Method of improving oxide growth rate of selective oxidation processes

A method of selectively oxidizing materials of a composite substrate is provided. The method includes disposing the composite substrate in a chamber, the composite substrate including a silicon-containing layer and another layer. The method includes introducing an oxygen containing gas to the chamber and introducing a hydrogen containing gas to the chamber, wherein the oxygen containing gas and the hydrogen containing gas form a gas mixture, wherein the gas mixture comprises greater than 65% by volume of the hydrogen containing gas. The method includes pressurizing the chamber, and heating the chamber to a predetermined temperature for a predetermined time. The method includes causing the hydrogen containing gas and the oxygen containing gas to react, and selectively oxidizing the silicon-containing layer of the composite substrate relative to the other layer of the composite substrate. The predetermined temperature is established after introducing the hydrogen containing gas, the chamber is pressurized to a pressure between 399.966 hPa (300 Torr) and 799.932 (600 Torr), and the hydrogen containing gas and the oxygen containing gas react inside the chamber.