Effect of mechanical stress for thin SiO/sub 2/ films in TDDB and CCST characteristics

摘要

The effects of mechanical stress for thin SiO/sub 2/ films in TDDB (time-dependent dielectric breakdown) and CCST (constant-current stress test) are discussed. Compressive stress induced by a WSi/sub 2/ layer enhances generation of native traps induced by electron injection and degrades the CCST characteristics of MOS capacitors. In TDDB characteristics, the compressive stress decreases the intrinsic lifetime for thin SiO/sub 2/ films. The tensile stress induced by the plasma SiO layer does not degrade the CCST characteristics. The generation of interface states by electron injection is enhanced on the MOS capacitors by the tensile stress. The mechanical stress degrades the reliability of MOS capacitors with thin SiO/sub 2/ films.