FPGA Implementation of Scram Memory Testing Technique Using BISR Scheme

Abstract

As RAM is major component in present day SOC, by Improving the yield of RAM improves the yield of SOC. So the repairable memories play a vital role in improving the yield of chip .Built-in self-repair (BISR) technique has been widely used to repair embedded random access memories (RAMs). If each repairable RAM uses one self contained BISR circuit (Dedicated BISR scheme), then the area cost of BISR circuits in an SOC becomes high. This, results in converse effect in the yield of RAMs. This paper presents a reconfigurable BISR (Re-BISR) scheme for repairing RAMs with different sizes and redundancy organizations. An efficient redundancy analysis algorithm is proposed to allocate redundancies of defective RAMs. In the Re-BISR, a reconfigurable built-in redundancy analysis (Re-BIRA) circuit is designed to perform the redundancy algorithm for various RAMs. A built-in self-repair (BISR) scheme for random access memories (RAMs) with 2-D redundancy has a built-in redundancy analyzer (BIRA) for allocating the redundancy. The BIRA typically has a cache-like element called local bitmap for storing the fault information temporary. The BISR reuses the local bitmap to serve as spare bits such that it can repair more faults. In addition, a row/column/bit redundancy analysis (RCB-RA) algorithm for a RAM with spare rows, spare columns, and spare bits is presented. The Re-BISR structure has been synthesized and found that the area cost when compared with the Dedicated BISR structure is very small. This paper is implemented using Verilog HDL. Simulation and Synthesis is done using ModelSim and Xilinx ISE Tools.