2020 Volume 33 Issue 4 Pages 427-431
We have previously demonstrated that photoresist removal rate comparable to oxygen plasma is accomplished by optimizing the removal conditions with H radicals produced on hot metal filament surfaces from H2/N2 mixtures (H2:N2 = 10:90 vol%). N2 gas was used to dilute the concentration of the H2 gas and to reduce the risk of explosion. However, it is not clear how the dilution of H2 by N2 affects the removal rate. In this paper, we examined the relationship between the removal rate and the H2 content; the flow rate ratio of H2 to H2+N2. The removal rate increased with increasing the H2 content. In addition, the removal rate increased with increasing the substrate temperature according to an Arrhenius equation, when the H2 content was over 90%. However, below 60%, the removal rate decreased with increasing the temperature over 230 ± 5 ℃. Denaturation of photoresist, e.g. hardening and/or crosslinking, may be induced by substrate heating when the H-radical density is low. The removal rate decreases not only by the deficiency of H radicals but also by the denaturation of films in H2/N2 mixed systems.
