Abstract

Contact resistance from wafer acceptance test (WAT) data is one of the critical parameter to significantly affect fabrication process. While WAT data shows open/short fail, high resistance fail and leakage fail in contact chain structure, the first job in failure analysis (FA) field is to localize failure site. For example, High resistance failure and leakage failure sites can be localized by Infrared Ray Optical Beam Induced Resistance Change (IR-OBIRCH) detection. Most of open failure modes could be isolated by front side passive voltage contrast (PVC) technique. However, there is still a limitation to this technique while contacts are still connected to substrate in metal-1/contact/active chain structure. Active Voltage Contrast (AVC) [1, 2] is a good method to overcome this problem, but the major concern is how to mark the failure location in SEM based probing system. In this paper, we provide a novel backside passive voltage contrast method to improve the failure analysis technique. By thinning down silicon substrate to the active area, a new contact chain from active area is created. Therefore, novel backside PVC is applied to locate the failed site.

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