Disclosed is a method and apparatus for treating a substrate with a reaction solvent formed of supercritical ozone in a feed phase. The feed phase can be aqueous, e.g., formed of heated, deionized water, nonaqueous, e.g., formed of a dense fluid, such as supercritical carbon dioxide, liquid carbon dioxide, supercritical nitrogen or combinations the dense fluids or the feed phase can be a mixture of aqueous and nonaqueous phases.