FLASH MEMORY RELIABILITY

With reference to the mainstream technology, the most relevant failure mechanisms which affect yield and reliability of Flash memory are rev iewed, showing the primary role played by tunnel oxide defects. The ef fectiveness of a good test methodology combined with a proper product design for screening at wafer sort latent defects of tunnel oxide is h ighlighted as a key factor for improving Flash memory reliability. The degradation of device performance induced by program/erase cycling is discussed, covering both the behaviour of a typical cell and the evol ution of memory array distribution. The erratic erasure phenomenon is illustrated as the most relevant mechanism reported so far to cause si ngle bit failures in endurance tests. Finally, reliability implication s of multilevel cell concepts are briefly analysed. (C) 1998 Elsevier Science Ltd.