低氫含量之氧化矽介電層薄膜應用於銦鎵鋅金屬氧化物半導體元件之研究

Abstract

平面顯示器技術這個領域，目前最廣泛使用於TFT元件者，普遍以多晶矽膜或非晶矽膜作為主動層通道材料，雖然多晶矽TFT元件之載子遷移率大於100Vs/cm2，但是其也有生產成本過高和製程均勻度不好的缺點，再者非晶矽TFT元件雖然有較低的生產成本，但是其載子遷移率小於1cm2/Vs。近來a-IGZO (Amorphous Indium Gallium Zinc Oxide)其優越的元件電性引起相當多的注意，包含著載子遷移率可達10cm2/Vs至20cm2/Vs之間、臨界電壓變異和元件開關能力，a-IGZO 薄膜可於低溫下沉積非晶相，且有好的製程均勻性和能夠製作於軟性電子材料之上，或應用於驅動AMOLED(主動式有機光激發顯示器)之元件。此篇論文主要是研究低氫含量之氧化矽介電層應用於a-IGZO-TFT元件，假若TFT元件製程中，其氧化矽介電層之氫含量過高，則會使a-IGZO薄膜的特性由半導體轉化成導體，所以於氧化矽介電層薄膜沉積製程時降低氫含量制非常重要的，這會避免a-IGZO薄膜被轉化成為導體，此為研究之目的。在本研究a-IGZO-TFT元件製程中，於a-IGZO薄膜圖形定義後，以低氫含量之氧化矽(SiOx)薄膜，作為元件中蝕刻阻擋層(Etching Stop Layer)與絕緣護層(Passivation Layer)，成功將Top gate與Bottom gate 架構之元件製作完成，且元件量測結果顯示為半導體特性。

Nowadays, poly-silicon and amorphous-silicon generally have been used for active layer of TFT (Thin Film Transistor) device technology of TFT LCD (Liquid Crystal Display). Poly-silicon-TFT has high field-effect mobility of over 100Vs/cm2, but it has disadvantage of high running cost and bad processing uniformity. Moreover, amorphous silicon has lower process cost for less process steps, but its field-effect mobility is less than 1Vs/cm2. Recently, a-IGZO TFTs (amorphous Indium Gallium Zinc Oxide Thin Film Transistor) have attracted considerable attentions for their superior electrical properties including great field-effect mobility from 10Vs/cm2 to 20Vs/cm2, sub-threshold swing, and high on/off current ratio. Furthermore, a-IGZO film, which is deposited at low temperature with an amorphous phase, exhibits good uniformity and can be fabricated on plastic substrates for flexible electronic or AMOLED (Active Matrix Organic Light Emitting Display) driving TFT. This thesis discussed SiOx dielectric film with low hydrogen content for a-IGZO-TFTs. If hydrogen content of SiOx film was high, a-IGZO film will be transformed from semiconductor to conductor in the application of TFT device. It is important that hydrogen content of SiOx film is reduced when SiOx film is deposited. Therefore, hydrogen ion generated by SiH4 must be reduced when deposited SiOx film. The proposed process of a-IGZO-TFT utilized low hydrogen contents SiOx film as etching stop layer and passivation layer to produce top gate and bottom gate transistor components. Experimental results showed that a-IGZO film exhibit intrinsic semiconductor characteristic, which is main claim of the dissertation.