Ag Seed-Layer Formation by Electroless Plating for Ultra-Large-Scale Integration Interconnection

A high density of Pd catalytic particles is an important factor for obtaining a uniform and continuous Ag seed layer in electroless plating. Adequate surface pretreatment is critical for the formation of such a Pd catalytic particle population. In this study, electroless plating of Ag thin films on TiN substrates was performed using Sn sensitization and Pd activation as pretreatment methods. Sn surface sensitization improves surface wetting and aids in the formation of a Pd catalytic layer in surface-oxidative Pd activation. The Pd activation supported by Sn sensitization also accelerated the formation of a continuous thin Ag film. Furthermore, a thin Ag seed layer deposited on a patterned structure showed excellent conformality.This work was supported by KOSEF through the Research Center for Energy Conversion and Storage, and the Institute of Chemical Processing in Seoul National University

Local Corrosion of the Oxide Passivation Layer during Cu Chemical Mechanical Polishing

In this article, we analyze the effect of complexing agents in Cu chemical mechanical polishing slurry on the formation of oxide and the evolution of stress. The passivation property and surface morphology of the oxide on the surface showed significant differences depending on the kind of complexing agent. Oxalic acid showed fast oxide formation with poor passivation performance, and this caused large tensile stress evolution over 250 MPa in the Cu film. The synergetic effect of stress evolution and temperature increase due to the friction during the polishing caused severe pitting of the Cu surface after polishing in oxalic-acidbased slurry.This work was supported by the Korea Science and Engineering Foundation through the Research Center for Energy Conversion and Storage, the Fundamental Research and Development Program for Core Technology of Materials funded by the Korean Ministry of Commerce, Industry, and Energy, and by the Institute of Chemical Processes at Seoul National University

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

Silver Direct Electrodeposition on Ru Thin Films

Electrodeposition of Ag was performed on Ru thin films following electrochemical reduction of native Ru oxide. Oxide reduction in a tetramethylammonium hydroxide solution was critical for the formation of continuous Ag film, and a large overpotential was important for high-density nucleation. From a kinetics viewpoint, the thermal stability of the Ag film was improved by the application of a more negative potential, which suggested that better nucleation density at the initial stage of growth induced better substrate adhesion. Suppression of growth by addition of an organic additive generated a larger and more uniformly distributed initial population of Ag particles, and as a result a smooth film was obtained.This work was supported by KOSEF through the Research Center for Energy Conversion and Storage (RCECS), the Institute of Chemical Processing (ICP) in Seoul National University, and Dongbu HiTek

Improvement in the Oxidation Resistance of Cu Films by an Electroless Co-Alloy Capping Process

Co-alloy films with various solution compositions CoB, CoWB, and CoW B P were deposited with an electroless technique on Cu films without Pd activation, and their oxidation barrier performance was analyzed. The degrees of oxidation of all films were intensively studied. CoB showed excellent capping performance as an oxidation barrier, whereas CoWB and CoW B P exhibited even poorer oxidation resistance than the case of bare Cu at 400°C. The depth profile of the film compositions and chemical states of the CoB film before and after oxidation was investigated, the results of which suggested that the oxidation of the B component in the film had a clear role in the prevention of continuous Cu diffusion to the surface. The multilayer structure of CoB/ CoW B P/Cu for obtaining both electromigration and oxidation resistance was optimized, showing excellent oxidation resistance comparable to a single-composition CoB film.Korea Science and Engineering Foundation (KOSEF), which is funded by the Ministry of Education, Science and Technology (no. 2008-02857), and by the KOSEF through the Research Center for Energy Conversion and Storage (RCECS)

Comparisons of the Effects of Stent Eccentricity on the Neointimal Hyperplasia between Sirolimus-Eluting Stent versus Paclitaxel-Eluting Stent

PURPOSE: Previous studies suggested that asymmetric stent expansion did not affect suppression of neointimal hyperplasia (NIH) after sirolimus-eluting stents (SES) implantation. The aim of this study was to evaluate the effects of stent eccentricity (SE) on NIH between SES versus paclitaxel-eluting stents (PES) using an intravascular ultrasound (IVUS) analysis from the randomized trial. MATERIALS AND METHODS: Serial IVUS data were obtained from Post-stent Optimal Expansion (POET) trial, allocated randomly to SES or PES. Three different SE (minimum stent diameter divided by maximum stent diameter) were evaluated; SE at the lesion site with maximal %NIH area (SE-NIH), SE at the minimal stent CSA [SE-minimal stent area (SE-MSA)], and averaged SE through the entire stent (SE-mean). We classified each drug-eluting stents (DES) into the concentric (≥ mean SE) and eccentric groups (< mean SE) based on the mean value of SE. RESULTS: Among 301 enrolled patients, 233 patients [SES (n = 108), PES (n = 125)] underwent a follow-up IVUS. There was no significant correlation between %NIH area and SE-NIH (r = - 0.083, p = 0.391) or SE-MSA (r = - 0.109, p = 0.259) of SES. However, SE-NIH of PES showed a weak but significant correlation with %NIH area (r = 0.269, p < 0.01). As to the associations between SEmean and NIH volume index, SES revealed no significant correlation (r = - 0.001, p = 0.990), but PES showed a weak but significant correlation (r = 0.320, p < 0.01). However, there was no difference in the restenosis rate between the eccentric versus concentric groups of both DES. CONCLUSION: This study suggests that lower SE of both SES and PES, which means asymmetric stent expansion, may not be associated with increased NIH.ope