Annealing temperature influenced physical properties of Al2TiO5 thin films for MIS devices

Abstract

Aluminium titanate (Al2TiO5) thin films were deposited at room temperature by DC reactive magnetron sputtering. To make appropriate films for potential gate dielectric applications, we investigated the influence of annealing temperature on the structural, chemical and dielectric properties of Al2TiO5 thin films. From XPS studies, in as-deposited films, it has been observed that the presence of Al3+ and Ti4+oxidation states which correspond to Al2O3 and TiO2 respectively. After annealing at 400 °C in oxygen ambient, the binding energies of Al 2p, Ti 2p and O 1s were shifted by ~ 1 eV towards lower binding energy. This indicates the formation of an intermediate compound of Al2O3 and TiO2. The extracted Al, Ti and O ratio was 2:1:5 and it confirms the formation of Al2TiO5. XRD studies indicate that the as-deposited films were amorphous in nature. After annealing at 400 °C, diffraction peak at 2θ = 50.6° along (200) plane corresponds to aluminum titanate (Al2TiO5) has been observed. Metal-Insulator-Semiconductor (MIS) capacitors were fabricated and characterized to estimate the dielectric properties of the deposited films. The as-deposited films show low dielectric constant (κ = 8.1) and high leakage current density (J = 2.4x10-2 A/cm2 at -1V) values. After annealing at 400 °C the films show improved dielectric constant (κ = 9.4) and leakage current density (J = 4.6x10-9 A/cm2 at -1V) values. The enhancement in the device properties can be attributed to the improved oxide and interface quality after annealing. Equivalent oxide thickness (EOT) of less than 1nm is required to use Al2TiO5 as an alternate gate dielectric to SiO2 in CMOS industry. To achieve this scaling of the dielectric thickness (<5 nm) is needed, which is under investigation. Copyright © 2017 VBRI Press.