Study of the decomposition mechanism of PMMA-type polymers by hydrogen radicals

• The removal rate of the main chain scission type polymers was faster than that of the main chain cross-linking type polymers.
• The removal rate was slow in the case of the main chain scission type polymers with a benzene ring.
• The removal rate was slow according to increasing bulkiness of α-side chain in the main chain scission type polymers.

The relationship between the chemical structure of PMMA-type polymers and the removal rate by hydrogen radicals was examined. Hydrogen radicals are known to have superior reduction ability and can be generated by decomposing H2 on hot-wire surfaces. PMMA-type polymers, which are widely used as base polymers for ArF resist, have many variations with the difference in the substituents. The removal rate of the main chain scission type polymers was faster than that of the main chain cross-linking type polymers. In the main chain cross-linking type polymers, it is considered that reduction decomposition of polymer was inhibited apparently according to occurrence to simultaneously reduce decomposition by hydrogen radicals and main chain cross-link. The removal rate was slow in the case of the main chain scission type polymers with a benzene ring. We guessed that the polymer with a benzene ring was a stable structure by resonance stabilization of a benzene ring. We found that the removal rate was slow according to increasing bulkiness of α-side chain in the main chain scission type polymers. It is considered that etching resistance increases with increasing bulkiness of α-side chain of polymer.