The in-situ study of growth rate on silicon oxidations via ambient pre…
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" In many years, the silicon oxidation process has been thoroughly investigated with various surface science analytical tools, focusing on chemical and structural information on SiO2/Si interface, electronic structures, and the detailed kinetics of oxidation processes. Especially, with x-ray photoelectron spectroscopy (XPS), important knowledge on the oxidation process are disclosed, such as the different chemical oxidation states, the local atomic structures, and the unique growth modes at the interfaces. [see e.g. Y. Enta et al., J. Vac. Sci. Tech. 16, 1716 (1998); S. Dreiner et al., Phys. Rev. Lett. 93, 126101 (2004)].
However, due to the short inelastic attenuation lengths of photoelectrons, as well as the requirement of high vacuum in the electron spectrometer, only the model study of oxidation process has been carried out, i.e. ultrahigh-to-high-vacuum conditions (10-10 to 10-6 torr) and/or after oxidation treatment in a preparation chamber.
In an attempt to close this pressure gap, we have used a newly developed ambient pressure (AP) XPS endstation at the Advanced Light Source (ALS) [D.F. Ogletree, Rev. Sci. Inst. 73, 3872 (2002)] to study the growth rates of silicon oxide and the nature of the chemical bonding at the interface between the silicon and the oxygen at ambient pressures of oxygen and water up to 1 torr in real time. The measured growth rates of silicon oxidation at various substrate temperatures and gas pressures indicate that the growth rate of oxide is very rapid up to the thickness of one monolayer, and that this is followed by a second fast regime up to ca. 2 nm oxide thickness, after which the reaction rate slows considerably. In addition, we have determined the difference of initial growth modes and rates between oxygen and water, which suggest an important parameter on initial growth conditions at the interface.
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However, due to the short inelastic attenuation lengths of photoelectrons, as well as the requirement of high vacuum in the electron spectrometer, only the model study of oxidation process has been carried out, i.e. ultrahigh-to-high-vacuum conditions (10-10 to 10-6 torr) and/or after oxidation treatment in a preparation chamber.
In an attempt to close this pressure gap, we have used a newly developed ambient pressure (AP) XPS endstation at the Advanced Light Source (ALS) [D.F. Ogletree, Rev. Sci. Inst. 73, 3872 (2002)] to study the growth rates of silicon oxide and the nature of the chemical bonding at the interface between the silicon and the oxygen at ambient pressures of oxygen and water up to 1 torr in real time. The measured growth rates of silicon oxidation at various substrate temperatures and gas pressures indicate that the growth rate of oxide is very rapid up to the thickness of one monolayer, and that this is followed by a second fast regime up to ca. 2 nm oxide thickness, after which the reaction rate slows considerably. In addition, we have determined the difference of initial growth modes and rates between oxygen and water, which suggest an important parameter on initial growth conditions at the interface.
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