薄膜電晶體的溫度係數模型以及玻璃基板上具溫度補償功能之參考電壓電路

Abstract

低溫複晶矽(low temperature poly-silicon, LTPS)薄膜電晶體(thin-film transistors, TFT)已被視為一種材料廣泛地應用於可攜帶式系統產品中，例如數位相機、行動電話、個人數位助理(PDA) 、筆記型電腦等等，這是由於低溫複晶矽薄膜電晶體的電子遷移率(electron mobility)約是傳統非晶矽(amorphous silicon)薄膜電晶體的百倍大。此外，低溫複晶矽技術可藉由將驅動電路整合於顯示器之週邊區域來達到輕薄、巧小且高解析度的顯示器。這樣的技術也將越來越適合於系統整合型面板(system-on-panel/system-on-glass)應用之實現。本論文首先針對了低溫多晶矽電晶體製程下玻璃基板上的薄膜電晶體作了分別對改變其偏壓電流、雷射能量以及通道寬度等相關的溫度量測，並提出了薄膜電晶體的溫度係數模型，使用此模型為基礎，設計出一在玻璃基板上具溫度補償功能之參考電壓電路設計，並使用三微米的低溫多晶矽薄膜電晶體製程來做驗證。此新提出的具溫度補償之參考電壓電路的實驗結果，證實在操作電壓為十伏時其溫度係數為一百九十五ppm/°C。此新提出的具溫度補償功能之參考電壓電路可以應用於面板系統上，提供類比電路設計之精準電壓基礎。

The temperature coefficient (TC) of n-type polycrystalline silicon thin-film transistors (poly-Si TFTs) is investigated in this work. The relationship between TC and the activation energy is observed and explained. From the experimental results, it is also found that TC is not sensitive to the deviation of the laser crystallization energy. On the contrary, channel width can effectively modulate the TC of TFTs. Furthermore, the temperature coefficient model has been advanced in the thesis. By using the diode-connected poly-Si TFTs with different channel widths, the first voltage reference circuit with temperature compensation for precise analog circuit design on glass substrate is proposed and realized. From the experimental results in a LTPS process, the output voltage of voltage reference circuit with temperature compensation exhibits a very low TC of 195 ppm/°C, between 25°C and 125°C. The proposed voltage reference circuit with temperature compensation can be applied to design precise analog circuits for System-on-Panel (SoP) or System-on-Glass (SoG) applications, which enables the analog circuits to be integrated in the active matrix LCD (AMLCD) panels.