Sol-gel ZrO2 and ZrO2-Al2O3 nanocrystalline thin films on Si as high-k dielectrics

Currently, the conventional dielectric, SiO2 or SiON is being replaced by alternative materials to suppress high leakage currents observed at low film thickness. In this work, thin layers of ZrO2 and (ZrO2)x(Al2O3)1-x, deposited on Si substrates are obtained by sol-gel method. The structural and electrical properties as a function of the annealing temperature are studied. Usually, the post-annealing temperature of 700 deg. C leads to re-crystallization in ZrO2 layers, which can induce high leakage current and severe mass transport along the grain boundaries. The purpose is to amorphisize the films by adding aluminium oxide and in this way improve their electrical behaviour. Structural analysis shows that ZrO2 films are crystallized, meanwhile the mixed oxide films remain in amorphous state even after high temperature annealing. The obtained results are encouraging and determine the (ZrO2)x(Al2O3)1-x films as a promising material with good dielectric properties.