• Title/Summary/Keyword: Oxide thin film transistors

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Hybrid Insulator Organic Thin Film Transistors With Improved Mobility Characteristics

  • Park, Chang-Bum;Jin, Sung-Hun;Park, Byung-Gook;Lee, Jong-Duk
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07b
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    • pp.1291-1293
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    • 2005
  • Hybrid insulator pentacene thin film transistors (TFTs) were fabricated with thermally grown oxide and cross-linked polyvinylalcohol (PVA) including surface treatment by dilute ploymethylmethacrylate (PMMA) layers on $n^+$ doped silicon wafer. Through the optimization of $SiO_2$ layer thickness in hybrid insulator structure, carrier mobility was increased to above 35 times than that of the TFT only with the gate insulator of $SiO_2$ at the same transverse electric field. The carrier mobility of 1.80 $cm^2$/V-s, subthreshold swing of 1.81 V/decade, and $I_{on}$/ $I_{off}$ current ratio > 1.10 × $10^5$ were obtained at low bias (less than -30 V) condition. The result is one of the best reported performances of pentacne TFTs with hybrid insulator including cross-linked PVA material at low voltage operation.

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Solution-Processed Inorganic Thin Film Transistors Fabricated from Butylamine-Capped Indium-Doped Zinc Oxide Nanocrystals

  • Pham, Hien Thu;Jeong, Hyun-Dam
    • Bulletin of the Korean Chemical Society
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    • v.35 no.2
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    • pp.494-500
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    • 2014
  • Indium-doped zinc oxide nanocrystals (IZO NCs), capped with stearic acid (SA) of different sizes, were synthesized using a hot injection method in a noncoordinating solvent 1-octadecene (ODE). The ligand exchange process was employed to modify the surface of IZO NCs by replacing the longer-chain ligand of stearic acid with the shorter-chain ligand of butylamine (BA). It should be noted that the ligand-exchange percentage was observed to be 75%. The change of particle size, morphology, and crystal structures were obtained using a field emission scanning electron microscope (FE-SEM) and X-ray diffraction pattern results. In our study, the 5 nm and 10 nm IZO NCs capped with stearic acid (SA-IZO) were ligand-exchanged with butylamine (BA), and were then spin-coated on a thermal oxide ($SiO_2$) gate insulator to fabricate a thin film transistor (TFT) device. The films were then annealed at various temperatures: $350^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$, and $600^{\circ}C$. All samples showed semiconducting behavior and exhibited n-channel TFT. Curing temperature dependent on mobility was observed. Interestingly, mobility decreases with the increasing size of NCs from 5 to 10 nm. Miller-Abrahams hopping formalism was employed to explain the hopping mechanism insight our IZO NC films. By focusing on the effect of size, different curing temperatures, electron coupling, tunneling rate, and inter-NC separation, we found that the decrease in electron mobility for larger NCs was due to smaller electronic coupling.

Effects of Hydrogen Injection by In-Situ and Plasma Post-Treatment on Properties of a ZnO Channel Layer in Transparent Thin Film Transistors (증착시 및 플라즈마 후처리에 의한 수소 주입이 투명 박막 트랜지스터에서 산화아연 채널층의 물성에 미치는 영향)

  • Bang, Jung-Hwan;Kim, Won;Uhm, Hyun-Seok;Park, Jin-Seok
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.1
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    • pp.35-40
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    • 2010
  • We have investigated the effects of hydrogen injection via in-situ gas addition ($O_2$, $H_2$, or $O_2$ + $H_2$ gas) and plasma post-treatment (Ar or Ar + H plasma) on material properties of ZnO that is considered to be as a channel layer in transparent thin film transistors. The variations in the electrical resistivity, optical transmittance and bandgap energy, and crystal quality of ZnO thin films were characterized in terms of the methods and conditions used in hydrogen injection. The resistivity was significantly decreased by injection of hydrogen; approximately $10^6\;{\Omega}cm$ for as-grown, $1.2\;{\times}\;10^2\;{\Omega}cm$ for in-situ with $O_2/H_2\;=\;2/3$ addition, and $0.1\;{\Omega}cm$ after Ar + H plasma treatment of 90 min. The average transmittance of ZnO films measured at a wavelength of 400-700 nm was gradually increased by increasing the post-treatment time in Ar + H plasma. The optical bandgap energy of ZnO films was almost monotonically increased by decreasing the $O_2/H_2$ ratio in in-situ gas addition or by increasing the post-treatment time in Ar + H plasma, while the post-treatment using Ar plasma hardly affected the bandgap energy. The role of hydrogen in ZnO was discussed by considering the creation and annihilation of oxygen vacancies as well as the formation of shallow donors by hydrogen.

Analysis and Improvement of Reliability in IGZO TFT for Next Generation Display

  • Fujii, Mami;Fuyuki, Takashi;Jung, Ji-Sim;Kwon, Jang-Yeon;Uraoka, Yukiharu
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.326-329
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    • 2009
  • We investigated the degradation of $In_2O_3-Ga_2O_3$-ZnO (IGZO) thin-film transistors (TFTs), which is promising device for driving circuits of nextgeneration displays. We performed the electronic stress test by applying gate and drain voltage. We discussed the degradation mechanism by thermal analysis and device simulation.

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A study of electrical stress on short channel poly-Si thin film transistors (짧은 채널 길이의 다결정 실리콘 박막 트랜지스터의 전기적 스트레스에 대한 연구)

  • 최권영;김용상;한민구
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.8
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    • pp.126-132
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    • 1995
  • The electrical stress of short channel polycrystalline silicon (poly-Si) thin film transistor (TFT) has been investigated. The device characteristics of short channel poly-Si TFT with 5$\mu$m channel length has been observed to be significantly degraded such as a large shift in threshold voltage and asymmetric phenomena after the electrical stress. The dominant degradation mechanism in long channel poly-Si TFT's with 10$\mu$m and 20$\mu$m channel length respectively is charage trappling in gate oxide while that in short channel device with 5.mu.m channel length is defect creation in active poly-Si layer. We propose that the increased defect density within depletion region near drain junction due to high electric field which could be evidenced by kink effect, constitutes the important reason for this significant degradation in short channel poly-Si TFT. The proposed model is verified by comparing the amounts of the defect creation and the charge trapping from the strechout voltage.

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Study on contact resistance on the performance of Oxide thin film transistors (산화물 박막 트랜지스터 동작에 대한 접촉 저항의 영향)

  • Lee, Jae-Sang;Chang, Seong-Pil;Koo, Sang-Mo;Lee, Sang-Yeol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.04b
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    • pp.63-64
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    • 2009
  • The TFTs have been fabricated with 3 different geometry SID electrodes which have the same channel W/L ratio (W/L = 5) due to constant channel resistance, The 3 samples have different channel widths (350, 150, and $25\;{\mu}m$) and channel lengths (70, 30, and $5\;{\mu}m$) by fixed channel W/L ratio simultaneously on one chip for reliable comparisons. Resultant on-current and field effect mobility are proportional to the channel width, while the subthreshold swing is inversely proportional to the channel width mainly due to the change of contact resistance. These results show that the contact resistance strongly affects the device performances and should be considered in the applications.

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Modeling of Electrical Characteristics in Poly Silicon Thin Film Transistor with Process Parameter (다결정 실리콘 박막 트랜지스터에서 공정 파라미터에 따른 전기적 특성의 모델링)

  • Jung, Eun-Sik;Choi, Young-Sik;Lee, Yong-Jae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.201-204
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    • 2001
  • In this paper, for modeling of electrical characteristics in Poly Silicon Thin Film Transistors with process parameters set up optimum values, So, the I-V characteristics of poly silicon TFT parameters are examined and simulated in terms of the variations in process parameter. And these results compared and analyzed simulation values with examination value. The simulation program for characteristic analysis used SUPREM IV for processing, Matlab for modeling by mathematics, and SPICE for electric characteristic of devices. Input parameter for simulation characteristics is like condition of device process sequence, these electric characteristic of $I_D-V_D$ $I_D-V_G$, variations of grain size. The Gate oxide thickness of poly silicon are showed similar results between real device characteristics and simulation characteristics.

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Effect of Growth Temperature on the Properties of ZnO Films Grown by MOCVD (MOCVD로 제작한 ZnO의 성장온도에 따른 특성 변화)

  • Seo Hyun-Seok;Jeong Eui-Hyuk;Jo Jung-Yol;Choi Yearn-Ik;Seo O-Gweon
    • Journal of the Semiconductor & Display Technology
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    • v.4 no.4 s.13
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    • pp.9-12
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    • 2005
  • Characteristics of ZnO films grown on $Si-SiO_2$ substrates at temperatures of $200\sim400^{\circ}C$ by metalorganic chemical vapor deposition were investigated. The growth rates and mobilities of ZnO films were dependent on growth temperatures. The field-effect mobilities measured in thin-film transistor structure were $15cm^2/Vsec$.

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Effects of Hf addition in thin-film-transistors using Hf-Zn-O channel layers deposited by atomic layer deposition

  • Kim, So-Hui;An, Cheol-Hyeon;Jo, Hyeong-Gyun
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2013.05a
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    • pp.138-139
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    • 2013
  • 본 연구는 ZnO-TFT 소자에 Hf의 첨가에 따른 소자 특성 및 게이트 바이어스 스트레스에 대한 특성에 대해 분석을 하였다. Hf-Zn-O 박막은 Hf의 조성이 증가함에 따라 작아지는 grain size로 인해 TFT 소자의 전계효과 이동도와 게이트 바이어스 스트레스에서의 문턱전압의 변화가 더 커지는 것을 확인하였다. 한편, Hf이 14at% 함유된 HZO-TFT에서는 이동도는 현저히 저하되었지만, 게이트 바이어스 스트레스에서의 문턱전압의 변화가 현저히 개선되는 것을 확인하였는데, 이는 Hf의 조성이 증가함에 따라 비정질화 되어 grain boundaries에 의한 trap의 영향이 줄어든 결과를 확인하였다. 또한, 전계효과 이동도와 소자의 안정성을 확보하기 위해, poly-ZnO와 amorphous-HZO로 구성된 다중층 채널 구조를 이용한 TFT소자에서는 전계효과 이동도과 소자의 안정성이 개선된 결과를 보였다. 이는 채널과 게이트 산화물의 interface charge trap의 감소와 back-channel effect가 감소한 결과임을 확인하였다.

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Study on Contact Resistance on the Performance of Oxide Thin Film Transistors (산화물 박막 트랜지스터 동작에 대한 접촉 저항의 영향)

  • Lee, Jae-Sang;Koo, Sang-Mo;Lee, Sang-Yeol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.9
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    • pp.747-750
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    • 2009
  • The TFTs have been fabricated with 3 different geometry SID electrodes which have the same channel W/L ratio (W/L = 5) due to constant channel resistance, The 3 samples have different channel widths (350, 150, and 25 ${\mu}m$) and channel lengths (70, 30, and 5 ${\mu}m$) by fixed channel W/L ratio simultaneously on one chip for reliable comparisons. Resultant on-current and field effect mobility are proportional to the channel width, while the subthreshold swing is inversely proportional to the channel width mainly due to the change of contact resistance. These results show that the contact resistance strongly affects the device performances and should be considered in the applications.