Evaluation of Decomposition Property of Photoresist by Oxygen Radicals Using Helium-Oxygen Mixtures

Abstract

We have previously demonstrated that photoresist removal rate is enhanced by adding a trace amount of O 2 to the atmosphere in which H radicals are produced from H 2 on a hot metal filament. In this case, not only H radicals but also O and OH radicals are produced. The populations of O and OH radicals are a few hundredth parts of that of H radicals, but these radicals must play important roles. It is not clear which radicals contribute more to the enhancement of the removal rate. We used He/O 2 mixtures in this study, instead of H 2 /O 2 , to produce O radicals without co-producing H and OH to make clear the contribution of O radicals on the removal rate. The removal rate increased slightly with increasing the O 2 additive amount when the filament was unheated. This may be caused by thermal oxidation. On the other hand, the removal rate with a hot filament decreased by the addition of O 2. In short, the removal rate is not enhanced by O radicals. The enhancement in H 2 /O 2 mixtures must only be ascribed to OH radicals.

Photoactive Compounds Effects on Removal Rate for Polystyrene-type Polymers by H₂/O₂ Mixture Activated by Hot Tungsten Wire

“…Not only are O radicals less abundant; they are also less reactive than H radicals. Their contribution to the removal processes must be minor [1,16]. The CH3 group attacked by the active species becomes CH2*; it can play a role as a decay site for benzene rings on side chains.…”