Impact of layer thickness on the ferroelectric behaviour of silicon doped hafnium oxide thin films

The ferroelectric behaviour of silicon doped hafnium oxide has been investigated using metal–insulator–metal capacitor structures for film thicknesses of 9 and 27 nm, annealing temperatures between 450 and 1000 °C and silicon contents from 0 to 8.5 cat%. For the 9 nm thick films, an improvement of the ferroelectric remanent polarization was revealed for decreasing silicon content and increasing annealing temperature, which corresponds well with the HfO2 structural phases observed by x-ray diffraction. An increase of the film thickness up to 27 nm induced an apparent decrease of the remanent polarization and modified the temperature dependence. This change in the ferroelectric properties was shown to be determined by the different crystallization behaviour of the thick films with respect to the thin films.

► We investigated the ferroelectric behaviour of Si-doped HfO2 layers. ► The effects of film thickness, Si-content and annealing conditions were examined. ► Increasing Si content induced reduction of the remanent polarization (Pr). ► A significant decrease of Pr was detected with increasing film thickness. ► Crystallization under mechanical confinement was shown to be essential.