Selective Oxidation of Silicon in High Pressure Steam

The selective oxidation of silicon was investigated using a high pressure oxidation apparatus at a steam pressure of 6.6 kg/cm 2 (6.4 atm) and at temperatures between 800° and 1100°C. The conversion characteristics of the silicon nitride film into silicon dioxide film in high pressure steam was analyzed on the basis of the well‐known linear‐parabolic relationship. The activation energy for the parabolic rate constant was found to be about 3.15 eV, which was about 5 times larger than that (0.7 eV) for silicon. On the other hand, the activation energy for the linear rate constant was about 1.25 eV which was a little smaller than that (2.03 eV) for silicon. The conventional silicon nitride film was found to be able to mask the selective oxidation even in the high pressure steam. The lateral oxidation of the silicon substrate beneath the masking nitride film occurred rapidly with decreasing oxidation temperature at the fixed pressure. The suppression of the lateral oxidation can be achieved by increasing the thickness of the masking nitride film and also by decreasing that of the oxide pad. This high pressure oxidation process was compatible with the conventional atmospheric process.