The dry etch resistance of metal‐free organic materials, mainly resist materials, has been studied. Etch rates have been measured under argon ion‐beam, oxygen ion‐beam, and oxygen plasma etching conditions. It is found that the etch rate under ion bombardment has a linear dependence on the of the etched materials, where , , and denote the total number of atoms in a monomer unit, the number of carbon atoms in a monomer unit, and the number of oxygen atoms in a monomer unit, respectively. The results indicate that the dry etch resistance under ion bombardment is determined by the effective carbon content in a material. The etch rates of the polymers in an oxygen plasma condition have no simple correlation with the effective carbon content in a material. This implies that etching mechanism under ion bombardment differs from the etching mechanism by radical species.