Solutions for Post-Etch Residue Removal (PERR)

Abstract

The present invention relates to a composition for removing post-etch residues from a substrate, the substrate comprising a surface of a molybdenum layer, the composition comprising: (a) 10 to 60% by mass of a water-miscible organic solvent; (b) 4 to 15 mass% C1 to C 12 amine (c) 0.5 to 4 mass% C4 to C 16 Quaternary ammonium hydroxide; (d) 0.1 to 5 mass% of C2 to C 10 Polyols; (e) 0.01 to 3% by mass of polyethyleneimine; and (f) water Includes.

Description

[Technical Field]

[0001] The present invention relates to compositions, uses and methods for post-etch residue removal (PERR) of molybdenum-containing substrates, particularly semiconductor substrates. [Background technology]

[0002] Resists such as deep ultraviolet photoresists or electron beam resists are used in microlithography techniques for manufacturing a wide range of electrical devices, such as semiconductor integrated circuits (ICs), liquid crystal panels, organic electroluminescence (EL) panels, printed circuit boards, micromachines, DNA chips, and microplants, especially ICs with LSI (large-scale integrated circuits) or VLSI (very large-scale integrated circuits).

[0003] Copper is traditionally used as a low-resistivity or wiring material in electrical devices, particularly vias and interconnects in integrated circuits. As copper usage increases, electrical structure dimensions become smaller, and IC functionality becomes larger, low-k and ultra-low-k dielectric materials must be used to avoid wiring resistance issues and wiring delays due to increased wiring capacitance. This challenging development has required, and continues to require, continuous optimization of manufacturing methods and the materials used therein.

[0004] Although damascene patterning required overcoming many technical challenges, copper-based interconnects have been successfully implemented at successive technology nodes. As local BEOL interconnect pitches advance to 20 nm and below (for technology nodes beyond N2), the resistance of Cu metal lines increases rapidly at these small dimensions due to electron scattering at surfaces and grain boundaries. Furthermore, Cu metal lines require liners to prevent Cu diffusion in the dielectric material. Because these liners require a certain thickness to prevent diffusion, scaling Cu interconnects without scaling the liner thickness results in a relatively large increase in metal resistance as a function of decreasing critical dimension.

[0005] Ruthenium (Ru) and molybdenum (Mo) are interesting candidates that promise lower resistivity than Cu at very small dimensions. A key advantage of Ru and Mo is that both materials can be patterned by direct metal etching, as was the case with Al before the Cu interconnect era. Furthermore, both Ru and Mo can be integrated barrier-free, so reduced resistivity is expected when Ru or Mo are integrated at small dimensions.

[0006] Molybdenum may have many benefits sought after in the art, such as being useful as a conductor in back-end-of-line (BEOL) or mid-end-of-line (MEOL) applications, or in buried power rails or work function layers in logic applications, and wordlines or bitlines in advanced memory applications.

[0007] For copper, many so-called all-wet post-etch residue removal (PERR) processes have been developed and are disclosed in the prior art.

[0008] WO 2010 / 127941 A discloses a post-etch residue removal composition, which contains a liquid composition comprising at least two polar organic solvents selected from the group consisting of solvents that do not contain N-alkylpyrrolidone, hydroxylamine, or hydroxylamine derivatives, and that exhibit a certain removal rate at 50°C for a 30-nm-thick polymeric barrier antireflective layer containing a deep ultraviolet absorbing chromophore in the presence of 0.06 to 4% by weight of dissolved tetramethylammonium hydroxide, based on the total weight of each test solution, and at least one quaternary ammonium hydroxide.

[0009] The patterning challenges for direct metal etching of ruthenium and molybdenum with a metal pitch of 32 nm or less are described, for example, in J.Vac.Sci.Technol.B 40, 032802 (2022). They reported that approximately 2 nm of MoO was deposited on Mo metal lines patterned by a direct metal etching process. xWe expect sidewalls to form, and for larger lines this could be a major obstacle to integrating Mo into future interconnects.

[0010] Therefore, in addition to removing all other etch residues, especially dry etch residues, (a) A low static etching rate of molybdenum, which avoids damage to the structure because molybdenum is less noble than copper; (b) good, preferably complete, removal of molybdenum etch residues, especially etch residues containing molybdenum oxides; There is a strong need for cleaning compositions that are capable of cleaning wafer structures containing molybdenum that exhibit: [Prior art documents] [Patent documents]

[0011] [Patent Document 1] WO 2010 / 127941 A [Non-patent literature]

[0012] [Non-Patent Document 1] J.Vac.Sci.Technol.B 40,032802(2022) Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide a post-etch residue removal composition that allows for good PERR efficiency, removal of etch residues, particularly molybdenum etch residues, most particularly molybdenum oxide residues, and good compatibility with substrates, particularly molybdenum.A further object of the present invention is to provide a composition that exhibits essentially complete removal of molybdenum etch residues (essentially oxides) while not essentially attacking molybdenum. [Means for solving the problem]

[0014] One embodiment of the present invention is a composition for removing post-etch residues from a substrate, the substrate comprising a surface of a molybdenum layer, the composition comprising: (a) 10 to 60% by mass of a water-miscible organic solvent; (b) 4 to 15 mass% C1 to C 12 amine (c) 0.5 to 4 mass% C4 to C 16 Quaternary ammonium hydroxide; (d) 0.1 to 5 mass% of C2 to C 10 Polyols; (e) 0.01 to 3% by mass of polyethyleneimine; and (f) water Includes.

[0015] The composition also effectively protects the molybdenum conductor lines while removing essentially all etch residue.

[0016] Another embodiment of the present invention is a method of using the compositions described herein to remove post-etch residues from a semiconductor substrate, including the surface of a molybdenum layer.

[0017] Yet another embodiment of the present invention is a method for removing post-etch residues from a substrate, the substrate comprising a surface of a molybdenum layer, the method comprising: (a) providing a microelectronic device surface including a molybdenum layer surface and post-etch residue thereon; (b) providing a composition described herein; (c) contacting the surface with the composition for a time and at a temperature effective to remove post-etch residues without damaging the molybdenum layer; Includes. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows a schematic diagram of the substrate used in Example 3. [Figure 2]FIG. 2 shows the substrate treated with composition C1.1 of Example 3. [Figure 3] FIG. 3 shows the substrate treated with composition 1.4 of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0019] The subject composition of the present invention comprises (a) 10 to 60% by mass of a water-miscible organic solvent; (b) 4 to 15 mass% C1 to C 12 amine (c) 0.5 to 4 mass% C4 to C 16 Quaternary ammonium hydroxide; (d) 0.1 to 5 mass% of C2 to C 10 Polyols; (e) 0.01 to 3% by mass of polyethyleneimine; and (f) water Includes.

[0020] definition As used herein, a "layer" refers to a portion of a substrate that is discretely disposed on the surface of the substrate and has a composition that is distinguishable from adjacent layers.

[0021] "C x The term "C" means that each group contains x C atoms. x ~C y "Alkyl" means an alkyl having x to y carbon atoms, and unless expressly specified, includes unsubstituted straight-chain, branched, and cyclic alkyl. As used herein, "alkanediyl" means a diradical of a straight-chain, branched, or cyclic alkane, or a combination thereof.

[0022] All percentages, ppm or equivalent values ​​are by weight relative to the total weight of the respective composition unless otherwise specified. The terms "wt%" and "% by weight" are used interchangeably herein.

[0023] "Post-etch residue" refers to materials remaining after gas-phase plasma etching processes, such as back-end-of-line ("BEOL") dual damascene processing, or wet etching processes. Post-etch residues may be organic, organometallic, organosilicon, or inorganic in nature, such as silicon-containing materials, carbon-based organic materials, and etching gas residues such as oxygen and fluorine. When a molybdenum layer is etched, molybdenum etch residues, such as molybdenum oxides, may be, and usually are, present. Depending on the substrate and etching method, such molybdenum oxides may also contain other non-oxidizing compounds.

[0024] All citations are incorporated herein by reference.

[0025] Water-miscible organic solvents The cleaning composition includes one or more water-miscible organic solvents, which serve to dissolve other components in the composition and improve the removal efficiency and solubility of organic residues from the wafer surface.

[0026] The term "water-miscible organic solvent" in the context of the present invention preferably means that an organic solvent meeting this requirement is miscible with water in a ratio of at least 1:1 (w / w) at 20°C and ambient pressure. Examples of water-miscible organic solvents that can be used include: (a) ethers, such as, but not limited to, tripropylene glycol methyl ether, propylene glycol propyl ether, diethylene glycol n-butyl ether (BDG), dipropylene glycol methyl ether (DPM); (b) Sulfur-containing solvents: (i) sulfones, such as (but not limited to) sulfolane; (ii) sulfoxides, such as, but not limited to, dimethyl sulfoxide (DMSO); (c) alcohols, such as, but not limited to, tetrahydrofurfuryl alcohol, or linear or branched C2-C6 alkanols, such as ethanol, n-propanol, and isopropanol; (d) 4-methylmorpholine-4-oxide, trimethylamine-N-oxide, triethylamine-N-oxide, triethanolamine-N-oxide, pyridine-N-oxide, N-formylmorpholine, N-ethylmorpholine-N-oxide, N-ethylpyrrolidine-N-oxide; or (e) Mixtures thereof Examples include:

[0027] The water-miscible organic solvent may be protic or aprotic. Preferably, the water-miscible organic solvent is aprotic.

[0028] Preferred solvents are dimethyl sulfoxide, diethyl sulfoxide, methyl ethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, methyl phenyl sulfoxide, and 1,1'-dihydroxyphenyl sulfoxide, and sulfolane, or mixtures thereof. Most preferred solvents are dimethyl sulfoxide, sulfolane, and mixtures thereof.

[0029] For many applications, the amount of water-miscible organic solvent in the composition can be a range having a beginning and an end point selected from the following list of weight percents: 10, 12, 15, 20, 25, 29, 30, 33, 35, 40, 45, 50, 54, 59.9, and 60. Examples of such ranges of solvent include about 10 to about 60 weight percent of the composition, or about 12 to about 50 weight percent, or about 15 to about 45 weight percent, or about 0.5 weight percent to about 30 weight percent, or about 1 to about 30 weight percent, or about 12 to about 40 weight percent, or about 20 to about 49.9 weight percent, or about 25 to about 55 weight percent, or about 30 to about 40 weight percent.

[0030] In particular embodiments, the compositions according to the invention as defined herein may further comprise, as optional additional components: one or more water-miscible organic solvents, preferably selected from the group consisting of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, isopropanol, butyl diglycol, butyl glycol, sulfolane (2,3,4,5-tetrahydrothiophene-1,1-dioxide), and mixtures thereof; more preferably selected from the group consisting of THF, NMP, DMF, DMSO, sulfolane, and mixtures thereof.

[0031] In a preferred embodiment, the total amount of one or more water-miscible organic solvents in the cleaning composition is about 15 to about 55% by weight, preferably about 20 to about 50% by weight, more preferably about 25 to about 45% by weight, and even more preferably about 30 to about 40% by weight, based on the total weight of the composition.

[0032] amine The cleaning composition includes one or more amines, which aid in removing polymeric residues from the wafer substrate.

[0033] Preferably, the amine is different from other components in the composition, particularly the water-miscible organic solvent and the polyol. More preferably, the amine contains no substituents other than amino and hydroxyl, particularly no substituents other than amino and a single hydroxyl.

[0034] In a preferred embodiment, the amine is a C1-C 10 Alkylamines and C2-C 10 The most preferred are alkanolamines C2 to C 10 It is an alkanolamine.

[0035] Alkylamines are chemical compounds that contain at least one alkyl-substituted amine group.Alkylamines can be any alkylamines that are effective as the cleaning compounds described, including primary, secondary, and tertiary amine compounds.Specific useful alkylamines include monoalkylamines such as ethylamine, ethylenediamine, diethylenetriamine, triethylenediamine, tetraethylenepentamine (TEPA), triethylenetetraamine, ethylenediamine, hexamethylenediamine, triethylamine, trimethylamine, diglycolamine, and morpholine.

[0036] Preferred alkylamines are those containing one or two primary, secondary or tertiary amino groups. (a) contains one primary amino group; (b) contains one secondary or tertiary amino group It is an alkylamine.

[0037] Alkanolamine is a chemical compound that contains an amine group substituted with at least one hydroxyl group, preferably one single hydroxyl group.Alkanolamine can be any alkanolamine that is effective as the cleaning compound described, including primary amine compounds, secondary amine compounds and tertiary amine compounds.Alkanolamine compounds have at least one alkanol substituent (e.g., methanol, ethanol, etc.) and one, two or three alkanol, alkyl or alternative organic substituents. Specific useful alkanolamines include primary alkanolamines such as monoethanolamine (MEA), aminoethylethanolamine, N-methylaminoethanol, aminoethoxyethanol, aminoethoxyethoxyethanol, butoxypropylamine, methoxypropylamine, butoxyisopropylamine, 2-ethylhexylisopropoxyamine, ethanolpropylamine, ethylethanolamine, N-hydroxyethylmorpholine, aminopropyldiethanolamine, dimethylaminoethoxyethanol, diethanolamine, N-methyldiethanolamine, monoethanolamine, triethanolamine, 1-amino-2-propanol, 3-amino-1-propanol, diisopropylamine, amine, aminomethylpropanediol, N,N-dimethylaminomethylpropanediol, aminoethylpropanediol, N,N-dimethylaminoethylpropanediol, isopropylamine, 2-amino-1-butanol, aminomethylpropanol, aminodimethylpropanol, N,N-dimethylaminomethylpropanol, isobutanolamine, diisopropanolamine, 3-amino,4-hydroxyoctane, 2-aminobutylethanol, tris(hydroxymethyl)aminomethane (TRIS), N,N-dimethyltris(hydroxymethyl)aminomethane, hydroxypropylamine, hydroxyethylamine, tris(hydroxyethyl)aminomethane, and combinations thereof.

[0038] Preferred alkanolamines are those containing one or two hydroxy groups and one or two primary, secondary or tertiary amino groups. Even more preferred are: (a) containing one or two hydroxy groups and one secondary or tertiary amino group; (b) containing one hydroxy group and one or two secondary or tertiary amino groups It is an alkanolamine.

[0039] A particularly preferred alkanolamine is 2-(methylamino)ethan-1-ol (N-methylaminoethanol).

[0040] The one or more amines can be present in an amount of about 4 to about 15% by weight, preferably about 5 to about 14% by weight, more preferably about 6 to about 11.5% by weight, even more preferably about 7 to about 13% by weight, and most preferably about 8 to about 12% by weight.

[0041] Quaternary ammonium hydroxide The cleaning composition may contain one or more C4-C6 as a pH adjuster to adjust the pH to an alkaline range. 16 Contains quaternary ammonium hydroxide.

[0042] The quaternary ammonium hydroxide may be present in the composition in an amount of from about 0.5 to about 4% by weight. Preferably, the compositions of the present invention contain 0.7 to 3.5% by weight, more preferably 1 to 3% by weight, and most preferably 1.5 to 2.5% by weight of at least one quaternary ammonium hydroxide.

[0043] Preferably, the quaternary ammonium hydroxide may be selected from the group consisting of tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and (2-hydroxyethyl)triethylammonium hydroxide.

[0044] Preferably, the quaternary ammonium hydroxide may be selected from C4 to C8 alkyl quaternary ammonium hydroxides, in particular tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0045] Polyol The cleaning composition may comprise one or more of C2 to C 10 Contains polyols, which help to increase surface wetting and dissolve polymer residues from the wafer surface.

[0046] Preferably, the polyol is different from the other components in the composition, particularly the water-miscible organic solvent and the amine. More preferably, the polyol contains no substituents other than hydroxyl.

[0047] In a preferred embodiment, C2 to C 10 The polyol has the formula HOCH2(CHOH) k CH2OH (wherein k is 0 or an integer of 1 to 8).

[0048] In a preferred embodiment, C2 to C 10 The polyol is selected from ethylene glycol, glycerol, erythritol, threitol, arabitol, xylitol, ribitol, mannitol, sorbitol, galactitol, fucitol, iditol, inositol, volemitol, propylene glycol, 1,4-butanediol, diethylene glycol, and combinations thereof.

[0049] Particularly preferred is a combination of a C4 to C8 polyol, preferably sorbitol, with a C2 or C3 polyol, preferably ethylene glycol.

[0050] Polyols are C2 to C 10 It may be present in an amount of about 0.1 to about 5% by weight of the polyol, preferably about 0.2 to about 4.5% by weight, more preferably about 0.3 to about 4% by weight, even more preferably about 0.4 to about 3% by weight, and most preferably about 0.5 to about 2.5% by weight.

[0051] In a preferred embodiment, the polyol comprises or consists essentially of about 0.3 to 1 wt. % of a C4 to C8 polyol and about 0.5 to 1.5 wt. % of a C2 or C3 polyol.

[0052] Polyethyleneimine (PEI) The cleaning composition includes one or more polyethyleneimine-type molybdenum corrosion inhibitors that significantly reduce corrosion of molybdenum, particularly molybdenum metal lines, during the removal of post-etch residues from wafer surfaces.

[0053] It has been found that the addition of polyethyleneimine reduces the etch rate of blanket PVD Mo compared to compositions without polyethyleneimine, yet still allows for good, preferably complete, removal of etch residues.

[0054] A polyethyleneimine backbone is understood to mean a compound comprising a saturated hydrocarbon chain with terminal amino functions interrupted by secondary and tertiary amino groups. Such a backbone may be linear or branched. Of course, different polyethyleneimine backbones can also be used in mixture with one another.

[0055] The backbone comprises primary, secondary and tertiary amine nitrogen atoms connected by "linking" units. It should be emphasized that the backbone essentially comprises three types of units, and these groups may be distributed in any order along the backbone.

[0056] The units constituting the polyalkyleneimine main chain are: (a) primary units having the formula [H2N-C2H4]- and -NH2 terminating the main chain and any branched chains; (b) a secondary amine unit having the formula: [ka] and (c) a tertiary amine unit, which is a branch point of the main chain and the secondary main chain, having the formula: [ka] (In the formula, A E1 represents the continuation of the chain structure due to branching).E1 may contain all of the above primary, secondary and tertiary amine units except the terminal group -NH2.

[0057] Cyclization can occur during the formation of the polyamine backbone, so that cyclic polyamines can be present in the parent polyalkyleneimine backbone mixture. The primary and secondary amine units of the cyclic alkyleneimines can be modified by the addition of polyoxyalkylene units, as can linear and branched polyalkyleneimines.

[0058] The polyalkyleneimines of the present invention can be prepared by polymerizing ethyleneimine in the presence of a catalyst, such as, for example, carbon dioxide, sodium bisulfite, sulfuric acid, hydrogen peroxide, hydrochloric acid, acetic acid, etc. Specific methods for preparing these polyalkyleneimine backbones are disclosed in U.S. Pat. Nos. 2,182,306, 3,033,746, 2,208,095, 2,806,839, and 2,553,696.

[0059] Furthermore, the polyalkyleneimine main chain may be partially substituted with an alkylating agent. 12 Alkyl, C2-C 12 Alkenyl, C2-C 12 Alkynyl, C6-C 20 Alkylaryl, C6-C 20 Aryl alkyl, C6-C 20 Preferred substituents are C1-C6 alkyl, C6-C 12 Alkylaryl C6-C 12 Aryl alkyl and C6-C 12 The aryl group may be selected from phenyl or naphthyl. L1 ]- and -NH2 are groups R L3 may be substituted with. Suitable examples of alkylating agents include organic compounds containing active halogen atoms, such as aryl alkyl halides, alkyl halides, alkenyl halides, and alkynyl halides. Furthermore, compounds such as alkyl sulfates, alkyl sultones, and epoxides can also be used. Non-limiting examples of corresponding alkylating agents include benzyl chloride, propane sultone, dimethyl sulfate, and (3-chloro-2-hydroxypropyl)trimethylammonium chloride. It is preferred to use dimethyl sulfate and / or benzyl chloride.

[0060] In a preferred embodiment, the polyethyleneimine is unsubstituted. Depending on the pH of the composition, the amino groups in the polyethyleneimine may exist in a protonated form.

[0061] Mass average molecular weight M of polyalkyleneimine w The mass average molecular weight M of the polyalkyleneimine main chain may be about 800 g / mol to about 50,000 g / mol. w The lower limit of the mass average molecular weight M is generally about 800 g / mol, preferably about 1,200 g / mol, and more preferably about 1,500 g / mol. w The upper limit of the molecular weight is generally about 50,000 g / mol, preferably about 25,000 g / mol, more preferably about 20,000 g / mol, and most preferably about 10,000 g / mol. A particularly preferred range is 800 to 25,000 g / mol, most particularly 1,000 to 4,000 g / mol. Molecular weight can be determined by size exclusion chromatography, such as GPC, using polymethyl methacrylate (PMMA) as a standard and hexafluoroisopropanol + 0.05% potassium trifluoroacetate as an eluent.

[0062] Polyethyleneimine may be present in an amount of about 0.01 to about 3 wt.%, preferably about 0.015 to about 2 wt.%, more preferably about 0.2 to about 1.5 wt.%, even more preferably about 0.2 to about 1 wt.%, and most preferably about 0.2 to about 0.5 wt.%. Low amounts of polyethyleneimine have been found to be sufficient to protect molybdenum on the wafer surface. Higher concentrations are possible but do not significantly improve the corrosion inhibition performance of polyethyleneimine.

[0063] water The etching compositions of the present invention are aqueous-based and therefore contain water. Water has several functions, such as dissolving one or more components of the composition, as a carrier for the components, as an aid in residue removal, as a viscosity modifier for the composition, and as a diluent. Preferably, the water employed in the composition is deionized (DI) water. The range of water described in the following paragraph includes all water in the composition from any source.

[0064] For most applications, the weight percent of water in the composition will be in a range having a beginning and an end point selected from the following group of numbers: 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 92, 94, and 96. Examples of ranges of water that can be used in the composition include, for example, about 20 to about 80 weight percent water, or about 25 to about 75 weight percent water; or about 30 to about 72 weight percent water, or about 35 to about 70 weight percent water, or about 40 to about 65 weight percent water, or about 45 to about 55 weight percent water. Still other preferred embodiments of the present invention can include an amount of water to achieve the desired weight percent of the other ingredients.

[0065] Dispersants The composition may further comprise a dispersing agent in the form of a polyalkoxylated polyethyleneimine. By "polyalkoxylated polyethyleneimine" is meant polyethyleneimine in which the N-hydrogen atom is substituted with a polyoxyalkylene group comprising C2-C6 oxyalkylene units, preferably C2-C4 oxyalkylene repeat units, more preferably C2-C3 oxyalkylene repeat units, and most preferably C2 oxyalkylene repeat units. The polyalkoxylated polyethyleneimine in combination with polyethyleneimine further supports cleaning of the wafer surface.

[0066] Generally, the polyalkyleneimine backbone of the polyalkoxylated polyalkyleneimine can be prepared as described above. Polyalkoxylation is then carried out by reacting the respective alkylene oxide with a polyalkyleneimine, particularly polyethyleneimine. The synthesis of polyalkylene oxide groups is known to those skilled in the art. Comprehensive details are described, for example, in "Polyoxyalkylenes" in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Electronic Release. When two or more different alkylene oxides are used, the polyoxyalkylene group formed may be a random copolymer, a gradient copolymer, or a block copolymer.

[0067] Modifying the NH units in the polymer backbone with oxyalkylene units can be achieved, for example, by first reacting a polymer, preferably polyethyleneimine, with one or more alkylene oxides, preferably ethylene oxide, propylene oxide, or a mixture thereof, in the presence of 80% by weight or less of water in an autoclave equipped with a stirrer at a temperature of about 25 to about 150°C. In the first step of the reaction, an amount of alkylene oxide is added such that nearly all hydrogen atoms of the NH units of the polyalkyleneimine are converted to hydroxyalkyl groups, resulting in a monoalkoxylated polyalkyleneimine. Water is then removed from the autoclave. A basic catalyst, such as sodium methylate, potassium tert-butylate, potassium hydroxide, sodium hydroxide, sodium hydride, or an alkali ion exchanger, is added to the reaction product of the first step of alkoxylation in an amount of 0.1 to 15% by mass of alkylene oxide based on the addition product obtained in the first step of alkoxylation, and then alkylene oxide is added to the reaction product of the first step to obtain a polyalkoxylated polyalkyleneimine containing the intended average number of alkylene oxide units per NH unit of the polymer. The second step can be carried out at a temperature of, for example, about 60 to about 150°C. The second step of alkoxylation can be carried out in an organic solvent such as xylene or toluene. To accurately quantify the amount of alkylene oxide added, it is desirable to determine the number of primary and secondary amine groups in the polyalkyleneimine prior to alkoxylation. Alternatively, polyalkoxylation can be achieved by graft polymerization of polyethyleneimine.

[0068] The polyalkoxylated polyalkyleneimine can be optionally functionalized with functional groups other than H in a further reaction step. The additional functionalization can serve to modify the properties of the polyalkoxylated polyalkyleneimine. For this purpose, the hydroxyl groups present in the polyoxyalkylated polyalkyleneimine are converted by a suitable agent capable of reacting with hydroxyl groups.

[0069] The type of functionalization depends on the desired end use. Depending on the functionalizing agent, the chain ends can be made hydrophobic or more hydrophilic. Esterification of the hydroxy groups with acids is one typical reaction.

[0070] In one embodiment, the alkoxylated polyalkyleneimine is used without further functionalization.

[0071] In another embodiment, carboxylic acid-functionalized polyalkoxylated polyethyleneimine can be obtained by Michael addition reaction with suitable α,β-unsaturated species, such as acrylic acid or methacrylic acid. Preferably, the polyalkoxylated polyethyleneimine is functionalized with carboxylic acid groups. Michael addition or Michael 1,4 addition is the reaction between a Michael donor (enolate or other nucleophile, such as an amine) and a Michael acceptor (usually an α,β-unsaturated carbonyl / carboxyl) to form a carbon-carbon bond at the β-carbon of the acceptor, thereby producing a Michael adduct. This reaction is also called aza-Michael addition. Details of this reaction are described in Addition and Substitution at CC π-Bonds by M. Mauduit and A. Denicourt-Nowicki, Comprehensive Organic Synthesis (2nd Edition), 2014.

[0072] Furthermore, the polyalkoxylated polyethyleneimine may have a high degree of branching, and preferably, the polyalkoxylated polyethyleneimine is highly branched. As used herein, the term "highly branched" refers to a highly branched polymer that typically exhibits a globular structure. Hyperbranched polymers usually exhibit substantial irregularity in branching pattern and structure, which typically results in substantial variation in molecular weight (often referred to as polydispersity). One useful measure for assessing the amount of branching present in a polymer is the degree of branching. As used herein, the term "degree of branching" refers to the ratio of (a) the total number of branched repeat units contained in the polymer to (b) the total number of repeat units contained in the polymer. Hyperbranched polymers having any appropriate degree of branching can be employed in the compositions described herein. In certain embodiments, hyperbranched polymers exhibit a degree of branching of at least about 4 to 20 monomer units per molecule. In general, care should be taken when interpreting the degree of branching information for hyperbranched polymers. For example, certain hyperbranched polymers may exhibit a degree of branching of less than about 0.2, while containing one or more hyperbranched polymer moieties (or subunits) exhibiting a degree of branching of about 0.2 or greater. This is the case, for example, when a hyperbranched polymer core is chain extended with long chains of linear repeating units. If fully chain extended, the overall branching degree of such a polymer may be less than about 0.2.

[0073] The mass average molecular weight M of the polyalkoxylated polyalkyleneimine w The weight average molecular weight M of the polyalkoxylated polyalkyleneimine may be from about 500 g / mol to about 500,000 g / mol. w The lower limit of the mass average molecular weight M is generally about 1500 g / mol, preferably about 2500 g / mol, and more preferably about 5000 g / mol. wThe upper limit of the molecular weight is generally about 500,000 g / mol, preferably about 150,000 g / mol, more preferably about 50,000 g / mol, and most preferably about 25,000 g / mol. A particularly preferred range is 800 to 25,000 g / mol, most particularly 5,000 to 25,000 g / mol. Molecular weight can be determined by size exclusion chromatography, such as GPC, using polymethyl methacrylate (PMMA) as a standard and hexafluoroisopropanol + 0.05% potassium trifluoroacetate as an eluent.

[0074] The average number of oxyalkylene units in the polyoxyalkylene group is 1 to about 30, preferably 2 to 25, more preferably 3 to 20, and most preferably 5 to 15 per N-hydrogen atom in the polyalkyleneimine.

[0075] The polyalkoxylated polyalkyleneimine may be present in an amount of about 0.01 to about 1 wt. %, preferably about 0.012 to about 0.8 wt. %, more preferably about 0.15 to about 0.6 wt. %, even more preferably about 0.02 to about 0.5 wt. %, and most preferably about 0.02 to about 0.3 wt. It has been found that amounts of polyalkoxylated polyalkyleneimine less than 0.01 wt. % are insufficient to enhance the cleaning performance of the composition. While it is possible to further increase the concentration beyond 1 wt. %, performance does not improve further. Furthermore, because many components are involved in achieving the composition, a delicate balance is generally required to ensure colloidal stability. However, the presence of large amounts (greater than 1 wt. %) of (polymeric) components such as polyalkoxylated polyethyleneimine can be detrimental to the long-term stability of multi-component systems, especially in substantially aqueous media.

[0076] chelating agents The cleaning composition may optionally include one or more chelating agents.

[0077] Preferred chelating agents include 1,2-cyclohexylene denitrilotetraacetic acid, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione, acetylacetonate, 2,2'-azanediyldiacetic acid, ethylenediaminetetraacetic acid, etidronic acid, methanesulfonic acid, acetylacetone, 1,1,1-trifluoro-2,4-pentanedione, 1,4-benzoquinone, 8-hydroxyquinoline, salicylideneaniline; tetrachloro-1,4-benzoquinone, 2-(2-hydroxyphenyl)-benzoxazole, 2-(2-hydroxyphenyl)-benzothiazole, hydroxyquinolinesulfonic acid, sulfosalicylic acid, salicylic acid, pyridine, 2-ethylpyridine, 2-methoxypyridine, 3-methoxypyridine, 2-picoline, dimethylpyridine, piperidine, piperazine, ethylamine, methylamine, isopropyl alcohol, and the like. butylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diglycolamine, methyldiethanolamine, pyrrole, isoxazole, bipyridine, pyrimidine, pyrazine, pyridazine, quinoline, isoquinoline, indole, 1-methylimidazole, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidinedithiocarbamate, dimethyl malonate, methyl acetoacetate, N-methylacetoacetamide, tetramethylammonium thiobenzoate, 2,2,6,6-tetramethyl-3,5-heptanedione, tetramethylthiuram disulfide, lactic acid, ammonium lactate, formic acid, propionic acid, γ-butyrolactone, and mixtures thereof.

[0078] The chelating agent may be 1,2-cyclohexylene denitrilotetraacetic acid (CDTA) or may include, in addition to CDTA, one or more of the other chelating agents listed above.

[0079] Also preferred are compositions according to the invention as defined herein, wherein the amount of one or more chelating agents present is from about 0.01 to about 4% by weight, preferably from about 0.02 to about 1% by weight, more preferably from about 0.05 to about 0.8% by weight, based on the total weight of the composition.

[0080] surfactants The composition may also further comprise one or more surfactants.

[0081] Preferred surfactants are (i) anionic surfactants, preferably selected from the group consisting of ammonium lauryl sulfate, fluorosurfactants, preferably perfluorinated alkylsulfonamide salts (preferably perfluorinated, N-substituted alkylsulfonamide ammonium salts, PNAAS), perfluorooctane sulfonate, perfluorobutane sulfonate, perfluorononanoate, and perfluorooctanoate; alkyl-aryl ether phosphates, and alkyl ether phosphates; (ii) a zwitterionic surfactant, preferably selected from the group consisting of (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) (“CHAPS”), cocamidopropyl hydroxysultaine (CAS RN 68139-30-0), {[3-(dodecanoylamino)propyl](dimethyl)-ammonio}acetate, phosphatidylserine, phosphatidylethanolamine, and phosphatidylcholine; and (iii) a nonionic surfactant, preferably selected from the group consisting of glucoside alkyl ether, glycerol alkyl ether, cocamide ethanolamine, and lauryl dimethyl aminooxide; is selected from the group consisting of:

[0082] A more preferred surfactant in the composition according to the present invention is or contains a perfluorinated N-substituted alkylsulfonamide ammonium salt. A preferred surfactant (E) in the composition according to the present invention does not contain a metal or metal ion.

[0083] Also preferred are compositions according to the invention as defined herein, wherein the amount of one or more surfactants present is from about 0.0001 to about 1% by weight, preferably from about 0.0005 to about 0.5% by weight, more preferably from about 0.001 to about 0.01% by weight, based on the total weight of the composition.

[0084] Specific surfactants for use in the compositions described herein include bis(2-ethylhexyl) phosphate, perfluoroheptanoic acid, perfluorodecanoic acid, trifluoromethanesulfonic acid, phosphonoacetic acid, dodecenylsuccinic acid, dioctadecyl hydrogen phosphate, octadecyl dihydrogen phosphate, dodecylamine, dodecenylsuccinic acid monodiethanolamide, lauric acid, palmitic acid, oleic acid, juniperic acid, 12-hydroxystearic acid, and dodecyl phosphate; polyoxyethylene lauryl ether (Emalmin NL-100 (Sanyo), Brij 30, Brij 98, Brij 35), dodecenylsuccinic acid monodiethanolamide (DSDA, Sanyo), ethylenediaminetetrakis(ethoxylate-block-propoxylate) tetrol (Tetronic 90R4), polyethylene glycol (e.g., PEG 400), polypropylene glycol, polyethylene or polypropylene glycol ether, block copolymers based on ethylene oxide and propylene oxide (Newpole PE-68 (Sanyo), Pluronic L31, Pluronic 31R1, Pluronic L61, Pluronic F-127) (Dynol 607), polyoxypropylene sucrose ether (SN008S, Sanyo), t-octylphenoxypolyethoxyethanol (Triton X100), 10-ethoxy-9,9-dimethyldecan-1-amine (TRITON® CF-32), polyoxyethylene (9) nonylphenyl ether, branched (IGEPAL CO-250), polyoxyethylene (40) nonylphenyl ether, branched (IGEPAL CO-890), polyoxyethylene sorbitol hexaoleate, polyoxyethylene sorbitol tetraoleate, polyethylene glycol sorbitan monooleate (Tween 80), sorbitan monooleate (Span 80), a combination of Tween 80 and Span 80, alcohol alkoxylates (e.g., Plurafac RA-20), alkyl polyglucosides, ethyl perfluorobutyrate, 1,1,3,3,5,5-hexamethyl-1,5-bis[2-(5-norbornen-2-yl)ethyl]trisiloxane, monomeric octadecylsilane derivatives such as SIS6952.0 (Siliclad, Gelest), siloxane-modified polysilazanes such as PP1-SG10 Siliclad Glide 10 (Gelest), silicone-polyether copolymers such as Silwet L-77 (Setre Chemical Company, Silwet ECO Spreader Momentive), and ethoxylated fluorosurfactants (ZONYL® FSO-100, ZONYL® FSN-100); cetyltrimethylammonium bromide (CTAB), heptadecanefluorooctanesulfonic acid, tetraethylammonium, stearyltrimethylammonium chloride (Econol TMS-28, Sanyo), 4-(4-diethylaminophenylazo)-1-(4-nitrobenzyl)pyridium bromide, cetylpyridinium chloride monohydrate, benzalkonium chloride, benzethonium chloride, benzyldimethyldodecylammonium chloride, benzyldimethylhexadecylammonium chloride, hexadecyltrimethylammonium bromide, dimethyldioctadecylammonium chloride, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium p-toluenesulfonate, didodecyldi Examples of suitable surfactants include, but are not limited to, methylammonium bromide, di(hydrogenated tallow)dimethylammonium chloride, tetraheptylammonium bromide, tetrakis(decyl)ammonium bromide, Aliquat® 336, and oxyphenonium bromide, guanidine hydrochloride (C(NH)Cl), or triflate salts such as tetrabutylammonium trifluoromethanesulfonate, dimethyldioctadecylammonium chloride, dimethyldihexadecylammonium bromide, and di(hydrogenated tallow)dimethylammonium chloride (e.g., Arquad 2HT-75, Akzo Nobel), and bromide-containing surfactants such as 1-hexadecyltrimethylammonium bromide.

[0085] In some embodiments, the compositions of the present invention are free or substantially free of any or all of the above surfactants.

[0086] composition Other commonly known ingredients such as dyes, chemical modifiers, biocides, etc. may be included in the cleaning compositions in conventional amounts, for example, up to about 1%, about 5%, or about 10% by weight of the total composition, provided that they do not adversely affect the performance of the composition.

[0087] Alternatively, the cleaning composition is free or substantially free of any or all of dyes, chemical modifiers, and biocides.

[0088] The cleaning compositions are typically prepared by mixing the ingredients in a container at room temperature until all solids are dissolved in the aqueous medium.

[0089] Generally, the pH of the composition may range from 8 to 14. In a preferred embodiment, the pH of the etching composition is from about 9 to about 13, more preferably from about 10 to about 13, and most preferably from about 11 to about 12.5.

[0090] Particularly preferably, the cleaning composition comprises: (a) 10 to 60% by weight of a water-miscible aprotic organic solvent, especially a sulfoxide or sulfone, most especially dimethyl sulfoxide or sulfolane; (b) 4 to 15 mass% C1 to C 12 amines, especially alkanolamines, most especially 2-(methylamino)ethan-1-ol; (c) 0.5 to 4 mass% C4 to C 16 quaternary ammonium hydroxides, in particular C4 to C8 quaternary ammonium hydroxides, in particular tetramethylammonium hydroxide or tetraethylammonium hydroxide; (d) 0.1 to 5 mass% of C2 to C 10 Polyols, in particular of the formula HOCH2(CHOH) kCH2OH (wherein k is 0 or an integer from 1 to 8), most particularly sorbitol, ethylene glycol or mixtures thereof; (e) 0.01 to 3% by weight of polyethyleneimine, in particular unsubstituted polyethyleneimine, most in particular polyethyleneimine having a weight average molecular weight of 600 to 50,000 g / mol; (f) water; (g) optionally 0.01 to 2% by weight of polyalkoxylated polyethyleneimine, in particular polyalkoxylated, in particular polyethoxylated polyethyleneimine, with 5 to 15 per NH group Comprises or consists essentially of

[0091] Another particularly preferred cleaning composition is: (a) 20 to 50% by mass of a water-miscible aprotic organic solvent; (b) 7 to 13 mass% amine (c) 1 to 3 mass percent quaternary ammonium hydroxide; (d) 1 to 3 mass% C2 to C 10 Polyols; (e) 0.02 to 3% by weight of polyethyleneimine; (f) water; and (g) optionally, a polyalkoxylated polyethyleneimine Comprises or consists essentially of

[0092] It is preferred that the amine is different from the water-miscible organic solvent and the polyol, and / or that the water-miscible organic solvent is different from the amine and the polyol, and / or that the polyol is different from the amine and the water-miscible organic solvent. It is particularly preferred that all components of the composition are different compounds.

[0093] "Essentially" in this context means that the content of other compounds other than those specifically mentioned is less than 1% by weight, preferably less than 0.1% by weight, even more preferably less than 0.01% by weight, and most preferably below the detection limit.

[0094] Also particularly preferred are compositions according to the invention as defined herein, wherein the composition consists of compounds as defined herein and based on the examples, and the sum of all components in the composition is 100% by weight of the total composition.

[0095] application In another aspect, a method for removing post-etch residues from a substrate is provided, wherein the substrate comprises a surface of a molybdenum layer, the method comprising: (a) providing a microelectronic device surface including a molybdenum layer surface and post-etch residue thereon; (b) providing a composition described herein; (c) contacting the surface with the composition for a time and at a temperature effective to remove post-etch residues without damaging the molybdenum layer; Includes.

[0096] Such layers may include, but are not limited to, conductive lines in a semi-damascene structure. It will be appreciated that it is common to produce concentrated forms of the compositions that are diluted before use. For example, the compositions may be produced in a more concentrated form that is then diluted with water or other ingredients at the manufacturer before and / or during use.

[0097] In using the compositions described herein, the compositions are typically contacted with the device structure for a sufficient time of about 1 minute to about 200 minutes, preferably about 1 minute to about 10 minutes, at a temperature ranging from about 30° C. to about 90° C., preferably about 35° C. to about 60° C. Such contact times and temperatures are exemplary, and any other suitable time and temperature conditions effective to achieve the required removal selectivity can be employed.

[0098] After achieving the desired etching effect, the composition can be easily removed from the microelectronic device to which it was previously applied, for example, by rinsing, cleaning, or other removal step(s) as desired and effective in the given end-use application of the composition of the present invention. For example, the device may be rinsed with a rinse solution comprising deionized water, an organic solvent, and / or dried (e.g., spin-drying, N2, vapor drying, etc.).

[0099] Preferably, the composition has a Mo etch rate of 7 A / min or less.

[0100] The contacting step is optionally followed by a rinsing step, which may be carried out by any suitable means, such as rinsing the substrate with deionized water by immersion or spray techniques. In a preferred embodiment, the rinsing step may be carried out using a mixture of deionized water and an organic solvent, such as isopropanol.

[0101] Following the contacting step and optional rinsing step is an optional drying step, which may be accomplished by any suitable means, such as isopropanol (IPA) vapor drying, heat, or centripetal force.

[0102] The etching compositions described herein can be advantageously used in processes for the manufacture of semiconductor devices, including selectively removing post-etch residues from surfaces of microelectronic devices that include the molybdenum layers described herein.

[0103] The following examples further illustrate the invention without limiting its scope. [Example]

[0104] Etching experiments were carried out using blanket and semi-damascene specimens containing a 47.5 nm thick PVD Mo layer.

[0105] 100 ml of etching solution was placed in a 150 ml beaker and placed in a temperature-controlled water bath. Next, a 2.5 cm x 2.5 cm specimen of each substrate was immersed in the test solution at the desired temperature while the solution was stirred at 250 rpm. Both blanket and semi-damascene etching were performed for 2 minutes, followed by rinsing with DIW for 30 seconds and drying with an N2 gun. Blanket etching experiments were performed at 40 °C and 60 °C, while semi-damascene etching experiments were performed at 40 °C.

[0106] The thickness of the blanket specimens was determined by XRF measurements. The semi-damascene specimens were characterized by TEM.

[0107] The etching rate was calculated according to the following formula:

[0108]

number

[0109] Example 1 A 100 g semi-aqueous solution with Mo inhibitor was prepared by adding the following ingredients in the given order: 1. 49.5g of DIW 2. 34g of DMSO (BASF) 3. 10.3g of 2-methylethanolamine (ACROS) 4. 1g of ethylene glycol (BASF) 5. 4 g of a 25 wt% TMAH solution in DIW (BASF) 6. 0.6g of sorbitol (BASF) 7. 0.025 g of acrylic acid functionalized polyethoxylated PEI (Mw=25000 g / mol) with an average of 10 EOs per NH group, also referred to as "polyethoxylated PEI" (BASF); 8. 0.025 g of PEI (Mw=2000 g / mol, manufactured by BASF).

[0110] During mixing, the solution was stirred with a magnetic stir bar at a speed of 100 rpm.

[0111] Different Mo inhibitor concentrations and different M w A solution with PEI was prepared in the same order as above, with the amount of DIW adjusted to give the desired Mo inhibitor concentration.

[0112] Mass average molar mass M w The Mo etching rates (ER) of polyethyleneimine (PEI) solutions with different concentrations of 2000 g / mol at 40 and 60 °C were measured using blank specimens. The compositions and results are shown in Table 1.

[0113] [Table 1]

[0114] Comparative Example C1.1, which contains no Mo inhibitor, exhibited higher Mo etch rates than formulations containing different concentrations of PEI. Comparative Example C1.3, which contains 0.005 wt.% PEI, exhibited no Mo etch inhibition compared to Comparative Example C1.1 without PEI, indicating that the inhibitor concentration was not sufficient to protect the Mo surface. A 1 wt.% PEI concentration could also be used, but the corrosion inhibition was slightly less effective.

[0115] Example 2 The Mo etching rates (ER) of polyethyleneimine (PEI) solutions with different molecular weights at 40°C and 60°C were measured using blank specimens. The results are shown in Table 2.

[0116] [Table 2]

[0117] The results show that the etching of Mo was reduced in all solutions using PEI with different molecular weights.

[0118] Example 3 A 32 nm metal pitch semi-damascene dry etch test structure (manufactured by IMEC) shown schematically in Figure 1 was treated with cleaning compositions C1.1 and 1.4. Post-etch residues were present on the surface of each layer.

[0119] The substrates were examined by TEM. As can be seen in Figures 2 and 3, in contrast to composition C1.1 (Figure 3), composition 1.4 (Figure 3) removed much better post-etch residues, especially at the bottom of the lines, while leaving the Mo lines themselves unaffected.

Claims

1. 1. A composition for removing post-etch residues from a substrate, the substrate comprising a surface of a molybdenum layer, the composition comprising: (a) 10 to 60% by weight of a water-miscible organic solvent; (b) 4 to 15 mass% C １ ~C １２ amine (c) 0.5 to 4 mass% C ４ ~C １６ Quaternary ammonium hydroxide; (d) 0.1 to 5 mass% C ２ ~C １０ Polyol; (e) 0.01 to 3% by weight of polyethyleneimine; and (f) Water A composition comprising:

2. 2. The composition according to claim 1, wherein the organic solvent is a sulfur-containing aprotic organic solvent, in particular chosen from sulfoxides and sulfones.

3. 3. The composition of claim 2, wherein the organic solvent is selected from dimethyl sulfoxide, diethyl sulfoxide, methyl ethyl sulfoxide, dipropyl sulfoxide, and sulfolane.

4. The amine is C １ ~C １０ Alkylamines and C ２ ~C １２ 3. The composition according to claim 1, wherein the amine is selected from alkanolamines.

5. The composition of claim 4, wherein the amine is selected from 2-methylethanolamine.

6. The quaternary ammonium hydroxide is C ４ ~C ８ 3. The composition according to claim 1, wherein the alkyl quaternary ammonium hydroxide is selected from alkyl quaternary ammonium hydroxides, in particular tetramethylammonium hydroxide and tetraethylammonium hydroxide.

7. Said C ２ ~C １０ The polyol has the formula HOCH ２ (CHOH) ｋ CH ２ 3. The composition according to claim 1, wherein the compound is selected from the group consisting of: OH (wherein k is 0 or an integer from 1 to 8).

8. Said C ２ ~C １０ 3. The composition of claim 1 or 2, wherein the polyol is selected from ethylene glycol, glycerol, erythritol, threitol, arabitol, xylitol, ribitol, mannitol, sorbitol, galactitol, fucitol, iditol, inositol, volemitol, propylene glycol, 1,4-butanediol diethylene glycol, and combinations thereof.

9. 3. The composition according to claim 1, wherein the polyethyleneimine has a weight average molecular weight of 600 to 50,000 g / mol, preferably 800 to 25,000 g / mol.

10. 3. The composition of claim 1 or 2, wherein the polyethyleneimine is unsubstituted.

11. 3. The composition of claim 1 or 2, further comprising a polyalkoxylated polyethyleneimine.

12. 3. The composition according to claim 1 or 2, having a pH of 10 to 13, preferably 11 to 12.

5.

13. (a) 20 to 50% by weight of a water-miscible organic solvent; (b) 7 to 13% by weight of an amine (c) 1 to 3% by weight of a quaternary ammonium hydroxide; (d) 1 to 3 mass% C ２ ~C １０ Polyol; (e) 0.02 to 3% by weight of polyethyleneimine; (f) water; and (g) optionally, a polyalkoxylated polyethyleneimine 3. The composition of claim 1 or 2, consisting essentially of:

14. 3. A method of using the composition of claim 1 or 2 for removing post-etch residues from a semiconductor substrate comprising a surface of a molybdenum layer.

15. 1. A method for removing post-etch residues from a substrate, the substrate comprising a surface of a molybdenum layer, the method comprising: (a) providing a microelectronic device surface comprising the surface of the molybdenum layer and post-etch residue thereon; (b) providing a composition according to claim 1 or 2; (c) contacting the surface with the composition for a time and at a temperature effective to remove the post-etch residue without damaging the molybdenum layer; A method comprising:

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