Interface Structure and Dielectric Properties of SrTiO3Thin Film Sputter-Deposited onto Si Substrates

Authors:
Publisher website
Google Scholar
Abstract
SrTiO3thin film preparation onto Si substrates using RF magnetron sputtering has been studied for a high capacitance density required for the next generation of LSI's. Structural and chemical analysis on the interface between SrTiO3film and Si was carried out with cross-sectional TEM, EDX, and AES. Dielectric properties were measured on AuTi/SrTiO3/Si/Ti/Au capacitors. The as-grown dielectric films on Si were analyzed and found to consist of three layers; SiO2, amorphous SrTiO3and crystalline SrTiO3, from interface toward film surface. By annealing at 600 °C, the amorphous SrTiO3layer was recrystallized, and consequently the capacitance value increased. A typical specific capacitance was 4.7 fF/μm2and the leakage current was in the order of 10−8A/cm2, for 180 nm thick SrTiO3film. The dielectric constant decreased from 147 to 56 with decreasing SrTiO3film thickness from 480 nm to 80 nm. This is due to the low dielectric constant SiO2layer (ε=3.9) at the interface. From the film thickness dependence of the ε value, the SiO2layer thickness was calculated to be 3.9 nm, which agreed well with the value directly observed in the TEM.To avoid SiO2layer formation, barrier layers between SrTiO3and Si have been studied. Among various refractory and noble metals, RuSi and a multi-layer of Pt/Ti have been found to be promising candidates for the barrier material. When RuSi film or Pt/Ti film was formed between SrTiO3film and Si substrate, dielectric constant of about 190 was obtained in dependent of the SrTiO3film thickness in the range of 80–250 nm. Analysis on the barrier layers was performed by means of RBS, XPS and XRD.

This publication has 10 references indexed in Scilit: