SiOxNy / SiNz 閘極絕緣層特性用於薄膜液晶顯示器

Abstract

非晶矽薄膜電晶體技術被廣泛的使用於高信賴度、高解析度、高性能以及大尺寸之主動式液晶多媒體顯示器上。閘極絕緣層在薄膜電晶體是很重要的一層薄膜，為了得到好的電性特性表現及電漿輔助化學氣相沉積產能，在下層的閘極絕緣層就必須要由氮氧化矽改為氮化矽以便成膜時能具有ㄧ致性。早期閘極絕緣層都是以使用下層為氮氧化矽加上層氮化矽為主，如此在電漿輔助化學氣相沉積成膜時會耗費較長時間及材料，如此ㄧ來產能自然就會減少費用就會提高。本論文利用田口式實驗法則去找出最適合的下閘極絕緣層，完成後再依相同法則去找到更適合應用於薄膜液晶顯示器的上閘極絕緣層之氮化矽薄膜，因為這一層往往會決定電晶體的各種特性表現；其中包括電晶體其電性表現、光學特性及物理特性等等。為求高性能及高品質液晶顯示器，電晶體的開關必須非常明確，ㄧ般電晶體開關電流比約需在10E5以上。另一方面通常會特別注意關閉時電流是否過高，這個問題可藉由有效的電漿表面處理來獲得較低的漏電流來改善薄膜液晶顯示器整體特性表現。

Amorphous silicon (a-Si:H) TFT technology is widely used in highly reliable, high resolution, high performance and large size active matrix liquid crystal displays (AMLCDs) that are necessary for multimedia applications. The gate insulator is important layer of TFT structure. For good electrical performance and throughput of PECVD, the bottom insulator should be changed from silicon oxygen nitride to silicon nitride. On early stages, the gate insulator was made of silicon oxy-nitride (SiON) for bottom insulator and silicon nitride (SiN) for top insulator, the longer PECVD deposition of SiON will affect the process throughput and cost even its properties of performance are better on some items, a more suitable bottom insulator was needed to improve throughput. This thesis use Takuchi analysis to find better and uniform silicon nitride film which gives rise to better TFT performance. In fact, SiNtop is main factor that property will influence TFT threshold voltage directly. In order to achieve high quality AMLCDs, it is very important to fabricate TFTs with high on-current and low off-current and the off current had better < 10-12A, efficient plasma ashing treatment on TFT can reduce leakage between drain and source.