Defect detection from visual abnormalities in manufacturing process using IDDQ

Abnormal I_DDQ (quiescent V_DD supply current) indicates the existence of physical damage in a circuit. Using this phenomenon, a CAD-based fault diagnosis technology has been developed to enhance the manufacturing yield of logic LSI. This method to detect the fatal defect fragments in several abnormalities identified with wafer inspection apparatus includes a way to separate various leakage faults, and to define the diagnosis area encircling the abnormal portions. The proposed technique progressively narrows the faulty area by using logic simulation to extract the logic states of the diagnosis area, and by locating test vectors related to abnormal I_DDQ. The fundamental diagnosis way employs the comparative operation of each circuit element to determine whether the same logic state with abnormal I_DDQ exists in normal logic state or not