Ultrathin silicon dioxide layers with a low leakage current density formed by chemical oxidation of Si

Chemical oxidation of Si by use of azeotrope of nitric acid and water can form 1.4-nm-thick silicon dioxide layers with a leakage current density as low as those of thermally grown SiO2 layers. The capacitance-voltage (C-V) curves for these ultrathin chemical SiO2 layers have been measured due to the low leakage current density. The leakage current density is further decreased to similar to1/5 (cf. 0.4 A/cm(2) at the forward gate bias of 1 V) by post-metallization annealing at 200degreesC in hydrogen. Photoelectron spectroscopy and C-V measurements show that this decrease results from (i) increase in the energy discontinuity at the Si/SiO2 interface, and (ii) elimination of Si/SiO2 interface states and SiO2 gap states. (C) 2002 American Institute of Physics.