Method and system for modifying patterned photoresist using multi-step ion implantation

A method of reducing the roughness profile in a plurality of patterned resist features provided on a first surface of a substrate, wherein each patterned resist feature includes a first sidewall and a second sidewall opposite the first sidewall, the method comprising:

• providing the plurality of patterned resist features with a total ion dose by:
• exposing, in a first exposure, the first surface of the substrate to a first ion dose at a first tilt angle that is greater than about five degrees from a substrate normal wherein the first ion dose impinges on the first sidewall of the plurality of patterned resist features;
• exposing, in a second exposure, the first surface of the substrate to a second ion dose at a second tilt angle that is greater than about five degrees from the substrate normal wherein the second ion dose impinges on the second sidewall of the plurality of patterned resist features;
• exposing, in a third exposure, the first surface of the substrate to a third ion dose at a third tilt angle that is greater than about five degrees from the substrate normal, wherein the third ion dose impinges on the first sidewall of the plurality of patterned resist features;
• and
• exposing, in a fourth exposure, the first surface of the substrate to a fourth ion dose at a fourth tilt angle that is greater than about five degrees from the substrate normal, wherein the fourth ion dose impinges on the second sidewall of the plurality of patterned resist features, wherein the total ion dose is equivalent to a sum of the first, second, third and fourth ion doses.