USING INDEPENDENT COMPONENT ANALYSIS BASED PROCESS MONITORING IN TFT-LCD MANUFACTURING

Large-sized Flat-Panel Displays (FPDs) have become increasingly important for use in PC monitors and TVs. To improve the yield of Liquid Crystal Display (LCD) panels, process control becomes a critical task in LCD manufacturing. In this paper we propose a control chart based on Independent Component Analysis (ICA) to monitor TFT-LCD process variations. The proposed method can be effectively used in monitoring an LCD critical process parameter called Total Pitch (TP). TP is a parameter that is used to control alignment errors in the TFT-LCD process. TP variations may cause serious defects like mura (brightness unevenness of a panel) and small bright points on the display area of LCD panels. Since the collected data may be a mixture of noise and different source signals, ICA is first applied to separate mixed signals into independent data. Further, X-bar and R control charts are used to monitor the separated source signals. Experimental results on real measured TP data collected from the TFT-LCD process showed that the proposed method can reliably detect process variation.