Dramatic reduction of gate leakage current of ultrathin oxides through oxide structure modification

Abstract

We study in detail a new effect, phonon-energy-coupling enhancement (PECE) effect, produced by rapid thermal processing (RTP). It includes two aspects: (1) strengthening Si–D bonds and Si–O bonds and (2) change of energy band structure and effective mass. It is shown that not only Si–D bonds but also Si–O bonds have been strengthened dramatically, leading to enhancement of robustness of the oxide structure and the oxide/Si interface. For thick oxides (>3 nm), the gate leakage current has been reduced by two-orders of magnitude and the breakdown voltage has been improved by ∼30% due to phonon energy coupling. For ultrathin oxides (2.2 nm), the direct tunnelling current has been reduced by five orders of magnitude, equivalent to that of HfO₂, probably due to increased effective mass and barrier height.