Therefore, at the first step of bubble preliminary investigation, the
sputtered area and bubbles were observed by Energy-dispersive Xray
spectroscopy (EDS) analysis to confirm whether there was Ar
gas inside those bubbles. However, Argon could not be detected by
the EDS of the field emission-SEM (JEOL, JSM-7300F).
Fig. 3(d) presents damage from the micro arc discharge [7]
during discharge. After micro plasma was generated using the 2.5
sccm GFR condition for approximately 30 s, an arc discharge could
be seen on an oscilloscope monitor monitoring the discharge
current waveform. For long time plasma operation, the arc
discharge is initiated because high Id can cause an increase in
electrode temperature. The arc discharge occurs when the electrode
temperature is high enough for thermionic electron emission
[2]. The discharge current waveform changed from linear line to
a short pulse and back to linear line in less than a nano second
(approximately 0.55 ns) when a micro arc discharge occurred, and
the frequency of the arc discharge increased when Td increased. The
number of melting spots caused by the micro arc discharge has
consistency with the number of observed short pulses on the
oscilloscope monitor. In addition, heating from the arc discharge
caused Si peeling.