Delta-IDDQ Testing of Resistive Short Defects

This paper addresses the efficiency of I_DDQ and more specifically Delta- I_DDQ testing when using a realistic short defect model that properly considers the relation between the resistance of the short and its detectability. The results clearly show that the Delta-I_DDQ approach covers a large number of resistive shorts missed by conventional logic testing, requiring only a relatively small vector set. In addition a significant number of defects which are proven to be undetectable by logic testing but may deteriorate and result in reliability failures are detected. The Delta- I_DDQ threshold and thus the equipment sensitivity is shown to be critical for the test quality. Furthermore, the validity of the traditional I_DDQ fault models when considering resistive short defects is found to be limited. For instance, the use of the fault-free next-state function for sequential I_DDQ fault simulation is shown to result in a wrong classification of some resistive short defects. This is the first systematic study of I_DDQ testing of resistive short defects. The impact of the threshold on the defect coverage is quantified for the first time. Although the simulation results are based upon a 0.35mum technology, the results and methodology can be transferred to state-of-the-art and NanoTechnologies