Plasma Formation and Collision Processes

In addition to the capacitor-coupled reactor shown in Fig. 1, there are two other classes of reactors, namely, those coupled with an inductor and those excited by microwaves. Various gases are used depending on the materials treated, as Table 1 (Samukawa, 1999) summarizes. 

Figtire 2 illustrates collisions and reactions of particles in a low-temperature plasma used for plasma CVD (for instance, the formation of a-Si H films by SiH4, on the left-hand side) and for plasma etching (for instance, microprocessing 

Aluminium alloys Chlorides CCI4, BCI3, SiCU, CI2, HCl 

Let us discuss further collisions and reactions in chemical etching of Si and Si02 in a CF4 plasma. Electron energy-loss spectra (Kuroki et al, 1992) of CF4 show broad bands without vibrational structure, indicating that most of the low-lying excited states have repulsive adiabatic potential surfaces, leading to immediate dissociation. In other words, electron collisions mostly result in the dissociation of CF4 into CF3, CF2, CF, and other radicals (Winters and Inokuti, 1982), which are all chemically reactive, as represented by 

Radicals, subexcitation electrons, and ions react predominantly with ground-state molecules of the major constituent, which are most abundant, and less frequently among themselves. Through diffusion and repeated secondary reactions. 

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