Preparation and characterization of high-k praseodymium and lanthanoid oxide thin films prepared by pulsed laser deposition

Several lanthanoid oxide thin films such as those of PrOx, Sm2O3, Tb4O7, Er2O3 and Yb2O3 have been prepared on Si(100) wafers by the pulsed laser deposition method (PLD). PrOx film shows thin SiO2-equivalent oxide thickness (EOT) and low leakage current simultaneously. On the other hand, SmOx thin film does not show good properties. It is revealed by XPS spectra of the PrOx film that the deposition in O-2 ambient of 0.2 Torr produces an interfacial SiO2 or silicate layer. The sample deposited in a high vacuum at RT has only an ultra-thin interfacial layer, but hysteresis in the C-V characteristic and leakage current are large. Other techniques have been carried out to reduce the energy of ablated particles in order to prevent the growth of an interfacial layer. In the deposition method using a shadow mask, very flat thin films were obtained. However, the deposition rate was very low, and growth of the interfacial layer could not be prevented. By enlarging the distance between substrate and target, the smallest EOT with the PrOx film in our study has been obtained by the reduction of the energy of ablated particles.