Polishing composition and method of polishing a substrate having enhanced defect inhibition

Abstract

An aqueous alkaline chemical mechanical polishing composition includes a quaternary phosphonium compound having aromatic groups which enables enhanced reduction of defects on silicon oxide substrates and enables good silicon oxide removal rates during chemical mechanical polishing. The chemical mechanical polishing composition is stable.

Claims

1. A chemical mechanical polishing composition consisting of water; an abrasive; optionally a pH adjusting agent; optionally a biocide; a pH greater than 7; and a quaternary phosphonium compound having formula (I): ##STR00006## wherein R is selected from the group consisting of phenyl, benzyl, and linear or branched C.sub.1-C.sub.4 alkyl; and X is an anion selected from the group consisting of Br.sup.−, I.sup.−, F.sup.− and OH.sup.−.

2. The chemical mechanical polishing composition of claim 1, wherein the chemical mechanical polishing composition consists of the water; 0.1 to 40 wt % of the abrasive; optionally the pH adjusting agent; optionally the biocide; the pH greater than 7; 0.001 to 1 wt % of the quaternary phosphonium compound having the formula (I): ##STR00007## wherein R is selected from the group consisting of phenyl, benzyl, and linear or branched C.sub.1-C.sub.4 alkyl; and X is an anion selected from the group consisting of Br.sup.−, I.sup.−, F.sup.− and OH.sup.−.

3. The chemical mechanical polishing composition of claim 1, wherein the chemical mechanical polishing composition consists of the water; 5 to 25 wt % of the abrasive, wherein the abrasive is a colloidal silica abrasive; the pH adjusting agent; the biocide; a pH of 8-13; 0.01 to 1 wt % of the quaternary phosphonium compound having the formula (I): ##STR00008## wherein R is selected from the group consisting of phenyl, benzyl, and linear or branched C.sub.1-C.sub.4 alkyl; and X is an anion selected from the group consisting of Br.sup.−, Cl.sup.−, I.sup.−, F.sup.− and OH.sup.−.

4. The chemical mechanical polishing composition of claim 3, wherein the pH adjusting agent is selected from the group consisting of potassium hydroxide, sodium hydroxide, ammonium salts and mixtures thereof.

5. The chemical mechanical polishing composition of claim 1, wherein the quaternary phosphonium compound is selected from the group consisting of tetraphenyl phosphonium bromide, tetraphenyl phosphonium chloride, benzyltriphenyl phosphonium bromide, benzyltriphenyl phosphonium chloride, ethyltriphenyl phosphonium bromide, ethyltriphenyl phosphonium chloride, methyltriphenyl phosphonium bromide, methyltriphenyl phosphonium chloride and mixtures thereof.

6. A method for chemical mechanical polishing of a substrate, comprising: providing a substrate, wherein the substrate comprises silicon oxide; providing a chemical mechanical polishing composition consisting of water; an abrasive; optionally a pH adjusting agent; optionally a biocide; a pH greater than 7; a quaternary phosphonium compound having (I): ##STR00009## wherein R is selected from the group consisting of phenyl, benzyl, and linear or branched C.sub.1-C.sub.4 alkyl; and X is an anion selected from the group consisting of Br.sup.−, Cl.sup.−, I.sup.−, F.sup.− and OH.sup.−; providing a chemical mechanical polishing pad with a polishing surface; creating dynamic contact at an interface between the polishing surface of the chemical mechanical polishing pad and the substrate with a down force of 3 to 35 kPa; and dispensing the chemical mechanical polishing composition onto the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; and wherein some of the silicon oxide is removed from the substrate.

7. The method of chemical mechanical polishing a substrate of claim 6, wherein the quaternary phosphonium compound is selected from the group consisting of tetraphenyl phosphonium bromide, tetraphenyl phosphonium chloride, benzyltriphenyl phosphonium bromide, benzyltriphenyl phosphonium chloride, ethyltriphenyl phosphonium bromide, ethyltriphenyl phosphonium chloride, methyltriphenyl phosphonium bromide, methyltriphenyl phosphonium chloride and mixtures thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) As used throughout this specification the following abbreviations have the following meanings, unless the context indicates otherwise: L=liters; mL=milliliters; kPa=kilopascal; Å=angstroms; nm=nanometers; min=minute; rpm=revolutions per minute; wt %=percent by weight; RR=removal rate; mmol=millimoles; Br.sup.−=bromide; Cl.sup.−=chloride; I.sup.−=iodide; F.sup.−=fluoride; OH.sup.−=hydroxide; PS=Polishing Slurry of the Invention; PC=Comparative Polishing Slurry.

(2) The term “chemical mechanical polishing” or “CMP” refers to a process where a substrate is polished by means of chemical and mechanical forces alone and is distinguished from electrochemical-mechanical polishing (ECMP) where an electric bias is applied to the substrate. The term “TEOS” means the silicon oxide formed from the decomposition of tetraethyl orthosilicate (Si(OC.sub.2H.sub.5).sub.4). The term “composition” and “slurry” are used interchangeably through-out the specification. The term “halide” means chloride, bromide, fluoride and iodide. The terms “a” and “an” refer to both the singular and the plural. All percentages are by weight, unless otherwise noted. All numerical ranges are inclusive and combinable in any order, except where it is logical that such numerical ranges are constrained to add up to 100%.

(3) The chemical mechanical polishing composition of the present invention is useful for polishing a substrate comprising silicon oxide. The chemical mechanical polishing composition consists of water; an abrasive; optionally a pH adjusting agent; optionally a biocide; a pH greater than 7; and a quaternary phosphonium compound for reducing defects and enhancing the removal rate of silicon oxide from a substrate having formula (I):

(4) ##STR00005##
wherein R is selected from the group consisting of phenyl, benzyl, and linear or branched C.sub.1-C.sub.4 alkyl; and X is an anion selected from the group consisting of Br.sup.−, Cl.sup.−, I.sup.−, F.sup.− and OH.sup.−. The term “enhanced silicon oxide removal rate” used herein describes the removal rate of silicon oxide (for removal rate measured in A/min) resulting from polishing a substrate with the chemical mechanical polishing composition containing a quaternary phosphonium compound with an aromatic group means that at least the following expression is satisfied:
A>A.sub.0
wherein A is the silicon oxide removal rate in Å/min for a chemical mechanical polishing composition containing a claimed quaternary phosphonium compound used in the method of the present invention of polishing a substrate, as measured under the polishing conditions set forth in the Examples; A.sub.0 is the silicon oxide removal rate in Å/min obtained under identical conditions with only silica abrasives present.

(5) The term “improved polishing defectivity performance” used herein describes the defectivity performance obtained through the inclusion of a compound having formula (I) in the chemical mechanical polishing composition used for the chemical mechanical polishing method of the present invention means that at least the following expression is satisfied:
X<X.sub.0
wherein X is the defectivity (i.e., post CMP/hydrogen fluoride (HF) scratches or defects) for a chemical mechanical polishing composition containing the substances used in the method of the present invention, as measured under the polishing conditions set forth in the Examples; and X.sub.0 is the defectivity (i.e., post CMP/hydrogen fluoride scratches or defects) obtained under identical conditions with only silica abrasives present.

(6) Preferably, the chemical mechanical polishing compositions of the present invention include a quaternary phosphonium compound in amounts of 0.001 to 1 wt %, more preferably, from 0.01 to 1 wt %, most preferably, from 0.1 to 0.5 wt %.

(7) Exemplary quaternary phosphonium compounds are tetraphenyl phosphonium bromide, tetraphenyl phosphonium chloride, benzyltriphenyl phosphonium bromide, benzyltriphenyl phosphonium chloride, ethyltriphenyl phosphonium bromide, ethyltriphenyl phosphonium chloride, methyltriphenyl phosphonium bromide and methyltriphenyl phosphonium chloride. Mixtures of such quaternary phosphonium compounds can be included in the chemical mechanical polishing compositions of the present invention.

(8) The water contained in the chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention is preferably at least one of deionized and distilled to limit incidental impurities.

(9) The chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention contains 0.1 to 40 wt % abrasive; preferably, 5 to 30 wt % abrasive, more preferably, 10 to 20 wt %. The abrasive used preferably has an average particle size of <200 nm; more preferably 75 to 150 nm; most preferably 100 to 150 nm.

(10) Abrasives for use in the chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention include, for example, inorganic oxides, inorganic hydroxides, inorganic hydroxide oxides, metal borides, metal carbides, metal nitrides, polymer particles and mixtures comprising at least one of the foregoing. Suitable inorganic oxides include, for example, silica (SiO.sub.2), alumina (Al.sub.2O.sub.3), zirconia (ZrO.sub.2), ceria (CeO.sub.2), manganese oxide (MnO.sub.2), titanium oxide (TiO.sub.2) or combinations thereof. Modified forms of these inorganic oxides, such as, organic polymer coated inorganic oxide particles and inorganic coated particles can also be utilized if desired. Suitable metal carbides, borides and nitrides include, for example, silicon carbide, silicon nitride, silicon carbonitride (SiCN), boron carbide, tungsten carbide, zirconium carbide, aluminum boride, tantalum carbide, titanium carbide, or combinations thereof.

(11) The preferred abrasive for use in the chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention is colloidal silica. Preferably, the colloidal silica used contains at least one of precipitated silica and agglomerated silica. Preferably, the colloidal silica used has an average particle size of <200 nm, more preferably, 75 to 150 nm, most preferably, 100 to 150 nm; and accounts for 0.1 to 40 wt %, preferably, 5 to 30 wt %, more preferably, 10 to 20 wt % of the chemical mechanical polishing composition. Examples of commercially available colloidal silica are Klebosol™ II 1630 colloidal silica with 139 nm average particle size; Klebosol™ II 1630 colloidal silica with 145 nm average particles size; and Klebosol™ II 1730 colloidal silica with 130 nm particle size all manufactured by Merck KgAA, Darmstadt, Germany, all available from DuPont.

(12) Optionally, the chemical mechanical polishing composition contains biocides, such as KORDEK™ MLX (9.5-9.9% methyl-4-isothiazolin-3-one, 89.1-89.5% water and <1.0% related reaction product) or KATHON™ ICP III containing active ingredients of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, each manufactured by International Flavors & Fragrances, Inc., (KATHON and KORDEK are trademarks of International Flavors & Fragrances, Inc.).

(13) When biocides are included in the chemical mechanical polishing composition of the present invention, the biocides are included in amounts of 0.001 wt % to 0.1 wt %, preferably, 0.001 wt % to 0.05 wt %, more preferably, 0.001 wt % to 0.01 wt %, still more preferably, 0.001 wt % to 0.005 wt %.

(14) The chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention has a pH of >7, preferably 7 to 12, more preferably 10 to 11.

(15) The chemical mechanical polishing composition used can optionally include one or more pH adjusting agent to maintain the pH within a preferred range. Preferably, the pH adjusting agent is chosen from one or more of sodium hydroxide, potassium hydroxide, and ammonium salts, such as halide or nitrate salts.

(16) The substrate polished in the chemical mechanical polishing method of the present invention comprises silicon oxide. The silicon oxide in the substrate includes, but is not limited to, borophosphosilicate glass (BPSG), plasma enhanced tetraethyl ortho silicate (PETEOS), thermal oxide, undoped silicate glass, high density plasma (HDP) oxide.

(17) The chemical mechanical polishing pad used in the chemical mechanical polishing method of the present invention can by any suitable polishing pad known in the art. The chemical mechanical polishing pad can, optionally, be chosen from woven and non-woven polishing pads. The chemical mechanical polishing pad can be made of any suitable polymer of varying density, hardness, thickness, compressibility and modulus. The chemical mechanical polishing pad can be grooved and perforated as desired.

(18) The quaternary phosphonium compound having formula (I) contained in the chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention results in an improved polishing defectivity performance. Preferably, the inclusion of the quaternary phosphonium compounds having formulae (I) in the chemical mechanical polishing compositions provides a >50% reduction in polishing defectivity (i.e., post CMP/hydrogen fluoride scratches), as measured under the polishing conditions set forth in the Examples. That is, at least the following equations is preferably satisfied:
(X.sub.0−X)/X.sub.0*100>50;
wherein X is the polishing defectivity (i.e., post CMP/hydrogen fluoride scratches or defects) for a chemical mechanical polishing composition containing the quaternary phosphonium compound according to formula (I) and used in the method of the present invention, as measured under the polishing conditions set forth in the Examples; and X.sub.0 is the polishing defectivity (i.e., post CMP/hydrogen fluoride scratches or defects) obtained under identical conditions with only silica abrasives present, or silica abrasive and a symmetrical quaternary phosphonium compound.

(19) The chemical mechanical polishing composition used in the chemical mechanical polishing method of the present invention enables operation with a low nominal polishing pad pressure, for example at 3 to 35 kPa. The low nominal polishing pad pressure improves polishing performance by reducing scratching and other undesired polish defects and minimizes damage to fragile materials.

(20) The following examples are intended to illustrate the present invention but are not intended to limit its scope.

(21) In the following Examples, unless otherwise indicated, conditions of temperature and pressure are ambient temperature and standard pressure.

(22) The following materials were used in the Examples that follow:

(23) The polishing removal rate experiments were performed on eight-inch blanket wafers. An Applied Materials Mirra® polisher was used for examples 1-2 and an Applied Materials Reflexion® polisher was used for examples 3-4. Polishing examples 1-2 were performed using an VisionPad 5000/K7™ polyurethane polishing pad and polishing examples 3-4 were performed using an IC1010 polyurethane polishing pad (both commercially available from Rohm and Haas Electronic Materials CMP Inc.) with a down force of 20.7 kPa (3 psi), a chemical mechanical polishing slurry composition flow rate of 150 mL/min in examples 1-2 and 250 mL/min in examples 3-4, a table rotation speed of 93 rpm and a carrier rotation speed of 87 rpm. The removal rates were determined by measuring the film thickness before and after polishing using a KLA-Tencor FX200 metrology tool. The defectivity performances reported in the Examples was determined using a Scanning Electron Microscope after a hydrogen fluoride post polishing wash (“Pst HF”). All the TEOS wafers after Pst-HF wash were inspected using a Surfscan® SP2 defect inspection system available from KLA-Tencor. The defects information, including their coordinates on the wafer, was recorded in KLARF (KLA Results File) which was then transferred to eDR-5200 defect review system available from KLA-Tencor. A random sample of 100 defect images were selected and reviewed by eDR-5200 system. These 100 images were classified into various defect types, for example, chatter marks (scratches), particles and pad debris. Based on classification results from these 100 images, the total number of scratches on the wafer was determined.

EXAMPLE 1

Chemical Mechanical Polishing Compositions, TEOS RR and Defect Reduction

(24) Aqueous chemical mechanical polishing slurries were prepared as shown in Table 1 below. Aqueous 2 wt % KOH as added to each slurry to maintain the desired pH.

(25) TABLE-US-00001 TABLE 1 Benzyltriphenyl Methyltriphenyl Phosphonium Phosphonium Abrasive Chloride Bromide Slurry (wt %) (wt %) (wt %) pH PC-1 16 0 0 10.7 SC-1 16 0.081 0 10.7 SC-2 16 0 0.074 10.7
Abrasive: Klebosol™ II 1630 colloidal silica with 139 nm average particle size manufactured by Merck KgAA, Darmstadt, Germany, available from DuPont.

(26) TABLE-US-00002 TABLE 2 TEOS Pst-HF Pst-HF Slurry RR Defect Counts Scratches PC-1 3881 515 486 SC-1 4041 246 119 SC-2 4089 188 100
The slurries of the invention showed significant TEOS RR and reduced defect counts and reduced scratches in comparison to the comparative slurry.

EXAMPLE 2

Chemical Mechanical Polishing Compositions, TEOS RR and Defect Reduction

(27) Aqueous chemical mechanical polishing slurries were prepared as shown in Table 3 below. Aqueous 2 wt % KOH as added to each slurry to maintain the desired pH.

(28) TABLE-US-00003 TABLE 3 Tetrabutyl Tetraphenyl Phosphonium Phosphonium Abrasive Bromide Chloride Slurry (wt %) (wt %) (wt %) pH PC-2 16 0 0 10.7 PC-3 16 0.09 0 10.7 SC-3 16 0 0.1 10.7
Abrasive: Klebosol™ II 1630 colloidal silica with 139 nm average particle size manufactured by Merck KgAA, Darmstadt, Germany, available from DuPont.

(29) TABLE-US-00004 TABLE 4 TEOS Pst-HF Pst-HF Slurry RR Defect Counts Scratches PC-2 2868 638 422 PC-3 2811 600 204 SC-3 3165 232 151
The slurry of the invention which included tetraphenyl phosphonium chloride exhibited enhanced TEOS RR and reduced defects and scratches compared to the two comparatives.

EXAMPLE 3

Chemical Mechanical Polishing Compositions, TEOS RR and Scratch Reduction

(30) Aqueous chemical mechanical polishing slurries were prepared as shown in Table 3 below. Aqueous 2 wt % KOH as added to each slurry to maintain the desired pH.

(31) TABLE-US-00005 TABLE 5 Methyltriphenyl Tetraphenyl Phosphonium Phosphonium Abrasive Bromide Chloride Slurry (wt %) (wt %) (wt %) pH PC-4 15.5 0 0 10.7 SC-4 15.5 0.074 0 10.7 SC-5 15.5 0.05 0 10.7 SC-6 15.5 0.1 0 10.7 SC-7 15.5 0 0.078 10.7 SC-8 15.5 0 0.052 10.7 SC-9 15.5 0 0.104 10.7
Abrasive: Klebosol™ II 1630 colloidal silica with 139 nm average particle size manufactured by Merck KgAA, Darmstadt, Germany, available from DuPont.

(32) TABLE-US-00006 TABLE 6 Pst-HF Slurry TEOS RR Scratches PC-4 2899 311 SC-4 3101 120 SC-5 3049 179 SC-6 3044 65 SC-7 3113 176 SC-8 3080 124 SC-9 3171 175
The slurries of the invention had significantly increased TEOS RR and reduced scratches in comparison to the comparative slurry which excluded the quaternary phosphonium compounds.

EXAMPLE 4

Stability of Chemical Mechanical Polishing Compositions

(33) Aqueous chemical mechanical polishing compositions were prepared to test their stability. The pH of the compositions was maintained at 10.7. The sample were left at static conditions of room temperature and pressure for 2 weeks then visually checked.

(34) TABLE-US-00007 TABLE 7 Methyltriphenyl Tetraphenyl Phosphonium Phosphonium Abrasive Bromide Chloride Colloidal Pst-HF Slurry (wt %) (mmol) (mmol) Stability Scratches PC-5 15.5 0 0 Stable 311 SC-10 15.5 0.0021 0 Stable 120 SC-11 15.5 0.0014 0 Stable 179 SC-12 15.5 0.0028 0 Stable 65 SC-13 15.5 0.0050 0 Very — thick SC-14 15.5 0.0080 0 Com- — pletely gelled SC-15 15.5 0 0.0021 Stable 176 SC-16 15.5 0 0.0014 Stable 124 SC-17 15.5 0 0.0028 Stable 175 SC-18 15.5 0 0.0050 Very — thick SC-19 15.5 0 0.0080 Com- — pletely gelled
Abrasive: Klebosol™ II 1630 colloidal silica with 139 nm average particle size manufactured by Merck KgAA, Darmstadt, Germany, available from DuPont.

(35) The chemical mechanical polishing compositions of the present invention were stable where the quaternary phosphonium compounds were at concentrations of 0.0021-00028 mmols.