Oxidation of Chemically‐Vapor‐Deposited Silicon Nitride and Slnglem‐Crystal Silicon

Abstract

Oxidation of {111} single‐crystal silicon and dense, chemically‐vapor‐deposited silicon nitride was done in clean silica tubes at temperatures of 1000° to woo°C. The oxidation rates of silicon nitride under various atmospheres (dry O2, wet O2, wet inert gas, and steam) were several orders of magnitude slower than those of silicon under the identical conditions. The activation energy for the oxidation of silicon nitride decreased from 330 to 259 kJ/mol in going from dry O2 to steam while that for Si decreased from 120 to 94 kJ/mol. The parabolic rate constant for Si increased linearly as the water vapor pressure increased. However, the parabolic rate constant for silicon nitride showed nonlinear dependency on the water vapor pressure in the presence of oxygen. The oxidation kinetics of silicon nitride is explained by the formation of nitrogen compounds (NO and NH3) at the reaction interface and the counterpermeation of these reaction products.

Corrosion of Ceramic Materials

“…The oxidation of silicon nitride typically occurs with parabolic kinetics (Choi et al (1989), Du et al, 1989a;Schiroky et al (1986); Ogbuji and Opila, 1995), is dependent on oxygen partial pressure, and is independent of nitrogen partial pressure (Du et al, 1989a). These three observations show that the oxidation kinetics are controlled by oxygen transport across a growing scale.…”

“…The only study where pure Si3N4 has been studied in a clean water vapor-containing environment is that by Choi et al (1989). In this study, the oxidation rate is found to depend on carrier gas and in addition, a complicated dependence on water vapor partial pressure is observed.…”

“…Enhanced parabolic oxidation ratesof Sic _and Si_N_,due tO Contamination from furnace tubes used in oxidation experiments have also been observed (Choi et al, 1989;Opila, 1995;Ogbuji and Opila, 1995;Fox, 1998). This enhancement is also attributed to Na impurities from impurities in alumina tubes (Opila, 1995).…”

“…These three observations show that the oxidation kinetics are controlled by oxygen transport across a growing scale. However, it is also well known that the oxidation of pure Si3N4 in clean conditions at temperatures less than 1500°C are much lower than the oxidation rates of Si and SiC (Choi et al, 1989;Duet al, 1989a;Ogbuji and Opila, 1995) as shown in Figure 6. This has been attributed to the formation of a silicon oxynitride layer which forms below the silica scale during oxidation of SigN4.…”

Improvement of high-temperature oxidation resistance to water vapor by alumina coating on beta-sialon ceramic

“…[3][4][5][6] Therefore, for the application in high-temperature and high P H2O conditions, environmental barrier coating (EBC) to water vapor is needed. Alumina (Al 2 O 3 ) and mullite (3Al 2 O 3 2SiO 2 ) have been utilized as barrier coating materials because of high chemical stability and mechanical properties.…”