Low-temperature oxidation of SiGe by liquid-phase deposition

Low-temperature silicon dioxide (SiO₂) films were grown on silicon germanium (SiGe) surfaces using the liquid-phase deposition (LPD) method. The growth solutions of LPD-SiO₂ are hydrofluorosilicic acid (H₂SiF₆) and boric acid (H₃BO₃). It was found that the growth rate increases with increasing temperature and concentration of H₃BO₃. The Auger electron spectroscopy profile shows that no pileup of Ge atoms occurs at the interface of SiO₂/SiGe after the LPD-SiO₂ growth. Al/LPD-SiO₂/p-SiGe MOS capacitors were prepared to determine capacitance-voltage (C-V) and current-voltage (I-V) characteristics. In our experiments, a low leakage current density of 8.69 × 10⁻⁹ A/cm² under a 2 MV/cm electric field was observed. Such a value is much smaller than those of plasma- and thermal-oxides as a result of no plasma damage and a lower growth temperature. Moreover, lower oxide charges and interface charge densities of 3.82 × 10¹⁰ cm⁻² and 1.12 × 10¹¹ eV⁻¹ cm⁻², respectively, were achieved in our LPD-SiO₂ compared to direct photochemical-vapor-deposition-SiO₂.