• 한국자기학회지
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• 제10권5호
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• pp.232-236
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• 2000

Cr을 하지층으로 사용한 CoSm 박막은 고기록밀도 수평 자기기록 매체로 가능성이 커 이에 대한 관심이 집중되고 있다. 본 연구에서는 dc 마그네트론 스퍼터링법으로 제작한 CoSm 박막의 자기적 성질의 Ar 가스 스퍼터링 압력 의존성을 조사하였다. 특히 고기록밀도 자기기록 매체에서 magnetic switching volume V＊은 자기기록 매체에 기록된 정보의 열적 안정성, 자화반전 및 잡음을 이해하는데 중요한 자료가 된다. 따라서 본 연구에서는 동일 조건에서 제작한 하지층 Cr위에 스퍼터링 압력을 달리하여 자성층 CoSm을 성장시켜 switching volume의 스퍼터링 압력 의존성을 규명하도록 하였다. 연구 결과 switching volume은 스퍼터링 압력이 증가할수록 감소하며, 그 크기는 9.0-5.2$\times$$10^{-18}$ $cm^3$ 범위 내에 있었다. Switching volume V＊를 이용하여 계산한 switching 단위의 크기는 22 nm 보다 작으며, 이 크기는 고기록 밀도수평 자기기록매체의 열적 안정성에 대한 Sharrock 조건을 만족한다.

• 한국전기전자재료학회논문지
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• 제19권10호
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• pp.907-911
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• 2006

In this paper, we propose a new structure that improves the on-state voltage drop and switching speed in Insulated Gate Bipolar Transistors(IGBTs), which can be widely used in high voltage semiconductors. The proposed structure is unique in that the collector area is divided by $SiO_2$, whereas the conventional IGBT has a planar P+ collector structure. The process and device simulation results show remarkably improved on-state and switching characteristics. Also, the current and electric field distribution indicate that the segmented collector structure has increased electric field near the $SiO_2$ corner, which leads to an increase of electron current. This results in a decrease of on-state resistance and voltage drop to $30%{\sim}40%$. Also, since the area of the P+ region is decreased compared to existing structures, the hole injection decreases and leads to an increase of switching speed to 30 %. In spite of some complexity in process procedures, this structure can be manufactured with remarkably improved characteristics.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권3호
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• pp.166-176
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• 2007

Radio frequency (RF) microelectromechanical systems (MEMS) have been pursued for more than a decade as a solution of high-performance on-chip fixed, tunable and reconfigurable circuits. This paper reviews our research work on RF MEMS switches and switching circuits in the past five years. The research work first concentrates on the development of lateral DC-contact switches and capacitive shunt switches. Low insertion loss, high isolation and wide frequency band have been achieved for the two types of switches; then the switches have been integrated with transmission lines to achieve different switching circuits, such as single-pole-multi-throw (SPMT) switching circuits, tunable band-pass filter, tunable band-stop filter and reconfigurable filter circuits. Substrate transfer process and surface planarization process are used to fabricate the above mentioned devices and circuits. The advantages of these two fabrication processes provide great flexibility in developing different types of RF MEMS switches and circuits. The ultimate target is to produce more powerful and sophisticated wireless appliances operating in handsets, base stations, and satellites with low power consumption and cost.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3511-3532
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• 2019

Coverage-guided fuzzing is an efficient solution that has been widely used in software testing. By guiding fuzzers through the coverage information, seeds that generate new paths will be retained to continually increase the coverage. However, we observed that most samples follow the same few high-frequency paths. The seeds that exercise a high-frequency path are saved for the subsequent mutation process until the user terminates the test process, which directly affects the efficiency with which the low-frequency paths are tested. In this paper, we propose a fuzzing solution, ER-Fuzz, that truncates the recording of a high-frequency path to influence coverage. It utilizes a deep learning-based classifier to locate the high and low-frequency path transfer points; then, it instruments at the transfer position to promote the probability low-frequency transfer paths while eliminating subsequent variations of the high-frequency path seeds. We implemented a prototype of ER-Fuzz based on the popular fuzzer AFL and evaluated it on several applications. The experimental results show that ER-Fuzz improves the coverage of the original AFL method to different degrees. In terms of the number of crash discoveries, in the best case, ER-Fuzz found 115% more unique crashes than did AFL. In total, seven new bugs were found and new CVEs were assigned.

• Journal of Magnetics
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• 제15권3호
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• pp.103-107
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• 2010

We investigated spin-polarized current switching of Pac-man type II (PM-II) nanoelements in Pac-man shaped nanoscale spin-valves (Co/Cu/Py) using micromagnetic simulations. The effects of slot angle and antiferromagnetic (AFM) layer were simulated to obtain optimum switching in less than 2 ns. At a critical slot angle of $105^{\circ}$, the lowest current density for anti-parallel to parallel (AP-P) switching was observed due to no vortex or antivortex formation during the magnetic reversal process. All other slot angles for AP-P formed a vortex or antivortex during the magnetization reversal process. Additionally, a vortex or anti-vortex formed for all slot angles for parallel to anti-parallel (P-AP) switching. The addition of an AFM layer caused the current density to decrease significantly for AP-P and P-AP at slot angles less than $90^{\circ}$. However, at slot angles greater than $90^{\circ}$, the current density tended to decrease by less amounts or actually increased slightly as shape anisotropy became more dominant. This allowed ultra-fast switching with 5.05 and $5.65{\times}10^8\;A/cm^2$ current densities for AP-P and P-AP, respectively, at a slot angle of $105^{\circ}$.

• 마이크로전자및패키징학회지
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• 제27권4호
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• pp.77-81
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• 2020

Resistive RAM (ReRAM)은 전이금속 산화물의 저항변화 특성을 이용하는 차세대 비휘발 메모리로 전이금속산화물 내의 산소공공의 재분포를 통한 저항변화 특성을 이용한다. 따라서 저항변화 특성을 위해 전이금속산화물 내에는 일정량 이상의 산소공공이 요구되며 이를 위해서는 박막 형성 공정에서 산화 수를 조절할 수 있는 공정이 필요하다. 본 연구에서는 직접패턴이 가능한 photochemical metal organic deposition (PMOD) 공정을 사용하여 UV 노출에 의해 photochemical metal organic precursor의 ligand가 분해되는 과정에서 전기장을 인가하여 박막내의 산화 수를 조절하는 실험을 진행하였다. Electric field assisted PMOD (EFAPMOD) 법을 이용하여 FeOx 박막의 산화 수 조절이 가능함을 x-ray photoelectron spectroscopy (XPS) 분석과 I-V 측정을 통하여 확인하였으며, EFAPMOD 공정 중 인가하는 전압의 크기를 조절하여 박막의 산화 수를 조절할 수 있음을 확인하였다. 따라서 EFAPMOD 공정 중 인가전압의 크기를 이용하여 저항변화 특성에 적합한 적정한 산화수를 가지는 금속산화물 박막을 얻고 그 저항변화 특성을 조정할 수 있음을 확인하였다.

• 산업클러스터
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• 제2권1호
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• pp.28-43
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• 2008

본 고에서 우리나라의 클러스터들이 세계에서 경쟁력 있는 혁신클러스터로 자리매김 할 수 있는 잠재경로와 클러스터의 형성을 촉진할 수 있는 정책개입의 방향에 대하여 탐색하고자 한다. 세계적인 클러스터가 되기 위해서는 클러스터의 구성원들이 끊임없이 변하는 자본주의 경제의 전환력에 대하여 집단적으로 대응하는 것이 필요하고 그 과정에서 각기 독특한 경쟁력이 창출된다는 것이 이 논문의 핵심적 주장이다. 우리나라는 급속한 경제성장 과정에서 다양한 자산들을 축적하였고 이런 자산들은 우리나라에서 세계적인 선도 클러스터를 창출하는 데 효과적으로 활용될 수 있다. 이 과정은 실리콘밸리와 같은 유일한 모델을 베끼는 것이 아니라 한국의 지역적 조건에 맞는 독자적인 모델을 창출하는 것이다. 이를 위해서 우리나라 혁신클러스터의 재창조 과정이 요구된다.

• 한국항해학회지
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• 제21권3호
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• pp.75-81
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• 1997

현재 자동차나 선박등에 사용하는 직류모터 속도 제어용 스위칭 소자는 스위칭 과전압으로 인하여 때때로 손상되거나 오작동을 일으키기쉽다. 본논문은 dc 모터 제어용 반도체 스위칭소자의 내성특성을 개선한 것이다. 이를 위하여, 먼저 저전압 보호소자인 비리스터나 제너 다이오드 등 가운데에서 스위칭 과전압에 대해 내성을 갖는 이상적인 소자를 선택하기 위해 과전압 보호자의 등가회로를 분석 하였다. 나아가서 국제규정에서 정의된 의사 과전압 파형의 적절한 선택, 스위칭 소자의 손상과정과 손상원인을 규명하고, 순시과전압 전류의 변화에 따른 각각의 임피던스 조건을 고려하여 직류모터 제어용 반도체 스위칭 소자의 내성특성 개선하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.378.1-378.1
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• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.176-183
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• 1995

The present work is concerned with the switching conduction characteristics of PI LB films in metal insulator metal sandwiches. By applying various DC voltage bias to MIM junctions, conduction characteristics of junctions can be changed between the high-voltage low-current(off) condition, the low-voltage high-current (on) condition and the medium(mid) condition. Switching conduction characteristics can be also observed in MIM junctions employing some aromatic compounds as insulators. Switching conduction characteristics is assumed to be owing to the existence of aromatic rings, space charge in films, impurities on metal-insulator interface, and difference in work functions of base and top electrodes metal. To study the conduction process of on, off, and mid conductions, we measured I-V, d$^{2}$V/d I$^{2}$-V characteristics of junctions with several different top electrodes under various temperatures. Small conductance changes of junctions can be measured by observing the second derivative, d$^{2}$V/dI$^{2}$, of I-V curve. A dynamical technique is used to get the second derivatives. That is, a finite modulation of the current is applied to the junctions and the second harmonic of the voltage is detected.