應用雙主動層於銦鎵鋅氧薄膜電晶體之接面穩定性改善研究

Abstract

非晶態銦鎵鋅氧化物的高載子移動率、可低溫製成、以及在可見光下具有高透明度等特性，使其成為當今熱門的薄膜電晶體主動層材料並逐漸取代傳統非晶矽半導體材料。然而，非晶態銦鎵鋅氧薄膜電晶體仍存在半導體層與絕緣層間之接面缺陷，影響了其效能發揮。 鑑於此，本論文提出雙主動層結構，先於絕緣層上沉積非晶態銦鎵氧為第一主動層，再沉積非晶態銦鎵鋅氧為第二主動層，以此結構改善其接面缺陷問題，並同時檢驗其於正負偏壓應力與短波長光線照射之電性變化，以求得到高穩定及高可靠度的非晶態銦鎵鋅氧化物薄膜電晶體。此外，亦與單一主動層之非晶態銦鎵鋅氧化物薄膜電晶體進行比較。 實驗結果顯示，沉積雙主動層薄膜之表面粗糙度較單一主動層薄膜更為平滑，此外具雙主動層的薄膜電晶體展現出比單主動層薄膜電晶體更小的次臨界搖擺值，且在正負偏壓應力與短波長光線照射下也呈現較穩定的結果；同時，遲滯現象也獲得明顯改善。因此，雙主動層結構能有效減少位於半導體層與絕緣層接面間的缺陷態。

a-IGZO has been demonstrated successfully as the active layer in TFTs, but the electrical reliability of a-IGZO TFTs still have some issues needs to be concerned. The method about reducing interface defect of a-IGZO TFTs have rarely been reported. Therefore, a double-active-layered structure with a-IGO/a-IGZO was adopted for interface alignment of a-IGZO TFTs in this study. According to analytical results, a smoother surface roughness of 0.25nm in a-IGZO thin film was obtained by the a-IGO/a-IGZO stacked structure. The double a-IGO/a-IGZO TFTs exhibited sub-threshold swing (S.S) of 0.4 V/decade and hysteresis of 0.40V, whereas the single-layered a-IGZO TFTs showed S.S of 0.93 V/decade and hysteresis of 1.35V. The improved interface of a-IGO/a-IGZO TFTs also presented less charge trapping under stressing. Therefore, a-IGO as alignment layer reduce the interface trapping effectively.