Analysis And Improvement Of TFT-LCD Blue Twill

As one of the current mainstream display technologies,thin-film transistor liquid crystal display（TFT-LCD）has been developed over the past 30 years,which contains several different technical directions,namely high-temperature polycrystalline silicon,low-temperature polycrystalline silicon and amorphous silicon technology.Each technology has a certain degree of advantages and disadvantages.The most widely used one is amorphous silicon technology,which has rapidly occupied most market share owing to its huge merits in production cost,technical maturity and product quality.In order to ensure that the products can pass the reliability test,it is necessary to verify the problems that may occur in the actual use process in advance.This paper mainly studies the causes of the blue twill of TFT-LCD during the reliability test and the corresponding improvement scheme.The blue twill is mainly caused by the difference in the threshold voltage(V_th)of the red,green and blue sub-pixels,which results in a large difference in the leakage power of different pixels.There are two main factors in the generation of V_th.The first compressive stress causes the amorphous silicon semiconductor layer to be mismatched with the stress of the insulating layer to produce defect states at the interface,and the amorphous silicon film layer or the gate insulating layer itself.The Si-H bond,the Si-Si bond,and the NH bond may both be broken to form a defect state.The second is the V_th shift caused by the negative voltage of the long-term gate voltage.According to the reason of V_th offset,this paper provides two strategies,the main contents are as follows:1)Through the improvement of the film quality,suppression of defect density in the interface between the amorphous silicon and the insulating layer during the production process of the back channel of the 4-mask process through the O₂ ion treatment,the standard process parameters for the upper and lower electrode energy4KV/4KV,the pressure 100 m Torr processing time 70 seconds,At the same time,the number of floating keys was reduced by hydrogen processing before Si N_x film formation.The above strategies remarkably reduce the defect density of the film and the offset of the V_th.2)Implement of POA（Photo Spacer on Array）process facilitated to reduce TFT pressure about 1/4 of the original when the force is applied when the pressure is inversely proportional to the force area,while the upper and lower surface area of PS（Photo Spacer）difference is large.This process also aids to suppress the defect state and reduce the V_th offset.Both solutions have passed the reliability verification,and developed fabrication standards.The research results will provide powerful theoretical and technical support for the improvement of TFT-LCD display quality in the future.