Al Plasma Etch
Special Problems:
1. Aluminum is not etched by fluorine, because AlF3 is not volatile. Chlorine or bromine are used, which are highly corrosive to equipment.
2. AlCl3, the etch product, is highly corrosive to the remaining aluminum film, and must be removed quickly after plasma etching.
3. Native aluminum oxide is an etch resistant barrier, which is removed by Hydrogen plasma reduction and/or by sputtering by bombardment with Argon at high energies.
4. Aluminum often has a few percent of Silicon or Copper. Silicon is removed by the Chlorine, Copper is not and requires a special process.
