Gate oxide wear out using novel polysilazane-base inorganic as nano-scaling shallow trench filling

The phenomenon of floating gate (FG) crystallization and extrinsic gate oxide breakdown (V_bd) are discussed using polysilazane-base inorganic material SOD (Spin-On-Dielectric) as shallow trench isolation (STI) filling for 50 nm flash memory fabrication. The pinholes are found along the FG grain boundary in wide active regions because of tensile stress induced by SOD material in STI process, thus gate oxide wears out by following wet cleaning steps. The chemical oxide formation during FG deposition can effectively inhibit gate oxide early breakdown. Moreover, FG sheet resistance (R_s) in 550 °C/air deposition condition can significantly reduce about 20% in comparison with 520 °C/O₂ and 400 °C/N₂ conditions.