以氧化鋅錫為基底的溶液製程半導體與電晶體之研究

Studies of Zinc Tin Oxide Based Solution-Processed Semiconductors and Thin Film Transistors

蔡効伯(Shiao-Po Tsai)

指導教授 ： 吳忠幟

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.10020

摘要

透明金屬氧化物半導體近幾年來因為其高載子遷移率、高透明性，以及適合在低溫下沉積而受到矚目。金屬氧化物薄膜由於其傳導帶取決於重金屬陽離子的球形對稱S軌域重疊，使得不論在結晶態或非結晶態都可以具有良好的載子遷移率，也因此可以使用在較低溫的製程上，可廣泛使用於平面顯示器以及軟性電子等。
目前金屬氧化物半導體層的製作仍以真空沉積的方式為主流，例如磁控濺鍍(RF magnetron sputtering)、脈衝雷射蒸鍍(pulse laser deposition, PLD)或是熱蒸鍍(evaporation)的製程。而本論文中使用的溶液製程提供了另一個製程方法；溶液製程具有簡單、低成本、適用於大尺寸的薄膜沉積以及可在一般大氣環境下製作的優點，近年來也受到矚目。
另一方面，隨著銦的價格因為稀有而上漲，同時含銦的金屬氧化物半導體會對環境造成不良的影響，不含銦類型的金屬氧化物半導體系統開始受到重視。本論文使用的氧化鋅錫(zinc-tin oxide)的系統，具有高載子遷移率、材料容易取得的特性，是未來極具潛力的金屬氧化物半導體系統。
在本論文中，將探討以金屬氯化物作為前驅物材料，沉積氧化鋅錫半導體，並研究臨界電壓與製程程序以及退火溫度與時間的關係。我們開發出三種不同製程步驟可以使氧化鋅錫半導體TFT分別成為增強型(enhancement mode)或空乏型(depletion mode)的N型通道TFT。藉由這兩種形式的電晶體，我們可以實現空乏型負載的反相器電路，並展示其與增強型負載反相器的差異，提供溶液製程氧化物TFT電路更多樣的選擇與設計空間。

關鍵字

氧化物半導體 ； 薄膜電晶體 ； 溶液製程 ； 氧化鋅錫 ； 空乏型 ； 增強型

並列摘要

Transparent metal oxide thin film transistors have drawn much attention recently due to high mobility, transparency, and feasible fabrication at low temperatures. Since the conduction band of metal oxide semiconductors is dominated by heavy-metal cations’ spherical s orbital overlapping, high carrier mobility can be achieved both in crystalline and amorphous states, thus making possible fabrication at low temperature and wide applications in flat panel displays and flexible electronics.
Most metal oxide semiconductors TFTs are fabricated by vacuum deposition, such as RF magnetron sputtering, pulsed laser deposition, and thermal evaporation. However, the cost is relatively high. Solution processes studied in this thesis provide another fabrication method. Solution processes have the advantages of low cost, large-area deposition, and processing in the ambient environment. On the other hand, due to rising indium prices and bad environmental effects of indium-based metal oxide semiconductors, indium-free metal oxide semiconductors are being widely pursued. The In-free zinc-tin oxide system studied in this thesis has high mobility and becomes one potential metal oxide semiconductor.
In this thesis, we used metal chloride precursors to deposit zinc-tin oxide semiconductors, and studied the relationship between TFT characteristics (e.g. threshold voltages) and annealing conditions (e.g. annealing sequences, annealing time and temperature etc.). Based on such results, we developed three different fabrication processes of solution-processed zinc-tin oxide TFTs capable of controlling TFTs into the depletion mode or enhancement mode. Using these two types of thin film transistors, we implemented depletion-load inverters and demonstrated improvements in inverter characteristics compared to the enhancement-load inverters.

並列關鍵字

oxide semiconductors ； thin film transistors ； solution processes ； zinc tin oxide ； depletion mode ； enhancement mode

參考文獻

chapter 1:

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[4] F. V. Shallcross. (1963) “Cadmium Selenide Thin-Film Transistors.” Proceedings of the IEEE, vol. 51, pp. 851–851.