對應低溫多晶矽薄膜電晶體變動性之電路模擬技術之研究

Abstract

雷射再結晶的低溫多晶矽薄膜電晶體(LTPS TFT)廣泛應用在主動式矩陣的顯示器(active matrix display)及其驅動電路，因而備受矚目。在本篇論文，首先將統計性研究探討低溫多晶矽薄膜電晶體(LTPS TFT)變動性之特性，並提出二種適當描述變動性的非高斯函數式，其正確性指標高達0.9。 根據提出的函數式，建立一個考慮元件參數變異的新描述模式，並將其應用在電路模擬，以差動對與環形震盪器為例，比較其電路中元件參數用新提出方法與傳統高斯分配所產生後模擬電路的輸出結果。模擬結果顯示出，用提出的新方法模擬電路與實際量測到的元件參數直接帶入模擬的結果非常相像，這足以反應所提出模式的正確性。 根據模擬結果，如同環形震盪器之類的數位電路，其電路成效主要受區域的變動性所主導。相反地，如同差動對之類的類比電路，其電路成效主要受微小範圍的變動性(micro variation)所影響。

Laser recrystallized low temperature poly-silicon (LTPS) films have attracted attention for their applications in thin-film transistors (TFTs), which are widely used in active matrix displays and its driving circuits. In this thesis, the variation characteristics of LTPS TFTs are statistically investigated. Two kinds of non-Gaussian equations are proposed to fit the variation behaviors, which the coefficients of determination are both near 0.9, reflecting the validity of the model. Based on the proposed model, a new description of device parameter considering variation is provided and is applied in circuit simulation. Taking the differential pair and ring oscillator as the benchmarks, the proposed method of device parameter generation are compared with the conventional Gaussian distribution with the output performance of the circuit. It can be seen that the performance of the proposed model behaves much like those parameters from the measured device parameter, which reflects the validity of the proposed model. According to the simulation results, the circuit performance of a digital circuit, such as ring oscillator, is dominated by the variation in the range. On the contrary, the circuit performance of an analog circuit, such as differential pair is dominated by micro variation of devices.