高效能非晶矽閘極驅動電路之設計、製造與特性量測

Abstract

嵌入式閘極驅動電路可應用於不同製程下的薄膜電晶體，如多晶矽、非晶矽和金屬氧化物半導體。因非晶矽薄膜電晶體的製程技術最為成熟且其產品應用最為寬廣，針對非晶矽閘極電路的探討也較為廣泛。非晶矽閘極驅動電路的研究和開發常隨著面板產品需求而逐漸改良與精進以期可以逐漸與多晶矽產品相匹敵。在目前熱門高解析度的面板產品中，所搭配的非晶矽閘極驅動電路就需要更嚴謹的設計以達到更高效能輸出而縮短與多晶矽產品的差異。一般而言，低雜訊與高可靠度的非晶矽閘極驅動電路為符合目前中高階液晶顯示器的主要基本需求；此外因為高解析度、高品質的面板，非晶矽閘極驅動電路的驅動能力也須隨之提升。受限於非晶矽材料元件的低電子移動率與不穩定性，非晶矽閘極驅動電路需尋求在電路架構上與驅動方式上的突 破以符合目前中高階產品規格。 隨著平面顯示器在日常生活的應用越來越廣泛，液晶螢幕顯示器製造技術發展也日趨純熟與穩定發展，小至攜帶型液晶手錶，到一般的智慧型手機、平板電腦、桌上型螢幕，大到上百吋的電視螢幕，液晶螢幕顯示器已完全融入現代電子化的生活之中。台灣是全球面板主要供應地，面板產業及其週邊設備、材料的公司也都蓬勃發展，對於目前製作技術純熟和生產成本較低的非晶矽製程的液晶面板成為目前液晶螢幕顯示器主流商品。因此其相關影像品質提升與高規格產品之技術也逐年被探討與應用。 本文中研究四組不同的非晶矽閘極驅動電路設計，包括提出新的驅動方式，在第三章提出一種有別於一般的時脈輸入訊號，使電路的可靠度可有效提升之外也可降低輸出訊號雜訊；在第四章提出一種相較其他改善方式可達到提升輸出驅動能力而又不耗損過多功耗的驅動方法，以上兩章皆是以改變驅動方式之作法提升電路效能，而另一種概念則是改變電路架構也可提升電路效能，第五章中提出一種新式電路架構可內部產生新的下拉訊號供電路達到高可靠度與低雜訊輸出；第六章則提出為縮短輸出的下降時間將原有電路作新的元件連接之作，使其產生更有力的下拉訊號使輸出下降時間有效縮短且並不影響整體電路佈局空間。 總之，本文所研究之四組電路皆實際下線於面板五代廠的非晶矽薄膜電晶體製程而產生電路樣本，實體驅動後的輸出特性數據可完整的被收集並分析。由量測數據顯示各電路皆可達到設計目標要求並應用實現於面板上，提供非晶矽閘極驅動電路面板設計上較佳的改善對策之外，也可在日後新製程的電晶體的驅動電路設計上一起應用。

The embedded gate driver circuits can be applied in various thin-film-transistor (TFT) processes, such as poly-silicon, amorphous-silicon (a-Si) and metal oxide semiconductor. Because of the mature process technology and extensive applications in a-Si TFT technology, the relative research and development are more common in current years. The a-Si gate (ASG) driver circuits are always imported to be applied in high-level liquid crystal display (LCD) panels. Moreover, it may be compared with the poly-silicon panel with embedded gate driver circuits by more advanced development in a-Si technique. In the popular LCD product with high-resolution panel, the rigorous specification makes ASG to be designed to output superior performance. The high reliability and low noise are the two main basic requirements for ASG circuits integrated in the medium and high level LCD. In order to meet the requirements, the driving capability of ASG circuits have to be enhanced by novel circuit design and advanced process. Because of the low electron mobility of a-Si material, the novel driving methods and special circuit structures can be adopted in ASG circuit to achieve the final designated goals. The LCD application has become so widespread that there is much merchandise with LCD panels in the consumer electronics. Therefore, the fabrication of LCD tends to developed and established for most fields. The more advanced techniques are still studied and researched to highly improve the quality of LCD product. Taiwan is the main supply place for LCD panels in the world, LCD factories and associated industries, such as the material suppliers and equipment manufacture, are strikingly developing. It is still the main stream for a-Si TFT-LCD product in current display panel marketing. Therefore, ASG technology could be extensively studied and applied in LCD topics. In this study, there were four particular ASG circuits proposed to explain the novel driving methods and innovative circuit structures individually. These circuits could enhance the ASG output performance effectively. In Chapter 3, a modulated clock signals were imported in ASG circuit to improve the reliability and reduce the noise. Unlike other original clock signals, the proposed clock signals were divided to two types, AC and DC frames. In Chapter 4, another driving method was introduced to enhance the ASG driving capability effectively but increase a little power consumption. In Chapter 5, an entire new ASG circuit were introduced to show the better reliability and lower output noise. The novel structure in the circuit created two complementary pull-down signals to keep the circuit stable. In Chapter 6, a new device connection in ASG circuit was used to reduce the output fall time. Moreover, the added device occupied such less layout area that the total circuit area were consistent. The ASG circuits that have been proposed and discussed in the chapters all were fabricated in a-Si TFT process to produce the real circuit samples. By inputting the driving signals in the samples, the data of output performance, such as the rise/fall time, ripple noise, power consumption, and so on, could be probed and analyzed. The measured results were fully meets performance expectation and verified to be applied in real LCD panels. Furthermore, there were some a-Si TFT measured to be certified the useful driving methods and circuits. The related operations and connection in the circuits, the measured results, and the experiment were all described and discussed in each chapter.