WO2025088012A1

WO2025088012A1 - Compositions and methods for removal of tungsten and dielectric layers

Info

Publication number: WO2025088012A1
Application number: PCT/EP2024/080028
Authority: WO
Inventors: Te Yu Wei; Shih Chieh Yeh; Tsung Yu Tsai; Michael Lauter
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-10-26
Filing date: 2024-10-24
Publication date: 2025-05-01
Anticipated expiration: 2026-04-26
Also published as: TW202523818A

Abstract

The presently claimed invention relates to dielectric polishing composition and methods thereof. The presently claimed invention particularly relates to a composition comprising: (A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, and a zeta potential ≤ -35 mV at a pH in the range of from ≥ 2.0 to ≤ 6.0; (B) at least one corrosion inhibitor selected from at least one guanidine derivative; (C) at least one iron (III) oxidizer; (D) at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pI) of ≥ 6.5; (E) at least one stabilizer; and (F) an aqueous medium, wherein the pH of the composition is in the range of from ≥ 2.0 to ≤ 4.3, and wherein the composition has a polyacrylamide content ≤ 1 ppm.

Description

Compositions and methods for removal of tungsten and dielectric layers

Technical Field

The presently claimed invention relates to compositions and methods for polishing dielectric. The presently claimed invention particularly relates to compositions and methods that provide high selectivity towards removal of dielectric versus tungsten.

Background

Fabrication of Integrated circuits (ICs) is a multi-step process. The first steps (also called front- end-of-line or FEOL steps) involve the patterning of individual devices such as transistors (for example C-MOSFETs) by suitable techniques (such as photo-lithography or ion implant) on the semiconductor. This is followed by insertion of metal wires/plugs and insulating layers (such as dielectric) to interconnect the various devices (also called back-end-of-line or BEOL steps). With the continuous shrink of the feature size in the ultra-large-scale integrated circuits (IILSI) technology, multi-level interconnects need to be formed.

Metals such as tungsten, cobalt, ruthenium and copper are commonly employed as connects and the selection of specific metal is done on the basis of its position in the architecture. For instance, a common first metal interconnect (metal layer 0) is a tungsten plug inserted in a dielectric layer (such as silicon dioxide). On the other hand, during BEOL steps copper is the most commonly deposited metal, but for the lower interconnect levels (for e.g., metal layers 1 - 4) tungsten and cobalt are also commonly employed.

CMP (Chemical mechanical planarization) has been found to be the key enabling technology for multi-level interconnect formation, as it can initiate both local and global planarization and at the same time provide a good surface quality, in terms of an excellent mirror-like defect-free surface finish. Purely mechanical polishing or (fine) grinding will provide excellent planarization, but dull surfaces. On the other hand, purely chemical polishing (anisotropic etching) will provide only poor planarization results, but excellent mirror-like surface finish.

Herein, CMP utilizes the interplay of chemical and mechanical action to achieve the desired planarity and finish of the to-be-polished surfaces. Mechanical action is usually carried out by the interaction of the CMP composition comprising a finely dispersed abrasive and the polishing pad which is typically pressed onto the to-be-polished surface and mounted on a moving platen. In a typical CMP process step, a rotating wafer holder brings the to-be-polished wafer in contact with a polishing pad. The CMP composition is usually applied between the to-be-polished wafer and the polishing pad.

Typical CMP compositions or slurries comprise one or more abrasives (insoluble/dispersed) components along with soluble components. The chemical action is provided by said soluble components of the CMP composition. Commonly, for achieving metal CMP, the chemical components are commonly tailored by balancing a corroding component (for example an acid, base or oxidiser) with a suitable inhibitor. However, it is important that the soluble and insoluble components are compatible to ensure colloidal stability. Colloidally unstable solutions or agglomerates can damage the surface and fine structures on the wafer to be polished by scratching. Therefore, in order to achieve suitable planarization and surface quality, a precise selection of components and their concentrations would be necessary for obtaining a suitable CMP composition.

In addition, the properties (for example etching) of several or all of the above-mentioned metals might have to be considered, when a slurry is designed, depending on the integration scheme. For instance, when fabricating ICs involving tungsten (metal 0), CMP is employed to remove the metal and liner/barrier overburden until a planar metal 0 (or higher) layer is exposed.

U.S. 6,083,419 A, for instance, describes a CMP composition comprising a compound that is capable of etching tungsten, at least one inhibitor of tungsten etching, wherein the inhibitor of tungsten etching is a compound including at least one functional group selected from nitrogen containing heterocycles without nitrogen-hydrogen bonds, sulphides, oxazolidines or mixtures of functional groups in one compound.

In cases such as U.S. 6,083,419 A, since the intended end point for such applications is the dielectric (for e.g., silicon oxide layer obtained by CVD deposition with tetraethylorthosilicate or TECS), state of art slurries are tailored to achieve high tungsten versus silicon oxide removal rate. US 2019/0211227 and US 2019/0211228, for instance, aim at achieving high selectivity of tungsten removal by employing surface-modified colloidal silica particles bearing a negative charge. As is well-known, one consequence of using compositions displaying high selectivity towards metal (for instance tungsten) removal, is that the embedded metal wiring/plug (flanked by dielectric on either side) gets preferentially eroded to create a dish-like depression, leading to the name- dishing. Dishing, however, is not restricted to metal versus dielectric, but can also affect any interface on the surface of substrate wherein the selectivity of one component versus the other in terms of removal rate exists. A particularly effective measure to combat this is a well- balanced removal rate for both components across the interface.

Also, in order to enable new integration schemes, the selective removal of dielectric is highly desirable. US 8,492,277 provides methods for polishing involving use of a composition comprising acyclic organosulfonic acid to provide selectively high removal rates for silicon oxide and silicon nitride. Similar results were achieved by US 8,513,126 utilizing compositions comprising quaternary ammonium salts. More recently, WO 2023/186762 A1 discloses compositions that achieve such high selectivity via presence of a combination of guanidine derivatives, iron (III) salt(s), potassium phosphate salt(s), polyacrylamide(s) along with suitable stabilizers such as EDTA.

US 2022/0033682 A1 discloses a chemical mechanical polishing composition for polishing tungsten or molybdenum, which comprises, consists essentially of, or consists of a water based liquid carrier, abrasive particles dispersed in the liquid carrier, an amino acid selected from the group consisting of arginine, histidine, cysteine, lysine, and mixtures thereof, an anionic polymer or an anionic surfactant, and an optional amino acid surfactant.

US 2019/0051537 A1 discloses a polishing composition, containing, as initial components: water; an oxidizing agent; arginine or salts thereof; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally, a pH adjusting agent; and, optionally, a surfactant; and, optionally, a biocide.

However, as is well-known in the field of semiconductor development, the presence of trace amounts of unwanted impurities such alkali metals (for e.g., potassium) on the surface of the wafers, can have adverse effects on the performance. Consequently, each ingredient utilized in CMP compositions must be selected carefully, owing to its economic impact as well as the unwanted footprint it leaves, on the surface of the wafers in the form of debris/residue. Therefore, there is always scope for development of improved and more economical compositions. Moreover, in presence of metals such as tungsten and cobalt which are easily removed in acidic conditions, there is an unmet need for obtaining compositions and methods that allow removal of dielectric with high selectivity over tungsten and/or cobalt, while maintaining a high surface quality.

Summary

Surprisingly, it was found that the compositions of the presently claimed invention as described hereinbelow provide surprisingly high selectivity towards removal of dielectric versus tungsten.

Accordingly, in one aspect of the presently claimed invention, a dielectric polishing composition comprising:

(A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, and a zeta potential < -35 mV at a pH in the range of from > 2.0 to < 6.0;

(B) at least one corrosion inhibitor selected from at least one guanidine derivative;

(C) at least one iron (III) oxidizer;

(D) at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pl) of > 6.5;

(E) at least one stabilizer; and

(F) an aqueous medium, wherein the pH of the composition is in the range of from > 2.0 to < 4.3, and wherein the composition has a polyacrylamide content < 1 ppm.

In another aspect, the presently claimed invention is directed to a process for the manufacture of a semiconductor device comprising the chemical mechanical polishing of a substrate (S) used in the semiconductor industry, substrate (S) comprises:

(i) tungsten and/or

(ii) tungsten alloys; and

(iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material. in the presence of the composition as described herein.

In another aspect, the presently claimed invention is directed to the use of a composition described herein for polishing a substrate (S) comprising: (i) tungsten and/or (ii) tungsten alloys; and (iii) at least one dielectric layer.

The presently claimed invention is associated with at least one of the following objectives:

(1) The compositions and the methods of the presently claimed invention aim to provide selective removal of dielectric layer over other metals such as tungsten and/or cobalt. (2) The compositions and the methods of the presently claimed invention aim at providing high silicon oxide (SiCh) removal rates, while ensuring low tungsten (W) removal rates.

(3) The compositions and the methods of the presently claimed invention aims to prevent unwanted etching of tungsten (W) during chemical mechanical polishing of tungsten-containing substrates.

(4) The compositions and the methods of the presently claimed invention aims to prevent/inhibit unwanted dishing of tungsten during chemical mechanical polishing while maintaining optimum control over dielectric/oxide/TEOS dishing.

(5) The composition of the presently claimed invention aims to provide a stable formulation or dispersion, wherein no phase separation or agglomeration occurs.

(6) The composition of the presently claimed invention aims to provide suitable removal rates for the dielectric, while preventing unwanted surface defects and ensuring high surface quality.

Other objects, advantages and applications of the presently claimed invention will become apparent to those skilled in the art from the following detailed description.

Detailed description

The following detailed description is merely exemplary in nature and is not intended to limit the presently claimed invention or the application and uses of the presently claimed invention. Furthermore, there is no intention to be bound by any theory presented in the preceding technical field, background, summary or the following detailed description.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of".

Furthermore, the terms "(a)", "(b)", "(c)", "(d)" etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the presently claimed invention described herein are capable of operation in other sequences than described or illustrated herein. In case the terms “(A)”, “(B)” and “(C)” or "(a)", "(b)", "(c)", "(d)", "(i)", "(ii)" etc. relate to steps of a method or use or assay there is no time or time interval coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below.

In the following passages, different aspects of the presently claimed invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to "one embodiment" or "an embodiment" or “preferred embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the presently claimed invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" or “in a preferred embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment but may refer. Furthermore, the features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the subject matter, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

Furthermore, the ranges defined throughout the specification include the end values as well, i.e., a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.

For the purposes of the presently claimed invention, ‘% by weight’ or ‘wt.% ‘as used in the presently claimed invention is with respect to the total weight of the composition. Further, sum of wt.% of all the compounds, as described hereinbelow, in the respective component adds up to 100 wt-%.

For the purposes of the presently claimed invention, substrate is defined as a semiconductor wafer made of silicon or similar semi-metals used for making micro-electronic devices.

For the purposes of the presently claimed invention, polishing refers to chemico-mechanical removal of specific layers on the substrate during CMP process. Mechanical action is usually carried out by a polishing pad which is typically pressed onto the to-be-polished surface and mounted on a moving platen. In a typical CMP process step, a rotating wafer holder brings the to-be-polished wafer in contact with a polishing pad. The CMP composition is usually applied between the to-be-polished wafer and the polishing pad.

For the purposes of the presently claimed invention, a corrosion inhibitor is defined as a chemical compound forming a protective molecular layer on the surface of a metal.

For the purposes of the presently claimed invention, a stabilizer is defined as a chemical compound that forms soluble, complex molecules with iron (III) ions, inactivating the ions so that they cannot normally react with other elements or ions, (such as silicate or phosphate) to produce precipitates or scale. In absence of stabilizer, the unwanted interaction between iron (III) oxidizer and silicon -based composition, as presently claimed, was found to result in colloidal instability of compositions.

For the purposes of the presently claimed invention, an oxidizing agent is defined as a chemical compound which can oxidize the to-be-polished substrate or one of its layers.

For the purposes of the presently claimed invention, a pH adjusting agent is defined as a compound which is added to the composition in order to have its pH value adjusted to the required value. For the purposes of the presently claimed invention, a buffering agent is defined as component that can resist pH change upon the addition of an acidic or basic components.

For the purposes of the presently claimed invention, an isoelectric point or pl is the pH at which the amino acid carries no net electrical charge (Properties of Analytes and Matrices Determining HPLC Selection, Serban C. Moldoveanu, Victor David, in Selection of the HPLC Method in Chemical Analysis, 2017).

A lower dielectric constant can increase the frequency at which a circuit can operate. Dielectric materials with lower dielectric constant used in metallization of IC production (mainly BEOL) are called low-k materials (dielectric constant k for example 3.5 or lower) or ultralow-k materials (dielectric constant k for example 2.5 and lower). Several low-k materials are available under the trade name Black Diamond from Applied Materials (see in general also US 6,974,777 B2 or Hosali et.al., Analyzing damage from ultralow-k CMP, Solid State Technology, 48 (11) pg. 33, 2005). Detailed description of a method to produce low k materials and their deposition can be found in McClatchie et.al., Low Dielectric Constant Oxide Films Deposited Using CVD Techniques, DUMIC Conference Proceedings, (1998), page 311 ff. For the purposes of the presently claimed invention, a low-k material is a material having a k value (dielectric constant) of less than 3.5, preferably less than 3.0, more preferably less than 2.7. An ultra-low-k material is a material having a k value (dielectric constant) of less than 2.4.

For the purposes of the presently claimed invention, "colloidal silica" refers to silicon dioxide that has been prepared by condensation polymerization of Si(OH)₄. The precursor Si(OH)₄ can be obtained, for example, by hydrolysis of high purity alkoxysilanes, or by acidification of aqueous silicate solutions. Such colloidal silica can be prepared in accordance with U.S. Pat. No. 5,230,833 or can be obtained as any of various commercially available products, such as the Fuso® PL-1 , PL-2, and PL-3 products, and the Nalco 1050, 2327 and 2329 products, as well as other similar products available from DuPont, Bayer, Applied Research, Nissan Chemical, Nyacol and Clariant.

For the purposes of the presently claimed invention, the “particle size” and “mean particle size” are used interchangeably. Mean particle size is defined as the dso value of the particle size distribution of the colloidal silica particles (A) in the aqueous medium (F).

The term “essentially free”, for the purposes of the presently claimed invention, means that the composition does not comprise any concentration of said component that can influence the polishing functionality of the composition. Preferably the component is below 1 ppm, more preferably below 0.1 ppm, most preferably below the detection limit. For instance, preferably the composition is essentially free from polyacrylamide and/or alkali metal such as potassium, preferably the concentration of polyacrylamide and/or alkali metal such as potassium is below 1 ppm in the composition. However, any trace quantity of such components that may remain on the semiconductor surface as part of the residue from a pre-CMP process step, is not prejudicial to the polishing application involving the composition described herein.

For the purposes of the presently claimed invention, the mean particle size is measured for example using dynamic light scattering (DLS) or static light scattering (SLS) methods. These and other methods are well known in the art, see e.g., Kuntzsch, Timo; Witnik, Ulrike; Hollatz, Michael Stintz; Ripperger, Siegfried; Characterization of Slurries Used for Chemical-Mechanical Polishing (CMP) in the Semiconductor Industry; Chem. Eng. Technol; 26 (2003), volume 12, page 1235. To the result of such a measurement literature commonly refers to as secondary particle size. Under these methods DLS is a preferred method.

For the purposes of the presently claimed invention, for dynamic light scattering (DLS), typically a Malvern Zetasizer ZSP or Horiba LB-550 V (DLS, dynamic light scattering measurement) or any other such instrument is used. This technique measures the hydrodynamic diameter of the particles as they scatter a laser light source (for example A = 650 nm), detected at an angle of for example 90° or 173° to the incoming light. Variations in the intensity of the scattered light are due to the random Brownian motion of the particles as they move through the incident beam and are monitored as a function of time. Autocorrelation functions performed by the instrument as a function of delay time are used to extract decay constants; smaller particles move with higher velocity through the incident beam and correspond to faster decays.

For the purposes of the presently claimed invention, the decay constants are proportional to the diffusion coefficient, D_t, of the inorganic abrasive particle and are used to calculate particle size according to the Stokes-Einstein equation:

where the suspended particles are assumed to (1) have a spherical morphology and (2) be uniformly dispersed (i.e., not agglomerated) throughout the aqueous medium. This relationship is expected to hold true for particle dispersions that contain < 1 % by weight of solids (solid concentration) as there are no significant deviations in the viscosity of the aqueous dispersant, in which = 0.96 mPa s (at T = 22 °C). The particle size distribution of the fumed or colloidal silica particle dispersion is usually measured in a plastic cuvette at 0.1 to 1 .0 % solid concentration and dilution, if necessary, is carried out with the dispersion medium or ultra-pure water.

For the purposes of the presently claimed invention, the BET surface of the colloidal silica particles is determined according to DIN ISO 9277:2010-09. To the result of such a measurement literature commonly refers to as primary particle size.

For the purposes of the presently claimed invention, the measurement techniques disclosed are well known to a person skilled in the art.

In an aspect of the presently claimed invention, a dielectric polishing composition comprising:

(C) at least one iron (III) oxidizer;

(E) at least one stabilizer; and

The composition has a polyacrylamide content < 1 ppm or in other words the composition is essentially free from polyacrylamide. In certain cases, a polyacrylamide content > 1 ppm may have a negative impact on the semiconductor topography. More preferably, the composition has a polyacrylamide content < 0.5 ppm, even more preferably < 0.1 ppm. For purposes of the presently claimed invention, the composition is essentially free from polyacrylamide and polyacrylamide copolymers. Copolymers of polyacrylamide may be cationic, anionic or non-ionic polyacrylamide copolymers. The presence of polyacrylamide copolymers in the composition leads to unwanted silicon oxide (dielectric) dishing. Most preferably, the amount of polyacrylamide or polyacrylamide copolymers in the composition is < 0.01 ppm.

The composition is essentially free from alkali metal. Preferably, the composition contains < 1 ppm of alkali metals. The alkali metal refers to group I elements of the periodic table preferably selected from lithium, sodium, potassium, rubidium, cesium, or francium, more preferably the composition is essentially free from lithium, sodium, and potassium, even more preferably essentially free from sodium or potassium, most preferably essentially free from potassium.

Alkali metals such as sodium or potassium are commonly introduced into CMP compositions via the use of acid/base or buffering agents, however, their presence can interfere with the electronics on the surface of the wafer and have detrimental effect on the final performance. Preferably, the amount of sodium or potassium in the composition is < 1 ppm, even more preferably < 0.1 ppm, most preferably < 0.01 ppm.

The composition is essentially free from phosphoric acid or salts thereof. The composition is essentially free from phosphoric acid salts such as organic phosphate or alkali metal phosphates, for instance potassium dihydrogen phosphate or sodium dihydrogen phosphate. Preferably, the composition contains < 1 ppm of phosphoric acid or salts thereof. Phosphoric acid or salts thereof can combine with metals to form unwanted salts that have low water solubility. Consequently, their presence can lead to a requirement of additional filtration step(s), thus leading to increased process costs.

The dielectric polishing composition of the present invention comprises the components (A), (B), (C), (D), (E), and water and optionally further components as described below.

(A) Surface - modified colloidal silica particles

According to the presently claimed invention, the composition comprises a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, and a zeta potential < -35 mV at a pH in the range of from > 2.0 to < 6.0.

Well known silica-selective compositions typically are known to utilize ceria, however, said abrasive is noted to result in unacceptable dull finish. Similar unwanted observation was noted when utilizing fumed silica. Preferably, the surface-modified silica particles have a zeta potential < -35 mV, more preferably, < -36 mV, even more preferably, < -37 mV, and most preferably < -38 mV, at a pH in the range of from > 2.0 to < 6.0.

Preferably, the surface-modified silica particles have a zeta potential > -50 mV, more preferably, > -45 mV, and most preferably > -40 mV, at a pH in the range of from > 2.0 to < 6.0.

Preferably, the surface-modified silica particles have a zeta potential of from -50 mV to -35 mV, more preferably of from -40 mV to -35 mV, even more preferably of from -45 mV to -35 mV, and most preferably of from -39 mV to -35 mV, at a pH in the range of from > 2.0 to < 6.0.

The surface-modified silica particles are preferably amorphous and not agglomerated and thus typically occur in the form of discrete spheres that are not crosslinked with each other and contain hydroxyl groups on the surface. Surface-modified colloidal silica particles are obtainable by methods known in the art such as ion-exchange of silicic acid salt, or by sol-gel technique (e.g., hydrolysis or condensation of a metal alkoxide, or peptization of precipitated hydrated silicon oxide, etc.).

The silica particles are known to be stabilized by a permanent electrical charge on their surface to prevent agglomeration and to ensure colloidal stability. The charge can be positive or negative. Because of defects observed on surface of substrates when positively charged (or cationic) silica particles are employed for polishing (refer Figure 2b), a negative charge is considered as essential. This is depicted in the defect-free surface in Figure 2a, wherein the substrate was planarized with a composition comprising negatively charged (or anionic) silica particles. The charge on the surface is expressed by the zeta potential. The zeta potential of silica particles (not surface functionalized) depends on the pH value of the aqueous medium (refer Figure 1). At pH higher than 8 the zeta potential is equal or lower than - 35 mV, i.e., low enough to ensure colloidal stability. Without being bound by theory, it is believed that at acidic pH (for example pH 2-6), as a consequence of the interaction of the silica with the protons of the media, the charge on the surface is reduced (zeta potential typically for example between +10 and -10 mV). Typical correlation of zeta potential and pH can be found in the literature (Esumi et.al., Bull. Chem. Soc. Jpn., Vol. 61 , 1988). Low surface charge can lead to formation of agglomerates as soon as shear forces (for example through filtration or polishing action) arise.

The zeta potential may be affected by presence of additives. However, as would be easily understood by the skilled person, one or more of the mentioned components having negligible or no influence on surface charge of the particles would likely have no significant effect on the zeta potential of particles (A) and therefore the zeta potential < -35 mV could still be achievable despite their presence during measurement. Preferably, the zeta potential measurements mentioned herein for component (A) are made in absence of other components, i.e., the surface-modified silica particles (A) have a zeta potential < -35 mV when measured in isolation or substantially in absence of other components (B) to (E). The measurements outlined in figures 1-4, have been made in absence of other components.

Preferably the surface modified colloidal silica particles (A) having a negative zeta potential of < -35 mV at a pH in the range of from > 2.0 to < 6.0 are silica particles anionically modified with metallate ions or modified with sulfonic acid moieties. The term "anionically modified with metallate ions" as utilized herein in particular refers to silica particles where metallate ions (i.e., M(OH)4') are incorporated in the surface of the silica particle replacing Si(OH)4 sites and creating a permanent negative charge, as explained in WO 2006/028759 A2.

Preferably, the surface modified colloidal silica particles (A) having a negative zeta potential of < -35 mV at a pH in the range of from > 2.0 to < 6.0 are silica particles anionically modified with metallate ions. More preferably, the metallate ions are selected from aluminate, stannate, zincate, or plumbate.

Even more preferably, the surface modified colloidal silica particles (A) having a negative zeta potential of < -35 mV at a pH in the range of from > 2.0 to < 6.0 are silica particles anionically modified with aluminate. Such surface modified colloidal silica particles are disclosed e.g., in WO 2006/7028759 A2.

More preferably, the surface modified colloidal silica particles of component (A) having a negative zeta potential of < -35 mV at a pH in the range of from > 2.0 to < 6.0 are silica particles anionically modified with sulfonic acid. Sulfonic acid-modified aqueous anionic silica sols which are highly stable under acidic conditions are disclosed e.g., in WO 2010734542 A1 . Herein, a sulfonic acid- modified aqueous anionic silica sol is obtained by a method wherein a silane coupling agent having a functional group which can be chemically converted into a sulfonic acid group is chemisorbed onto the colloidal silica, and then the functional group is converted into a sulfonic acid group. A preferred type of silica dispersion to be used for this type of chemical reaction is a silica dispersion with a zeta potential function like Figure 1 (unmodified silica particles), where the charge on the particle surface is low in the acidic regime. The same is identified as a sign that the surface of the silica is clean and the silane can easily react with the groups on the silica surface. If the charge on the silica particles before charging the reaction with the silane coupling agent in the acidic regime (for example pH 2-3) is already high (for example -36 or -50 mV) then it is interpreted as a sign that the silica surface is not clean and already modified. The silane coupling agent may not be able to cover the surface sufficiently and the charge on the surface subsequently after reaction and conversion may remain low. A surface modified particle dispersion with a zeta potential of for example -23 mV for example pH 2-6 can have a low colloidal stability. This means that the dispersion can be easily destabilized by processes like filtration or CMP, where shear forces appear. In such a case, a filtered silica dispersion measured by DLS methods for example with a Malvern Zetasizer ZSP (refer Figure 3) will provide signal with high variation, that cannot be interpreted easily as a mean particle size. Other methods, like sedimentations methods, must be used here to assess colloidal stability. On the other hand, the silica particles anionically modified with sulfonic acid are noted to yield a readily-measurable stable DLS signal (refer Figure 4).

Preferably, the concentration of the surface modified colloidal silica particles (A) is in the range of from > 3.2 wt.% to < 13.0 wt.%, based on the total weight of the composition. The concentration of the surface modified colloidal silica particles (A) is preferably not more than 13.0 wt.%, more preferably not more than 10.0 wt.%, particularly not more than 9.5 wt.%, even more preferably not more than 9.0 wt.%, more preferably not more than 8.5 wt.%, even more preferably not more than 8.0 wt.%, for example not more than 7.5 wt.%, based on the total weight of the composition. It is observed that particle concentration beyond 10 wt.% lead to colloidal instability of composition. The concentration of the surface modified colloidal silica particles (A) is preferably at least 3.2 wt.%, more preferably at least 3.5 wt.%, even more preferably at least 3.8 wt.%, particularly at least 4.0 wt.%, even more preferably at least 4.1 wt.%, still more preferably at least 4.2 wt.%, more preferably at least 4.3 wt.%, even more preferably at least 4.5 wt.%, still more preferably at least 4.8 wt.%, most preferably at least 5.2 wt.%, based on the total weight of the composition. It is observed that particle concentration below 3.2 wt.% leads to an unwanted high tungsten dishing and also low dielectric removal selectivity, i.e., low silicon oxide to tungsten removal rate ratio. The concentration of the surface modified colloidal silica particles (A) is more preferably in the range of from > 4.5 wt.% to < 8.5 wt.%, based on the total weight of the composition.

The surface modified colloidal silica particles (A) can be preferably contained in the composition in various particle size distributions. The particle size distribution of the surface modified colloidal silica particles (A) can be monomodal or multimodal. In case of a multimodal particle size distribution, a bimodal particle size distribution is often preferred. For the purposes of the presently claimed invention, a monomodal particle size distribution is preferred for the surface modified colloidal silica particles (A).

According to the presently claimed invention, the average particle diameter of the surface modified colloidal silica particles (A) is in the range of from 60 nm to 200 nm, determined according to dynamic light scattering technique. The mean or average particle size of the surface modified colloidal silica particles (A) can vary within a wide range. The mean particle size of the surface modified colloidal silica particles (A) is preferably in the range of from > 60 nm to < 190 nm, preferably in the range of from > 60 nm to < 180 nm, more preferably in the range of from > 62 nm to < 150 nm, more preferably in the range of from > 65 nm to < 140 nm, particularly preferably in the range of from > 68 nm to < 130 nm, particularly most preferably in the range of from > 70 nm to < 120 nm, in each case measured with dynamic light scattering techniques using instruments for example a Zetasizer ZSP or a High Performance Particle Sizer (HPPS) from Malvern Instruments, Ltd. or Horiba LB550.

The surface modified colloidal silica particle (A) preferably can be of various shapes. Thereby, the particles (A) may preferably be of one or essentially only one type of shape. However, it is also possible that the particles (A) have different shapes. For instance, two types of differently shaped particles (A) may be present. For example, (A) can have the shape of agglomerates, cubes, cubes with bevelled edges, octahedrons, icosahedrons, cocoons, nodules or spheres with or without protrusions or indentations.

Preferably, the surface modified colloidal silica particles (A) are spherical, cocoon-shaped or a mixture of spherical and cocoon-shaped particles. The spherical particles may be with or without protrusions or indentations. The cocoon-shaped particles may be with or without protrusions or indentations. Cocoon-shaped particles are preferably particles with a minor axis of from > 10 nm to < 200 nm, and preferably a ratio of major/minor axis of from > 1.4 to < 2.2, more preferably of from > 1.6 to < 2.0. Preferably, they have an averaged shape factor of from > 0.7 to <0.97, more preferably of from > 0.77 to < 0.92, preferably an averaged sphericity of from > 0.4 to < 0.9, more preferably of from > 0.5 to < 0.7 and preferably an averaged equivalent circle diameter of from > 41 nm to < 66 nm, more preferably of from > 48 nm to < 60 nm, in each case determined by transmission electron microscopy and scanning electron microscopy. Most preferably, the surface modified colloidal silica particles (A) are spherical or essentially spherical. The spherical or essentially spherical particles have a ratio of major/minor axis > 0.9.

For the purposes of the presently claimed invention, the determination of the shape factor, the sphericity and the equivalent circle diameter of cocoon-shaped particles is explained hereinbelow. The shape factor gives information on the shape and the indentations of an individual particle and can be calculated according to the following formula: shape factor = 4TT (area I perimeter2)

The shape factor of a spherical particle without indentations is 1. The value of the shape factor decreases when the number of indentations increases. The sphericity gives information on the elongation of an individual particle using the moment about the mean and can be calculated according to the following formula, wherein M are the centres of gravity of the respective particle: sphericity = (Mxx - Myy)-[4 Mxy2 + (Myy-Mxx)2]0.51 (Mxx - Myy)+[4 Mxy2 + (Myy-Mxx)2]0.5 elongation = (1 / sphericity)0.5 wherein

Mxx = Z (x-xmean)² /N

Myy = Z (y-ymean)² /N

Mxy = Z [(x-xmean)*(y-ymean)] /N

N number of pixels forming the image of the respective particle x, y coordinates of the pixels xmean mean value of the x coordinates of the N pixels forming the image of said particle ymean mean value of the y coordinates of the N pixels forming the image of said particle

The sphericity of a spherical particle is 1 . The value of the sphericity decreases, when particles are elongated. The equivalent circle diameter (also abbreviated as ECD in the following) of an individual non-circular particle gives information on the diameter of a circle which has the same area as the respective non-circular particle. The averaged shape factor, averaged sphericity and averaged ECD are the arithmetic averages of the respective property, related to the analysed number of particles.

For the purposes of the presently claimed invention, the procedure for particle shape characterization is as follows. An aqueous cocoon-shaped silica particle dispersion with 20 wt.% solid content is dispersed on a carbon foil and is dried. The dried dispersion is analyzed by using Energy Filtered-Transmission Electron Microscopy (EF-TEM) (120 kilo volts) and Scanning Electron Microscopy secondary electron image (SEM-SE) (5 kilo volts). The EF-TEM image having a resolution of 2k, 16 Bit, 0.6851 nm/pixel is used for the analysis. The images are binary coded using the threshold after noise suppression. Afterwards, the particles are manually separated. Overlying and edge particles are discriminated and not used for the analysis. ECD, shape factor and sphericity as defined before are calculated and statistically classified.

(B) Corrosion inhibitor According to the presently claimed invention, the composition comprises at least one corrosion inhibitor selected from at least one guanidine derivative.

As may be observed from Table 1 hereinbelow, the corrosion inhibitor selected from at least one guanidine derivative prevents unwanted corrosion of tungsten as well as high tungsten dishing.

Preferably, the at least one guanidine derivative is selected from buformin, phenformin, guanine, proguanil hydrochloride, 2-guanidinobenzimidazole, polyhexamethylene biguanide hydrochloride, polyaminopropyl biguanide, chlorhexidine or chlorhexidine salts.

More preferably, guanidine derivative is selected from chlorhexidine or chlorhexidine salts. Chlorhexidine or salts thereof are known to degrade over prolonged period of time into chemical sub-species, however, the degradation itself or the presence of degradation products in the composition is noted to have little or no impact on the CMP activity outlined herein. The concentrations of said degradation products would vary with conditions (temperature/pressure etc.). Some of the likely degradation products as outlined in table 11-1 on page 19 of thesis titled- Studies on the mechanisms of solid state and solution instability of drugs by Zhixin Zong are reproduced below. The manipulation of degradation products and/or their concentration to enhance activity would be considered routine for a skilled person. Proposed Structure

Another suitable guanidine derivative is alexidine (A/¹,A/¹-(Hexane-1 ,6-diyl)bis[A/³-(2- ethylhexyl)imidodicarbonic diamide])

Preferably, the chlorhexidine or chlorhexidine salts include the degradation products listed hereinabove.

Preferably, the corrosion inhibitor (B) is chlorohexidine.

Preferably, the corrosion inhibitor (B) is selected from chlorohexidine salts.

More preferably, the chlorhexidine salts are selected from the group consisting of chlorhexidine gluconate, chlorhexidine digluconate, chlorhexidine hydrochloride, chlorhexidine dihydrochloride, chlorhexidine acetate, chlorhexidine diacetate, chlorhexidine hexametaphosphate, chlorhexidine metaphosphate and chlorhexidine trimetaphosphate.

Most preferably, the corrosion inhibitor is selected from the group consisting of chlorhexidine, chlorhexidine gluconate, and chlorhexidine digluconate.

Preferably, the corrosion inhibitor (B) is present in an amount in the range of from > 0.001 wt.% to < 0.05 wt.%, based on the total weight of the composition. More preferably, the corrosion inhibitor (B) is present in an amount of not more than 0.04 wt.%, most preferably not more than 0.03 wt.%, based on the total weight of the composition. The amount of (B) is preferably at least 0.002 wt.%, more preferably at least 0.003 wt.%, based on the total weight of the composition. The concentration of the corrosion inhibitor (B) is more preferably in the range of from > 0.003 wt.% to < 0.03 wt.%, based on the total weight of the composition.

(C) Iron (III) oxidizer

According to the presently claimed invention, the composition comprises at least one iron (III) oxidizer (C).

As may be observed from Table 1 hereinbelow, the iron (III) oxidizer (C) oxidizes the to-be-pol- ished substrate or one of its layers, thus ensuring a chemical contribution to the removal rate and a high surface quality.

Preferably, the iron (III) oxidizer (C) is selected from iron (III) salts or compounds with nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, acetic acid, o-phosphorylethanolamine, phosphonic acid, or mixtures thereof.

More preferably, the iron (III) oxidizer (C) is selected from iron (III) nitrate or hydrates thereof. Even more preferably, the iron (III) oxidizer (C) is iron (III) nitrate. Preferably, the concentration of the iron (III) oxidizer (C) is in the range of from > 0.003 wt.% to < 0.1 wt.%, based on the total weight of the composition. More preferably, the iron (III) oxidizer (C) is present in an amount of not more than 0.08 wt.%, even more preferably not more than 0.07 wt.%, most preferably not more than 0.05 wt.%, most preferably not more than 0.03 wt.%, based on the total weight of the composition. The amount of (C) is preferably at least 0.0035 wt.%, more preferably at least 0.004 wt.%, most preferably at least 0.0045 wt.%, based on the total weight of the composition. When amount of (C) is below < 0.003 wt%, unwanted high dielectric dishing is noted. On the other hand, when amount of (C) > 0.1 wt.%, unwanted high tungsten MRR and dishing is observed. The concentration of the iron (III) oxidizer (C) is more preferably in the range of from > 0.0045 wt.% to < 0.03 wt.%, most preferably is in the range of from > 0.0048 wt.% to < 0.02 wt.%, based on the total weight of the composition.

(D) Buffering agent

According to the presently claimed invention, the composition comprises at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pl) of > 6.5.

As may be observed from Table 1 hereinbelow, the buffering agent (D) specifically prevents unwanted dishing of dielectric layer during chemical mechanical polishing while allowing suitable maintenance of pH and high silicon oxide (dielectric) removal rate.

Chemically, a buffering agent consists of a weak acid and its conjugate base or a weak base and its conjugate acid. For instance, lysine having -NH₂ group (strong base) and its protonated ammonium form (having -NHa⁺ group or conjugate acid form) combine to provide a buffering agent when in solution (such as when present in the aqueous composition of the presently claimed invention with a pH in the range of from > 2.0 to < 6.0). Amino acids are noted to have a buffering region ±1 pH unit from their pKa values. For the presently claimed invention, this would be around the pKa1 of the corresponding amino acid (lysine, arginine and histidine have a pKa1~ 2.18, 2.17 and 1.82, respectively, refer: Carey and Giuliano (2011) Amino acids, peptides and proteins. Organic Chemistry 8 th Edition, 25, 1126 McGraw Hill, ISBN-13: 978-0077354770).

For basic amino acids mentioned here, the isoelectric point (pl) may be conveniently calculated by averaging pKa values for the two amine groups (two of the least acidic pKa values). For instance, in case if lysine- pKa values of amine groups are 8.95 and 10.53 and the calculated pl is 9.74. Similarly, the pl of arginine is 10.76 and histidine is 7.59. Furthermore, the pKa values are obtainable by titration of the groups against suitable acid/base. Preferably, the buffering agent (D) is a basic amino acid having an isoelectric point (pl) of > 6.9, more preferably > 7.0, even more preferably > 7.2 most preferably > 7.5.

Preferably, the buffering agent (D) is a basic amino acid selected from lysine, arginine, or histidine. More preferably, the buffering agent (D) is a basic amino acid selected from arginine, or histidine, most preferably the buffering agent (D) is arginine.

Amino acids are known to occur as L or R optical isomers, wherein, the L-form is biologically relevant and common. For the purposes of the presently claimed invention, both isomers function similarly and can be employed, however, a preference may be given towards L form for economic reasons. Preferably, the basic amino acid is selected from L or R isomers. Preferably, the concentration of the buffering agent (D) is in the range of from > 0. 1 wt.% to < 0.78 wt.%, based on the total weight of the composition. More preferably, the buffering agent (D) is present in an amount of not more than 0.75 wt.%, even more preferably not more than 0.73 wt.%, most preferably not more than 0.7 wt.%, based on the total weight of the composition. The presence of (D) in an amount > 0.78 wt.% leads to an unwanted increase in silicon oxide (dielectric) dishing. On the other hand, the presence of (D) in an amount < 0.1 wt.% leads to insufficient pH stabilization. The amount of (D) is preferably at least 0.15 wt.%, more preferably at least 0.2 wt.%, even more preferably at least 0.25 wt.%, most preferably at least 0.28 wt.%, based on the total weight of the composition. The concentration of buffering agent (D) is more preferably in the range of from > 0.15 wt.% to < 0.75 wt.%, most preferably is in the range of from > 0.25 wt.% to < 0.73 wt.%, based on the total weight of the composition.

In a preferred embodiment buffering agent (D) is selected from histidine or arginine and is present in amount of > 0.15 wt.% to < 0.75 wt.% based on the total weight of the composition.

In another preferred embodiment buffering agent (D) is arginine and is present in amount of > 0.15 wt.% to < 0.75 wt.% based on the total weight of the composition

(E) Stabilizer

According to the presently claimed invention, the composition comprises at least one stabilizer (E).

Without being bound by theory, it is expected that agglomerate-formation is highly prevalent when employing incompatible components such as silica particles, iron (III) salts, among others. However, as may be observed from Table 1 hereinbelow, the stabilizer (E) ensures colloidal stability.

Preferably, the at least one stabilizer (E) is selected from acetic acid, acetylacetonate, o-phos- phorylethanolamine, phosphonic acid, alendronic acid, acetic acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, oxalic acid, maleic acid, gluconic acid, muconic acid, ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, di- ethylene-triamine-pentaacetic acid, bis(salicyliden)ethylendiamin, aminotris(meth- ylenephosphonic acid), diethylene-triamine-pentakis(methylphosphonic acid), ethylene-diamine- tetra(methylene-phosphonic acid), or mixtures thereof.

More preferably, the at least one stabilizer (E) is selected from phthalic acid, citric acid, adipic acid, oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, oxalic acid, maleic acid, gluconic acid, muconic acid, ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine- pentaacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethy- lene-triamine-pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof.

Even more preferably, the at least one stabilizer (E) is selected from ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, di- ethylene-triamine-pentaacetic acid, bis(salicyliden)ethylendiamin, aminotris(meth- ylenephosphonic acid), diethylene-triamine-pentakis(methylphosphonic acid), ethylene-diamine- tetra(methylene-phosphonic acid), or mixtures thereof.

Most preferably, the at least one stabilizer (E) is ethylenediaminetetraacetic acid.

Preferably, the concentration of the stabilizer (E) is in the range of from > 0.005 wt.% to < 0.15 wt.%, based on the total weight of the composition. More preferably, the stabilizer (E) is present in an amount of not more than 0.1 wt.%, even more preferably not more than 0.08 wt.%, most preferably not more than 0.03 wt.%, based on the total weight of the composition. The amount of (E) is preferably at least 0.0055 wt.%, more preferably at least 0.006 wt.%, most preferably at least 0.008 wt.%, based on the total weight of the composition. The concentration of the stabilizer

(E) is more preferably in the range of from > 0.0055 wt.% to < 0.08 wt.%, most preferably is in the range of from > 0.008 wt.% to < 0.03 wt.%, based on the total weight of the composition.

(F) Aqueous medium

According to the presently claimed invention, the composition comprises an aqueous medium (F). The aqueous medium (F) can be of one type or a mixture of different types of aqueous media.

The aqueous medium (F) can preferably be any medium which contains water. Preferably, the aqueous medium (F) is a mixture of water and an organic solvent that is miscible with water. Representative examples of organic solvents include, but are not limited to, Ci to C3 alcohols, alkylene glycols and alkylene glycol derivatives.

More preferably, the aqueous medium (F) is water. In a preferred embodiment of the presently claimed invention, the aqueous medium (F) is deionized water.

For the purposes of the presently claimed invention, if the amounts of the components other than (F) are in total y wt.% t of the composition, then the amount of (F) is (100-y) wt.% of the composition.

The amount of the aqueous medium (F) in the composition is preferably not more than 99.9 wt.%, more preferably not more than 99.6 wt.%, most preferably not more than 99 wt.%, particularly preferably not more than 98 wt.%, particularly not more than 97 wt.%, for example not more than 95 wt.%, based on the total weight of the composition. The amount of the aqueous medium (F) in the composition is preferably at least 65 wt.%, more preferably at least 75 wt.%, most preferably at least 85 wt.%, particularly preferably at least 88 wt.%, particularly at least 90 wt.%, for example at least 92.5 wt.%, based on the total weight of the composition.

The properties of the composition may depend on the pH of the corresponding composition. According to the presently claimed invention, the pH of the composition is in the range of from > 2.0 to < 4.3. Preferably, the pH value of the composition is < 4.2, more preferably < 4.1 , most preferably < 4.05, particularly preferably < 4.0, particularly most preferably < 3.5. The pH value of the composition is preferably > 2.1 , more preferably > 2.3, most preferably > 2.5, particularly preferably > 2.6, particularly most preferably > 2.8. The pH value of the composition is preferably in the range of from > 2.1 to < 4.2, preferably from >2.3 to < 4.1 , more preferably from > 2.5 to < 4.0, most preferably from > 2.8 to < 3.5. Preferably, the composition further comprises an additive selected from pH adjusting agent, oxidizing agent, wetting agent, dispersing agent, biocide, or mixtures thereof. More preferably, the at least one additive is different from the components (A), (B), (C), (D), (E) and (F) and is optionally added in addition to said components.

Preferably, the at least one pH adjusting agent is selected from the group consisting of inorganic acids, carboxylic acids, amine bases, ammonium hydroxides, including tetraalkylammonium hydroxides. Preferably, the at least one pH adjusting agent is selected from the group consisting of nitric acid, sulfuric acid, and ammonia. More preferably, the pH adjusting agent is nitric acid.

The amount of the at least one pH adjusting agent is preferably not more than 10 wt.%, more preferably not more than 2 wt.%, most preferably not more than 0.5 wt.%, particularly not more than 0.1 wt.%, for example not more than 0.05 wt.%, based on the total weight of the composition. The amount of the at least one pH adjusting agent is preferably at least 0.0005 wt.%, more preferably at least 0.005 wt.%, most preferably at least 0.025 wt.%, particularly at least 0.1 wt.%, for example at least 0.4 wt.%, based on the total weight of the composition.

Preferably, the composition of the presently claimed invention can further contain at least one oxidizing agent.

Preferably, the at least one oxidizing agent is selected from the group consisting of organic peroxides, inorganic peroxides, nitrates, persulfates, iodates, periodic acids, periodates, permanganates, perchloric acids, perchlorates, bromic acids and bromates. Said oxidizing agent is optionally present in addition to the iron (III) oxidizer.

More preferably, the at least one oxidizing agent is hydrogen peroxide.

Preferably, the at least one oxidizing agent is present in an amount in the range of > 0.01 wt.% to < 1.0 wt.%, based on the total weight of the composition.

Preferably, the concentration of the at least one oxidizing agent is not more than 5.0 wt.%, even more preferably not more than 2.0 wt.%, even more preferably not more than 1.0 wt.%, even more preferably not more than 0.8 wt.%, most preferably not more than 0.5 wt.%, in each case based on the total weight of the composition. The concentration of the at least one oxidizing agent is at preferably at least 0.01 wt.%, more preferably at least 0.05 wt.%, most preferably at least 0.1 wt.%, in each case based on the total weight of the composition.

More preferably, the concentration of hydrogen peroxide as oxidizing agent is > 0.01 wt.% to < 1.0 wt.%, even more preferably > 0.05 wt.% to < 1.0 wt.%, most preferably > 0.05 wt.% to < 0.5 wt.%, particularly preferably > 0.01 wt.% to < 0.1 wt.%, in each case based on the total weight of the composition.

The processes for preparation of compositions for chemical mechanical polishing are generally known. These processes may be applied to the preparation of the composition of the presently claimed invention. This can be carried out by dispersing or dissolving the components described hereinabove (A), (B), (C), (D) and (E) in the aqueous medium (F), preferably water, and optionally by adjusting the pH value through adding an acid, and/or a base (a pH adjusting agent). For this purpose, the customary and standard mixing processes and mixing apparatuses such as agitated vessels, high shear impellers, ultrasonic mixers, homogenizer nozzles or counter flow mixers, can be used.

A preferred embodiment of the presently claimed invention is directed to a composition comprising the following components:

(A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, and a zeta potential < -35 mV at a pH of from > 2.0 to < 6.0;

(C) at least one iron (III) oxidizer;

(E) at least one stabilizer selected from ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pen- taacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethylene- triamine-pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof; and

Another preferred embodiment of the presently claimed invention is directed to a composition comprising the following components:

(A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, a zeta potential < -35 mV at a pH of from > 2.0 to < 6.0, and having concentration in the range of from > 3.2 wt.% to < 13.0 wt.%, based on the total weight of the composition;

(B) at least one corrosion inhibitor selected from at least one guanidine derivative and having concentration in the range of from > 0.001 wt.% to < 0.05 wt.%, based on the total weight of the composition;

(C) at least one iron (III) oxidizer in the range of from > 0.003 wt.% to < 0.1 wt.%, based on the total weight of the composition;

(D) at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pl) of > 6.5 and having concentration in the range of from > 0. 1 wt.% to < 0.78 wt.%, based on the total weight of the composition;

(E) at least one stabilizer selected from ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pen- taacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethylene- triamine-pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof and having concentration in the range of from > 0.005 wt.% to < 0.15 wt.%, based on the total weight of the composition; and (F) an aqueous medium, wherein the pH of the composition is in the range of from > 2.0 to < 4.3, and wherein the composition has a polyacrylamide content < 1 ppm.

(E) at least one stabilizer selected from ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pen- taacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethylene- triamine-pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof and having concentration in the range of from > 0.005 wt.% to < 0.15 wt.%, based on the total weight of the composition; and

(F) an aqueous medium, wherein the pH of the composition is in the range of from > 2.0 to < 4.3, wherein the composition has a polyacrylamide content < 1 ppm, and wherein the composition has an alkali metal content < 1 ppm.

(A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, a zeta potential < -35 mV at a pH of from > 2.5 to < 6.0, and concentration in the range of from > 0.3 wt.% to < 7.0 wt.%, based on the total weight of the composition;

(B) at least one corrosion inhibitor selected from at least one guanidine derivative and having concentration in the range of from > 0.003 wt.% to < 0.03 wt.%, based on the total weight of the composition;

(C) at least one iron (III) oxidizer in the range of from > 0.0048 wt.% to < 0.02 wt.%, based on the total weight of the composition; (D) at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pl) of > 6.5 and having concentration in the range of from > 0.15 wt.% to < 0.75 wt.%, based on the total weight of the composition;

(E) at least one stabilizer selected from ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pen- taacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethylene- triamine-pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof and having concentration in the range of from > 0.008 wt.% to < 0.03 wt.%, based on the total weight of the composition; and

(F) an aqueous medium, wherein the pH of the composition is in the range of from > 2.5 to < 4.3, and wherein the composition has a polyacrylamide content < 1 ppm.

(B) at least one corrosion inhibitor selected from at least one guanidine derivative elected from buformin, phenformin, guanine, proguanil hydrochloride, 2-guanidinobenzimidazole, polyhexamethylene biguanide hydrochloride, polyam-inopropyl biguanide, chlorhexidine or chlorhexidine salts, preferably chlorhexi-dine or chlorhexidine salts and having concentration in the range of from > 0.003 wt.% to < 0.03 wt.%, based on the total weight of the composition;

(C) at least one iron (III) oxidizer in the range of from > 0.0048 wt.% to < 0.02 wt.%, based on the total weight of the composition; at least one buffering agent (D) selected from lysine, arginine, or histidine and having concentration in the range of from > 0.15 wt.% to < 0.75 wt.%, based on the total weight of the composition;

Process for the manufacture of a semiconductor device

In another aspect, the presently claimed invention is directed to a process for the manufacture of a semiconductor device comprising the chemical mechanical polishing of a substrate (S) used in the semiconductor industry, substrate (S) comprises (i) tungsten and/or

(ii) tungsten alloys; and

(iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material, in the presence of the composition as described herein.

Preferably, the dielectric layer is selected from silicon oxide, silicon nitride, or combinations thereof.

Preferably, the ratio of material removal rate (MRR) of silicon oxide to the material removal rate (MRR) of tungsten is < 15.0, more preferably < 14.5. Still more preferably, the ratio of material removal rate (MRR) of silicon oxide to the material removal rate (MRR) of tungsten is in the range of from 3:1 to 15:1. Most preferably, the ratio of material removal rate (MRR) of silicon oxide to the material removal rate (MRR) of tungsten is in the range of from 3.5:1 to 10:1. Without being bound by theory, a high selectivity of TEOS/silicon oxide versus tungsten (low silicon oxide to tungsten ratio > 15.0) may lead to unwanted micro-scratches or surface roughness.

Preferably, the static etch rate (SER) of tungsten < 30 ppb. More preferably, the static etch rate (SER) of tungsten < 25 ppb. Even more preferably, the static etch rate (SER) of tungsten < 23 ppb. Most preferably, the static etch rate (SER) of tungsten < 22 ppb.

Preferably, the material removal rate (MRR) of silicon oxide is > 300 A/min. More preferably, the material removal rate (MRR) of silicon oxide is > 350 A/min. Even more preferably, the material removal rate (MRR) of silicon oxide is > 420 A/min. Most preferably, the material removal rate (MRR) of silicon oxide is > 450 A/min.

Preferably, the material removal rate (MRR) of tungsten is < 200 A/min. More preferably, the material removal rate (MRR) of tungsten is < 180 A/min. Most preferably, the material removal rate (MRR) of tungsten is < 130 A/min.

The semiconductor device which can be manufactured by the process according to the presently claimed invention is not particularly limited. The semiconductor devices can be electronic components comprising semiconducting materials, as for example silicon, germanium, and lll-V materials. Semiconductor devices can be those which are manufactured as single discrete devices or those which are manufactured as integrated circuits (ICs) consisting of several devices manufactured and interconnected on a wafer. Semiconductor devices can be two terminal devices for example a diode, three terminal devices for example a bipolar transistor, four terminal devices for example a Hall effect sensor or multi-terminal devices. Preferably, the semiconductor device is a multi-terminal device. Multi-terminal devices can be logic devices as integrated circuits and microprocessors or memory devices as random-access memory (RAM), read only memory (ROM) and phase change random access memory (PCRAM). Preferably the semiconductor device is a multi-terminal logic device. In particular, the semiconductor device is an integrated circuit or microprocessor.

Generally, in integrated circuits tungsten (W) is used for MO or M1 interconnects. The excess tungsten above the dielectrics, can be removed by the chemical mechanical polishing process known. Generally, this tungsten/tungsten alloy can be produced or obtained in different ways, such as ALD, PVD or CVD processes. Generally, this tungsten and/or tungsten alloy can be of any type, form, or shape. This tungsten and/or tungsten alloy preferably has the shape of a layer and/or overgrowth. If this tungsten and/or tungsten alloy has the shape of a layer and/or overgrowth, the tungsten and/or tungsten alloy content is preferably more than 90%, more preferably more than 95%, most preferably more than 98%, particularly more than 99%, for example more than 99.9% by weight of the corresponding layer and/or overgrowth. This tungsten and/or tungsten alloy has been preferably filled or grown in trenches or plugs between other substrates, more preferably filled or grown in trenches or plugs in dielectric materials like for example SiO2, silicon, low-k (BD1 , BD2) or ultra-low-k materials, or other isolating and semiconducting material used in the semiconductor industry. For example, in the Through Silicon Vias (TSV) middle process insulating materials such as polymers, photoresist and/or polyimide can be used as insulating material between the subsequent processing steps of wet etch and CMP for insulating/isolating properties after revealing the TSV from the backside of the wafer.

Use

Preferably, the at least dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material. More preferably, the dielectric layer comprises silicon oxide, silicon nitride, or combinations thereof.

Preferably, the composition is for use in semiconductor manufacture and processes thereof.

The presently claimed invention is illustrated in more detail by the accompanying figures.

Figure 1 shows influence of pH on zeta potential values of the surface - modified colloidal silica particles, i.e. , component (A), i.e. , measured by electrophoretic measurement. The colloidal silica particles having two different particle sizes of 75 and 109 nm were investigated.

Figure 2 depicts surface images (obtained by SEM) of substrates polished using compositions. Substrates polished with composition according to the invention comprising anionic colloidal silica particles is shown in Figure 2a, whereas the substrates polished with cationic colloidal silica particles is shown in Figure 2b.

Figure 3 depicts DLS measurement of a filtered silica dispersion measured with a Malvern Zetasizer ZSP when the zeta potential of surface - modified colloidal silica particles is > -35 mV at a pH in the range of from > 2.0 to < 4.5. The measurement indicates the inability of DLS method to record stable measurement when the zeta potential of surface - modified colloidal silica particles is > -35 mV at a pH in the range of from > 2.0 to < 4.5. The zeta potential of silica particles was set at -23 mV at pH 2.8 with 0.1 M potassium chloride for measurements.

Figure 4 depicts DLS measurement of a filtered silica dispersion measured with a Malvern Zetasizer ZSP when the zeta potential of surface - modified colloidal silica particles is < -35 mV at a pH in the range of from > 2.0 to < 4.5. The composition according to the presently claimed invention has at least one of the following advantages:

(1) The compositions and the methods of the presently claimed invention show a high selectivity for removal of silicon oxide versus tungsten.

(2) The compositions and the methods of the presently claimed invention show an improved performance in inhibition of etching, especially inhibition of etching of tungsten and cobalt (as evidenced by low SER values).

(3) The composition of the presently claimed invention provides a stable formulation or dispersion, wherein no phase separation or agglomeration occurs, especially in the acidic regime.

(4) The composition of the presently claimed invention allows easy processability, such as compatibility towards industrially relevant steps such as microfiltration.

(5) The process of the presently claimed invention is easy to apply and requires as few steps as possible.

(6) The compositions and the methods of the presently claimed invention allows good tunability, thus high silicon oxide (SiCh) removal rates are achievable, while ensuring low tungsten (W) removal rates.

(7) The composition of the presently claimed invention aims to provide suitable removal rates as mentioned above, while preventing unwanted surface defects and ensuring high surface quality.

(8) The compositions and the methods of the presently claimed invention inhibits unwanted dishing of tungsten layer while maintaining a low level of dielectric layer dishing during chemical mechanical polishing.

Embodiments

In the following, there is provided a list of embodiments to further illustrate the present disclosure without intending to limit the disclosure to the specific embodiments listed below.

1. A dielectric polishing composition comprising:

(C) at least one iron (III) oxidizer;

(E) at least one stabilizer; and

2. The composition according to embodiment 1 , wherein the surface-modified colloidal silica particles have a zeta potential of from -35 mV to -50 mV at a pH in the range of from > 2.0 to < 6.0. 3. The composition according to any of the previous embodiments, wherein the concentration of the surface - modified colloidal silica particles (A) is in the range of from > 3.2 wt.% to < 13.0 wt.%, based on the total weight of the composition.

4. The composition according to any of the previous embodiments, wherein the guanidine derivative is selected from buformin, phenformin, guanine, proguanil hydrochloride, 2- guanidinobenzimidazole, polyhexamethylene biguanide hydrochloride, polyaminopropyl biguanide, chlorhexidine or chlorhexidine salts, preferably chlorhexidine or chlorhexidine salts.

5. The composition according to any of the previous embodiments, wherein the concentration of the corrosion inhibitor (B) is in the range of from > 0.001 wt.% to < 0.05 wt.%, based on the total weight of the composition.

6. The composition according to any of the previous embodiments, wherein the wherein the pH of the composition is in the range of from > 3.0 to < 4.5.

7. The composition according to any of the previous embodiments, wherein the iron (III) oxidizer (C) is selected from iron (III) nitrate or hydrates thereof.

8. The composition according to any of the previous embodiments, wherein the concentration of the iron (III) oxidizer (C) is in the range of from > 0.003 wt.% to < 0.1 wt.%, based on the total weight of the composition.

9. The composition according to any of the previous embodiments, wherein the buffering agent (D) is a basic amino acid selected from lysine, arginine, or histidine.

10. The composition according to any of the previous embodiments, wherein the concentration of the buffering agent (D) is in the range of from > 0. 1 wt.% to < 0.78 wt.%, based on the total weight of the composition.

11. The composition according to any of the previous embodiments, wherein the stabilizer (E) is selected from acetic acid, acetylacetonate, o-phosphorylethanolamine, phosphonic acid, alendronic acid, acetic acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, oxalic acid, maleic acid, gluconic acid, muconic acid, ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pentaacetic acid, bis(salicyliden)ethylendiamin, aminotris(meth- ylenephosphonic acid), diethylene-triamine-pentakis(methylphosphonic acid), ethylene- diamine-tetra(methylene-phosphonic acid), or mixtures thereof.

12. The composition according to any of the previous embodiments, wherein the concentration of the stabilizer (E) is in the range of from > 0.005 wt.% to < 0.15 wt.%, based on the total weight of the composition.

13. The composition according to any of the previous embodiments, wherein the composition has a potassium content < 1 ppm. 14. The composition according to any of the previous embodiments, wherein composition further comprises an additive selected from pH adjusting agent, oxidizing agent, wetting agent, dispersing agent, biocide, or mixtures thereof.

15. The composition according to any of the previous embodiments, wherein the composition is for polishing a substrate (S) wherein the substrate (S) comprises: (i) tungsten and/or (ii) tungsten alloys; and (iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material.

16. A process for the manufacture of a semiconductor device comprising the chemical mechanical polishing of a substrate (S) used in the semiconductor industry wherein the substrate (S) comprises

(i) tungsten and/or

(ii) tungsten alloys; and

(iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material, in the presence of a composition as defined in any of the previous embodiments.

17. The process according to embodiment 16, wherein the ratio of material removal rate (MRR) of silicon oxide to the material removal rate (MRR) of tungsten is in the range from 2:1 to 100:1.

18. The process according to any of embodiments 16 to 17, wherein the static etch rate (SER) of tungsten is < 30 ppb.

19. The process according to any embodiments 16 to 18, wherein the material removal rate (MRR) of silicon oxide is > 300 A/min.

20. The process according to any embodiments 16 to 19, wherein the material removal rate (MRR) of tungsten is < 200 A/min.

21. Use of the composition according to any of embodiments 1 to 15 for polishing a substrate (S) comprising: (i) tungsten and/or (ii) tungsten alloys; and (iii) at least one dielectric layer.

22. The use according to embodiment 21 , wherein the at least one dielectric is selected from silicon, silicon oxide, silicon nitride, or low-k material.

While the presently claimed invention has been described in terms of its specific embodiments, certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the presently claimed invention.

Examples

The presently claimed invention is illustrated in detail by the working examples which follow. More particularly, the test methods specified hereinafter are part of the general disclosure of the application and are not restricted to the specific working examples. The general procedure for the preparation of the slurry and the experiments is described below.

Components:

• silica particles commercially available under the tradename Fuso® PLXC (cationic particle) and Fuso® PL5D (anionic particle) available from Fuso Chemical Corporation

• chlorhexidine and chlorhexidine digluconate available from Sigma Aldrich

• deionized water available from BASF SE

• polyacrylamide (Mn = 10000 g/mol) available from Sigma Aldrich

• ethylenediaminetetraacetic acid (EDTA) available from Sigma Aldrich

• Iron nitrate nonahydrate available from Sigma Aldrich

• L-arginine available from Sigma Aldrich

• L-Histidine available from Sigma Aldrich

• L-Lysine available from Sigma Aldrich

• L-Glycine available from Sigma Aldrich

Slurry composition:

The slurry composition comprises:

(A) silica particles a particle size of from 60 nm to 200 nm, and a zeta potential < -35 mV at a pH of from > 2.0 to < 6.0

(B) corrosion inhibitor: chlorhexidine digluconate

(C) an oxidizing agent: iron (III) nitrate

(D) buffering agent: lysine, histidine or arginine;

(E) stabilizer: ethylenediaminetetraacetic acid (EDTA); and

(F) deionized water (DIW)

Methods

Inorganic particles (A) used in the Examples

The examples in accordance with the present invention contained colloidal silica particles (A1) having an average average secondary particle size (d2) of 109 nm (as determined using dynamic light scattering (DLS) techniques via a Malvern Zeta Sizer ZSP instrument). The silica surface has been modified by sulfonic acid moieties.

Procedure for particle shape characterization

An aqueous cocoon-shaped silica particle dispersion with 20 wt.% solid content was dispersed on a carbon foil and was dried. The dried dispersion was analyzed by using Energy Filtered- Transmission Electron Microscopy (EF-TEM) (120 kilo volts) and Scanning Electron Microscopy secondary electron image (SEM-SE) (5 kilo volts). The EF-TEM image with a resolution of 2k, 16 Bit, 0.6851 nm/pixel was used for the analysis. The images were binary coded using the threshold after noise suppression. Afterwards the particles were manually separated. Overlying and edge particles were discriminated and not used for the analysis. ECD, shape factor and sphericity as defined before were calculated and statistically classified. Measurement of zeta potential

The zeta potential value was measured with a Malvern Zetasizer ZSP (software version 7.11) equipped with a DTS1070 disposable folded capillary cell. Measurements were recorded at 25 C and 0.1% solids concentration. To ensure this, the sample solution (aqueous) was filtered through Millex SV Low Protein Durapore PVDF Membrane (5 pm). The zeta-potential was calculated from the measured electrokinetic mobility and the particle size, as obtained from the DLS measurements and fitted on Smoluchowski model.

Measurement of particle size- Dynamic light scattering (DLS)

Measurement was carried out with a Malvern Zetasizer ZSP equipped with a semi-micro polystyrene cuvette. Measurements were carried out at 25°C by dispersing particles (A) in water (0.1 %). Instrument settings: Dispersant: water (Viscosity: 0.8872 mPa*s; Rl 1.330); 5 measurements, each 60s; Automatic attenuator selection yes: measurement position fixed at 4.65; analysis model: General purpose. The sample solution (aqueous) was filtered through Millex SV Low Protein Durapore PVDF Membrane (5 pm).

Figures 3 and 4 depict DLS measurement of a filtered silica dispersion measured with a Malvern Zetasizer ZSP when the zeta potential of surface-modified colloidal silica particles is > -35 mV and < -35 mV at a pH in the range of from > 2.0 to < 6.0, respectively. The figure 3 indicates the inability of DLS method to record stable measurement when the zeta potential of surface - modified colloidal silica particles is > -35 mV at a pH in the range of from > 2.0 to < 6.0 (zeta potential adjusted by KCI). On the other hand, stable signal could be recorded when the zeta potential of surface - modified colloidal silica particles is < -35 mV at a pH in the range of from > 2.0 to < 6.0 (refer Figure 4).

Procedure for preparation of the slurry composition

The components in the slurry composition were thoroughly mixed and all mixing procedures were carried out under stirring. An aqueous stock solution of each compound (A), (B), (C), (D) and (E) was prepared by dissolving the desired amount of the respective compound in ultra-pure water (UPW). The pH of the stock solution was adjusted to required value by use of nitric acid/phos- phoric acid. The stock solutions of (B) had a concentration of 20 wt.% chlorhexidine digluconate solution, that of (C) of 0.08 wt.%. For (A) a dispersion was used as provided by the supplier, typically about 20% - 30% abrasive concentration by weight.

Alternatively, the oxidizing agent (C) can be used in the form of a Fe(lll)EDTA solution obtainable by commonly known methods. For instance, as reported by Lind et. al., Stereochemistry of Eth- ylenediamintetraacetato Complexes, Inorganic Chemistry Vol. 3, No 1, 1964 (page 34 f).

The final composition was passed through a 0.1 pm syringe filter prior to CMP. Filtration being an industrially important process, the colloidal stability of the composition is further highlighted by its ability to remain colloidally stable despite microfiltration.

Measurement of pH

The pH - value was measured with a pH combination electrode (Schott, blue line 22 pH electrode).

Static Etch Rate (SER) Experiment W

SER experiments were carried out as the following: • A tungsten (W) coated wafer was cut into several 2.5x2.5 cm coupons and washed with deionized water (DIW).

• Each coupon was treated with 0.1 % citric acid solution for 4 min and then washed with DIW.

• 300ml of freshly prepared slurry was put into a beaker and brought to 60 °C.

• The tungsten (W) coupon was placed into the slurry and kept in the slurry for 10 min. in the SER apparatus.

• The tungsten (W) coupon was removed and rinsed 1 min with DIW and dried with nitrogen.

• The concentration of tungsten ions was measured by ICP-MS in the slurry post etching.

Standard CMP process for barrier polishing wafers:

GnP POLI-500 polishing tool is used for the planarization of semiconductor thin films on silicon wafer with coupon size. This tool is available in several different configurations depending upon the user’s need for the carrier type, pad and conditioning. The CMP parameters setup on GnP tool, such as polishing pressure, disk dressing pressure, slurry flow rate, carrier/platen rotation speed, would be built before polishing to obtain the expected planarity and material removal rate.

Before the polishing process begins, the pad on the platen is conditioned. Conditioning involves using a diamond disk to remove any debris or hardened material from the pad surface and restore its optimal texture. The coupon wafer is placed face-down on the carrier with a specific membrane holder, the center of membrane has a square groove and its size match the coupon wafer.

The CMP process starts by bringing the rotating polishing pad and the wafer into contact. The slurry flows onto the pad and the carrier goes down to touch the rotating pad. The slurry is evenly dispersed on the pad during the rotation. The rotation of the platen generates a relative motion between the wafer and the pad, creating a shearing force that removes excess material from the wafer surface. The abrasive particles in the slurry remove the material on wafer, while the chemicals provide selectivity and optimize the polishing rate.

After the CMP process, the surface of wafer is thoroughly cleaned to remove any residual slurry, particles, or contaminants for analysis of post-process measurements.

Material removal rate

The polishing experiments for determining the material removal rate were performed on 300 mm blanket wafers installed on an Applied Materials 300 mm Reflexion polishing machine.

The polishing removal rate experiments were performed on 300 mm blanket 15 kA-thick TEOS sheet wafers from Ramco, W blanket wafer also from Ramco, and Ti and TiN blanket wafers available from AMT Inc. All polishing experiments were performed using an H600 polyurethane polishing pad (commercially available from Fujibo Inc.) paired with a typical down pressure of 13.8 kPa (2.0 psi), a chemical mechanical polishing composition flow rate of 300 mL/min, a table rotation speed of 123 rpm and a carrier rotation speed of 117 rpm unless specified otherwise. An A189L diamond pad conditioner (commercially available from 3M Company) was used to dress the polishing pad. The polishing pad was broken in with the conditioner using a down force of 5.0 lbs (2.3 kg) for 30 minutes at 101 rpm (platen)/ 108 rpm (conditioner). The material removal rate of W is determined using KLA-Tencor RS-100C metroloygy tool. The material removal rate of TEOS is determined using KLA-Tencor OP-5300 metroloygy tool.

Surface defect measurement using AFM: Parksystem NX10 - Atomic force microscopy (AFM) is a technique used to image the surface of a sample at atomic resolution. It produces images by a sharp tip scanning across the surface of the sample by the non-contact mode. The AFM probe is mounted on a cantilever, which acts as a tiny spring that detects forces between the tip and the sample surface. These forces can include van der Waals forces, electrostatic forces, magnetic forces and more. The interactions between the tip and the sample lead to tiny deflections of the cantilever.

The sample is placed on a stable stage under the AFM instrument, and the surface of the sample would be clean and optimized for the analysis. The AFM probe is brought close to the surface of the sample using a piezoelectric scanner. As the tip approaches the surface, atomic forces between the tip and the sample become significant. The piezoelectric scanner moves the sample stage to achieve the desired scan. The scanner records the height/position of the probe as it moves, using a laser beam deflection method to detect the deflection of the cantilever. A position-sensitive photodetector constantly monitors the deflection of the cantilever caused by the atomic forces. A laser beam is directed onto the back of the cantilever, and the deflection of the cantilever is detected. This information is used in a feedback loop to adjust the vertical position of the probe, keeping the deflection within a desired range. This maintains a constant force between the tip and the sample.

At each position, the data on the height or displacement of the cantilever is collected. This data is used to construct a topographic image of the sample's surface. The raw data is processed and analyzed to create the final image. Algorithms are used to convert the height data into a visual representation.

Dishing measurement

Parksystem NX10 - Atomic force microscopy (AFM) is a technique used to image the surface of a sample at atomic resolution. It produces images by a sharp tip scanning across the surface of the sample by the non-contact mode. The AFM probe is mounted on a cantilever, which acts as a tiny spring that detects forces between the tip and the sample surface. These forces can include van der Waals forces, electrostatic forces, magnetic forces and more. The interactions between the tip and the sample lead to tiny deflections of the cantilever.

The sample is placed on a stable stage under the AFM instrument, and the surface of the sample would be clean and optimized for the analysis. The AFM probe is brought close to the surface of the sample using a piezoelectric scanner. As the tip approaches the surface, atomic forces between the tip and the sample become significant. The piezoelectric scanner moves the sample stage to achieve the desired scan. The scanner records the height/position of the probe as it moves, using a laser beam deflection method to detect the deflection of the cantilever. A position-sensitive photodetector constantly monitors the deflection of the cantilever caused by the atomic forces. A laser beam is directed onto the back of the cantilever, and the deflection of the cantilever is detected. This information is used in a feedback loop to adjust the vertical position of the probe, keeping the deflection within a desired range. This maintains a constant force between the tip and the sample. At each position, the data on the height or displacement of the cantilever is collected. This data is used to construct a topographic image of the sample's surface. The raw data is processed and analyzed to create the final image. Algorithms are used to convert the height data into a visual representation.

The measurement is scanned from a point on the boundary A to position B. For instance, B is identified as a center point in a silicon oxide/dielectric plug/wiring which is flanked by metal such as tungsten (position A is located on the tungsten). Step height are recorded as B-A for both pre and post CMP samples. The post CMP minus pre CMP height values are mentioned below, whereby in case of dishing there would be a negative value.

Table 1 : Inventive Examples- all concentrations are in wt.% with respect to total composition.

*the concentration of buffering agent was 0.5 wt.% unless specified.

Table 1 contd.

able 2: Comparative Examples- all concentrations are in wt.% with respect to total composition.

the concentration of buffering agent was 0.5 wt.% unless specified.

Results of experiments

Table 3

Discussion of results

Table 3 shows the Static Etching Rate or Static Etch Rate (SER), Material Removal Rates (MRR), as well as the Tungsten and dielectric (TEOS) dishing values of different compositions. The combination of various components (A) to (F) were noted to be critical in providing acceptable polishing efficiency as well as solution stability for inventive examples 1-11. The zeta potentials of unmodified silica particles were found to increase under acidic regime (pH < 7) (refer Figure 1). However, surprisingly, the surface-modified colloidal silica particles were found to maintain consistently low zeta potential (in the range -35 to -60 mV), thus providing colloidal stability even under acidic regime. Substrates polished with composition according to the invention comprising anionic colloidal silica particles (Figure 2a) were found to reveal smooth surface, whereas the cationic colloidal silica particles (Figure 2b) were found to result in agglomerates which are clearly visible on surface of substrate (corresponding to comparative example C9). The addition of chlorhexidine or chlorhexidine digluconate as corrosion inhibitor (B) in combination with basic amino acid having an isoelectric point (pl) of > 6.5 (D) in the composition not only provides a SER of tungsten below 30 ppb at the pH ranges provided, but also suitably low dishing of both tungsten and dielectric (TEOS). It was further noted that the addition of chlorhexidine to the composition in the absence of component (D) (comparative example C1) or the absence of components (B) (comparative example C4) leads to unwanted effects, such as high TEOS dishing and high tungsten (W) SER as well high tungsten dishing, respectively. Furthermore, a number of basic amino acids having an isoelectric point (pl) of > 6.5 were tested and as can be seen from the results outlined in Table 3, the compositions comprising these buffering agents reveal suitable results. On the other hand, the presence of neutral amino acid such as glycine (comparative example C2) was noted to result in an unwanted high tungsten dishing as well as TEOS dishing.

The compositions of the examples according to the presently claimed invention show improved performance of high SiO2 (TEOS) MRR, low tungsten MRR, low tungsten SER, high inhibition of tungsten as well as optimum control over TEOS dishing, while having colloidal or high dispersion stability as well as low alkali content.

Claims

1. A dielectric polishing composition comprising:

(A) surface - modified colloidal silica particles comprising a negatively - charged group on the surface of the particles, wherein the surface-modified colloidal silica particles have a negative charge, a particle size of from 60 nm to 200 nm, and a zeta potential < -5 mV at a pH in the range of from > 2.0 to < 6.0, wherein the concentration of the surface modified colloidal silica particles (A) is in the range of from > 3.2 wt.% to < 13.0 wt.%;

(C) at least one iron (III) oxidizer, wherein the concentration of the iron (III) oxidizer (C) is in the range of from > 0.003 wt.% to < 0.1 wt.%;

(D) at least one buffering agent selected from at least one basic amino acid having an isoelectric point (pl) of > 6.5, wherein the concentration of the buffering agent (D) is in the range of from > 0. 1 wt.% to

< 0.78 wt.%;

(E) at least one stabilizer, wherein the stabilizer (E) is selected from acetic acid, acety- lacetonate, o-phosphorylethanolamine, phosphonic acid, alendronic acid, acetic acid, phthalic acid, citric acid, adipic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, oxalic acid, maleic acid, gluconic acid, muconic acid, ethylenediaminetetraacetic acid, propylene diaminetetraacetic acid, N,N-bis(carboxymethyl) alanine, nitrilo-triacetic acid, diethylene-triamine-pentaacetic acid, bis(salicyliden)ethylendiamin, aminotris(methylenephosphonic acid), diethylene-triamine- pentakis(methylphosphonic acid), ethylene-diamine-tetra(methylene-phosphonic acid), or mixtures thereof; and

2. The composition according to any of claim 1 , wherein the guanidine derivative is selected from buformin, phenformin, guanine, proguanil hydrochloride, 2-guanidinobenzim- idazole, polyhexamethylene biguanide hydrochloride, polyaminopropyl biguanide, alexi- dine, chlorhexidine or chlorhexidine salts, preferably chlorhexidine or chlorhexidine salts.

3. The composition according to any of claims 1 to 2, wherein the wherein the pH of the composition is in the range of from > 3.0 to < 4.5.

4. The composition according to any of claims 1 to 3, wherein the iron (III) oxidizer (C) is selected from iron (III) nitrate or hydrates thereof.

5. The composition according to any of claims 1 to 4, wherein the buffering agent (D) is a basic amino acid selected from lysine, arginine, or histidine.

6. The composition according to any of claims 1 to 5, wherein the composition has a potassium content < 1 ppm.

7. The composition according to any of claims 1 to 6, wherein composition further comprises an additive selected from pH adjusting agent, oxidizing agent, wetting agent, dispersing agent, biocide, or mixtures thereof.

8. The composition according to any of claims 1 to 7, wherein the composition is for polishing a substrate (S) wherein the substrate (S) comprises: (i) tungsten and/or (ii) tungsten alloys; and (iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material.

9. A process for the manufacture of a semiconductor device comprising the chemical mechanical polishing of a substrate (S) used in the semiconductor industry wherein the substrate (S) comprises

(i) tungsten and/or

(ii) tungsten alloys; and

(iii) at least one dielectric layer selected from silicon, silicon oxide, silicon nitride, or low-k material, in the presence of a composition as defined in any one of claims 1 to 8.

10. The process according to claim 9, wherein the ratio of material removal rate (MRR) of silicon oxide to the material removal rate (MRR) of tungsten is in the range from 2:1 to 100:1.

11. The process according to any of claims 9 to 10, wherein the static etch rate (SER) of tungsten is < 30 ppb.

12. The process according to any claims 9 to 11 , wherein the material removal rate (MRR) of silicon oxide is > 300 A/min.

13. The process according to any claims 9 to 12, wherein the material removal rate (MRR) of tungsten is < 200 A/min.

14. Use of the composition according to any of claims 1 to 8 for polishing a substrate (S) comprising: (i) tungsten and/or (ii) tungsten alloys; and (iii) at least one dielectric layer.