A Development of Low-Temperature Silicon Oxidation Enhanced by Fluorine Catalysis

Low-temperature oxidation of silicon by using fluorine-增强oxidation is developed. Theknowledge and results obtained through this research project are as follow1. A 50a thick oxide layer is grown even at 400 - C for 30 min by fluorine-enhanced thermal oxidationusing an < o_2 > + < nf_3 > gas mixturewhen the < nf_3 > concentration is about 10%.2. the enhancement of the oxidation rate originates inthe catalytic effect of the fluorine radicals which enhance the oxidation reactions in the < sio_2 >-Si interface.3. An oxide layer of more than 60 A can be grown even at 400 - C for 20 min at < nf_3 >concentration少超过0.5% under ArF excimer laser irradiation. Further lowering of the oxidationtemperature to 300 C would be possible in higher < nf_3 > concentration range.4. Fluorine atomsincorporated in the oxide layer grown by the fluorine-enhanced oxidation are substituted by oxygen原子through post-annealing in pure oxygen gas at the same temperature as oxidation，5. Annealing of the oxide in pure ammonia gas at thesame temperature as oxidation results in the formation of nitrided oxide as a consequence thatfluorine atoms incorporated in as-grown oxide are substituted by nitrogen atoms.6. The interfacetrap densities and the dielectric breakdown strength of the MOS structures are remarkably improvedby the post-annealing in pure oxygen, wet oxygen7. Thin gate oxide films with high qualities can be formed by using an ultraclean oxidation technology. The interface trap densities of < sio_2 > -Si interface near midgap are ofthe order of <10^9> <cm^(-2)> <eV^(-1)>，and the dielectric breakdown strength of < sio_2 > is above 10 MV/cm。

Low-temperature oxidation of silicon by using fluorine-enhanced oxidation is developed. The knowledge and results obtained through this research project are as follow: 1. A 50 A thick oxide layer is grown even at 400゜C for 30 min by fluorine-enhanced thermal oxidation using an <O_2> + <NF_3> gas mixture, when the <NF_3> concentration is about 10%.2. The enhancement of the oxidation rate originates in the catalytic effect of the fluorine radicals which enhance the oxidation reactions in the <SiO_2> -Si interface.3. An oxide layer of more than 60 A can be grown even at 400゜C for 20 min at <NF_3> concentration less than 0.5% under ArF excimer laser irradiation. Further lowering of the oxidation temperature to 300゜C would be possible in higher <NF_3> concentration range.4. Fluorine atoms incorporated in the oxide layer grown by the fluorine-enhanced oxidation are substituted by oxygen atoms through post-annealing in pure oxygen gas at the same temperature as oxidation, and can be effectively removed in wet oxygen.5. Annealing of the oxide in pure ammonia gas at the same temperature as oxidation results in the formation of nitrided oxide as a consequence that fluorine atoms incorporated in as-grown oxide are substituted by nitrogen atoms.6. The interface trap densities and the dielectric breakdown strength of the MOS structures are remarkably improved by the post-annealing in pure oxygen, wet oxygen, and pure ammonia gas.7. Thin gate oxide films with high-qualities can be formed by using an ultra clean oxidation technology. The interface trap densities of <SiO_2> -Si interface near midgap are of the order of <10^9> <cm^(-2)> <eV^(-1)> , and the dielectric breakdown strength of <SiO_2> is above 10 MV/cm.