• 전자공학회논문지
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• 제51권3호
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• pp.45-54
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• 2014

전류제한 에피 구조를 적용하여 MINT에서 개발한 최적화된 공정방법으로 InP Gunn 다이오드 칩을 제작하고 칩을 이용하여 MINT의 최적화된 조건을 이용하여 패키지 하였다. 또한 제작된 패키지 InP Gunn 다이오드의 RF 특성을 측정하기 위하여 2체배 구조의 W-band 도파관 FTO(Fixed Tuned Oscillator)를 설계 및 제작하였다. 패키지된 InP Gunn 다이오드는 ceramic ring, Au plating stud와 lid 그리고 Maltese cross로 구성되어있다. 측정된 20개의 InP Gunn 다이오드는 최대 전류가 399 mA의 전류특성을 가지고 92.9~94.78 GHz에서 발진하였고 11.8~17.8 dBm 의 출력전력을 얻었다.

• 대한화학회지
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• 제44권3호
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• pp.200-206
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• 2000

실리콘 웨이퍼를 일정한 두께로 에칭하여 실리콘 웨이퍼 표면 근처의 특정영역에 존재하는 금속불순물을 정량하였다. HF와 $HNO_3$의 부피비를 1:3으로 혼합한 용액 5mL로 20분간 실리콘 웨이퍼와 반응 시켰을 때 1${\mu}m$ 두께로 웨이퍼 전면을 균일하게 에칭할 수 있었다. 에칭 후, 용액을 중발하기 위해 마이크로파 오븐을 사용하였는데 증발과정에서 spike한 Cu, Ni, Zn, Cr, Mg 및 K의 회수율은 99∼105%였다,Cu를 오염시킨 epitaxial 실리콘 웨이퍼의 경우 에칭법으로 전처리를 하여 ICP${\cdot}MS$로 측정한 결과, Cu는 뒷면의 표면으로부터 1∼2${\mu}m$ 안의 polysilicon영역에 집중적으로 분포하였고 Cu 농도를 1${\mu}m$두께의 범위에서 정량할 수 있었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.56-60
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• 2000

Cube texture를 갖는 Ni기판위에 MOCVD(Metal Chemical Vapor Deposition)를 이용하여 NiO, CeO$_2$, YBCO 박막을 제조하였다. NiO(200)와 CeO$_2$(200) buffer layer는 450${\sim}$470$^{\circ}$C에서 10분간 MOCVD방법으로 (100)<001>Ni 기판위에 직접 증착하였다. 제조된 NiO, CeO$_2$ buffer layer는 조직이 치밀하며 표면의 상태가 매우 좋으며 Ni기판 위에 epitaxial하게 성장하였다. NiO는 Ni기판과 NiO<100>//Ni<100>의 방위관계를 가지고 성장하였으며, CeO$_2$는 증착조건에 따라 CeO$_2$ <100>//Ni<100> 및 CeO$_2$ <110>//Ni<100> 의 방위관계를 가지고 성장하였다. 증착된 NiO막과 CeO$_2$막에서 균열은 발생하지 않았다. MOCVD법으로 표면에 biaxial texture를 갖는 ceramic buffer를 증착시킨 NiO/Ni및 CeO$_2$/Ni 기판위에 YBCO박막을 MOCVD법으로 제조하였다. YBCO막은 기판온도 800$^{\circ}$C,증착압력 10torr, 산소분압을 0.7torr로 하여 10분간 행하였다. 공급원료의 조성에 따라 YBCO의 막의 texture와 형성되는 상이 변화되었다. NiO/Ni및 CeO$_2$/Ni 기판 위에 증착된 YBCO막은 c축 배향성을 가지고 성장하였으며, -scan 및 ${\varphi}$ -scan으로 측정한 (500)면의 in-plane과 (110)면의 out-of-plane의 FWHM(Full Width Half Maximum)값은 각각 10$^{\circ}$ 미만으로 우수하였다.

• Progress in Superconductivity
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• 제11권2호
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• pp.123-127
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• 2010

The properties of buffer layer for thermal and chemical stability in coated conductor is a very important issue. $CeO_2$ has desirable thermal and chemical stability as well as good lattice match. In this study, $CeO_2$ was deposited by electron beam deposition. The MgO(001) single crystal and LMO buffered IBAD substrate(LMO/IBAD-MgO/$Y_2O_3/Al_2O_3$/Hastelloy) were used as substrates, which have $\Delta\phi$ values of ${\sim}8.9^{\circ}$. The epitaxial $CeO_2$ films was deposited with high deposition rate of $12{\sim}16\;{\AA}/sec$. During deposition, the change of oxygen partial pressure(${\rho}O_2$) does not cause change in c-axis texture. In case of $CeO_2$ on MgO single crystal, the substrate temperature was optimized at $750^{\circ}C$ with superior $\Delta\phi$ and $\Delta\omega$ value. Otherwise, In case of LMO buffered IBAD substrate, It was optimized at $650^{\circ}C$ with increasing its deposition thickness of $CeO_2$, which was finally obtained with best $\Delta\phi$ value of $5.5^{\circ}$, $\Delta\omega$ value of $2^{\circ}$ and Ra value of 2.2 nm.

• Progress in Superconductivity
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• 제11권2호
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• pp.100-105
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• 2010

Reel-to-reel deposition of $Y_2O_3$ has been performed on Ni-5%W metal substrates using the RF-sputtering method. The epitaxial orientation of $Y_2O_3$ buffer layers to the base bi-axially textured substrate was well identified using ${\theta}-2{\theta}$, out-of-plane ($\omega$), and in-plane ($\phi$) scans in X-ray diffraction analysis. The optimization of $Y_2O_3$ seed layers in reel-to-reel fashion were investigated varying the deposition temperature, sputtering power, and pressure for its significant roles for the following buffer stacks and superconducting layers. $Y_2O_3$ were all grown epitaxially on bi-axially textured metal substrates at 380 watts and 5 mTorr in the temperature range of $600-740^{\circ}C$ with higher $Y_2O_3$ (400) intensities at ${\sim}710^{\circ}C$. It was found that the $\Delta\omega$ values were $1-2^{\circ}$ lower but the $\Delta\phi$ values were above $1^{\circ}$ higher than that of Ni-W substrates. As the sputtering power increased from 340 to 380 watts, $\Delta\omega$ and $\Delta\phi$ values showed decreased tendency. Even in the small window of deposition pressure of 3-7 mTorr, the $Y_2O_3$ (400) intensities increased and $\Delta\omega$ and $\Delta\phi$ values were reduced as sputtering pressure increased.

• 한국재료학회지
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• 제9권5호
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• pp.528-532
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• 1999

Y$_2$O$_3$films were grown on SiO$_2$-covered Si(111), and hydrogen-terminated Si(111), and hydrogen-terminated Si(111) substrates at 50$0^{\circ}C$ by ultrahigh vacuum ionized cluster beam deposition (UHV-ICB). The microstructures and growth behavior of these films have been investigated by transmission electron diffraction (TED) and high-resolution transmission electron microscopy(HREM). The TED results show that the $Y_2$O$_3$grown on the SiO$_2$-Si has the epitaxial relationship of (11-1)Y$_2$O$_3$∥(111)Si and [-110]Y$_2$O$_3$∥[-110]Si. The film on the H-Si substrate contains YS\ulcorner and amorphous YSi\ulcornerO\ulcorner layers at the interface, having the orientation relationship each other. For the YSi\ulcorner and the Si substrate, the relationship is (0001)YSi\ulcorner∥(111)Si and [1-210]YSi\ulcorner∥∥[-110]Si. For the $Y_2$O$_3$and the YSi\ulcorner ; the relationship is as follows: (11-1)Y$_2$O$_3$∥(0001)YSi\ulcorner and [-110]Y$_2$O$_3$∥[1-210]YSi\ulcorner(111)Y$_2$O$_3$∥(0001)YSi\ulcorner and [-110]Y$_2$O$_3$∥[1-210]YSi\ulcorner. Explanation is given to describe the formation mechanisms of the interfacial phases of SiO\ulcorner, YSi\ulcornerO\ulcorner and YSi\ulcorner. It is shown that the crystallinity of the $Y_2$O$_3$film on the SiO$_2$-Si(111) is better than that of $Y_2$O$_3$on H-Si(111).

• 한국재료학회지
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• 제9권8호
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• pp.849-853
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• 1999

본 연구에서는 액상성장법(LPE법)으로 $Bi_2$-x(sub)$LSr_2$Ca(sub)1+x(sub)$LCu_2$O(sub)8+d (x(sub)L=0, 0.05, 0.1, 0.2) 막(film)을 작성하여 초전도특성을 알아보았고, XPS 측정으로 얻은 Sr3d과 Ca2p의 피크분해 결과와 EPMA 측정 결과를 통하여 각 layer에 있어서 원자들의 분포상태에 관하여 조사하였다. 작성한 막(film)의 c-축의 길이는 x(sub)L(융해조성비)의 증가에 따라 단조로이 증가하였고, 임계온도 T(sub)c는 x(sub)L=0.1 부근에서 최고치를 나타내고 있었다. x(sub)L의 변화에 따른 임계온도 T(sub)c와 c-축의 길이의 변화는 BiO-layer에 있는 과잉산소의 변화에 의한 것이며, SrO-layer에서 원소들의 분포상태와 결손이 초전도특성 및 결정구조에 영향을 미치고 있음을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.77-80
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• 2001

Crystallographic and magnetic characteristics of CoCr-based magnetic thin film for perpendicular magnetic recording media were influenced on preparing conditions. In these, there is that substrate temperature was parameter that increases perpendicular coercivity of CoCrTa magnetic layer using recording layer. While preparation of CoCr-based doublelayer, by optimizing substrate temperature, we expect to increase perpendicular anisotropy of CoCr magnetic layer and prepare ferromagnetic recording layer with a good quality by epitaxial growth. CoCrTa/Si doublelayer showed a good dispersion angle of c-axis orientation $\Delta\theta_{50}$ caused by inserting amorphous Si underlayer which prepared at underlayer substrate temperature 250C. Perpendicular coercivity was constant, in-plane coercivity was controlled a low value about 200Oe. This result implied that Si underlayer could restrain growth of initial layer of CoCrTa thin film, which showed bad magnetic properties effectively without participating magnetization patterns of magnetic layer. In case of CoCrTa/Si that prepared with ultra thin underlayer, crystalline orientation of CoCrTa was improved rather underlayer thickness 1nm, it was expected that amorphous Si layer played a important role in not only underlayer but also seed layer.

• Progress in Superconductivity
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• 제8권2호
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• pp.175-180
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• 2007

High temperature superconductor $YBa_2Cu_3O_{7-x}$ (YBCO) films have been grown by in-situ electron beam evaporation on artificial metal tapes such as ion-beam assisted deposition (IBAD) and rolling assisted biaxially textured substrates (RABiTS). Deposition rate of the YBCO films is $10{\sim}100{\AA}/sec$. X-ray diffraction shows that the films are grown epitaxially but have inter-diffusion phases, like as $BaZrO_3\;or\;BaCeO_3$, at their interfaces between YBCO and yttrium-stabilized zirconia (YSZ) or $CeO_2$, respectively. Secondary ion mass spectroscopy depth profile of the films confirms diffused region between YBCO and the buffer layers, indicating that the growth temperature ($850{\sim}900^{\circ}C$) is high enough to cause diffusion of Zr and Ba. The films on both the substrates show four-fold symmetry of in-plane alignment but their width in the -scan is around $12{\sim}15^{\circ}$. Transmission electron microscopy shows an interesting interface layer of epitaxial CuO between YBCO and YSZ, of which growth origin may be related to liquid flukes of Ba-Cu-O. Resistivity vs temperature curves of the films on both substrates were measured. Resistivity at room temperature is between 300 and 500 cm, the extrapolated value of resistivity at 0 K is nearly zero, and superconducting transition temperature is $85{\sim}90K$. However, critical current density of the films is very low, ${\sim}10^3A/cm^2$. Cracking of the grains and high-growth-temperature induced reaction between YBCO and buffer layers are possible reasons for this low critical current density.

• 한국진공학회지
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• 제13권3호
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• pp.109-113
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• 2004

InP에서 열처리 온도와 시간 및 활성화 온도에 따른 Zn의 확산의 특성을 electrochemical capacitance-voltage 법으로 조사하였다. InP층은 metal organic chemical vapor deposition를 이용하여 성장하였으며, 화산방법으로는 $Zn_3P_2$ 확산과 박막과 rapid thermal annealing를 사용하였다. 최대의 정공 농도를 갖는 p-lnP 층은 $550^{\circ}C$에서 5분 동안 확산과 활성화를 한 시료에서 얻었고, Zn의 농도는 $1\times10^{19}\textrm{cm}^{-3}$이었다. $550^{\circ}C$에서 5-20 분 동안 확산을 수행한 결과 정공농도의 확산 깊이는 1.51 $\mu\textrm{m}$에서 3.23 $\mu\textrm{m}$로 이동하였고, Zn의 확산계수는 $5.4\times10^{-11}\textrm{cm}^2$/sec이었다. 활성화 시간의 증가로, Zn가 더 깊게 확산하지만, 정공농도는 거의 변화가 없었다. 이는 도핑된 영역의 과잉의 침입형 Zn가 도핑되지 않은 영역으로 빠르게 확산하고 치환형 Zn로 변한다는 것을 의미한다. 정공농도는 $SiO_2$ 박막의 두께가 1,000$\AA$ 이상이어야 안정적으로 분포된다.