Non-acidic composition for copper electroplating comprising a grain refiner

Abstract

The present invention provides a composition for depositing copper on a semiconductor substrate, the composition comprising (a) copper ions; (b) a grain refiner of formula (G1a) or (G1b) or salts thereof; (c) a complexing agent; and (d) optionally a buffer or a base to adjust the pH to a pH of from 7 to 13; wherein RG1 is a carbamoyl group of formula (I); RG2 is selected from the group consisting of (a) carboxyl, (b) sulfonate, (c) sulfate (d) carbamoyl, (e) C1 to C4 alkoxy, (f) halogen, (g) CN, and (h) C6-C12 aryl, which aryl is unsubstituted or substituted by one or more of the groups (a) to (h); and 0 XG1 is selected from C1 to C6 alkanediyl, which may be interrupted by one or two O; RG11, RG12 are independently selected from H, C1 to C4 alkyl, C6 to C12 aryl, C6 to C12 arylalkyl; C6 to C12 alkylaryl; wherein the pH of the composition is from 7 to 13.

Description

[0001] Non -acidic composition for copper electroplating comprising a grain refiner

[0002] Description

[0003] The present invention relates to a non-acidic composition for depositing a copper layer onto a semiconductor substrate, its use and a deposition process by using such composition.

[0004] Background of the Invention

[0005] Filling of small features, such as vias and trenches, by metal electroplating is an essential part of the semiconductor manufacture process. It is well known that the presence of organic substances as additives in the electroplating bath can be crucial in achieving a uniform metal deposit on a substrate surface and in avoiding defects, such as voids and seams, within the metal lines.

[0006] Void-free bottom-up filling of submicrometer-sized interconnect features by using acidic copper electroplating baths on a copper seed is well known in the art.

[0007] With further decreasing aperture size of the features like vias or trenches to dimensions of below 5 nanometers and even below 3 nanometers, respectively, the filling of the interconnects with copper becomes especially challenging, also since the copper seed deposition prior to the copper electrodeposition might exhibit inhomogeneity and nonconformity and thus further decreases the aperture sizes particularly at the top of the apertures. The smaller the size of the feature and the higher the aspect ratio of the feature become the more difficult it is to get a continuous seed on the side walls of the feature without significant seed overhang.

[0008] To avoid these difficulties a non-copper seed such as cobalt or ruthenium was proposed in WO 2019 / 199614 A1. An acidic electroplating solution for plating copper on a non-copper liner layer includes a low copper concentration, acidic pH, organic additives, and bromide ions as a copper complexing agent. Also WO 2022 / 012932 discloses an acidic bromide containing copper electroplating bath.

[0009] However, cobalt is a less noble metal compared to copper and quickly corrodes in the presence of an acid and oxygen, particularly if copper is present, too. On the other hand, non-acidic electroplating baths that would show less cobalt corrosion provide bad filling and dirty copper fillings due to the use of complexings agents that are required to keep copper in solution.

[0010] For other applications and in combination with other metals non-acidic copper alloy electroplating baths are known, e.g., from US 4 177 131, FR 1 427 282, and FR 2 187935. WO 2009 / 109271 discloses a cyanide free tin alloy electrolyte bath comprising N-methyl pyrrolidone, preferably an acid or a pyrophosphate source, or an organic gloss agent. US 2019 / 0330753 A1 discloses a nickel or nickel alloy electroplating solution containing an N-substituted pyridinium compound. US 2010 / 0155257 A1 discloses an aqueous, non-acidic, cyanide-free electrolyte bath for deposition of zinc alloy layers on substrate surfaces, comprising a pyridinium compound. US 2018 / 0363156 A1 discloses a nickel electroplating composition comprising a source of nickel ions, one or more sources of acetate ions, sodium saccharinate and an N-benzylpyridinium sulfonate compound; carbamate compounds are used for comparison.

[0011] Non-acidic compositions for copper electroplating copper on a copper or other metal seeds are generally known in the art. For example, WO 2015 / 086180 discloses a copper electroplating bath comprising copper ions and a promoter of nucleation of metallic copper on said substrate, characterized in that the promoter of nucleation of copper is a combination of 2,2'-bipyridine, imidazole and an electrochemically inert cation selected from the group consisting of cesium (Cs+), alkylammonium and mixtures thereof to improve the nucleation of copper on the most resistive materials that are a barrier to the diffusion of copper such as ruthenium or cobalt.

[0012] WO 2023 / 126257 discloses a neutral or alkaline copper electroplating composition comprising a grain refiner of formula

[0013]

[0014] wherein RG1or RG2’ comprises at least one Ci to C« carboxyl group or group XG1is -XG11-C(O)-O-)-XG12-.

[0015] There is still a need for a copper electroplating composition that allows a homogeneous, smooth and void-free deposition of copper in small, recessed features, such as vias or trenches, of semiconductor substrates.

[0016] It is therefore an object of the present invention to provide an electroplating composition that is capable of providing a substantially void-free filling of features on the nanometer and / or on the micrometer scale with copper on a noncopper metal seed, particularly a cobalt seed. It is also an object of the present invention to provide an electroplating composition that is capable of depositing a homogeneous, smooth and void-free copper seed layer on a non-copper metal seed, particularly a cobalt seed

[0017] For resistivity reasons, it is also beneficial that the copper layer deposited on the cobalt seed layer exhibits a low resistivity. A low resistivity of the copper deposit is supported by a low impurity level in the deposited copper film which means that little C, N, S, O, H, Cl, P or other elements than copper are incorporated in the copper film during the copper electrodeposition.

[0018] Summary of the Invention The present invention provides a copper electroplating bath that may generally be used in two ways:

[0019] 1. With the bath a copper seed layer is deposited onto the semiconductor substrate to allow using a state-of-the art acidic copper on copper electroplating bath to fill the respective recessed features; and

[0020] 2. With the bath a direct void-free filling, ideally a bottom-up filling, of the recessed features may also be achieved.

[0021] Therefore, the present invention provides a composition for depositing copper on a semiconductor substrate, the composition comprising

[0022] (a) copper ions;

[0023] (b) a grain refiner of formula G1 a or G1 b

[0024]

[0025] or salts thereof

[0026] (c) a complexing agent; and

[0027] (d) optionally a buffer or a base to adjust the pH to a pH of from 7 to 13;

[0028] wherein

[0029] RG1is a carbamoyl group of formula

[0030]

[0031] RG2is selected from the group consisting of (a) carboxyl, (b) sulfonate, (c) sulfate (d) carbamoyl, (e) Ci to C« alkoxy, (f) halogen, (g) CN, and (h) C6-Ci2aryl, which aryl is unsubstituted or substituted by one or more of the groups (a) to (h); and

[0032] XG1is selected from Ci to Ce alkanediyl, which may be interrupted by one or two 0;

[0033] RG11, RG12are independently selected from H, Ci to C« alkyl, Ce to C12 aryl, Ce to C12 arylalkyl; Ce to C12 alkylaryl;

[0034] wherein the pH of the composition is from 7 to 13.

[0035] The invention further relates to the use of a metal plating bath comprising a composition as defined herein for depositing copper on substrates comprising recessed features having an aperture size of 50 nanometers or less, 15 nm or less, 10 nm or less or even 5 nm or less essentially without forming voids, preferably by bottom. up fill.

[0036] The invention further relates to a process for depositing copper on a semiconductor substrate comprising a recessed feature having an aperture size of 50 nm or less, preferably 15 nm or less, the recessed feature comprising a metal seed, the process comprising

[0037] (a) bringing a composition as described herein into contact with the metal seed,

[0038] (b) applying a current for a time sufficient to deposit a continuous seed of copper onto the surface of the recessed feature or to completely fill the recessed feature with copper.

[0039] The non-acidic copper electroplating composition according to the invention provides a substantially void-free filling of features on the nanometer and / or on the micrometer scale with copper on a non-copper metal seed, particularly a cobalt seed. It also allows depositing a homogenous, smooth and void-free seed layer on a non-copper metal seed, particularly a cobalt seed. A further advantage of the present invention is that the deposited copper, e.g. a completely filled recessed feature or a continuous seed, has a much lower impurity level.

[0040] Detailed Description of the Invention

[0041] The non-acidic compositions according to the inventions comprise copper ions, a complexing agent, and an additive of formula G1 as described below.

[0042] Definitions

[0043] As used herein, the term “alkylaryl” means an aryl that is substituted by an alkyl, such as but not limited to 2, 3, or 4-toluyl. The term “arylalkyl” means an alkyl that is substituted by aryl, such as but not limited to benzyl.

[0044] The term “Cx” means that the respective group comprises x numbers of C atoms. The term "Cxto Cyalkyl" means alkyl with a number x to y of carbon atoms and, unless explicitly specified, includes unsubstituted linear, branched and cyclic alkyl. As used herein, “alkyl” refers to linear, branched or cyclic alkyl or a combination thereof. As used herein, “alkanediyl” refers to a diradical of linear, branched or cyclic alkanes or a combination thereof.

[0045] The term “particularly” or “preferably” shall indicate non-limiting advantageous examples of a generic term and shall have the meaning of “such as but not limited to”. By providing preferred embodiments that are covered by a generic term it is not intended to limit the generic term in any way.

[0046] All percent, ppm or comparable values refer to the weight with respect to the total weight of the respective composition except where otherwise indicated. The term “wt%” means % by weight. The term ppm means part per million by mass. All cited documents are incorporated herein by reference.

[0047] Grain refiner

[0048] It has been found that the grain refiner of formula G1 a or G1b

[0049]

[0050] or salts thereof are particularly useful additives for non-acidic electroplating of copper on semiconductor substates, particularly those comprising submicrometer-sized recessed features, most particularly those having aperture sizes having nanometer or micrometer scale, preferably aperture sizes having 50 nanometers or less, 15 nm or less, 10 nm or less or even 5 nm or less. Preferred are grain refiners of formula G1b.

[0051] In formula G1a and G1b

[0052]

[0053] RG2is selected from the group consisting of (a) carboxyl, (b) sulfonate, (c) sulfate (d) carbamoyl, (e) OH or Ci to C4 alkoxy, (f) halogen, (g) ON, and (h) C6-C12 aryl, which aryl is unsubstituted or substituted by one or more of the groups (a) to (g);

[0054] RG3is selected from the group consisting of (a) Ci to C4 alkyl, (b) OH or Ci to C4 alkoxy, (c) halogen, and (d) ON; RG4is a Ci to C4 alkyl group;

[0055] XG1is selected from Ci to C6alkanediyl, which is unsubstituted or substituted by one or two OH and which may be interrupted by one or two 0; and

[0056] RG11, RG12are independently selected from H, Ci to C4 alkyl, Ce to C12 aryl, Ce to C12 arylalkyl; Ce to C12 alkylaryl; n is 0, 1, or 2. In the carbamoyl group RG1the amide group may form a primary (RG11, RG12= H), secondary (RG11H, RG12= H) or tertiary (RG11, RG12H ) amide. Preferred substituents RG11, RG12are independently H, methyl, ethyl, propyl, phenyl, benzyl, or toluyl.

[0057] The carbamoyl group RG1may be in 2 (ortho), 3 (meta), or 4 (para) position to the N atom, preferably in 3 or 4 position. Unless there is a negatively charged functional group in the molecule, a counter-ion is required in the composition. Generally, the counter-ion may be any inorganic or organic anion that does not interfere with the molecule itself or with its application in a non-acidic copper electroplating composition. Typical counter ions are sulfate, lower alkyl sulfonate, chloride, acetate, and tosylate. Preferred counter ions are sulfate or methane sulfonate.

[0058] The heteroaromatic ring bearing the carbamoyl group may comprise one or two further substituents RG3. Such groups may be selected from (a) Ci to C4alkyl, preferably methyl, ethyl or propyl, most preferably methyl, ethyl; (b) OH or Ci to C4alkoxy, preferably OH, methoxy, ethoxy or propoxy, most preferably OH, methoxy or ethoxy; (c) halogen, preferably F or Cl; and (d) CN. In another preferred embodiment, no further groups RG3are present, i.e. n is 0.

[0059] The nitrogen atom in the heteroaromatic ring is quaternized by a Ci to C4alkyl group (formula G 1 a) or by group -XG1-RG2(formula G1b).

[0060] In a preferred embodiment, the spacer group XG1is a Ci to C4alkanediyl, which may be unsubstituted or substituted by one OH and which may be interrupted by one 0, preferably from unsubstituted Ci to C4alkanediyl or a Ci to C4alkanediyl that is substituted by one OH.

[0061] In a preferred embodiment, the group RG2is (a) sulfonate, (b) carbamoyl, (c) OH or Ci to C4alkoxy, or (d) phenyl, which phenyl may be unsubstituted or substituted by one or more of the groups (a) to (c), preferably sulfonate or unsubstituted phenyl.

[0062] Preferred grain refiners of formula G1a are

[0063]

[0064]

[0065] or its salts, particularly it chlorides, wherein m is 1, 2, or 3.

[0066] Particularly preferred grain refiners of formula G1a are

[0067]

[0068]

[0069] and salts thereof. Particularly preferred grain refiners of formula G 1a are 1-benzyl-3-carbamoylpyridin-1 -ium chloride or (3-(3-carbamoylpyridin-1-ium-1 -yl)propane-1 -sulfonate).

[0070] Preferred grain refiners of formula G1b are

[0071]

[0072] wherein m is 1, 2, or 3.

[0073] In general, the total amount of the grain refiners in the electroplating bath is from 0.5 ppm to 10000 ppm based on the total weight of the plating bath. The grain refiners according to the present invention are typically used in a total amount of from about 0.1 ppm to about 1000 ppm based on the total weight of the plating bath and more typically from 1 to 100 ppm, although greater or lesser amounts may be used.

[0074] SIMS measurements of copper films plated with a grain refiner in the plating bath exhibit that the amount of C, N, S, O, H, Cl, P or other elements than copper incorporated in the copper film during the copper electrodeposition is smaller than in copper films plated without grain refiner in the plating bath.

[0075] Complexing agent

[0076] The copper electroplating composition also comprises a complexing agent to keep the copper ions in solution and to avoid their precipitation.

[0077] The complexing agent may particularly be selected from polyamines, aminocarboxylic acids, aminophosphonic acids, alkanolamines, polyalcohols, hydroxycarboxylic acids, hydroxyphosphonic acids, thioureas, and polycarboxylic acids.

[0078] Without limitation, useful polyamines are methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, or hexaethyleneheptamine, or combinations thereof.

[0079] Without limitation, useful amino carboxylic acids are ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraaminehexaacetic acid (TTHA), ethylenediaminetetrapropionic acid, nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), Iminodipropionic acid (IDP), metaphenylenediaminetetraacetic acid, 1,2-diaminocyclohexane-N, N, N ', N '-tetraacetic acid, diaminopropionic acid, combinations thereof, or salts thereof.

[0080] Without limitation, useful alkanolamines are monoethanolamine, diethanolamine, triethanolamine, monopropanolamine; Dipropanolamine, tripropanolamine, or combinations thereof.

[0081] Without limitation, useful hydroxycarboxylic acids are tartaric acid, citric acid, malic acid, gluconic acid, glycolic acid, lactic acid, glucoheptonic acid, combinations thereof, or salts thereof.

[0082] Without limitation, useful hydroxyphosphonic acids are 1 -Hydroxyethylidene-1, 1 -diphosphonic acid (etidronic acid), combinations thereof, or salts thereof.

[0083] Thioureas are thiourea and thiourea derivatives.

[0084] Without limitation, a useful polyalcohol is sorbitol. Preferred complexing agents are hydroxycarboxylic acids such as but not limited to citric acid, tartaric acid and hydroxyphosphonic acids such as but not limited to etidronic acid.

[0085] Particularly preferred complexing agents are alkanolamines comprising:

[0086] (i) at least one primary, secondary or tertiary amino group, and

[0087] (ii) at least one branched C3to Cs hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and

[0088] (ii) in sum at least 3 hydroxy groups; and

[0089] which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate.

[0090] According to another embodiment the alkanolamine comprise:

[0091] (i) at least one primary, secondary or tertiary amino group, and

[0092] (ii) at least two, preferably three C3to C8hydroxyalkyl groups bound to the at least one amino group; and (iii) at least one carboxy, sulfonate or sulfate group or at least 4 hydroxy groups.

[0093] As used herein, “branched” means that the respective group comprises at least one carbon atom that forms a branching point, i.e. comprises, besides the at least one bond or chain to the at least one amine group, at least two, preferably tree hydroxalkyl groups. For compounds where the branching point is directly bonded to the amino group, this means that the branching point is a secondary or tertiary carbon atom. For compounds where the branching point is not directly bonded to the amino group but via an alkanediyl group, this means that the branching point is a tertiary or quaternary carbon atom.

[0094] In a preferred embodiment the alkanolamine is a compound of formula C1 or C2

[0095]

[0096] wherein

[0097] XC1, XC2are independently a Ci to C4 alkanediyl;

[0098] XC3is a Ci to C4 alkanediyl;

[0099] RC1is selected from H, a Ci to C4alkyl, -XC1-OH, -XC1-COOH, and RC11;

[0100] RC11is

[0101]

[0102] RC2, RC2’ are independently selected from H, a Ci to C4 alkyl, -XC1-OH, and -XC1-COOH;

[0103] RC3, RC3’areindependently selected from H, a Ci to C4 alkyl, -XC1-OH, and -XC1-COOH;

[0104] RC4is selected from H, a C1to C4alkyl, and -XC1-OH, and -XC1-COOH;

[0105] XC11is a C1to C6alkanediyl.

[0106] In another preferred embodiment the alkanolamine is selected from compounds of formula C1a, C1 b, C1c, or C1 d

[0107]

[0108] wherein

[0109] XC1, XC2, XC3, XC4are independently a C1to C3alkanediyl;

[0110] RC1is selected from H, a C1to C4alkyl, -XC1-OH, and RC11;

[0111] RC2, RC2’ are independently selected from H, a Ci to C3 alkyl, and -XC1-OH;

[0112] RC3, RC3’areindependently selected from a Ci to C3 alkyl and -XC1-OH;

[0113] RC4is selected from H, a C1to C4alkyl, and -XC1-OH; XC11is a Ci to C4alkanediyl;

[0114] Particularly preferred alkanolamines are bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane, tris(hydroxymethyl)aminomethane or its salts, 1,3-bis(tris(hydroxymethyl)methylamino)propane, 2-Amino-2-methyl-1,3-propanediol, and N-[1,3-Dihydroxy-2-(hydroxymethyl)propan-2-yl]glycine or its salts.

[0115] The complexing agent may be used alone or in any combination, and the content of the complexing agent in the plating bath is usually such that the ratio between the molar concentration of complexing agent and the molar concentration of copper ions is in the range from 1:1 to 6:1, preferably from 1.5:1 to 5:1, more preferably from 1.7:1 to 4:1, most preferably from 1.8:1 to 3:1. The exact ratio depends on the specific complexing agent and needs to be adjusted in line with its complexing properties, particularly the number of coordination sites to copper.

[0116] The absolute concentration of the complexing agent is preferably in the range of from 2 to 1000 mmol / l, more preferably from 4 to 200 mmol / l, most preferably from 10 to 100 mmol / l.

[0117] Buffer / base

[0118] The composition optionally comprises a buffer or a base (also referred to as “pH adjustor”) to adjust the pH to a pH of from 7 to 13.

[0119] Without limitation, typical bases are metal, preferably alkaline or alkaline earth metal hydroxides, carbonates, NH4OH, alkyl ammonium hydroxides, and the like. Preferred are metal hydroxides, particularly alkaline earth metal hydroxides. Most preferred bases are NaOH, KOH, and combinations thereof.

[0120] The alkylammonium ions may for example be compounds of formula (N-RB1RB2RB3RB4)+in which RB1; RB2; RB3; and RB4independently selected from H and a C1-C4 alkyl, provided that at least one of RB1; RB2; RB3; and RB4is a C1-C4 alkyl.

[0121] A C1-C4 alkyl may be for example methyl, ethyl, n-propyl or n-butyl. Preferred alkylammonium ions are tetraalkylammonium, for example tetramethylammonium, tetraethylammonium, tetrapropylammonium or tetrabutylammonium, methyltriethylammonium and ethyltrimethylammonium.

[0122] The cations are supplied in the form of salts, for example a sulfate salt. The counter-ion of the cation in the salt is preferably the same counter-ion than the counter-ion of the copper(ll) salt. Other Additives

[0123] A large variety of further additives may typically be used in the bath to provide desired surface finishes for the copper plated metal. Usually more than one additive is used with each additive forming a desired function. Advantageously, the electroplating baths may contain one or more of wetting agents or surfactants like Lutensol®, Plurafac® or Pluronic® (available from BASF) to get rid of trapped air or hydrogen bubbles and the like. Further components to be added are stress reducers, levelers and mixtures thereof.

[0124] In a further embodiment, surfactants may be present in the electroplating composition in order to improve wetting. Wetting agents may be selected from nonionic surfactants, anionic surfactants and cationic surfactants.

[0125] In a preferred embodiment non-ionic surfactants are used. Typical non-ionic surfactants are fluorinated surfactants, polyglycols, or poly oxyethylene and / or oxypropylene containing molecules.

[0126] In a particular embodiment, the composition is free of any polyethyleneimine or any sulfur-containing additives or both. In another embodiment, the composition is free of N-methyl pyrrolidone or pyrophosphate or both.

[0127] In another embodiment, the composition is free of 2,2'-bipyridine, alkylammonium, or both. In another embodiment, the composition is free of acetate ions, sodium saccharinate, an N-benzylpyridinium compound, or a combination thereof.

[0128] Defect reducing agent

[0129] The copper electroplating composition may optionally comprise a defect reducing agent.

[0130] Preferred defect reducing agents are those of formula S1

[0131] RS1Z= RS2(S1)

[0132] or salts thereof,

[0133] wherein

[0134] RS1is selected from XS-YS;

[0135] RS2is selected from RS1and RS3;

[0136] Xsis selected from linear or branched C1to C10alkanediyl, linear or branched C2to C10alkenediyl, linear or branched C2to C10alkynediyl, and -XS6-(O-C2H3RS6)m-;

[0137] YSis selected from ORS3, NRS3RS4, N+RS3RS4RS5and NH-(C=O)-RS3;

[0138] RS3, RS4, RS5are the same or different and are selected from (i) H, (ii) C5to C20aryl, (iii) C1to C10alkyl (iv) C6to C20arylalkyl, (v) C6to C20alkylaryl, which may be substituted by OH, SO3H, COOH or a combination thereof, and (vi) -(C2H3RS6-O)n-RS6, and wherein RS3and RS4may together form a ring system, which may be interrupted by O or NRS7;

[0139] XS6is C1to C6alkanediyl;

[0140] m, n are integers independently selected from 1 to 30;

[0141] RS6is selected from H and C1to C5alkyl;

[0142] S S3

[0143] RS7is selected from RS6and XS——RS3

[0144] SIMS measurements of copper films plated with a defect reducing agent in the plating bath exhibit that the amount of C, N, S, 0, H, Cl, P or other elements than copper incorporated in the copper film during the copper electrodeposition is smaller than in copper films plated without defect reducing agent in the plating bath.

[0145] In the defect reducing agents of formula S1, RS1is selected from XS-YS, wherein XSis a divalent spacer group selected from linear or branched C1to C10alkanediyl, linear or branched C2to C10alkenediyl, linear or branched C2to C10alkynediyl, and -XS6-(O-C2H3RS6)m-. m is an integer selected from 1 to 30, preferably from 1 to 15, even more preferably from 1 to 10, most preferably from 1 to 5. The spacer XS6is C1to C6alkanediyl, preferably methanediyl, ethanediyl, propanediyl or butanediyl, most preferably methanediyl or ethanediyl.

[0146] In a first preferred embodiment XSis selected from linear or branched C1to C6alkanediyl, preferably from C1to C4alkanediyl.

[0147] In a second preferred embodiment XSis selected from methanediyl, ethane-1,1-diyl and ethane-1,2-diyl. In a third preferred embodiment XSis selected from propan-1,1-diyl, butane-1,1-diyl, pentane-1,1-diyl, and hexane-1,1-diyl. In a fourth preferred embodiment XSis selected from propane-2,2-diyl, butane-2,2-diyl, pentane-2,2-diyl, and hexane-2,2-diyl.

[0148] In a fifth preferred embodiment XSis selected from propane-1,2-diyl, butane-1,2-diyl, pentane-1,2-diyl, and hexane-1,2-diyl. In a sixth preferred embodiment XSis selected from propane-1,3-diyl, butane-1,3-diyl, pentane-1,3-diyl, and hexane-1,3-diyl.

[0149] YSis a monovalent group and may be selected from ORS3, with RS3being selected from (i) H, (ii) C5to C20aryl, preferably C5, C6, and C10aryl, (iii) C1to C10alkyl, preferably C1to C6alkyl, most preferably C1to C4alkyl (iv) C6to C20arylalkyl, preferably C6to C10arylalkyl, (v) C6to C20alkylaryl, all of which may be substituted by OH, SO3H, COOH or a combination thereof, and (vi) -(C2H3RS6-O)n-RS6. In a preferred embodiment, RS3may be C1to C6alkyl or H. RS6may independently be selected from H and C1to C5alkyl, preferably from H and C1to C4alkyl, most preferably H, methyl or ethyl. As used herein, aryl comprises carbocyclic aromatic groups as well as heterocyclic aromatic groups in which one or more carbon atoms are exchanged by one or more N or 0 atoms. As used herein, arylalkyl means an alkyl group substituted with one or more aryl groups, such as but not limited to benzyl and methylpyridine. As used herein, alkylaryl means an aryl group substituted with one or more alkyl groups, such as but not limited to toluyl.

[0150] In another preferred embodiment, RS3is selected from H to form a hydroxy group. In another preferred embodiment, RS3is selected from polyoxyalkylene groups of formula -(C2H3RS6-O)n-RS6. RS6is selected from H and C1to C5alkyl, preferably from H and C1to C4alkyl, most preferably from H, methyl or ethyl. Generally, n may be an integer from 1 to 30, preferably from 1 to 15, most preferably from 1 to 10. In a particular embodiment polyoxymethylene, polyoxypropylene or a poly(oxymethylene-co-oxypropylene) may be used. In another preferred embodiment, RS3may be selected from C1to C10alkyl, preferably from C1to C6alkyl, most preferably methyl and ethyl.

[0151] Furthermore, YSmay be an amine group NRS3RS4, wherein RS3and RS4are the same or different and may have the meanings of RS3described for ORS3above.

[0152] In a preferred embodiment, RS3and RS4are selected from H to form an NH2group. In another preferred embodiment, at least one of RS3and RS4, preferably both are selected from polyoxyalkylene groups of formula -(C2H3RS6-O)n-RS6. RS6is independently selected from H and C1to C5alkyl, preferably from H and C1to C4alkyl, most preferably H, methyl or ethyl. In yet another preferred embodiment, at least one of RS3and RS4, preferably both are selected from C1to C10alkyl, preferably from C1to C6alkyl, most preferably methyl and ethyl.

[0153] R33and R34may also together form a ring system, which may be interrupted by 0 or NR37. R37may be selected from S1 S2

[0154] R36and R — = — R. Preferably the ring system is formed by two substituents R33and R34which are bound to the same N atom. Such ring system may preferably comprise 4 or 5 carbon atoms to form a 5 or 6 membered carbocyclic system. In such carbocyclic system one or two of the carbon atoms may be substituted by oxygen atoms.

[0155] Furthermore, YSmay be a positively charged ammonium group N+RS3RS4RS5. RS3, RS4, RS5are the same or different and may have the meanings of RS3described for ORS3and NRS3RS4above. In a preferred embodiment RS3, RS4and RS5are independently selected from H, methyl or ethyl. In one embodiment at least one of RS3, RS4and RS5, preferably two, most preferably all, are selected from polyoxyalkylene groups of formula -(C2H3RS6-O)n-RS6.

[0156] m may be an integer selected from 1 to 30, preferably from 1 to 15, even more preferably from 1 to 10, most preferably from 1 to 5.

[0157] In the defect reducing agents of formula S1 RS2may be either RS1or RS3as described above. If RS2is RS1, RS1may be selected to form a symmetric compound (both RS1s are the same) or an asymmetric compound (the two RS1s are different). In a preferred embodiment RS2is H.

[0158] Particularly preferred aminoalkynes are those in which

[0159] (a) RS1is XS-NRS3RS4and RS2is H;

[0160] (b) RS1is XS-NRS3RS4and RS2is Xs- NRS3RS4with Xsbeing selected from linear Ci to C4 alkanediyl and branched C3 to Ce alkanediyl.

[0161] Particularly preferred hydroxyalkynes or alkoxyalkynes are those in which

[0162] (a) RS1is XS-ORS3and RS2is H;

[0163] (b) RS1is XS-ORS3and RS2is XS-ORS3with Xsbeing selected from linear Ci to C4 alkanediyl and branched C3 to Ce alkanediyl.

[0164] Particularly preferred alkynes comprising an amino and a hydroxy group are those in which RS1is XS-ORS3, particularly XS-OH, and RS2is Xs- NRS3RS4with Xsbeing independently selected from linear Ci to C4 alkanediyl and branched C3 to Ce alkanediyl.

[0165] The amine groups in the defect reducing agents may be selected from primary (RS3, RS4is H), secondary (RS3or RS4is H) and tertiary amine groups (RS3and RS4are both not H).

[0166] The alkynes may comprise one or more terminal triple bonds or one or more non-terminal triple bonds (alkyne functionalities). Preferably, the alkynes comprise one or more terminal triple bonds, particularly from 1 to 3 triple bonds, most preferably one terminal triple bond.

[0167] Particularly preferred specific primary aminoalkynes are:

[0168]

[0169] Particularly preferred specific tertiary aminoalkynes are:

[0170]

[0171] Other preferred defect reducing agents are those in which the rests R33and R34may together form a ring system, which is optionally interrupted by 0 or NR33. Preferably, the rests R33and R34together form a C5 or Ce bivalent group in which one or two, preferably one, carbon atoms may be exchanged by 0 or NR37’ with R37being selected from hydrogen, methyl or ethyl.

[0172] An example of such compounds is:

[0173]

[0174] It may be received by reaction of propargyl amine with formaldehyde and morpholine.

[0175] Another preferred defect reducing agent comprising a saturated heterocyclic system is:

[0176]

[0177] In this case RS3and RS4together form a ring system which is interrupted by two NRS3groups, in which RS3is selected from CH2-C≡C-H. This defect reducing agent comprises three terminal triple bonds.

[0178] The amino groups in the defect reducing agents may further be quaternized by reaction with alkylating agents such as but not limited to dialkyl sulphates like DMS, DES or DPS, benzyl chloride or chlormethylpyridine. Particularly preferred quaternized defect reducing agents are:

[0179]

[0180] Particularly preferred specific aminoalkynes comprising OH groups are:

[0181]

[0182]

[0183] Also in this case the rests RS3and R54may together form a ring system, which is optionally interrupted by O or NRS3. Preferably, the rests RS3and RS4together form a C5 or Ce bivalent group in which one or two, preferably one, carbon atoms may be exchanged by O or NRS7’ with RS7being selected from hydrogen, methyl or ethyl.

[0184] Examples for such compounds are:

[0185]

[0186] These may be received by reaction of propargyl alcohol with formaldehyde and piperidine or morpholine, respectively.

[0187] By partial reaction with alkylating agents mixtures of defect reducing agents may be formed. In one embodiment, such mixtures may be received by reaction of 1 mole diethylaminopropyne and 0.5 mole epichlorohydrin, 1 mole diethylaminopropyne and 0.5 mole benzylchloride, 1 mole diethylaminopropyne with 0.9 mole dimethyl sulphate, 1 mole dimethyl propyne amine and 0.33 mole dimethyl sulphate, or 1 mole dimethyl propyne amine and 0.66 mole dimethyl sulphate. In another embodiment such mixtures may be received by reaction of 1 mole dimethyl propyne amine and 1.5, 1.9, or 2.85 mole dimethyl sulphate, 1 mole dimethyl propyne amine and 0.5 mole epichlorohydrin, 1 mole dimethyl propyne amine and 2.85 diethyl sulphate, or 1 mole dimethyl propyne amine and 1.9 mole dipropyl sulphate.

[0188] In a further embodiment, the defect reducing agents may be substituted by SO3H (sulfonate) groups or COOH (carboxy) groups. Specific sulfonated defect reducing agents may be but are not limited to butynoxy ethane sulfonic acid, propynoxy ethane sulfonic acid, 1,4-di-(P-sulfoethoxy)-2-butyne, 3-(|3-sulfoethoxy)-propyne. In one embodiment a single defect reducing agent may be used in the copper electroplating baths. In another embodiment two or more of the defect reducing agents are used in combination.

[0189] In general, the defect reducing agents are typically used in an amount of about 0.1 ppm to about 30000 ppm, based on the total weight of the plating bath. Particularly suitable amounts of defect reducing agent useful in the present invention are 1 to 10000 ppm, and more particularly 10 to 1000 ppm.

[0190] Composition

[0191] A wide variety of metal plating baths may be used with the present invention. Metal electroplating baths typically comprise or essentially consist of a copper ion source, a grain refiner, a complexing agent, optionally a defect reducing agent, optionally a base or a buffer, optionally an electrolyte, and optionally further additives as described above.

[0192] The plating baths are typically aqueous. The term “aqueous” means that the plating bath is water based. The water may be present in a wide range of amounts. Any type of water may be used, such as distilled, deionized or tap. Preferably the plating bath is a solution of the compounds described herein in water. Preferably the water is electronic grade deionized water. Other solvents besides water may be present in minor amounts but preferably water is the only solvent.

[0193] The metal ion source may be any compound capable of releasing copper ions to be deposited in the electroplating bath in sufficient amount, i.e. is at least partially soluble in the electroplating bath. In other preferred embodiment the metal comprises copper and comprise tin in amount of below 0.1 g / l, preferably below 0.01 g / l, most preferably no tin. Most preferably there are essentially no other alloying metal ions than copper ions present in the composition. In this context “alloying metal” means a metal that it can be electrodeposited with copper as an alloying metal from an aqueous solution. Without limitation, typical alloying metals are subgroup metals such as but not limited to Sn (to form a bronze), Zn (to form a brass), Ni, Co, Mn, Ag, W, Au, and Pb. Preferred alloying metals are Mn, Zn (to form a brass), Ni, Co, Mn, Ag, and W. More preferred are Zn and Mn, most preferred is Mn. Typical non-alloying metals are those of groups I metals like sodium or potassium or of group II metals like magnesium or calcium. In a preferred embodiment, the composition is free of tin. In another preferred embodiment the composition is free of any alloying metal ions. Most preferably no metal ions are present in the composition except those present in the buffer or base or in the optional electrolyte. Particularly for depositing copper into a feature having an aperture size of 15 nm or below an additional electrolyte is disadvantageous since a lower conductivity of the composition leads to a more equal deposition into the feature.

[0194] In a preferred embodiment the composition does not contain any boric acid. In another preferred embodiment, the electroplating composition does not comprise any reducing agents that reduces the copper ions to metallic copper.

[0195] It is preferred that the copper ion source is soluble in the plating bath to release 100 % of the metal ions. Suitable copper ion sources are metal salts and include, but are not limited to, metal sulfates, metal halides, metal acetates, metal nitrates, metal fluoroborates, metal alkylsulfonates, metal arylsulfonates, metal sulfamates, metal gluconates and the like. It is preferred that the metal is copper. It is further preferred that the source of copper ions is copper sulfate, copper chloride, copper acetate, copper citrate, copper nitrate, copper fluoroborate, copper methane sulfonate, copper phenyl sulfonate and copper p-toluene sulfonate. Copper sulfate pentahydrate and copper methane sulfonate are particularly preferred. Such metal salts are generally commercially available and may be used without further purification.

[0196] The copper ion source may be used in the present invention in any amount that provides sufficient metal ions for electroplating on a substrate.

[0197] Copper is typically present in an amount in the range of from about 0.2 to about 300 g / l of the plating solution. Generally, the defect reducing agent is useful in low copper, medium copper and high copper baths. Low copper means a copper concentration from about 0.3 to about 20 g / l. Even lower concentration of from about 0.1 to about 5 g / l, 0.1 to 1 g / l may be advantageous in view of cobalt corrosion.

[0198] The pH of the electroplating composition is in the range of from about 7 to about 13, preferably from about 7 to about 12, more preferably from about 7 to about 12, most preferably from about 7 to about 11.

[0199] The electroplating composition is free of any cyanide ions.

[0200] In a preferred embodiment the composition is essentially free from chloride ions except chloride ions present in the defect reducing agent (e.g. if it is positively charged) or the optional grain refiner (e.g. if an inner salt is used).

[0201] Essentially free from chloride means that the additional chloride is below 1 ppm, particularly below 0.1 ppm. It is most preferred that the composition does not contain any additional anions, particularly chloride ions, except those present in the grain refiner or in the optional defect reducing agent. Particularly for depositiing copper into a feature having an aperture size of 15 or below any additional anions are disadvantageous since a lower conductivity of the composition leads to a more equal deposition into the feature.

[0202] In another preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) copper ions;

[0203] (b) a grain refiner of formula G1a or G1b; and

[0204] (c) a complexing agent, particularly a hydroxycarboxylic acid, most particularly citric acid; (d) optionally a buffer or a base to adjust the pH to a pH of from 7 to 13;

[0205] (e) optionally a defect reducing agent, particularly a defect reducing agent of formula S1

[0206] RS1ZZ RS2(S1)

[0207] (f) optionally a non-ionic surfactant.

[0208] In yet another preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) copper ions;

[0209] (e) a grain refiner of formula G1a or G1b.

[0210] (c) a complexing agent, particularly a hydroxycarboxylic acid or alkanolamine;

[0211] (d) a base, particularly a hydroxide, to increase the pH to a pH of from 7 to 13; and

[0212] (e) a defect reducing agent of formula S1

[0213] _S1 „S2

[0214] R - ZZ R (S1)

[0215] In yet another preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) copper ions;

[0216] (e) a grain refiner of formula G1a or G1b.

[0217] (c) a hydroxycarboxylic acid or alkanolamine;

[0218] (d) a hydroxide, particularly NaOH or KOH, to increase the pH to a pH of from 7 to 13; and

[0219] (e) a defect reducing agent of formula S1

[0220] RS1- RS2(S1)

[0221] Process

[0222] According to one embodiment of the present invention an non-acidic copper electroplating bath comprising a composition as described herein may be used for depositing copper on substrates comprising recessed features having an aperture size of 50 nanometers or less, which features preferably comprise a seed of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, or alloys thereof, preferably of cobalt or ruthenium, most preferably of cobalt.

[0223] An electrolytic bath is prepared comprising copper ions, a complexing agent, and at least one grain refineraccording to the invention. A dielectric substrate having the seed layer is placed into the electrolytic bath where the electrolytic bath contacts the at least one outer surface and the three dimensional pattern having a seed layer in the case of a dielectric substrate. A counter electrode is placed into the electrolytic bath and an electrical current is passed through the electrolytic bath between the seed layer on the substrate and the counter electrode. At least a portion of copper is deposited into at least a portion of the three dimensional pattern wherein the deposited copper is substantially void-free.

[0224] The present invention is useful for depositing a layer comprising copper on a variety of substrates, particularly those having nanometer and variously sized apertures. For example, the present invention is particularly suitable for depositing copper on integrated circuit substrates, such as semiconductor devices, with small diameter vias, trenches or other recessed features. In one embodiment, semiconductor devices are plated according to the present invention. Such semiconductor devices include, but are not limited to, wafers used in the manufacture of integrated circuits.

[0225] In order to allow a deposition of copper on a substrate comprising a dielectric surface a seed layer needs to be applied to the surface. Such seed layer may consist of cobalt, iridium, osmium, palladium, platinum, rhodium, and ruthenium or alloys comprising such metals. Preferred is the deposition of copper on a cobalt seed. The seed layers are described in detail e.g. in US20140183738 A.

[0226] The underlying seed layer may be deposited or grown by chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), electroplating, electro less plating or other suitable process that deposits conformal thin films. In an embodiment, the cobalt seed layer is deposited to form a high quality conformal layer that sufficiently and evenly covers all exposed surfaces within the openings and top surfaces. The high quality seed layer may be formed, in one embodiment, by depositing the cobalt seed material at a slow deposition rate to evenly and consistently deposit the conformal seed layer. By forming the seed layer in a conformal manner, compatibility of a subsequently formed fill material with the underlying structure may be improved. Specifically, the seed layer can assist a deposition process by providing appropriate surface energetics for deposition thereon.

[0227] In one embodiment the substrate comprises submicrometer sized features and the copper deposition is performed to fill the submicrometer sized features. Most preferably the submicrometer-sized features have an (effective) aperture size of 10 nm or below and / or an aspect ratio of 4 or more. More preferably the features have an aperture size of 7 nanometers or below, most preferably of 5 nanometers or below. Preferably the features bear a cobalt seed layer on which copper is electrodeposited.

[0228] In another embodiment a seed of copper is deposited onto the seeded surface of the substrate. Preferably this substrate comprises recessed features having an aperture size of 50 nm or below and / or an aspect ratio of 4 or more. Preferably the substrate bears a cobalt seed layer on which the copper seed layer is electrodeposited.

[0229] As used herein, “seed of copper” means a continuous thin layer of copper having a thickness of about 5 nm to about 15 nm. The aperture size according to the present invention means the smallest diameter or free distance of a feature before plating, i.e. after seed deposition. The terms “aperture” and “opening" are used herein synonymously.

[0230] The electrodeposition current density should be chosen to promote the void-free filling behavior. A range of 0.1 to 40 mA / cm2is useful for this purpose. In a particular example, the current density can range from 1 to 10 mA / cm2. In another particular example, the current density can range from 0.5 to 5 mA / cm2.

[0231] Typically, substrates are electroplated by contacting the substrate with the plating baths of the present invention. The substrate typically functions as the cathode. The plating bath contains an anode, which may be soluble or insoluble. Optionally, cathode and anode may be separated by a membrane. Potential is typically applied to the cathode. Sufficient current density is applied and plating performed for a period of time sufficient to deposit a metal layer, such as a copper layer, having a desired thickness on the substrate. Suitable current densities include, but are not limited to, the range of 1 to 250 mA / cm2. Typically, the current density is in the range of 1 to 60 mA / cm2when used to deposit copper in the manufacture of integrated circuits. The specific current density depends on the substrate to be plated, the agents and additives selected and the like. Such current density choice is within the abilities of those skilled in the art. The applied current may be a direct current (DC), a pulse current (PC), a pulse reverse current (PRC) or other suitable current. Pulse current (PC) is preferred. Typical temperatures used for the copper electroplating are from 10°C to 50°C, preferably 20°C to 40°C, most preferably from 20°C to 35°C.

[0232] In general, when the present invention is used to deposit metal on a substrate such as a wafer used in the manufacture of an integrated circuit, the plating baths are agitated during use. Any suitable agitation method may be used with the present invention and such methods are well-known in the art. Suitable agitation methods include, but are not limited to, inert gas or air sparging, work piece agitation, impingement and the like. Such methods are known to those skilled in the art. When the present invention is used to plate an integrated circuit substrate, such as a wafer, the wafer may be rotated such as from 1 to 300 RPM and the plating solution contacts the rotating wafer, such as by pumping or spraying. In the alternative, the wafer need not be rotated where the flow of the plating bath is sufficient to provide the desired metal deposit.

[0233] In one embodiment copper is deposited in recessed features according to the present invention without substantially forming voids within the metal deposit.

[0234] As used herein, void-free fill may either be ensured by an extraordinarily pronounced bottom-up copper growth while perfectly suppressing the sidewall copper growth, both leading to a flat growth front and thus providing substantially defect free trench / via fill (so-called bottom-up-fill) or may be ensured by a so-called V-shaped filling.

[0235] As used herein, the term "substantially void-free", means that at least 95% of the plated apertures are void-free. Preferably that at least 98% of the plated apertures are void-free, mostly preferably all plated apertures are void-free. As used herein, the term "substantially seam-free", means that at least 95% of the plated apertures are seam-free. Preferably that at least 98% of the plated apertures are seam-free, mostly preferably all plated apertures are seam-free.

[0236] Plating equipment for plating semiconductor substrates are well known. Plating equipment comprises an electroplating tank which holds Cu electrolyte and which is made of a suitable material such as plastic or other material inert to the electrolytic plating solution. The tank may be cylindrical, especially for wafer plating. A cathode is horizontally disposed at the upper part of tank and may be any type substrate such as a silicon wafer having openings such as trenches and vias. The wafer substrate is typically coated with a seed layer of Cu or other metal or a metal containing layer to initiate plating thereon. An anode is also preferably circular for wafer plating and is horizontally disposed at the lower part of tank forming a space between the anode and cathode. The anode is typically a soluble anode.

[0237] These bath additives are useful in combination with membrane technology being developed by various tool manufacturers. In this system, the anode may be isolated from the organic bath additives by a membrane. The purpose of the separation of the anode and the organic bath additives is to minimize the oxidation of the organic bath additives.

[0238] The cathode substrate and anode are electrically connected by wiring and, respectively, to a rectifier (power supply). The cathode substrate for direct or pulse current has a net negative charge so that Cu ions in the solution are reduced at the cathode substrate forming plated Cu metal on the cathode surface. An oxidation reaction takes place at the anode. The cathode and anode may be horizontally or vertically disposed in the tank.

[0239] While the process of the present invention has been generally described with reference to semiconductor manufacture, it will be appreciated that the present invention may be useful in any electrolytic process where a substantially void-free copper deposit is desired. Such processes include printed wiring board manufacture. For example, the present plating baths may be useful for the plating of vias, pads or traces on a printed wiring board, as well as for bump plating on wafers. Other suitable processes include packaging and interconnect manufacture. Accordingly, suitable substrates include lead frames, interconnects, printed wiring boards, and the like.

[0240] All percent, ppm or comparable values refer to the weight with respect to the total weight of the respective composition except where otherwise indicated. All cited documents are incorporated herein by reference.

[0241] The following examples shall further illustrate the present invention without restricting the scope of this invention. Examples

[0242] Example 1: Synthesis of grain refiners

[0243] Example 1a: 1-benzyl-3-carbamoylpyridin-1-ium chloride

[0244] To nicotinamide (4.00 g, 32.7 mmol, 1.0 equiv) acetonitrile (30 mL) added. Susequently benzyl chloride (5.06 g, 40.0 mmol, 1.22 equiv) was added and the mixture was heated to reflux for 4 hours. After cooling to room temperature, the formed precipitate was filtered off and washed with acetonitrile (10 mL). After drying of the filter residue in vacuo, 1-benzyl-3-carbamoylpyridin-1-ium chloride (97.5 wt.-% by quantitative1H-NMR, 5.40 g, 21.1 mmol, 65% yield) was isolated as a pale-yellow solid.1H NMR (400 MHz, DMSO-d6) δ 5.95 (s, 2H), 7.36 - 7.48 (m, 3H), 7.62 (dd, J = 7.5, 1.9 Hz, 2H), 8.10 - 8.23 (m, 1H), 8.29 (dd, J = 7.9, 6.2 Hz, 1H), 8.87 (d, J = 7.7 Hz, 1H), 9.05 (d, J = 8.1 Hz, 1H), 9.36 (d, J = 6.1 Hz, 1H), 9.84 (s, 1H).

[0245] Example 1b: 1-benzyl-4-carbamoylpyridin-1-ium chloride

[0246] Synthesis according to Example 1a gave access to 1-benzyl-4-carbamoylpyridin-1-ium chloride (96.2 wt.-% by quantitative1H-NMR, 59% yield).1H NMR (500 MHz, Deuterium Oxide) δ 5.92 (s, 2H), 7.54 (s, 5H), 8.39 (d, J = 6.3 Hz, 2H), 9.03 - 9.19 (m, 2H).

[0247] Example 1c: 1-benzyl-3-(methylcarbamoyl)pyridin-1-ium chloride

[0248] Synthesis according to Example 1a gave access to 1-benzyl-3-(methylcarbamoyl)pyridin-1-ium chloride (97.7 wt.-% by quantitative1H-NMR, 77% yield).1H NMR (500 MHz, Deuterium Oxide) δ 3.01 (s, 3H), 5.94 (s, 2H), 7.55 (s, 5H), 8.22 (dd, J = 8.1, 6.2 Hz, 1H), 8.89 (dt, J = 8.2, 1.5 Hz, 1H), 9.10 (dt, J = 6.3, 1.4 Hz, 1H), 9.34 (d, J = 1.7 Hz, 1H).

[0249] Example 1d: 1-benzyl-3-(diethylcarbamoyl)pyridin-1-ium chloride

[0250] Synthesis according to Example 1a gave access to 1 -benzyl-3-(diethylcarbamoyl)pyridin-1 -ium chloride (97.3 wt.-% by quantitative1H-NMR, 55% yield).1H NMR (500 MHz, Deuterium Oxide) δ 1.04 (t, J = 7.2 Hz, 3H), 1.25 (t, J = 7.2 Hz, 3H), 3.24 (q, J = 7.2 Hz, 2H), 3.57 (q, J = 7.2 Hz, 2H), 5.90 (s, 2H), 7.40 - 7.61 (m, 5H), 8.21 (dd, J = 8.1, 6.1 Hz, 1H), 8.65 (dt, J = 8.1, 1.5 Hz, 1H), 8.93 - 9.22 (m, 2H).

[0251] Example 1e: 1-benzyl-4-(phenylcarbamoyl)pyridin-1-ium chloride Synthesis according to Example 1a gave access to 1-benzyl-4-(phenylcarbamoyl)pyridin-1-ium chloride (71.3 wt.-% by quantitative1H-NMR, 65% yield).1H NMR (500 MHz, Deuterium Oxide) δ 5.93 (s, 2H), 7.28 (tt, J = 7.4, 1.2 Hz, 1 H), 7.39 - 7.52 (m, 2H), 7.54 - 7.70 (m, 7H), 8.34 - 8.45 (m, 2H), 8.97 - 9.20 (m, 2H).

[0252] Example 1f: (3-(3-carbamoylpyridin-1-ium-1-yl)propane-1-sulfonate)

[0253] To a solution of nicotinamide (4.00 g, 32.8 mmol, 1.0 equiv) in methanol (19 mL) was added 1,3-propanesultone (4.00 g, 32.8 mmol, 1.0 equiv). After stirring at room temperature for 40 hours, the formed precipitate was filtered off and dried in vacuo. 3-(3-carbamoylpyridin-1-ium-1-yl)propane-1 -sulfonate (97.6 wt.-% by quantitative1H-NMR, 6.50 g, 26.0 mmol, 79% yield) was isolated as a white powder.1H NMR (400 MHz, DMSO-d6) δ 2.26 (q, J = 7.1 Hz, 2H), 2.45 (m, 2H), 4.78 (t, J = 7.0 Hz, 2H), 8.13 (s, 1 H), 8.25 (dd, J = 8.1, 6.1 Hz, 1 H), 8.54 (s, 1 H), 8.90 (d, J = 8.1 Hz, 1H), 9.20 (d, J = 6.1 Hz, 1H), 9.46 (s, 1H).

[0254] Example 1g: 3-(4-carbamoylpyridin-1-ium-1-yl)propane-1-sulfonate

[0255] Synthesis according to Example 1f gave access to 3-(4-carbamoylpyridin-1-ium-1-yl)propane-1 -sulfonate (98.4 wt.-% by quantitative1H-NMR, 79% yield).1H NMR (500 MHz, Deuterium Oxide) δ 2.52 (p, J = 7.4 Hz, 2H), 3.03 (t, J = 7.2 Hz, 2H), 4.87 (t, J = 7.5 Hz, 2H), 8.41 (d, J = 6.4 Hz, 2H), 9.04 - 9.18 (m, 2H).

[0256] Example 1h: 3-(3-(methylcarbamoyl)pyridin-1-ium-1-yl)propane-1-sulfonate

[0257] Synthesis according to Example 1f gave access to 3-(3-(methylcarbamoyl)pyridin-1 -ium-1 -yl)propane-1 -sulfonate (98.7 wt.-% by quantitative1H-NMR, 78% yield).

[0258] 1H NMR (500 MHz, Deuterium Oxide) δ 2.52 (p, J = 7.4 Hz, 2H), 3.04 (t, J = 7.2 Hz, 2H), 4.88 (t, J = 7.5 Hz, 2H), 8.23 (dd, J = 8.1, 6.1 Hz, 1H), 8.87 (dq, J = 8.3, 1.2 Hz, 1H), 9.08 (d, J = 6.1 Hz, 1H), 9.33 (d, J = 2.0 Hz, 1H).

[0259] Example 1i: 3-(3-(diethylcarbamoyl)pyridin-1-ium-1 -yl)propane-1 -sulfonate

[0260] Synthesis according to Example 1f gave access to 3-(3-(diethylcarbamoyl)pyridin-1 -ium-1 -yl)propane-1 -sulfonate (88.6 wt.-% by quantitative1H-NMR, 75% yield).

[0261] 1H NMR (500 MHz, Deuterium Oxide) δ 1.07 – 1.20 (m, 3H), 1.27 (t, J = 7.2 Hz, 3H), 2.51 (p, J = 7.3 Hz, 2H), 3.02 (t, J = 7.2 Hz, 2H), 3.28 - 3.39 (m, 2H), 3.59 (q, J = 7.3 Hz, 2H), 4.85 (t, J = 7.5 Hz, 2H), 8.22 (dd, J = 8.0, 6.2 Hz, 1 H), 8.65 (dt, J = 8.1, 1.5 Hz, 1 H), 9.05 (dt, J = 6.2, 1.4 Hz, 1 H), 9.13 (d, J = 1.7 Hz, 1 H).

[0262] Example 2: Copper electroplating experiments The grain refiner of Example 1a and of Example 1f have been used as grain refiner alone without any further additives. A blanket wafer substrate was used, featuring a 120 A CVD cobalt seed layer deposited on a 50 A tantalum nitride (TaN) layer.

[0263] Comparative example 2a

[0264] A plating bath was prepared by combining deionized (DI) water, 0.5 g / l copper as copper sulfate, and citric acid in a molar ratio of 2:1 to Cu. The pH was adjusted to 7.5 using a sodium hydroxide or potassium hydroxide solution. A copper layer was electroplated onto the blanket wafer substrate by immersing it in the plating bath at 25 °C and applying a direct current of -1.0 mA / cm2for 300 seconds. The electroplated copper layer was then annealed at 275 °C for 5 minutes in nitrogen gas and analyzed using X-ray fluorescence (XRF) and a four-point probe. The resulting copper film had a thickness of 74 nm and a sheet resistance of 0.75 Ω / □, translating to a copper resistivity of 5.53 μΩ·cm.

[0265] Comparative Example 2b

[0266] The experiment in Example 2a was repeated with the addition of 1 ml / l of a 0.9 wt% solution of 3-carboxy-1-phenylmethylpyridinium (WO 2023 / 126257) in DI water as a grain refiner. The resulting copper film had a thickness of 71 nm, a sheet resistance of 0.62 Ω / □, and a copper resistivity of 4.45 μΩ·cm. This indicates a 20% reduction in copper resistivity compared to Example 2a.

[0267] Example 2c

[0268] The experiment in Example 2a was repeated with the addition of 1 ml / l of a 0.9 wt% solution of the grain refiner prepared in Example 1a in DI water as a grain refiner. The resulting copper film had a thickness of 74 nm, a sheet resistance of 0.54 Ω / □, and a copper resistivity of 4.02 μΩ·cm. This indicates a 27% reduction in copper resistivity compared to Example 2a.

[0269] Example 2d

[0270] The experiment in Example 2a was repeated with the addition of 1 ml / l of a 0.9 wt% solution of the grain refiner prepared in Example 1f in DI water as a grain refiner. The resulting copper film had a thickness of 76 nm, a sheet resistance of 0.56 Ω / □, and a copper resistivity of 4.29 μΩ·cm. This indicates a 22% reduction in copper resistivity compared to Example 2a.

Claims

Claims1. A composition for depositing copper on a semiconductor substrate, the composition comprising(a) copper ions;(b) a grain refiner of formula G1a or G1bor salts thereof(c) a complexing agent; and(d) optionally a buffer or a base to adjust the pH to a pH of from 7 to 13;whereinRG1is a carbamoyl group of formulaRG2is selected from the group consisting of (a) carboxyl, (b) sulfonate, (c) sulfate (d) carbamoyl, (e) OH or Ci to C4 alkoxy, (f) halogen, (g) ON, and (h) Ce-Ci2 aryl, which aryl is unsubstituted or substituted by one or more of the groups (a) to (g);RG3is selected from the group consisting of (a) Ci to C4 alkyl, (b) OH or Ci to C4 alkoxy, (c) halogen, and (d) ON;RG4is a C1to C4alkyl group;XG1is selected from Ci to Ce alkanediyl, which is unsubstituted or substituted by one or two OH and which may be interrupted by one or two 0; andRG11, RG12are independently selected from H, Ci to C4 alkyl, C6to C12aryl, C6to C12arylalkyl; C6to C12alkylaryl;n is 0, 1, or 2;wherein the pH of the composition is from 7 to 13.

2. The composition according to claim 1, wherein the grain refiner is a compound of formula G1 a.

3. The composition according to claim 2, whereinRG2is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, H and CN;andXG1is a Ci to C4 alkanediyl, which is unsubstituted or substituted by one OH and which may be interrupted by one 0.

4. The composition according to anyone of the preceding claims, wherein RG11and RG12are independently H, methyl, ethyl, propyl, phenyl, benzyl, or toluyl.

5. The composition according to anyone of the preceding claims, wherein the grain refiner is a compound of formula G2a, G2b, or salts thereof6. The composition according to anyone of the preceding claims, wherein the grain refiners are selected from7. The composition according to anyone of claims 1 or 4, wherein the grain refiner is selected from formula G3a or G3b:

8. The composition according to anyone of the preceding claims, further comprising a defect reducing agent of formula S1RS1= RS2(S1)or salts thereof,whereinRS1is selected from XS-YS;RS2is selected from RS1and RS3;XSis selected from linear or branched C1to C10alkanediyl, linear or branched C2to C10alkenediyl, linear or branched C2to C10alkynediyl, and -XS6-(O-C2H3RS6)m-;YSis selected from ORS3, NRS3RS4, N+RS3RS4RS5and NH-(C=O)-RS3;RS3, RS4, RS5are the same or different and are selected from (i) H, (ii) C5to C20aryl, (iii) C1to C10alkyl (iv) C6to C20arylalkyl, (v) C6to C20alkylaryl, which may be substituted by OH, SO3H, COOH or a combination thereof, and(vi) -(C2H3RS6-O)n-RS6, and wherein RS3and RS4may together form a ring system, which may be interrupted by O or NRS7;XS6is C1to C6alkanediyl;m, n are integers independently selected from 1 to 30;RS6is selected from H and C1to C5alkyl;© ©RS7is selected from RS6and XS——RS3.

9. The composition according to anyone of the preceding claims, wherein the composition is free of any cyanide ions.

10. The composition according to anyone of the preceding claims, wherein the composition is free of tin ions.

11. The composition according to anyone of the preceding claims, wherein the composition is free of any alloying metal ions.

12. The composition according to anyone of the preceding claims, which has a pH of 7 to 11.

13. The composition according to anyone of the preceding claims, which does not comprise any chloride ions besides those present in the grain refiner; if present, in the buffer or base; or, if present, in the defect reducing agent.

14. The composition according to anyone of the preceding claims, wherein the buffer or base is a hydroxide.15 The composition according to anyone of the preceding claims, essentially consisting of(a) copper ions;(b) a grain refiner of formula G1a or G1b; and(c) a complexing agent;(d) optionally a base to adjust the pH to a pH of from 7 to 13;(e) optionally a defect reducing agent of formula S1RS1 -RS2(S1). and(f) optionally a non-ionic surfactant.

16. Use of a composition according to anyone of the preceding claims for depositing copper on a semiconductor substrate comprising recessed features having an aperture size 50 nanometers or less, particularly 15 nm or less.

17. The use according to claim 16, wherein the recessed features have an aspect ratio of 4 or more.

18. The use according to claim 16 or 17, wherein the semiconductor substrate is a dielectric substrate onto which a conducting seed layer is placed, wherein the seed layer consists of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, or alloys thereof.

19. A process for depositing copper on a semiconductor substrate comprising a recessed feature having an aperture size of 50 nm or less, preferably 15 nm or less, the recessed feature comprising a metal seed, the process comprising(a) bringing a composition according to anyone of claims 1 to 15 into contact with the metal seed, (b) applying a current for a time sufficient to deposit a continuous seed of copper onto the metal seed of the recessed feature or to completely fill the recessed feature.

20. The process according to claim 19, wherein the seed layer consists of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, or alloys thereof, preferably of cobalt.

21. The process according to claims 20, wherein the seed consists of cobalt.

22. The process according to claims 20, wherein the seed consists of ruthenium.

23. The process according to anyone of claims 19 to 22, wherein the recessed feature is completely filled with copper.

24. The process according to anyone of claims 19 to 23, wherein a continuous seed of copper is deposited onto the metal seed of the recessed feature.

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