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홍완식,Hong, Wan-Shick 한국진공학회 2014 진공 이야기 Vol.1 No.3
Vacuum growth of thin films via chemical vapor deposition (CVD) methods has been extensively used in modern semiconductor and flat panel display industries. The CVD processes have a wide range of variation and are categorized according to their working conditions, power sources, precursor materials, and so forth. Basic components and process steps common to all CVD branches are discussed. In addition, characteristics and applications of two major CVD techniques - LPCVD and PECVD - are reviewed briefly.
쇼트키 장벽 관통 트랜지스터 구조를 적용한 실리콘 나노점 부유 게이트 비휘발성 메모리 특성
손대호,김은겸,김정호,이경수,임태경,안승만,원성환,석중현,홍완식,김태엽,장문규,박경완,Son, Dae-Ho,Kim, Eun-Kyeom,Kim, Jeong-Ho,Lee, Kyung-Su,Yim, Tae-Kyung,An, Seung-Man,Won, Sung-Hwan,Sok, Jung-Hyun,Hong, Wan-Shick,Kim, Tae-You,Jang, Moo 한국진공학회 2009 Applied Science and Convergence Technology Vol.18 No.4
쇼트키 장벽 관통 트랜지스터에 실리콘 나노점을 부유 게이트로 사용하는 비휘발성 메모리 소자를 제작하였다. 소스/드레인 영역에 어븀 실리사이드를 형성하여 쇼트키 장벽을 생성하였으며, 디지털 가스 주입의 저압 화학 기상 증착법으로 실리콘 나노점을 형성하여 부유 게이트로 이용하였다. 쇼트키 장벽 관통 트랜지스터의 동작 상태를 확인하였으며, 게이트 전압의 크기 및 걸어준 시간에 따른 트랜지스터의 문턱전압의 이동을 관찰함으로써 비휘발성 메모리 특성을 측정하였다. 초기 ${\pm}20\;V$의 쓰기/지우기 동작에 따른 메모리 창의 크기는 ${\sim}5\;V$ 이었으며, 나노점에 충분한 전하 충전을 위한 동작 시간은 10/50 msec 이었다. 그러나 메모리 창의 크기는 일정 시간이 지난 후에 0.4 V로 감소하였다. 이러한 메모리 창의 감소 원인을 어븀 확산에 따른 결과로 설명하였다. 본 메모리 소자는 비교적 안정한 쓰기/지우기 내구성을 보여주었으나, 지속적인 쓰기/지우기 동작에 따라 수 V의 문턱전압 이동과 메모리 창의 감소를 보여주었다. 본 실험 결과를 가지고 실리콘 나노점 부유게이트가 쇼트키 장벽 트랜지스터 구조에 접목 가능하여 초미세 비휘발성 메모리 소자로 개발 가능함을 확인하였다. We fabricated a Si nano floating gate memory with Schottky barrier tunneling transistor structure. The device was consisted of Schottky barriers of Er-silicide at source/drain and Si nanoclusters in the gate stack formed by LPCVD-digital gas feeding method. Transistor operations due to the Schottky barrier tunneling were observed under small gate bias < 2V. The nonvolatile memory properties were investigated by measuring the threshold voltage shift along the gate bias voltage and time. We obtained the 10/50 mseconds for write/erase times and the memory window of $\sim5V$ under ${\pm}20\;V$ write/erase voltages. However, the memory window decreased to 0.4V after 104seconds, which was attributed to the Er-related defects in the tunneling oxide layer. Good write/erase endurance was maintained until $10^3$ write/erase times. However, the threshold voltages moved upward, and the memory window became small after more write/erase operations. Defects in the LPCVD control oxide were discussed for the endurance results. The experimental results point to the possibility of a Si nano floating gate memory with Schottky barrier tunneling transistor structure for Si nanoscale nonvolatile memory device.
고희석 SiH4 가스를 이용하여 증착한 저온 PECVD 실리콘 질화물 박막의 기계적, 전기적 특성연구
노길선 ( Kil Sun No ),금기수 ( Ki Su Keum ),홍완식 ( Wan Shick Hong ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.8
We report on electrical and mechanical properties of silicon nitride (SiNx) films deposited by a plasma enhanced chemical vapor deposition (PECVD) method at 200℃ from SiH4 highly diluted in N2. The films were also prepared from SiH4 diluted in He for comparison. The N2 dilution was also effective in improving adhesion of the SiNx films, fascilitating construction of thin film transistors (TFTs). Metalinsulator-semiconductor (MIS) and Metal-insulator-Metal (MIM) structures were used for capacitance-voltage (C-V) and current-voltage (I-V) measurements, respectively. The resistivity and breakdown field strength of the SiNx films from N2-diluted SiH4 were estimated to be 1×1013Ω · cm, 7.4 MV/cm, respectively. The MIS device showed a hysteresis window and a flat band voltage shift of 3 V and 0.5 V, respectively. The TFTs fabricated by using these films showed a field-effect mobility of 0.16 cm2/Vs, a threshold voltage of 3 V, a subthreshold slope of 1.2V/dec, and an on/off ratio of >106.
200℃ 이하 저온 공정으로 제조된 다기능 실리콘 질화물 박막의 조성이 전기적 특성에 미치는 영향
금기수 ( Ki Su Keum ),황재담 ( Jae Dam Hwang ),김주연 ( Joo Youn Kim ),홍완식 ( Wan Shick Hong ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.4
Electrical properties as a function of composition in silicon nitride (SiNx) films grown at low temperatures (<200℃) were studied for applications to photonic devices and thin film transistors. Both siliconrich and nitrogen-rich compositions were successfully produced in final films by controlling the source gas mixing ratio, R=[(N2 or NH3)/SiH4], and the RF plasma power. Depending on the film composition, the dielectric and optical properties of SiNx films varied substantially. Both the resistivity and breakdown field strength showed the maximum value at the stoichiometric composition (N/Si=1.33), and degraded as the composition deviated to either side. The electrical properties degraded more rapidly when the composition shifted toward the silicon-rich side than toward the nitrogen-rich side. The composition shift from the siliconrich side to the nitrogen-rich side accompanied the shift in the photoluminescence characteristic peak to a shorter wavelength, indicating an increase in the band gap. As long as the film composition is close to the stoichiometry, the breakdown field strength and the bulk resistivity showed adequate values for use as a gate dielectric layer down to 150℃ of the process temperature.
Single ZnO Nanowire Inverter Logic Circuits on Flexible Plastic Substrates
강정민(Jeongmin Kang),이명원(Myeongwon Lee),구상모(Sang-Mo Koo),홍완식(Wan-Shick Hong),김상식(Sangsig Kim) 대한전기학회 2010 전기학회논문지 Vol.59 No.2
In this study, inverter logic circuits on a plastic substrate are built with two top-gate FETs in series on a single ZnO nanowire. The voltage transfer characteristics of the ZnO nanowire-based inverter logic circuit exhibit a clear inverting operation. The logic swing, gain and transition width of the inverter logic circuit is about 90 %, 1.03 and 1.2 V, respectively. The result of mechanical bending cycles of the inverter logic circuit on a plastic substrate shows that the stable performance is maintained even after many hundreds of bending cycles.
과량의 N2에 희석된 SiH4 가스를 이용한 150℃ 저온 PECVD 실리콘 질화물 박막의 물성이 TFT 소자 특성에 미치는 영향
노길선 ( Kil Sun No ),금기수 ( Ki Su Keum ),홍완식 ( Wan Shick Hong ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.3
We report on the electrical properties of silicon nitride (SiNX) films deposited at 150℃ from highly diluted SiH4 in N2 by a plasma enhanced chemical vapor deposition (PECVD) method. The films were also prepared below 200℃ for comparison. Although the N2 dilution gas acted as a source of nitrogen atoms inside the SiNX film, it was necessary to introduce NH3 to obtain good dielectric quality in the low-temperature films. An amount of NH3 equal to the net SiH4 in the gas mixture was found to be adequate, and further addition of NH3 resulted in little improvement. For SiNX films deposited at 150℃, the NH3 addition decreased the C-V hysteresis (△Vth) from 15 V to 3 V, and increased the resistivity and the breakdown field strength from 109 Ωcm and 4 MV/cm to 1013 Ωcm and 7 MV/cm, respectively. When these films were applied as a gate dielectric layer, the resulting TFT prepared at 150℃ showed an on/off current ratio higher than 105, a threshold voltage of 1.1 V, a subthreshold slope of 1.2 V/dec, and a field effect mobility of 0.04 cm2/Vsec. Under a dc bias stress of VD = VG = 25 V, the on-current of this TFT was stable over a period of 5000 seconds.