• 센서학회지
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• 제27권2호
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• pp.93-98
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• 2018

In this paper, an energy-efficient 11.49-bit successive approximation register (SAR) capacitance-to-digital converter (CDC) for capacitive sensors with a figure of merit (FoM) of 31.6 pJ/conversion-step is presented. The CDC employs a SAR algorithm to obtain low power consumption and a simplified structure. The proposed circuit uses a capacitive sensing amplifier (CSA) and a dynamic latch comparator to achieve parasitic capacitance-insensitive operation. The CSA adopts a correlated double sampling (CDS) technique to reduce flicker (1/f) noise to achieve low-noise characteristics. The SAR algorithm is implemented in dual operating mode, using an 8-bit coarse programmable capacitor array in the capacitance-domain and an 8-bit R-2R digital-to-analog converter (DAC) in the charge-domain. The proposed CDC achieves a wide input capacitance range of 29.4 pF and a high resolution of 0.449 fF. The CDC is fabricated in a $0.18-{\mu}m$ 1P6M complementary metal-oxide-semiconductor (CMOS) process with an active area of 0.55 mm2. The total power consumption of the CDC is $86.4{\mu}W$ with a 1.8-V supply. The SAR CDC achieves a measured 11.49-bit resolution within a conversion time of 1.025 ms and an energy-efficiency FoM of 31.6 pJ/step.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.41.2-41.2
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• 2011

Recently, scaling down of ULSI (Ultra Large Scale Integration) circuit of CMOS (Complementary Metal Oxide Semiconductor) based electronic devices become much faster speed and smaller size than ever before. However, very narrow interconnect line width causes some drawbacks. For example, deposition of conformal and thin barrier is not easy moreover metallization process needs deposition of diffusion barrier and glue layer. Therefore, there is not enough space for copper filling process. In order to overcome these negative effects, simple process of copper metallization is required. In this research, Cu-V thin alloy film was formed by using RF magnetron sputter deposition system. Cu-V alloy film was deposited on the plane $SiO_2$/Si bi-layer substrate with smooth and uniform surface. Cu-V film thickness was about 50 nm. Cu-V layer was deposited at RT, 100, 150, 200, and $250^{\circ}C$. XRD, AFM, Hall measurement system, and XPS were used to analyze Cu-V thin film. For the barrier formation, Cu-V film was annealed at 200, 300, 400, 500, and $600^{\circ}C$ (1 hour). As a result, V-based thin interlayer between Cu-V film and $SiO_2$ dielectric layer was formed by itself with annealing. Thin interlayer was confirmed by TEM (Transmission Electron Microscope) analysis. Barrier thermal stability was tested with I-V (for measuring leakage current) and XRD analysis after 300, 400, 500, 600, and $700^{\circ}C$ (12 hour) annealing. With this research, over $500^{\circ}C$ annealed barrier has large leakage current. However V-based diffusion barrier annealed at $400^{\circ}C$ has good thermal stability. Thus, thermal stability of vanadium-based thin interlayer as diffusion barrier is good for copper interconnection.

• 전자공학회논문지
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• 제54권7호
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• pp.29-35
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• 2017

본 논문에서는 고속 데이터 전송을 위해 orthogonal frequency division multiplexing (OFDM) 시스템에 적용 가능한 고속 fast Fourier transform (FFT) 프로세서를 제안하였다. 제안하는 FFT 프로제서는 높은 처리율을 만족하기 위해 mixed-radix 알고리즘과 8개의 병렬 경로를 가지는 multipath delay commutator (MDC) 파이프라인 구조를 채택하였다. 하드웨어 복잡도를 줄이기 위해서 새로운 스케줄링 기법들을 적용하여 twiddle factor 연산을 위한 read-only memories (ROM)의 크기를 줄이는 구조와 복소 상수 곱셈기의 수를 줄이는 구조를 제안한다. 제안하는 구조는 지연 소자와 연산 사이클의 증가 없이 하드웨어 복잡도를 줄일 수 있다. 또한, IEEE 802.11 ac/ad와 같은 고속 OFDM 시스템을 위해 64/128/256/512-포인트 FFT 연산이 가능하다. 제안하는 FFT 프로세서는 Verilog-HDL로 모델링하여 Samsung 65nm 공정 라이브러리로 합성하여 0.36mm2의 면적과 330MHz의 동작 주파수에서 2.64 GSample/s를 보이고 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.407-407
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• 2014

Nanotechnology, especially vertically grown silicon nanowires, has gotten great attentions in biology due to characteristics of one dimensional nanostructure; controllable synthetic structure such as lengths, diameters, densities. Silicon nanowires are promising materials as nanoelectrodes due to their highly complementary metal-oxide-semiconductor (CMOS) - and bio-compatibility. Silicon nanowires are so intoxicated that are effective for bio molecular delivery and electrical stimulation. Vertical nanowires with integrated Au tips were fabricated for electrical intracellular interfacing with PC-12 cells. We have made synthesized two types of nanowire devices; one is multi-nanowires electrode for bio molecular sensing and electrical stimulation, and the other is single-nanowires electrode respectively. Here, we demonstrate that differentiation of Nerve Growth Factor (NGF) treated PC-12 cells can be promoted depending on different magnitudes of electrical stimulation and density of Si NWs. It was fabricated by both bottom-up and top-down approaches using low pressure chemical vapor deposition (LPCVD) with high vacuuming environment to electrically stimulate PC-12 cells. The effects of electrical stimulation with NGF on the morphological differentiation are observed by Scanning Electron Microscopy (SEM), and it induces neural outgrowth. Moreover, the cell cytosol can be dyed selectively depending on the degree of differentiation along with fluorescence microscopy measurement. Vertically grown silicon nanowires have further expected advantages in case of single nanowire fabrication, and will be able to expand its characteristics to diverse applications.

• 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.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.330-338
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• 2017

Purpose: The smartphone is actively being used in many research fields, primarily in medical and diagnostic applications. However, there are cases in which smartphone-based systems have been developed for agriculture, environment, and food applications. The purpose of this review is to summarize the research cases using smartphone cameras in agriculture, environment, and food. Methods: This review introduces seventeen research cases which used smartphone cameras in agriculture, food, water, and soil applications. These were classified as systems involving "smartphone-camera-alone" and "smartphone camera with optical accessories". Results: Detecting food-borne pathogens, analyzing the quality of foods, monitoring water quality and safety, gathering information regarding plant growth or damage, identifying weeds, and measuring soil loss after rain were presented for the smartphone-camera-alone system. Measuring food and water quality and safety, phenotyping seeds, and soil classifications were presented for the smartphone camera with optical accessories. Conclusions: Smartphone cameras were applied in various areas for several purposes. The use of smartphone cameras has advantages regarding high-resolution imaging, manual or auto exposure and focus control, ease of use, portability, image storage, and most importantly, programmability. The studies discussed were achieved by sensitivity improvements of CCDs (charge-coupled devices) and CMOS (complementary metal-oxide-semiconductor) on smartphone cameras and improved computing power of the smartphone, respectively. A smartphone camera-based system can be used with ease, low cost, in near-real-time, and on-site. This review article presents the applications and potential of the smartphone and the smartphone camera used for various purposes in agriculture, environment, and food.

• ETRI Journal
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• 제42권5호
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• pp.781-789
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• 2020

In this study, an E-band low-noise amplifier (LNA) monolithic microwave integrated circuit (MMIC) has been designed using silicon-germanium 130-nm bipolar complementary metal-oxide-semiconductor technology to suppress unwanted signal gain outside operating frequencies and improve the signal gain and noise figures at operating frequencies. The proposed impedance-controllable filter has series (R_s) and parallel (R_p) resistors instead of a conventional inductor-capacitor (L-C) filter without any resistor in an interstage matching circuit. Using the impedance-controllable filter instead of the conventional L-C filter, the unwanted high signal gains of the designed E-band LNA at frequencies of 54 GHz to 57 GHz are suppressed by 8 dB to 12 dB from 24 dB to 26 dB to 12 dB to 18 dB. The small-signal gain S₂₁ at the operating frequencies of 70 GHz to 95 GHz are only decreased by 1.4 dB to 2.4 dB from 21.6 dB to 25.4 dB to 19.2 dB to 24.0 dB. The fabricated E-band LNA MMIC with the proposed filter has a measured S₂₁ of 16 dB to 21 dB, input matching (S₁₁) of -14 dB to -5 dB, and output matching (S₂₂) of -19 dB to -4 dB at E-band operating frequencies of 70 GHz to 95 GHz.

• 센서학회지
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• 제28권1호
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• pp.41-46
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• 2019

In order to develop novel thermal imaging materials for microbolometer applications, $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ ($0.18{\leq}x{\leq}0.26$) thin films were fabricated using metal-organic decomposition. Effects of Cu content on the electrical properties of the annealed films were investigated. Spinel thin films with a thickness of approximately 100 nm were obtained from the $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ films annealed at $380^{\circ}C$ for five hours. The resistivity (${\rho}$) of the annealed films was analyzed with respect to the small polaron hopping model. Based on the $Mn^{3+}/Mn^{4+}$ ratio values obtained through x-ray photoelectron spectroscopy analysis, the hopping mechanism between $Mn^{3+}$ and $Mn^{4+}$ cations discussed in the proposed study. The effects of $Cu^+$ and $Cu^{2+}$ cations on the hopping mechanism is also discussed. Obtained results indicate that $[(Ni_{0.3}Mn_{0.7})_{1-x}Cu_x]_3O_4$ thin films with low temperature annealing and superior electrical properties (${\rho}{\leq}54.83{\Omega}{\cdot}cm$, temperature coefficient of resistance > -2.62%/K) can be effectively employed in applications involving complementary metal-oxide semiconductor (CMOS) integrated microbolometer devices.

• 한국지구과학회지
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• 제34권6호
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• pp.588-601
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• 2013

최근 지구물리 물리탐사 분야에서 경사각과 방위각 정보는 시추공 물리검층 및 물리탐사 자료보정을 위한 시추공 편차검층, 이동형 실시간 자료획득 시스템, 기타 지구물리 모니터링 시스템 등 다양하게 활용되면서 그 중요성이 높아지고 있다. 특히 최근 셰일가스의 개발이 가능하게 한 방향시추 기술에서도 경사각과 방위각 정보는 필수일 정도로 그 응용범위가 매우 넓다. 따라서 여러 분야에 응용될 수 있는 경사각과 방위각 측정 시스템의 초소형 옥외 저전력 운용이 절실해졌다. 본 논문에서는 최신 CMOS 저전력, 고성능 MCU 및 멤스(MEMS) 자세방위기준장치(AHRS)를 도입하여 초소형, 저전력으로 제작된 다용도 야외시험용 실시간 경사각과 방위각 연속 측정 시스템 개발 연구의 결과를 제시하고자 한다. 시스템은 최소 지름 42 mm의 존데 내에 설치될 수 있도록 초슬림 형태로 제작되었으며 실시간 데이터 획득이 가능할 뿐만 아니라 엔코더, DGPS 연동으로 운용 확장이 가능하여 다양한 응용이 기대된다.

• 지질공학
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• 제30권1호
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• pp.17-30
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• 2020

광학영상화검층은 광원과 CMOS 영상 센서를 이용하여 시추공벽을 이미지로 구현하는 물리검층 기술로 지하의 불연속면에 대한 여러 가지 원위치 정보를 고분해능으로 제공한다. 최근 시추공영상화검층은 지반침하 모니터링, 암반 무결성 평가, 응력으로 인한 단열 변화 탐지, 극지에서의 빙하 연대측정 등 그 활용범위가 매우 다양해졌다. 현재 국내외로 많이 이용되고 있는 시추공영상화검층 시스템은 장비 사양에 따라 한계점을 가지고 있어 적용 범위에 대한 검증과 여러 가지 시추공 환경에 대한 적절한 품질관리가 필요하다. 그러나 광학영상화검층의 자료로 도출되는 이미지는 원위치 정보로 정확도, 구현도, 신뢰성에 대한 검증에 직접적인 비교 확인이 어렵다. 본 논문에서는 신뢰성 있는 고품질 자료 취득 방법과 자료 처리 방법을 확인하기 위해 시추공 환경과 유사한 모듈화 된 균열모형시추공을 설계·제작하여 현재까지 보고되지 않은 실험에 대한 결과를 얻고자 하였다. 검출기 자기계 방향 확인의 정확성을 검증하고, 노출시간에 따른 색상의 구현도 및 균열의 분해능 관계, 정확한 간극 측정을 위한 자료 처리 방법 등을 제시하였다. 다양한 시추공 환경을 모사한 균열모형시추공 실험을 통해 고분해능의 신뢰성 높은 광학영상화검층의 자료 취득 및 해석이 가능할 것으로 기대된다.