• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.408-408
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• 2012

It is well known that magnetic random access memory (MRAM) is nonvolatile memory devices using ferromagnetic materials. MRAM has the merits such as fast access time, unlimited read/write endurance and nonvolatility. Although DRAM has many advantages containing high storage density, fast access time and low power consumption, it becomes volatile when the power is turned off. Owing to the attractive advantages of MRAM, MRAM is being spotlighted as an alternative device in the future. MRAM consists of magnetic tunnel junction (MTJ) stack and complementary metal- oxide semiconductor (CMOS). MTJ stacks are composed of various magnetic materials. FePt thin films are used as a pinned layer of MTJ stack. Up to date, an inductively coupled plasma reactive ion etching (ICPRIE) method of MTJ stacks showed better results in terms of etch rate and etch profile than any other methods such as ion milling, chemical assisted ion etching (CAIE), reactive ion etching (RIE). In order to improve etch profiles without redepositon, a better etching process of MTJ stack needs to be developed by using different etch gases and etch parameters. In this research, influences of $O_2$ gas on the etching characteristics of FePt thin films were investigated. FePt thin films were etched using ICPRIE in $CH_4/O_2/Ar$ gas mix. The etch rate and the etch selectivity were investigated in various $O_2$ concentrations. The etch profiles were studied in varying etch parameters such as coil rf power, dc-bias voltage, and gas pressure. TiN was employed as a hard mask. For observation etch profiles, field emission scanning electron microscopy (FESEM) was used.

• 한국정보과학회논문지:시스템및이론
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• 제32권5호
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• pp.209-218
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• 2005

본 논문에서는 현실세계의 사용자와 주변 환경의 컨텍스트를 이용하여 가상환경과 상호작용하는 컨텍스트 기반 분산 갸상 환경 시스템을 제안한다. 제안된 시스템은 컨텍스트를 이용변경, 공유함으로써 다음과 같은 특징을 갖는다. 첫째, 가상환경의 응용서비스는 사용자의 신원, 연령, 언어 등의 컨텍스트에 따라 가상 환경을 제어하기 위한 인터페이스를 변경함으로써 개인화된 상호작용 환경을 보장한다. 둘째, 가상 환경에 있는 대상물을 제어하는 사용자의 입력 장치 신호를 컨텍스트 정보로 추상화함으로써 사용자가 다른 가상 환경 시스템으로 이동하여도 동일한 입력 장치를 가지고 해당 대상물을 제어할 수 있는 가상 환경과 장치의 적응적 접근성(adaptive access)을 보장한다. 마지막으로 분산 가상 환경 시스템들은 가상환경 변화에 대한 컨텍스트를 공유하여 이기종의 가상 환경 시스템 사이에서 발생하는 데이타 표현의 불일치성을 제거함으로써 이기종 분산 가상 환경 사이의 효과적인 동기화 메카니즘(synchronization)을 제공한다. 따라서 CIVE는 원격회의, 게임, 가상문화 관람 등과 같이 짐차 보편화되고 있는 가상환경 응용분야에서 활용될 수 있다.

• 한국통신학회논문지
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• 제34권1B호
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• pp.56-66
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• 2009

전통적인 서버/클라이언트 구조에서 클라이언트는 이미 알고 있는 서버에 접속하여 정보를 얻거나 웹 검색 등과 같은 방식으로 정보나 서비스를 이용하였다. 그러나 최근에 다양한 장치들이 인터넷에 접속 가능하게 되었으며, 이들 장치들이 제공하는 정보와 서비스의 갱신 주기가 짧고, 서비스 제공자이면서 동시에 서비스 소비자가 되는 특징을 보인다. 이런 상황에서는 네트워크 상에 존재하는 새로운 정보나 서비스를 찾기에는 전통적인 방식이 부적합하다. 본 논문에서는 장치가 네트워크에 접속되면 서비스의 프로파일을 주변의 모든 장치들에게 방송 형태로 알리는 서비스 푸시 모델을 제안한다. 임의의 네트워크 장치가 새로 연결되면 네트워크 상에 이미 존재하는 서비스 프로파일 목록을 한 번에 얻거나 서비스 제공자로부터 새로 푸시된 서비스 프로파일을 즉각적으로 얻게 되어 언제든지 서비스를 이용할 수 있다. 본 논문에서는 P2P 네트워크를 기반으로 하는 JXTA 플랫폼을 이용하여 서비스 푸시 시스템을 구현하고 실험을 통해 서비스 푸시 시 서비스 프로파일 전파 시간, 네트워크 진입시 서비스 목록을 받는데 걸리는 시간, 서비스 호출에 따른 실행 응답 시간 등을 측정하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.472-472
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• 2011

The capacitive coupled plasma (CCP) has been extensively used in the semiconductor industry because it has not only good uniformity, but also low electron temperature. But CCP source has some problems, such as difficulty in varying the ion bombardment energy separately, low plasma density, and high processing pressure, etc. In this reason, dual frequency CCP has been investigated with a separate substrate biasing to control the plasma parameters and to obtain high etch rate with high etch selectivity. Especially, in this study, we studied on the etching of $SiO_2$ by using the pulse-time modulation in the dual-frequency CCP source composed of 60 MHz/ 2 MHz rf power. By using the combination of high /low rf powers, the differences in the gas dissociation, plasma density, and etch characteristics were investigated. Also, as the size of the semiconductor device is decreased to nano-scale, the etching of contact hole which has nano-scale higher aspect ratio is required. For the nano-scale contact hole etching by using continuous plasma, several etch problems such as bowing, sidewall taper, twist, mask faceting, erosion, distortions etc. occurs. To resolve these problems, etching in low process pressure, more sidewall passivation by using fluorocarbon-based plasma with high carbon ratio, low temperature processing, charge effect breaking, power modulation are needed. Therefore, in this study, to resolve these problems, we used the pulse-time modulated dual-frequency CCP system. Pulse plasma is generated by periodical turning the RF power On and Off state. We measured the etch rate, etch selectivity and etch profile by using a step profilometer and SEM. Also the X-ray photoelectron spectroscopic analysis on the surfaces etched by different duty ratio conditions correlate with the results above.

• 전기전자학회논문지
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• 제24권1호
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• pp.200-207
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• 2020

본 논문에서는 보안 감시용 레이다 시스템을 위한 저복잡도 특징점 추출기를 제안하고, 이의 FPGA 기반 설계 결과를 제시하였다. 특징점 추출기의 메모리 요구량을 최소화하기 위해 레이다 스펙트로그램 전체에 대한 통계처리를 요구하는 프레임 단위의 특징점을 배제하고, 단위 도플러 프로파일에서 추출 가능한 특징점을 적용하였다. 제안된 특징점 추출기는 Verilog-HDL을 이용하여 RTL 설계 후, Xilinx Zynq-7000 FPGA를 활용하여 구현되었으며, 기존 연구대비 58.3%의 slice 및 98.3%의 메모리 요구량을 감소 가능함을 확인하였다. 또한, 제안된 특징점 추출기가 통합된 레이다 기반 보안 감시 시스템을 통해 차, 자전거, 보행자 및 전동 킥보드에 대한 분류 실험이 수행되었고, 성능 분석 결과 93.4%의 정확도 성능을 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.168-168
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• 2008

Dimension of a transistor has rapidly shrunk to increase the speed of device and to reduce the power consumption. However, it is accompanied with several problems like direct tunneling through the gate dioxide layer and low conductivity characteristic of poly-Si gate in nano-region. To cover these faults, study of new materials is urgently needed. Recently, high dielectric materials like $Al_2O_3$, $ZrO_2$, and $HfO_2$ are being studied for equivalent oxide thickness (EOT). However, poly-Si gate is not compatible with high-k materials for gate-insulator. Poly Si gate with high-k material has some problems such as gate depletion and dopant penetration problems. Therefore, new gate structure or materials that are compatible with high-k materials are also needed. TiN for metal/high-k gate stack is conductive enough to allow a good electrical connection and compatible with high-k materials. According to this trend, the study on dry etching of TiN for metal/high-k gate stack is needed. In this study, the investigations of the TiN etching characteristics were carried out using the inductively coupled $BCl_3$-based plasma system and adding $Cl_2$ gas. Dry etching of the TiN was studied by varying the etching parameters including $BCl_3$/Ar gas mixing ratio, RF power, DC-bias voltage to substrate, and $Cl_2$ gas addition. The plasmas were characterized by optical emission spectroscopy analysis. Scanning electron microscopy was used to investigate the etching profile.

• 한국광학회지
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• 제16권1호
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• pp.79-84
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• 2005

정력 오차 허용 범위를 증가 시켜서 효과적인 수동정렬이 가능토록 하기 위한 단일 모드 대형 코어 폴리머 광도파로를 구현하였다. 대형 코어 광도파로는 TEC(thermally expanded core) 광섬유의 모드와 일치하는 큰 도파모드를 가진다. 이로 인해 광섬유와 도파로의 정렬오차로 인한 모드 결합 손실을 줄일 수 있게 된다. 코어와 클래딩의 굴절률 차이가 5 ${\times}$ $10^{-4}$ 인 폴리머 재료를 이용하여 25 ${\times}$ 25 $\mu\textrm{m}$$^2$ 크기의 정사각형 광도파로를 제작하였으며 도파모드 관측결과 단일모드로 동작함을 확인하였다. 이와 같이 두꺼운 형태의 광도파로 구조 제작을 위하여 자외선 경화를 이용한 인젝션 몰딩(injection molding) 공정을 사용하였다. 제작된 광도파로 소자를 TEC 광섬유와 정렬연결을 할 때 정렬오차가 4.5 $\mu\textrm{m}$ 까지 증가하더라도 삽입손실 증가는 0.5 dB 이하고 유지됨을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.24-30
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• 2010

The void ratio and elastic moduli are design parameters used in geotechnical engineering to understand soil behavior. Elastic and electromagnetic waves have been used to evaluate the various soil characteristics due to high resolution. The objective of this study is to evaluate the void ratio and elastic moduli based on elastic wave velocities and electrical resistivity. The Field Velocity Resistivity Probe (FVRP) is developed to obtain the elastic and electromagnetic wave profiles of soil during penetration. The Piezoelectric Disk Elements (PDE) and Bender Elements (BE) are used as transducers for measuring the elastic wave velocities such as compressional and shear wave velocities. The Electrical Resistivity Probe (ERP) is also installed for capturing the electrical resistivity profile. The application test is carried out on the southern coast of the Korean peninsula. The field tests are performed at a depth of 6~20 m, at 10 cm intervals for measuring elastic wave velocities and at 0.5cm intervals for measuring electrical resistivity. The elastic moduli such as constraint and shear moduli are calculated by using measured elastic wave velocities. The void ratios are also evaluated based on the elastic wave velocities and the electrical resistivity. Furthermore, the converted void ratios by using FVRP are compared with the volumetric void ratio obtained by a standard consolidation test. The comparison shows that the void ratios based on the FVPR match the volume based void ratio well. This study suggests that the FVRP may be a useful device to effectively determine the elastic moduli and void ratio in the field.

• 한국전기전자재료학회논문지
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• 제31권6호
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• pp.377-385
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• 2018

For the investigation of dopant profiles in implanted $Si_{1-x}Ge_x$, the implanted B and As profiles are measured using SIMS (secondary ion mass spectrometry). The fundamental ion-solid interactions of implantation in $Si_{1-x}Ge_x$ are discussed and explained using SRIM, UT-marlowe, and T-dyn programs. The annealed simulation profiles are also analyzed and compared with experimental data. In comparison with the SIMS data, the boron simulation results show 8% deviations of $R_p$ and 1.8% deviations of ${\Delta}R_p$ owing to relatively small lattice strain and relaxation on the sample surface. In comparison with the SIMS data, the simulation results show 4.7% deviations of $R_p$ and 8.1% deviations of ${\Delta}R_p$ in the arsenic implanted $Si_{0.2}Ge_{0.8}$ layer and 8.5% deviations of $R_p$ and 38% deviations of ${\Delta}R_p$ in the $Si_{0.5}Ge_{0.5}$ layer. An analytical method for obtaining the dopant profile is proposed and also compared with experimental and simulation data herein. For the high-speed CMOSFET (complementary metal oxide semiconductor field effect transistor) and HBT (heterojunction bipolar transistor), the study of dopant profiles in the $Si_{1-x}Ge_x$ layer becomes more important for accurate device scaling and fabrication technologies.

• The Korean Journal of Pain
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• 제33권3호
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• pp.258-266
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• 2020

Background: The genicular nerve block (GNB) is demonstrated from several reports to alleviate pain and improve knee functionality in patients with chronic knee osteoarthritis (OA). Ultrasound (US)-guided GNB has been the most used imaging method. This study aimed to compare the effectiveness of US-guided versus blind GNB in the treatment of knee OA. Methods: This prospective, randomized clinical trial included patients with knee OA based on American College of Rheumatology diagnostic criteria. The patients were evaluated for clinical and dynamometer parameters at the baseline, 4 weeks after treatment, and 12 weeks after treatment. The patients underwent blind injection or US-guided injection. Results: When compared with the baseline, both groups showed significant improvement in pain, physical function, and quality of life parameters. Significant differences were observed between the groups for clinical parameters (30-second chair stand test, 6-minute walk test) in favor of the US-guided group. On the other hand, blind injection was more significantly effective on some parameters of the Nottingham Health Profile. There wasn't any significant improvement in isokinetic muscle strength for either group. Conclusions: This study demonstrated that both US-guided and blind GNB, in the treatment of knee OA, were effective in reducing symptoms and improving physical function. GNB wasn't an effective treatment for isokinetic muscle function. US-guided injections may yield more effective clinical results than blind injections.