Composition for copper electroplating on a metal seed

Abstract

Therefore, the present invention provides an acidic aqueous composition for copper electroplating comprising (a) copper ions; (b) halide ions; and (c) a propylene oxide substituted amine additive; its use for copper electroplating and a process of copper electroplating.

Description

[0001] Composition for copper electroplating on a metal seed

[0002] The present invention relates to a composition for copper electroplating comprising copper ions and a seed protecting and nucleation agent.

[0003] Background of the Invention

[0004] Formation of metal wiring interconnects in integrated circuits (ICs) can be achieved using a damascene or dual damascene process. Typically, trenches or holes are etched into dielectric material, such as silicon dioxide, located on a substrate. The holes or trenches may be lined with one or more liner layers and barrier layers. Then a thin layer of copper may be deposited in the holes or trenches that can act as a copper seed layer. Thereafter, the holes or trenches may be filled with copper.

[0005] Conventional copper deposition typically occurs in two steps. First, a copper seed layer is deposited on the substrate using a PVD process. Second, copper is electroplated on the seed layer to fill the holes or trenches. Techniques have been developed that avoid depositing a copper seed layer using PVD by directly electroplating copper on barrier or liner layers. However, challenges exist in directly electroplating copper on barrier or liner layers.

[0006] One class of additives are the so-called suppressors, suppressing agents or sometimes simply surfactants. Suppressors are used to provide a substantially bottom- up filling of small features like vias or trenches. The smaller the features are the more sophisticated the additives have to be to avoid voids and seams. In literature, a variety of different suppressing compounds have been described. The mostly used class of suppressors are polyether compounds like polyglycols or polyalkylene oxides like ethylene oxide propylene oxide copolymers.

[0007] WO 2006 / 053242 A1 discloses amine-based polyoxyalkylene suppressors comprising oxyethylene and oxyproylene groups. The amine may be methylamine, ethylamine, propylamine, ethylendiamine, diethylenetriamine, diaminopropane, diethyleneglykol diamine or triethylenglycol diamine. The copolymers may have block, alternating or random structure.

[0008] WO 2010 / 115717, WO 2011 / 012475, and WO 2018 / 114985 disclose compositions comprising suppressors based on particular amine started polyalkoxyalkylene copolymers comprising oxyethylene and oxyproylene groups for copper electrodeposition on copper seeds.

[0009] 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 becomes the more difficult it is to get a continuous seed on the side walls of the feature without significant seed overhang.

[0010] To avoid these difficulties associated with a non-copper liner layer such as cobalt or ruthenium is proposed in WO 2019 / 199614 A1. An electroplating solution for plating copper on a non-copper liner layer includes a low copper concentration, low acid concentration (higherpH), organic additives, and bromide ions as a copper complexing agent.

[0011] The consequence of using bromide is that the electrochemical properties of the additives change significantly which makes their selection more difficult than for composition used for plating without bromide. Electrochemical investigations of polyalkylene copolymer suppressor type reveal that the properties of the suppressing agents are significantly changed since the suppressing effect is increased in the presence of bromide compared to the case without bromide. The presence of bromide will likely influence the adsorption / desorption behavior of the suppressor.

[0012] Furthermore, cobalt is an interesting barrier metal between copper and the dielectric, and may be used as a seed layer for copper electrodeposition. Cobalt is a less noble metal compared to copper and quickly corrodes in the presence of an acid and oxygen, particularly if copper is present, too. On the other hand, alkaline electroplating bath 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.

[0013] WO2022 / 012932 discloses an acidic aqueous composition for copper electroplating comprising including bromide ions and a suppressor comprising a poly(oxy(C3 to Ce)- alkylene)-block-poly(oxyethylene) group that is bound to an amine by the poly(oxy(C3 to Ce)alkylene part, or a poly(oxyethylene)-block-poly(oxy(C3 to Ce )alkylene)-block- poly(oxyethylene) that is bound to an amine by the poly(oxyethylene) part, which both have a poly(oxyethylene) content of from 5 to 30 % by weight.

[0014] However, particularly due to the low thickness of the cobalt seed, corrosion of cobalt is still a problem when using acidic copper electroplating compositions. Furthermore, also in copper plating on a copper or other metal seeds, with further shrinking dimensions there is still a need for additives that allow a voidless and seamless filling.

[0015] It is therefore an object of the present invention to provide a copper electroplating composition that is capable of providing a substantially voidless and seamless filling of features on the nanometer scale comprising a metal seed with a copper electroplating bath, particularly an acidic copper electroplating bath.

[0016] It is a further object of the present invention to provide an electroplating bath that is capable of providing a filling of recessed features having a cobalt seed layer, or other metal seeds of metals less noble than copper, with copper and providing a low or at least reduced corrosion of the cobalt or other metal seed layer. Furthermore, it is important to provide additives that are compatible with electroplating compositions that comprise bromide ions.

[0017] It is a further object of the present invention to provide an additive that provides bottom- up fill capability, particularly into features having an aperture size of 10, particularly 5 nm and below.

[0018] Summary of the Invention

[0019] Surprisingly, it has now been found, that polypropoxylated amine additives defined herein show good or even better bottom-up filling as well as a good or even better corrosion inhibition of a cobalt or other metal seed layer.

[0020] Therefore, the present invention provides an acidic aqueous composition for copper electroplating comprising

[0021] (a) copper ions;

[0022] (b) halide ions, particularly chloride and / or bromide ions, most particularly chloride and bromide ions; and

[0023] (c) at least one additive of formula S1 wherein

[0024] Xs1is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS4°;

[0025] RS1is selected from -(C3H6-O)m-H, -XS4-N[-(C3H6-O)m-H]2, Zs, XS5-ZS, XS4-N(ZS)2;

[0026] RS2, RS3, RS4are selected from H, RS1, or RS4°, or RS3and an adjacent group RS4or, if n>2, two adjacent groups RS4together form a divalent group Xs2;

[0027] RS4° is a linear or branched C1-C20 alkyl, which may optionally be substituted hydroxy, alkoxy, or alkoxycarbonyl;

[0028] Zsis a group of formula S3;

[0029] Xs2is selected from a linear or branched C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS40; and

[0030] Xs3is a linear or branched Ci to C12 alkanediyl, which may be interrupted by O and S atoms or substituted by O-RS31;

[0031] Xs4is a linear or branched Ci to C12 alkanediyl;

[0032] Xs5is a divalent group comprising at least one C2 to Ce polyoxyalkylene;

[0033] RS31, RS32are independently selected from (a) -(C3H6-O)m-H or (b) a further branching group to form a multiple branching group (ZSp)p(RS31RS32)2P;

[0034] ZSpis selected from or m is an integer of from 1 to 30; n is an integer of from 0 to 6. p is an integer of from 2 to 4.

[0035] The invention further relates to the use of a copper electroplating bath comprising a composition as described herein for depositing copper on substrates comprising recessed features having an aperture size of 30 nanometers or less, which features comprise a metal seed.

[0036] The invention further relates to a process for depositing a copper layer comprising the steps

[0037] (a) providing a substrate comprising a nanometer-sized recessed feature, which feature comprises a metal, particularly a cobalt seed layer;

[0038] (b) contacting the composition as described herein with the substrate, and

[0039] (c) applying a current to the substrate for a time sufficient to deposit a metal layer onto the metal seed layer and to fill the nanometer sized feature.

[0040] The additive provides a good nucleation of copper on the metal seed layer. It allows electroplating over thin seed layers and fast bottom-up fill in both large and small features without causing voids or seams. Furthermore, the additive effectively suppresses corrosion of the metal seed layer.

[0041] The suppressing agents according to the present invention are particularly useful for filling of small recessed features, particularly those having aperture sizes of 20 nm or below, particularly 10 nm or below, most particularly 5 nm or below.

[0042] Brief description of the Figures

[0043] Fig. 1 shows a SEM image of a patterned wafer substrate that was used for copper electroplating in the examples B1a to B4b; Fig. 2a shows a SEM image of partially filled trenches after copper electroplating according to example B1a;

[0044] Fig. 2b shows a SEM image of fully filled trenches after copper electroplating according to example B1b;

[0045] Fig. 3a shows a SEM image of partially filled trenches after copper electroplating according to example B2a;

[0046] Fig. 3b shows a SEM image of fully filled trenches after copper electroplating according to example B2b;

[0047] Fig. 4a shows a SEM image of partially filled trenches after copper electroplating according to example B3a;

[0048] Fig. 4b shows a SEM image of fully filled trenches after copper electroplating according to example B3b;

[0049] Fig. 5a shows a SEM image of fully filled trenches after copper electroplating according to example B4a;

[0050] Fig. 5b shows a SEM image of partially filled trenches after copper electroplating according to example B4b;

[0051] Detailed Description of the Invention

[0052] Additives according to the invention

[0053] It was found that the electroplating compositions according to the invention comprising at least one additive as described below show extraordinary performance in feature filling that are nanometer sized and have a cobalt liner or other metal seed. The additive acts as a suppressing agent as well as a metal corrosion inhibitor, especially for cobalt. The additive is also referred to herein as “suppressing agent”.

[0054] Besides the electrolyte the aqueous composition according to the present invention comprises at least one additive of formula S1

[0055] Generally, the suppressing agent consists of an amine starter comprising one or more polyoxypropylene side chains. In formula S1 , if n>0, Xs1is a spacer group within the amine starter. It may be a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, preferably unsubstituted. Such alkanediyl spacer may optionally be interrupted by O, S or NRS4°. In a first preferred embodiment Xs1is Ci-Ce alkanediyl, more preferably C1-C4 alkanediyl, most preferably methanediyl, 1 ,2-ethanediyl or 1 ,3-propanediyl. In a second preferred embodiment heteroatoms are present and Xs1may be -(CH2)q-[Q-(CH2)r]s-, wherein Q is selected from O, S and NRS4°, q and r are integers from 1 to 6, s is an integer from 1 to 4 and q + r s is the total number of C atoms in Xs1. Particularly preferred is a spacer with Q=O and q=r = 1 or 2, and s=1. Useful substituents may be hydroxy, alkoxy, and alkoxycarbonyl.

[0056] Generally, n may be an integer from 0 to 6. Preferably n is an integer from 0 to 4, most preferably n is 0, 1 or 2.

[0057] In another embodiment n may be an integer from 1 to 6. Preferably n is an integer from 1 to 4, most preferably n is 1 or 2.

[0058] In a first embodiment, group RS1is a poly(oxypropylene) group -(CsHe-COm-H, also known in the art as polypropylene oxide. The poly(oxypropylene) is also referred to herein as “PO”. m may be an integer of from 1 to 30, preferably from 2 to 28, more preferably from 3 to 25, most preferably from 4 to 20.

[0059] In a second embodiment RS1is a nitrogen-containing branching group -XS4-N[-(C3He- O)m-H]2.

[0060] In a third embodiment group RS1comprises a braching group Zs, XS5-ZS, or XS4-N(Zs)2, wherein Zsis a group of formula S3:

[0061] In formula S3, Xs3is a linear or branched Ci to C12 alkanediyl, which may be interrupted by O and S atoms or substituted by O-RS31, Preferably Xs3is a Ci to Ge alkanediyl, more preferably methanediyl, ethanediyl, propanediyl or butanediyl, most preferably methanediyl or ethanediyl. Xs4is a linear or branched Ci to C12 alkanediyl. Preferably Xs3is a Ci to Ce alkanediyl, more preferably methanediyl, ethanediyl, propanediyl or butanediyl, most preferably methanediyl or ethanediyl. RS31and RS32are independently selected from either (a) -(CsHe-COm-H or (b) a further branching group to form a multiple branching group (ZSp)p(RS31RS32)2P.

[0062] Herein ZSpis selected from

[0063] Preferably RS31and RS32are both oxypropylene groups -(CsHe-COm-H. p may be an integer from 2 to 4, preferably 2.

[0064] The compounds of formula S1 with RS1= Zsmay be prepared in two steps. First, a multi amine is reacted with a compound that introduces a branching group (further also referred to a “branching agent”), such as but not limited to an epoxide or a carbonate ester of formula

[0065] In a second step the reaction product is reacted with proylene oxide to form the respective suppressing agents according to the invention.

[0066] If RS1is XS5-ZS, a three-step process is required. In a first step the amine starter is reacted with a first portion of the C2 to Ce alkylene oxide, preferably propylene oxide, followed by reaction with the compound that introduces a branching group and afterwards again with a second portion of the propylene oxide as described above. In formula S1 , RS2, RS3, RS4are either selected from H, RS1, RS4°; or RS3and an adjacent group RS4or, if n>2, two adjacent groups RS4may together form a divalent group Xs2. In the latter case Xs2may be selected from a linear or branched C1-C12 alkanediyl, which may optionally be interrupted by O, S or NRS4°. RS4° may be (a) linear or branched C1-C20 alkyl, which may optionally be substituted by hydroxyl, alkoxy or alkoxycarbonyl, and (b) linear or branched C1-C20 alkenyl, which may optionally be substituted by hydroxyl, alkoxy or alkoxycarbonyl. Preferably RS4° is a Ci to Ce alkyl or a Ci to C12 hydroxyalkyl. Preferably Xs2is selected from a linear or branched Ci-Ce alkanediyl, more preferably from a C1-C4 alkanediyl, most preferably from methyl or ethyl or propyl. In this case Xs1is preferably selected so as to form a 5 or 6 membered ring system.

[0067] In a preferred embodiment, all groups RS2, RS3, RS4are a polyoxypropylene group RS1as defined above.

[0068] Generally, m may be an integer of from 2 to 30, preferably from 3 to 28, more preferably from 4 to 25, most preferably from 5 to 20.

[0069] Generally, the number average molecular mass Mnof the suppressing agent may be from about 300 to about 25 000 g / mol, preferably 500 to 15000 g / mol. In one embodiment the molecular mass Mnof the suppressing agent is from about 500 to about 8000 g / mol, preferably from about 1000 to about 6000 g / mol, even more preferably from about 1200 to about 3500 g / mol, most preferably from about 1400 to about 3000 g / mol. A low molecular weight increases the solubility of the suppressing agent in the composition.

[0070] A first preferred embodiment is an additive of formula (S2a) wherein

[0071] RS1has the prescribed meanings;

[0072] RS2, RS3and RS4are selected from RS1or RS4°, preferably RS1; r is an integer from 1 to 8, preferably 2 to 6, most preferably 2, 3 or 4;

[0073] RS4° has the prescribed meanings and is preferably Ci to Ce alkyl or Ci to

[0074] C12 hydroxyalkyl; and is 1 , 2, or 3.

[0075] A second preferred embodiment is an additive of formula (S2b)

[0076] RS1has the prescribed meanings;

[0077] RS2is selected from RS1or RS40, preferably RS1;

[0078] RS40has the prescribed meanings and is preferably Ci to Ce alkyl or Ci to C12 hydroxyalkyl; and

[0079] Xs1, Xs2are independently a Ci to C3 alkanediyl, preferably Xs1and Xs2are both ethanediyl or either Xs1or Xs2is methanediyl and the other of Xs1and Xs2is propanediyl.

[0080] Such compounds may be prepared by starting from cyclic amines, such as but not limited to piperazin, methylpiperazin, ethylpiperazin, propylpiperazin, butylpiperazin, and the like.

[0081] A third preferred embodiment is an additive of formula (S2c) wherein

[0082] RS1has the prescribed meanings;

[0083] RS2and RS3are selected from RS1or RS4°, preferably RS1;

[0084] RS4° has the prescribed meanings and is preferably Ci to Ce alkyl or Ci to

[0085] C12 hydroxyalkyl; and

[0086] Xs1, Xs11, Xs3are independently a Ci to C3 alkanediyl, preferably Xs1and Xs2are both ethanediyl or either Xs1or Xs2is methanediyl and the other of Xs1and Xs2is propanediyl.

[0087] A fourth preferred embodiment is an additive of formula (S2d) wherein

[0088] RS1has the prescribed meanings; RS2, RS3and RS4are selected from RS1or RS4°, preferably RS1;

[0089] RS4° has the prescribed meanings and is preferably Ci to Ce alkyl or Ci to

[0090] C12 hydroxyalkyl; and

[0091] Xs1, Xs11, Xs3are independently a Ci to C3 alkanediyl, preferably Xs1and Xs2are both ethanediyl or either Xs1or Xs2is methanediyl and the other of Xs1and Xs2is propanediyl.

[0092] Such compounds of embodiments three and four may be prepared by starting from aminoalkylated cyclic amines, such as but not limited to bisaminoethyl piperazin, bisaminopropyl piperazin, bisaminobutyl piperazin, and the like.

[0093] A fifth embodiment is an additive of formula S1 wherein

[0094] RS1is selected from -(CsHe-COm-H,

[0095] RS2, RS3and RS4are RS1;

[0096] Xs1is a Ci to C3 alkanediyl; and m is an integer of from 5 to 30.

[0097] A sixth preferred embodiment is an additive of formula S3 wherein RS1, RS2, RS3and RS41are -(C3H6-O)m-H; RS42is -XS4-N[-(C3H6-O)m-H]2;

[0098] Xs4is a linear or branched Ci to Ce alkanediyl, preferably C2to C4 alkanediyl , most preferably ethane-1 ,2-diyl; m is an integer of from 2 to 20, preferably 3 to 15, most preferably 4 to 10; j is 1 to 5, preferably 1 or 2, most preferably 1.

[0099] Further useful polyamine starters are described in WO 2018 / 073011 , which are explicitly incorporated herein by reference for this purpose.

[0100] Plating Bath

[0101] A wide variety of metal plating baths may be used with the present invention. Metal electroplating baths typically contain a copper ion source, halide ions, an electrolyte, the suppressing agent, and optionally further additives such as but not limited to accelerators, levelers, surfactants.

[0102] 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.

[0103] The suppressing agents of the invention are typically used in an amount of about 0.1 ppm to about 1000 ppm, based on the total weight of the plating bath. Particularly suitable amounts of suppressor useful in the present invention are 1 to 700 ppm, and more particularly 10 to 500 ppm.

[0104] 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 a preferred embodiment, no further metals besides copper are present 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.

[0105] 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.

[0106] The copper ion source may be used in the present invention in any amount that provides sufficient metal ions for electroplating on a substrate. 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 suppressor 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.

[0107] Also mixtures of metal salts may be electroplated according to the present invention. Thus, alloys, such as but not limited to copper-tin having up to about 2 percent by weight tin, may be advantageously plated according to the present invention. The amounts of each of the metal salts in such mixtures depend upon the particular alloy to be plated and is well known to those skilled in the art.

[0108] In general, besides the copper ions, halide ions, particularly chloride and / or bromide ions, and at least one of the suppressing agents according to the present invention the present copper electroplating compositions preferably include an electrolyte, one or more sources of metal ions and optionally other additives like accelerators and / or levelers.

[0109] Such electrolytes may contain a source of chloride ions, e.g. in form of copper chloride or hydrochloric acid. A wide range of chloride ion concentrations may be used in the present invention such as from about 0 to about 500 ppm. Typically, the chloride ion concentration is in the range of from about 1 to about 100 ppm, preferably from about 10 ppm to about 100 ppm, most preferably from 20 to 80 ppm, based on the plating bath. It is preferred that the electrolyte is sulfuric acid or methanesulfonic acid, and preferably a mixture of sulfuric acid or methanesulfonic acid and a source of chloride ions. The acids and sources of halide ions useful in the present invention are generally commercially available and may be used without further purification.

[0110] If a cobalt or other non-copper seeds are used, bromide ions may preferably be present. Typically, the chloride ion concentration is in the range of from about 0.25 to about 250 ppm, preferably from about 5 to about 100 ppm, most preferably from about 10 to about 80 ppm. The use of bromide ions is described in more detail in

[0111] US 8268 155 B1 or WO 2019 / 199614 A1 , which are incorporated herein by reference.

[0112] The electroplating baths of the present invention may be prepared by combining the components in any order. It is preferred that the inorganic components such as metal salts, water, electrolyte and optional halide ion source, are first added to the bath vessel followed by the organic components such as leveling agents, accelerators, suppressors, surfactants and the like.

[0113] Typically, the plating baths of the present invention may be used at any temperature from 10 to 65 °C or higher. It is preferred that the temperature of the plating baths is from 10 to 35 °C and more preferably from 15 to 30 °C.

[0114] Suitable acidic electrolytes include such as, but not limited to, sulfuric acid, acetic acid, fluoroboric acid, alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid and trifluoromethane sulfonic acid, arylsulfonic acids such as phenyl sulfonic acid and toluenesulfonic acid, sulfamic acid, hydrochloric acid, phosphoric acid, and the like. In a particular embodiment the electrolyte does not comprise pyrophosphoric acid. The acids are typically present in an amount in the range of from about 0.1 to about 300 g / l. The plating bath may be a high, a medium or a low acid bath. Low acid baths usually comprise one or more acids in a concentration below 15 g / l or even below 10 g / l or 5 g / l. As used herein, “acidic” means that the pH of the plating bath is below 7, preferably below 5. More preferably the pH of the acidic plating bath is below 4, even more preferably below 3, most preferably below 2.

[0115] In a particular embodiment the suppressors of this invention may be used in low copper electrolyte compositions typically containing about below 20 g / l copper ions, in combination with typically about 0.1-15 g / l acid like sulfuric acid and with chloride ions typically in the range of about 10-400 ppm by weight, preferably in combination with bromide ions.

[0116] Other additives

[0117] The electroplating baths according to the present invention may include one or more optional additives. Such optional additives include, but are not limited to, accelerators, other suppressors, levelers, surfactants and the like.

[0118] Any accelerators may be advantageously used in the plating baths according to the present invention. Accelerators useful in the present invention include, but are not limited to, compounds comprising one or more sulfidic sulphur atoms (such as but not limited to sulfide, disulfide or thiol groups) and one or more sulfonic / phosphonic acid group or their salts. Preferably the composition further comprises at least one accelerating agent. Preferred accelerators have the general structure MAO3XA-RA1-(S)n-RA2, with:

[0119] - MAis a hydrogen or an alkali metal (preferably Na or K)

[0120] - XAis P or S, preferably S

[0121] - n = 1 to 6, preferably 1 or 2

[0122] - RA1is selected from Ci-Cs alkyl group or heteroalkyl group, an aryl group or a heteroaromatic group. Heteroalkyl groups will have one or more heteroatom (N, S, O) and 1-12 carbons. Carbocyclic aryl groups are typical aryl groups, such as phenyl, naphtyl. Heteroaromatic groups are also suitable aryl groups and contain one or more N,0 or S atom and 1-3 separate or fused rings.

[0123] - RA2is selected from H or (-S-RA1'XAC>3MA), with RA1' being identical or different from RA1.

[0124] More specifically, useful accelerators include those of the following formulae:

[0125] MAO3S-RA1-SH

[0126] MAO3S-RA1-S-S-RA1’-SO3MAMAO3S-Ar-S-S-Ar-SO3MAwith RA1is as defined above and Ar is Aryl.

[0127] Particularly preferred accelerating agents are:

[0128] SPS: bis-(3-sulfopropyl)-disulfide disodium salt

[0129] MPS: 3-mercapto-1-propansulfonic acid, sodium salt

[0130] Other examples of accelerators, used alone or in mixture, include, but are not limited to: MES (2-Mercaptoethanesulfonic acid, sodium salt); DPS (N,N- dimethyldithiocarbamic acid (3-sulfopropylester), sodium salt); UPS (3-[(amino- iminomethyl)-thio]-1 -propylsulfonic acid); ZPS (3-(2-benzthiazolylthio)-1- propanesulfonic acid, sodium salt); 3-mercapto-propylsulfonicacid-(3-sulfopropyl)ester; methyl-(ra-sulphopropyl)-disulfide, disodium salt; methyl-(ra-sulphopropyl)-trisulfide, disodium salt.

[0131] Such accelerators are typically used in an amount of about 0.1 ppm to about 3000 ppm, based on the total weight of the plating bath. Particularly suitable amounts of accelerator useful in the present invention are 1 to 500 ppm, and more particularly 2 to 100 ppm. Any additional suppressor may be advantageously used in the present invention. Suppressors useful in the present invention include, but are not limited to, polymeric materials, particularly those having heteroatom substitution, and more particularly oxygen substitution. It is preferred that the suppressor is a polyalkyleneoxide. Suitable suppressors include polyethylene glycol copolymers, particularly polyethylene glycol polypropylene glycol copolymers. The arrangement of ethylene oxide and propylene oxide of suitable suppressors may be block, alternating, gradient, or random. The polyalkylene glycol may comprise further alkylene oxide building blocks such as butylene oxide. Preferably, the average molecular mass of suitable suppressors exceeds about 2000 g / mol. The starting molecules of suitable polyalkylene glycol may be alkyl alcohols such as methanol, ethanol, propanol, n-butanol and the like, aryl alcohols such as phenols and bisphenols, alkaryl alcohols such as benzyl alcohol, polyol starters such as glycol, glycerin, trimethylol propane, pentaerythritol, sorbitol, carbohydrates such as saccharose, and the like, amines and oligoamines such as alkyl amines, aryl amines such as aniline, triethanol amine, ethylene diamine, and the like, amides, lactams, heterocyclic amines such as imidazol and carboxylic acids.

[0132] Optionally, polyalkylene glycol suppressors may be functionalized by ionic groups such as sulfate, sulfonate, ammonium, and the like.

[0133] If further suppressors are used, they are typically present in an amount in the range of from about 1 to about 10,000 ppm based on the weight of the bath, and preferably from about 5 to about 10 000 ppm. Preferably no further suppressing agent than the suppressing agent according to the invention is present in the plating bath.

[0134] Leveling agents can advantageously be used in the metal plating baths according to the present invention. The terms “leveling agent” and “leveler” are used herein synonymously. Preferably the composition further comprises at least one leveling agent.

[0135] Suitable leveling agents include, but are not limited to, one or more of polyethylene imine and derivatives thereof, quaternized polyethylene imine, polyglycine, poly(allylamine), polyaniline, polyurea, polyacrylamide, poly(melamine-co- formaldehyde), reaction products of amines with epichlorohydrin, reaction products of an amine, epichlorohydrin, and polyalkylene oxide, reaction products of an amine with a polyepoxide, polyvinylpyridine, polyvinylimidazole as described e.g. in

[0136] WO 2011 / 151785 A1 , polyvinylpyrrolidone, polyaminoamides as described e.g. in WO 2011 / 064154 A2 and WO 2014 / 072885 A2, WO 2019 / 043146 A1 , or copolymers thereof, nigrosines, pentamethyl-para-rosaniline hydrohalide, hexamethylpararosaniline hydrohalide, di- or trialkanolamines and their derivatives as described in WO 2010 / 069810, and biguanides as described in WO 2012 / 085811 A1.

[0137] Furthermore, a compound containing a functional group of the formula N-R-S may be used as a leveling agents, where R is a substituted alkyl, unsubstituted alkyl, substituted aryl or unsubstituted aryl. Typically, the alkyl groups are (Ci-C6)alkyl and preferably (Ci-C4)alkyl. In general, the aryl groups include (C6-C2o)aryl, preferably (Ce- Cw)aryl. Such aryl groups may further include heteroatoms, such as sulfur, nitrogen and oxygen. It is preferred that the aryl group is phenyl or napthyl. The compounds containing a functional group of the formula N-R-S are generally known, are generally commercially available and may be used without further purification. In such compounds containing the N-R-S functional group, the sulfur ("S") and / or the nitrogen ("N") may be attached to such compounds with single or double bonds. When the sulfur is attached to such compounds with a single bond, the sulfur will have another substituent group, such as but not limited to hydrogen, (Ci-Ci2)alkyl, (C2-Ci2)alkenyl, (Ce-C2o)aryl, (Ci-Ci2)alkylthio, (C2-Ci2)alkenylthio, (Ce-C2o)arylthio and the like.

[0138] Likewise, the nitrogen will have one or more substituent groups, such as but not limited to hydrogen, (Ci-Ci2)alkyl, (C2-Ci2)alkenyl, (Cy-Cio)aryl, and the like. The N-R-S functional group may be acyclic or cyclic. Compounds containing cyclic N-R-S functional groups include those having either the nitrogen or the sulfur or both the nitrogen and the sulfur within the ring system.

[0139] In general, the total amount of leveling agents in the electroplating bath is from 0.5 ppm to 10 000 ppm based on the total weight of the plating bath. The leveling agents are typically used in a total amount of from about 0.1 ppm to about 1 000 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.

[0140] A large variety of further additives may typically be used in the bath to provide desired surface finishes for the Cu 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 accelerators, levelers, sources of halide ions, grain refiners and mixtures thereof. Most preferably the electroplating bath contains both, an accelerator and a leveler in addition to the suppressor according to the present invention. Other additives may also be suitably used in the present electroplating baths. Process

[0141] According to one embodiment of the present invention a 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 30 nanometers or less, which features comprise a copper seed or other metal seed like cobalt.

[0142] A further embodiment of the present invention is a process for depositing a copper layer comprising the steps

[0143] (a) providing a substrate comprising a nanometer-sized recessed feature, which feature comprises a metal seed layer like a copper seed or cobalt seed layer;

[0144] (b) contacting the composition as described herein with the substrate, and

[0145] (c) applying a current to the substrate for a time sufficient to deposit a metal layer onto the metal seed layer, particularly a copper or cobalt seed layer, and to fill the nanometer sized feature.

[0146] The present invention is useful for depositing a copper layer on a variety of metal seeded 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 apertures that are provided with a metal seed layer. 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.

[0147] Usually, the metal cobalt seed layer has a thickness of 40 nm to 1.5 nm, preferably of 2 to 10 nm.

[0148] Preferably, the static corrosion of the metal, particularly the cobalt seed layer in the electroplating composition is 10 nm / min or below, preferably 5 nm / min or below, most preferably 3 nm / min or below. As used herein, “static corrosion” means that the electroplating composition is brought into contact with the substrate without applying any electric potential or mechanic abrasion.

[0149] Most preferably the submicrometer-sized features have an (effective) aperture size from 1 to 30 nanometers and / or an aspect ratio of 4 or more. More preferably the features have an aperture size of 25 nanometers or below, most preferably of 20 nanometers or below.

[0150] 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. A convex shape is a feature having an aperture size being at least 25 %, preferably 30 %, most preferably 50 % smaller than the biggest diameter or free distance of the feature before plating.

[0151] 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 0.5 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 leveling agent 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.

[0152] 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 150 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.

[0153] Copper is deposited in apertures according to the present invention without substantially forming voids within the metal copper deposit. By the term "without substantially forming voids", it is meant that 95% of the plated apertures are void-free. It is preferred that 98% of the plated apertures are void-free, mostly preferred is that all plated apertures are void-free.

[0154] 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 coated with a seed layer of metal, such as but not limited to copper or cobalt. Such metal seed layer may be applied by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or the like. 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.

[0155] 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.

[0156] 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.

[0157] Preferably the substrate comprises nanometer sized features and the deposition is performed to fill the micrometer or nanometer sized features, particularly those having an aperture size from 1 to 30 nm and / or an aspect ratio of 4 or more. The additives are even capable of void-free filling features having aperture sizes of 15 nm, particularly 10 nm or below and aspect ratios of 4 or more.

[0158] 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.

[0159] Analytical Methods

[0160] The number average molecular weight (Mn) was determined by1H-NMR and / or TAI- spectroscopy (Fa.Bruker, 400 MHz) at room temperature (25°C) using CDCh as deuterated solvent. For processing the spectra the program MestReNova was used. For the calculation of the experimental PO conversion, the integral at 1.11-1.28 (-CH3) were referenced to the theoretical PO repeating units. The integral at 3.36-3.60 (minus number of protons of the starter) divided by three (CH2CH of the PO) give the actual experimental repeating units of the PO in the molecule. By using TAI-NMR, additional to the experimental PO conversion, the number of 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 secondary OH signals of the propylenoxide to 5.12 ppm. In doubt, this method is the standard to determine the molecular mass of the suppressing agents according to the invention.

[0161] Alternatively, the molecular mass of the suppressing agents may also be determined by size-exclusion chromatography (SEC). 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.

[0162] The amine number was determined according to DIN 53176 by titration of a solution of the polymer in acetic acid with perchloric acid.

[0163] Examples

[0164] Example A: Synthesis of Suppressors

[0165] Several suppressors have been synthesized by polyalkoxylation of the respective starters. Example A1 : Synthesis of Suppressor 1

[0166] Bisaminopropyl piperazin (600,9 g) was placed under nitrogen atmosphere into a 2 I autoclave and heated up to 100 °C. Then propylene oxide (696,9 g) was added over a period of 11 h. The mixture post-reacted for 6 h. The yellow intermediate product 1 (1285 g) having an amine number of 518 mg KOH / g was obtained.

[0167] The intermediate product 1 (151 ,4 g) and potassium tert-butoxide (1.05 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1.5 bar and the mixture was homogenized at 130 °C for 1 h. Then propylene oxid (548,8 g) was added at 130 °C over a period of 9 h, reaching a maximum pressure of 5 bar. To complete the reaction, the mixture post-reacted for 6 h at 130 °C at a pressure of 5 bar. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Suppressor 1 was obtained as orange liquid (695 g) with an amine value of 115 mg KOH / g and a number average molecular mass (Mn) of 1 977 g / mol (theoretical 2 000 g / mol).

[0168] Example A2: Synthesis of Suppressor 2

[0169] The intermediate product 1 of example 1 (216,3 g) and potassium tert-butoxide (1.13 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1.5 bar and the mixture was homogenized at 130 °C for 1 h. Then propylene oxid (522 g) was added at 130 °C over a period of 8 h, reaching a maximum pressure of 5 bar. To complete the reaction, the mixture post-reacted for 6 h at 130 °C at a pressure of 5 bar. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Suppressor 2 was obtained as yellowish liquid (746 g) with an amine value of 149 mg KOH / g and a number average molecular mass (Mn) of 1397 g / mol (theoretical 1478 g / mol). Example A3: Synthesis of Suppressor 3

[0170] Ethylene diamine (97 g) was placed under nitrogen atmosphere into a 3.5 I autoclave and heated up to 80 °C. Then glycidol (478.2 g) was added over a period of 22 h. The mixture post-reacted for 8 h. The yellow intermediate product 2 (575 g) having an amine number of 300 mg KOH / g was obtained.

[0171] The intermediate product 2 (123 g) and potassium tert-butoxide (1 ,2 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1.5 bar and the mixture was homogenized at 130 °C for 1 h. Then propylene oxid (741.6 g) was added at 130 °C over a period of 10 h, reaching a maximum pressure of 5 bar. The mixture post-reacted for 6 h. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Suppressor 3 was obtained as yellowish liquid (864 g) with an amine value of 45 mg KOH / g and a number average molecular mass (Mn) of 2 389 g / mol (theoretical 2 505 g / mol).

[0172] Example A4: Synthesis of Suppressor 4

[0173] Trisaminoethylamine (396 g) was placed under nitrogen atmosphere into a 3.5 I autoclave and heated up to 100 °C. Then propylene oxide (943,7 g) was added over a period of 10 h. The mixture post-reacted for 10 h. A yellow intermediate product 3 (1346 g) having an amine value of 453 mg KOH / g was obtained.

[0174] The intermediate product 3 (256.5 g) and potassium tert-butoxide (1.25 g) were placed into a 3.5 I autoclave. After nitrogen neutralization, the pressure was adjusted to 1.5 bar and the mixture was homogenized at 130 °C for 1 h. Then propylene oxid (1023 g) was added at 130 °C over a period of 12 h, reaching a maximum pressure of 5 bar. The mixture post-reacted for 6 h. Then, the temperature was decreased to 80 °C and volatile compounds were removed in vacuum at 80 °C. Suppressor 4 was obtained as orange liquid (1260 g) with an amine value of 90 mg KOH / g and a number average molecular mass (Mn) of 2684 g / mol (theoretical 2469 g / mol).

[0175] Example B: Copper electroplating experiments

[0176] For the plating experiments two patterned wafer substrates were used as shown in Fig.1 . The wafer substrates were bearing a Cu seed. The features shown in Fig. 1 had a diameter of about 30 nm at the top of the opening and a diameter of about 22 nm at half height of the feature and a depth of about 89 nm.

[0177] Example B1a: Electroplating with suppressor 1 , partial fill

[0178] A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS and 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 1 as prepared in example A1 .

[0179] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 3.4 s. The thus electroplated copper layer was investigated by SEM inspection.

[0180] The result is shown in Fig. 2a which provides the SEM image of the trenches partially filled with copper. Fig. 2a shows that the copper is deposited on the bottom of the feature while the deposition on the side walls of the feature is suppressed.

[0181] Example B1b: Electroplating with suppressor 1 , full fill A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS and 8.0 ml / l of a 1.14 wt % solution in DI water of suppressor 1 as prepared in example A1.

[0182] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 27.0 s. The thus electroplated copper layer was investigated by SEM inspection.

[0183] The result is shown in Fig. 2b which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting significant voids or seams in the fully filled trenches as shown in Fig. 2b.

[0184] Example B2a: Electroplating with suppressor 2, partial fill

[0185] A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 2 as prepared in example A2.

[0186] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 3.4 s. The thus electroplated copper layer was investigated by SEM inspection.

[0187] The result is shown in Fig. 3a which provides the SEM image of the copper filled trenches. The neighboring trenches are partly filled without exhibiting voids or seams as shown in Fig. 3a.

[0188] Example B2b: Electroplating with suppressor 2, full fill

[0189] A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 2 as prepared in example A2. A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 27.0 s. The thus electroplated copper layer was investigated by SEM inspection.

[0190] The result is shown in Fig. 3b which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting voids or seams in the fully filled trenches as shown in Fig. 3b.

[0191] Example B3a: Electroplating with suppressor 3, partial fill

[0192] A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 3 as prepared in example A3.

[0193] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 3.4 s. The thus electroplated copper layer was investigated by SEM inspection.

[0194] The result is shown in Fig. 4a which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting voids or seams in the partially filled trenches as shown in Fig. 4a.

[0195] Example B3b: Electroplating with suppressor 3, full fill

[0196] A plating bath was prepared by combining DI water, 40.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 3 as prepared in example A3.

[0197] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 27.0 s. The thus electroplated copper layer was investigated by SEM inspection. The result is shown in Fig. 4b which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting voids or seams in the fully filled trenches as shown in Fig. 4b.

[0198] Example B4a: Electroplating with Suppressor 4, partial fill

[0199] A plating bath was prepared by combining DI water, 5.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 4 as prepared in example A4.

[0200] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 3.4 s. The thus electroplated copper layer was investigated by SEM inspection.

[0201] The result is shown in Fig. 5a which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting voids or seams in the partially filled trenches as shown in Fig. 5a.

[0202] Example B4b: Electroplating with Suppressor 4, full fill

[0203] A plating bath was prepared by combining DI water, 5.0 g / l copper as copper sulfate, 10.0 g / l sulfuric acid, 0.050 g / l chloride ion as HCI, 0.028 g / l of SPS, 8.0 ml / l of a 1.14 wt% solution in DI water of suppressor 4 as prepared in example A4.

[0204] A copper layer was electroplated onto a wafer substrate with features provided with a copper seed layer as shown in Fig. 1 by contacting the wafer substrate with the above described plating bath at ambient temperature applying a direct current of -3.00 mA / cm2for 27.0 s. The thus electroplated copper layer was investigated by SEM inspection.

[0205] The result is shown in Fig. 5b which provides the SEM image of the copper filled trenches. The neighboring trenches are equally filled without exhibiting voids or seams in the fully filled trenches as shown in Fig. 5b.

Claims

Claims1 . An acidic aqueous composition for copper electroplating comprising(a) copper ions;(b) halide ions; and(c) at least one additive of formula S1whereinXs1is selected from a linear, branched or cyclic C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS4°;RS1is selected from -(C3H6-O)m-H, -XS4-N[-(C3H6-O)m-H]2, Zs, XS5-ZS, XS4-N(ZS)2;RS2, RS3, RS4are selected from H, RS1, or RS4°, or RS3and an adjacent group RS4or, if n>2, two adjacent groups RS4together form a divalent group Xs2;RS4° is a linear or branched C1-C20 alkyl, which may optionally be substituted hydroxy, alkoxy, or alkoxycarbonyl;Zsis a group of formula S3;Xs2is selected from a linear or branched C1-C12 alkanediyl, which may be substituted or unsubstituted, and which may optionally be interrupted by O, S or NRS4°; andXs3is a linear or branched Ci to C12 alkanediyl, which may be interrupted by O and S atoms or substituted by O-RS31;Xs4is a linear or branched Ci to C12 alkanediyl;Xs5is a divalent group comprising at least one C2 to Ce polyoxyalkylene;Rs3i, RS32are independently selected from (a) -(C3H6-O)m-H or (b) a further branching group to form a multiple branching group (ZSp)p(RS31RS32)2P;ZSpis selected fromm is an integer of from 1 to 30; n is an integer of from 0 to 6. p is an integer of from 2 to 4.

2. The composition according to claim 1 , wherein Xs1is selected from (a) a Ci-Ce alkanediyl, preferably methanediyl, ethanediyl or propanediyl, and (b) -(CH2)q-[Q- (CH2)r]s-, wherein Q is selected from O, S or NR40, q and r are integers from 1 to 6, s is an integer from 1 to 4 and q + r s is the total number of C atoms in Xs1.

3. The composition according to anyone of the preceding claims, wherein the number average molecular mass Mnof the additive is from 1000 to 6000 g / mol, preferably from 1200 to 3500 g / mol.

4. The composition according to anyone of the preceding claims, wherein n is 0, 1 , or 2; andRS2, RS3, RS4are independently selected from RS1.

5. The composition according to anyone of the preceding claims, comprising an additive of formulaor an additive of formula (S2b)or an additive of formula (S2c)S2or an additive of formula (S2d)whereinRS1, n, have the prescribed meanings;RS2, RS3and RS4are independently RS1or RS4°, preferably RS1;^si xsn xS2are independently a Ci to C3alkanediyl; and r is an integer from 1 to 8, preferably from 2 to 6.

6. The composition according to anyone of the preceding claims, whereinRS1is -(C3H6-O)m-H,RS2, RS3and RS4are RS1;Xs1is a Ci to C3alkanediyl; and m is an integer of from 4 to 25.

7. The composition according to anyone of the preceding claims, whereinwhereinRS1, RS2, RS3and RS41are -(C3H6-O)m-H;RS42is -XS4-N[-(C3H6-O)m-H]2;Xs4is a linear or branched Ci to Ce alkanediyl; m is an integer of from 2 to 20; j is 1 or 2.

8. The composition according to claim 7, whereinRS1, RS2, RS3and RS41are -(C3H6-O)m-H;RS42is -XS4-N[-(C3H6-O)m-H]2;Xs4is a linear or branched C2to C4 alkanediyl, preferably ethane-1 ,2-diyl; m is an integer of from 3 to 15; j is 1.

9. The composition according to anyone of the preceding claims, wherein the halide ions comprise chloride ions in a concentration of from 10 to 100 ppm, preferably from 20 to 80 ppm.

10. The composition according to anyone of the preceding claims, wherein the halide ions comprise bromide ions in a concentration of from 5 to 100 ppm, preferably from 20 to 80 ppm.11 . The composition according to anyone of the preceding claims, further comprising an accelerator comprising one or more sulfidic sulphur atoms and one or more sulfonic or phosphonic acid group or their salts.

12. Use of a copper electroplating bath comprising a composition according to anyone of claims 1 to 11 for depositing copper on substrates comprising recessed features having an aperture size of 10 nanometers or less, preferably 5 nm or less, which features comprise a metal seed layer, particularly a copper or cobalt seed layer.

13. A process for depositing a copper layer comprising the steps(a) providing a substrate comprising a nanometer-sized recessed feature, which feature comprises a metal seed layer, particularly a copper or cobalt seed layer;(b) contacting a composition according to any one of claims 1 to 11 with the substrate, and(c) applying a current to the substrate for a time sufficient to deposit a copper layer onto the metal seed layer and to fill the nanometer sized feature.

14. A process according to claim 13, wherein the feature comprises a cobalt seed layer and the static corrosion of the cobalt seed layer by the electroplating composition is 10 nm / min or below, preferably 5 nm / min or below.

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