Effects of low temperature annealing on the ultrathin La2O3 gate dielectric; comparison of post deposition annealing and post metallization annealing

This work reports the effects of low-temperature post-deposition annealing (PDA) and post-metallization annealing (PMA) on the electrical properties of ultrathin (with EOT ranging from 1.29 nm to 2.33 nm) La2O3 gate dielectric films. We found that positive charges were generated during the PDA as evidenced by the negative flat-band voltage (VFB) shift. Forming of La-silicate interface layer and a reduction in the channel mobility are found for the PDA samples at temperature higher than 300°C. Better electrical characteristics were achieved by the PMA. The PMA sample has a peak channel mobility of 319 cm2 /Vs.