Non-acidic composition for copper electroplating comprising an alkanolamine complexing agent

Abstract

The present invention provides a composition, a use and a process for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (ii) at least one branched C3 to C8 hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and (ii) in sum at least 3 hydroxy groups; and which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate, and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13.

Description

[0001]Non-acidic composition for Copper electroplating comprising an alkanolamine complexing agent.Description The present invention relates to a non-acidic composition for depositing a copper layer onto a semiconductor substrate, its use and a deposition process using such composition. Background of the Invention 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. 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. 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 non- conformity 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. To avoid these difficulties a non-copper metal 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. WO 2022 / 012932 discloses an acidic bromide containing copper electroplating bath. However, cobalt and ruthenium are less noble metals compared to copper and quickly corrode in the presence of an acid and oxygen, particularly if copper is present, too. On the other hand, alkaline 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. Also, neutral or alkaline compositions for copper electroplating copper on a copper or other metal seeds are generally known in the art. JP 2002004081 A discloses an electroplating solution containing copper ions 0.05 to 2.0 mol / l, preferably 0.2 to1.0 mol / l, of a complexing agent and having a pH in the range of 4 to 10. The complexing agent may preferably be chosen from a polyamine, an aminocarboxylic acid, an aminoalkanol compound, a carboxylic acid and a salt thereof, a cyclic acid imide compound, and an organic phosphonic acid. WO 2023 / 126257 and WO 2023 / 126259 disclose non-acidic copper electroplating composition comprising specific defect reducing agents and grain refiners. The composition comprises a complexing agent which may be selected from polyamines, aminocarboxylic acids, aminophosphonic acids, aminoalcohols, polyalcohols, hydroxycarboxylicacids, hydroxyphosphonic acids, thioureas, and polycarboxylic acids. The complexing agents are used in an amountof from 0.01 to 2 mol / l, preferably from 0.1 to 0.6 mol / l. US 2023 / 227992 discloses an alkaline electrodeposition solutions that may produce superconformal fill of metal in features such as features having a critical dimension of about 20 nm or less. The electro- plated metal may be copper. The copper may be electro plated on a substrate material that is less noble than copper. There is still a need for a copper electroplating composition that allows a void-free deposition of copper in small recessed features, such as vias or trenches, of semiconductor substrates, on seeds of a metal that has a lower normal potential than copper, particularly on cobalt. It is therefore an object of the present invention to provide an electroplating composition that can provide 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 is also an object of the present invention to provide an electroplating composition that can deposit a homogeneous, smooth and void-free copper layer on a non-copper metal seed, particularly a cobalt seed. For resistivity reasons, it is also beneficial that the copper layer deposited on the metal 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. Therefore, it is a further object of the present invention to provide a non-acidic electroplating composition that is capable of depositing a copper layer on a non-copper metal seed, particularly a cobalt seed, which copper layer has a low impurity level. Summary of the Invention The present invention provides a composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (ii) at least one branched C3to C8hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and (iii) in sum at least 3 hydroxy groups; and which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate, and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13. Another embodiment of the present invention is a composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising: (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (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 in sum at least 4 hydroxy groups; and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13. 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. 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 layer, the process comprising: (a) bringing a composition according to anyone of claims 1 to 10 into contact with the metal seed layer, (b) applying a current for a time sufficient to deposit a continuous layer of copper onto the metal seed layer of the recessed feature or to completely fill the recessed feature. The neutral or alkaline copper electroplating composition according to the invention provides a homogenous and smooth deposition in features on the nanometer and / or on the micrometer scale with copper on a metal seed layer, particularly a non-copper metal seed layer, more particularly on a cobalt seed layer. A further advantage of the present invention is that the deposited copper, either a completely filled recessed feature or a continuous thin copper layer, has a much lower impurity level. Detailed Description of the Invention The compositions according to the inventions comprise 1 to 500 mmol / l copper ions; at least one complexing agent as described below which is present in a molar concentration 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; optionally a buffer or abase to adjust the pH to a pH of from 6 to 13; and an aqueous solvent . The composition is non-acidic and has a pHfrom 6 to 13. Advantages of the subject non-acidic copper electroplating compositions are a strongly reduced corrosion of less noble metal seed layers, particularly Co seed layers, and a more homogeneous copper deposition on highly resistive seeds like thin ruthenium. If a component fits into multiple definitions of the constituents of the composition described herein, it is attributed to each constituent separately. For example, if the grain refiner or defect reducing agents are basic compounds or may even be sufficient to adjust the pH to the require range on its own without the need for another specific buffer or base, it is attributed to the base and the grain refiner or defefect reducing agent, respectively. Complexing agent The copper electroplating composition comprises an alkanolamine-type complexing agent to keep the copper ions in solution, to avoid its precipitation. Surprisingly, it was found that the subject complexing agents are particularly useful for reducing the corrosion of metal seed layers that are less noble than copper. According to a first embodiment the complexing agent is selected from an alkanolamine comprising: (i) at least one primary, secondary or tertiary amino group, and (ii) at least one branched C3 to C8 hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and (iii) in sum at least 3 hydroxy groups; and which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate According to another embodiment the complexing agent is selected from an alkanolamine comprising: (i) at least one primary, secondary or tertiary amino group, and (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 in sum at least 4 hydroxy groups. The complexing agent is present in a molar concentration 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. 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. In a preferred embodiment the alkanolamine is a compound of formula C1 or C2 wherein XC1, XC2are independently a C1 to C4 alkanediyl; XC3is a C1 to C4 alkanediyl; RC1is selected from H, a C1 to C4 alkyl, -XC1-OH, -XC1-COOH, and RC11; ; RC2, RC2’ are independently selected from H, a C1to C4alkyl, -XC1-OH, and -XC1-COOH; RC3, RC3’ are independently selected from H, a C1to C4alkyl, -XC1-OH, and -XC1-COOH; RC4is selected from H, a C1 to C4 alkyl, and -XC1-OH, and -XC1-COOH; XC11is a C1 to C6 alkanediyl. In another preferred embodiment the alkanolamine is selected from compounds of formula C1a, C1b, C1c, or C1d wherein XC1, XC2, XC3, XC4are independently a C1 to C3 alkanediyl; RC1is selected from H, a C1 to C4 alkyl, -XC1-OH, and RC11; RC2, RC2’ are independently selected from H, a C1 to C3 alkyl, and -XC1-OH; RC3, RC3’ are independently selected from a C1 to C3 alkyl and -XC1-OH; RC4is selected from H, a C1 to C4 alkyl, and -XC1-OH; XC11is a C1 to C4 alkanediyl; 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. 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. 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. Buffer / base The composition is nonacidic. The composition optionally comprises a buffer or a base (the base is also referred to as^“pH^adjustor”)^to adjust or maintain the pH at a pH of from 6 to 13 during the electroplating process. 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 or alkaline earth metal hydroxides. Most preferred bases are NaOH, KOH, and combinations thereof. Alkylammonium ions may for example be compounds of formula (N-RB1RB2RB3RB4)+in which RB1;RB2;RB3; and RB4independently selected from H and a C1-C4alkyl, provided that at least one of RB1;RB2;RB3; and RB4is a C1-C4alkyl. A C1-C4alkyl may be for example methyl, ethyl, n-propyl or n-butyl. Preferred alkylammonium ions are tetra- alkylammonium, for example tetramethylammonium, tetraethylammonium, tetrapropylammonium or tetrabutylammonium, methyltriethylammonium and ethyltrimethylammonium. Particularly preferred alkylammonium hydroxides are tetramethylammonium hydroxide or tetraethylammonium hydroxide.The buffer or base may be the same or different from the other component since some of theother components may already be sufficient to adjust the pH to the specified claim range. In oneembodiment no other buffer or base besides the other components are present. In anotherembodiment there is at least one other buffer or base besides the other components present inthe composition, i.e. the buffer or base is different from the other components, particularly thegrain refiner, the defect reducing agent, and a surfactant, if present.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(II) salt. If required, the buffer or based is present in a concentration of 0.001 to 5% by weight, preferably 0.005 to 3% by weight, most preferably 0.01 to 2% by weight. Defect reducing agent The copper electroplating bath may optionally comprise a defect reducing agent. A defect reducing agent is a chemical additive used to minimize or prevent the formation of defects in the plated metal layer. Defects can include voids, cracks, rough surfaces, nodules, or other imperfections that can negatively impact the quality and functionality of the plated material. Defect reducing agents typically work by modifying the electroplating process to promote a more uniform and smooth deposition of metal. They can help to improve thesurface morphology, reduce stress, enhance adhesion, and minimize the occurrence of defects. The use of thedefect reducing agents further provides very low resistivity and electromigration due to very low impurity levels of non-metals like carbon, oxygen, nitrogen, sulfur and chlorine in the plated copper layer. Some types of defect reducing agents used in metal electroplating include: - Alkynols or alkyne amines: These compounds, such as propargyl alcohol or propargylamine, can act as defect reducing agents by inhibiting the growth of metal grains during electroplating. - Certain arylalkylamines, such as benzylamine or phenethylamine, can also act as defect reducing agents. In a first preferred embodiment a defect of formula D1 (D1) is used. In the additives of formula D1, RD1is selected from XD-YD, wherein XDis a divalent spacer group selected from linear or branched C1 to C10 alkanediyl, linear or branched C2 to C10 alkenediyl, linear or branched C2 to C10 alkynediyl, and - XD6-(O-C2H3RD6)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 XD6is C1 to C6 alkanediyl, preferably methanediyl, ethandiyl, propanediyl or butanediyl, most preferably methanediyl or ethandiyl. Preferably XDis selected from linear or branched C1 to C6 alkanediyl, preferably from C1 to C4 alkanediyl. In a second preferred embodiment XDis 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. In a fifth preferred embodiment XDis 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. YDis a monovalent group and may be selected from ORD3, with RD3being selected from (i) H, (ii) C5 to C20 aryl, 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-RD6. In a preferred embodiment, RD3may be C1to C6alkyl or H. RD6may 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 O 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. In another preferred embodiment, RD3is selected from H to form a hydroxy group. In another preferred embodiment, RD3is selected from polyoxyalkylene groups of formula -(C2H3RD6-O)n-RD6. RD6is 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, RD3may be selected from C1to C10alkyl, preferably from C1to C6alkyl, most preferably methyl and ethyl. Furthermore, YDmay be an amine group NRD3RD4, wherein RD3and RD4are the same or different and may have the meanings of RD3described for ORD3above. In a preferred embodiment, RD3and RD4are selected from H to form an NH2 group. In another preferred embodiment, at least one of RD3and RD4, preferably both are selected from polyoxyalkylene groups of formula -(C2H3RD6-O)n-RSD6. RD6is independently selected from H and C1 to C5 alkyl, preferably from H and C1 to C4 alkyl, most preferably H, methyl or ethyl. In yet another preferred embodiment, at least one of RD3and RD4, preferably both are selected from C1 to C10 alkyl, preferably from C1 to C6 alkyl, most preferably methyl and ethyl. form a ring system, which may be interrupted by O or NRD7. RD7may be selected from Preferably the ring system is formed by two substituents RD3and RD4which 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. Furthermore, YDmay be a positively charged ammonium group N+RD3RD4RD5. RD3, RD4, RD5are the same or different and may have the meanings of RD3described for ORD3and NRD3RD4above. In a preferred embodiment RD3, RD4and RD5are independently selected from H, methyl or ethyl. In one embodiment at least one of RD3, RD4and RD5, preferably two, most preferably all, are selected from polyoxyalkylene groups of formula -(C2H3RD6-O)n-RD6. 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. In the additives of formula S1 RD2may be either RD1or RD3as described above. If RD2is RD1, RD1may be selected to form a symmetric compound (both RD1s are the same) or an asymmetric compound (the two RD1s are different). Particularly preferred aminoalkynes are those in which (a) RD1is XD-NRD3RD4and RD2is H; (b) RD1is XD-NRD3RD4and RD2is XD- NRD3RD4with XDbeing selected from linear C1to C4alkanediyl and branched C3 to C6 alkanediyl; Particularly preferred hydroxyalkynes or alkoxyalkynes are those in which (a) RD1is XD-ORD3and RD2is H; (b) RS1is XD-ORD3and RD2is XD-ORD3with XDbeing selected from linear C1to C4alkanediyl and branched C3to C6alkanediyl; Particularly preferred alkynes comprising an amino and a hydroxy group are those in which RS1is XD-ORD3, particularly XD-OH, and RS2is XD- NRD3RD4with XDbeing independently selected from linear C1to C4alkanediyl and branched C3to C6alkanediyl; The amine groups in the additives may be selected from primary (RD3, RD4is H) , secondary (RD3or RD4is H) and tertiary amine groups (RD3and RD4are both not H). 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. Particularly preferred specific primary aminoalkynes are: Particularly preferred specific secondary aminoalkynes are: Other preferred additives are those in which the rests RS3and RS4may together form a ring system, which is optionally interrupted by O or NRS3. Preferably, the rests RS3and RS4together form a C5 or C6 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. An example of such compounds is: It may be received by reaction of propargyl amine with formaldehyde and morpholine. Another preferred additive comprising a saturated heterocyclic system is: In this case RS3and RS4together a system interrupted by two NRS3groups, in which RS3is selected from CH2-C^C-H. This additive comprises three terminal triple bonds. The amino groups in the additives 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 additives are: Particularly preferred specific pure hydroxyalkynes are: Particularly preferred specific aminoalkynes comprising OH groups are: Also in this case the rests RS3and RS4may together form a ring system, which is optionally interrupted by O or NRS3. Preferably, the rests RS3and RS4together form a C5or C6bivalent 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. Examples for such compounds are: These may be received by reaction of propargyl alcohol with formaldehyde and piperidine or morpholine, respectively. By partial reaction with alkylating agents mixtures of additives 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. In a further embodiment, the additives may be substituted by SO3H (sulfonate) groups or COOH (carboxy) groups. Specific sulfonated additives may be but are not limited to butynoxy ethane sulfonic acid, propynoxy ethane sulfonic acid, 1,4-di-(^-sulfoethoxy)-2-butyne, 3-(^-sulfoethoxy)-propyne. In a second preferred embodiment a defect reducing agent of formula S1 may preferably be used, wherein RS1is (a) H or C1-C4alkyl; (b) a block poly(oxyethylene-co-C3-C4-oxyalkylene), a block poly(C3-C4-oxyalkylene-co-oxyethylene), or a random poly(oxyethylene-co-C3-C4-oxyalkylene), all having (i) a number average molecular mass Mw of from 500 to 5000 g / mol, and (ii) an oxyethylene content of from 8 to 98 % by weight, or (c) a polyoxyethylene having a number average molecular mass Mn of from 180 g / mol to 3500 g / mol; RS2, RS3, RS4are independently selected from RS1and RS5;XS1, XS2 are independently selected from a linear or branched C1 to C4 alkanediyl, a linear or branched C2 to C4alkenediyl, linear or branched C2to C4alkynediyl, and -XS6-(O-C2H3RS6)o-; RS6is H, methyl or ethyl; XS6is methanediyl, ethanediyl, propanediyl, or butanediyl; YSis phenylene, naphthylene or a divalent N-heterocyclic 5 or 6 membered ring system with one or two nitrogen atoms, all of which are unsubstituted or substituted by 1, 2 or 3 groups RS5; o integer from 1 to 6; p, q are independently 0 or 1; In a first alternative the amino substituent RS1in formula S1 is either H, i.e. it is an unsubstituted amino group, or it is a C1-C4 alkyl, preferably methyl, ethyl or propyl. Longer alkyl is generally possible but leads to a reduced solubility of the defect reducing agent. The defect reducing agents according to this first embodiment have a number average molecular mass Mnof from 500 to 5000 g / mol, preferably from 1000 to 4000 g / mol. In a second alternative RS1in formula S1 is either a block poly(oxyethylene-co-C3-C4-oxyalkylene), a block poly(C3- C4-oxyalkylene-co-oxyethylene), or a random poly(oxyethylene-co-C3-C4-oxyalkylene). The defect reducing agents according to this second embodiment have a number average molecular mass Mnof from 500 to 5000 g / mol, preferably from 1000 to 4000 g / mol. Furthermore, they have an oxyethylene content of from 8 to 98 % by weight, preferably from 10 to 70 % by weight, most preferably from 10 to 40 % by weight. As^used^herein,^“block^poly(oxyethylene-co-C3-C4-oxyalkylene)”^means^that^the^amino^group^is^first^substituted^by^a^ polyoxyethylene group (EO) followed by a poly(C3-C4-oxyalkylene) group (AO), further also referred to as –(EO)n- (AO)m.^In^contrast,^a^“block^poly(C3-C4-oxyalkylene-co-oxyethylene)”^means^that^the^amino^group^is^first^substituted^ by a poly(C3-C4-oxyalkylene) group (AO) followed by a polyoxyethylene group (EO), further also referred to as – (AO)m-(EO)n.^A^“random^poly(oxyethylene-co-C3-C4-oxyalkylene)”^is^a^copolymer^that^is^prepared^from^a^mixture^of^ ethylene oxide and the C3-C4-alkylene oxide, further also referred to as –EOn / POm. The oxyethylene content refers to the content of oxyethylene in relation to the sum of oxyethylene and the C2-C4-oxyalkylene in the RS1side chains. Preferred C3-C4-oxyalkylene groups are oxypropene (or oxypropylene) and oxybutene groups, that are received by reaction with propylene oxide or butene oxide, respectively. Preferably RS1is a block poly(oxyethylene-co-C3-C4-oxyalkylene) or a random poly(oxyethylene-co-C3-C4- oxyalkylene) having (i) a number average molecular mass Mn of from 1000 to 4000 g / mol, and (ii) an oxyethylene content of from 8 to 98 % by weight. In a third alternative the amino substituent RS1in formula S1 is a polyoxyethylene, i.e. an ethylene oxide homopolymer. The defect reducing agents according to this third embodiment have a number average molecular mass Mnof from 180 g / mol to 3500 g / mol, preferably of from 300 to 2500 g / mol, most preferably of from 400 to 1500 g / mol. Preferably RS1is a polyoxyethylene having a number average molecular mass Mnof from 300 g / mol to 2500 g / mol; The further amino substituents RS2, RS3, RS4are either the same as RS1or are RS5, preferably RS2, RS3, and RS4are the same as RS1. If different from RS1, RS5is a C1to C4alkyl, preferably methyl, ethyl or propyl; or RS5is a C1to C4alkoxy, preferably methoxy, ethoxy or propoxy.XS1, XS2 are independently selected from linear or branched C1 to C4 alkanediyl, linear or branched C2 to C4alkenediyl, linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-; In spacer groups -XS6-(O-C2H3RS6)o- o is an integer that may be in the range of from 1 to 6, preferably 1 to 4, most preferably 1, 2 or 3; RS6is H, methyl or ethyl, preferably H; and is methanediyl, ethanediyl, propanediyl, or butanediyl, preferably ethanediyl or propanediyl, most preferably ethanediyl. Preferred groups XS1, XS2are methanediyl, ethane-1,1-diyl and ethane-1,2-diyl, propanediyl-1,1-diyl, propanediyl-1,2- diyl, propanediyl-1,3-diyl, particularly methanediyl, ethane-1,1-diyl and ethane-1,2-diyl. If the spacer groups XS1or XS2are present, then p or q are 1, respectively. If the spacer groups XS1or XS2are not present, then p or q is 0. In a first embodiment p is 1 and q is 0. In another preferred embodiment p and q are both 1. The divalent aromatic group YSmay by phenylene, naphthylene or a divalent N-heterocyclic 5 or 6 membered ring system with one or two nitrogen atoms, all of which are unsubstituted or substituted by 1, 2 or 3 groups RS5. Preferred groups YSare phenylene, naphthylene or a divalent pyridine group. More preferably YSis 1,2-phenylene, 1,3-phenylene or 1,4-phenylene, most preferably 1,3-phenylene or 1,4-phenylene. In a preferred alternative the defect reducing agent is a compound of formula S2 wherein the substituents RS1,RS1,RS1,RS1, and RS5and spacers XS1and XS2may have the prescribed meanings and wherein the number of substituents n is 0, 1, or 2, preferably 0 or 1, most preferably 0. In formula S2 RS5is a C1 to C4 alkyl, preferably methyl, ethyl or propyl; or RS5is a C1 to C4 alkoxy, preferably methoxy, ethoxy, or propoxy. In one embodiment a single defect reducing agent according to the invention are used in the copper electroplating baths, which is preferred. In another embodiment two or more of the defect reducing agents are used in combination. In general, the defect reducing agents are preferably used in an amount of about 5 ppm to about 500 ppm, based on the total weight of the plating bath. Particularly suitable amounts of defect reducing agent useful in the present invention are 10 to 300 ppm, and more particularly 20 to 100 ppm. Other amounts may be used if needed. Grain refiner The copper electroplating composition may optionally comprise a grain refiner. Typical grain refiners are N-heteroaromatic compounds. They help to control the growth of copper grains, resulting in a finer grain structure. Particularly if used in combination with a defect reducing agent, very low resistivity and electromigration due to very low impurity levels of non-metals like carbon, oxygen, nitrogen, sulfur and chlorine in the plated copper layer can be achieved. Preferred grain refiners are those of formula G1a and G1b or salts thereof, wherein RG1is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, and CN; RG2is selected from one or more H, C1 to C4 carboxyl, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; and XG1is selected from C1 to C6 alkanediyl or a group -XG11-C(O)-O-XG12-; XG11is selected from a chemical bond or C1 to C4 alkandiyl; XG12is selected from a chemical bond or C1 to C4 alkandiyl; and wherein RG1or RG2,comprises at least one C1 to C4 carboxyl group, or group XG1is -XG11-C(O)-O-)-XG12-. In a first preferred embodiment the grain refiner is a compound of formula G1 or salts thereof, wherein RG1is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, and CN; RG2is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, H and CN; and XG1is a C1to C4alkanediyl; and wherein RG1or RG2comprises at least one C1to C4carboxyl group. Particularly preferred grain refiners of the first embodiment are those of formula G2a or G2b or salts thereof wherein RG21is selected from one or more H, C1 to C3 alkyl, C1 to C4 alkoxy, halogen, and CN; RG22is selected from one or more H, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; and XG1is methandiyl, ethanediyl, propanediyl or butanediyl. A particularly preferred grain refiner of formula G2b is 3-carboxy-1-penylmethylpyridinium (inner salt). In a second preferred embodiment the grain refiner is a compound of formula G1 or salts thereof, wherein RG1is selected from one or more H, C1 to C4 carboxyl, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; RG2is selected from one or more H, C1 to C4 carboxyl, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; and XG1is a group -XG11-C(O)-O-)-XG12-; XG11, XG12are independently selected from C1to C4alkandiyl. Particularly preferred grain refiners of the second embodiment are those of formula G3a, G3b, G3c, or salts thereof wherein RG31is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, and CN; RG32is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, C1to C6carboxy, halogen, and CN; and XG32is selected from a chemical bond or C1 to C4 alkandiyl. Particularly preferred grain refiners of formula G3b are 4-(Methoxycarbonyl)benzyl pyridine-3-carboxylate and benzyl pyridine-3-carboxylate. In general, the grain refiners are preferably used in an amount of about 5 ppm to about 500 ppm, based on the total weight of the plating bath. Particularly suitable amounts of defect reducing agent useful in the present invention are 10 to 300 ppm, and more particularly 20 to 100 ppm. Other amounts may be used if needed. 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. Other Additives 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. In a preferred embodiment, the composition is free of any of such compounds. 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. 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. In a preferred embodiment, the composition is free of any polyethyleneimine or any sulfur-containing additives or both. In a preferred embodiment, the composition is free of any non-ionic surfactants, particularly surfactants. Composition 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, the complexing agent, optionally a defect reducing agent, optionally a grain refiner, optionally a base or a buffer, optionally an electrolyte, optionally further additives as described herein, and an aqueous solvent. The plating baths are aqueous solutions.^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. The source of the metal ions (i.e. the copper ions and the corresponding counter ions) 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. Generally, besides copper, the electroplating composition may comprise an alloying metal in amount of below 0.1 g / l, preferably below 0.01 g / l, most preferably no alloying metal. 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. Typical non-alloying metals are those of groups I metals like sodium or potassium or of group II metals like magnesium or calcium. 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 or below any additional cations, particularly metal ions, are disadvantageous since a lower conductivity of the composition leads to a more equal deposition into the feature. 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 reduce the copper ions to metallic copper. It is preferred that the source of copper ions 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. The copper ion source may be used in the present invention in any amount that provides sufficient metal ions for electroplating on a substrate. In the intended applications copper is typically present in an amount in the range of from about 1 to about 500 mmol / l of the plating solution. Preferred copper concentrations are 2 to 300 mmol / l, more preferred 3 to 100 mmol / l, even more preferred 4 to 50, most preferred 5 to 20 mmol / l. Lower concentrations of from about 1 to about 50 mmol / l are advantageous in view of cobalt corrosion and homogenous copper layer deposition. The pH of the electroplating composition is non-acidic, i.e. neutral or basic. The pH is in the range of from about 6 to about 13, preferably from about 6.5 to about 12, more preferably from about 7 to about 10, most preferably from about 7 to about 9. The electroplating composition should be free of any cyanide ions. In a preferred embodiment the composition is essentially free of 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). 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 defect reducing agent or the optional grain refiner. Particularly for depositiong 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. In a preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) 1 to 500 mmol / l of a source of copper ions and the corresponding counter anions of the copper ions source; (b) the alkanolamine in a molar concentration 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; (d) optionally a buffer or base to adjust the pH to a pH of from 6 to 13, preferably from 7.5 to 12; (e) optionally a grain refiner of formula G1a or G1b; and (f) optionally a defect reducing agent of formula D1 or formula S1; (g) optionally a non-ionic surfactant; and (h) water. In another preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) 1 to 500 mmol / l of a source of copper ions; (b) the alkanolamine in a molar concentration 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; (d) 0 or 0.001 to 5% by weight of a base to adjust the pH to a pH of from 6 to 13; (e) 0 or 0.5 ppm to 10000 ppm of a grain refiner of formula G1a or G1b; and (f) 0 or 0.1 ppm to 30000 ppm of a defect reducing agent of formula D1 or formula S1; (g) 0 or 0.1 ppm to 30000 ppm of a non-ionic surfactant; and (h) water. In yet another preferred embodiment the electroplating composition comprises, essentially consists of, or consists of (a) 1 to 500 mmol / l of a source of copper ions; (b) the alkanolamine in a molar concentration 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; (d) 0 or 0.001 to 5% by weight of a base to adjust the pH to a pH of from 6 to 13; (e) 0 or 0.5 ppm to 10000 ppm of a grain refiner of formula G1a or G1b; and (f) 0 or 0.1 ppm to 30000 ppm of a defect reducing agent of formula D1 or formula S1; (h) water. Process According to one embodiment of the present invention a neutral or alkaline 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 thin layer of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tantalum, or alloys thereof, preferably of cobalt or ruthenium, most preferably of cobalt. An electrolytic bath comprising copper ions and at least one additive according to the invention is prepared. A dielectric substrate comprising the metal 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. 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.In order to allow a deposition on a substrate comprising a dielectric surface, a thin metal layer (also referred to herein as metal seed layer) needs to be applied to the surface. Such seed layer may consist of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tantalum, or alloys comprising such metals. Preferably the seed consist of cobalt or ruthenium. In a particular embodiment the seed consists of cobalt. In another particular embodiment the seed consists of ruthenium. The seed layers are described in detail e.g. in US20140183738 A. 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, a 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. 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. In another embodiment a thin layer 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 non-copper metal seed layer, particularly a cobalt seed layer on which the thin copper layer is electrodeposited. As^used^herein,^“thin copper layer”^or^“copper^layer”^means a continuous thin layer of the respective metal having a thickness of about 5 nm to about 15 nm, or even thinner, depending on the aperture size of the respective recessed feature. The aperture size according to the present invention means the smallest diameter or free distance of a feature before plating, i.e. after non-copper metal seed^deposition.^The^terms^“aperture”^and^“opening"^are^used^herein^ synonymously. 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. 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, suchas 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. A pulse current 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. 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. In one embodiment the recessed feature is completely filled with copper by using a composition as described herein. In another embodiment a continuous thin layer of copper is deposited onto the metal seed of the recessed feature. The copper may be deposited in recessed features according to the present invention without substantially forming voids within the metal deposit. As used herein, void-free deposition 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. Or it may be achieved by void-free conformal plating on the surface of the semiconductor substrate, including the recessed features. As used herein, the term "substantially void-free", means that at least 95% of the plated recessed features are void- free. Preferably that at least 98% of the plated recessed features are void-free, mostly preferably all plated recessed features 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. Plating equipment for plating semiconductor substrates is well known. Plating equipment comprises an electroplating tank which holds the 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 copper or, preferably, other non- copper 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. 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. 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. While the process of the present invention has been generally described with reference to interconnect manufacture, it will be appreciated that the present invention may be useful in any electrolytic process where a homogeneous, smooth and void-free copper layer is desired. Suitable processes, particularly for thin copper layer deposition or copper layer repair or copper layer enhancement, include packaging, in particular copper electrodeposition into through silicon vias (TSV) as well as for bump plating on wafers. Another application is the 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. Embodiments The following embodiments are particularly preferred separately and in combination with any other embodiment: 1. A composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (ii) at least one branched C3to C8hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and (ii) in sum at least 3 hydroxy groups; and which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate, and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13. 2. The composition according to embodiment 1, wherein the alkanolamine comprises at least 4 hydroxy groups. 3. The composition according to anyone of the preceding embodiments, wherein the pH is from 6.5 to 12, preferably from 7 to 11, most preferably from 7.5 to 10. 4. The composition according to anyone of the preceding embodiments, wherein the alkanolamine is a compound of formula C1 wherein XC1, XC2are independently a C1 to C4 alkanediyl; RC1is selected from H, a C1 to C4 alkyl, -XC1-OH, -XC1-COOH, and RC11; RC11is ; are a C4alkyl, -XC1-OH, and -XC1-COOH; RC3, RC3’ are independently selected from H, a C1to C4alkyl, -XC1-OH, and -XC1-COOH; RC4is selected from H, a C1to C4alkyl, and -XC1-OH, and -XC1-COOH; XC11is a C1 to C6 alkanediyl. The composition according to embodiment 4, wherein the alkanolamine is selected from compounds of formula C1a, C1b, C1c, or C1d ; wherein XC1, XC2, XC3, XC4are independently a C1 to C3 alkanediyl; RC1is selected from H, a C1 to C4 alkyl, -XC1-OH, and RC11; RC2, RC2’ are independently selected from H, a C1 to C3 alkyl, and -XC1-OH; RC3, RC3’ are independently selected from a C1 to C3 alkyl and -XC1-OH; RC4is selected from H, a C1 to C4 alkyl, and -XC1-OH; XC11is a C1to C4alkanediyl; 6. The composition according to embodiment 5, wherein the alkanolamine is selected from bis(2- hydroxyethyl)amino-tris(hydroxymethyl)methane, tris(hydroxymethyl)aminomethane or its salts, 1,3- bis(tris(hydroxymethyl)methylamino)propane, and N-[1,3-Dihydroxy-2-(hydroxymethyl)propan-2-yl]glycine or its salts. 7. The composition according to anyone of the preceding embodiments, wherein the alkanolamine is present in an amount from 2 to 100 mmol / l, preferably from 5 to 50 mmol / l. 8. The composition according to anyone of the preceding embodiments, which essentially does not comprise any alloying metal ions. 9. The composition according to anyone of the preceding embodiments, wherein the buffer or base is a hydroxide. 10. The composition according to anyone of the preceding embodiment, comprising a grain refiner selected from a N-heteroaromatic compound, particularly a compound of formula G1a or G1b, or salts thereof wherein RG1is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, and CN; RG2is selected from one or more H, C1to C4carboxyl, C1to C4alkyl, C1to C6alkoxy, halogen, and CN; and XG1is selected from C1 to C6 alkanediyl or a group -XG11-C(O)-O-XG12-; XG11is selected from a chemical bond or C1 to C4 alkandiyl; XG12is selected from a chemical bond or C1 to C4 alkandiyl; and wherein RG1or RG2,comprises at least one C1 to C4 carboxyl group, or group XG1is -XG11-C(O)-O-)-XG12-. The composition according to anyone of the preceding embodiments, comprising a defect reducing agent selected from (a) an alkynol or an alkyne amine, particularly a compound of formula D1 (D1) and (b) an arylalkylamine, particularly a compound of formula S1, wherein RD1is selected from XD-YD; RD2is selected from RD1and RD3; XDis selected from linear or branched C1to C10alkanediyl, linear or branched C2to C10alkenediyl, linear or branched C2to C10alkynediyl, and -XD6-(O-C2H3RD6)m-; YDis selected from ORD3, NRD3RD4, N+RD3RD4RD5and NH-(C=O)-RD3; RD3, RD4, RD5are 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) -(C2H3RD6-O)n-RS6, and wherein RD3and RD4may together form a ring system, which may be interrupted by O or NRD7; XD6is C1 to C6 alkanediyl; m, n are integers independently selected from 1 to 30; RD6is selected from H and C1 to C5 RD7is selected from RD6and - RS1is (a) H or C1-C4 alkyl; (b) a block poly(oxyethylene-co-C3-C4-oxyalkylene), a block poly(C3-C4-oxyalkylene-co-oxyethylene), or a random poly(oxyethylene-co-C3-C4-oxyalkylene), all having (i) a number average molecular mass Mwof from 500 to 5000 g / mol, and (ii) an oxyethylene content of from 8 to 98 % by weight, or (c) a polyoxyethylene having a number average molecular mass Mn of from 180 g / mol to 3500 g / mol; RS2, RS3, RS4are independently selected from RS1and RS5; RS5is selected from a C1 to C4 alkyl and a C1 to C4 alkyoxy; XS1, XS2are independently selected from a linear or branched C1 to C4 alkanediyl, a linear or branched C2 to C4 alkenediyl, a linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-; RS6is H, methyl or ethyl; XS6is methanediyl, ethanediyl, propanediyl, or butanediyl; YSis phenylene, naphthylene or a divalent N-heterocyclic 5 or 6 membered ring system with one or two nitrogen atoms, all of which are unsubstituted or substituted by 1, 2 or 3 groups RS5; o integer from 1 to 6; p, q are independently 0 or 1; The composition according to anyone of the preceding embodiments, essentially consisting of (a) 1 to 500 mol / l copper ions and the corresponding counter ions; (b) the alkanolamine in a molar concentration 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; (d) optionally a base to adjust the pH to a pH of from 7 to 13; (e) optionally a grain refiner of formula G1a or G1b; and (f) optionally a defect reducing agent of formula D1 or S1; (g) optionally a non-ionic surfactant; and (h) rest water. The composition according to embodiment 12, consisting of (a) 1 to 500 mol / l of a soluble copper salt; (b) the alkanolamine in a molar concentration 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; (d) 0 or 0.01 to 3% by weight of a base to adjust the pH to a pH of from 7 to 13; (e) 0 or 5 to 500 ppm of a grain refiner of formula G1a or G1b; (f) 0 or 5 to 500 ppm of a defect reducing agent of formula D1 or S1 (g) 0 or 0.001 to 1% by weight of a non-ionic surfactant; and (h) rest water. Use of a composition according to anyone of the preceding embodiments for depositing copper on a semiconductor substrate comprising recessed features having an aperture size 50 nanometers or less, particularly 15 nm or less and comprising a metal seed layer. Use of a composition according to anyone of the embodiments 1 to 13 for depositing copper on a semiconductor substrate comprising recessed features having an aperture size 1 to 100 micrometer, having an aspect ratio of 4 or more, and comprising a metal seed layer. 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 layer, the process comprising (a) bringing a composition according to anyone of embodiments 1 to 10 into contact with the metal seed layer, (b) applying a current for a time sufficient to deposit a continuous layer of copper onto the metal seed layer of the recessed feature or to completely fill the recessed feature. The process according to embodiments 16, wherein the metal seed layer consists of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tantalum, and alloys thereof. A composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (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 (in sum) at least 4 hydroxy groups; and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13. The composition according to embodiment 18, wherein the alkanolamine is a compound of formula C2 wherein XC1, XC2, XC1’, XC2’are independently a C1 to C4 alkanediyl; to C4 hydroxyalkyl, and RC11; XC11is a C1 to C6 alkanediyl; and wherein (a) at least one of the groups RC1, XC1, or XC2is substituted by carboxy, sulfonate or sulfate, or (b) the in sum of hydroxy groups in the alkanolamine is at least 4. 20. The composition according to embodiment 19, wherein the alkanolamine is selected from N,N-Bis(2- hydroxyethyl)glycine, 3-[N-N-bis(hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, and N,N,N',N'- tetrakis(2-hydroxyethyl)ethylenediamine. 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. The following examples shall further illustrate the present invention without restricting the scope of this invention. Examples For the cobalt corrosion experiments a blanket wafer substrate was used bearing a Co seed. The Co seed thickness was measured by XRF before and after the corrosion experiment. Example 1 to 7: Co corrosion experimentsA plating bath was prepared by combining DI water, 0.5 g / l copper as copper sulfate, 16 mmol / l of a complexingagent in a molar ratio of 2:1 to Cu, and a solution of sodium hydroxide or potassium hydroxide to adjust to the specified pH. A blanket wafer substrate bearing a cobalt seed layer was brought into contact with the described plating bath at 25 °C without applying any current at 300 RPM. After 90 s the wafer substrate was removed and rinsed with water at pH 9-10 and dried. The following complexing agents were used: CA1 BisTris: bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane CA2 Tris / Tris-Base: tris(hydroxymethyl)aminomethane or its salt (*HCl) CA3 Bis Tris Propane: 1,3-bis(tris(hydroxymethyl)methylamino)propane CA4 DIPSO: 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid CA5 EDA + 4 EO: Ethylene diamine ethoxylated with 4 mol ethylene oxide per mol ethylene diamine CA6 Tricine: N-[1,3-Dihydroxy-2-(hydroxymethyl)propan-2-yl]glycine CA7 Bicine: N,N-Bis(2-hydroxyethyl)glycine The results of the corrosion experiments as described above are shown in Table 1 which provides the loss of Co thickness with the individual complexing agent. The reduction of Co thickness due to corrosion was determined by XRF thickness measurement before and after the corrosion experiment. Table 1 Reduction of Co thickness Example Complexing agent Conc. [mmol / l] pH [nm] 1 BisTris 16 9 0.00 2 Tris-Base 16 11 0.13 3 Bis Tris Propane 16 9 1.25 4 DIPSO 16 11 0.52 5 EDA + 4 EO 16 11 0.58 6 Tricine 16 9 0.87 7 Bicine 16 11 0.53 Table 1 shows that the complexing agents are capable of effectively avoid Co corrosion. A proper pH needs to be selected to get best results depending on the pKsvalues of the respective complexing agent.

Claims

Claims 1. A composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (ii) at least one branched C3to C8hydroxyalkyl group bound to the at least one amino group, the hydroxyalkyl group comprising at least two terminal hydroxy groups; and (iii) in sum at least 3 hydroxy groups; and which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate, and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13.

2. The composition according to claim 1, wherein the alkanolamine comprises at least 4 hydroxy groups.

3. The composition according to anyone of the preceding claims, wherein the pH is from 6.5 to 12, preferably from 7 to 11, most preferably from 7.5 to 10.

4. The composition according to anyone of the preceding claims, wherein the alkanolamine is a compound of formula C1wherein XC1, XC2are independently a C1to C4alkanediyl; -XC1-COOH, and RC11;; RC2, RC2’ are independently selected from H, a C1 to C4 alkyl, -XC1-OH, and -XC1-COOH; RC3, RC3’ are independently selected from H, a C1 to C4 alkyl, -XC1-OH, and -XC1-COOH;RC4is selected from H, a C1 to C4 alkyl, and -XC1-OH, and -XC1-COOH; XC11is a C1to C6alkanediyl.

5. The composition according to claim 4, wherein the alkanolamine is selected from compounds of formula C1a, C1b, C1c, or C1dwherein XC1, XC2, XC3, XC4are independently a C1 to C3 alkanediyl; RC1is selected from H, a C1to C4alkyl, -XC1-OH, and RC11; RC2, RC2’ are independently selected from H, a C1to C3alkyl, and -XC1-OH; RC3, RC3’ are independently selected from a C1to C3alkyl and -XC1-OH; RC4is selected from H, a C1 to C4 alkyl, and -XC1-OH; XC11is a C1 to C4 alkanediyl;6. The composition according to claim 5, wherein the alkanolamine is selected from 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.

7. The composition according to anyone of the preceding claims, wherein the alkanolamine is present in an amount from 2 to 100 mmol / l, preferably from 5 to 50 mmol / l.

8. The composition according to anyone of the preceding claims, which essentially does not comprise any alloying metal ions.

9. The composition according to anyone of the preceding claims, wherein the base is a hydroxide.

10. The composition according to anyone of the preceding claims, comprising a grain refiner selected from a N- heteroaromatic compound, particularly a compound of formula G1a or G1b, or salts thereofwherein RG1is selected from one or more H, C1 to C4 carboxyl, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; RG2is selected from one or more H, C1 to C4 carboxyl, C1 to C4 alkyl, C1 to C6 alkoxy, halogen, and CN; and XG1is selected from C1 to C6 alkanediyl or a group -XG11-C(O)-O-XG12-; XG11is selected from a chemical bond or C1 to C4 alkanediyl; XG12is selected from a chemical bond or C1to C4alkanediyl; and wherein RG1or RG2,comprises at least one C1to C4carboxyl group, or group XG1is -XG11-C(O)-O-)-XG12-.

11. The composition according to anyone of the preceding claims, comprising a defect reducing agent selected from (a) an alkynol or an alkyne amine, particularly a compound of formula D1 (D1)wherein RD1is selected from XD-YD; RD2is selected from RD1and RD3; XDis selected from linear or branched C1to C10alkanediyl, linear or branched C2to C10alkenediyl, linear or branched C2to C10alkynediyl, and -XD6-(O-C2H3RD6)m-; YDis selected from ORD3, NRD3RD4, N+RD3RD4RD5and NH-(C=O)-RD3; RD3, RD4, RD5are 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) -(C2H3RD6-O)n-RS6, and wherein RD3and RD4may together form a ring system, which may be interrupted by O or NRD7; XD6is C1 to C6 alkanediyl; m, n are integers independently selected from 1 to 30; RD6is selected from H and C1to C5alkyl; RD7is selected from RD6and - ; ; and (b) an arylalkylamine, particularly a compound of formula S1,wherein RS1is (a) H or C1-C4 alkyl; (b) a block poly(oxyethylene-co-C3-C4-oxyalkylene), a block poly(C3-C4-oxyalkylene-co- oxyethylene), or a random poly(oxyethylene-co-C3-C4-oxyalkylene), all having (i) a number average molecular mass Mw of from 500 to 5000 g / mol, and (ii) an oxyethylene content of from 8 to 98 % by weight, or (c) a polyoxyethylene having a number average molecular mass Mn of from 180 g / mol to 3500 g / mol; RS2, RS3, RS4are independently selected from RS1and RS5; RS5is selected from a C1to C4alkyl and a C1to C4alkyoxy; XS1, XS2 are independently selected from a linear or branched C1 to C4 alkanediyl, a linear or branchedC2 to C4 alkenediyl, a linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-; RS6is H, methyl or ethyl; XS6is methanediyl, ethanediyl, propanediyl, or butanediyl; YSis phenylene, naphthylene or a divalent N-heterocyclic 5 or 6 membered ring system with one or two nitrogen atoms, all of which are unsubstituted or substituted by 1, 2 or 3 groups RS5;o integer from 1 to 6; p, q are independently 0 or 1.

12. The composition according to anyone of the preceding claims, essentially consisting of (a) 1 to 500 mmol / l copper ions and corresponding counter ions; (b) the alkanolamine in a molar concentration 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; (d) optionally a buffer or base to adjust the pH to a pH of from 7.5 to 12; (e) optionally a grain refiner of formula G1a or G1b; and (f) optionally a defect reducing agent of formula D1 or formula S1; (g) optionally a non-ionic surfactant; and (h) rest water.

13. The composition according claim 12, consisting of (a) 1 to 500 mol / l of a soluble copper salt; (b) the alkanolamine in a molar concentration 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; (d) 0 or 0.01 to 3% by weight of a buffer or base to adjust the pH to a pH of from 7 to 13; (e) 0 or 5 to 500 ppm of a grain refiner of formula G1a or G1b; (f) 0 or 5 to 500 ppm of a defect reducing agent of formula D1 or S1 (g) 0 or 0.001 to 1% by weight of a non-ionic surfactant; and (h) rest water.

14. 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 of 50 nanometers or less, particularly 15 nm or less and comprising a metal seed layer.

15. Use of a composition according to anyone of claims 1 to 13 for depositing copper on a semiconductor substrate comprising recessed features having an aperture size 1 to 100 micrometer, having an aspect ratio of 4 or more, and comprising a metal seed layer.

16. 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 layer, the process comprising (a) bringing a composition according to anyone of claims 1 to 13 into contact with the metal seed layer, (b) applying a current for a time sufficient to deposit a continuous layer of copper onto the metal seed layer of the recessed feature or to completely fill the recessed feature.

17. The process according to claims 16, wherein the metal seed layer consists of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, tantalum, and alloys thereof.

18. A composition for electrodepositing copper on a semiconductor substrate comprising recessed features, the recessed features comprising a metal seed layer, the composition comprising (a) 1 to 500 mmol / l copper ions; (b) a complexing agent selected from an alkanolamine comprising (i) at least one primary, secondary or tertiary amino group, and (ii) at least two, preferably three C3 to C8 hydroxyalkyl groups bound to the at least one amino group; and (iii) at least one carboxy, sulfonate or sulfate group or in sum at least 4 hydroxy groups; and which is present in a molar concentration 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; (c) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; and (d) an aqueous solvent; wherein the pH of the composition is from 6 to 13.

19. The composition according to claim 18, wherein the alkanolamine is a compound of formula C2wherein XC1, XC2, XC1’, XC2’are independently a C1 to C4 alkanediyl; RC1is selected from a C1 to C4 alkyl or a C1 to C4 hydroxyalkyl, and RC11;; XC11is a C1to C6alkanediyl; and wherein (a) at least one of the groups RC1, XC1, or XC2is substituted by carboxy, sulfonate or sulfate, or (b) the in sum of hydroxy groups in the alkanolamine is at least 4.

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