Removal of Polymers for KrF and ArF Photoresist Using Hydrogen Radicals Containing a Small Amount of Oxidizing Radicals

Abstract

Photoresist removal method using hydrogen radicals, which are produced on a tungsten hot-wire catalyst, is effective to resolve some environmental and industrial problems in conventional methods for the fabrication of electronic devices. However, its removal rate is not as good as that of the conventional ones. We have previously described that the removal rate of a positive-tone novolac photoresist is enhanced by the addition of a small amount of oxygen gas to the atmosphere, in which hydrogen radicals are produced. Oxidizing radicals, such as OH and O radicals, can be produced together with H radicals. In present study, we examined the effects of oxygen addition on base polymers of KrF and ArF photoresists: the former 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 photoresist. On the other hand, the effects on PMMA were different from the cases of the novolac photoresist and PVP. Results were ascribed to the presence or absence of benzene rings, the properties of polymers and the reactivity of oxidizing radicals.

Effects of Nitrogen Dilution on the Photoresist Removal Rate by Hydrogen Radicals

“…The experiment apparatus and the procedure were similar to those described elsewhere [8][9][10][11][12]. The H 2 gas (≥99.99%; Takamatsu Teisan Co.) flow rate was varied between 0 and 50 sccm using a mass flow controller (PE-D20; HORIBA STEC).…”

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

“…The experiment apparatus and the procedure were similar to those described elsewhere [10][11][12][13][14]. The He gas (≥99.99%; Takamatsu Teisan Co.) flow rate was fixed at 100 sccm using a mass flow controller.…”

“…To produce OH radicals, we examined a way of adding a trace amount of O 2 to the atmosphere in which H radicals are produced from H 2 on metal hot filament surfaces. The removal rate was found to be a few times higher than that in pure H 2 systems [10][11][12][13][14]. Not only OH radicals but also O radicals can be produced in such H 2 /O 2 mixed systems [5,15].…”

“…Our earlier study demonstrated that the enhancement has been observed when the gas flow rate of O 2 against that of H 2 is less than 10% [10][11][12][13][14]. This saturation has been ascribed to the decrease in the H radical density.…”

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

“…The environmental burdens and costs caused by harmful chemicals used for photoresist removal processes during conventional semiconductor manufacturing are regarded as important shortcomings. To overcome these difficulties, we have studied an "environmentally friendly" photoresist removal method using radicals generated by activating H2/O2 mixed gas on a hot filament surface [1][2][3][4]. This method allows oxidizing O radicals and OH radicals to coexist in a reducing H radical atmosphere [5][6][7].…”