Superconformal Cobalt Fill through the Use of Sacrificial Oxidants

Cyclic voltammetry (CV), chronopotentiometry and quartz crystal microbalance were used to study the effect of Malachite Green (MG) on bottom-up growth of cobalt. The addition of MG not only inhibited the reduction of Co2+ but also accelerated the hydrogen evolution process. The metal reduction process was enhanced as well as the current efficiency was higher with the increase of pH. The bottom-up growth of cobalt can be achieved with the potential of -1.20V. Induction-diffusion-adsorption superconformal electrodeposition mechanism was proposed to illustrate the synergistic effect of MG and pH on the growth of cobalt. On one hand, the MG concentration gradient and pH gradient could be formed to achieve a growth rate difference within blind vias so as to obtain bottom-up growth (diffusion-adsorption effect). On the other hand, the growth rate difference was intensified due to the accelerating effect of MG on HER so as to boost the cobalt superfilling (induction effect).

supporting

confidence: 76%

Induction-Diffusion-Adsorption Process of Malachite Green for Cobalt Superconformal Electrodeposition

Ma¹,

Li²,

Ren³

et al. 2023

“…While conventional copper deposition (i.e., the damascene process 11 ) required the use of a combination of organic additives-namely, a suppressor, an accelerator, and a leveller-to achieve superconformal filling, in case of cobalt electrodeposition the parasitic hydrogen evolution itself can assure the void-free bottom-up filling of trenches and vias. This effect was recently explained based on a "differential current efficiency fill" (DCEF) mechanism, 12 according to which the acid (H + ) content of the bath acts a sacrificial oxidant, the reduction of which creates pH gradients that promote a difference in the metal deposition rates between the wafer surface and the bottom of the features. 12,13 In order to fine-tune superconformal filling, either the acid content of the depositing bath is to be changed (practically applied pH values usually vary between 2 and 4) or buffer components (typically boric acid, H 3 BO 3 ) can be added to the bath.…”

mentioning

confidence: 99%

A Model for the Faradaic Efficiency of Base Metal Electrodeposition from Mildly Acidic Baths to Rotating Disk Electrodes

Kovács

Grozovski

Moreno‐García

et al. 2020

Base metal electrodeposition is inevitably accompanied by parasitic hydrogen evolution. This results in a less-than-unity Faradaic efficiency (FE M ) of metal deposition that is known to depend on many factors like the applied current density, the composition (primarily, the metal ion concentration and the pH) of the depositing bath, and the rate of convection. Analysing how FE M values depend on the current density j under well-defined transport conditions (e.g., by the use of rotating disk electrodes) became an integral part of industrial approaches to the screening of bath compositions applied for base metal electroplating. Yet FE M (j) curves are still not very well understood, and most studies content themselves with their mere qualitative analysis, reaching no conclusions as to the mechanisms of the underlying reactions. We attempt to fill this gap by creating a simple model for FE M (j) curves based on first principles. The presented model can very well be fitted to experimental data obtained for the electrodeposition of nickel and of cobalt, and it yields a consistent set of kinetic and transport parameters over a broad range of pH, rotation rates and current densities. The presented model thus paves the way towards a knowledge-driven benchmarking strategy of base metal electroplating baths.

“…Some cobalt superconformal fill mechanisms for through silicon vias 5 and submicrometer trenches [6][7][8] have been reported in the literature. One such mechanism is termed S-shaped negative differential resistance (S-NDR), which functions by competition between additive adsorption/desorption and consumption characterized by hysteresis and inhibition breakdown in CV.…”

mentioning

confidence: 99%

“…7 Recently the differential current efficiency fill mechanism was proposed to give superconformal cobalt fill in sub-50 nm interconnect features. 8 In our previous paper, we proposed a hydrogen induced deactivation (HID) model for cobalt bottom-up fill in sub-5 nm features. 9 In this work, the additive deactivation is further studied and hydrogen reducz E-mail: Jun.Wu@atotech.com tion is believed to cause the additive deactivation.…”

mentioning

confidence: 99%

Mechanism of Cobalt Bottom-Up Filling for Advanced Node Interconnect Metallization

Wafula

Branagan

et al. 2018

A mechanism of cobalt bottom-up trench fill for advanced node interconnect metallization was studied. The mechanism in question employs a single additive which suppresses cobalt plating and directly impacts the plating rate. Hydrogen, generated simultaneously during plating by electrolysis, reacts with the suppressor via hydrogen reduction, and the product of this reaction is a deactivated form of the suppressor. The local plating rate is governed by the relative concentrations of the activated/deactivated forms. Cyclic voltammetry (CV) shows that the suppressor deactivation is impacted by electrochemical potential, suppressor concentration, rotation rate, and pH, all of which may be controlled to generate bottom up fill in interconnects. Such impacts were confirmed on the plating of patterned coupons. This hydrogen reduction-induced deactivation mechanism provides a theoretical explanation for bottom-up plating in a single additive bath, and the factors that may impact the bottom-up filling.