Electrical fault isolation of intermittent frequency-dependent BRAM functional failure using fast frequency initialized read-only test and failure pattern commonality analysis

Block Random Access Memory (BRAM) is a dedicated 18K/36Kbits hard logic configurable memory module embedded in Field Programmable Gate Array (FPGA) devices. BRAMs can be inferred as First In, First Out (FIFO) buffers, single or dual port, and cascading memory blocks accessed via by-1, 2, 4, 9,18, and 36 modes. Physical failure analysis (PFA) of intermittent read and write failures evident only at fast frequency mode due to void-like metal defect in 36K(36,864 bits) BRAM block is very difficult and complex. Conventional PFA techniques such as OBIRCH and photon emission analysis cannot be used to localize the failure because of frequency dependency and intermittency of failure. Nano-probing each metal trace is almost impossible for an extremely wide area of memory array. This paper will discuss the fast-frequency, initialized read-only diagnostic and failing signature commonality analysis technique and how it was utilized to quantify and localize the defect of an intermittent BRAM failure. A metal-void defect was found as an evidence of this intermittent failure electrically fault isolated by the technique described in this paper.