of each shaped abrasive composite is typically substantially the same, but it is envisaged to have composites of varying heights in a single structured abrasive article. The height of the composites with respect to the backing or to the land between the composites generally may be less than about 2,000 micrometers; for example, in a range of from about 10 micrometers to about 250 micrometers. The base dimension of an individual shaped abrasive composite may be about 5,000 micrometers or less, particularly about 1,000 micrometers or less, and more particularly less than 500 micrometers. The base dimension of an individual shaped abrasive composite is typically greater than about 50 micrometers, particularly greater than about 100 micrometers. The base of the shaped abrasive composites may abut one another, or may be separated from one another by some specified distance.

Adjacent shaped composites may share a common shaped abrasive composite land or bridge-like structure which contacts and extends between facing sidewalls of the composites. Typically, the land structure has a height of no greater than about 33 percent of the vertical height dimension of each adjacent composite. The shaped abrasive composite land may be formed from the same slurry used to form the shaped abrasive composites. The composites are "adjacent" in the sense that no intervening composite may be located on a direct imaginary line drawn between the centers of the composites. At least portions of the shaped abrasive composites may be separated from one another so as to provide the recessed areas between the raised portions of the composites.

The linear spacing of the shaped abrasive composites may range from about 1 shaped abrasive composite per linear cm to about 200 shaped abrasive composites per linear cm. The linear spacing may be varied such that the concentration of composites may be greater in one location than in another. For example, the concentration may be greatest in the center of the abrasive article. The areal density of the composite may range, in some embodiments, from about 1 to about 40,000 composites per square centimeter. One or more areas of the backing may be exposed, i.e., have no abrasive coating contacting the at least translucent film backing. The shaped abrasive composites are typically set out on a backing in a predetermined pattern or set out on a backing at a predetermined location, although this is not a requirement. For example, in the abrasive article made by providing slurry between the backing and a production tool having cavities therein, the predetermined pattern of the composites will correspond to the pattern of the cavities on the production tool. The pattern may be thus reproducible from article to article. In one embodiment, the shaped abrasive composites may form an array or arrangement, by which may be meant that the composites are in a regular array such as aligned rows and columns, or alternating offset rows and columns. If desired, one row of shaped abrasive composites may be directly aligned in front of a second row of shaped abrasive composites. Typically, one row of shaped abrasive composites may be offset from a second row of shaped abrasive composites.

In another embodiment, the shaped abrasive composites may be set out in a "random" array or pattern. By this it may be meant that the composites are not in a regular array of rows and columns as described above. For example, the shaped abrasive composites may be set out in a manner as disclosed in U. S. Pat. Nos. 5,672,097 and 5,681,217 (both to

Hoopman et al.). It will be understood, however, that this "random" array may be a predetermined pattern in that the location of the composites on the abrasive article may be predetermined and corresponds to the location of the cavities in the production tool used to make the abrasive article.

Exemplary production tools include rolls, endless belts, and webs, and may be made of a suitable material such as for example, metal (e.g., in the case of rolls) or polymer films (e.g., in the cases of endless belts and webs).

Provided structured abrasive articles may be generally circular in shape, e.g., in the form of an abrasive disc. Outer edges of the abrasive disc are typically smooth, or may be scalloped. The structured abrasive articles may also be in the form of an oval or of any polygonal shape such as triangular, square, rectangular, and the like. Alternatively, the abrasive articles may be in the form of a belt. The abrasive articles may be provided in the form of a roll, typically referred to in the abrasive art as abrasive tape rolls. In general, the abrasive tape rolls may be indexed or moved continuously during the wafer planarization process. The abrasive article may be perforated to provide openings through the abrasive coating and/or the backing to permit the passage of the working fluid before, during and/or after use; although, in advantageous embodiments the structured abrasive articles are substantially free of, or even completely free of, such perforations. The abrasive layer can be applied to a front surface, i.e. a first major surface, of a backing. The second major surface of the backing, i.e. the side of the backing opposite the abrasive layer can typically be contacted with a subpad during use. In some cases, the structured abrasive article can be secured to the subpad. An attachment interface layer may be directly bonded to the second major surface of the backing. The attachment interface layer may be used to bond the structured abrasive article to another substrate, e.g. a subpad or a platen. The attachment interface layer can be an adhesive, a pressure-sensitive adhesive or an adhesive transfer tape (i.e. a double sided tape), which can be applied to the opposing surface of the backing. Suitable mechanical fastening device(s) may also be used. Suitable subpads are disclosed, for example, in U.S. Pat. Nos. 5,692,950 and 6,007,407 (both to Rutherford et al). If using optical detection methods, the subpad, and any platen on which it rests, should have at least one appropriately sized window (e.g., an opening or transparent insert) to permit a continuous optical path from a light source (e.g., a laser) through the platen and subpad.

Provided structured abrasive articles may be used for abrading and/or polishing workpieces such as wafers containing silicon (e.g., silicon wafers, glass wafers, etc.) or other metals and including those wafers having an oxide layer on an outer surface thereof. For example, the structured abrasive articles may be useful in abrading and/or polishing a dielectric material deposited on the wafer and/or the wafer itself. Additionally, it is contemplated that the provided abrasive article can be useful in abrading or polishing other materials such as sapphire or other minerals. Variables that affect the wafer polishing rate and characteristics include, for example, the selection of the appropriate contact pressure between the wafer surface and abrasive article, type of working fluid, relative speed and relative motion between the wafer surface and the abrasive article, and the flow rate of the working fluid. These variables are interdependent, and are typically selected based upon the individual wafer surface being processed.

Structured abrasive articles according to the present disclosure may be conditioned, for example, by abrading the surface using a pad conditioner (e.g., with diamond grits held in a metal matrix) prior to and/or intermittently during the wafer planarization process. One useful conditioner is a CMP pad conditioner (typically mounted on a rigid backing plate), part no. CMP-20000TS, available from Morgan Advanced Ceramics of Hayward, CA.

In general, since there can be numerous process steps for a single semiconductor wafer, the semiconductor fabrication industry expects that the process will provide a relatively high removal rate of material. The material removal rate obtained with a particular abrasive article will typically vary depending upon the machine conditions and the type of wafer surface being processed. However, although it is typically desirable to have a high conductor or dielectric material removal rate, the conductor or dielectric material removal rate may be selected such that it does not compromise the desired surface finish and/or topography of the wafer surface.

Referring now to Fig. 2, polishing apparatus 200 is used in an exemplary method of abrading a surface of a wafer. In this method, structured abrasive article 100 contacts and is secured to subpad 210, which is in turn secured to platen 220. Subpad 210, which may comprise a foam (e.g., a polyurethane foam) or other compressible material, has first window 212 therein, and platen 220 has second window 222 therein. Wafer holder 233 is mounted to a head unit 231 that is connected to a motor (not shown). Gimbal chuck 232 extends from head unit 231 to wafer holder 233. Wafer holder 233 helps secure wafer 240 to head unit 231 and also prevent the semiconductor wafer from becoming dislodged during planarization. Wafer holder 233 extends alongside of wafer 240 at ring portion 233 a. Ring portion 233 a (which is optional) may be a separate piece or may be integral with wafer holder 233. Wafer 240 is brought into contact with the abrasive layer 120 of structured abrasive article 100, and the wafer 240 and abrasive layer 120 are moved relative to one another. The progress of polishing/abrading is monitored using laser beam 250 which passes through second window 222, first window 212, and structured abrasive article 100 and is reflected off oxide surface 242 of wafer 240 and then retraces its path. Optional working fluid 260 may be used to facilitate the abrading process. Reservoir 237 holds optional working fluid 260 which is pumped through tubing 238 into the interface between semiconductor wafer and the abrasive layer. Useful working fluids include, for example, those listed in U.S. Pat. No. 5,958,794 (Bruxvoort et al.).

In general, wafer surface finishes that are substantially free of scratches and defects are desired. The surface finish of the wafer may be evaluated by known methods. One method is to measure the Rt value, which provides a measure of roughness, and may indicate scratches or other surface defects. The wafer surface is typically modified to yield an Rt value of no greater than about 0.4 nanometers, more typically no greater than about 0.2 nanometers, and even more typically no greater than about 0.05 nanometers. Rt is typically measured using a laser interferometer such as a Wyko RST PLUS interferometer (Wyko

Corp., Tucson, AZ), or a Tencor profilometer (KLA-Tencor Corp., San Jose, CA). Scratch detection may also be measured by dark field microscopy. Scratch depths may be measured by atomic force microscopy. Wafer surface processing may be conducted in the presence of a working fluid, which may be selected based upon the composition of the wafer surface. In some applications, the working fluid typically comprises water. The working fluid may aid processing in

combination with the abrasive article through a chemical mechanical polishing process.

During the chemical portion of polishing, the working fluid may react with the outer or exposed wafer surface. Then during the mechanical portion of processing, the abrasive article may remove this reaction product.

The current trend in memory storage devices and other electronics is miniaturization. There is a need for abrasive articles that can polish wafers that have very small features without producing defects. Some exemplary devices have features as small as 32 nm, 28 nm or even 20 nm. To polish these wafers, it is important that the abrasive article be able to create a smooth surface with very few defects at a relatively high rate. In addition after polishing, the wafer, which can be 100 mm or more in diameter, needs to have a uniform profile with minimal dishing. It has been surprisingly found that structured abrasive articles that include an abrasive layer having an acidic complexing agent and optionally, a nonionic surfactant, dispersed therein, can remove material from thermal oxide wafers at rates exceeding 500 A/min with low defects, low nitride removal rate and good WIWNU.

Objects and advantages of this disclosure are further illustrated by the following non- limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and, details, should not be construed to unduly limit this disclosure.

Examples

The present invention is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following example are on a weight basis.

MATERIALS

A wetting and dispersing additive, available under the trade designation

D-l l l "DISPERBYK-1 1 1" from BYK-Chemie USA, Inc., Wallingford,

Connecticut

2-hydroxyethyl methacrylate, available from Rohm and Haas Co.,

2-HEMA

Philadelphia, Pennsylvania

2-phenoxyethyl acrylate, available under the trade designation "SR 339"

SR 339

from Sartomer Company, Exton, Pennsylvania

Trimethylolpropane triacrylate, available under the trade designation

SR 351

"SR 351" from Sartomer Company

L-Arg L-Arginine, available from Sigma-Aldrich Co. LLC, St Louis, Missouri

L-Proline, available from Spectrum Chemical, New Brunswick,

L-Pro

New Jersey

A secondary alcohol ethoxylate, nonionic surfactant available under the

T-15-7-S

trade designation "TERGITOL 15-7-S", from Sigma-Aldrich Co. LLC

Gamma-methacryloxypropyltrimethoxy silane, available under the trade

A- 174 designation "SILQUEST A- 174 SILANE" from Momentive Performance

Materials, Inc., Columbus, Ohio

A non- ionic silane dispersing agent available under the trade designation

A-1230 "SILQUEST A- 1230 SILANE" from Momentive Performance Materials,

Inc.

Phenothiazine, available from Cytec Industries, Woodland Park,

Phth

New Jersey

A free-radical photoinitiator, (phenyl bis(2,4,6-trimethylbenzoyl)

IRG 819 phosphine oxide, available under the trade designation "IRGACURE

819" from Ciba Specialty Chemicals, Tarrytown, New York

A thermal free-radical initiator, 2, 2'-azobis(2,4-dimethylvaleronitrile,

VAZO 52 available under the trade designation "VAZO 52" from E. I. du Pont de

Nemours and Co., Wilmington, Delaware

Hydroquinone monomethyl ether, available from Eastman Chemical

HQME

Company, Kingsport, Tennessee

2-(2-methoxyethoxy)ethoxyacetic acid, available from Archimica,

2-2-MEEAA

Springfield, Missouri

1 -methoxy-2-propanol, available from Dow Chemical Corporation, l-M-2-Pr

Midland, Michigan

A translucent polycarbonate/PBT based film, 7 mils (0.18 mm) in

Backing 1 thickness, available under the trade designation "BAYFOL CR6-2" from

Bayer Corporation, Pittsburgh, Pennsylvania

TEST METHODS

Wafer Polishing

The fixed abrasive webs were used to polish 300 mm diameter thermal silicon oxide, and PECVD silicon nitride blanket wafers, as well as, oxide/nitride pattern wafers with an MIT764 test pattern using a CMP polisher available under the trade designation

REFLEXION polisher from Applied Materials, Inc. of Santa Clara, CA. One of the polishing stations of the web tool was fitted with a web carriage suitable for mounting and running FA webs on the polishing tool. A subpad, available under the trade designation "3M CMP FIXED ABRASIVE P7100 SUB PAD" from the 3M Company, St. Paul, Minnesota, was mounted to the platen of the polisher. A fixed abrasive web was mounted in the carriage assembly of the polisher, such, that, the web lined up with and over the subpad mounted on the platen. The process conditions were as follows:

Platen Speed: 40 rpm.

Head Speed: 32 rpm.

Head Pressures: Retaining Ring 4.2 psi, Zone 1 3.4 psi, Zone2 1.9 psi, Zone3 2.0 psi, Zone4 2.0 psi and Zone5 2.0 psi.

Polishing time: 60 sec. per blanket wafers and 30 sec. per pattern wafer.

Web Increment: 3 mm per wafer.

Polishing Fluid (standard): 2.5 wt% L-Proline in DI Water at pH 10.5.

Flow Rate : 200 ml/min.

In some cases, an additive was added to the standard polishing solution described above, see Table 1 for the various additives and concentrations used. The pH of the solution was adjusted to 10.5 using potassium hydroxide Oxide removal rate and non-uniformity was measured on 300 mm blanket oxide wafers. The average silicon nitride loss on a 50 μιη line on a silicon oxide and silicon nitride pattern wafer is shown in Table 1.

The oxide and nitride removal rate measurements for both blanket and pattern wafers were made using a NovaScan 3060 ellipsometer which is integrated with the REFLEXION polisher and was supplied by Applied Materials. Blanket oxide and nitride wafers were measured with a 25 -pt diameter scan with 3 mm edge exclusion. Nitride loss measurements were made near the center lines of 50 micron lines/50 micron space arrays. The pattern wafers were measured at 7 different die starting at the wafer center and moving to the outermost die. Each new web was tested with a minimum of 25 blanket oxide wafers, followed by the pattern wafer, and then the blanket nitride wafer. The average removal rate from the last 10 blanket oxides was reported as the oxide removal rate. Nitride removal rate data and nitride loss data was obtained from the single nitride blanket wafer and pattern wafer, respectively. If additional testing was done on the same web, using a different polishing fluid, the same test sequence was used, except only 10 blanket oxide wafers were polished and the average of the last 5 wafers was reported for the oxide removal rate. Example 1: Fixed Abrasive Web with L-Arginine in the Binder

Preparation of Ceria Dispersion 1

A ceria dispersion was prepared as follows: 11.4045 kg Ce-A was poured into a mixing vessel and then 703 g of 2-2-MEEAA, 568 g of β-CEA, and 2.7907 kg of l-M-2-Pr were slowly added while mixing using a polytetrafluoroethylene-coated blade. The mixture was heated to 50°C and mixed overnight. The mixture was then transferred into a rotary evaporator and excess water was removed under reduced pressure. The resultant dispersion, Ceria Dispersion 1, had a solids content of 49.54 percent. Preparation of Slurry 1

Ceria Dispersion 1, 1,243.4 g, and 18.5 g of D-l 11 were added to a mixing vessel and mixed. To this mixture was added 3.49 g of 2-HEMA, 8.85 g of SR 339, 67.86 g of SR 351, 3.81 g of β-CEA, 14.0 g of L-Arg and 0.42 g of Phth dissolved in 20 g of l-M-2-Pr. The mixture was mixed using a polytetrafluoroethylene-coated blade for 30 minutes and then transferred to a rotary evaporator to remove the l-M-2-Pr. After solvent removal, the slurry was cooled to room temperature, and then 0.71 g of IRG 819, 0.71 g of VAZO 52 and 0.18 g of HQME were added, followed by mixing for two hours, yielding Slurry 1.

Preparation of Fixed Abrasive Web 1

Fixed abrasive articles of the present invention were formed using a microreplication fabricating technique as described in U.S. Pat. No. 5,152,917 (Pieper et al). A roll of polypropylene production tool, 30 inches (76 cm) in width, was provided. The polypropylene production tool was polypropylene film that had a hexagonal array (350 micrometers on center) of hexagonal columnar cavities (125 μιη wide and 30 μιη deep), corresponding to a 10 percent cavity area. The production tool was essentially the inverse of the desired shape, dimensions, and arrangement for the abrasive composites in the final structured abrasive article. Slurry 1 was coated between the cavities of production tool and Backing 1 using a casting roll and a nip roll (nip force of 1,300 pounds (5.78 kN) and then passed through a UV curing station having an UV light source (V Bulb, Model EPIQ available from Fusion UV Systems, Inc., Gaithersburg, Maryland), at a line speed of 10 feet/min (3.0 m/min) and a total exposure of 6.0 kW/inch (15.2 kW/cm). The polypropylene tooling was separated from backing 1, resulting in a cured, abrasive layer, having precisely-shaped abrasive composite, adhered to backing 1, Fixed Abrasive Web 1, i.e., Example 1. Polishing results for wafers polished with Example 1 are shown in Table 1.

Example 2: Fixed Abrasive Web with L-Arginine and Tergitol in the Binder

Preparation of Slurry 2

Ce-A, 969.6 g and 9.8 g of D-l 11 were added to a mixing vessel and mixed. To this mixture was added 4.49 g of 2-HEMA, 11.37 g SR 339, 87.24 g SR 351, 3.0 grams of L-Arg, 6.0 g T-15-7-S and 0.54 g Phth dissolved in 20 g l-M-2-Pr. The mixture was mixed using a polytetrafluoroethylene-coated blade for 30 minutes and then transferred to a rotary evaporator to remove the l-M-2-Pr. After solvent removal, the slurry was cooled to room temperature, and then 0.99 g IRG 819, 0.99 g VAZO 52 and 0.25 g HQME were added, followed by mixing for two hours, yielding Slurry 2.

Preparation of Fixed Abrasive Web 2

A fixed abrasive web was fabricated using the identical procedure as that described in Example 1 , except Slurry 2 was used in place of Slurry 1. The resulting fixed abrasive was designated Fixed Abrasive Web 2, i.e. Example 2. Polishing results for wafers polished with Example 2 are shown in Table 1.

Example 3: Fixed Abrasive Web with L-Proline in the Binder

Preparation of Slurry 3

Ceria Dispersion 1, 1,253.8 g, and 18.5 g of D-l 11 were added to a mixing vessel and mixed. To this mixture was added 3.49 g of 2-HEMA, 8.85 g of SR 339, 67.86 g of SR 351, 3.81 g of β-CEA, 70 g of solution of 20% L-Proline in 50/50 ratio of water/ l_M-2-Pr and 0.42 g of Phth dissolved in 20 g of l-M-2-Pr. The mixture was mixed using a

polytetrafluoroethylene-coated blade for 30 minutes and then transferred to a rotary evaporator to remove the l-M-2-Pr. After solvent removal, the slurry was cooled to room temperature, and then 0.74 g of IRG 819, 0.74 g of VAZO 52 and 0.185 g of HQME were added, followed by mixing for two hours, yielding Slurry 3.

Preparation of Fixed Abrasive Web 3

A fixed abrasive web was fabricated using the identical procedure as that described in Example 1 , except Slurry 3 was used in place of Slurry 1. The resulting fixed abrasive was designated Fixed Abrasive Web 3, i.e. Example 3. Polishing results for wafers polished with Example 3 are shown in Table 1.

Comparative Example 4: Fixed Abrasive Web without Additives

Preparation of Slurry 4

Ceria Dispersion 1, 1,243.4 g, and 18.5 g of D-l 11 were added to a mixing vessel and mixed. To this mixture was added 3.48 g 2-HEMA, 8.85 g SR 339, 67.86 g SR 351, 3.81 grams of β-CEA, and 0.42 grams of Phth dissolved in 20 g of l-M-2-Pr. The mixture was mixed using a polytetrafluoroethylene-coated blade for 30 minutes and then transferred to a rotary evaporator to remove the l-M-2-Pr. The slurry was cooled to room temperature and then 0.74 g of IRG 81, 0.74 g of VAZO 52 and 0.18 g of HQME were added, followed by mixing for two hours, yielding Slurry 4.

Preparation of Comparative Fixed Abrasive Web 4

A fixed abrasive web was fabricated using the identical procedure as that described in

Example 1 , except Slurry 4 was used in place of Slurry 1. The resulting fixed abrasive was designated Comparative Fixed Abrasive Web 4, i.e. Comparative Example 4. Polishing results for wafers polished with Comparative Example 4 are shown in Table 1. It should be noted that the general composition of Example 1 and Example 3, i.e. without the indicated variation, is comparable to that of Comparative Example 4.

Comparative Example 5: Fixed Abrasive Web without Additives

Preparation of Slurry 5

825.3 g of CE-A, 295.9 g of l-M-2-Pr and 8.2 g of D-l 11 were added to a mixing vessel and mixed. To this mixture was added 3.64 g of 2-HEMA, 8.78 g SR 339, 68.34 g

SR 351, 8.24 grams of β-CEA and 0.45 g Phth dissolved in 20 g l-M-2-Pr. The mixture was mixed using a polytetrafluoroethylene-coated blade for 30 minutes and then transferred to a rotary evaporator to remove the l-M-2-Pr and water. After solvent removal, the slurry was cooled to room temperature, and then 0.80 g IRG 819, 0.80 g VAZO 52 and 0.44 g HQME were added, followed by mixing for two hours, yielding Slurry 5.

Preparation of Comparative Fixed Abrasive Web 5

A fixed abrasive web was fabricated using the identical procedure as that described in Example 1 , except Slurry 5 was used in place of Slurry 1. The resulting fixed abrasive was designated Comparative Fixed Abrasive Web 5, i.e. Comparative Example 5. Polishing results for wafers polished with Comparative Example 5 are shown in Table 1. It should be noted that the general composition of Example 2, i.e. without the indicated variations, is comparable to that of Comparative Example 5. Table 1

Examining the data of Table 1, surprisingly low nitride loss values can be obtained by using abrasive articles of the present invention.

Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows. All references cited in this disclosure are herein incorporated by reference in their entirety.

Claims

Claims:

1. A structured abrasive article comprising:

a backing having first and second opposed major surfaces;

a structured abrasive layer disposed on and secured to the first major surface, wherein the structured abrasive layer comprises:

a polymeric binder;

abrasive particles dispersed in the binder; and

a first additive dispersed in the binder, wherein the first additive is a

multidentate acidic complexing agent,

wherein the multidentate acidic complexing agent comprises an amino acid, a dipeptide formed from an amino acid and combinations thereof.

2. The structured abrasive article according to claim 1 wherein the amino acid is selected from the group consisting of: alanine, proline, glycine, histidine, lysine, arginine, ornithene, cysteine, tyrosine, and combinations thereof.

3. The structured abrasive article according to claim 2 wherein the amino acid is one of L-proline, L-arginine and combinations thereof.

4. The structured abrasive article according to claim 1 wherein the acidic complexing agent constitutes about 0.1 to 3.0 % by weight of the structured abrasive layer.

5. The structured abrasive article according to claim 1 wherein the abrasive layer further comprises a second additive, wherein the second additive is selected from the group consisting of nonionic surfactant, silicon surfactant, fluorosurfactant, water soluble polymer and combinations thereof.

6. The structured abrasive article according to claim 5 wherein the second additive is a nonionic surfactant.

7. The structured abrasive article according to claim 6 wherein the nonionic surfactant is a polyether nonionic surfactant.

8. The structured abrasive article according to claim 6 wherein the nonionic surfactant constitutes about 0.1 to 3.0 % by weight of the structured abrasive layer.

9. The structured abrasive article according to claim 6 wherein the nonionic surfactant selected from the group consisting of: linear primary alcohol ethoxylate, secondary alcohol ethoxylate, branched secondary alcohol ethoxylate, octylphenol ethoxylate, acetylenic primary alcohol ethoxylate, acetylenic primary di-alcohol ethoxylate, alkane di-alcohol, hydroxyl-terminated ethylene oxide-propylene oxide random copolymer, fluoroaliphatic polymeric ester, and combinations thereof.

10. The structured abrasive article according to claim 6 wherein the nonionic surfactant has a hydrophile-lipophile balance of about 4 and 20.

11. The structured abrasive article according to claim 6, wherein the nonionic surfactant has a hydrophile-lipophile balance of at least about 10.

12. The structured abrasive article according to claim 1, wherein the polymeric binder comprises an acrylic polymer.

13. A structured abrasive article according to claim 1, further comprising an attachment interface layer directly bonded to the second major surface.

14. A method of abrading a workpiece comprising:

contacting at least a portion of a structured abrasive article with a surface of a

workpiece; and

moving at least one of the workpiece or the structured abrasive layer relative to the other to abrade at least a portion of the surface of the workpiece, wherein the structured abrasive article comprises:

a backing having first and second opposed major surfaces; and a structured abrasive layer disposed on and secured to the first major surface, wherein the structured abrasive layer comprises:

a polymeric binder;

abrasive particles dispersed in the binder; and a first additive dispersed in the binder, wherein the first additive is a

multidentate acidic complexing agent,

15. The method according to claim 14, wherein the workpiece comprises dielectric containing wafer surfaces.

16. The method according to claim 14, wherein the acidic complexing agent constitutes about 0.1 % and 3 % by weight of the structured abrasive layer.

17. The method according to claim 14, wherein the wherein the amino acid is selected from the group consisting of: alanine, proline, glycine, histidine, lysine, arginine, ornithene, cysteine, tyrosine, and combinations thereof.

18. The method according to claim 14 wherein the abrasive layer further comprises a second additive, wherein the second additive is selected from the group consisting of nonionic surfactant, silicon surfactant, fluorosurfactant, water soluble polymer and combinations thereof.

19. The method according to claim 18, wherein the second additive is a nonionic surfactant.

20. The method according to claim 19, wherein the nonionic surfactant is a polyether nonionic surfactant.

21. The method according to claim 19, wherein the nonionic surfactant selected from the group consisting of: linear primary alcohol ethoxylate, secondary alcohol ethoxylate, branched secondary alcohol ethoxylate, octylphenol ethoxylate, acetylenic primary alcohol ethoxylate, acetylenic primary di-alcohol ethoxylate, alkane di-alcohol, hydroxyl-terminated ethylene oxide-propylene oxide random copolymer, fluoroaliphatic polymeric ester, and mixtures thereof.

22. The method according to claim 19, wherein the nonionic surfactant constitutes about 0.1 to 3.0 % by weight of the structured abrasive layer.

23. The method according to claim 19, wherein the nonionic surfactant has a hydrophile- lipophile balance of between about 4 and 20.