Dear igor, I guess that after a plasma treatment, you may have Cl incorporated into the surface, even when the depth amounts to only some few nm, it is sub-surface Cl, and not just adsorbed Cl. While adsorbed Cl may be remove by water-rinsing, ventually high-pressure water rinsing, sub-surface water cannot be that easily removed. You may try dry-ice cleaning ... Please share your experience. Best regards, Dirk

I would do a O2 plasma to scavenge all the Chlorine which is chemisorbed to the surface. It does not hurt the Al2O3 layer.

Hi, as Dirk mentioned, DI water rinsing right after etching is quite efficient. It avoids corrosion issue of Aluminum. Or at least for a while (about few days) because the deepply adsorbed Chlorine might come out at the surface and react with water vapor and aluminum to form aluminium hydroxides