JP2017053031A - Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acid copper electroplating bath for electroplating a low internal stress and good ductility copper deposit.SOLUTION: There is provided a method for electroplating a thin film on a relatively thin substrate using an acid copper electroplating bath including one or more kind of copper ion sources, one or more kind of electrolytes, one or more kind of polyallylamines, one or more kind of (O-ethylene dithiocarbonate)-S-(3-sulfopropyl)-ester, acids thereof or alkali metal salts thereof and one or more kind of suppressors. It is preferred that the polyallylamine included in the acid copper electroplating bath has a weight average molecular weight of 1000 g/mol or more and has a concentration of 1 to 10 ppm.SELECTED DRAWING: None

Description

  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 for electroplating low internal stress copper deposits with good ductility, wherein the acidic copper electroplating bath comprises polyallylamine in combination with certain sulfur-containing accelerators. It relates to a plating bath.

  The internal or intrinsic stress of electrodeposited metals is a well-known phenomenon caused by defects in the electroplated crystal structure. After the electroplating operation, such defects attempt to self-correct and induce a force that shrinks (tensile strength) or expands (compressive stress) into the precipitate. This stress and its relaxation can be problematic. For example, when electroplating primarily on one side of a substrate, it may cause the substrate to bend, warp and distort, depending on the flexibility and stress magnitude of the substrate. Stress can cause the deposits to adhere poorly to the substrate, resulting in blistering, peeling, or cracking. This is especially true when it is difficult to adhere a substrate, such as a semiconductor wafer or one having a relatively smooth surface topography. In general, the magnitude of the stress is proportional to the thickness of the precipitate, which can be a problem when thicker precipitates are needed, or limit the thickness of the precipitate that can actually be achieved. Can do.

  Most metals, including copper deposited from the acid electroplating process, exhibit internal stress. Commercial copper acid electroplating processes utilize a variety of organic additives that beneficially modify the electroplating process and deposit properties. It is also known that deposits from such electroplating baths can be self-annealed at room temperature. Such transformation of the grain structure during self-annealing simultaneously leads to a change in the stress of the precipitate, often increasing it. Not only is the internal stress itself a problem, it is usually subject to changes in aging over time as the precipitates self-anneal, resulting in unpredictability.

  The basic mechanism for reducing the intrinsic stress in copper electroplating is not well understood. Parameters such as reduced deposit thickness, current density, i.e. reduced plating rate, choice of substrate type, seed layer or underplate, electroplating bath composition, e.g. anion type, additives, impurities, and It is known that contaminants affect the stress of precipitates. Although such experimental means to reduce stress have been utilized, they are usually inconsistent or reduce the efficiency of the electroplating process.

  Another important parameter of the copper deposit is its ductility. Ductility can be defined as the ability of a solid material to deform under tensile stress. In order to prevent or reduce the possibility of copper cracking over time under tensile stress, copper precipitates with high ductility are desirable. Ideally, copper precipitates have a relatively low internal stress and high ductility, but there is usually a reciprocal relationship between internal stress and ductility. Accordingly, there remains a need for methods that not only reduce internal stress in copper electroplating baths and copper deposits, but also provide good or high ductility.

  The acidic copper electroplating bath comprises one or more copper ion sources, one or more electrolytes, one or more polyallylamines, (O-ethyldithiocarbonate) -S- (3-sulfopropyl)- 1 type or more of ester, its acid, and its salt, and 1 or more types of inhibitor are included.

  The method comprises a substrate comprising at least one copper ion source, at least one electrolyte, at least one polyallylamine, and (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester. Contacting with an acidic copper electroplating bath comprising at least one of acid, its acid and its salt and at least one inhibitor, and applying low internal stress and high ductility copper on the substrate Plating.

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

  This acidic copper precipitate is of low internal stress with a relatively large grain structure. Internal stress and grain structure are substantially unchanged when the precipitates age, thus increasing the predictability of the copper electroplating bath and the precipitates plated therefrom. Because the low internal stress copper deposits have good or high ductility as well, the copper deposits do not crack easily on the substrate, in contrast to many conventional copper deposits. Copper electroplated from the baths of the present invention has a good balance of low internal stress and ductility not found when electroplating copper from many conventional copper baths. Use this copper electroplating bath to deposit a copper film on a relatively thin substrate without substantial concern that the thin substrate may warp, bend, warp, swell, peel, or crack. be able to.

Unless the context clearly indicates otherwise, the following abbreviations have the following meanings: ° C = degrees Celsius, g = grams, mL = milliliters, L = liters, ppm = parts per million = mg / L, A = amps = Amp, DC = direct current, dm = decimeter, mm = millimeter, μm = micrometer, nm = nanometer, Mw = weight average molecular weight (g / mol), SEM = scanning electron microscope, ASD = A / dm ² , 2.54 cm = 1 inch, lbf = pound weight = 4.44822162 N, N = Newton, psi = pound / square inch = 0.06805 atmospheres, 1 atmosphere = 1.13325 × 10 ⁶ dynes / square centimeter, and RFID = radio Authentication.

  As used throughout this specification, the terms “deposition”, “plating”, and “electroplating” are used interchangeably. The term “moiety” means a part of a molecule or a functional group. portion

Is equal to —CH ₂ —CH ₂ . The indefinite articles “a” and “an” include both the singular and the plural. The term “ductility” means the ability of a solid material to deform under tensile stress. The term “tensile stress” means the maximum stress that a material can withstand before failure.

  All percentages and ratios are by weight unless otherwise indicated. All ranges are inclusive and can be combined in any order except where it is clear that such numerical ranges are constrained to add up to 100%.

  The copper metal electroplating bath provides a thin film copper deposit having a combination of low internal stress and high ductility. Copper metal includes one or more copper ion sources, one or more electrolytes, one or more polyallylamines, (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester, By electroplating from a low stress and high ductility acidic copper bath containing one or more of acids or salts thereof and one or more inhibitors, the copper precipitates have low internal stress and high It has ductility, preferably minimal stress change when copper precipitates age, and high ductility. Low internal stress copper precipitates can have a matte appearance with a relatively large grain size during precipitation, typically 2 microns or more. The acidic, low stress, high ductility copper bath may also include one or more chloride ion sources and one or more conventional additives normally included in acidic copper electroplating baths. Preferably, the one or more chloride ion sources are included in the acidic copper electroplating bath.

  Preferably, the one or more polyallylamine has the general formula:

  (Wherein the variable “n” is a number such that Mw is 1000 g / mol or more). Preferably, the Mw of the polyallylamine of the present invention ranges from 4000 g / mol to 60,000 g / mol, more preferably from 10,000 g / mol to 30,000 g / mol.

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

  One or more of (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester, its acid, and its alkali metal salt is copper electroplated in an amount of 100 ppm to 300 ppm, preferably 120 ppm to 220 ppm. Included in the plating bath. The acidic form of the ester is 3-[(ethoxythioxomethyl) thio] -1-propanesulfonic acid. Alkali metal salts are potassium salt of (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester and sodium of (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester Contains salt. Preferably, the potassium salt of (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester is included in the copper electroplating bath. Without being bound by theory, (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester and its alkali metal salt in combination with one or more polyallylamines have low internal stress and high ductility. It is thought that the combination of the copper metal film deposits of this is possible.

  If desired, one or more additional promoters may be included in the low stress and high ductility acidic copper electroplating bath. Such an accelerator is preferably a compound that, in combination with one or more inhibitors, can provide an increase in plating rate at a given plating potential. Such optional accelerators include 3-mercapto-1-propanesulfonic acid, ethylenedithiodipropylsulfonic acid, bis- (ω-sulfobutyl) -disulfide, methyl- (ω-sulfopropyl) -disulfide, N, N -Dimethyldithiocarbamic acid (3-sulfopropyl) ester, 3-[(amino-iminomethyl) -thiol] -1-propanesulfonic acid, 3- (2-benzylthiazolthio) -1-propanesulfonic acid, bis- (sulfo Propyl) -disulfides and their alkali metal salts. Preferably, such accelerators are removed from the copper electroplating bath.

  If optional accelerators are included, they are included in an amount of 1 ppm or more. Typically, such accelerators 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 contained in the low stress and high ductility acidic copper electroplating bath include polyoxyalkylene glycol, carboxymethyl cellulose, nonylphenol polyglycol ether, octanediol bis- (polyalkylene glycol ether), octanol polyalkylene glycol ether, Examples include, but are not limited to, 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. Such inhibitors are 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, most preferably 0.1 g / L. Included in an amount of ~ 1 g / L.

Suitable copper ion sources are copper salts, copper halides such as copper sulfate and copper chloride, copper acetate, copper nitrate, copper tetrafluoroborate, copper alkyl sulfonate, copper aryl sulfonate, copper sulfamate, perchlorine Although copper acid and copper gluconate are mentioned, it is not limited to these. Exemplary copper alkanesulfonates include copper alkanesulfonate (C ₁ -C ₆ ) and more preferably copper alkanesulfonate (C ₁ -C ₃ ). Preferred copper alkane sulfonates are copper methane sulfonate, copper ethane sulfonate, and copper propane sulfonate. Exemplary copper aryl sulfonates include, but are not limited to, copper benzene sulfonate and copper p-toluene sulfonate. A mixture 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. Usually, the copper salt is present in an amount sufficient to provide a plating solution with a copper ion content of 10 to 400 g / L. The electroplating bath does not contain any alloy metal. The electroplating bath is directed to thin film copper deposits that are not copper alloy deposits or any other metal or metal alloy.

  Suitable electrolytes include sulfuric acid, acetic acid, fluoroboric acid, methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, alkane sulfonic acid such as trifluoromethane sulfonic acid, aryl sulfonic acid such as benzene sulfonic acid, p-toluene sulfone. Acids, sulfamic acid, hydrochloric acid, hydrobromic acid, perchloric acid, nitric acid, chromic acid, and phosphoric acid are included, but are not limited to these. Mixtures of acids may be used in the metal plating bath. Preferred acids include sulfuric acid, methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, hydrochloric acid, and mixtures thereof. The acid may be present in an amount ranging from 1 to 400 g / L. Electrolytes are generally commercially available from various suppliers and may be used without further purification.

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

  A leveling agent may be included in the acidic copper electroplating bath. Such smoothing agents include organic sulfosulfonates such as 1- (2-hydroxyethyl) -2-imidazolidinethione (HIT), 4-mercaptopyridine, 2-mercaptothiazoline, ethylenethiourea, thiourea, Step, etc. No. 6,610,192, No. 7,128,822 to Wang et al., No. 7,374,652 to Hayashi et al., And No. 6,800,188 to Hagiwara et al. Include, but are not limited to: Such leveling agents may be included in conventional amounts. If they are included, they may be included in an amount of 1 ppb to 1 g / L. Preferably, the leveling agent is removed from the bath.

  Conventional nonionic, anionic, cationic, and amphoteric surfactants may be included in the electroplating bath. Such surfactants are well known in the art and many are commercially available. Usually the surfactant is nonionic. In general, the surfactant is included in conventional amounts. Usually they may be included in the electroplating bath in an amount of 0.05 g / l to 15 g / L.

  Halogen ions include chloride, fluoride, and bromide. Such halides are usually added to the bath as water-soluble salts or water-soluble acids. Preferably, the copper electroplating bath contains 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 may be included in the bath in an amount of 20 ppm to 500 ppm, preferably 20 ppm to 100 ppm.

  The low stress, high ductility acidic copper electroplating bath has a pH in the range of less than 1 to less than 7, preferably less than 1 to 5, more preferably less than 1 to 2, and most preferably a pH in the range of less than 1 to 1.

  The electroplating may be performed by a DC plating method, a pulse plating method, a pulse inversion plating method, a light induction plating method (LIP), or a light assist plating method. Preferably, the low stress, highly ductile copper film is plated by DC, LIP, or light assisted plating. In general, the current density ranges from 0.5 to 50 ASD depending on the application. Usually the current density is in the range of 1-20 ASD, or for example 4-20 ASD or 15-20 ASD. The electroplating is performed at a temperature in the range of 15 ° C to 80 ° C, or such as room temperature to 60 ° C, or such as 20 ° C to 40 ° C, or such as 20 ° C to 25 ° C.

  The internal stress and ductility of the copper film may be determined using conventional methods. Typically, low internal stress is measured using a precipitate stress analyzer available from, for example, Specialty Testing and Development (Jacobs, PA). The low internal stress is the formula S = U / 3T × K, where S is the stress (psi), U is the number of deflection increments on the calibrated scale, and T is the thickness of the precipitate (inches ) And K is the test strip calibration constant). The constant may vary and is provided by a precipitate stress analyzer. The low internal stress is measured immediately after plating and then after several days of aging, preferably after 2 days, a copper film is deposited on a substrate, such as a conventional copper / beryllium alloy test strip. Internal stress is measured at room temperature immediately after electroplating and after aging. In order to measure the internal stress, the room temperature may be varied, but the room temperature is usually in the range of 18 ° C to 25 ° C, preferably 20 ° C to 25 ° C. A copper film, preferably 1-10 μm, more preferably 1-5 μm, is plated on the test strip. The initial internal stress measured immediately after plating of copper 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. For example, after aging for 2 days, the internal stress may range from 300 psi to 900 psi, preferably 300 psi to 850 psi, more preferably 300 psi to 840 psi at room temperature. Although the internal stress may vary slightly 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.

  Ductility is measured using conventional elongation tests and equipment. Preferably, the elongation test is performed using an industry standard IPC-TM-650 method with equipment such as an Instron tensile tester 33R4464. Copper is electroplated onto a substrate such as a stainless steel panel. Usually, copper is electroplated as a thin film on a substrate with a thickness of 50-100 μm, preferably 60-80 μm. Copper is peeled from the substrate and annealed for 1 to 5 hours, preferably 2 to 5 hours. The annealing is performed at a temperature of 100 to 150 ° C., preferably 110 to 130 ° C., and then the copper is brought to room temperature. The elongation or load of the maximum tensile stress is usually not a preset parameter. By increasing the maximum tensile stress loading, the material can withstand prior to failure or cracking, resulting in higher or better ductility. Usually, the elongation is carried out under a load having 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 8% or more, preferably 9% to 15%.

  Low stress, high ductility acidic copper for plating copper on relatively thin substrates such as 100-220 μm, or for example, 100-150 μm semiconductor wafers, or on the sides of substrates where warping, bending, or distortion is a problem Electroplating baths and methods are used. Also, low stress, high ductility acidic copper electroplating baths are used to plate copper when deposit blistering, peeling, or cracking is common and difficult to adhere to the substrate. May be. For example, the method includes printed circuits and wiring boards such as flexible circuit boards, flexible circuit antennas, RFID tags, electrolytic foils, semiconductor wafers for photovoltaic devices, and interdigitated rear contact solar cells, heterogeneous layers with intrinsic thin layers. It may be used in the manufacture of solar cells, including junction (HIT) cells and full plating front contact cells. The acidic copper electroplating bath is preferably used for plating copper in a thickness range of 1 μm to 5 mm, more preferably 5 μm to 1 mm. When copper is used as the principle conductor in the formation of solar cell contacts, copper is preferably plated to a thickness range of 1 μm to 60 μm, more preferably 5 μm to 50 μm.

  Acidic copper deposits are of low internal stress with a relatively large grain structure. Also, internal stress and grain structure are substantially unchanged when the precipitates age, thus increasing the predictability of the performance of the copper electroplating bath and precipitates plated therefrom. Because low internal stress copper deposits have good ductility as well, they do not crack easily on the substrate, in contrast to many conventional copper deposits. Copper electroplated from the baths of the present invention has a good balance of low internal stress and ductility not found when electroplating copper from many conventional copper baths. A copper electroplating bath may be used to deposit copper on a relatively thin substrate without substantial concern that the substrate may warp, bend, warp, swell, peel, or crack.

  The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof.

Example 1
The following acidic copper electroplating bath aqueous solution was prepared.

[table]

  The components of the copper electroplating bath were constructed using conventional experimental procedures in which organics were added to water followed by inorganic components. Agitation or vibration was applied while applying heat at a temperature below 30 ° C. to ensure that all of the components were dissolved in water. The bath was brought to room temperature before electroplating the copper. The pH of the acidic copper electroplating bath ranged from less than 1 to 1 during room temperature and copper electroplating.

Example 2
Two flexible copper alloy foil test strips were coated with dielectric on one side, allowing single-side plating on the uncoated side. The test strip was taped to a support substrate with a plater tape and placed in a Haring cell containing an acidic copper plating bath having the formulation of bath 1 in the table in Example 1. The bath was maintained 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 ASD so that 5 μm thick copper was deposited on the uncoated surface of each strip. After plating was completed, the test strip was removed from the Haring cell, rinsed with a wafer, and allowed to dry to remove the plater tape 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 formula S = U / 3T × K where S is the stress (psi) and U is the number of deflection increments on the calibrated scale. T is the deposit thickness (inches) and K is the test strip calibration constant. After aging the test strip for 2 days, the stress on each strip was determined to be 837 psi. After aging, the internal stress of the copper precipitate remained substantially the same.

  Elongation tests were also performed using the industry standard IPC-TM-650 method. 75 μm copper was plated on stainless steel panels at 3.8 ASD. After plating, the copper film was peeled off and annealed at 125 ° C. for 4 hours. A tensile test was performed with an Instron tensile tester 33R4464. The elongation of bath 1 was 14% and the maximum tensile stress load was 76 lbf. The results show that the internal stress of the copper deposit electroplated from the bath containing polyallylamine and the potassium salt of (O-ethithiothiocarbonate) -S- (3-sulfopropyl) -ester is low and ductile. It showed that.

Example 3 (comparison)
Two flexible copper / beryllium alloy foil test strips were coated with a dielectric on one side, allowing single side plating on the uncoated side. The test strip was taped to the support substrate with a plater tape and placed in a Haring cell containing the 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 ASD so that 5 μm thick copper was deposited on the uncoated surface of each strip. After plating was completed, the test strip was removed from the Haring cell, rinsed with a wafer, and allowed to dry to remove the plater tape from the test strip. The test strip was inserted into the screw clamp at one end of the precipitate stress analyzer. The internal stress of the copper deposit on the strip was determined to be 211 psi. Stress is the formula S = U / 3T × K, where S is the stress (psi), U is the number of deflection increments on the calibrated scale, and T is the thickness of the precipitate in inches. And K is the test strip calibration constant). After aging the test strip for 2 days, the stress on 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 stainless steel panels at 3.8 ASD. After plating, the copper film was peeled off and annealed at 125 ° C. for 4 hours. A tensile test was performed with an Instron tensile tester 33R4464. The elongation of copper plated from bath 2 was 7% and the load at maximum tensile stress was only 50 lbf. Although the internal stress was low, the copper ductility was not as high as bath 1 with polyallylamine. Bath 2 was typically an example of a conventional acidic copper electroplating bath for electroplating a copper film with low internal stress but undesirable low ductility.

Example 4 (comparison)
Two flexible copper / beryllium alloy foil test strips were coated with a dielectric on one side, allowing single side plating on the uncoated side. The test strip was taped to the support substrate with a plater tape and placed in a Haring 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 ASD so that 5 μm thick copper was deposited on the uncoated surface of each strip. After plating was completed, the test strip was removed from the Haring cell, rinsed with a wafer, and allowed to dry to remove the plater tape from the test strip. The test strip was inserted into the screw clamp at one end of the precipitate stress analyzer. The internal stress of the copper deposit on the strip was determined to be 1156 psi. Stress is the formula S = U / 3T × K, where S is the stress (psi), U is the number of deflection increments on the calibrated scale, and T is the thickness of the precipitate in inches. And K is the test strip calibration constant). After aging the test strip for 2 days, the stress on 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 stainless steel panels at 3.8 ASD. After plating, the copper film was peeled off and annealed at 125 ° C. for 4 hours. A tensile test was performed with an Instron tensile tester 33R4464. The elongation percentage of copper deposited from bath 3 was 16%, and the load at maximum tensile stress was 62 lbf. The ductility of the copper film plated from bath 3 was good, but the internal stress was in excess of 1000 psi. Bath 3 was another example of conventional acidic copper electroplating with high internal stress but good ductility.

Example 5 (comparison)
Two flexible copper / beryllium alloy foil test strips were coated with a dielectric on one side, allowing single side plating on the uncoated side. Branched polyethyleneimine has Mw = 2000 g / mol and has the general formula:

  (Wherein y is a number such that the weight average molecular weight of the linear polyethyleneimine is about 2000 g / mol), with the exception that the test strip was replaced with 0.75 ppm linear polyethyleneimine. The support substrate was taped with a plater tape and placed in a Haring cell containing the same acidic copper plating bath as bath 1.

  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 ASD so that 5 μm thick copper was deposited on the uncoated surface of each strip. After plating was completed, the test strip was removed from the Haring cell, rinsed with a wafer, and allowed to dry to remove the plater tape from the test strip. The test strip was inserted into the screw clamp at one end of the precipitate stress analyzer. The internal stress of the copper deposit on the strip was determined to be 631 psi. Stress is the formula S = U / 3T × K, where S is the stress (psi), U is the number of deflection increments on the calibrated scale, and T is the thickness of the precipitate in inches. And K is the test strip calibration constant). After aging the test strip for 2 days, the stress on 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. After plating, the copper film was peeled off and annealed at 125 ° C. for 4 hours. A tensile test was performed with an Instron tensile tester 33R4464. The elongation of copper from the bath was 11.8% and the load at maximum tensile stress was 78 lbf. The ductility was high, but the internal stress after aging exceeded 1000 psi, indicating poor bath performance. The results for bath 4 with linear polyethyleneimine are substantially the same as those for the copper bath except for the combination of polyallylamine and the potassium salt of (O-ethidithiocarbonate) -S- (3-sulfopropyl) -ester. It was the same.

Claims (8)

  One or more sources of copper ions, one or more electrolytes, one or more polyallylamines, (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester, its acid, or its An acidic copper electroplating bath comprising at least one of alkali metal salts and at least one inhibitor.   The acidic copper electroplating bath according to claim 1, wherein the one or more polyallylamines have a weight average molecular weight of 1000 g / mol or more.   The acidic copper electroplating bath of claim 1, wherein the one or more polyallylamine is in an amount of 1 to 10 ppm.   The said one or more (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -esters, acids thereof, or alkali metal salts thereof in an amount of 100 ppm to 300 ppm. Acid copper electroplating bath. a) Substrate comprising one or more copper ion sources, one or more electrolytes, one or more branched polyallylamines, and (O-ethyldithiocarbonate) -S- (3-sulfopropyl) -ester Contacting with a copper electroplating bath comprising one or more of the acids or alkali metal salts thereof and one or more inhibitors;
b) electroplating high ductility copper with low internal stress on the substrate from the copper electroplating bath.   6. The method of claim 5, wherein the low internal stress, highly ductile copper 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, an internal stress of 300 psi to 900 psi after aging, and an elongation of 8% or more at a maximum tensile stress of 50 lbf or more.