Structure and dielectric properties of low fluence excimer laser annealing of sol-gel HfO2 thin films deposited on Si wafer

Sol-gel HfO₂ thin films, prepared from etoxid precursor, were deposited onto silicon wafer substrates by dip-coating. Low fluence multipulse excimer laser processing was used for sol-gel film densification. The small duration of the laser pulse heating limits the quantity of oxygen atoms arriving from the surface at the HfO₂/Si interface. Laser irradiations were performed using a XeCl (308 nm) excimer laser, with a homogeneous laser beam. The nanostructure evolution of the laser irradiated films, using different laser fluences between 30 and 120 mJ/cm² and different number of pulses, was studied by systematic cross section transmission electron microscope (XTEM) observations. Dielectric constant measurements were performed on the sol-gel HfO₂ films samples after laser annealing. The optimum laser processing conditions were found to be a laser fluence of 80 mJ/cm² and 5000 to 10000 laser pulses. In these conditions, uniform densified HfO₂ amorphous films with a dielectric constant of about 25 were obtained.