Production of ultrafine atmospheric pressure plasma jet with nano-capillary

The atmospheric pressure plasma jet (APPJ) has been developed to apply to the ultrafine process for future material processing. In this study, we tried to reduce the diameter of APPJs by using micro- or nano-capillary tubes. To measure the existence of the bullet-like charged particles from the capillary tip, the plasma flow generated from capillary tubes with a diameter of about 100 nm to 5 μm were analyzed by the electrostatic probe. The average propagation velocities of the plasmas flow were estimated from the time differences between the probe signal and spiky discharge current signal. The results show that the velocity of plasma jet delivered from 1 μm ϕ capillary gradually decreased from 11 to 2 km/s due to a collisional drag force with air with an increase of the distance from capillary tips. From the analysis of etching pattern of resist film by the APPJ with a 500 nm diameter capillary, it was confirmed that the depth and width of the treated trench on the resist film were roughly 30 – 50 nm and 500 – 700 nm, respectively.