Effect of 2-Mercapto-5-benzimidazolesulfonic Acid in Superconformal Cu Electroless Deposition

Superconformal Cu electroless deposition is demonstrated in a CuSO4–EDTA–HCHO (where EDTA is ethylenediaminetetraacetic acid) electrolyte containing 2-mercapto-5-benzimidazolesulfonic acid (MBIS). MBIS reveals a concentration-dependent effect in the deposition rate on planar substrates, whereby acceleration at low concentration and suppression at high concentration are evident. The half-cell reaction experiments show that the acceleration effect of MBIS is mainly associated with the cathodic reaction, while MBIS inhibits the oxidation of HCHO in the anodic reaction. The addition of MBIS offers preferential Cu electroless deposition at the bottom of 500 nm wide trenches. Poly(ethylene glycol) improved the surface roughness, maintaining the shape evolution of superconformal feature filling.The authors are grateful to Dr. Thomas P. Moffat at NIST for helpful discussions. This research was supported by the Nano R&D program through the Korea Science and Engineering Foundation funded by the Ministry of Education, Science and Technology (no. 2008-02857

Optimization of a Pretreatment for Copper Electroless Deposition on Ta Substrates

We investigated pretreatment methods for Cu electroless deposition on a Ta substrate. The native oxide on the substrate was effectively etched by the addition of HNO3 to a HF diluted solution and this was confirmed though X-ray photoelectron spectroscopy and chronopotentiometry. To form the Pd catalyst for Cu electroless deposition, a two-step Sn sensitization and Pd activation was carried out. The oxide removal enhanced the adsorption of the Sn ions on the Ta substrate and led to well distributed Pd clusters through Pd activation. By measuring the resistivity of the film, the Sn sensitization time and the Pd activation time were optimized through changes in the incubation time, at which the sheet resistance abruptly decreased by the film formation via the coalescence of Cu grains. The resistivity of the Cu electroless film deposited using the optimized pretreatment conditions was 3.59 cm, which was further reduced to 2.7 cm through an annealing process.This work was supported by KOSEF through the Research Center for Energy Conversion and Storage RCECS , Dongbu Electronics, and by the Institute of Chemical Processes ICP

Two-step filling in Cu electroless deposition using a concentration-dependent effect of 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid

This paper describes electroless Cu filling of trenches with different widths ranging from 130 to 300 nm, using a concentrationdependent effect of 3-N,N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid DPS . With a fixed DPS concentration, it is shown that these trenches with different dimensions cannot be superfilled simultaneously. This is presumably caused by different surface concentrations of the adsorbed additive, which depends on the feature size and surface area. A two-step filling method is employed to superfill those trenches, which is also effective in control of the deposited Cu amounts to obtain uniform growth front regardless of the trench dimensions.This work was supported by a Korea Research Foundation grant funded by the Korean Government MOEHRD grant no. KRF- 2006-352-D00052 . The authors are grateful for the support of the Research Center for Energy Conversion and Storage RCECS , Dongbu HiTek Company, Ltd., and the Institute of Chemical Processes ICP

Complete genome sequence of Middle East respiratory syndrome coronavirus KOR/KNIH/002_05_2015, isolated in South Korea

The full genome sequence of a Middle East respiratory syndrome coronavirus (MERS-CoV) was identified from cultured and isolated in Vero cells. The viral genome sequence has high similarity to 53 human MERS-CoVs, ranging from 99.5% to 99.8% at the nucleotide level. © 2015 Kim et al.

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe