Reduced Leakage Current in Al2O3/TiO2/Al2O3 Dielectric Stacks Grown by Pulsed Laser Deposition

We have grown metal-insulator-metal (MIM) capacitors with TiO2 and Al2O3/TiO2/Al2O3 (ATA) as dielectric thin films using pulsed laser deposition (PLD) on platinized silicon (Pt-Si) substrates. TiO2 thin film thickness was maintained at similar to 40 nm for both TiO2 and ATA based MIM structures. ATA based MIM structures with two different Al2O3 thicknesses of 3nm and 6nm were grown. The as grown MIM structures were characterized by current-voltage (J-V), capacitance -frequency (C-F) and capacitance-voltage (C-V) measurements. We have observed a minimum leakage current density of similar to 2.03 x 10(-8) A/cm(2)at 3V for ATA based MIM structures with Al2O3 barrier layer thickness similar to 6 nm which is less than that of TiO2 based MIM structures by orders of magnitude. Abrupt decrease in the leakage current of ATA based MIM structures is due to the introduction of Al2O3 on both sides of TiO2 which offers a potential barrier to the flow of carriers and minimize the leakage paths. Capacitance density was found to be invariant with both the variation in voltage and frequency. Observed low leakage current density and invariance of capacitance density with applied voltage and frequency demonstrates its potential in various higher frequency capacitive storage circuit applications.