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 pO2=10kPa. 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 Qf=4×1012cm-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=0.95nm with Jg=1.1×10-2A/cm2 was found for binary HfO2 layer with 4 nm physical thickness. Lowest leakage current density Jg=1.9×10-7A/cm2 was for a 4 nm laminate deposited at 420 °C and with a cooling rate of 2 °C/min during PDA.