Investigation of organic impurities adsorbed on and incorporated into electroplated copper layers

Stangl, M.; Dittel, V.; Acker, Jörg; Hoffmann, Volker; Gruner, W.; Strehle, Steffen; Wetzig, K.

doi:10.1016/j.apsusc.2005.02.006

Cited by 31 publications

(18 citation statements)

References 3 publications

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“…Fragments of organic additives and their breakdown products accumulate in the electroplating bath, and are often incorporated in the Cu deposit, especially at grain or morphological boundaries. [23][24][25] It is commonly known that excess incorporation has a harmful impact on the Cu mechanical properties, such as ductility and tensile strength. Compositional analysis of various commercial PCB Cu foils, by SIMS and GDMS, indicated that tens of parts per million (ppm) of impurities could result in unacceptably high voiding levels for certain microelectronic applications.…”

Section: Introductionmentioning

confidence: 99%

Toward a Better Understanding of the Effect of Cu Electroplating Process Parameters on Cu3Sn Voiding

Yin

Wafula

Dimitrov

et al. 2011

Journal of Elec Materi

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Kirkendall voiding'' in the interfacial Cu 3 Sn intermetallic compound is often observed in solder joints made between Sn-containing alloys and Cu interconnect pads, during extended thermal aging or electromigration testing. It is commonly believed that voids arise from the Kirkendall effect, i.e., the imbalance of diffusion fluxes of Cu and Sn atoms in Cu 3 Sn. However, recent studies have demonstrated that the propensity for voiding is greatly affected by the amount of organic impurities incorporated during Cu electroplating. The level of impurities was shown to depend on various electroplating parameters, such as current density, bath temperature, bath age, etc. In this study, a general picture is proposed to provide a better understanding of the effect of electroplating process parameters on Cu 3 Sn voiding. The picture correlates the level of impurity incorporation to (1) the applied electroplating overpotential, and (2) the crystallographic orientation of the Cu deposit. As a first-order approximation, the picture is supported by a variety of electroplating experiments, secondary-ion mass spectroscopy (SIMS), and x-ray diffraction (XRD) analysis.

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Section: Introductionmentioning

confidence: 99%

Toward a Better Understanding of the Effect of Cu Electroplating Process Parameters on Cu3Sn Voiding

Yin

Wafula

Dimitrov

et al. 2011

Journal of Elec Materi

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“…It is generally accepted in the cluster community that clusters generated in similar sources are free from oxidation or other contamination (see, for example, the mass and photoelectron spectra in [4]). Hence, the purity of the Cu clusters which can in principle be at least as good as in iPVD processes, is in strong contrast with the significant level of impurities that are incorporated into interconnect structures by ECD processes [19]. Although selective filling has been demonstrated in electro-deposition and a chemical vapor deposition (CVD) process [20], this is the first time it has been achieved with a technique which intrinsically produced high purity metal.…”

Section: A Selective Trench Fillingmentioning

confidence: 98%

Selective Filling and Sintering of Copper Nanoclusters for Interconnect

Tee

Lassesson

Lith

et al. 2007

IEEE Trans. Nanotechnology

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Abstract-In copper interconnect technology, dielectric trenches are patterned, filled with copper, and polished. We report a cluster-based deposition technology that provides efficient trench filling and excellent selectivity between trenches and plateaus on damascene structures. The selectivity arises due to the propensity for reflection of clusters from the planar surfaces between trenches. Trenches of sub-200 nm widths, with various diffusion barriers and seed layers, and up to 5 : 1 aspect ratios have been completely filled with copper clusters. We also show that copper clusters can be sintered into a seed layer using hydrogen annealing. Thus, dense copper films within trenches are obtained. Preliminary results from planar samples show that the resistivity is around 2.3 10 8 m

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“…Therefore, chloride ions may not play as important a role in microvoiding as S atoms. 21,22 Elements such as C, H, and O have very high diffusivities in copper and therefore do not play an important role in microvoiding at the solder-copper interface. 20,22 This is further supported by Fig.…”

Section: Effect Of Electroplating Parametersmentioning

confidence: 99%

“…17 Electroplating is the preferred process for forming copper interconnects and pads for circuit boards. [18][19][20][21][22] During the process of electroplating many types of organic additives such as Na 2 [SO 3 (CH 2 ) 3 S] 2 (SPS) and polyethylene glycol (PEG) are used in the electrochemical bath as brighteners and wetting agents to achieve desired properties in the plated copper surfaces. It has been shown that these large organic additive molecules can become incorporated into the metal as plating proceeds.…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that these large organic additive molecules can become incorporated into the metal as plating proceeds. 18,19,[21][22][23][24] These large molecules can easily break down into smaller impurity atoms (sulfur, chlorine, fluorine, bromine, carbon, sodium, and potassium) and molecules and affect the microvoiding propensity during further processing of circuit boards. It has also been shown that electroplating parameters such as wetting agents, brighteners, and current density can directly affect the voiding propensity individually.…”

Section: Introductionmentioning

confidence: 99%

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Microvoid Formation at Solder–Copper Interfaces During Annealing: a Systematic Study of the Root Cause

Kumar

Smetana²,

Love

et al. 2011

Journal of Elec Materi

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The electrodeposition conditions that contribute to microvoid formation during isothermal aging of Pb-free solder-electrodeposited copper were evaluated in a systematic series of processing experiments. The results of 2 K full-factorial design of experiment are presented to show the effect of prescreened electroplating parameters such as brighteners, wetting agent, bath age, and current density on the propensity for microvoiding at solder-copper interfaces after annealing at 125°C for 40 days. It was found that the amount of microvoiding is greatly affected by bath age, wetting agent, brightener, and their interactions. Time-of-flight secondary-ion mass spectroscopy and glow discharge spectroscopy allowed us to establish a correlation between impurities incorporated in copper during electroplating and microvoiding at the solder-copper interface.

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Investigation of organic impurities adsorbed on and incorporated into electroplated copper layers

Cited by 31 publications

References 3 publications

Toward a Better Understanding of the Effect of Cu Electroplating Process Parameters on Cu3Sn Voiding

Toward a Better Understanding of the Effect of Cu Electroplating Process Parameters on Cu3Sn Voiding

Selective Filling and Sintering of Copper Nanoclusters for Interconnect

Microvoid Formation at Solder–Copper Interfaces During Annealing: a Systematic Study of the Root Cause

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