Current VLSI devices have very complicated circuit designs and very small feature size. As a result, fault isolation on failing devices becomes a more and more challenging task. Although backside photoemission technique is commonly used to detect the failure site covered with multiple metal layers, it has the disadvantages of more time consumption and less success rate. Without a localized failure site, it will be very difficult, sometime even impossible, to find the physical evidence for the failures. This article describes a method that has been successfully used for isolating the wordline leakage on a memory FLASH device using FIB cutting and passive voltage contrast on the leaky wordline. The concept of this article is not just limited to this application; rather it can be used for all similar types of fault isolation work for other applications.

C4 (Controlled Collapse Chip Connection) failure analysis compared to conventional packages (DIP- LCC- QFP, etc.) is not trivial. For instance, one has to thin the C4 die for IR microscope inspection or for photon emission analysis. Then, after failure analysis on the die, it must be removed for deprocessing or further analysis. Three methods and techniques will be discussed for removing the C4 die from the package without damaging the die. However, for each technique it is very important to know the condition of the die and package prior to die removal. The method used will differ, for example, if the die is thinned or not.