有源层厚度对InSnZnO薄膜晶体管的影响
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摘要
在室温下,采用射频磁控溅射法制备了氧化铟锡锌(ITZO)薄膜作为薄膜晶体管(TFT)的有源层, ITZO薄膜厚度分别为16, 25, 36, 45和55 nm。采用X射线衍射仪(XRD)、扫描电镜(SEM)和紫外-可见光分光光度计测试分析了不同厚度ITZO薄膜的结晶情况、表面形貌及光学特性的变化规律,并使用半导体特征测试仪表征了ITZO TFT的输出特性及转移特性,研究了有源层厚度对ITZO TFT电学性能的影响。结果表明:不同厚度的ITZO薄膜均为非晶结构,成膜致密,薄膜在可见光范围内的平均透过率均高于85%。在界面态密度(N■)和载流子浓度的共同影响下,当有源层厚度为36 nm时, ITZO TFT电学性能最优。其场效应迁移率(μ_(FE))为14.04 cm~2·(V·s)~(-1),开关比(I_(on/off))为1×10~6,亚阈值摆幅(S)仅有0.5 V·dec~(-1)。此外,有源层厚度的增大可以削弱空气中水分和氧气对TFT的侵蚀,提高器件的稳定性。因此可以通过改变有源层厚度来调控TFT的性能。
InSnZnO thin film transistors(ITZO TFT) were prepared by radio frequency(RF) magnetron sputtering at room temperature. The thickness of ITZO films was 16, 25, 36, 45 and 55 nm. Their crystallinity, morphology and optical characteristics were investigated by X-ray diffraction(XRD), scanning electron microscope(SEM) and ultraviolet-visible(UV-Vis) spectrophotometer. Meanwhile, the output characteristics and transfer characteristics of TFT were analyzed by semiconductor characterization system. The influence of the active layer thickness on the electrical performance of ITZO TFT was studied. The results showed that the ITZO films with different thickness were amorphous and compact; the average transmittance was over 85% for all the films. Under the combined effect of interface state density and carrier concentration, ITZO TFT exhibited optimal electrical characteristics when the ITZO active layer thickness was 36 nm. Its field-effect mobility(μ_(FE)), on/off radio(I_(on/off)) and sub-threshold swing(S) were 14.04 cm~2·(V·s)~(-1), 1×10~6 and 0.5 V·dec~(-1), respectively. Additionally, increasing the active layer thickness could weaken the erosion on the TFT by water and oxygen, then further enhance the device′s stability. Thus, the performance of TFT could be controlled by varying active layer thickness.
InSnZnO thin film transistors(ITZO TFT) were prepared by radio frequency(RF) magnetron sputtering at room temperature. The thickness of ITZO films was 16, 25, 36, 45 and 55 nm. Their crystallinity, morphology and optical characteristics were investigated by X-ray diffraction(XRD), scanning electron microscope(SEM) and ultraviolet-visible(UV-Vis) spectrophotometer. Meanwhile, the output characteristics and transfer characteristics of TFT were analyzed by semiconductor characterization system. The influence of the active layer thickness on the electrical performance of ITZO TFT was studied. The results showed that the ITZO films with different thickness were amorphous and compact; the average transmittance was over 85% for all the films. Under the combined effect of interface state density and carrier concentration, ITZO TFT exhibited optimal electrical characteristics when the ITZO active layer thickness was 36 nm. Its field-effect mobility(μ_(FE)), on/off radio(I_(on/off)) and sub-threshold swing(S) were 14.04 cm~2·(V·s)~(-1), 1×10~6 and 0.5 V·dec~(-1), respectively. Additionally, increasing the active layer thickness could weaken the erosion on the TFT by water and oxygen, then further enhance the device′s stability. Thus, the performance of TFT could be controlled by varying active layer thickness.
引文
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[17] Yang T L, Song S M, Xin Y Q, Li Y H, Du G Q, Han S H. Effect of film thickness on the structural, electrical and optical properties of ZnO:Y films [J]. Journal of Synthetic Crystals, 2012, 41(5): 1190.(杨田林, 宋淑梅, 辛艳青, 李延辉, 杜桂强, 韩圣浩. 薄膜厚度对ZnO:Y 薄膜结构及光电特性的影响 [J]. 人工晶体学报, 2012, 41(5): 1190.)
[18] Chen Z F, Han D D, Zhao N N, Wu J, Cong Y Y, Dong J C, Zhao F L, Zhang S D, Zhang X, Zhang X, Wang Y, Liu L F. Performance improvement of tin-doped zinc oxide thin-film transistor by novel channel modulation layer of indium tin oxide/tin zinc oxide [A]. Japanese Journal of Applied Physics [C]. Tsukuba, Japan, 2015. 54.
[19] Tong Y, Wang K L, LiuY Y, Li Y H, Song S M, Yang T L. Effects of RF power on structure, morphology and photoelectric properties of ITZO thin films [J]. Journal of Synthetic Crystals, 2015, 44(9): 2338.(童杨, 王昆仑, 刘媛媛, 李延辉, 宋淑梅, 杨田林. 射频功率对ITZO薄膜结构、 形貌及光电特性的影响 [J]. 人工晶体学报, 2015, 44(9): 2338.)
[2] Chen Z F, Han D D, Zhao N N, Cong Y Y, Wu J, Huang L L, Dong J C, Zhao F L, Liu L F, Zhang S D, Zhang X, Wang Y. High-performance full transparent tin-doped zinc oxide thin-film transistors fabricated on glass at low temperatures [J]. Electronics Letters, 2014, 50(20): 1463.
[3] Pi J E, Ryu M K, Hwang C S, Park S H, Yoon S M, Lym H K, Kim Y K, Oh H S, Park K C. A simple shift register circuit for depletion-mode oxide TFTs [J]. Solid-State Electronics, 2013, 79: 2.
[4] Kim M J, Choi D K. Effect of enhanced-mobility current path on the mobility of AOS TFT [J]. Microelectronics Reliability, 2012, 52(7): 1346.
[5] Glueck J. A simplified a-Si:H TFT process for large-area AMLCDs [J]. Journal of the Society for Information Display, 1997, 5(3): 189.
[6] Kouvatsos D N, Voutsas A T, Michalas L, Farmakis F V, Papaioannou G J. Device degradation behavior and polysilicon film morphology of thin film transistors fabricated using advanced excimer laser lateral solidification techniques [J]. Thin Solid Films, 2007, 515(19): 7413.
[7] Kwon S H, Jung J H, Cheong W S, Lee G H, Song P K. Dependence of electrical and mechanical durability on Zn content and heat treatment for co-sputtered ITZO films [J]. Current Applied Physics, 2012, 12: 59.
[8] Gomes L, Marques A, Branco A, Araujo J, Simoes M, Cardoso S, Silva F, Henriques I, Laia C A T, Costa C. IZO deposition by RF and DC sputtering on paper and application on flexible electrochromic devices [J]. Displays, 2013, 34(4): 326.
[9] Carcia P F, Mclean R S, Reilly M H, Nunes G. Transparent ZnO thin-film transistor fabricated by RF magnetron sputtering [J]. Applied Physics Letters, 2003, 82(7): 1117.
[10] Ahn J S, Lee K B. Control of the threshold voltage by using the oxygen partial pressure in sputter-deposited InGaZnO4 thin-film transistors [J]. Journal of the Korean Physical Society, 2012, 60(10): 1625.
[11] Buchholz D B, Liu J, Marks T J, Zhang M, Chang R P. Control and characterization of the structural, electrical and optical properties of amorphous zinc-indium-tin oxide thin films [J]. Acs Applied Materials and Interfaces, 2009, 1(10): 2147.
[12] Liang Y, Jang K S, Velumani S, Nguyen C P T, Yi J S. Effects of interface trap density on the electrical performance of amorphous InSnZnO thin-film transistor [J]. Journal of Semiconductors, 2015, 36(2): 024007.
[13] Li Z Y, Lü Y B, Zhao J F, Song S M, Yang B B, Xin Y Q, Wang K L, Yang T L. Fabrication and the electrical and optical properties of nitrogen-doped In-Sn-Zn oxide thin-film transistors [J]. Chinese Journal of Luminescence, 2017, 38(12): 1622.(李治玥, 吕英波, 赵继凤, 宋淑梅, 杨波波, 辛艳青, 王昆仑, 杨田林. 氮掺铟锡锌薄膜晶体管的制备及其光电特性[J]. 发光学报, 2017, 38(12): 1622.)
[14] Liu Y Y, Zhao J F, Li Y H, Song S M, Xin Y Q, Yang T L. Fabrication and characterization of In2O3-SnO2-ZnO thin film transistor [J]. Chinese Journal of Vacuum Science and Technology, 2016, 36(4): 391.(刘媛媛, 赵继凤, 李延辉, 宋淑梅, 辛艳青, 杨田林. 溅射气压对铟锡锌氧化物薄膜晶体管性能的影响 [J]. 真空科学与技术学报, 2016, 36(4): 391.)
[15] Feng Z P, Wei F, Zhao H B, Yang Z M. Electrochromic behavior of WO3 thin films prepared by radio frequency magnetron sputtering [J]. Chinese Journal of Rare Metals, 2016, 40(9): 902.(冯志鹏, 魏峰, 赵鸿滨, 杨志民. 射频磁控溅射WO3薄膜电致变色性能研究 [J]. 稀有金属, 2016, 40(9): 902.)
[16] Han D D, Huang L L, Yu W, Cong Y Y, Zhang X, Wang Y. Effects of channel layer thickness on characteristics of flexible nickel-doped zinc oxide thin-film transistors [J]. Ieee Transactions on Electron Devices, 2017, 64(5): 1997.
[17] Yang T L, Song S M, Xin Y Q, Li Y H, Du G Q, Han S H. Effect of film thickness on the structural, electrical and optical properties of ZnO:Y films [J]. Journal of Synthetic Crystals, 2012, 41(5): 1190.(杨田林, 宋淑梅, 辛艳青, 李延辉, 杜桂强, 韩圣浩. 薄膜厚度对ZnO:Y 薄膜结构及光电特性的影响 [J]. 人工晶体学报, 2012, 41(5): 1190.)
[18] Chen Z F, Han D D, Zhao N N, Wu J, Cong Y Y, Dong J C, Zhao F L, Zhang S D, Zhang X, Zhang X, Wang Y, Liu L F. Performance improvement of tin-doped zinc oxide thin-film transistor by novel channel modulation layer of indium tin oxide/tin zinc oxide [A]. Japanese Journal of Applied Physics [C]. Tsukuba, Japan, 2015. 54.
[19] Tong Y, Wang K L, LiuY Y, Li Y H, Song S M, Yang T L. Effects of RF power on structure, morphology and photoelectric properties of ITZO thin films [J]. Journal of Synthetic Crystals, 2015, 44(9): 2338.(童杨, 王昆仑, 刘媛媛, 李延辉, 宋淑梅, 杨田林. 射频功率对ITZO薄膜结构、 形貌及光电特性的影响 [J]. 人工晶体学报, 2015, 44(9): 2338.)