Liquid marbles have been shown to be a novel micro-reactor to synthesize polyperoxides by the radical alternating copolymerization of the 1,3-diene monomer with oxygen in a good yield. Oxygen gas is effectively absorbed as a comonomer by the large and permeable gas-liquid interface of the liquid marbles.
In this paper, we describe the use of ozone microbubbles
in photoresist
removal from silicon wafers. Ozonized water has attracted much attention
as an environmental friendly cleaning method in semiconductor manufacturing.
However, it would be desirable to enhance the oxidative ability of
ozonized water for practical application. The existence of microbubbles
in ozonized water has been shown to significantly enhance the photoresist
removal rate due to an elevated dissolved ozone concentration (approximately
2.5 times that of ordinary ozone bubbling) and a direct effect of
the microbubbles (removal rate is approximately 1.3 times faster than
water with the same concentration of dissolved ozone without microbubbles).
Additionally, the ozone microbubble solution was able to effectively
remove a high-dose ion-implanted photoresist, which is extremely resistant
to removal by ozonized water and other wet chemicals because of its
amorphous carbon-like layer, or “crust”. Electron spin
resonance experiments were also performed without the influence of
serious metal contamination and indicated the presence of hydroxyl
radicals, which are thought to be formed by interaction of ozone with
hydroxide ions adsorbed at the gas–water interface upon collapse
of the microbubbles. The hydroxyl radicals play an important role
in photoresist removal by the ozone microbubble treatment.
We investigated an environmentally friendly method using atomic hydrogen generated by contact catalysis on a tungsten hot-wire catalyzer to remove photoresist instead of using chemicals and its effects on a Si-wafer surface. We eventually obtained a photoresist removal rate of 2.5 mm/min attributable to a reaction of atomic hydrogen with a positive-tone novolak photoresist, without thermal shrinkage of the photoresist film during atomic hydrogen irradiation because the photoresist shrank only under the influence of substrate heating by the catalyzer. The effects of atomic hydrogen irradiation on the substrate surfaces cannot be confirmed.
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