Electrical and structural characterization of PLD grown CeO₂-HfO₂ laminated high-k gate dielectrics

The electrical and physical properties of CeO₂-HfO₂ nanolaminates deposited by pulsed laser deposition (PLD) are investigated. The properties of the nanolaminates are compared with binary CeO₂ and HfO₂ thin films. Layers were deposited using CeO₂ and HfO₂ targets at substrate temperatures between 220 and 620 °C in 10 Pa Ar+H₂ or O₂. In situ post deposition anneal (PDA) was achieved by controlled cooling down to room temperature with p_O2 = 10 kPa. Nanolaminates starting with CeO₂ show lower EOT and leakage compared to layers starting with HfO₂. TEM and XRD analyses showed thickness-dependent crystallinity of the layers, varying from amorphous to highly oriented polycrystalline phase. C-V and I-V measurements were done on the capacitors. Lowest fixed-charge density Q_f = 4 × 1 0¹² cm^{- 2} was found for the nanolaminates deposited at 520 °C. The k values of the nanolaminates extracted by the EOT-physical thickness plots were found to be 141, 48 and 22, for deposition temperatures 420, 520 and 620 °C, respectively. Higher k value for lower deposition temperatures is explained by the thickness dependent morphology of the layers. An EOT = 0.95 nm with J_g = 1.1 × 1 0^{- 2} A / cm² was found for binary HfO₂ layer with 4 nm physical thickness. Lowest leakage current density J_g = 1.9 × 1 0^{- 7} A / cm² was for a 4 nm laminate deposited at 420 °C and with a cooling rate of 2 °C/min during PDA.