Bis-(3-sodiumsulfopropyl disulfide) Decomposition with Cathodic Current Flowing in a Copper-Electroplating Bath

Lee, Wen Hsi; Hung, Chi Cheng; Chang, Shih Chieh; Wang, Ying Lang

doi:10.1149/1.3254165

Cited by 18 publications

(19 citation statements)

References 24 publications

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“…A large number of studies have reported degradation effects associated with interactions between Cu͑II͒/Cu͑I͒ and SPS 2− /MPS − in these types of cells. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] At the same time, interactions with atmospheric O 2 and the reduction intermediate H 2 O 2 may also have a direct or indirect role in thiol/disulfide chemistry. 8,23 To investigate these inter- Table III. 4 2− x is equal to g g −1 .…”

Section: D180mentioning

confidence: 99%

Characterization and Purification of Commercial SPS and MPS by Ion Chromatography and Mass Spectrometry

Brennan¹,

Phillips²,

Yang³

et al. 2011

J. Electrochem. Soc.

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SPS ͑bis-͑3-sulfopropyl͒ disulfide͒ is an essential electrolyte additive used in the fabrication of copper interconnects by electrodeposition. In electroplating baths, the disulfide component of SPS may be cleaved to form the thiol analog, MPS ͑3-mercaptopropyl sulfonate͒, by either homogenous interactions with the Cu͑I͒ reaction intermediate or by dissociative adsorption onto the copper surface. However, mechanistic studies into the role of these additives in copper electrodeposition are presently constrained by limited knowledge of the purity of commercially available SPS and MPS. This report details the use of ion chromatography ͑IC͒ and electrospray ionization mass spectrometry to characterize aqueous solutions of commercial SPS and MPS source materials. Sulfate ͑2.0%͒ and propane disulfonic acid ͑0.9%͒ ͑PDS͒ were determined to be the principal impurities in SPS ͑96.3% estimated purity, mass fraction͒. IC fractionation was used to purify and isolate SPS for surface and electroanalytical studies. Stability of SPS, MPS, and PDS in the presence of O 2 and Cu͑II͒ was also examined. No degradation of SPS or PDS in aqueous solution was observed over a 3-month period. Solutions of MPS were metastable to O 2 saturation, but the addition of Cu͑II͒ resulted in formation of SPS by dimerization as well as parasitic PDS generation.State-of-the-art Cu wiring for microelectronic circuitry is fabricated by electrochemical deposition. 1,2 The electroplating process requires the use of a specific combination of additives in an acidic Cu͑II͒ plating bath to enable void-free filling of recessed surface features such as trenches and vias. Commercial additive packages comprised at least three species: Cl − , an accelerator such as bis-͑3-sulfopropyl͒ disulfide ͑SPS͒, and a polyether-based suppressor such as polyethylene glycol ͑PEG͒ or a related block or branched copolymer. 3,4 Chloride is a required coadsorbate for the formation of the inhibiting PEG layer as well as the subsequent formation of the SPS-derived accelerating surface phase. Feature filling involves a competition between SPS and the polyether for Cl − -saturated Cu surface sites. 2,3 As the local surface area decreases, such as within a filling trench, the more tightly bound SPS-derived adsorbates remain on the surface while the polyether suppressor is displaced into the electrolyte. This displacement results in an accelerated rate of Cu deposition on the SPS-enriched concave surface segments, leading to bottom-up superconformal filling. Several quantitative descriptions of feature filling based on the curvature enhanced accelerator coverage ͑CEAC͒ mechanism are available. 2-6 Nevertheless, much remains unknown about the physical and chemical nature of the SPS-derived accelerator surface phase.A recent scanning tunneling microscope ͑STM͒ study of SPS adsorption on a Cl − saturated Cu͑100͒ surface revealed a plurality of lattice gas species diffusing on top of, or within, the Cl − adlayer. 7 In addition to the dimer-like SPS species, smaller molecules suggestive of th...

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Section: D180mentioning

confidence: 99%

Characterization and Purification of Commercial SPS and MPS by Ion Chromatography and Mass Spectrometry

Brennan¹,

Phillips²,

Yang³

et al. 2011

J. Electrochem. Soc.

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“…The additives exist in the form of complex, such as SPS-Cl --Cu 2+ . [2][11] The numerical simulation is based on the following assumptions: 1)additives are in the forms of accelerator complexes or inhibitor complexes in the electrolyte and these complexes are electropositive; 2)before the electrodeposition starts, adsorptions of the additives is completed and the adsorption process abides by the rule which is the strength of PEG adsorption is higher than the strength of SPS adsorption;3)there is only one species on the sites of electrode; 4)competing adsorption between SPS and PEG decides the concentration of additives; 5)electrodepostition velocity was decided to the surface coverage of the accelerator. The electrodeposition process is explained by this assumption.…”

Section: Numerical Modelmentioning

confidence: 99%

“…Commonly plating baths employed for Cu-electro-plating purposes have at least three or four components: a polyether such as poly (ethylene glycol) (PEG) or polyalkylene glycols, a sulfonate-terminated thiol or disulfide catalyst such as bis(3-sodiumsulfopropyl disulfide) (SPS) or NaSH(CH 2 ) 3 SO 3 (MPS), a halide ion such as chloride ions (Cl − ), and a nitrogen-based small molecule or polymer leveler. [2] Some numerical models of electrodepostion have been developed to explain the superfilling process. The CEAC mechanism model which exactly described the superfilling process of Dual-Damascene and CVD (chemical vapor deposition) was built by T.P.Moffat etc.…”

Section: Introductionmentioning

confidence: 99%

A numerical model for bottom-up copper electrodeposition of TSV with additives

Luo

Feng

Gao

et al. 2013

2013 3rd IEEE CPMT Symposium Japan

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The kinetics which explained the copper Superfilling by electrodeposition was investigated since the copper electrodeposition became the standard technique for TSV. In order to interpret the bottom-up Superfilling process conveniently and exactly, a numerical model focused on the mass which can make the copper deposition in the via is built. This model only considered the effect of accelerator and cupric which directly affect the electrodeposition velocity in the via. The effect of two species in the numerical model is represented to two reaction constants k r and k A . Both of two constants are the compound parameters including desorption, adsorption and reaction of deposition mass. Experimental electrodeposition of variable dimension via is used to verify the accuracy of a numerical model. The results show that the model can demonstrate the electrodeposition process of via which is 50μm in diameter.

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“…However, the electrodic activity of SPS is also important. 15,16 Based on the mass-spectrum data obtained by Hung et al 17 and West et al, 18 together with information from Atotech Inc., 19 SPS breakdown in a standard copper electrolytic bath may be summarized by Fig. 1, although more interconversions and other breakdown products were reported.…”

mentioning

confidence: 99%

“…Both pathways, however, may eventually lead to PDS, which has been shown to be the most stable byproduct of SPS decomposition. [16][17][18] The reduction of SPS to MPS has also been associated with the catalytic action of SPS through various hypothesized mechanisms, many involving stabilization of cuprous complexes at the electrode surface. [20][21][22][23][24][25][26] The ferric/ferrous redox couple is utilized in copper electrolytes for plating printed circuit boards, and has been considered for implementation in on-chip metallization of copper.…”

mentioning

confidence: 99%

Interaction between SPS and MPS in the Presence of Ferrous and Ferric Ions

Volov

West

2011

J. Electrochem. Soc.

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The ferric/ferrous redox couple interacts with bis-(3-sulfopropyl) disulfide (SPS), leading to increased amounts of 3-mercaptopropyl sulfonate (MPS) in solution. SPS is an essential organic additive in the electrochemical deposition of copper from acidic cupric sulfate electrolytes onto printed circuit boards and integrated circuits. Electrochemical studies show that the accelerating action of SPS is dependent on the ferric/ferrous concentration ratio, with weakening dependence at increasing cupric sulfate concentration. HPLC and electrochemical results suggest that an increased concentration of MPS in the presence of the redox couple is the primary cause of the increased acceleration. Equilibrium estimates of MPS generation by the introduced redox chemistry partially explain these observations; the standard reduction potential of SPS to MPS reduction is estimated to be in a range between 0.3 and 0.4 V vs. SHE. However, the amount of acceleration goes through a maximum at an intermediate ferric-ferrous ratio, possibly because SPS may be converted to MPS via both an oxidative and a reductive pathway.

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Bis-(3-sodiumsulfopropyl disulfide) Decomposition with Cathodic Current Flowing in a Copper-Electroplating Bath

Cited by 18 publications

References 24 publications

Characterization and Purification of Commercial SPS and MPS by Ion Chromatography and Mass Spectrometry

Characterization and Purification of Commercial SPS and MPS by Ion Chromatography and Mass Spectrometry

A numerical model for bottom-up copper electrodeposition of TSV with additives

Interaction between SPS and MPS in the Presence of Ferrous and Ferric Ions

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