© 2018SPST. Photoresist removal method using hydrogen radicals, which are produced on a tungstehot-wire catalyst, is effective to resolve some environmental and industrial problems conventional methods for the fabrication of electronic devices. However, its removal rate not as good as that of the conventional ones. We have previously described that the removarate of a positive-tone novolac photoresist is enhanced by the addition of a small amount oxygen gas to the atmosphere, in which hydrogen radicals are produced. Oxidizing radicalssuch as OH and O radicals, can be produced together with H radicals. In present study, wexamined the effects of oxygen addition on base polymers of KrF and ArF photoresists: thformer is poly(vinyl phenol) (PVP), and the latter is poly(methyl methacrylate) (PMMA)Effects of oxygen addition on PVP was confirmed, as was found for the novolac photoresisOn the other hand, the effects on PMMA were different from the cases of the novolaphotoresist and PVP. Results were ascribed to the presence or absence of benzene rings, thproperties of polymers and the reactivity of oxidizing radicals.