A Method Overcomed The Impact Of Process Parameter In I_DDTtesting

The IDDT testing can detect defects by different IDDT between the defect-free circuits and the defect ones. When the defect is activated, if the difference is marked, then we can say some defects are detected. But, even same integrated circuits manufactured by same technics also have different process parameter, and with the application of very deep submicron, some process variations can effect on circuit operation. In IDDT testing, same integrated circuits manufactured by same technics can draw different IDDT due to the process variations between the circuits even though an identical test vector is applied to them. When the difference is marked, it is difficult to determine whether the variation in IDDT is due to process variation or is due to defects. And if we disregard the effects of process variation on circuit operation, it is very possible that we consider that defects are detected.So, a method should be brought forward to overcome the problem of the process variation in IDDT testing. And in IDDQ testing, two integrated circuits of the same design can also draw different IDDQ values for the same set of input test vectors due to process variations between the two circuits. The concept of"current signatures"was proposed to distinguish the good circuit and defect ones more effectively. Current signatures do not detect defects by a single pass/fail threshold, but by the character of the signatures. From the measured values of IDDQ, a current signature is generated. The current signature includes an ordering of the IDDQ measurements from the smallest value to the largest value. The impact of process variation in IDDQ can be overcomed effectively according to the invariance of current signatures. In this paper, the concept of"current signatures"is applied to the IDDT testing. A method which may overcome the impact of process parameters variation in IDDT is propsed by according to the invariance of current signatures, and is validated by PSPICE simulation. Experimental results show that this methold can overcome the impact of process parameters variation in IDDT a certain extent, and is feasible.