关键词: 反熔丝型FPGA, 失效分析, Flash Pro5, FIB 制样, Obirch测试, SEM检查

Abstract: Anti-fuse FPGAs are core chips widely used in the aerospace field, and the accuracy of their failure analysis is directly related to the safety of aerospace vehicles. Anti-fuse FPGA is a one-time programmable device. It does not require an external configuration memory, and the program is burned into the anti-fuse. Online debugging cannot be carried out, and it is also impossible to use tools like SignalTAP to capture signal wareforms online. This paper aims at the fault problem of a certain type of anti-fuse device, infers the possible causes, constructs a fault tree, and investigates the doubts one by one. Using Flash Pro5 combined with the upper computer software, leading out and observing the internal signals of the normal devices and abnormal devices step by step according to the connection relationship in the data netlist. By comparison, the fault location is founded. Then, test points are introduced by FIB sample Preparation, and the resistance between test points is tested by Obirch. Combined with SEM electrom microscope scanning, layer-by-layer test and inspection are carried out, and slicing is performed to confirm the specific failure point and failure cause. Finally, failure mechanism analysis is carried out to verify the reliability of the analysis. 

Key words: anti-fuse FPGA, failure analysis, Flash Pro5, FIB sample preparation, obirch test, SEM inspection