Characteristics of Silicon Oxide Gate MOS Capacitors Formed by Rapid Thermal Oxidation and Annealing

Ultra-thin silicon oxide (SiO₂) insulating films have been obtained by rapid thermal oxidation (RTO) and annealing (RTA), using different temperatures of 600, 700, 800 and 960degC for 40s, in oxygen and nitrogen, respectively. Characterization by Ellipsometry (for fixed refractive index of 1.46), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) analyses reveals oxide thickness values between 2 and 10 nm, and the presence of Si-0 bonds, confirming the ultra-thin silicon oxide film formation, respectively. Theses films have been used as gate insulators in MOS capacitors. These devices, with different Al, Al/Ti, N⁺ Poly-Si gate electrodes and sintering at 450degC in forming gas, were fabricated. MOS capacitors were used to obtain capacitance-voltage (C-V) and current-voltage (1-V) measurements. A relative dielectric constant of 3.9 was adopted to extract the Equivalent Oxide Thickness (EOT) of films from C-V curves under strong accumulation condition, resulting in values between 2 nm and 10 nm. Leakage gate current densities between 10 mA/cm² and 2 A/cm² were obtained by I-V measurements for gate voltage of -1 V. These results indicate that the obtained dielectric gates can be used for MOS technologies with dimensions higher than 130 nm.