나노급 두께 니켈실리사이드의 적외선 흡수 특성

윤기정,한정조,송오성,Yoon, Ki-Jeong,Han, Jeung-Jo,Song, Oh-Sung 한국재료학회 2007 한국재료학회지 Vol.17 No.6

We fabricated thermaly evaporated 10 nmNi/(poly)Si films to investigate the energy saving property of silicides formed by rapid thermal annealing (RTA) at the temperature of $300{\sim}1200^{\circ}C$ for 40 seconds. Moreover, we fabricated $10{\sim}50$ nm-thick ITO/Si films with a rf-sputter as reference films. A four-point tester was used to investigate the sheet resistance. A transmission electron microscope (TEM) and an X-ray diffractometer were used for the determination of cross sectional microstructure and phase changes. A UV-VISNIR and FT-IR (Fourier transform infrared rays spectroscopy) were employed for near-IR and middle-IR absorbance. Through TEM analysis, we confirmed $20{\sim}70nm-thick$ silicide layers formed on the single and polycrystalline silicon substrates. Nickel silicides and ITO films on the single silicon substrates showed almost similar absorbance in near-IR region, while nickel silicides on polycrystalline silicon substrate showed superior absorbance above 850 nm near-IR region to ITO films. Nickel silicide on polycrystalline substrate also showed better absorbance in middle IR region than ITO. Our result implies that nano-thick nickel silicides may have exellent absorbing capacity in near-IR and middle-IR region.

Microstructure Evolution of the Ir-inserted Ni Silicides with Additional Annealing

윤기정,송오성 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.1

Thermally-evaporated 10 nm-Ni/1 nm-Ir/(poly)Si structures were fabricated in order to investigate the thermal stability of Ir-inserted nickel silicide after additional annealing. The silicide samples underwent rapid thermal annealing at 300℃ to 1200℃ for 40 s, followed by 30 min annealing at the given RTA temperatures. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates, mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution x-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope were used to determine the cross-section structure and surface roughness. The silicide, which formed on single crystal silicon substrate with surface agglomeration after additional annealing, could defer the transformation of Ni(Ir)Si to Ni(Ir)Si2 and was stable at temperatures up to 1200℃. Moreover, the silicide thickness doubled. There were no outstanding changes in the silicide thickness on polycrystalline silicon. However, after additional annealing, the silicon-silicide mixing became serious and showed high resistance at temperatures >700℃. Auger depth profiling confirmed the increased thickness of the silicide layers after additional annealing without a change in composition. For a single crystal silicon substrate, the sheet resistance increased slightly due to the significant increases in surface roughness caused by surface agglomeration after additional annealing. Otherwise, there were almost no changes in surface roughness on the polycrystalline silicon substrate. The Ir-inserted nickel monosilicide was able to maintain a low resistance in a wide temperature range and is considered suitable for the nano-thick silicide process. Thermally-evaporated 10 nm-Ni/1 nm-Ir/(poly)Si structures were fabricated in order to investigate the thermal stability of Ir-inserted nickel silicide after additional annealing. The silicide samples underwent rapid thermal annealing at 300℃ to 1200℃ for 40 s, followed by 30 min annealing at the given RTA temperatures. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates, mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution x-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope were used to determine the cross-section structure and surface roughness. The silicide, which formed on single crystal silicon substrate with surface agglomeration after additional annealing, could defer the transformation of Ni(Ir)Si to Ni(Ir)Si2 and was stable at temperatures up to 1200℃. Moreover, the silicide thickness doubled. There were no outstanding changes in the silicide thickness on polycrystalline silicon. However, after additional annealing, the silicon-silicide mixing became serious and showed high resistance at temperatures >700℃. Auger depth profiling confirmed the increased thickness of the silicide layers after additional annealing without a change in composition. For a single crystal silicon substrate, the sheet resistance increased slightly due to the significant increases in surface roughness caused by surface agglomeration after additional annealing. Otherwise, there were almost no changes in surface roughness on the polycrystalline silicon substrate. The Ir-inserted nickel monosilicide was able to maintain a low resistance in a wide temperature range and is considered suitable for the nano-thick silicide process.

저온 ALD로 제조된 TiO₂ 나노 박막 물성 연구

윤기정,송오성,Yoon, Ki-Jeong,Song, Oh-Sung 한국재료학회 2008 한국재료학회지 Vol.18 No.10

We fabricated 10 nm-$TiO_2$ thin films for DSSC (dye sensitized solar cell) electrode application using ALD (atomic layer deposition) method at the low temperatures of $150^{\circ}\;and\;250^{\circ}$. We characterized the crosssectional microstructure, phase, chemical binding energy, and absorption of the $TiO_2$ using TEM, HRXRD, XPS, and UV-VIS-NIR, respectively. TEM analysis showed a 10 nm-thick flat and uniform $TiO_2$ thin film regardless of the deposition temperatures. Through XPS analysis, it was found that the stoichiometric $TiO_2$ phase was formed and confirmed by measuring main characteristic peaks of Ti $2p^1$, Ti $2p^3$, and O 1s indicating the binding energy status. Through UV-VIS-NIR analysis, ALD-$TiO_2$ thin films were found to have a band gap of 3.4 eV resulting in the absorption edges at 360 nm, while the conventional $TiO_2$ films had a band gap of 3.0 eV (rutile)${\sim}$3.2 eV (anatase) with the absorption edges at 380 nm and 410 nm. Our results implied that the newly proposed nano-thick $TiO_2$ film using an ALD process at $150^{\circ}$ had almost the same properties as thsose of film at $250^{\circ}$. Therefore, we confirmed that the ALD-processed $TiO_2$ thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices.

Pt와 Ir 첨가에 의한 니켈모노실리사이드의 고온 안정화

윤기정,송오성,Yoon, Ki-Jeong,Song, Oh-Sung 한국마이크로전자및패키징학회 2006 마이크로전자 및 패키징학회지 Vol.13 No.4

We fabricated thermally evaporated 10 nm-Ni/(poly)Si, 10 nm-Ni/l nm-Ir/(poly)Si and 10 nm-Ni/l nm-Pt/(poly)Si films to investigate the thermal stability of nickel monosilicides at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides of 50 nm-thick were formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to examine sheet resistance. A scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An X-ray diffractometer and an Auger depth profiler were used for phase and composition analysis, respectively. Nickel silicides with platinum have no effect on widening the NiSi stabilization temperature region. Nickel silicides with iridium farmed on single crystal silicon showed a low resistance up to $1200^{\circ}C$ while the ones formed on polycrystalline silicon substrate showed low resistance up to $850^{\circ}C$. The grain boundary diffusion and agglomeration of silicides lowered the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.

연하장애를 가진 뇌졸중 환자에서 비위관 삽입이 연하 기능에 미치는 영향

윤기정,최경효,양서연 대한연하장애학회 2015 대한연하장애학회지 Vol.5 No.2

Objective: To determine whether the use of a nasogastric (NG) tube influenced swallowing function in stroke patients with dysphagia. Method: Thirty stroke patients with dysphagia (20 men and 10 women, average age=61.4±15.8 years) were included. All patients used NG tubes for nutrition supply and did not show massive aspiration on videofluoroscopic swallowing study (VFSS). VFSS was done using barium (5 ml each) as a contrast medium to evaluate swallowing function. The swallowing trigger time, pharyngeal transit time, duration of pharyngeal response were measured with and without the NG tube. Presence of residual material, aspiration, and movement pattern of the hyoid (degree of anterior and superior displacement) were also recorded using VFSS with and without the NG tube. Result: Swallowing trigger time decreased slightly after removal of the NG tube, but the reduction was not statistically significant (P=0.28). Pharyngeal transit time and duration of pharyngeal response showed no significant change after removal of the NG tube. The presence of aspiration did not change either. Anterior and superior excursion of the hyoid bone did not differ statistically with or without the NG tube. More residual material was found after swallowing with the NG tube in place (P=0.04). Conclusion: NG tube placement did not influence laryngeal elevation, swallowing reflex, and aspiration severity in stroke patients with dysphagia. Therefore, direct swallowing therapy with NG tube placement may be a safe training method.

장려상-대공간 구조

윤기정,김현정,고용,Yun, Gi-Jeong,Kim, Hyeon-Jeong,Go, Yong 한국건축구조기술사회 2007 건축구조 Vol.14 No.3

EMC 시뮬레이션에 의한 AlGaAs 내 전자의 에너지

윤기정 동의공업대학 2000 論文集 Vol.26 No.1

In this paper, free electron energies in AlGaAs bulk due to electric field using EMC(Ensemble Monte Carlo) simulation are described. They are calculated as a function of Al mole fractions of AlGaAs, barrier widths of AlGaAs bulk, temperatures, and electric fields. Mole fractions are varied with x=0.3, 0.4, 0.5 and 0.7, barrier widths are from 100 to 500 [Å], and temperatrues are between 77 and 300 [K]. In the results of simulations, electron energy depends on barrier width and Al mole fraction, significantly, It is increased linearly with electric field, when barrier width is 100 [Å] and, when x = 0.3. And, when x = 0.4, it is increased with nearly linearity, when x = 0.5, it is with nearly non-linearity, and when x=0.7, it is with perfect non-linearity. Linearity is decreased with rise of temperature and with enhancement of barrier width. And electron energy with below x=0.4 is larger than one with above x=0.5. Also, electron energy with higher temperature is lager than that with lower one. Electric field effects stronger than temperature on electron energy, while effect of temperature decreases with stronger electric field. In case of indirect transition type, that is, above x=0.5, transition type is more dominant in electron energy than electric field or temperature.

GaAs/AlGaAs 양자 우물 구조의 제한적 특성 해석

윤기정,김원호 동의공업대학 1999 論文集 Vol.25 No.1

The impact ionization rates of GaAs/AlGaAs quantum well at temperature 77, 100, 150, 200, 250, 300 [K] are calculated. These are important parameters to design the infrared detector APD. The effects on the impact ionization rates by the parameters of quantum well structure, such as well-width, barrier-width, barrier-height and doping density m the well, are analyzed, using Ensemble Monte Carlo method, scattering and tunneling effects. As the width of the quantum well increases, the impact ionization rate increases in the range of the small well width but gradually the increment slows down. Due to the effect of the energy of the injected electrons into the well from the barrier, as well as the tunneling effect in the barrier, the impact ionization rate increases with the range of the smaller barrier width and decreases with the range of the larger barrier width. Thus, there exists a barrier width to maximize the impact ionization rate. The impact ionization rate is very sensitive to the variation of the doping density. It is found that there is a limit to the doping density to confine the electrons in the quantum well effectively.

고준위 도핑된 AlGaAs/GaAs 양자 우물의 충돌 이온화율

윤기정,황성범,송정근,홍창희 대한전자공학회 1996 전자공학회논문지-A Vol.33 No.4

The impact ionization rate of thethighly-doped AlGaAs/GaAs quantum well structure is calculated, which is an important parameter ot design theinfrared detector APD and the novel neural device. In conjunction with ensemble monte carlo method and quantum mechanical treatment, we analyze the effects of the parameters of quantum well structure on the impact ionization rate. Since the number of the occupied subbands increases while the energy of the subbands decreases as the width of quantum well increases, the impact ionization rate increases in the range of th esmall well width but gradually the increament slows down and is finally saturated. Due to the effect of the energy of the injected electrons into the quantum well and the tunneling through the barrier, the impact ionization rate increases for the range of the small barrier width and decreases for the range of the large barrier width. Thus, there exists a barrier width to maximize the impact ionzation rate for a mole fraction x, and the barrier width moves to the larger vaue as the mole fraction x increases. The impact ionization rate is much more sensitive to the variation of the doping density than that of the other quantum well parameters. We found that there is a limit of the doping density to confine the electronics in the quantum well effectively.

GaAs MIS 구조의 C-V 특성의 온도 변화 측정

윤기정,강양원,홍창희 동아대학교 공과대학 부설 한국자원개발연구소 1991 硏究報告 Vol.15 No.1

In this paper, we described the C-V(Capacitance-Voltage) characteristics in the GaAs MIS(Metal-Insulator-Semiconductor) structure. In particular, we took the interest in the shift of flat-band voltage due to the cooling down the semiconductor to the low temperature. The change of the work function difference is depend on the variation of the temperature. Furthermore, when the deep states in the semiconductor are near the interface between the insulator and semiconductor, the effects of them are superior to work function difference. As the results, the deviation of the V_(FB) is about 0.7 volts as the temperature decrease from 300 [k] to 130 [K]