具保護層之非晶態銦鎵鋅氧薄膜電晶體穩定性研究

Abstract

透明非晶態銦鎵鋅氧化物的載子遷移率已超越使用在液晶螢幕面板中的非晶態矽，並實現透明電子產品。與環境的水氧反應和偏紫外光波段波長的吸收造成非晶態銦鎵鋅氧薄膜電晶體的不穩定性，在商品化的過程將是一個重大的議題。本論文藉由加入一層通道保護層降低非晶態銦鎵鋅氧與外界反應的機會，利用濺鍍方式沉積氧化矽和氮化矽為通道保護層，首先探討通道保護層對非晶態銦鎵鋅氧薄膜電晶體的元件特性影響；進一步研究具通道保護層的元件放置環境中與在照光的情況下，臨界電壓隨時間變化有穩定的效果。此外對非晶態銦鎵鋅氧薄膜電晶體給予直流偏壓測試，發現具通道保護層的元件有較佳的可靠度。從薄膜特性、電性的穩定度與元件的可靠度比較，結果指出氮化矽比氧化矽適合當通道保護層。

The discovery of transparent oxides with high mobility realizes the transparent electronics and is being used for LCD backplane. The electrical instability of amorphous indium-gallium-zinc oxide (IGZO) thin film transistors is caused by two mechanisms：the interaction of oxygen and moisture in the ambience and the absorption of the light in near-ultraviolet region. To be electronic products, the electrical stability is a key issue. In the thesis, we studied on the sputtered SiOx and SiNx which serve as the passivation layer on the back channel to prevent the a-IGZO films from interacting with the ambience. First, film properties of the passivation layer are investigated and the effect of the passivation layer on the back channel of a-IGZO TFT is discussed. Further, the passivated devices with a stable threshold voltage as the function of time in the ambience and under light illumination are studied. The passivated a-IGZO TFTs present an improved reliability in comparison with the unpassivated devices under DC bias stress. By comparing the properties of the passivation layer, the electrical stability, and the device reliability, SiNx is found to be more suitable than SiOx as passivation for higher density in the structure and lower threshold voltage shift in the electrical properties.