Research On Blue Picture Twill In TFT-LCD Cu 4Mask Process

Since the beginning of the 21 st century,with the development of science and technology,the display performance has been continuously improved,which has led to the continuous development of liquid crystal displays toward large sizes,high refresh rates and high definition.The continuous progress of thin film transistor technology requires thin film transistors with low wiring resistance and low RC delay.The conventional aluminum process can no longer meet the growing demand for high-end products.The resistivity of copper metal materials is only 65% of the resistivity of aluminum metal materials,and it has better film-forming properties,so the copper process comes into being.At the same time,in order to reduce the production cost,it is necessary to reduce the mask process.Compared with the 5 mask process(5Mask),the 4 mask process(4Mask)has relatively fewer steps but high process requirements.Due to the simultaneous introduction of copper wiring and the 4Mask process,a new type of mura,namely the blue screen twill mura,appeared in the development and production of TFT-LCD panels.The production of blue screen twill mura seriously affects the reliability of the product.Therefore,the elimination of blue screen twill mura is a major problem to be solved urgently for the development of the Cu / Cu 4Mask process.First of all,in the design and production process of TFT-LCD liquid crystal panels,the causes of mura are various and need to be analyzed and improved from various aspects such as design,manufacturing process and materials.Starting from the basic structure and working principle of TFT-LCD,the article establishes a theoretical basis for the subsequent analysis of the cause of mura through the improvement of the process.Secondly,according to the cause of the blue screen twill mura,through the phenomenon analysis,find out the regularity of the blue screen twill mura.Due to the complicated mura genesis,this paper proposes to make a preliminary determination of the cause of the blue screen twill mura by charging and discharging and pressing.Then investigate the occurrence phenomenon,causes and countermeasures of each twill mura,and finally analyze the key points of the process to find out the cause of the formation of the blue screen twill mura,and provide an improvement direction for the subsequent elimination of the blue screen twill mura.Thirdly,the article studies the improvement method of the blue screen diagonal mura.First,research on the improvement of TFT electrical properties,and found that increasing the threshold voltage can reduce the blue screen twill Mura to a certain extent.Second,to improve the back channel contamination of TFT devices,this article proposes an oxygen ashing process(O2 Ashing).And Tof-SIMS analysis performed to verify the reliability of the samples of different processing time,the processing time is found at more than 30 s,which can effectively improve the picture blue denim mura.But there is a problem of small black spots,and the process conditions need to be continuously optimized.Thirdly,the replacement of Cu Stripper material with LTC water-based material can also improve the blue screen twill mura.Finally,through DOE experiment verification,taking into account the problem of blue screen twill and small black dots caused by copper oxidation,the O2 Ashing process parameters and the optimal process parameters are obtained.This promotes the large-scale application of the O2 Ashing process to existing plants and achieves the first mass production of the Cu / Cu 4Mask process in China.