• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.202-202
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• 2010

불순물이 첨가되는 이원계 및 다원계 투명전도성 산화막들은 불순물의 첨가량에 따라서 전기적 그리고 광학적 특성의 변화를 나타낸다. 조성비에 따른 특성 변화를 조사하기 위하여 산화아연 타겟과 산화갈륨 타겟을 이용하여 혼합 스퍼터링 방식을 이용하여 인듐, 갈륨 등이 소량 첨가된 산화아연막(IGZO)을 증착하였다. Triple Co-sputter의 인가 전력을 변화시켜 가면서 박막 구성 원소들의 성분비 변화에 따른 전기적 그리고 광학적 특성을 조사하였다. 증착된 박막들은 조성비에 따라 전기적 그리고 광학적 특성이 변화되는 것을 확인하였다. 실온에서 유리기판 위에 증착된 박막은 저항률이 $2^*10^{-3}\;{\Omega}-cm$의 전기적 특성을 보였고, 투과도가 400~800nm 파장 범위 내에서 80% 이상의 광학적 특성을 보였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.207-208
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• 2012

GZO( Ga-doped ZnO) 및 ZTO (zinc tin Oxide) 박막을 DC, RF magnetron sputtering 공정을 이용하여 증착한 후, 대기 및 진공상태에서 200, $300^{\circ}C$ 조건으로 30분 동안 열처리하였다. ZTO/GZO 박막의 전기적 특성은 ZTO 층과 GZO 층의 두께 비에 의존함을 확인 할 수 있었다. 본 연구에서는 GZO단일 박막과 ZTO/GZO double layer 박막의 열처리 온도에 따른 구조적, 전기적, 광학적 특성을 비교검토 하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2016년도 임시총회 및 하계학술연구발표회
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• pp.133-133
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• 2016

• 대한전자공학회논문지SD
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• 제42권1호
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• pp.9-17
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• 2005

공진주파수 스펙트럼법을 이용하여 ZnO 와 AIN 압전박막의 임피던스 특성 및 전기기계결합계수 특성에 대해 조사하였다. 압전박막의 두께가 얇을수록 전체적인 임피던스 응답 피크의 크기가 감소하였으며, 기판의 두께가 얇을수록 응답 피크의 모드 수가 감소하는 것이 관찰되었다. 입력 Kt² 값으로부터 평가된 Kt² 값을 통해 압전박막의 두께보다 기판의 두께 변화에 대한 영향이 더 큼을 알 수 있었고, 기판의 acoustic 임피던스에 의해서도 Kt² 값이 감소함을 알 수 있었다. 전극 효과가 첨가되면 임피던스 응답 피크의 크기가 감소하였으며, 전극의 acoustic 임피던스가 커짐에 따라 응답피크는 더 작아졌다. 공진주파수 스펙트럼법에서 전극은 질량부하로 고려되기 때문에 전극 효과가 첨가된 경우 Keff² 값은 증가하며, 전극의 acoustic 임피던스가 크면 그 효과는 더 커졌다. 공진주파수 스펙트럼법을 이용한 시뮬레이션을 통해 기판, 압전체, 전극으로 이루어진 composite 공진기의 특성 분석과 설계까지도 가능함을 알 수 있었다.

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

• Transactions on Electrical and Electronic Materials
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• 제18권1호
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• pp.55-57
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• 2017

Amorphous oxide thin film transistors (TFTs) were fabricated with 0.5 wt% silicon doped zinc tin oxide (a-0.5SZTO) thin film deposited by radio frequency (RF) magnetron sputtering. In order to investigate the effect of annealing treatment on the electrical properties of TFTs, a-0.5SZTO thin films were annealed at three different temperatures ($300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$ for 2 hours in a air atmosphere. The structural and electrical properties of a-0.5SZTO TFTs were measured using X-ray diffraction and a semiconductor analyzer. As annealing temperature increased from $300^{\circ}C$ to $500^{\circ}C$, no peak was observed. This provided crystalline properties indicating that the amorphous phase was observed up to $500^{\circ}C$. The electrical properties of a-0.5SZTO TFTs, such as the field effect mobility (${\mu}_{FE}$) of $24.31cm^2/Vs$, on current ($I_{ON}$) of $2.38{\times}10^{-4}A$, and subthreshold swing (S.S) of 0.59 V/decade improved with the thermal annealing treatment. This improvement was mainly due to the increased carrier concentration and decreased structural defects by rearranged atoms. However, when a-0.5SZTO TFTs were annealed at $700^{\circ}C$, a crystalline peak was observed. As a result, electrical properties degraded. ${\mu}_{FE}$ was $0.06cm^2/Vs$, $I_{ON}$ was $5.27{\times}10^{-7}A$, and S.S was 2.09 V/decade. This degradation of electrical properties was mainly due to increased interfacial and bulk trap densities of forming grain boundaries caused by the annealing treatment.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.466-468
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• 2012

Amorphous InGaZnO (${\alpha}$-IGZO) thin-film transistors (TFTs) are are very promising due to their potential use in thin film electronics and display drivers [1]. However, the stability of AOS-TFTs under the various stresses has been issued for the practical AOSs 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 ${\alpha}$-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 ${\alpha}$-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 ${\alpha}$-IGZO thin film. In this paper, we have confirmed that the NOIs accelerated by the self-bias were one of the dominant causes of instability in ${\alpha}$-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 ${\alpha}$-IGZO TFTs by this new deposition method.

• 한국진공학회지
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• 제21권3호
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• pp.142-150
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• 2012

CIGS 박막 태양전지 기판소재인 소다라임유리 표면에 플라즈마 전처리 후 DC 마그네트론 스퍼터링 방법으로 Mo 박막을 제조하였다. 증착압력과 증착시간 변화에 따른 Mo 박막의 물리적, 전기적 특성을 분석하였고, 셀렌화 처리 조건에 따른 $MoSe_2$ 생성 여부와 경향성을 연구하였으며, Mo 박막 두께에 따른 AZO/i-ZnO/CdS/CIGS/Mo/SLG 구조의 태양전지를 제조하여 그 특성을 분석 및 평가하였다. 증착압력이 4.9 mTorr에서 1.3 mTorr로 감소할수록 치밀하고 결정입자 사이의 공극이 적고, 증착속도가 감소하고 전기저항도가 낮은 Mo 박막이 증착되었다. 증착온도가 상온에서 $200^{\circ}C$로 증가할수록 Mo 박막은 치밀한 구조를 가지고 결정성은 향상되어 면저항이 낮게 나타났다. 셀렌화 시간이 길어질수록 Mo 박막 층은 줄어들고, $MoSe_2$ 층 생성두께가 커지는 것을 알 수 있었고, 열처리로 인해 결정화 되면서 전체 박막의 두께가 줄어들었으며, $MoSe_2$ 층의 배양성은 c축이 Mo 표면과 수직 방향으로 성장된 것을 알 수 있었다. Mo 박막의 두께가 1.2 ${\mu}m$와 0.6 ${\mu}m$인 AZO/i-ZnO/CdS/CIGS/Mo/SLG 구조로 이루어진 CIGS 박막 태양전지를 제조하였다. Mo 박막의 두께가 1.2 ${\mu}m$일 때 보다 0.6 ${\mu}m$일 때 CIGS 박막 태양전지의 변환 효율은 9.46%로 비교적 우수한 특성을 나타났다. CIGS 박막 태양전지에서 하부전극인 Mo 박막 특성은 유리기판 및 광흡수 층과의 계면 형성 따라 큰 영향을 미친다는 것을 알 수 있었고, 유리기판의 플라즈마 처리와 Mo 박막의 두께조절로 Na 효과 및 $MoSe_2$층 형성 제어함으로써 CIGS 박막 태양전지의 특성 개선에 효과를 가질 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.324-326
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• 2016

In this study, we have investigated indium tin zinc oxide (ITZO) as an active channel for non-volatile memory (NVM) devices. The electrical and memory characteristics of NVM devices using multi-stack gate insulator SiO2/SiOx/SiOxNy (OOxOy) with Si-rich SiOx for charge storage layer were also reported. The transmittance of ITZO films reached over 85%. Besides, ITZO-based NVM devices showed good electrical properties such as high field effect mobility of 25.8 cm2/V.s, low threshold voltage of 0.75 V, low subthreshold slope of 0.23 V/dec and high on-off current ratio of $1.25{\times}107$. The transmission Fourier Transform Infrared spectroscopy of SiOx charge storage layer with the richest silicon content showed an assignment at peaks around 2000-2300 cm-1. It indicates that many silicon phases and defect sources exist in the matrix of the SiOx films. In addition, the characteristics of NVM device showed a retention exceeding 97% of threshold voltage shift after 104 s and greater than 94% after 10 years with low operating voltage of +11 V at only 1 ms programming duration time. Therefore, the NVM fabricated by high transparent ITZO active layer and OOxOy memory stack has been applied for the flexible memory system.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.52-52
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• 2018

Only approximately 30% of fossil fuel energy is used; therefore, it is desirable to utilize the huge amounts of waste energy. Thermoelectric (TE) materials that convert heat into electrical power are a promising energy technology. The TE materials can be formed either as thin films or as bulk semiconductors. Generally, thin-film TE materials have low energy conversion rates due to their thinness compared to that in bulk. However, an advantage of a thin-film TE material is that the efficiency can be smartly engineered by controlling the nanostructure and composition. Especially nanostructured TE thin films are useful for mitigating heating problems in highly integrated microelectronic devices by accurately controlling the temperature. Hence, there is a rising interest in thin-film TE devices. These devices have been extensively investigated. It is demonstrated that transparent amorphous oxide semiconductors (TAOS) can be excellent thermoelectric (TE) materials, since their thermal conductivity (${\kappa}$) through a randomly disordered structure is quite low, while their electrical conductivity and carrier mobility (${\mu}$) are high, compared to crystalline semiconductors through the first-principles calculations and the various measurements for the amorphous In-Zn-O (a-IZO) thin film. The calculated phonon dispersion in a-IZO shows non-linear phonon instability, which can prevent the transport of phonon. The a-IZO was measured to have poor ${\kappa}$ and high electrical conductivity compared to crystalline $In_2O_3:Sn$ (c-ITO). These properties show that the TAOS can be an excellent thin-film transparent TE material. It is suggested that the TAOS can be employed to mitigate the heating problem in the transparent display devices.