Line edge smoothing with jittered twist

An ion beam system, comprising:

• an ion source configured to generate an ion beam;
• a beam steering system configured to direct the ion beam along a beam direction;
• a substrate support system including a rotatable substrate holder;
• and
• a control system programmed to:
• generate the ion beam using the ion source;
• scan the ion beam across a substrate held inclined relative to the ion beam by the rotatable substrate holder;
• and
• while the scan is in progress, oscillate the substrate between first and second orientations.

A method of line edge smoothing, comprising:

• generating an ion beam using an ion beam system including an ion source configured to generate the ion beam, and a beam steering system configured to direct the ion beam along a beam direction;
• directing the ion beam toward a surface of a wafer having an edge and a feature orientation defined relative to an alignment feature on the edge, using the beam steering system, wherein the wafer surface is inclined relative to the ion beam;
• scanning the ion beam over the wafer surface by varying the beam direction, translating the wafer, or both;
• and
• while scanning the ion beam across the wafer surface, rotating the wafer so that an angular difference between a projection of the ion beam onto the wafer surface and the feature orientation oscillates between positive and negative values.