トリフルオロメチルトリフルオロビニルエーテル混合ガスを用いた60 Hz非平衡大気圧プラズマによるビア底残渣のドライデスミア

抄録

This study examined dry removal of CO₂ laser via bottom residue using 60 Hz nonequilibrium atmospheric pressure plasma with trifluoromethyl trifluorovinyl ether (C₃F₆O) mixing gas. (‘Removal of residue’ is defined as ‘de-smear’ in this paper.) Existing wet de-smear processing with KMnO₄ will have a technical limitation for fine via that diameter is 50 μm or less. A dry process technology that allows fine via de-smearing is necessary for fine-pitch printed circuit board manufacturing. Results show that via bottom residue was de-smeared successfully using the plasma treatment with 2.0% of C₃F₆O mixing to argon gas. For tetrafluoromethane (CF₄), 10.0% mixing was necessary for the plasma dry de-smearing. The global warming potential of C₃F₆O is close to zero as 4.57 × 10⁻⁴, so the result of de-smearing with 2.0% of C₃F₆O mixing ratio (the mixing ratio is 1/5 of CF₄) gives us high expectations of conducting a low environmental impact practical manufacturing process. The optical emission spectra of the plasma were measured, and found that the intensity of CF₂ radical and CF₃ radical correspond to the result of the via bottom residual ratio. It reveals that CF₂ radical and CF₃ radical are active species to volatilize SiO₂ filler residue. The gas molecule of C₃F₆O, which includes the fluoroalkyl ether group, is easily dissociated with low energy electrons. The 60 Hz nonequilibrium atmospheric pressure plasma has high density of low-temperature (energy) electrons. Therefore, the via bottom residue was de-smeared successfully using the atmospheric pressure plasma with a low mixing ratio of C₃F₆O.