利用氮中性粒子束處理非晶氧化銦鎵鋅薄膜電晶體在閘極偏壓不穩定性研究

Abstract

非晶銦鎵鋅氧薄膜電晶體目前已被廣泛研究，並且應用在下世代主動式陣列顯示器，其具備較好的場效遷移率(>10 cm2/V·S)，較大的開關電流比(>106)，較小的次臨界擺幅和較穩定的電性。但是其可靠度問題依然十分重要，特別是由閘極偏置應力導致的閾值電壓漂移現象，這是制約其長期使用的關鍵。 在這篇論文中，我們使用真空磁濺鍍(RF-Sputter)和大氣電漿(APPJ)來沉積銦鎵鋅氧主動層。為了研究閘極偏置導致的閾值電壓漂移現象，我們應用氮中性粒子束處理於銦鎵鋅主動層。通過比較不同元件在正閘極偏置應力和負閘極偏置光照應力下的表現，我們對其中的機制進行了詳盡的討論。利用這些機制，我們成功抑制了閾值電壓在這兩種應力下的漂移。由於非晶銦鎵鋅氧重摻雜氮有禁帶變窄現象，我們提出了異質結模型以解釋實驗結果。

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors have attracted many attention for next generation active-matrix displays due to their better field-effect mobility (>10 cm2/V·S), larger Ion/Ioff ratio (>106), smaller subthreshold swing (S.S.). However, it is still important to improve the reliability of a-IGZO TFTs, especially for gate bias induced threshold voltage shift which is the critical issue for long term application. In this research, the active channel layer was deposited by RF-Sputter and Atmospheric Pressure Plasma-enhanced Jet (APPJ). The Neutral Beam Nitrogen (NBN) treatment was applied to both samples so as to investigate the gate bias induced Vth shift. We had discussed the mechanisms in detail by comparing different samples under positive gate bias stress (PGBS) and negative gate bias illumination stress (NBIS). By using these mechanisms, we had successfully suppressed the Vth shift under both PGBS and NBIS. A heterojunction model was put forward to explain the experiment result as the heavily doped a-IGZO (a-IGZO:N) showed band gap narrowing effect.