Evaluating the top electrode material for achieving an equivalent oxide thickness smaller than 0.4 nm from an Al-doped TiO₂ film.

The effects of Pt and RuO2 top electrodes on the electrical properties of capacitors with Al-doped TiO2 (ATO) films grown on the RuO2 bottom electrode by an atomic layer deposition method were examined. The rutile phase ATO films with high bulk dielectric constant (>80) were well-grown because of the local epitaxial relationship with the rutile structured RuO2 bottom electrode. However, the interface between top electrode and ATO was damaged during the sputtering process of the top electrode, resulting in the decrease in the dielectric constant.

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).

Controlling work function and damaging effects of sputtered RuO₂ gate electrodes by changing oxygen gas ratio during sputtering.

RuO₂ metal gates were fabricated by a reactive sputtering method under different O₂ gas ratios. For the given sputtering power of 60 W, a ∼13% O₂ ratio was the critical level below or over which RuO₂ film has hyperstoichiometric and stoichiometric compositions, which resulted in a difference in the effective work function by ∼0.2 eV.