Journal of the Institute of Electronics and Information Engineers (전자공학회논문지)

The Institute of Electronics and Information Engineers (대한전자공학회)
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Stability Enhancement of IZOthin Film Transistor Using SU-8 Passivation Layer

SU-8 패시베이션을 이용한 솔루션 IZO-TFT의안정성 향상에 대한 연구

  • Kim, Sang-Jo (Department of Electrical and Computer Engineering, Pusan National University) ;
  • Yi, Moonsuk (Department of Electronic Engineering, Pusan National University)
  • 김상조 (부산대학교 전자전기컴퓨터공학과) ;
  • 이문석 (부산대학교 전자공학과)
  • Received : 2014.12.06
  • Accepted : 2015.07.07
  • Published : 2015.07.25
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Abstract

In this work, SU-8 passivated IZO thin-film transistors(TFTs) made by solution-processes was investigated for enhancing stability of indium zinc oxide(IZO) TFT. A very viscous negative photoresist SU-8, which has high mechanical and chemical stability, was deposited by spin coating and patterned on top of TFT by photo lithography. To investigate the enhanced electrical performances by using SU-8 passivation layer, the TFT devices were analyzed by X-ray phtoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FTIR). The TFTs with SU-8 passivation layer show good electrical characterestics, such as ${\mu}_{FE}=6.43cm^2/V{\cdot}s$, $V_{th}=7.1V$, $I_{on/off}=10^6$, SS=0.88V/dec, and especially 3.6V of ${\Delta}V_{th}$ under positive bias stress (PBS) for 3600s. On the other hand, without SU-8 passivation, ${\Delta}V_{th}$ was 7.7V. XPS and FTIR analyses results showed that SU-8 passivation layer prevents the oxygen desorption/adsorption processes significantly, and this feature makes the effectiveness of SU-8 passivation layer for PBS.

본 연구에서는 SU-8을 절연층으로 사용해 솔루션 공정을 바탕으로 하여 Indium Zinc Oxide(IZO) thin film transistor(TFT)의 안정성을 향상에 대해 연구하였다. 매우 점성이 강하며 negative lithography 용으로 사용되는 SU-8은 기계적, 화학적으로 높은 안정도를 가진다. 그리고 이 SU-8을 사용해 TFT층의 위에 스핀코팅을 사용해 절연막 층을 쌓고 photo lithography를 이용해 patterning을 하였다. SU-8층에 의한 positive bias stress(PBS)에 대한 전기적 특성 향상의 이유를 연구하기 위해 TFT에 X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FTIR) 분석을 시행하였다. SU-8을 절연층으로 한 TFT는 좋은 전기적 특성을 보였으며, 전류점멸비, 전자이동도, 문턱전압, subthreshold swing이 각각 $10^6$, $6.43cm^2/V{\cdot}s$, 7.1V, 0.88V/dec로 측정되었다. 그리고 3600초 동안 PBS를 가할 시 ${\Delta}V_{th}$는 3.6V로 측정되었다. 그러나 SU-8 층이 없는 경우 ${\Delta}V_{th}$는 7.7V 였다. XPS와 FTIR을 분석한 결과, SU-8 절연층이 TFT의 산소의 흡/탈착을 차단하는 특성에 의해 PBS에 강한 특성을 나타나게 함을 확인하였다.

Keywords

References

  1. E. Fortunato, P. Barquinha and R. Martins, "Oxide Semiconductor Thin-Film Transistors: A Review of Recent Advances", Advanced Materials, vol. 24, no. 22, pp.2945-2986, 2012. https://doi.org/10.1002/adma.201103228
  2. Dong Hyeok Choi, In-Bo Shim, Tae Joon Kouh, and Chul Sung Kim, "Microstructure of the Oriented Hexagonal HoMnO3 Thin Films by PLD", Journal of Magnetics, vol. 12, No. 4, pp.141-143, 2007. https://doi.org/10.4283/JMAG.2007.12.4.141
  3. Han Seo, Mi-Jung Ji, Yong-Tea An, Byeong-Kwon Ju, and Byung-Hyun Choi, "Effect of the Deposition Temperature on the Transmittance & Electrical Conductivity of $In_{1.6}Zn_{0.2}Sn_{0.2}O_{3-{\delta}}$ Thin Films Prepared by RF-magnetron Sputtering", Journal of the Korean Ceramic Society, Vol. 49, No. 6, pp. 663-668, 2012. https://doi.org/10.4191/kcers.2012.49.6.663
  4. W. Jonathan .Hennek, Y Xia, E. Ken, C. Mark. Hersam, F. Antonio, and T. J. Marks, "Reduced Contact Resistance in Inkjet Printed High-Performance Amorphous Indium Gallium Zinc Oxide Transistors", Appl. Mater and Interface, vol 4. pp.1614-1619, 2012. https://doi.org/10.1021/am201776p
  5. Y Wang, X W Sun, G.K.L. Goh,, H.V .Demir, YY Hong, "Influence of Channel Layer Thickness on the Electrical Performances of Inkjet-Printed In-Ga-Zn Oxide Thin-Film Transistors", IEEE Transactions on Electron Devices, vol. 58, pp.480-485, 2011. https://doi.org/10.1109/TED.2010.2091131
  6. G. H. Kim, H. S. Kim, H. S. Shin, B. D. Ahn, K. H. Kim, H. J. Kim, "Inkjet-printed InGaZnO thin film transistor", Thin Solid Films, vol. 517, pp. 4007-4010, 2009. https://doi.org/10.1016/j.tsf.2009.01.151
  7. M. J. Yu, Y. H. Yeh, C. C. Cheng, C. Y. Lin, G. T. Ho, B.C.M Lai, ., C. M. Leu,T. H. Hou, , Y. J. Chan, "Amorphous InGaZnO thin-film transistors compatible with roll-to-roll fabrication at room temperature", IEEE Electron Device Letters, vol.33, pp.47-49, 2012. https://doi.org/10.1109/LED.2011.2170809
  8. D. H. Lee, Y. J. Chang, G. S. Herman and C. H. Chang, "A General Route to Printable High-Mobility Transparent Amorphous Oxide Semiconductors", Adv. Mater, vol. 19, pp.843-847, 2007. https://doi.org/10.1002/adma.200600961
  9. J. H. Park, W. J. Choi, J. Y. Oh, S. S. Chae, W. S. Jang, J. Lee, S. Song K. M. Baik, H. Koo, "Low-Temperature, Aqueous-Solution Processed Zinc Tin Oxide Thin Film Transistor", J. Appl Phys, vol. 50, pp.070201, 2011. https://doi.org/10.7567/JJAP.50.070201
  10. J. H. Park, W. J. Choi, S. S. Chae, J. Y. Oh, J. Lee, S. Song, K. M. Baik, K. Hong, "Structural and Electrical Properties of Solution-Processed Gallium-Doped Indium Oxide Thin-Film Transistors", J. Appl. Phys, vol. 50, pp. 080202, 2011. https://doi.org/10.7567/JJAP.50.080202
  11. S., H. Jeong, Y. G, Moon, J, Facchetti, A., Marks, T. "Role of Gallium Doping in Dramatically Lowering Amorphous-Oxide Processing Temperatures for Solution-Derived Indium Zinc Oxide Thin-Film Transistors", Adv Mater, vol.22, pp.1346-1350, 2010. https://doi.org/10.1002/adma.200902450
  12. D. H. Kang, H. Lim, C. J. Kim, I. H. Song, J. C. Park, and Y. S. Park,, "Amorphous gallium indium zinc oxide thin film transistors: Sensitive to oxygen molecules", Appl Phys Lett, vol. 90, pp.192101, 2007. https://doi.org/10.1063/1.2723543
  13. K. H. Lee, J. S. Jung, K. S. Son, J. S. Park, T. S. Kim, R. Choi, J. K. Jeong, J. Y. Kwon, B. W. Koo and S. Y. Lee, "The effect of moisture on the photon-enhanced negative bias thermal instability in Ga-In-Zn-O thin film transistors", Appl Phys Lett, vol. 95, pp.232106, 2009. https://doi.org/10.1063/1.3272015
  14. J. S. Park, J. K. Jeong, H. J. Chung , Y. G. Mo, H. D. Kim, "Electronic transport properties of amorphous indium-gallium-zinc oxide semiconductor upon exposure to water", Appl Phys Lett, vol. 92, pp.072104, 2008. https://doi.org/10.1063/1.2838380
  15. S. H. Choi, M. K. Han, "Effect of Deposition Temperature of SiOx Passivation Layer on the Electrical Performance of a-IGZO TFTs", IEEE Electron Device Letters, vol. 33, pp. 396-398, 2012. https://doi.org/10.1109/LED.2011.2181320
  16. H. S. Seo, J. U. Bae, D. H. Kim, Y. J. Park, C. D. Kim, I. B. Kang, I. J. Chung, J. H. Choi and J. M. Myoung, " Reliable Bottom Gate Amorphous Indium-Gallium-Zinc Oxide Thin-Film Transistors with TiOx Passivation Layer", Solid-State Letters, vol. 12, pp.H348-351, 2009. https://doi.org/10.1149/1.3168522
  17. T.Arai, N.Morosawa, K.Tokunaga, Y.Terai, E. Fukumoto, T.Nakayama, T. Yamaguchi, and T. Sasaoka, SID Symposium Digest of Tech, vol. 41, pp. 1033, 2010.
  18. Y. Ko, S. Bang, S. Lee, S. Park, J. Park, and H. Jeon, "The effects of a HfO2 buffer layer on Al2O3-passivated indium-gallium-zinc-oxide thin film transistors", physica status solidi (RRL) - Rapid Research Letters, vol. 5, pp.403-405, 2011. https://doi.org/10.1002/pssr.201105340
  19. A. Olziersky, P. Barquinha, A. Vila, L. Pereira, G. Goncalves, E. Fortunato, R. Martins, J. R. Morante, "Insight on the SU-8 resist as passivation layer for transparent $Ga_2O_3-In_2O_3$ ZnO thin-film transistors", J. Appl. Phys, vol. 108, pp.064505, 2010. https://doi.org/10.1063/1.3477192
  20. M. Egginger, S. Bauer, R. Schwodiauer, H. Neugebauer, N. S. Sariciftci, "Current versus gate voltage hysteresis in organic field effect transistors", Monatshefte für Chemie - Chemical Monthly, vol. 140, pp. 735-750, 2009. https://doi.org/10.1007/s00706-009-0149-z
  21. M. E. Lopes, H. L. Gomes, M. C. R. Medeiros, P. Barquinha, L. Pereira, E. Fortunato, R. Martins and I. Ferreira, "Gate-bias stress in amorphous oxide semiconductors thin-film transistors", Appl hys Lett, vol. 95, pp.063502, 2009. https://doi.org/10.1063/1.3187532
  22. M. K. Gunde, N. Hauptman, M. Macek, M. Kunaver, "The influence of hard-baking temperature applied for SU8 sensor layer on the sensitivity of capacitive chemical sensor", Appl. Phys. Lett, vol. 95, pp.673-680, 2008.
  23. J. K. Chen, F. H. Ko, H. K. Chen, C. T. Chou, H. L.Chen. and F. C. Chang, "Effect of fluoroalkyl substituents on the reactions of alkylchlorosilanes with mold surfaces for nanoimprint lithography", J. Vacuum Science & Technology B, vol. 22, pp.492, 2004. https://doi.org/10.1116/1.1645884
  24. K. H. Lee, J. H. Park, Y. B. Yoo, W. S. Jang, J. Y. Oh, S. S. Chae, K. J. Moon, J. M. Myoung, and H. K. Baik, "Effects of Solution Temperature on Solution-Processed. High-Performance Metal Oxide Thin-Film Transistors", Appl materials & interfaces, vol. 5, pp. 2585-2592, 2013. https://doi.org/10.1021/am3032629
  25. E. Fortunato, P. Barquinha, A. Pimentel, A. Goncalves, A. Marques, L. Pereira, R. Martins, "Recent advances in ZnO transparent thin film transistors", Thin Solid Films, vol. 487, pp.205-211, 2005. https://doi.org/10.1016/j.tsf.2005.01.066
  26. J. P. Bermundo, Y. Ishikawa, H. Yamazaki, T. Nonaka and Y. Uraoka, "Highly Reliable Polysilsesquioxane Passivation Layer for a-InGaZnO Thin-Film Transistors", J. Solid State Science and Technology, vol. 3, pp.Q16-Q19, 2013. https://doi.org/10.1149/2.011402jss