Structure and dielectric properties of ultra-thin ZrO_2 films for high-k gate dielectric application prepared by pulsed laser deposition

摘要

ZrO_2 thin films have been prepared on Pt-coated silicon substrates and directly on n-Si(100) substrates by the pulsed laser deposition (PLD) technique using a ZrO_2 ceramic target under different deposition conditions. X-ray diffraction showed that the films prepared at 400 ℃ in 20 Pa oxygen ambient remained amorphous. Differential thermal analysis was carried out to study the crystallization behavior of ZrO_2. The dielectric constant of ZrO_2 was determined to be around 24 by measuring a Pt/ZrO_2/Pt capacitor structure. Sputtering depth profile X-ray photoelectron spectroscopy was used to investigate the interfacial characteristics of ZrO_2-Si stacks. A Zr silicate interfacial layer was formed between the ZrO_2 layer and the silicon substrate. The equivalent oxide thickness (EOT) and leakage current densities of the films with 6.6 nm physical thickness post-annealed in O_2 and N_22 ambient were investigated. An EOT of 1.65 nm with a leakage current of 36.2 mA/cm~2 at 1 V gate voltage for the film post-annealed in N_2 has been obtained. ZrO_2 thin films prepared by PLD have acceptable structure and dielectric properties required by a candidate material of high-k gate dielectrics.