Non referential method for defects inspection of TFT-LCD pad

Detecting defects is important technology of the TFT-LCD (Thin Film Transistor-Liquid Crystal Display) production process for quality control. For high quality and improving productive, defect detection is performed on each manufacturing process. In array process, defect inspection is divided into inspection for active matrix area and inspection for pad area. Inspection on active matrix area has used period of pattern to detect defect. As pad has non repetitive pattern, period can not be used for defect detection. Therefore, defects on pad have been detected by referential method comparing to pre-stored reference pad image. Subtraction has been used for comparison with reference pad. This method is problematic for pad defect inspection due to variance in the shapes of pad, illumination change and alignment error. In this paper, we propose the inspection method making up for limitation of referential method which has been used for TFT-LCD pad. Inspection is performed by applying morphological method to each horizontal line. By finding valley of each line, defect is detected.