鋁摻雜於銦鋅錫氧化物薄膜電晶體技術之研究

Abstract

本論文研究之透明非晶態氧化銦鋅錫半導體，其兼具非晶矽材料的高均勻性以及低溫多晶矽材料的高載子遷移率之優點，並擁有低溫沉積以及高可見光穿透率等物理特性，因此極有機會取代非晶矽與多晶矽成為下世代的薄膜電晶體材料。研究中，摻入微量具有強離子勢能的氧化鋁期望能得到更加穩定的元件通道層。我們首先探討鋁摻雜氧化銦鋅錫薄膜元件電特性，然後研究元件保護層對於鋁摻雜氧化銦鋅錫薄膜電晶體元件的影響，探討電漿輔助式化學氣相沉積儀沉積二氧化矽薄膜於元件作為保護層，透過調整製程前驅物並搭配氧氣退火來進一步優化元件特性，藉由材料特性分析的佐證來說明元件電特性上的變化。其最佳化的元件具有27.25 cm2/Vs的載子遷移率，-0.55 V的臨界電壓以及0.315 V/decade的次臨界擺幅。具有保護層覆蓋的元件電特性有明顯的改善，缺陷能態密度也相對降低。在對光敏感度量測，元件皆不受可見光範圍之波長影響。在常壓環境下的電性可靠度測試中，有保護層覆蓋的元件較不受閘極應力與影響。在照光環境下做負閘極偏壓應力測試，元件劣化程度會增加，但加熱可使元件恢復。

The transparent amorphous oxide semiconductor (TAOS) has attracted a lot of attention as the channel layer of thin film transistors (TFTs). Among these materials, the indium gallium zinc oxide (InGaZnO: IGZO) semiconductor is most popular and considered as the promising candidates for array technology owing to the electrical characteristics of high transparency, high mobility, good uniformity, low-temperature deposition. However, the average field-effect mobility of a-IGZO TFTs is not high enough (≧20 cm2/Vs) for future display applications in ultra-high definition (UHD) display. The amorphous indium zinc tin oxide (InZnSnO: IZTO) has been studied in this thesis for achieving high mobility TFTs. In this work, high performance IZTO incorporated with small amount aluminum (Al) of strong ionic potential, is prepared to achieve stable channel layer in TFTs. First, the electrical performance of Al-doped a-IZTO (AlInZnSnO: AIZTO) TFTs is investigated. Then, the SiO2 deposited by Plasma-enhanced chemical vapor deposition (PECVD) are adopted as the passivation layer. The optimized performance of passivated TFTs is obtained by adjusting the reactive precursor during passivation layer deposition and temperature of post annealing. The optimized device of passivated a-AIZTO TFT exhibited mobility of 27.25 cm2/V-s, threshold voltage of -0.55 V and subthreshold swing of 0.315 V/decade. Furthermore, the stability of the passivated devices are significantly improved and the density of states (DOS) are relatively reduced. The TFTs show insensitivity in visible light. The device would degrade after negative bias illumination stress (NBIS), but it could be recovered by heat treatment.