Investigation of the oxidation kinetics of C54-TiSi2 on (001)Si by transmission electron microscopy

Abstract

A transmission electron microscopy study of oxidation kinetics of C54-TiSi2 for both dry and wet oxidation has been carried out. Precautions were taken to determine the activation energies of oxidation in the temperature and time regime where the islanding of TiSi2 did not occur. For dry oxidation, activation energies for parabolic and linear growth were found to be 1.97 and 2.50 eV (with an error bar of ±0.1 eV), respectively. On the other hand, activation energies for parabolic and linear growth were found to be 1.88 and 2.10 eV (with an error bar of ±0.1 eV), respectively, for wet oxidation. The activation energy of parabolic rate constant is seen to be substantially different from those obtained previously. The difference is attributed to the occurrence and absence of islanding during oxidation in the previous and present study, correspondingly. The closeness of linear activation energy of TiSi2 oxidation with that of pure silicon is thought to be due to the fact that both are related to the breaking of the Si—Si bonds at the silicon surface. Orthorhombic TiO2 was observed to form on the surface of all samples wet oxidized at 880–1040 °C for 5–70 min. For dry oxidized samples, no TiO2 was detected in samples dry oxidized at 880–940 °C for 5–50 min and at 920 °C for up to 6 h. However, in samples dry oxidized at 920 °C for 10–15 h, TiO2 was found to form. For dry oxidation, it is thought that although the formation energy of TiO2 is considerably higher than that of SiO2, the nucleation barrier for forming TiO2 is higher. Only after prolonged oxidation was the nucleation barrier overcome and led to the formation of TiO2.