• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.208.2-208.2
• /
• 2015

최근 산화물 반도체에 대한 연구가 활발하게 이루어지고 있다. 비정질 산화물 반도체인 In-Ga-Zn-O(IGZO)는 기존의 비정질 실리콘에 비해 공정 단가가 낮으며 넓은 밴드 갭으로 인한 투명성을 가지고 있고, 저온 공정이 가능하여 다양한 기판에 적용이 가능하다. 반도체의 공정 과정에서 열처리는 소자의 특성 개선을 위해 필요하다. 일반적인 열처리 방법으로 furnace 열처리 방식이 주로 이용된다. 그러나 furnace 열처리는 시간이 오래 걸리며 일반적으로 고온에서 이루어지기 때문에 최근 연구되고 있는 유리나 플라스틱, 종이 기판을 이용한 소자의 경우 기판이 손상을 받는 단점이 있다. 이러한 단점들을 극복하기 위하여 저온 공정인 마이크로웨이브를 이용한 열처리 방식이 제안되었다. 마이크로웨이브 열처리 기술은 소자에 에너지를 직접적으로 전달하기 때문에 기존의 다른 열처리 방식들과 비교하여 에너지 전달 효율이 높다. 또한 짧은 공정 시간으로 공정 단가를 절감하고 대량생산이 가능한 장점을 가지고 있으며, 저온의 열처리로 기판의 손상이 없기 때문에 기판의 종류에 국한되지 않은 공정이 가능할 수 있을 것으로 기대된다. 따라서 본 연구에서는 마이크로웨이브 열처리가 소자의 전기적 특성 개선에 미치는 영향을 확인하였다. 제작된 IGZO 박막 트렌지스터는 p-type bulk silicon 위에 thermal SiO2 산화막이 100 nm 형성된 기판을 사용하였다. RCA 클리닝을 진행한 후 RF sputter를 사용하여 In-Ga-Zn-O (1:1:1) 을 70 nm 증착하였다. 이후에 Photo-lithography 공정을 통하여 active 영역을 형성하였고, 전기적 특성 평가가 용이한 junctionless 트랜지스터 구조로 제작하였다. 후속 열처리 방식으로 마이크로웨이브 열처리를 1000 W에서 2분간 실시하였다. 그리고 기존 열처리 방식과의 비교를 위해 furnace를 이용하여 N2 가스 분위기에서 $600^{\circ}C$의 온도로 30분 동안 열처리를 실시하였다. 그 결과, 마이크로웨이브 열처리를 한 소자의 경우 기존의 furnace 열처리 소자와 비교하여 우수한 전기적 특성을 나타내는 것을 확인하였다. 따라서 마이크로웨이브를 이용한 열처리 공정은 향후 저온 공정을 요구하는 소자 공정에 활용될 수 있을 것으로 기대된다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.160-160
• /
• 2015

InGaZnO (IGZO) thin-film transistors (TFTs) are very promising due to their potential use in high performance display backplane [1]. However, the stability of IGZO TFTs under the various stresses has been issued for the practical IGZO applications [2]. Up to now, many researchers have studied to understand the sub-gap density of states (DOS) as the root cause of instability [3]. Nomura et al. reported that these deep defects are located in the surface layer of the IGZO channel [4]. Also, Kim et al. reported that the interfacial traps can be affected by different RF-power during RF magnetron sputtering process [5]. It is well known that these trap states can influence on the performances and stabilities of IGZO TFTs. Nevertheless, it has not been reported how these defect states are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOI) can be generated by electron attachment in oxygen atom near target surface and accelerated up to few hundreds eV by self-bias of RF magnetron sputter; the high energy bombardment of NOIs generates bulk defects in oxide thin films [6-10] and can change the defect states of IGZO thin film. In this study, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in IGZO TFTs when the channel layer was deposited by conventional RF magnetron sputtering system. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process [9-10] to eliminate the NOI bombardment effects and present how much to be improved the instability of IGZO TFTs by this new deposition method.

• Bulletin of the Korean Chemical Society
• /
• 제28권10호
• /
• pp.1751-1755
• /
• 2007

The interaction of ammonium hydroxide (NH4OH) with zircaloy-4 (Zry-4) was investigated using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) methods. In order to study the surface chemistry of NH4OH/Zry-4 system, the binding energies of N1s, O1s and Zr3d electrons were monitored. The N1s peak intensity was remarkably increased by following cycles of Ar+ sputtering of NH4OH dosed Zry-4 surface at room temperature. Because the nitrogen stayed under the subsurface region was diffused out onto the Zry-4 surface after oxygen concentration was decreased. These could be occurred after the surface oxygen was diffused into the bulk or desorbed out from the surface until Ar+ fluence was 6.0 × 1016 Ar+/cm2 then the surface was relatively atomic deficient state. The O1s peak intensity was decreased by stepwise Ar+ sputtering. After many cycles of Ar+ sputtering, the peak intensities of Zr3d peaks did not change much but the shape of the peak clearly did change. This implies that the oxidation state of zirconium was changed during stepwise Ar+ sputtering of NH4OH/Zry-4. The Zr3d peak intensity of zirconium nitride (ZrNx) increased as the intensity of N1s (from zirconium nitride) increased but the Zr3d peak intensity of zirconium oxide (ZrOx) decreased due to the depopulation of the oxygen species on the surface region. We also observed that the peak intensity of Zr4+ was nearly same after Ar+ sputtering processes but the peak intensity of metallic zirconium increased compared to that of before the sputtering process was performed.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제1권2호
• /
• pp.95-102
• /
• 2001

Hafnium oxide thin films for gate dielectric were deposited at $300^{\circ}C$ on p-type Si (100) substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed in $O_2$ and $N_2$ ambient at various temperatures. The effect of hydrogen treatment in 4% $H_2$ at $350^{\circ}C$ for 30 min on the electrical properties of $HfO_2$for gate dielectric was investigated. The flat-band voltage shifts of $HfO_2$capacitors annealed in $O_2$ambient are larger than those in $N_2$ambient because samples annealed in high oxygen partial pressure produces the effective negative charges in films. The oxygen loss in $HfO_2$films was expected in forming gas annealed samples and decreased the excessive oxygen contents in films as-deposited and annealed in $O_2$ or $N_2$ambient. The CET of films after hydrogen forming gas anneal almost did not vary compared with that before hydrogen gas anneal. Hysteresis of $HfO_2$films abruptly decreased by hydrogen forming gas anneal because hysteresis in C-V characteristics depends on the bulk effect rather than $HfO_2$/Si interface. The lower trap densities of films annealed in $O_2$ambient than those in $N_2$were due to the composition of interfacial layer becoming closer to $SiO_2$with increasing oxygen partial pressure. Hydrogen forming gas anneal at $350^{\circ}C$ for samples annealed at various temperatures in $O_2$and $N_2$ambient plays critical role in decreasing interface trap densities at the Si/$SiO_2$ interface. However, effect of forming gas anneal was almost disappeared for samples annealed at high temperature (about $800^{\circ}C$) in $O_2$ or $N_2$ambient.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.131-131
• /
• 2009

Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility ($\sim900cm^2/Vs$). These electronic properties allow high breakdown voltage, high-speed switching capability, and high temperature operation compared to Si devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances, the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. This paper studies different channel dimensons ($L_{CH}$ : $0.5{\mu}m$, $1\;{\mu}m$, $1.5\;{\mu}m$) and their effect on the the device transient characteristics. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship. with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. We observe an increase in the turn-on and turn-off time with increasing the channel length. The switching time in 4H-SiC DMOSFETs have been found to be seriously affected by the various intrinsic parasitic components, such as gate-source capacitance and channel resistance. The intrinsic parasitic components relate to the delay time required for the carrier transit from source to drain. Therefore, improvement of switching speed in 4H-SiC DMOSFETs is essential to reduce the gate-source capacitance and channel resistance.

• 한국방재학회 논문집
• /
• 제8권5호
• /
• pp.23-33
• /
• 2008

최근 국내에서 케이블을 이용한 Extradosed 교 형식의 대교들이 건설되고 있다. 이러한 교량에서 자동차 충돌등으로 인한 화재에 의해 교량이 손상을 입는 사고가 발생되고 있어 화재에 대한 안정성해석이 필요하다. 본 연구에서는 케이블 교량형식 중 최근 국내에서 사용빈도가 높은 Extradosed 교 형식을 해석모델로 하였으며, 상용소프트웨어인 Solid Works 2007을 사용하여 모델링하고, COSMOS FloWorks 2007소프트웨어에 의한 열전달 해석 및 열응력 해석을 통하여 교량위 화재 발생시 와이어, 사재방재 파이프 및 그 주변에 대한 열유동 해석 및 사재방재 케이블의 안전을 검토하였다. 열원의 온도가 일정한 경우에 대해 다음 3개의 중요변수를 해석변수로 사용하였다. : (1)방호책과 열원사이의 거리, (2)풍속, (3) 스테인레스 강관의 끝단의 높이.

• 대한전자공학회논문지
• /
• 제18권4호
• /
• pp.49-61
• /
• 1981

N+P, N+PP+ 형 태양전지를 제조하여 얻은 실험자료들을 근거로 실리콘 접합형 태양전지에 일반적으로 적용할 수 있는 컴퓨터 모의 실험 프로그램을 개발하고, 이의 유용성을 확인하였다. 이 모의 실험 프로그램은 N+P, P+N, N+PP+, P+NN+형의 실리콘 태양전지에 적용할 수 있는 것으로, 입사광은 AMI, 등강도 광원, 인공조명으로 많이 사용되는 GE -ELH 광원이고, AR코팅은 Si3N4형과 투과도가 파장에 관계없는 일정형 2종류가 있으며, 프로그램에서 이들 전지의 구조, 광원, AR 코팅 종류에 대한 파장 특성분포도 쉽게 변화시킬 수 있도록 되어 있다. 이 모의실험의 결과들을 토대로 N+와 P 영역에서의 평균도오핑농도와 전지의 두께, AMI 스펙트럼에 대한 집광도, 앞면 접합깊이에 대하여 효율이 최대가 되는 최적치들을 구하였으며, 앞면의 표면 재결합 속도, 접합부에서의 캐리어의 유효 수명, 누설저항에 대하여는 허용 한계치로, 기타 효율변화인자로서 동작온도 직렬저항과 전기장의 세기에 대하여는 효율의 변화율로서 파라미터들이 효율에 미치는 영향들을 분석하였다.

• 한국표면공학회지
• /
• 제38권1호
• /
• pp.1-6
• /
• 2005

Ni-15at.% W coatings with film thicknesses of 20-40 ㎛ were electroplated on a steel substrate, and their oxidation behavior was investigated at 700 and 800℃ in air. For comparison, a pure Ni coating and a bulk Ni were also oxidized. The Ni-15at.%W coating displayed the worst oxidation resistance, due to the formation of less-protective NiO, Fe₂O₃, NiFe₂O₄ and NiWO₄. The corrosion behavior Ni-15at.%W coatings electroplated on a steel substrate was similarly investigated at 700 and 800℃ in the Ar-l%SO₂ atmosphere. For comparison, the uncoated steel substrate was also corrosion-tested in the Ar-l %SO₂ atmosphere. Severe scale spallation and the internal corrosion of the steel that occurred in the uncoated substrate were not observed in the coated specimen. However, it seemed that the Ni-15at.%W coating cannot be a potential candidate as a sulfidation-resistant coating, due to the formation of less-protective NiO, NiS, WO₃ and NiWO₄.

• 한국결정성장학회지
• /
• 제24권3호
• /
• pp.127-132
• /
• 2014

$Y_2O_3$-BN 세라믹 복합체를 제작하기 위해서, 분말 입도 $3{\sim}10{\mu}m$인 $Y_2O_3$ 분말을 분산한 슬러리에 pH 조절제인 NaOH를 첨가하였으며 결합제로는 PVA, 가소제로는 PEG를, BN 분말과 혼합하고, 분무건조(spray drying)공정을 거쳐 $Y_2O_3$ 혼합 분말을 제조하였다. ${\O}14mm$ 크기의 $Y_2O_3$-BN 시편을 성형하고, $1550^{\circ}C$ 및 $1600^{\circ}C$에서 소결하여 $Y_2O_3$-BN 복합체를 제작하였다. BN 투입량과 소결온도의 변수에 따른 미세구조, 순도, 꺽임강도, 열팽창계수, 밀도, 체적저항, 내플라즈마 특성을 조사하였다.

• 한국세라믹학회지
• /
• 제50권2호
• /
• pp.157-162
• /
• 2013

The need for lead-free piezoceramics has caused a renewal of interest in $BaTiO_3$-based systems. Recently, it was found that ceramics in the $(Ba,Ca)(Zr,Ti)O_3$ system have properties comparable to those of $Pb(Zr,Ti)O_3$. However, these ceramics require rather high sintering temperatures of $1450-1550^{\circ}C$. In this work, the effect of $TiO_2$ and CuO addition on the sintering behavior, microstructure, dielectric and piezoelectric properties of $(Ba_{0.85}Ca_{0.15})(Zr_{0.1}Ti_{0.9})O_3$ (BCTZ) ceramics will be discussed. BCTZ ceramics were prepared by the mixed oxide route and 1 mol % of $TiO_2$ or CuO was added. Undoped and doped ceramics were sintered at $1350^{\circ}C$ for 1-5 h. CuO was found to be a very effective sintering aid, with samples sintered for 1 h at $1350^{\circ}C$ having a bulk density of 95% theoretical density; however the piezoelectric properties were greatly reduced, probably due to the small grain size.