利用環型震盪器探討元件變異對低溫多晶矽薄膜電晶體電路效能之研究

Abstract

低溫多晶矽薄膜電晶體(LTPS TFT)最近幾年在液晶顯示器(AMLCD)應用中之所以會是眾所注目的焦點，是因為其優異的元件特性。然而，由於複晶矽層不規則的晶粒邊界分佈，低溫多晶矽薄膜電晶體有較差的均勻性，同時元件參數呈現大範圍變動。元件變異的來源可由其元件分佈的距離來區分為宏觀(macroscopic)及微觀(microscopic)兩類。 本論文主要是探討低溫多晶矽薄膜電晶體的元件特性變動問題對數位電路效能的影響。在探討微觀元件變異的效應上，我們可以預測其變異的範圍並且更進一步的在模擬及量測間得到一致的結論。在探討宏觀元件變異的效應上，我們說明一個新的觀念來評估宏觀元件變異對電路效能的影響。同時，我們也藉由比較是否考慮微觀元件變異來驗證它對電路效能的影響將會呈現平均化。總結上面分析的結果，我們可以提出一套有效率的模擬方法來考量複晶矽薄膜電晶體的元件變異性以獲得高良率的低溫多晶矽薄膜電晶體數位電路。

Low temperature poly-silicon silicon (LTPS) thin film transistors (TFTs) have recently attracted much attention in the application on the integrated peripheral circuits of active matrix liquid crystal displays (AMLCDs). However, due to the irregularly distributed grain boundary, LTPS TFTs have poor uniformity and suffer from huge variation. Device variation sources can be divided into micro variations characterized by short correlation distances and macro variations characterized by long correlation distances. The thesis studies the issues about the device characteristic variation of LTPS TFT affecting on the digital logic circuit performance. On the microscopic device variation aspect, we predict its variation range and the consistence between measurement and simulation results are also presented. On the macroscopic device variation aspect, we demonstrate a new concept on how to simulate macroscopic device variation effect on LTPS TFT circuit performance. Meanwhile, the microscopic device variation effect on circuit performance is evaluated to be as averaged type by doing the comparison between with and without it. With these analysis results, we can provide efficient methods to characterize and model circuit variation to obtain high-yield LTPS TFT digital circuits.