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스퍼터링 공정 압력이 InZnO 박막트랜지스터의 광학 및 전기적 특성에 미치는 영향
박지민,김형도,장성철,김현석,Park, Ji-Min,Kim, Hyoung-Do,Jang, Seong Cheol,Kim, Hyun-Suk 한국재료학회 2020 한국재료학회지 Vol.30 No.4
Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30㎠/Vs) and large on/off ratio.
Park, Jae Chul,Lee, Ho-Nyeon,Im, Seongil American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.15
<P>Thin-film transistor (TFT) is a key component of active-matrix flat-panel displays (AMFPDs). These days, the low-temperature poly silicon (LTPS) TFTs are to match with advanced AMFPDs such as the active matrix organic light-emitting diode (AMOLED) display, because of their high mobility for fast pixel switching. However, the manufacturing process of LTPS TFT is quite complicated, costly, and scale-limited. Amorphous oxide semiconductor (AOS) TFT technology is another candidate, which is as simple as that of conventioanl amorphous (a)-Si TFTs in fabrication but provides much superior device performances to those of a-Si TFTs. Hence, various AOSs have been compared with LTPS for active channel layer of the advanced TFTs, but have always been found to be relatively inferior to LTPS. In the present work, we clear the persistent inferiority, innovating the device performaces of a-IZO TFT by adopting a self-aligned coplanar top-gate structure and modifying the surface of a-IZO material. Herein, we demonstrate a high-performance simple-processed a-IZO TFT with mobility of ∼157 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>, SS of ∼190 mV dec<SUP>–1</SUP>, and good bias/photostabilities, which overall surpass the performances of high-cost LTPS TFTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-15/am401128p/production/images/medium/am-2013-01128p_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am401128p'>ACS Electronic Supporting Info</A></P>
Amorphous In-Ga-Zn-O Transparent Thin-film Transistors Prepared by Using a Combinatorial Approach
주홍렬,Joonchul Moon,신용수,이기용,임영철,Sanghui Kim,Changwoo Park 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4
Transparent thin-film transistors (TTFTs) with amorphous InGaZnO (a-IGZO) channels have ben prepared by using a combinatorial thin-film synthesis approach. The In composition ratio, In(%)[= In×10 In+Zn+Ga(%)], of the channel of the TTFTs varied with position from 50% to 85%. This alowed us to study TTFTs characteristics as a function of channel composition. The mobility, the on-off ratio and the threshold voltage of the TTFTs varied from 0.2 cm/V·s to 13 cm/V·s, 3 × 100 to 8 × 107 and -24 to 20 V, respectively. The TTFT with In(%) = 60 % showed a mobility as high as 13 cm/V·s with an on-off ratio of 5.8 × 107 and a threshold voltage of 14 V.
Byung Du Ahn,Hyun-Suk Kim,You Seung Rim,Jin-Seong Park,Hyun Jae Kim Institute of Electrical and Electronics Engineers 2014 IEEE transactions on electron devices Vol. No.
<P>The effects of oxygen high-pressure annealing (O<SUB>2</SUB> HPA) on the performance and instability of amorphous Ge-In-Ga-O (a-GIGO) thin-film transistors (TFTs) were examined. The TFTs with HPA under 30 atm O<SUB>2</SUB> ambient exhibited consistently better stability against the applied temperature stress and positive gate bias stress. We demonstrate that the superior stability of the HPA-treated device can be correlated with the evolution of electronic structure in a-GIGO thin films, as measured by spectroscopic ellipsometry, which reveals the significantly reduced band edge states below the conduction band by the O<SUB>2</SUB> HPA treatment. Based on the Meyer-Neldel rule, the total density of subgap states energy distribution, including the interfacial and semiconductor bulk trap densities, was also extracted and compared, which can support the experimental observation.</P>
신지훈,최덕균 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4
To investigate the effect of oxygen on the optical and the electrical properties of amorphous InGaZnO (a-IGZO), we prepared thin lms by RF magnetron sputtering in various oxygen atmospheres at room temperature and the thin-film transistors (TFTs) were evaluated. The oxygen concentration during the deposition process affected both the optical band-gap and the mobility of a IGZO-based devices. As the oxygen concentration in the processing chamber during deposition was increased, the optical band-gap and the saturation mobility decreased concurrently. The highest optical band-gap and the best device performance were obtained from the a-IGZO film deposited in an atmosphere of 10 % oxygen. The a-IGZO lm deposited at this condition exhibited an optical band-gap of 3.29 eV and the transistors fabricated with this film revealed a saturation mobility of 2.6 cm2/Vs, a subthreshold swing of 0.93 V/decade, an on-off current ratio of 107 and a threshold voltage of 13.9 V.
Long Life-Time Amorphous-InGaZnO TFT-Based Shift Register Using a Reset Clock Signal
Hoon Jeong,Byung Kook Choi,Hoon-Ju Chung,Sang Gul Lee,Yong Min Ha,Jin Jang IEEE 2014 IEEE electron device letters Vol.35 No.8
<P>We report a long life-time shift register (SR) made of amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The life-time of an SR is determined by the stability of the pull-down TFT, which is always under positive bias stress (PBS). To compensate for the nonrecovering characteristic of a-IGZO TFTs, the gate ON time of the pull-down TFT is reduced from 50% to 5% duty ratio by introducing a reset clock signal. By fitting the TFT's PBS-induced threshold voltage shifts to stretched exponentials, the life-time of the SR is estimated to increase from 1.7 to 17.5 years, owing to the reset clock signal with short-term duty.</P>
Jaewook Jeong,Joonwoo Kim,Soon Moon Jeong Institute of Electrical and Electronics Engineers 2014 IEEE transactions on electron devices Vol. No.
<P>In this paper, we investigated the variations in electrical characteristics of amorphous indium-gallium-zinc-oxide thin-film transistors using a gated-multiprobe method when additional probe electrodes are on the back-channel region. We found that the resistance of the probe region is much smaller than that of the nonprobe region, which can be modeled by a series connection of transistors and resistors indicating that the probe region is independent of V<SUB>GS</SUB> and induces a decrease in effective channel length. We also performed technology computer aided design (TCAD) simulations and found that the effective channel length decreases and drain current increases, which is consistent with the experiments.</P>
Tae Soo Jung,Si Joon Kim,Chul Ho Kim,Joohye Jung,Jaewon Na,Sabri, Mardhiah Muhamad,Hyun Jae Kim Institute of Electrical and Electronics Engineers 2015 IEEE transactions on electron devices Vol. No.
<P>Germanium (Ge) doping effects on solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs) were investigated. Ge doping increased the carrier concentration of Ge-doped IZO (Ge: IZO) thin films from 3.32 x 10(14) to 3.13 x 10(15) cm(3) by Ge substitution for zinc (Zn). Ge easily substituted for Zn in the IZO active layer, due to its comparably small atomic radius. By this substitution, Ge doping provided additional valence electrons to the active layer, resulting in a value for the field-effect mobility of a Ge: IZO TFT that was almost two times greater than that of a pristine IZO TFT. Consequently, despite the Ge: IZO TFT being a quaternary system, it displayed a better electrical performance and stability at low processing temperatures, thus demonstrating the feasibility of this device for flexible displays.</P>
Solution-Processed Al<sub>2</sub>O<sub>3</sub> 확산층을 이용한 Sputtering IZO Thin Film Transistor의 안정성 향상
황남경,임유성,이정석,이세형,이문석,Hwang, Namgyung,Lim, Yooseong,Lee, Jeong Seok,Lee, Sehyeong,Yi, Moonsuk 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.5
This research introduces the sputtered IZO thin film transistor (TFT) with solution-processed $Al_2O_3$ diffusion layer. IZO is one of the most commonly used amorphous oxide semiconductor (AOS) TFT. However, most AOS TFTs have many defects that degrade performance. Especially oxygen vacancy in the active layer. In previous research, aluminum was used as a carrier suppressor by binding the oxygen vacancy and making a strong bond with oxygen atoms. In this paper, we use a solution-processed $Al_2O_3$ diffusion layer to fabricate stable IZO TFTs. A double-layer solution-processed $Al_2O_3$-sputtered IZO TFT showed better performance and stability, compared to normal sputtered IZO TFT.
홍성환,박정우,김희준,김영규,김현재 한국정보디스플레이학회 2016 Journal of information display Vol.17 No.3
In this review, the multi-stacked active-layer (MSAL) structures for the solution-processed amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) are summarized to improve their electrical characteristics and stabilities based on the authors’ previous researches. The MSAL structures can overcome an inherent weakness of the solution-processed AOS TFTs, which is the creation of porosities from solvent volatilization. Furthermore, by modifying each layer, the performance and reliability of the solution-processed AOS TFTs could be improved more. Here, the fundamental studies of MSAL structures with homo-stacked active-layer TFTs are presented, and the various modulations of active layers in hetero-stacked active-layer TFTs are covered. In addition, the effect of the interface between the stacked layers is also discussed.