• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.651-659
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• 2010

In this paper, a new six-port direct conversion receiver for high-speed multi-band multi-mode wireless communication system such as software defined radio(SDR) is proposed. The designed receiver is composed of two CMOS four-port BPSK receivers and a dual-band one-stage polyphase filter for quadrature LO signal generation. The four-port BPSK receiver, implemented in 0.18 ${\mu}m$ CMOS technology for the first time in microwave-band, is composed of two active combiners, an active balun, two power detector, and an analog decoder. The proposed polyphase filter adopt type-I architecture, one-stage for reduction of the local oscillator power loss, and LC resonance structure instead of using capacitor for dual-band operation. In order to extent the operation RF bandwidth of the proposed six-port receiver, we include I/Q phase and amplitude calibration scheme in the six-port junction and the power detector. The calibration range of the phase and amplitude mismatch in the proposed calibration scheme is 8 degree and 14 dB, respectively. The validity of the designed six-port receiver is successfully demonstrated by modulating M-QAM, and M-PSK signal with 40 Msps in the two-band of 900 MHz and 2.4 GHz.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.17-25
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• 1999

Tungsten nitride($WN_x$) films were deposited by PECVD method on silicon nitride($WSi_3N_4$) substrate. The characteristics of $WN_x$ film were investigated with changing various processing parameters ; substrate temperature, gas flow rate, rf power, and different nitrogen sources. The nitrogen composition in $WN_x$ film varied from 0 to 45% according to the $NH_3$ and $N_2$ flow rate. The highest deposition rate of 160 nm/min was obtained for the $NH_3$ gas and relatively low deposition rate of $WN_x$ films were formed by $N_2$ gas. $WN_x$ films deposited on $WSi_3N_4$ substrate had higher deposition rate than that of TiN and Si substrates. The purity of $WN_x$ film were analyzed by AES and higher purity $WN_x$ films were deposited using $NH_3$ gas. The XRD analysis indicates a phase transition from polycrystalline tungsten(W) to amorphous tungsten nitride($WN_x$), showing improved etching profile of $WN_x$ films Thick $WN_x$ films were deposited on various substrates such as Tin, NiCr and Al and maximum thickness of $1.6 {\mu}m$ was obtained on the Al adhesion layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.73-73
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• 2000

안티퓨즈 소자는 프로그램 가능한 절연층의 상하 각각에 금속층이나 다결정 실리콘 등의 전도 가능한 전극으로 구성된다. 프로그램은 상하 전극간에 임계전압을 가했을 때 일어나게 되며 이때 절연층이 파괴되므로 비가역적이어서 재사용은 불가능하게 된다. 안티퓨즈 소자는 이러한 프로그램 특성으로 인하여 메모리 소자를 이용한 스위치 보다 속도나 집적도 면에서 우수하다. FPGAsdp 사용되는 안티퓨즈 소자는 집적도의 향상과 적정 절열파괴전압 구현을 위해 절연막의 두께를 감소시키는 것이 바람직하다. 그러나 두께나 감소될 경우 바닥전극의 hillock에 큰 영향을 받게 되며, 그로 인해 절연막의 두께를 감소시키는 것는 한계가 있는 것으로 보고되어 있다. 본 논문에서는 낮은 구동 전압에서 동작하고 안정된 on/pff 상태를 갖는 Al/TiO2-SiO2/Mo 형태의 안티퓨즈 소자를 제안하였다. 만들어진 antifuse cell은 0.6cm2 크기로 약 300개의 샘플을 제작하여 측정하였다. 비저항이 6-9 $\Omega$-cm인 P형의 실리콘 웨이퍼에 RF 마그네트론 스퍼터링(RF magnetron sputtering) 방법으로 하부전극인 Mo를 3000 증착하였다. SiO2는 안티퓨즈에서 완충막의 역할을 하며 구조적으로 antifuse cell을 완전히 감싸고 있는 형태로 제작되었다. 완충막 구조를 만들기 dln해 일반적인 포토리소그라피(Photo-lithography)작업을 거처 형성하였다. 형성된 hole의 크기는 5$mu extrm{m}$$\times$5$\mu\textrm{m}$ 이었다. 완충막이 형성된 기판위에 안티퓨즈 절연체인 SiO2를 PECVD 방식으로 100 증착하였다. 그 후 이중 절연막을 형성시키기 위해 LPCVD를 이용하여 TiO2를 150 증착시켰다. 상부 전극은 thermal evaporation 방식으로 Al을 250nm 증착하여Tejk. 하부전극으로 사용된 Mo 금속은 표면상태가 부드럽고 녹는점이 높은 매우 안정된 금속으로, 표면위에 제조된 SiO2의 특성을 매우 안정되게 유지시켰다. 제안된 안티푸즈는 이중절연막을 증착함으로서 전체적인 절연막의 두께를 증가시켜 바닥전극의 hillock의 영향을 적게 받아 안정성을 유지할 수 있도록 하였다. 또한, 두 절연막 사이의 계면 반응에 의해 SiO2 막을 약화시켜 절연막의 두께가 두꺼워졌음에도 기존의 SiO2 절연막의 절연 파괴 전압 및 누설 전류오 비교되는 특성을 가졌다. 이중막을 구성하고 있는 안티퓨즈의 ON-저항이 단일막과 비교해 비슷한 것을 볼 수 잇는데, 그 이유는 TiO2에 포함된 Ti가 필라멘트에 포함되어 있어 필라멘트의 저항을 감소시켰기 때문으로 사료된다. 결국 이중막을 구성시 ON-저항 증가에 의한 속도 저하 요인은 없다고 할 수 있다. 5V의 절연파괴 시간을 측정한느 TDDB 테스트 결과 1.1$\times$103 year로 기대수치인 수십 년보다 높아 제안된 안티퓨즈의 신뢰성을 확보 할 수 있었다. 제안된 안티퓨즈의 이중 절연막의 두께는 250 이고 프로그래밍 전압은 9.0V이고, 약 65$\Omega$의 on 저항을 얻을수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.902-911
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• 2003

Using InGaP/GaAs HBT power cells with a 2.0${\times}$20$\mu\textrm{m}$$^2$ emitter area of a unit HBT, a two stage MMIC power amplifier has been developed for IMT-2000 handsets. An active-bias circuit has been used for temperature compensation and reduction in the idling current. Fitting on measured S-parameters of the HBT cells, circuit elements of HBT's nonlinear equivalent model have been extracted. The matching circuits have been designed basically with the extracted model. A two stage HBT MMIC power amplifier fabricated using ETRI's HBT process. The power amplifier produces an 1-㏈ compressed output power(P$\_$l-㏈/) of 28.4 ㏈m with 31% power added efficiency(PAE) and 23-㏈ power gain at 1.95 GHz in on-wafer measurement. Also, the power amplifier produces a 26 ㏈m output power, 28% PAE and a 22.3-㏈ power gain with a -40 ㏈c ACPR at a 3.84 ㎒ off-center frequency in COB measurement.quency in COB measurement.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.227-228
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• 2006

In this paper, we introduce the design and fabrication of 60 GHz low noise amplifier MMIC for IEEE802.15.3c WPAN system. The 60 GHz LNA was designed using ETRI's $0.12{\mu}m$ PHEMT process. The PHEMT shows a peak transconductance ($G_{m,peak}$) of 500 mS/mm, a threshold voltage of -1.2 V, and a drain saturation current of 49 mA for 2 fingers and $100{\mu}m$ total gate width (2f100) at $V_{ds}$=2 V. The RF characteristics of the PHEMT show a cutoff frequency, $f_T$, of 97 GHz, and a maximum oscillation frequency, $f_{max}$, of 166 GHz. The performances of the fabricated 60 GHz LNA MMIC are operating frequency of $60.5{\sim}62.0\;GHz$, small signal gain ($S_{21}$) of $17.4{\sim}18.1\;dB$, gain flatness of 0.7 dB, an input reflection coefficient ($S_{11}$) of $-14{\sim}-3\;dB$, output reflection coefficient ($S_{22}$) of $-11{\sim}-5\;dB$ and noise figure (NF) of 4.5 dB at 60.75 GHz. The chip size of the amplifier MMIC was $3.8{\times}1.4\;mm^2$.

• Journal of Sensor Science and Technology
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• v.3 no.1
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• pp.40-45
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• 1994

$112^{\circ}$ rot. x-cut $LiTaO_{3}$ wafer was used as the substrate of SAW gas sensor. Dual delay line SAW device with IDTs which consist of the reference delay line and the sensing delay line was fabricated using photolithigraphy. Each IDTs had 10 finger pairs and finger spacing is 10 microns. One delay line channel is the reference, while the second is the sensing channel with Pb-phthalocyanine film in the propagation path. Pb-phthalocyanine film which is p-type organic semiconductor was evaporated in $10^{-5}$ torr vacuum using shadow mask selectively. Dual delay line oscillator was constructed by using the rf amplifier and AGC. Frequency of the IDTs had the range of $87{\sim}$89 MHz oscillation frequency. Oscillation frequency shifts were investigated as a function of the temperature and the concentration of $NO_{2}$ gas.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.767-777
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• 2012

Annular Biofilm Reactor (ABR) equipped with coupons of three different pipe materials (STS 304, PVC, PE) was used to generate drinking water biofilm samples. The level of assimilable organic carbon (AOC) during the sample generation period was $37.3{\mu}g/L$, and this level did not seem to be low enough to limit the formation of biofilm in this study. Terminal-restriction fragment length polymorphism (T-RFLP) analyses determined T-RF profile as early as 3 h of exposure on PVC coupons. Average surface roughness ($R_a$) measured by atomic force microscopic analyses was 125.7 nm for PVC, and this value was higher than for STS (71.6 nm) and PE (74.0 nm). However, biofilm formation was faster on STS (6 h) than on PE (12 h), which indicated that surface roughness might not be the only factor that controlled the initiation of biofilm development. Upon detection of the T-RF peaks, richness (S) and diversity indices such as Shannon (H) and Simpson (1/D) demonstrated a rather slow increase until 48 h followed by rapid increase regardless of the pipe materials. Differences of microbial community structures among the biofilm samples were determined based on the cluster analysis using Jaccard coefficients (Sj). Biofilm communities could be divided into two distinct groups according to the exposure time regardless of the pipe materials. First group contained a young (< 48 h) biofilm samples (10 out of 11) but second group contained a mature (${\geq}$ 48 h) samples (11 out of 14). Results suggested that, due to the complexity of biofilm, the targeting of the first group of cluster was crucial for optimizing the management of drinking water distribution systems and controlling microbial growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.231-231
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• 2010

Thermoelectric properties of a multi-layered thin film, which was composed with indium selenide and bismuth telluride, were investigated. The structure of the layered thin film is Bi-Te /In-Se/Bi-Te and it was prepared on sapphire substrate by RF magnetron sputter using stoichiometric $Bi_2Te_3$ (99.9%) and $In_2Se_3$(99.99%) target at room temperature. Then, it was annealed at temperature range of 150 - $500^{\circ}C$ in Ar ambient. Structural characterizations were done using X-ray diffraction(XRD, BRUKER, D8, 60kW) and transmission electron microscopy (TEM, FEI, Tecnai, F30 S-Twin), respectively. Cross-section of multi-layer structure was observed by Scanning electron microscopy (SEM). The resistivity and Seebeck coefficient of these samples were also measured by conventional equipment at room temperature. The maximum value of power factor was $1.16\;{\mu}W/k^2m$ at annealing temperature of $400^{\circ}C$.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.2
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• pp.89-95
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• 2003

In this paper, we have designed and fabricated high conversion gain Q-band active sub-harmonic mixers for a receiver of millimeter wave wireless communication systems. The fabricated active sub-harmonic mixer uses 2nd harmonic signals of a low local oscillator (LO) frequency. The fabricated mixer was successfully integrated by using $0.1{\;}\mu\textrm{m}$GaAs pseudomorphic high electron mobility transistors (PHEMTs) and coplanar waveguide (CPW) structures. From the measurement, it shows that maximum conversion gain of 4.8 dB has obtained at a RF frequency of 40 GHz for 10 dBm LO power of 17.5 GHz. Conversion gain from the fabricated sub-harmonic mixer is one of the best reported thus far. And a phase noise of the 2nd harmonic was obtained -90.23 dBc/Hz at 100 kHz offset. The active sub-harmonic mixer also ensure a high degree of isolations, which are -35.8 dB from LO-to-IF and -40.5 dB from LO-to-RF, respectively, at a LO frequency of 17.5 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.415-415
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• 2011

국제핵융합실험로(ITER)에 장착되는 한국형 헬륨 냉각 고체형 증식(Helium Cooled Solid Breeder : HCSB) 시험 블랑켓(Test Blanket Module : TBM)은 ITER 참여국 중 유일하게 중성자 반사 재료를 채택한 것이 특징이다. 중성자 반사재료로는 지름 1 mm 내외의 흑연 페블을 사용 할 예정이다. 흑연은 중성자 반사특성은 우수하지만 기계적 특성이 비교적 좋지 않다는 단점이있다. 뿐만 아니라, 산화나 화재 등에 대해서도 취약하기 때문에 흑연이 노출된 상태로 사용하는 것은 위험부담이 클 수밖에 없다. 따라서 흑연을 코팅해서 사용하기 위한 연구개발이 진행 중이며, 코팅 후보물질로는 저방사화 및 고경도의 특성을 갖는 SiC가 유력시 되고 있다. 흑연위에 SiC를 코팅하는 방법은 여러 가지가 있으며, 그 중에서 비교적 간단한 RF Sputtering, PECVD를 이용해서 SiC를 코팅하고 그 특성을 평가했다. RF Sputtering에서 흑연의 온도를 상온으로 두었을 때는 SiC가 결정으로 성장되지 않는 것을 확인할 수 있었으며, $900^{\circ}C$ 이상의 온도에서 열처리과정을 거친 후 결정이 형성되는 것을 확인할 수 있었다. 그리고 열처리 온도가 $1200^{\circ}C$ 부근에서는 SiC nano-wire가 형성되는 것을 확인할 수 있었다. PECVD의 경우 전구체 물질로 사용된 $SiH_4$와 $CH_4$의 비율에 따라서 SiC의 형성비율이 다른 것을 알 수 있었으며, 결정 상태는 성장시 기판온도에 크게 의존하는 것을 확인할 수 있었다. 최근에는 보다 효율적으로 SiC를 코팅하기 위하여 흑연페블을 spouting시키면서 코팅할 수 있는 CVD 장치를 설계-제작했으며, 전구체 물질로는 $SiH_4$, $Si(CH_3)_4$, $CH_3$ $SiCl_3$ 등이 사용될 예정이다.