KR20170035783A - Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits - Google Patents

Abstract

Acid copper electroplating baths provide improved low internal stress copper deposits with good ductility. The acid copper electroplating baths comprise: one or more polyallylamines; and certain sulfur containing accelerators. The acid copper electroplating baths are used to electroplate thin films on relatively thin substrates to provide thin film copper deposits having low internal stress and high ductility.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an acidic copper electroplating bath and a method of electroplating a low internal stress and a good ductile copper deposit. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

Field of invention

The present invention relates to a copper electroplating bath for electroplating low internal stress copper deposits having good ductility. More particularly, the present invention relates to a copper electroplating bath for electroplating low internal stress copper deposits having good ductility, wherein said acid copper electroplating bath comprises a polyallylamine with any sulfur containing accelerator.

BACKGROUND OF THE INVENTION

The intrinsic or intrinsic stress of the electrodeposited metal is a well known phenomenon caused by defects in the electroplated crystal structure. After the electroplating operation, such defects are attempted to self-correct, which induces the force on the deposit to contract (tensile strength) or expand (compressive stress). Such stresses and their mitigation can be problematic. For example, if electroplating occurs predominantly on one side of the substrate, it can cause curling, bowing and warping of the substrate depending on the flexibility of the substrate and the scale of the stress. Stress can cause poor adhesion of deposits to the substrate resulting in blistering, peeling or cracking. This is particularly the case with a semiconductor wafer or a substrate which is difficult to adhere, such as those having a relatively smooth surface shape. In general, the magnitude of the stress is proportional to the thickness of the deposit, which can be problematic if a thick deposit is needed, or it can limit the deposit thickness that is achievable in effect.

Most metals, including copper deposited from an acid electroplating process, exhibit internal stress. Commercial copper electroplating processes use a variety of organic additives to advantageously modify the electroplating process and deposition characteristics. It is also known that deposits from such electroplating baths can undergo room temperature self-annealing. During such self-annealing, the conversion of the grain structure simultaneously results in a change in the deposit stress and often increases it. The internal stress itself may be a problem, and typically, the deposition itself becomes self-annealing over time, which is liable to change during aging and becomes unpredictable.

The fundamental mechanism of mitigating the inherent stresses in copper electroplating is not well known. A decrease in the current density, that is, a decrease in the plating rate, a substrate type, a seed layer or an under plate selection, an electroplating composition such as an anion type, an additive, an impurity and a contaminant Is known to affect the electrodeposition stress. Empirical means to reduce such stresses have been used but are typically inconsistent or impair the efficiency of the electroplating process.

Another important parameter of copper deposits is its ductility. Ductility is defined as the ability of a solid material to deform under tensile stress. Copper deposits with high ductility are desired to prevent or reduce the likelihood of cracking copper under tensile stress over time. Ideally, copper deposits have relatively low internal stress and high ductility; There is typically a tradeoff between internal stress and ductility. Thus, there is still a need for copper electroplating baths and copper electroplating methods that not only alleviate internal stresses in copper deposits, but also provide good or high ductility.

SUMMARY OF THE INVENTION

The acidic copper electroplating bath comprises at least one copper ion source, at least one electrolyte, at least one polyallylamine, at least one (O-ethyldithiocarbonate) -S- (3-sulfopropyl) Salts, and one or more inhibitors.

The method comprises contacting the substrate with at least one source of copper ions, at least one electrolyte, at least one polyallylamine, at least one (O-ethyldithiocarbonato) -S- (3-sulfopropyl) A salt, and an acidic copper electroplating bath comprising at least one inhibitor; Lt; RTI ID = 0.0 > low < / RTI > internal stress on the substrate and high soft copper.

The present invention also relates to a copper film having an initial internal stress of 0 psi to 950 psi and an internal stress after aging of 300 psi to 900 psi and an elongation of 8% or more at a load of a maximum tensile stress of 50 lbf or more.

Acidic copper deposits have a low internal stress with relatively large grain structure. The internal stress and grain structure increases substantially the performance of the copper electroplating bath and the predictability of the deposited deposit from it since it does not change substantially as the deposit ages. The low internal stress copper deposits also have good or high ductility, whereby the copper deposits do not readily crack on the substrate in contrast to many conventional copper deposits. Electroplated copper from the bath of the present invention has a good balance between low internal stress and ductility, and this property has not been found when electroplating copper from many conventional copper baths. The copper electroplating bath can be used to deposit a copper film on the substrate without substantial concern about the possibility of bending, curling, warping, blistering, peeling, or cracking a relatively thin substrate.

DETAILED DESCRIPTION OF THE INVENTION

The following abbreviations have the following meanings unless expressly specified otherwise contextually: C = Celsius temperature; g = gram; mL = milliliters; L = liters; ppm = million fractions = mg / L; A = ampere = Amps; DC = DC; dm = decimeter; mm = millimeter; μm = micrometer; nm = nanometer; Mw = weight average molecular weight (g / mol); SEM = scanning electron microscope photograph; ASD = A / dm ² ; 2.54 cm = 1 inch; lbf = pound-force = 4.44822162 N; N = Newton; psi = pound / square inch = 0.06805 atmospheric; 1 atmosphere = 1.01325x10 ⁶ dynes / square centimeter; And RFID = radio frequency identification.

"는 -CH₂-CH₂-이다. 부정관사("a" 및 "an")는 단수 및 복수 둘 모두를 포함한다. 용어 "전성"은 인장 응력 하에 변형하는 고체 물질의 능력을 의미한다. 용어 "인장 응력"은 물질이 실패(failing)하기 전에 견디는 최대 응력을 의미한다.As used throughout this specification, the terms "depositing "," plating "and" electroplating "are used interchangeably. The term "moiety" means a moiety or functional group of a molecule. Moiety "

And - "is -CH ₂ -CH ₂ is an indefinite article. (" A "and" an ") includes both two singular and plural terms" non-conductive "refers to the ability of the solid material deformed under tensile stress. The term "tensile stress" refers to the maximum stress that a material can withstand before failing.

All percentages and ratios are by weight unless otherwise indicated. All ranges are inclusive and combinable in any order, except where it is evident that the sum of such numerical ranges is constrained to be at most 100%.

A copper metal electroplating bath provides thin film copper deposits having a combination of low internal stress and high ductility. The copper metal is selected from the group consisting of one or more copper ion sources, one or more electrolytes, one or more polyalylamines, one or more (O-ethyldithiocarbonato) -S- (3-sulfopropyl) And at least one inhibitor, whereby the copper deposit is characterized by a low internal stress and a high ductility, preferably a minimum change in stress when aging the copper deposit and a high ductility Respectively. Low internal stress copper deposits may have a matte appearance with a relatively large deposited grain size, such as grain sizes typically of 2 microns or greater. Acids, low stress, high ductility copper baths may also include one or more chloride ion sources typically included in an acidic copper electroplating bath and one or more conventional additives. Preferably, one or more chloride ion sources are included in the acidic copper electroplating bath.

Preferably the at least one polyallylamine has the general formula:

Here, the variable "n" is a number such that Mw is 1000 g / mol or more. Preferably, the polyallylamine Mw of the present invention is in the range of 4000 g / mole to 60,000 g / mole, more preferably 10,000 g / mole to 30,000 g / mole.

The polyallylamine is included in the acidic copper electroplating bath in an amount of 1 to 10 ppm, preferably 1 to 5 ppm, more preferably 1 to 2 ppm.

One or more (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester, its acid and its alkali metal salt may be used in amounts of 100 ppm to 300 ppm, preferably 120 ppm to 220 ppm And is included in the copper electroplating bath. The acid form of the ester is 1-propanesulfonic acid, 3 - [(ethoxycytomethyl) thio] -. The alkali metal salt may be selected from the group consisting of (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester, potassium salt and (O-ethyldithiocarbonato) -S- ≪ / RTI > Preferably, (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester and potassium salt are included in the copper electroplating bath. Without being bound by theory, the (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester and its alkali metal salts in combination with one or more polyallylamines have low internal stress and high ductility Copper metal foil deposits.

Optionally, one or more additional accelerators may be included in the low stress and high ductile acid copper electroplating baths. Such accelerators are preferably compounds which, along with one or more inhibitors, can lead to an increase in the plating rate at a given plating potential. Such optional accelerators include 3-mercapto-1-propanesulfonic acid, ethylenedithiodipropylsulfonic acid, bis- (omega -sulfobutyl) -disulfide, methyl- (omega -sulfopropyl) (3-sulfopropyl) ester, 3 - [(amino-iminomethyl) -thiol] -1-propanesulfonic acid, 3- (2-benzylthiazolylthio) , Bis- (sulfopropyl) -disulfide, and alkali metal salts thereof. Preferably, such accelerators are excluded from the copper electroplating bath.

When an optional accelerator is included, it is included in an amount of 1 ppm or more. Typically, such an accelerator may be included in the acidic copper electroplating bath in an amount of 2 ppm to 500 ppm, more typically 2 ppm to 250 ppm.

Inhibitors included in low stress, high ductile acidic copper electroplating baths include, but are not limited to, polyoxyalkylene glycols, carboxymethylcellulose, nonylphenol polyglycol ethers, octanediol bis- (polyalkylene glycol ethers), octane Oleic acid polyglycol ester, polyethylene propylene glycol, polyethylene glycol, polyethylene glycol dimethyl ether, polyoxypropylene glycol, polypropylene glycol, polyvinyl alcohol, stearic acid polyglycol ester, and stearyl alcohol polyglycol ether. Lt; / RTI > ether. Such inhibitors are present in an amount of 0.1 g / L to 10 g / L, preferably 0.1 g / L to 5 g / L, more preferably 0.1 g / L to 2 g / L and most preferably 0.1 g / L To 1 g / L.

Suitable copper ion sources are copper salts and include, but are not limited to: copper sulfate; Copper halides such as copper chloride; Copper acetate; Copper nitrate; Copper tetrafluoroborate; Copper alkyl sulphonate; Copper aryl sulfonate; Copper sulfamate; Copper perchlorate and copper gluconate. Exemplary copper alkanesulfonates include copper (C ₁ -C ₆ ) alkanesulfonates and more preferably copper (C ₁ -C ₃ ) alkanesulfonates. Preferred copper alkanesulfonates are copper methanesulfonate, copper ethanesulfonate and copper propanesulfonate. Exemplary copper aryl sulfonates include, but are not limited to, copper benzenesulfonate and copper p-toluenesulfonate. Mixtures of copper ion sources may be used. One or more salts of metal ions other than copper ions may be added to the acidic copper electroplating bath. Typically, the copper salt is present in an amount sufficient to provide 10 to 400 grams of copper ion per 1 L of plating solution. The electroplating bath does not contain any alloy metal. The electroplating bath is not a copper alloy deposit or any other metal or metal alloy, but a thin film copper deposit.

Suitable electrolytes include, but are not limited to, sulfuric acid, acetic acid, fluoroboric acid, alkanesulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid and trifluoromethanesulfonic acid, arylsulfonic acids such as benzenesulfonic acid, p- Sulfonic acid, sulfamic acid, hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid, chromic acid and phosphoric acid. The acid mixture can be used in the present metal plating bath. Preferred acids include sulfuric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, hydrochloric acid, and mixtures thereof. The acid may be present in an amount ranging from 1 to 400 g / L. The electrolyte is generally commercially available from a variety of sources and can be used without further purification.

One or more optional additives may also be included in the electroplating composition. Such additives include, but are not limited to, lubricants, surfactants, buffers, pH adjusters, halide ion sources, organic acids, chelating agents, and complexing agents. Such additives are well known in the art and can be used in conventional amounts.

A smoothing agent may be included in the acidic copper electroplating bath. Such smoothing agents include, but are not limited to, organic sulfosulfonates such as 1- (2-hydroxyethyl) -2-imidazolidinethione (HIT), 4-mercaptopyridine, 2-mercaptothiazoline, ethylene U. S. Patent No. 6,610,192 to Thiourea, Thiourea and Step, US Patent No. 7,128,822 to Wang et al., U.S. Patent No. 7,374,652 to Hayashi et al., And U.S. Patent No. 6,800,182 to Hagiwara et al. Lt; / RTI > Such a smoothing agent can be contained in a conventional amount. If it is included, it can be contained in an amount of 1 ppb to 1 g / L. Preferably, the smoothing agent is excluded from the bath.

Conventional non-ionic, anionic, cationic and amphoteric surfactants may be included in the acidic copper electroplating bath. Such surfactants are well known in the art and many are commercially available. Typically, the surfactant is nonionic. Generally, the surfactant is included in conventional amounts. Typically it can be included in the electroplating bath in an amount from 0.05 g / l to 15 g / l.

Halogen ions include chloride, fluoride and bromide. Such halides are typically added to the bath as a water soluble salt or acid. Preferably, the copper electroplating bath comprises chloride. The chloride is preferably introduced into the bath as hydrochloric acid or as sodium chloride or potassium chloride. Preferably the chloride is added to the bath as hydrochloric acid. Halogen can be included in the bath in amounts of 20 ppm to 500 ppm, preferably 20 ppm to 100 ppm.

The low stress, highly ductile acidic copper electroplating bath has a pH range of less than 1 to less than 7, preferably less than 1 to 5, more preferably less than 1 to 2, most preferably less than 1 to 1 .

The electroplating may be DC plating, pulse plating, pulse reverse plating, light induced plating (LIP) or photo-assisted plating. Preferably, the low stress, high ductile copper film is plated by DC, LIP or photo-assisted plating. In general, the current density is in the 0.5-50 ASD range, depending on the application. Typically, the current density is in the range of 1-20 ASD or such as 4-20 ASD or 15-20 ASD. The electroplating is carried out at a temperature of from 15 캜 to 80 캜 or from, for example, from room temperature to 60 캜 or from, for example, 20 캜 to 40 캜 or from, for example, 20 캜 to 25 캜.

The internal stress and ductility of the copper film can be determined using conventional methods. Typically low internal stresses are measured using an electrodeposition stress analyzer available from Specialty Testing and Development Co., Jacobus, PA. The low internal stress can be determined by the equation S = U / 3TxK, where S is the stress in psi, U is the increment of deflection at the corrected scale, T is the deposit thickness in inches, Is a correction constant. The constant can be variable and is provided by an electrodeposition stress analyzer. Low internal stress is measured after aging immediately after plating and several days after plating, preferably two days after depositing the copper film on a substrate, such as a conventional copper / beryllium alloy test strip. Immediately after electroplating and after aging, internal stress measurements are made at room temperature. The room temperature can be variable, but for the measurement of internal stress, the room temperature is typically in the range of 18 캜 to 25 캜, preferably 20 캜 to 25 캜. Preferably, a copper film of 1-10 占 퐉, more preferably 1-5 占 퐉, is plated on the test strip. The initial internal stress measured immediately after copper plating on the substrate may range from 0 psi to 950 psi, preferably from 0 psi to 900 psi, more preferably from 0 psi to 850 psi at room temperature. After aging, for example, for 2 days, the internal stress may be in the range of 300 psi to 900 psi, preferably 300 psi to 850 psi, more preferably 300 psi to 840 psi at room temperature. While the internal stress may be slightly variable from the 2 day aging period, the measurement of the internal stress of the copper film of the present invention typically does not change significantly at room temperature after the 2 day aging period.

The electrical properties are measured using conventional elongation tests and apparatus. Preferably, the elongation test is performed using an industrial standard IPC-TM-650 method by an apparatus such as an Instron pull tester 33R4464. Copper is electroplated on a substrate, such as a stainless steel panel. Copper is typically electroplated on a substrate as a thin film with a thickness of 50-100 [mu] m, preferably 60-80 [mu] m. The copper is peeled from the substrate and annealed for 1 to 5 hours, preferably for 2 to 5 hours. The annealing is performed at a temperature of 100-150 占 폚, preferably 110-130 占 폚, and then the copper is allowed to reach room temperature. The elongation or load of the maximum tensile stress is typically not a pre-determined parameter. The greater the load of the maximum tensile stress that the material can withstand before failure or cracking, the higher or better the ductility. Typically, the elongation is performed at a load of a maximum tensile stress of 50 lbf or more. Preferably, the elongation is performed at 60 lbf or more. More preferably, the elongation is performed at a load of a maximum tensile stress of 70 lbf to 90 lbf. The elongation is in the range of 8% or more, preferably 9% to 15%.

Low stress, high ductility acidic copper electroplating baths and electroplating methods can be used to deposit copper on a relatively thin substrate, such as a semiconductor wafer of 100-220 [mu] m or 100-150 [mu] m, or on a side of the substrate where bending, It is used for plating. The low stress, high ductility, acidic copper electroplating bath can also be used for plating copper on substrates that are difficult to attach, such as blistering, peeling, or cracking of deposits. For example, the method can be applied to printed circuits and wiring boards, such as flexible circuit boards, flexible circuit antennas, RFID tags, electrolytic foils, interdigitated rear contact solar cells, A heterojunction with intrinsic thin layer; HIT) cells and fully plated front contact cells, as well as for the manufacture of semiconductor wafers for photovoltaic devices and solar cells. The acidic copper electroplating bath is preferably used for plating copper to a thickness in the range of 1 μm to 5 mm, more preferably 5 μm to 1 mm. When copper is used as the main conductor in the formation of contacts for solar cells, the copper is preferably plated in a thickness range of 1 [mu] m to 60 [mu] m, more preferably 5 [mu] m to 50 [mu] m.

Copper deposits have a low internal stress with relatively large grain structure. In addition, the internal stress and grain structure increases the performance of the copper electroplating bath and the predictability of the deposited deposit from it since it does not substantially change as the deposit ages. The low internal stress copper deposit also has good ductility, whereby it does not readily crack on the substrate in contrast to many conventional copper deposits. Electroplated copper from the bath of the present invention has a good balance between low internal stress and ductility, and this property has not been found when electroplating copper from many conventional copper baths. The copper electroplating bath can be used to deposit copper on the substrate without substantial concern about the possibility of bending, curling, warping, blistering, peeling, or cracking a relatively thin substrate.

The following examples are provided to demonstrate the present invention, but are not intended to limit its scope.

Example 1

The following aqueous copper electroplating baths were prepared.

table

The components of the copper electroplating bath were prepared using conventional laboratory procedures in which the organic material was added to water and then the inorganic ingredients were added. Stirring or shaking was carried out while applying heat at a temperature below 30 ° C to ensure that all components were dissolved in water. The bath was allowed to reach room temperature before copper electroplating. The pH of the acidic copper electroplating bath was in the range of less than 1 to 1 during room temperature and during copper electroplating.

Example 2

One side of the two flexible copper alloy foil test strips was coated with a dielectric to enable single side plating on the uncoated side. The test strips were taped to a support substrate with a flitestack and placed in a Harling cell containing an acidic copper plating bath having the formulation of Bath 1 in the table in Example 1. The bath was kept at room temperature. A copper metal strip was used as the anode. The test foil strip and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASDs to deposit 5 [mu] M thick copper on the uncoated side of each strip. After plating was complete, the test strip was removed from the Harring cell, rinsed with water, dried, and the glutathione tape removed from the test strip. The internal stress of the copper deposit on the strip was determined to be 838 psi. The stress was determined using the equation S = U / 3TxK, where S is the stress (psi), U is the increment of deflection at the corrected scale, T is the deposit thickness in inches and K is the test strip correction It is a constant. After aging the test strip for 2 days, the stress for each strip was determined to be 837 psi. The internal stress remained substantially the same for copper deposits after aging.

Elongation tests were also performed using the industry standard IPC-TM-650 method. 75 μm copper was plated on a stainless steel panel at 3.8 ASD. The copper film was peeled off after plating and annealed at 125 DEG C for 4 hours. The pull test was performed on the Instron Draw Tester 33R4464. The elongation for Bath 1 was 14% and the load at maximum tensile stress was 76 lbf. This result shows that the internal stress is low and the ductility is high with respect to the electroplated copper deposit from the bath containing polyallylamine and (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester, potassium salt I showed the sound.

Example 3 (comparative)

One side of the two flexible copper / beryllium alloy foil test strips was coated with a dielectric to enable single side plating on the uncoated side. The test strips were taped to the support substrate with a fluttering tape and placed in a Harling cell containing an acidic copper plating bath 2. The bath was at room temperature. A copper metal strip was used as the anode. The test foil strip and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASDs to deposit 5 [mu] M thick copper on the uncoated side of each strip. After plating was complete, the test strip was removed from the Harring cell, rinsed with water, dried, and the glutathione tape removed from the test strip. The test strip was inserted at one end into the screw clamp of the electrodeposition stress analyzer. The internal stress of the copper deposit on the strip was determined to be 211 psi. The stress was determined using the equation S = U / 3TxK, where S is the stress (psi), U is the increment of deflection at the corrected scale, T is the deposit thickness in inches and K is the test strip correction It is a constant. After aging the test strip for 2 days, the stress for each strip was determined to be 299 psi.

Elongation tests were also performed using the industry standard IPC-TM-650 method. 75 μm copper was plated on a stainless steel panel at 3.8 ASD. The copper film was peeled off after plating and annealed at 125 DEG C for 4 hours. The pull test was performed on the Instron Draw Tester 33R4464. The elongation for plated copper from Bath 2 was 7% and the load at maximum tensile stress was only 50 lbf. Even though the internal stress was low, the ductility of the copper was not as high as in Bath 1, which contained polyallylamine. Bath 2 was an example of a conventional acidic copper electroplating bath that typically electroplated a copper film with low internal stress but undesirably low ductility.

Example 4 (comparative)

One side of the two flexible copper / beryllium alloy foil test strips was coated with a dielectric to enable single side plating on the uncoated side. The test strips were taped to the support substrate with a fluttering tape and placed in a Harling cell containing the acidic copper plating bath 3 in the table of Example 1. The bath was at room temperature. A copper metal strip was used as the anode. The test foil strip and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASDs to deposit 5 [mu] M thick copper on the uncoated side of each strip. After plating was complete, the test strip was removed from the Harring cell, rinsed with water, dried, and the glutathione tape removed from the test strip. The test strip was inserted at one end into the screw clamp of the electrodeposition stress analyzer. The internal stress of the copper deposit on the strip was determined to be 1156 psi. The stress was determined using the equation S = U / 3TxK, where S is the stress (psi), U is the increment of deflection at the corrected scale, T is the deposit thickness in inches and K is the test strip correction It is a constant. After aging the test strip for 2 days, the stress for each strip was determined to be 1734 psi.

Elongation tests were also performed using the industry standard IPC-TM-650 method. 75 μm copper was plated on a stainless steel panel at 3.8 ASD. The copper film was peeled off after plating and annealed at 125 DEG C for 4 hours. The pull test was performed on the Instron Draw Tester 33R4464. The elongation for the copper deposits from Bath 3 was 16% and the load at maximum tensile stress was 62 lbf. Even though the ductility from the bath 3 to the plated copper film was excellent, the internal stress exceeded 1000 psi, and these values were not good. Bath 3 was another example of a conventional acidic copper electroplating with high internal stress but good ductility.

Example 5 (comparative)

One side of the two flexible copper / beryllium alloy foil test strips was coated with a dielectric to enable single side plating on the uncoated side. The test strips were taped to the support substrate with a fluttered tape and acidic copper similar to Bath 1, except that the branched polyethyleneimine was replaced with 0.75 ppm linear polyethyleneimine with Mw = 2000 g / mol and the general formula: Were placed in a Harling cell containing a plating bath:

Here, y is a number such that the weight average molecular weight of the linear polyethyleneimine is about 2000 g / mole.

A copper metal strip was used as the anode. The test foil strip and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASDs to deposit 5 [mu] M thick copper on the uncoated side of each strip. After plating was complete, the test strip was removed from the Harring cell, rinsed with water, dried, and the glutathione tape removed from the test strip. The test strip was inserted at one end into the screw clamp of the electrodeposition stress analyzer. The internal stress of the copper deposits on the strip was determined to be 631 psi. The stress was determined using the equation S = U / 3TxK, where S is the stress (psi), U is the increment of deflection at the corrected scale, T is the deposit thickness in inches and K is the test strip correction It is a constant. After aging the test strip for 2 days, the stress for each strip was determined to be 1578 psi.

Elongation tests were also performed using the industry standard IPC-TM-650 method. A 75 μm thick copper film was plated on a stainless steel panel at 3.8 ASD. The copper film was peeled off after plating and annealed at 125 DEG C for 4 hours. The pull test was performed on the Instron Draw Tester 33R4464. The elongation to copper from the bath was 11.8% and the load at maximum tensile stress was 78 lbf. Even at high levels of ductility, the internal stress exceeded 1000 psi after aging, which indicated poor bath performance. The results of Bath 4 with linear polyethyleneimine were substantially the same as those with copper baths except for the combination of polyallylamine and (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester, potassium salts.

Claims (8)

(O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester, an acid or an alkali thereof, or a salt thereof, An acidic copper electroplating bath comprising a metal salt and at least one inhibitor. The acidic copper electroplating bath of claim 1, wherein said at least one polyallylamine has a weight average molecular weight of at least 1000 g / mol. The acidic copper electroplating bath of claim 1, wherein said at least one polyallylamine is present in an amount of from 1 to 10 ppm. The process according to claim 1, wherein said at least one (O-ethyldithiocarbonato) -S- (3-sulfopropyl) -ester, its acid or its alkali metal salt is present in an amount of from 100 ppm to 300 ppm, Acidic copper electroplating bath. A process for preparing a substrate, comprising the steps of: a) contacting a substrate with at least one copper ion source, at least one electrolyte, at least one branched polyallylamine, at least one (O-ethyldithiocarbonato) -S- (3- With an acid or an alkali metal salt thereof and at least one inhibitor; And
b) electroplating high soft copper of low internal stress on the substrate from the copper electroplating bath. 6. The method of claim 5, wherein the high soft copper of the low internal stress has a thickness of 1 [mu] m to 5 mm. 6. The method of claim 5, wherein the substrate is a flexible circuit board, a flexible circuit antenna, a REID tag, an electrolytic foil or a semiconductor. A copper film having an initial internal stress of 0 psi to 950 psi and an internal stress after aging of 300 psi to 900 psi and an elongation at load of a maximum tensile stress of at least 50 lbf of 8%