Oxide Particle Induced Leakage in Flash Memory Endurance Test

In this paper, two NOR flash memory test vehicle samples, which failed in endurance cycling stress test, were investigated. The failure location is first determined by electrical test bitmapping. Subsequent failure analysis showed a SiO_x particle at the failure location, which is provided by bitmap. The oxide particle is chemically different from surrounding inter-metal dielectric oxide, containing F and having higher Si:O ratio (Si rich) compared to normal inter-metal dielectric (IMD). We suspected that a SiO_x particle was the root cause of leakage causing checkerboard failure. The hypothesis is that the oxide particle is not neutral but positively charged; during an endurance test, the charges would be activated by thermal heating and driven by an electrical field, and would finally form a leakage path between two metal lines. The particle is different from normal inter-metal dielectric in its stoichiometry, unusually Si-rich. This makes it easier for charge transport