Kyung Ju Park

Pulse Electrodeposition for Improving Electrical Properties of Cu Thin Film

Pulse deposition, which has an advantage to apply relatively high current density by supplement of Cu ions during off-time, was applied to deposit 250 nm Cu film. The microstructural change during off-time was to be investigated. The differences between constant potential and pulse deposition were due to the change during off-time. The application of pulse deposition led to the increase in the Cu(111) intensity and the reduction in the film resistivity compared to constant potential deposition. The film characteristics were further improved as the duty cycle decreased. The change during the off-time was verified to be grain growth in contact with the electrolyte. Additionally, it was clarified that the grain growth completed in a second, unlike self-annealing process, which proceeded for tens of hours, and affected within about 2.0 nm of Cu film from the surface. Under optimum conditions, pulse deposition led to 50% enhancement in Cu(111) intensity and 30% reduction in resistivity compared to the constant potential deposition.

Electrodeposition of Cu-Ag Film in Cyanide-Based Electrolyte

Cu has been used for fabricating many of surface coatings and interconnections in the semiconductors. The properties of Cu films have been improved to enhance the characteristics of coatings or interconnections ever since it was introduced. In general, alloy or mixture films such as Cu-Ni, Cu-Pt, Cu-Au, and Cu-Ag, have good mechanical properties. Among them, Cu-Ag is known for adequate mechanical property, high electrical conductivity and suitable deformality. In this presentation, the Cu-Ag films, which were made by means of electrodeposition in cyanide-based electrolyte, will be introduced. Electrodeposition was performed in 3-electrode system. Cu blanket wafer, which has the structure of Cu seed layer (60 nm, PVD) / Ta (7.5 nm, PVD) / TaN (7.5 nm, PVD) / SiO2, was employed as a working electrode. The 99.9% Cu or Ag electrodes and Ag/AgCl electrode were used for a counter and reference electrode, respectively. The basic electrolyte contained KAg(CN)2, CuCN, KCN. The KCN played a role of complexing agent. Cu-Ag alloy plating was implemented in cyanide bath, because cyanide bath has a possibility to make Cu-Ag alloy without any problem such as precipitation of Ag caused by halide ion in halide bath. To analyze the characteristics of electrolyte, electrochemical analyses such as linear sweep voltammetry (LSV) and chronoamperometry were conducted with various concentrations of Ag, Cu, and KCN. Then, the Cu-Ag film was deposited with static potential method, and film resistivity, orientation, and composition were investigated through 4-point probe, xray diffraction (XRD), field emission scanning electron microscope (FESEM), and auger electron spectroscopy (AES). Finally, annealing process was carried out at 300°C for 1 hr in nitrogen atmosphere, to change the microstructure of the film. Figure 1 shows the LSV curves according to the CuCN concentration, and it revealed that the Cu reduction took place at near the -0.7 V. The reduction current density was proportional to the concentration of CuCN. On the other hand, the Ag was reduced at 1.0 V, which was lower than that of Cu, as shown in figure 2. Moreover, from figure 2, it could be known that the Cu reduction, compared to Ag reduction, was more favorable at higher potential than – 1.15 V, however it was overwhelmed by the Ag reduction current at lower than – 1.15 V. Based on the data, the electrodeposition was implemented varying the concentration of CuCN and KAg(CN)2, and the deposition potential in this study. Figure 3 shows one of the XRD results of Cu-Ag film. Before the annealing, the (111) orientations of Cu and Ag were detected, and it implied that the film was mixture of Cu and Ag. However, after annealing, the Cu peak disappeared and Ag peak shifted to the right. It might relate to the alloy formation. To investigate this phenomenon in depth, the experiments, performed varying the concentration ratio of Cu and Ag, KCN concentration, applied potential and annealing condition, are in progress.

Design and Implementation of an InfiniBand System Interconnect for High-Performance Cluster Systems

InfiniBand technology is being accepted as the future system interconnect to serve as the high-end enterprise fabric for cluster computing. This paper presents the design and implementation of the InfiniBand system interconnect, focusing on an InfiniBand host channel adapter (HCA) based on dual ARM9 processor cores The HCA is an SoC tailed KinCA which connects a host node onto the InfiniBand network both in hardware and in software. Since the ARM9 processor core does not provide necessary features for multiprocessor configuration, novel inter-processor communication and interrupt mechanisms between the two processors were designed and embedded within the KinCA chip. Kinch was fabricated as a 564-pin enhanced BGA (Bail Grid Array) device using 0.18 CMOS technology Mounted on host nodes, it provides 10 Gbps outbound and inbound channels for transmit and receive, respectively, resulting in a high-performance cluster system.