Non-acidic composition for copper electroplating comprising a defect reduction agent

Abstract

The present invention provides a composition for depositing copper on a semiconductor substrate, the composition comprising (a) copper ions; (b) a defect reducing agent of formula S1 or S3 (c) a complexing agent; and (d) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; wherein RS1 is (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 Mn 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, RS4 are independently selected from RS1 and RS5; RS5 is selected from a C1 to C4 alkyl and a C1 to C4 alkyoxy; XS1, XS2 are 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-; XS3 is a linear or branched C1 to C8 alkanediyl, a linear or branched C2 to C8 alkenediyl, a linear or branched C2 to C8 alkynediyl, and -XS6-(O-C2H3RS6)o-; RS6 is H, methyl or ethyl; XS6 is methanediyl, ethanediyl, propanediyl, or butanediyl; YS is phenylene, naphthylene or a divalent aromatic 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; 231209WO01 36 ZS is a monovalent aromatic N-heterocyclic 5 or 6 membered ring system comprising 1, 2, or 3 nitrogen atoms, and which monovalent aromatic N-heterocyclic 5 or 6 membered ring system is unsubstituted or substituted by 1, 2 or 3 groups RS5; o integer from 1 to 6; p, q are independently 0 or 1; wherein the pH of the composition is from 6 to 13.

Description

[0001] Non-acidic composition for copper electroplating comprising a defect reduction agent

[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. WO 2022 / 012932 discloses an acidic bromide containing copper electroplating bath.

[0009] 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.

[0010] Also alkaline 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'-bipy ridine, imidazole and an electrochemically inert cation selected from the group consisting of cesium (Cs2+), 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. WO 2023 / 126259 discloses a composition for non-acidic copper electroplating on a metal seed comprising copper ions; an alkynol or alkyne amine additive, a complexing agent; and optionally a buffer or base to adjust the pH to a pH of from 7 to 13.

[0011] US 2023265576 A1 discloses an acidic aqueous composition for copper electroplating that comprises (a) copper ions; (b) bromide ions; and (c) at least one additive of formula wherein

[0012] Xs1is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by 0, S or NRS4°;

[0013] RS1is a monovalent

[0014] (a) poly(oxy(C3 to Ce )alkylene)-block-poly(oxyethylene) group which is bound to the N-atom by the poly(oxy(C3 to Ce )alkylene part, or

[0015] (b) a poly(oxyethylene)-block-poly(oxy(C3 to Ce )alkylene)-block-poly(oxyethylene), which both have a poly(oxyethylene) content of from 5 to 30 % by weight;

[0016] RS2, RS3, RS4

[0017] (a) are selected from H, RS1, RS40, or

[0018] (b) RS3and an adjacent group RS4or, if n>2, two adjacent groups RS4may together form a divalent group Xs3;

[0019] RS4° is selected from (a) linear or branched C1-C20 alkyl, which may optionally be substituted by hydroxy, alkoxy or alkoxycarbonyl, and (b) linear or branched C1-C20 alkenyl, which may optionally be substituted by hydroxyl, alkoxy or alkoxycarbonyl;

[0020] Xs3is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by 0, S or NRS4°; and n is an integer of from 1 to 6.

[0021] Regarding corrosion of a non-copper metal seed, particularly of a cobalt seed, there is still the need for improvements.

[0022] 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. 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. It is also an object of the present invention to provide a copper electroplating composition that shows low corrosion of a non-copper metal seed, particularly a cobalt seed that is bromide ion free.

[0023] 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, 0, 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.

[0024] Summary of the Invention

[0025] The present invention provides a copper electroplating bath that may generally be used in two ways:

[0026] 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

[0027] 2. With the bath a direct void-free filling, ideally a bottom-up filling, of the recessed features may also be achieved.

[0028] Therefore, the present invention provides a composition for depositing copper on a semiconductor substrate, the composition comprising

[0029] (a) copper ions;

[0030] (b) a defect reducing agent of formula S1 or S3

[0031] (c) a complexing agent; and

[0032] (d) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; wherein RS1is

[0033] (a) H or C1-C4 alkyl;

[0034] (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

[0035] (i) a number average molecular mass Mnof from 500 to 5000 g / mol, and

[0036] (ii) an oxyethylene content of from 8 to 98 % by weight, or

[0037] (c) a polyoxyethylene having a number average molecular mass Mnof from 180 g / mol to 3500 g / mol;

[0038] RS2, RS3, RS4are independently selected from RS1and RS5;

[0039] RS5is selected from a Ci to C4 alkyl and a Ci to C4 alkyoxy;

[0040] Xs1, Xs2are independently selected from a linear or branched Ci to C4 alkanediyl, a linear or branched C2 to C4 alkenediyl, a linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-;

[0041] Xs3is a linear or branched Ci to Ca alkanediyl, a linear or branched C2 to Ca alkenediyl, a linear or branched C2 to C8alkynediyl, and -XS6-(O-C2H3RS6)o-;

[0042] RS6is H, methyl or ethyl;

[0043] Xs6is methanediyl, ethanediyl, propanediyl, or butanediyl;

[0044] Ysis phenylene, naphthylene or a divalent aromatic 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;

[0045] Zsis a monovalent aromatic N-heterocyclic 5 or 6 membered ring system comprising 1 , 2, or 3 nitrogen atoms and which aromatic N-heterocyclic 5 or 6 membered ring system is unsubstituted or substituted by 1 , 2 or 3 groups RS5;

[0046] 0 integer from 1 to 6; p, q are independently 0 or 1 ; wherein the pH of the composition is from 6 to 13.

[0047] 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.

[0048] 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

[0049] (a) bringing a composition as described herein into contact with the metal seed,

[0050] (b) applying a current for a time sufficient to deposit a continuous seed of copper onto the surface of the recessed feature or to partially or completely fill the recessed feature with copper. The neutral or alkaline 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.

[0051] Brief description of the Figures

[0052] Figs. 1 to 5 show REM images of electrodeposited copper films that were used for the optical classification according to examples 2.

[0053] Detailed Description of the Invention

[0054] The compositions according to the inventions comprise copper ions, and an additive of formula S1 as described below (also referred to herein as “defect reducing agent”).

[0055] 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 a defect reducing agent in the plating bath.

[0056] Defect reducing agent

[0057] It was found that the additives of formula S1 or S3 are particularly useful additives for neutral or alkaline 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. In a first embodiment 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 may have a number average molecular mass Mnof from 400 to 8000 g / mol, preferably 500 to 5000 g / mol, more preferably from 1000 to 4000 g / mol.

[0058] In a second embodiment 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 may have a number average molecular mass Mnof from 400 to 8000 g / mol, preferably 500 to 5000 g / mol, more 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.

[0059] 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.

[0060] Preferred C3-C4-oxyalkylene groups are oxypropene (or oxypropylene) and oxybutene groups, that are received by reaction with propylene oxide or butene oxide, respectively.

[0061] Preferably RS1is a block poly(oxyethylene-co-C3-C4-oxyalkylene) or a random poly(oxyethylene-co-C3-C4- oxyalkylene) having

[0062] (i) a number average molecular mass Mnof from 800 to 8000 g / mol, particularly 1000 to 4000 g / mol, and (II) an oxyethylene content of from 8 to 98 % by weight.

[0063] In a third embodiment the amino substituent RS1in formula S1 is a polyoxyethylene, i.e. an ethylene oxide homopolymer. The defect reducing agents according to this third embodiment may 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 Ci to C4 alkyl, preferably methyl, ethyl or propyl; or RS5is a Ci to C4 alkoxy, preferably methoxy, ethoxy or propoxy.

[0064] Xs1, Xs2are independently selected from linear or branched Ci to C4 alkanediyl, linear or branched C2 to C4 alkenediyl, linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-. Preferably Xs1and / or Xs2are linear. In spacer groups -XS6-(O-C2H3RS6)o- 0 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.

[0065] Preferred groups Xs1, Xs2are methanediyl, ethane-1 ,1 -diyl and ethane-1 ,2-diyl, propane-1 ,1 -diyl, propane-1 , 2-diyl, propane-1 , 3-diyl, particularly methanediyl, ethane-1 , 1 -diyl and ethane-1 , 2-diyl.

[0066] If in formula S1 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 . Preferably p, q, or both p and q are 1 .

[0067] 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.

[0068] In formula S3 Zsmay be a monovalent aromatic N-heterocyclic 5 or 6 membered ring system comprising 1 , 2, or 3 nitrogen atoms. The monovalent aromatic N-heterocyclic 5 or 6 membered ring system may be unsubstituted or substituted by 1 , 2 or 3 groups RS5, preferably unsubstituted. Preferably Zscomprises two N atoms.

[0069] In formula S3 Xs3may be a linear or branched C2 to Ca alkanediyl, a linear or branched C2 to Ca alkenediyl, a linear or branched C2 to Ca alkynediyl, and -XS6-(O-C2H3RS6)o-. Preferably Xs3is linear. In spacer groups -XS6-(O-C2H3RS6)o- 0 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 propanediyl.

[0070] Preferred groups Xs3are ethane-1 , 2-diyl, propane-1 , 2-diyl, propane-1 , 3-diyl, butane-1 ,2-diyl, butane -1 , 3-diyl, butane -1 ,4-diyl, particularly ethane-1 , 2-diyl, propane-1 , 3-diyl, and butane -1 ,4-diyl. The monovalent aromatic N-heterocyclic 5 or 6 membered ring system Zsmay be bound to the bridging group Xs3via the one or mor N atoms or via a C atom.

[0071] In a preferred embodiment the defect reducing agent of formula S1 is a compound of formula S2 wherein the substituents RS1, RS2, RS3, RS4, 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.

[0072] In formula S2 RS5is a Ci to C4 alkyl, preferably methyl, ethyl or propyl; or RS5is a Ci to C4 alkoxy, preferably methoxy, ethoxy, or propoxy.

[0073] Particularly preferred compounds according to formula S2 are polyalkoxylates of 1 ,3-xylylene diamine (1,3- bis(aminomethyl)benzene) or 1 ,4-xylylene diamine (1 ,4-bis(aminomethyl)benzene), 1 ,3-bis(aminoethyl)benzene, 1 ,4- bis(aminoethyl)benzene, 1 ,3-bis(aminopropyl)benzene, and 1,4-bis(aminopropyl)benzene,.

[0074] In a preferred embodiment the defect reducing agent of formula S3 are compounds of formula S4, S5 or S6 wherein the substituents RS1, RS3, and RS5and spacer Xs1may have the prescribed meanings and wherein the number of substituents n is 0, 1 , or 2, preferably 0 or 1 , most preferably 0.

[0075] Particularly preferred compounds according to formula S4 are polyalkoxylates of 1 H-lmidazole-1 -propanamine, 1 H- lmidazole-2-propanamine, 1 H-lmidazole-5-propanamine, and 2,2’-[[2-(1 H-l midazole-4-yl)ethyl]imino]bis-ethanol.

[0076] A particularly preferred compound according to formula S5 is a polyalkoxylate of 1 H-Pyrrole-1-propanamine.

[0077] Particularly preferred compounds according to formula S6 are polyalkoxylates of 2-Picolylamine, 3-Picolylamine, 4- Picolylamine, 2,6-Pyridinedimethanamine, 2,4-Pyridinedimethanamine, and 4-(3-aminopropyl)-4H-1 ,2,4-triazole.

[0078] 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.

[0079] In general, the defect reducing agents of the invention are preferably 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. Also other amounts may be used if needed.

[0080] Complexing agent

[0081] The copper electroplating composition also comprises a complexing agent to keep the copper ions in solution and to avoid its precipitation.

[0082] The complexing agent may particularly be selected from polyamines, aminocarboxylic acids, aminophosphonic acids, aminoalcohols, polyalcohols, hydroxycarboxy lie acids, hydroxyphosphonic acids, thioureas, and polycarboxylic acids.

[0083] Without limitation, useful polymines are methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, or hexaethyleneheptamine, or combinations thereof.

[0084] 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. Without limitation, useful amino alcohols (alkanolamines) are monoethanolamine, diethanolamine, triethanolamine, monopropanolamine; Dipropanolamine, tripropanolamine, or combinations thereof.

[0085] In one embodiment the alkanolamine comprise:

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

[0087] (ii) at least one branched C3 to Ca 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 which alkanolamine is unsubstituted or substituted by carboxy, sulfonate or sulfate

[0089] In another embodiment the alkanolamine comprisies:

[0090] (I) at least one primary, secondary or tertiary amino group, and

[0091] (II) at least two, preferably three C3 to Ca hydroxyalkyl groups bound to the at least one amino group; and (ill) at least one carboxy, sulfonate or sulfate group or at least 4 hydroxy groups.

[0092] 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 .

[0093] In yet another embodiment the alkanolamine is a compound of formula C1 or C2 wherein

[0094] XC1, XC2are independently a Ci to C4 alkanediyl;

[0095] XC3is a Ci to C4 alkanediyl;

[0096] RC1is selected from H, a Ci to C4alkyl, -XC1-OH, -XC1-COOH, and RC11;

[0097] RC11is

[0098] RC2, RC2’ are independently selected from H, a Ci to C4 alkyl, -XC1-OH, and -XC1-COOH;

[0099] RC3, RC3’areindependently selected from H, a Ci to C4 alkyl, -XC1-OH, and -XC1-COOH;

[0100] RC4is selected from H, a Ci to C4 alkyl, and -XC1-OH, and -XC1-COOH; XC11is a Ci to Ce alkanediyl.

[0101] In yet another embodiment the alkanolamine is selected from compounds of formula C1 a, C1 b, C1 c, or C1 d wherein

[0102] XC1, XC2, XC3, XC4are independently a Ci to C3 alkanediyl;

[0103] RC1is selected from H, a Ci to C4 alkyl, -XC1-OH, and RC11;

[0104] RC2, RC2’ are independently selected from H, a Ci to C3 alkyl, and -XC1-OH;

[0105] RC3, RC3’areindependently selected from a Ci to C3 alkyl and -XC1-OH;

[0106] RC4is selected from H, a Ci to C4 alkyl, and -XC1-OH;

[0107] XC11is a Ci to C4 alkanediyl;

[0108] 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.

[0109] Without limitation, useful hydroxyphosphonic acids are 1 -Hydroxyethylidene-1,1 -diphosphonic acid (etidronic acid), combinations thereof, or salts thereof. Thioureas are thiourea and thiourea derivatives.

[0110] Without limitation, a useful polyalcohol is sorbitol.

[0111] 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. Particulerly preferred complexing agents are the alokanolamines as described above, particularly bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane, tris(hydroxymethyl)aminomethane or its salts, 1 ,3-bis(tris(hydroxy methyl) methylamino)propane, 2-Amino-2-methyl- 1 ,3-propanediol, and N-[1 ,3-Dihydroxy-2-(hydroxymethyl)propan-2-yl]glycine or its salts..

[0112] 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.

[0113] The complexing agent may be used alone or in any combination, and the content of the complexing agent in the plating bath is usually from 10 to 2000 mmol / l, preferably from 100 to 600 mmol / l In another embodiment the concentration of the complexing agent in the composition 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.

[0114] Buffer / base

[0115] The composition is non acidic, i.e neutral (pH about 6-8) or basic (> about 8). The composition optionally comprises a buffer or a base (also referred to as “pH adjustor”) to adjust the pH to a pH of from 6 to 13, preferably 7 to 13, more preferably from 6.5 to 12, more preferably from 7 to 10, most preferably from 7 to 9.

[0116] 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.

[0117] 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. 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.

[0118] 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.

[0119] Grain refiner

[0120] The copper electroplating composition may optionally comprise a grain refiner. Generally, useful grain refiners are carbocyclic aromatic or N-heteroaromatic compounds, particularly those comprising carboxyl, carbamoyl, or sulfonyl functional groups.

[0121] Preferred grain refiners are those of formula G1 a and G1 b or salts thereof, wherein

[0122] RG1is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to C alkoxy, halogen, and CN;

[0123] RG2is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN; and

[0124] XG1is selected from Ci to Ce alkanediyl or a group -XG11-C(0)-0-XG12-;

[0125] XG11is selected from a chemical bond or Ci to C4 alkandiyl;

[0126] XG12is selected from a chemical bond or Ci to C4 alkandiyl; and wherein RG1or RG2’ comprises at least one Ci to C4 carboxyl group, or group XG1is -XG11-C(0)-0-)-XG12-.

[0127] In a first preferred embodiment the grain refiner is a compound of formula G1 or salts thereof, wherein

[0128] RG1is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN; RG2is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to C alkoxy, halogen, H and CN; and XG1is a Ci to C4 alkanediyl; and wherein RG1or RG2comprises at least one Ci to C4 carboxyl group.

[0129] Particularly preferred grain refiners of the first embodiment are those of formula G2a or G2b or salts thereof wherein

[0130] RG21is selected from one or more H, Ci to C3 alkyl, Ci to C4 alkoxy, halogen, and CN;

[0131] RG22is selected from one or more H, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN; and XG1is methandiyl, ethanediyl, propanediyl or butanediyl.

[0132] A particularly preferred grain refiner of formula G2b is 3-carboxy-1 -penylmethylpyridinium (inner salt).

[0133] In a second preferred embodiment the grain refiner is a compound of formula G1 or salts thereof, wherein

[0134] RG1is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN;

[0135] RG2is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN; and

[0136] XG1is a group -XG11-C(0)-0-)-XG12-;

[0137] XG11, XG12are independently selected from Ci to C4 alkandiyl.

[0138] Particularly preferred grain refiners of the second embodiment are those of formula G3a, G3b, G3c, or salts thereof wherein

[0139] RG31is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN;

[0140] RG32is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, Ci to Ce carboxy, halogen, and CN; and

[0141] XG32is selected from a chemical bond or Ci to C4 alkandiyl.

[0142] Particularly preferred grain refiners of formula G3b are 4-(Methoxycarbonyl)benzyl pyridine-3-carboxylate and benzyl pyridine-3-carboxylate.

[0143] Another preferred embodiment is a grain refiner of formula H1 a or H1 b 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 H1 b.

[0144] In formula H1 a and H1 b

[0145] RH1is a carbamoyl group of formula

[0146] RH2is 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);

[0147] RH3is selected from the group consisting of (a) Ci to C4 alkyl, (b) OH or Ci to C4 alkoxy, (c) halogen, and (d) ON;

[0148] RH4is a Ci to C4 alkyl group;

[0149] XH1is 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; and

[0150] RH11, RH12are 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.

[0151] In the carbamoyl group RH1the amide group may form a primary (RH11, RH12= H), secondary (RH11+ H, RH12= H) or tertiary (RH11, RH12+ H ) amide. Preferred substituents RH11, RH12are independently H, methyl, ethyl, propyl, phenyl, benzyl, or toluyl.

[0152] The carbamoyl group RH1may 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.

[0153] The heteroaromatic ring bearing the carbamoyl group may comprise one or two further substituents RH3. Such groups may be selected from (a) Ci to C4 alkyl, preferably methyl, ethyl or propyl, most preferably methyl, ethyl; (b) OH or Ci to C4 alkoxy, 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 RH3are present, i.e. n is 0. The nitrogen atom in the heteroaromatic ring is quaternized by a Ci to C4 alkyl group (formula H1a) or by group -XH1-RH2(formula H1 b).

[0154] In a preferred embodiment, the spacer group XH1is a Ci to C4 alkanediyl, which may be unsubstituted or substituted by one OH and which may be interrupted by one 0, preferably from unsubstituted Ci to C4 alkanediyl or a Ci to C4 alkanediyl that is substituted by one OH.

[0155] In a preferred embodiment, the group RH2is (a) sulfonate, (b) carbamoyl, (c) OH or Ci to C4 alkoxy, 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.

[0156] Preferred grain refiners of formula H1 a are or its salts, particularly it chlorides, wherein m is 1 , 2, or 3.

[0157] Particularly preferred grain refiners of formula H1 a are and salts thereof. Particularly preferred grain refiners of formula H1 a are 1-benzyl-3-carbamoylpyridin-1-ium chloride or (3-(3-carbamoylpyridin-1-ium-1-yl)propane-1-sulfonate).

[0158] Preferred grain refiners of formula H1 b are wherein m is 1, 2, or 3.

[0159] In general, if present, the total amount of the grain refiners in the electroplating bath may be from 0.5 ppm to 10000 ppm based on the total weight of the plating bath. The additives 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.

[0160] 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.

[0161] Other Additives

[0162] 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.

[0163] In a further embodiment, surfactants may be present in the electroplating composition in order to improve wetting.

[0164] 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.

[0165] In a preferred embodiment, the composition is free of any polyethyleneimine or any sulfur-containing additives or both.

[0166] Composition

[0167] 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 defect reducing agent, a complexing agent, optionally a grain refiner, optionally a base or a buffer, optionally an electrolyte, and optionally further additives as described herein.

[0168] 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.

[0169] 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 aquous 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 depositiong 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.

[0170] In a preferred embodiment the composition does not contain any boric acid.

[0171] 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 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.

[0172] The copper ion source may be used in the present invention in any amount that provides sufficient metal ions for electroplating on a substrate.

[0173] 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.

[0174] 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, more preferably from about 7 to about 9, even more preferably from about 7.2 to about 9, most preferably from about 7.5 to about 9.

[0175] The electroplating composition is free of any cyanide ions.

[0176] In a preferred embodiment the composition is essentially free of halide ion, particularly of chloride ions and bromide ions except halide, particularly 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 halide, chloride or bromide means that the additional halide, particularly chloride or bromide is below 1 ppm, particularly below 0.1 ppm. It is most preferred that the composition does not contain any additional anions, particularly halide ion, most particularly chloride or bromide ions, except those present in the defect reducing agent or the optional grain refiner. 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.

[0177] In another preferred embodiment the electroplating composition essentially consists of or consists of

[0178] (a) copper ions;

[0179] (b) a defect reducing agent of formula S1 or S2

[0180] (c) optionally 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 6 to 13;

[0181] (e) optionally a grain refiner, particularly a grain refiner of formula G1 a, G1b, H1 a, or H1 b; and

[0182] (f) optionally a non-ionic surfactant.

[0183] In yet another preferred embodiment the electroplating composition essentially consists of or consists of

[0184] (a) copper ions;

[0185] (b) a defect reducing agent of formula S1 or S2

[0186] (c) optionally a complexing agent, particularly a hydroxycarboxylic acid, most particularly citric acid;

[0187] (d) a base, particularly a hydroxide, to increase the pH to a pH of from 7 to 13; and

[0188] (e) a grain refiner of formula G1a, G1b, H1 a, or H1 b.

[0189] In yet another preferred embodiment the electroplating composition essentiall consists of or consists of

[0190] (a) copper ions;

[0191] (b) a defect reducing agent of formula S1 or S2

[0192] (c) optionally a hydroxycarboxylic acid, most particularly citric acid;

[0193] (d) a hydroxide, particularly NaOH or KOH, to increase the pH to a pH of from 7 to 13; and

[0194] (e) a grain refiner of formula G1a, G1b, H1 a, or H1 b.

[0195] Process

[0196] 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 seed of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, or alloys thereof, preferably of cobalt or ruthenium, most preferably of cobalt.

[0197] An electrolytic bath is prepared comprising copper ions and at least one additive according 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.

[0198] 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.

[0199] Such semiconductor devices include, but are not limited to, wafers used in the manufacture of integrated circuits.

[0200] In order to allow a deposition 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. 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] As used herein, “seed of copper” means a continuous thin layer of the respective metalcopper having a thickness of about 5 nm to about 15 nm.

[0205] 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.

[0206] 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.

[0207] 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. 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.

[0208] 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.

[0209] In one embodiment the recessed feature is completely filled with copper by using a composition as described herein. In another embodiment a continuous seed of copper is deposited onto the metal seed of the recessed feature.

[0210] The copper may be deposited in recessed features according to the present invention without substantially forming voids within the metal deposit.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] The following examples shall further illustrate the present invention without restricting the scope of this invention. Examples

[0219] The number average molecular weight (Mn) was determined by1H-NMR and / or TAI-spectroscopy (Fa.Bruker, 400 MHz) at room temperature (25°C) using CDCI3 as deuterated solvent. For processing the spectra, the program MestReNova was used. For calculation, the integral at 1 .1 1 -1 .28 were referenced to the theoretical PO repeating units x 3 protons of the PO (-CH3). The integral at 3.36-3.60 (minus number of protons of the starter), (minus the total protons (CH3) of the PO repeating units) divided by four give the actual experimental repeating units of the EO in the molecule. By using TAI-NMR, additional to the experimental EO conversion and thus the EO:PO ratio, the number of EO and PO end groups could be determined. Therefore, the sample was derivatized by reaction of the alcohol end groups with trichloro acetyl isocyanate to transform the hydroxy groups into the corresponding trichloro acetyl urethane derivatives, shifting the NMR signal to 4.43 ppm (primary OH), respectively to 5.12 ppm (secondary OH). In doubt, this method is the standard to determine the molecular mass of the suppressing agents according to the invention.

[0220] Alternatively, the molecular mass of the suppressing agents may also be determined by size-exclusion chromatography (SEC). In this case polystyrene is used as standard and tetrahydrofuran as eluent. The temperature of the column is 30°C, the injected volume 30 pl (pliter) and the flow rate 1 .0 ml / min.

[0221] The amine number was determined according to DIN 53176 by titration of a solution of the polymer in acetic acid with perchloric acid.

[0222] Example 1 : Preparation of defect reducing agents

[0223] Synthesis of Intermediate Products

[0224] 1.3-Xylylene diamine (408.6 g) was placed under nitrogen atmosphere into a 2 I autoclave and heated up to 100 °C. Then ethylene oxide (528 g) was added over a period of 5 h. The mixture was allowed to post react for 6 h. A yellow product (937 g) having an amine number of 6.37 mmol / g was obtained (intermediate product 1 ).

[0225] 1.4-Xylylene diamine (1000 g) was placed under nitrogen atmosphere into a 3.5 I autoclave and heated up to 100 °C. Then ethylene oxide (1293.3 g) was added over a period of 20 h. The mixture was allowed to post react for 6 h. A yellow product (2284.5 g) having an amine number of 6.37 mmol / g was obtained (intermediate product 2).

[0226] 1 -(3-Aminopropyl)imidazole (1001.4 g) was placed under nitrogen atmosphere into a 3.5 I autoclave and heated up to 100 °C. Then ethylene oxide (704.8 g) was added over a period of 1 1 h. The mixture was allowed to post react for 6 h. A yellow product (1688 g) having an amine number of 9.0 mmol / g was obtained (intermediate product 3). Example 1.1

[0227] The intermediate product 1 (156.1 g) and potassium tert-butoxide (1.8 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1 .0 bar and the mixture was homogenized at 130 °C for 1 h. Then propylene oxide (725 g) was added at 130 °C over a period of 6 h, reaching a maximum pressure of 5 bar. To complete the reaction, the mixture was allowed to post-react for 6 h at 130 °C. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Surfactant 1.1 was obtained as orange liquid (880 g) having an amine number of 1.13 mmol / g and a number average molecular mass (Mn) of 1.769 g / mol (theoretical 1.764 g / mol).

[0228] Example 1.2

[0229] The intermediate product 2 (109.3 g) and potassium tert-butoxide (1.3 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1 .0 bar and the mixture was homogenized at 130 °C for 1 h. Then ethylene oxide (92.5 g) and propylene oxide (691 .2 g) were added at 130 °C over a period of 13 h, reaching a maximum pressure of 6 bar. To complete the reaction, the mixture was allowed to post-react for 6 h at 130 °C. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Surfactant 1 .2 was obtained as orange liquid (885 g) having an amine number of 0.80 mmol / g and a number average molecular mass (Mn) of 2.500 g / mol (theoretical 2.551 g / mol).

[0230] Example 1.3

[0231] The intermediate product 2 (296.8) and potassium tert-butoxide (3.32 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1 .0 bar and the mixture was homogenized at 130 °C for 1 h. Then ethylene oxide (41,8 g) and propylene oxide (1875) were added at 130 °C over a period of 66 h, reaching a maximum pressure of 6 bar. To complete the reaction, the mixture was allowed to post-react for 6 h at 130 °C. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Surfactant 1 .4 was obtained as orange liquid (2208 g) having an amine number of 0.83 mmol / g and a number average molecular mass (Mn) of 2.409 g / mol (theoretical 2.330 g / mol).

[0232] Example 1.4

[0233] 1 ,3-Xylylene diamine (544.8) was placed under nitrogen atmosphere into a 3.5 I autoclave and heated up to 100 °C. Then ethylene oxide (704.8 g) was added over a period of 11 h. The mixture was allowed to post react for 6 h. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Surfactant 1.13 was obtained as yellow product (1242 g) having an amine number of 6.36 mmol / g and a number average molecular mass (Mn) of 314 g / mol (theoretical 312 g / mol)

[0234] Example 1.5

[0235] The intermediate product 3 (64.2 g) and potassium tert-butoxide (2.0 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1 .0 bar and the mixture was homogenized at 130 °C for 1 h. Then ethylene oxide (556.9 g) was added over a period of 8 h, reaching a maximum pressure of 6 bar. The mixture post-reacted for 6 h at 130°C. Afterwards propylene oxide (769.2 g) was added at 130 °C over a period of 12 h, reaching a maximum pressure of 6 bar. To complete the reaction, the mixture was allowed to post-react for 6 h at 130 °C. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Surfactant 1.5 was obtained as orange liquid (1148 g) having an amine number of 0.42 mmol / g and a number average molecular mass (Mn) of 4.761 g / mol (theoretical 4.618 g / mol).

[0236] Example 2: Copper electroplating experiments

[0237] For the plating experiments a blanket wafer substrate was used bearing a 120 A CVD Co seed on a 50 A TaN layer.

[0238] The electrodeposited copper film was optically classified by visual inspection (OC) of photographs of the wafer surface in the following way:

[0239] -2: pronounced defects, black / dark appearance as shown in Fig. 1 .

[0240] -1 : certain amount swirls and defects, brighter and more shiny than OC -2 as shown in Fig. 2.

[0241] -0: less swirls and defects compared to OC -1 , brighter and more shiny compared to OC-1 as shown in Fig. 3.

[0242] +1 : only very few swirls and slight defects like slightly darker patches brighter and more shiny compared to OC 0 as shown in Fig. 4.

[0243] +2: nearly no defects at all, very bright, mirror like appearance as shown in Fig. 5.

[0244] Comparative Example 2.1 : Cu electroplating without defect reducing agent

[0245] A plating bath was prepared by combining DI water, 0.5 g / l copper as copper sulfate, citric acid in a molar ratio of 2:1 to Cu, and a solution of sodium hydroxide or potassium hydroxide to adjust a pH of 7.5. A copper layer was electroplated onto a blanket wafer substrate bearing a cobalt seed layer by contacting the wafer substrate with the above described plating bath at 25 °C and applying a direct current of -20 mA / cm2for 100 s at 100 RPM. The plated wafers were classified optically as described above. The surface of the plated Cu film exhibited a signature of swirl defects that resulted in an optical classification of -1 as shown Table 1 .

[0246] Example 2.2: Cu electrodeposition with defect reducing agent

[0247] The experiment as described in comparative example 1 was repeated with addition of 10 ml / l or 25 ml / l of a solution in DI water of 0.9 wt% of a defect reducing agent as described in example 1.1 to 1 . 5 to the plating bath.

[0248] The plated wafers were classified optically as described above. The result depicted in Table 1 show that the addition of a defect reducing agent according to the invention significantly reduces the defects in the electroplated copper film.

[0249] Example 2.3: Cu electrodeposition with defect reducing agent and grain refiner

[0250] The experiment as described in Example 2 was repeated with addition of 10 ml / l of a solution in DI water of 0.9 wt% of the defect reducing agent 1.2 and 1.5 of Table 1 and 10 ml / l of a solution in DI water of 0.9 wt% of 3 -Carboxy- 1- penylmethylpyridinium (inner salt with Na+and Cl available from BASF SE). The grain refiner helps to reduce the roughness of the electrodeposited copper layer.

[0251] The plated wafers were classified optically as described above. The results depicted in Table 1 show that the addition of a defect reducing agent according to the invention in combination with a grain refiner further reduces the defects in the electroplated copper film.

[0252] Table 1 block = EO followed by PO; homo = EO homopolymer; random = statistical EO / PO copolymer

Claims

Claims1 . A composition for depositing copper on a semiconductor substrate, the composition comprising(a) copper ions;(b) a defect reducing agent of formula S1 or S3(c) a complexing agent; and(d) optionally a buffer or a base to adjust the pH to a pH of from 6 to 13; whereinRS1is(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 Mnof 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 Mnof from 180 g / mol to 3500 g / mol;RS2, RS3, RS4are independently selected from RS1and RS5;RS5is selected from a Ci to C4 alkyl and a Ci to C4 alkyoxy;Xs1, Xs2are independently selected from a linear or branched Ci to C4 alkanediyl, a linear or branched C2 to C4 alkenediyl, a linear or branched C2 to C4 alkynediyl, and -XS6-(O-C2H3RS6)o-;Xs3is a linear or branched Ci to Ca alkanediyl, a linear or branched C2 to Ca alkenediyl, a linear or branched C2 to Ca alkynediyl, and -XS6-(O-C2H3RS6)o-;RS6is H, methyl or ethyl;Xs6is methanediyl, ethanediyl, propanediyl, or butanediyl;Ysis phenylene, naphthylene or a divalent aromatic 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;Zsis a monovalent aromatic N-heterocyclic 5 or 6 membered ring system comprising 1 , 2, or 3 nitrogen atoms and which aromatic N-heterocyclic 5 or 6 membered ring system is unsubstituted or substituted by 1 , 2 or 3 groups RS5;o integer from 1 to 6; p, q are independently 0 or 1 ; wherein the pH of the composition is from 6 to 13.

2. The composition according to claim 1 , wherein RS1is a block poly(oxyethylene-co-C3-C4-oxyalkylene) or a random poly(oxyethylene-co-C3-C4-oxyalkylene) having an oxyethylene content of from 8 to 98 % by weight, and the defect reducing agent has a number average molecular mass Mnof from 800 to 8000 g / mol, preferably from 1000 to 4000 g / mol.

3. The composition according to claim 1 , wherein RS1is a polyoxyethylene and the defect reducing agent has a number average molecular mass Mnof from 300 g / mol to 2500 g / mol;4. The composition according to anyone of the preceding claims, wherein RS2, RS3, and RS4are RS1.

5. The composition according to anyone of the preceding claims, wherein Xs1, Xs2are independently selected from methanediyl, 1,1 ethanediyl and 1 ,2 ethanediyl.

6. The composition according to anyone of the preceding claims, wherein Ysis phenylene or naphthylene.

7. The composition according to claim 6, wherein p, q, or both p and q are 1 .

8. The composition according to anyone of the preceding claims, p and q are 1 .

9. The composition according to anyone of the preceding claims, wherein the defect reducing agent is a compound of formula 2wherein n is 0, 1 , or 2.

10. The composition according to claim 9, wherein Xs1and Xs2are independently selected from methanediyl or ethanediyl.1 1 . The composition according to anyone of claims 1 to 8, wherein the defect reducing agent is a compound of formula 4wherein n is 0, 1 , or 2, preferably 0 or 1 , most preferably 0.

12. The composition according to claim 1 1 , wherein Xs3is ethanediyl, propanediyl or butanediyl.

13. The composition according to anyone of the preceding claims, which further comprises a grain refiner of formula G1 a or G1 bor salts thereof, whereinRG1is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN;RG2is selected from one or more H, Ci to C4 carboxyl, Ci to C4 alkyl, Ci to Ce alkoxy, halogen, and CN; andXG1is selected from Ci to Ce alkanediyl or a group -XG11-C(O)-O-XG12-;XG11is selected from a chemical bond or Ci to C4 alkandiyl;XG12is selected from a chemical bond or Ci to C4 alkandiyl; and wherein RG1or RG2’ comprises at least one Ci to C4 carboxyl group, or group XG1is -XG11-C(O)-O-)-XG12-.

14. The composition according to anyone of the preceding claims, which further comprises a grain refiner of formula H1 a or H1 bor 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; whereinRH1is a carbamoyl group of formulaRH2is 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);RH3is selected from the group consisting of (a) Ci to C4 alkyl, (b) OH or Ci to C4 alkoxy, (c) halogen, and (d) ON;RH4is a Ci to C4 alkyl group;XH1is 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; andRH11, RH12are independently selected from H, Ci to C4 alkyl, Ce to C12 aryl, Ce to C12 arylalkyl; Ce to C12 alkyl aryl; n is 0, 1 , or 2;15. The composition according to anyone of the preceding claims, which essentially does not comprise any alloying metal ions.

16. The composition according to anyone of the preceding claims, which essentially does not comprise any chloride or bromide, or both chloride and bromide.

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

18. The composition according to anyone of the preceding claims, wherein the pH of the composition is from 7 to 12.

19. The composition according to anyone of the preceding claims, essentially consisting of(a) copper ions;(b) a defect reducing agent of formula S1 , S2, S3, or S4;(c) a complexing agent;(d) optionally a base to adjust the pH to a pH of from 7 to 13;(e) optionally a grain refiner of formula G1 a, G1b, H1 a, or H1 b; and(f) optionally a non-ionic surfactant.

20. 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.21 . 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 19 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.

22. The process according to claims 21 , wherein the seed consists of cobalt, iridium, osmium, palladium, platinum, rhodium, ruthenium, molybdenum, and alloys thereof.

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