Low Temperature Oxidation of Silicon(100) Substrates Using Atomic Oxygen
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ABSTRACT Low temperature oxidation process of Si(100) substrates using atomic oxygen has been proposed. For the generation of atomic oxygen, microwave plasma remotely attached on the oxidation chamber was used. In the microwave plasma, the large amount of rare gas and a small amount of 02 gas mixture was supplied. The existence of the large amount of rare gas controls the plasma energy to some restricted values associated with the metastable states of the rare gas. Consequently, using Kr as mixed rare gas, atomic oxygen were efficiently generated instead of excited 02 molecules with any vibrational or ionized states. The oxidation kinetics of crystalline Si using this process was shown to be diffusion limiting, even if the oxide thickness was less than several nm. The activation energy of B, which is referred to as the parabolic rate constant, was found to be as low as 0.14eV In addition, lower interface trap density of 2.6 X 101 /cm 2/eV at the mid gap could be achieved for the as-grown Si02/Si(100) interface at the processing
temperature of 500C. INTRODUCTION As the size of the electronic devices in the semiconductor chip has strictly been restricted, the precise control of the film thickness as well as the planer dimensions tends to become essentially important than before. Thin silicon dioxide (SiO2) films are one of the most principal materials in electronic devices because it must sustain large electric field in switching transistors and hot carrier injection in flash memories. So far, the thermal oxidation techniques with oxygen molecules have been widely used to fabricate Si02/Si structure because of its good electrical properties and chemical stabilities. This technique, however, always involves high processing temperatures (usually > 800C), which would give rise to several undesirable diffusion-related and high temperature-sensitive effects that may hinder the performance of small electronic devices and other integrated circuit components. The use of excited oxygen species such as excited oxygen molecules (02*), 02 ions (02-), or oxygen atoms (0*) as an oxidant instead of grounded oxygen molecules (02) is one of the potential methods to oxidize crystal silicon with lower temperature. Plasma assisted techniques [1-6] such as so-called plasma anodization or plasma oxidation enable the lower temperature oxidation of crystal silicon because of the generation of these excited species within the plasma before oxidation. Since oxygen gas alone has been used as an active medium for the most of these conventional plasma assisted techniques, however, the generated oxygen species have wide energy distribution that is a reflection of the plasma energy. Consequently, since many kinds of active species must be formed and would contribute the oxidation, the control of the oxidation reaction might be difficult. In addition, the plasma damage ascribed to the charged species at the Si02/Si interface as much as the film surface would be a severe problem for the thin SiO2 film fabrication. 239 Mat. Res. Soc. Symp. Proc. Vol
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