The effect of shallow (< 500 Å) implanted ions on the formation of thermal hillocks in thin (5000 Å) patterned Al9 9w%Si1w%, films was studied. The ions were implanted by plasma immersion ion implantation (PIII) and the gases (N2, O2, and Ar) used in the implantation ranged from completely inert to highly reactive with Al. The voltages used to accelerate the ionized molecules were 2.5 kV to 30 kV. This corresponds to implant depths of 50 Å to 400 Å. The nominal doses were adjusted to achieve a ∼20% dopant concentration over the fullwidth- at-half-maximum of the calculated implant profile. Following implant, the samples were sintered at 450°C for 30 minutes and inspected for thermal hillock formation by scanning electron microscopy. We find that PIII is effective in suppressing thermal hillock formation for implant depths greater than 60 Å.