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Busan, South Korea

Lee Y.W.,Pukyong National University | Kim E.-S.,Korea University | Shin B.-S.,Pusan National University | Lee S.-M.,Fabrication Center
Journal of Electrical Engineering and Technology | Year: 2012

In this paper, a high-performance optical gating in a junction device based on a vanadium dioxide dioxide (VO2) thin film grown by a sol-gel method was experimentally demonstrated by directly illuminating the VO2 film of the device with an infrared light at ~1554.6 nm. The threshold voltage of the fabricated device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which was ~4.9 times as large as that obtained in the previous device fabricated using the VO2 thin film deposited by a pulsed laser deposition method. The rising and falling times of the optical gating operation were measured as ~50 ms and ~200 ms, respectively, which were ~20 times as rapid as those obtained in the previous device.reakdown. Source

Kim Y.,Pukyong National University | Noh T.K.,Pukyong National University | Lee Y.W.,Pukyong National University | Kim E.-S.,Busan University of Foreign Studies | And 2 more authors.
Journal of the Korean Physical Society | Year: 2013

In this study, we have demonstrated a fiber-optic hydrogen sensor using a polarization-diversity loop interferometer composed of a polarization beam splitter, two quarter-wave plates, and a polarization-maintaining fiber coated with palladium whose thickness was ~400 nm. One dip in the output interference spectrum of the proposed sensor, chosen as a sensor indicator, was observed to spectrally shift with increasing hydrogen concentration. At a hydrogen concentration of 4%, the sensing indicator showed a wavelength shift of ~2. 48 nm. The response time of the proposed sensor was measured as 10-12. 5 s and did not show significant dependence on the hydrogen concentration except for a hydrogen concentration of 4%. In particular, compared with other hydrogen sensors based on side-polished fibers or fiber gratings, the proposed sensor is much more durable because UV illumination or physical/chemical etching process is not necessary for the optical fiber and thus is highly resistant to external stress applied on a transverse axis of an optical fiber. © 2013 The Korean Physical Society. Source

Choi W.-C.,Fabrication Center
Microsystem Technologies | Year: 2011

This paper describes the design and fabrication of a MEMS guide plate, which was used for a vertical probe card to test a wafer level packaged die wafer. The size of the fabricated MEMS guide plate was 10.6 × 10.6 cm. The MEMS guide plate consisted of 8,192 holes to insert pogo pins, and four holes for bolting between the guide plate and the housing. To insert pogo pins easily, an inclined plane was defined at the back of each hole. Pitch and diameter of the hole were 650 and 260 μm, respectively. In order to define inserting holes and inclined planes at an exact position, silicon MEMS technology was used such as anisotropic etching, deep reactive etching and more. Silicon was used as the material of the guide plate to reduce alignment mismatch between the pogo pins and solder bumps during a high temperature testing. A combined probe card with the fabricated MEMS guide plate showed good x-y alignment and planarity errors within ±9 and ±10 μm at room temperature, respectively. In addition, x-y alignment and planarity are ±20 and ±16 μm at 125°C, respectively. The proposed MEMS guide plate can be applied to a vertical probe card for burn-in testing of a wafer level packaged die wafer because the thermal expansion coefficient of the MEMS guide plate and die wafer is same. © 2010 Springer-Verlag. Source

Lim J.-H.,Pukyong National University | Ryu J.-Y.,Pukyong National University | Choi W.-C.,Fabrication Center
Transactions on Electrical and Electronic Materials | Year: 2013

This paper describes the highly productive process technologies of microprobe arrays, which were used for a probe card to test a Dynamic Random Access Memory (DRAM) chip with fine pitch pads. Cantilever-type microprobe arrays were fabricated using conventional micro-electro-mechanical system (MEMS) process technologies. Bonding material, gold-tin (Au-Sn) paste, was used to bond the Ni-Co alloy microprobes to the ceramic space transformer. The electrical and mechanical characteristics of a probe card with fabricated microprobes were measured by a conventional probe card tester. A probe card assembled with the fabricated microprobes showed good x-y alignment and planarity errors within ±5 μm and ±10 μm, respectively. In addition, the average leakage current and contact resistance were approximately 1.04 nA and 0.054 ohm, respectively. The proposed highly productive microprobes can be applied to a MEMS probe card, to test a DRAM chip with fine pitch pads. © 2013 KIEEME. All rights reserved. Source

Choi W.-C.,Fabrication Center | Ryu J.-Y.,Pukyong National University
Journal of Semiconductor Technology and Science | Year: 2011

This paper presents a new programmable compensation circuit (PCC) for a System-on-Chip (SoC). The PCC is integrated with 0.18-μm BiCMOS SiGe technology. It consists of RF Design-for- Testability (DFT) circuit, Resistor Array Bank (RAB) and digital signal processor (DSP). To verify performance of the PCC we built a 5-GHz low noise amplifier (LNA) with an on-chip RAB using the same technology. Proposed circuit helps it to provide DC output voltages, hence, making the RF system chain automatic. It automatically adjusts performance of an LNA with the processor in the SoC when it goes out of the normal range of operation. The PCC also compensates abnormal operation due to the unusual PVT (Process, Voltage and Thermal) variations in RF circuits. Source

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