A method of contact level PVC enhancement

PVC (Passive Voltage Contrast), as a basic localization method by using SEM, has been widely used in IC failure analysis process. Because of the difference of under layer structure, the secondary emission induced charge accumulation and the surface potential may also be different. Generally, we use it to judge the structure under CT is good or not. But PVC method does not always work well for all cases. We need to consider about the PVC method used for fault isolation case by case, due to the difference of device structure. In this paper, we will provide some typical cases, such as in ROM, by using a particular modified PVC method enhancing PVC result. We will discuss the limitation of normal PVC in memory cell array. And an optimal solution will be given.