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60Hz非平衡大気圧プラズマによるビア底残達のドライデスミア

摘要

急速な電子機器の小型化や高機能化にともない，プリント配線板の高密度化が進み，近い将来ビア径50μm以下のビアが求められる。しかし，ビア加工にレーザー光を使用している現状では，ビア底面に樹脂成分とフィラー成分の残液が残ってしまう。%This study examined dry removal of CO_2 laser via bottom residue using 60 Hz nonequilibrium atmospheric pressure plasma with trif-luoromethyl trifluorovinyl ether (C_3F_6O) mixing gas. ( Removal of residue' is defined as de-smear' in this paper.) Existing wet de-smear processing with KMnO_4 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 C_3F_6O mixing to argon gas. For tetrafluoromethane (CF_4), 10.0% mixing was necessary for the plasma dry de-smearing. The global warming potential of C_3F_6O is close to zero as 4.57 × 10~(-4), so the result of de-smearing with 2.0% of C_3F_6O mixing ratio (the mixing ratio is 1/5 of CF_4) 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 CF_2 radical and CF_3 radical correspond to the result of the via bottom residual ratio. It reveals that CF_2 radical and CF_3 radical are active species to volatilize SiO_2 filler residue. The gas molecule of C_3F_6O, 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 C_3F_6O.