a-IGZO 薄膜電晶體的製作與特性分析

Abstract

由於a-IGZO具有在非晶下較高的載子遷移率，加上利用射頻濺鍍的低溫製程和大面積的均勻性，使得a-IGZO非常適合作為將來面板的主要材料。在本篇論文當中，我們成功的利用了射頻濺鍍的方式製造a-IGZO薄膜電晶體。藉由調整製程過程中的氧流量與沉積的時間，我們研究不同沉積氧流量下以及不同通道厚度下a-IGZO電晶體的特性。為了提升電性，我們也製造了兩層通道的結構。 有鑑於我們所製作的元件中出現奇怪的hump現象，因此我們也使用了變頻量測的方式去萃取density of state (DOS) 來解釋。並且為了改善hump現象，我們使用了真空退火的方式，去改善其電性。 針對可靠度方面，我們也討論環境的氣體分子對於元件電性的影響，同樣地使用退火的方式來改善。由於使用於面板的元件會經常處於照光和偏壓的條件之下，所以諸如positive bias stress，negative bias stress，light stress，positive bias light stress 和negative bias light stress等特性也作了測試與討論。

With the high mobility of IGZO material in the amorphous phase, and the merits of low process temperature and large area uniformity associated with the RF sputter, a-IGZO is widely considered as one of the most promising materials for the manufacturing of flat-panel displays. In this thesis, we have successfully fabricated a-IGZO TFTs by RF sputter. We studied the effects of different deposition oxygen flow and the channel thickness on the device performance. In addition, we have also fabricated a-IGZO TFTs with double active layers for improving the electrical performance. In order to explain the strange hump phenomenon in our studies, multi-frequency CV measurements were used to extract the DOS. We also found that a vacuum annealing is useful for eliminating the hump phenomenon. For reliability issues, we have studied the effects of the surrounding ambient gas molecules, and used vacuum annealing for improvements. The instability of positive bias stress, negative bias stress, light stress, positive bias light stress and negative bias light stress were also investigated.