Fault-Aware Page Address Remapping Techniques for Enhancing Yield and Reliability of Flash Memories

Abstract

Based on the fault behaviors of conventional fault models, the 1-safe and 0-safe fault types are derived in this paper. We can try to store the safe value of a flash cell such that the fault effects can be masked. To boost the masking probability, both the data inversion (DI) and the page address remapping (PAR) techniques are also proposed. DI tries to complement the data bits to be programmed if their values derivate from the safe values of the corresponding faulty flash cells. PAR manipulates the logical-to-physical mapping of data words and the buffer words such that faulty cells can be programmed with their safe values. Since most of the fault effects are masked, we can reduce the strength of the adopted ECC or the amount of incorporated redundancies. The corresponding hardware architectures are also developed. A simulator is developed to evaluate the hardware overhead, repair rate, and reliability. According to experimental results, these measures can be improved significantly with negligible hardware overhead.