Improvement Of Crosstalk In TFT-LCD Process

The thin film transistor liquid crystal display (TFT-LCD) industry is rapidly developing, particularly in the field of small and medium size flat-panel displays. However, if TFT-LCD technology can comprehensively replace other flat panel display technologies, some challenges like large panel size, high resolution and high picture quality requirements still need to be overcomed. The reduction of panel size will result in many problems, e.g., the TFT width is narrower and the pixel spacing is smaller, which will increase the impact of crosstalk, flicker, image sticking, etc.. These become several major challenges to upgrade picture quality. Particularly following the TN-LCD technology, newly developed VA and IPS-type LCDs with new electrode design will more easily lead to crosstalk problems.However, improvent of LCD drivers has been the main method used to suppress crosstalk. But it is unstable, and for different types of products even for one kind of product it also needs a specific drive code. This is obviously not efficient. Using new structures to improve the crosstalk is mainly by increasing the line spacing, but it will reduce the aperture ratio and high resolution,which is contrary to the direction of TFT-LCD development. To fundamentally solve the crosstalk, it is more and more important to find the relationship between fabrication process and crosstalk.This paper studies the origin of crosstalk through the analysis of its strong correlation processes. The first chapter introduces the basic principles of TFT-LCD and crosstaIk phenomena. The second chapter introduces the preparation and testing methods of TFT-LCD, and the third and fouth chapters are mainly to find the strong correlations between crosstalk and processes:1. Vertical crosstalk improvementFirstly, this section analyzes the LCD screen with vertical crosstalks and determines the characteristics of the TFT off-state anomalies leading to vertical crosstalks. Then the theoretical analysis of the off-state TFT reaveals the main process factor which causes the abnormal TFT characteristics is dry etch process. Dry etch DOE tests are carried out to verify the impact of dry etch on the off-state TFT characteristics. This section also studies the large anomalies of I-off in a large glass and eventually improves the I-off uniformity. Finally the best dry etch conditions is determined.2. The improvement of horizontal crosstalk and the coupling capacitanceThe common electrode line resistance is reduce by increasing the the PVD metal film thickness, which further reduces the common electrode line delay and eliminates the horizontal crosstalk. This section also analyzes the coupling capacitance and the relationship between coupling capacitor and crosstalk. The minimum distance between the pixel electrode (ITO) and the signal line (S/D) is then determined, which provides data for further pixel aperture ratio improvement.