Fragment-ion variations in a pulsed plasma

Detailed study of fragment ion-intensity variations that are specific in a pulsed plasma is described. In this paper the experiments are carried out using CF4 plasma. We measure the short-time variation of each fragment-ion intensity for a few seconds just after plasma ignition. The results show that most of the short-time variations take place in 2 or 3 s just after plasma ignition, but the variation tendency of the reacted product fragment ions is completely different from the others. At the instance of plasma ignition, the ion intensities of CF+, CF2+ and CF3+ have their highest values and then sharply decrease, but that of SiF+ has the lowest value at first and then increases. The etching rate is considered to need a few seconds after plasma ignition until it has a stable value. The ion species abundance is considered to reflect the corresponding neutral fragment abundance, although the ionization rate of every fragment is different.