Correlation between the reliability of ultrathin ISSG SiO 2 and hydrogen content

The electrical characteristics of NMOS capacitors fabricated using high quality, ultra-thin SiO₂, grown by in-situ steam generation (SSG) in a rapid thermal processing system, and a clustered amorphous SI gate electrode is reported. The results show that, in addition to the enhanced growth rate of ISSG oxides, the lower stress-induced leakage current and significantly improved reliability of ISSG SiO₂ such as a longer time-to-breakdown characteristics, as compared to SiO_{2, such as a longer time-to-breakdown under a constant voltage stress and larger charge-to-breakdown characteristics, as compared to SiO(subscript 2} of similar equivalent oxide thickness grown by rapid thermal oxidation (RTO). In addition, it is also found that the reliability of ISSG oxide is considerably improved as the H₂ percentage increases. The result of Fourier- transformed IR spectroscopy indicates that ISSG oxides exhibit lower compressive strain than RTO oxides. Such appreciably improved reliability of ISSG oxide and reduced compressive strain may be explained by the reduction of defects within the structural transition layer between SiO₂ and Si substrate, such as weak Si-Si bonds and strained Si-O bonds, by highly reactive oxygen atom s which are hypothesized to be dissociated from the molecular oxygen due to the presence of hydrogen.