Structural and electrical characterization of phase evolution in epitaxial Gd2O3 due to anneal temperature for silicon on insulator application

Abstract

In this work, we understand the post-deposition anneal temperature effects on structural and electrical (leakage current and trap density) properties of epitaxial Gd₂O₃ film grown on Si (111) substrate using a cost-effective and High-Volume Manufacturing capable radio frequency sputtering method. It is found that the Rapid Thermal Annealing (RTA) at an optimum temperature of 850 °C enhances the crystallinity of the cubic phase in film. However, at higher RTA temperatures (>900 °C to 1050 °C), Si out-diffusion in Gd₂O₃ film is manifested as the reason for phase evolution towards the amorphous phase. The electrical characterization shows the film's low leakage current density of 100 nA/cm². Moreover, increased breakdown voltage and field are observed with increasing RTA temperature. The frequency-dependent Capacitance-Voltage analysis shows a parallel shift accompanied by a kink at a lower frequency, indicating the presence of interface traps (D_it) with a range of time constants. After the forming gas annealing, a significant reduction in D_it is observed. The low leakage current density, low D_it and high crystallinity make Gd₂O₃ a promising candidate as a buried oxide in Silicon on Insulator MOSFETs.