Reliability assessment of low |Vt| metal high-κ gate stacks for high performance applications

SILC analysis is a powerful tool for the assessment of breakdown characteristics of high-kappa devices. By applying the SILC analysis during high field stress, we determined that the degradation mechanism for LaO_x capped devices was drastically different as compared to the conventional Hf-based gate stacks. The La atoms diffused into the interfacial layer disrupting the SiO₂ structure which may affect the reliability of the La-doped stacks. On the other hand, similar analysis applied to the stacks with the Ru-Al bi-layer gate electrode demonstrated that the Al-contained stacks were similar to that of the baseline samples indicating that Al atoms, which preferentially substitute for Si in SiO₂, did not generate defects contributing to SILC.