The invention encompasses a method of removing at least some of a material from a semiconductor substrate. A feed gas is fed through an ozone generator to generate ozone. The feed gas comprises at least 99.999% O₂ (by volume). The ozone, or a fragment of the ozone, is contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate. The invention also encompasses another method of removing at least some of a material from a semiconductor substrate. A mixture of ozone and organic solvent vapors is formed in a reaction chamber. At least some of the ozone and solvent vapors are contacted with a material on a semiconductor substrate to remove at least some of the material from the semiconductor substrate.