• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.380-381
• /
• 2012

Bioinspired sea urchin-like structures were fabricated on silicon by inductively coupled plasma (ICP) etching using lens-like shape hexagonally patterned photoresist (PR) patterns and subsequent metal-assisted chemical etching (MaCE) [1]. The lens-like shape PR patterns with a diameter of 2 ${\mu}m$ were formed by conventional lithography method followed by thermal reflow process of PR patterns on a hotplate at $170^{\circ}C$ for 40 s. ICP etching process was carried out in an SF6 plasma ambient using an optimum etching conditions such as radio-frequency power of 50 W, ICP power of 25 W, SF6 flow rate of 30 sccm, process pressure of 10 mTorr, and etching time of 150 s in order to produce micron structure with tapered etch profile. 15 nm thick Ag film was evaporated on the samples using e-beam evaporator with a deposition rate of 0.05 nm/s. To form Ag nanoparticles (NPs), the samples were thermally treated (thermally dewetted) in a rapid thermal annealing system at $500^{\circ}C$ for 1 min in a nitrogen environment. The Ag thickness and thermal dewetting conditions were carefully chosen to obtain isolated Ag NPs. To fabricate needle-like nanostructures on both the micron structure (i.e., sea urchin-like structures) and flat surface of silicon, MaCE process, which is based on the strong catalytic activity of metal, was performed in a chemical etchant (HNO3: HF: H2O = 4: 1: 20) using Ag NPs at room temperature for 1 min. Finally, the residual Ag NPs were removed by immersion in a HNO3 solution. The fabricated structures after each process steps are shown in figure 1. It is well-known that the hierarchical micro- and nanostructures have efficient light harvesting properties [2-3]. Therefore, this fabrication technique for production of sea urchin-like structures is applicable to improve the performance of light harvesting devices.

• Journal of Surface Science and Engineering
• /
• v.46 no.6
• /
• pp.248-257
• /
• 2013

It is generally recognized that thin Pd-Cu alloy films fabricated by sputtering show a wide range of microstructures and properties, both of which are highly dependent on the sputtering conditions. In view of this, the present study aims to investigate the relationship between the performance of hydrogen separation membranes and the microstructure of Pd alloy films depending on sputtering deposition conditions such as substrate temperature, working pressure, and DC power. We fabricated thin and dense Pd-Cu alloy membranes by the micro-polishing of porous Ni support, an advanced Pd-Cu sputtered multi-deposition under the conditions of high substrate temperature / low working pressure / high DC power, and a followed by Cu-reflow heat-treatment. The result of a hydrogen permeation test indicated that the selectivity for $H_2/N_2$ was infinite because of the void-free and dense surface of the Pd alloy membranes, and the hydrogen permeability was 10.5 $ml{\cdot}cm^{-2}{\cdot}min^{-1}{\cdot}atm^{-1}$ for a 6 ${\mu}m$ membrane thickness.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.2
• /
• pp.1-9
• /
• 2002

The intermetallic formation between Sn-Ag-(Cu) solders and metal pads in a real BGA package was characterized using SEM, EDS, and XRD. The intermetallic phase formed in the interface between Sn-Ag-Cu and Au/Ni/Cu pad is likely to be ternary compound of $(Cu,Ni)_6Sn_5$ from EDS analysis High concentration of Cu was observed in the solder/Ni interface. XRD analysis confirmed that $\eta -Cu_6 Sn_5$ type was intermetallic phase formed in the interface between Cu containing solders and Ni substrates and $Ni_3$Sn_4$ intermetallic was formed in the Sn-Ag solder/Ni interface. The thickness of intermetallic phase increased with the reflow times and Cu concentration in solder.

• Journal of the Microelectronics and Packaging Society
• /
• v.19 no.3
• /
• pp.77-82
• /
• 2012

In this paper, the research of IC embedded PCB process is carried out. For embedding chips into PCB, solder-balls on chips were etched out and ABF(Ajinomoto Build-ip Film), prepreg and Cu foil was laminated on that to fabricate 6 layer build-up board. The chip of which solder ball was removed was successfully interconnected with PCB by laser drilling and Cu plating. However, de-lamination phenomenon occurred between chip surface and ABF during reflow and thermal shock. To solve this problem, de-smear and plasma treatment was applied to PI(polyimide) passivation layer on chip surface to improve the surface roughness. The properties of chip surface(PI) was investigated in terms of AFM(Atomic Force Micrometer), SEM and XPS (X-ray Photoelectron Spectroscopy). As results, nano-size anchor was evenly formed on PI surface when plasma treatment was combined with de-smear(NaOH+KMnO4) process and it improved thermal shock reliability ($260^{\circ}C$-10sec solder floating).

• Journal of the Microelectronics and Packaging Society
• /
• v.19 no.3
• /
• pp.31-36
• /
• 2012

In this study, the complex vibration reliability of Sn-3.5Ag and Sn-0.7Cu having a high melting temperature was investigated. For manufacturing of BGA test samples, Sn-3.5Ag and Sn-0.7Cu balls were joined on BGA chips finished by ENIG and the chips were mounted on PCB finished OSP by using reflow process. For measuring of resistance change during complex vibration test, daisy chain was formed in the test board. From the results of resistance change and shear strength change, the reliability of two solder balls was compared and evaluated. During complex vibration for 120 hours, Sn-0.7Cu solder was more stable than Sn-3.5Ag solder in complex vibration test.

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.3
• /
• pp.9-17
• /
• 2008

Cu mushroom bumps were formed by electrodeposition and flip-chip bonded to Sn substrate pads. Contact resistances of the Cu-mushroom-bump joints were measured and compared with those of the Sn-planar-bump joints. The Cu-mushroom-bump joints, processed at bonding stresses ranging from 19.1 to 95.2 MPa, exhibited contact resistances near $15m\Omega$/bump. Superior contact-resistance characteristics to those of the Sn-planar-bump joints were obtained with the Cu-mushroom-bump joints. Contact resistance of the Cu-mushroom-bump joints was not dependent upon the thickness of the as-elecroplated Sn-capcoating layer ranging from $1{\mu}m$ to $4{\mu}m$. When the Sn-cap-coating layer was reflowed, however, the contact resistance was greatly affected by the thickness and the reflow time of the Sn-cap-coating layer.

• Journal of Welding and Joining
• /
• v.25 no.2
• /
• pp.82-88
• /
• 2007

Sn-3.0Ag-0.5Cu lead fee solder was generally utilized in electronics assemblies. But it is insufficient to research about activation energy(Q) that is applying to evaluate the solder joint reliability of environmental friendly electronics assemblies. Therefore this study investigated Q values which are needed to IMC formation and growth of Sn-3.0Ag-0.5Cu/Cu and Sn-40pb/Cu solder joints during aging treatment. We bonded Sn-3.0Ag-0.5Cu and Sn-40Pb solders on FR-4 PCB with Cu pad$(t=80{\mu}m)$. After reflow soldering, to observe the IMC formation and growth of the solder joints, test specimens were aged at 70, 150 and $170^{\circ}C$ for 1, 2, 5, 20, 60, 240, 960, 15840, 28800 and 43200 min, respectively. SEM and EDS were utilized to analysis the IMCS. From these results, we measured the total IMC$(Cu_6Sn_5+Cu_3Sn)$ thickness of Sn-3.0Ag-0.5Cu/Cu and Sn-40Pb/Cu interface, and then obtained Q values for the IMC$(Cu_6Sn_5,\;Cu_3Sn)$ growth of the solder joints.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.8 no.2
• /
• pp.128-133
• /
• 2008

Phase-change random access memory (PRAM) chip cell phase of amorphous state is rapidly changed to crystal state above 160 Celsius degree within several seconds during Infrared (IR) reflow. Thus, on-board programming method is considered for PRAM chip programming. We demonstrated the functional 512Mb PRAM with 90nm technology using several novel core circuits, such as metal-2 line based global row decoding scheme, PN-diode cells based BL discharge (BLDIS) scheme, and PMOS switch based column decoding scheme. The reverse-state standby current of each PRAM cell is near 10 pA range. The total leak current of 512Mb PRAM chip in standby mode on discharging state can be more than 5 mA. Thus in the proposed BLDIS control, all bitlines (BLs) are in floating state in standby mode, then in active mode, the activated BLs are discharged to low level in the early timing of the active period by the short pulse BLDIS control timing operation. In the conventional sense amplifier, the simultaneous switching activation timing operation invokes the large coupling noise between the VSAREF node and the inner amplification nodes of the sense amplifiers. The coupling noise at VSAREF degrades the sensing voltage margin of the conventional sense amplifier. The merit of the proposed sense amplifier is almost removing the coupling noise at VSAREF from sharing with other sense amplifiers.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.39 no.1
• /
• pp.31-36
• /
• 2002

Low energy boron ions were implanted into the preamorphized and crystalline silicon substrates to form 0.2${\mu}m$ $p^+-n$ junctions. The rapid thermal annealing(RTA) was used to annihilate the crystal defects due to implantation and to activate the implanted boron ions, and the furnace annealing was employed to reflow the BPSG(bolo-phosphosilicate glass). The implantation conditions for Gepreamorphization were the energy of 45keV and the dose of 3$\times$1014cm-2. BF2 ions employed as a p-type dopant were implanted with the energy of 20keV and the dose of 2$\times$1015cm-2. The thermal conditions of RTA and furnace annealing were $1000^{\circ}C$/10sec and $850^{\circ}C$/40min, respectively. The junction depths were measured by SIMS and ASR techniques, and the 4-point probe was used to measure the sheet resistances. The electrical characteristics were analyzed via the leakage currents of the fabricated diodes. The single thermal processing with RTA produced shallow junctions of good qualities, and the thermal treatment sequence of furnace anneal and RTA yielded better junction characteristics than that of RTA and furnace anneal.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1994.04a
• /
• pp.340-340
• /
• 1994

Since total hepatic ischemia(IS) occurs with transplantation, there has been interest in evaluating hepatic function after ischemia and subsequent reflow of blood. Four groups of animals were studied: group 1 (sham), group 2 (30mins IS), group 3 (60mins IS), and g.cup 4 (90mins IS). Serum transaminase(STA), wet weight-to-dry weight ratio(W/D), lipid peroxides(LPO), glucose-6-phosphatase(G-6-Pase) activity, Na$\^$+//K$\^$+/-ATPase(ATPase) activity were measured at 1, 5 and 24hrs after hepatic ischemia. Significant changes occurred between 1 and 5hrs of reperfusion. STA was 3579${\pm}$401, 4593${\pm}$675 and 6348${\pm}$808 U/L in group 2, 3 and 4 respectively. These changes were ischemic time-dependent manner. W/D in group 3 and 4 were significantly increased than that in sham group at all time points measured. In sham group, the level of LPO in the liver microsome remained constant at approximately 0. 5nmole MDA formed/mg protein througllout the experiment, In all ischemic groups on the other hand, the level of LPO started to increase at ischemia and markedly increased at all reperfusion period. Similar to STA, these changes were also dependent on duration of ischemia. Although G-6-Pase activity remained unchanged in both group 2 and group 3 until 5hrs of reperfusion, marked decrease in G-6-Pase activity was observed at grcup 4. ATPase activity was significantly decreased at 1, 5 and 24 hrs of reperfusion in group 3, whereas it was not changed in group 2. Furthermore, ATPase activity in group 4 started to decrease at ischemia and markedly decreased for entire reperfusion period. These data suggest that severity of hepatocellular injury is associated with period of ischemia as well as period of reperfusion.