Tin or tin alloy electroplating composition containing a pyrazole-type antioxidant

Abstract

The present invention relates to a compound comprising tin ions, optionally alloying metal ions, and a compound of formula X1a [Case 1] TIFF2024538419000029.tif23133 or formula X1b [Case 2] TIFF2024538419000030.tif29127 or formula X1c [C3] TIFF2024538419000031.tif36131 or formula X1d [C4] TIFF2024538419000032.tif27137 or formula X1e [C5] TIFF2024538419000033.tif38133 or at least one tautomer of formula X1a, X1b, X1c, X1d and X1e (In the formula, R X1 , R X1a is, independently, (a) H, and (b) all are unsubstituted or OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 Aryl alkyl, with the proviso that when the antioxidant is of formula X1a, R X1 is C5~C 12 Aryl or C6-C 15 Not alkylaryl, R X2 teeth, (a) H, OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , and (b) all are unsubstituted or OH, OR X3 , -CO-RX3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 Aryl alkyl, In formula X1a, at least one R X2 is OH, and in formula X1a, R X1 is t-butyl, R X2 2 is C5~C 12 Aryl or -CO-R X3 Instead, R X3 is H or C1-C6 alkyl, n is a group R X2 (the number of providing an aqueous composition comprising wherein no further metal ions are present in the composition other than tin ions and at least one of silver ions, indium ions and bismuth ions; The composition does not contain any reducing agent other than the compounds of formulae X1a-X1e.

Description

[Technical field]

[0001] The present invention relates to tin or tin alloy electroplating compositions containing antioxidants, methods of use thereof, and methods of electroplating tin or tin alloys. [Background technology]

[0002] Metals and metal alloys are commercially important, particularly in the electronics industry where they are often used as electrical contacts, final finishes and solders.

[0003] Lead-free solders, such as tin, tin-silver, tin-copper, tin-bismuth, tin-silver-copper, etc., are common metals used in solders. These solders are often deposited on semiconductor substrates by metal electroplating baths.

[0004] A typical tin plating solution contains dissolved tin ions, water, an acid electrolyte such as methanesulfonic acid in an amount sufficient to render the bath conductive, antioxidants, and proprietary additives to improve plating uniformity and the quality of the metal deposit with respect to surface roughness and void formation. Such additives usually include surfactants and grain refiners.

[0005] Certain applications of lead-free solder plating are challenging in the electronics industry, for example when used as a capping layer for copper pillars, where a relatively small amount of lead-free solder, such as tin or tin-silver solder, is deposited on the copper pillar.

[0006] Tin is used in plating compositions in the 2+ oxidation state. Dissolved Sn 2+ From Sn 4+ and Sn 4+Hydrolysis of tin may result in the formation of insoluble SnO2 during electroplating, especially during storage of the plating bath. Not only does the formation of insoluble tin waste valuable tin metal and increase operating costs, but excess tin mud in the plating solution can also have a detrimental effect on the electroplating process. To reduce the formation of insoluble tin oxide in the tin plating solution, antioxidant components are usually added to the plating bath.

[0007] No. 4,871,429 discloses an electrolyte for electroplating tin or tin-lead alloys, which comprises a soluble divalent tin compound, a soluble alkyl or alkylol sulfonic acid in an amount sufficient to provide a solution having a pH of less than about 3, at least one wetting agent, and a hydroxyphenyl compound in an amount sufficient to reduce or prevent the formation of tetravalent tin and tin oxide sludge. Preferred hydroxyphenyl compounds include pyrocatechol, hydroquinone, resorcinol, phloroglucinol, pyrogallol, 3-aminophenol, or hydroquinone sulfate.

[0008] WO2019 / 201753 A1 discloses a composition for tin and tin alloy electroplating, which may contain one or more antioxidants, such as hydroquinone, and hydroxylated and / or alkoxylated aromatic compounds, including sulfonic acid derivatives of the aromatic compounds, preferably the following: hydroquinone; methylhydroquinone; resorcinol; catechol; 1,2,3-trihydroxybenzene; 1,2-dihydroxybenzene-4-sulfonic acid; 1,2-dihydroxybenzene-3,5-disulfonic acid; 1,4-dihydroxybenzene-2-sulfonic acid; 1,4-dihydroxybenzene-2,5-disulfonic acid; 2,4-dihydroxybenzenesulfonic acid, and p-methoxyphenol.

[0009] CN 107502927 A discloses a tin methanesulfonate electroplating bath containing one or more primary antioxidants selected from phenol, o-diphenol, m-diphenol, p-diphenol, and their derivatives substituted with carboxyl, amino, nitro, and sulfonic groups, and (2R,3S)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-benzopyran-3,5,7-triol as an auxiliary antioxidant.

[0010] KR 10 1175062 B1 discloses a lead-free solder tin-silver plating bath containing divalent tin ions, monovalent silver ions, a conductive salt, a silver ion complexing agent, a leveling agent, and antioxidants, among others catechol, hydroquinone, ascorbic acid, ascorbate, and 2-phenylenediamine.

[0011] CN102732918 A discloses a tin electroplating bath containing tin ions and an antioxidant such as a pyrazolone. The tin bath further contains gold ions and a brightener.

[0012] JP2001262391 A discloses a tin electroplating bath containing tin ions and 1,3-dimethylpyrazolone. The tin bath further contains copper ions, silver ions, and additives such as surfactants.

[0013] WO 2017 / 061443 A1 relates to a tin or tin alloy coated copper powder for preparing a conductive paste containing the tin or tin alloy coated copper powder. To produce such tin coated copper powder, a tin electroless bath is disclosed that contains tin ions and a reducing agent such as a phosphoric acid compound, a borohydride compound, or a hydrazine derivative. As an example of the hydrazine derivative, 3-methyl-5-pyrazolone is given. However, reducing agents that can electrolessly reduce tin(II) to elemental tin have a negative effect on the electroplating process and should be avoided.

[0014] US 2021 / 025070 A1 discloses a tin electroplating bath and method for filling micrometer recesses without substantially forming voids in the metal deposit for use as contacts and solders in the electronics industry.

[0015] There remains a strong need for antioxidants that have excellent long-term antioxidant efficacy and stability, good or even excellent solubility in aqueous media, low toxicity, and do not inhibit the electroplating process. It is also desirable for electroplating compositions to exhibit little or no discoloration during use. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] US 4 871 429 [Patent Document 2] WO2019 / 201753 A1 [Patent Document 3] CN 107502927A [Patent Document 4] KR10 1175062 B1 [Patent Document 5] CN102732918A [Patent Document 6] JP2001262391A [Patent Document 7] WO 2017 / 061443 A1 [Patent Document 8] US 2021 / 025070 A1 Summary of the Invention [Problem to be solved by the invention]

[0017] It is therefore an object of the present invention to provide a tin or tin alloy electroplating antioxidant that has excellent long-term antioxidant effect and stability and reduces discoloration. Another object of the present invention is to provide an antioxidant that exhibits good or even excellent solubility in aqueous media. Yet another object of the present invention is to provide an antioxidant that is less toxic. Yet another object of the present invention is to provide an antioxidant that does not interfere with the electroplating process, and in particular allows for the deposition of substantially planar tin or tin alloy layers using tin or tin alloy electroplating baths, filling features on a micron scale without substantial formation of defects such as, but not limited to, voids. Also, it should not interfere with the electroplating process by electroless reduction of tin or tin alloy ions to the respective elemental metals. [Means for solving the problem]

[0018] Summary of the Invention The present invention relates to a compound comprising tin ions, optionally alloying metal ions, and a compound of formula X1a [ka] Or formula X1b [ka] or formula X1c [ka] Or formula X1d [ka] or formula X1e [ka] or at least one antioxidant of the tautomers of formulae X1a, X1b, X1c, X1d and X1e (In the formula, R X1 , R X1a is, independently, (a) H, and (b) all are unsubstituted or OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 Aryl alkyl, with the proviso that when the antioxidant is of formula X1b, R X1 is C5~C 12 Aryl or C6-C 15 Not alkylaryl, R X2 teeth, (a) H, OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , and (b) all are unsubstituted or OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 Aryl alkyl, In formula X1a, at least one R X2 is OH, and in formula X1a, R X1 is t-butyl, R X2 2 is C5~C 12 Aryl or -CO-R X3 Instead, R X3 is H or C1-C6 alkyl, n is a group R X2 (the number of The present invention provides an aqueous composition comprising:

[0019] A further embodiment of the present invention is the use of an antioxidant as described herein in a bath for depositing a tin or tin-alloy containing layer, wherein the tin-alloy containing layer comprises an amount of alloy metal between 0.01 and 10 wt. %.

[0020] Yet another embodiment of the present invention comprises: a) contacting a substrate with a tin-alloy electroplating bath comprising a composition described herein; and b) applying a current density to the substrate for a time sufficient to deposit a tin-alloy layer on the substrate. This is a method for depositing a tin or tin alloy layer on a substrate by

[0021] The antioxidant according to the present invention can be advantageously used in bonding technologies such as, but not limited to, bump formation processes, the manufacture of tin or tin alloy bumps, typically with heights and widths of 1-200, preferably 3-100, most preferably 5-50 micrometers, circuit board technologies or electronic packaging processes. In one particular embodiment, the substrate has micrometer-sized features and deposition is carried out to fill the micrometer-sized features, where the micrometer-sized features have a size of 1-200 micrometers, preferably 3-100 micrometers.

[0022] The antioxidant used in the plating composition according to the present invention has low toxicity compared to commonly used antioxidants such as catechol. The antioxidant has excellent long-term antioxidant effect and stability, and is less likely to discolor. The antioxidant exhibits good or even better solubility in aqueous media compared to conventional antioxidants. Furthermore, the antioxidant does not interfere with the electroplating process, and in particular allows for the deposition of substantially planar tin or tin alloy layers using tin or tin alloy electroplating baths, filling features on a micron scale without substantial formation of defects such as, but not limited to, voids. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Detailed Description of the Invention Antioxidants Tin or tin alloy electroplating compositions according to the present invention include at least one of the antioxidants according to formulas X1a-X1e.

[0024] [ka]

[0025] In one embodiment, R X1 and R X1a may be H. In another embodiment, R X1 and R X1a are all unsubstituted or OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 When the antioxidant is of formula X1b, R X1 is C6~C 15 Alkylaryl or C6-C 15 It is important to note that R is not an aryl alkyl group, as otherwise it would not function properly as an antioxidant. X1 is (a) H, and (b) all unsubstituted or -CO-OR X3 OR -SO2-OR X3 More preferably, R is selected from C1-C6 alkyl, phenyl, and C1-C4 alkylphenyl, each of which is substituted with X1 is selected from methyl, ethyl or butyl, in particular t-butyl.

[0026] In one embodiment, R X2 H, OH, OR X3 , -CO-R X3 , -CO-ORX3 , and -SO2-OR X3 In another embodiment, R X2 are all unsubstituted or OH, OR X3 , -CO-R X3 , -CO-OR X3 , -SO2-OR X3 , CN, halogen, or a combination thereof; C1-C6 alkyl, C1-C6 alkenyl, C5-C 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 In formula X1a, at least one R X2 In formula X1a, R X1 is t-butyl, R X2 2 is C5~C 12 Aryl or -CO-R X3 The substituents R X2 If present, each R X2 can be independently selected. X2 H, OH, OR X3 , -CO-R X3 , -CO-OR X3 , and -SO2-OR X3 ; and OH, OR X3 , -CO-R X3 , -CO-OR X3 , or -SO2-OR X3 More preferably, R is selected from C1-C4 alkyl, phenyl, and C1-C4 alkylphenyl, each of which is substituted with X2 is H, OH, -CO-R X3 , methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, t-butyl, and phenyl, preferably H, OH, methyl and ethyl, which may be unsubstituted or substituted with OH.

[0027] In general, R X3may be H or C1-C6 alkyl, preferably H or C1-C4 alkyl, more preferably H or C1-C3 alkyl, and most preferably H, methyl or ethyl.

[0028] n is a group R X2 In formula X1a and X1b, it is 3, and in formula X1c, it is 2. In formula X1b, there are two substituents R X2 It should be noted that there exists

[0029] As used herein, "alkyl" and "alkanediyl" refer to linear, branched or cyclic alkyl or alkanediyl groups, respectively. As used herein, "aromatic" or "aryl" refer to monocyclic or bicyclic carbocyclic aromatic groups. As used herein, "alkenyl" and "alkenediyl" refer to linear, branched or cyclic alkenyl or alkenediyl groups, respectively. As used herein, "arylalkyl" refers to an alkyl group substituted with one or more aryl groups, particularly one or more phenyl groups, most particularly one phenyl group. As used herein, "alkylaryl" refers to an aryl group substituted with one or more C1-C6 alkyl groups, particularly one or more C1-C4 alkyl groups, more particularly one or more methyl, ethyl or propyl groups, most particularly one or two methyl or ethyl groups.

[0030] It should be noted that some of the lactam compounds of formulae X1a, X1b, X1c and X1d are in equilibrium with the tautomeric lactim form, for example:

[0031] [ka]

[0032] Although only the lactam forms are referred to in this application, the tautomeric lactam forms are also intended to be encompassed.

[0033] Substituent R X2n The positions are numbered as follows:

[0034] [ka]

[0035] In a preferred embodiment, the antioxidant is of formula X1a, where R X1 is selected from C1-C4 alkyl, R X2 1 or R X2 2 is OH and the other R X2 1. R X2 2, and R X2 3 is H, methylethyl, propyl or butyl, or -CO-R X3 It is.

[0036] Preferred antioxidants of formula X1a are:

[0037] [Table 1]

[0038] Particularly preferred antioxidants of formula X1a are:

[0039] [ka]

[0040] In another preferred embodiment, the antioxidant is of formula X1b, where R X1 is selected from H and C1-C4 alkyl; the first R X2 1 is H and the second R X2 1 is selected from H, C1-C4 alkyl, -SO3H, COOH, and COCH3; and R X2 2 is selected from H and C1-C4 alkyl.

[0041] Preferred antioxidants of formula X1b are:

[0042] [Table 2]

[0043] Particularly preferred antioxidants of formula X1b are:

[0044] [ka]

[0045] In another preferred embodiment, the antioxidant is of formula X1c, wherein R X1 is selected from H, C1-C4 alkyl and phenyl; R X1a is selected from H and C1-C4 alkyl; the first R X2 1 is H and the second R X2 1 is selected from H, C1-C4 alkyl, -SO3H, COOH, and COCH3; and R X2 2 is selected from H and C1-C4 alkyl.

[0046] Preferred antioxidants of formula X1c are:

[0047] [Table 3]

[0048] Particularly preferred antioxidants of formula X1c are:

[0049] [ka]

[0050] In another preferred embodiment, the antioxidant is of formula X1d, wherein R X1 is selected from H and C1-C4 alkyl; and R X2 is selected from H, C1-C4 alkyl, -SO3H, COOH and COCH3.

[0051] Preferred antioxidants of formula X1d are:

[0052] [Table 4]

[0053] In another preferred embodiment, the antioxidant is of formula X1e, wherein R X1 is selected from H, C1-C4 alkyl and phenyl; R X1a is selected from H and C1-C4 alkyl; the first R X2 1 is H and the second R X2 1 is selected from H and C1-C4 alkyl; the first R X2 1 is H and the second R X2 1 is the first R X2 1 is H and the second R X2 1 is selected from H, C1-C4 alkyl, -SO3H, COOH, and COCH3; and R X2 2 is selected from H and C1-C4 alkyl.

[0054] Preferred antioxidants of formula X1e are:

[0055] [Table 5]

[0056] Particularly preferred antioxidants of formula X1e are:

[0057] [ka]

[0058] Those skilled in the art will appreciate that more than one antioxidant may be used, however, it is preferred to use only one antioxidant in the electroplating composition.

[0059] A wide variety of other additives can usually be used in the bath to provide the desired surface finish to the plated tin or tin alloy bumps. Usually, two or more additives are used, each additive performing a desired function. Advantageously, the electroplating bath can contain one or more of a leveling agent, a surfactant, a grain refiner, a complexing agent in the case of alloy deposition, an antioxidant, and mixtures thereof. Most preferably, the electroplating bath contains a surfactant and optionally a grain refiner in addition to the leveling agent according to the invention. Other additives can also be suitably used in the electroplating bath of the invention.

[0060] Leveling Agent The electroplating composition may further comprise a leveling agent. It will be understood by those skilled in the art that more than one leveling agent may be used, however, it is preferred to use only one leveling agent.

[0061] Suitable leveling agents include, but are not limited to, polyaminoamides and derivatives thereof, polyalkanolamines and derivatives thereof, polyethyleneimines and derivatives thereof, quaternized polyethyleneimines, polyglycines, poly(allylamine), polyanilines, polyureas, polyacrylamides, poly(melamine-co-formaldehyde), reaction products of amines with epichlorohydrin, reaction products of amines with epichlorohydrin and polyalkylene oxides, reaction products of amines with polyepoxides, polyvinylpyridines, polyvinylimidazoles, polyvinylpyrrolidones, or copolymers thereof, nigrosine, pentamethyl-para-rosaniline hydrohalide, hexamethyl-pararosaniline hydrohalide, or compounds containing a functional group of the formula NRS, where R is a substituted alkyl, unsubstituted alkyl, substituted aryl, or unsubstituted aryl. Typically, the alkyl group is a C1-C6 alkyl, preferably a C1-C4 alkyl. In general, the aryl group is a C6-C 20 Aryl, preferably C6-C 12The aryl group may further include heteroatoms such as sulfur, nitrogen, oxygen, etc. The aryl group is preferably phenyl or naphthyl. Compounds containing a functional group of formula NRS are generally known, generally commercially available, and can be used without further purification.

[0062] In such compounds containing NRS functional groups, sulfur ("S") and / or nitrogen ("N") may be bonded to such compounds by single or double bonds. When sulfur is bonded to such compounds by a single bond, it is not limited to hydrogen, C1-C 12 Alkyl, C2-C 12 Alkenyl, C6-C 20 Aryl, C1-C 12 Alkylthio, C2-C 12 Alkenylthio, C6-C 20 Similarly, the nitrogen may have one or more substituents, such as hydrogen, C1-C4, aryl, arylthio, arylsulfonyl ... 12 Alkyl, C2-C 12 Alkenyl, C7-C 10 NRS functional groups include, but are not limited to, aryl. NRS functional groups may be acyclic or cyclic. Compounds containing cyclic NRS functional groups include those having either nitrogen or sulfur, or both nitrogen and sulfur, in the ring system.

[0063] Further levelling agents are trialkanolamine condensates, such as those described in WO 2010 / 069810.

[0064] In a preferred embodiment, a fluorinated α,β-unsaturated carbonyl compound of formula L1a can be used as a leveling agent:

[0065] [ka]

[0066] (In the formula, R L1 is each group RL1 n are independently selected from -F, linear or branched C1 or C2 fluorinated C1-C6 alkyl; R L2 are C1-C6 alkyl, C1-C6 alkenyl, C5-C6 alkyl, C6-C6 alkoxy, or halogen, especially F, all of which are substituted with CN, OH, C1-C6 alkoxy, or halogen, especially F. 12 Aryl, C6-C 15 Alkylaryl, C6-C 15 is arylalkyl; R L3 is H, C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkoxy, or halogen, Cl, CN, and OH, preferably R L1 or H; X L1 teeth, (a) The following: (i) C3-C5 alkanediyl, (ii) C3-C5 alkenediyl, or (b) C5-C together with adjacent C=C double bonds 12 Forms an aromatic ring system; n is a group R L1 is a number selected from 1, 2 or 3, preferably 1 or 2, and most preferably 1).

[0067] As used herein, "fluorinated at the C1 or C2 position" means that there is at least one, and preferably two, F substitutions at the C1 or C2 position of the alkyl group.

[0068] Preferably, R L1 -F, -CR L3 2F, -CR L3 F, -CF3, -CFR L3 -CR L3 3. -CF2-CR L3 3. -CF2-CFR L3 3. -CF2-CF2R L3 and CF2-CF3, where R L3is selected from H and C1-C6 alkyl. Particularly preferred groups R L1 may be -F or perfluorinated C1-C4 alkyl, particularly -CF3. L1 If present, different groups R L1 Each specific substituent R L1 n , i.e. R L1 1. R L1 2, and R L1 Can be used for 3.

[0069] Further specific fluorinated α,β-unsaturated carbonyl compounds of formula L1a are described in unpublished European Patent Application No. 2003 / 0133634, which is incorporated herein by reference.

[0070] Generally, the total amount of leveling agent in the electroplating bath is 0.5 ppm to 10,000 ppm based on the total weight of the plating bath. The leveling agent according to the present invention is typically used in a total amount of about 100 ppm to about 10,000 ppm based on the total weight of the plating bath, although greater or lesser amounts may be used.

[0071] Surfactants One or more nonionic surfactants may be used in the composition of the present invention. Typically, the nonionic surfactant has an average molecular weight of 200 to 100,000, preferably 500 to 50,000, more preferably 500 to 25,000, and even more preferably 750 to 15,000. Such nonionic surfactants are typically present in the electrolyte composition at a concentration of 1 to 10,000 ppm, preferably 5 to 10,000 ppm, based on the weight of the composition. Preferred alkylene oxide compounds include, but are not limited to, polyalkylene glycols, such as alkylene oxide addition products of organic compounds having at least one hydroxy group and 20 or less carbon atoms, and tetrafunctional polyethers derived from the addition of different alkylene oxides to low molecular weight polyamine compounds.

[0072] Preferred polyalkylene glycols are polyethylene glycol and polypropylene glycol. Such polyalkylene glycols are generally commercially available from a variety of sources and can be used without further purification. Capped polyalkylene glycols, where one or more terminal hydrogens are replaced with hydrocarbyl groups, can also be suitably used. Examples of suitable polyalkylene glycols include those of the formula RO-(CXYCX'Y'O) n R', where R and R' are independently H, C2-C 20 Alkyl groups and C6-C 20 aryl groups; X, Y, X', and Y' are each independently selected from hydrogen, alkyl, such as methyl, ethyl, or propyl, aryl, such as phenyl, or aralkyl, such as benzyl; and n is an integer from 5 to 100,000. Typically, one or more of X, Y, X', and Y' are hydrogen.

[0073] Suitable EO / PO copolymers generally have a weight ratio of EO:PO of 10:90 to 90:10, preferably 10:90 to 80:20. Such EO / PO copolymers preferably have an average molecular weight of 750 to 15,000. Such EO / PO copolymers are available from various sources, for example, under the trade name "PLURONIC" (registered trademark) from BASF.

[0074] Suitable alkylene oxide condensation products of organic compounds having at least one hydroxy group and up to 20 carbon atoms include those having aliphatic hydrocarbons of 1 to 7 carbon atoms, unsubstituted aromatic compounds, or alkylated aromatic compounds having up to 6 carbons in the alkyl portion, such as those disclosed in US 5 174 887. The aliphatic alcohols may be saturated or unsaturated. Suitable aromatic compounds are those having up to 2 aromatic rings. The aromatic alcohols have up to 20 carbon atoms before being derivatized with ethylene oxide. Such aliphatic and aromatic alcohols may be further substituted, such as with sulfate or sulfonate groups.

[0075] Crystal Refining Agent The tin or tin alloy electroplating bath may further contain a grain refiner different from the leveller according to the invention. The grain refiner may be selected from compounds of formula G1 or G2: [ka] (Wherein, each R 1 are independently C1-C6 alkyl, C1-C6 alkoxy, hydroxy, or halogen; R 2 and R 3 is independently selected from H and C1-C6 alkyl; R 4 is H, OH, C1-C6 alkyl, or C1-C6 alkoxy; m is an integer of 0 to 2; each R 5 is independently C1-C6 alkyl; each R 6 is independently selected from H, OH, C1-C6 alkyl, or C1-C6 alkoxy; n is 1 or 2; and p is 0, 1, or 2.

[0076] Preferably, each R 1 R is independently C1 to C6 alkyl, C1 to C3 alkoxy, or hydroxy, and more preferably C1 to C4 alkyl, C1 to C2 alkoxy, or hydroxy. 2 and R 3 are independently preferably selected from H and C1-C3 alkyl, more preferably H and methyl. 4 is H, OH, C1-C4 alkyl or C1-C4 alkoxy, more preferably H, OH or C1-C4 alkyl. R 5 is preferably C1 to C4 alkyl, more preferably C1 to C3 alkyl. 6is preferably selected from H, OH, or C1-C6 alkyl, more preferably H, OH, or C1-C3 alkyl, even more preferably H or OH. m is preferably 0 or 1, more preferably m is 0. Preferably, n is 1. p is preferably 0 or 1, more preferably p is 0. Mixtures of first crystal refinement agents may be used, for example two different crystal refinement agents of formula 1, two different crystal refinement agents of formula 2, or a mixture of a crystal refinement agent of formula 1 and a crystal refinement agent of formula 2.

[0077] Exemplary compounds useful as such crystal refiners include, but are not limited to, cinnamic acid, cinnamaldehyde, benzylideneacetone, picolinic acid, pyridinedicarboxylic acid, pyridinecarboxaldehyde, pyridinedicarboxaldehyde, or mixtures thereof. Preferred crystal refiners include benzalacetone, 4-methoxybenzaldehyde, benzylpyridine-3-carboxylate, and 1,10-phenanthroline.

[0078] Further crystal refiners can be selected from α,β-unsaturated aliphatic carbonyl compounds. Suitable α,β-unsaturated aliphatic carbonyl compounds include, but are not limited to, α,β-unsaturated carboxylic acids, α,β-unsaturated carboxylic esters, α,β-unsaturated amides, and α,β-unsaturated aldehydes. Preferably, such crystal refiners are selected from α,β-unsaturated carboxylic acids, α,β-unsaturated carboxylic esters, and α,β-unsaturated aldehydes, more preferably α,β-unsaturated carboxylic acids, and α,β-unsaturated aldehydes. Exemplary α,β-unsaturated aliphatic carbonyl compounds include (meth)acrylic acid, crotonic acid, C1-C6 alkyl (meth)acrylates, (meth)acrylamides, C1-C6 alkyl crotonates, crotonamides, crotonaldehydes, (meth)acroleins, or mixtures thereof. Preferred α,β-unsaturated aliphatic carbonyl compounds are (meth)acrylic acid, crotonic acid, crotonaldehyde, (meth)acrylaldehyde or mixtures thereof.

[0079] The crystal refiner may be present in the plating bath of the present invention in an amount of 0.0001 to 0.045 g / l. Preferably, the crystal refiner is present in an amount of 0.0001 to 0.04 g / l, more preferably in an amount of 0.0001 to 0.035 g / l, and even more preferably in an amount of 0.0001 to 0.03 g / l. Compounds useful as first crystal refiners are generally commercially available from a variety of sources and may be used as is or may be further purified.

[0080] The compositions of the present invention can optionally contain further additives, such as antioxidants, organic solvents, complexing agents, and mixtures thereof. Although further levellers can be used in the plating baths of the present invention, it is preferred that the plating baths only contain the levellers according to the present invention.

[0081] More Antioxidants Additional antioxidants may optionally be added to the compositions of the present invention to help keep the tin in a soluble divalent state. However, it is preferred that no antioxidants other than those listed above are used. Thus, in a preferred embodiment, the electroplating composition does not contain any antioxidants or reducing agents other than those of formulas X1a-X1e. Exemplary additional antioxidants, if used, include, but are not limited to, hydroquinone, and hydroxylated and / or alkoxylated aromatic compounds, including sulfonic acid derivatives of such aromatic compounds, preferably including: hydroquinone; methylhydroquinone; resorcinol; catechol; 1,2,3-trihydroxybenzene; 1,2-dihydroxybenzene-4-sulfonic acid; 1,2-dihydroxybenzene-3,5-disulfonic acid; 1,4-dihydroxybenzene-2-sulfonic acid; 1,4-dihydroxybenzene-2,5-disulfonic acid; 2,4-dihydroxybenzenesulfonic acid, and p-methoxyphenol. Such antioxidants are disclosed in US 4 871 429. Other suitable antioxidants include, but are not limited to, vanadium compounds such as vanadyl acetylacetonate, vanadium triacetylacetonate, vanadium halides, vanadium oxyhalides, vanadium alkoxides, and vanadyl alkoxides. The concentrations of such reducing agents are well known to those skilled in the art, but typically range from 0.1 to 10 g / l, preferably from 1 to 5 g / l. Such antioxidants are generally commercially available from a variety of sources. It is particularly preferred to use certain antioxidants in pure tin electroplating compositions.

[0082] Complexing Agent The tin or tin alloy electroplating bath may further contain a complexing agent for complexing the tin and / or other metals present in the composition. A typical complexing agent is 3,6-dithia-1,8-octanediol. Further useful complexing agents are described in WO 2019 / 185 468 and unpublished International Patent Application No. PCT / EP2020 / 075 080.

[0083] Typical complexing agents are polyoxymonocarboxylic acids, polycarboxylic acids, aminocarboxylic acids, lactone compounds, and salts thereof.

[0084] Other complexing agents are organic thio compounds such as thioureas, thiols or thioethers, as disclosed in US 7628903, JP 4296358 B2, EP 0854206 A and US 8980077 B2.

[0085] electrolyte The composition includes tin and, optionally, alloying metal ions.

[0086] Generally, "aqueous" as used herein means that the electroplating compositions of the present invention comprise a solvent that includes at least 50% water. Preferably, "aqueous" means that the composition is mostly water, more preferably, the solvent is 90% water, and most preferably, the solvent consists essentially of water. Any type of water can be used, such as distilled water, deionized water, or tap water.

[0087] Tin The tin ion source can be any compound capable of releasing a sufficient amount of metal ions to be deposited in the electroplating bath, i.e., a compound that is at least partially soluble in the electroplating bath. The metal ion source is preferably soluble in the plating bath. Suitable metal ion sources are metal salts, including, but not limited to, metal sulfates, metal halides, metal acetates, metal nitrates, metal fluoroborates, metal alkylsulfonates, metal arylsulfonates, metal sulfamates, metal gluconates, and the like.

[0088] The metal ion source can be used in the present invention in any amount that provides sufficient metal ions for electroplating onto the substrate. When the metal is tin only, the tin salt is typically present in an amount ranging from about 1 to about 300 g / l of the plating solution. In one embodiment, no additional metals other than tin are present.

[0089] Alloy metals Optionally, the plating bath according to the present invention may contain one or more alloying metal ions. Suitable alloying metals include, but are not limited to, silver, gold, copper, bismuth, indium, zinc, antimony, manganese, and mixtures thereof. Preferred alloying metals are silver, copper, bismuth, indium, and mixtures thereof, more preferably silver, bismuth, and indium, and most preferably silver. The composition of the present invention is preferably lead-free. In one embodiment, there are no further metals present other than tin and at least one of silver, indium, and bismuth, and preferably the only metals present in the composition are tin and at least one of silver, indium, and bismuth. Most preferably, the alloying metal consists of silver ions, i.e. the only metals present in the composition are tin and silver.

[0090] As a source of alloying metal ions, any bath-soluble salt of the alloying metal can be suitably used. Examples of such alloying metal salts include, but are not limited to, metal oxides; metal halides; metal fluoroborates; metal sulfates; metal alkane sulfonates, such as metal methanesulfonates, metal ethanesulfonates and metal propanesulfonates; metal arylsulfonates, such as metal phenylsulfonates, metal toluenesulfonates and metal phenolsulfonates; metal carboxylates, such as metal gluconates and metal acetates. Preferred alloying metal salts are metal sulfates; metal alkane sulfonates; and metal arylsulfonates. When one alloying metal is added to the composition of the present invention, a binary alloy deposit is obtained. When two, three or more different alloying metals are added to the composition of the present invention, a ternary, quaternary or higher alloy deposit is obtained. The amount of such alloying metal used in the composition of the present invention depends on the particular tin alloy desired. The selection of such amount of alloying metal is within the ability of one skilled in the art. Those skilled in the art will appreciate that when using certain alloying metals, such as silver, additional complexing agents may be required. Such complexing agents (or complexing substances) are well known to those skilled in the art and may be used in any suitable amount.

[0091] The electroplating compositions of the present invention are suitable for depositing tin-containing layers, which may be pure tin layers or tin alloy layers. Exemplary tin alloy layers include, but are not limited to, tin-silver, tin-copper, tin-indium, tin-bismuth, tin-silver-copper, tin-silver-copper-antimony, tin-silver-copper-manganese, tin-silver-bismuth, tin-silver-indium, tin-silver-zinc-copper, and tin-silver-indium-bismuth. Preferably, the electroplating compositions of the present invention deposit pure tin, tin-silver, tin-silver-copper, tin-silver-bismuth, tin-silver-indium, and tin-silver-indium-bismuth, more preferably pure tin, tin-silver, or tin-copper.

[0092] The alloys deposited from the electroplating baths of the present invention contain tin in an amount ranging from 0.01 to 99.99 weight percent, and one or more alloying metals in an amount ranging from 99.99 to 0.01 weight percent, based on the weight of the alloy, as measured by either atomic adsorption spectroscopy (AAS), X-ray fluorescence (XRF), inductively coupled plasma (ICP), or differential scanning calorimetry (DSC). Preferably, the tin-silver alloys deposited using the present invention contain 90 to 99.99 weight percent tin, and 0.01 to 10 weight percent silver and other alloying metals. More preferably, the tin-silver alloy deposits contain 95 to 99.9 weight percent tin, and 0.1 to 5 weight percent silver and other alloying metals. Tin-silver alloys are the preferred tin alloy deposits, and preferably contain 90 to 99.99 weight percent tin, and 10 to 0.1 weight percent silver. More preferably, the tin-silver alloy deposit contains 95-99.9% by weight tin and 5-0.1% by weight silver. In many applications, a eutectic composition of the alloy may be used. The alloy deposited according to the invention is substantially free of lead, i.e. contains less than 1% by weight lead, more preferably less than 0.5% by weight, even more preferably less than 0.2% by weight lead, and even more preferably is free of lead.

[0093] bath In general, in addition to the metal ion source and at least one leveling agent according to the present invention, the metal electroplating composition of the present invention preferably comprises an electrolyte, i.e., an acidic or alkaline electrolyte, one or more metal ion sources, optionally halide ions, and optionally other additives such as surfactants and grain refiners. Such baths are typically aqueous. Water may be present in a wide range of amounts. Any type of water may be used, for example, distilled water, deionized water, or tap water.

[0094] Preferably, the plating baths of the present invention are acidic, i.e., have a pH of less than 7. Typically, the pH of tin or tin alloy electroplating compositions is less than 4, preferably less than 3, and most preferably less than 2.

[0095] The electroplating baths of the present invention can be prepared by combining the components in any order, although it is preferred that the inorganic components, such as metal salts, water, electrolyte, and any source of halide ions, be added to the bath container first, followed by the organic components, such as surfactants, grain refiners, levelers, etc.

[0096] Typically, the plating bath of the present invention can be used at any temperature of 10 to 65° C. or higher. The temperature of the plating bath is preferably 10 to 35° C., and more preferably 15 to 30° C.

[0097] Suitable electrolytes include, but are not limited to, sulfuric acid, acetic acid, fluoroboric acid, alkylsulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid and trifluoromethanesulfonic acid, arylsulfonic acids such as phenylsulfonic acid and toluenesulfonic acid, sulfamic acid, hydrochloric acid, phosphoric acid, tetraalkylammonium hydroxides, preferably tetraalkylammonium hydroxides, sodium hydroxide, potassium hydroxide, etc. The acid is typically present in an amount ranging from about 1 to about 300 g / l.

[0098] In one embodiment, at least one additive has a counterion Y selected from chloride, sulfate or acetate.o- where o is a positive integer.

[0099] Such electrolytes may optionally contain a halide ion source, such as chloride ions, such as tin chloride or hydrochloric acid. A wide range of halide ion concentrations may be used in the present invention, for example, from about 0 to about 500 ppm. Typically, the halide ion concentration ranges from about 10 to about 100 ppm based on the plating bath. The electrolyte is preferably sulfuric acid or methanesulfonic acid, more preferably a mixture of sulfuric acid or methanesulfonic acid and a chloride ion source. The acids and halide ion sources useful in the present invention are generally commercially available and may be used without further purification.

[0100] application The plating compositions of the present invention are useful in a variety of plating methods where a tin-containing layer is desired, and are particularly useful for depositing a tin-containing solder layer on a semiconductor wafer containing a plurality of conductive bonding features. Plating methods include, but are not limited to, horizontal or vertical wafer plating, barrel plating, rack plating, high speed plating such as reel-to-reel plating and jet plating, rackless plating, preferably horizontal or vertical wafer plating. A wide variety of substrates can be plated with the tin-containing deposition according to the present invention. The substrates to be plated are conductive and may include copper, copper alloys, nickel, nickel alloys, nickel-iron containing materials. Such substrates may be in the form of electronic components such as (a) lead frames, connectors, chip capacitors, chip resistors, and semiconductor packages, (b) plastics such as circuit boards, and (c) semiconductor wafers. Preferably, the substrate is a semiconductor wafer. Therefore, the present invention also provides a method for depositing a tin-containing layer on a semiconductor wafer, comprising the steps of: providing a semiconductor wafer comprising a plurality of conductive bonding features; contacting the semiconductor wafer with the above-mentioned composition; and applying a sufficient current density to deposit a tin-containing layer on the conductive bonding features. Preferably, the bonding features comprise copper and may be in the form of a pure copper layer, a copper alloy layer, or any interconnect structure comprising copper. Copper pillars are one preferred conductive bonding feature. Optionally, the copper pillars may comprise a top metal layer, such as a nickel layer. If the conductive bonding feature has a top metal layer, a tin or tin alloy solder layer is deposited on the top metal layer of the bonding feature. Conductive bonding features such as bond pads, copper pillars, etc. are well known in the art, as described in US 7,781,325, US 2008 / 0054459 A, US 2008 / 0296761 A, and US 2006 / 0094226 A.

[0101] method One embodiment of the present invention is the use of an antioxidant of formula X1a, X1b, X1c, X1d, or X1e in a bath for depositing a tin or tin-alloy containing layer, wherein the tin-alloy containing layer comprises an alloying metal selected from silver, copper, indium, and bismuth in an amount of 0.01-10 wt. %. Preferably, the deposited tin-alloy layer has an alloying metal content of 0.1-5 wt. %.

[0102] Another embodiment of the present invention comprises: a) contacting a substrate with a tin-alloy electroplating bath comprising a composition described herein; and b) applying a current density to the substrate for a time sufficient to deposit a tin-alloy layer on the substrate. This is a method for depositing a tin or tin alloy layer on a substrate by

[0103] As used herein, "recessed feature" refers to a via, trench, or other opening on a substrate, particularly an opening for depositing a solder bump. As used herein, "opening size" refers to the shortest distance across the opening of a recessed feature.

[0104] Preferably, the substrate includes recessed features having an opening size of 1 to 1000 micrometers and deposition is performed to at least partially fill the micrometer-sized recessed features. Most preferably, the recessed features have an opening size of 1 to 200 micrometers, preferably 3 to 100 micrometers.

[0105] Generally, when the present invention is used to deposit tin or tin alloys on substrates, the plating bath is agitated during use. Preferably, tin alloys are deposited, and the alloy metal content of the deposited tin alloy is 0.01-10% by weight. Any suitable agitation method may be used in the present invention, and such methods are well known in the art. Suitable agitation methods include, but are not limited to, sparging with inert gas or air, agitating the workpiece, impinging, and the like. Such methods are well known to those skilled in the art. When the present invention is used to plate integrated circuit substrates, such as wafers, the wafer is rotated at 1-150 RPM, and the plating solution is contacted with the rotating wafer by pumping or spraying. Alternatively, if the flow of the plating bath is sufficient to provide the desired metal deposition, the wafer need not be rotated.

[0106] Tin or tin alloy is deposited in the recesses according to the present invention without substantially forming voids in the metal deposit. The term "substantially without forming voids" means that there are no voids in the metal deposit larger than 1000 nm, preferably 500 nm, and most preferably 100 nm.

[0107] Plating apparatus for plating semiconductor substrates are well known. The plating apparatus includes an electroplating tank that holds an electrolyte of tin or tin alloy and is made of a suitable material such as plastic or other material that is inert to the electrolytic plating solution. The tank may be cylindrical, particularly for wafer plating. The cathode is positioned horizontally at the top of the tank and may be any type of substrate, such as a silicon wafer, having an opening.

[0108] These additives can be used with soluble and insoluble anodes, with or without a membrane separating the catholyte and anolyte.

[0109] The cathode substrate and the anode are electrically connected by wires and each is connected to a power source. The cathode substrate for direct or pulsed current has a net negative charge so that metal ions in the solution are reduced at the cathode substrate and the plated metal is formed on the surface of the cathode. The oxidation reaction occurs at the anode. The anode and cathode are arranged horizontally or vertically in the tank.

[0110] Typically, in making tin or tin alloy bumps, a photoresist layer is applied to a semiconductor wafer, followed by standard photolithographic exposure and development techniques to form a patterned photoresist layer (or plating mask) having openings or vias therein. The dimensions of the plating mask (thickness of the plating mask and size of the pattern openings) define the size and location of the tin or tin alloy layer that is deposited over the I / O pads and UBM.

[0111] All percentages, ppm, or equivalent values ​​are by weight relative to the total weight of the respective composition unless otherwise specified. All citations are incorporated herein by reference.

[0112] The following examples further illustrate the invention without limiting its scope. EXAMPLES

[0113] Nine antioxidants were tested. Antioxidants 1-6 are commercially available. Antioxidant 7 was synthesized according to Organic and Bio-Organic Chemistry (1985), (1), 81-6.

[0114] Synthesis of antioxidants 8 and 9: [ka] 1-(4-Hydroxy-1,5-dimethyl-pyrazol-3-yl)ethenone (1a) Methylglyoxal (40% aqueous solution, 529 g, 2.94 mol) was added to a solution of methylhydrazine (24 g, 0.511 mol) and acetic acid (44 g, 0.734 mol) in water (100 mL) under cooling (8-12 °C) similar to the procedure in the literature [1, 2]. After the addition was complete, the reaction mixture was heated to reflux for 4 h. The mixture was cooled to room temperature and extracted four times with 1.5 L of ethyl acetate. The combined organic layers were dried (Na2SO4) and the solvent was removed in vacuum. The crude product was purified using column chromatography (silica column, cyclohexane / ethyl acetate gradient). The product was isolated as a pale yellow solid (21 g, 0.133 mol, 26% yield).

[0115] 1-(1-tert-butyl-4-hydroxy-5-methyl-pyrazol-3-yl)ethenone (1b) To a solution of tert-butylhydrazine hydrochloride (24 g, 0.189 mol) in water (220 mL) were successively added methylglyoxal (40% aqueous solution, 136 g, 0.754 mol) and acetic acid (17 g, 0.283 mol). The reaction mixture was heated to reflux for 6 h. After cooling to room temperature, the mixture was extracted three times with 500 mL of ethyl acetate. The combined organic layers were washed with 500 mL of brine and dried (Na2SO4). After removing the solvent in vacuum, the crude product was purified using column chromatography (silica column, cyclohexane / ethyl acetate gradient). The product was isolated as pale yellow crystals (20.6 g, 0.106 mol, 56% yield).

[0116] Antioxidant 8: 3-Ethyl-1,5-dimethyl-pyrazol-4-ol (2a) A mixture of 1-(4-hydroxy-1,5-dimethyl-pyrazol-3-yl)ethenone (1a) (7.5 g, 48.6 mmol) and Raney nickel H0-50 (1.99 g) in 60 mL of 1,4-dioxane was pressurized to 66 bar with hydrogen gas. After heating to 170° C. (100 bar pressure), stirring was continued for 3 h. After depressurization, the reaction mixture was filtered and the filtrate was concentrated in vacuo. The crude product was purified using column chromatography (silica column, cyclohexane / ethyl acetate gradient). The product was isolated as a pale yellow solid (4.0 g, 28.5 mmol, 59% yield).

[0117] Antioxidant 9: 1-tert-butyl-3-ethyl-5-methyl-pyrazol-4-ol (2b) 2.5 g (12.8 mmol) of the slightly yellowish solid, 0.8 g of Raney nickel, and 60 ml of dioxane were pressurized with hydrogen gas to 61 bar. After heating to 170° C., stirring was continued for 3 h. After depressurization, the reaction mixture was filtered and the filtrate was concentrated in vacuo. The crude product was purified using column chromatography (silica column, cyclohexane / ethyl acetate gradient). The product was isolated as a pale yellow solid (1.5 g, 8.2 mmol).

[0118] literature [1] "Reactions of Glyoxals with Hydrazones: A new Route to 4-Hydroxypyrazoles", M. Begtrup, HPNytoft, J. Chem. Soc. Perkin Trans. 1985, 81-86.

[0119] [2] “Maximizing Lipophilic Efficiency: The use of Free-Wilson Analysis in the Designators of Acetyl-CoA Carboxylase”, KDFreeman-Cook et al., J.Med.Chem.2012,55,935-942.

[0120] Stability Testing A solution of silver and tin in methanesulfonic acid containing a complexing agent was prepared. To this solution, 0.3 g / l of antioxidant was added. The solution was placed in a cuvette for turbidity measurement. The sealed cuvette was stored at 50 °C. The turbidity was measured at regular time intervals and periodically opened to allow oxygen diffusion. Turbidity measurements were performed at rt using a Hach TL2350 (Hach Lange GmbH). A solution of silver and tin in methanesulfonic acid without antioxidant was used as a control.

[0121] If the turbidity was determined to be greater than 4 NTU (NTU = nephelometric turbidity units), the solution was considered unstable. If the stannous silver methanesulfonate solution with added antioxidant was stable for a longer time than the reference solution without added antioxidant, this indicates a good antioxidant ("+"). If the stannous silver methanesulfonate solution with added antioxidant was as stable as the reference solution without added antioxidant, this indicates that the antioxidant did not act as such ("o"). If the stannous silver methanesulfonate solution with added antioxidant was less stable compared to the reference solution without added antioxidant, this indicates that the antioxidant acted as a destabilizer ("-").

[0122] The antioxidant of Example 1 was subjected to the test procedures described above, and the results are shown in Table 1.

[0123] [Table 6]

Claims

1. 1. An aqueous composition for electrodepositing tin or a tin alloy, comprising tin ions, optionally alloying metal ions selected from silver, indium, and bismuth, and a tin-containing metal compound of formula X1a 【Chemistry 1】 or Formula X1b 【Chemistry 2】 or Formula X1c 【Transformation 3】 or Formula X1d 【Chemistry 4】 or Formula X1e 【Transformation 5】 or at least one antioxidant of the tautomers of formula X1a, X1b, X1c, X1d and X1e, (In the formula, R Ｘ１ , R Ｘ１ａ is, independently, (a) H, and (b) all unsubstituted or OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ -OR Ｘ３ , CN, halogen, or a combination thereof; １ ~C ６ Alkyl, C １ ~C ６ Alkenyl, C ５ ~C １２ Aryl, C ６ ~C １５ Alkylaryl, C ６ ~C １５ aryl alkyl, with the proviso that when the antioxidant is of formula X1b, R Ｘ１ is C ５ ~C １２ Aryl or C ６ ~C １５ Not alkylaryl, R Ｘ２ teeth, (a) H, OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ , -OR Ｘ３ , and (b) all unsubstituted or OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ -OR Ｘ３ , CN, halogen, or a combination thereof; １ ~C ６ Alkyl, C １ ~C ６ Alkenyl, C ５ ~C １２ Aryl, C ６ ~C １５ Alkylaryl, C ６ ~C １５ aryl alkyl, wherein in formula X1a at least one R Ｘ２ is OH, and in formula X1a, R Ｘ１ is t-butyl, R Ｘ２ ２ is C ５ ~C １２ Aryl or —CO—R Ｘ３ Instead, R Ｘ３ is H or C １ ~C ６ is alkyl, n is a group R Ｘ２ (The number of no additional alloying metal ions are present in the composition other than tin ions and at least one of silver ions, indium ions, and bismuth ions; The composition does not contain any reducing agent other than the compound of formula X1a-X1e.

2. R Ｘ１ are (a) H, and (b) all unsubstituted or —CO—OR Ｘ３ or -SO ２ -OR Ｘ３ C is substituted with １ ~C ６ Alkyl, phenyl, C １ ~C ４ The composition of claim 1 wherein the alkyl is selected from alkylphenyl.

3. R Ｘ２ But, H, OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ -OR Ｘ３ , and all are unsubstituted or OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , or -SO ２ -OR Ｘ３ C is substituted with １ ~C ４ Alkyl, phenyl, C １ ~C ４ 3. The composition of claim 1, wherein the alkyl is selected from alkylphenyl.

4. R Ｘ２ is unsubstituted or substituted with OH, H, OH, —CO—R Ｘ３ 3. The composition according to claim 1, wherein the alkyl group is selected from the group consisting of methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, t-butyl, and phenyl, preferably H, OH, methyl and ethyl.

5. 3. The composition of claim 1 or 2, wherein at least one antioxidant is a compound of formula X1a.

6. R Ｘ１ But C １ ~C ４ alkyl, and R Ｘ２ １ or R Ｘ２ ２ is OH, and the other R Ｘ２ １ , R Ｘ２ １ , and R Ｘ２ １ is H, methylethyl, propyl or butyl, or —CO—R Ｘ３ The composition of claim 5 , wherein

7. 2. The composition of claim 1, wherein the antioxidant is selected from antipyrine, 5-pyrazolone, 1,3-dimethyl-1H-pyrazol-5-ol, 1-phenylpyrazolidine-3,5-dione, 2-tert-butyl-4,5-dimethyl-pyrazol-3-ol, 1-(4-hydroxy-1,5-dimethyl-pyrazol-3-yl)-ethanone, 1,5-dimethyl-3-phenyl-pyrazol-4-ol, 3-ethyl-1,5-dimethyl-pyrazol-4-ol, 1-tert-butyl-3-ethyl-5-methyl-pyrazol-4-ol.

8. 3. A composition according to claim 1 or 2, comprising alloying metal ions including silver ions, preferably the only alloying metal consisting of silver ions.

9. 3. The composition of claim 1, wherein the pH of the composition is less than 4, preferably less than 3, and most preferably less than 2.

10. 3. The composition of claim 1 or 2, further comprising further additives selected from one or more surfactants, one or more levelers, and one or more crystal refiners.

11. 1. Use of an antioxidant of formula X1a, X1b, X1c, X1d, or X1e, or a tautomer of formula X1a, X1b, X1c, X1d, and X1e, in a bath for depositing a tin or tin-alloy containing layer, comprising the steps of: 【Transformation 6】 (In the formula, R Ｘ１ , R Ｘ１ａ is, independently, (a) H, and (b) all unsubstituted or OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ -OR Ｘ３ , CN, halogen, or a combination thereof; １ ~C ６ Alkyl, C １ ~C ６ Alkenyl, C ５ ~C １２ Aryl, C ６ ~C １５ Alkylaryl, C ６ ~C １５ aryl alkyl, with the proviso that when the antioxidant is of formula X1a, R Ｘ１ is C ５ ~C １２ Aryl or C ６ ~C １５ Not alkylaryl, R Ｘ２ teeth, (a) H, OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ , -OR Ｘ３ , and (b) all unsubstituted or OH, OR Ｘ３ , -CO-R Ｘ３ , -CO-OR Ｘ３ , -SO ２ -OR Ｘ３ , CN, halogen, or a combination thereof; １ ~C ６ Alkyl, C １ ~C ６ Alkenyl, C ５ ~C １２ Aryl, C ６ ~C １５ Alkylaryl, C ６ ~C １５ aryl alkyl, wherein in formula X1a at least one R Ｘ２ is OH, and in formula X1a, R Ｘ１ is t-butyl, R Ｘ２ ２ is C ５ ~C １２ Aryl or —CO—R Ｘ３ Instead, R Ｘ３ is H or C １ ~C ６ is alkyl, n is a group R Ｘ２ (The number of the tin-alloy-containing layer comprises an alloy metal in an amount of 0.01 to 10 wt. %; no additional alloying metal ions are present in the composition other than tin ions and at least one of silver ions, indium ions, and bismuth ions; The method of use, wherein the composition does not contain any reducing agent other than the compound of formula X1a-X1e.

12. 12. Use according to claim 11, wherein the deposited tin-alloy layer has an alloy metal content of 0.1 to 5 wt. %.

13. a) contacting a substrate with a tin-alloy electroplating bath comprising the composition of claim 1 or 2; and b) applying a current density to the substrate for a time sufficient to deposit a tin or tin-alloy layer on the substrate; 2. A method for depositing a tin or tin alloy layer on a substrate by:

14. 14. The method of claim 13, wherein a tin alloy is deposited and the alloying metal content of the deposited tin alloy is 0.01 to 10 wt. %.

15. 14. The method of claim 13, wherein the substrate comprises recessed features having opening sizes of 1 to 1000 micrometers, preferably 1 to 200 micrometers, most preferably 3 to 100 micrometers, and wherein deposition is carried out to at least partially fill the micrometer-sized recessed features.

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