To properly etch Al you will need a reactor with a load lock to prevent
moisture and also protect your operators from potentially dangerous
byproducts. That is because you will need to run a chemistry like BCL3 +
Chlorine to be able to etch through the Al2O3 that forms on the Aluminum then
a mixture of BCL3 and Chlorine with Argon or Helium to etch the bulk of the
Aluminum.