低溫多晶矽製程之畫素記憶體電路暨數位類比轉換器電路設計與實現

Abstract

近年來，有越來越多關於低溫複晶矽 (low temperature polycrystalline silicon, LTPS) 薄膜電晶體 (thin-film transistors, TFTs)的研究。這是因為這種技術已被廣泛地使用於可攜帶式系統產品中，例如數位相機、行動電話、筆記型電腦等。跟傳統的非晶矽 (amorphous silicon) 薄膜電晶體比起來，低溫複晶矽薄膜電晶體的電子遷移率約大了一百倍。這也是為什麼低溫複晶矽技術很適合用來將驅動電路整合於顯示器之周邊區域。藉由系統面板 (System-on-Panel, SOP) 之應用，可以實現輕薄、巧小且高解析度的顯示器。 由於綠能科技的興起，各式各樣的電子產品對於低功耗的需求越來越大，而這些新穎的電子產品常常伴隨著大量LCD面板的使用，因此出現了嵌入式畫素記憶體這樣的研究題目與方向，目的就是希望能夠降低LCD面板功率的消耗，進而使搭載這些LCD面板的電子產品能減少功率的耗損，以符合世界對於綠色產品日漸嚴格的標準。 此外，由於系統面板的發展，越來越多研究是將LCD面板的驅動電路(driving circuit)整合在面板上，而數位至類比轉換器在整個驅動電路中可以說是很重要的一環。其中循環式的數位至類比轉換器(cyclic DAC)比起其他的數位至類比轉換器，像是電阻式數位至類比轉換器(R-string DAC)、電流控制式數位至類比轉換器(current-steering DAC)等，擁有較小的功率消耗，也符合了前文所說對於低功耗的需求。 在本篇論文之中，首次提出了設計於玻璃基板上之數位時間調變嵌入式畫素記憶體電路以及雙向循環式數位類比轉換器電路，其中畫素記憶體電路已經在三微米低溫複晶矽薄膜電晶體製程下成功被驗證。利用此畫素記憶體電路，可以將面板的平均功耗降低；而所提出的雙向循環式數位類比轉換器電路可以將八位元的數位訊號，經由開關電容(switch capacitor)的切換，轉換成對應的類比值，而比起傳統的電阻式數位至類比轉換器電路，擁有較小的面積，也就是意味著擁有較小的功耗。這兩種電路未來將可以被整合在面板上，帶來更便利性的應用。

In recent year, there are more and more researches on the low temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs). That is because the wide use on the portable system such as digital camera, mobile phone, notebook and so on. Compared to the conventional amorphous silicon TFTs, the electron mobility of LTPS TFTs is about 100 times larger. That’s why LTPS technology is suitable to integrate the driving circuits on peripheral area of display. By realizing the System-on-Panel (SOP) applications, slim, compact, and high-resolution display can be achieved. The demand of low power has boosted for various electronic products because of the development of green technology. These fancy electronic products usually accompany large use of LCD panels. The research topics and directions of embedded pixel memory prompt in order to lower the power consumption of LCD panels. Further, to lower the power consumption of electronic products which contain these LCD panels in order to satisfy the world standard of green products. Besides, the development of SOP urges more and more researches about the integration of driving circuit on the glass substrate. D/A converter (DAC) is an essential part for the whole driving circuit. Cyclic DAC has smaller power consumption than some other kind of DAC, like R-string DAC, current-steering DAC and so on. In this thesis, a proposed on-panel digital time-modulation embedded pixel memory circuit and a two-direction cyclic DAC designed and implemented with the TFTs on glass substrate has been proposed in a 3-□m LTPS process. Also, the pixel memory circuit has been successfully verified. The average power consumption can be reduced with this pixel memory circuit. The propose two-direction cyclic DAC circuit can convert 8-bit digital signal into corresponding analog value with switching of the switch capacitor circuit. The cyclic DAC has smaller area rather than conventional cyclic DAC, which means lower power consumption. These two kinds of circuit can be integrated in the active matrix LCD (AMLCD) panels.