Patent ID: 7880151

Claim:
A method of processing a microscopic structure on a sample in a beam system by using a beam controller to direct a beam to a series of beam controller coordinates in a beam controller coordinate system in order to cause the beam to move along the surface of the sample to a series of predetermined points defined in a sample coordinate system, the beam controller coordinate system varying from the sample coordinate system because of positional drift of the beam relative to the sample, the method comprising: determining a desired beam path over the sample for processing the structure; determining a drift model for the beam system by repeated measurements of a reference mark over a period of time to determine an offset between the beam controller coordinate system and the location of the reference mark; aligning a beam coordinate system with a sample coordinate system for a sample loaded into the system by imaging a reference mark on the sample surface and determining an offset between the beam controller coordinate system and the sample coordinate system; correcting the beam controller coordinates using the offset; directing the beam to specified beam controller coordinates to cause the beam to process the sample; and using the drift model determined previously, determining a predicted offset for each beam coordinate and applying that offset to each of the beam controller coordinates as the beam is moved over the sample.