Interfacial Dead-Layer Effects in Hf-Silicate Films with Pt or RuO₂ Gates

The interfacial dead-layer (DL) effects at the interfaces between Hf-silicate films and Pt or RuO2 gate metals are examined. The Si content in the Hf-silicate film was controlled to vary the dielectric constant (k). The DL effect was strongly dependent on the k value of the Hf-silicate layer, and was suppressed when the Si content was increased to ∼80% (k ≈ 6). This Si content also coincides with the Fermi level pinning-free composition. Therefore, the optimum high-k gate dielectric structure could be a higher-k layer HfO2 capped with a lower-k layer (k ≈ 6) with minimum thickness (∼1 nm) for the best dielectric performance.