Structural and electrical characterization of Al/ZrO2/Si capacitors
ZrO2/Si thin films were fabricated using sputtering technique and the deposited films were annealed at temperatures of 873 K and 1073 K. From HRTEM analysis, it is observed that the as-deposited ZrO2 layers are partly amorphous and fully crystallize after post-deposition annealed at 1073 K. The dielectric constant of the as-deposited films was 15.0 and it increased to 29.0 with increase of annealing temperature to 873 K there after it decreased to 24.5 at higher temperature of 1073 K. The leakage current through the gate stack is reduced by several orders of magnitude after air annealing, consistent with the increase of SiOx layer thickness, as well as the reduction in trap density revealed by the reduced hysteresis effect observed in the C-V characteristics. The interfacial quality was improved notably for the devices annealed at a temperature of 1073 K. The plausible reason for the variations in the observed electrical characteristics could be due to the significant growth in the SiO2 at the interface between ZrO2 and Si substrate, which was also confirmed by the EELS/EDS analysis.