ABSTRACT
The mechanism for the reaction of trimethylaluminum (TMA, Al(CH3)3) with ozone (O3) was investigated in detail using density functional theory calculations to understand the atomic layer deposition processes that form aluminum oxide surfaces. We examined the reactions of TMA and some possible intermediates with O3 and revealed plausible paths to form methoxy (-OCH3), formate (-OCHO), bicarbonate (-CO3H), and hydroxyl (-OH) species. These species have been observed in previous experimental studies. It was shown that TMA easily reacts with O3 to generate the Al(CH3)2(OCH3)(O2) intermediate. The subsequent reaction between the OCH3 and O2 groups finally generated an intermediate having a formate group. When all of the CH3 groups are converted into OCH3 or OCHO, O3 will react with these groups. In the latter reaction, bicarbonate was shown to be formed.
ABSTRACT
Using ultraviolet (UV)-excited ozone gas, we prepared high-quality SiO(2) films that can be used as gate dielectric films on poly-silicon or silicon wafers without sample heating. The UV-excited ozone gas was generated by UV irradiation of highly concentrated ozone gas. During the UV-excited ozone process, UV light irradiates the sample surface directly through the ozone gas. Then, the temperature at the sample surface is increased by UV-light absorption at the surface. Estimation of this surface temperature is important for understanding the oxidation mechanism. We estimated the surface temperature obtained during UV irradiation to be about 300 degrees C by investigating the temperature dependence of the oxidation rate for oxygen gas. We have previously determined that almost no thermal decomposition of ozone gas occurs at this temperature, and that oxygen gas does not oxidize the Si substrate. Therefore, we concluded that the only oxidation species in the UV-excited ozone process is UV-excited ozone O((1)D).
