複晶矽薄膜電晶體製程效應之研究

Abstract

近來, 由於複晶矽薄膜電晶體 (poly-Si TFT) 在應用於 ULSI 高密度 靜態隨機存取記憶體(SRAM) 的負載電阻和大面積主動矩陣式液晶顯示器( AMLCD)之驅動電路方面深具潛力,故而廣受矚目.在本論文中,我們針對複 晶矽薄膜電晶體之製程效應加以探討.我們研究了電感耦合式電漿(ICNP) 對於薄膜電晶體特性所產生的影響,同時也研究了高溫快速退火(RTA)在複 晶矽薄膜上對雜質活化的影響. 首先,我們探討了引入氮對複晶矽薄膜 電晶體所產生的影響.我們利用電感耦合式電漿製程製作薄膜電晶體,實驗 結果顯示引入的氮對複晶矽薄膜電晶體具有鈍化缺陷的效果,其臨界電壓, 次臨界電壓擺幅,開關電流比以及場效載子移動率皆因此而淂到改善.此 外,熱載子可靠度也獲得改善. 其次,我們探討了高溫快速退火(RTA)在 複晶矽薄膜上對雜質活化程度的影響.我們發現了以DISILANE為反應氣體 源所製成之試片的片電阻教以SILANE為反應氣體源者為高,而低離子佈植 劑量和高離子佈植能量會產生高片電阻.此外,我們也發現了高溫快速退火 的溫度越高,試片的片電阻越低.然而,退火時間,昇溫速率,以及退火次數 對試片的片電阻並不產生影響. Recnetly, polysilicon thin film transistors (TFTs) are receiving lots ofattentions because their potential applications in the realization of three-dimensional (3-D) integration as load resistors in ULSI high-density staticrandom access memories (SRAMs) and large-area active-matrix liquid crystaldisplays (AMLCDs) with on-glass integrated driver circuits. In this thesis,process effects on polycrystalline silicon thin film transistors (poly-Si TFTs)are investigated. Specifically, the effects of applying a new inductivelycoupled nitrogen plasma (ICNP) treatment on the poly-Si TFTs are studied. Inaddition, dopant activation in poly-Si thin films by rapid thermal annealing(RTA) is also studied. Firstly, we investigated the effects of nitrogen incorporation on poly-SiTFTs. We fabricated thin film transistors using Inductively Coupled NitrogenPlasma (ICNP) process. The experimental results showed that the incorporated nitrogen showed passivation effects on the trap states in poly-Si TFTs. The threshold voltages, subthreshold swings, ON/OFF current ratios, and fieldeffect mobilities of the fabricated TFTs were improved. Moreover, the hot carrier reliability was also improved. Secondly, we investigated the degree of dopant activation by rapid thermal annealing (RTA) in polysilicon films. It was found that the sheet resistance ofthe disilane-based samples is higher than that of the silane-based samples. Inaddition, low dosage and high implant energy result in high resistance.However,the annealing time, ramp rate, and annealing cycle do not appear to affect the sheet resistance of the annealed samples.