SRAM Cell Engineering Failure Analysis Basing On Electrical Testing

SRAM is the mostly used test vehicle for new process tunning and production process monitor for most foundary. Through the addressability of SRAM, it is easy to determin the point of the fault, and then the PFA method was used to confirm the fault type and root cause. In the end we defined the process step which casued the fault, and thus fixed it.In this thesis, a new analysis flow has been proposed for the fault of a SRAM cell, which does not depend on physical fault analysis (PFA), but depend on electrical analysis by menas of the special test flow design and the DFT circult. The key contens are as follows:(1) The working principle of the SRAM cell was analyzed comprehensively, and the mechansims of low power supply fault as well.2) The model of low power supply fault was established. With the aid of the DFT circults and the special test flow, the electrical data were obtained and analysed, thus the fault positions could be located on the specifical MOSFET and the type of failure.3) The reliablity of the new method was confirmed by analysing the failure cells and comparing the new method-based data with the conventional PFA data.Compared with the conventional PFA methed, the new method based on analyzing of the electrical data is limited on principle, thus its precision is lower than the conventional method. However, it is non-destructive, less time consumption and capable of mass testing, therefore, this type of new method is more suitable for the application in the field of engineering anlysis.