利用電漿增強原子層沉積技術製作摻氮氧化鋅/氧化鎂鋅之異質結構薄膜電晶體

Nitrogen-Doped Zinc Oxide/Magnesium-alloyed Zinc Oxide Heterostructure Thin Film Transistor fabricated by Plasma Enhanced Atomic Layer Deposition

蘇彥齊(Yan-Chi Su)

指導教授 ： 李嗣涔

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.11274

摘要

本論文主要研究利用低溫原子層沉積技術成長摻氮濃度百分之五十之氧化鋅與鎂含量為百分之八、百分之十六及百分之三十三之氧化鎂鋅形成之異質結構所製作而成之薄膜電晶體。為了製作可操作之薄膜電晶體，藉由摻雜氮來佔據氧空缺的位置，進而形成受體以降低純氧化鋅擁有之高電子濃度及導電度。最佳之氧化鋅薄膜成長條件為摻氮濃度百分之五十以及氨氣流量速率為20 sccm時，此時，摻氮濃度百分之五十之氧化鋅的電子濃度及霍爾遷移率分別降為2.8x1017 cm-3 及9.2 cm2/V-sec。在異質結構中，聚集於氧化鎂鋅/摻氮濃度百分之五十之氧化鋅介面之大量片電子濃度是由於極化效應所造成，而由於二維電子氣系統之存在，異質結構中之片電子濃度及霍爾遷移率將高於單層摻氮濃度百分之五十之氧化鋅，擁有最佳條件之異質結構由鎂含量百分之十六之氧化鎂鋅及摻氮濃度百分之五十之氧化鋅所構成，並且此異質結構製作而成的薄膜電晶體，藉由將未完成的元件作350℃之熱退火改善，可得場效電子遷移率及電流開關比分別為17 cm2/V-sec及106.5，並且次臨界擺幅為2.3 V/decade。此外，再利用原子層沉積技術成長五十奈米的氧化鋁作為薄膜電晶體之保護層，可得場效電子遷移率及電流開關比分別為16　cm2/V-sec及106.8，並且次臨界擺幅為2.36 V/decade。將元件暴露於大氣中一個月後，其電性幾乎沒有太大的變動，因此原子層沉積技術成長的氧化鋁保護層，適合用於改善薄膜電晶體之特性以及元件長時間的保存。

關鍵字

原子層沉積技術 ； 摻氮氧化鋅 ； 氧化鎂鋅 ； 薄膜電晶體 ； 氧化鋁

並列摘要

In this thesis, the low temperature ZnO-based thin films fabricated by atomic layer deposition technique including single layer ZnO:N(50%), MgXZn1-XO/ZnO:N(50%) heterostructure TFTs with x = 0.08, 0.16 and 0.33 are investigated. In order to fabricate a operable TFT, it’s necessary to reduce the high electron concentration and conductivity of pure ZnO by doping the film with the nitrogen, which is used as dopant for O vacancies to form the acceptor states in ZnO. The optimal condition is at a flow rate of 20 sccm for NH3. Besides, the nitrogen atomic layer doping percentage is 50%. The electron concentration and Hall mobility of ZnO:N(50%) thin film are 2.8x1017 cm-3 and 9.2 cm2/Vs, respectively.
In a heterostructure, the considerable sheet electron concentration accumulated at the MgXZn1-XO/ZnO:N(50%) interface is due to the polarization effect. The sheet electron concentration and Hall mobility of the MgXZn1-XO/ZnO:N(50%) heterostructure are higher than that of the single ZnO:N(50%) layer due to the formation of two-dimensional electron gas. The optimal performance of MgXZn1-XO/ZnO:N(50%) heterostructure thin film transistor is obtained with x = 0.16. Besides, the characteristics of Mg0.16Zn0.84O/ZnO:N(50%) heterostructure TFT are improved by annealing the unfinished thin film transistor at the higher temperature (350℃), the field effect mobility (μe) and on/off current ratio are 17 cm2/V-sec and 106.5, respectively. Besides, the subthreshold swing is 2.3 V/decade. Furthermore, the Mg0.16Zn0.84O/ZnO:N(50%) heterostructure TFT is passivated by using the 50 nm thick ALD-Al2O3. The field effect mobility (μe) and on/off current ratio of Mg0.16Zn0.84O/ZnO:N(50%) heterostructure TFT with 50 nm thick ALD-Al2O3 passivation layer are 16 cm2/V-sec and 106.8, respectively. Besides, the subthreshold swing is 2.36 V/decade. The characteristics of the TFT with 50 nm thick ALD-Al2O3 passivation layer have no significant variations while the device is exposed to the atmosphere over one month. Therefore, the ALD-Al2O3 passivation is suitable candidate for device improvement and long-term storage.

並列關鍵字

atomic layer deposition (ALD) ； nitrogen-doped zinc oxide (ZnO:N) ； magnesium-alloyed zinc oxide (MgXZn1-XO) ； thin film transistor (TFT) ； aluminum oxide (Al2O3)

參考文獻

[1] Fortunato, E. M., Barquinha, P. M., Pimentel, A., Goncalves, A. M., Marques, A. J., Pereira, L. M., & Martins, R. F. Advanced Materials, 17(5), 590-594. (2005).

[2] Hosono, H. Thin Solid Films, 515(15), 6000-6014. (2007).

[3] Kim, I.-D., Choi, Y., & Tuller, H. L. Applied Physics Letters, 87(4), 043509-043509-043503. (2005).

[4] Huang, C.-I., Chin, H.-A., Wu, Y.-R., Cheng, I.-C., Chen, J. Z., Chiu, K.-C., & Lin, T.-S. Electron Devices, IEEE Transactions on, 57(3), 696-703. (2010).

[5] Wang, B.-S., Cheng, I.-C., & Chen, J.-Z. Paper presented at the Meeting Abstracts. (2012).