The Multi-Functional Role of Boric Acid in Cobalt Electrodeposition and Superfill

Abstract

Although alternative metals such as cobalt are becoming increasingly important as candidates for filling interconnects, questions remain regarding the role of boric acid, one of the primary bath components, in the electroplating process. This work demonstrates that boric acid has multiple functions in cobalt electroplating and superfill. Raman spectroscopy was used to determine speciation of boric acid in solution as a function of concentration and pH. Combining this with titration experiments, it was found that polyborate formation coincides with an increase in buffering capacity in the range of pH that is typical for cobalt electroplating. Atomic force microscopy and secondary ion mass spectrometry confirmed the correlation between hydroxide/oxide in the deposited film and the amount of boric acid in solution. Electrochemical experiments demonstrated that boric acid adsorbs to the electrode surface under certain conditions. Interconnect fill quality was also shown to be directly related to boric acid concentration. Boric acid is shown to be a necessary bath component due to its role in pH buffering and surface adsorption, affecting both blanket film plating and superfill of interconnects in the presence of a suppressor.

Magnetic structure and internal field nuclear magnetic resonance of cobalt nanowires

“…There have been numerous studies in the literature discussing the correlation between additive use and sample microstructure. [46][47][48] Here, all the observed peaks in the diffraction pattern are from cobalt, either in the fcc or hcp phase. Three peaks are observed around 44.31, 75.91 and 92.41, which can be assigned to either fcc or hcp, irrespective of the presence of organic additives in the electrolyte during electrodeposition or not.…”

Electrodeposited Cobalt Nanosheets on Smooth Silver as a Bifunctional Catalyst for OER and ORR: In Situ Structural and Catalytic Characterization

“…Cobalt/silver bimetallic catalytic surfaces were prepared by electrochemical deposition method in a three-electrode cell. Following previous studies, two different cobalt deposition solutions were used: 0.05 M CoCl 2 + 0.5 M B(OH) 3 36 or 1 mM H 2 SO 4 + 10 mM K 2 SO 4 + 1 mM CoSO 4 + 0.1 mM KCl. 37 All solutions were prepared in Milli-Q water (18.2 MΩ cm, TOC of 5 ppm).…”

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

“…At −1.16 V, the current density for H + reduction reached to −0.3 mA cm −2 at 0 rpm and −0.7 mA cm −2 at 800 rpm, which is attributed to the acceleration of H + reduction with the increasing speed. Besides, the slope before reaching −1.19 V is different from that after reaching −1.19 V, illustrating that the partial current was attributed to reduction of hydrogen ion (reaction 1 43 ) before reaching to −1.19 V, as well as the current caused by the water reduction (reaction 2 44 ) when potential was within −1.19 V to −1.22 V. 24,43 +…”

“…22 Generally, the Watts-based electrolyte or buffered sulfate electrolyte can be used to deposit Co film, in which boric acid has been added to stabilize the increasing pH in plating bath caused by polyborates and primarily triborate and occupy block surface sites to inhibit HER as well as facilitate cobalt deposition by the surface complex with cobalt. [23][24][25] In order to achieve bottom-up growth of cobalt deposit, appropriate additives should be introduced into plating bath to achieve growth rate difference in the blind vias. [26][27][28] And, this difference is consistent with the diffusion-adsorption mechanism.…”