Copper Electroplating with Polyethylene Glycol: Part II. Experimental Analysis and Determination of Model Parameters

101

Bottom-up Cu deposition in metallized through silicon vias (TSV) depends on a co-adsorbed polyether–Cl − suppressor layer that selectively breaks down within recessed surface features. This work explores Cu deposition when formation of the suppressor blocking layer is limited by the flux of Cl − . This constraint leads to a transition from passive surfaces to active deposition partway down the via sidewall due to coupling between suppressor formation and breakdown as well as surface topography. The impact of Cl − concentration and hydrodynamics on the formation of the suppressor surface phase and its potential-dependent breakdown is examined. The onset of suppression breakdown is related to the local Cl − coverage as determined by the adsorption isotherm or transport limited flux. A two-additive co-adsorption model is presented that correlates the voltammetric potential of suppression breakdown with the depth of the passive-active transition during TSV filling under conditions of transport limited flux and incorporation of Cl − . The utility of potential waveforms to optimize the feature filling process is demonstrated. At higher Cl − concentrations (≥80 μmol/L), sidewall breakdown during Cu deposition occurs near the bottom of the via followed by a shift to bottom-up growth like that seen at higher Cl − concentrations.

mentioning

confidence: 92%

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confidence: 99%

Effect of Chloride Concentration on Copper Deposition in Through Silicon Vias

Braun

Josell

Silva

et al. 2019

101

“…The rapid deactivation feature can be seen as large hysteretic voltammetric behavior characterized by an S-shaped negative differential resistance (S-NDR) by Moffat et al 18 Although cyclic voltammetry has been widely used in additive studies, [19][20][21][22][23][24] interpretation of the results is not easy because adsorption occurs at the same time as deactivation in conventional experimental arrangements. Accordingly, we constructed a microfluidic device in which rapid switching of the plating solution is enabled.…”

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confidence: 99%

Transitional Additive Adsorption with Co-Addition of Suppressor and Leveler for Copper TSV Filling

Tomie

Akita

Irita³

et al. 2020

Suppression of copper electrodeposition by two additives, suppressor and leveler, were studied using a microfluidic device. In industry, two suppressing agents, one a suppressor and the other a leveler, are usually added together into the plating bath for copper bottom-up TSV (Through Silicon Via) filling. Several studies, including our own previous one, suggest that the leveler is the essential agent for bottom-up filling, with its strong suppression and rapid deactivation. The suppressor shows moderate suppression and slow deactivation, and is believed to interfere with bottom-up deposition. It is unclear why bottom-up deposition is possible with co-addition of the suppressor and why co-addition is popular. In the present study, the suppressor and the leveler were supplied onto the plating surface sequentially, using a microchannel; it was found that the leveler replaces the suppressor. The leveler and suppressor were also supplied simultaneously; the suppressor initially covered most of plating surface, but the leveler gradually replaced the suppressor, and the plating surface was finally dominated by the leveler.

“…29,34,42,43 Suggested mechanisms for suppression breakdown include reduction of a Cu + halide-ether binding agent, [26][27][28] potential driven order-disorder transitions in the halide adlayer, 46 and disruption of the polymer adsorption process by the metal deposition process itself that, amongst other variants, can involve a change in the hydrophilicity of the interface. 12,24,[39][40][41]44,47,48 Significant research is underway to link electroanalytical results with metallurgical and spectroscopic measurements of deposit microstructure and residual additive components incorporated in the growing deposit both during and following suppression breakdown.…”

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confidence: 99%

Editors' Choice—Simulation of Copper Electrodeposition in Through-Hole Vias

Braun

Josell

John

et al. 2019

Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon vias (TSV) depend on spatially selective breakdown of a co-adsorbed polyether-chloride adlayer within the recessed surface features. In this work, a co-adsorption-dependent suppression model that has previously captured experimental observations of localized Cu deposition in TSV is used to explore filling of TH features. Simulations of potentiodynamic and galvanostatic TH filling are presented. An appropriate applied potential or current localizes deposition to the middle of the TH. Subsequent deposition proceeds most rapidly in the radial direction leading to sidewall impingement at the via center creating two blind vias. The growth front then evolves primarily toward the two via openings to completely fill the TH in a manner analogous to TSV filling. Applied potentials, or currents, that are overly reducing result in metal ion depletion within the via and void formation. Simulations in larger TH features (i.e., diameter = 85 μm instead of 10 μm) indicate that lateral diffusional gradients within the via can lead to fluctuations between active and passive deposition along the metal/electrolyte interface.