| 摘要: | 本研究以高功率脈衝磁控濺鍍技術製作氧化鎵(Ga₂O₃)薄膜，並進一步研究與分析其應用於薄膜電晶體(Thin-film Transistor, TFT)之元件特性。氧化鎵為一種具備超寬能隙與高崩潰電場的氧化物半導體材料，具備優異的功率承受能力與透明性，為次世代透明與高壓電子元件的重要候選材料。本研究主要探討製程溫度、氣體流量與退火條件對氧化鎵薄膜結構與電性之影響，並藉由TFT元件對其進行製作與電性量測。
實驗部分，首先以磁控濺鍍於300°C至600°C間進行薄膜沉積，並透過不同溫度條件下進行真空退火處理。藉由AFM、XRD與XPS等分析技術，評估薄膜之表面形貌、結晶變化與化學鍵結；此外，搭配SEM進行橫截面觀察，確認薄膜厚度與結構均勻性。元件製作方面，採用微影技術定義通道層及汲源極金屬圖案，利用源/汲極金屬沉積與閘極絕緣層堆疊等製程，構成橫向結構之氧化鎵TFT元件，並以Keithley SMU架設量測系統進行轉移與輸出特性測試。
結果顯示，高溫(600°C)沉積薄膜於經退火後會轉變為結晶性較高之β-Ga₂O₃，但通道層導電性下降，元件無法導通；相對地，中低溫(300°C)沉積並經450°C退火之薄膜維持部分非晶態結構，具備較佳導電性與開關能力，可成功製作出具場效特性之TFT元件。量測結果顯示，最佳元件可獲得明顯的汲極電流調變特性與基本開關能力。;This study employs High Power Impulsed Magnetron Sputtering (HiPIMS) to fabricate gallium oxide (Ga₂O₃) thin films and investigates their applications in Thin-film Transistors (TFTs). Ga₂O₃ is a wide-bandgap oxide semiconductor characterized by a large bandgap and high breakdown electric field, offering excellent power handling capability and optical transparency, making it a promising candidate for next-generation transparent and high-voltage electronic devices. The research focuses on the influence of deposition temperature, gas flow ratio, and annealing conditions on the structural and electrical properties of Ga₂O₃ thin films, and verifies the results through lateral-structured TFT devices.
In the experimental procedure, Ga₂O₃ films were deposited at substrate temperatures ranging from 300°C to 600°C, followed by vacuum annealing under various thermal conditions. Surface morphology, crystallinity, and chemical bonding states were characterized using Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS), respectively. Cross-sectional morphology and thickness were examined using Scanning Electron Microscopy (SEM). Device fabrication involved photolithography patterning, source/drain metal deposition, and gate insulator stacking to construct bottom-gate lateral TFTs. Electrical measurements of transfer and output characteristics were conducted using a Keithley SMU system.
The results indicate that films deposited at 600°C and subsequently annealed exhibited high crystallinity with β-Ga₂O₃ phase but poor conductivity, resulting in non-functional devices. In contrast, films deposited at 300°C and annealed at 450°C retained a partially amorphous structure with superior conductivity and switching capability, enabling functional TFT fabrication. The best-performing devices exhibited clear field-effect modulation and switching capability, highlighting the promise of low-temperature HiPIMS-grown Ga₂O₃ films for functional oxide electronics. |
