• 전력전자학회논문지
• /
• 제24권4호
• /
• pp.237-243
• /
• 2019

A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

• 한국전기전자재료학회논문지
• /
• 제36권1호
• /
• pp.23-28
• /
• 2023

This paper demonstrates a novel NAND flash memory structure and annealing configuration including through-silicon via (TSV) inside the silicon substrate to improve annealing efficiency using an electro-thermal annealing (ETA) technique. Compared with the conventional ETA which utilizes WL-to-WL current flow, the proposed annealing method has a higher annealing temperature as well as more uniform heat distribution, because of thermal isolation on the silicon substrate. In addition, it was found that the annealing temperature is related to the electrical and thermal conductivity of the TSV materials. As a result, it is possible to improve the reliability of NAND flash memory. All the results are discussed based on 3-dimensional (3-D) simulations with the aid of the COMSOL simulator.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제4권4호
• /
• pp.300-306
• /
• 2004

This paper reports a novel tunable bandpass filter using two-state switched inductor with direct-contact MEMS switches for wireless LAN applications. In our filter configuration, the switched inductor is implemented to obtain more stable and much larger frequency tuning ratio compared with variable capacitor-based tunable filter. The proposed tunable filter was fabricated using a micromachining technology and electrical performances of the fabricated filter were measured. The filter consists of spiral inductors, MIM capacitors and direct-contact type MEMS switches, and its frequency tunability is achieved by changing the inductance that is induced by ON/OFF actuations of the MEMS switches. The actuation voltage of the MEMS switches was measured of 58 V, and they showed the insertion loss of 0.1 dB and isolation of 26.3 dB at 2 GHz, respectively. The measured center frequencies of the fabricated filter were 2.55 GHz and 5.1 GHz, respectively. The passband insertion loss and 3-dB bandwidth were 4.2 dB and 22.5 % at 2.55 GHz, and 5.2 dB and 23.5 % at 5.1 GHz, respectively.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권10호
• /
• pp.438-442
• /
• 2005

Si nanocrystal (Si NC) memory device has several advantages such as better retention, lower operating voltage, reduced punch-through and consequently a smaller cell area, suppressed leakage current. However, the physical and electrical reasons for this behavior are not completely understood but could be related to interface states of Si NCs. In order to find out this effect, we characterized electrical properties of Si NCs embedded in a SiO$_{2}$ layer by scanning probe microscopy (SPM). The Si NCs were generated by the laser ablation method with compressed Si powder and followed by a sharpening oxidation. In this step Si NCs are capped with a thin oxide layer with the thickness of 1$\~$2 nm for isolation and the size control. The size of 51 NCs is in the range of 10$\~$50 m and the density around 10$^{11}$/cm$^{2}$ It also affects the interface states of Si NCs, resulting in the change of electrical properties. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift due to the trapped charges were monitored. The results were compared with C-V characteristics of the conventional MOS capacitor structure.

• 한국재료학회지
• /
• 제1권3호
• /
• pp.132-138
• /
• 1991

2충의 BPSG를 사용하는 서브마이크론 CMOS DRAM에 있어 전기적 특성에 관한 BPSG flow온도의 영향을 비교하였다. BPSG flow온도를 $850^{\circ}C/850^{\circ}C,\;850^{\circ}C/900^{\circ}C,\;900^{\circ}C/900^{\circ}C$의 3가지 다른 조합을 적용하여 문턱전압, 파괴전압, Isolation전압과 더불어 면저항과 접촉 저항을 조사하였다. $900^{\circ}C/900^{\circ}C$ flow의 경우 NMOS에서 문턱전압은 $0.8\mu\textrm{m}$ 미만의 채널길이에서 급격히 감소하나 PMOS 경우는 차이가 없었다. NMOS와 PMOS의 파괴전압은 각각 $0.7\mu\textrm{m}$와 $0.8\mu\textrm{m}$ 이하에서 급격히 감소하였다. 그러나 $850^{\circ}C/850^{\circ}C$ flow의 경우에는 NMOS와 PMOS모두 문턱전압과 파괴전압은 채널길이 $0.7\mu\textrm{m}$까지 감소하지 않았다. Isolation전압은 BPSG flow온도 감소에 따라 증가하였다. 면저항과 접촉 저항은 BPSG flow온도가 $900^{\circ}C$에서 $850^{\circ}C$로 감소됨에 따라 급격히 증가되었다. 이와 같은 결과는 열처리 온도에 따라 dopant의 확산과 활성화에 관련 있는 것으로 생각된다. 접촉 저항 증가에 대한 개선 방법에 대하여 고찰하였다.

• 한국전자파학회논문지
• /
• 제20권5호
• /
• pp.444-449
• /
• 2009

본 논문에서는 두 개의 대역에서 서로 다른 임의의 분배비를 갖는 이중 대역 가지 선로 결합기를 제안한다. 가지 선로 결합기의 선로들을 $\pi$-형 등가회로로 변환할 때 이 등가회로가 임의의 두 주파수에서 서로 다른 임피던스 특성을 갖고 두 주파수에 대하여 선로의 전기적 길이는 중심 주파수의 $\lambda/4$가 되도록 설계한다. 제안된 설계법의 타당성을 입증하기 위해서 0.9 GHz와 2 GHz에서 서로 다른 분배비를 갖는 결합기를 설계하였다. 분배비가 두 주파수에서 각각 1:1과 1:3이 되는 결합기를 설계, 제작 및 측정하였다. 측정 결과, 중심 주파수에서 삽입 손실은 0.33 dB 이내의 오차 범위를 보였고, 반사 손실과 격리 특성은 -18.07 dB 이상으로 매우 우수한 특성을 보였다.

• 전기전자학회논문지
• /
• 제13권4호
• /
• pp.23-27
• /
• 2009

실리콘 기판 상에 MBE (molecular beam epitaxy)로 형성된 GaSb 기반 p-channel HEMT 소자를 제작하기 위하여 오믹 접촉 형성 공정과 식각 공정을 연구하였다. 먼저 각 소자의 절연을 위한 메사 식각 공정 연구를 수행하였으며, HF기반의 습식 식각 공정과 ICP(inductively coupled plasma)를 이용한 건식 식각 공정이 모두 사용되었다. 이와 함께 소스/드레인 영역 형성을 위한 오믹 접촉 형성 공정에 관한 연구를 진행하였으며 Ge/Au/Ni/Au 금속층 및 $300^{\circ}C$ 60초 RTA공정을 통해 $0.683\;{\Omega}mm$의 접촉 저항을 얻을 수 있었다. 더불어 HEMT 소자의 게이트 형성을 위한 게이트 리세스 공정을 AZ300 현상액과 citric산 기반의 습식 식각을 이용하여 연구하였으며, citric산의 경우 소자 구조에서 캡으로 사용된 GaSb와 베리어로 사용된 AlGaSb사이에서 높은 식각 선택비를 보였다.

• Progress in Superconductivity
• /
• 제12권2호
• /
• pp.93-98
• /
• 2011

Pinning force is the mechanism between a superconductor and a permanent magnet and it provides a stable levitation. However, when external force greater than the pinning force such as the earthquake exerts, the levitated object may lose the levitating characteristic. In order to achieve more stabilized levitation, the copper plate was inserted in between a superconductor and permanent magnets. And by applying the eddy current effect caused from the relationship between a copper plate and permanent magnets, more stabilized levitation can be established. In this study, an optimized design was found based on various configurations of permanent magnet's polarity, thickness and area of copper plate, and the gap distance between copper plate and permanent magnet. As results, higher eddy current value was obtained at where the change of polarity exists in permanent magnet configuration, and the highest eddy current value was observed at the copper plate thickness of 5 mm and the area of 80 mm ${\times}$ 80 mm. From the resulted optimized conditions above, which are 7 mm gap distance between a superconductor and permanent magnets and 80 mm ${\times}$ 80 mm ${\times}$ 5 mm dimension of a copper plate, the stiffness value was 65 % increased comparing to without any copper plate insertion.

• Journal of Electrical Engineering and Technology
• /
• 제13권2호
• /
• pp.858-867
• /
• 2018

Analytical modeling equations are proposed for the conventional and modified three-section branch-line couplers. The analytical equations are explicit and capable of determining the characteristic impedance of each branch line for the coupler at desired coupling level as well as the suitability of broadband S-parameters analysis. In addition, a bandwidth extension and miniaturization of three-section branch-line coupler using slow-wave and meandering line structures were designed. The modified coupler, which is able to operate within frequencies from 1.5 to 3.32 GHz has been fabricated, tested and compared. A bandwidth extension of 600 MHz and 53% reduced size of the modified coupler have been achieved compared to a conventional coupler. The modified coupler has roughly insertion loss and coupling of -4 dB and -3.2 dB, while the isolation and return loss, respectively less than -14 dB with fractional bandwidth of 77 %, as well as phase imbalances less than $2^{\circ}$ over the operating bandwidth. Overall, the derived analytical model, simulation and measurement results demonstrated a good agreement.

• 한국광학회지
• /
• 제19권3호
• /
• pp.161-168
• /
• 2008

본 논문에서는 왼손(left-handed)과 오른손(right-handed) 방향으로 각각 $180^{\circ}$ 트위스트(${\pi}$-twist)된 액정상을 두 개의 안정상태로 가지는 쌍안정(bistable) 액정 디스플레이(liquid crystal display)를 제안한다. 제안된 소자는 액정과 자외선경화 폴리머 물질의 혼합물의 비등방성 상분리 방법으로 형성된 격벽에 의해 화소고립된(pixel-isolation) 구조를 가지며, 인가전압의 주파수에 따라 유전율 이방성의 부호가 바뀌는 이중주파수(dual-frequency) 특성의 네마틱(Nematic) 액정을 사용한다. 두 안정된 액정상 사이의 스위칭은 인가전압의 주파수를 연속적으로 변화시킴으로써 이루어지며, 주파수 변화에 따른 액정의 유체 효과에 의해 발생하므로 응답특성이 매우 빠르다. 두 액정상은 카이랄 도펀트(chiral dopant)가 아니라 격벽이 가지는 앵커링(anchoring)의 영향으로 안정화됐기 때문에 거의 동일한 탄성에너지(elastic free energy)를 가지게 되어 우수한 메모리 특성을 나타낸다. 또한, 위상지연필름을 이용한 투과형 광학보상을 통해 높은 정면 명암비(contrast ratio)를 가질 수 있다.