Thermal stability and electrical properties of Zr silicate films for high-k gate-dielectric applications, as prepared by pulsed laser deposition

Abstract

Zirconium silicate films with high thermal stability and good electrical properties have been prepared on n-Si(100) substrates and commercially available Pt-coated Si substrates to fabricate metal–insulator–metal (MIM) structures by the pulsed laser deposition (PLD) technique using a Zr0.69Si0.31O2-δ ceramic target. Rapid thermal annealing (RTA) in N2 was performed. X-ray diffraction indicated that the films annealed at 800 °C remained amorphous. Differential thermal analysis revealed that amorphous Zr silicate crystallized at 830 °C. X-ray photoelectron spectroscopy showed that RTA annealing of Zr silicate films at 900 °C led to phase separation. The dielectric constant has been determined to be about 18.6 at 1 MHz by measuring the Pt/Zr silicate/Pt MIM structure. The equivalent oxide thicknesses (EOTs) and the leakage-current densities of films with 6-nm physical thickness deposited in O2 and N2 ambient were investigated. An EOT of 1.65 nm and a leakage current of 31.4 mA/cm2 at 1-V gate voltage for the films prepared in N2 and RTA annealed in N2 at 800 °C were obtained. An amorphous Zr-rich Zr silicate film fabricated by PLD looks to be a promising candidate for future high-k gate-dielectric applications.